Assessment of Cochlear Synaptopathy in Young Adults’ Noise-induced Hearing Loss

Background: Cochlear synaptopathy, “hidden hearing loss,” is caused by damage to synapses between inner cochlear hair cells and auditory nerve fibers without causing appreciable alterations in audiometric thresholds. It is typically accompanied by prolonged exposure to recreational noise-induced hearing loss (NIHL). Objective: The objective of this study was to evaluate the “hidden hearing loss” caused by cochlear synaptopathy in young adults with NIHL. Materials and Methods: Forty-eight young adults were enrolled in this cross-sectional study and split equally into two groups: Group A, which included 24 participants with a history of prolonged noise exposure (defined as “constant usage of headphones more than 4 h daily for more than 2 years”), and Group B, which included 24 participants of the same age and gender (referred to as the “control group”). Pure tone audiometry and tympanometry, “Middle-Ear Muscle Reflex” (MEMR), electrocochleography (ECochG) with amplitude of summating potential (SP) and action potential (AP), SP/AP ratio, and speech-in-noise (SIN) testing using the QuickSIN test at signal-to-noise ratios (SNRs) were all used in the audiological evaluations. Results: Group A showed significantly higher in mean SP/AP ratio (0.36 ± 0.17 SD) compared to Group B (0.12 ± 0.08), with P < 0.012. QuikSIN test; in Group A showed lower performance, with a mean score of 8.6 ± 1.32 dB SNR loss, compared to Group B, 2.9 ± 0.8 dB, with P < 0.011. In Group A, elevate MEMR thresholds. Conclusion: ECochG and QuikSIN testing demonstrated valuable modalities in early diagnosis of cochlear synaptopathy in young adults with continuous noise exposure via raised SP/AP ratio and poorer SIN comprehension.