Oligodendrogliomas comprise 4–5% of central nervous system neoplasms. They arise in the cortical white matter and tend to grow slowly.131
Oligodendroglial tumors are closely related to fibrillary astrocytic tumors and are generally graded as oligodendroglioma, or anaplastic oligodendrogliomas if they have a high cell density, mitotic rate, and necrosis.132
Histologically, cells have the small rounded nuclei of oligodendrocytes with variable densities in cell population and pleomorphism. They display a characteristic “fried egg” appearance (see Figure 7) and may show necrosis infrequently.
Figure 7. Oligodendroglioma. 200 Microscopic section of uniform glial cells with characteristic "fried egg" appearance (arrow).
Oligodendrogliomas present with seizures in 70–90% of cases.24,25 Seizure patterns may be nonspecific: one-third of patients present with generalized seizures, one-third with partial seizures, and one-third with mixed seizure types.24 Younger patients often present with seizures and therefore are diagnosed earlier than adults, who may present with other neurologic symptoms.
In Olson’s study of 106 patients, the median age at presentation was 37 years. The overall median time to progression was 5 years, with a median survival of 17 years.
Presentation at a young age, seizures, and a Karnofsky Performance Status over 70 (able to live at home and care for self) are significant positive prognostic indicators for survival in low-grade tumors.24,133,134 Children who present with anaplastic oligodendroglioma have a survival time of only 17 months, compared to 72 months for children with low-grade neoplasms.135
Postoperative malignant progression of a low-grade oligodendroglioma can occur but generally requires long intervals.136
Surgical resection is the gold standard of treatment. A seizure-free success rate between 50% and 70% was reported postoperatively by Whittle.24 Adjuvant radiation therapy does not appear to increase survival and increases morbidity in up to 33% of patients.25,137
Postoperative chemotherapy with procarbazine, lomustine, and vincristine (PCV) for low-grade oligodendrogliomas may afford positive results in up to 62% of patients.138 PCV is also effective against high-grade tumors.139
Reviewed and revised March 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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