Phẫu Thuật Tai Mũi Họng Và Phẫu Thuật Đầu Cổ

Chapter 124
Acoustic Neuroma 1297
nerve outcomes are better when surgery is performed
in a center doing a high volume of such surgery. Rates
of good facial nerve function are 93% for middle fossa,
97% for retrosigmoid, and 78% for translabyrinthine
approaches in series of at least 100 patients.15 However,
it should be noted that patients’ self-reports of facial
nerve function are often worse than the surgeon’s
assessment.16
The case of a patient with good preoperative
hearing but tumor located laterally in the IAC deserves
special mention. When the tumor extends laterally into
the fundus, particularly if it is of inferior vestibular
nerve origin, the transverse crest will likely preclude
total tumor resection via the middle fossa approach
(Fig. 124-1). Additionally, it is diffi cult to achieve full
tumor resection while preserving hearing through a
retrosigmoid approach in this case as well. Therefore
such patients may opt for a translabyrinthine approach,
knowing that hearing loss will be traded for more com-
plete tumor resection and possibly a lower chance of
facial weakness.13
Radiosurgery offers the advantage of outpatient
treatment and minimal recovery time, and affords
excellent tumor control with low rates of cranial nerve
dysfunction.17,18 Many reports indicate that improved
hearing and facial nerve results are seen following ster-
eotactic radiosurgery (SRS) compared with microsur-
gery.19-21 In a series of patients treated at the University
of Pittsburgh with gamma knife radiosurgery using a
median dose of 13 Gy, a 97.1% rate of tumor control
was achieved with 1.1% rate of facial weakness, 2.6%
rate of trigeminal nerve dysfunction, and 71% rate of
“hearing level preservation.”22 However, high-frequency
hearing loss following SRS has been shown to correlate
with maximal cochlear dose and transient evoked
otoacoustic emissions (TEOAEs) worsened in 75% of
patients who had measurable TEOAEs before treat-
ment.23 At the University of Florida, linear accelerator-
based SRS results on 108 patients with AN treated after
1994 included a 93% rate of radiologic control, 5% rate
of facial neuropathy, and 2% trigeminal neuropathy.24
A meta-analysis of 1475 patients treated with gamma
knife radiosurgery between 1969 and 2000 documented
an 8% rate of tumor growth and an 8% rate of trigemi-
nal or facial neuropathy, and 4.6% of patients ultimately
required microsurgery.25 Hydrocephalus may also
develop following radiosurgery, requiring placement
of a ventriculoperitoneal shunt.26 Patients must be
informed of the eight cases of possible malignant trans-
formation reported in the literature, as well as the pos-
sibility that future surgical resection may be more
diffi cult.13,24,27 Some centers also offer conventionally
fractionated radiotherapy for AN.28 The principles and
details regarding our use of CyberKnife SRS are pro-
vided in Chapter 125.
Recent investigations have addressed quality of
life following treatment for AN. Several studies suggest
that SRS offers improved posttreatment quality of life
compared with microsurgery.20,29 Myrseth and col-
leagues reported better facial nerve function, as well as
better Glasgow Benefi t Inventory and SF-36 scores, in
patients treated with gamma knife versus microsurgery.
A prospective trial conducted at the Mayo Clinic showed
that patients undergoing microsurgery experienced a
decline in several subscales of the Health Status Ques-
tionnaire postoperatively; this decline was not seen in
patients treated with gamma knife radiosurgery.20 Addi-
tionally, the Dizziness Handicap Inventory scores were
better for the gamma knife group.20
Understanding the typical growth characteristics of
AN facilitates the physician’s decision regarding what
treatment should be offered to the patient. Overall, we
consider surgical resection to be the preferred method
in the management of AN in young (younger than 65
years of age), healthy patients. An estimation of the
patient’s longevity must be considered. Patients who are
otherwise healthy and have a family history of survival
into their late ninth decade can be considered for surgi-
cal intervention. Patients between 65 and 70 years of
age are evaluated on the basis of factors that include
their health, neurologic examination, tumor size, tumor
location, rate of growth, hearing status in each ear, and
family medical history. We acknowledge that gamma,
electron, or proton beam radiation should also be con-
sidered effective alternative methods for stopping tumor
growth. In the face of documented growth of the tumor,
we recommend radiation for patients older than 70
years of age or for patients who have tumors beyond the
IAC who are medically unstable. We offer the option of
photon beam or gamma radiation to patients who have
a recurrence of a previously resected tumor. We also
recommend radiation to patients who have had subtotal
removal of a large tumor where total resection might
have the potential to produce adverse surgical morbid-
ity. In the elderly or medically compromised patient, a
small tumor without associated neurologic symptoms
other than unilateral hearing loss can be followed over
time, observing for evidence of tumor growth. Repeat
MRI is obtained in 6 months to compare tumor size. If
tumor growth becomes manifest, radiation treatment is
suggested, and if no growth has occurred, the MRI scan
Figure 124-1. T1-weighted magnetic resonance image with con-
trast showing a right internal auditory canal acoustic neuroma located
laterally in the fundus (arrow), above and below the transverse crest
(TC).

1298
Section 15
Temporal Bone
will be repeated in 6 months. The interval increases to
yearly and then every 3 years if there is no change in
the size of the tumor.
A treatment program must be individually tailored
for each patient with bilateral ANs (neurofi bromatosis-
2 [NF-2]). NF-2 patients may have other associated
intracranial tumors or tumors of the spinal cord and
must be diligently examined and imaged to determine
the tumor status as well as their medical stability for
intracranial surgery. The size of the tumors and the
hearing status must be accurately determined. Manage-
ment options include surgical resection, surgical decom-
pression to allow for tumor growth, radiation, and
observation. Until recently, we considered radiation
therapy to be a reasonable alternative in the manage-
ment of bilateral tumors. However, the poor hearing
results following gamma radiation do not justify this
method as the preferred, exclusive treatment alterna-
tive when hearing is intact. Furthermore, the long-term
outcome of irradiating NF-2 tumors is unknown at this
time. Given that these tumors often present in young
people, it may be necessary to follow them for periods
up to 50 years. If tumor growth occurs despite radiation
therapy, complete surgical removal may be technically
more diffi cult because of the radiation therapy, with
greater likelihood of neurologic consequences. We
have had experience using an auditory brain stem
implant inserted at the time of tumor removal for
patients with bilateral ANs. The device provides sound
awareness to an anacoustic ear but has not provided the
excellent speech recognition achieved with cochlear
implants. In summary, one must judiciously decide
which patient would be ideally suited for radiation
therapy.
Other than the exceptions noted previously, most
patients are considered to be surgical candidates for
excision of the tumor. Various factors must be evalu-
ated in order to formulate a treatment plan. The status
of the patient’s hearing is the predominant issue that
dictates the surgical approach. There is great contro-
versy as to what is considered useful hearing. Patients
with hearing thresholds better than 50-dB speech recep-
tion threshold (SRT) and 50% speech discrimination
(DISC) (word recognition) are considered candidates
for a hearing preservation procedure. However, the size
and location of the tumor must be taken into account
when attempting to save hearing. It can be argued that
any hearing should be preserved in order to provide
sound localization. Thus hearing levels of 70 dB SRT
and 30% DISC may be considered usable hearing suit-
able for a hearing aid. Hearing in the contralateral side
must also be considered. If hearing function is normal
in the uninvolved ear, then preservation of poor hearing
will not be psychoacoustically useful to the patient.
Patients with tumors that extend greater than 2 cm into
the cerebellopontine angle (CPA) are unlikely to have
preservation of hearing regardless of the preoperative
hearing status. However, if preoperative hearing is
good, it is reasonable to attempt hearing preservation
through a retrosigmoid approach if the tumor does not
extend laterally to the fundus of the IAC.
The translabyrinthine approach is used to remove
tumors in most patients with hearing levels greater than
50-dB SRT and less than 50% DISC. This approach may
also be used in patients with good hearing, if the tumor
extends past the transverse crest in the IAC and the
patient is willing to sacrifi ce hearing for more complete
tumor resection. The translabyrinthine approach is
reported to have a 9% rate of postoperative CSF leak,
and depending on the size of the tumor, a 73% rate of
House-Brackmann Grade I-II facial function. This rate
increases to 78% in high-volume centers.15 The trans-
labyrinthine approach is also used for NF-2 patients
with poor hearing in whom an auditory brain stem
implant is anticipated.
The retrosigmoid approach is useful for patients
with serviceable hearing and greater than 0.5-cm tumor
extension into the CPA. We also favor the retrosigmoid
approach for removing very large tumors when the
brain stem is compressed and shifted to the contralat-
eral side. The disadvantage of this approach is its limited
access to the lateral IAC. The retrosigmoid approach
has been reported to have a 30% rate of hearing pres-
ervation overall, a 92% rate of House-Brackmann Grade
I-II facial function at all centers, and an 11% rate of
postoperative CSF leak. Notably, there is a 21% rate of
postoperative headache following this approach.15
The middle fossa approach is useful for excising
tumors that are contained within the IAC or that extend
less than 0.5 cm into the CPA at the porus. Further-
more, caution must be observed for patients older than
60 years of age. The dura in these patients is often thin
and subject to lacerations. This may be accompanied by
annoying venous bleeding, making the middle fossa
dissection challenging and making obtaining a water-
tight dural closure diffi cult. This approach offers a 53%
rate of hearing preservation overall and an 89% rate of
House-Brackmann Grade I-II facial function.15 Rates of
hearing preservation correlate with tumor size and vary
by center, and may be improved with near fi eld whole
eighth nerve monitoring in small tumors.30 For tumors
with more than 10-mm extension into the CPA, there
is a higher postoperative rate of hearing loss and facial
weakness when the middle fossa approach is used.31
There is a 6% rate of postoperative CSF leak and 8%
incidence of postoperative headaches.15
PREOPERATIVE PLANNING
A complete history is obtained regarding symptoms
including hearing status and tinnitus. Patients are ques-
tioned regarding diffi culty with ambulation, dysequilib-
rium, and vertigo. A history of headaches, facial
twitching, hypesthesia, or diffi culty with voice or swal-
lowing is sought.
Physical examination is focused on cerebellar func-
tion and the cranial nerves of the posterior fossa. Extra-
ocular movements are observed, looking for gaze-evoked
nystagmus. Facial and corneal sensations are tested in
order to evaluate the sensory distribution of the trigemi-
nal nerve. Facial movements are observed, seeking evi-
dence of weakness. The lower cranial nerves are assessed

Chapter 124
Acoustic Neuroma 1299
by testing oropharyngeal tactile sensation and vocal
cord mobility. The patient’s tandem gait is observed,
and other evidence of cerebellar dysfunction, including
dysmetria and dysdiadochokinesia, is sought.
A complete audiogram, consisting of air and bone
pure-tone thresholds and speech audiometry, is
obtained. Identifying rollover (worsening word recogni-
tion with increased presentation levels) further sup-
ports a retrocochlear lesion. Despite knowing that a
patient has a posterior fossa tumor suggestive of an AN,
ABR is frequently obtained, especially when hearing
function is present. Evidence of interpeak latency shifts
or change in waveform morphology is investigated. Fur-
thermore, if good waveforms are readily identifi able,
the ABR test provides a useful baseline for intraopera-
tive auditory monitoring if a hearing preservation pro-
cedure is undertaken (Fig. 124-2).
Once a presumed diagnosis of AN is made, vestibu-
lar testing may be obtained. The fi ndings on caloric
stimulation provide information regarding the degree
of vestibular loss owing to the tumor. A signifi cantly
reduced vestibular response informs the surgeon and
patient that postoperative vertigo and dizziness should
be at a minimum. The fi ndings of reduced responses
on caloric stimulation are considered to be indicative
of superior vestibular nerve function. This information
may be useful when planning a middle fossa approach.
Normal residual caloric responses imply sparing of the
superior vestibular nerve and the tumor originating
from the inferior vestibular nerve. Unfortunately, the
fi nding of a reduced vestibular response to caloric stim-
ulation is not diagnostic of superior vestibular nerve
tumor origin. It has been shown that a reduced caloric
response can be demonstrated in 60% of tumors arising
from the inferior division (Fig. 124-3).32 In summary,
we do not routinely obtain vestibular testing in diagnos-
ing or planning treatment for patients suspected of
having an AN.
Radiologic imaging is critical in diagnosing and
managing a tumor in the posterior fossa. A presumptive
diagnosis of an AN is determined by the location and
shape of the tumor along with its signal characteristics
without and with contrast. The tumor size has an inverse
relation to the likelihood of preserving preoperative
hearing. The larger the tumor, the less likely that the
cochlear nerve and function can be maintained. As
tumors get larger than 2 cm, hearing preservation is
rarely successful. The same concern exists for the facial
Figure 124-2. A, Audiogram of a 24-year-old patient complaining
of right hearing loss. Note high-frequency sensorineural loss with
reduced word recognition score. B, Auditory brain stem response of
the same patient demonstrating a right interpeak latency shift of I-III
and I-V intervals consistent with retrocochlear pathology.
A
B
Figure 124-3. T1-weighted con-
trast-enhanced
axial
(A)
and
coronal (B) magnetic resonance
imaging scans. Note the right infe-
rior vestibular nerve schwannoma
(arrows) located in the posteroinfe-
rior fundus of the internal audi-
tory canal (IAC).

1300
Section 15
Temporal Bone
nerve. The removal of large tumors is more likely to
produce postoperative facial paresis or paralysis. Also,
facial nerve outcomes in cystic tumors have been
reported to be worse than in solid tumors.33
The MRI scan demonstrates the relationship of the
tumor to the surrounding brain. Brain stem compres-
sion may obstruct the fourth ventricle with resultant
hydrocephalus. The scan is also reviewed to determine
whether the tumor impinges on the fi fth or lower
cranial nerves. Removal of large tumors may produce
postoperative corneal and facial hypesthesia from
manipulation of the trigeminal nerve. Similarly, tumor
extending inferiorly low in the posterior fossa can affect
cranial nerves IX, X, and XI (Fig. 124-4). The surgeon
and patient must both be prepared for a possible post-
operative swallowing and laryngeal dysfunction.
The MRI scan is also reviewed in order to deter-
mine the lateral extent of the tumor. Patients with good
hearing and tumor limited to the IAC and extending
to the fundus are candidates for a middle fossa approach
(Fig. 124-5). Patients with good hearing and tumor
0.5 cm beyond the IAC into the CPA should undergo a
retrosigmoid approach if hearing is to be preserved.
However, tumor extending and fi lling the fundus
cannot be removed under direct microscopic vision.
Owing to limitations posed by the otic capsule, the
posterior wall of the IAC cannot be completely drilled
laterally, exposing the fundus. Identifying tumor within
the fundus on MRI requires thorough evaluation of this
area at the time of surgery.
The location of the jugular bulb can be determined
from the MRI scan. Blood and fl ow signal can be seen
on T1- and T2-weighted images. However, a more accu-
rate assessment of the bony and vascular anatomy of the
temporal bone is obtained with a CT scan. We fre-
quently obtain a thin-cut bone-windowed CT scan when
a hearing preservation procedure is planned or when
the jugular bulb is suspected on MRI of creating an
anatomic obstacle. The noncontrast bone-windowed
study shows the pneumatization of the temporal bone
relative to the IAC (Fig. 124-6). Knowing preoperatively
that the petrous bone is well pneumatized provides
additional landmarks when drilling around the IAC via
a middle fossa or retrosigmoid approach.
Collating the data presented previously helps deter-
mine which surgical approach is most appropriate and
provides information that may be predictive of success-
ful preservation of hearing. Negative predictive factors
include tumor size greater than 2.0 cm, evidence of
widening of the IAC, tumor extension laterally to the
fundus, and poor waveform morphology on ABR
testing.34,35
A
B
Figure 124-4. T1-weighted con-
trast-enhanced
magnetic
reso-
nance imaging scan of a left
acoustic neuroma. A, Axial image
showing a 3-cm tumor with com-
pression of the brain stem. The
fourth ventricle is patent (arrow).
B, Coronal image demonstrating
the inferior extent of the tumor.
Note the relationship to the
jugular fossa (arrow).
Figure 124-5. T1-weighted contrast-enhanced magnetic resonance
imaging scan of a right acoustic neuroma extending toward the
fundus, fi lling the internal auditory canal. The transverse crest is not
well outlined.

Chapter 124
Acoustic Neuroma 1301
Informed Consent
An excellent discussion of informed consent in acoustic
neuroma treatment was published in 2005.13 The author
stressed the importance of a balanced and unbiased
discussion of treatment options, which is most easily
afforded by a multidisciplinary team having experience
with both radiation and surgical modalities of treat-
ment. The decision process must be individualized for
each patient. There are numerous factors that must be
considered when formulating a treatment plan, both in
the mind of the physician and in what is proposed to
the patient. These factors include the chronologic and
physiologic age and health of the patient; characteris-
tics of the tumor such as size, location, and rate of
growth; a family history or presence of multiple intra-
cranial tumors (NF-2); hearing status of the ipsilateral
and contralateral ear, ABR waveform morphology, if
obtained; and the functional status of their vestibular
system. Surgeons should be aware that patients make
their treatment choices using information given to
them by physicians, patient education pamphlets, Inter-
net searches, discussions with other patients, and pub-
lished data.36 The inclination of the patient regarding
their preference for surgical or radiation treatment
infl uences their thought process. Some patients wish to
avoid surgery at any cost; other people are distressed
with the realization that tumor is present within their
head and prefer surgical excision. The importance of a
comprehensive and understandable informed consent
cannot be overemphasized. It is most important to
discuss with the patient and family the location of the
tumor and its relationship to the surrounding vascular,
dural, and neural structures. The treatment options
of observation, surgical removal, or radiation therapy
are reviewed. The risks, benefi ts, and outcomes are
explained. Although the physician may infl uence the
patient’s thinking, the fi nal decision for treatment rests
with the patient.
SURGICAL TECHNIQUE
Anesthesia
Removal of an AN is performed with the patient under
general endotracheal anesthesia. Long-acting muscle
relaxants are avoided in order to permit monitoring
of the facial nerve. Short-acting muscle relaxants are
employed at the start of the procedure during induc-
tion and intubation and following completion of tumor
removal when fi nal facial nerve thresholds are deter-
mined. Anesthesia is maintained with inhalation agents,
narcotics, and barbiturates. Neurophysiologic monitor-
ing is conducted for all procedures. This consists of
electrode placed to monitor cranial nerves V, VI, VII,
VIII, and X. Even if hearing is absent or to be sacrifi ced
with a translabyrinthine approach, the contralateral ear
is monitored because it provides feedback regarding
the status of the contralateral brain stem. Somatosen-
sory potentials are also evaluated during the case,
refl ecting the integrity of the lower brain stem and
peripheral nervous system (Fig. 124-7). A urinary cath-
eter is inserted, and antithrombotic stockings with
sequential compression devices are placed. The infra-
umbilical area of the abdomen is shaved and prepared
for potential removal of an adipose tissue graft.
Translabyrinthine Approach
A postauricular C-shaped incision begins 2 cm supe -
rior to the root of the auricle. The incision extends
Figure 124-6. Bone algorithm computed tomography scan of a
right acoustic neuroma. Note widening of the internal auditory canal.
Approximately 7 mm of bone from the posterior lip of the porus
acusticus can be drilled safely before the posterior semicircular canal
is entered (small arrows). Large arrows outline the margin of the
tumor.
Figure 124-7. Before turning the patient into the appropriate posi-
tion for the procedure, electrodes are inserted for monitoring the
cranial nerves and somatosensory potentials.

1302
Section 15
Temporal Bone
posteriorly and inferiorly 4 cm posterior to the postau-
ricular sulcus. It continues inferior and anterior to the
mastoid tip (Fig. 124-8). Superiorly, the skin incision
extends to the depth of the temporalis fascia. An ante-
rior-based skin fl ap is developed superfi cial to the tem-
poral fascia and fi broperiosteum overlying the mastoid
cortex. A second or more medial anterior-based fl ap is
created, consisting of incised temporalis fascia and
muscle and mastoid fi broperiosteum. This is developed
just anterior to the posterior edge of the skin incision
(Fig. 124-9). A small piece of temporalis muscle deep
to the temporalis fascia is harvested from the superior
limit of this fl ap.
Two self-retaining retractors are placed 90 degrees
to one another. Using a large cutting burr and suction
irrigation, a transcortical mastoidectomy is performed.
Once the antrum has been identifi ed, the bone dissec-
tion is enlarged to expose the lateral and inferior aspect
of the middle fossa dura, sinodural angle, sigmoid sinus,
and mastoid tip. The posterior bony canal wall is thinned
to fully expose the antrum, fossa incudis, epitympanum,
and air cells over the facial recess. The bone overlying
the sigmoid sinus and retrosigmoid posterior fossa dura
must be removed. This is initially accomplished with
cutting and then using diamond burrs. Preservation of
an island of bone (Bill’s island) over the sigmoid sinus
minimizes direct trauma to the wall of the sinus from
retraction (Fig. 124-10).
In order to obtain a watertight closure and avoid
CSF rhinorrhea, the eustachian tube is obliterated
through an extended facial recess approach. The incus
is separated from the stapes and removed. The poste-
rior buttress is drilled to increase exposure of the
middle ear. Pieces of Surgicel and muscle are placed
through the enlarged facial recess directly into the
eustachian tube (Fig. 124-11). If space permits, the
short process and body of the incus are also placed into
the eustachian tube after removing the incus long
process. Additional small pieces of Surgicel and muscle
are placed into the eustachian tube orifi ce.
A labyrinthectomy is then performed. The dissec-
tion continues through the horizontal semicircular
Figure 124-8. Incision for a translabyrinthine approach. The trans-
verse and sigmoid sinuses are illustrated.
1 cm
Figure 124-9. The deeper incision divides the temporalis muscle
just superior to the linea temporalis and continues in a curvilinear
direction through the fi broperiosteal layer over the mastoid cortex,
1 cm anterior to the posterior skin fl ap.
Figure 124-10. The transmastoid approach requires exposure of
the middle and posterior fossa dura, leaving an island of bone over
the sigmoid sinus. The antrum is opened, and the incus is identifi ed.
The posterior bony canal wall is thinned, with a bone remaining over
the vertical facial nerve. The digastric ridge is outlined inferiorly.

