magnum. Burr holes are then placed on either side
just below the transverse sinus. Bilateral sharp dis-
section and the use of a Kerrison punch on the
dorsal rim of the foramen magnum will create an
entry point for the footplate of the craniotome to
turn a bone flap up to the burr holes. When con-
necting both burr holes along the transverse sinus,
care is taken not to injure an often-present occipi-
tal sinus in younger patients. In older children, a
significant midline bony ridge can necessitate the
use of a high-speed drill to complete the craniot-
omy. The bone flap is then elevated by cutting the
occipital membrane at the foramen magnum.
Meticulous hemostasis and padding of the craniot-
omy edges at this point prevents blood from enter-
ing the field after opening of the dura. The dura is
incised in a Y-shaped fashion with the straight
limb of the Y extending down across the plane of
the foramen magnum. Bleeding is controlled with
a step-by-step suturing of the dural edges or the
application of hemoclips. The cerebellar hemi-
spheres and the tonsils are immediately exposed;
incision of the arachnoid with drainage of CSF usu-
ally leads to a relaxed situation in the operating
field.9,13
Transvermian approach: After identification of
the anatomical landmarks, the vermis is incised in
its inferior part. The two halves of the vermis and
the cerebellar tonsils are carefully retracted
laterally, exposing the dorsal aspect of a fourth
ventricular midline tumor. Both posterior inferior
cerebellar arteries are usually seen and also dis-
placed laterally. Planes around the tumor can be
developed using cottonoids. In large tumors, cen-
tral debulking with an ultrasound aspirator will
allow for less traction when following the tumor–
cerebellum interface later on. The noninvaded side
of the cerebellar peduncle is first dissected expos-
ing the floor of the fourth ventricle and the
aqueduct. The transvermian approach allows for a
better visualization of the rostral tumor aspects
compared to the telovelar approach described in
the following. However, it is limited in its lateral
exposure, and the occurrence of cerebellar mutism
is believed to be higher when the vermis is split
and manipulated.9,14,15
Telovelar approach: The telovelar approach
avoids splitting of the vermis and therefore tries to
reduce the occurrence of cerebellar mutism. After
a suboccipital posterior fossa craniotomy, the cere-
bellomedullary fissure is entered and the cerebel-
lar tonsils are retracted laterally. On the floor of
the fissure, the inferior medullary velum and the
tela choroidea are encountered, the latter forming
the caudal part of the roof of the fourth ventricle.
After incising the tela choroidea, the fourth ven-
tricle can be explored laterally to the foramina of
Luschka on both sides. This allows the resection of
midline tumors extending laterally. However, the
rostral parts of a midline tumor are visualized less
well by this approach.9,13,14,15,16
Transtentorial approach: Some midline tumors
in the posterior fossa may extend high up to the
quadrigeminal plate and the pineal region. In this
localization, the working angle is suboptimal com-
ing from a telovelar approach, and a transvermian
approach would result in the destruction of the
vermis with a consecutive high risk for cerebellar
mutism. In this setting, a transtentorial approach
can provide optimal visualization. A parasagittal
craniotomy in the parietal region gives interhemi-
spheric access to the superior aspect of the tento-
rium. The latter is incised and the most cranial part
of the posterior fossa can be entered. The distance
to the tumor, however, becomes considerably long
and the use of intraoperative neuronavigation is
almost mandatory. In addition, injury to the
straight sinus may result in substantial bleeding
deep down in the operation field, limiting the use
of this surgical approach to experienced hands.1
Cerebellar Hemispheric Tumors
Accessing cerebellar hemispheric tumors is gener-
ally not as technically demanding. From a standard
midline suboccipital craniotomy, as described, the
tumor can be encountered by opening the cerebel-
lar hemisphere along the folia at the point of the
shortest distance of the tumor to the cerebellar
surface.9
Lateral and Anterior Tumors
Retromastoid approach: This approach behind the
sigmoid sinus covers most lateral tumors of
the cerebellopontine angle. Again, the position of
the transverse sinus is approximated by a line
from the inion to the external auditory canal. The
patient is positioned in a lateral decubitus fashion.
From a curvilinear incision just medial to the mas-
toid, the bone is exposed. The sigmoid sinus is usu-
ally localized beneath the mastoid groove, and the
connection of transverse and sigmoid sinus is
found under the asterion. A single burr hole is
placed inferiorly to the asterion and medially to
the mastoid groove. A craniotomy flap is turned
from the burr hole medially. If necessary, bone can
be further removed with a drill or Kerrison
Posterior Fossa Tumors
157
punches to the anterior margin of the sigmoid
sinus. The dura is opened in a K-shaped fashion
and reflected with sutures. The cerebellum is then
displaced downward with brain retractors over
patties until drainage of CSF allows for a good visu-
alization of the cerebellopontine angle. From this
approach, the CNs from V to XII are accessible
together with the tumors of that region.13
Far lateral approach: To access tumors ventral of
the brainstem, the far lateral approach is used
combining a lateral suboccipital craniotomy with
the removal of the occipital condyle and the atlas
down to the sulcus arteriosus. This approach is not
straightforward even in experienced hands and
will not be further discussed here.
Surgical Adjuncts
Intraoperative Neuromonitoring
● The use of somatosensory evoked potential,
motor evoked potential, and brainstem auditory
evoked potential monitoring has become routine
in posterior fossa tumor surgery in most centers,
especially for surgery in the cerebellopontine
angle.9
● The impact of a best possible resection on
oncologic outcome potentially compromises
patient safety in regard to functional outcome.
The use of intraoperative neuromonitoring
should enable the surgeon to be safely as radical
as possible. There is circumstantial evidence to
this statement; class I evidence in randomized
trials cannot be obtained for obvious ethical
reasons.17
● The successful implementation of intraoperative
neuromonitoring strongly depends on the
teamwork of neurophysiologist (experience in
acquisition and interpretation), anesthetist
(using mainly intravenous anesthetic agents
without paralytics), and surgeon (experience to
tailor the procedure according to the monitoring
feedback).17
Intraoperative Ultrasound
The use of intraoperative ultrasound is a reliable,
fast, real-time, repeatable, and inexpensive adjunct
to help the surgeon throughout the tumor resec-
tion. It is especially helpful in:
● Localizing the ventricles and guiding an EVD
catheter during insertion.
● Localizing major vascular structures in the
Doppler mode.
● Visualizing the tumor during approach and
assessing for residual tumor after resection.
● Visualizing CSF pathways (i.e., flow through the
aqueduct).
● Ruling out major hemorrhage into brain or
ventricles.
Neuronavigation
● The use of intraoperative neuronavigation in
posterior fossa tumor surgery is possible,
although registering the patient’s head in the
prone or lateral position can be more
demanding and the accuracy of the obtained
registration must be carefully verified.
● Some surgeons feel that the use of
neuronavigation in the posterior fossa does not
give too much additional information, as the
anatomical landmarks are quite straightforward.
In the authors’ view, however, neuronavigation
is certainly useful when tailoring the
craniotomy, especially its relations to the
transverse and sigmoid sinus. Some evidence
suggests that an exposed transverse sinus is
more susceptible to air embolism, thrombosis,
and hemorrhage, resulting in the
recommendation to avoid carrying a suboccipital
craniotomy on or over the transverse sinus.18
Intraoperative MRI
A growing number of centers are implementing int-
raoperative MRI (iMRI) as a surgical adjunct. Advo-
cates of this technique argue that it influences intra-
operative surgical decision-making in a significant
amount of their patients, especially when a gross
total resection is the surgical goal. It therefore might
reduce the number of patients who need revision
surgery for residual disease. The technique is safe
for the pediatric population, although no prospec-
tive data exist whether the use of iMRI has a posi-
tive impact on oncologic outcome.19,20
Closure
Meticulous hemostasis before closure is naturally a
general neurosurgical principle and is especially
important in the posterior fossa, where hematoma
formation next to the brainstem can have rapid
devastating consequences. In addition, the occur-
rence of intraventricular hemorrhage often signifi-
cantly extends hospitalization and certainly is not
helpful when trying to avoid a shunt. The authors
recommend a watertight dural closure, although
Tumor
158
there is no class I evidence available for that state-
ment, regarding CSF leaks, infections, and the for-
mation of pseudomeningoceles.21,22,23 The choice
of materials for dural augmentation (which is usu-
ally necessary) and dural sealant is at the discre-
tion of the surgeon. The abundance of available
products on the market is an indication of the fact
that there is no perfect combination of product
and technique. The authors recommend dural aug-
mentation with allograft, sutured in a watertight
fashion, and the application of some sealant (i.e.,
fleece bound or liquid fibrin glue). Then the bone
flap is fixed with sutures or plates, and a meticu-
lous multilayered closure of the muscles and espe-
cially the fascia and a running sutured skin closure
are performed. Drains should be avoided when-
ever possible.
20.3.2 Postoperative
Management
General
Extubation immediately after the procedure is
usually possible and allows for a postoperative
neurologic examination. Admission to the inten-
sive care unit for at least overnight observation is
mandatory with close assessment of neurological
status and laboratory parameters.
Early MRI within 48 hours of surgery is routine
for postoperative imaging in most centers. This has
therapeutic consequences, as, in some tumors,
revision surgery has to be considered in case of
residual disease. The short interval to imaging is
essential to di erentiate between residual tumor
and postsurgical changes.1
In case an EVD has been placed, CSF is routinely
sent for cell count and bacteriology. When output
volumes decrease, the drainage level is incremen-
tally raised and the EVD eventually clamped. In an
asymptomatic patient, the drain is then removed
and the insertion site sutured. In case of symp-
toms, imaging and CSF diversion surgery must be
discussed early.
Management of Complications
Hydrocephalus
See Management of Hydrocephalus.
Cerebellar Ataxia
Cerebellar ataxia is the most common complica-
tion of posterior fossa surgery. While the portion
of the tumor invading one cerebellar peduncle can
be resected aggressively, care should be taken to
leave the other peduncle intact. Under this aspect,
postoperative cerebellar ataxia usually resolves
within weeks.9 Steroids are routinely given in the
attempt to accelerate clinical recovery.
Cerebellar Mutism
Cerebellar mutism (CM) is one of the feared com-
plications after posterior fossa surgery. The litera-
ture on this syndrome is extensive but still the
pathophysiology is poorly understood. CM is
defined as a transient and delayed-onset (1–6 days
postoperatively) mutism after a period of normal
postoperative speech production. Clinical symp-
toms accompanying CM include: oropharyngeal
apraxia, ataxia, hypokinesia, visual disturbances,
and neurobehavioral symptoms (i.e., emotional
lability).24
Proven risk factors for CM are: brainstem inva-
sion, midline tumors, and MB histology. Possible
risk factors comprise: preoperative language
impairment, younger age, radical resection, inci-
sion of the vermis, and large tumor size.24
CM was believed to be a relatively benign com-
plication, given its spontaneous remission and
transient character. In more recent studies, how-
ever, formal neuropsychological evaluation of chil-
dren with CM shows that a ected patients are
often left with significant neuropsychological
impairment, including problems of attention,
memory, processing speed, and verbal fluency, as
well as behavioral deficits.24,25,26
Cranial Nerve Dysfunction
CN dysfunction is due to manipulation of either
the nerves themselves or the brainstem at the level
the CN nuclei. Nuclear CN impairment has a
smaller chance of recovery.9
The spectrum seen after posterior fossa surgery
includes abducens palsy, facial weakness, internu-
clear ophthalmoplegia, horizontal gaze palsy,
swallowing di culty, and vocal cord palsy.9
In tum ors that arise from the brainstem or
involve the lower CNs or the floor of the fourth
ventricle, a delayed extubation with the presence
of an ENT team to assess vocal cords and pharyn-
geal m otility is recom mended. In children
a ected by vocal cord paralysis or insensate
pharynges, an early tracheostomy and gastro-
stomy should be discussed to prevent aspiration
pneum onitis.1
Posterior Fossa Tumors
159
Neurocognitive Defects
Apart of CM described earlier, posterior fossa
tumors and their treatment (especially radiation
therapy in infants) can result in significant impair-
ment of the patient’s neurocognitive functioning.
Risk factors for postoperative neurocognitive defi-
cits are the presence of preoperative deficits,
severe hydrocephalus, invasion of the brainstem,
and histological diagnosis of MB.25
Pseudomeningocele and CSF Leak
Even with the most meticulous closure techniques,
postoperative pseudomeningocele formation and
CSF leakage cannot completely be avoided. Evi-
dently, a CSF leak significantly enhances the risk of
wound infection and bacterial meningitis. Pseudo-
meningocele formation occurs in 25% and should
first be conservatively managed and observed in
the absence of a CSF leak.9,23 In the presence of CSF
leakage, however, a rapid surgical wound revision
with insertion of a lumbar drain is needed to pre-
vent infection. Recurrent CSF leaks or recurrent
pseudomeningoceles can also be a symptom of
hydrocephalus and will need CSF diversion sur-
gery to control.9
Wound Infection and Bacterial
Meningitis
Wound infections after posterior fossa surgery are
especially feared, as they not only prolong hospi-
talization but also add significant morbidity to the
procedure (i.e., postinfectious hydrocephalus).
Wound infections must lead to rapid revision sur-
gery, followed by empiric antibiotic treatment
until cultures allow for a resistance-adapted anti-
biotic regime. The Infectious Diseases Service
should always be consulted.
Aseptic Meningitis
The presence of blood in the subarachnoid space
can lead to postoperative headaches, fever, irrita-
bility, photophobia, neck sti ness, and CSF pleocy-
tosis, mimicking bacterial meningitis. The latter
has to be excluded with CSF cultures. Aseptic men-
ingitis can best be prevented with a meticulous
hemostasis before closing. It usually responds well
to low-dose steroid administration.9
20.4 Specific Pediatric Posterior
Fossa Tumors
20.4.1 Overview
The “big three” tumors in the pediatric posterior
fossa are: (1) medulloblastoma (MB), (2) pilocytic
astrocytoma (PA), and (3) ependymoma (EP).4 Less
common are atypical teratoid/rhabdoid tumor (AT/
RT), choroid plexus papilloma (CPP), and choroid
plexus carcinoma (CPC). Occasionally encountered
and not further discussed here are ganglioglioma,
teratoma, hemangioblastoma, and dermoid/epi-
dermoid cyst. All other tumor entities are very
rare. Brainstem gliomas are covered elsewhere in
this book.
20.4.2 Medulloblastoma
Epidemiology
MB is the most common malignant solid neoplasm
of childhood and accounts for 25% of all pediatric
brain tumors.4,9 Eighty-five percent of all MBs arise
from the cerebellar vermis, and a minority are
found within the cerebellar hemispheres. Histori-
cally, MBs were considered to be PNETs (primitive
neuroectodermal tumors) located in the posterior
fossa—di erentiating them from supratentorial
PNETs. Current genetic fingerprinting, however,
strongly suggests that supratentorial PNETs are
genetically identical to other known tumor enti-
ties. Therefore, the term “PNET” disappeared in
the current WHO classification.27,28
The m edian age at diagnosis is 7 years, w ith a
slight predom inance for Caucasian m ales. A ser-
ies of predisposition syndrom es are associated
with the occurrence of MB, including Gorlin’s
syndrom e, Turcot’s syndrom e, and Li–Fraum eni
syndrom e.29
Pathology
MBs are considered WHO grade 4 tumors.28 His-
torically, histology appreciated four subtypes: (1)
classic type, (2) desmoplastic/nodular type, (3) MB
with extensive nodularity, and (4) large cell/
anaplastic type.30 Although there was some corre-
lation of histological subtype and oncologic
outcome, recent genotyping of MB tissue led to a
novel stratification with a far better clinical
Tumor
160
correlation. This novel stratification was adopted
in the current WHO classification and is now listed
in combination with the histologically defined
subtypes.28,31,32,33 Table 20.1 summarizes genetic
profile, histology, and impact on prognosis. There
is no doubt that genetic fingerprinting will
become increasingly important in tumor stratifica-
tion in general, and our knowledge on this topic is
rapidly evolving.
Imaging
MB shows a wide variability on its MRI appear-
ance. Typically, a T1-hypointense, T2-hyperintense,
and patchy contrast-enhancing midline posterior
fossa tumor corresponds to an MB. Calcifications
and cyst formations are seen.4 Leptomeningeal
seeding is appreciated in one-third of the patients,
usually along the spinal canal. The presence of spi-
nal metastases on neuroimaging interestingly does
not correlate with a positive CSF cytology and vice
versa.4
Management
Patient survival and quality of life have signifi-
cantly improved with the development of the
current standard treatment regime of surgery,
radiotherapy, and chemotherapy. However, this
treatment leads to considerable morbidity,
especially in infants younger than 3 years. Even if
long-time survival is common nowadays, parents
and patients have to face the fact that after cranio-
spinal irradiation—to name one of the problems
the percentage of individuals with academic
degrees is significantly lower compared to the gen-
eral population.34
In the very near future, however, treatment
paradigms will dramatically change for MB
patients. The implementation of genetic finger-
printing led to an abundance of new treatment
protocols always in the context of multicenter tri-
als. The traditional triad of surgery and radioche-
motherapy obviously still has its place, especially
in standard and high-risk situations. The identifi-
cation of low-risk subgroups, however, will very
soon lead to treatment de-escalation with an
expected reduction of toxic side e ects—without
compromising oncologic survival. Moreover, poten-
tial drug targets are identified and evaluated—
especially in SHH tumors.35
Surgery
Gross total resection is the goal of surgery in MB
and the main predicting factor regarding oncologic
outcome. Historically, residual tumor of more than
1.5 cm 2 (subtotal resection) was believed to justify
revision surgery.36 This statement is challenged in
a recent trial.5 It appears that there still is a role for
best possible resection but not at too high a risk.
