[Cochlear responses and auditory brainstem response functions in adults with auditory neuropathy/ dys-synchrony and individuals with normal hearing]

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 co-chlear responses [otoacoustic emissions and cochlear microphonics] and auditory brainstem response in some adults with auditory neuropathy/ dys-synchrony and subjects with normal hearing. 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. 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's 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 co-chlear 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. Audi-tory brainstem response had no response in auditory neuropathy/dys-synchrony patients even with low stimuli rates. 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

[Auditory neuropathy: audiologic and clinical evidence]

The disorder known as "Auditory neuropathy [AN]" is not new but has recently become more clearly defined and understood. Auditory neuropathy is a form of hearing impairment in which the cochlear function is normal but neural transmission in the auditory pathway is disordered. This condition accounts for approximately 7% of permanent childhood hearing loss and 0.2-4% of high risk neonates. Case Reports: Four children [three boys and one girl] younger than two years with auditory neuropathy symptoms are presented. Based on audiologic and clinical findings there were high risk factors in two cases. In each case, absent auditory brainstem response [ABR], absent acoustic reflexes, present cochlear microphonics [CM] and present transient evoked otoacoustic emissions [TEOAE] were shown. This section discusses the clinical profile of cases regarding etiology [neonatal insults, infectious processes, genetic and syndromic factors], age of symptom onset, prevalence of AN/AD, outer hair cells function, audiogram, and acoustic reflexes in relation to other studies