Human Auditory Nerve Action Potentials and Brain Stem Evoked Responses: Latency-Intensity Functions in Detection of Cochlear and Retrocochlear Abnormality

Abstract

• Latency-intensity (L-I) functions for (1) the auditory nerve action potential (AP) N₁ peak, (2) the brain stem evoked response (BER) V peak, and (3) the N₁-V interval were related to hearing level and lesion location. The AP L-I curves tended to steepen with increasing 4 to 8 kHz hearing level. This relationship was identical for cochlear and retrocochlear ears, except for a few retrocochlear ears with "inappropriate AP preservation." Both high-frequency cochlear loss and retrocochlear abnormality prolonged peak V latency, but retrocochlear abnormality generally prolonged it more. Among cochlear-loss ears, as 4 to 8 kHz hearing levels increased, N₁-V intervals decreased and L-I curve slopes increased. In contrast, retrocochlear abnormality greatly prolonged N₁-V intervals. As a retrocochlear sign, N₁-V prolongation was slightly more reliable than V prolongation. (Arch Otolaryngol 104:709-717, 1978)