Isolated Fourth Ventricle Hydrocephalus

Mental deterioration and signs of cerebellar dysfunction developed 5 years after lateral ventricle shunting in 36-year-old hydrocephalic female patient. Fourth ventricle enlargement was seen on CT scan. Reevaluation of the cerebrospinal fluid pathways with metrizamide ventriculography showed isolated fourth ventricle with aqueductal stenosis. Shunting of the fourth ventricle with an Y-connector returned the patient to normal neurological status.