Cochlear processes affecting wave V latency of the auditory evoked brain stem response. A study of patients with sensory hearing loss.

The effects of inner ear pathologies on wave V latency of the auditory evoked brain stem response (BSR) were studied in 12 selected patients with flat, low-frequency, severe high-frequency, and gradual high-frequency sensory hearing loss. In patients with flat and low-frequency sensory hearing loss (Meniere's disease), the latencies of wave V at intensities 4--10 dB greater than their response thresholds were roughly the same as those in normal-hearing subjects. In patients with severe high-frequency sensory hearing loss (sharp cut-off at about 2 or 3 kHz), the latencies of wave V were always delayed, compared with those in normal-hearing subjects. In patients with gradual high-frequency sensory hearing loss, the latency of wave V was delayed according to the degree of hearing loss (as determined by pure tone audiometry) above 2 kHz. The data are interpreted as showing that the wave V latency is sensitive to a kind of recruiting phenomenon in the transduction process as well as being an index of the pressure wave travel time to the cochlear portion responsible for the elicitation of the BSR.