Epidermoid cysts of the fourth ventricle.

The location of epidermoid cysts within the fourth ventricle is rare. The Authors present three cases operated on. The most frequent symptom was ataxia. Increased intracranial pressure and hydrocephalus were rare even when the tumors were large in size and filled up the fourth ventricle. Neuroradiological data are presented. Surgical removal was generally easy though the tumor invaded the cisterns and a true peritumoral capsule was found only in the lower part of the ventricular floor. The bursting of the cyst followed by continuous production of keratin with subsequent invasion of cisterns and foramina is suggested as a possible mechanism to explain the tumoral growing.