Gliomas
Epidemiology
Most common primary brain tumors. Incidence increases with age. M:F ratio 1:1.6.
Astrocytomas: 25% of all brain tumors. Before age 25, 67% are astrocytomas in posterior fossa; after age 25, 90% supratentorial.
Oligodendrogliomas: Median age at diagnosis, 50. Rare in children.
Ependymomas: More common in children; 10% of all pediatric intracranial tumors.
Pathology
Gliomas originate from glial cells or their precursors. Include astrocytomas, oligodendrogliomas, ependymomas. Some tumors may have both astrocytic and oligodendroglial features (“mixed” gliomas), or contain foci of different grades.
Highly infiltrative (with exception of pilocytic astrocytoma).
Familial Conditions
About 5% of gliomas are familial. Due to loss of a tumor-suppressor gene. Syndromes include neurofibromatosis (types 1 and 2), Li-Fraumeni syndrome, Turcot syndrome (includes several disorders with familial polyposis).
Clinical Features
Symptoms and Signs
Spectrum similar in all grades of glial tumors: symptoms may be generalized (headache, nausea, vomiting, lethargy, personality or behavioral changes) or focal (seizures, hemiparesis, aphasia, ataxia, cranial neuropathies).
Seizures are presenting symptom in >80% with low-grade glioma; most patients with high-grade glioma present with prominent focal sensory or motor symptoms.
Most common site for ependymoma: fourth ventricle, causing obstructive hydrocephalus.
Imaging Characteristics
Astrocytoma, Oligodendroglioma
Low-grade: non-enhancing, infiltrative mass seen best on T2 or FLAIR MRI. Typically in frontal or temporal lobe.
High-grade: large, contrast-enhancing, with surrounding edema.
Ependymoma
Heterogeneous, well-delineated, contrast-enhancing. Occasionally with hemorrhage, calcification.
Treatment and Prognosis
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