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Hearing Science Research

Identifying Three Otopathologies in Humans

Elder, Adele; Parker, Mark PhD

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doi: 10.1097/01.HJ.0000755496.85722.9e
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Individuals with a hearing threshold lower than 25 dB HL may experience difficulty hearing in the presence of noise. Therefore, under complex listening environments when various background noises are introduced, communication can be difficult and even debilitating. A recently published study was conducted to effectively uncover the etiology of this communication issue in order to better treat individuals in the field of audiology (Hear Res. 2020 Dec;398:108079. doi: 10.1016/j.heares.2020.108079. Epub 2020 Sep 24. PMID: 33011456). Findings from this research not only bring validity to patients’ audiologic concerns but also call attention to the need for reevaluation of the audiologic test battery and normative data values. This research sheds light on the value of hearing health care and allows for more effective use of resources.

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The study was designed to uncover which, if any, significant relationships existed between hearing in noise (HIN) performance, outer hair cell (OHC) function, and auditory nerve (AN) function. The variables were selected from the basic audiometry test battery and included: HIN testing, such as QuickSIN, OHC function tested with distortion product otoacoustic emissions (DPOAE), and AN function measured by electrocochleography (ECochG). The data was analyzed using person correlations and a regression analysis. From this analysis, it was determined that the independent variables—DPOAE SNR, the AP amplitude in ECochG testing, and the product of DPOAE SNR—multiplied by the CAP amplitude have an effect on the results of QuickSIN testing. It was hypothesized that HIN difficulty is derived either from AN dysfunction, OHC dysfunction, or a combination of the two.

The research revealed that there are two types of otopathologies, namely cochlear synaptopathy and OHC dysfunction, which contribute to hidden hearing loss defined as an otopathology present in persons hearing within normal limits (less than 25 dB HL). This data also describes the presence of AN untuning secondary to OHC dysfunction, which is a third otopathology not adequately described by the audiogram. Each of these three otopathologies are undetected by the standard audiometric test battery, often causing the common complaint of difficulty hearing in presence of noise. The data show that hearing in the presence of noise is primarily governed by OHC function while AN untuning also plays a less significant role.

Discussions regarding hidden hearing loss have dominated research in recent years yet have failed to establish patterns indicating an etiology. Without knowing the generation site of dysfunction, further research cannot move towards treatment or prevention. Fortunately, audiological results from this study indicate that OHC dysfunction appears to be the common denominator in individuals with hearing thresholds within normal limits, causing difficulty hearing in the presence of noise. The data provided by the present study has the potential to drive future decisions regarding the standard audiometric testing battery and move toward creating a new standard of testing that reflects the value of each patient.

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