Variations And Characteristics Of Cochlear Microphonic And Otoacoustic Emissions In Children With Auditory Neuropathy Spectrum Disease

Abstract

Research background and objective : Auditory neuropathy(AN) is a clinically recent medical term that was first described in 1996  and its diagnosis is based on the Auditory Brainstem Response (ABR) absent or with grossly abnormal morphology at high stimulus levels with  Otoacoustic emissions (OAEs) and/or cochlear microphonic (CM) present. The aimed of this study to investigate The characteristics of both the CM and the OAEs among a group of children who have been diagnosed with AN in addition to analyze Hearing loss (HL)risk factors.   Materials and Methods : A retrospective review  of the clinical records of a group of children reviewing the Audiology center at Syrian Organization for Persons with Disabilities -AAMAL between 1/1/2018 and 1/11/2019  and who have been diagnosed with AN,The research included studying the results of the Distortion Product otoacostic emissions( DPOAE) - characteristics of CM waves ( latency - amplitude duration of  CM),and variations of each of the two tests according to presence of risk factors or not, pathology of  middle ear ,and the use of hearing aids(HAs) or not. Amplitude of CM waves was studied through the measurement of peak to peak amplitude and divided it into three categories , Latency and duration were studied from the appearance of a first  sinusoidal wave that reverse when change polarity , and until the end of the waves.   Results : The number of cases diagnosed with unilateral or bilateral auditory neuropathy was 58 cases(110 ears).52 cases diagnosed with bilateral AN , one of which was  transient AN,  and 6 cases with unilateral AN. Mean age was  33 months ± 23 months , males 33 case (57%) and females 25 case (43). OAEs were conducted in 87 ears and were present in 26 ears (31.5)%  and absent in 61 ears (68.5%) .CM was recorded in 99 ears. A statistically significant difference was found in CM amplitude mean between the ears with OAEs present and the ears with OAEs absent,  and in the ears not used hearing aids compared to the ears used hearing aids .Also a statistically significant difference in the CM duration  between the ears with tympanogram type A or As compared to the ears with tympanogram type B, and no significant statistical difference was observed in the rest of the measurements . The most common risk factor presented as a single factor was nuclear jaundice (Kernicterus) , and there were no statistical differences in the characteristics of the OAEs and CMs depending on the presence or absence of risk factors . Of the 10 cases that MRI were performed, it was found one case with absence of the cochlear nerve and 3 cases with cochlear nerve  hypoplasia, of which, two cases were associated with hypoplasia of the  optic  nerve.   Conclusions : Characteristics and specifications of each of CMs and OAEs are varying between the cases , depending on the presence of OAEs or absence - depending on the pathology of the middle ear , and there may be a clear  effect of using of hearing aids on the absence of OAEs or absence of CM but this effect may also be related to age or within the course of the disease, and needs further studies . Emphasis must be placed on the MRI for all cases diagnosed with AN  to rule out the presence of a concomitant neurological injury, absence or atrophy of the cochlear nerve in order to establish an accurate diagnosis and appropriate management of the case.