CHAPTER

9

Pediatric Brain
Tumors

Ann Marie Flannery
Farivar Yaghmai

The frequency, location, prognosis, and presenting signs and

symptoms of pediatric brain tumors are areas of frequent

misconception. Pediatric brain tumors are not rare; they
represent the most common solid tumor of childhood and the
second most common malignancy of childhood.

1

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2

Three to

five new cases are seen per 100,000 children per year.

Pediatric tumors of the central nervous system (CNS) are

classically distributed with a posterior fossa preponderance.
However, in clinical practice, more than 50 percent of pedi-
atric tumors of the CNS are supratentorial.

3

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4

This incidence

may reflect patterns of referral rather than change in inci-
dence.

The prognosis of pediatric brain tumors is better than is

generally assumed. The most common tumors can be treated
with surgery alone or with a combination of surgical and
adjuvant therapies.

CLINICAL PRESENTATION

Although numerous types of brain tumors occur during
infancy and childhood, the clinical presentations tend to be
rather nonspecific for a particular type of brain tumor. Signs
and symptoms of increased intracranial pressure predomi-
nate. In an infant with an open fontanel, the symptoms may
include irritability and failure to thrive. The signs include a
full fontanel and increasing head circumference.

3

The lesions causing this clinical presentation are di-

verse and include large supratentorial mass lesions or infra-
tentorial lesions that obstruct CSF pathways and cause resul-
tant hydrocephalus.

In older children, increased intracranial pressure is typi-

fied by headache, lethargy, and vomiting. The symptoms in
young children and infants are nonspecific and are fre-
quently mistaken for non-CNS problems, such as formula

intolerance, gastroenteritis, or school phobia. It is not rare
for a brain tumor to remain undiagnosed until the child
becomes extremely ill or focal localizing neurological signs
develop. This may lead to significant parental anger. Parents
should be reassured that the diagnosis of a pediatric brain
tumor can be extremely difficult to make without a very
high index of suspicion.

Other signs that may be seen with pediatric brain tumors

include papilledema, ataxia, and sixth cranial nerve palsy.
Signs such as hemiparesis or focal seizures may herald a
supratentorial brain tumor. Visual loss in the child and
inattention to visual stimuli suggest tumors associated with
the visual pathways, such as a craniopharyngioma, optic
nerve glioma, or hypothalamic glioma. Posterior fossa

tumors often cause ataxia and gait disturbances in addition

to signs of increased intracranial pressure. Brainstem glio-
mas have a characteristic presentation with cranial nerve
palsies, especially sixth and seventh, often associated with
ataxia. Unlike other pediatric brain tumors, signs and symp-
toms of increased intracranial pressure are not usually seen
until late in brainstem gliomas.

SURGERY

In most cases, the surgical approach to a pediatric brain
tumor is dictated by its location rather than the age of the
child. Most supratentorial brain tumors are treated as de-
scribed in the preceding chapter on adult brain tumors.
Craniopharyngiomas, tumors commonly seen in childhood,.,
are described in Chap. 12. •

Important principles in the surgical treatment of pediatric

brain tumors include attention to thermal regulation and
positioning. The pediatric circulating blood volume is ap-
proximately 75 cc per kilogram in children greater than 1

141

142

CHAPTER 9

year of age. Newborns have approximately 80 cc per kilo-
gram. Premature infants may have up to 105 cc per kilo-
gram. The circulating blood volume is relatively small;
therefore, meticulous hemostasis is an essential part of pedi-
atric neurosurgery.

5

Children have a larger surface-to-volume ratio than adults.

They have tendency to decrease their core temperature in a
cold operating room. Hypothermia can lead to complications

including cardiac arrhythmias and hypotension. As a result,

preservation of normal core temperature is very important
during the preoperative positioning, operation, and postoper-
ative periods.

Positioning of children for surgery is generally similar to

that used for adults. Surgical judgment is called for in
balancing the risks of pin fixation versus the benefits of
immobilization. Most pediatric neurosurgeons avoid the use
of the pin head holders in children less than 4 years of age
because of the relative fragility of the infant skull. Skull
fractures and epidural hematomas are known complications

of the use of the pin fixation in children. Often in a child, a

horseshoe head holder can be substituted.

