AUDITORY-EVOKED POTENTIALS IN EPILEPTIC PATIENTS

Auditory brain stem response (ABR) and middle latency response (MLR) w ere recorded in 49 epileptic patients.-Responses were evoked and recor ded at 90 dB nHL down to threshold. A statistically significant number of epileptic patients showed elevated ABR (30.1%) and MLR (40.7%) thr esholds, even though their pure-tone audiograms showed normal hearing sensitivity. Threshold elevation was more frequent in subjects with gr and mal epilepsy compared to subjects with temporal lobe epilepsy refl ecting poorer response in the former subgroup. Furthermore, chronicity of illness was significantly related to the elevated ABR and MLR thre sholds in grand mal patients in contrast to patients with temporal lob e epilepsy. On the other hand, the effect of antiepileptic drugs did n ot seem to be significantly related to the elevated thresholds in both subgroups. Threshold elevation was attributed to a disturbance in the neurotransmitters of the brain stem as well as other subcortical stru ctures. The inhibitory effect of the efferent auditory pathway on the incoming neural signals was also suggested to explain such elevated th resholds.