Brain stem glioma

BRAIN STEM GLIOMA
31.08.2016 BRAIN STEM GLIOMA NINAS

Key concept
• MRI can differentiate malignant from benign
lesions
• Trend: lower grade tumors tend to occur in the
upper brainstem, and higher grade tumors in the
Lower brainstem/medulla
• Usually presents with multiple cranial nerve
palsies and long tract findings.
• Most are malignant, have poor prognosis, and are
not surgical candidates.
• Role of surgery primarily limited to dorsally
exophytic lesions and shunting.

• Brainstem gliomas (BSG) tend to occur during
childhood and adolescence (77% are < 20 yrs
old
• They comprise 1% of adult tumor
• BSG are one of the 3 most common brain
tumors in pediatrics.

PRESENTATION
• Upper brainstem tumors tend to present with
cerebellar findings and hydrocephalus
• Lower brainstem tumors tend to present with
multiple lower cranial nerve deficits and long
tract finding.

• Due to their invasive nature, signs and
symptoms usually do not occur until the
tumor is fairly extensive in size.

SIGNS AND SYMPTOMS:
1. Gait disturbance
2. Headache
3. Nausea/vomiting
4. Cranial nerve deficits: diplopia, facial asymmetry
5. Distal motor weakness in 30%
6. Papilledema in 50%
7. Hydrocephalus in 60%, usually due to aqueductal
obstruction (often late, except with periaqueductal
tumors, e.g. below)
8. Failure to thrive (especially in age ≤ 2 yrs)

PATHOLOGY
• Heterogeneous group.
• There may be a tendency towards lower grade
tumors in the upper brainstem (76% were
low-grade) versus the lower brainstem (100%
of the glioblastomas were in the medulla)

LOCATION OF BRAIN STEM GLIOMAS
A- tectal glioma
B- focal midbrain tumor
C- focal intrinsic pontine
glioma
D- doral/exophytic glioma
E- Diffuse Intrinsic Pontine
Glioma
F- focal medullary glioma
G- cervicomedullary glioma

• A cystic component is seen rarely.
• Calcifications are also rare.

Growth patterns that can be identified by MRI that may
correlate with prognosis
• 1. diffuse: all are malignant (most are anaplastic
astrocytomas, the rest are glioblastomas). On MRI these
tumors extend into the adjacent region in vertical axis (e.g.
medullary tumors extend into pons and/or cervical cord) with
very little growth towards obex, remaining intraaxial.
• 2. cervicomedullary: most (72%) are low-grade astrocytomas.
The rostral extent of these tumors is limited to the
spinomedullary junction. Most bulge into the obex of the 4th
ventricle (some may have an actual exophytic component).

• 3. focal: extent limited to medulla (does not
extend up into pons nor down into spinal cord).
Most (66%) are low-grade astrocytomas
• 4. dorsally exophytic: may be an extension of
“focal” tumors . Many of these may actually be
low grade gliomas including:
• a) Pilocytic astrocytomas,
• b) Gangliogliomas : very rare, only 13 cases
reported as of 1984. Compared to other BSGs,
these patients tend to be slightly older and the
medulla is involved more frequently.

Evaluation
• MRI
• The diagnostic test of choice. MRI evaluates
status of ventricles, gives optimal assessment of
tumor (CT is poor in the posterior fossa) and
detects exophytic component.
• T1WI: almost all are hypointense, homogeneous
(excluding cysts).
• T2WI: increased signal, homogeneous (excluding
cysts).
Gadolinium enhancement is highly variable.

COMPUTED TOMOGRAPHY
• Most do not enhance on CT, except possibly
an exophytic component.
• If there is marked enhancement, consider
other diagnoses (e.g. high grade vermian
astrocytoma).

Treatment
Surgery
• Biopsy: should not be performed when the
MRI shows a diffuse infilt rating brainstem
lesion (does not change treatment or
outcome).
• Treatment is usually non -surgical.

• Exceptions where surgery may be indicated:
– 1. tumors with a dorsally exophytic component2: see
below these may protrude into 4th ventricle or CP
angle tumor which tend to enhance with IV contrast,
tend to be lower grade.
– 2. some success has been achieved with non-
exophytic tumors that are not malignant
astrocytomas.
– (surgery in malignant astrocytomas is without benefit)
– 3. shunting for hydrocephalus

Dorsally exophytic tumors
• These tumors are generally histologically benign (e.g.
gangliogliomas) and are amen able to radical subtotal resection.
• Prolonged survival is possible, with a low incidence of disease
progression at short-term follow-up.
• Surgical goals in exophytic tumors include:
– 1. enhanced survival by subtotal removal of exophytic component
broad attachment to the floor of 4th ventricle is typical and usually
precludes complete excision (although some “safe entry” zones have
been described. An ultrasonic aspirator facilitates debulking.
– 2. establishing diagnosis: radiographic differentiation of exophytic
brainstem gliomas tumors from other lesions (e.g. medulloblastoma,
ependymoma and dermoids) may be difficult.
– 3. tumors that demonstrate recurrent growth after resection remained
histologically benign and were amenable to re-resect ion.

• Complications of surgery generally consisted
of exacerbation of pre-operative symptoms
(ataxia, cranial nerve palsies) which usually
resolved with time.

Medical Management
• No proven chemotherapeutic regimen.
• Steroids are usually administered.
• In pediatrics, there is some indication of
response to temozolomide.

Radiation
• Tradition ally given as 45–55 Gy over a six
week period, five days per week. When
combined with steroids, symptomatic
improvement occurs in 80% of patients.
• Possible improved survival with so called
“hyperfractionation” where multiple smaller
doses per day are used.

Prognosis
• Most children with malignant BSG will die within
6–12 months of diagnosis.
• XRT may not prolong survival in patients with
grade III or IV tumors.
• A subgroup of children have a more slowly
growing tumor and may have up to 50% five-year
survival.
• Dorsally exophytic tumors comprised of pilocytic
astrocytomas may have a better prognosis.

Brain stem glioma

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