A preponderance of posterior fossa tumors in the pediatric

age group dictates that posterior fossa craniotomy is among
the most common procedures performed for tumors in chil-
dren by pediatric neurosurgeons. Although the sitting posi-
tion has been employed for children, the risk of air embo-

lism and the effects of excessive loss of CSF have led to the

adoption of the prone position for most posterior fossa
operations in children.

The surgical approach—following prone positioning on

chest roles for most posterior fossa brain tumors in pediatric
patients, especially cerebellar astrocytomas, medulloblasto-
mas, and ependymomas as described below—includes a
midline incision from approximately the external occipital
protuberance (inion) to the upper or mfflcervical levels,
usually about C2-C3. Following retraction of skin and mus-
cles, the occipital bone is removed, by craniotomy, which
we prefer, or a craniectomy; the dura is visualized and
incised by a Y-shaped incision; and the cerebellum is ex-
posed. This approach allows adequate access to the cerebel-

lar midline, fourth ventricle, and hemispheres.

Approaches to the cerebellar-pontine angles are similar to

those described for adults. However, the surgical position is
likely to be the "park bench" or lateral decubitus position to

avoid the risks of the sitting position in this population.

CEREBELLAR ASTROCYTOMA

The most common pediatric brain tumor is among the be-
nign and treatable. The cerebellar astrocytoma may occur at
any age from infancy to adulthood; however, the classic
presentation is in the school-age child at about 5 to 10 years
of age. A slowly growing tumor, astrocytoma, frequently
presents as described in the clinical section, with signs and

symptoms of increased intracranial pressure including head-

Figure 9-1 Cereblar astrocitoma,MRI.The low-signal cysts
outline the more dense tumor. The cerebellar tonsil has herniated
below the foramen magnum.

ache and vomiting, but the tumor is frequently not diagnosed
until ataxia and sixth nerve palsies herald the intracranial
location of the pathology.

Cerebellar astrocytomas are usually located in a hemi-

sphere, although they may be midline (Fig. 9-1). These
tumors may be either solid or cystic with an enhancing
nodule (Figs. 9-2 and 9-3). The most common histologic

pattern is pilocytic (Fig. 9-4).

Following the surgical approach through the midline, ef-

forts are made to resect the entire lesion. Complete resection
is usually possible and results in cures. Many patients with
cerebellar astrocytomas have been followed for periods of
over 25 years. Follow-up has shown that, although late
recurrences are possible, surgical cure may be expected.

7

Additional therapy is rarely indicated in the treatment of

cerebellar astrocytomas, although when tumors with ana-
plastic histologic features are found, adjuvant therapy is
indicated.

8

MEDULLOBLASTOMAS

The most common malignant brain tumor of childhood is the
medulloblastoma, sometimes referred to as the posterior fossa
primitive neuroectodermal tumor (PNET). As cerebellar astro-
cytomas, medulloblastomas may present at any age but are
commonly seen in children of preschool and early school
years. They present with clinical signs and symptoms, reflect-
ing the tendency of these midline posterior fossa tumors to
cause hydrocephalus, usually including headache, lethargy,
vomiting, papilledema, sixth nerve cranial palsies, and ataxia.

Medulloblastomas are highly cellular tumors composed of

relatively undifferentiated cells. Theoretically, this tumor is

PEDIATRIC BRAIN TUMORS

143

Figure 9-2 Cerebellar astrocytoma. A. MRI, sagittal section. This tumor is lower

signal than the brain. B. MRI, following gadolinium enhancement. The tumor enhances

mliomogeneously. C. MRI, same patient, cross section. The fourth ventricle is present

but displaced by the tumor, which arises from the cerebellum.

derived from the granular cell layer in the cerebellar vermis
(Fig. 9-5). These tumors tend to be midline (Figs. 9-6 and 9-7).

Patients who undergo total or near-total resection of the

tumor have an overall better outcome than similar patients
who receive biopsy only or very limited resection.

9

Medul-

loblastoma has a tendency to have spread by the time of
diagnosis. Cells are frequently transported along cerebro-
spinal fluid (CSF) pathways.

