Atlas-of-Neurosurgical-Techniques-Spine-and-Peripheral-Nerves

Table9-1
Preoperative Planning
9
Extended Maxillotomy Approach for High ClinicalPathology
81
Exposure of Maxilla and Nasal Cavity
Computed tomography
and magnetic
resonance
imaging
scans of skull base
and
cervical
spine
Panorex ofthe
mandible
and
maxilla
Anteroposterior/lateral
cephalograms
Possible angiogram
Dental consultation
Dental impressions
Interdental splint
Typedand crossed
for two
units
packed
red
blood
cells
arereviewed.Dental impressions are mandatory on all
patientsin the unfortunate
event of maxillary
necrosis. An
interdentalsplint is made from the dental impressions
by a
prosthodontistto prevent malocclusion
postoperatively.
The
patientshouldbe typed and crossed for two units of packed
redbloodcells. Preoperative
culture
of the oral and nasal
floraisnotroutinely performeds (Table 9-1).
. SurgicalTechniques
Tracheostomy
Anelectivetracheostomy is performed
at the beginning
of
theprocedure.Ifthe patient is at risk for brain stem/spinal
cordcompressionwith neck extension, an awake tra-
cheostomyisperformed under local anesthesia.
Otherwise,
thepatientis routinely intubated
prior to tracheostomy.
Electivetracheotomy
has several
advantages.
The tra-
cheostomyremoves the interference
by a nasal endotra-
chealtube.Interdentalfixation is required at the end of the
procedure;therefore, an oral endotracheal
tube is not an
option.Apatient with a tracheostomy
is unable to perform
aValsalvamaneuver, thereby decreasing
the risk of dehis-
cenceofthe pharyngotomy suture line and cerebrospinal
fluid(CSF)leakage.Ifthe patient requires posterior cervical
stabilizationat alater date, the tracheostomy allows the pa-
tientobeanesthetized easily for this second procedure. If
not,thetracheostomyis removed as soon as mechanical
ventilationis not required.
PatientPositioning
Aftertracheostomy, the bed is rotated
180 degrees.
During
stabilizationwith a Mayfield head holder, the patient
may
beawakenedto assess worsening
of brain stem/spinal
cord
compressionsymptoms during
positioning.
If the patient
hasastablecervical spine, a shoulder
roll is placed
to aid
neckextension.AC-arm fluoroscope is positioned over the
chest;thiswill be moved superiorly
after the maxillary
os-
teotomiesand pharyngotomy
are completed.
Cottonoids
soakedwith oxymetazoline
are placed in each nasal cavity
fordecongestion.The face is prepped
with Betadine
solu-
tiononly,anda Betadine-soaked sponge is place intraorally.
Erich arch bars are anchored to the maxilla and mandible
with 24-gauge wires. The arch bars are used to place the
teeth in interdental fixation at the end ofthe procedure. The
maxillary gingivobuccal sulcus, nasal floor and septum, and
palate are injected with 1/2%lidocaine with epinephrine
1:200,000. Leaving a 1 cm cuff, an incision is made with a
guarded needlepoint cautery in the gingivobuccalsulcus be-
tween the left and right second premolars (Fig. 9-2). The
parotid duct papillae are carefullyavoided.
The soft tissues of the maxilla are elevated superiorly in
the subperiosteal
plane to the level of the infraorbital
nerves, which should be clearly identified (Fig. 9-3). Pos-
terolaterally, the dissection is performed to the maxillary
tuberosity. Using Cottle and curved Freer elevators, the
nasal mucosa is elevated from the inferior meatus, nasal
floor, maxillary crest, and nasal septum bilaterally. Thispre-
vents lacerating the nasal mucosa during osteotomies and
decreases the risk of nasal airway problems postoperatively.
The nasal septum is separated from the maxillary crest us-
ing a flat or U-shaped osteotome (Fig. 9-4). Alternatively,
the cartilaginous septum can be reflected laterally ("swing-
ing door" technique), and the bony septum can be removed
for access to the sphenoid sinus.
Preparation for LeFort IOsteotomy
The markings for the LeFort Iosteotomy are made above the
level of the dental roots. The canine root is easily palpated
and the panorex of the maxilla will aid in placement. The
marking extends bilaterally from the piriform aperture just
below the attachment of the inferior turbinate to the lateral
(zygomaticomaxillary)buttress of the midfacial skeleton.
Titanium miniplates with 2.0mm screws are used for rigid
fixation ofthe osteotomies during closure.Typically,four-hole
L-shaped plates are placed over the medial and lateral but-
tresses, the structural "beams" ofthe face(Fig.9-5). Tomain-
tain exact dental occlusion postoperatively, the plates and
screws are placed into position prior to osteotomy and then
removed. It is important to keep the screws and plates in ex-
act orientation on the back table. The reciprocating saw used
for osteotomy will remove 1 to 2 mm of bone. Ifthe edges are
touching at the end of repair, malocclusion may occur. Pre-
plating the horizontal osteotomy ensures that the small gap
will be maintained for perfect occlusionpostoperatively.
Palatal Split
The hard and soft palate is split prior to LeFort osteotomy
while the maxilla is stable. ADingman retractor is placed to
open the oral cavity (Fig.9-6). An incision is marked in the
midline hard and soft palate. It deviates laterally to either
side of the uvula to maintain the shape of this delicate
structure. A full-thickness incision with a no. 11 blade is
made in the soft palate to the posterior aspect of the hard
palate (Fig.9-7). The incision is continued anteriorly in the
oral mucosa of the hard palate to the medial incisors. The
oral mucosa is elevated a few millimeters from the hard
palate bilaterally to prevent maceration during midline

82
OccipitocervicalJunction:AnteriorApproach
Figure 9-2
Gingivobuccal
incision for maxillary exposure. Note arch bars and location
of parotid duct papilla.
----
l
Figure 9-3
Exposure of maxilla with
preservation
of infraorbital
nerves. The nasal mucosa is carefully
elevated.
The dashed line represents the
location of the LeFort Iosteotomy.

9
ExtendedMaxillotomy Approachfor HighClinicalPathology
83
Figure9-4
Thecartilaginous and bony nasal septum is separated from the maxillary crest with an osteotome.
------
Figure9-5
Preplating of medial and lateral buttresses
prior to osteotomy.
Depending on the anatomy of the tooth roots. the orientation
of the
medialbuttress
plates
may vary.

84
OccipitocervicalJunction:AnteriorApproach
1
Figure 9-6
Intraoral exposure with Dingman retractor. The dashed line indicates the palatal incision.
Figure 9-7
Palatal incision with all three layers of the soft palate incised.

9
Extended Maxillotomy Approach for HighClinicalPathology
85
osteotomy.Asthe nasal mucosa is retracted, a midline os-
teotomyismade in the hard palate using a reciprocating
sawfromposterior to anterior up to the medial incisors
(Fig.9-8). To avoid damage to the tooth roots, a fine os-
teotomeis used to complete the osteotomy between the
medialincisorsto the piriform aperture (Fig. 9-9).
LeFortIOsteotomy
TheLeFortIosteotomyisalso performed with the reciprocat-
ingsaw.Again.the nasal mucosa is protected. The saw is place
alongtheposterolateralwallofthe maxilla,and the osteotomy
isperformedin a medial direction to the piriform aperture
(Fig.9-9).Itisvery important to make the cut exactly on the
markingsand between the drill holes for the titanium screws.
Eachmaxillaryhalf remains attached to the skull base via
thepterygoidplates.Awide curved osteotome is placed pos-
teriorlybetween the maxillary tuberosity and pterygoid
plates,anddetachmentfrom the skull base is performed. An
indexfingerofthe opposite hand is placed intraorally in the
retromolarareato palpatecompletion of the osteotomy (Fig.
9-10).Eachmaxillaryhalfis then down-fractured with Rowe
maxillarydisimpactionforceps to complete the skull base
separationand fracture the posterior maxillary sinus wall
(Fig.9-11).The maxillary halves are gently retracted
later-
ally;theironlyblood supply is the greater palatine arteries.
AnangledCrockardpharyngeal retractor is used to separate
the maxillary halves. This
allows
exposure
of
the
nasopharynx
andposteriorpharyngeal wall (Fig.9-12).
VerticalPharyngotomy
Thetubercleof(1 is palpated and positioning is confirmed
byfluoroscopy.Amidline linear pharyngotomy is made in
theposteriornasopharyngeal and oropharyngeal mucosa to
Figure 9-8
Midlineosteotomy of the hard palate with a reciprocat-
ing saw.Noteprotection ofthe nasalmucosawitha retractor.
the body of (3. The incisionis carried to the level of the
white. shiny prevertebral fascia. At this point. (2, (1, and
clivus are covered with several ligaments (Fig.9-13). Expo-
sure isverified with fluoroscopy,and the case is turned over
to the neurosurgery team.
Figure9-9
LeFortIosteotomy performed after midline palatalsplit.

86
OccipitocervicalJunction:AnteriorApproach
,.
'~f
B
Figure 9-10
Separation of maxilla from skull base with curved osteotome.
(A) Intraoral view. (8) Lateral view.
A

9
ExtendedMaxillotomy Approachfor HighClinicalPathology
87
Figure 9-11 Placement of Rowe maxillary disim-
paction forceps for down-fracture
of each maxillary
half.
Figure9-12
Separation of maxillary halves with exposure of posterior pharynx and nasopharynx.

88
Occipitocervical
Junction:
Anterior Approach
..
Figure 9-13
Exposure after posterior pharyngotomy.
. Conclusion
The extended maxillotomy approach to the skull base pro-
vides excellent exposure of the midline craniovertebral
junction from the superior clivus to the body of the third
cervicalvertebra(C3).Accesscanbeextendedsuperiorlyto
the sphenoid sinus by removing the bony nasal septum.
References
1.
Cocke EW. Robertson
JH. Robertson
JT. et al. The extended
maxillo-
tomy
and subtotal
maxillectomy
for excision
of skull base tumors.
Arch Otolaryngol
Head Neck Surg 1990;116:92-104
2.
James D. Crockard HA.Surgical access to the base of skull and upper cer-
vical spine by extended maxillotomy. Neurosurgery 1991 ;29:411-416
3.
Catalono
PJ. Biller HF. Extended
osteoplastic
maxillotomy:
a versatile
new procedure
for wide access to the central skull base and infratem-
poral fossa. Arch Otolaryngol
Head Neck Surg 1993;119:394-400
When compared with the transoral approach. the extended
maxillotomy approach is technically more difficult; extends
the operative time by approximately
6 hours; and has
greater potential morbidity. It is critical that the surgeons
identify the exact extent of the lesion preoperatively to de-
termine the appropriate approach.
4.
Williams
WG. Lo LJ.Chen YR.The LeFort I-palatal
split approach
for
skull base tumors:
efficacy. complications.
and outcome.
Plast Recon-
str Surg 1998;102:2310-2319
5.
Crockard
HA. The transmaxillary
approach
to the clivus. In: Sekhar
LN.Janecka
IP.eds. Surgery of Cranial Base Tumors. New York: Raven;
1993:235-244

10
RetropharyngealApproach to the
OccipitocervicalJunction
DennisE.McDonnell and Steven J. Harrison
. Indications
. Contraindications
. Advantages
. Disadvantages
. Patient Selection
. Objectives
. Planesofthe Cervical Fascia
Theretropharyngealapproach is an alternative
for the tran-
soralapproachto the ventral occipitocervical
junction.
It is
designedto expose the basiocciput
of clivus, anterior
rim of
foramenmagnum, and rostral cervical segments
of C1-C4,
avoidingthe bacteriallycontaminated environment of the
oralcavityandpharynx.This exposure allows relief of basi-
larimpressionand compression
with broader and safer lati-
tudesthan those available via the transoral
route. Indica-
tionsforthisprocedure,pathological processes, anatomical
perspectives,technical aspects,
and complications
of this
approachalong with the author's
clinical
experience
are
discussedin this and the following chapter.
. Indications
. Basilarimpression
. Occipitocervical osseous
anomalies
. Rheumatoid arthritis
. Pyogenic retropharyngeal
abscesses
. Chordomas
. Meningiomas
. Neurofibromas
. Fractures (chronic)
Thenaturalhistory of basilar impression is progressive
myelopathythat leads to quadraparesis and respiratory
Reprintedwith permission from Thieme Medical Images from
'CervicalofCraniovertebral Junction."
.
Surgical Techniques
Anesthesia
Positioning
Incision
Approach
Superficial Anatomical landmarks
Deep Anatomical landmarks
Preserving the Anterior Archof C1
.
ClinicalExperience
paralysis and ultimately death. This sad course can be
averted by surgical decompression
and stabilization
of
the occipitocervical junction. The pathological compressive
lesion may be posterior or anterior to the cervicomedullary
junction of the neural axis. Chronic"glacial"instability is also
an integral part of the pathological process. Etiologymay be
developmental, genetic, or acquired. The acquired lesions are
inflammatory, neoplastic, or traumatic in origin.1These are
dynamic anatomical abnormalities that are diagnosed and
imaged by x-rays, computed tomography (CT),and magnetic
resonance imaging (MRI)of the occipitocervical junction.2-4
Occipitocervical osseous anomalies of developmental
origin arise from defective segmentation in embryonic pre-
cursors of the first four sclerotomes. Hypoplasia of the dens,
atlantoaxial instability, and chronic dislocation may occur
as developmental abnormalities in congenital conditions
such as Down syndrome (trisomy 21). Neurodysgenetic
lesions such as Chiari Iand syringomyelia may be seen upon
diagnostic imaging of developmental osseous abnormalities
in this region.
Rheumatoid arthritis is the most common inflammatory
condition affecting this region. The inflammatory dissolu-
tion of craniovertebral
support ligaments, including the
transverse ligament, which secures the dens to the anterior
arch of the atlas, leads to instability. Concomitant bone ero-
sion of atlantoaxial lateral masses and occipital condyles
allows cranial settling and rostral migration of C2 into the
foramen magnum and more ventral impingement on the
neural axis.5.GOsteoporosis also accelerates subluxation of
these bone structures and impedes surgical attempts of
arthrodesis to treat this condition. Pyogenic retropharyn-
geal abscesses can cause bone and ligament destruction
89

