Answer and Discussion of Quiz Set: N-017

1.    Which of the following is the most common site for oligodendrogliomas?

A.  Frontal and parietal lobe of the cerebral hemispheres

B.  Cerebellum

C.  Brainstem (midbrain, pons, medulla)

D.  Spinal cord

E.  Optic nerve

Answer and Discussion: The answer is (A). For oligodendroglioma, the incidence is directly proportional to the amount of white matter and therefore its highest incidence is seen in the cerebral hemispheres. They are most common in the frontal and parietal lobe, followed by the temporal lobe and occipital lobe. These tumors are usually found as a solitary lesion in a cortical or subcortical location and, uncommonly, in the deep gray matter. Occasional cases are seen in the cerebellum and brain stem. They are rare in the spinal cord. When an oligodendroglioma is seen in in the spinal cord, one must rule out leptomeningeal dissemination of an oligodendroglioma in the brain. Oligodendroglioma in the optic cord is exceedingly rare although rare case reports exist.