Chapter 124
Acoustic Neuroma 1303
canal, which is used as the initial landmark for the
horizontal segment and second genu of the facial nerve.
A thin shell of bone is left over the distal horizontal,
second genu, and vertical portions of the facial nerve.
The pink color of the nerve can be seen through the
bone. The labyrinthectomy is taken through the vesti-
bule and the medial wall of the otic capsule. It is neces-
sary to remove all bone from the middle and posterior
fossa dura, sinodural angle, and jugular bulb. This is
initially accomplished with cutting and then using
diamond burrs. Once the bone is of appropriate thick-
ness, it can be removed with a dissecting instrument
such as a Lempert, Penfi eld, duckbill, Freer, or Cottle
elevator (Fig. 124-12).
The IAC is skeletonized for at least 180 degrees of
its posterior circumference. It is important to remove
bone both superior and inferior to the IAC. During the
exposure of the inferior aspect of the IAC and dome of
the jugular bulb, the cochlear aqueduct is entered and
CSF is typically encountered (Fig. 124-13). The trough
superior to the IAC and inferior to the middle fossa
dura is drilled cautiously. The lateral aspect of the IAC
is further dissected with a small diamond burr. In addi-
tion to drilling the IAC laterally to the fundus, a trough
superior to the IAC is developed to provide access to
the superior and lateral aspect of the tumor (see Video
124-1). The fi nal bony dissection is over the labyrin-
thine portion of the facial nerve. At this point, Bill’s bar,
separating the facial nerve and superior division of the
vestibule nerve, is identifi ed.
The dome of the jugular bulb may extend superi-
orly to the level of the IAC. This limits the working
space for addressing both the IAC and CPA portions of
the tumor. It is necessary to decompress this area of its
overlying bone. The lining over the jugular bulb is thin
so caution is needed when drilling over this area. Once
the bone is removed, a neuropatty may be used to
further compress the bulb inferiorly. Placing Surgicel
under the neuropatty provides compression and
packing of this area. The inferior trough can then be
completed with jugular bulb displaced inferiorly from
the surgical fi eld (see Video 124-2).
The presigmoid dura is coagulated with bipolar
cautery to obtain surface hemostasis. The dura and
periosteum of the IAC are cut in a lateral-to-medial
direction to give access to the IAC. The posterior fossa
dura is cut sharply beginning just anterior to the sigmoid
Figure 124-11. The incus is removed from the fossa incudis, and
the facial recess is extended by drilling the posterior buttress. The
eustachian tube is packed with Surgicel and muscle using a curved
pick.
Figure 124-12. A labyrinthectomy has been completed, opening
into the vestibule. The more medial bone of the middle fossa tegmen
and posterior fossa is removed. The endolymphatic duct and sac are
identifi ed. The subarcuate artery may persist in the solid angle.
Superior trough
Bill’s bar
Inferior trough
Figure 124-13. The IAC is skeletonized, creating a superior and
an inferior trough. Bill’s bar is identifi ed. Bone from the posterior
lip of the porus acusticus must be removed. The cochlear aqueduct
is located superior to the jugular bulb.

1304
Section 15
Temporal Bone
sinus. The incision of the dura continues toward the
dural ring, defi ning the posterior rim of the porus. It
then continues both superior and inferior to the IAC,
providing wide access to the posterior fossa (Fig. 124-14;
see also Video 124-3). The dural over the IAC is then
opened. A McElveen knife permits dissection with a
rounded tip and then cutting of the dural with the
sharp portion of the instrument (see Video 124-4). The
lateral insertion of the superior vestibular nerve is
sharply dissected away from the facial nerve. Tumor
present laterally in the fundus will be encountered at
this time and is also sharply dissected away from the
facial nerve.
Small tumors limited to the IAC and the area of the
porus can be removed in a lateral-to-medial direction.
Unless the cochlear nerve is involved, it is best to leave
it undisturbed, so as to avoid any potential injury to the
perineural vessels that may also supply the facial nerve.
The facial nerve monitor and stimulator are invaluable
for performing this procedure. The minimal current
output of the nerve stimulator should be used in order
to establish current thresholds.
When operating on large tumors, the specimen will
need to be removed in a piecemeal fashion. The tumor
is initially dissected in a subarachnoid plane. Prominent
surface vessels are coagulated with bipolar cautery.
When most of the tumor is in the CPA, the capsule of
the tumor is entered with sharp dissection (Fig. 124-15).
Tumors with a fi rm consistency may need to be soft-
ened with cup forceps. Sections of the tumor are then
removed with scissors dissection or Takahashi’s forceps.
Bipolar cautery not only assists in control of hemostasis
but also shrinks the tumor, facilitating removal. The
location of the facial nerve must be verifi ed before
cautery is applied. More rapid debulking of the central
part of the tumor is accomplished with ultrasonic aspi-
ration. The facial nerve is usually stretched over the
anterior and medial surface of the tumor but, in some
cases, may be located either inferiorly or superiorly.
Rarely, the facial nerve is in a posterosuperior location.
Debulking of the central part of the tumor leaves the
tumor capsule with the adherent facial nerve. Identifi -
cation of the facial nerve and cochlear vestibular
complex at the brain stem facilitates removal of residual
tumor. Care is taken to identify and preserve the ante-
rior inferior cerebellar artery (AICA), which often lies
between the seventh and the eighth nerves. The tumor
capsule is moved posteriorly and inferiorly. The facial
nerve stimulator is used to locate the facial nerve or its
root entry zone on the brain stem. Cutting the proximal
stump of the eighth nerve facilitates removal of the
Facial
nerve
Superior
vestibular
nerve
Inferior vestibular
nerve
B
A
Cochlear nerve
Figure 124-14. A, The incisions
in the IAC and posterior fossa dura
are demonstrated. B, The IAC is dis-
sected circumferentially, creating a
superior and an inferior trough.
The posterior fossa dura is opened.
Figure 124-15. Hemostasis is controlled on the capsule of the
tumor with bipolar cautery. The tumor surface is entered with sharp
dissection. The core of the tumor is then removed. The facial nerve
is frequently located on the anterosuperior pole of the tumor.

Chapter 124
Acoustic Neuroma 1305
tumor (Fig. 124-16; see also Video 124-5). Dissection is
then continued from the medial to the lateral direction.
The remaining tumor capsule is sharply dissected away
from the facial nerve. The wound, dura, and posterior
fossa are irrigated with saline solution. Hemostasis is
ensured with bipolar coagulation.
Disrupting the facial nerve in order to completely
remove an AN is a rare occurrence. However, when it
does occur, effort should be made to repair the nerve
primarily. With the nerve having been stretched by the
enlarging tumor, primary reapproximation may be fea-
sible. Owing to the lack of epineurium, it may be diffi -
cult to get more than one 8-0 nylon suture placed to
reapproximate the disrupted ends of the facial nerve.
A few drops of fi brin glue may be used to further secure
the anastomosis. This is facilitated by placing small
pledgets of Gelfoam around the reapproximated nerve
ends. If there is inadequate length to perform a primary
anastomosis, then a cable graft using the sural or greater
auricular nerve is performed.
The edges of the posterior fossa dura are reapproxi-
mated using interrupted or running 4-0 dural sutures
(silk or Nurolon). A convenient needle to use in this
tight area is an Ethicon TF-4.11 Complete closure is not
possible owing to the dural defect at the IAC. Similar
to a clothesline, the suture spans the dura defect, pro-
viding a lattice support for the next step of obliteration
of the wound with adipose tissue (Fig. 124-17; see also
Video 124-6). Abdominal fat, harvested from the infra-
umbilical area of the abdomen, is soaked in the
bacitracin solution. Pieces of fat and temporalis muscle
that were obtained earlier in the procedure are placed
through the facial recess, fi lling the middle ear. The
aditus is completely blocked with muscle. A small piece
of Surgicel secures the muscle plug. The abdominal fat
is then cut into strips and advanced through the dural
defect (Fig. 124-18). The remainder of the mastoid
cavity is also packed with abdominal fat. Fibrin glue is
applied around the fat (see Video 124-7). The wound
is closed in three layers. The mastoid cortical defect is
covered with a titanium plate fi xed to the temporal
bone with self-tapping screws. The fi broperiosteal and
temporalis muscle fascial fl ap is closed with interrupted
Facial nerve
Facial
nerve
AICA
Cochleo-
vestibular
nerves
Figure 124-16. After the tumor is debulked, the capsule may be
moved posteriorly and inferiorly to identify the proximal facial nerve
and cochleovestibular bundle. A loop of the anterior inferior cerebel-
lar artery (AICA) is frequently found between the nerves. The proxi-
mal end of the tumor is coagulated with the bipolar cautery and the
cochleovestibular nerves are transected.
Figure 124-17. The remaining edges of the porus and posterior
fossa dura are reapproximated to support the fat graft. Note the
ribbon-like attenuation of the facial nerve at the porus.
Figure 124-18. The ends of strips of fat are placed through the
dural openings into the posterior fossa.

1306
Section 15
Temporal Bone
sutures. The subcutaneous skin fl ap is also approxi-
mated with the same suture. A running interlocking 4-0
Nurolon suture closes the skin. Skin staples may also be
used. Antibiotic ointment and a Telfa pad are placed
over the incision, and a sterile pressure dressing is
applied.
Middle Fossa Approach
The patient is positioned supine on the table and placed
in a Mayfi eld head holder with the head turned with
the involved ear facing the ceiling. The hair is shaved
in the preauricular region from the tragus to the supe-
rior temporal line. Electrodes for facial nerve monitor-
ing are placed. In order to monitor the ABR, a sound
source is placed into the ear canal affi xed with a foam
rubber plug and bone wax to secure the ear phone.
This is covered with an Op-Site dressing, and the area
is prepared and draped. Extraction of fl uid from the
soft tissue of the brain permits easier retraction of the
temporal lobe. Techniques used to shrink and soften
the brain include removal of CSF via a spinal drain,
mild dehydration using intravenous mannitol and furo-
semide, and lowering the patient’s partial pressure of
carbon dioxide (Pco2) through hyperventilation. A
lumbar drain, although not used routinely, is inserted
after induction of general anesthesia by turning the
patient in a lateral position. The patient is returned to
the supine position once the catheter has been secured.
Mannitol and furosemide are given at the time the skin
incision is made.
The design of the skin incision depends in part on
the surgeon’s preference but also on the goal of the
surgery. Figure 124-19 shows three common modifi ca-
tions of the preauricular skin incision used for the
middle fossa approach to the IAC. We prefer an inci-
sion that extends vertically with a slight curve at the
superior extent depicted by line B. The incision is out-
lined, and a solution of 1% lidocaine (Xylocaine) with
1 : 100,000 epinephrine is injected to help with hemo-
stasis during the initial elevation of the skin fl ap. Once
the skin and subcutaneous tissues have been incised
and the skin fl aps undermined, the area of the tempo-
ralis fascia and muscle above the root of the zygoma will
be exposed. The temporalis muscle is incised in order
to create an inferiorly based pedicled fl ap at its origin.
The temporalis muscle is cut along the linea temporalis
above the mastoid and continues vertically and superi-
orly to the superior temporal line. A cuff of fascia and
periosteum is preserved superiorly for suture reapproxi-
mation at the conclusion of the procedure. Anteriorly,
the descending temporalis muscle incision divides the
muscle body as it extends toward the zygomatic arch. A
periosteal elevator is used to mobilize the temporalis
muscle inferiorly to the root of the zygoma. Hemostasis
is obtained with bipolar coagulation or bone wax. The
temporalis muscle is also retracted inferiorly with a
2-0 Dexon or silk suture. The external auditory canal,
root of the zygoma, and glenoid fossa are important
landmarks.
A temporal craniotomy is then performed over the
squamous portion of the temporal bone. The craniot-
omy fl ap is positioned approximately one-third poste-
rior to and two-thirds anterior to the external auditory
canal. It measures approximately 5 cm in the vertical
dimension and 4 cm in anteroposterior width. The infe-
rior aspect of the craniotomy is based on the root of the
zygoma and should be placed as low as possible. The
fl ap is dissected with a medium cutting burr that defi nes
the perimeter of the bone fl ap (Fig. 124-20). Another
method of turning the bone fl ap is to place four burr
holes at each corner of the bone dissection. A cranio-
tome with a footed attachment on a high-speed drill is
used to fi nely cut the two vertical and superior horizon-
tal bone cuts, connecting the burr holes. Because of
anatomic limitations, it is often diffi cult to use the
footed attachment for the inferior horizontal cut. The
inferior horizontal cut is made with a round cutting or
matchstick burr. Using an elevator, the bone fl ap is
lifted while the underlying dura is cautiously detached
from the inner table. The dura underlying the craniot-
omy site is elevated. Hemostasis is secured with bipolar
coagulation. Once the bone fl ap is removed, the infe-
rior aspect of the craniotomy should be lowered to the
level of the fl oor of the middle fossa using a rongeur
or cutting burr (Fig. 124-21). Rough edges of the cra-
niotomy site and bone fl ap are smoothed with a rongeur
or drill. The dura is elevated from the fl oor of the
middle fossa. Dissection requires patience and slow but
progressive retraction of the temporal lobe. Adequate
brain softening should have been achieved from the
previously administered osmotic agents.
Familiarity with the surface anatomy of the fl oor of
the middle fossa is essential to facilitate this operative
approach. The most lateral adhesion of dura occurs at
the petrosquamous suture. Anteriorly, the middle men-
ingeal artery enters through the foramen spinosum.
A
B
C
Figure 124-19. Skin incisions available for a middle fossa approach
to an acoustic neuroma. Our preference is B.

Chapter 124
Acoustic Neuroma 1307
The lesser and greater superfi cial nerves run parallel
from the sphenopetrosal groove. The greater superfi -
cial petrosal nerve (GSPN) courses from posterior to
anterior, leaving the geniculate ganglion through the
facial hiatus. Deep to the GSPN lies the horizontal
portion of the petrous carotid artery. Lateral to the
carotid artery is the tensor tympani muscle above and
the eustachian tube below. The internal carotid artery
courses medially and inferiorly to the mandibular divi-
sion of the trigeminal nerve (V3). The arcuate emi-
nence lies posteriorly and medially on the fl oor of the
middle fossa. This is the bony convexity of the superior
semicircular canal. Posterior to the arcuate eminence
is the tegmen of the mastoid. The superior petrosal
sinus runs obliquely from posterolateral to anterome-
dial and forms the medial boundary separating the
middle from the posterior fossa. This anatomy relative
to the ossicles, geniculate ganglion, facial nerve, IAC,
vestibular labyrinth, and cochlea is demonstrated in
Figure 124-22.
Using an operating microscope, a Lempert eleva-
tor, and small suction, the dura is elevated from the
fl oor of the middle fossa in a lateral-to-medial and pos-
terior-to-anterior direction. Laterally, within the fi rst
10 mm of dural elevation, the petrosquamous suture
line is encountered. The dura may be fi rmly attached
along this suture line, and occasionally, a few small
perforating veins will be noted and can be coagulated
or waxed. Further medially and anteriorly, the next
landmark along the fl oor of the middle fossa is the
middle meningeal artery. Commonly, venous bleeding
from a periarterial venous plexus will be encountered
and should be controlled with bipolar electrocautery or
small pledgets of Surgicel. The middle meningeal artery
is isolated by circumferential dissection around the
artery. Although not routinely necessary, if extended
exposure is needed, the artery is cauterized and then
divided using microscissors. It is helpful to dissect the
artery far enough to allow a small cuff of vessel to be
retained on both the cranial and the dural sides. Unsuc-
cessful hemostasis is controlled with a hemoclip.
Figure 124-20. A, A craniotomy, 5 × 4 cm, is developed with a
medium-sized cutting burr. It is positioned two-thirds anterior and
one-third posterior to the external auditory canal. B, Photograph of
right ear showing the outline of the bone fl ap before elevation. The
temporalis muscle is transposed anteriorly and inferiorly.
A
B
Figure 124-21. The inferior aspect of the craniotomy site is
enlarged, removing sharp protruding edges. A rongeur or drill burr
is used to smooth the edges.

1308
Section 15
Temporal Bone
Dissection of the dura from posterior to anterior
avoids injury to the geniculate ganglion from retro-
grade elevation of the GSPN. The prominence in the
fl oor of the middle fossa is the arcuate eminence, which
is another key landmark. The middle fossa dura is ele-
vated medially until the edge of the petrous bony ridge
is palpated. Care is taken not to tear the superior petro-
sal sinus. The dura is dissected along the ridge of the
petrous bone. Once the middle fossa dura has been
dissected to the level of the sulcus of the superior petro-
sal vein, a retractor is repositioned and secured. Two
methods of retracting the dura and temporal lobe have
been used. The fi rst method is with a Greenberg retrac-
tor secured to a Mayfi eld head holder. The second
method is to use a House-Urban or Fisch middle fossa
retractor. The rigid blade elevating the temporal lobe
is then placed.
Important landmarks for identifying the IAC are
the arcuate eminence and the GSPN leading posteriorly
toward the geniculate ganglion (Fig. 124-23). The
course of the GSPN and arcuate eminence form an
angle of approximately 120 degrees. A line bisecting
this angle forms a 60-degree angle with both the GSPN
and the arcuate eminence. This line, parallel with the
external auditory canal, overlies the course of the IAC.
If the anatomy is uncertain, then the arcuate eminence
is bluelined to defi ne the superior semicircular canal.
Another method for identifying the IAC is by retro-
grade dissection of the GSPN. This will identify the
geniculate ganglion and, in turn, the labyrinthine
segment of the facial nerve. Meticulous and careful dis-
section is necessary in the labyrinthine segment because
the basal turn of the cochlea lies immediately anterior
and lateral to this structure.
Once the important landmarks are determined,
drilling is begun at the most medial aspect of the pre-
sumed location of the IAC. This area provides a wide
margin of error, allowing the surgeon to work in a safe
but rapid fashion. If the arcuate eminence is not obvious,
drilling posteriorly will identify the mastoid tegmen and
air cells. These can then be followed anteriorly until the
dense otic capsule bone of the superior semicircular
canal is identifi ed. An additional method for identifying
the anatomic structures is by drilling over the tegmen
tympani to identify the ossicles, horizontal portion of
the facial nerve, and geniculate ganglion. The nerve
can then be traced proximally toward the IAC. It is
necessary to expose at least 180 degrees of circumfer-
ence of the IAC, especially medially. As the dissection
Geniculate
ganglion
Arcuate
eminence
GSPN
Figure 124-23. The greater superfi cial petrosal nerve (GSPN)
exiting the facial hiatus and the arcuate eminence are noted. Dissec-
tion begins medially where the proximal IAC and the superior lip of
the porus acusticus are identifi ed.
Figure 124-24. Drilling over the IAC is continued laterally, expos-
ing the proximal fallopian canal containing the labyrinthine segment
of the facial nerve. The IAC may also be identifi ed by retrograde dis-
section of the greater superfi cial petrosal nerve to the geniculate
ganglion.
Figure 124-22. The anatomy deep to the fl oor of the middle fossa
is illustrated. The middle meningeal artery has been divided. The
greater superfi cial petrosal nerve can be traced posteriorly in the
geniculate ganglion. The facial nerve courses between the basal turn
of the cochlear and ampullated end of the superior semicircular
canal. The ossicles are demonstrated.

Chapter 124
Acoustic Neuroma 1309
of the IAC progresses from medial to lateral, the extent
of circumferential dissection of the IAC must be reduced
so that the upper basal turn of the cochlea and ampul-
lated portion of the superior semicircular canal are not
inadvertently entered (Fig. 124-24).
Following completion of all bone drilling exposing
the IAC, the IAC is entered. The dura is opened most
safely on the posterior aspect of the IAC, away from the
facial nerve, refl ecting the dura anteriorly (Fig. 124-25).
It is important to dissect the tumor away from the facial
nerve carefully and sharply. If the tumor originates
from the inferior vestibular nerve, the fascicles of the
superior vestibular nerve are sharply divided and dis-
sected. This also facilitates identifi cation and isolation
of the facial nerve. It is preferable to remove the tumor
from a medial to a lateral direction, avoiding stretch
and injury to the labyrinthine segment of the facial
nerve and the cochlear nerve. The proximal end of the
vestibular nerve is cut, and the tumor is carefully dis-
sected laterally. However, if the tumor obscures the
CPA it may need to be debulked or removed from
lateral to medial (Fig. 124-26). If hearing is to be pre-
served, care is taken not to cauterize vessels that are
running along the course of the cochlear nerve.
Despite having a fl ap of dura and periosteum over
the IAC, a watertight closure cannot be obtained. Fat is
harvested from the abdomen and is soaked in bacitra-
cin solution, and small pledgets are placed into the roof
of the IAC. Hemostasis is ensured over the middle fossa
dura. Any other tears or defects in the dura are primar-
ily closed or repaired (Fig. 124-27). Two dura tacking
sutures reapproximate the dura to the edges of the
craniotomy through burr holes made previously. The
bone fl ap is then replaced over the dura and secured
with miniplates. The temporalis muscle fl ap is carefully
reapproximated with absorbable sutures. A Jackson-
Pratt drain is placed subcutaneously attached to a closed
system and the wound is drained overnight. Skin is
closed subcutaneously with 2-0 Dexon or Vicryl sutures.
The skin closure is completed with a running 4-0 nylon
suture or staples.
Retrosigmoid Approach
The patient is placed supine on the table and general
oral endotracheal anesthesia is induced. Appropriate
venous and arterial lines are secured. Electrodes for
facial nerve and ABR testing are placed. A sound source
and ear mold are secured within the external auditory
meatus of both ears. The patient is repositioned by ele-
vating the ipsilateral shoulder, back, and hip, which are
supported with wedges of rolled blankets or pillows.
This assists with access to the suboccipital region. Gel
pads lining the operating room table avoids pressure
necrosis to the dependent hip and lateral thorax. Addi-
tional exposure is accomplished with neck fl exion and
head rotation toward the contralateral ear. A Mayfi eld
head holder with three-point skeletal fi xation is secured.
The postauricular hair is shaved and a curvilinear
Figure 124-25. The dura overlying the superior vestibular nerve is
incised along the posterior wall of the IAC. Tumor is evident through
the dural opening.
Figure 124-26. The tumor is separated sharply from the facial
nerve. In this situation, the superior vestibular nerve is divided distally
and the tumor is dissected from lateral to medial.
Figure 124-27. Fat is placed in the defect in the dura over the roof
of the internal auditory canal. The middle fossa dura will be tacked
laterally to the edges of the craniotomy defect when the retractor is
removed.

1310
Section 15
Temporal Bone
oblique skin incision is marked over the retrosigmoid
suboccipital area 2 cm medial to the mastoid process or
1 cm medial to the hairline (Fig. 124-28). The patient
is prepared and draped in the usual sterile fashion.
The incision is carried down to the suboccipital
muscles. The occipital bone is exposed by subperiosteal
muscle dissection and elevation in line with the inci-
sion. This exposes the lateral suboccipital bone medi-
ally and the mastoid process laterally. An emissary vein
is typically encountered and requires bipolar coagula-
tion, ligation, or compression with bone wax.
Using a high-speed drill, a suboccipital craniotomy
is performed, exposing the dura of the cerebellar hemi-
sphere. The limits of the exposure are the transverse
sinus superiorly and the sigmoid sinus anteriorly. Hemo-
stasis is obtained throughout the wound. Air cells that
have been opened into the mastoid are obliterated with
bone wax. Opening of the posterior fossa dura is per-
formed to maximize exposure and facilitate closure.
This depends on the anatomy of the transverse and
sigmoid sinus and the posterior fossa exposure. The
incision may be either semilunar or cruciate. The dural
incision frequently used is demonstrated in Figure
124-29.
Entrance into the posterior fossa should be inferior
to permit medial and superior elevation of the cerebel-
lar hemisphere. This technique facilitates entry into the
subarachnoid space and opening of the cerebellopon-
tine cistern, which permits further relaxation of the
cerebellum once CSF has been drained. The dura of
the posterior fossa is opened. The operating micro-
scope is brought into the fi eld. The cerebellum is pro-
tected with a rubber dam and neuropatties. The
arachnoid membrane encasing the cisterna magna
needs to be opened. This allows egress of CSF, which
reduces the pressure in the posterior fossa avoiding
potential herniation of the cerebellum out of the
wound. The lower cranial nerves IX through XI are
identifi ed. Further dissection inferiorly and medially
provides exposure to the hypoglossal nerve as demon-
strated in Video 124-8. If exposure cannot be main-
tained easily, a self-retaining Greenberg retractor is
placed into position. The cerebellar hemisphere and
fl occulus are identifi ed and retracted in a superomedial
direction. This technique further relaxes the cerebel-
lum, thereby providing exposure of the tumor (Fig.
124-30). Similarly, the root entry zone of the seventh
and eighth cranial nerves is identifi ed. The position
and integrity of the seventh nerve should be verifi ed
initially with electrical stimulation. The origin from the
brain stem can be located at the root entry zone of the
ninth cranial nerve. Once the location and integrity of
the proximal facial nerve is confi rmed, a Tefl on felt
pledget is placed over the nerve for protection and
subsequent identifi cation (see Video 124-9). If the
cochlear division of the eighth cranial nerve is identi-
fi ed, a direct nerve monitoring electrode is placed at its
root entry zone if a hearing preservation procedure is
A
B
Figure 124-28. A, The patient is positioned supine on the operat-
ing table, using an ipsilateral shoulder roll for additional rotation.
Mayfi eld pin fi xation secures the head position. The incision is
marked on the skin. B, Positioning of patient for right retrosigmoid
procedure. (A, Redrawn from Sekhar LN, Janecka IP [eds]: Surgery of
Cranial Base Tumors. New York, Raven Press, 1993.)
Sigmoid sinus
Transverse
sinus
Figure 124-29. The retrosigmoid craniotomy is limited by the
transverse sinus superiorly and the sigmoid sinus anteriorly. The cur-
vilinear and stellate incision in the dura is illustrated.