90
OccipitocervicalJunction:AnterolateralApproach
resulting in ventral neural compression. Usually the com-
pressive process is due to bone destruction, instability, and
cranial settling, but chronic granulomatous lesions and pan-
nus also produce direct mass effect upon the neural axis.7
Neoplasms cause bone destruction
and direct neural
compression in this region. These may be primary or
metastatic tumors of the bone or neural tumors, which can
be extra-axial or intra-axial. Chordomas tend to occur in
this location as well as destructive metastatic tumors to the
vertebral body of C2 and/or adjacent segments. Menin-
giomas arising from the clivus, anterior rim of foramen
magnum, or ventral spinal canal are treacherous in this
region. Neurofibromas of Recklinghausen's disease causing
ventral neural compression in this location also challenge
the patient with progressive paralysis.
Fractures tend to occur because the occipitoatlantoaxial
complex is a transition zone and allows for half of head
movement in flexion, extension, and rotation. Fractures
involve ligamentous support structures as well as bony
elements, leading to craniovertebral instability. Nonunion
fractures of the dens and subluxation of the atlas on the axis
may result in ventral compression of the neural axis causing
chronic pain and progressive myelopathy. The os odon-
toideum is an independent bone rostral to the body of C2
but separated from it and located in the position of the dens.
It is a chronic unstable condition due either to nonunion of
an odontoid fracture, which occurred in childhood, or a con-
genital failure of the ossification centers of the dens to as-
similate with the body of the axis. The orthotopic type is in
the normal position of the dens; the dystopic type is more
rostrally located and related to the clivus. I
Symptoms and signs of neural compression at the occipi-
tocervical junction are multiple and varied. They are due to
direct compression of the medulla, spinal cord, cranial
nerves, cervical roots, and/or vascular structures (arterial,
capillary, or venous) that supply these structures. Congeni-
tal lesions may be associated with external physical charac-
teristics such as short neck, cervical web, low hairline,
torticollis, and limited neck movement. Myelopathy is usu-
ally present but of variable severity. It can be manifested by
early fatigue in ambulation to monoparesis, hemiparesis, or
quadriparesis. Central cord myelopathy is a common pre-
sentation with upper extremity weakness and relative spar-
ing of lower extremity strength. Gait disturbance
with
clumsiness
and
stumbling
is frequent.
Hyperreflexia,
clonus, extensor planter responses, and a Hoffmann re-
sponse are also frequent findings. Posterior column distur-
bance with impaired joint and position sense is much more
common than numbness and hypalgesia unless the process
is advanced. Dysesthesias and cold sensations in the hands
are noticed early in the process.s Urinary hesitancy and fre-
quency imply myelopathic bladder disturbance. Respiratory
disturbance and intermittent
sleep apnea occur and are
particularly ominous. Periods of acute apnea may herald
rapid neurological deterioration and are life threatening.
Cranial nerve dysfunction can result in dysphagia, palatal
paralysis, shoulder weakness, and loss of hearing. Nystag-
mus can occur from brain stem compression. The most
common symptom is suboccipital pain that radiates to
the vertex. Characteristically, head movement aggravates
the pain. Pain is particularly severe for patients
with
rheumatoid cranial settling and patients with traumatic or
neoplastic lesions involving the ligamentous instability or
bone destruction.9
Patients presenting with findings that suggest a lesion in
the occipitocervicaljunction should have plain x-rays ofthe
skull and cervical spine, including an open-mouth view.
Bone assimilation defects, platybasia, basilar invagination,
dens defects, cranial settling, and spinal segmentation
defects can all be suggested with these simple studies. MRI
is the diagnostic procedure of choice because this tech-
nology allows direct imaging of the neural axis. MRIcan
demonstrate
compressive distortion, demyelination, sy-
ringomyelia, and presence of neural tissue abnormalities,
such as Chiari malformation.3.4 Surgical treatment will be
determined by individual pathology of each patient as is
determined by these diagnostic studies.lo.n
.
Contraindications
. Lesionsthat extend rostral to pharyngeal tubercle
.
Lesions that extend too caudally
.
Severe spinal instability
.
Poor wound healing capacity
.
Systemic instability
The rostral limit of this exposure is the pharyngeal tuber-
cle, which is the origin attachment of the superior pharyn-
geal constrictor muscle. This is on the ventral surface of the
clivus at the symphysis between the basisphenoid and ba-
siocciput. If the pathological lesion extends rostral to the
pharyngeal tubercle, another route of approach should be
chosen.
.
Advantages
. Allows for exposure of the basiocciput of the clivus,
anterior rim of foramen magnum, and rostral cervical
segments of C1-C4
.
Compared with transoral, provides broader, more exten-
sile exposure
.
Better wound healing than transoral incision because
more layers
. Any lesion involving the ventral craniocervical junc-
tion that is approachable
by the transoral route can
be approached
by the transcervical
retropharyngeal
approach.
. This is a noncontaminated
route offering an advantage
in avoiding infection.
.
Thisisa safer approach for managing ventral intradural le-
sions at the basion and rostral cervical region, avoiding
lower cranial nerves and controlling cerebral spinal
fluid.
.
It allows for C1 anterior arch arthrodesis to C3 using
structural support graft and instrumental
screw/plate

10
RetropharyngealApproachto the OccipitocervicalJunction
91
fixation for a one-stage stabilization following odon-
toidectomy.
. Thisoffers wider exposure of the lateral mass articu-
lations of (1 and (2 laterally
and the basiocciput
ros-
trally,which is preferable
for neoplastic
spinal
lesions
here.
. Itis a straightforward
procedure
that can be mastered
byany spinal surgeon
familiar
with
the anatomy
and
followingwide facial exposure
of sequential
anatomical
landmarks.
. Itdoesnot require specialized instruments
other than the
usualretraction devices for anterior
cervical spinal
surgery,although the microscope, pneumatic
high-speed
drill,laser,and fluoroscope are advantageous
adjuncts
to
performingthis procedure.
. Preemptiveplacement
of a lumbar
subarachnoid
drain
will helpto avoid cerebrospinal fluid ((SF) fistula and
retropharyngealpseudomeningocele.
. Disadvantages
. Technicallymore difficult than transoral
. Lessdirectapproach for select pathologies (e.g.,lesion of
C2dens)
. Moreanatomicalstructures at risk during the approach
. Mostsurgeons are not familiar with this approach
andhave reservations about using it for uncommon
lesions.
. Midlineorientation may be confused because the pa-
tient'sheadisrotated contralateral to the perpendicular
midsagittalorientation familiar to the surgeon. Atten-
tiontoanatomicallandmarks helps to avoid such disori-
entation.
. Thehypoglossal nerve is usually impaired
causing
speechandswallowingdysfunction for a variable period
oftime.
. Retractionofthe superior pharyngeal constrictor muscle
canleadto protracted dysphagia that may require tube
feedingforup to several weeks.
. Thesuperiorlaryngeal nerve is vulnerable to traction
injurythat can lead to voice hoarseness
and risk of
aspiration.Thisis almost always temporary but may also
requiretransabdominalgastrojejunaltube feeding.
. PatientSelection
Atrialofskulltraction will determine if chronic malalign-
mentofthe occipitocervical junction is reducible or not.
Cranialtongsare applied under local anesthesia with the
patientsupine and usually with the cervical spine in exten-
sion.Thetrajectory of traction force must be dictated by
the individual patient's
abnormality.
Achieving
normal
alignmentby traction usually decompresses
the neuraxis:
thenoccipital cervical
fusion
in the
position
of normal
alignment is all that is needed to treat the condition. When
traction is not successful in reducing malalignment, then
direct surgical decompression will be required to decom-
press the neuraxis. Ifanterior decompression is necessary,
either the transoral or parapharyngeal approach can be
used.12.13The parapharyngeal approach is preferable if the
lesion requires exposure of the (1-(2 lateral masses, is cau-
dal to the midclivus, requires corpectomy caudal to (2, or
requires opening ofthe dura.
.
Objectives
The extrapharyngeal approach has been described by many
authors.14-19 It is initiated
with a transverse
incision
through the platysma muscle and is directed to the sub-
mandibular
triangle. It will progress beneath
the sub-
mandibular gland, inferior to the digastric muscle, inferior
to the hypoglossal nerve, superior to the greater cornu of
the hyoid bone, posteriorly past the superior pharyngeal
constrictor muscle, to the retropharyngeal
space and the
precervical fascia. The key to exposure is wide dissection of
the cervical fascial planes, which when opened become av-
enues of access to the ventral occipitocervical junction.
These planes appear complex and formidable, but when
divided into layers identified by familiar structures that
serve as guides, the dissection and approach of this route
are straightforward.20-23
.
PlanesoftheCervicalFascia
The layers of cervical fascia and the spaces have been stud-
ied extensively; the following description is from the work
of Grodinski and Holyoke published in 1938, based on the
dissection of75 adult cadavers and five full-term fetuses.24
There are three major layers: superficial. middle, and deep.
The middle and deep layers split into superficial, middle,
and deep subdivisions illustrated by Pernkopf.25
Superfidalfasda is a continuous sheet extending from the
mandible to the axillae and upper chest and inserting into
the skin over these areas. It is moderately loose and it en-
closes the platysma muscle. The platysma also inserts
chiefly into the superficial cervical fascia and skin. There is
a potential fascial space within the subcutaneous fat super-
ficial to the platysma muscle and a potential fascial space
beneath the platysma.
Middlefasda is the pretracheal or visceral layer.It fuses in
the midline with the superficial fascia to form the linea
alba. It envelops the buccopharyngeal and strap muscles. It
inserts on the hyoid bone and encloses the trachea, esopha-
gus, and thyroid gland.
Deepfasda separates into the superficial,middle, and deep
layers.The superficial layer ofdeep fasciaencloses the stern-
ocleidomastoid muscle. It is anchored to the posterior aspect
of the hyoid bone. Rostral to the hyoid bone it is fused with
the middle and superficial layersand investsthe structures of
the submandibular triangle, encapsulates the submandibular
gland, and fuses with the anterior sheath of the anterior and

92
OccipitocervicalJunction:AnterolateralApproach
posterior bellies of the digastric muscle. Each muscle at-
tached to the hyoid bone is independently enclosed in a fas-
cial sheath. The middle or visceral fasciais fused with the su-
perficiallayer ofthe deep fasciacaudal to the hyoid.Laterally
the middle cervical fascia fuses with the superficial layer of
deep fascia at the hyoid bone and along the superolateral
boarder of the anterior belly of the omohyoid muscle. This
continues on to enclose the posterior belly of the omohyoid
muscle.The hyoidbone and thyroid cartilage anchor the cau-
dal pathways through the middle and superficial layer of the
deep cervical fascia, which extend to ensheathe the great
vessels and pericardium. This layer fuses laterally with the
alar fascia to form the anterior carotid sheath. The deepest
layer of cervical fascia consists oftwo main subdivisions: the
alar and prevertebral fasciae.The alar fasciaisa complete fas-
cial layer between the visceral and prevertebral fascia, be-
hind the pharynx and esophagus. The alar fascia fuses later-
ally with the prevertebral fasciaat the tips of the transverse
processes. The alar fascia courses anterolaterally to form the
medial wall of the carotid sheath. It swings posteriorly to
form the posterior and lateral walls ofthe carotid sheath and
fuses with the deep surfaceof the sheath enclosing the stern-
ocleidomastoid muscle. The alar fascia continues anteriorly
as an encircling carotid sheath. The alar fascia extends from
Submandibular gland
the skull base to C7at which level it fuses with the visceral
fascia. The prevertebral fascia lies anterior to the vertebral
bodies from the skull base to the coccyx. It extends laterally
and joins the alar fascia at the transverse processes, then
continues to ensheath the scalene muscles. As the scalene
fascia courses caudally, it ensheathes the subclavian vessels.
The prevertebral fasciacontinues into the upper thorax form-
ing Sibson's fascia, which covers the medial surface of the
first rib and continues over the pleural dome to fuse with the
posterior lateral wall of the carotid sheath and is thus related
to the alar fascia. Reflectionsof these fascial layers form po-
tential spaces of access and confinement. These potential
spaces become true spaces of access when they are opened
surgically in a precise manner defined by the anatomy ofthe
ensheathed structures.
This retropharyngeal approach requires dissection offas-
cial planes in the submandibular triangle rostral to the hy-
oid bone and adjacent to the superior pharyngeal constric-
tor muscle, ultimately accessing the space between the
vertebral bodies and the prevertebral fascia, which is lim-
ited laterally by the transverse processes and extends from
the skull base to the coccyx. The prevertebral space isa
ventral "highway" along the spinal column, which can be
exploited as a surgical access.
Digastric muscle
Figure 10-1
The patient's position is oriented with the head extended and rotated contralateral to the side of approach. The curvilinear incisionis
2 cm below and parallel to the lower edge of the mandible.