10

Following surgical resection, patients with medulloblasto-

mas are staged clinically. Staging depends on the size of the
primary tumor and the extent of its spread. Important factors
include the preoperative size of the tumor and whether or not
hydrocephalus is present, intraoperative findings including in-
volvement of the brainstem, and extent of resection (Fig. 9-8).
Postoperatively, CSF is examined for tumor cells. Evidence of
spread of disease is sought by examining bone marrow and by
looking for "drop" metastases along the spinal subarachnoid

space. Myelography has been used to detect metastatic disease;

however, in many medical centers, magnetic resonance imag-

ing (MRI) of the spine with gadolinium enhancement has been
found to be more sensitive and less invasive.

Since the period 1965-1970, survival with medulloblastoma

has improved significantly.

11

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3

Supplementation of surgery by

radiation therapy to the posterior fossa and craniospinal axis
provided the first improvement. The addition of adjuvant
chemotherapy has resulted in further prolongation of survival

without significant morbidity.

12

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14

A variety of chemothera-

peutic regimens has shown some success, including: CCNU,
vincristine, and prednisone; CCNU, procarbazine, and predni-
sone (MOPP); and cisplatin and vincristine. 12,13,15,16

BRAINSTEM GLIOMAS

Brainstem gliomas frequently present in school-aged chil-
dren (6-12 years). Unlike many of the tumors discussed in

this chapter, brainstem gliomas do not usually present with

(A)

(B)

(C)

144

Figure 9-3 Cystic juvenile cerebellar astrocytoma. In this unfixed
surgical specimen, a large, cystic, thin-walled cavity (held at the

edges with surgical clamps) forms the main bulk of the tumor. The

cyst was filled with 15 ml of amber fluid that coagulated in a tube
at room temperature. The active parts of the tumor are two "mural
nodules" seen as the solid parts at the right (larger), and the left
(smaller) sides of the cystic cavity. The freestanding solid tumor

tissue is part of the larger mural nodule.

signs or symptoms of increased intracranial pressure. The

classic presentation includes cranial nerve palsies, especially

of the sixth and seventh nerves, often combined with signs
of cerebellar dysfunction such as ataxia and nystagmus. The
tumor usually infiltrates the pons; thus pontine cranial nerve
palsies are usually seen before signs of increased intracranial
pressure caused by obstruction of the fourth ventricle by the
expanding tumor mass (Fig. 9-9B).

On computerized tomography (CT), brainstem gliomas

are hypodense lesions usually in the region of the pons, and
enhancement by contrast media is variable. MRI demon-
strates the tumor clearly and is the preferred technique for

imaging. While the most common type of braiflstem glioma

Figure 9-5 Medullobiastoma. This is a transverse section of
cerebellum and brainstem at the midpons level. Notice the
infiltrating tumor that has greatly enlarged the surface area of
cerebellum. In the central parts of the cut surface of cerebellum,
bulk of pure tumor is seen, whereas in the periphery, infiltration
of cerebellar folia and the subarachnoid space is noticeable.

involves the pons, any part of the brainstem may be in-
volved. Others are radiographically classified exophytic, fo-
cally cystic, or at the cervicomedullary junction.

17

MRI

outlines these variations (Fig. 9-9A and B).

TREATMENT

Brainstem gliomas have a highly variable prognosis, de-

pending on location and tumor type. Improvements need to

Figure 9-4 Juvenile (pilocytic) astrocyloma of cerebellum. This
tumor is one of the most benign gliomas. Many examples have a
cystic component. In this photomicrograph, a microcystic area is
seen to one side. The surrounding astrocytes have round and ovoid
small nuclei. The other part of the tumor shows a denser
architecture with more prominent pilocytic elements. Minimal
surgical hemorrhage is noted. H&E xlOO.

Figure 9-0 MeuuiioDlastoma. in this example, the potential of

tumor for neuroblastic differentiation is noticeable. There is an
abundance of Homer-Wright rosettes. These are round and off-
round formations of tumor cells surrounding a fibrillar zone without

a lumen or vessel. H&E x200.

PEDIATRIC BRAIN TUMORS

145

Figure 9-7 Medulloblastoma. A. MRI, coronal section. This
densely enhancing posterior fossa lesion is a medulloblastoma. The

midline position is a characteristic. B. MRI, sagittal section, same

patient. This tumor arises from the cerebellar vermis.

be sought in the measurement of the diffuse pontine and
malignant types.