Chapter 124
Acoustic Neuroma 1311
undertaken. If the nerve is not identifi ed, the wire elec-
trode is placed in the vicinity of the lateral recess, supe-
rior to the ninth cranial nerve, which is in close
proximity to the cochlear nucleus. If the tumor is too
large to permit direct visualization of the brain stem,
the tumor must be debulked.
Excision of the tumor is done in a systematic fashion
incorporating identifi cation of the facial nerve, control
of surface and parenchymal bleeding, and tumor
removal. The dissection is carried out in a subarachnoid
plane. The location of the facial nerve should be deter-
mined before removing tumor. A stimulator is used to
map the surface of the tumor, assuring the facial nerve
is not displaced on the posterior surface of the tumor.
Once this is verifi ed, bipolar forceps are used to coagu-
late vessels located on the surface of the tumor. Sharp
dissection provides an entry point to the parenchyma
of the tumor. The capsule of the tumor is opened and
a representative portion is taken with a cup forceps for
frozen section confi rmation of the pathology. This will
also assure that a specimen has been received by the
pathology laboratory. The core of the tumor is progres-
sively removed (“gutted”) using an ultrasonic aspiration
device leaving the outer walls of the tumor intact. Much
of the bulk of the tumor resection is executed in this
manner. The contents within the suction portion of this
instrument are not readily available for histologic analy-
sis, emphasizing the need for sending a frozen section.
Decompressing the central core of the tumor thins the
capsular walls allowing for further dissection of the
tumor capsule away from normal structures such as
the brain stem, tentorium, and trigeminal nerve.
The surface of the tumor is again stimulated, looking
for the position of the facial nerve. When it is verifi ed
that the nerve is not over the area being dissected, the
capsule is again bipolared, controlling any surface
vessels or bleeding. The capsule is then resected, dimin-
ishing the size of the remaining tumor in the CPA.
Video 124-10 demonstrates this sequence and tech-
niques for excision of the tumor.
If changes in auditory brain stem evoked potentials
should occur, this part of the procedure is curtailed and
retraction loosened. If ABR changes occur despite elim-
ination of retraction, pieces of Gelfoam soaked in
papaverine may inhibit vasoconstriction.
The facial nerve typically travels over the anterosu-
perior aspect of the tumor. Tumor dissection is contin-
ued until the walls of the anterior and superior capsule
remain. Care is taken to avoid trauma to the AICA or
the posterior inferior cerebellar artery (PICA) during
the dissection. Neuropatties or rolled Tefl on felt pled-
gets are used between the tumor capsule and the sur-
rounding cerebellum, brain stem, cranial nerves, vessels,
or tentorium. It may be necessary to dissect tumor from
the fi fth cranial nerve, depending on the size and loca-
tion. The petrosal vein (Dandy’s vein) is located supe-
riorly and laterally in the posterior fossa, just inferior
to the tentorium. Excessive stretch on this vessel leads
to tear, resulting in bleeding that may be diffi cult to
control. It is prudent to identify the vein and divide it
using bipolar coagulation and microscissors. The petro-
sal vein can be safely sacrifi ced if it obstructs access to
the tumor or if bleeding occurs. Video 124-11 demon-
strates sacrifi cing the petrosal vein.
The tumor is further mobilized from the inferior
aspect of the capsule. The direction of the dissection is
between the brain stem and the capsule, keeping in
mind the location of the facial nerve. Once the dissec-
tion plane is defi ned, pledgets of Tefl on are placed to
maintain separation of tumor from the surrounding
normal structures (see Video 124-12).
Figure 124-30. Right retrosigmoid approach to an acoustic
neuroma. A Greenberg retractor blade over a cottonoid patty gently
retracts the cerebellum, exposing the tumor.
Gelfoam
Gelfoam
Figure 124-31. The tumor has been partially gutted and resected.
A right-angled hook is used to palpate the posterior bony meatus of
the porus acusticus. A medially (posteriorly) based dural fl ap is
incised and elevated. Gelfoam is placed superior and inferior to the
tumor in preparation for drilling.

1312
Section 15
Temporal Bone
In most cases, tumor is present in the IAC. The
lateral extent can be determined from the contrast-
enhanced T1-weighted MRI or CT scan. When adequate
debulking is achieved or if the tumor is of small size,
the porus of the IAC is identifi ed. This can be con-
fi rmed by palpating the posterior edge of the lip with
a right-angled hook. Bipolar coagulation is performed
over the posterior surface of the petrous bone outlining
the rectangular fl ap. A number 15 blade is used to cut
the posterior fl ap of dura, which can be based either
laterally or medially (posteriorly) along the petrous
bone to the level of the operculum (see Video 124-13).
This can usually be palpated with a Rosen dissector
(Fig. 124-31). Care is taken to preserve the endolym-
phatic sac when hearing preservation is attempted.
Gelfoam is placed superior and inferior to the tumor
to avoid excessive bone dust from settling in the opera-
tive fi eld.
Using a cutting burr, the posterior aspect of the
porus and IAC is drilled. This is continued in a semicir-
cumferential fashion, outlining the superior and infe-
rior aspects of the IAC (see Video 124-14). Dissection
is continued approximately 7 mm laterally. However,
the extent of dissection is determined by the lateral
extent of the tumor. In addition, a bone-windowed CT
scan defi nes the relationship of the lateral aspect of the
tumor to the posterior semicircular canal and vestibule.
Similarly, although bone detail is absent, MRI clearly
identifi es whether tumor extends to the fundus. Drill-
ing is continued initially with a cutting burr and then
with smaller diamond burrs to create a trough both
superior and inferior to the IAC (see Video 124-15).
The exposure necessary requires the posterior 180 to
270 degrees of the IAC to be drilled.
The edges of the remaining IAC should be pal-
pated with a narrow elevator. The dura is initially ele-
vated from the underlying bone both superiorly and
inferiorly. It is at this point that the surgeon can deter-
mine whether the amount of bone that has been
removed is suffi cient (see Video 124-16). The dura cov-
ering the posterior aspect of the IAC is then opened
inferiorly exposing the underling tumor (Fig. 124-32).
The tumor is then dissected away from the dura lining
the IAC superiorly and inferiorly (see Video 124-17).
If the tumor does not extend to the fundus, the
lateral extent of the tumor is identifi ed. A facial nerve
monitor and stimulator are crucial to the success of this
part of the procedure. Removal of tumor from the IAC
can begin once the facial nerve has been identifi ed. The
facial nerve is routinely positioned in the anterior supe-
rior quadrant of the IAC. A facial nerve stimulator-
dissector is used to initially confi rm the location of the
facial nerve (see Video 124-18). It is typically a distinct
nerve at the distal fundus. Dissection can be accom-
plished with an excavator carefully separating the tumor
from the facial nerve (see Video 124-19). The direction
of dissection at this point is from lateral to medial. In a
hearing preservation procedure, great care must be
taken to avoid traction of the cochlear nerve as it is
rolled medially. As the tumor is rolled out medially, it
may remain attached to the lateral vestibular nerve.
Sharp dissection is necessary to divide the vestibular
nerve to release the tumor from the facial nerve (see
Video 124-20). The facial nerve can be severely fl at-
tened along the anterior canal wall, especially at the
anterior lip of the porus (see Video 124-21).
It is diffi cult to directly view the extreme lateral
extent of the tumor occupying the fundus. The last 2
to 3 mm of the posterior bony wall of the IAC remains
intact in hearing preservation procedures. Curved exca-
vators are used to scoop out the remaining tumor (Fig.
124-33). Favorable dissection and excision occur when
Figure 124-32. The internal auditory canal is outlined by drilling
a trough superiorly and inferiorly. The dura of the IAC is incised
inferiorly (dotted line), away from the facial nerve.
Cranial
nerves
IX, X, XI
Facial
nerve
Cochlear
nerve
Vestibular
nerves
Trigeminal
nerve
Figure 124-33. The tumor is debulked centrally but extends into
the fundus. The fundus is attenuated in the proximal internal audi-
tory canal. A curved excavator rolls the most lateral extent of the
tumor medially.

Chapter 124
Acoustic Neuroma 1313
the lateral tumor is blunted and rolls out intact. Care
is taken when dissecting the fi bers of the vestibular
nerve laterally in order to avoid injury to the underlying
facial nerve entering the labyrinthine segment. Angled
rigid telescopes occasionally help view this area to deter-
mine whether complete resection has been achieved.
The central aspect of the tumor is removed from
the IAC. Kartush stimulating dissectors are frequently
used in this part of the procedure. The facial nerve is
identifi ed anterosuperiorly using a nerve stimulator.
The facial nerve is frequently fl attened, and meticulous
dissection is performed, removing tumor from the
nerve. Similar techniques are employed for the cochlear
nerve, which is located anterior and inferior within the
IAC. The focus of attention in the IAC dissection shifts
between the facial nerve and the cochlear nerve, if
hearing is to be preserved. Alteration in the ABR fi fth-
wave latency or amplitude warrants cessation of dissec-
tion in that area and relaxing the retractors if in place.
Similarly, it is best to cease dissection around the facial
nerve if the monitoring device indicates spontaneous
neural fi ring, suggesting irritation or injury. Attention
is turned to other areas of dissection.
Once the facial nerve is identifi ed, the bulk of
tumor in the CPA must be further debulked and
removed. The ultrasonic aspirator can quickly vaporize
the tumor. The facial nerve requires ongoing protec-
tion as the dissection proceeds. As the dissection pro-
ceeds, pledgets of Tefl on felt are positioned over the
critical structures (brain stem, cranial nerves, and sig-
nifi cant vessels) for protection. Various instruments are
available to sharply remove the tumor including scis-
sors, a round knife, and sharp facial nerve stimulator/
dissectors (see Video 124-22).
The residual tumor lies at the anterior face of the
petrous bone. Meticulous dissection is undertaken from
both a medial and lateral direction. The protective felt
pledgets are removed from the nerve proximally to
keep the nerve in view as the tumor is sharply dissected
(see Video 124-23). The most diffi cult region is at the
anterior wall of the petrous bone, central to the lip of
the anterior porus, where the facial nerve is most often
fl attened and attenuated. Tumor must be meticulously
dissected, often in a small piecemeal fashion (see Video
124-24). We accept leaving microscopic foci of tumor
on the facial nerve if total removal would signifi cantly
compromise the integrity of the nerve. Resection of any
residual tumor from the porus acusticus and CPA is
completed. The vestibular nerves are divided proxi-
mally near the brain stem. Hearing preservation is
attempted if a plane of dissection is obtained between
the vestibular nerve and the cochlear nerve. Care is
taken to avoid injury to the internal auditory artery (Fig.
124-34).
Once tumor excision is completed, hemostasis is
secured. The anesthesiologist is notifi ed that monitor-
ing is no longer necessary, permitting the use of para-
lytic agents. This facilitates a smoother emergence from
general anesthesia. The wound is then irrigated with
bacitracin solution. To prevent CSF rhinorrhea postop-
eratively, the bony edges of the IAC are checked for
opened air cells. Bone wax on a cottonoid patty is com-
pressed into open cells. If the temporal bone is well
pneumatized, a muscle plug is gently placed within the
IAC and supported with a piece of Surgicel. All neu-
ropatties and rubber dams are removed.
The edges of the posterior fossa dura are reapproxi-
mated with 4-0 Nurolon. If desiccation has occurred, it
may be necessary to supplement the dural closure with
homograft dura, pericardium, or fascia. Isolation of the
dura from the suboccipital muscles likely minimizes
long-term headaches. A wafer of Gelfoam or Duragen
is compressed and placed over the dura. A cranioplasty
over the occipital and mastoid bony defect is performed
using a titanium mesh plate. The wound is closed in
multiple layers using uninterrupted sutures of Dexon.
Skin is closed using staples or 4-0 Nurolon. A sterile
pressure dressing is applied, and the procedure is ter-
minated. The anesthetic is reversed, and depending on
its depth and concern for the patient’s neurologic
status, extubation may be done in the operating room
or subsequently in the recovery room.
PATHOLOGY
The histopathology of acoustic neuroma can vary.
There may be gross and microscopic cystic areas. There
are two predominant patterns of cellular architecture.
The fi rst is called Antoni A, which is characterized by
sheets of dense, organized, palisading nerve cells. The
other pattern is Antoni B, demonstrating a looser array
with a cystic stroma (Fig. 124-35). It is unclear whether
the morphology of these patterns has direct implication
toward the biologic activity of these tumors.
Facial
nerve
Cochlear
nerve
Facial
nerve
Figure 124-34. The tumor remains pedicled on the vestibular
nerves. The facial nerve runs medial and superior to the tumor. The
cochlear nerve is intact inferiorly. Hearing preservation requires
meticulous dissection of the tumor away from the proximal cochlear
nerve.

1314
Section 15
Temporal Bone
POSTOPERATIVE MANAGEMENT
Regardless of the approach, a sterile pressure dressing
is applied and remains in place for 2 days. Patients are
monitored in an intensive care unit in the immediate
postoperative period. Hourly vital signs and neurologic
checks are recorded while the patient is in the intensive
care unit. Blood pressure and urine output are carefully
monitored for evidence of increased intracranial pres-
sure, diabetes insipidus, or the inappropriate secretion
of antidiuretic hormone. The risk of pulmonary emboli
is minimized postoperatively with continued use of
sequential compression devices until the patient is
ambulating. Depending on the patient’s degree of alert-
ness, oral intake is advanced from clear liquids to solids
as tolerated.
Immediate-onset or delayed facial paresis may
occur. Patients with a poor Bell’s phenomenon are at
greater risk for corneal exposure. If inadequate eye
closure is noted, comprehensive care of the cornea is
provided to avoid desiccation and ulceration. Topical
artifi cial tears are instilled every 2 hours or as needed.
Ophthalmic ointment is placed in the lower conjuncti-
val fornix at night. A clear eye shield or moisture
chamber is used during the day for further
protection.
Patients are encouraged to ambulate as soon as
possible. Depending on the degree of residual vestibu-
lar function existing before surgery, patients may
experience mild to severe vertigo and dysequilibrium
following surgery. Patients with tumors that eliminated
vestibular function preoperatively will experience less
dysequilibrium. Nystagmus toward the contralateral
side is often evident during the fi rst few postoperative
days. The long-term use of vestibular suppressants, such
as meclizine, is avoided. Supportive care with antinause-
ants is provided as needed.
Patients are carefully observed for CSF leakage.
This may occur directly through the incision or via the
eustachian tube and out the nose. Clear watery rhinor-
rhea is evidence of a CSF leak. If the fl uid content is in
question, the specimen is sent for β2-transferrin analy-
sis. Management of this problem is reviewed under
Complications later in this chapter. The dressing is
removed on the second postoperative day. Bulging and
pulsation of the wound following a translabyrinthine
approach warrant replacement of a pressure dressing
for a few more days. This fi nding has been minimized
with the use of a miniplate over the transmastoid crani-
otomy and fat graft. Wound care consisting of twice-
daily cleansing with peroxide and the application of an
antibiotic ointment is provided. The abdominal wound
used for a fat graft is inspected daily. The Penrose or
Jackson-Pratt drain is removed when minimal drainage
appears on the bandage, usually between the fi rst and
the third day postoperatively. Patients are discharged 4
to 6 days following the surgery, depending on the integ-
rity of dural closure, nutrition, and ability to ambulate.
MRI scanning is routinely obtained postoperatively.
Patients manifesting a change in mental status or focal
neurologic defi cits also warrant urgent imaging to
determine whether there is evidence of a bleed, hema-
toma, or vascular compromise. Sutures or staples are
removed 10 to 14 days postoperatively. An MRI scan is
obtained 6 months following surgery. This provides a
baseline scan from which to compare subsequent
images. The next scan is obtained 1 year later or 18
months following surgery. Dural enhancement often
seen on the fi rst scan is stabilized or less intense on
subsequent scans. A third scan is obtained in 3 years. If
this is also normal, a fi nal scan is obtained in 5 years
(Table 124-1).
COMPLICATIONS
Regardless of the surgical approach, patients undergo-
ing excision of AN may experience complications.
These may occur both intraoperatively or postopera-
tively. Problems that may occur during the surgical pro-
cedure are similar to those of any other intracranial
A
B
Figure 124-35. Histologic patterns of cellular architecture in acoustic neuroma. A, Antoni A. B, Antoni B.

Chapter 124
Acoustic Neuroma 1315
operation. The skin fl aps and dura should be handled
in an atraumatic fashion. Undue retraction and desic-
cation must be avoided. In particular, during the middle
fossa approach, tears in the dura may be created during
elevation of the temporal lobe. Once recognized, the
tear should be repaired primarily at that time.
Bleeding may be arterial or venous. The most
common sources of venous bleeding are from the
sigmoid or transverse sinuses during translabyrinthine
or retrosigmoid approaches. A superior petrosal sinus
may also be lacerated during the middle fossa or trans-
labyrinthine approach. Small defects may be closed
with bipolar forceps. Larger defects should be covered
with Surgicel and compression applied. The superior
petrosal sinus may need to be ligated or clipped and
divided in order to secure hemostasis. Arterial bleeding
in the posterior fossa is a serious complication. This
must be controlled. Bleeding from small vessels may be
stopped with bipolar coagulation. Serious neurologic
sequelae may result from injury to the AICA or PICA.
These vessels are carefully dissected away from the
tumor and, if necessary, isolated with neuropatties.
Other methods that may be used to control bleeding
include
topical
microfi bular
collagen
hemostat
(Avitene), bipolar coagulation, and hemoclips.
Compression or retraction on the brain stem may
be manifested by changes in the ABRs and somatosen-
sory potentials. More signifi cant consequences result in
hemodynamic instability manifested by hypertension or
hypotension with bradycardia.
Large tumors approached through the posterior
fossa may be in proximity to cranial nerves V, IX, X,
and XI. Meticulous surgical technique must be exer-
cised in order to avoid trauma to these nerves. Although
sequelae may not be evident intraoperatively, a vocal
cord paresis at the time of extubation may compromise
laryngeal function and protection.
Another rare but serious intraoperative complica-
tion is air embolus. This occurs secondary to the opening
of a large venous sinus, permitting air to be sucked into
the vessel. A change in the auditory output of the pre-
cordial Doppler stethoscope is one of the earlier indica-
tors of this event. The patient’s hemodynamic status is
subsequently compromised. Management consists of
occluding the open vessel and turning the patient to
the left side, head down. If a Swan-Ganz catheter is in
place, air can be aspirated from the right atrium. A
large piece of Surgicel is packed into the sinus, and
compression with a neuropatty is applied.
POSTOPERATIVE COMPLICATIONS
Facial Paresis/Paralysis
Facial paralysis is not actually a complication of the
procedure but rather an accepted risk. In the immedi-
ate postoperative period, this is more likely to occur
with a middle fossa approach but is also dependent on
the size and adherence of the tumor. If a mild paresis
exists (less than House-Brackmann grade III), then
comprehensive eye care may not be needed. However,
with incomplete eye closure, poor Bell’s phenomenon,
and slow blinking, artifi cial tears, ophthalmic ointment,
and a clear moisture chamber are provided. An ana-
tomically intact facial nerve with low stimulation thresh-
olds at the conclusion of the procedure implies a good
prognosis for facial recovery. However, if large stimula-
tion intensities were necessary to evoke a response, then
return of function may not be evident for many months.
In this event, we suggest that a gold weight be inserted.
Ectropion may develop in older patients with increased
skin laxity. Tightening of the lower lid with a lateral
tarsal strip may be warranted. Rarely, the facial nerve
must be divided in order to accomplish complete tumor
removal. In this case, immediate end-to-end anastomo-
sis or cable grafting provides the best functional
outcome. Approximately 46% of patients who undergo
cable grafting will recover to a House-Brackmann
grade III, and an additional 25% will recover to grade
IV.37
Hearing Loss
Similar to facial nerve injury, hearing loss is another risk
that frequently occurs following tumor resection,
despite attempts at hearing preservation. Despite having
good ABR waveforms at the conclusion of the proce-
dure, complete hearing loss may still occur. The risk of
hearing loss increases with tumor size, particularly for
those tumors with greater than 15 mm in the CPA.38
Worse preoperative hearing, increasing wave V latency,
and inferior vestibular nerve origin have also been
reported to increase the risk of hearing loss.39 Postop-
erative hearing loss is more common in patients with
signifi cant adhesion between the tumor and cochlear
nerve.40 Additionally, patients who initially have pre-
served hearing following the retrosigmoid approach
may go on to lose hearing in the operated ear at a rate
exceeding that in the contralateral ear.41 This result is
contradicted by a report from the House Ear Institute,
which found that surgery did not affect the postopera-
tive progression of hearing loss in the operated ear.24
Cerebrospinal Fluid Leak
When CSF leak occurs, it is usually evident through the
incision or manifested as clear, watery rhinorrhea. It is
unusual to observe CSF otorrhea in that the tympanic
membrane and external auditory canal should not have
been violated. A ballotable collection of CSF under-
neath the skin fl aps is treated with a pressure dressing.
The head of the bed should remain elevated. If clear
fl uid leaks through the incision, then the skin closure
Table 124-1
POSTOPERATIVE MAGNETIC
RESONANCE IMAGING SCHEDULE
Time Following Surgery
Interval
3 mo
3 mo
15 mo
1 yr
51 mo
3 yr
111 mo
5 yr