10
Retropharyngeal Approach to the Occipitocervical Junction
93
. SurgicalTechniques
Anesthesia
Awakeintubation under local topical anesthesia
and
fiberopticairway visualization
may be required to avoid ex-
cessivemovement of the head and neck during tracheal
in-
tubationand induction
of anesthesia.
Patients
bedridden
due to advanced
high
cervical
myelopathy
should
be
consideredfor elective tracheotomy.
If ventilator
support
isrequiredfor several days, tracheotomy
will offer early
advantagein management
of such patients
due to pharyn-
gealswellingand upper airway obstruction
that often ac-
companythis procedure.
Positioning
Thepatientis supine with the head on a sponge support
or
horseshoeheadrest and in skull traction
if necessary.
The
headis rotated 30 degrees
away from the surgeon
and in
extension.This head position
raises the mandible
up and
awayfromthe surgeon's line of sight to the field. The fluo-
roscopeis positioned for lateral projection
and the operat-
ingmicroscopewith laser shutter attachment
is draped and
available.
Incision
Various incisions
have been
proposed:
transverse,
T,
oblique. and hockey-stick.20-23 Most cases can be ade-
quately exposed through a transverse incision 2 cm below
and parallel to the mandible, extending from the angle
of the mandible to beyond the midline. taking care to
avoid injuring the marginal mandibular branch of the facial
nerve, which supplies the mental muscles of the lower lip
(Fig.10-1).
Approach
The keyto adequate exposureis wide sharpdissectionof
each fascial plane, beginning with development of a wide
subcutaneous flap on each side of the incision superficial to
the platysma muscle (Fig. 10-2). Anatomical landmarks
identify each plane and guide the way. Each landmark is
dissected free of its fascial sheath and preserved both
anatomically and functionally. The fascia is kept taut with
countertraction, using pickup forceps as the dissection con-
tinues; this helps to define the fascial layer that isbeing dis-
sected. When lifted and opened, the areolar fibrous texture
of the fascia becomes evident. Its transparency allows a
view of the structures it contains. Wide opening of each
Figure 10-2
Widedissection ofthe
subcutaneous layer opens the most
superficiallayerofthe cervicalfascia,
exposing the outer surface of the
platysma muscle. Care is taken to
avoid injuryto the mental branch of
the facial nerve, which can cause a
droop ofthe ipsilaterallowerlip.

94
Occipitocervical Junction: Anterolateral Approach
fascial layer in a sequential, methodical manner will ensure
adequate exposure of the deeper structures while preserv-
ing the intervening ones. This dissection can be compared
with that required on a cadaver in the anatomy laboratory
for anatomical presentation. Therefore, this procedure re-
quires "cadaveric" dissection of the cervical fascia and its
enclosed structures. The skin flaps can now be retracted to
expose the superficial surface of the platysma muscle.
Superficial Anatomical landmarks
PlatysmaMuscle
The medial edge of the platysma is elevated in the midline,
a hole is cut in the medial fascial raphe (linea alba) to pass
though the superficial to the middle fascial layer. Vertical
dissection determines this layer in a cephalocaudal direc-
tion. The fascial sheet thus formed is cut longitudinally in
the midline for 6 cm from the mandibular symphysis to the
median notch of the superior thyroid cartilage (Fig. 10-3).
This defines the medial edge of the platysma muscle and
initiates vertical access to allow freer retraction of deeper
structures. The medial edge of the platysma muscle is now
elevated
to dissect and free the undersurface
of the
platysma. This maneuver opens the middle (visceral) layer
and superficial layer of the deep fascia.The platysma isthen
transected, in line with the primary incision. The platysma
flaps thus formed are retracted.
Submandibular
Gland
The next fascial layer is identified by the submandibular
gland, which bulges under the superficial layer of the
deep cervical fascia (Fig. 10-4). The inferior edge of the
gland is elevated. The fascial capsule is opened, under-
mined, and dissected in line with the incision. The facial
artery and vein are dissected along their course. This
maneuver further opens this fascial plane. The facial vein
is transected. The facial artery is preserved. Dissection
of the facial artery proximally leads to the reflection of
the alar fascia as it forms the carotid sheath and the
lateral limit of this exposure. The facial artery is dissected
and retracted with the submandibular
gland superiorly
to expose the next landmark, the tendon of the digastric
muscle.
DigastricMuscleand Tendon
The tendon of the digastric muscle is identified as a glisten-
ing white cord running parallel to the course of the incision
Figure
10-3
The
medial
border
of the
platysma
muscle is found at the midline and
split vertically from the mental symphysis to
the notch of the thyroid cartilage; this initiates
access to the next fascial layer.

10
RetropharyngealApproachto the OccipitocervicalJunction
95
beneath
theinferioredge of the submandibular gland. This
leadstothenextfasciallayer.Afascial sling tethers this ten-
dontothe greater wing of the hyoid bone. By transecting
thisfascialslingalongthe course of the tendon, the tendon
isfreedand retracted rostrally toward
the mandible.
This
retractionis facilitated by freeing the undersurface
of the
anteriorand posterior digastric muscle bellies. This then ex-
posesthe next fascial plane. The hypoglossal
nerve comes
intoviewcoursingjust deep, slightly inferior, and parallel to
thedigastric tendon.
HypoglossalNerve
Thehypoglossalnerve is gently dissected along its course
andis carefullypreserved (Fig. 10-5). Posterolaterally
thedissectionis carried along the nerve trunk toward the
descendinghypoglossal ramus, which is another
guide to
theregionof the carotid artery. Again, it is not necessary
to
dissectalongthe medial border of the carotid sheath unless
segments
caudalto (4 are to be exposed. Thus freed, the
hypoglossal
nerveisretracted superiorly, exposing the hyo-
glossusmuscle.The greater cornu of the hyoid bone now
comes
intoview.
HyoidBone
Figure 10-4
The platysma muscle is
transected;
lifting the tissues with
grasping forceps and giving counter
traction assists with the dissection.
Thisexposes the next fasciallayer.Re-
traction of the platysma flapsexposes
the submandibularglandas wellasthe
facial artery and vein. Dissection of
these structures opens the next layer
of cervicalfascia.The anterior bellyof
the digastric muscle isexposed when
the facial vein is transected and the
submandibular gland is elevated and
retracted superiorly.
The greater cornu of the hyoid bone can now be seen and
palpated. The fascia overlying it is opened along the course
of the hyoid bone to the carotid sheath. The carotid artery is
easily palpated and is the lateralmost limit of this dissec-
tion. It is retracted
laterally. This maneuver opens the
retropharyngeal space. It is not necessary to cut any mus-
cles, nerves, or vessels. The superior laryngeal nerve (SLN)
is vulnerable to injury at this juncture. The SLNcourses
deep to the internal carotid artery along the middle pharyn-
geal constrictor muscle toward the superior cornu of the
hyoid bone and adjacent to the superior pharyngeal con-
strictor muscle. The SLNis not seen in the dissection of this
approach. However, the SLNcan be injured by stretch from
retraction. Wide dissection of the fascialplanes as described
here should tend to protect the SLNfrom retraction injury
because less force is required to separate the tissues that
are freed by wide fascial dissection. The SLNis not involved
in the soft tissues retracted superiorly for this exposure. It
would be more vulnerable to injury if the deep cervical fas-
cia were opened inferiorly in the lateral exposure. Ifaccess
to (4 and lower cervical segments is needed, the SLNis

96
OccipitocervicalJunction:AnterolateralApproach
identified and preserved; a separate approach to the lower
segments is then made.
Superior Pharyngeal Constrictor Muscle
The pharyngeal constrictor
muscles are retracted medialIy by
a deep, right-angled
retractor. The retropharyngeal
areolar
tissue, comprising the alar and prevertebral fasciae, is opened
with scissors. The anterior
surface of C2 and C3 is easily pal-
pated. The prominence
of the anterior tubercle of C1 is pal-
pated and is the focus of rostral orientation.
The midline of
tne cervical spine orients the midsagittal
plane identified be-
tween the longus colli and longus capitis muscles (Fig. 10-6).
Deep Anatomical landmarks
Longus Colli - Capitis Muscles
The converging medial boarders of the longus colli mus-
cles are cauterized and elevated from the anterolateral
Superior
pharyngeal
constrictor m.
Figure 10-5
Transecting the fascialin.
vestment of the digastric muscle exposes
and frees the next landmark and opens
the next layer of cervical fascia. The di-
gastric tendon
is separated
from its fas-
cial sling at the hyoid bone and retracted
superiorly. This exposes the hypoglossal
nerve, the next landmark, and the next
layer of cervical fascia. Dissection ofthe
hypoglossal nerve opens this layer ofcer-
vical fascia and allows retraction
of the
nerve to expose the next landmark, the
greater cornu of the hyoid bone. Open.
ing the
fascia along
the
hyoid bone
exposes the lateral wall of the superior
pharyngeal constrictor muscle.
surfaces of C2 and C3 by sharp dissection. The retractor
blade engaged along the dissected muscle border is used
to separate the longus colli muscles. This preliminary soft
tissue retraction initiates access to deep structures. The
microscope is adjusted to the field. A quick glimpse with
the fluoroscope in the lateral projection wilI assist the
surgical orientation. The potassium titaniumoxide
phos-
phate (KTP586) or C02 laser is advantageous in separat-
ing the longus colli and longus capitis muscles from their
medial attachments. Laser dissection facilitates the expo-
sure of the anterior arch of C1 and the atlas and axis lat-
eral mass articulations. It alIows muscle separation up to
the pharyngeal tubercle of the basiocciput26 (Fig. 10-7).
View of these most rostral structures
requires rostral re-
traction
using a deep, narrow, right-angled
retractor
blade. This retraction is critical for exposure and access.
The medial half of the C1and C2 lateral masses and ante-
rior rim of the foramen magnum and the basiocciput ros-
tral to the anterior arch of C1 should be in view before
proceeding.

Figure10-6
Retractionof the superiorpharyngeal
constrictor opens the retropharyngeal space and
exposes the alar fascia, precervical fascia, and longus
collimuscles. Theanterior tubercle of (1 identifiesthe
midline.
Mandibular ridge
II 1
\
Anterior tubercle
/
(arch of C1)
;.;;/.\ 1:
.
=-"-11I
, ":::1
r /.11\
\~
@ 1997, S. Harrison/MCG
-a~"./"\-a.$ca.ro-
Figure10-7
The longus colli muscles are dissected from the arch of (1 and the anterior surface of (2 and O. The laser, controlled
through the
microscopeattachment,facilitatesthis. The surgeon's perspectiveisrotated 30 degrees and ina rostrallyobliquedirection,and constant attention
tothisisrequiredto maintain correct orientation.
97

98
OccipitocervicalJunction:AnterolateralApproach
MedianTubercleC1AnteriorArch
The (1 anterior tubercle is a guide, which helps to maintain
orientation with the midsagittal plane. The surgeon's per-
spective to the field is upward and angled 45 degrees. The
C1 arch, base of dens, pre-dens space, and lateral mass
articulations are seen (Fig.10-8). Laserremoval of overlying
soft tissue clears the view. The dens, body of (2, and
atlantotransverse ligament can be removed without remov-
ing the anterior arch of (1 if so desired.
TransverseCervicalLigament
The transverse ligament is a tough, rather thick, delineated,
pale yellow.ligamentous belt behind the dens. The ligament
comes
into view
after
the
dens
has been
resected
(Fig. 10-9). It is a guide after the (1 arch and odontoid
have been removed because they may be obscured by
the destructive
changes of disease. The dura may be
densely
adherent
to
the
posterior
surface
of
the
transverse ligament and adjacent tectorial membrane. Sharp
microdissection of the tectorial membrane is necessary to
separate it from the underlying dura. Activebleeding from
epidural veins can be troublesome but is ultimately con-
trolled by bipolar coagulation and packing with topical he-
mostatic material. The dura isvulnerable to laceration at this
juncture. which would then be a source of (SF leakage and
subsequent pseudomeningocele formation.
Anterior Rim Foramen Magnum
The anterior rim of the foramen magnum and caudal basioc-
ciput can be palpated and seen between
the attachments
of
the longus capitis muscles. These attachments can be sepa-
rated using laser to expose bony elements for drilling away
if required.
Clival/PharyngealTubercle
The pharyngeal tubercle is the rostral limit of this exposure.
Ahole drilled into the clivus rostral to the anterior rim can
serve as an anchor site for rostral soft tissue retraction, asil-
lustrated in the next chapter. This bone ridge can also be
drilled away if necessary for lesion exposure or neural de-
compression.
Bone Resection
With this approach. the rotated and extended head position
can confuse the surgeon's orientation. The ipsilateral (1-(2
lateral mass articulation is more forward and can be misin-
terpreted for the anterior arch of (1, leading to disorienta-
tion. The surgeon must keep these perspectives in mind
while using this approach. The anatomy of this region has
been well described and must be familiar to the sur-
geon.27.28Ahigh-speed. pneumatic drill with cutting buris
used to resect the bone (Fig. 10-8). Removing the anterior
arch of (1 offers a view of the dens and adjacent articula-
tions. The dens is removed by starting at the apex, working
caudally, keeping the base intact for control and orientation.
By thinning like an eggshell, a diamond bur can then be
used to complete the removal and avoid inadvertent injury
of adjacent tissues. The medial wall of the lateral masses
can be removed to widen the ventral exposure; this ishelp-
ful if the lesion is intradural. The transverse ligament is
identified for orientation (Fig. 10-9).
Figure 10-8
The anterior arch of (1 isbeingre-
moved, which exposes the dens. The dens isbest
drilled away from its apex toward its base.

10
Retropharyngeal Approach to the Occipitocervical Junction
99
Atlanta-occipital membrane
and longi~dinalligament
"'~I
, I ,~!
I
@ 1997, S. Harrison/MCG
TectorialMembrane
Thetransverseligament combines the tectorial membrane
alongwith the apical bursa. cruciform. and tectorial
ligamentsto form a composite of the posterior longitudi-
nalligament.Thismust be separated from the dura and re-
moved.The KTP586 or C02 laser slightly defocused
at 5 to
lOWallows"notouch"removalofthese structures.These
ligamentsand pannus can be thick. tough, and adherent
withlongstandinginstability at C1-C2. The anterior rim of
theforamenmagnum can now be removed.
Theventral dural sac bulging and pulsating
into the re-
sectionsiteensures that decompression of the neuraxis is
completeand adequate.
Preservingthe Anterior Arch of (1
Thecaudalto rostral trajectory
of the surgeon's
perspective
offeredbythisapproach allows for the resection of the deep
Figure 10-9
Thetransverse ligamentisthe next landmark.
It is identified as a thick fibrous transverse band. It may be
obscured bychronic inflammation and scarring. The trans-
verse ligament along with the posterior longitudinalliga-
ment must be removed to adequately decompress the
neuralaxis.
landmark structures described to be accomplished and still
preserve the anterior arch of C1.This orients the midline
and can buttress a strut graft between the C1arch and the
superior epiphysis of C3.Anterior arthrodesis. surgical clo-
sure, and postoperative support measures are discussed in
the next chapter.
.
ClinicalExperience
The author's experience with this transcervical retropha-
ryngeal approach is summarized
in Table 10-1. There
are 23 patients in the series, evenly divided between 11
men and 12 women. Their ages ranged from 14 to 88
years. Seven patients developed CSFleaks; two required
permanent
lumboperitoneal
shunt to control the CSF
leak and resultant
retropharyngeal
pseudomeningocele
(Table 10-1).

