PEDBASE.org - The Pediatric Database - Detailed information of BRAIN STEM GLIOMA

BRAIN STEM GLIOMA

DEFINITION:

A neuroglial solid tumor of the brain stem characterized by obstructive hydrocephalus and cerebellar signs.

EPIDEMIOLOGY:

incidence: ?
- 3rd most common tumor of the posterior fossa
- accounts for 10% of all pediatric brain tumors
age of onset:
- peak age: 5-10 yrs
risk factors:
- M = F

PATHOGENESIS:

1. Tumor Origin

pons > medulla > midbrain
obstructive hydrocephalus results from the local extension of the tumor mass along white matter tracts and into the cere-bellar peduncles, 4th ventricle, ependymal, and subarachnoid spaces
tumor may be:

1. Diffuse

most common type of brain stem glioma
arise in the pons
usually anaplastic astrocytoma with poor survival

2. Focal

isolated cystic or solid tumor in medulla & brain stem
most often low-grade astrocytoma
5 yr survival: 50-60%

3. Exophytic

dorsal - penetrate thru the ependymoma into the 4th ventricle causing obstructive hydrocephalus
less malignant pathology with good prognosis
lateral - invade the 7th & 8th CN as they exit the brainstem
mainly malignant with poor prognosis

cervico- - involve the cervicomedullary junction medullary - generally low-grade tumor with good progno.

2. Histologic Types

histogically these tumors are composed of a heterogeneous group of gliomas
malignant (60-70%)
- anaplastic astrocytoma, glioblastoma multiforme
low grade (30-40%)
- astrocytomas (low grade), gangliogliomas, JPA
may be associated with a deletion of chrom. 9p

3. Poor Prognosticators

diffuse malignant subgroup:
- short duration of symptoms
- bilateral CN dysfunction
- large volume of residual tumor
- diffuse hypointensity on MRI

CLINICAL FEATURES:

1. Primary Tumor

depend on whether the tumor is diffuse, focal, or exophytic
30% will have hydrocephalus

1. Diffuse

have symptoms lasting wks -> months (rapid growth)
common triad reflects diffuse brain stem involvement:
- ataxia
- bilateral dysfunction of the cranial nerves
- long tract signs

2. Focal

more isolated and have protracted symptoms (mo.-> yrs)
behavioral changes with varying combinations of unilateral deficits: - cerebellar
- cranial nerves (6th, 7th)
- upper motor signs (pyramidal tract signs)

3. Exophytic

dorsal - obstructive hydrocephalus with increased ICP & protracted vomiting, FTT
lateral - facial and auditory nerve dysfunction
cervico- - neck pain, dysfunction of the lower CN, medullary spastic quadriparesis

2. Metastases

1. Leptomeninges - rare (< 15%)

INVESTIGATIONS:

1. Imaging Studies

1. MRI

T2-weighted imaging
diffuse - symmetric pontine enlargement
focal - localized signal
exophytic - dorsal, lateral, and cervicomedullary enhancing

2. Pathology

tumor

3. Biologic

CSF - cytology

MANAGEMENT:

1. Surgery (based on tumor origin)

Diffuse - empirical radiation wtih surgery not indicated
Focal - surgery indication for histologic typing, tumor removal, cyst drainage, and relief of obstructed CSF
Exophytic - surgery indicated for all types with same indications as for focal type
most recurrences occur in the post. fossa (80-90%) or neuroaxis (15%) within 18 months with only a <10% survival rate; treatment consists of reoperation, radiation, and salvage chemotherapy

2. Radiation (adjuvant)

doses of >5,000 cGy will increase survival rates
local field radiation since recurrence usually in poster. fossa
used in all cases except if tumor ganglioglioma or JPA
may use hyperfractionated protocol (bid)

3. Chemotherapy (adjuvant)

benefit not yet proven
CCNU, vincristine, prednisone

Pediatric Database - BRAIN STEM GLIOMA

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