1316
Section 15
Temporal Bone
is augmented with single interrupted sutures. Liquid
collodion is an effective skin sealant and can be painted
over the wound if a slow leak persists. If this is not ade-
quate for controlling the leak, then a lumbar drain is
placed. The catheter is connected to a Buretrol device,
which provides accurate monitoring of CSF drainage.
By adjusting the height of the Buretrol device, a drain-
age rate of 6 to 10 mL/hr is maintained. The lumbar
drain remains in place for 3 to 4 days. If the CSF leak
or rhinorrhea persists but is subsiding, an additional 2
days may be needed. However, if an active leak remains
despite 5 days of lumbar drainage, then reexploring the
wound is necessary. Careful obliteration of any exposed
air cells with bone wax, muscle, or fat will minimize the
risk of CSF leak; some surgeons employ endoscopes to
inspect the temporal bone for unseen exposed air
cells.42 For patients in whom petrous apex air cells open
directly into the eustachian tube, obliteration of the
entire length of the tube can be accomplished using a
combined transaural/transnasal approach.43
Meningitis
Patients developing new-onset headache with fever,
vomiting, and a change in mental status should be
immediately evaluated for meningitis. Bacterial menin-
gitis occurs in approximately 2.5% of patients, although
aseptic meningitis may be seen in up to 20% of patients.13
A spinal tap identifi es increased white blood cell counts
with a shift to the left, elevated protein, and reduced
glucose levels. A Gram stain may identify an organism
that will direct one’s choice for antibiotic coverage.
Vancomycin and an aminoglycoside or a third-genera-
tion cephalosporin, such as ceftazidime or ceftriaxone,
are used. If the Gram stain is negative and the culture
shows no growth, antibiotics may be discontinued, and
a presumed diagnosis of aseptic meningitis given.
However, if the culture is positive, antibiotics are con-
tinued for 7 to 10 days.
Intracranial Bleeding
Delayed postoperative bleeding usually occurs during
the fi rst 3 to 5 days. This may be intracerebral or cere-
bellar bleeding or a subdural collection or hematoma.
Patients may manifest symptoms of altered mental
status, lethargy, somnolence, limb weakness, or aphasia.
An emergency CT scan is obtained to identify the nature
of intracranial pathology. A noncontrast study is ade-
quate to demonstrate a bleed or hematoma. In addi-
tion, hydrocephalus may be evident on the scan.
Management is dictated based on the fi ndings of the
scan.
Seizures
Seizures following translabyrinthine or retrosigmoid
resection of ANs are rare. These are more likely to
occur with a supratentorial injury following middle
fossa retraction. Problems with receptive or expressive
aphasia may occur from excessive retraction and injury
to the left temporal lobe. The surgeon must be aware
of the degree of temporal lobe retraction exerted
through a middle fossa approach. Emergent treatment
consists of intravenous diazepam and a loading dose of
phenytoin. Oral phenytoin is continued postoperatively
for 4 to 6 months.
Trigeminal Nerve Dysfunction
Large ANs can extend superiorly through the tento-
rium and anteriorly to the petrous apex. Injury to the
trigeminal nerve more typically affects V1 and V2
(sensory divisions) as opposed to V3 (the motor divi-
sion). Facial hypesthesia and analgesia may result. This
defi cit, in conjunction with a facial nerve paralysis, is
a potentially devastating combination injury. The
hypesthesia of the cornea along with lagophthalmos
intensifi es the likelihood of corneal injury. Despite
comprehensive prophylactic eye care, it may be neces-
sary to perform medial and lateral tarsorrhaphies to
minimize the dystrophic and erosive changes that may
occur in the cornea. Similarly, the lateral ala of the nose
is subject to ischemic necrosis. Patients can manually
traumatize the involved insensate nares, initiating
destruction of the alar rim.
Lower Cranial Nerve Injury
Tumors that extend inferiorly are in close approxima-
tion to cranial nerves IX, X, and XI. The multiple fi ne
fascicles of these cranial nerves may be injured during
dissection. Despite anatomic integrity of these cranial
nerves, pharyngeal and laryngeal dysfunction may
result. Patients may develop dysphagia, dysphasia, aspi-
ration, and breathy voice. Nasogastric tube feeding may
be necessary if aspiration persists. Temporary resolu-
tion may be augmented with Gelfoam injection of the
involved vocal cord. If the surgeon believes that sub-
stantial intraoperative injury has occurred, then a type
I thyroplasty, which is reversible, can provide longer-
lasting relief (see Chapter 38).
Headache
Postoperative pain in the incision is common with any
procedure. Patients undergoing a middle fossa approach
may experience pain on mastication owing to tempo-
rary temporalis muscle dysfunction. Similarly, pain
in the posterior aspect of the neck frequently
occurs following a suboccipital approach. Symptoms
are usually relieved with application of heat, parenteral
or oral narcotics, and eventually, nonsteroidal anti-
infl ammatory medication. Regardless of the approach,
headache and stiffness of the neck may develop 5 to 7
days postoperatively. Lumbar puncture and fl uid analy-
sis are warranted to rule out bacterial or aseptic men-
ingitis. Xanthochromic CSF with few white cells,
secondary to red blood cell breakdown, is the likely
cause of meningeal irritation. Steroids are usually pre-
scribed if routine analgesics are ineffective. Long-term
postoperative headache is associated with the retrosig-
moid approach. Symptoms may present for upward of
1 year. Treatment consists of nonsteroidal anti-infl am-
matory medications, nerve block, and rarely wound
revision or rhizotomy.

Chapter 124
Acoustic Neuroma 1317
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9. Wootten CT, Kaylie DM, Warren FM, et al: Management of brain
herniation and cerebrospinal fl uid leak in revision chronic ear
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fi rst 500 cases of acoustic neuroma surgery. Otolaryngol Head
Neck Surg 124:645-651, 2001.
15. Harsha WJ, Backous DD: Counseling patients on surgical options
for treating acoustic neuroma. Otolaryngol Clin North Am
38:643-652, 2005.
16. Martin HC, Sethi J, Lang D, et al: Patient-assessed outcomes after
excision of acoustic neuroma: Postoperative symptoms and
quality of life. J Neurosurg 94:211-216, 2001.
17. Chung WY, Liu KD, Shiau CY, et al: Gamma knife surgery for
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18. Lunsford LD, Niranjan A, Flickinger JC, et al: Radiosurgery of
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23. Ottaviani F, Neglia CB, Ventrella L, et al: Hearing loss and
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Head Neck Surg 128:1308-1312, 2002.
24. Friedman RA: The surgical management of Bell’s palsy: A review.
Am J Otol 21:139-144, 2000.
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29. Myrseth E, Moller P, Pedersen PH, et al: Vestibular schwannomas:
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PEARLS
• Given the current accepted alternatives of
management, patients must receive a comprehensive
discussion addressing surgical removal, stereotactic
radiation treatment, and monitoring the tumor for
further growth over time.
• Consideration should be given to observing the
tumor with serial MRI scans in people older than
age 70 years with small tumors.
• CT imaging can be helpful to identify a high jugular
bulb providing useful information in anticipation of
a translabyrinthine approach.
• Every effort should be given to complete all bone
drilling and dissection before the dura is opened.
• Temporary placement of Tefl on pledgets, which are
less adherent than neuropatties, protect critical
structures that are isolated as the dissection
proceeds.
PITFALLS
• Inadequate exposure will signifi cantly impede safe
and complete access to the tumor for total removal.
• Proceeding with tumor dissection in the presence of
the facial nerve monitor device indicating neurotonic
discharge (irritation) may result in preventable
irreversible injury. Attention should be directed to
another area.
• Excessive manipulation and retraction of the
temporal lobe during middle fossa surgery may
result in brain injury, seizures, and dysphasia,
especially on the left side.
• The use of the bipolar electrocautery adjacent to the
facial nerve may cause permanent injury.
• Aggressive retraction and dissection of the tumor
from the fundus can avulse the delicate cochlear and
facial nerve fi bers, resulting in hearing loss and facial
weakness.
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1318
Section 15
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in acoustic neuroma surgery: Importance of adhesion between
the cochlear nerve and the tumor. J Neurosurg 97:337-340,
2002.
41. Chee GH, Nedzelski JM, Rowed D: Acoustic neuroma surgery:
The results of long-term hearing preservation. Otol Neurotol
24:672-676, 2003.
42. Sanna M, Taibah A, Russo A, et al: Perioperative complications
in acoustic neuroma (vestibular schwannoma) surgery. Otol Neu-
rotol 25:379-386, 2004.
43. Selesnick SH, Liu JC, Jen A, et al: Management options for cere-
brospinal fl uid leak after vestibular schwannoma surgery and
introduction of an innovative treatment. Otol Neurotol 25:580-
586, 2004.

Chapter 125
Glomus Tumors
Barry E. Hirsch
Paraganglioma or glomus tumor is a tumor of the neu-
roendocrine system derived from neural crest cells and
chemoreceptor cells. The tumor was termed a chemodec-
toma by Mulligan in 1950.1 The ability to pick up chro-
mium salts led to the designation of the histologic
staining characteristic as chromaffi n or nonchromaffi n
positive. The largest concentration of paraganglionic
cells is with the adrenal medulla. The other predomi-
nant locations of paraganglionic tissue are found in the
branchiomeric chemoreceptor system of the aortic
arch, carotid bifurcation, and temporal bone. Guild
described the location of other glomus bodies within
the temporal bone, identifying an average of 2.82 foci,
half of which were in the jugular bulb and one fourth
on the promontory of the cochlea.2 The term com-
monly accepted to describe neoplastic tumors of the
paraganglionic receptors is glomus tumor. Glomus tumors
of the temporal bone are neoplasms arising from nor-
mally occurring paraganglionic bodies or formations
that are located on the dome of the jugular bulb and
along the course of Jacobson’s nerve (ninth cranial
nerve) onto the cochlear promontory. On rare occa-
sions, these tumors take origin from the facial nerve.3
The tumors of the temporal bone may be grouped into
two categories: those arising from the middle ear (prom-
ontory) and those arising from the jugular bulb. These
are termed glomus tympanicum tumors and glomus jugulare
tumors. As tumor expansion occurs, it may be diffi cult
to distinguish the precise origin of the lesion. Thus
larger tumors involving both the middle ear and the
jugular bulb are termed jugulotympanic glomus tumors.
Although most tumors are sporadic, familial glomus
tumors may occur in 20% of patients with glomus
tumors. Many of the tumors are multicentric and bilat-
eral at the time of presentation, which typically occur
at an earlier age in successive generations in families
harboring genetic mutations. Investigation into the
hereditary patterns of familial paraganglioma has
resulted in the identifi cation of four loci termed PGL1,
PGL2, PGL3, and PGL4. The fi rst two loci were found
on chromosome 11 at bands 11q23.1 and 11q13.1. Both
regions are associated with an autosomal dominant
pattern and maternal imprinting. Inheriting the gene
from the mother portends a lower incidence of trans-
mission compared with passing the gene onto offspring
from the father. Mutation in genes responsible for pro-
duction of proteins that are critical components of a
cellular oxygen-sensing system may permit proliferation
of chief cells in paraganglionic cells. The loci for PGL3
and PGL4 are on chromosome 1. Heth wrote an excel-
lent review of the basic science of glomus jugulare
tumors.4
Glomus tumors are slow-growing, invasive, highly
vascular neoplasms that are in critical proximity to the
lower cranial nerves. Although locally destructive,
glomus tumors are rarely considered to be malignant.
It may be diffi cult to determine whether a glomus tumor
is malignant. Some of the histologic features suggestive
of malignancy include increase in mitotic activity,
necrosis in the center of the cell nests, and vascular
invasion. The hallmark of aggressive malignant behav-
ior is the presence of tumor in the regional lymph
nodes or distant organs confi rmed with histologic
examination.
Metastatic tumors have been found in the verte-
brae, ribs, spleen, and lungs. In a series of 175 temporal
bone glomus tumors, 5.1% were classifi ed as malignant.
Conventional external beam radiation therapy (XRT)
is not advocated as the primary modality of treatment
because viable tumor cells can remain following radia-
tion treatment. Five-year survival for malignant glomus
tumors of the temporal bone is 71.2%.5
1319

1320
Section 15
Temporal Bone
Two classifi cation systems have been offered for
nomenclature and staging. Fisch described and modi-
fi ed a classifi cation system based on the size and extent
of the tumor (Table 125-1).6,7 There are four categories
(A, B, C, and D) of staging tumors, from limited to the
middle ear cleft (type A) to large lesions demonstrating
intracranial extension (type D). The Glasscock and
Jackson classifi cation system divides the tumors into
tympanic or jugulare tumors (Table 125-2).8 Each group
is further subdivided into four types of progressively
larger tumors, from small lesions limited to the site of
origin to more extensive tumors involving regional
areas of the temporal bone. Although the latter system
attempts to defi ne the anatomic origin of the tumor,
both classifi cations address the pertinent issues of tumor
size, petrous apex or carotid artery involvement, and
intracranial extension. This provides critical informa-
tion necessary to design an operative approach and
plan.
PATIENT SELECTION
Patients with glomus tumors frequently report a history
of symptoms of pulsatile tinnitus, hearing loss, aural
fullness, and not uncommonly, cranial nerve dysfunc-
tion such as facial paresis, dysphasia, or hoarseness.
Patients should be questioned regarding symptoms
including tachycardia, palpitations, headaches, pallor,
excessive perspiration, nausea, and problems of control
of blood pressure, all of which are related to excess
catecholamine secretion by the tumor. A complete oto-
logic and head and neck examination is required. The
tympanic membrane and middle ear space are inspected
for tumor. When tumor is in the middle ear, a red mass
is noted behind the tympanic membrane, and pulsation
can be observed under high magnifi cation (Fig. 125-1).
The patient should be evaluated for evidence of weak-
ness or dysfunction of cranial nerves VII, VIII, IX, X,
XI, and XII. Both sides of the neck are palpated
for mass lesions in the jugulodigastric and carotid
bifurcation areas. Audiometry should be performed to
determine the presence of a conductive, mixed, or sen-
sorineural hearing loss.
Once a glomus tumor has been presumptively diag-
nosed by the history and physical examination, the diag-
nosis and evaluation of the type and extent of the tumor
are required. Along with a history of pulsatile tinnitus
or the presence of a vascular mass in the middle ear,
radiologic imaging can demonstrate characteristic
features strongly suggestive of glomus tumor. On
computed tomography (CT) scanning, these features
include the location of the lesion, bone erosion around
the jugular bulb and carotid artery, and enhancement
following administration of contrast. Large glomus tym-
panicum tumors can extend inferiorly into the hypo-
tympanum and erode trabeculated bone toward the
jugular bulb. Similarly, glomus jugulare tumors expand
superiorly toward the hypotympanum and middle ear.
It can occasionally be diffi cult to defi nitively character-
ize the site of origin. The differential diagnosis of an
Table 125-1
GLOMUS TUMOR CLASSIFICATION:
FISCH
Type
Description
A
Tumor limited to middle ear cleft (promontory)
B
Tumor confi ned to middle ear, hypotympanum,
and mastoid
C1
Tumor eroding jugular bulb and carotid
foramen; not invading carotid artery
C2
Tumor involving infralabyrinthine and apical
temporal bone; erosion of vertical carotid artery
C3
Tumor involving infralabyrinthine and apical
temporal bone; erosion of horizontal carotid
artery
C4
Tumor involving infralabyrinthine and apical
temporal bone; tumor grows to foramen
lacerum and cavernous sinus
D1
Intracranial tumor <2 cm
D2
Intracranial tumor >2 cm; e, extradural;
i, intradural
Di3
Unresectable intracranial extension
Data from Fisch U: Infratemporal fossa approach for glomus
tumors of the temporal bone. Ann Otol Rhinol Laryngol 91:474-
479, 1982; and Fisch U, Mattox D: Classifi cation of glomus tem-
poral tumors. In Fisch U, Mattox D (eds): Microsurgery of the
Skull Base. Stuttgart and New York, Georg Thieme, 1988, pp
149-153.
Table 125-2
GLOMUS TUMOR CLASSIFICATION:
GLASSCOCK-JACKSON
Type
Description
Glomus Tympanicum
I
Small mass limited to promontory
II
Tumor completely fi lling middle ear space
III
Tumor fi lling middle ear and extending into
mastoid
IV
Tumor fi lling middle ear, extending into
mastoid or through tympanic membrane to fi ll
external auditory canal; may extend anterior to
carotid
Glomus Jugulare
I
Small tumor involving jugular bulb, middle ear,
and mastoid
II
Tumor extending under internal auditory canal;
may have intracranial extension
III
Tumor extending into petrous apex; may have
intracranial extension
IV
Tumor extending beyond petrous apex into
clivus or infratemporal fossa; may have
intracranial extension
Data from Jackson CG, Glasscock ME, Harris PF: Glomus
tumors: Diagnosis, classifi cation, and management of large lesions.
Arch Otolaryngol 108:401-410, 1982.

Chapter 125
Glomus Tumors 1321
expanding, bone-eroding enhancing tumor in the
jugular fossa region include neurofi broma, schwan-
noma, lymphoma, meningioma, and metastatic disease.
Biopsy is to be avoided owing to the vascular nature of
the tumor. Only after the extent of tumor is defi ned
(middle ear, jugular bulb, carotid artery, clivus, intra-
cranial, or intradural extension) can decisions regard-
ing optimal management be made. Glomus tumors are
rarely malignant. However, because of their propensity
for progressive and invasive growth and involvement of
major vessels and lower cranial nerves, treatment is rou-
tinely required. It is only the occasional asymptomatic
small tumor in an older person that can be followed up
radiographically for evidence of growth.
Paragangliomas can also occur with other endo-
crine tumors associated with familial syndromes. Such
tumors include carcinoma of the thyroid gland, medul-
lary carcinoma of the thyroid, and those found with
multiple endocrine neoplasia (MEN) type I, consisting
of pituitary adenoma, parathyroid adenoma, and pan-
creatic islet cell adenoma.
Treatment options for glomus tumors of the tem-
poral bone include observation with serial scanning to
monitor for growth, microsurgical excision, and radia-
tion therapy. Complete surgical resection minimizes
the chance for recurrence but may entail signifi cant
morbidity. Radiation therapy does not eliminate the
tumor but is intended to halt tumor progression. Pro-
ponents for surgery suggest radiation is indicated for
palliation, following incomplete tumor excision or for
patients who are medically infi rm or elderly. However,
there is strong evidence indicating that radiotherapy
could also be considered the defi nitive treatment strat-
egy for skull base glomus tumors. Glomus jugulare
tumors have traditionally been treated by fractionated
XRT. Hinerman and colleagues summarized their
experience of 53 patients with 55 temporal bone tumors
(46 were glomus jugulare and 9 were glomus tympani-
cum tumors). Patients received megavoltage radiation
over a continuous course. With almost half of the
patients followed up for 15 years, local tumor control
was achieved in 93% of the previously untreated tumors
and 92% of those previously treated.9 The long-term
results using stereotactic radiosurgery remain to be
seen, but some early experience suggests there may be
insuffi cient control of tumor if the planning treatment
volume is kept too tight.10 In a series of 42 patients
treated with gamma knife surgery, 19 received radiation
as their primary therapy and 23 patients for recurrent
glomus jugulare tumor. The mean follow-up was 44
months (range 6 to 149 months). Although this is con-
sidered a relatively short period of time, tumor control
was accomplished, in that 31% decreased in size, 67%
were unchanged, and the only one that grew was in a
patient who failed previous radiation therapy.11
We propose that healthy, young (younger than 65
years of age) patients should consider surgical resec-
tion. Large glomus tumors usually encroach on the
ninth and tenth cranial nerves, putting them at risk
during resection. Asymptomatic patients must be
assessed as to whether they could tolerate the conse-
quences of pharyngeal and laryngeal dysfunction.
If sacrifi ce of the ninth and tenth cranial nerves is
anticipated, patients with limited pulmonary reserve
would be unlikely surgical candidates. In contrast,
patients with a history of dysphagia or hoarseness who
demonstrate vocal cord dysfunction can better tolerate
sacrifi ce of the ninth and tenth cranial nerves. These
people have typically developed compensatory mecha-
nisms to minimize problems with swallowing and
aspiration.
Large glomus jugulare tumors in relatively asymp-
tomatic patients pose a signifi cant dilemma in their
optimal management. Specifi cally, patients having large
tumors where surgical resection will likely incur new
postoperative lower cranial nerve defi cits often results
in signifi cant morbidity. The possible need for a trache-
otomy, nasogastric tube placement, or percutaneous
gastrostomy feeding tube, along with complications of
aspiration, pneumonia, inanition, and weakness of
the shoulder and tongue, must be considered by the
patient and their family as well as the physicians and
surgeons involved with the patient’s care. Although
radiation treatment in a relatively young person is not
without short- or long-term risk, the aforementioned
complications may have immense impact on the
patient’s future quality of life. Long-term results follow-
ing total resection of class C and D tumors revealed that
full rehabilitation may take 1 to 2 years. In a series by
Briner and colleagues, 97% of patients fi nally resumed
improved function, deeming their postoperative dys-
phasia tolerable and allowing a more normal social
life.12
The optimal management program for patients 65
years of age and older should be individualized. Older
patients with compromised pulmonary function or
other chronic unstable medical conditions are not good
surgical candidates. Radiation therapy has been shown
to be an effective method for tumor palliation and thus
is a reasonable alternative treatment.
Figure 125-1. Left tympanic membrane with a pulsatile circum-
scribed vascular tumor fi lling the inferior portion of the middle
ear.