100
OccipitocervicaI
Junction: Anterolateral
Approach
Table 10-1
ClinicalSeriesofPatientsWho Underwent TranscervicalResectionof CranialVertebraljunction lesions
Clinical Series
Patient
Preop
Neurofunc-
Result
Op Date
Sex
Age
Diagnosis
Function
Duration
Pathology
Complications
Poster Fusion
tional
Time
DB8/20/85
M
42
Chordoma
NeckPain
6 weeks
Chordoma
None
9/3/85
left IX,X
Died5year;
C1-(2
Clivus +
palsy
postop
dissolution
C1- C2
Recurrence
WR10/18/85
F
60
Angled Fx
Quad-
9 months
Thickfibrosis
CSFfistula
10/31/85
Independent 6 months
(2 APdia
paretic
Nonunion Fx
7mm
DD2/3/86
M
31
Osodon-
Quad-
4 years
Odontoid
SIADH
2/11/86
Spasticgait
6 months
toideum
paretic
loose
Self-care
Basilar
Unstable
impression
fibrosis
jS 11/12/86
M
43
Osodon-
Quad-
3 years
Odontoid
None
11/25/86
Neuro intact
3 months
toideum
paretic
loose
Backto work
Basilar
Unstable
impression
fibrosis
TS11/24/87
M
16
Neurofi-
Quad-
3 months
Mult.
CSFfistula
12/11/87
Mild
3 years
bromas
paretic
neurofib.
spasticity
ventral
cervical
Carpenter
canal
roots
work
C2- C7
jD 3/1/88
F
66
Rheuma-
Quad-
2 years
Rheumatoid
Bronchial
3/9/88
Neuro intact
2 years
toid pannus
paretic
pannus
spasm
Independent
odontoid
MS11/10/89
F
63
Cabreast
Neckpain
3 months
Pathcom-
Airway
Anterior
Neuro intact
6 months
metastasis
pression
obstruction
fusion
Independent
Died 1year
PathFxC2
FxC2
advanced
Ca
AR1/26/90
F
36
Hangman's
Neckpain
2 weeks
UnstableFx
None
Anterior
Neuro intact
2 months
Fx
C2+ HNP
fusion
Independent
C2+ HNP
C2- C3
C2- C3
DY6/15/90
M
64
Rheumatoid
Quad-
8 months
Anterior
CSFfistula
6/26/90
Died cardiac
6/27/90
sublux
paretic
subluxation
arrest, coagu-
C1-C2
C1-C2
lopathy
VS6/18/90
F
45
Meningioma
Mild
ventral
myelopathy 1 year
Meningioma
CSFfistula
6/29/90
Neuro intact
3 months
foramen
ventral
Independent
mag C1
compression
AS5/5/91
M
42
Tpllodontoid
Mild
8 years
Odontoid
Dysphagia
5/15/91
Neuro intact
3 months
Fx,unstable
myelopathy
loosescar
Independent
Med ret
nonunion
AR6/29/92
F
14
Plexiform
Neckpain
1year
Neurofibroma CSFfistula
7/10/92
Neuro intact
6 months
neurofibro-
Independent
matC1-C2
EF4/19/93
M
21
Ewing's
Neckpain
8 months
Ewing's
None
5/3/93
Neuro intact
2 months
sarcoma
sarcoma
Indpendent
Died
C1 + C2
3 yearsPO
ES11/15/93
F
60
Odontoid
Myelopathy 3 years
Anterior
None
11/23/93
Neuro intact
6 months
agenesis
Ataxic
subluxation
Occipto C5
Independent
Housewife
Sclerosis
Quad-
C1- (2
C1-(2
paretic
Sclerosis
Basilar
C1- C2
impression
WB11/7/95
M
47
Basilar
Neckpain
3 months
Chiarirep
Pinsite
Anterior
Mild spastic
6 months
impression
Mild
8/15/93
infection
fusion
Walkswith
Worksas
X-linked
myelopathy
Odontoid
Halo
C1-C3 +
cane
barber
hypophos-
Weak
settled
brace
plate
phate
upper
ventral
removed
ricketts
exts
compression
at 8 weeks
100

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Bone joint Surg Am 1969;51 :1621 - 1626
10
Retropharyngeal
Approach to the Occipitocervical
Junction
101
Patient
Preop
Poster Fusion Neurofunc-
Result
OpDate
Sex Age Diagnosis
Function
Duration
Pathology
Complications
tional
Time
MCS
1/23/96 F
31
Osodon-
Headache
6 months
Occipito.
None
1/30/96
Neurointact
3 months
toideum
Mild
encephalocele
Occipto T1
AsymptomaticHousewife
ventral
myelopathy
rep aschild
compression
BifidC1 arch
VSM7/9/96
F
55
Basilar
Neckpain
9 months
Platybasia
Duraltear
7/12/96
Neurointact
4 months
impression
Mild
Basilar
CSF
Occipto C4
Asymptomatic
myelopathy
impression
controlled
byLPdrain
]157/15/96M
41
Meningioma
Bedridden
1year
Neuralaxis
Duralgraft
Anterior
Residual
6 months
anterior
Quadriplegiaprogression compress
LPdrain
fusion
spastic
foramen
Ventral
C1-(3
+
Ambulates
mag
tumor
Plate
walker
WP10/21/96M
54
Basilar
Neckpain
3years
Anttranslation Persistent
10/28/96
Neurointact 6 months
impression
C1wirefusion dysphagia
Remove
Noneckpain Recovered
Cervical
1983
SIPjejunostomy fusion
Playingolf Dysphagia
kyphosis
Ventral
Bowel
occiput
Reiter's
compression
obstruction
toG
syndrome
JE512/17/96F
76
Meningioma
Mild
9 months
Neuralaxis
Dysphagia
Anteriorfusion Neurointact 2 months
anterior
myelopathy
compression
clearing
C1-(3
+
Gait
Activewith
foramen
Unsteady
Ventral
LPdrain
plate
normalized family
mag
gait
tumor
1wk
BG3/3/97
F
61
Rheumatoid
Bedridden
6 months
Odontoid +
Intubated +
Anterior
No change
'Died
sublux
Quadriplegia
pannus
ventilator
fusion
Halo brace
7/28/97
C1-(2
ventral
Jejunostomy
C1+ (3 plate
Respiratory
compression
fed
failure
AMB7/11/97F
25
Obesity +
Neck pain
4 months
Platybasia +
Tracheotomy +
7/25/97
Neurointact 4 months
Apert's synd
following
odontoid
pneumonitis
Occiput to C4
-work
Basilar
MVA
hypoplasia
CSFleak/
6 months -
impression
LPdrain
school
OMcD1/26/99M
88
Odontoid
Neck pain
5 weeks
Odontoid
Previous
Ant fusn C1+
Dementia,
Rehab
Fxtype II
Traumatic
retrolisthesis
tracheotomy
C3 plate/halo
otherwise
nurse
retrolisthesis
encephalopa-
+ feeding
intact
thy
jejunostomy
Ant,anterior;AP,anteroposterior;
Ca, carcinoma; CSF,cerebrospinal fluid; dia, diameter; Ext, extremities;
Fx,fracture; Fusn, fusion; HNP,herni-
atednucleuspulposis;LP,lumboperitoneal; Mag,magnum at foramen magnum; Medret, medicalretirement; MVA,motor vehicleaccident;
neural.neurological;occip,occipital;Op,operative; Path Fx,pathlogicalfracture; PO,postoperative; Rep,repaired;SIADH,syndrome ofinap-
propriateantidiuretichormone secretion; sublux, subluxation; synd, syndrome; Tp II,type IIodontoid fracture.

102
OccipitocervicalJunction:AnterolateralApproach
17.
Whitesides
TJ. McDonald A. Lateral retropharyngeal
approach
to the
upper cervical spine. Orthop Clin North Am 1978;9:1115 -1127
18.
Lesion F.Autricque
A, Franz K.et al. Transcervical
approach
and screw
fixation
for
upper
cervical
spine
pathology.
Surg
Neurol
1987;27:459-465
19.
McAfee PC. Bohlman
HH. Riley LHJr. et al. The anterior
retropharyn-
geal approach
to the upper
part of the cervical spine. J Bone Joint Surg
Am 1987;69:1371-1383
20.
McDonnell
DE.Anterolateral
cervical
approach
to the craniovertebral
junction.
In: Rengachery
55. Wilkins
RH. eds. AANS Operative
Atlas.
Vol 1 (3). Baltimore:
Williams and Wilkins;
1991 :147 -164
21.
Vardiman
AB, Dickman CA. Sonntag
VKH. The modified
anterolateral
retropharyngeal
approach
to the craniovertebral
junction:
anatomic
and practical
considerations.
BNl Q 1994;10:26-34[p3]
22.
McDonnell DE.Harrison SJ.High cervical retropharyngeal
approach to the
craniovertebral
junction.
In: Hadley MN, ed. Perspectives
in Neurolo-
gical Surgery. Vol 7. St. Louis: Quality Medical Publishing; 1996:121-141
23.
McDonnell
DE. Harrison
SJ. Lateral
approach
to the craniocervical
complex. Tech Neurosurg
1998;4:306-318[p4][p5]
24. Grodinsky M, Holyoke E.The fasciae and fascial spaces of the head,
neck. and adjacent
regions. AmJ Anat 1938;63:367
-408[p6][p7]
25.
Pernkopf
E. Topography
of the neck. In: Ferner
H, ed. Atlas ofTopo-
graphical
and
Applied
Human
Anatomy.
Vol 1. Philadelphia:
WB
Saunders;
1963 :232 - 273
26.
Panje W, Scher N. Karnell M. Transoral
carbon
dioxide
laser ablation
for cancer, tumors, and other diseases. Arch Otolaryngol Head Neck
Surg 1989;115:681-688
27.
de Olivera E, Rhoton ALJr. Peace DA. Microsurgical
anatomy
of there-
gion to the foramen
magnum.
Surg NeuroI1985;24:293-352
28.
Rock JP. Tomecek
FJ, Ross L. Transoral
surgery:
an anatomic
study.
Skull Base Surg 1993;3:109-116[p8]

11
Closureof the Retropharyngeal Approach to
theOccipitocervical Junction
DennisE.McDonnell and Steven J. Harrison
. Indications
. Contraindications
. Advantages
. Disadvantages
. SurgicalTechniques
CompleteNeural Decompression
Retraction
Dural Closure
Closureofthe high cervical parapharyngeal wound is easy
andstraightforward
because only facial planes are opened.
Softtissue structuresresume normal anatomical alignment
whenthe retraction is removed. However, several steps of
preventionwill reduce the complications that can accom-
panythisapproach. Alsothis approach allows for direct pri-
maryarthrodesis between the anterior arch of C1 and the
superiorepiphysis of C3,using an allograft structural sup-
portstrutand screw/plate fixation.
. Indications
. Pathologicalcompressive
lesions. anterior
or posterior,
tothecervicomedullaryjunction
. Chronic"glacial"instability
. Occipitocervicalosseous
anomalies
of developmental
origin
. Inflammatoryconditions affecting this region
. Rheumatoidarthritis
. Osteoporosis
. Neoplasm-primary
or metastatic
. Fractures
. Contraindications
. Limitedexposure if the lesion extends rostral to the pha-
ryngealtubercle
Cerebrospinal FluidDiversion
Craniovertebral Stabilization
Primary C1Archto C3Strut Arthrodesis
Airway Control
Nutritional Support
.
Outcomes
.
Complications
.
Conclusions
. Advantages
.
Allows for exposure of the basiocciput of the clivus, an-
terior rim of foramen magnum, and rostral cervical seg-
ments of C1-C4
.
Compared with transoral, provides broader, more exten-
sHeexposure
. Betterwoundhealingthan transoralincisionbecause
more layers
. The noncontaminated
field helps to avoid infection; a
distinct advantage if the dura has been entered or if
there isa cerebrospinalfluid(CSF)leak.
. The dura can be closed more directly with this ap-
proach; afibringlue closurewill not be diluted out by
exposure to saliva or other oral secretions.
.
Direct C1to C3arthrodesis using a structural strut graft
between the anterior arch ofC1 (preserved by using this
approach) and the superior
epiphysis of C3 can be
placed and internally fixed using a screw/plate construct
through the anterior arch of C1and the body of C3.
.
It offers the possibility of a single-stage closure and inter-
nal fixation of an unstable
craniovertebral junction
following a surgically destabilizing
procedure.
.
Disadvantages
.
Technicallymore difficult than transoral
.
Lessdirect approach for select pathologies (e.g., lesion of
C2dens)
103

104
Occipitocervical Junction: Anterolateral Approach
Retraction
. More anatomical structures at risk during the approach
.
Upper airway edema can cause mechanical obstruction
interfering with adequate ventilation so that intubation
with mechanical ventilator support may be required for
several days.
. Superior constrictor dyspraxia can result in debilitating
dysphagia that requires tube feeding of liquid formula to
maintain adequate nutrition.
.
Hypoglossal nerve, superior laryngeal nerve (SLN),and
glossal pharyngeal nerve dysfunction can occur from re-
traction and may persist for several weeks. Such func-
tional sequelae are almost always temporary but can
be a serious debilitating addition to the patient's overall
condition.
. SurgicalTechniques
Complete Neural Decompression
For neurological function to recover from mechanical com-
pression, the compression has to be effectively removed.
Adequate neuraxis decompression is assured when the ven-
tral surface of the dura bulges into the opened corpectomy
defect (Fig. 11-1). The dura may be transparent enough to
reveal pial surface vessels and cord pulsation. Bleedingfrom
dural venous sinuses and epidural veins in this region can
be particularly challenging. The usual techniques of bipolar
electrocoagulation, topical collagen fiber, thrombin and
gelatin foam, gentle tamponade with cotton pledgets, and
patience are used for hemostasis.
Adequate retraction
is required to efficiently accomplish the
goal and fully exploit the advantage
of this approach. Criti.
cisms of it refer to the deep, narrow,
off-midline
access,
which can be overcome
by retraction
and the surgical mi.
croscope. Anarrow 90 degree angled retractor helps tolift
the soft tissues
rostrally
initially. The deep blades of the
Cloward (Codman, Randolph, MA) or Caspar (Aesculap, San
Francisco,
CA) self-retaining
retraction
systems
are ade-
quate for retraction
of the longus capitis muscles. The table.
mounted Thompson-Farley (Thompson, Traverse City,MI)
retraction
system is a useful alternative
instrument
for reo
traction of rostral and medial soft tissues.! The author
prefers a modified
Taylor-type
retractor
that is secured in
an anchor hole drilled into the clivus just rostral to the an-
terior rim of the foramen
magnum
(Fig. 11-1). The handle
of this retractor
is secured to the surgical drapes using elas.
tic bands with a Kocher forceps gripping the sheets through
an ether screen support mounted
at the table head.2,3
Dural Closure
The dura cannot usually be closed primarily here.4An auto.
graft fascia lata or allograft fascia is tacked to the dural edge
at multiple sites using a strong cutting, and semicircle, nee.
die. The P-2 Ethicon needle Uohnson &Johnson, Somerville,
NJ) or the PR-1 needle (Davis and Geck, Wayne, NJ) is useful
for suturing
in tight spaces. The suture size is 5-0 Polydiox.
anone, which is used for traction suture and dural patch clo.
sure.
This can also
be supplemented
with
fibrin
glue,
Cryoprecipitate can be applied topically over the graft,
which is then sprayed with thrombin.
This produces
a thick
Figure 11-1
Bulging of the dura into the resec-
tion site ensures adequate decompression. Note
the position of the retractor point that hasbeenin-
serted into a drill hole within the clivus.