Across all genetic subtypes of MB, there was no
Table 20.1 Integrated medulloblastoma stratification in the context of clinical significance28
Genetic profile
Histology
Prognosis
10%
MB, WNT-activated
Classic type
Low-risk tumor
Large cell/anaplastic type (very rare) Uncertain clinicopathological significance
30%
MB, SHH-activated,
TP53-mutant
Classic type
Uncommon, high-risk tumor
Large cell/anaplastic type
High-risk tumor; prevalent in children
aged 7–17 y
Desmoplastic/nodular type
(very rare)
Uncertain clinicopathological significance
MB, SHH-activated,
TP53-wildtype
Classic type
Standard-risk tumor
Large cell/anaplastic type
Uncertain clinicopathological significance
Desmoplastic/nodular type
(very rare)
Low-risk tumor in infants; prevalent in
infants and adults
Extensive nodularity
Low-risk tumor of infancy
25%
MB, non-WNT/non-SHH,
group 3
Classic type
Standard-risk tumor
Large cell/anaplastic type
High-risk tumor
35%
MB, non-WNT/non-SHH,
group 4
Classic type
Standard-risk tumor
Large cell/anaplastic type (rare)
Uncertain clinicopathological significance
Abbreviation: MB, medulloblastoma.
Posterior Fossa Tumors
161
di erence in overall survival (OS) when comparing
subtotal (>1.5 cm 2
residual) to near-total
(<1.5 cm 2 residual) to gross total (no residual)
resection. However, there is a di erence in pro-
gression-free survival comparing subtotal and
near-total/gross total resection.5 Apart from onco-
logic outcome, tumor removal obviously allows for
tissue diagnostic and also treats accompanying
hydrocephalus.
Radiation Therapy
MBs are reasonably radiosensitive and the imple-
mentation of craniospinal irradiation significantly
prolonged survival, especially because these tumors
are prone to seed along the neuraxis. Radiotherapy
to the developing nervous system is mainly respon-
sible for long-term neuropsychological sequelae,
especially in children younger than 3 years. For
that reason, every e ort is made to avoid radiother-
apy in these patients, or to postpone it until the age
of 3 has been reached.37 Acute side e ects of radio-
therapy comprise drowsiness, nausea, headache,
lethargy, and fatigue. Long-term changes include
cognitive impairment, growth abnormalities, hypo-
pituitarism, hearing loss, moyamoya vasculopathy,
and secondary neoplasms.38
Chemotherapy
Chemotherapy remains standard as an adjuvant
treatment for MB patients. Treatment protocols,
however, are rapidly changing and evolving,
according to the novel MB stratification. A dedi-
cated team of neuro-oncologists is indispensable
to take the lead in the adjuvant treatment, as its
complexity greatly increased with expanding
knowledge about these tumors. This knowledge
led to a number of trials with several treatment
arms to especially reduce treatment toxicity. In
addition to that, trial substances specifically tar-
geting genetic pathway changes in MB subtypes
are available and will hopefully soon lower side
e ects in standard treatment or o er salvage treat-
ment for progressive disease.35
Follow-up
During treatment, MRI of brain and spine are
recommended every 3 months for 18 months,
followed by MRI of the brain every 6 months and
MRI of the spine every 12 months, until the
patient is in remission for 5 years. After that,
annual MRI of brain and spine is performed.39
20.4.3 Pilocytic Astrocytoma
Epidemiology
PA is the most common pediatric cerebellar neo-
plasm and occurs at a mean age of 7 years.4 There
is no gender predilection, and these tumors are
rarely diagnosed under 1 or over 40 years of age.9
Fifty percent are seen within the cerebellar hemi-
spheres, but PAs can be found in any location of
the neuraxis—the optic pathway, thalamus, and
hypothalamus being also common sites.4
Pathology
PAs are considered WHO grade 1 tumors.28 They
show a benign biological behavior with a slow
growth, good macroscopic delineation, and high
survival rates. Histologically, a biphasic pattern of
loose glial and compacted piloid tissue is typical,
the latter with abundant Rosenthal’s fibers. On the
immunohistochemical and molecular level, the
demonstration of a high proliferative index does
not correlate with a worse clinical course.40 In cer-
ebellar PAs, a single “signature” mutation leads to
the activation of the MAPK pathway, an interesting
future drug target.41 While supratentorial and
brainstem PAs have a strong association with neu-
rofibromatosis type 1, cerebellar PAs do not show
this feature and are mostly sporadic tumors.4 In
supratentorial and brainstem PAs, the status of the
BRAF gene (mutation vs. fusion) has a big impact
on biological behavior and BRAF evaluation is
about to become routine in the diagnostic workup
for these tumors.42
Imaging
Four patterns are typical morphologic imaging
findings: (1) an enhancing mural nodule with a
nonenhancing cyst, (2) an enhancing mural nodule
with an intensely enhancing cyst, (3) a solid mass
with no cystic component, and (4) a necrotic
mass with a central nonenhancing zone.43 Lepto-
meningeal dissemination is seen, but not incom-
patible with long-term survival.44
Management
Surgery
Complete resection of a PA is considered cura-
tive.45 The resection of the mural nodule is crucial;
the role of resection of the cyst wall is discussed
controversially, as there seems to be no impact on
Tumor
162
survival. Subtotal resection leads to higher recur-
rence rates, but does not a ect survival. Therefore,
the risk of returning to the operating room for
postoperative residual tumor must be carefully
balanced against the option of serial MRI follow-
up.45 There is no role for upfront adjuvant radia-
tion therapy or chemotherapy in PA. These options
are reserved for recurrence or leptomeningeal
spread.4 When chemotherapy is considered, the
knowledge of the BRAF status will allow for an
individual prognosis: tumors with a BRAF fusion
respond much better than tumors with a BRAF
V600E mutation.42
Follow-up
When early postoperative imaging demonstrates
gross total resection, MRI at 3 months is recom-
mended, followed by annual MRI. In the case of
residual tumor, imaging intervals should be tail-
ored accordingly. As in other tumor entities,
genetic fingerprinting led to a growing number of
multicenter trials investigating optimal treatment
for genetically di erent PAs.42
20.4.4 Ependymoma
Epidemiology
EP is the third most frequent brain tumor in the
pediatric population and can be located through-
out the CNS.46 Seventy percent of all EPs occur in
the posterior fossa—frequently in infants and
young children—while older children and adults
are more prone to supratentorial and spinal EPs.
The mean age at the time of diagnosis is 4 years,
but a quarter of all patients are younger than 3
years. Males are 1.4 times more likely to develop
EP than females are.9
Pathology
The new WHO classification still di erentiates sube-
pendymoma and myxopapillary EP (grade 1), classic
(grade 2), and anaplastic EP (grade 3).28 In addition,
RELA fusion–positive EPs are newly listed. This mu-
tation is reserved for supratentorial tumors and is
quite consistently found.47 Similar to MBs, supra-
and infratentorial EPs are genetically di erent. The
elucidation of that finding will most certainly have
therapeutic implications in the future.
Histologically, EPs are glial neoplasms arising
from ependymal cell layers adjacent to the ventric-
ular system or the central spinal canal.8 Histology
of EP is quite uniform, showing cells with oval or
round nuclei, typically arranged in pseudorosettes
around vessels. Similar to MB, there is no connec-
tion of histomorphologic features to the clinical
course (within the same WHO grade).46 For poste-
rior fossa EPs, transcriptional profiling showed the
existence of two large subgroups: posterior fossa A
and B EPs (PFA and PFB). PFA patients are younger,
have laterally located tumors with a balanced
genome, and are much more likely to exhibit
recurrence, metastasis at recurrence, and death,
compared to PFB patients.48
Imaging
EPs in the posterior fossa are found either midline,
arising from the roof or floor of the fourth ven-
tricle (likely PFB EPs), or in the cerebellopontine
angle (likely PFA EPs), encasing CNs and vascular
structures, rendering resection extremely chal-
lenging. Typically, EPs appear hypointense in T1,
hyperintense in T2, and hyperintense in FLAIR
(fluid-attenuated inversion recovery) studies. Cal-
cifications and intratumoral hemorrhages are
common.4 Leptomeningeal seeding does occur,
mostly in the lumbosacral region, and 10% of the
patients do have a positive CSF cytology at presen-
tation.4
Management
Surgery
EP is a surgical disease. Complete surgical resec-
tion is the therapeutic goal and primary significant
predictor of oncologic outcome. In fact, 5-year sur-
vival rate drops from 70 to 30% when residual
tumor is appreciated on early postoperative MRI.49
This circumstance warrants the strong considera-
tion of second-look surgery to chase tumor rem-
nants. The tendency to encase neurovascular
structures, however, makes aggressive resection
especially in the cerebellopontine angle a danger-
ous endeavor, and is connected with significant
morbidity.49 Recurrences should also be addressed
surgically if possible, as they often occur at the pri-
mary tumor site.49 Unfortunately, prognosis of
recurrent EP is very poor, with a median survival
time ranging from 8 to 24 months.49
Radiation Therapy
EPs are radiosensitive, making adjuvant radiation
therapy mandatory in patients older than 3 years.
About 45 to 56 Gy are administered to the tumor
Posterior Fossa Tumors
163
bed. In the absence of spinal dissemination in imag-
ing or CSF cytology, craniospinal irradiation is not
indicated, as it did not show to lower distant treat-
ment failure rate.49 Re-irradiation or radiosurgery
can be considered in children with recurrent EP,
although morbidity of re-irradiation is high.50,51
Chemotherapy
Currently, there is no established chemotherapy pro-
tocol in the treatment of EP. Bridging chemotherapy
in infants is administered—usually cyclophosphamide
and vincristine—to defer radiotherapy, but response
rates are as low as 50%.52
Follow-up
The intervals of follow-up imaging largely depend
on the achievement of a surgical gross total resec-
tion and should be chosen on an individual basis.
The presence of residual tumor should warrant a
closer follow-up, as relapses are frequent.
20.4.5 Atypical Teratoid/Rhabdoid
Tumor
Epidemiology
AT/RT is a relatively new tumor entity, listed in the
WHO classification since 2000.28 AT/RTs form 1% of
all pediatric brain tumors. A third occurs in the
cerebellum or cerebellopontine angle. There is a
3:2 male predominance, and the median age of
onset lies at 26 months. CSF dissemination is iden-
tified in 25% of the patients at the time of diagno-
sis. The prognosis is dismal, with an OS of 18
months without dissemination and 8 months with
dissemination.53
Pathology
Using conventional histopathologic methods, AT/RTs
show nests or sheets of rhabdoid cells, but also
contain regions that are indistinguishable to MB.
This circumstance led to the relatively late first
description of AT/RTs in 1987. This also implies the
possibility of sampling error in small biopsies.4
Immunohistological staining for nuclear INI1 (absent
in AT/RT and present in MB) and the identification
of monosomy 22 help in placing the diagnosis.54
Imaging
There are no characteristic imaging features for
AT/RT. The tumor shows similarities with MB, with
an isointense T1 signal, heterogeneous T2 signal,
and a patchy contrast enhancement.4
Management
Surgery
Similar to all tumors discussed, gross total resec-
tion of AT/RTs treats the consequences of a poste-
rior fossa mass lesion, allows for tissue diagnosis,
and is also believed to have a positive impact on
oncologic outcome, although this e ect is not as
satisfying as with MBs or EPs.55 The interface
between cerebellum and AT/RTs can be ill-defined,
and tumors found in the cerebellopontine angle
often encase neurovascular structures, rendering
resection di cult. Gross total resection is feasible
in about 30% of the patients.9
Radiation Therapy
Postoperative radiation therapy is statistically e ec-
tive. The gain in median OS, however, is only
10 months (OS 8.5 months without, 18.4 months
with radiotherapy).55 Many patients show evidence
of disseminated disease at presentation, so usually
craniospinal irradiation is administered. The known
restrictions for the irradiation of children younger
than 3 years apply, being of special importance in
AT/RTs, as a large proportion of patients is younger
than 3 years at the time of diagnosis.
Chemotherapy
Standard chemotherapy has not proven to be partic-
ularly e ective in AT/RT. This led to the evaluation
of high-dose alkylator-based chemotherapy with
stem cell rescue.56 The addition of intrathecal che-
motherapy in recent studies increased OS at 2 years
to 70%.55 Novel approaches include the administra-
tion of a dendritic cell–based vaccination, reported
as being successful in individual patients.57
Follow-up
Short survival times in patients diagnosed with
AT/RT usually lead to symptom-based follow-up
imaging.
20.4.6 Choroid Plexus Papilloma
and Choroid Plexus Carcinoma
Epidemiology
Choroid plexus tumors are rare and comprise 0.5%
of all pediatric CNS neoplasms.4 They can occur in
Tumor
164
all age groups, but 70% of them are diagnosed before
the age of 2 years. Male patients are a ected more
frequently with a ratio of 1.3:1.58 Anatomically, they
are distributed along the ventricular system, the
choroid plexus as the tissue of origin given. In
younger children, the lateral ventricles are a ected
more frequently, whereas in older children and
adults choroid plexus tumors are localized rather in
the fourth ventricle and the cerebellopontine
angle.58
Pathology
According to the WHO, three classes of choroid
plexus tumors are di erentiated: CPP is assigned a
WHO grade 1 and its anaplastic variant a grade 2.
CPC receives a WHO grade 3.28 Histologically, CPPs
resemble normal choroid plexus tissue. CPP does
not show necrosis, brain invasion, or mitotic fig-
ures, in contrast to CPC, where marked cytological
atypia, nuclear pleomorphism, frequent mitoses,
vascular proliferation, hemorrhage, and brain infil-
tration are seen.59 Anaplastic CPPs present an
intermediate degree of nuclear atypia and mitotic
figures.58 A number of genetic syndromes are
known to predispose to CPP and CPC, like Li–Frau-
meni syndrome, neurofibromatosis type 2, Aicar-
di’s syndrome, Down’s syndrome, and von Hippel–
Lindau disease.60 This led to the discovery of a
range of chromosomal imbalances at the molecu-
lar level of these tumors.60
Imaging
Homogenous tumors with a “frondlike” appear-
ance in close anatomical relation to the ventricular
system and associated hydrocephalus are the typi-
cal imaging appearance of choroid plexus tumors.
They appear isointense in T1 and heterogeneous in
T2 sequences, with a marked contrast enhance-
ment. Di erentiation of CPP from CPC is not possi-
ble on imaging, although CPC is more prone to
brain invasion and peritumoral edema than CPP.
Calcifications are common.58
Management
Surgery
Again, the extent of surgical resection is a signifi-
cant prognostic factor, especially in CPC.4 The
marked vascularity of these tumors is one of
the surgical challenges. This even led to the imple-
mentation of preresectional chemotherapy to
minimize blood loss.61 Resection of a WHO grade 1
CPP is considered curative. Anaplastic CPPs are
primarily managed surgically, and adjuvant
treatment is discussed when dissemination or
recurrence occurs.59
Radiation Therapy
Radiation therapy is indicated in CPCs and ana-
plastic CPPs with postoperative residual disease,
recurrence, or dissemination.58 As in all pediatric
brain tumors, radiation therapy is deferred in chil-
dren younger than 3 years whenever possible.
Chemotherapy
The combination of radiation therapy and chemo-
therapy is routinely adm inistered in CPC.62 With
this treatment regime, OS at 2 years is 100% for
CPP, 89% for anaplastic CPP, and 36% for CPC.59 The
use of preresectional chemotherapy in CPC—after
biopsy to establish the diagnosis—has to be given
strong consideration. Given the young age of the
patients, upfront surgical resection can lead to the
loss of several blood volumes. After chemotherapy,
tumor tissue becomes fibrotic and less vascular-
ized, allowing for a relatively bloodless removal.61
Follow-up
Follow-up intervals are dictated by the WHO grad-
ing of choroid plexus tumors. In CPP grade 1,
annual MRI of the brain after early resection con-
trol is su cient. In anaplastic CPP and CPC, close
MRI observation of brain and spine is recom-
mended.
20.5 Common Clinical
Questions
1. Name the three most common tumors in the
pediatric posterior fossa and the most
important factor for a good oncologic outcome.
2. What are clinically important features of a
posterior fossa mass lesion?
3. What are the main predicting factors for a
persistent hydrocephalus after resection of a
posterior fossa tumor?
4. What histological subtypes are di erentiated in
medulloblastoma and what is the reason for the
proposal of a new genetic stratification?
5. What is the primary option when residual
ependymoma is seen on postresectional early
MRI?
Posterior Fossa Tumors
165
6. What is an intriguing histological feature of
pilocytic astrocytoma when correlated to
clinical outcome?
20.6 Answers to Common
Clinical Questions
1. The three most common tumors in the pediatric
posterior fossa are: (1) medulloblastoma,
(2) pilocytic astrocytoma, and (3) ependymoma.
The achievement of a good resection is the most
important factor for a good oncologic outcome
in all three.
2. Special to posterior fossa mass lesions is their
anatomical relation to vital structures in a
confined space. Hydrocephalus due to blockage
of CSF pathways can result in rapid clinical
deterioration; invasion of brainstem or
encasement of lower CNs can lead to significant
morbidity.
3. Risk factors for a postresectional hydrocephalus
comprise: (1) age <2 years, (2) presence of
transependymal edema, (3) preresectional
moderate or severe hydrocephalus, (4) presence
of cerebral metastases, and (5) histological
diagnosis of medulloblastoma, ependymoma, or
dorsal exophytic brainstem glioma.
4. Histologically, four types of medulloblastomas
(MB) are di erentiated: (1) classic MB,
(2) desmoplastic/nodular-type MB, (3) MB
with extensive nodularity, and (4) large cell
anaplastic MB. The clinical prognosis, however,
correlates better with the new molecular
stratification.
5. The prognosis of ependymoma strongly
depends on surgical gross total resection. In
case of postoperative residual tumor,
reoperation must be considered if resection of
the remnant seems to be safely possible.