1322
Section 15
Temporal Bone
PREOPERATIVE PLANNING
The granules contained within the chief cells of these
tumors contain the precursors for catecholamine syn-
thesis. Patients with intermittent or labile hypertension
or those with signs and symptoms of a hypermetabolic
state should be evaluated for a secreting tumor. Unlike
the adrenal gland, glomus tumors lack the enzyme
phenylethanolanine N-methyltransferase, which con-
verts norepinephrine to epinephrine. This is why
norepinephrine is the mostly commonly secreted che-
motransmitter. Urine collected for 24 hours is screened
for metanephrine, vanillylmandelic acid, epinephrine,
and norepinephrine. Because the incidence of secret-
ing glomus tumors is low (1% to 3%), elevated levels of
these vasoactive peptides should also prompt investiga-
tion for pheochromocytoma. A CT scan of the abdomen
is used to rule out a retroperitoneal adrenal or extra-
adrenal tumor. Magnetic resonance imaging (MRI) can
also be used, but it may be plagued by movement arti-
fact. Further diagnostic evaluation is necessary when
elevated levels of serum or urine catecholamine precur-
sors and metabolites are identifi ed. The workup for
potential metastatic disease may also demand other
radiographic techniques to locate sites of distant spread.
Imaging with 123I MIBG (metaiodobenzylguanidine)
scintigraphy is picked up by active endocrine tissue
such as paraganglioma, pheochromocytoma, and neu-
roblastoma. Anesthesia consultation for coordinating
pharmacologic blockade is warranted for patients with
elevated catecholamine levels. Both α- and β-adrenergic
blockers such as phentolamine and propranolol, respec-
tively, may be necessary.
Patients considered to be surgical candidates must
have the extent of tumor involvement delineated. This
entails imaging techniques that defi ne the relationship
of the tumor to critical anatomic structures. Currently,
the diagnosis is usually made with contrast-enhanced
CT or MRI scans. Bone-windowed, thin-cut (1.5-mm)
CT images defi ne the relationship of the tumor to the
carotid artery, sigmoid sinus, jugular bulb, pars nervosa,
middle ear, facial nerve, otic capsule, and posterior
fossa (Fig. 125-2). MRI enhances the evaluation of
glomus tumors of the temporal bone and skull base.
Contrast-enhanced MRI identifi es the tumor often with
a speculated pattern described as “salt and pepper”
vascularity with greater sensitivity in demonstrating
tumors of the skull base. In addition to delineating the
tumor, MRI demonstrates the relationship of the sur-
rounding soft tissues and major vessels.
The soft tissue resolution and information obtained
from MRI scans help differentiate tumor from sur-
rounding soft tissue, brain parenchyma, and mucosal
changes within the temporal bone (Fig. 125-3). The
relatively new technique of magnetic resonance angiog-
raphy (MRA) also shows the relationship of the tumor
to carotid artery, sigmoid sinus, and jugular bulb (Fig.
125-4). MRA shows the proximity of the tumor or dis-
placement of the major vessels along with the predomi-
nant blood supply. MR venography highlights the
anatomy of the transverse, sigmoid, and petrosal sinuses;
Figure 125-2. Bone-windowed computed tomography (CT) scan
demonstrating the left middle ear and a hypotympanic mass (white
arrow) infi ltrating and eroding bone between the carotid artery (black
arrowhead), the jugular vein (large black arrow), and the medial aspect
of the facial nerve (small black arrow). The pars nervosa is not affected
(white arrowhead).
T
Figure 125-3. T1-weighted magnetic resonance imaging (MRI)
scan with contrast showing a glomus tumor (T) occupying the right
jugular fossa extending to the skull base. Note the internal carotid
arteries (arrows).
the jugular bulb; and the descending jugular vein. It is
most helpful if the patency of these venous structures
can be verifi ed or if thrombosis is present. Although
occasionally fraught with diffi culty in interpretation,
information regarding fl ow characteristics in these

Chapter 125
Glomus Tumors 1323
vessels may be helpful in determining the degree of
tumor involvement and obstruction to fl ow.
Until the techniques and interpretation of MRA
become consistently reliable and comprehensively
informative, four-vessel cerebral angiography remains
necessary. Angiography should be obtained when CT
imaging identifi es a large tumor or when carotid artery
involvement is suspected or identifi ed. The data gained
from this study provide critical information needed to
institute a management plan. The location and extent
of tumor are identifi ed by the vascular blush. The four-
vessel study also identifi es other paragangliomas that
may be present in the head and neck area (Fig. 125-5).
Patients with multiple paragangliomas have a higher
incidence of similar tumors being identifi ed in other
family members.
An effective method of screening these individuals
is with a contrast-enhanced CT scan of the temporal
bone (skull base) and neck, down to the level of the
carotid bifurcation. It is imperative to know whether
multiple paragangliomas or carotid body tumors are
present on the ipsilateral or contralateral side in order
to avoid the potential devastating complications related
to bilateral lower cranial nerve compromise. Arteriog-
raphy demonstrates the blood supply to the lesion. The
major blood supply of glomus jugulare tumors is from
the ascending pharyngeal artery. When a signifi cant
feeding vessel is identifi ed, selective angiography and
embolization using polyvinyl alcohol or Gelfoam is per-
formed. Large lesions (glomus jugulare) are routinely
embolized 1 to 2 days before surgical resection (Fig.
125-6).
Figure 125-4. Magnetic resonance angiography (MRA) scan
showing a tumor (white arrow) in the right skull base compressing the
vertical portion of the carotid artery (black arrow). The carotid artery
and jugular vein are superimposed (black arrowhead).
Figure 125-5. Left common carotid arteriogram of a patient with
contralateral glomus jugulare demonstrating carotid body (large
arrow) and glomus vagale (small arrow) tumors. The internal carotid
artery is anteromedially displaced (arrowhead).
A
B
Figure 125-6. A, Preemboliza-
tion arteriogram revealing right
glomus jugulare tumor with char-
acteristic blush (arrowhead).
B,
Postembolization study confi rms
effective
occlusion
of
major
feeding vessels. Tumor blush is sig-
nifi cantly diminished.

1324
Section 15
Temporal Bone
Based on CT scan fi ndings demonstrating extensive
involvement, intraoperative carotid artery injury, repair,
or resection may be anticipated. In this situation, at the
time of the arteriogram, a balloon catheter is also used
to functionally test the competency of the contralateral
cerebral blood supply and circle of Willis. Balloon test
occlusion (BTO) of the ipsilateral internal carotid
artery (ICA) helps determine whether the patient can
tolerate carotid artery occlusion or sacrifi ce. Xenon
blood fl ow studies during BTO provide an objective
and quantitative measure of cerebral blood fl ow. This
information helps the surgical team determine whether
carotid artery sacrifi ce will be tolerated. Failure to suc-
cessfully tolerate BTO or if inadequate blood fl ow is
demonstrated indicates that carotid artery repair or
bypass will be necessary if injury or sacrifi ce occurs.
Other members of the skull base team (neurosurgeons,
vascular surgeons) are alerted if intracranial tumor is
present or vascular repair is likely.
Finally, the venous phase of the arteriogram also
reveals whether the sigmoid sinus is patent or occluded,
demonstrates other venous outfl ow pathways, and indi-
cates the status of the contralateral sigmoid sinus and
jugular vein (Fig. 125-7). If no venous obstruction is
shown, then the venous drainage of the dominant side
is also demonstrated. The relationship of the ipsilateral
vein of Labbé to the transverse sinus should be defi ned.
Although tumor does not usually extend this far proxi-
mal in the venous drainage system, this information
should be confi rmed.
Large glomus jugulare tumors are more likely to
encroach on the ICA and the lower cranial nerves. The
option of subtotal resection of a large tumor could be
considered if cranial nerve function is normal preop-
eratively and compromise or sacrifi ce is anticipated to
achieve complete resection. Determination is made
based on imaging, assessing whether the pars nervosa
(medial aspect of the jugular bulb) is involved. Intradu-
ral extension of tumor in this area would defi ne the
need for resection of the entire jugular bulb and pars
nervosa. This approach is planned preoperatively based
on the patient’s preference for maintaining normal
physiologic function of phonation, respiration, and
swallowing. Similar strategy for planned subtotal resec-
tion can be given if the carotid artery is involved.
Perioperative systemic antibiotics are not given for
glomus tumors isolated to the middle ear or mastoid
space. Prophylaxis is provided if cerebrospinal fl uid
(CSF) exposure is anticipated. Patients with large lesions
(glomus jugulare) should have blood held for type and
screen. Autologous donation for potential transfusion
can be planned in advance.
The importance of a comprehensive and under-
standable informed consent cannot be overemphasized.
It is most important to discuss with the patient and
family the location of the tumor and its relationship to
the surrounding vascular, dural, and neural structures.
The treatment options of observation, surgical removal,
or radiation therapy are reviewed. The risks, benefi ts,
and outcomes are explained. The discussion must be
delivered to assure that the patient understands the
signifi cance of potential loss of lower cranial nerve
function. The potential need for additional surgical
procedures to manage complications following tumor
removal should be discussed. These include eye protec-
tion with a gold weight and possible lower lid tighten-
ing, tracheotomy, vocal cord medialization procedures,
gastrostomy tube, or CSF lumbar drainage. Delivery of
a comprehensive informed consent should be docu-
mented in the patient’s medical record.
STEREOTACTIC RADIOSURGERY
Fractionated XRT has been the conventional method
for radiation treatment. Newer techniques using a
frame-based linear accelerator, gamma radiation from
cobalt delivered through the gamma knife, or photon
beam from a robot-mounted mini-linear accelerator
such as the CyberKnife are available for single or mul-
tiple focused treatments (fractions) providing submilli-
meter accuracy in treatment delivery. This author
prefers the CyberKnife system for various reasons. It is
a robotic-assisted mini-linear accelerator delivering 6
megavolts of photon beams with 6 additional degrees
of freedom compared with conventional gantry-
mounted accelerator (Fig. 125-8A). It is a frameless
localization and delivery system that avoids the minor
morbidity of placing a head frame on the patient,
making it ideal for fractionated treatment. More impor-
tant, the system allows for treatment of tumors that
extend below the skull base, such as glomus jugulare
tumors that grow inferiorly within the jugular vein or
glomus vagale tumors located high in the neck. The
gamma knife system has its fi eld of delivery limited at
the skull base.
A variety of imaging modalities such CT, positron
emission tomography, and MRI can be fused and
Figure 125-7. Venous phase of a carotid arteriogram showing
marked attenuation of right sigmoid sinus and jugular vein fl ow with
patency of the contralateral side.

Chapter 125
Glomus Tumors 1325
anatomy of the temporal bone is also used to verify the
location of the tumor and identifi es other important
structures to be protected from the full dose of deliv-
ered radiation. These are called critical structures and
serve as avoidance structures that can be preferentially
protected during treatment. At our institution, contour-
ing the tumor is done both by the surgeon and radia-
tion oncologist. The planned treatment is then created
and reviewed with the radiation physicist and ultimately
approved by the radiation oncologist. The tumor is
radiated with 18 or 21 Gy to the 80% isodose line in
three fractions. The dose at the margin of the tumor is
usually close to the prescription dose of 18 or 21 Gy,
unless there is a critical structure immediately adjacent
to the tumor. Minimizing treatment to a critical struc-
ture would lower the dose at the margin of the tumor.
The maximum tumor dose is 22.5 or 26.25 Gy at the
100% dose (see Fig. 125-8B). A thermoplastic mask
(Aquaplast) is created at the time of simulation and
tightly immobilizes the patient’s head and neck, and
offers similar degrees of accuracy to the more invasive
gamma knife frame. Each of three treatments is given
for approximately 30 minutes delivered every other day.
No sedation, intravenous fl uids, or hospitalization are
necessary (see Fig. 125-8C).
Radiation therapy may incur long-term complica-
tions such as osteonecrosis, chronic otitis externa,
breakdown of skin, eustachian tube dysfunction, and
the potential development of malignant tumor. Acute
cranial nerve dysfunction (hearing loss, imbalance or
vertigo, facial paresis, vocal fold weakness, dysphagia)
can occur and may be transient.
SURGICAL TECHNIQUES
Unless the lesion is small and clearly limited to the
middle ear promontory, all procedures are performed
with the patient under general endotracheal anesthesia
using inhalation and intravenous techniques. Muscle
relaxants are avoided, so that intraoperative monitoring
of cranial nerves VII, IX, X, XI, or XII can be
performed.
Glomus Tympanicum Tumors
The surgical approach for glomus tympanicum tumors
is dictated by the size of the lesion. Small tumors limited
to the mesotympanum and hypotympanum without
involvement of the jugular bulb are removed through
a transcanal approach. Larger lesions usually require a
postauricular approach to provide greater exposure. A
postauricular approach is also necessary when the infe-
rior annulus is not adequately visualized through the
external auditory meatus. This is often due to a promi-
nent bulge from the anterior wall or a high fl oor of the
ear canal.
Under the operating microscope, local anesthesia
is injected as a four-quadrant block into the skin of the
external auditory meatus. The same local solution is
infi ltrated into the skin of the postauricular sulcus.
Lateral canal incisions at 12 o’clock and 6 o’clock
are made and connected with a vertical incision
A
B
C
Figure 125-8. A, CyberKnife robotic radiosurgery system manufac-
tured by Accuray, Sunnyvale, California. B, Contour and isodose
treatment plan for a left jugular paraganglioma extending into the
upper neck. C, Patient positioned on the CyberKnife treatment table
secured by Aquaplast mask.
displayed by overlapping the images. The tumor map is
contoured, outlining the fi eld of interest using informa-
tion from the fused scan, although treatment is based
on CT confi rmation. The soft tissue signal from the
MRI scan allows the tumor to be outlined. The bony

1326
Section 15
Temporal Bone
approximately 5 mm from the annulus. The posterior
canal skin fl ap that is based laterally is back-elevated
within the canal. The fl ap is also known as the vascular
strip. A postauricular incision is made and carried down
to cortical mastoid bone. The spine of Henle is a good
landmark for the slope of the posterior bony ear canal.
The postauricular and canal fl ap incisions are con-
nected and the ear is retracted anteriorly with a self-
retaining retractor.
A tympanomeatal fl ap based on the anterior third
of the medial ear canal is created. This incision extends
from the 12-o’clock to the 4-o’clock position in a right
ear or from the 12-o’clock to the 8-o’clock position
in a left ear. The incision should preserve 5 mm of
skin lateral to the annulus. The tympanomeatal fl ap
is elevated, preserving the chorda tympani nerve. The
margins of the tumor are dissected and elevated to
isolate the vascular supply to the lesion (Fig. 125-9).
Excision of a tumor that involves the hypotympanum
requires greater exposure by removal of the inferior
tympanic ring with a microear drill (Fig. 125-10). When
the inferior margin of the tumor cannot be visualized,
the tympanic bone can be taken down to the fl oor of
the hypotympanum. If tumor infi ltrates the trabecu-
lated air cells of the hypotympanum, these cells and
tumor are removed using a diamond burr. The use of
microbipolar forceps facilitates hemostasis during
removal of the tumor (Fig. 125-11). Often a pedicled
vessel feeding the tumor can be found and should be
electrocoagulated (see Video 125-1).
The vascular supply from the tympanic plexus is
isolated and cauterized. If this is not possible, then the
tumor is coagulated with the bipolar cautery and
removed, and subsequent hemostasis is obtained. Small
cotton balls soaked with 1 : 1000 epinephrine are useful
to temporarily compress sites of bleeding during tumor
removal from the middle ear. Oxidized cellulose com-
pressed over the tumor is another effective method for
obtaining temporary hemostasis. After the tumor is
removed and hemostasis is obtained, the tympanome-
atal fl ap is returned to its anatomic position. Depend-
ing on the extent of hypotympanic exposure, it may be
necessary to support the inferior aspect of the fl ap with
a medially placed temporalis fascia graft or Gelfoam
placed in the hypotympanum. A silk sleeve supported
with cotton balls or Gelfoam is used for a canal
dressing.
Jugulotympanic Glomus Tumors
Jugulotympanic tumors that involve the middle ear,
jugular bulb, and hypotympanic air cells are usually
too large to remove through a transcanal approach.
The tumor may erode bone near the carotid artery
(Fisch type C1, Glasscock-Jackson tympanicum type IV,
Figure 125-9. Transtympanic approach to a glomus tumor isolated
within the middle ear.
Figure 125-10. A microear drill is used to access narrow or small
areas. Drill bits are available as cutting and diamond burrs.
Figure 125-11. Microbipolar forceps facilitate cautery in the
middle ear and can be used through an ear speculum.

Chapter 125
Glomus Tumors 1327
or jugulare type I). It is usually not necessary to develop
the exposure of the infratemporal fossa (ITF) and
upper neck required for large glomus jugulare tumors.
The initial transcortical mastoid approach is similar to
that described for mastoidectomy (see Chapter 115).
An incision is made 1 cm posterior to the postauricular
crease. The skin, subcutaneous tissue, and fi broperios-
teal layer over the mastoid cortex are incised and ele-
vated from a posterior and anterior direction. Dissection
is taken to the spine of Henle and the posterior aspect
of the external auditory meatus. A transcortical mas-
toidectomy is performed with cutting burrs and suction
irrigation. Landmarks to be identifi ed are the antrum,
mastoid tegmen, horizontal semicircular canal, fossa
incudus, and short process of the incus. The sigmoid
sinus is skeletonized to provide maximal exposure
between the sigmoid sinus and the vertical portion of
the facial nerve. The tumor may be encountered in the
infralabyrinthine retrofacial air cells. Following an
imaginary line drawn along the body of the incus and
short process, the facial recess (posterior tympanotomy)
is developed with cutting and then diamond burrs.
Extending the facial recess toward the tympanic ring
greatly improves exposure to the posterior mesotympa-
num and hypotympanum. It is necessary to sacrifi ce the
chorda tympani nerve with an extended facial recess
approach.
Attention is then turned to the external auditory
canal (EAC). A tympanomeatal fl ap is developed from
the 12-o’clock to the 5-o’clock position (for a right ear).
Elevation of the tympanic membrane exposes the
middle ear portion of the tumor. At this point, the
surgeon must determine whether tumor can be removed
with the given exposure. If extensive tumor involves the
tympanic bone and hypotympanum, the infratympanic
facial recess approach is extended (Fig. 125-12).13 It
may be necessary to create a “fallopian bridge” by
skeletonizing the distal vertical portion of the facial
nerve in order to remove all tumor. The margins of
the tumor are dissected and defi ned. Hemostasis
and tumor shrinkage are obtained with bipolar or
microbipolar forceps. Tumor is removed with cup
forceps (see Video 125-2). A cotton ball with epineph-
rine is used to temporarily control bleeding (see Video
125-3). If the exposure is still inadequate, the posterior
canal wall may need to be taken down. If the tumor is
more extensive than anticipated, management follows
the description for glomus jugulare tumors (see Glomus
Jugulare Tumors [Fisch types C1 and C2] later in this
chapter).
Whether the canal wall is left up or taken down,
tympanic membrane and ossicular chain reconstruc-
tion are undertaken as needed. When the incus is
removed in order to facilitate tumor removal from the
area around the stapes, an incus interpositioning is
performed. If the malleus is absent, then stapes aug-
mentation is achieved with either a partial ossicular
replacement prosthesis or an ossicular remnant of the
incus body or malleus head (see Chapter 114).
If the posterior canal wall is intact, the posterior
canal skin fl ap (vascular strip or Koerner’s fl ap) is
replaced along the posterior bony wall and the ear is
returned to its anatomic position. A pack is placed in
the external ear canal. Options for this include a silk
sleeve, rosebud packing, Gelfoam, continuous gauze, or
ointment. The author’s group’s preference is to use a
silk sleeve bolstered with antibiotic-impregnated cotton
balls.
If the posterior canal wall is taken down, a medial
rosebud packing is placed (see Chapter 113). (Gelfoam
may also be used to secure the tympanic membrane or
graft.) The pinna is then returned to its anatomic posi-
tion, placing the posterior canal wall skin fl ap into the
mastoid cavity. A packing of antibiotic-impregnated
continuous gauze is placed through the external audi-
tory meatus and into the mastoid cavity. For both
approaches, the postauricular incision is closed using
4-0 Nurolon suture. A sterile mastoid dressing is
applied.
A
B
Figure 125-12. Access to the glomus tumor in the middle ear and
hypotympanic space is achieved by extending the facial recess
approach. Opening the retrofacial infralabyrinthine air cells provides
exposure of the posterior margins of the tumor.

1328
Section 15
Temporal Bone
Glomus Jugulare Tumors
(Fisch Types C1 and C2)
Skin Incision
Preoperative determination of tumor extension pro-
vides information for the operative approach. Jugulare
tumors with limited carotid involvement (Fisch types C1
and C2) may permit preservation of the posterior bony
canal wall. A postauricular mastoidectomy incision
located 3 cm posterior to the pinna extends over the
lower border of the mastoid tip, through an upper neck
skin crease, toward the greater cornu of the hyoid bone
(Fig. 125-13). A second, deeper incision positioned
1 cm anteriorly through the musculoperiosteum layer
over the mastoid cortex creates a “stepped” fl ap that
facilitates closure at the end of the procedure. The
musculoperiosteum layer cortex is elevated anteriorly
toward the EAC. The neck incision goes through the
subcutaneous tissue and platysma muscle, with preser-
vation of the greater auricular nerve, which is harvested
to its maximal length.
Neck Dissection
Dissection in the upper neck provides identifi cation
and isolation of cranial nerves X, XI, and XII and the
great vessels. The neck dissection isolates the tail of the
parotid from the sternocleidomastoid muscle (SCM).
The spinal accessory nerve (CN XI) is identifi ed at the
anterior border of the SCM. Using cutting cautery, the
SCM is released from its mastoid attachment and
retracted posteriorly. The 11th cranial nerve is followed
superiorly toward the jugular vein, identifying the 10th
and 12th cranial nerves and the common, internal, and
external carotid arteries. The tail of the parotid is ele-
vated superiorly and anteriorly in order to identify the
posterior belly of the digastric muscle. The posterior
belly of the digastric muscle is dissected from the digas-
tric groove and retracted superiorly in order to expose
the inferior contents of the jugular fossa and stylomas-
toid foramen (Fig. 125-14). The jugular vein, common
carotid artery, ICA, and cranial nerves are isolated and
tagged with appropriately colored vascular loops. The
ascending pharyngeal and occipital arteries are usually
encountered and need to be ligated. The lower cranial
nerves, jugular vein, and carotid artery are further dis-
sected superiorly to the inferior aspect of the tumor.
Transtemporal Dissection
A transcortical mastoidectomy is performed. The perti-
nent landmarks to be identifi ed are the horizontal semi-
circular canal, incus, mastoid tegmen, sinodural angle,
and sigmoid sinus. Management of the posterior bony
canal wall depends on the extent of the tumor. Tumors
with extensive involvement of the carotid artery (Fisch
types C3 and C4), extension into the clivus, invasion into
the cochlea (anacousis), or destruction of lateral peri-
facial air cells often require a canal wall down proce-
dure, along with transposition of the facial nerve.
Tumors that are less extensive may be removed through
an extended facial recess approach. Similar to the
approach for a small jugulotympanic glomus tumor, the
extended facial recess approach begins superiorly at
the chorda facial recess. Using the vertical portion
of the facial nerve as the medial dissection limit, the
tympanic bone is drilled from a superior-to-inferior-
to-anterior direction. The chorda tympanic nerve is
sacrifi ced. The lateral limit of the extended facial recess
is the tympanic ring. Retrofacial and infralabyrinthine
air cells and bone are removed to the stylomastoid
foramen. The facial nerve is skeletonized, leaving egg-
shell-thin coverage surrounding a “fallopian bridge”
(see Fig. 125-12).
The digastric ridge is delineated within the mastoid
cavity. Dissection is continued anteriorly toward the
stylomastoid foramen. Thinning the bone to eggshell
thickness along the lateral inferior aspect of the digas-
tric ridge facilitates removal of the mastoid tip using a
rongeur. It is necessary to expose the posterior fossa
dura both posterior and anterior to the sigmoid sinus.
Some bone is left over the proximal sigmoid sinus near
Figure 125-13. Skin incision for large glomus tumor when the
carotid artery, jugular vein, and lower cranial nerves must be
identifi ed.
Figure 125-14. The postauricular incision is carried into the neck.
The carotid artery, jugular vein, and lower cranial nerves are isolated.
The sternocleidomastoid and digastric muscles are retracted.