11
Closureof the RetropharyngealApproachto the OccipitocervicalJunction
105
coagulumthat augments the dural repair seal.4.5Fibrin glue
isnowcommercially available as a double syringe serving as
mixer-injector(Tissucol; Immuno, Vienna, Austria)6 or Tis-
seelVHKit;Baxter, Deerfield, IL).Composite baffles of fascia
lataandasmallbone plate have also been described in suc-
cessfullyclosing the defect transorally
by wedging the bone
platebehindthe cranial spinal bone defect?
Cerebrospinal
Fluid Diversion
Acatheterplaced percutaneously
via a Touhey needle into
thelumbarsubarachnoid space at the time of the procedure
andtracked subcutaneously
to an external
collection
sys-
temisan effective prophylaxis
for pseudomeningocele
and
external(SF cutaneous
fistula. This drainage
can be left in
placeforseveral days so long as the tube has been tracked
subcutaneouslya few centimeters.
This drainage
can be
broughtto continuous drainage for most effective results.
Excessivedrainage of CSFcan lead to intracranial
hypoten-
sionand headache. CSFdrainage should be monitored
closelytoavoidcomplications of this maneuver. Recent ex-
periencewith use of a computerized IVpump to regulate
drainageflowof spinal CSFhas all but eliminated lumbar
(SFdrainage complications.s
CraniovertebralStabilization
Spinalstabilizationis important to consider in preoperative
planning.Skulltongs can be placed prior to the procedure.
Lighttractionwith 5 to 10 Ib is maintained through out the
procedure.A rope attached
to the traction
device is hung
overanetherscreen support frame and the angle adjusted,
asthesurgeon requires. Traction
can be maintained
as a
temporizingmeasure after the procedure
until the final pos-
teriorstabilization is accomplished
if this is subsequently
staged.Osseous fusion in situ is also an option, particularly
withthislateralapproach. The C1-C2 lateral masses can be
exposed
andareavailable for interarticular arthrodesis by
bonegraftinsertor transarticular screw. An intact C1ante-
riorarchcanbeused as an anchoring site for a notched strut
graftopurchase(Fig.11-2). These alternatives imply that
theatlanto-occipitalarticulation is intact, and this must be
discernedprior to fashioning the fusion construct. Other-
wisetheocciputmust be included in the arthrodesis, which
canbetenuousfromthis anterior approach for lackof a solid
anchoring
siterostrallyinto the clivus.9
Externalorthosis,such as a halo brace, is usually not ade-
quateasthesolesource of stability after this procedure. It is
usefulin supplementing surgical arthrodesis and can be
continuedfor several months, depending on the inherent
stabilityof the surgical fusion construct. Occipitocervical
arthrodesis
isperformed as a subsequent procedure if there
isoccipitocervicalinstability.The author prefers to keep the
patientin skeletaltraction until the posterior occipital cer-
vicalfusioniscompleted at a later date.
PrimaryC1Archto C3 Strut Arthrodesis
Thelateralparapharyngealapproach allows for complete re-
sectionofthe (2 odontoid complex, including the adjacent
ligaments,while maintaining the anterior arch of C1.This
still leads to inherent instability that must be addressed.lo
The interval between the inferior edge of the anterior arch of
C1to the superior end plate of C3is measured with a caliper.
A tricorticate iliac crest strut or allograft humerus strut is
notched at the cephalic end so that the notch engages the
anterior C1arch. The flat caudal end of the graft is then lev-
ered into position over the superior epiphyseal surface of
the C3 body. A narrow curved osteotome can serve as the
lever and be worked like a shoehorn to position the lower
end of the graft to effect a "press fit" of the construct (Fig.
11-2). Manual traction on the mandible or skull tongs can
assist in placement of the graft. This is then secured with a
screw plate fixation device. Anonrigid bicorticate screw fix-
ation through the graft and C1arch and C3is preferred be-
cause the screws can be angled as needed. The Caspar plate
(Aesculap, San Francisco, CA)has been used with success
(Fig. 11-3). Either autograft or allograft bone can be used
depending upon individual patient requirements. Allograft
tibia or humerus has been found to be about the correct di-
mensional width and affords circumferential cortical bone to
bolster strength of the support strut. The medullary cavity is
packed with autogenous bone from the resected C2body or
iliaccrest to facilitate bone fusion.l1

106
Occipitocervical Junction: Anterolateral Approach
Figure 11-3
ACaspartitanium plate
ispositioned and secured usingbicorti-
cate screw purchase into the anterior
archofC1and bodyofC3.Anautograft
or allograft of iliac bone crest can
be used as the strut graft between C1
and C2.
Airway Control
Awake tracheal intubation under local anesthesia is fre-
quently required to avoid manipulation of the patient's neck
and risking increased impairment. Preemptive tracheotomy
is the preferred tactic when the patient is immobilized by
myelopathic
quadriparesis.
Upper
airway
obstruction
caused by soft tissue swelling in the postoperative period is
a major consideration with this procedure. particularly with
myelopathic and debilitated patients. Toensure a compe-
tent upper airway,endotracheal intubation may be required
for several days with the patient in a head-up position until
the edema resolves. A positive end-expiratory pressure of
5 cm H20 on the ventilator tends to prevent atelectasis.
Nursing the patient in a rotokinetic bed can assist with pul-
monary drainage in selected patients.
Nutritional Support
Optimal nutrition
is important
to the recovery of any
stressed patient. Often patients who have chronic myelopa-
thy are already nutritionally depleted. The pharyngeal and
upper airway edema that occurs following this procedure
impedes swallowing for several days and at times weeks.
Maintenance of the metabolic balance is facilitated by
preoperative placement of a feeding gastrostomy/jejunos-
tomy to insure enteric alimentation. Effectively supplying
nutritional
support
helps
to avoid mucosal bacterial
translocation and sepsis; it also helps to promote earlier
rehabilitation
of these patients. With patients who are
already debilitated by their disease prior to surgical treat-
ment, preemptive placement of some form of enteric access
is advisable. This would allow for enteric nutritional sup-
port from the very beginning of the patient's convalescence.
.
Outcomes
Agesof the 23 patients ranged from 14 to 88 years. Most
patients presented with complaint of neck pain. Basilar
impression was seen in five patients. rheumatoid (1-(2
subluxation in four, failed odontoid fractures in five pa.
tients. os odontoideum in three patients. multiple neurofi-
bromas in three patients. ventral craniovertebral menin-
gioma in three patients, and one patient each presented
with chordoma, Ewing'ssarcoma, and metastatic breast car.
cinoma involving (1-(2.
Eighteen (79%) presented with
myelopathy and five (22%)were neurologically intact. Four
patients either died or were not improved. with 20 patients
(87%)being improved. Seven patients underwent anterior
C1 to (3 strut-graft fusions and the remaining 17 patients
underwent a posterior cervical arthrodesis. The procedure
is well tolerated (Table 11-1).
Table 11-1
Clinical Series of Patients Who Underwent Transcervical Resection of Cranial Vertebral Junction lesions
ClinicalSeries
Patient
Preop
Com-
Posterior
Neurofunc-
Result
Op Date
Sex Age
Diagnosis
Function
Duration
Pathology
plications
Fusion
tional
Time
DB8/20/85
M
42
Chordoma
Neck
6 weeks
Chordoma
None
9/3/85
LeftIX.X
Died5
C1-(2
pain
clivus+
palsy
years
dissolution
C1-C2
recurrence
postop
WR10/18/85
F
60
AngledFx
Quad-
9 months
Thick
CSFfistula 10/31/85
Independent
6 months
C2APdia
paretic
fibrosis
7mm
NonunionFx
DD2/3/86
M
31
Os
Quad-
4 years
Odontoid
SIADH
2/11/86
Spasticgait
6 months
odontoideum
paretic
loose
Self-care
Basilar
Unstable
impression
fibrosis

Patient Op Date JS 11/12/86 TS 11/24/87 JD 3/1/88 MS 11/10/89 AR 1/26/90 DY 6/15/90 VS 6/18/90 AS 5/5/91 AR 6/29/92 EF 4/19/93 ES 11/15/93 WB 11/7/95 MCS 1/23/96 VSM 7/9/96 JLS 7/15/96 11 Closure of the Retropharyngeal Approach to the Occipitocervical Junction 107 Sex Age Diagnosis M 43 Os odontoideum Preop Function Quad- paretic 3 years Basilar impression M 16 Neurofibromas Quad-paretic 3 months ventral canal C2-C7 F 66 Rheumatoid Quad-paretic 2 years pannus odontoid F 63 Ca breast Neck pain 3 months metastasis Path Fx C2 Com- Poster plications Fusion! Neurofunc- tional F M F M F F M F M 36 64 45 42 14 21| 60 47 31 55 41 Duration Pathology Hangman's Fx Neck pain C2+HNP C2-C3 2 weeks Rheumatoid Quad- sublux C1-C2 paretic 8 months Meningioma ventral Mild myelopathy foramen mag C1 Tpli odontoid Fx Mild myelopathy Unstable nonunion Plexiform Neck pain neurofibroma C1-C2 Ewing's Neck pain sarcoma C1 + C2 Odontoid agenesis Sclerosis Myelopathy Ataxic Quad-paretic C1-C2 Basilar impression Basilar Neck pain impression Mild X-linked myelopathy hypophosphate Weak ricketts upper exts Os odontoideum Ventral Headache Mild myelopathy compression Basilar impression Neck pain Mild myelopathy 1 year 8 years 1 year 8 months 3 years Meningioma anterior foramen mag Bedridden Quadriplegia 1111 Odontoid None 11/25/86 loose Unstable fibrosis Mult. neurofib. CSF fistula 12/11/87 cervical roots Neuro intact Back to work Mild spasticity Carpenter work Rheumtoid pannus Bronchial 3/9/88 spasm Neuro intact Independent Path compression Fx C2 Airway Anterior obstruction fusion Neuro intact Independent Unstable Fx C2+HNP C2-C3 Anterior Subluxation C1-C2 Meningioma Ventral compression None Anterior fusion Neuro intact Independent CSF Fistula 6/26/90 CSF fistula 6/29/90 Died cardiac arrest Coagulopathy Neuro intact Independent Odontoid loose scar Dysphagia 5/15/91 Neuro intact Independent Neurofibroma CSF fistula 7/10/92 Neuro intact Independent Ewing's sarcoma None 5/3/93 Neuro intact Indpendent Anterior Subluxation C1-C2 Sclerosis C1-C2 None 11/23/93 Neuro intact Occip to C5 Indepedent Pin site Anterior infection fusion Halo brace C1-C3 + removed at plate 8 week None Mild spastic Walks with cane Result Time 3 months 3 years 2 years 6 months Died 1 year Advanced Ca 2 months 6/27/90 3 months 3 months Med ret 6 months 2 months Died 3 years PO 6 months Housewife Jalnil ion Occip. encephalocele rep as child Bifid C1 arch Platybasia Basilar impression Neural axis Compress ventral tumor 6 months Works as barber 1/30/96 Occiput to T1 Neuro intact 3 months Asymptomatic Housewife Dural tear 7/12/96 CSF Occiput controlled to C4 by LP drain Dural graft Anter fusn LP drain C1-C3 + plate Neuro intact 4 months Asymptomatic Residual spastic 6 months Ambulates walker (Continued)