6. The presence of high mitotic activity, cellular
atypia, and microvascular proliferation does not
a ect grading and clinical outcome of PA.
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Tumor
168
21 Brainstem Gliomas
Mari L. Groves, Rafael U. Cardenas, Nir Shimony, George I. Jallo
21.1 Introduction
Primary brainstem tumors encompass 10 to 20% of
all central nervous system tumors in the pediatric
population.1
They most commonly present in
childhood with a mean age of diagnosis of 7 to 9
years,2,3 although they can occur at any age. There
are 150 to 300 cases each year4,5 in the United
States. There is no gender predilection. In the
adults, brain stem tumors are rarer, comprising
only about 2% of all brain tumors,6 and represent a
greater diversity of pathology.7 Approximately 80%
of brainstem gliomas are di use intrinsic pontine
gliomas (DIPGs) and carry a poor prognosis.1 How-
ever, the remaining 15 to 20% of brainstem gliomas
are low-grade astrocytomas, and these portend a
more favorable course. Magnetic resonance imag-
ing (MRI) provides the most precise information
regarding the tumor epicenter and most likely
diagnosis, which can then predict its biological
behavior.8 Choux and colleagues proposed a radio-
graphic classification that defines brain tumors by
four types: di use (type I), intrinsic focal (type II),
exophytic focal (type III), and cervicomedullary
(type IV)9 ( Fig. 21.1).
● Type I tumors are di use brainstem gliomas and
account for 75% of all brainstem tumors. Di use
lesions are typically hypointense on T1-weighted
sequences that are noncontrast enhancing and
have some hyperintensity on T2-weighted
images. These lesions are most commonly found
within the pons and are malignant fibrillary
astrocytomas (WHO grade III or IV).
● Type II lesions are focal, intrinsic tumors that can
be cystic or solid. These lesions are most
commonly low-grade gliomas (WHO I or II).
T1-weighted images show variable contrast
enhancement, but uniform enhancement can be
characteristic of pilocytic astrocytomas.
● Type III lesions are defined as focal exophytic
tumors that arise from the subependymal glial
tissue of the fourth ventricle and grow both
dorsal and laterally.
● Type IV lesions are cervicomedullary tumors
with a presentation and behavior similar to
intramedullary spinal cord gliomas. These
lesions are typically low grade, noninfiltrative
with growth that is confined by the white
matter of the corticospinal tract and medial
lemniscus.
Fig. 21.1 Four types of brain tumors:
(a) type I, diffuse; (b) type II, focal;
(c) type III, dorsally exophytic; and
(d) type IV, cervicomedullary.
169
21.2 Anatomy
The brainstem, or mesencephalon, is composed of
the midbrain, pons, and medulla. These are then
broken into four areas: the ventricular cavity, roof,
tegmentum, and base10 ( Fig. 21.2).
● Ventricular cavity: extending from the rostral
extent of the cerebral aqueduct of Sylvius to the
obex and the beginning of the central canal of
the spinal cord. Comprises the central canal as
well as the fourth ventricle.
● Roof: overlying the ventricular cavity and
comprised of the choroid plexus and tela
choroidea of the fourth ventricle, the cerebellum,
and the tectum.
● Tegmentum: ventral to the ventricular cavity
and containing the cranial nerves (CNs) and
their nuclei, major long ascending tracts, and the
reticular formation.
● Base: comprised of the medullary pyramids,
ventral pons, and crura cerebri of the midbrain.
The major long descending tracts including the
corticospinal, corticobulbar, and corticopontine
tracts also traverse this space.
CN III through XII are located within the brainstem
and are grouped into longitudinal columns. These
columns carry their own functional distinction
with motor nuclei located medially and sensory
nuclei located laterally. The medial columns are
composed of somatic and visceral motor nuclei.10
● Column 1: immediately adjacent to midline and
composed of neurons that innervate the striated
muscles of the head and neck arising from
embryonic myotomes.
– Oculomotor nucleus (III): located in the
midbrain at the level of the superior colliculus,
just ventral to the cerebral aqueduct.
– Trochlear nucleus (IV): located in the
m idbrain at the level of the inferior
colliculus, just ventral to the cerebral
aqueduct.
– Abducens nucleus (VI): located in the pons,
just ventral to the floor of the fourth ventricle.
– Hypoglossal nucleus (XII): located in the
medulla, just ventral to the floor of the fourth
ventricle.
● Column 2: located lateral and ventral to column
1 and comprised of neurons that innervate the
striated muscles of the head and neck derived
from the branchial arches.
– Motor nucleus of the trigeminal nerve (V):
located in the pons.
– Facial motor nucleus (VII): located in the pons.
– Nucleus ambiguous (IX and X): located in the
medulla.
Fig. 21.2 Sagittal profile of the brain-
stem. There are four major parts of the
brainstem that are contiguous
throughout the medulla, pons, and
midbrain: ventricular cavity, roof, teg-
mentum, and base. (Reproduced with
permission from Alberstone et al.10)
Tumor
170
– Nucleus of the spinal accessory nerve (XI):
extends from the medulla into the cervical
region of the spinal cord.
● Column 3: located immediately lateral to
column 1: consists of nuclei of preganglionic
parasympathetic neurons.
– Edinger–Westphal nucleus (III): located in
midbrain.
– Superior and inferior salivatory nuclei (VII and
IX, respectively): located in medulla.
– Dorsal motor nucleus of the vagus (X): located
in medulla.
● Lateral columns containing three sensory nuclei.
Each sensory nucleus receives inputs from
several di erent CN.
– Trigeminal sensory nucleus, comprised of
three distinct nuclei: the mesencephalic
nucleus, main sensory nucleus, and the spinal
trigeminal tract nucleus.
– Vestibular and cochlear nuclei: extending from
the rostral medulla into the pons.
– Solitary nucleus: located in the medulla.
There are four long tracts, two ascending and two
descending, that traverse the brainstem.
● The spinothalamic tract is the most lateral in the
brainstem.
● The medial lemniscus, corticospinal, and
corticobulbar tracts lie medially within the
brainstem.
● The reticular formation extends from the higher
cortical regions and the thalamus to the spinal
cord and consists of the parvocellular zone and
the magnocellular zone. These interneurons are
responsible for motor, respiratory and
cardiovascular control, sensory control, and
consciousness.
21.3 Examination
Physical examination of patients with brainstem
lesions includes a thorough neurological exam
with special attention to CN function. Three
important components should be ascertained dur-
ing the workup: signs and symptoms related to
the intra-axial component, signs and symptoms of
hydrocephalus, and symptom onset. A complete
clinical picture includes a thorough history and
physical. A historical account may include old
school pictures that may be helpful to track new
cranial neuropathies, declining school perform-
ance, recurrent upper respiratory tract infections,
or changes in voice.11 More malignant lesions will
present with rapidly presenting symptoms,
whereas low-grade lesions present with a longer
prodrome of months to years. They can impact
multiple CN signs, ataxia, long tract signs, or cere-
bellar signs.12 Interruption of corticospinal tract
fibers will result in upper motor neuron syn-
dromes including the loss of fine motor skills,
spasticity, initial hyporeflexia followed by hyperre-
flexia, and up-going extensor plantar reflex.12 The
most common cranial neuropathies are CN VI and
VII weakness.13
● Tectal lesions primarily compress the sylvian
aqueduct causing obstructive hydrocephalus and
oculomotor paresis.
● Midbrain lesions are typically low-grade
gliomas.
● Focal pontine lesions have a poorer prognosis
and present with facial paresis, hearing loss, or
long tract findings.
● Focal medullary lesions present with lower CN
deficits manifesting as vocal changes,
swallowing di culty, or pneumonias due to
microaspirations.
● Tumors with a large dorsal exophytic component
present with symptoms due to direct
compression of the brainstem or with elevated
intracranial pressure.
● Obstructive hydrocephalus manifests as
headaches, ataxia, intractable vomiting, blurry
vision secondary to papilledem a, and torticollis.
● Cervicomedullary tumors may also present with
medullary dysfunction as well as cervical cord
dysfunction. This includes chronic neck pain,
progressive cervical myelopathy with associated
weakness, and spasticity.
21.4 Nonsurgical Management
Treatment options include:
● Radiation therapy/radiosurgery.
● Chemotherapy.
● Immunotherapy and other experimental
therapies.
Nonsurgical management is the mainstay of ther-
apy in more malignant lesions, such as di use pon-
tine tumors. Patients with anaplastic astrocytoma
or glioblastoma typically have poor prognosis and
should be managed with palliative therapies. For
patients who went biopsy and found to have muta-
tion K27 M, prognosis is poor and the lesion should
be treated as high grade glioma regardless to the
tumor appearane in imaging. For these lesions, sur-
gery has a very limited role and includes possible
biopsy or cerebrospinal fluid (CSF) diversion since
Brainstem Gliomas
171
surgical resection carries significant morbidity with
a low likelihood of altering therapy or outcomes.
High-risk medical patients, or those with significant
comorbidities, should be considered for nonopera-
tive management.
● Di use glioma of midline structures (former
DIPG): undergo standard conventional radiation
therapy consisting of daily fractions given 5 days
a week for up to 6 weeks with a total dose of
approximately 54 Gy.1,5,14,15
● Radiation does not change overall survival, but
there is a prolongation of progression-free
survival.16
● Once tumor progression is noted in DIPG,
patients will rapidly deteriorate. The median
time between progression and death range from
1 to 4.5 months.1
● Historically, there is no clear survival benefit
with chemotherapy as a stand-alone therapy or
as an adjunct to radiotherapy for DIPG.1
● Using specific molecular targets as well as
antiviral therapy may increase the utility of
adjuvant chemotherapy in some tumor
subtypes.
Low-grade lesions such as midbrain or tectal
tumors may be observed, as the natural history of
these lesions is quite indolent. These patients typi-
cally do well following treatment of the obstruc-
tive hydrocephalus.17,18,19 Systematic surveillance
should be implemented to assess for any worsen-
ing hydrocephalus or tumor growth. In cases of
type II to IV lesions that are unresectable or parti-
ally resected, radiation and chemotherapy may be
o ered. These regimens are typically based on
protocols developed for the treatment of supraten-
torial lesions. Tumor response was correlated with
higher Karnofsky performance score, higher
peripheral dose, smaller tumor volume, and longer
symptom duration before radiation on univariate
analysis and with Karnofsky performance score
alone on multivariate analysis.
21.5 Surgical Indications
Surgery for brainstem tumors should be o ered
for focal lesions, if there is a questionable diagno-
sis, or if the biopsy results will alter treatment for
a patient in a prospective clinical trial ( Fig. 21.3).
Fig. 21.3 Treatment paradigm for brainstem gliomas.
Tumor
172
Surgical treatment should also take into considera-
tion if there is concern for obstructive hydrocepha-
lus. If there is obstruction at the level of the
cerebral aqueduct, an endoscopic third ventricu-
lostomy (ETV) may be considered. Patients who
undergo an ETV have an 80 to 100% chance of
remaining shunt-free with excellent control of the
hydrocephalus.1,19,20
Appropriate candidates are identified based on
the location and focality of the brainstem lesion.
Surgical goals aim to resect as much tumor as pos-
sible while minimizing neurological sequelae. This
is more amenable in focal tumors, as surgical mor-
bidity is higher given the proximity to critical
areas of the brainstem.13 Brainstem biopsy may be
indicated in more atypical type I tumors to provide
a histopathological diagnosis as well as prognostic
information and to guide therapeutic decision-
making for more atypical lesions.21
21.6 Surgical Technique
Most operative approaches to brainstem tumors
require a suboccipital, telovelar approach. For
lesions that seem to be laterally situated, a suboc-
cipital paramedian approach may be considered.
Preoperative considerations:
● Intraoperative monitoring is key for safe
resection of brainstem lesions. This includes
brainstem function monitoring of auditory
evoked potential and somatosensory evoked
potential. CN monitoring includes CN III, VI, VII,
IX, X, and XII and should be set up to record
direct motor stimulation from the floor of the
fourth ventricle.
● Microsurgical equipment needed: an operating
microscope, microsurgical dissectors, an
ultrasonic surgical aspiratory device, and a
retraction device.
Operative considerations:
● Anesthesiologists should expect
neuromonitoring.
● The length of the endotracheal tube should be
taken into consideration as the patients will be
placed with neck flexion.
● Patients are placed in a prone position.
● Frazier burr hole may be prepared in the event
CSF relaxation is needed.
● Internal debulking should be employed for all
intrinsic brainstem tumors.
● The safest point of entry is typically where the
intrinsic tumor is closest to the surface entry
point. This should also be put in context of safe
entry zones in the floor of the fourth ventricle
( Fig. 21.4).
– Zone 1: Suprafacial triangle measures 16 mm
in greatest distance. This region is superior to
the facial colliculus and 5 mm lateral to the
midline and away from the medial
longitudinal fascicle. It will extend superiorly
to below the trochlear nucleus.
– Zone 2: Infrafacial triangle measures <9 mm
and is located inferior to the facial colliculus
and the abducens nucleus. The mediolateral
borders include the medial longitudinal
fascicle and the facial nucleus, respectively.
– Other sulci can provide a zone of safe entry:
supracollicular sulcus, the infracollicular
sulcus, the lateral mesencephalic sulcus, the
median sulcus, the area acustica, the posterior
intermediate sulcus, the posterior median
fissure below the obex, and the posterior
lateral sulcus.
21.7 Complications
Surgical complications include stroke, CN deficits,
motor or sensory deficits, brainstem hemorrhage,
CSF leak, pseudomeningocele formation, meningi-
tis, or hydrocephalus. CN deficits include transient
or permanent diplopia, facial palsy, dysphagia,
vocal cord paralysis, or loss of cough or gag with
the need for a tracheostomy or gastrostomy tube.
● Retraction injury may cause direct damage,
edema, or infarction from compromise of the
adjacent vessels, leading to facial sensory, motor,
auditory, and speech deficits.
● Transient bradycardia and hypotension may be
seen when working close to the nuclei of CN V
and IX. When this occurs, cease manipulation of
the surgical site until symptoms improve. Any
attempt to proceed with surgery could lead to a
cardiac event.
● Cerebellar mutism and pseudobulbar syndromes
may result from excessive traction along the
cerebellar hemispheres and transection of the
vermis. Cerebellar mutism is a transient
complication, and patients will experience a lack
of speech output with intact speech
comprehension. This may be associated with an
oral pharyngeal apraxia.
● Splitting the cerebellar vermis may also cause
equilibratory disturbances with truncal ataxia,
staggering gait, oscillation of the head and trunk,
and nystagmus on assuming an erect position.
Brainstem Gliomas
173
● The posterior inferior cerebellar artery wraps
around and underneath the cerebellar tonsils. It
is susceptible to damage during the initial
approach and tumor resection.
● Internal debulking is key as there is typically not
a clear plane between the tumor and the
brainstem. Attempts to create a plane will lead
to damage of the surrounding brainstem as well
as perpetuate retraction injury and lead to
postoperative CN defects.
● Avoid excessive bipolar use along the brainstem.
Most bleeding will stop with gentle pressure
and/or antifibrinolytic agents. Chasing bleeding
vessels within the brainstem will result in
additional CN defects.
● If intraoperative neurom onitoring changes
occur from possibly ischem ic changes,
then raising the mean arterial pressure (MAP)
to a high-norm al range should be attempted
as in a standard stroke protocol. This should
be used in the context of adequate
hemostasis.
● Dexamethasone should be used postoperatively
to help address retraction injury edema.
Fig. 21.4 Safe entry zones of the brainstem. Artist’s rendering of the brainstem from a dorsal view (a) with illustrated
safe entry zones and relevant nuclei and neural structures. The infrafacial and suprafacial triangles are highlighted as
safe entry zones in the dorsal pons. Corresponding axial sections through the (b) upper, (c) mid, and (d) lower pons are
illustrated. Am, nucleus ambiguus of CN IX and X with parasympathetics on its medial border; AP, area postrema; AqD,
aqueduct of Sylvius; CTT, central tegmental tract; FC, facial colliculus; HT, hypoglossal triangle; IC, inferior colliculus; ICP,
inferior cerebellar peduncle; IF, infrafacial triangle; ION, inferior olivary nucleus; MCP, middle cerebellar peduncle; ML,
medial lemniscus; MLF, medial longitudinal fascicle; MS, median sulcus; N, nucleus; Obx, obex; P, pyramid; Pn TPF,
pontine nuclei and transverse pontine fibers; SCP superior cerebellar peduncle; SF, suprafacial triangle; SL, sulcus
limitans; SLI, sulcus limitans incisure; SM, striae medullares; Ss and Si, superior and inferior salivatory nuclei; ST, spinal
trigeminal tract; STT, spinothalamic tract; TB, trapezoid body; Vcs, chief (sensory) nucleus of CN V; Vm, mesencephalic
nucleus of CN V; Vms, motor (mastication) nucleus of CN V; VT, vagal triangle; Xd, dorsal vagal nucleus; IV, trochlear
nucleus; VI, abducens nucleus; VII, facial nucleus and fiber tracks and nerve; VIII, vestibular nucleus and nerve; XII,
hypoglossal nucleus and nerve. (Reproduced with permission from Sabbagh et a. [Fig. 58.4].22)
Tumor
174
● Prior to extubation, patients should be evaluated
for adequate motor and respiratory drive. Lower
pontine and medullary lesions may require
intubation postoperatively until this can safely
be assessed. If there has been compromise,
patients may experience a gradual CO2 retention
and respiratory collapse due to an inadequate
respiratory drive.