Chapter 125
Glomus Tumors 1329
the sinodural angle (above Donaldson’s line). The
sigmoid sinus is carefully dissected free from the overly-
ing roof of bone. This exposure provides access to
extraluminal packing or suture ligation of the sinus.
Dissection with the drill is continued along the sigmoid
sinus toward the jugular bulb. All bone must be removed
from this area. The tumor is now removed.
This approach provides exposure of, but limited
controlled access to, the infratemporal carotid artery
(Fig. 125-15). Preoperative imaging determines whether
distal and proximal control of the petrous carotid artery
is necessary to safely remove all tumor. If the tumor
does not erode the bone surrounding the carotid artery,
this canal wall-up, extended facial recess approach pro-
vides appropriate exposure.
Tumor Isolation and Removal
Venous bleeding may occur from the sigmoid sinus,
jugular vein, condylar vein, or inferior petrosal sinus.
The fi rst two are controlled at the onset of tumor
removal. The sigmoid sinus may be occluded by either
extraluminal packing or ligation. Extraluminal occlu-
sion is performed with oxidized cellulose that is packed
under a retained shelf of bone covering the proximal
sigmoid sinus. If this is not successful or feasible, liga-
tion of the sinus is performed by making small openings
in the dura anterior and posterior to the sigmoid sinus.
An aneurysm needle is passed from posterior to ante-
rior deep to the sigmoid sinus. The needle is blindly
passed medial to, but hugging, the sigmoid sinus, avoid-
ing injury to the intracranial contents (cerebellum). A
long 2-0 silk ligature is passed through the aneurysm,
needle up to its mid length, and the aneurysm needle
is withdrawn. The suture is then cut in half, so as to
leave two separate ligatures (Fig. 125-16). A small piece
of muscle is harvested and placed over the sigmoid
sinus, and the fi rst suture is tied and secured. The
second suture is similarly tied, thus providing double
ligation and occlusion of the sigmoid sinus.
The jugular vein in the neck is doubly ligated at this
time. The proximal stump of the jugular vein in the
neck is dissected superiorly toward the jugular bulb and
fossa (Fig. 125-17). Care is taken to preserve the spinal
accessory nerve. It is usually necessary to pass the proxi-
mal stump of the jugular vein medial to the spinal
accessory nerve in order to facilitate the superior dis-
section. The distal extratemporal ICA should be in
direct view as the jugular vein is dissected toward the
jugular bulb. The styloid process and its muscular
attachments may need to be removed in order to gain
access to the skull base.
The sigmoid sinus is opened distal to the ligatures
in order to inspect the intraluminal contents. Usually,
the medial wall of the sigmoid sinus is not invaded by
Figure 125-15. Transmastoid tumor dissection isolating the
sigmoid sinus, vertical facial nerve along the extended facial recess,
digastric ridge, neck vessels, and lower cranial nerves.
Figure 125-16. The extended facial recess approach exposes the
tumor in the hypotympanum. The vertical portion of the facial nerve
remains in place. The proximal sigmoid sinus can be isolated by
extraluminal packing or suture ligation.
Figure 125-17. Proximal control of the sigmoid sinus is achieved.
Surgicel packing can also be used to occlude the proximal sigmoid
sinus. The jugular vein is divided, and the proximal segment is dis-
sected into the jugular fossa. The anterior plane of dissection is along
the carotid artery, which is not shown (see Fig. 125-16).

1330
Section 15
Temporal Bone
tumor unless there is intracranial extension. The infe-
rior aspect of the sigmoid sinus is incised in a longitu-
dinal direction toward the jugular bulb. The tumor is
sequentially isolated from a posterior-to-anterior direc-
tion, dissecting the superior, lateral, and inferior walls
of the sigmoid sinus from the medial wall. Bipolar coag-
ulation is usually needed to obtain hemostasis and
shrink the tumor. The lateral and superior aspect of the
jugular bulb are dissected toward the superior extent of
the tumor. Tumor often occludes the jugular bulb.
However, once the tumor is removed from this area,
brisk bleeding may be encountered from the multiple
orifi ces of the inferior petrosal sinus and condylar vein.
The medial jugular fossa is packed with oxidized cellu-
lose. This dissection is performed medial (deep) to the
vertical portion of facial nerve and stylomastoid area.
Care must be taken to avoid trauma or pressure to the
medial (deep) surface of the facial nerve. Tumor often
remains in the hypotympanum and middle ear. This is
removed by working both medial and lateral to the
facial nerve.
Certain intraoperative fi ndings may necessitate a
canal-wall-down procedure. The fi rst is the need for
increased exposure of tumor invading the carotid
artery. Also, limited space in the retrofacial and infra-
labyrinthine areas may require transposition of the
facial nerve in order to provide adequate exposure of
the tumor. Reconstruction of the tympanic membrane
and ossicular chain can still be performed as needed.
Unless the medial wall of the jugular bulb or
sigmoid sinus is removed, CSF is not encountered.
However, the dead space created by the removal of
bone and tumor requires partial obliteration with
abdominal fat. Packing of the ear canal is identical to
that described previously. A Hemovac drain is placed
deep to the neck skin fl aps. The postauricular wound
is closed in three layers, reapproximating the musculo-
periosteum, subcutaneous tissue, and skin.
Large Glomus Jugulare Tumors
(Fisch Type C2 or Greater)
A large postauricular C-shaped incision begins 3 cm
superior to the pinna. If it is known that an ITF dissec-
tion is necessary to gain access to the distal ICA, then
the incision begins anterior and superior to the pterion.
The incision extends posteriorly and inferiorly 3 to
4 cm posterior to the helical rim, continues inferiorly
across the lower border of the mastoid tip, and through
upper neck skin crease toward the greater cornu of the
hyoid bone in anticipation of isolation of the great
vessels and lower cranial nerves. This creates an anteri-
orly based fl ap, which will include the pinna. The supe-
rior incision and dissection are taken down to the level
of the temporalis fascia.
The EAC is transected medial to the cartilaginous
bony junction. The skin of the proximal canal is dis-
sected away from the underlying cartilaginous canal,
and the cartilage is removed. This leaves a cuff of exter-
nal auditory meatus skin that will be everted by placing
superior and inferior sutures in the canal skin. The
ends of these sutures are passed retrograde through the
EAC. This facilitates eversion of the cuff of the external
auditory meatus skin, which is reapproximated in a
linear fashion with interrupted sutures of 4-0 Dexon
(Fig. 125-18). A deep fl ap of fi broperiosteum is devel-
oped in order to create a second layer for closure of the
external meatus. This 2.5- × 2.5-cm fl ap is based on the
posterior aspect of the subcutaneous tissue of the EAC.
It is sutured anteriorly to the subcutaneous tissue of the
skin just deep to the tragus.
Neck Dissection
The approach and dissection in the neck are identical
to that previously described for smaller glomus jugulare
tumors. The great vessels and cranial nerves are isolated
and tagged with vessel loops. A moistened lap sponge
is left in the wound during the infratemporal fossa
dissection.
Infratemporal Fossa Dissection
Preoperative evaluation will determine the degree of
involvement of the carotid artery or clivus. Extensive
tumors involving the horizontal portion of the carotid
artery and petrous apex require dissection of the ITF.
This approach provides necessary exposure for control
of the distal ICA. The upper limb of the skin incision
must be extended toward the forehead, just superior to
the pterion. The superior skin fl ap is elevated superfi -
cial to the temporalis fascia down to the level of the
zygomatic arch. Care is taken to go medial to the deep
cervical fascia in order to avoid injury to the temporal
branches of the facial nerve. Dissection with electrocau-
tery facilitates removal of the attachments of temporalis
fascia to the arch and body of the zygoma. Similarly, the
fascial attachment of the masseter muscle is removed
from the inferior surface of the zygomatic arch, which
Figure 125-18. The ear canal is transected. A fi broperiosteal fl ap
based on the posterior canal has been created. The ear canal skin is
everted with a horizontal suture passed through the distal cuff of
canal skin. (Redrawn from Gantz BJ, Fisch U: Modifi ed transotic approach
to the cerebellopontine angle. Arch Otolaryngol 109:253, 1983. Copyright
1983, American Medical Association.)

Chapter 125
Glomus Tumors 1331
is circumferentially isolated from surrounding tissue.
Using the reciprocating saw, osteotomy cuts permit
removal of the zygomatic arch. The periosteum at the
origin of the temporalis muscle is cut, and the muscle
is dissected from the temporal fossa.
The dissection is continued in a subperiosteal plane
into the ITF (Fig. 125-19). Venous bleeding is often
encountered and controlled with bipolar coagulation
and oxidized cellulose. Inferior and anterior retraction
of the mandibular condyle widens the exposure.
However, should complete exposure and control of the
carotid artery be necessary, then resection of the man-
dibular condyle improves surgical access to the vertical
segment of the carotid. The attachment of the ptery-
goid muscle to the neck of the condyle is divided with
electrocoagulation. The condyle may be removed with
a reciprocating saw. Dissection in the ITF is directed
toward the foramen ovale (trigeminal nerve V3) and
foramen spinosum (middle meningeal artery). Control
of the carotid artery is obtained by performing an
inferior frontotemporal craniotomy. A craniotomy is
performed by placing burr holes through which the
underlying dura is elevated and bone fl ap removed.
Additional exposure of the petrous apex and carotid
artery at the infratemporal skull base is accomplished
with a dissecting drill and rongeurs. The horizontal
segment of the petrous ICA is identifi ed and isolated
by this extradural middle fossa dissection. This approach
facilitates the subtemporal ITF exposure of pertinent
petrous artery landmarks: V3, greater superfi cial petro-
sal nerve, and middle meningeal artery.
Transtemporal Dissection
Complete mastoidectomy is performed. The approach
and dissection are identical to that previously described
for smaller glomus jugulare tumors (Fisch type C2 or
Figure 125-19. Removing the zygomatic arch permits mobilization
of the temporalis muscle, exposing the infratemporal fossa. Soft tissue
dissection isolating the extratemporal facial nerve, great vessels, and
lower cranial nerves is demonstrated. The tumor has not been
exposed in the temporal bone.
greater). Exposure of the dura of the posterior fossa
anterior and posterior to the sigmoid sinus must be
performed in anticipation of opening the dura, possible
resection of the dura, and removal of the tumor. Most
tumors require complete exposure of the middle ear
and necessitate removing the posterior canal wall along
with the epithelium of the medial EAC and tympanic
membrane. Reconstruction of the middle ear is usually
not feasible owing to the extent of the lesion and the
need to obliterate the eustachian tube to avoid CSF
rhinorrhea. If function of the cochlea is to be pre-
served, the incudostapedial joint is separated through
the facial recess approach. The ossicles lateral to the
stapes and the tympanic membrane may be removed.
The posterior bony canal wall is taken down to the level
of the horizontal and vertical portion of the facial nerve.
Similarly, the anterior canal wall must be removed to
the level of the parotid gland and periosteum of the
glenoid fossa. Tumor extending into the middle ear is
encountered at this time. The vertical segment of the
facial nerve interferes with access to large tumors fi lling
the jugular fossa and invading the carotid artery. Facial
nerve transposition is usually necessary to achieve
optimal exposure. The facial nerve is decompressed
from the geniculate ganglion to the stylomastoid
foramen with cutting and then diamond burrs. Favor-
able anatomy may permit more limited mobilization of
the facial nerve from its second genu (Fig. 125-20).
Precise dissection and isolation of the facial nerve
in the stylomastoid foramen is diffi cult. The transposi-
tion is facilitated by cutting the remaining tendon and
fi bers of the digastric muscle within the mastoid proxi-
mal to the stylomastoid foramen. The muscle, along
with the contents of the stylomastoid foramen, is ele-
vated from the underlying bone in a posterior-to-
anterior direction. The facial nerve is then dissected
Figure 125-20. Radical mastoidectomy has been performed by
removing the posterior canal wall medially to the skeletonized facial
nerve. The digastric ridge is dissected in preparation for removing
the mastoid tip and mobilizing the facial nerve. The tumor in the
middle ear and mastoid is evident.

1332
Section 15
Temporal Bone
away from the fallopian canal. The cuff of fi brous tissue
surrounding the facial nerve is sutured anteriorly to the
periparotid fascia, providing retraction of the vertical
and horizontal facial nerve. Complete removal of the
tympanic ring and remaining mastoid tip can then be
accomplished. The styloid process is identifi ed and
removed by releasing the stylohyoid and styloglossal
tendons from the tip of the styloid (Fig. 125-21).
Tumor Isolation and Removal
The tumor is removed. The sigmoid sinus is isolated
proximally, and the jugular vein is ligated in the upper
neck (Fig. 125-22). Resection of the tumor follows the
same sequence as that previously described for less
extensive glomus jugulare tumors. Tumor found supe-
rior to the jugular bulb and into the middle ear is dis-
sected away from the otic capsule. If erosion into the
inner ear occurs, further drilling of the otic capsule
facilitates removal of the tumor.
Remaining tumor is carefully dissected off the
carotid artery in a subadventitial plane, which com-
pletes the extradural dissection and removal of the
tumor. The fi brocartilaginous ring surrounding the
carotid artery at the skull base must be divided to
achieve this plane (Fig. 125-23).
If intracranial tumor is found, the dura of the pos-
terior fossa is opened. The medial wall of the sigmoid
sinus and jugular bulb typically require resection. Care
is taken to preserve the neural contents of the pars
nervosa. Signifi cant intracranial extension of tumor
and jugular bulb involvement obviate successful nerve
preservation. Tumor is removed from the cerebello-
pontine angle (Fig. 125-24). Often the intracranial
Figure 125-21. The facial nerve has been mobilized anteriorly,
exposing the tumor in the mastoid, middle ear, and jugular bulb
areas. The tendons attached to the styloid process have been divided.
Retraction of the mandible permits isolation of the carotid artery.
Figure 125-22. The proximal sigmoid sinus and jugular vein are
suture ligated. The tumor is carefully dissected off the carotid artery.
The lateral sigmoid sinus is opened.
Figure 125-23. The sigmoid sinus and jugular vein have been
divided. The inferior aspect of the tumor is dissected off the carotid
artery in a subadventitial plane.
portion of the tumor has been devascularized by the
skull base dissection. Should a large amount of intra-
cranial tumor remain with limited exposure, then a
retrosigmoid craniotomy is performed. This additional
exposure would be anticipated based on preoperative

Chapter 125
Glomus Tumors 1333
imaging and planning. A second-stage procedure may
be required if a large amount of residual tumor is
present. When all tumor has been removed and hemo-
stasis achieved, the wound is then closed. Care is taken
to ensure obliteration of the eustachian tube to avoid
postoperative CSF rhinorrhea. The body of the incus, a
small piece of muscle, and oxidized cellulose are packed
into the eustachian tube. Large defects in the dura are
repaired primarily with grafts of temporalis fascia,
although watertight closure in this area can be diffi cult.
Other fascial tissue available include galea, pericra-
nium, and fascia lata. It also may be necessary to close
the small openings in the dura where the sigmoid sinus
was ligated. Small pieces of muscle are bolstered over
these defects with fi gure-of-eight sutures in the dura.
Fat is harvested from the abdominal wall. The wound
is copiously irrigated with a bacitracin solution, and the
fat is placed into the temporal bone defect area.
Patients with large lesions requiring removal of pos-
terior fossa dura and grafting are at greater risk for CSF
leaks. Additional tissue may be necessary to provide
watertight closure of the wound. The temporalis muscle
can be elevated and transposed posteriorly and inferi-
orly in order to facilitate this closure. It is usually neces-
sary to remove the root of the zygoma in order to
pedicle and rotate the entire temporalis muscle. The
edges of the temporalis muscles are approximated to
the SCM and semispinalis and splenius capitis muscles
(Fig. 125-25). Extensive tumors that require a transotic
capsule approach with large areas of temporal bone
resection create considerable dead space that may not
be adequately obliterated with abdominal fat. In some
cases, it may be necessary to fi ll the defect with a free
fl ap of rectus abdominis muscle. The SCM and proxi-
mal posterior belly of the digastric muscles are also
reapproximated to the fi broperiosteal tissue on the skin
fl ap that covered the mastoid cortex. A small Hemovac
drain is tunneled through a stab incision in the poste-
rior neck and placed in the inferior aspect of the neck
dissection and left to gravity drainage overnight. The
skin fl ap is returned to its anatomic position and closed
in a three-layer fashion. A running locking suture reap-
proximates the skin. Staples may also be used. A sterile
compression mastoid and neck dressing are applied.
POSTOPERATIVE CARE
The level and intensity of postoperative monitoring and
management are dictated by the extent of the surgical
procedure and the neurovascular structures encoun-
tered. Small lesions that were approached through an
endaural incision receive basic postoperative care. Vital
signs are monitored on a routine basis. The ear packing
is changed as needed. The patient should be ready for
discharge the following morning.
Tumors excised by a combined transmeatal post-
auricular approach are managed in a similar fashion. A
mastoid dressing that was placed postoperatively is
removed the following morning. Patients are instructed
to change the external canal cotton ball as needed. The
postauricular incision is cleaned with peroxide or
alcohol, and a topical antibiotic ointment is applied
twice a day. Patients are seen 7 to 10 days postopera-
tively. Those patients with an endaural approach have
the packing removed and the tympanic membrane
inspected for integrity. Those with a combined approach
have their sutures and outer ear canal packing removed.
The patient is instructed to use topical ear drops twice
a day, and the inner packing is removed 1 week later.
Patients with more extensive tumors requiring
resection of dura frequently have the external ear canal
closed as a blind sac. If a Hemovac neck drain is placed,
it is removed the day following surgery. A pressure
dressing remains for 3 days. Patients are carefully
assessed for function of the lower cranial nerves. Oral
intake is commenced if dysphagia and aspiration do not
occur. Corneal protection with a moisture chamber,
artifi cial tears, and ointment at night are provided if
facial paresis is present. Patients are encouraged to be
Figure 125-24. The dura is resected when tumor invades the pos-
terior fossa and additional exposure is needed. Tumor in this area
often requires sacrifi ce of lower cranial nerves. Dural grafting is neces-
sary. (Redrawn from Sekhar LN, Janecka IP [eds]: Surgery of Cranial Base
Tumors. New York, Raven Press, 1993.)
Figure 125-25. The temporalis muscle is rotated posteriorly and
inferiorly to provide a vascularized graft, facilitating wound closure.

1334
Section 15
Temporal Bone
out of bed the following day. Management of complica-
tions or cranial nerve injury is detailed in the following
section. Sutures are removed 7 to 10 days postopera-
tively. In order to assess the status of the excised tumor,
a baseline scan is obtained postoperatively at 3 months.
MRI with fat suppression technique helps differentiate
the varied tissue densities within the operative site. Any
suspicious areas identifi ed on the scan prompt a repeat
scan in 6 months. Otherwise, imaging is obtained in 1
year. If this is negative for tumor, a scan is obtained 1
year later.
COMPLICATIONS
The potential complications following glomus tumor
surgery are numerous and depend on the location and
extent of the tumor. The postoperative complications
following glomus tumor surgery can be divided into
those that pertain to problems with the wound, bleed-
ing, CSF leak, neurologic, and cranial nerve defi cits.
A seroma or hematoma may compromise wound
healing. Glomus jugulare tumors require a large skin
fl ap and dissection into the neck. Obtaining a water-
tight closure may be diffi cult with regard to the integrity
of the dura. For this reason, a Hemovac drain remains
only until the following day. It is kept to gravity drainage
as opposed to negative pressure. A pressure dressing is
also applied to the wound to minimize the possibility of
seroma or hematoma. A collection of CSF (pseudo-
meningocele) is managed by maintaining a pressure
dressing and elevating the head. If the CSF collection
continues to expand, then lumbar drainage is instituted
for 3 to 5 days.
Injury to cranial nerves results in functional defi cits
that must be addressed. Transposition of the facial
nerve usually results in temporary facial paresis or paral-
ysis. It is diffi cult to predict when the return of facial
function will occur. Corneal protection is necessary if
the patient has inadequate eye closure. Topical artifi cial
tears are used throughout the day. Ophthalmic oint-
ment is placed in the lower conjunctival sulcus at night.
Additional daytime protection with a clear plastic mois-
ture chamber provides comfort and minimizes corneal
desiccation. Long-term eye protection is effectively pro-
vided with placement of a gold weight in the sub orbic-
ularis oculi muscle/pretarsal space (see Chapter 121).
A lower lid–tightening procedure is recommended for
patients with laxity of the lower lid or those demonstrat-
ing ectropion.
Complications related to the tympanic membrane
and ossicular chain can occur when excising tympanic
or jugulotympanic glomus tumors. During an endaural
approach with the tympanomeatal fl ap elevated, inad-
vertent contact with a microbipolar forceps to the tym-
panic membrane may result in ischemia and necrosis.
A tympanic membrane perforation may result, requir-
ing a patch or formal myringoplasty (see Chapter 113).
Persistent conductive hearing loss as a result of ossicular
chain reconstruction can be subsequently revised or
treated with a hearing aid. The maximal conductive
hearing loss that results from obliteration of the middle
ear space and closure of the ear canal is more diffi cult
to manage. Unless a deep cuff of tissue is constructed
to create an external auditory meatus that would fi t
an ear mold, the use of a hearing aid will not be
successful.
Injury or sacrifi ce to the ninth and tenth cranial
nerves in patients who previously were asymptomatic
results in problems of dysphagia, aspiration, and hoarse-
ness. Despite the patient being under general anesthe-
sia, it is reasonable to perform an intraoperative vocal
cord medialization procedure (thyroplasty type I) while
the neck is open (see Chapter 41). If the 10th cranial
nerve is anatomically intact, then postoperative assess-
ment is determined when the patient is awake.
Injury to the spinal accessory nerve results in shoul-
der drop and dysfunction. Postoperative physical reha-
bilitation therapy should be requested once the patient
is ambulatory.
Tumors that extend inferiorly into the neck may
put the hypoglossal nerve at risk. This would be unusual
unless there is an associated large glomus vagale or
carotid body tumor. Dysmotility of the tongue may
result in mild dysarthria and problems with deglutition.
Functionally, this injury alone is usually well tolerated.
However, in combination with injury to the ninth and
tenth cranial nerves, hypoglossal injury puts the patient
at greater risk for dysphagia and aspiration. Thus
patients who are clinically symptomatic postoperatively
should be evaluated for a vocal cord medialization pro-
cedure. An arytenoid adduction procedure augments
the closure of the posterior glottic chink, which further
minimizes the potential for aspiration. Tracheotomy
may still be necessary for uncontrolled aspiration and
pulmonary toilet. Cricopharyngeal myotomy further
relaxes the upper esophageal sphincter, which facili-
tates swallowing.
Watertight closure may be diffi cult when the dura
is resected and repaired. Avoidance of a CSF leak is
accomplished by meticulous obliteration of the eusta-
chian tube, packing of the mastoid cavity with fat, and
three-layer closure to the muscle and fi broperiosteum,
subcutaneous tissue, and skin. Due to the critical struc-
tures adjacent to glomus tumors including the lower
cranial nerves, carotid artery, jugular vein and venous
sinuses, the dura, brain and spinal fl uid serious compli-
cations of lateral skull base surgery do occur. The mor-
tality from management of the carotid artery has
resulted from cerebrovascular complications. In a large
series of glomus tumors of the temporal bone treated
surgically, the rate of CSF leak was 11.6% and incidence
of aspiration pneumonia was 5.3%.5 The incidence of
postoperative CSF leak dropped to 4.5% when dural
closure or reconstruction involved a vascularized local,
regional, or free fl ap.14
If CSF leak occurs through the skin or nose despite
a pressure dressing, lumbar drainage is instituted. This
is maintained at 6 to 10 mL/hr over 3 to 5 days. Although
rarely necessary, persistent CSF leak may warrant wound
reexploration.
Ongoing problems with aspiration may pre -
vent resumption of oral intake. In the immediate

