Special Session: Uncovering Hidden Hearing Loss: Noise Exposure, Tinnitus and AgingNoise-Induced Hearing Disorders: Hidden and Not-So-Hidden Injuries The phrase “hidden hearing loss” has been used to refer to 1) decreased amplitude of wave I of the auditory brainstem response (ABR) in the absence of threshold deficits; 2) loss of the synaptic connections between the inner hair cells (IHCs) and the auditory nerve dendrites (“cochlear synaptopathy”) in the absence of outer hair cell (OHC) loss; and 3) tinnitus, hyperacusis, hearing-in-noise deficits, or other suprathreshold hearing disorders that occur independent of hearing loss. The anatomical pathology and supra-threshold functional deficits have been termed “hidden” because they are not captured by the measures most commonly used during human audiometric assessment (the audiogram, and otoacoustic emission (OAE) tests) or in animal studies (ABR threshold, OAE threshold or amplitude, OHC counts). In reality, hearing in noise and tinnitus are common patient complaints, not-so-hidden to either the patient or the audiologist when the appropriate test battery is completed. This session will briefly review specific patterns of cell death, changes in sound evoked OAE and ABR responses, and both threshold shift and deficits “beyond the audiogram” that can be measured in clinical and research laboratory settings. Limitations in the ability to diagnose specific underlying pathology will be summarized, and emerging tools reviewed. A major focus of this session will be review of the current portfolio of clinical trials related to hidden hearing loss, which, as noted above, is not hidden to either the patient or the audiologist when the appropriate test battery is performed. Considerations in the design of clinical trials for prevention or amelioration of two specific suprathreshold deficits, tinnitus and hearing in noise deficits, will be presented. As investigational inner ear medicines targeting hearing loss, tinnitus, and hearing-in-noise deficits enter clinical testing under the regulatory oversight of the US Food and Drug Administration, patient inclusion and exclusion criteria will need to be developed, and criteria for clinically significant patient benefit will be needed. At this time, there are no drugs approved by the FDA for such indications, but there is an active drug development pipeline with major efforts across academic labs, pharmaceutical and biotechnology companies, and venture capital investments.
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