A study of hearing in the elderly using non-invasive electrocochleography and auditory brainstem responses.

The auditory brainstem responses exhibited normal interpeak intervals of waves I-III and I-V in a group of 31 elderly people (mean age 82 years), indicating normal conduction through the brainstem. The amplitudes of the waves I, III and V were significantly reduced and the peaks I, III and V showed a delay in latency, reflecting a predominantly lower level of activity in the elderly cochlea. Extratympanic electrocochleography yielded significantly reduced amplitudes of the N1 component of the action potential, summating potential and cochlear microphonics in the elderly compared to the young controls. A heterogeneity of patterns of input/output functions was observed and interpreted as either an absence of recruitment, as partial or as complete recruitment. The findings are in keeping with pathological evidence of severe damage to outer hair cells and complete atrophy of part of the basal coil.