21.8 Postoperative Care
Early perioperative care should identify immediate
CN deficits to ensure safe extubation and adequate
respiratory drive. Patients who do not have an ad-
equate respiratory drive should be considered for
early tracheostomy to help facilitate early mobili-
zation and rehabilitation. Patients with cerebellar
mutism or oral pharyngeal dysphagia may not be
safe for oral intake, and if there is concern for per-
sistent aspiration, then a gastrostomy tube should
be considered. Other CN abnormalities should be
assessed. If the patient has incomplete eye closure,
adequate corneal care as well as a potential lead
weight may be considered. For more permanent
facial weakness, a facial nerve transfer may be con-
sidered to help with facial reanimation. Surgery
within the pons may result in transient or perma-
nent diplopia. If this occurs, ophthalmologic
treatment with special eyeglass prisms may be
necessary.23
An MRI should be obtained to evaluate the
extent of resection as well as any concerns within
the surgical site. If an intraventricular drain was
used during surgery, this should be weaned in a
standard fashion. Perioperative steroids will also
need to be weaned over a 1- to 2-week course.
21.9 Outcomes
The prognosis for patients with DIPG is extremely
poor, with a prognosis similar to glioblastoma.
DIPGs carry a 10% overall survival rate at 2 years,
with a median survival time of <1 year.1,12,14,24 The
median survival for pediatric patients is 18 months
after diagnosis.1,16
Other focal brainstem tumors have a better
prognosis. One series of focal tumors described a
4-year survival rate of 87.4% and a 4-year disease-
free survival rate of 58.8%.14 The most important
prognostic factor was the extent of resection.
Another series of low-grade brainstem tumors had
a 5-year progression-free survival and overall sur-
vival rate of 57 and 89%, respectively.25 In this ser-
ies, pathology was an important prognostic factor
on survival, with pilocytic astrocytomas having a
1-year survival rate of 95 ± 5% versus fibrillary
astrocytomas at 23 ± 11%.26 For low-grade lesions,
surgical re-resection may be considered for
patients who have had growth within an area of
recurrent tumor, or in patients whose initial sur-
gery was halted due to changes in intraoperative
monitoring or vital sign abnormalities.
Factors associated with poor outcome12,26:
● Di use glioma of midline structures (former
DIPG).
● Age younger than 2 years.
● Presence of CN palsies, particularly abducens
nerve palsy.
● Long tract signs on symptoms.
● Pontine location.
● Encasement of the basilar artery.
● Shorter duration of symptoms before diagnosis.
Factors associated with favorable outcomes12,14:
● Patients with neurofibromatosis.
● Older age.
● Longer duration of symptoms before diagnosis.
21.10 Surgical Pearls
● Internal debulking is key as there is typically not
a clear plane between the tumor and the
brainstem. Attempts to create a plane will lead
to damage of the surrounding brainstem, as well
as perpetuate retraction injury and lead to
postoperative CN defects.
● Retraction injury may cause direct damage,
edema, or infarction from compromise of the
adjacent vessels, leading to facial sensory, motor,
auditory, and speech deficits.
● Transient bradycardia and hypotension may be
seen when working close to the nuclei of CN V
and IX. When this occurs, cease manipulation of
the surgical site until symptoms improve. Any
attempt to proceed with surgery could lead to a
cardiac event.
● Avoid excessive bipolar use along the brainstem.
Most bleeding will stop with gentle pressure
and/or antifibrinolytic agents. Chasing bleeding
vessels within the brainstem will result in
additional CN defects. If intraoperative
neuromonitoring changes occur from possibly
ischemic changes, then raising the MAP to a
high-normal range should be attempted as in a
standard stroke protocol. This should be used in
the context of adequate hemostasis.
● Dexamethasone should be used postoperatively
to help address retraction injury edema.
Brainstem Gliomas
175
● Prior to extubation, patients should be evaluated
for adequate motor and respiratory drive. Lower
pontine and medullary lesions may require
intubation postoperatively until this can safely
be assessed. If there has been compromise,
patients may experience a gradual CO2 retention
and respiratory collapse due to an inadequate
respiratory drive.
21.11 Common Clinical
Questions
1. How do brainstem gliomas commonly present?
2. What is the role of surgery for DIPGs?
3. What preoperative considerations must be
made for patients with brainstem gliomas?
4. What is the clinical indication for a second
surgical resection?
21.12 Answers to Common
Clinical Questions
1. Three important components should be
ascertained during the initial workup for a
brainstem lesion: signs and symptoms related
to the intra-axial component (paying special
attention to CN dysfunction), signs and
symptoms of hydrocephalus, and symptom
onset. The more rapidly progressive lesions
typically portend a poor prognosis.
2. For patients presenting with atypical DIPGs, a
biopsy may be indicated for diagnosis and to
help guide therapeutic strategies. The need for
CSF diversion should also be assessed as these
patients are at risk for obstructing the normal
CSF outflow pathway.
3. Intraoperative neuromonitoring is key for
avoiding complications. Patients should have
appropriate brainstem reflexes and centers
monitored. The endotracheal tube should be at
the appropriate length to account for neck
flexion. A Frazier burr hole should be prepared
in the event that CSF relaxation is needed.
Internal debulking should be employed for all
intrinsic brainstem tumors to limit damage to
the surrounding brainstem and minimize
retraction edema.
4. For low-grade lesions, surgical re-resection may
be considered for patients who have had
growth within an area of recurrent tumor, or in
patients whose initial surgery was halted due to
changes in intraoperative monitoring or vital
sign abnormalities.
References
[1] Hargrave D, Bartels U, Bou et E. Di use brainstem glioma in
children: critical review of clinical trials. Lancet Oncol. 2006;
7(3):241–248
[2] Littman P, Jarrett P, Bilaniuk LT, et al. Pediatric brain stem
gliomas. Cancer. 1980; 45(11):2787–2792
[3] Berger MS, Edwards MS, LaMasters D, Davis RL, Wilson CB.
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302
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[5] Walker DA, Punt JA, Sokal M. Clinical management of brain
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Albright AL, Pollack IF, Adelson PD, eds. Principles and
Practice of Pediatric Neurosurgery. 3rd ed. New York, NY:
Thieme; 2015
[9] Choux M, Lena G, Do L. Brainstem tumors. In: Choux M, Di
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2006; 22(9):1127–1135
[15] Bartels U, Hawkins C, Vézina G, Kun L, Souweidane M, Bou et
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(1):119–125
[16] Frazier JL, Lee J, Thomale UW, Noggle JC, Cohen KJ, Jallo GI.
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[17] Ternier J, Wray A, Puget S, Bodaert N, Zerah M, Sainte-Rose C.
Tectal plate lesions in children. J Neurosurg. 2006; 104(6)
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[18] Wellons JC, III, Tubbs RS, Banks JT, et al. Long-term control of
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(1):63–67, discussion 67–68
[19] Javadpour M, Mallucci C. The role of neuroendoscopy in the
management of tectal gliomas. Childs Nerv Syst. 2004; 20
(11–12):852–857
[20] Pollack IF, Ho man HJ, Humphreys RP, Becker L. The long-
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[21] Cartmill M, Punt J. Di use brain stem glioma. A review of
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[23] Jallo GI, Freed D, Roonprapunt C, Epstein F. Current
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Brainstem Gliomas
177
22 Intramedullary Spinal Cord Tumors
Karl F. Kothbauer
22.1 Introduction
Tumors arising from tissue elements within the
spinal cord are a small subgroup of central nervous
system (CNS) tumors in children. They are consid-
ered particularly threatening because of their
localization in between densely packed fiber tracts
that are all essential for motor control, movement
coordination, and di erent modalities of sensa-
tion. Some of the first operations in adults were
performed in the first decade of the 19th century
by Eiselsberg in Vienna1 and Elsberg in New York.2
Later, Greenwood pioneered intramedullary sur-
gery in the 1950s,3,4,5 and subsequently, series in
the modern era of microsurgery appeared,6,7,8,9
also including series of children.10
22.2 Neurosurgical
Management of Intramedullary
Spinal Cord Tumors11,12,13,14,15,
16,17,18,19
22.2.1 Diagnostic Evaluation
Symptoms such as neck or back pain or neurologic
dysfunction most often lead to spinal imaging
before a pediatric neurosurgeon is consulted.12
Obtaining a detailed history and a diligent neuro-
logical exam is essential.
Magnetic resonance imaging (MRI) of the entire
spine is the imaging modality of choice.
Spinal tap for cerebrospinal fluid (CSF) analysis
is not required for the diagnostic workup of the
great majority of spinal cord tumors.
Interdisciplinary management and evaluation,
particularly involving pediatric neurology and
oncology, is essential not only for brain tumors but
also for spinal cord tumors.
22.2.2 Preoperative Management
The preoperative workup can mostly be done in an
outpatient setting.
Steroids can be useful for symptomatic patients
and are administered upon hospital admission.
Preoperative blood work must include a coagu-
lation status and a type-and-screen evaluation.
22.2.3 Surgical Considerations
General
The great majority of intramedullary tumors can be
removed with elective surgery. However, as with
brain tumors, the psychological impact on patients
newly diagnosed with a spinal cord tumor and their
parents must be taken very seriously.20 Preoperative
communication with the family is extremely impor-
tant. Obtaining written consent from the parents
should be done as early as possible to ensure su -
cient time to consider the decision for surgery.
Phone calls from the operating room by the
anesthesiologist to update the family on the prog-
ress of surgery were found to be extremely well
received by all families.
Blood loss in spinal cord surgery in children is
usually limited, but may be a factor for younger
children and infants with a small total blood vol-
ume. The anesthesia team (availability of blood
products), scrub nurse (preparation of Cottonoids,
hemostatic materials, working bipolar coagulation
forceps, and suction), and surgeon (meticulous
hemostasis) should anticipate blood loss and pay
close attention to blood loss during the surgery
(including “hidden blood” in drainage bags, drapes,
and Cottonoids).
At a minimum of 30 minutes before incision,
perioperative surgical antibiotic prophylaxis is
administered, usually cefazolin 30 mg/kg, together
with a single dose of steroids on induction (i.e.,
dexamethasone 4–8 mg).
Positioning
All surgeries for removal of intramedullary spinal
cord tumors are performed with the patient in
prone position. A rigid head fixation (Sugita or
Mayfield) is used for all cervical and upper thora-
cic exposures at least down to T5. For surgeries fur-
ther caudally, a neutral head positioning in a soft
headrest or a sideways position of the head can be
used. However, care has to be taken to avoid too
strong lateral rotation for long cases.
It is essential to use soft pads to avoid positional
injuries to knees, hips, elbows, toe tips, etc. Soft gel
rolls must be used in a body-parallel or transverse
fashion to ensure relaxed position of the abdomen
to minimize venous pressure.
178
Approach
A linear midline incision is used. The laminae are
exposed in an anatomic layer, preserving the
integrity of the musculature and the fascia using a
monopolar cautery, utilizing the coagulation
mode. It is imperative to gently pull the muscle
layers laterally in toto but not forge between them
as this will cause bleeding, poor wound healing,
and pain. The exposed laminae are cut out laterally
using a pediatric craniotome. Depending on the
number of levels exposed in children, it may be
possible to leave the cranial attachment intact and
just pull the laminae aside and cover them with
drapes. Otherwise, they are removed and pre-
served. After careful hemostasis, the wound sur-
face is covered with large Cottonoids laterally from
the skin to the dura. Then the dura is opened cra-
niocaudally and tacked up laterally. Sometimes,
the arachnoid can be opened separately and tacked
sideways to expose the cord.
Surgical Adjuncts
Intraoperative Neuromonitoring
The use of motor evoked potential (MEP) and
somatosensory evoked potential monitoring must
be routine for spinal cord tumor surgery. Including
anal sphincter MEPs and monitoring of bulboca-
vernosus reflex may be useful in cases involving
the conus.21,22
The best possible extent of resection carries a
significant risk of neurological injury. The use of
intraoperative neuromonitoring enables the sur-
geon to be as radical as possible and still preserve
long-term function.
The successful application of intraoperative neu-
romonitoring strongly depends on the teamwork
of neurophysiologist (experience in acquisition
and interpretation), anesthesiologist (using only
intravenous anesthetic agents without muscle
relaxants), and surgeon (experience to tailor the
procedure according to the monitoring feed-
back).22
Intraoperative Ultrasound23
Intraoperative ultrasound is an easy-to-use imag-
ing adjunct for spinal cord surgery. It is especially
helpful in:
● Determining the craniocaudal extent of the solid
tumor portion.
● Making sure the laminar exposure is su cient.
● Visualizing cystic tumor component.
● Visualizing residual tumor which may not be
apparent on the microscopic view.
Intraoperative Imaging
Intraoperative imaging other than ultrasound at
this time is mainly limited to fluoroscopy to deter-
mine the correct level of the spinal exposure. It
may well be that in the near future the extent of
resection of intramedullary tumors will also be
determined intraoperatively using intraoperative
MRI.
Fluorescent dyes (5-ALA) are used for a variety
of brain tumor resections, particularly glioblas-
toma. The use of 5-ALA fluorescence has also been
reported in adult spinal cord tumors.24
Ultrasonic Aspirator
The ultrasound aspirator is an essential tool for all
neurosurgical tumor resections and also has a key
function in spinal cord tumor removal.25 However,
the use of intraoperative MEP monitoring has
allowed identifying intraoperative events of signif-
icance for postoperative neurological dysfunction.
One important result was the observation of intra-
operative injury attributed to the use of the ultra-
sound aspirator (CUSA). This was interpreted such
that the propagation of ultrasound in intact tissue
reaches the surrounding spinal cord tissue and
causes injury there. Since the CUSA continues to be
essential for resection of tumors, its utilization
was modified to remove tumor portions only after
at least partially detaching them rather than going
into the intact tumor volume with the CUSA for a
primary internal debulking.
Microsurgical Laser
The microsurgical laser is an extremely useful tool
for surgery on the spinal cord,26 as it allows for
incision into very soft and particularly very firm
tumor tissue with great precision and an accept-
able tissue depth penetration. Laser used in con-
junction with the microsuction permits piecemeal
resection similar to the use of bipolar and suction
but without the bipolar’s e ect of the vasculature,
or its electrical artifact prohibiting simultaneous
monitoring.
22.2.4 Closure
Meticulous hemostasis of the resection cavity is
mandatory. Based on experiences documented by
intraoperative monitoring changes, the bipolar
coagulation of small bleeding vessels in the wall of
Intramedullary Spinal Cord Tumors
179
the resection cavity, particularly near the anterior
spinal artery, must be avoided. Small bleeders can
be controlled by Gelfoam, Avitene, or Floseal®, or
simply by mild compression and irrigation. The
dura must be closed using a running locked 4–0
suture. Braided or monofilic sutures can be used. It
appears that braided sutures have less propensity
for CSF leakage along the suture stitches, but no
clear evidence for this exists. The dura can be cov-
ered with Surgicel. Routine use of additional
hemostatic materials is not required and can be
limited to specific circumstances.
Sometimes, epidural veins may bleed again once
the dural tack-up is released for closure. These
venous hemorrhages are usually well controlled
by bipolar coagulation of the veins toward the
lateral edges of the spinal canal. Bleeding from
bony elements can be controlled with bone wax.
The laminae that were removed at the beginning
of surgery should be reinserted with fixation on
both sides on every level. In younger children,
small burr holes must be made in the laminae and
the lateral stumps of the cut laminae. Fixation is
made using size 1 Vicryl sutures. In older children,
titanium microplates, normally used for craniot-
omy flaps, are optimal for this fixation. It is essen-
tial to ensure that the spinal canal is not narrowed
by tilted or displaced laminae to avoid spinal cord
compression.27 The soft-tissue closure begins with
not-too-tight 1 Vicryl resorbable sutures to adapt
the paraspinal muscles. These sutures should
include the spinous processes and/or the interspi-
nous ligaments in order to reconstruct the func-
tional integrity between muscles and the osseous
elements. The aponeurotic fascial layer must then
be sutured tightly, preferably with inverted suture
technique. This is the realistically “watertight”
layer which should be closed with extreme care to
avoid CSF leakage. Subcutaneous 3–0 Vicryl
sutures are applied in an inverted fashion. The skin
should be closed using a running-locked suture
technique as the final barrier for CSF leakage and
with meticulous care to achieve skin adaptation.
As a rule, no wound drains are used in order to
minimize CSF leakage and infection.
22.2.5 Postoperative
Management
General
All patients are extubated in the operating room
after surgery and then transferred to a pediatric
intensive care unit for a duration of about 24 hours.
Vitals signs and pain score are documented
every 30 minutes until about 5 hours postopera-
tively and hourly thereafter. Checkup of key neuro-
logical functions, particularly motor function, is
assessed at the same time.
Pain results from a rather large back incision
with a large wound surface and significant detach-
ment of the spinal muscles. Pain therefore must be
treated prophylactically and on an as-needed basis
to ensure a low level of postoperative pain. Intra-
thecal injection of morphine at the end of surgery
has been shown to be an extremely e ective pain
management for the first 24 hours.28
On the first postoperative day, MRI is routinely
performed to assess the extent of tumor removal
and the presence of spinal cord compression due
to hemorrhage or displaced laminae.
Following imaging, the patient is transferred to a
regular floor. Steroids are tapered over a 5-day period.
The patient is encouraged to move freely and
receives assistance by physiotherapists for initial
mobilization. Getting out of bed should be accom-
plished on day 1 or no later than day 2. Depending
on the initial status and the progress of recovery, it
may be possible to discharge the child home after
about a week from the operation. If the neurologi-
cal situation requires inpatient neurorehabilita-
tion, this should be organized in a timely fashion.
Most of the time, the plan will be outlined already
before surgery, to minimize delays due to waiting
times and insurance approvals.