Chapter 125
Glomus Tumors 1335
postoperative period, nutritional support is provided by
nasogastric feeding. Despite efforts to provide glottic
competence with swallowing therapy, a gastrostomy or
jejunostomy feeding tube may be necessary.
Management of intraoperative injury to the ICA is
dictated by results of BTO and xenon blood fl ow studies.
Demonstration of inadequate contralateral perfusion
requires preservation of the ipsilateral carotid. Lacera-
tion or tear is either primarily repaired or replaced with
a saphenous vein graft. Despite data providing assur-
ance of adequate contralateral fl ow, ligation of the
carotid artery may result in progressive thrombus for-
mation and possible emboli. Patients in whom a carotid
artery was repaired or grafted should have postopera-
tive studies, such as Doppler ultrasound, MRA, or trans-
femoral arteriography, to determine the status of the
ICA. Patients exhibiting ischemic neurologic compro-
mise should be considered for embolectomy or
heparinization.
References
1. Mulligan RM: Chemodectomy in the dog. Am J Pathol 26:680-
681, 1950.
2. Guild SR: The glomus jugulare, a nonchromaffi n paraganglion,
in man. Ann Otol Rhinol Laryngol 62:1045-1071, 1953.
3. Bartels LJ, Pennington J, Kamerer DB, et al: Primary fallopian
canal glomus tumors. Otolaryngol Head Neck Surg 102:101-105,
1990.
4. Heth J: The basic science of glomus jugulare tumors. Neurosurg
Focus 17:E2, 2004.
5. Manolidis S, Shohet JA, Jackson CG, et al: Malignant glomus
tumors. Laryngoscope 109:30-34, 1999.
6. Fisch U: Infratemporal fossa approach for glomus tumors of the
temporal bone. Ann Otol Rhinol Laryngol 91(5 Pt 1):474-479,
1982.
7. Fisch U, Rouleau M: Facial nerve reconstruction. J Otolaryngol
9:487-492, 1980.
8. Jackson CG, Glasscock ME 3rd, Harris PF: Glomus tumors. Diag-
nosis, classifi cation, and management of large lesions. Arch
Otolaryngol 108:401-410, 1982.
9. Hinerman RW, Mendenhall WM, Amdur RJ, et al: Defi nitive
radiotherapy in the management of chemodectomas arising in
the temporal bone, carotid body, and glomus vagale. Head Neck
23:363-371, 2001.
10. Feigenberg SJ, Mendenhall WM, Hinerman RW, et al: Radiosur-
gery for paraganglioma of the temporal bone. Head Neck 24:384-
389, 2002.
11. Pollock BE: Stereotactic radiosurgery in patients with glomus
jugulare tumors. Neurosurg Focus 17:E10, 2004.
12. Briner HR, Linder TE, Pauw B, et al: Long-term results of surgery
for temporal bone paragangliomas. Laryngoscope 109:577-583,
1999.
13. Jackson CG: The infratympanic extended facial recess approach
for anteriorly extensive middle ear disease: A conservation tech-
nique. Laryngoscope 103(4 Pt 1):451-454, 1993.
14. Jackson CG, McGrew BM, Forest JA, et al: Lateral skull base
surgery for glomus tumors: Long-term control. Otol Neurotol
22:377-382, 2001.
PEARLS
• Arteriography and venous outfl ow studies are
helpful for large tumors by identifying the blood
supply of the tumor, the proximity of the major
vessels, occlusion of the ipsilateral jugular vein,
patency of the contralateral venous drainage system,
and the opportunity for tumor embolization before
surgical resection.
• Stereotactic radiotherapy may provide effective
control of tumor when given as the primary
modality of treatment, following recurrence of
tumor, or as part of the planned strategy for
subtotal resection.
• Small cotton balls soaked with 1 : 1000 epinephrine
are useful to temporarily compress sites of bleeding
during tumor removal from the middle ear.
• Rotation of a vascularized temporoparietal fascia/
muscle fl ap is an effective reconstructive technique
for closure of a cranial and dural defect, minimizing
the risk of CSF leak.
• The potential morbidity of newly acquired cranial
nerve dysfunction (CN VII-XII) following resection of
large glomus jugulare tumors demands a
comprehensive discussion with the patient and
family and documentation of the informed consent
containing the options, risks, and benefi ts of the
treatment.
• Intraoperative severe and diffi cult to control
hypertension may occur in patients with
unrecognized preoperative symptoms and signs of a
vasoactive-secreting tumor.
• Incomplete assessment of patients with a family
history of paraganglioma may proceed toward
subsequent growth of multicentric tumors resulting
in more diffi cult management decisions affecting the
cranial nerves and great vessels of the head and
neck.
• Following resection of a glomus jugulare tumor,
sacrifi ce of a patent sigmoid sinus and jugular vein
when the contralateral central venous outfl ow is
insuffi cient may result in intracranial hypertension.
• Unexpected facial nerve injury can result if
involvement of the vertical portion of the facial nerve
from posterior tumor extension in the middle ear
and hypotympanum is not recognized.
PITFALLS
• Failure to recognize potential compromise of the
lower cranial nerves following resection of large
glomus jugulare tumors may incur signifi cant
postoperative morbidity and changes in the quality
of life.

Chapter 126
Cholesterol Granuloma and Congenital
Epidermoid Tumors of the Temporal Bone
Barry E. Hirsch and Alec Vaezi
Expansile destruction of the petrous apex may be due
to congenital epidermoid tumor or cholesterol granu-
loma. The etiology, incidence, and management of cho-
lesterol granuloma and congenital epidermoid tumor
within the temporal bone are different. Distinguishing
between these two processes was diffi cult before the
advent of computed tomography (CT) and magnetic
resonance imaging (MRI), especially when the lesion
or tumor originated medially and anteriorly within the
petrous apex.
Pathology extending in this area challenges the
neurotologic team to comprehensively evaluate and
effectively manage these lesions. Abnormalities in the
petrous apex may be silent for many years because of
the depth and isolation of this area. Once the pathology
encroaches on surrounding vital structures such as the
dura and brain, carotid artery, orbit, 4th through 11th
cranial nerves, and otic capsule, symptoms and signs
will become apparent. Pathology in the petrous apex is
often identifi ed incidentally or when diagnostic imaging
is performed for vaguely described symptoms such as
lightheadedness; retro-orbital, ear, vertex, or occipital
head pain; tinnitus; visual blurriness; or diplopia. Just
as the causes and radiologic fi ndings differ, so do the
management strategies and surgical approaches.
PERTINENT ANATOMY
The petrous apex is a wedge-shaped structure that occu-
pies the medial and anterior aspect of the temporal
bone. The petrous apex is inferior, medial, anterior,
and superior to the otic capsule. The superior surface
forms the fl oor of the middle cranial fossa. Along this
surface pass the greater and lesser superfi cial petrosal
nerves and is the exit point for the middle meningeal
artery through the foramen spinosum. At the tip of the
petrous apex lies a depression containing the gasserian
ganglion of the trigeminal nerve. The petroclinoid liga-
ment forms the attachment of the tip of the petrous
apex to the sphenoid bone. This area is termed Meckel’s
cave, through which passes the fi fth cranial nerve. The
sixth cranial nerve is located just medially and passes
through Dorello’s canal. The horizontal portion of the
carotid artery lies posteromedial to V3, and its bony
covering is often dehiscent. The anterolateral surface
of the petrous bone contains the genu of the carotid
artery and its horizontal segment. The bony opening of
the eustachian tube passes in an anterior, inferior, and
medial direction toward the nasopharynx. The jugular
bulb and vein exit the inferior surface of the petrous
bone through the jugular foramen. The 9th, 10th, and
11th cranial nerves also leave the skull base through the
pars nervosa of the jugular fossa. The carotid foramen
lies anterior to the jugular bulb on the inferior surface
of the petrous bone. The posteromedial surface of the
temporal bone faces the posterior fossa. Openings into
this surface include the internal auditory canal (IAC),
which contains the cochlear, vestibular, facial, and
intermedius nerves; the operculum, which contains the
endolymphatic duct and sac; and the aperture for the
subarcuate artery. The posterior aspect of the temporal
bone contains the mastoid cavity and faces the sigmoid
sinus and posterior fossa (Fig. 126-1).
The petrous bone can be conceptually and
functionally divided into anterior and posterior
compartments.1 This division is in a coronal direc -
tion passing through the IAC. Pathology in the poste-
rior compartment is readily accessed through a
transmastoid or translabyrinthine approach. Congeni-
tal cholesteatomas of the middle ear are frequently
1337

1338
Section 15
Temporal Bone
accessed via the external auditory meatus. Abnormali-
ties in the anterior compartment, including the petrous
apex, require more complex approaches.
Access to the Petrous Apex
Approaches to the petrous apex require an understand-
ing of the anatomy of the temporal bone and surround-
ing vital structures of the skull base and posterior,
middle, anterior, and infratemporal fossae. Access to
the petrous apex is limited because of its anatomic loca-
tion. The position of the otic capsule, facial nerve, and
carotid artery obviates direct and complete exposure to
this centrally located area.
Before the availability of antibiotics, suppurative
disease of the petrous apex was a common sequela of
otitis media and was associated with high morbidity
and mortality. Historically, various transtemporal
approaches have been described to gain access to the
relatively isolated area of the petrous apex via the
air cell tracts surrounding the otic capsule. These
approaches were predominantly used for the manage-
ment of infectious complications of otitis media causing
petrous apicitis (Fig. 126-2). The various routes through
the temporal bone include
1. The supralabyrinthine tract inferior to the middle
fossa dura
2. The subarcuate tract beneath the superior semicir-
cular canal
3. The air cells of the zygomatic root
4. The small triangular region of bone between the
genu of the carotid artery and the cochlea
5. The retrofacial infralabyrinthine tract
6. The infracochlear air cell tract
The fi rst four routes are effective for draining an abscess
or suppurative infl ammation in the petrous apex but
may not adequately provide permanent aeration to this
remote area. The latter two routes do provide a more
reliable and wider opening to the petrous apex. The
infracochlear approach was described by Farrior and
then modifi ed by Brackmann and coworkers to adapt
the approach for drainage of petrous apex cholesterol
granuloma.2,3
The development of advanced endoscopic tech-
niques and instrumentation has provided access to the
petrous apex though the nose, nasopharynx, sphenoid
sinus, and base of the skull. The transnasal approach
enters the petrous bone anteriorly and is medial to the
carotid artery. The conventional lateral approaches
passing superior or inferior to the temporal bone
require careful consideration of the carotid artery and
otic capsule. Specifi c indications and limitations must
be recognized when planning surgical treatment of
pathology in the petrous apex.
Lesions of the Petrous Apex
With more extensive use of high-defi nition CT and
MRI, lesions of the petrous apex are now often identi-
fi ed before they become large and destructive. Most
lesions of the petrous apex remain quiescent and grow
slowly until they affect neighboring neurovascular struc-
tures, including the cranial nerves, brain, orbit, or
carotid artery, or extend into the middle ear. Patients
suffering from lesions of the petrous apex most often
Eustachian
tube
Anterior
V3
V2
GSPN
Superior
Medial
Posterior
Inferior
Facial
nerve
Figure 126-1. Petrous portion of the temporal bone. A coronal
plane through the internal auditory canal separates the posterior and
anterior petrous apex. The greater superfi cial petrosal nerve (GSPN)
runs along the superior surface of the petrous bone. The gasserian
ganglion and the mandibular division of the trigeminal nerve are
located in the apex.
4
6
5
1
2
3
Figure 126-2. Drainage approaches to the petrous apex. 1, Supra-
labyrinthine tract inferior to the middle fossa dura; 2, subarcuate tract
beneath the superior semicircular canal; 3, air cells of the zygomatic
root; 4, small triangular region of bone between the genu of the
carotid artery and the cochlea; 5, retrofacial infralabyrinthine tract;
6, infracochlear air cell tract.

Chapter 126
Cholesterol Granuloma and Congenital Epidermoid Tumors of the Temporal Bone 1339
complain of hearing loss, dizziness, tinnitus, and head-
ache (40% to 60%). Abnormalities of the cranial nerves
causing symptoms and signs such as facial twitching or
weakness or diplopia are less common (5% to 15%) but
raise greater suspicion for pathology in the petrous
apex. Extension of disease into the middle ear may
result in conductive hearing loss, but perforation of the
tympanic membrane with subsequent otorrhea is rare
(5%).4,5 Facial numbness, amaurosis fugax, vertigo,
transient ischemic attacks, ataxia, dysmetria, and inco-
ordination can also occur.
Lesions of the petrous apex can be classifi ed into
three categories: cystic, solid, and radiographic anoma-
lies. A retrospective study analyzing lesions of the
petrous apex determined cystic lesions to be the most
common source of pathology.4 Such lesions include
cholesterol granuloma (60%), cholesteatoma (10%),
and mucocele (3%). Second in frequency are solid
tumors, a heterogeneous group that includes chondro-
sarcoma (6%), chondroma (3%), cavernous hemangi-
oma (3%), and metastatic carcinoma (2%). The least
common category is radiographic anomalies such as
retained secretions (6%) and asymmetrical pneumati-
zation (3%). That said, lesions of the petrous apex are
quite rare and represent only about 0.5% of pathology
found on MRI performed for sudden hearing loss, ves-
tibular symptoms, or tinnitus.6
Cholesterol Granuloma
Cholesterol granuloma is a comprehensive term describ-
ing a loculated cystic or solid foreign body reactive
process directed against cholesterol crystals resulting
from the by-products of degraded blood. Terms synony-
mous with cholesterol granuloma include cholesterol,
chocolate, dark brown, or blue dome cysts. Cholesterol gran-
uloma was originally described by Politzer in 1869 as
idiopathic hemotympanum.7 In 1929, Shambaugh
introduced this term to the English literature.8 Choles-
terol granuloma was not reported in the petrous apex
until House and Brackmann described the fi nding in
1982, which was subsequently recognized as a distinct
clinical entity in 1985.9,10 Although these cysts represent
the most common lesion of the petrous apex, they
remain quite rare, with an incidence of less than 0.6
case per million per year.11
Cholesterol granuloma may develop in diverse loca-
tions, including the peritoneal cavity, pleura, and para-
nasal sinus. Cholesterol granuloma originating in the
temporal bone can be divided into two categories: cho-
lesterol granuloma of the tympanomastoid compart-
ment and cholesterol granuloma of the petrous apex.
Each type has distinctive clinical behavior and patho-
genesis. Cholesterol granuloma of the tympanomastoid
compartment is typically painless and preceded by
chronic otitis, is associated with limited pneumatization
in the temporal bones, and rarely erodes bone. Choles-
terol granuloma also frequently forms outside the
middle ear in patients with well-pneumatized temporal
bones who have acute and chronic mastoid infl amma-
tion associated with obstruction of the aditus ad antrum.
This process is often isolated to one or a few mastoid
air cells located toward the mastoid tip or cortex. In
contrast, cholesterol granuloma of the petrous apex is
often found in patients with dry ears and highly pneu-
matized temporal bones and is associated with chronic
deep otic or retro-orbital pain, as well as neuropathy of
cranial nerves V, VI, and occasionally VII. These lesions
extensively erode or expand bone.
The pathogenesis of cholesterol granuloma is
unknown and somewhat controversial. The inciting
event is presumed to be infl ammation and hemorrhage
in an area of compromised aeration and drainage.
Anaerobic breakdown of blood leads to the formation
of cholesterol crystals and a subsequent sterile foreign
body reaction. The granuloma blocks ventilation, and
as a consequence the reaction propagates and results
in growth of the cyst. Thus, maintaining good aeration
of the cyst is imperative to prevent recurrence after
drainage. Curiously, petrous apex cholesterol granu-
loma develops preferentially in hyperpneumatized tem-
poral bones. Extensive pneumatization is possibly
associated with a defect in bone marrow–air cell separa-
tion observed on CT. Highly vascular bone marrow may
provide a continuous source of bleeding to the growing
cyst.12 The supply of blood may also result from newly
described venules located preferentially in the well-
pneumatized petrous apex.13
The contents of cholesterol granuloma demon-
strate a characteristic appearance by both gross observa-
tion and histologic examination. The contents of the
cyst typically include a yellow-brown, viscous glue-like
fl uid with glittering crystals detectable by the unaided
eye. The brown discoloration is thought to be derived
from metabolized hemosiderin. A green-yellow color is
a manifestation of its lipid contents, and the glistening
refractive properties are attributed to the cholesterol
crystals. Histologically, the cyst is characterized by cho-
lesterol crystals surrounded by foreign body reactive
giant cells and fi brous connective tissue containing
round cells, macrophages, and evidence of neovascular-
ization (Fig. 126-3). Cholesterol granuloma does not
contain squamous epithelium or keratin debris. Similar
to congenital epidermoid tumor, cholesterol granu-
loma of the petrous apex is an indolent, slowly growing
cystic tumor eroding bone that eventually becomes
symptomatic once the lesion has extended to involve
the dura and brain, cavernous sinus, carotid artery,
orbit, cranial nerves, or otic capsule.
Congenital Epidermoid Tumors
Congenital epidermoid tumors of the temporal bone
can have their origin in the middle ear, geniculate gan-
glion area, mastoid process, squamous epithelium,
petrous apex, jugular foramen, or posterior fossa. Con-
genital epidermoid tumors are also termed congenital
cholesteatoma, keratosis, primary keratoma, inclusion cyst,
and pseudomucocele, especially when they are located
within the middle ear.14 The histopathology of congeni-
tal cholesteatoma or epidermoid tumor demonstrates a
squamous epithelium–lined cyst fi lled with keratin
debris. There are no additional dermal elements other
than a surrounding outer layer of connective tissue that

1340
Section 15
Temporal Bone
may be moderately vascular. The theory that these
tumors may originally develop from congenital epithe-
lial cell rests was proposed by Von Remak in 1854.15
According to Schuknecht, congenital epidermoid
tumors occur in fi ve sites in the temporal bone: (1) the
petrous apex, (2) the middle ear, (3) the mastoid, (4)
the cerebellopontine angle (CPA), and (5) the external
auditory canal (EAC).14
Congenital epidermoid tumors of the petrous apex
are believed to originate in the foramen lacerum during
cephalic fl exure of the head in early embryonic devel-
opment with trapping of epithelial components. The
cyst grows slowly. Similar to cholesterol granuloma, the
symptoms relate to the space-occupying nature of the
mass. These lesions become symptomatic by progres-
sively compressing the eustachian tube, the trigeminal
nerve, or the IAC and its contents or by stretching the
dura. Congenital epidermoid tumors of the petrous
apex may extend into the middle ear space. These
tumors remain quiescent until they affect the cranial
nerves, brain, orbit, or carotid artery or extend into the
middle ear and cause further hearing loss or otorrhea.
Hearing loss is the most common initial symptom.16
Signs and symptoms of facial nerve involvement char-
acterized by paresis, synkinesis, twitching, and paralysis
are the second most common manifestation of congeni-
tal epidermoid tumors of the petrous apex.17
Establishing that a cholesteatoma of the middle ear
is of congenital origin can be controversial. It is argued
that eustachian tube dysfunction, retraction of the tym-
panic membrane, middle ear infections, and epithelial
migration from insertion of a myringotomy tube are the
forces that trap epithelium in the middle ear space.
However, Michaels clearly demonstrated an epidermoid
formation in the anterior superior middle ear mucosa
in 54% of embryos examined at 10 weeks of gestation.18
With normal development of the temporal bone, the
epidermoid formation should undergo regression by 33
weeks of gestational age. The cause of congenital cho-
lesteatoma is considered to be lack of regression and
continued growth of the epidermoid formation.
The differential diagnosis of a white mass within or
medial to the tympanic membrane also includes con-
genital cholesteatoma of the petrous apex extending to
the middle ear, osteoma of the tympanic ring or scutum,
tympanosclerosis, or an inclusion cyst originating within
the tympanic membrane. It is presumed that congenital
epidermoid tumors are present from birth and con-
tinue to grow. Congenital cholesteatoma of the middle
ear is most commonly identifi ed at 4 years of age, but
the age at diagnosis may range from infancy to the
second decade of life.19 Congenital cholesteatoma of
the middle ear is often diagnosed on routine physical
examination or during evaluation of a child with uni-
lateral or bilateral hearing loss or otorrhea. When
detected early, the epithelial pearl is typically located in
the anterosuperior quadrant of the middle ear space
(Fig. 126-4). Progression of disease with breakdown of
the cyst laterally through the tympanic membrane
results in bacterial colonization and otorrhea. Break-
down within the middle ear permits extension of disease
throughout the middle ear, mastoid, and temporal
bone and results in chronic otitis media and mastoid-
itis. Once recurrent otorrhea and middle ear involve-
ment are established, it is almost impossible to
distinguish congenital cholesteatoma of the middle ear
from acquired cholesteatoma. Congenital middle ear
epidermoid or cholesteatoma may extend into the
petrous apex, but they are not usually as extensive as
primary lesions originating in this area. Furthermore,
growth of a congenital middle ear epidermoid gener-
ally results in early identifi cation because of signs and
symptoms of conductive hearing loss and otorrhea.
Congenital epidermoid tumors of the mastoid are
also proposed to be of embryologic origin. They develop
in patients lacking a history of recurrent otitis media,
eustachian tube dysfunction, and attic retraction. Fre-
quently, epidermoid tumor of the mastoid is manifested
Figure 126-3. Histopathology of cholesterol granuloma. Note the
large cholesterol crystal surrounded by a foreign body reaction with
giant cells, macrophages, and fi brous connective tissue.
Figure 126-4. Congenital cholesteatoma located in the antero-
superior quadrant of the right ear behind an intact tympanic
membrane.