Localization of brainstem gliomas and identification of

histology directs treatment plans and prognosis. Patients
with gliomas located outside the pons—including focal
cystic, exophytic, and cervicomedullary tumors—fre-
quently benefit from debulking. Prolonged survival is re-
ported.

18

~

20

Patients with diffuse gliomas which involve the pons and

other portions of the brainstem are not surgical candidates.

Stereotaxic biopsy may be indicated. Imaging by MRI, how-

ever, is usually diagnostic. Therapy usually includes conven-
tional radiation to the tumor. Experimental protocols include
twice-daily radiation therapy treatments to increase the toler-
ance without increasing toxicity. The outlook for diffuse

pontine gliomas, however, is poor, even with radiation ther-
apy. Only 30 percent of treated children survive for 1 year
and 5-year survival is less than 10 percent.

21

Chemotherapy

has improved survival in small trials.

22

If a brainstem glioma

has a malignant pathological picture on biopsy, survival will
be zero percent at 12 months, despite therapy.

PRIMITIVE NEUROECTODERMAL
TUMORS (PNET)

PNETs of children are supratentorial lesions which tend to
grow rapidly. Like other pediatric brain tumors, these lesions
often present with signs of increased intracranial pressure,

iincluding: increasing head circumference; emesis; lethargy;
Eand, most commonly in the older child, headache. Focal

neurological deficits and seizures may also occur.

The diagnosis is usually made by CT, MRI, or ultrasound

(Fig. 9-10). The hemispheral mass is often quite large by the
time of diagnosis. PNETs are usually enhanced with contrast
although the pattern of enhancement may not be homoge-
nous (Fig. 9-11).

23

PNETs are poorly differentiated tumors that occur in the

cerebral hemispheres but appear histologically similar to

medulloblastomas. Medulloblastomas are sometimes re-

ferred to as PNETs of the posterior fossa.

TREATMENT

When possible, a gross total resection is attempted in these

large cerebral lesions. Occasionally, involvement of deep
structures or functional areas precludes total excision. Post-
operatively, an evaluation similar to that in medulloblasto-
mas should search for metastatic lesions. Spread may be by
CSF pathways and evaluation includes a myelogram or MRI
of the spine with gadolinium. The CSF is sampled for tumor
cells postoperatively. The bone marrow is aspirated and
examined for tumor cells.

Following surgery and tumor staging, additional therapy

is probably beneficial. Radiation therapy has been useful in
the treatment of some PNET patients.

24

Radiation in young

children frequently causes developmental delay and is there-
fore avoided. Younger patients, especially those less than 3
years, may have prolonged survival when given chemother-
apy. Chemotherapy has also been used efficiently with radi-
ation therapy in children more than 36 months. The drugs
and dosages employed are similar to those utilized for me-

dulloblastomas. Data on the effectiveness of these ap-

proaches is currently under evaluation.

( A )

(B)

146

CHAPTER 9

Figure 9-8 Postoperative medulloblastoma. A. MRI, sagittal

section. Removal leaves an enlarged fourth ventricle. B. MRI,
sagittal section following gadolinium. The enhancement in the
subarachnoid space outlines posterior fossae structures, especially

the pons. This enhancement is seen with metastatic spread ot
medulloblastoma. C. Coronal section, MRI, with gadolinium
enhancement. The subarachnoid spread of tumor outlines the
medulla, brachium pontins, cerebellar folia, and midbrain.

GLIOMAS OF THE OPTIC PATHWAYS TREATMENT

Gliomas of the optic pathways may involve optic nerves, the

optic chiasm, or the optic tracts. Often they extend onto the
hypothalamus. These anatomic involvements cause the clini-
cal presentation to include visual loss and endocrinological
dysfunction in addition to the classic findings of pediatric
brain tumors.

When such tumors occur in the first year of life, the

chiasm and structures posterior to it are often involved.
Affected infants have macrocephaly, irritability, and ocular

findings, including spasmus nutans. Older children may have

visual loss, and visual field defects can be documented.
Endocrinological dysfunction may include the diencephalic

syndrome and precocious puberty.

25

Tumors that are con-

fined to the orbit are often stable or very slowly growing

lesions which occasionally cause proptosis.