Management of Complications
Postoperative Neurologic Deficits
Postoperative paralysis is possible after spinal cord
surgery. Its interpretation depends on the intraopera-
tive findings of MEP and D-wave monitoring. If the
neurophysiologic data predict a temporary motor
deficit (loss of MEPs with preservation of D-wave), a
paraparesis is the expected postoperative status and
does not require further treatment other than careful
examination to detect a trend toward improvement
and initial supportive physiotherapy. Should neuro-
monitoring indicate intact motor control (MEPs
present at the closing baseline) and the patient
exhibits para- or monoparesis, then immediate MRI
reimaging or even immediate revision of the surgical
site must be considered. MEP monitoring is 100%
sensitive to postoperative motor deficits29 and there-
fore a late surgical problem such as hematoma or
spinal cord swelling within the dural sac must be
considered. Both require timely revision.
Tumor
180
A certain degree of postoperative sensory dys-
function must be considered as normal after spinal
cord tumor resection.
Bladder Management
A Foley catheter is inserted after induction of
anesthesia for intraoperative fluid management
and bladder emptying. Usually, the catheter is
removed on the second or third postoperative day.
It may take a few days for bladder emptying to
normalize. Both long-term incontinence and over-
flow bladder are rare after spinal cord tumor
removal, unless the tumor directly involved the
conus medullaris.
Pseudomeningocele and CSF leakage
Even in the best of surgical hands, the “watertight”
dural closure is not a complete assurance that CSF
will not seep into the epidural space and the
wound—hence, the importance of a meticulous
multilayer closure! Thus, a degree of CSF accumu-
lation in the tissue or between layers is often seen
on postoperative MRI scans, and sometimes, accu-
mulation is also visible and/or palpable under the
skin. Most of the time, this will subside without in-
tervention. In such large “pseudomeningoceles,”
some action may be necessary, and the first meas-
ure is prescribing acetazolamide (250 mg every
12 hours), which reduces the production of CSF by
about 50%.30 Clinical experience exists as to the
e cacy of this treatment.
Nevertheless, CSF under the skin is a manage-
able problem. CSF leakage through the incision
may be a sign of poor wound closure or of incipi-
ent infection, or in rare cases an indicator for
hydrocephalus. CSF leakage must prompt blood-
work to assess the presence of infection, a spinal
tap with release of at least 20 mL of CSF to divert
pressure and obtain CSF analysis. In some cases,
the skin may be resutured and the leak stopped
with a few single stitches. In the absence of infec-
tion and of further leakage, the patient may be
observed as an inpatient and after a few days the
leakage may resolve. If it does not, and/or if infec-
tion is present, a wound revision to irrigate and
completely reclose is necessary. At that time, it is
most often useful to insert a temporary lumbar
CSF drain and keep the patient on strict bedrest to
assist wound healing. Drainage should be pres-
sure-controlled at ear level and limited to a maxi-
mum average of 20 to 25 mL/hour.
Spinal Deformity
Kyphosis or scoliosis may occur after spinal cord
tumor surgery.31,32
Sometimes, particularly in
cystic tumors, scoliosis is part of the presenting
clinical syndrom e, and may progress following the
compromise to spinal stability by the operation. In
children and young adults in particular, it is desir-
able to avoid large stabilization surgery as the
growth of the spine may be significantly impaired
by stabilization. Stabilization may even be a cause
for progressive deformity if it interferes with
normal growth! Nevertheless, if kyphosis with
subsequent spinal canal narrowing and spinal cord
compression occurs, corrective surgery may none-
theless be required. It is an important principle to
provide posterior decompression first, if a front-
back approach is necessary, as an anterior correc-
tion without prior posterior decompression carries
a significant risk for surgical compression and
paraplegia.
Wound Infection and Bacterial
Meningitis
Wound infections after spinal cord surgery appear
to be very rare. If they occur, they may be associ-
ated with CSF leakage and the same principles
apply as stated earlier. If overt wound infection
with dehiscence and purulent secretion is clini-
cally seen, urgent, i.e., same-day, wound revision
using extensive irrigation and debridement is indi-
cated. If this occurs, only a limited number of
resorbable sutures should be used for closure and
the skin is best closed with deep 0 braided sutures
using the Donati technique. In this situation, a
wound drain with minimal or no suction cannot
be avoided. A separate lumbar CSF drain may be
needed as well. After obtaining microbiology sam-
ples, empiric antibiotics should be started, and
antibiotic regimen improved as cultures and sensi-
tivity testing become available.
22.3 Specific Types of
Intramedullary Spinal Cord
Tumors
22.3.1 Overview
The distribution of tumor types in the pediatric
population significantly di ers from the adult. In
children, the prevailing tumor type is pilocytic
Intramedullary Spinal Cord Tumors
181
astrocytoma,10,19 while in adults ependymomas
are most frequent. Gangliogliomas occur as well as
other rare tumor types such as hem angioblasto-
mas.33
Malignant tumors such as glioblastoma are very
rare and usually manifest with rapid neurologic
deterioration.34
Dissemination of tumors from
other locations, such as medulloblastomas, may be
found. Intermediate-type tumors graded WHO
3 have been reported35 and are believed to require
adjuvant treatment including chemotherapy and,
depending on the patient’s age, also radiation.
22.3.2 Pilocytic Astrocytoma
Epidemiology
They comprise more than half of all intramedullary
tumors in childhood.12,19,36
Imaging
Pilocytic astrocytomas are more frequently cen-
trally located but may have eccentric extensions.
Cystic components are frequent and these tumors
typically show enhancement with gadolinium. Dif-
ferential diagnosis vis-à-vis ependymomas can be
di cult based on MRI alone.
Management
Most complete surgical resection with the preser-
vation of neurologic function is the cornerstone of
treatment.14,18,36,37,38 There is ample evidence and
experience about the rationale for surgical resec-
tion early on39,40 as well as the optimal outcome
achieved by gross total resection,19 albeit small
remnants of tumor appear not to a ect this out-
come.14
Surgery
Gross total resection must be attempted and is
often possible. However, the surgical strategy
should put priority on the preservation of neuro-
logic function, particularly the ability to walk.
Therefore, the last remnants of a tumor need not
be chased, as small residual appears not to signifi-
cantly impact survival.14 If a large residual remains
at a time when neuromonitoring indicates that no
further injury can be tolerated, it is quite possible
to switch to a two-stage resection.
The particulars of pilocytic astrocytoma resec-
tion are defined by its frequent appearance of
having a tumor capsule and thus a well-visible
demarcation to the surrounding normal tissue.
This may mimic the appearance of ependymoma.
However, pilocytic astrocytomas also have areas of
di use margins to the spinal cord just like a di use
astrocytoma would have. And this dual appearance
must be considered in order to avoid a resection
attempt which may cause injury to the normal
cord, as one gets “into a wrong layer” when dis-
secting a capsulelike surface further into a di use
margin area. The laser is useful to detach tumor
tissue and the CUSA to remove such detached
tumor bulk. Neuromonitoring with MEPs should
constantly be used to always know the functional
integrity of the motor pathways. Cysts should be
opened early on to achieve decompression in the
event of swelling upon dural incision.
Radiation Therapy
There is no rationale to treat pediatric patients
with low-grade spinal cord astrocytomas (di use
of pilocytic) with radiation therapy. The downside
of additional cord injury, grow th arrest of the
a ected parts of the spine, or even asymmetric
growth may be negative consequences. However, if
unusual tumor types are found with WHO 3 or
even 4,35 radiotherapy may well be necessary to
prolong survival.
Chemotherapy
The use of chemotherapy based on temozolomide
has been tried anecdotally but is not an estab-
lished treatment for pilocytic astrocytomas. Pro-
gression-free survival of 5 years has been observed
in patients with grow th of residual disease. Higher
grade tumors may require chemotherapy with
either temozolomide or other regimens.41
Follow-up
The MRI scan on postoperative day 1 serves as a
quality control for surgery. After 3 months, a base-
line MRI should be obtained to assess the presence
or absence of residual tumor, cystic formations,
scarring, and cord atrophy. If there is no residual
tumor, yearly follow-up MRIs are indicated. There
is no evidence as to the overall duration of follow-
up. It may or may not be acceptable to cease yearly
MRIs after a decade.
If residual tumor is found, a first follow-up scan
is scheduled for 6 months, and if the residual is
stable, yearly scans thereafter are planned.
Tumor
182
22.3.3 Ganglioglioma
Epidemiology
These are the third most common intramedullary
tumor in childhood comprising 12% of pediatric
intramedullary tumors.19
Imaging
Gangliogliomas appear to form large tumors, often
with considerable cystic components. They are
more irregular in texture and configuration than
pilocytic astrocytomas, and certainly more so than
ependymomas. They also tend to form nodules of
solid tumor and cystic components.
Management
Surgery
Complete resection is attempted with very similar
aspects as those for pilocytic astrocytomas.
The other aspects are the same as in pilocytic
astrocytoma.
22.3.4 Ependymoma
Epidemiology
It is the second most common tumor type in chil-
dren.19
Pathology
Ependymomas are glial neoplasms arising from
ependymal cell layers adjacent to the ventricular
system or the central spinal canal. Histology of
ependymoma is quite uniform, showing cells with
oval or round nuclei, typically arranged in pseu-
dorosettes around vessels. Classic ependymoma is
grade 2 in the WHO scheme. Subependymomas
are rare variants which are classified as WHO 1 as
are the conus-cauda variant, the myxopapillary
ependymoma.17
Imaging
Ependymomas typically are central tumors. They
often develop “polar” cyst with some hemorrhagic
component. They most often homogenously
enhance with gadolinium administration.
Management
Surgery
The complete resection is most important in this
subgroup, as they may be considered cured when
removed completely. The resection most often is
possible along a cleavage plane which surrounds
the entire tumor. Only in the anterior wall the
tumor vessels arise usually from the anterior spinal
artery and must be carefully dissected away from
the tumor to avoid vascular injury and subsequent
ischemia. It is imperative to avoid bipolar coagula-
tion of these vessels, particularly too close to the
anterior spinal artery. It has been clearly shown in
the analysis of monitoring data that injury occurred
at the time of vessel obliteration. Alternatively, mild
compression usually stops bleeding, and if it does
not, new hemostatic materials such as Floseal® will.
Subependymomas42 appear to be sometimes
septated with stretches of normal tissue between
tumor strands. This may be di cult to detect but
important to avoid injury.
Radiation Therapy
Radiation is avoided in all spinal cord ependymo-
mas. However, recently a survival benefit was
demonstrated in myxopapillary ependymoma43
patients who underwent surgery plus radiation
versus those who only underwent surgery. How-
ever, the downside of radiation treatment to the
growing spine must still be carefully weighed
against this probably small benefit.
Chemotherapy
No e ective chemotherapy is available for spinal
cord ependymomas.
Follow-up
The intervals of follow-up imaging largely depend
on the achievement of a surgical gross total resec-
tion and should be chosen on an individual basis.
The presence of residual tumor should warrant a
closer follow-up, as relapses are possible.
22.3.5 Di use Astrocytoma and
Mixed Gliomas
Epidemiology
Usually these astrocytoma variants figure in the
“other” category of publications.19 Therefore, their
Intramedullary Spinal Cord Tumors
183
true incidence is di cult to know. Nevertheless,
di use astrocytomas and gliomas with oligoden-
droglias components do occur.
Imaging
These rare tumors may have the di use, nonen-
hancing characteristics their cousins in the brain
have. However, tumors of mixed histological com-
position may be heterogeneous and thus appear
with nodules, cysts, and asymmetric cord enlarge-
ments, very similar to the appearance of pilocytic
tumors.
Management
Surgery
Complete resection with consideration of the
aspects put forth earlier on pilocytic astrocytomas
is the preferred surgical goal.
Radiation Therapy
In low-grade tumors, no adjuvant treatment is
warranted.
Chemotherapy
In low-grade tumors, no adjuvant treatment is
warranted.
Follow-up
The follow-up can be the same as for pilocytic
astrocytomas.
22.3.6 Hemangioblastoma
Epidemiology
Hemangioblastomas are the typical spinal cord
tumors of patients a ected by the autosomal dom-
inant von Hippel–Lindau disease. These patients
often have multiple spinal cord hemangioblasto-
mas, which may grow unpredictably, form cysts
and significant spinal cord edema, and thus may
require multiple surgeries over the years.44
Imaging
Hemangioblastomas typically have intense vascu-
larization, which is shown well both on gadoli-
nium-enhanced and on T2 images. They typically
but not in every case develop adjacent cysts and
frequently cause intense cord edema, presumably
as a precursor to cyst formation. This is the tumor
type that can be conclusively diagnosed on imaging
alone. Very rarely, for instance in a high cervical or
craniocervical localization, it may be indicated to
perform a preoperative angiogram. Partial emboli-
zation of feeding arteries may be possible at that
time, rendering the surgical resection somewhat
easier by reducing the intense blood flow through
these tumors.
Management
Surgery
Only complete surgical resection is possible for
hemangioblastomas. They are very well delineated
and can be meticulously removed from the cord
with minimal damage. The presence of cysts may
make the exposure easier. Large tumors must be
approached with great care as the thin capsule
may easily permit hemorrhage, which may be
uncontrollable until the entire tumor is removed
and the feeding arteries obliterated. Under no cir-
cumstances must the draining vein or veins be
coagulated first, as this would result in intense
swelling and hemorrhage and subsequent cord
damage.
Hemangioblastomas cannot be partially
removed as bleeding would stop only after the
entire lesion is gone. Still the use of neuromonitor-
ing is helpful to reassure the surgeon of intact
pathways and to indicate whether spinal cord
edema reaches a threatening intensity. If this is the
case, the dura must not be closed primarily after
tumor removal. It may be necessary to insert a lon-
gitudinal dural extension graft to prevent a type of
“compartment syndrome” of the cord within the
dural sac.
Radiation Therapy
No adjuvant treatment is warranted.
Chemotherapy
No adjuvant treatment is warranted.
Follow-up
Once resected, hemangioblastomas with docu-
mented complete removal can be considered
cured and do not require yearly follow-up.
However, in patients with von Hippel–Lindau
disease, lifelong follow-up with yearly imaging is
strictly required to ensure early detection of newly
arising or progressive tumors.
Tumor
184
22.3.7 High-grade Glial Tumors
Epidemiology
High-grade tumors, particularly glioblastomas of
the spinal cord, are rare but they do occur.34,45
Pathology
Glioblastomas are a rare exception. They have the
same tissue characteristics as glioblastomas in the
brain. Anaplastic astrocytoma has been described
and frequently follows the di use astrocytoma
pattern with added features of vascular prolifera-
tion and increased cellularity. Mixed astrocytomas
with anaplastic features have been rarely seen. The
grade 3 ganglioglioma is a rare type which also
has received some attention.35
Imaging
The appearance of malignant tumors on MRI is
heterogeneous. Di use anaplastic astrocytomas
can appear as di use, even nonenhancing exten-
sions of the cord. Contrast enhancement, nodules,
and cystic components can all occur. Most likely,
these tumors are eccentric in the cord, may extent
through the pia to the cord surface, and cause sig-
nificant adjacent edema.
Surgery
The extent of resection should be strictly limited
to what is functionally permissible based on neu-
romonitoring in order to absolutely avoid a signifi-
cant motor deficit.34 In malignant tumors, such
dysfunction is more likely to be present already
before surgery. Surgery is essential to establish the
histologic diagnosis, which determines the choice
of adjuvant treatment and follow-up.
Adjuvant Therapy
Radiation Therapy
Radiation therapy can be indicated even in chil-
dren older than 3 years to improve progression-
free survival. To minimize the impact of radiation
on the growth of the spine, proton beam radiation
may be considered to avoid a large dose absorp-
tion into the vertebral bodies and the facet joints.
Chemotherapy
For glioblastomas, the standard treatment plan for
cerebral glioblastomas would be used46 in the
same way as for those occurring in the brain. Other
treatments have been tried with some success.35,41
22.4 Summary
Neurological and oncologic outcome must be
clearly distinguished.
The neurologic result of spinal cord tumor resec-
tion depends on a number of factors. The one
documented factor independently contributing to
the postoperative outcome, usually the motor out-
come and more specifically the ability to walk, is
the preoperative baseline. The better the motor
status before surgery, the more likely the postope-
rative motor function will be satisfactory as well.39,
40 This is well understood with a concept of
ongoing structural damage to the motor pathways,
which may reach a critical level only at which clin-
ical dysfunction begins to appear. At this stage, the
compensatory mechanisms may already be close
to being exhausted and thus the ability of the spi-
nal cord to tolerate the inevitable trauma of sur-
gery limited.
The approach into the cord practically always is
through the posterior part, thus injuring the sen-
sory pathways. Therefore, almost always some
degree of sensory dysfunction is present after sur-
gery.18 Usually, this does not result in a significant
degree of long-term morbidity as compensation
occurs and is supported by neurorehabilitation.
The motor outcome of spinal cord surgery in
children is remarkably favorable.10,11,12,14,19,36,38,47
Paraplegia is and should be an extreme exception.
The oncologic outcome is determined by the
type and grade of the histological diagnosis on one
side and the extent of resection on the other.13,14,
19,36 The progression-free survival is clearly longer
with gross total resection than subtotal resection.
The work of Constantini et al has shown that small
tumor residuals as determined on postoperative
MRI scans do not change this outcome unless the
resection is less than about 85%, below which pro-
gression will occur frequently and early.14 Clearly,
high-grade tumors have an unfavorable prognosis
as compared to low-grade tumors.34
22.5 Common Clinical
Questions
1. Name the most common tumor in the spinal
cord in children.
2. What is the typical presentation of a low-grade
astrocytoma in the thoracic cord in children?
Intramedullary Spinal Cord Tumors
185
3. What is the treatment of choice for
intramedullary spinal cord hemangioblastoma?
4. What is the role of adjuvant treatment for
intramedullary astrocytomas WHO 3?
5. What is the best technique for small vessel
bleeder hemostasis after spinal cord tumor
resection?
22.6 Answers to Common
Clinical Questions
1. Pilocytic astrocytoma.
2. Nocturnal back pain.
3. Complete surgical resection alone.
4. Most complete surgical resection followed by
chemotherapy and radiation treatment (for
children older than 3 years).