.
Complications
Ofthe 23 patients in the authors' series, most had ipsilateral
hypoglossal nerve palsy with hemiglossal atrophy, which
always improved but was evident in almost every patient
even after several years (Table 11-1). However, no patient
complained of glossal dysfunction. Eightpatients developed
a CSFfistula. of which four required treatment via place-
ment of a permanent lumboperitoneal shunt. Two of these
shunts were eventually removed. with no recurrence of the
retropharyngeal pseudomeningocele. There were two oper-
ative deaths, both 60+-year-old women with C1-C2 sub-
luxation due to chronic rheumatoid arthritis. They had been
bedridden for several months and were on long-term ex-
ogenous steroid therapy. One died of coagulopathy and the
other of respiratory failure; unable to be weaned from me-
chanical ventilator support. Dysphagia, which persisted for
several months requiring long-term gastrojejunal enteric
tube feeding, occurred in three patients. This is due to dys-
functional contractility of the upper pharynx and probably
a stretch injury to the SLN.This resolved in all three pa-
tients. Voice hoarseness caused by SLNdysfunction oc-
curred in four patients. This SLNdysfunction resolved even-
tually in all but one patient who had breast carcinoma
metastatic to C2and who died one year after surgical resec-
tion, from systemic metastases.
. Conclusions
The retropharyngeal approach to the occipitocervical junc-
tionis predicatedon carefuland completedissectionofse-
quentiallayers of cervical fascia investing the submandibu-
lar triangle. Intraoperative use of the operative microscope
and lateral projection fluoroscopy improves the surgeon's
vision and orientation throughout this procedure. Thispro-
cedure offers a wider exposure with more versatility and
safety than the transoral route to this region. Laser facili-
tates dissection of the thick ligaments and muscle/tendon
insertions that otherwise add to the difficulty of surgically
exposingthe deepstructuresavailableto this approach.The
complication of dural CSFleakage is easily managed bya
shunting
procedure. with minimal risk of infection or
meningitis.Potentialcomplicationscanbe reducedbypre-
emptive measures such as judicious tracheotomy, place-
ment of transcutaneous enteric access, anterior stabilization
utilizing the preserved C1anterior arch, and preoperative
percutaneous
lumbar CSFdrainage. Chronic rheumatoid
arthritis and long-term immunosuppressive drug therapy
are conditions that put patients at higher risk for complica-
tions with this procedure. Such patients should probably
undergoposterioroccipitalcervicalarthrodesis.ratherthan
an anterior fusionproceduredue to osteoporosisandsoft
bone quality.
108
Occipitocervical
Junction:
Anterolateral
Approach
Patient
Preop
Com-
Poster
Neurofunc-
Result
Op Date
Sex
Age Diagnosis
Function
Duration
Pathology
plications
Fusion
tional
Time
WP10/21/96
M
54
Basilar
Neckpain
3years
Ant
Persistent
10/28/96
Neurointact 6months
impression
translation C1 dysphagia
Remove
Noneckpain Recovered
CervicaI
Wirefusion
SIP
fusn
Playinggolf
Dysphagia
kyphosis
1983
jejunostomy
occip
Reiter's
Ventral
Bowel
toG
syndrome
compression
obstruction
JES12/17/96
F
76
Meningioma
Mild
9 months
Neuralaxis
Dysphagia
Ant
Neurointact 2 months
anterior
myelopathy
compression
clearing
fusion
Gait
Active
foramen mag
Unsteady
Ventral
LPdrain
C1-C3 +
normalized
with
gait
tumor
1wk
plate
family
BG3/3/97
F
61
Rheumatoid
Bedridden
6 months
Odontoid+
Intubated +
Anterfusion Nochange
Died
subluxC1-(2
Quadriplegia
pannus
ventilator
C1+(3
Halobrace
7/28/97
Ventral
Jejunostomy
plate
Respiratory
compression
fed
failure
AMB7/11/97
F
25
Obesity+
Neckpain
4 months Platybasia+
Tra-
7/25/97
Neurointact 4 months
Apert's synd
following
odontoid
cheotomy+
Occip to C4
-work
Basilar
MVA
hypoplasia
pneumonitis
6 months-
impression
CSFleak/
school
LPdrain
DMcS1/26/99
M
88
OdontoidFx
Neckpain
5weeks
Odontoid
Previous
Antfusn
Dementia,
Rehab
type II
Traumatic
retrolisthesis
tracheotomy C1+C3
otherwise
nurse
retrolisthesis
encephlopathy
+feeding
plate/halo
intact
jejunostomy
Ant, anterior; AP,anteroposterior; Ca, carcinoma; (SF, cerebrospinal fluid; dia, diameter; Ext,extremities; Fx,fracture; Fusn, fusion:
HNP,herniated nucleus pulposis; LP,lumboperitoneal, Mag, magnum at foramen magnum; Med ret, medical retirement; MVA,motor
vehicle accident; neural, neurological; occip, occipital; Op, operative; Path Fx,pathological fracture; PO, postoperative; Rep, repaired;
SIADH,syndrome of inappropriate antidiuretic hormone secretion; sublux, subluxation; synd, syndrome; Tp II,type IIodontoid
fracture.

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ENT. Vol 5.
NewYork:Springer-Verlag;
1994:59-67
7.
Bonkowski JA.Gibson RD.Snape L.Foramen magnum meningioma:
transoral resection with a bone baffle to prevent CSFleakage.JNeuro-
surg 1990;72:493-496
8. HoulePJ. Vender JR.Fountas K. McDonnell DE.FickJR. Robinson J.
Pump-regulated
lumbar
subarachnoid
drainage.
Neurosurg
2000;46:
929-932
9.
de Andrade
JR. Macnab
I. Anterior
occipito-cervical
fusion
using an
extra-pharyngeal
exposure.J
Bone Joint Surg Am 1969;51 :1621-1626
10.
Dickman
CA. Locantro J. Fessler RG.The influence
oftransoral
odon-
toid resection
on stability
of the craniovertebral
junction. JNeurosurg
1992;77:525-530
11. Vender JR.Harrison SJ. McDonnell DE.Fusion and instrumentation at
C1-3
via the high anterior
cervical
approach.
J Neurosurg
(spine
I)
2000;92:24-29

12
Posterior Suboccipital and Upper Cervical
Exposure of the Occipitocervical Junction
Gary L. Rea and Vijay G.R. Kumar
.
Indications
. Advantages
.
Disadvantages
The posterior approach to the suboccipital and upper cervi-
cal spine region is one of the most common neurosurgical
procedures. This versatile approach allows exposure of the
posterior fossa and the occipitocervical region for decom-
pressions and/or fusions with fixation from the occiput to
(3. Aswith other approaches, the surgeon must be attentive
to details specific to the procedure and must determine the
optimum patient positioning.
.
Indications
Exposure of posterior fossa and occiput cervical region for
.
Decompression
.
Fusion with fixation from occiput to (3
.
Advantages
. Familiarand versatile approach
.
Allowsfor decompression and fusion in a single approach
. Prone positioning reduces risk of air embolism and im-
proves access for surgeon and assistant.
.
Disadvantages
.
Lateraldissectionplacesthe vertebralarteryandgreater
occipitalnerveat risk.
.
Prone positioning requires operator to stand and in-
creasescompressiononthe chest.
There are three positions for posterior suboccipitocervical
exposure: sitting, lateral, and prone. The sitting position
110
decreases the risk of bleeding by lowering venous pressure,
but .itincreases the risk of air embolus and hypotension.t-J
The lateral position allows the surgeon to sit and decreases
the risk of air embolus, but it tends to obstruct those assist-
ing the physician.
The prone position, arguably the most common, allows
easy access for the surgeon and assistant and involvesa
very small risk of air emboli or hypotension. Its disadvan-
tages include the potential for compression of the chest, the
theoretical
possibility of increased bleeding (compared
with the sitting position), and a more tiring position (Le.,
standing) for the surgeon.4
With the prone position, very careful attention must be
paid to padding the patient and to the position of the
patient's neck. The chest must be padded to allow fullexcur-
sion; this can be done with side gel rolls. Also, the face,
elbows, hands, knees, genitalia, and feet must be ade-
quately protected to avoid nerve compression injuries or
skin necrosis.5-10
To guard against cord injury, the head should be firmly
immobilized with a Mayfield-type head holder. This pro-
vides access to the face for anesthesia, puts no pressure on
the face, and allows control of the neck.11.12Ideally,the neck
should be placed in a neutral position with normal spinal
alignment. This can be documented by x-ray. Ifdecompres-
sion is planned, the neck may be slightly flexed for im-
proved access to the occipitocervical junction. On the other
hand, if a mass is present at this level, then full flexion
could lead to compression of the cervicomedullary region.
Having no fewer than three fingerbreadths from the sternal
notch to the chin can lessen this risk. Ifan occipitocervical
fusion/fixation is the goal, then a neutral position docu-
mented by lateral (-spine is ideal. In obese patients, ben-
zoin and tape can be used to pull the skin and decrease the
neck skin folds.6 Ideal positioning is not always possible,
and the surgeon must balance the need for exposure with
the risks of cord compression and neck venous obstruction.

12
PosteriorSuboccipitaland UpperCervicalExposureof the OccipitocervicalJunction
111
Themidline incision extends from 2 em above the exter-
naloccipital protuberance
to as far as C7. depending
upon
theexposuresnecessary (Fig. 12-1). The C2 spinous
process
isusuallypalpable beneath
the skin;
whereas.
C3 is quite
smallandnot easily felt until
one has dissected
down to the
fascia.Theinitial
incision
with
the skin knife
is done after
theskin, subcutaneous
tissues.
and muscles
are injected
withMarcaine and epinephrine
(if not contraindicated)
to
decreasebleeding and postoperative
pain.
Self-retainingretractors are put into place. and the unipo-
larelectrocautery is used after the incision
has reached the
fascia.After the trapezius. which
attaches to the fascia. is di-
vided.the (2 spinous process is easily
palpable.
Then the
occiput is exposed by dissecting the attached trapezius and
semispinalis capitus laterally with electrocautery
to mini-
mize bleeding. The posterior tubercle of the atlas is identi-
fied. and subperiosteal dissection is performed
14-15 mm
laterally on both sides (Fig. 12-2). Further lateral dissection
increases the risk of vertebral artery or greater occipital
nerve injury. Next. the unipolar electrocautery is used to re-
move the muscle attachments to (2 and C3(or further ifin-
dicated) out to the facets. Gauze pads are swept laterally
with the Cobb elevator to control bleeding and clean the
lamina further. The self-retaining
retractors are inserted
further. The region is now exposed for decompression. fu-
sion/fixation. or any combination procedure.
Agure12-1
Posterior exposure to fascia. Skin incision in this case extends from above the external occipital protuberance
to (7. Knifeor electro-
cautery canbe used to perform subperiosteal dissection to expose the lamina.

112
Occipitocervical Junction: Posterior Approach
Figure 12-1 (Continued)

12
PosteriorSuboccipitaland UpperCervicalExposureof the OccipitocervicalJunction
113
I
r
'I
'I
l" rrfV.
.).
Figure12-2
Subperiostealdissection of(1. The electrocautery isused
to remove muscle and ligamentum attachments to (1 laterally to no
more than 14to 15mm.

114
OccipitocervicalJunction:PosteriorApproach
References
1.
Bedford RF.Surgery of the Spine in Clinical Anesthesiology
and Neuro-
surgery. 2nd ed. New York: Butterworth-Heinemann;
1991 :265-276
2.
Michenfelder JD. Martin JT. Altenberg
BM. Evaluation
of an ultrasonic
device for the diagnosis of air embolism. Anesthesiology
1972:36: 164-177
3.
Zeidman
SM. Ducker TB. Posterior
cervicallaminoforaminotomy
for
radiculopathy:
review
of 172 cases. Neurosurgery
1993;33:356-362
4.
Gingrich KM.The sitting position
of anesthesia:
overcoming
the risks.
Welcome trends. Anesthesiology
1992;10:3
5.
Ellis Sc. Massive
swelling
of the
head
and
neck.
Anesthesiology
1975;42: 102-103
6.
Epstein JA. Epstein
NE. The surgical
management
of cervical
spinal
stenosis.
spondylosis
and myelo-radiculopathy
by means
of the pos-
terior
approach.
In: The Cervical
Spine
Research
Society
Editorial
Committee.
eds. The Cervical Spine. 2nd ed. Philadelphia:
JB Lippin-
cott; 1989:626-643
7.
Keykhad
MM. Rosenberg
H. Bilateral
foot-drop
after
craniotomy
in
the sitting position. Anesthesiology
1979;51: 163-164
8.
Marshall
WK. Bedford RF. Miller ED. Hemodynamics
in the seated po.
sition. Anesth Analg 1982;61 :201
9.
McAllister
RG. Macroglossia:
a positional
complication.
Anesthesiol.
ogy 1974;40:199-200
10.
Parkes
BJ. Postoperative
peripheral
neuropathies.
Surgery
1973;74:
348-357
11.
Benzel EC. Cervical
spondylotic
myelopathy:
posterior
surgical ap-
proaches.
In: Menezes
and Sonntag.
eds. Principles
of Spinal Surgery.
New York: McGraw-Hill;
1996:571-580
12.
Stewart
DH. Krawchenko
J. Patient
positioning.
In Wilkens
RH and
Rengachery
SS. eds. Neurosurgery.
New York; McGraw-Hill;
1985:
452-457

13
SuboccipitalCraniectomy and Cervical
laminectomyfor Chiari Malformation
VijayG.R. Kumar,
Edward Kosnik,
and
Garyl.Rea
. Indications
. Contraindications
. Advantages
. Disadvantages
. SurgicalTechniques
In1891,Hans Chiari described
and categorized
the hind-
brainhernias that today bear his name.1 The Chiari malfor-
mationisassociated with syringohydromyelia
in -50 to 75%
ofpatients.2-6The primary surgical treatment
ofthis
abnor-
malityis a suboccipital craniectomy and upper cervical
laminectomy7-13to decompress
the
foramen
magnum,
alongwithvaryingdegrees of dural, arachnoid, and cerebel-
lartonsillardecompression.
Themidline approach in the prone position
provides ex-
cellentbilateral exposure. The access is through
relatively
avasculartissue, causes minimal disruption
of nerve supply,
andhasa low risk of damaging
important
neurovascular
structures.The exposure
also permits
harvesting
of a liga-
mentumnuchaegraft for dural closure, thereby avoiding
theneedforartificialsubstitutes or another incision.14-19
. Indications
. Foramenmagnumdecompression forChiarimalformation
. Cerebellarand brain
stem
tumors
at the level of the
foramenmagnum
. Intracerebellarhemorrhage
. Arachnoidcysts
. Contraindications
. Basilarinvagination
. Irreducibleatlantoaxial
subluxation
. Advantages
.
Excellentbilateralexposure
.
Minimaldisruptionofnervesupply
.
low riskofdamagingimportantneurovascularstructures
.
Permits harvesting of a ligamentum nuchae graft for
dural closure
.
Disadvantages
.
Soft tissue traction can injure the vertebral artery.
. Watertightdural closure essentialto preventcere-
brospinal fluid (CSF)leak
.
SurgicalTechniques
The positioning and initial incision are the same as in pa-
tients undergoing occipitocervical fusion/fixation. At the
level of the fascia, however, a Y-shaped incision is made
in the fascia and muscle and is deepened to the level of
the occipital bone (Fig. 13-1). The V-shaped upper mus-
cle fascia flap is opened to the occipital bone and re-
flected superiorly. This maneuver allows ready identifica-
tion of the ligamentum nuchae in the midline. Beginning
on one side, working from above downward, the ligament
nuchae is dissected from its point of attachment
to the
muscles laterally and inferiorly to the spinous processes
of C1-C3 and its attachment
to the skull base. A similar
115

