= malignant tumors of glial cells growing along white matter tracts with tendency to increase in grade with time; may be multifocal
Incidence: 30–40% of all primary intracranial tumors; 50% of solitary supratentorial masses
- contrast enhancement:
- increases in proportion to degree of anaplasia
- intensity of enhancement diminishes with steroid therapy
CELL OF ORIGIN
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FREQUENCY OF INTRACRANIAL GLIOMAS
- Glioblastoma multiforme 51%
- Astrocytoma 25%
- Ependymoma 6%
- Oligodendroglioma 6%
- Spongioblastoma polare 3%
- Mixed gliomas 3%
- Astroblastoma 2%
Age peak: middle adult life
Location: cerebral hemispheres; spinal cord; brainstem + cerebellum (in children)
Incidence: 1%; 12–15% of all pediatric brain tumors; 20–30% of infratentorial brain tumors in children
Histo: usually anaplastic astrocytoma / glioblastoma multiforme with infiltration along fiber tracts
Age: in children + young adults; peak age 3–13 years; M÷F = 1÷1
- become clinically apparent early before ventricular obstruction occurs
- ipsilateral progressive multiple cranial nerve palsies
- cerebellar dysfunction: ataxia, nystagmus
- contralateral hemiparesis, eventually respiratory insufficiency
Location: pons >midbrain >medulla; often unilateral at medullopontine junction
- Medullary + mesencephalic gliomas are more benign than pontine gliomas!
Growth pattern:
- diffuse infiltration of brainstem with symmetric expansion + rostrocaudal spread into medulla / thalamus + spread to cerebellum
- focally exophytic growth into adjacent cisterns (cerebellopontine, prepontine, cisterna magna)
- asymmetrically expanded brainstem
- flattening + posterior displacement of 4th ventricle + aqueduct of Sylvius
- compression of prepontine + interpeduncular cistern (in upward transtentorial herniation)
- paradoxical widening of CP angle cistern with tumor extension into CP angle
- paradoxical anterior displacement of 4th ventricle with tumor extension into cisterna magna
CT:
- isodense / hypodense mass with indistinct margins
- hyperdense foci (= hemorrhage) uncommon
- absent / vague (minimal / patchy) contrast enhancement (50%)
- ring enhancement in necrotic / cystic tumors (= most aggressive tumors)
- prominent enhancement in exophytic lesion
- hydrocephalus uncommon (because of early symptomatology)
MR: (best evaluation in subtle cases)
- hypointense on T1WI + hyperintense on T2WI
- often only subtle enhancement
- ± engulfment of basilar artery
Angio:
- anterior displacement of basilar artery + anterior pontomesencephalic vein
- posterior displacement of precentral cerebellar vein
- posterior displacement of posterior medullary + supratonsillar segments of PICA
- lateral displacement of lateral medullary segment of PICA
Prognosis: 10–30% 5-year survival rate
Rx: radiation therapy
DDx: focal encephalitis, resolving hematoma, vascular malformation, tuberculoma, infarct, multiple sclerosis, metastasis, lymphoma
Hypothalamic-Chiasmatic Glioma
Origin: often undeterminable: hypothalamic gliomas invade chiasm, chiasmatic gliomas invade hypothalamus
Incidence: 10–15% of supratentorial tumors in children
Age: 2–4 years; M÷F = 1÷1
Associated with: von Recklinghausen disease (20–50%)
- diminished visual acuity (50%) ← optic atrophy
- diencephalic syndrome (in up to 20%): marked emaciation, pallor, unusual alertness, hyperactivity, euphoria
- short stature (in 20%) ← reduction in growth hormone
- obese child, sexual precocity, diabetes insipidus
- suprasellar hypodense lobulated mass with dense inhomogeneous enhancement
- heterogeneous lesion ← cyst formation, necrosis, calcifications
- hypointense on T1WI + hyperintense on T2WI + FLAIR
- obstructive hydrocephalus
DDx: hypothalamic hamartoma, ganglioglioma, choristoma