Brainstem auditory evoked potential recording in patients with epilepsy.

The brain stem auditory evoked potential (BSAEP) was recorded in 32 normal control subjects and 81 epileptic patients. Statistically significant differences in regard to sex and laterality of ear stimulated were found to exist in both groups. The epileptic patients also had significantly longer latencies for all wave components and interwaves I-III as well as I-IV than the normal controls. There were no differences in regard to interwave latency III-V. Clinically significant latency prolongations (more than three standard deviations from the norm) were encountered especially in regard to waves I and III. Correlations of wave and interwave latencies with a large variety of clinical variables showed that statistically significant relationships existed mainly in regard to presence or absence of brain damage and the severity of the seizure disorder, as expressed by the number of different seizure types to which a given patient was subject. Waves II and III showed the most consistent latency prolongations for these variables. Anticonvulsant medication levels did affect wave latencies, but apart from Primidone, it involved waves IV through VII rather than II and III. Carbamazepine levels were related to prolongation of I-III interwave latency. It is concluded that severely brain-damaged epileptic patients have demonstrable brain stem dysfunction affecting mainly the medullo-pontine rather than midbrain or thalamic structures.