Audiological Findings in Hidden Hearing Loss: A Scoping Review

Hidden hearing loss (HHL) is characterized by normal audiometric thresholds accompanied by speech perception difficulties, especially in noise, and tinnitus. This study aims to investigate the effects of noise exposure on HHL and evaluate the effectiveness of various audiological test batteries and psychophysical and perceptual measurement methods. This scoping review was carried out by the Joanna Briggs Institute framework and was reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Scoping Reviews (PRISMA-ScR) standards. A literature search was conducted in PubMed and ScienceDirect using the keywords “hidden hearing loss” and “cochlear synaptopathy (CS).” English-language articles published between 2010 and 2023 were screened, and 29 studies involving adults were included. The findings are based on results obtained from audiological test batteries as well as psychophysical and perceptual assessment methods. In groups at risk for HHL and/or CS, elevation of high-frequency audiometric thresholds is associated with early effects of noise exposure and provides an early warning of noise-induced auditory impairment. Studies generally show that noise exposure causes significant changes in auditory brainstem response parameters (decrease in wave I amplitude). Decreases in action potential (AP) amplitude on ECochG, along with the associated increase in the summation potential/AP ratio, may also help assess HHL and/or CS. In conclusion, noise exposure leads to dysfunction in both the peripheral and central auditory systems in the context of HHL and/or CS.