Both MRI and CT may show these tumors, but the resolu-

tion of involvement seen with an MRI scan is superior. The
MRI may show no contrast enhancement, variable enhance-
ment, or intense uniform enhancement. The contrast pattern
does not correlate with the pathological grade of the tumors
(Fig. 9-12).

The differential diagnosis of lesions for optic pathways

varies with the clinical situation. These tumors are fre-
quently associated with neurofibromatosis. In children with-

out neurofibromatosis (NF), the differential includes germin-

omas, craniopharyngiomas, and pituitary tumors. Children
with masses of the optic pathways, who do not have NF,
may need surgery for diagnostic purposes prior to starting

other therapy.

27

_____

Treatment options may include surgical debulking for large
lesions.

26

Radiation therapy has been useful in slowing

growth in tumors with proven histology that are very likely
to be gliomas such as those with progressive growth in
patients with NF. Chemotherapy has also shown promise in
small numbers of patients.

27

EPENDYMOMAS

Ependymomas are CNS tumors that may be found supraten-

torially and infratentorially. In children, the posterior fossa

location predominates. These tumors usually arise from the
fourth ventricle and spread directly by CSF metastasis
through the CSF pathways. The clinical presentation is very

similar to that of other midline posterior fossa tumors with

early nonspecific signs and symptoms, including headache,
irritability, emesis, and failure to thrive. Later developments
may include ataxia, papilledema, and cranial nerve palsies,
especially of the sixth cranial nerve (Fig. 9-13).

The age of onset of symptoms tends to be younger than

other posterior fossa tumors. The peak age of occurrence in
children is 1 year, the mean age at diagnosis is 5 years,
averaging just over 3 years.

26

Ependymomas also occur in

the adult population, where 23 years is the mean age of
presentation.

29

The overall mean age of presentation is about

16 years.

30

The relationship between histopathological appearance

(A)

(B)

(C)

PEDIATRIC BRAIN TUMORS

147

Figure 9-9 Pontine glioma. A. Tl-weighted sagittal MRI. This
low-grade glioma has diffusely enlarged the brainstem from
diencephalon to lower pons. The medulla and cervical cord are
spared. Brainstem glioma. B. This is a midsagittal section of
brain at autopsy at approximately 8 months after the MRI in
Fig. 9A, showing the left cerebral hemisphere. Notice that the
infiltrating tumor has markedly enlarged the volume of pons and

(B)

medulla. The tumor in its anterior and inferior parts blends into
the structure of pons and medulla. In its central and posterior
parts, it has formed a rather pure tumor mass with variegated
texture (hemorrhage, necrosis) and has evolved into a markedly
anaplastic glioma (glioblastoma multiforme). Notice the slit-like
fourth ventricle.

and outcome has caused significant discussion. Evaluation
of the prognostic importance of histological features such as
anaplasia and the number of mitoses favors the use of the
latter rather than the former to predict survival.

31

Anaplastic ependymomas usually have a poor prognosis,

however. Even tumors with a more benign pathological
appearance may behave malignantly.

Figure 9-10 Right cerebral PNET. CT scan with and without
contrast. This tumor is isointense with brain before contrast but
enhances brilliantly and uniformly.

TREATMENT

The surgical approach to posterior fossa ependymomas is

similar to that for medulloblastomas and other midline poste-

rior fossa tumors. If possible, the tumor should be completely
removed. The outlook for this tumor is not as favorable as for

medulloblastoma, even with gross total resection.

32

Postoperatively, residual or metastatic tumor is sought by

checking CSF cytology, screening bone marrow aspirates,

and biopsy for tumor cells, as well as by use of MRI of the

spine with gadolinium or a myelogram to look for metastatic
deposits along the spinal subarachnoid space.

Treatment includes radiation therapy and may include

chemotherapy. A variety of radiation doses and protocols
has been used, as well as a number of chemotherapeutic
agents. To date, however, no therapy has been found to be
very effective. The 5-year survival rate is approximately 20
percent

35

TERATOMAS

Teratomas are seen most commonly in neonates and young

infants.

34

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35

They are frequently found in the pineal region,

supratentorially, and in the sacrococcygeal region.

