Oligodendrogliomas are a type of glioma that are believed to originate from the oligodendrocytes of the brain or from a glial precursor cell. They occur primarily in adults (9.4% of all primary brain and central nervous system tumors) and are only rarely found in children (4% of all primary brain tumors). The median age of diagnosis for oligodendroglioma is 41 years of age. Males account for 75% of these cases.

=Aetiology= The aetiology of oligodendrogliomas is unknown. Some studies have linked oligodendroglioma with a viral cause, a single case report has linked oligodendroglioma to irradiation of pituitary adenoma.

=Symptoms= In anywhere from fifty to eighty percent of cases, the first symptom of an oligodendroglioma is the onset of seizure activity. They occur mainly in the frontal lobe thus affecting personality. Headaches combined with increased intracranial pressure are also a common symptom of oligodendroglioma. Depending on the location of the tumor, any neurological deficit can be induced, from visual loss, motor weakness and cognitive decline. A Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) scan is necessary to characterize the anatomy of this tumor (size, location, heter/homogeneity). However, final diagnosis of this tumor, like most tumors, relies on histopathologic examination (biopsy examination).

=Histopathological Grading= Oligodendrogliomas are classified according to World Health Organization guidelines as grade II or anaplastic (malignant) grade III.

=Molecular Genetics= By far, the most common structural deformity found is co-deletion of chromosomal arms 1p and 19q. The high frequency of co-deletion (~70%) is a striking feature of this glial tumour, and is considered as a "genetic signature" of oligodendroglioma. The putative major tumour genes on these loci remain elusive due to loss of the whole chromosomal arms. However, the cell cycle regulator CDKN2C located on 1p is occasionally homozygously deleted or mutated, indicating a small contribution to tumourigenesis.

Anaplastic tumors may show disruption of p53 or Rb cell cycle pathways. Losses of CDKN2A/2B on 9p21 is correlated with malignant progression to grade III.

=Treatment= A surgeon will typically remove as much of the tumor as he or she can without damaging other critical, healthy brain structures. Often, surgery is followed up by chemotherapy, radiation, or a mix of both. Oligodendrogliomas tend to reappear; these recurrent tumors are then treated the same way as the initial tumor, with sometimes more aggressive chemo or radiation therapy. Recently, stereotactic surgery has proven successful in treating small tumors that have been diagnosed early.

Currently, the life expectancy of a person with a high-grade brain tumor is five to eight years from diagnosis and eight to ten years for low-grade patients. There is some life expectancy variation, however, between different subsets of brain tumor. Some cases have been recorded of people surpassing these odds; with aggressive treatment and close monitoring, it is possible to outlive the typical life expectancies for both low grade and high grade oligodendrogliomas.

Oligodendrogliom