5. Irrigation, mild compression, Avitene. Avoid
bipolar coagulation.
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[29] Kothbauer KF, Deletis V, Epstein FJ. Motor-evoked potential
monitoring for intramedullary spinal cord tumor surgery:
correlation of clinical and neurophysiological data in a series
of 100 consecutive procedures. Neurosurg Focus. 1998; 4(5):
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[30] Rubin RC, Henderson ES, Ommaya AK, Walker MD, Rall DP.
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[31] McGirt MJ, Chaichana KL, Attenello F, et al. Spinal deformity
after resection of cervical intramedullary spinal cord tumors
in children. Childs Nerv Syst. 2008; 24(6):735–739
[32] Yao K, Kothbauer KF, Bitan F, Constantini S, Epstein FJ, Jallo
GI. Spinal deformity and intramedullary tumor surgery.
Childs Nerv Syst. 2000; 16:530
[33] Deutsch H, Shrivistava R, Epstein F, Jallo GI. Pediatric
intramedullary spinal cavernous malformations. Spine. 2001;
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KF, Jallo GI. Extent of surgical resection of malignant
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Intramedullary Spinal Cord Tumors
187
23 Tumors of the Spinal Column
Dominic N.P. Thompson, Nir Shimony
23.1 Introduction
In pediatric practice, spinal tumors are less fre-
quent than intracranial tumors and also much less
common than in adult practice. Approximately
one-third of spinal tumors in childhood are extra-
dural, the remainder being intramedullary or
intradural but extramedullary.
The term spinal column tumors is used here to
encompass those tumors that arise in the extra-
dural space and the paraspinal regions as well as
from the bony and cartilaginous elements of the
spine. A variety of tumor types, both benign and
malignant, may be encountered in these locations,
although both the age of the patient and the ana-
tomical site of origin will aid in refining the di er-
ential diagnosis in individual cases.
The management of spinal column tumors is
guided by:
● Biology of the tumor.
● Neurological status of the patient.
● Spinal deformity or instability.
Tumors of extradural origin are more likely to be
malignant than intradural tumors. Spinal column
tumors may be part of a more systemic malignant
disease and, in such cases, surgery alone is unlikely
to be curative; it is therefore important that
these cases be managed by a multidisciplinary
neuro-oncology team to ensure that the timing,
objectives, and extent of surgery are agreed and
appropriate.
Severe neurological deterioration mandating
emergency intervention is rare in pediatric spinal
column tumors, and thus, there is usually time to
permit appropriate investigations and planning of
intervention.
Vertebral collapse with deformity or instability
will mean that spinal stabilization will have to be
considered as part of the surgical strategy. Even if
there is no evidence of deformity or instability at
the outset, late postsurgical deformity is a signifi-
cant risk following laminectomy or laminoplasty,
particularly in a growing child, and these risks
need to be factored into the clinical decision-
making process.1
23.2 Clinical Presentation
23.2.1 Pain
Spinal pain is present in up to two-thirds of cases
of spinal tumor at the time of diagnosis. The pain
is frequently poorly localized and may have been
present for many months. Constant pain or pain of
increasing intensity, pain that wakes the child at
night, or pain that is associated with radicular
spread or sensory impairment is of particular sig-
nificance and warrants prompt investigation.2,3
23.2.2 Weakness
Along with pain, weakness is one of the common-
est findings in children with spinal tumor. In the
infant, weakness can be easily overlooked until the
late stages of spinal cord compression. In an older
child, a limp, fatigability, a tendency to trip, or falls
may be the manifestations of lower limb weak-
ness. Examination findings are typically those of
upper motor neurone type with hyperreflexia.
23.2.3 Mass
Extension of a spinal or paraspinal mass into the
adjacent soft tissue can result in a palpable mass
in a thin child. A soft-tissue mass in association
with a bone tumor is suggestive of malignancy.
23.2.4 Spinal Deformity
Scoliosis is present in approximately one-quarter
of cases. Rapid curve progression or atypical or
left-sided curves should prompt the search for an
underlying spinal lesion or spinal cord anomaly.
Torticollis may herald the presence of a tumor
involving the upper cervical spine or cranioverte-
bral junction.
23.2.5 Sphincter Disturbance
This is an unusual presenting symptom in child-
hood but one that is easily overlooked as it may
not have been recognized by the parent or child.
188
Findings include an enlarged bladder, incomplete
bladder emptying, a history of urinary infection,
or frank incontinence. Disturbance of rectal
continence is less com m on and, when it occurs,
is a later sign; neurogenic sphincter disturbance
alm ost always a ects the bladder first.
23.3 Investigations
Numerous modalities are available to investigate
spinal tumors; investigations are chosen with the
following in mind:
● Refining the di erential diagnosis.
● Evaluating the site and extent of the lesion, and
its e ect on the neuraxis (spinal cord and nerve
roots).
● Evaluating the extent of bone involvement.
● Assessment of spinal deformity.
● Determination of instability.
The most commonly required investigations are
the following.
23.3.1 Spinal MRI
The whole spine should be imaged with and with-
out contrast. Magnetic resonance imaging (MRI)
provides the best modality to assess the e ect of
the lesion on the neuraxis.4
23.3.2 Spinal CT
High-resolution computed tomography (CT) scan
(using bone window algorithm) of the involved
area is used where detailed bony information is
required, for example, in assessing extent of bone
involvement or suitability for instrumental fixa-
tion. CT-guided biopsy of the lesion will be useful
in cases of suspected malignancy.
23.3.3 Plain X-rays
Plain X-rays are unlikely to provide additional
diagnostic information, although they often have a
role in assessing spinal deformity or in cases of
suspected instability, for example, flexion/exten-
sion X-rays in cervical lesions.
23.3.4 Additional Investigations
There are certain investigations there are spe-
cific to the workup of certain tum or types
( Table 23.1).
23.4 Tumor Types
A wide range of tumor types can involve the spinal
column either primarily or secondarily as a result
of extension from adjacent tissues. Some of the
more common benign and malignant tumors of
the spinal column encountered in pediatric neuro-
surgical practice are shown in Box 23.1.
Box 23.1 Spinal column tumor types
in children
● Malignant:
– Neuroblastoma.
– Osteogenic sarcoma.
– Ewing’s sarcoma (peripheral PNET).
– Chordoma.
– Lymphoma.
– Metastases.
● Benign:
– Hemangioma of bone.
– Aneurysmal bone cyst.
– Osteoid osteoma/osteoblastoma.
– Histiocytosis.
23.4.1 Malignant
Malignant tumors of the spinal column present
with spinal pain (this may have a radicular compo-
nent), painful scoliosis, gait disturbance, or limb
weakness. Bladder (or rarely bowel) incontinence
is seen in lumbosacral malignancies when the
Table 23.1 Additional investigations that may be used in
the evaluation of particular tumor types
Investigation
Tumor type
Urinary catecholamines
Neuroblastoma (diagnosis)
MiBG scan
Neuroblastoma (staging)
Bone marrow aspirate
Neuroblastoma, lymphoma,
Ewing’s sarcoma (staging)
Radioisotope scan
Osteoid osteoma
Skeletal survey
Histiocytosis, malignant
bone tumors (staging)
CT chest/abdomen
Malignant bone tumors
(osteosarcoma, Ewing’s
sarcoma)
Spinal angiography
Hemangioma of bone,
aneurysmal bone cyst
Abbreviations: CT, computed tomography; MiBG,
metaiodobenzylguanidine.
Tumors of the Spinal Column
189
conus or cauda equina are involved, although it is
an unusual presenting feature in tumors higher in
the spinal column. Systemic features such as
weight loss and night sweats may be present par-
ticularly in lymphoma and Ewing’s sarcoma (EWS).
Malignant tumors of the spinal column require
multidisciplinary approach. Accurate pathological
diagnosis can be di cult but is an essential prereq-
uisite to treatment. CT-guided biopsy or open
biopsy will usually be required in the first instance,
although, in cases presenting with spinal compres-
sion, tumor tissue will be obtained at the time of
the decompression procedure. Because of the pro-
pensity for hematogenous spread, staging investi-
gations including CT chest, ultrasound abdomen,
and bone marrow aspiration are required.
Surgery should be considered as an adjunctive
therapy in the management of malignant tumors
of the spinal column. Neoadjuvant and adjuvant
chemotherapy have improved the prognosis for
many malignant tumors largely due to their ability
to shrink tumors, reduce vascularity, and thus
optimize the chances of gross total resection.
Neuroblastoma
Spinal neuroblastoma (NB) is predominantly a
tumor of infancy and younger children. The
histogenesis of NB is uncertain, although these
tumors are thought to originate in neural crest–
derived peripheral nerve progenitors. Spinal NB
commonly occurs along the sympathetic chain
(and adrenal gland) and so is typically centered on
the paravertebral region with secondary extension
through the intervertebral foramina into the intra-
spinal compartment. The cells of origin are
involved in catecholamine secretion, and this fea-
ture is exploited in diagnosis and workup, as
metabolites from the catecholamine synthesis
pathway are excreted via the kidney and can be
detected in the urine. The metabolic activity of
these tumors is also utilized in staging the disease;
the radionuclide MiBG (metaiodobenzylguanidine)
is taken up by NB and will permit identification of
metastatic disease. Some of these tumors show a
phenomenon of maturation toward more favor-
able pathology either on treatment or spontane-
ously, and so a spectrum of tumors ranging from
malignant to benign is recognized in pediatric
patients (neuroblastoma, ganglioneuroblastomas,
ganglioneuroma; Fig. 23.1a).
The mainstay of treatment for NB is chemother-
apy. Surgical decompression is reserved for cases
presenting with severe deficit or rapidly evolving
neurology; however, there is a high rate of post-
surgical spinal deformity.
Fig. 23.1 Radiological appearances of spinal column tumors. (a) Paravertebral ganglioneuroma. (b) Hemangioma of
bone. (c) Aneurysmal bone cyst. (d) Osteoid osteoma. (e) LCH (vertebra plana).
Tumor
190
Osteogenic Sarcoma
Osteogenic sarcoma (OS) is the most common pri-
mary bone neoplasm in children and typically
presents around the time of puberty. However, spi-
nal involvement (either as primary lesion or site of
metastasis) is seen in only 5% of cases.5 Imaging
reveals bone destruction, with a soft-tissue mass
demonstrating variable degrees of mineralization.
Tissue diagnosis is established by open or CT-
guided biopsy. Neoadjuvant chemotherapy is used
to reduce tumor volume, followed by maximal sur-
gical resection of the involved field. Five-year sur-
vival for all OS is approximately 18%; spinal
involvement portends a worse prognosis.
Ewing’s Sarcoma (Peripheral PNET)
Also a tumor of the teenage years, 10% of cases of
EWS involve the spine; however, in contrast with
OS, there is a predilection for the lumbosacral re-
gion.5 Histologically, these small round blue cell
tumors are considered part of the primitive neuro-
ectodermal tumor (PNET) spectrum. Metastatic
spread is present in up to half of cases at the time
of presentation.2 On MRI, EWS appears as an area
of lytic bone destruction with an associated mass
lesion. As with OS, accurate tissue diagnosis is
essential. Neoadjuvant chemotherapy is the initial
treatment of choice, followed by wide local resec-
tion usually with instrumented fixation; radiation
therapy is then used for postsurgical residual dis-
ease. Five-year survival is approximately 40%.
Lymphoma
Lymphoma involving the spine is rare and usually
occurs late in the disease. Most lymphomas that
involve the spine in childhood are B-cell lympho-
mas of the non-Hodgkin type and tend to occur in
the adolescent age group. Spinal lymphoma char-
acteristically spreads along nerve roots and
through the intervertebral foramina. Pathological
fractures are present in up to one-quarter of
patients. Chemotherapy is the mainstay of treat-
ment; surgery is reserved for cases of spinal dis-
ease refractory to primary treatment or for clinical
symptoms or signs of spinal cord compression.
Chordoma
It is a rare tumor of notochordal origin with a
predilection for the craniovertebral junction and
the sacrum (together, these two sites comprise
over two-thirds of cases). Subtypes include classi-
cal, chondroid, and dedi erentiated; the latter has
a more aggressive natural history. Immunohisto-
chemical techniques are often required to distin-
guish chordoma from chondrosarcoma that has a
more favorable prognosis. Gross total en bloc
resection provides the best long-term survival;
however, this is usually only feasible for small vol-
ume, localized tumors (<30 mL). Chordoma is only
moderately radiosensitive; however, proton beam
therapy has increased the dose of radiotherapy
that can be safely delivered to residual or recurrent
tumors. There is a high rate of local recurrence,
and 5-year survival is approximately 60%.
23.4.2 Benign
Within the spectrum of benign spinal tumors,
there are those that can be considered benign with
favorable natural history (e.g., Langerhans cell his-
tiocytosis [LCH] and osteoid osteoma) and those
that are benign but locally aggressive (e.g., aneur-
ysmal bone cyst [ABC], giant cell tumor of bone).6,7
Hemangioma
Hemangioma of bone is commonly an entirely
benign, incidental MRI finding appearing as a dis-
crete area of high T2 signal within the vertebral
body. No treatment or follow-up is indicated. On
occasion, however, spinal hemangioma can
present as a locally infiltrative lesion with exten-
sion into the paraspinal tissues and spinal canal,
resulting in spinal compression. On CT scan, these
lesions have a characteristic pattern of vertical tra-
beculation ( Fig. 23.1b). These are highly vascular
tumors, and where surgical intervention is
required (usually due to pain or radiculomyelop-
athy), preoperative angiography and embolization
should be considered. Following embolization,
radical surgical excision with spinal reconstruction
can be achieved. Successful treatment has also
been described using vertebroplasty or direct
ethanol injection. Focal radiotherapy may be
required in cases of residual or recurrent disease.8
Aneurysmal Bone Cyst
This is a benign but locally aggressive lesion, and
can occur in isolation or in conjunction with
another pathology such as fibrous dysplasia or
giant cell tumor of bone. ABCs commonly originate
in the posterior elements but extension to the
vertebral body is frequent. They characteristically
Tumors of the Spinal Column
191
consist of well-demarcated cysts, frequently con-
taining chocolate-colored fluid due to old blood
products, surrounded by a thin wall of reactive
bone that tends to expand the vertebra and produ-
ces a “soap bubble” appearance on CT or MRI
( Fig. 23.1c). Despite the name, they are not par-
ticularly vascular at surgery (in contrast with
hemangioma). Pain is the commonest presentation.
Treatment options vary according to site and mode
of presentation. The radiological features are usu-
ally diagnostic, and preliminary biopsy is rarely
necessary. Where there is evidence of spinal com-
pression, either en bloc resection or extensive cur-
ettage with grafting should be performed. Gross
total resection should be the goal of therapy;
instrumented spinal fixation will be required in
most cases.9 Postsurgical surveillance is required as
there is a significant risk of local recurrence, partic-
ularly in partially resected lesions.10 Transarterial
selective embolization has hitherto been used as an
adjunct to surgery; however, recent evidence sug-
gests that this modality should be considered as a
primary definitive treatment for ABC in the
absence of instability or neurological compro-
mise.11 In children, due to the potentially hazard-
ous late e ects, radiotherapy is generally reserved
for instances where primary treatment has failed.12
Osteoid Osteoma/Osteoblastoma
The distinction between these two entities is
essentially a matter of size; pathological appearan-
ces are indistinguishable. Small lesions <1.5 cm are
termed osteoid osteoma, while the larger version
is referred to as osteoblastoma. Clinical presenta-
tion is with local spinal pain that typically
responds to nonsteroidal anti-inflammatory drugs.
Neurological deficits are more commonly seen
with osteoblastoma; also, osteoblastoma tends to
have a higher rate of recurrence. Radiologically,
there is often a central nidus of dense bone, fre-
quently with sclerosis of the surrounding bone,
resulting in a lucent halo around the lesion (this
finding is more consistent in osteoid osteoma)13
( Fig. 23.1d). These appear as “hot spots” on
radionuclide scanning. Complete surgical resection
is the principal treatment. Radiotherapy is
reserved for recurrence.
23.4.3 Langerhans Cell
Histiocytosis
Langerhans cells are dendritic cells that are part of
the immune system. LCH may occur as an isolated
bone lesion (unifocal LCH), previously termed eosi-
nophilic granuloma, or with multiple bony lesions
(multifocal unisystem LCH). A more malignant
form with widespread extraosseous tissue involve-
ment is recognized (multifocal multisystem LCH).
In children, 80% of cases are unifocal and the spine
is involved in up to 25% of cases. The classical spi-
nal appearance of LCH is vertebra plana
( Fig. 23.1e). There is often an associated soft le-
sion; although spinal cord compression is rare,
pain rather than neurological compromise is the
most common presentation.14 Needle biopsy may
be required for diagnosis. Treatment is indicated
for multifocal lesions or extension into the spinal
canal. Treatment consists of steroids, bisphospho-
nates, and chemotherapy, with a bracing regime to
control spinal deformity. The role of surgery is lim-
ited to rare instances of spinal compression or
cases of progressive spinal deformity.
23.4.4 Giant Cell Tumor of Bone
It is an extremely rare tumor in pediatric practice.
These are locally aggressive tumors that require en
bloc complete resection in order to attain long-
term disease control.
23.4.5 Anatomical Site of Origin
Spinal column tumors show a predilection for cer-
tain patterns of growth and this can be of help in
refining the di erential diagnosis ( Fig. 23.2). This
should be considered a rough guide and there will
of course be exceptions.
23.4.6 Age
It is also important to consider the age of the child
as many tumors have a propensity to occur at par-
ticular times in childhood ( Fig. 23.3).
23.5 Treatment Considerations
In children with vertebral column tumors, ma-
nagement strategies are formulated according to:
● Grade and stage of the tumor.
● The role of surgery in relation to other
oncological modalities.
