Objective Test of Cochlear Dead Region: Electrophysiologic Approach using Acoustic Change Complex

Soojin Kang,Il Joon Moon,Heesung Park,Carolyn J Brown,Jihwan Woo,Sung Hwa Hong

doi:10.1038/s41598-018-21754-7

Abstract

The goal of this study was to develop an objective and neurophysiologic method of identifying the presence of cochlear dead region (CDR) by combining acoustic change complex (ACC) responses with threshold-equalizing noise (TEN) test. The goal of the first study was to confirm whether ACC could be evoked with TEN stimuli and to also optimize the test conditions. The goal of the second study was to determine whether the TEN-ACC test is capable of detecting CDR(s). The ACC responses were successfully recorded from all study participants. Both behaviorally and electrophysiologically obtained masked thresholds (TEN threshold and TEN-ACC threshold) were similar and below 10 and 12 dB SNR in NH listeners, respectively. HI listeners were divided into HI (non-CDR) and CDR groups based on the behavioral TEN test. For the non-CDR group, TEN-ACC thresholds were below 12 dB which were similar to NH listeners. However, for the CDR group, TEN-ACC thresholds were significantly higher (≥12 dB SNR) than those in the NH and HI groups, indicating that CDR(s) can be objectively detected using the ACC. Results of this study demonstrate that it is possible to detect the presence of CDR using an electrophysiologic method.

Highlights

While PTCs are considered the gold standard for detecting cochlear dead region (CDR)(s), they are time-consuming to obtain and are rarely measured in clinical settings
While the electrophysiological measures are not as sensitive as the behavioral measures, the threshold-equalizing noise (TEN)-acoustic change complex (ACC) thresholds were below the 10 dB criterion of CDR(s) proposed by Moore et al.[32]
The dashed line on the right panel indicates potential criterion that we suggest to confirm the presence of CDR in an electrophysiologic TEN-ACC test

Summary

Introduction

While PTCs are considered the gold standard for detecting CDR(s), they are time-consuming to obtain and are rarely (if ever) measured in clinical settings. The TEN test is relatively simple and fast to administer and studies have shown that it can be an effective method for identifying CDRs in hearing-impaired listeners[1,3,14]. It requires behavioral responses from the subject which is inappropriate for infants/young children, individuals who are not inclined to cooperate or individuals with developmental delays or other cognitive challenges. The goal of the second study was to evaluate the feasibility of using the TEN-ACC test to detect CDR(s) in HI listeners

Methods

Results

Conclusion