Updated: May 4, 2009
Oligodendrogliomas (ODs) are primary glial brain tumors that are divided into grade II and anaplastic grade III tumors (World Health Organization [WHO] criteria). Typically, they have an indolent course, and patients may survive for many years after symptom onset. Their good prognosis relative to other parenchymal tumors probably stems from inherently less aggressive biological behavior and a favorable response to chemotherapy, a recently discovered finding based on genetic characteristics.
Oligodendrogliomas arise in the cerebral hemispheres and are distributed among the frontal, parietal, temporal, and occipital lobe, in approximately a 3:2:2:1 ratio. Rarely, they can arise in the cerebellum, brain stem, and spinal cord. They usually occur in the cerebral white matter and are very cellular, with uniform nuclei. They react with glial fibrillary acidic protein on immunostaining.
The incidence of oligodendrogliomas ranges from 5-19% of all intracranial tumors. The newer studies showed incidence of oligodendrogliomas to be around 25% of all gliomas. This may be explained by the improvements in the treatment of oligodendrogliomas, prompting neuropathologists to favor the diagnosis.
No difference in the incidence of oligodendroglioma exists worldwide.
The morbidity and mortality profile for oligodendrogliomas is much better than for astrocytic tumors. However, it also depends on tumor location and pressure effects, as with any other intracranial lesion. The median survival from initial diagnosis of all low-grade oligodendrogliomas (LGOs) is 4-10 years, but it is only 3-4 years for anaplastic oligodendrogliomas.
No difference exists among the races.
Oligodendrogliomas occur in both sexes, with a male-to-female predominance of 2:1.
Oligodendrogliomas may be diagnosed at any age but occur most commonly in young and middle-aged adults, with a median age at diagnosis of 40-50 years. In children, only 6% of gliomas are diagnosed as oligodendrogliomas.
Physical findings depend on the location of the tumor.
No causes or risk factors are known. Occasional clustering occurs in some families, although the mode of inheritance is unknown. Patients with anaplastic oligodendrogliomas who have loss of heterozygosity on 1p or combined loss of heterozygosity on 1p and 19q survive substantially longer (mean, 10 y) than patients whose tumors lack these genetic changes (mean, 2 y).
| Arteriovenous Malformations | Low-Grade Astrocytoma |
| Brainstem Gliomas | Meningioma |
| CNS Melanoma | Metastatic Disease to the Brain |
| Frontal Lobe Syndromes | Primary CNS Lymphoma |
| Glioblastoma Multiforme | |
| HIV-1 Associated Opportunistic Infections: CNS
Toxoplasmosis | |
| HIV-1 Associated Opportunistic Neoplasms: CNS
Lymphoma |
Other CNS tumors (eg, meningioma, metastasis, astrocytoma, glioblastoma)
Brain abscess
CNS toxoplasmosis
Lymphoma
Vascular malformations
Routine laboratory workup is not helpful. If seizures are noted, include EEG, serum electrolyte studies, and if necessary a lumbar puncture in the metabolic workup for seizure, after excluding intracranial pathology with an imaging study. These routine tests help exclude other causes of seizure (eg, electrolyte imbalance, metabolic abnormalities).
Diagnostic imaging studies are the most important part of the workup.
Definite diagnosis in confirmed by stereotactic or open biopsy of the lesion. Currently, MR spectroscopy is performed regularly in some centers to differentiate the tumor from other benign lesions and to define the aggressiveness of the tumor, although this is in the investigational phase. In the future, it may offer another noninvasive modality of investigation.
Macroscopic
Grossly, oligodendrogliomas appear as well defined, solid, and pinkish grey, frequently with areas of calcification and sometimes with areas of necrosis and cystic degeneration. Intratumoral hemorrhage may be present and in some patients may be massive and responsible for sudden death.
Microscopic
Oligodendrogliomas are distinctive, consisting of homogeneous, compact, rounded cells with distinct borders and clear cytoplasm surrounding a dense central nucleus, giving them a "fried egg" appearance.
To call a tumor a mixed oligoastrocytoma, the minimum proportion of astrocyte is variable but ranges from 10-25%. In most instances, the diagnosis of oligodendroglioma is apparent. Confusion can arise with intraventricular oligodendrogliomas, which can appear similar to central neurocytoma. Under light microscopy, neuronal differentiation (eg, Homer Wright rosette formation) can indicate a diagnosis of central neurocytoma, but immunohistochemical markers such as synaptophysin may be necessary to confirm the diagnosis.4
Most oligodendrogliomas are slow-growing indolent tumors; however, they occasionally behave in a more malignant manner when initially diagnosed, or an indolent tumor may evolve into an aggressive one. Malignant tumors demonstrate increased cellularity, nuclear pleomorphism, endothelial proliferation, mitotic activity, and necrosis. Different grading systems are available for malignant tumors, but most pathologists use a simple two-tier grading system, diagnosing tumors without anaplastic features as oligodendroglioma tumors and as anaplastic oligodendroglioma if several of the malignant features are present.5
No other staging workup is required.
