[Brain stem auditory evoked potentials for assessment of isolated fourth ventricle in three patients]

Isolated fourth ventricle is an untoward but interesting complication caused by the shunt procedure, which has been recognized since the introduction of CT scanning. Auditory brain stem evoked potentials (BAEPs) were recorded in a patient with isolated fourth ventricle for assessment of brain stem function. Case 1. A 9-year-old boy. He had undergone repair of the lumbosacral meningocele at birth, followed by shunting procedures, including repeated shunt revision, for hydrocephalus which subsequently developed. CT scanning on admission revealed typical findings of isolated fourth ventricle, while neurological examination disclosed no abnormalities. BAEPs on admission revealed normal waves both in amplitude and latency. This patient has been doing well without further shunting procedures. Case 2. A 17-year-old male was admitted with complaints of headache, diplopia, nystagmus and ataxic gait. He had a history of operation for radical removal of cerebellar astrocytoma and lateral ventriculo-peritoneal shunt at 9 years of age. CT scanning on admission revealed a typical isolated fourth ventricle, and fourth ventricle-peritoneal shunt was performed. Postoperative serial BAEPs revealed gradual improvement of brain-stem function. Clinically he has been symptom-free thereafter except for slight nystagmus. Case 3. A 2-year-old female suffering from hydrocephalus developed after neonatal intraventricular hemorrhage and ventriculitis. After repeated revision of a lateral ventriculo-peritoneal shunt, she was admitted in semicoma with vomiting and opisthotonic posture. CT study revealed an isolated fourth ventricle and preoperative BAEPs showed marked abnormalities. Although fourth ventricle-peritoneal shunt was performed, no remarkable change in BAEPs was obtained, and neurological deficit of considerable degree persisted.(ABSTRACT TRUNCATED AT 250 WORDS)