Cochlear microphonics recording during ABR threshold testing in children

Abstract

Objective: It is agreed that the cochlear microphonic (CM) arises mainly from the normal outer hair cells (OHCs) in cochlea. The aim of this research is to study the CM characteristics in different hearing profiles and reflect the usefulness of recording CM simultaneously during Auditory Brainstem Response (ABR) threshold testing in children. Methods: This is a retrospective study that included 33 cases comprised of children with autism spectral disorders (ASD), children with cochlear sensorineural hearing loss (SNHL), children with auditory neuropathy spectrum disorder (ANSD) and 41 normal hearing healthy children as controls. The children’s ages ranged from 0.5 to 96 months. Both the CM and ABR waves were simultaneously recorded using alternating split polarity ABR. Results: CM amplitudes and thresholds in normal hearing children with ASD did not significantly differ from normal hearing healthy children. CM were preserved in children with ANSD despite the absence of distortion product OAE responses, but in a significantly lower amplitude than those with DPOAE. There was no statistically significant correlation between the children’s ages and CM amplitude at any intensity level and in any of the different child groups, except in the controls where there was a statistically significant negative correlation between the children’s ages and CM amplitude at 70dBnHL, while there was a statistically significant positive correlation between the children’s ages and CM threshold. There were no differences in the CM amplitude between the two ears at any intensity level in all of the different groups of children. Conclusion: Children with ASD showed comparable outer hair cell function to normal hearing healthy children, reflecting absence of any peripheral hyperacusis due to loudness recruitment. CM should always be searched for when testing young children when there is absence of ABR response with absence or presence of otoacoustic emissions, to avoid any false negative results for ANSD. CM can be preserved in children with SNHL with loudness recruitment. This finding could be confused with ANSD, so CM should be traced down to its threshold for an appropriate diagnosis.

The audiological characteristics of infant auditory neuropathy patients without otoacoustic emission

“…Previous studies showed that the amplitude of CM in AN patients with DPOAE absent was significantly lower than that in normal subjects and AN patients with DPOAE present, and the nonlinear characteristics decreased on the I/O function curve in patients without DPOAE response, with a more linear tendency in amplitude increasing. 15 , 18 , 19 , 20 In this study, under various stimulation intensities, the CM amplitude of OAE absent group was lower than that of OAE present group, consisted with previous studies. It also found that compared with OAE present group, the CM threshold was higher and duration was shorter in OAE absent group.…”

“…Conceivably, CM might be recorded in the absence of OAE if receptor potentials remained intact yet the complex mechanisms underlying active processes and OHCs motility in the cochlea were disrupted. 20 Previous studies showed that the amplitude of CM in AN patients with DPOAE absent was significantly lower than that in normal subjects and AN patients with DPOAE present, and the nonlinear characteristics decreased on the I/O function curve in patients without DPOAE response, with a more linear tendency in amplitude increasing. 15,[18][19][20] In this study, under various stimulation intensities, the CM amplitude of OAE absent group was lower than that of OAE present group, consisted with previous studies.…”

“…Receptor potentials played a role in the generation of OAE, but OAE also depended on OHC motility. Conceivably, CM might be recorded in the absence of OAE if receptor potentials remained intact yet the complex mechanisms underlying active processes and OHCs motility in the cochlea were disrupted 20 …”

“…Conceivably, CM might be recorded in the absence of OAE if receptor potentials remained intact yet the complex mechanisms underlying active processes and OHCs motility in the cochlea were disrupted. 20 …”

Early diagnosis of Auditory Neuropathy in children: a systematic review

“…However, according to McKnight et al ( 2018) and Lang-Roth et pode estar presente apenas o MC, sendo que as OEA podem estar presentes ou ausentes. Dabbous (2016) reforça esta última teoria, afirmando que a realização das OEA em conjunto com a pesquisa do MC é complementar. Este autor defende ainda que o MC pode estar presente mesmo que as OEA estejam ausentes se apenas os mecanismos e a mobilidade das CCE tiverem sido danificados.…”