35

The

clinical signs and symptoms of the intracranial tumor reflect

(A)

14ft

CHAPTER 9

Figure 9-1 PNET, MRI, transaxial, T-2 weighted. This left

frontopanetai P N E T surrounded by a large area 01 pentumoral
vasogenic edema.

the increased intracranial pressure and include macroce-
phaly, a full fontanel, irritability, and lethargy. Teratomas

include tissue from all three germ cell layers.

35

Teratomas are usually debulked and are completely re-

sected if possible. Benign teratomas have a favorable prog-
nosis after complete excision.

36

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37

Malignant teratomas or

teratocarcinomas are less favorable, but, occasionally, in-
fants with malignant teratomas survive.

EPIDERMOID TUMORS

Epidermoids are frequently called "pearly tumors." The
glistening white appearance is due to the capsule of stratified

squamous epithelium. Derived from a single germ cell layer

of the developing embryo, epidermoid tumors grow slowly
and are located along the cisterns in the cerebellopontine
angle or in the parasellar area, but they may occur at other
locations including the fourth ventricle, lateral ventricles,
cerebrum, cerebellum, and brainstem (Fig. 9-14).

39

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41

The CT appearance of epidermoids is that of a low-den-

sity lesion that does not enhance with contrast. The MRI
appearance is hypointense compared to brain in the Tl-
weighted image and hyperintense in the T2-weighted image
(Fig. 9-15).«

The clinical presentation reflects the slowly growing na-

ture of these tumors and their anatomical location. Symp-
toms are often gradual in onset and may include signs of
increased intracranial pressure, cranial nerve dysfunction,
endocrine dysfunction, aseptic meningitis, and seizures.

40

Treatment of epidermoid tumors is excision. The lesions

should be removed in toto whenever possible. The capsule
may be densely adherent to other structures, and viable
portions of capsule that are not removed reform tumors.
Residual epidermoid cells, however, grow slowly, and the

patient may remain asymptomatic for prolonged periods.

40

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43

Figure 9-12 Optic chiasm glioma. T-l weighted, coronal
MRI. The optic chiasm (arrow) is diffusely enlarged by a
chiasmatic glioma. __

DERMOID TUMORS

Dermoid tumors are composed of epidermoid cells plus
dermal elements which may include hair. The tumors en-
large slightly more rapidly than epidermoid tumors and thus
commonly present in the first two decades of life. Dermoids
are characteristically midline tumors. They are also often

associated with sinus tracts that extend from the skin deep to

the tumor.

Symptoms of these tumors reflect their tendency to be

midline lesions and the resultant hydrocephalus. If a dermal

sinus is present, bouts of bacterial meningitis may occur.
Occasionally, the tumors cause chemical meningitis.

Imaging reflects the midline location and the high fat

content of these lesions. CT shows a hypodense lesion. The
signals on MRI reflect a higher fat content than that of the
brain.

Surgery for dermoids is similar to that for epidermoids.

Problems include the adherence of the capsule to intracranial

structures and the risk of spilling of the tumor contents.

Both inclusion tumors are benign, and the overall outlook

is generally good but dependent on the risks of, and outcome

from, the surgical resection.

39

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43

PEDIATRIC BRAIN TUMORS

149

Figure9-13 Ependymoma. T-l weighted
saginal (A) and coronal (B) MRI. The

tumor mass enhances inbomogeneously
with contrast and extends into the fourth
ventricle.

(15)

TUMORS OF THE PINEAL REGION

Tumors in the pineal region include tumors found in other
parts of the brain, such as gliomas, epidermoids, dermoids,

and meningiomas, all of which are described elsewhere.
Tumors that are unique to the pineal region are grouped into

two categories: (1) germ cell tumors, derived from nests of

primitive, totipotential germ cells that occur in midline

structures, and (2) pinealomas, including pineocytomas and

Figure 9-14 Epidcrmoid cyst of suprasellar region. In this sagittal
hemisection of brain, a large, round, thin-walled epidermoid cyst
is seen. The contents are friable keratinous material. This cyst was
an incidental autopsy finding in a middle-aged woman,
retrospectively with some hypothalamic-pituitary dysfunction. The
inset shows the typical wall structure of an epidermoid cyst. H&E
x63. There is an external fibrous matrix on which sits a thin,
compressed layer of squamous epithelium, slowly producing the
keratinous matter, filling the interior of the cyst. In contrast with
dermoid cysts, no skin appendages are found within the wall of the
cyst.

pinealoblastomas, which are believed to be derived from
parenchymal pineal cells.

