Unveiling the Cochlear Physiology Behind Hidden Hearing Loss

Purpose: The study is aimed at identifying the cochlear physiology behind hearing impairment at extended high frequencies (EHF) despite having a normal threshold in conventional audiogram. Secondly, it is compared with the levels of Distortion Product Oto Acoustic Emissions (DPOAE). Methods: A total of 21 participants were included in the study, who have EHF loss with normal Pure tone Audiometry (PTA) thresholds. EHF testing was performed exclusively at 10 kHz, 12.5 kHz, 14 kHz, and 16 kHz using Modified Hughson-Westlake procedure. Distortion Product OAE levels were also estimated at 2 kHz, 4 kHz, and 5 kHz. Results: Significant correlation between EHF loss and DPOAE levels was seen in 10 out of the 21 participants (47.6% of the total) for one or more of the standard frequencies and ears. Whereas DPOAE’s were present in the remaining participants. Conclusions: Reduced or absent DPOAE levels with EHF loss in spite normal audiogram results reveal the potential aetiology as Cochlear Synaptopathy leading to Hidden Hearing Loss. This demands the inclusion of EHF audiometry for unveiling Hidden Hearing Loss in assessing young and adult population. It brings forth a significant change in the outcomes of Early Intervention.