Evaluation of brainstem auditory evoked responses in congenital hydrocephalus.

Brainstem auditory evoked responses (BAER) were studied in 20 children with clinically diagnosed and CT-confirmed congenital hydrocephalus before and after shunt surgery. Ninety-five percent of the children showed abnormal responses preoperatively. Prolonged wave V latency was the most common abnormality, followed by increased interwave latencies. Total absence of evoked responses was more common in children with communicating hydrocephalus. Following shunt surgery 50% of cases returned to normal and 20% showed a significant improvement. Abnormalities persisted in 10% of cases. BAER abnormalities referrable to caudal brainstem dysfunction recovered first, following CSF diversion. Study of BAER is useful for identifying physiological brainstem abnormalities in hydrocephalic children and promises to be a sensitive non-invasive diagnostic tool for the detection of "non-infective complications" of shunt surgery, if performed serially during follow up.