Individualize treatment of an oligodendroglioma depending on the presence or absence of symptoms, location and biological aggressiveness of the tumor, extent of possible surgical resection, and histopathology and degree of anaplasia. Treatment options vary from conservative treatment of some patients with serial imaging studies and no intervention to aggressive multimodal treatment including surgical resection, radiotherapy, and chemotherapy in others. Because most patients either develop or present with seizures, anticonvulsive therapy is recommended once the patient is diagnosed with oligodendroglioma.
The standard chemotherapeutic treatment for oligodendrogliomas is combination chemotherapy with PCV. While modifications of the timing and dosage of this regimen (increasing dose, decreasing time interval to every 6 wk), are beyond the scope of this article, interested readers can review the references cited in Bibliography. Physicians prescribing chemotherapy should be aware of the treatment regimens and monitoring required. PCV chemotherapy is administered every 6 weeks or 8 weeks for a total of 6 cycles. If the treatment should fail, radiation therapy, other clinical trials for recurrent gliomas, or other drugs may be considered.
This combination of agents inhibits cell growth and differentiation.
Oral chemotherapy drugs administered in combination (PCV) on a specific chemotherapeutic schedule.
Procarbazine: 60 mg/m2/d PO for 14 d
Vincristine: 2 mg IV twice per cycle
CCNU: 110 mg/m2 PO on first d of each cycle
Administer combination of 3 drugs on a specific chemotherapeutic schedule q6-8wk
Not established
Sympathomimetic amines, barbiturates, phenothiazines, alcohol, and other CNS depressants can increase toxicity; foods containing high amounts of tyramine can increase toxicity owing to weak monoamine oxidase properties; concurrent mitomycin-C may cause acute pulmonary reaction
Documented hypersensitivity; preexisting bone marrow aplasia
X - Contraindicated; benefit does not outweigh risk
Only a physician trained in the appropriate use of chemotherapy should administer these drugs; for details, please refer to standard oncology textbooks
Caution in preexisting renal or hepatic disease (reduce dose); caution in patients with severe cardiopulmonary or hepatic impairment and patients with preexisting neuromuscular disease
After the initial surgical resection and rehabilitation, the patient may require further inpatient care depending on the development of complications from either therapy or tumor recurrence. Appropriate intervention also depends on the nature of complications (eg, surgery for recurrence, steroid therapy for increased vasogenic edema).
After initial appropriate management, closely monitor the patient with the family for tumor recurrence or chemotherapy-induced adverse effects. Monitor with regular follow-up care and MRI scans every 3 months initially and then every 6 months to 1 year.
Patients with seizures require appropriate seizure medications even after surgery. Over time, the dose of the medications can be reduced, depending on the frequency of seizures.
Transfer depends on the residual neurological deficit. The patient may be fully ambulatory or may need appropriate transfer arrangements (eg, cane, wheelchair).
Closely observe the patient for any complications resulting from continuing treatment, such as radiation necrosis from radiation therapy or neuropathy from chemotherapy.
Throughout the entire process, educate the patient and family through regular follow-up care and involvement of support groups to cope with physical, emotional, and spiritual stress. With proper education, the patient and family can develop good insight into the course and prognosis of the tumor.
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oligodendroglioma, OD, LGO, anaplastic oligodendroglioma, glial brain tumor, intracranial tumors, low-grade oligodendrogliomas
ABM Salah Uddin, MD, Consulting Staff, Department of Internal Medicine, St Vincent's Hospital
ABM Salah Uddin, MD is a member of the following medical societies: American Academy of Neurology, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.
Tambi Jarmi, MD, Resident Physician, Department of Internal Medicine, Carraway Methodist Medical Center
Tambi Jarmi, MD is a member of the following medical societies: American College of Physicians and American Medical Association
Disclosure: Nothing to disclose.
Amy A Pruitt, MD, Associate Professor of Neurology, University of Pennsylvania; Attending Neurologist, Hospital of the University of Pennsylvania
Amy A Pruitt, MD is a member of the following medical societies: American Academy of Neurology
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.
Jorge Kattah, MD, Head, Program Director, Professor, Department of Neurology, University of Illinois College of Medicine at Peoria
Jorge Kattah, MD is a member of the following medical societies: American Academy of Neurology, American Neurological Association, and New York Academy of Sciences
Disclosure: Biogen Honoraria Consulting; Bayer Corporation Honoraria Consulting
Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.
Stephen A Berman, MD, PhD, Professor, Department of Internal Medicine, Section of Neurology, Dartmouth Medical School; Chief, Neurology Service, White River Junction Veterans Medical Center
Stephen A Berman, MD, PhD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, and Phi Beta Kappa
Disclosure: Nothing to disclose.