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.