Oligodendrogliomas of the fourth ventricle: report of two cases.

Oligodendrogliomas comprise approximately 4% of the total of brain tumours, and of this group only 7% are found in the posterior fossa, including 2% in the fourth ventricle. Oligodendrogliomas of the fourth ventricle therefore comprise less than one case in 1,000 to 1,500 brain tumours (0 08 %). One cannot expect to encounter much more than one in a lifetime even in a large-neurosurgical experience. In 1928 Van Bogaert and Martin reported an oligodendroglioma filling the fourth ventricle. In 1950 Earnest, Kernohan, and Craig in a review of 200 oligodendrogliomas found 14 to be in the posterior fossa, four of which were in the fourth ventricle. Additional literature from 1928 to 1950 reported oligodendrogliomas of the posterior fossa (Banus and Bueno, 1929; Agostini, 1933; Garkarvi, 1936; Wycis, 1948), two of which were in the fourth ventricle, (Banus and Bueno, 1929; Garkavi, 1936). Thus, of a total of 25 posterior fossa tumours, seven were in the fourth ventricle, indicating that approximately 25% of the posterior fossa oligodendrogliomas were in the fourth ventricle. Another interesting fact noted by Krueger and Krupp (1952) in age distribution of posterior fossa oligodendrogliomas was that they usually made themselves known before the age of 21, while supratentorial involvement usually became evident between 35 to 45 years of age. This would not necessarily indicate that the tumours began at an earlier age in the posterior fossa, but that perhaps symptoms began earlier since the room for expansion was more limited. The same may well be true of cerebellar astrocytomas.