44

Nonneoplastic pineal region cysts are common at au-

topsy.

45

MRI has also revealed that asymptomatic cysts

occur frequently (Fig. 9-16).

46

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47

Occasionally a benign cyst,

because of size and location, can become large enough to
cause symptoms (Fig. 9-17). Symptoms will include head-
ache and gaze paresis, with or without hydrocephalus and
papilledema and pineal apoplexy with acute hydrocephalus.

Surgical excision of the cyst will usually result in improve-
ment.

4K

CLINICAL PRESENTATION

Obstruction to CSF flow results in hydrocephalus, making
the clinical presentation of tumors of the pineal region

similar to that of other tumors that present with increased
intracranial pressure. Pineal region tumors are associated
with Parinaud's syndrome, which includes "nystagmus re-
tractorius," paresis of upward gaze, inability to converge,
and midposition, unreactive pupils. Nystagmus retractorius
is the appearance of the globe being withdrawn into orbit
when an attempt is made to converge. These findings are
thought to be due to compression of the quadrigeminal

plate.

49

Pineal tumors may invade adjacent structures, including

the basal ganglia, hypothalamus, thalamus, internal capsule,
inferior collicular plate, and adjacent midbrain structures and
fornixes.

DIAGNOSIS

Computerized tomography and magnetic resonance imaging
show ventricular enlargement and the pineal region mass.

(A)

150

CHAPTER 9

Characteristic findings include a lesion that is hypointense or
isointense compared with brain prior to contrast. Contrast

enhancement usually shows a uniform uptake (Fig. 9-18).

THERAPY

In the past, the therapy of tumors of the pineal region was
limited because of the risks of surgery. Therapy advocated at
that time included only ventricular shunting and radiother-
apy.

35

Currently, recommended therapy includes resection

under direct vision. Resection is beneficial because there are
multiple types of tumors in this region, and improvements in
surgical technique, especially the use of the microscope, has

greatly enhanced the outcome. Tumors in the pineal region

may be totally removed.

The pineal region is approached by one of three ways.

The occipital transtentorial approach elevates the occipital

Figure 9-15 Epidermoid tumor. A. CT

scan. The low-density (black) mass on the
sphenoid wing is an epidermoid tumor. B.
MRI, same patient. The Tl-weighted MRI

reveals the fat density of the epidermoid
tumor and allows differentiation from a
CSF collection.

lobe and divides the tentorium to reach the pineal region.

50

The infratentorial, supracerebellar approach achieves access
by retracting the cerebellum down and working in the space
between the tentorium and the cerebellum.

51

Both of these

approaches were initially described with patients in the sit-
ting position. A modification of positioning, the "Concorde

position," may be more suitable for pediatric patients as they

can be operated on in a prone position, with a decreased
incidence of air embolism.

52

This modification is described

with the infratentorial approach.

A transcallosal approach has also been utilized in a pedi-

atric population with excellent results. The mortality, in the

period of CT and the operating microscope, is about 4.3
percent. This approach is similar to most transcallosal proce-
dures. The patient is positioned supine with the head ele-

vated and flexed.

53

The choice of approach to tumors of the pineal region

depends on the preference and the experience of the surgeon.

Figure 9-16 Pineal region cyst. Tl-
weighted coronal MRI. A. The thickened,
enhancing rim of this pineal region cyst
contrasts with its nonenhancing, low signal
center. The cyst has no mass effect or
edema. The T-2 weighted image is presented
inB.

(A)

(B)

PEDIATRIC BRAIN TUMORS

151

Figure 9-17 Cyst of pineal body. In this horizontal cut of the
region of midbrain, an incidental pineal body cyst is seen in the
lower midportion of this very low power pictomicrograph. A cyst

of this size is a common autopsy finding. Cysts of dimensions to

be demonstrable by imaging are seen in about 3-4 percent of

population; larger cysts should not be mistaken for genuine
neoplastic lesions.

