[Epidermoid of the third ventricle--report of a case].

A rare case of epidermoid of the third ventricle was experienced. The patient was a fifteen years old boy, who had been hospitalized four years earlier due to acute hydrocephalus. The ventriculography at that time revealed a large cystic tumor containing heterogeneous mass filling the entire third ventricle, which seemed to be a dermoid or epidermoid. Ventricular drainage and ventriculo-peritoneal shunt were performed and he was discharged one month later without any complaint. On February 10th 1983, he was re-admitted with severe headache, nausea and showing markedly increased intracranial pressure and right hemianopsia. Computerized tomography scans demonstrated a large round low density mass in the entire third ventricle extending into the prepontine cistern. Radical operation was performed by the anterior transcallosal approach. After dissecting the interhemispheric fissure, a longitudinal incision about 15 mm long was made in the anterior part of the corpus callosum and the tumor was removed. Mild diabetes insipidus and subdural effusion appeared postoperatively. The patient was discharged on April 7th with right hemianopsia and returned to school. The anterior transcallosal approach seemed to be a good operative procedure in such large third ventricle tumor cases since it allowed excellent exposure of the third ventricle and minimized postoperative neurological deficits.