Brain stem auditory evoked potentials in Arnold-Chiari malformation: possible prognostic value and changes with surgical decompression.

Symptomatic Arnold-Chiari malformation (Chiari II) is a recently described clinical entity, the natural history and surgical management of which remain controversial. The brain stem auditory evoked potentials (BAEPs) have been described as abnormal in 50 to 86% of children with myelomeningocele. We present the case of a full-term infant with myelomeningocele, shunted hydrocephalus, and Chiari II malformation who was surgically treated by decompression when she was 3 weeks old. BAEPs recorded immediately after decompression showed dramatic improvement over BAEPs recorded immediately before decompression, an improvement that could not be attributed to maturation of the central nervous system. It is postulated that in further large series the degree of abnormality in BAEPs may be of value in predicting the clinical course of these patients. The current status of BAEPs as they apply to the evaluation of posterior fossa anomalies is reviewed.