Oligodendrogliomas are primary glial brain tumours that are divided into grade II and anaplastic grade III tumours (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 tumours 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. The incidence of oligodendrogliomas ranges from 5-19% of all intracranial tumours. They 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. The morbidity and mortality (length of survival) profile for oligodendrogliomas is much better than for astrocytic tumours. However, it also depends on tumour location and pressure effects, as with any other intracranial lesion. The most common presenting symptom is seizure, observed at diagnosis in as many as half of patients. As many as 80% of patients have seizures at some time during their illness.Depending on the location of the tumour, the seizure can be simple partial, complex partial, or generalized.

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 grade 3) who have loss of heterozygosity on 1p or combined loss of heterozygosity on 1p and 19q survive substantially longer than patients whose tumours lack these genetic changes. (Each pair of human chromosome contains a long arm q and a short arm p. Loss of heterozygosity (LOH) in a cell represents the loss of normal function of one allele {One member of a pair or series of genes that occupy a specific position on a specific chromosome} of a gene in which the other allele was already inactivated.)


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


Historically, surgery has been the mainstay of treatment for oligodendrogliomas. The extent of resection depends in large part on the location of the tumour and its proximity to "eloquent" brain areas. If possible, the goal is total resection of the tumour. In patients who undergo total gross resection, no further treatment may be necessary (this depends on tumour grade and surveillance is an option usually for grade 2 tumours only), but the patient must be followed up for clinical or radiologic recurrence.


The role of chemotherapy for the treatment of oligodendroglioma was well established by several studies using nitrosourea-based therapy. Most used procarbazine, lomustine (CCNU), and vincristine, a combination chemotherapy regimen (ie, PCV). Several studies have evaluated the role of temozolomide as second-line chemotherapy for recurrent oligodendroglioma and showed a response rate of about 25% for patients relapsing after PCV therapy. Recently it has been shown that initial treatment post surgery for grade 3 gliomas including oligodendrogliomas with either radiotherapy or chemotherapy (either with PCV or Temozolomide) did not make any difference to the overall progression free survival (NOA-04 study). The extent of surgical removal of the tumour was an important prognostic factor in this study.

Radiation therapy

Various studies compared the effects of radiation therapy before and after the maximal surgical resection. The studies showed that the immediate postoperative irradiation in patients with low grade gliomas (grade 2) increases the median progression-free survival by 2 years without affecting the overall survival. This result suggests that radiation therapy can be withheld until a clinical or radiologic progression occurs to delay the sequelae of cranial irradiation.