116
OccipitocervicalJunction:PosteriorApproach
Figure 13-1
The Y-shaped
incision is made at the fascia level. The
upper V portion is carried to the occipital bone at to level of the fora-
men magnum. The subsequent
V-shaped fascia muscle flap is held su-
periorly by a retraction
suture. The ligamentum
nuchae is exposed by
the base of the V-shaped incision.
dissection is now performed on the opposite side. This
usually yields a graft -4 to 7 cm long, 3 cm wide, and 2 to
3 mm thick.14 The harvested
graft is placed in saline-
soaked gauze.
The occiput and the appropriate
cervical lamina are
exposed in the previously described manner. However,
because the Chiari malformation is associated with bony
abnormalities at the foramen magnum, due care must be
taken. The posterior arch of atlas may be abnormally high,
bifid, or even fused to the occiput and may not be appreci-
ated as a separate structure.
Once the posterior arch is identified. the muscle is re-
moved subperiosteally, and the occipital craniotomy is
begun. The craniectomy of the occipital bone is performed
Figure 13-2
The high-speed drill is used to make multiplebur
holes to the dura. Then curettes, dural separators, rongeurs, and
punchesare usedto complete the craniectomy.
using a high-speed drill and rongeurs (Fig. 13-2). The
decompression is 2.5 to 3 cm in diameter and about
the same measurement upward from the rim of the foramen
magnum. The bone is removed piecemeal
across the
midline and then down to the foramen. taking care to pro-
tect the underlying dura. The vertebral artery is avoidedby
taking care to removebone only,without pulling onsoft
tissues.
The arch of C1 is now thinned out with the high-speed
drill and excised using small Kerrison rongeurs. A 2.5to
3 cm segment is removed, again taking care to avoidthe
vertebral artery. Apartial or complete laminectomy of(2is
performed in a similar fashion if this is deemed necessary
to unroof the cerebellar tonsils.

13
SuboccipitalCraniectomyandCervicalLaminectomyfor ChiariMalformation
117
Thecerebellar hemisphere dura is opened on one side,
thentheother;then these incisionsare connected in the
midline.Atthis stage, the dura is carefully separated from
theunderlyingarachnoid, which is left intact if possible.
Duralvascularlakes may be encountered and are best dealt
withbyplacing liga clips on the dural edges. Tight dural
horizontalbands compressing
the cerebellar
tonsils may be
occasionallyencountered;
these must be divided. Stay su-
turesretractthe dural edges. The arachnoid is now opened
inahorizontal fashion at the level of the cerebellar
tonsils
undermicroscope
illumination
and
magnification.
Mi-
crodissectionbetween
the cerebellar
tonsils is performed,
andarachnoidadhesions are divided.20
Thepreviously harvested
ligamentum
nuchae
graft
is
nowcutin the shape of a numeral 7 and sutured
in a water-
tightfashion to the dura (Fig. 13-3).
As part of the dural
closure,tenting sutures are used to secure the dura and the
freshlygrafteddural material to the cervical musculature to
vitalizethetissue and promote watertight closure.
Thewound is copiously
irrigated
with antibiotic
solution
andinspected for bleeding. A layered closure is performed.
Thecervical musculature
is loosely
tacked
together
to
eliminateany dead
space.
The deep
cervical
fascia
is
reapproximatedcarefully
in the midline
with interrupted
Vicrylsutures. The subcutaneous
tissues are apposed
together,and the skin is closed with subcuticular
Vicryl. An
occlusivedressingis applied. Awound drain is not routinely
used.
References
I. ChiariH.Uber Veranderungen
des Kleinhims infalge von Hydrocephalie
des Grosshims.
Dtsch
Med
Wochenschr
1891; 17: 1172- 1175
2. PaulKS. Lyle RH. Strang
FA. Dutton
J. Arnold-Chiari
malformation:
re-
viewof71
cases.J
Neurosurg
1983;58:183-187
3. Menezes AH. Chiari
I malformations
and
hydromyelia:
complications.
Pediatr Neurosurg
1991-92;17:146-
154
4. Nohria V. Oakes
WJ. Chiari
I malformation:
a review
of 43 patients.
Pediatr Neurosurg
1990-91
;16:222-227
5. Pillay PRoAwad
IA. Little
JR. Hahn
JE Symptomatic
Chiari
malforma-
tionin adults: a new classification based on magnetic resonance
imagingwith clinical and prognostic significance. Neurosurgery
1991;28:639-645
6. ElsterAD, Chen MY. Chiari I malformations:
clinical
and radiologic
reappraisal.Radiology 1992;183:347-353
7. DysteGN.Menezes AH, VanGilder Jc. Symptomatic
Chiari malforma-
tions:an analysis of presentation,
management.
and long-term
out-
come.JNeurosurg 1989;71:159-168
8. MenezesAH. Smoker WRK. Dyste GN. Syringomyelia.
Chiari malfor-
mationsand hydromyelia.
In: Youmans JR. ed. Neurological
Surgery.
3rded. Philadelphia: Saunders;
1990: 1421-1459
9. FaulhauerK.Loew K.The surgical
treatment
of syringomyelia:
long-
tenmresults.ActaNeurochir (Wien) 1978;44:215-222
10. Garcia-UriaJ.Leunda G. Carrillo R, Bravo G. Syringomyelia: long-
term results after posterior
fossa decompression.
J Neurosurg
1981:54:380-383
Figure 13-3
The dura isopened inthe shape of a numeral 7 with
the opening overthe left and rightcerebellarhemispheresand the ver-
tical limbextending down to (1 or (2. The ligamentum nuchae graft
issutured into this openingwitha runningwatertight suture.
11.
Lewy WJ. Mason L. Hahn JE Chiari malformation
presenting
in adults:
a surgical experience
in 127 cases. Neurosurgery
1983;12:377-390
12.
BatzdorfU.
Chiari I malformation
with syringomyelia:
evaluation
of
surgical
therapy
by
magnetic
resonance
imaging.
J Neurosurg
1988;68:726-730
13.
Piper JG. Muhonen
MG. Sawin p. Menezes
AH. Chiari malformation
database
report:
long-term
follow-up
review
of surgical
treatment
modalities.J
Neurosurg
1994;80:383A
14.
Kosnik EJ.Use of ligamentum
nuchae
graft for dural closure
in poste-
rior fossa surgery:
technical
report. J Neurosurg
1998:89: 155-156
15.
Banerjee
T. Meagher
IN. Hunt WE. Unusual
complications
with the
use of silastic dural substitute.
Am Surg 1974;40:434-437
16.
Cohen AR. Aleksik S. Ransohoff J. Inflammatory
reaction
to synthetic
dural substitute:
case report. J Neurosurg
1989:70:633-635
17.
Ng TN. Chan KH, Leung SY.et al. An unusual
complication
of silastic
dural substitute.
Neurosurgery
1990:27:491 -493
18.
Simpson
D. Robson A. Recurrent
subarachnoid
bleeding
in associatiotf
with
dural
substitute:
report
of
three
cases.
J
Neurosurg
1984;60:408-409
19.
Thadani
V, Penar
PL. Partington
J, et at. Creutzfeldt-Jakob
disease
probably
acquired
from a cadaveric
dura
mater
graft: case report. J
Neurosurg
1988;69:766-769
20.
Piper JG. Menezes
AH. Chiari malformation
in the adult. In: Menezes
AH. Sonntag
VKH. eds. Principles
of Spinal Surgery. Vol 1. New York:
McGraw-Hili;
1996:379-394

14
Posterior Occipitocervical Fusion
and Stabilization Using Bent Titanium
Rodsand Cables
Vijay G.R. Kumar and Gary L. Rea
.
Indications
Congenital
Acquired
.
Contraindications
.
Advantages
Congenital
or acquired
pathology
of the
upper
cervical
spine and craniovertebraljunction
can lead to bony instability
and neural compression. Common congenital anomalies are os
odontoideum,
basilar impression,
assimilation
of atlas, and
Down, Klippel-Feil,and Morquio's syndromes.! Acquired abnor-
malities may be due to trauma, rheumatoid arthritis, neoplastic
disease, ankylosing spondylitis, or postsurgery instability.2-4
Patients with occipitocervical instability may be asymp-
tomatic in the presence of minor anatomical changes. How-
ever, as instability increases (with resultant neural com-
pression), a variety of signs and symptoms may occur.
Occipital headaches, neck pain, cranial nerve dysfunction,
ataxia, cervical myelopathy, and autonomic dysfunction
have all been described.
The basic tenets of occipitocervical fusion include neural
decompression, restoration of normal anatomical relation-
ships, and bony fusion. Decompression, either anterior or
posterior, should be done first if compressive deformity is
fixed and not corrected by realigning traction.3.5
The use of bent titanium rods and cables provides rigid
internal fixation obviating the need for external fixation.
This permits early patient mobilization and rehabilitation.
The technique is safe, effective, and cost-efficient.6-8
.
Indications
Congenital
. Occipitoatlantal instability
.
Presence of subaxial cervical laminectomies
.
Congenital anomalies
118
.
Disadvantages
.
SurgicalTechniques
.
SalientTechnicalNotes
. Os odontoideum
.
Basilarimpression
.
Assimilation of atlas
.
Down,Klippel-Feil,and Marquio's syndromes
Acquired
. Trauma
.
Rheumatoid arthritis
.
Neoplastice disease
.
Ankylosingspondylitis
.
Postsurgery instability
.
Contraindications
.
Atlantoaxialinstabilitywith bonydestruction prevent-
ingfixationofC1-C2alone
.
Irreduciblesymptomaticanteriorcompression
.
Advantages
.
Obviatesthe needforexternalimmobilization
.
Permitsearlymobilizationand rehabilitation
.
Cost-efficient
. Rigid

14
Posterior Occipitocervical Fusion and Stabilization Using Bent Titanium Rods and Cables
119
. Disadvantages
. Requires
passage
of sublaminar
cables
. Gapsbetweentherodsandthe laminaewill resultin in-
adequate
fixationof thevertebraeandexcessivemotion.
. Unableto addressirreducible symptomatic anterior
compression
. SurgicalTechniques
Positioning
andexposureare detailed in Chapter 12. A neu-
tralheadpositionis important becausefusionjfixation
will
bedone.
Aftertheocciput,the foramen magnum region, and the ap-
propriatecervicalvertebraeare exposed, threaded titanium
K-wireofsufficient sizeand rigidity is bent and cut to con-
formtothe occipitocervical region and the cervical levels
necessary
foradequate fixation. Although this usually in-
eludes CI,C2,and C3,occasionally fixation may require ex-
posing the entire cervical spine (Le.,to C7).
A high-speed drill removes bone overlying the dura for
wire fixation holes on both sides of the cephalad corners of
the bent rods (Fig. 14-1). The posterior rim of the foramen
magnum is enlarged, and single holes for wire passage
are made on the lateral side of the rectangle, permitting
attachment
to the foramen
magnum. The ligamentum
fIavum is removed completely at its cephalad and caudad
attachments at each cervical level to be fused, and often a
notch is placed to seat the cable firmly (Fig. 14-2). Doing
this is critical to allow passageof the sublaminar cables.
Cablesare now passed through the occipital holes at the
foramen magnum and sublaminar holes at the appropriate
cervical levels. This is facilitated by the presence of leader
segments in the cables, which can be contoured to an ap-
propriate shape permitting
easier passageand pickup. It is
advisable to decorticate the occiput and the cervicallami-
nae and lateral masses of the fusion levels prior to seating
the rectangle. The rod is positioned,
and the cables are
Figure14-1
The two cephalad
bur holes allow wire to be placed around the upper bends in the rod. The lower holes at the foramen magnum
accommodate
cablethat holdsthe rod at the foramen magnum, takingadvantage ofthe thickbone inthis region.

120
OccipitocervicalJunction:PosteriorApproach
Figure 14-2
The lamina at (2 is notched to provide afixed point of
attachment for the cable.thereby decreasingthe risk of slipping.
passed carefully around it in an orderly and symmetrical
fashion, avoiding overlapping or knotting. The cablesat
the bends of the rod must be placed carefully to avoid
vertical translocation, telescoping, or settling of the fusion
construct (Fig. 14-3). The rod should contact all bone
surfaces.Gapsbetween the rods and the laminaewillre-
sult in inadequate fixation of the vertebrae and excessive
motion.
Although passage of the wires at the foramen magnum
can be tedious because of the thickness
and strength
of the
cortical bone, it is strongly recommended. Because the (1
arch is often removed or is deficient, this anchoring at the
foramen magnum is very important.
Morcellizedcancellousbone graftis nowplacedoverthe
previouslydecorticated bone surfaces around the rod.
The wound is irrigated with antibiotic solution and in-
spected forbleeding.Alayeredclosure is performedafter
insertinga suctiondrain under the paraspinalmuscles.The
cervical musculature is loosely tacked together to eliminate
any dead space. The deep cervical fascia is reapproximated
in the midline with interrupted sutures. The subcutaneous
tissues are drawn together, and the skin is closed with sub-
cuticular sutures.
Figure 14-3
The wires are placed at the
cephaladends of the bent rod and at the fora-
men magnum. The rod should be bent so
that it isflush with the bone.

