Auditory Brain Stem Response and Middle Latency Response in Hearing Test

Abstract

The auditory brain stem response (BSR) and the middle latency response (MLR) were recorded in 44 hearing-impaired adult subjects, and the relation between the subjective threshold to the stimuli and the response threshold was studied.Tone pips at 500, 1000, 2000 and 4000Hz with 2-cycle rise-decay time and one-cycle peak were delivered with the intensity of 10, 20 and 30dB above the subjective threshold.No significant difference was found between the normal-hearing and the hearing-impaired subjects in Po, Na and Pa to each stimulus intensity, and the thresholds for these components were 10 to 20dB above the subjective threshold.It should be noted that hearing-impaired subjects could evoke the response for the same stimulus intensity above the subjective threshold as normal subjects.The mean latency of the BSR (Po) from subjects with conductive hearing losses was equal to those from normal subjects. The latency-intensity curves (L-I curves) in these subjects sifted to the right side, of the normal L-I curves with same wiveture. With regard to subjects with sensori-neural hearing losses, the latency was shortened in all tone pips except 4000Hz.These results suggested that the BSR (Po) and the MLR (Na, Pa) are reliable in threshold audiometry of adults with hearing losses.