● The need to preserve of neurological function.
● The perceived e ect of the tumor or surgical
treatment on spinal stability and deformity.
For some malignant tumors, neoadjuvant treatment
with chemotherapy or radiotherapy can optimize
Tumor
192
the chances of successful surgical resection. Addi-
tionally, embolization can significantly reduce the
vascularity of tumors such as hemangioma, thus
reducing operative risk and facilitating radical surgi-
cal resection ( Table 23.2).
23.5.1 Surgical Planning
Once surgery is required, detailed multimodality
imaging is essential to preoperative planning.
Types of tumor resection include the following.
En Bloc Resection
For primary malignant tumors of bone, a complete
oncological resection preserving all tumor margins
should be pursued where possible. These are, how-
ever, complex surgeries requiring extensive expo-
sures and reconstructive instrumentation. While
most experience is in adults, these techniques can
be applied to selected pediatric cases.
Determining the extent of resection, the surgical
approach and the implications for spinal recon-
struction can be aided by the use of a reproducible
and validated approach to tumor staging such as
the Weinstein-Boriani-Biagini (WBB) system.15
Using this method, the vertebra is divided into
radial segments and a series of concentric zones
from intradural to extraspinal. This system is then
used to define the most appropriate technique of
en bloc resection. Broadly speaking, the following
three types of resection are described.
Fig. 23.2 Common sites of origin for
pediatric spinal column tumors.
Fig. 23.3 Spinal column tumors
according to age at presentation.
Tumors of the Spinal Column
193
Vertebrectomy
En bloc excision of the vertebral body and poste-
rior elements, this is achieved either via separate
anterior and posterior approaches or via a single
posterior approach.
Sagittal Resection
For tumors that are lateralized to the vertebral
bodies or posterior elements, a segmental resec-
tion may be performed comprising part of the ver-
tebral body and any involved ipsilateral pedicle or
hemilamina.
Posterior Arch Resection
An en bloc removal of the entire lamina and spi-
nous process in circumstances where the pedicles
are not involved.
23.5.2 Intralesional Resection
Most benign lesions are amenable to less extensive
surgery and can be satisfactorily treated by an
intralesional approach using piecemeal resection
or curettage.
23.6 Complications and Their
Prevention
Spinal tumor surgery, particularly major tumor
resections, carry significant risks, many of which
can be anticipated, and measures can be taken to
minimize them.
23.6.1 Neurological
The spinal cord may be compromised at the time
of presentation due to direct compression from
the lesion or vertebral collapse, and remains
vulnerable during tumor surgery. Perioperative
steroid treatment is commenced prior to surgery.
Intraoperative neurophysiological monitoring
(motor evoked potentials, somatosensory evoked
potentials) is generally recommended for all but
the most minor of cases.
23.6.2 Vascular
Major blood loss should be anticipated; cross-
matched blood and clotting factors are ordered
preoperatively. Preoperative embolization should
be considered in particular circumstances such as
spinal hemangioma.
23.6.3 Deformity
The integrity of the spinal column may be compro-
mised by tumor involvement or by surgical inter-
vention. In many cases, spinal instrumentation will
need to be performed concomitantly with the
tumor resection; young age does not preclude the
use of spinal instrumentation.
If there is no deformity at the time of presenta-
tion, then these patients can be followed with
Table 23.2 Treatment strategies for spinal column tumors in children
Tumor
Primary treatment
Additional treatment
Malignant
Neuroblastoma
Neoadjuvant chemotherapy
Surgerya
Osteosarcoma
Neoadjuvant chemotherapy
Radical surgery
Ewing’s sarcoma
Neoadjuvant chemotherapy+ radiotherapy
Radical surgery
Lymphoma
Chemotherapy+ radiotherapy
Surgerya
Chordoma
Radical surgery
Proton beam radiotherapy
Benign
Hemangioma
Embolization/surgery
Radiotherapy
Aneurysmal bone cyst
Embolization/surgery
Radiotherapy
Osteoblastoma/osteoid osteoma
Surgery
None
Histiocytosis
Chemotherapy
Surgery (stabilization)
Note: For the child presenting with symptoms or signs of spinal cord compression, an initial emergency decompression
may be required. These strategies are based on a known diagnosis and absence of clinical spinal cord compression.
aThe role of surgery in these instances is for significant residual disease following first-line therapy.
Tumor
194
serial spinal X-rays to monitor for the emergence
of delayed deformity. A customized spinal brace
may reduce the rate of postsurgical deformity in
children considered at increased risk.
23.7 Surgical Pearls
● Spinal pain is the commonest presenting
symptom of spinal column tumors. Red flag
symptoms include pain that is constant,
nocturnal pain, pain with a radicular
distribution, and pain associated with abnormal
neurological examination.
● The spectrum of spinal column neoplasms in
children is di erent compared with adults. The
age of the patient and position of the tumor
within the vertebra are valuable in refining the
di erential diagnosis.
● A soft-tissue mass associated with a bone tumor
is suggestive of malignancy.
● Malignant spinal column tumors are rarely
treated with surgery alone; these tumors require
a coordinated multidisciplinary neuro-oncology
approach.
● The potential for spinal deformity should be
incorporated into neurosurgical management
plan. Risk factors for progressive spinal
deformity include: young age, scoliosis at the
time of presentation, involvement of vertebral
body and posterior elements, and multiple level
laminectomies.
● Infection, particularly tuberculosis, can
masquerade as a spinal column tumor. Consider
ethnic background, history of foreign travel, and
presence of systemic symptoms.
23.8 Common Clinical
Questions
1. Which spinal column tumors typically occur in
the posterior neural arch?
2. Can tumor resection be combined with spinal
reconstruction?
3. What factors influence the neurosurgical
management in an 18-month-old child found to
have a paraspinal tumor with intraspinal
extension?
23.9 Answers to Common
Clinical Questions
1. Osteoid osteoma, osteoblastoma, ABC, and
giant cell tumors of bone typically arise in
or primarily involve the posterior neural
arch.
2. Spinal reconstruction, using strut grafting or
instrumental fixation, can be used at the time of
initial tumor resection. Typically, this is the case
for malignant tumors requiring en bloc
resections or where there is significant
deformity at the time of presentation.
3. The commonest spinal column tumor in this
age group with this pattern of grow th is NB.
Diagnosis can be made on the basis of urinary
catecholamines or biopsy. The primary
treatment modality in this instance will be
chemotherapy. Even with intraspinal extension,
immediate commencement of steroids and
chemotherapy can result in rapid tumor
regression without the need for neurosurgical
intervention. Surgical decompression is
reserved for cases presenting with clear
neurological deficit or as second-line treatment
for residual disease persisting after
chemotherapy.
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[6] Harrop JS, Schmidt MH, Boriani S, Sha rey CI. Aggressive
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[8] Acosta FL, Jr, Sanai N, Chi JH, et al. Comprehensive
management of symptomatic and aggressive vertebral
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[9] Zenonos G, Jamil O, Governale LS, Jernigan S, Hedequist D,
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[10] Novais EN, Rose PS, Yaszemski MJ, Sim FH. Aneurysmal bone
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Tumors of the Spinal Column
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[12] Burch S, Hu S, Berven S. Aneurysmal bone cysts of the spine.
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Tumor
196
V
Section V
Cerebrovascular Disorders
24 Aneurysms
198
25 Arteriovenous Malformations 205
26 Pediatric Cavernous
Malformations
213
24 Aneurysms
Edward R. Smith
24.1 Introduction and Anatomy
Aneurysms are one of the most common vascular
anomalies of the central nervous system, but are
far less common in children than in adults. These
structurally abnormal areas of arterial wall can
cause bleeding, compression of adjacent struc-
tures, and concomitant loss of neurologic function.
The epidemiology, pathophysiology, presentation,
and treatment of pediatric intracranial aneurysms
have features distinct from those in adult patients.
24.2 Epidemiology and
Pathophysiology
It is estimated that the general prevalence of
unruptured, asymptomatic intracranial aneurysm
(across all ages) is 3.2% and only 0.5 to 4.6% of
these are present in children.1,2,3,4,5,6 Ruptured
aneurysms in the pediatric population are also
rare, with 0.6% of all aneurysmal subarachnoid
hemorrhage (SAH) comprised of patients younger
than 19 years.3,6,7 Given a total of approximately
18,300 SAH cases annually, this means that there
are only about 100 aneurysmal SAH cases each
year in children.8,9 Intracranial aneurysms are
more common in males than females (especially in
prepubertal children) at 2.7:1, with a shift to a
female preponderance (similar to adults) at 3:1 to
5:1 in the postpubertal population.6,10,11,12
Location and size of aneurysms in children di er
as compared to adults. Children are more likely to
harbor aneurysms in the posterior circulation (25% in
children vs. 8% in adults) and less likely to have ante-
rior cerebral artery aneurysms (5–10% in children vs.
34% in adults), but roughly the same for internal car-
otid artery and middle cerebral artery lesions.3,6,7,11,13
Children are less likely than adults to have multiple
aneurysms, and two to four times more likely to have
giant (>2.5 cm) aneurysms than adults.5,6,10,13
The etiology of aneurysms in the pediatric popu-
lation shifts with increasing age. Younger children,
particularly younger than 5 years, have the majority
of dissecting, fusiform aneurysms, while older chil-
dren have a majority of saccular aneurysms.6,10,13
Familial aneurysms are very rare, accounting for 5
to 20% of all reported cases in children and young
adults, but less than 5% of prepubertal cases.14,15
The causes of pediatric intracranial aneurysm are
summarized in Box 24.1.
Box 24.1 Causes of pediatric intra-
cranial aneurysm 5,6,10,11,13,16,17,18
● Saccular:
– 46–70%.
– More common in older children.
● Traumatic:
– 5–40%.
– Closed head injury, postsurgical.
● Infectious:
– 5–15%.
– Usually bacterial, often on more distal
branches of arterial tree due to embolic
nature of formation (staphylococcus, cardiac
disease).
● Other:
– Dissection (spontaneous and posttraumatic).
○ Genetic (polycystic kidney disease,
fibromuscular dysplasia, Marfan’s
syndrome, Ehler–Danlos, hereditary
hemorrhagic telangiectasia, Klippel–
Trénaunay).
– Hemodynamic (flow related from AVM or
moyamoya).
● Multiple:
– ~ 5%.
– Up to 15% of older children with aneurysms
have multiple lesions.
24.3 Presentation and
Evaluation
Most aneurysms are asymptomatic and often are
never detected. There are no formal screening
guidelines for children with a ected family mem-
bers, nor for most genetic disorders (see preceding
paragraph).19 Generally, only family members of
sibling pairs or three first-degree relatives who
harbor known intracranial aneurysms are recom-
mended for screening, usually with magnetic
resonance imaging (MRI)/magnetic resonance
angiography (MRA).14,15,16,19
For those that are found with symptoms, Box
24.2 and Box 24.3 outline the common presenta-
tions. In one series, over half of pediatric aneurysm
patients presented with SAH, 33% presented with
mass e ect symptoms, and 11% were found after
198
trauma.6 Children with SAH from aneurysm often
present with a low Hunt–Hess grade relative to
adults, usually 1 to 3.6,10,20,21
Box 24.2 Presentation of pediatric
intracranial aneurysm 5,6,10,11
● Headache:
– ~ 80%.
● Loss of consciousness:
– ~ 25%.
● Seizure:
– ~ 20%.
● Focal deficit:
– ~ 20%.
● Vision changes:
– ~ 10%.
Box 24.3 Hunt–Hess SAH
classification20,21
● Unruptured.
● Asymptomatic/mild headache.
● Cranial nerve palsy, severe headache, nuchal
rigidity.
● Mild focal deficit, lethargy, or confusion.
● Stupor, hemiparesis, decerebrate.
● Coma, moribund appearance.
Evaluation of a patient with a suspected SAH from
an aneurysm includes history, neurologic and
physical examination, and radiographic studies to
define the anatomy of the lesion. Up to 90% of
all nontraum atic SAH in children will result
from a structural lesion.22 These patients should
be screened w ith computed tom ography (CT)
scan, and if a vascular lesion is suspected, a CT
arteriogram (CTA) can be a m eans of identifying
the presence of an aneurysm .19 While lacking
the detail of a catheter-based arteriogram , CTA
a ords the treating physician an im m ediate
im age outlining key anatomy of a lesion, infor-
mation of critical importance in the setting of
an acutely ill child. Patterns of SAH in pediatric
aneurysm CT studies are summ arized in the Box
24.4 ( Fig. 24.1).
Box 24.4 Radiographic findings in
pediatric intracranial
aneurysm 5,6,10,11
● SAH, ~ 60%.
● Intraventricular hemorrhage, ~ 10–15%.
● Intracerebral hemorrhage, ~ 10–15%.
● Subdural, ~ 1–3%.
MRI is also useful in the diagnosis and delineation
of the three-dimensional anatomy of an aneurysm,
particularly with MRA. Overall, MRI/MRA was able
to identify the source of SAH correctly in 66% of
cases.22 In contrast, catheter-based digital subtrac-
tion angiography (DSA)—the “gold standard” of
imaging in aneurysm—was able to identify lesional
pathology in 97% of patients, versus 80% of the
time without DSA.23
Angiography generally
includes bilateral injection of both the internal
Fig. 24.1 Imaging appearance of aneurysmal subar-
achnoid hemorrhage on axial noncontrast head CT.
Note early ventricular dilatation in temporal horns.
Aneurysms
199
and external carotid arteries and the vertebral
arteries in order to visualize all of the vessels.
Three-dimensional angiography with computer-
generated reconstruction is increasingly employed
to depict lesional anatomy ( Fig. 24.2). With
catheter angiography, a recent analysis of 241
consecutive pediatric patients revealed a 0% com-
plication rate during the procedure and a 0.4%
postprocedural complication rate. Evaluation
should look for:
● Lesion size, orientation, and location.
● Neck anatomy.
● Daughter blisters.
● Other aneurysms (especially important with
infectious lesions).
If the aneurysm is fusiform, the segment of vessel
involved, delineation of normal borders, and
involvement of perforators are important.
Standard preoperative laboratory studies (com-
plete blood count, clotting times [prothrombin
time/partial prothrombin time], type and cross
[T&C] for blood bank, and a chemistry panel
[Chem 7]) should be considered as pretreatment
studies for aneurysms.
24.4 Treatment and Surgical
Indications
The decision to treat or observe a given aneurysm
can be complex and is best made by a multidisci-
plinary team including neurosurgeons, endovascu-
lar specialists, and neurologists. If treatment is
planned, success is predicated on removing the le-
sion from circulation while preserving normal
blood flow to the brain. This can be achieved by
open surgery, endovascular techniques, or a com-
bination of approaches (Box 24.5).
Box 24.5 Treatment approaches for
pediatric intracranial aneurysm
● Surgical:
– Clipping (obliteration of lesion).
– Clip reconstruction (rebuild arterial wall/lumen).
– Trapping of lesion (+ /– revascularization with
bypass).
● Endovascular:
– Embolization (coil/glue).
– Stenting (+ /– embolization).
– Parent artery occlusion.
The advent of endovascular therapy has revolu-
tionized the treatment of pediatric aneurysms,
providing options unavailable to earlier genera-
tions of physicians. The relatively noninvasive
nature of the approach is particularly attractive in
children. It is important to note that there is a
great deal of evolution of this field, limiting long-
term outcome data. Consequently, it is important,
when possible, to have cases reviewed at institu-
tions that o er both endovascular and open tech-
niques in order to provide a balanced approach to
formulating care plans.17,24
The rarity of pediatric aneurysms precludes firm
guidelines for treatment indications.19 In general,
aneurysms that have ruptured or that demonstrate
enlargement over time, or symptomatic lesions
should be considered for treatment. Depending on
location and patient status, it may be reasonable
to treat aneurysms greater than 3 mm in size,
Fig. 24.2 (a) Appearance of aneurysm on conventional digital subtraction angiography (DSA), with distal middle
cerebral dissecting lesion. (b) The same lesion visualized with three-dimensional reconstructions from the arteriogram.
(c) An intraoperative photograph, as preparation is being made for a distal bypass and concomitant trapping of the
aneurysm.
Cerebrovascular Disorders
200
particularly given the long expected lifespan of
children. Mycotic aneurysms sometimes will
regress with e ective antibiotic therapy, obviating
the need for other interventions. In addition, flow-
related aneurysms located proximal to a lesion
such as an arteriovenous malformation (AVM) may
regress following definitive treatment of the pri-
mary lesion (such as resection of the AVM), dem-
onstrating another scenario when direct aneurysm
treatment might not be required.25,26
While debatable, lesions 2 mm or smaller in size
and those located outside the subarachnoid space
are sometimes followed. Much controversy—on
both sides—surrounds the large study of unrup-
tured aneurysms published in 1998, but it is
important to recognize that these were predomi-
nantly adult patients, with questionable relation to
the pediatric population, given the di erences in
lifespan, aneurysm etiology, and risk factors.1,7
24.5 Surgical Technique
The variability of aneurysm size, location, and pre-
sentation makes each case unique. There is an
obvious di erence between a critically ill child
with an unexpected hemorrhage and an asympto-
matic lesion. However, there are general principles
able to be applied to all surgical cases.27
Approaches should be selected to maximize access
to the lesion, avoid eloquent neurologic cortex (if
possible), and a ord the surgeon visualization of
proximal vessels to achieve temporary clip place-
ment if needed. Placement of a ventriculostomy
(EVD) or lumbar drain can sometimes help with
brain relaxation or control of hydrocephalus, but it
is critical to recognize that overdrainage of cere-
brospinal fluid (CSF) can result in hemorrhage
from sudden shifts in aneurysmal transmural
pressure. Appropriate patient preparation, with
large-bore intravenous access, arterial line moni-
toring, and other adjuncts, such as a bladder cathe-
ter, is important. Controlling blood pressure and
administration of medications for antibiotic (with
an EVD) or antiepileptic control need to be consid-
ered. If trapping is an option, the availability of a
bypass graft (scalp artery, radial artery, etc.) with
access needs to be planned in advance.