Chapter 126
Cholesterol Granuloma and Congenital Epidermoid Tumors of the Temporal Bone 1341
as hearing loss associated with destruction of the ossicu-
lar chain or perforation of the tympanic membrane. As
it progressively expands into the middle ear, epider-
moid tumors of the mastoid may be diffi cult to differ-
entiate from middle ear cholesteatoma.
Intracranial epidermoid cysts are most commonly
located in the CPA. Congenital epidermoid tumors
account for 6% to 7% of all tumors found in the CPA.
It has been proposed that epidermoid tumors in the
CPA arise from either multipotential embryonic cells or
displaced cells of the otic capsule. They usually become
manifested during the third and fourth decades of life,
with a slight increased predilection in males.20 Because
of the close proximity of the cranial nerves, congenital
epidermoid tumors of the CPA are often accompanied
by symptoms of hearing loss, tinnitus, or vertigo. Facial
nerve signs of twitching and progressive weakness also
occur. Infi ltration of the dura by the tumor triggers the
trigeminal nerve and causes headaches. As the tumor
expands, cerebellar compression becomes manifested
by postural instability, ataxia, and dysarthria. Extension
anterosuperiorly and inferiorly will affect the 5th
through 12th cranial nerves and create increased intra-
cranial pressure, thereby causing headaches, nausea,
vomiting, and potential loss of consciousness.21 Because
of their propensity for causing central neurologic
symptoms and signs, congenital (primary) epidermoid
tumors of the posterior fossa are seen more frequently
by neurosurgeons.
Radiologic Imaging
Contemporary radiologic imaging modalities have
introduced a new era into the diagnosis and manage-
ment of temporal bone pathology. MRI can accurately
defi ne the soft tissue characteristics of these lesions and
detect intracranial extension and involvement of the
carotid artery and sigmoid sinus. CT demonstrates not
only the specifi c pattern of rearrangement and destruc-
tion induced by the lesion but also the anatomic rela-
tionships of the tumor to the otic capsule, middle ear,
carotid artery, and posterior and middle fossae. Despite
the concern for cost containment in contemporary
medicine, this is one area in which obtaining both
imaging formats greatly assists the surgeon in formulat-
ing the diagnosis and planning the operative approach.
Differentiation of lesions of the petrous apex is achieved
by observing characteristic fi ndings on both MRI and
CT (Table l27-1).
Data obtained from the variable stimulating and
capture techniques used with MRI (T1 versus T2 weight-
ing) help determine the nature of the temporal bone
pathology. A bright or hyperintense signal is observed
on unenhanced (non–contrast-enhanced) T1-weighted
images as a result of the presence of proteinaceous
fl uid, blood, or fat. A bright or hyperintense signal on
conventional spin-echo T2-weighted sequences is indic-
ative of fl uid. Because cholesterol granuloma is com-
posed of both methemoglobin breakdown products
with paramagnetic properties and serous fl uid, it is
characteristically bright on both T1- and T2-weighted
images (Fig. 126-5). The use of intravenous contrast
agents such as gadolinium does not provide signifi cant
additional information for this purpose. Although the
capsule of the cyst may demonstrate slight enhance-
ment with gadolinium because of localized neovascular-
ization, it is not usually evident because of the bright
signal already present on the non–contrast-enhanced
T1-weighted image. In addition to establishing the diag-
nosis, MRI is useful to track recurrence of cholesterol
granuloma after surgical drainage. When faced with the
presence of an opacifi ed surgical bed, MRI effectively
differentiates fl uid retention from accumulation of
cystic contents because only recurrence appears bright
on T1-weighted images. Similarly, epidermoid cysts also
have a characteristic appearance on MRI. An epider-
moid tumor is usually isodense relative to brain and
appears hypointense on T1-weighted imaging. However,
similar to cholesterol granuloma, epidermoid tumors
are bright on T2-weighted images. Also similar to cho-
lesterol granuloma, epidermoid cysts do not signifi -
cantly enhance with gadolinium, but slight peripheral
enhancement corresponding to the capsule may be
seen.22 However, if the cyst is infected or infi ltrated with
granulation tissue, it will demonstrate frank contrast
A
B
Figure 126-5. Petrous apex cho-
lesterol granuloma, preoperative
views. A, T1-weighted magnetic
resonance image (MRI), without
contrast enhancement, demon-
strating a bright left petrous apex
lesion (arrow) that is isointense
with fat. B, T2-weighted MRI
showing a bright left petrous apex
lesion (arrow) that is isointense
with
cerebrospinal
fl uid
and
perilymph.

1342
Section 15
Temporal Bone
enhancement. Arachnoid cysts may be diffi cult to dif-
ferentiate from epidermoid; both are fi lled with fl uid
and demonstrate low T1 and high T2 signal. In this
case, fl uid-attenuated inversion recovery (FLAIR)
sequence will help differentiate these two pathologies
because epidermoid cysts are bright on FLAIR se -
quences and arachnoid cysts are not. Chondrosarcoma;
metastasis from breast, kidney, and prostate cancer; and
mucocele are other pathologies of the petrous apex
that are bright on T2-weighted images but can be dis-
tinguished from epidermoid by differential examina-
tion of CT and MRI (see Table 126-1).
Newer MRI pulse sequences have been developed
that further help differentiate pathology in petrous
bone. FLAIR sequences appear similar to T2-weighted
sequences except that free fl uid such as cerebrospinal
fl uid (CSF) is suppressed. Proteinaceous fl uid, as seen
in most air cell pathology, remains bright. Most tumors,
including epidermoid tumors, will be bright on FLAIR
sequences, just as they are on T2-weighted sequences.
Diffusion-weighted imaging is a method of evaluating
the brownian motion of water molecules. Restricted
water diffusion, thought to be due to the waxy consis-
tency of epidermoid tumors, results in high signal
intensity (Fig. 126-6).
CT scanning provides signifi cant additional infor-
mation regarding the characteristics of petrous apex
lesions. Cholesterol granuloma and cholesteatoma both
appear as a smoothly marginated expanding mass. They
appear isointense or mildly hypointense relative to
nearby brain on soft tissue windowing. MRI with intra-
venous contrast does not show signifi cant enhancement
or provide additional information unless the cyst is
infected or infi ltrated by granulation tissue. However,
data obtained from a bone window algorithm are most
useful. The presence of temporal bone pneumatization
suggests that the lesion is probably a cholesterol granu-
loma. Congenital cholesteatoma is thought to inhibit
normal temporal bone aeration, development, and thus
pneumatization. The edges of cholesteatoma are scle-
rosed, eroded, and scalloped. Capsular calcifi cation is
occasionally seen. The size and location of the expan-
A
B
Figure 126-6. Magnetic resonance images of left petrous epidermoid tumor. A, Fluid-attenuated inversion recovery sequence showing a
bright signal in the petrous and lateral temporal bone (arrow). This excludes arachnoid cyst from the differential diagnosis. B, Diffusion-weighted
image showing a bright signal in the same location, which strongly suggests it to be consistent with an epidermoid tumor (arrow).
Table 126-1
CHARACTERISTIC RADIOLOGIC FINDINGS OF CHOLESTEROL GRANULOMA AND CONGENITAL
EPIDERMOID TUMOR
Lesion
MRI
CT
T1-Weighted
Contrast
Enhancement
T2-Weighted
Bone-Eroded
Margin
Contrast Enhancement
Cholesterol granuloma
Hyperintense
No
Hyperintense
Smooth
Occasional rim enhancement
Congenital epidermoid
tumor
Hypointense
No
Hyperintense
Smooth
No
CT, computed tomography; MRI, magnetic resonance imaging.

Chapter 126
Cholesterol Granuloma and Congenital Epidermoid Tumors of the Temporal Bone 1343
sile lesion are clearly demonstrated. The relationship of
the lesion or tumor to the otic capsule, ossicles, facial
nerve, IAC, internal carotid artery (ICA), jugular bulb,
and posterior fossa can be defi ned (Fig. 126-7). A bone-
windowed CT scan in combination with MRI and MR
angiography provides a road map for planning the
operative approach.
PREOPERATIVE EVALUATION
Patients with congenital cholesteatoma or cholesterol
granuloma will have had a presumptive diagnosis made
that was based on initial signs, symptoms, and radio-
logic fi ndings. Patients are questioned regarding their
otologic history and previous surgical procedures. It
should be determined whether they have had otorrhea,
hearing loss, tinnitus, vestibular symptoms, facial paresis
or twitching, diplopia, amaurosis fugax, or transient
ischemic attacks. They are also asked about the location
and severity of pain.
A complete neuro-otologic and head and neck
physical examination is performed. The status of the
tympanic membrane and middle ear space is evaluated.
Facial and corneal sensations are tested for evidence of
trigeminal nerve involvement. The full range of extra-
ocular motion should be confi rmed. Facial nerve func-
tion is carefully examined to look for evidence of
fasciculation, weakness, or synkinesis.
A complete assessment of hearing consisting of air
and bone conduction and speech audiometry is
obtained. It is important to evaluate auditory function
in both the involved and uninvolved ears. Operative
management may necessitate closing the ear canal,
which results in maximal conductive hearing loss. On
rare occasion, cochlear function may have to be sacri-
fi ced to completely remove an invasive cholesteatoma
or congenital epidermoid tumor. Therefore, the con-
tralateral ear should have normal hearing or be suitable
for aural rehabilitation with amplifi cation.
Radiologic imaging is critical in diagnosing and
planning treatment of cholesterol granuloma and con-
genital epidermoid tumors. These two pathologic proc-
esses affecting the temporal bone are similar in that
both CT and MRI are necessary to formulate the diag-
nosis and treatment plan. MRI defi nes the differential
diagnosis based on the characteristic signals generated
by the soft tissue and fl uid content of the tumor or cyst.
The tumor or cyst and the pneumatization tracts of the
temporal bone are identifi ed by bone-windowed CT. A
well-developed pneumatized temporal bone is more
amenable to exteriorization of epidermoid tumor and
to drainage and aeration of cholesterol granuloma than
a sclerotic temporal bone is. The location of the pathol-
ogy in the petrous apex in relation to the sphenoid
sinus should be examined. Expansion anteriorly toward
a large sphenoid sinus allows the surgeon to consider a
transnasal-transsphenoidal approach for management
of the lesion. The relationship of the jugular bulb to
the facial nerve and otic capsule is critical when a drain-
age procedure inferior to the otic capsule is likely. A
high and lateral jugular bulb obstructs retrofacial infra-
labyrinthine access to the petrous apex. In this situa-
tion, axial and coronal images are carefully reviewed to
determine whether the aeration and anatomy will
permit a transcanal infracochlear approach.
The surgeon may also obtain a CT scan with fi du-
cial markers in anticipation of performing surgery with
image guidance technology. Intraoperative localization
from an anterior approach is fairly accurate because the
skull base contains numerous bony landmarks that
allow registration of known anatomic sites. However,
despite proposed intraoperative accuracy to less than
2 mm,23 image guidance is not widely used in lateral
skull base approaches because of technical problems
with accurate registration and the fact that a 2-mm
error may be catastrophic in the small operative win -
dow afforded by the infracochlear or infralabyrinthine
approaches.
Large tumors within the petrous apex that approxi-
mate or encase the carotid artery warrant further
evaluation. MR angiography is useful in preoperative
planning to evaluate the anatomic relationship with the
vessel. It must be determined whether blood fl ow from
the contralateral side through the circle of Willis is
adequate if it is expected that the ipsilateral carotid
artery may be retracted, temporarily occluded, or
resected during the procedure. Balloon test occlusion
of the ipsilateral ICA provides reliable data for predict-
ing the patient’s tolerance to ICA manipulation or sac-
rifi ce; however, 15% of patients with normal collateral
supply may still experience a stroke if the artery is
sacrifi ced.24
It is important to reach a presumptive preoperative
diagnosis based on physical examination and radiologic
imaging fi ndings to provide the surgeon with the ability
Figure 126-7. Bone-windowed computed tomography scan reveal-
ing an expansile left petrous apex lesion with smooth margins and
isointense with brain (large arrow), consistent with cholesterol granu-
loma. Note the relationship to the carotid artery (small arrow).

1344
Section 15
Temporal Bone
to plan both the surgical approach and optimal man-
agement of the lesion. The specifi c surgical approach
depends on the presumed pathology; the location of
the tumor or cyst; the status of hearing, balance, and
facial nerve function; the likelihood of encountering
CSF; and the integrity of the carotid artery and the
middle and posterior fossa dura. Depending on
the nature, location, and extent of the pathology, the
likelihood of encountering CSF, the patient’s hearing
status, and facial nerve involvement, the surgeon can
anticipate whether total resection or exteriorization is
advisable. Meticulous preoperative planning allows
more aggressive and complete resection of recurrent
tumors, thereby decreasing the need for salvage
surgery.
The need for intraoperative facial nerve monitor-
ing is dictated by the proximity of the pathology to the
facial nerve and the likelihood that dissection, drain-
age, or resection of the tumor or cyst may place the
facial nerve in jeopardy. As with most otologic proce-
dures performed with the patient under general anes-
thesia, paralytic agents are avoided. General anesthesia
is maintained with inhalation agents, narcotics, and
hypnotics. Blood is typed and cross-matched for transfu-
sion or collected for autotransfusion if the carotid artery
is to be manipulated. The goals and risks of the proce-
dure along with the limited alternatives are reviewed
with the patient and family.
SURGICAL MANAGEMENT
Cholesterol Granuloma
Management of cholesterol granuloma and epidermoid
tumor is different. In contrast to a true cyst, the walls
of a cholesterol granuloma lack an epithelial lining. It
is therefore unnecessary to remove the capsule entirely
to successfully prevent recurrence or expansion of the
granuloma. As long as adequate drainage and ventila-
tion are maintained, the cyst should not recur. That
said, surgery is not always warranted. Because of
the indolent clinical course of cholesterol granuloma,
small, asymptomatic, or inaccessible cysts with tolerable
symptoms can be managed expectantly with frequent
clinical follow-up and serial radiologic imaging. Several
published series include long-term follow-up of patients
managed expectantly, and quite often the clinical symp-
toms and cyst dimensions remain stable.11,25
The specifi c surgical treatment of cholesterol gran-
uloma of the petrous apex depends on both the patient’s
hearing status at the time of surgery and the anatomic
relationship of the tumor with surrounding neuro-
vascular structures. For patients with nonserviceable
hearing, good surgical exposure becomes more impor-
tant than preservation of residual cochleovestibular
function (Table 126-2). Thus, when sensorineural
hearing loss is greater than 70 dB and word discrimina-
tion is less than 30%, cholesterol granuloma is drained
via a translabyrinthine or combined translabyrinthine-
transcochlear approach. The translabyrinthine ap -
proach provides greater exposure and drainage than
the retrofacial infralabyrinthine approach alone does.
Dissection through the temporal bone superior and
inferior to the IAC increases ventilation to the petrous
apex. If additional exposure is needed, the cochlea is
sacrifi ced.
There are two management philosophies for treat-
ment of patients with serviceable hearing. Some sur-
geons argue that total excision of the cyst wall best
prevents reaccumulation of the cyst’s contents. The
approach can involve a combination of middle, poste-
rior, or infratemporal fossa techniques for access.
Recurrence rates are low, and stenting is not necessary
when the entire cyst is removed.25 The drawback is the
Table 126-2
DECISION MAKING FOR MANAGEMENT OF CHOLESTEROL GRANULOMA AND
EPIDERMOID TUMOR
Cholesterol Granuloma
Good Hearing
Poor Hearing
Asymptomatic/Tolerable Symptoms
with Diffi cult Access
Complete Excision
Drainage
With or without Stent
No Stent
With Stent
Middle + posterior fossa
Middle fossa +
transpetrosal
Infracochlear
Infralabyrinthine
Middle fossa
Transsphenoidal
Translabyrinthine
Transcochlear
Observe
Serial magnetic resonance imaging or
computed tomography
Epidermoid Tumor
Preservation of Hearing
Sacrifi ce of Hearing
Canal wall down mastoidectomy
Preauricular subtemporal + infratemporal
Middle fossa + occipital
Translabyrinthine
Transcochlear
Transotic

Chapter 126
Cholesterol Granuloma and Congenital Epidermoid Tumors of the Temporal Bone 1345
possibility of entry through the dura with subsequent
potential complications, including CSF leak and chemi-
cal meningitis. However, most authors, including our-
selves, favor continuous drainage of the cyst into the
pneumatized mastoid or middle ear cavities with place-
ment of a permanent stent. Such drainage can be
accomplished through the nose into the sphenoid sinus
and nasopharynx. The transtemporal approaches of
choice are the transmastoid infralabyrinthine and the
transcanal infracochlear. Since 1990 the transcanal
infracochlear approach has been supplanting the infra-
labyrinthine approach because the infracochlear
approach for drainage of the cyst is achievable even in
the presence of a high jugular bulb.26 The success and
complication rates of the two surgeries are similar.
Overall, one can expect symptomatic relief in 80% of
patients with minimal complications.27 The drawback of
long-term drainage with permanent stenting is a high
recurrence rate of 15% to 60%, usually associated with
obstruction of the stent.28 The older literature described
the highest recurrence rate of 60% in patients drained
via a transethmoid, transsphenoid approach.28 A recent
retrospective series by Brackmann and Toh is very
encouraging for transtemporal drainage procedures; a
recurrence rate of only 3% was reported for cases in
which a stent was placed.27
A middle fossa or keyhole middle fossa approach
may produce adequate exposure but is not recom-
mended because it is technically diffi cult to maintain
cyst ventilation/drainage into the mastoid cavity or
eustachian tube via stenting.29 However, if establish-
ment of drainage is successful, recurrence rates
are similar to those of the infralabyrinthine approach.27
A middle fossa approach with stenting is a valid
option.
Transsphenoid drainage is an alternative to con-
sider in cases in which the cholesterol granuloma abuts
the posterior wall of the sphenoid sinus. This tech-
nique, originally described by Montgomery in 1977, was
performed through a contralateral external ethmoidec-
tomy approach.30 Knowledge of the surgical anatomy
plus the use of contemporary instrumentation such as
endoscopic sinus telescopes permits endonasal access
to the petrous apex tip directly through the sphenoid
sinus. However, inability to maintain a patent fi stula
through this approach may result in recurrence of the
cystic lesion. It is possible to enhance drainage of the
cyst when intraoperative navigation is used in conjunc-
tion with endoscopy; more aggressive drainage may be
achieved while avoiding damage to vital structures lying
behind the sinus wall.31
The development of minimally invasive endoscopic
neurosurgery may provide a valid option in the near
future for resection of petroclival tumors. The expanded
endonasal approach provides excellent access to petrous
apex tumors and has been applied to drainage proce-
dures for cholesterol granuloma and other tumors of
the anterior petrous bone. At this juncture the lack of
suffi cient follow-up makes it diffi cult to predict the
appropriateness of this type of approach for tumors of
the petrous apex. The procedure includes bilateral
sphenoidotomy and posterior maxillary antrostomy
with drilling of the petrous bone encasing the ICA.
Lateral mobilization of the carotid artery can be per-
formed to gain greater access to the petrous apex. Mar-
supialization of the granuloma into the sphenoid is
performed. Kassam and colleagues, experienced in
resection and debulking of petroclival tumors via the
expended endonasal approach, propose to use this
method for resection of cholesteatoma in addition to
cholesterol granuloma.32 It remains to be seen whether
the newer techniques of endoscopic nasal surgery will
provide more permanent drainage and lower the inci-
dence of recurrence.
Epidermoid of the Petrous Apex
In contrast to cholesterol granulomas, epidermoid
tumors must be excised completely; if tumor is left
behind, the cyst will recur. However, the tumor is often
tightly adherent to surrounding neurovascular struc-
tures and dura. It is believed that microrupture of the
capsule may occur and induce an infl ammatory reac-
tion that binds the tumor to surrounding structures.
Complete resection bears considerable risk because epi-
dermoid tumors frequently encase vital structures. At
the time of initial examination by an otolaryngologist,
cranial nerves are involved in the majority of patients
(85%). Hearing loss, vestibular defi cits, and facial weak-
ness are the most common, followed by defi cits in func-
tion of cranial nerves V and VI. In addition to affecting
nerves, tumors often involve major vessels (80%),
including the carotid artery in 50% of cases.33
It is important to completely excise the tumor
despite its intimate involvement with neurovascular
structures. Recurrence is likely when the surgeon tries
to preserve cranial nerve function and leaves epider-
moid lining in these areas. Ultimately, cranial nerve
defi cits are not spared because salvage procedures will
probably result in additional morbidity and sacrifi ce. In
summary, the goal of resection of epidermoid tumors
is safe but complete removal of tumor, which is facili-
tated by thorough preoperative planning and excellent
surgical exposure.
For wide exposure of the petrous apex, we recom-
mend the translabyrinthine approach. If the surgeon
needs good exposure of the carotid artery, conversion to
a transcochlear approach is possible. In the transotic
procedure described by Fisch, the EAC is closed, the
tympanic membrane and ossicles are removed, and
the facial nerve is transposed anteriorly.34 In the trans-
cochlear approach originally described by House and
colleagues, the facial nerve is displaced posteriorly.35
The drawbacks of these approaches are sacrifi ce of
cochlear and vestibular function, risk of CSF leak, and
facial nerve palsy secondary to mobilization of the facial
nerve to improve access, which may result in facial weak-
ness in up to 75% of cases.36 To avoid such complica-
tions, some surgeons advocate a middle fossa approach.
In the presence of intact cochlear function, we
prefer to manage congenital epidermoid tumors with a
canal wall down procedure if adequate exposure and

1346
Section 15
Temporal Bone
exteriorization of disease can be achieved. This requires
a well-pneumatized temporal bone with a high tegmen
tympani. Unfortunately, congenital epidermoid tumors
often originate in poorly pneumatized, contracted tem-
poral bones, thus making it diffi cult to adequately exte-
riorize the tumor with the cochlea intact. Exposure
is enhanced by sacrifi cing the cochlea and therefore
hearing.
Occasionally, wide marsupialization of an epider-
moid tumor is inadequate or unsafe. Total resection
becomes necessary when exteriorization results in a CSF
leak, when the dura or the carotid artery is exposed and
at risk for desiccation in an open cavity, or when the
opening of the marsupialized epidermoid cavity results
in a very narrow, circuitous tract that makes postopera-
tive examination and débridement diffi cult. In this situ-
ation, the entire tumor and its epithelial lining are
removed and the wound is obliterated.
Surgical Techniques
Tympanomeatal Approach for Congenital Middle
Ear Cholesteatoma
This approach is directed at isolated congenital middle
ear cholesteatoma characteristically located in the
anterosuperior quadrant of the middle ear. The patient
is positioned supine on the operating room table with
the head turned toward the contralateral ear. Using the
operating microscope, the ear canal is injected in four-
quadrant fashion with 2% lidocaine (Xylocaine) with
1:100,000 epinephrine. In young children, the anes-
thetic solution is diluted by half. After adequate local
anesthesia and vasoconstriction have been achieved, a
tympanomeatal fl ap based inferiorly is elevated. An inci-
sion is made lateral to the annulus from the 3- to the
9-o’clock positions. The tympanomeatal fl ap is elevated
to enter the middle ear in the posterosuperior quad-
rant. The tympanic membrane, including the pars fl ac-
cida, is carefully dissected off the scutum and over the
short process of the malleus. A sharp sickle knife or
curved pick is used to incise the thin layer of mucoperi-
osteum along the posterior aspect of the malleus handle.
The tympanic membrane is retracted inferiorly toward
the umbo to expose the epithelial tumor (Fig. 126-8).
The extent of inferior dissection of the tympanic mem-
brane is dictated by the size and location of the mass.
Using suction, right-angled picks, and curved excava-
tors, the tumor is carefully freed from its attachments
to bone and ossicles and removed (Fig. 126-9). Great
care is taken to remove the epithelial pearl intact and
avoid spillage of keratin in the middle ear and mastoid.
Once the pearl is removed, the ossicular chain is exam-
ined for integrity and mobility, and the tympanic mem-
brane is carefully inspected for a tear or perforation. If
a defect is identifi ed, it is repaired with a small piece of
wet Gelfoam or an underlay connective tissue graft
placed medial to the area. The tympanic membrane is
returned to its anatomic position. A silk sleeve is placed
over the tympanic membrane and supported by cotton
balls with ointment. The ear canal may also be packed
with Gelfoam moistened with antibiotic ear drops.
Figure 126-8. An inferiorly based tympanomeatal fl ap attached to
the umbo exposes the encapsulated keratin pearl.
Figure 126-9. Right-angled picks and excavators are used to
remove the keratin pearl intact.
More extensive primary cholesteatoma occupying
the epitympanum may require additional exposure via
a cortical mastoidectomy. Drilling is continued anteri-
orly through the root of the zygoma to expose the body
of the incus and head of the malleus. Tumor located in
this area frequently creates a conductive hearing loss.
Removal of the incus and possibly the head of the
malleus may be necessary to obtain access to the ante-
rior epitympanum. The canal wall may have to be taken
down to exteriorize any epitympanic disease that cannot
be completely removed. Reconstruction of the ossicular
chain is reviewed in Chapter 114. When the epithelial
lining of the cyst ruptures into either the middle ear or
the EAC, primary cholesteatoma of the middle ear
becomes diffi cult to distinguish from acquired chronic