Pineal tumors are very deep and surrounded by structures
that cannot be sacrificed or imperiled such as the vein of
Galen, the internal cerebral veins, and the basilar veins of
Rosenthal. The occipital transtentorial approach may give
better visualization of tumors straddling the tentorial notch
and extending above the tentorium. The infratentorial, supra-

cerebellar approach is probably best for tumors that extend
primarily below the tentorial notch,

54

avoiding the risk of

postoperative hemianopsia.

51

The transcallosal approach

allows excellent access to tumors that may have expanded

into the third ventricle.

Surgical therapy of pineal tumors improves the outcome

by decompressing large or malignant lesions, permitting
total excision of benign lesions, and establishing the patho-
logical identity of the tumor to allow for the safest, most-
effective postoperative therapy.

Additional therapy will be dictated by the pathological

identification of the tumor. Radiation therapy is particularly
important in the treatment of pineal germinomas, which are
very sensitive to relatively low doses of radiation therapy
(2000 cGy). Other tumors may be treatable by a combination

of radiation and chemotherapy.

CONCLUSION

The role of the neurosurgeon in the treatment of pediatric
brain tumors has become increasingly important and paral-
lels the improved outlook for children with brain tumors.
Although some tumors, such as intrinsic brainstem gliomas,
continue to have a poor prognosis, with others such as
cerebellar astrocytomas, medulloblastomas, and tumors of
the pineal region, surgery can be curative or provide the
basis for a multidisciplinary effort including radiation ther-
apy and chemotherapy, which is likely to lead to a cure or at
least long-term survival.

Figure 9-18 Pineal tumor. CT scan with
and without contrast. A. The pineal region
tumor is located posterior to the third
ventricle and is isointense with the brain. It
obstructs CSF flow from the third ventricle
and causes hydrocephalus, as demonstrated
by the enlarged ventricle. B. When iodinated
contrast is given, the tumor enhances and
becomes much more apparent.

1S2

CHAFFER r

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STUDY QUESTIONS

I. A 3-month-old female infant is seen because of increasing
circumference of the head. She is alert, but the head circum-
ference measures 40 cm in greatest diameter and the infant
weighs 9 Ib. She had lost weight during the last 2 months. A
CT shows large lateral and third ventricles and a mass in the
fourth ventricle.

1. What is the differential diagnosis? 2. What type of

shunting procedure might be considered? 3. What complica-
tions might result from shunting? 4. How might definitive
(surgical) therapy be accomplished? 5. What long-term

prognosis might be appropriate with the various lesions
which might be encountered?

II. A 6-year-old male is admitted with a history of many
headaches and projectile vomiting of 2 months. He had
papilledema and "split" cranial sutures.

1. What imaging studies would be appropriate? 2. Assum-

ing a posterior fossa tumor, how should it be approached
surgically? 3. Assuming the lesion is medulloblastoma, how
aggressive should the surgery be? 4. What adjunctive ther-
apy(ies) might be administered? 5. What is the long-term
prognosis?

III. An 8-year-old boy is seen with right-sided loss of
hearing. There is a history of recurrent infections on the

right. A cystic mass with MR! evidence of cholesterol is
obtained.

1. What is the most likely diagnosis? 2. What might be

the relationship to the recurrent middle ear infection?
3. How should the lesion be treated? 4. What hazards of
resection should the surgeon anticipate? 5. What would be
the long-term prognosis?

IV. A 10-year-old male is seen because of failing vision and
proptosis on the right. MRI with gadolinium shows a mass
involving the chiasm and both optic nerves, larger on the
right. The mass is only mildly enhanced by gadolinium.

1. What diagnoses might be considered? 2. What surgical

therapy might be considered? 3. What are the chances of
hydrocephalus? 4. How could hydrocephalus occur? 5. What
are the possibilities of seizures?

V. A 2-year-old infant has hydrocephalus evidenced by a
large head. A CT with contrast shows an enhancing lesion in

the left lateral ventricle in the area of the trigone.

1. What is the most likely diagnosis? 2. How should the

patient be treated? 3. Should a shunting procedure be con-

sidered first? If so, why, or if not, why not? 4. What is the

ultimate prognosis? 5. Is radiation therapy an appropriate
consideration? Under what conditions?