Role of cochlear microphonic in newborn hearing test

Abstract

BACKGROUND AND OBJECTIVES: Cochlear microphonic (CM) is an electrical potential generated by outer hair cells in response to acoustic stimulation. The aim of this study is to evaluate the significance of CM in neonatal hearing loss. SUBJECTS AND METHOD: From April 2013 to April 2014, 64 neonates hospitalized in neonatal intensive care unit were enrolled. Subjects underwent transient evoked otoacoustic emission (TEOAE), auditory brain stem response (ABR) and CM. We analyzed the results of hearing tests and the correlation between CM and the other test modalities. RESULTS: Ninety two ears showed normal ABR waves whereas the other 36 ears had abnormal ABR. There were two neonates who were suspected of auditory neuropathy because of the presence of TEOAE and CM. Among 14 ears who showed abnormal OAE results, 12 ears (86%) were identified as having CM. The amplitudes of CMs were correlated with the reproducibility of TEOAE (p<0.005). Between the ears with positive TEOAE and others with negative TEOAE, the amplitudes of CMs were significantly different (p<0.005). CONCLUSION: Many ears were identified with the presence of CM without TEOAE response because of the the vulnerability of OAE from middle ear status and environment. We suppose that CM might provide information on outer hair cell function to complement the OAE in neonatal hearing test.