References
14
Posterior Occipitocervical Fusion and Stabilization Using Bent Titanium Rods and Cables
121
1.Coria
F,Quintana F.Villalba M, Rebollo M. Berciano J.Craniocervical
abnormalities
in
Down's
syndrome.
Dev
Med
Child
Neurol
1983;25:252-255
2. MenezesA.VanGilder J, Clark C, EI-Khoury
G. Odontoid
upward
mi-
grationin rheumatoid arthritis: an analysis of 45 patients with "cra-
nialsettling."J Neurosurg1985;63:500-509
3. MenezesA,VanGilder J, Graf C, McDonnell
D. Craniocervical
abnor-
malities:
a
comprehensive
surgical
approach.
J
Neurosurg
1980;53:444-455
4. ReaG, Mullin B, Mervis
L, Miller
C. Occipitocervical
fixation
in
nontraumaticupper cervical instability. Surg NeuroI1993;40:255-261
5.
Menezes
AH. Craniovertebral
junction
anomalies.
In: Tindall
GT,
Cooper
PR, Barrow
DC, eds. Practice
of Neurosurgery.
Vol 3. Balti-
more: Williams & Wilkins;
1996:2729-2740
6.
Pikul B, Rea G. Application
of the Luque rectangle
fixation for occipito-
cervical and atlantoaxial
instability. In: Fessler RG.Haid RW, eds. Current
Techniques
in Spinal Stabilization. New York: McGraw-Hill;
1996:89-92
7.
Lunsford A, Crockard
H, Pozo J, Thomas N, Nelson I. Craniocervical
in-
stability
treated
by contoured
loop fixation.
J Bone Joint
Surg
Br
1986;68: 173-177
8.
McKenzie A, Uttley D, Marsh H, Bell B. Craniocervical
stabilization
us-
ing Luque/Hartshill
rectangles.
Neurosurgery
1990;26:32-36

15
Occipitocervical Encephaloceles:
Surgical Treatment
J. Parker Mickle
.
Indications
.
Contraindications
.
Advantages
.
Disadvantages
Congenital cranial anomalies are relatively rare, occurring
in -1 per 10,000 live births.! An occipital location is the
most common site for these anomalies. Large and exten-
sive craniocervical herniations are rare and most of these
are associated with other neural tube defects. Encephalo-
celes are embryological abnormalities
occurring during
the first month of gestation and probably result from a dis-
order of gastrulation termed limited dorsal myeloschisis.2
Depending on the degree of abnormality, these extracra-
nial herniations can be small and atretic and relatively
unimportant. or extensive with major abnormalities
in-
volving the brain and upper spinal cord. Today these le-
sions are easily diagnosed prenatally with ultrasound and
a good estimate of the severity of the lesion can be defined
prenatally. About 80%of encephaloceles
occur in the oc-
cipital region and -30% of these lesions are greater than
10 cm in their greatest diameter.3 Hydrocephalus occurs in
-50% of these cases. The contents of the occipitocervical
sac can vary tremendously, ranging from meninges only
with cerebrospinal fluid (CSF)to complete herniation of
major brain structures including cerebral cortex and hind-
brain. The prognosis in this entity is directly proportional
to the amount of brain found within the defect and also
the association of other congenital abnormalities in this
entity.
Preoperatively,
the contents
of the
occipitocervical
encephalocele can be well defined with ultrasound and
magnetic resonance imaging (MRI) studies. The surgeon
should be well prepared with a clear understanding of what
the goals are in the surgical repair of these before surgery
begins. Bloodloss can be extensive in these operations be-
cause there is often a profuse fibrovascular component in
the excisionof these lesions. In this location. the torcula and
lateral sinuses can be quite low with extensive vascular
122
.
Surgical Techniques
.
Outcomes
.
Complications
lakes draining the dural leaves involved with this complex
abnormality. Unless the lesion is open (a true anencephaly)
repair of these abnormalities can be performed on an elec-
tive basis.The goals in treatment are to remove the occipital
encephalocele while maintaining integrity of the vascular
and neural structures contained therein.
.
Indications
.
Occipital/high cervical encephalocele
. Myelomeningocele
. Largeposterior dural ectasias
.
Other miscellaneous open neural tube defects in region
.
Contraindications
.
Activesepsis or infection (relative)
.
Systemic instability or high medical risk
.
Anencephaly or lack of neurological function
.
Poor/grim prognosis
.
Lackof tissue coverage for closure
.
Advantages
. Preserves brain and spinal cord function
.
Protects repair by preventing CSFleaks

15
OccipitocervicalEncephaloceles:SurgicalTreatment
123
. Disadvantages
. Noimmediate bony reconstruction
. Bloodloss can be significant
. SurgicalTechniques
Thesurgicalexercise presented here is a relatively extensive
lesionextending from the occipital bone into the upper cer-
vicalspinewith a defect involving the occipital bone and
uppercervicalvertebra (Fig. 15-1). If the lesion is fully cov-
eredbyskinas demonstrated in this approach, the circum-
ferentialincision through the skin down to the dura is made
:Fig.15-2). This can be done with electrocautery,
which
minimizesblood loss in these small patients.
A plane is de-
velopedbetween the dura and the subcutaneous
tissues
andthisincisionis made such that adequate skin is avail-
ableforclosureat the termination of the dural reconstruc-
tionlaterinthe case.The bony defect can be circumferen-
tiallyexposed,thereby defining the extensive
neck of the
lesioncenteringinto the vault and upper cervical spine
(Fig.15-3).The dura can be entered and (SF drained, giving
thesurgeonthe ability to inspect
the contents
of the sac
(Fig. 15-4). Ifthe contents are fibrogliotic tissue, then this
mass can be transected flush with the skull and cervical
canal. As is usually the case in this area, normally function-
ing structures are herniated into the sac and must be pre-
served. If hydrocephalus is present, then an external ven-
tricular drain can be utilized during and after surgery to aid
in the initial repair and the return of structures within the
encephalocele to more normal positioning as well as to
allow the repair to heal while reducing the threat of (SF
leakage (Fig. 15-5). Once the skin and major part of the en-
cephalocele qave been removed, the dura can either be
closed primarily or reinforced with a dural patch graft
(Fig. 15-6). The dura can be adherent to the herniated cen-
tral nervous system tissue and must be carefully separated
form it. The dura, especially toward the cranial end of this
repair, can be quite vascular.
After the dura is closed in a watertight fashion, the sub-
cutaneous tissue and skin can be closed in a routine fashion.
The skin must be approximated perfectly so that healing
can occur rapidly.
Most of these lesions have a bony defect involving the oc-
cipital bones, which can be extensive at times. This defect
can be repaired later by any number of techniques such as
split-calvarial reconstruction or the use of hydroxyapatite
bone cement.
Figure 15-1
Thisfigure demonstrates an occipital
cervicalencephalocele.Thislesioncontains the herni-
ated neural tissue and meninges through the bony
defect.
-

124
OccipitocervicalJunction:PosteriorApproach
Dura
Figure 15-2
A circumferential
incision through
the skin is made down to the dura mater. Adequate
skin should be available for closure at theter.
mination
of the dural reconstruction.
Careful undermining
of the skin will enable the defect to be closed without
tension.
Care should also be taken
to prevent entrance into the encephalocele.

15
OccipitocervicalEncephaloceles:SurgicalTreatment
125
.....
Low lying torcula
Duralsac
Deep fascia and
muscle
figure15-3 The bony defect is circumferentially exposed thereby defining the neck of the encephalocele.
Dural edge
Arachnoid veil
over brain stem
Figure 15-4
The dura mater is incised and
drained of cerebrospinal fluid. The herniated tissue
is inspected
and if it consists of fibroglottic
scar,
then the nonfunctional is transected
at its base.

126
OccipitocervicalJunction:PosteriorApproach
Dural patch
graft
Ventriculostomy
..
)-.....
Figure 15-5
If hydrocephalus
is present, thenan
external ventricular drainage can be utilized during
and after surgery to aid in the initial repair and
healing phase. If hydrocephalus
persists,
the CS
shunting is indicated.
Figure 15-6
The dura mater
can be closed primarily or rein-
forced with dural patch graft.

. Outcomes
15
OccipitocervicalEncephaloceles:SurgicalTreatment
127
Theoutcome and the surgical
care of these complex
con-
genitalesionsare directly proportional
to their
size and the
extentof brain herniation.
Unfortunately,
with
the large le-
"\\)".\)T()~()undmorbidity
continues
to be common,
and at
(hispoint, the surgical
intervention
has little
to do with
long-termoutcome. The surgical
closure
of these
lesions
remainsa technical challenge, and in the smaller
lesions ex-
cellentoutcomes can be expected.
References
.
Complications
The complications associatedwith the repair of occipitocer-
vical encephaloceles include injury
to underlying
neural
structures, extensive blood loss, (SF leakage, and infection.
All of these potential outcomes can be minimized with ade-
quate preoperative visualization
and imaging and careful
surgical technique. Because-50% of these patients have hy-
drocephalus, early (SF diversion is critical in preventing (SF
leakageand infection.
ChapmanPH,Caviness VS.Subtorcular
occipital
encephaloceles:
con-
3.
Shokunlii
T. Adeloye A, Olumind A. Occipital encephaloceles
in 57 Niger-
cepts.PediatrNeurosurg1988:8:86-96[p1 ](p2)
ian children: a retrospective analysis. Childs Nerv Syst 1990;6:99-102
2. PangD, Dias MS. Cervical myelomeningoceles
Neurosurg
1993;33:
363-373
(p3((p4)

16
Posterior Atlantoaxial Fusion: Surgical
Anatomy and Technique Options
Indro Chakrabarti, Trent L.Tredway, and Larry T. Khoo
. Anatomy
Development
Surgical Anatomy
Regional Biomechanics
.
Surgical Techniques
Atlantoaxial instability may be induced by traumatic, con-
genital, neoplastic, infectious, rheumatologic, degenerative,
or iatrogenic etiologies. Traumatic conditions resulting in
atlantoaxial instability include transverse ligament ruptures
and odontoid fractures. Congenital conditions such as odon-
toid hypoplasia, aplasia, or os odontoideum may cause un-
stable C1-C2 segments as well. Rheumatoid arthritis is a
systemic immunologj,c disorder that can cause either or
both ligamentous and bony erosion with resultant laxity or
rupture of ligaments. Osteoarthritis at the Cl-C2 articula-
tion can be severe enough to require fusion. Finally,tumors
and infection can cause significant bony and ligamentous
destruction leading to instability. The common result of
each of these entities is a narrowed spinal canal secondary
to intermittent or chronic impingement of neural elements
and/or structural changes causing neurological deteriora-
tion, incapacitating deformity, or pain. Tofacilitate the fu-
sion rates and rehabilitation, internal fixation is generally
recommended.!
Instability in the upper cervical spine is defined in terms
of the atlantodental
interval (ADI).An ADIgreater than
5 mm is generally accepted as a sign of an unstable C1-C2
articulation.2 Halo braces, although able to reduce motion
in the subaxial cervical spine, are ineffective in the upper
cervical spine. Rigid internal fixation makes it possible to
avoid halo braces and their comorbidities and allows for
early patient mobilization and improved fusion rates. A
thorough knowledge of the atlantoaxial anatomy as well as
the articulations
and associated
neural
and vascular
anatomy is essential for safe, effectiveinstrumentation.
Several methods, including both anterior and posterior
techniques, for stabilization of the atlantoaxial region have
been developed. However, most surgeons use one of three
common posterior stabilization options. These include sub-
laminar wiring techniques, laminar clamps, and screw fixa-
tion. This chapter reviews the more commonly preferred
128
Anesthesia
Positioning
Exposure and Nuchal Musculature
Atlantoaxial
Stabilization Methods
Posterior Screw Fixation Methods
options for posterior atlantoaxial stabilization with internal
fixationdevices.Althougheachhas itsadvantagesanddis-
advantages, the best method will depend on each individual
patient as well as the surgeon's expertise.
. Anatomy
Development
Thecervicocranium, which includes from the occiput tothe
secondcervicalvertebraldisk,isembryologicallyand physi-
ologically distinct from the lower cervical spine.3 It hassev-
eral important distinctive anatomical and morphological
features that are crucial for surgical expertise in this area
(Fig.16-1). Theatlas (Cl) starts to ossifybeginningfrom
the lateralmassesduringintrauterinelife.Theanteriorarch
of the atlas may fuse from a single point at the anterior
tubercle. However, this may not be constant and multiple
ossification centers on either side of the anterior tubercle
may be present or the anterior arch can form from direct
extension from lateral masses. Anterior arch fusion is usu-
ally complete
between
the seventh
and tenth
years. The
posterior
arch tubercle
appears
in the second
year of life
with fusion by the fourth year.
The axis (C2) has a unique bony anatomy that forms from
at least five ossification
centers (Fig. 16-2). The body ofthe
axis is present and ossified from birth. The posterior
archis
only partly ossified at this time and by the second year
fuses posteriorly. The dens has two vertical ossification cen.
ters, which fuse in the midline by the seventh month ofin-
trauterine life.The tip of the dens will unite with the body
of the dens roughly by 10 or 11 years of life and is separated
by ossiculum terminale,
the ossification
center for the tip.If
it remains a nonunion,
then it is termed the os terminale.ln

Anterior tubercle
16
PosteriorAtlantoaxialFusion:SurgicalAnatomyandTechniqueOptions
129
Superior articular facet
Posterior arch
Posterior tubercle
Anterior tubercle
Transverse foramen
Transverse process
Transverse process
Inferior articular facet
Posterior tubercle
Figure 16-1
Anatomyofthe atlas ((1).
Figure 16-2
The ossificationof the AxisA-Body B - Neural arch (
- fusion of neural arches D - bifid spinous processes E - neurocentra I
synchondrosis
G - ossification center of tip of dens H - fusion of the
dens I - synchondrosis
between dens and neural arches J - subdental
synchodrosis