An isolated and sporadic auditory neuropathy (auditory nerve disease): report of five patients

Five patients of various ages with difficulty in speech discrimination were evaluated. All showed evidence of abnormal auditory brainstem responses (A BRs) beginning with the VIIIth cranial nerve. Broad summating potentials we re evoked on their electrocochleograms (EcochGs) and they all exhibited alm ost normal cochlear outer hair cell function by otoacoustic emissions (OAEs ) recordings. Behavioural audiometric testing revealed a mild to moderate e levation of pure-tone threshold in all patients. The shape of their pure-to ne losses varied, being predominantly low-frequency in four patients (risin g slope pattern) and flat across all frequencies in one patient. Speech int elligibility scores of all patients were poor and out of proportion to what would have been expected if threshold elevation of pure-tone was of cochle ar origin (i.e. markedly poor scores on the speech audiogram with good scor es on the auditory comprehension test). Patients were neurologically normal when the hearing impairment was first manifested. We suggest that this typ e of hearing impairment is due to an isolated and sporadic disorder of audi tory nerve function. It occurs in isolation and does not seem to be part of a generalized neuropathological process.