Background and Aim: Physiologic measures of cochlear and auditory nerve function may be of assistance in distinguishing between hearing disorders due primarily to auditory nerve impairment from those due primarily to cochlear hair cells dysfunction. The goal of present study was to measure of cochlear responses (otoacoustic emissions and cochlear microphonics) and auditory brainstem response in some adults with auditory neuropathy/ dys-synchrony and subjects with normal hearing.
Materials and Methods: Patients were 16 adults (32 ears) in age range of 14-30 years with auditory neuropathy/ dys-synchrony and 16 individuals in age range of 16-30 years from both sexes. The results of transient otoacoustic emissions, cochlear microphonics and auditory brainstem response measures were compared in both groups and the effects of age, sex, ear and degree of hearing loss were studied.
Results: The pure-tone average was 48.1 dB HL in auditory neuropathy/dys-synchrony group and the frequency of low tone loss and flat audiograms were higher among other audiogram&aposs shapes. Transient otoacoustic emissions were shown in all auditory neuropathy/dys-synchrony people except two cases and its average was near in both studied groups. The latency and amplitude of the biggest reversed cochlear microphonics response were higher in auditory neuropathy/dys-synchrony patients than control people significantly. The correlation between cochlear microphonics amplitude and degree of hearing loss was not significant, and age had significant effect in some cochlear microphonics measures. Auditory brainstem response had no response in auditory neuropathy/dys-synchrony patients even with low stimuli rates.
Conclusion: In adults with speech understanding worsen than predicted from the degree of hearing loss that suspect to auditory neuropathy/ dys-synchrony, the frequency of low tone loss and flat audiograms are higher. Usually auditory brainstem response is absent in this patients and use of both otoacoustic emissions and cochlear microphonics responses to measure cochlear hair cells function are suggested in them.