24.5.1 Preoperative Preparation
Communication with nursing and anesthesia
before the case will streamline care. In general,
equipment should include an operating micro-
scope, multiple suctions, a craniotome, bipolar
electrocautery (nonstick, if available), aneurysm
clips, and a retraction system. The anesthesia team
should prepare with multiple large-bore intrave-
nous catheters and attempt to have blood products
in the operating room. It is good practice to have
the microscope draped and clips selected prior to
opening the incision, in order to be prepared for
emergencies. Availability of intraoperative angiog-
raphy and/or indocyanine green (ICG) on the
microscope to confirm real-time aneurysm oblit-
eration with parent vessel patency is helpful
( Fig. 24.3). Agents to manage temporary clip-
ping, such as barbiturates or propofol, and hypo-
thermia and vasoactive medications are important.
Adenosine can be used to briefly reduce blood
flow in order to better visualize the anatomy of an
unexpected rupture.
24.5.2 Operative Approach
Blood pressure shifts should be minimized, partic-
ularly during pinning (sometimes local anesthetic
injection prior to pin placement can help to blunt
Fig. 24.3 Intraoperative image of aneurysm clipping
with (a) Conventional microscope, and (b) Indocyanine
green (ICG) dye image. Note ICG image demonstrates
patency of parent vessel (below clips) with complete
obliteration of aneurysm (no filling with dye).
Aneurysms
201
blood pressure changes). Frameless stereotaxy can
aid in operative planning, ensuring a wide opening
with full access to the aneurysm and good
visualization. Control of proximal vessels is key,
potentially including the carotid artery in the neck.
During the craniotomy, care should be taken to
avoid tearing the dura and subjacent vessels. Ultra-
sound can help with localization using real-time
imaging. Once open, a clear strategy should be
outlined prior to attacking the lesion.
Critical to aneurysm surgery is avoiding intra-
operative rupture. If SAH has already occurred,
gentle clot removal with sharp dissection when
possible can reduce risk of unexpected rupture.
Preparing a site for proximal control with tempo-
rary clip application is a good strategy. Once
ready to clip, careful inspection of surrounding
anatomy can help to ensure obliteration of the
aneurysm without inadvertent occlusion of small
perforators. Evaluation of parent vessel patency
and aneurysm occlusion can be performed with
intraoperative Doppler, ICG administration, and/or
catheter angiography.
24.6 Complications
● Bleeding from intraoperative rupture is the most
immediate complication of surgery, and risks are
magnified in smaller children, who have little
reserve. The loss of one-quarter of blood volume
can induce shock, and there may be rapid
decompensation in children, which mandates
careful monitoring and replacement of blood
products by the operative team.
● Stroke may occur from perforator/parent vessel
occlusion or emboli/dissection caused by injury
to the arterial tree during manipulation
(reported at 6–8%).10,17
● Hydrocephalus can result from blood in the
subarachnoid space or ventricles (reported at
14%).10
● Vasospasm can occur following SAH (reported in
21% of pediatric cases).10
● Cerebral salt wasting (CSW) is an often under-
recognized consequence of SAH and should be
considered in the posthemorrhage period if
major fluid or sodium shifts are observed.
Overall, surgical morbidity and mortality vary
widely dependent on age, aneurysm type, and
presentation. Recent series describe average
mortality rates of 1 to 3% and m orbidity rates of 8
to 14%.17,28
24.7 Postoperative Care and
Follow-up
Immediate postoperative care centers on confirm-
ing that the aneurysm has been fully obliterated
(with imaging) and maintaining hemodynamic
stability with good blood pressure control (keep-
ing the patient normotensive to sometimes
slightly hypertensive, in order to avoid vaso-
spasm). In general, most patients will spend a
period of time in the intensive care unit and then
often mobilize to the wards. In addition to imme-
diate operative complications, there are problems
specific to SAH, including hydrocephalus, vaso-
spasm, and CSW. For patients with SAH, the first
week or so after ictus is the key period for develop-
ing these conditions. Frequent neurologic exami-
nations should be supplemented with imaging
(such as CT/MRI for hydrocephalus and CTA/MRA/
transcranial Doppler/angiography for vasospasm).
Some patients may benefit from so-called triple-H
therapy—hypertension, hypervolemia, and hemo-
dilution—in order to reduce the risk of vasospasm
(only after aneurysm treatment).31,32 The use of
calcium channel–blocking agents, such as nimodi-
pine, is unclear in children.
Follow-up will frequently consist of an o ce visit
about 1 month postoperatively, then annually there-
after. In addition to the perioperative angiogram to
confirm obliteration of the aneurysm, an MRI/MRA at
6 months may be helpful as a baseline study, to be
compared to subsequent annual MRI/MRA. Imaging is
performed annually for 5 years, if feasible, with some
centers suggesting lifetime imaging every 3 to 5 years
thereafter.31 An angiogram (DSA) is often performed
at 1 year postoperatively to confirm durable cure.
24.8 Outcomes
There is a wide range of reported outcomes for pedia-
tric aneurysms, with “good” posttreatment outcomes
ranging from 13 to 95%and treatment-related mortal-
ity ranging from 3 to 100%.32 Shunting will be
required for 14% of patients with hydrocephalus after
SAH.10 Overall, from a clinical perspective, of patients
who survive treatment, 91% (with a mean of 25 years
of follow-up) go on to enjoy independent living, with
high rates of university graduation and employment.12
Radiographically, one study reviewed a group of 59
patients with aneurysms who were treated when
they were children and had an average of 34 years of
follow-up.33 In this series, 41% developed recurrent or
de novo aneurysms after treatment. The annual rate
Cerebrovascular Disorders
202
of hemorrhage was 0.4%, with four deaths. The only
identified risk factor adding to recurrent or de novo
aneurysm development was smoking.33 These data,
while obviously limited in part by the absence of cur-
rent imaging technologies and surgical techniques at
the time of patient treatment, nonetheless underscore
the need for continued follow-up in pediatric intracra-
nial aneurysm patients.
24.9 Surgical Pearls
● Ensure all equipment is prepared before starting
the case: draped microscope, clip selection,
multiple suctions, blood in the room.
● Communication with anesthesia and nursing is
critical to provide best care, including planned
clipping times and intraoperative rupture.
● Minimizing blood pressure shifts (such as using
deep local anesthesia for pinning) and CSF shifts
(limiting CSF drainage to a few milliliters at a
time) can reduce the risk of re-rupture.
● It is good practice to periodically zoom out and
inspect the surface of the brain for unexpected
bleeding or swelling. Misplaced retractors or
compression of veins can cause problems if
unrecognized.
● Sharp dissection and gentle retraction are
important to avoid tearing the aneurysm dome.
● Proximal control is critical, including
consideration of the neck if anterior circulation
aneurysms are being treated.
● Intraoperative imaging tools (ICG, angiography)
can improve the accuracy of clip placement and
parent/perforator vessel preservation.
24.10 Common Clinical
Questions
1. What are some modifiable risk factors that
contribute to aneurysm formation in children?
2. If an aneurysm is found in a child, what are the
screening recommendations for siblings and
other relatives?
3. Where are the most common locations of
traumatic aneurysms?
4. What steps are helpful in the immediate
management of a child presenting with a
hemorrhage from an aneurysm?
24.11 Answers to Common
Clinical Questions
1. While adult intracranial aneurysms are often
associated with modifiable risk factors—
including hypertension, obesity, high
cholesterol, diabetes, and alcohol and drug
abuse—the only shared major risk seems to be
smoking. It makes sense for children to control
all the other risk factors as well, but smoking
appears to have a major contribution,
particularly to the development of recurrent or
growing residual aneurysms.6,33
2. There are no fixed screening
recomm endations for family m em bers of
children found to harbor intracranial
aneurysm s. While the risk of acquired
aneurysms (posttraumatic, postinfectious,
postsurgical, etc.) in related family m em bers
is not genetic, the evidence for or against
screening relatives of children with
spontaneous aneurysm s is lim ited. Current
data suggest increased risk with a sibling pair
or three first-degree relatives with known
aneurysms.14,15,16
3. Traumatic intracranial aneurysms can occur
after trauma or surgery. They are most
commonly found in the anterior circulation,
especially around the cavernous sinus and
pericallosal artery.16,30
4. The following steps are warranted for the child
who presents with an intracranial hemorrhage.
It is important to note that severity of
presentation can vary greatly and thus
treatment has to be individually tailored. If a
child presents with an SAH without a clear
etiology on initial evaluation, aneurysm (and
AVM) should be considered and a CT angiogram
(CTA) may be helpful in the acute setting to
identify the presence of a lesion. (If no clear
lesion is found, repeat imaging in 4–6 weeks
with MRI/MRA should be performed to evaluate
the hemorrhage cavity after the clot has
cleared.)
● Access: large-bore intravenous (at least two),
arterial line, bladder catheter (airway
intubation if unable to protect airway), and
nasogastric tube if intubated.
● Blood pressure control (labetalol or
Nipride) with goal of norm otension
for age.
● Intracranial pressure control—external
ventricular drain if hydrocephalus
(Note: avoid overdrainage of CSF to
prevent re-rupture, often no more
than 5 mL at a time), Head of bed (HOB)
elevated.
● Antiepileptic medication if concern for
seizure.
Aneurysms
203
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major artery thrombosis proximal to dominant feeders: a case
report [in Japanese]. No Shinkei Geka. 1995; 23(4):371–376
[27] Sanai N, Auguste KI, Lawton MT. Microsurgical management
of pediatric intracranial aneurysms. Childs Nerv Syst. 2010;
26(10):1319–1327
[28] Kakarla UK, Beres EJ, Ponce FA, et al. Microsurgical treatment
of pediatric intracranial aneurysms: long-term angiographic
and clinical outcomes. Neurosurgery. 2010; 67(2):237–249,
discussion 250
[29] Origitano TC, Wascher TM, Reichman OH, Anderson DE.
Sustained increased cerebral blood flow with prophylactic
hypertensive hypervolemic hemodilution (“triple-H”
therapy) after subarachnoid hemorrhage. Neurosurgery.
1990; 27(5):729–739, discussion 739–740
[30] Nahed BV, Ferreira M, Naunheim MR, Kahle KT, Proctor MR,
Smith ER. Intracranial vasospasm with subsequent stroke
after traumatic subarachnoid hemorrhage in a 22-month-old
child. J Neurosurg Pediatr. 2009; 3(4):311–315
[31] Tonn J, Ho mann O, Hofmann E, Schlake HP, Sörensen N,
Roosen K. “De novo” formation of intracranial aneurysms:
who is at risk? Neuroradiology. 1999; 41(9):674–679
[32] Huang J, McGirt MJ, Gailloud P, Tamargo RJ. Intracranial
aneurysms in the pediatric population: case series and
literature review. Surg Neurol. 2005; 63(5):424–432,
discussion 432–433
[33] Koroknay-Pál P, Niemelä M, Lehto H, et al. De novo and
recurrent aneurysms in pediatric patients with cerebral
aneurysms. Stroke. 2013; 44(5):1436–1439
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25 Arteriovenous Malformations
Edward R. Smith
25.1 Introduction and Anatomy
Arteriovenous malformations (AVMs) are relatively
common intracranial developmental vascular
anomalies consisting of direct arterial-to-venous
connections without intervening capillaries. There
is no functional neural tissue within the confines
of the lesion.1 Malformations can range from sim-
ple single-channel arteriovenous fistulas to a com-
plex tangled nidus connecting enlarged feeding
arteries to draining veins (including vein of Galen
malformations, reviewed as a distinct entity in
another chapter of this book). AVMs have the
capacity to grow, particularly in children, likely
through a combination of hemodynamic changes
(mechanical stretch and enlargement of vessels)
and vasculogenesis (developing new vessels in res-
ponse to elaboration of vascular grow th factors
and ischemic drive). Enlargement of an AVM
seems to alter the adjacent brain. Functional mag-
netic resonance imaging (MRI) data have sug-
gested that the presence of an AVM in an eloquent
area of the brain may be associated with “migra-
tion” of the function to adjoining cortex or to the
homolog on the contralateral hemisphere.2,3 This
migration or displacement of functional neuronal
tissue has important implications for surgical plan-
ning.
While most AVMs are thought to be isolated
developmental lesions, there are known genetic
conditions predisposing individuals to multiple
AVMs. Mutations in RASA-1 (a GTPase activating
protein) are associated with problems in vessel
development, including familial high-flow arterio-
venous lesions and/or cutaneous capillary malfor-
mations in a small number of families.4 Hereditary
hemorrhagic telangiectasia (HHT) is a genetic con-
dition that predisposes a ected individuals to
AVMs throughout the body. Thirty-five percent of
multiple intracranial AVMs associated with HHT
were in children, while the mean age at presenta-
tion for HHT is 35 years.5
Aneurysms are also found in conjunction with
many AVMs. In approximately 7 to 25% of cases of
cerebral AVM, there is an associated arterial aneur-
ysm on a feeding pedicle. The prevailing hypothe-
sis is that these aneurysms are flow-related and
are most commonly seen in high-flow lesions.
These flow-related aneurysms can spontaneously
regress following the reduction in blood flow after
treatment of the AVM.6,7
25.2 Epidemiology and
Pathophysiology
AVM is the most common symptomatic high-flow
intracranial vascular abnormality in adults and
children.8 The overall frequency of detection for
AVMs—including asymptomatic lesions found at
autopsy—was 1.4% (46 among 3,200 brain tumor
cases).9 Looking only at those lesions detected
because of symptoms, the annual incidence was
reported as 1.1 per 100,000.10 Of those that are
symptomatic, about 20% will manifest before 15
years of age.11 Children comprise 12 to 18% of all
AVMs from major centers, and the overall preva-
lence in children is about 0.02% of the pediatric
population.12,13,14,15 Most AVMs present in adult-
hood, with a mean age of presentation of appro-
ximately 30 to 40 years. AVMs are equally
distributed between males and females in the
pediatric population.
Neurological signs and symptoms commonly
relate to intracranial or subarachnoid hemorrhage
from a vessel in the malformation or from a coex-
istent arterial aneurysm. Symptoms may also
relate to cerebral ischemia that is due to diversion
of blood to the AVM from the normal cerebral cir-
culation (“steal”) or secondary to stagnation caus-
ing increased venous pressure secondary to the
AVM. Enlarged anomalous vessels may compress
or distort adjacent cerebral tissue or cause
obstructive hydrocephalus by interfering with the
normal circulation or cerebrospinal fluid. Commu-
nicating hydrocephalus can result from earlier
hemorrhage or venous hypertension.
25.3 Presentation and
Evaluation
Hemorrhage and seizure are the most common
presenting symptoms for pediatric AVM, but find-
ings may also include headache, focal neurologic
deficits, and cognitive decline.16,17,18,19 Children
with AVM are more likely to present with intracra-
nial hemorrhage than adults: 80 to 85% in some
205
pediatric series.13,20 For children known to have an
AVM, the annual risk of hemorrhage has been esti-
mated at 2 to 4%.21,22 Hemorrhagic events from an
AVM in childhood have been associated with a 25%
mortality rate.23 In contrast to earlier reports sug-
gesting that smaller AVMs may have a higher risk
of bleeding, more recent data have shown that size
is not a major determinant in the risk for hemor-
rhage.24,25 A spontaneous intraparenchymal hem-
orrhage in a child should raise concerns for the
presence of an AVM or tumor. Rebleeding rates
have been reported to be approximately 6% within
the first 6 months.
Evaluation of a patient with an AVM includes
history, neurologic and physical examination, and
radiographic studies to define the anatomy of the
lesion.26 Most patients present with a new neuro-
logical deficit: unusually severe headache (“worst
headache of my life”) or seizure. These patients
should be screened with computed tomography
(CT) scan, and if a vascular lesion is suspected, a CT
arteriogram (CTA) can be a means of identifying
the presence of an AVM. While lacking the detail
of a catheter-based arteriogram, CTA a ords the
treating physician an immediate image outlining
key anatomy of a lesion, information of critical
importance in the setting of an acutely ill child.
MRI is also useful in the diagnosis and delinea-
tion of the three-dimensional anatomy of an AVM.
MRI better localizes parenchymal structures rela-
tive to the AVM, even if there is a high suspicion of
AVM based on the CT or CTA findings and angiog-
raphy is planned. Chronic ischemic changes, pre-
sumably a result of “steal” phenomenon or venous
hypertension, may be identified on MRI as bright
signal of the surrounding brain on FLAIR (fluid-
attenuated inversion recovery) or T2 images
( Fig. 25.1).
Catheter-based digital subtraction angiography
(DSA) is the “gold standard” of imaging in AVM,
establishing the nature and extent of the lesion to
its blood supply and its venous drainage.27 Angiog-
raphy generally includes bilateral injection of both
the internal and external carotid arteries and the
vertebral arteries in order to visualize all of the
vessels supplying the AVM ( Fig. 25.2). Three-
dimensional angiography with computer-gener-
ated reconstruction is increasingly employed to
depict lesional anatomy. It is important to under-
score that 15% of cerebral AVMs receive some
Fig. 25.1 Imaging appearance of AVM
on MRI. Axial T2 images show typical
flow voids in right frontal lobe (green
arrowhead) and prominent arterial
feeder from anterior cerebral artery
(red arrowhead).
Fig. 25.2 Appearance of AVM on catheter digital sub-
traction angiography (DSA). Lateral right internal
carotid artery injection demonstrates high-flow right
frontal AVM. Note markedly dilated feeding artery
(green arrowhead) and cluster of dysplastic vessels
comprising the nidus (red arrowhead).
Cerebrovascular Disorders
206