Decreased sound tolerance (DST) is an underappreciated condition that affects the lives of a significant portion of the general population. There is lack of agreement regarding definitions, specific components, prevalence, methods of evaluation, and methods of treatment. Limited data are available on the results of treatments. Research is scant and constrained by the lack of an animal model. This article proposes a definition of DST and its division into hyperacusis and misophonia. The potential mechanisms of these phenomena are outlined, and the results of treatment performed at Emory University are presented. Out of 201 patients with DST, 165 (82%) showed significant improvement. Of 56 patients with hyperacusis (with or without misophonia), 45 (80%) showed significant improvement. This proportion was higher for the group with hyperacusis and concurrent misophonia (33 of 39, or 85%) and lower for patients with hyperacusis only (13 of 17, or 76%). Effectiveness of treatment for misophonia with or without hyperacusis was identical (152 of 184, 83% and 139 of 167, 83%, respectively, for misophonia accompanied by hyperacusis and for misophonia only). Even with current limited knowledge of DST, it is possible to propose specific mechanisms of hyperacusis and misophonia and, based on these mechanisms, to offer treatments in accordance with the neurophysiological model of tinnitus. These treatments are part of Tinnitus Retraining Therapy (TRT), which is aimed at concurrently treating tinnitus and DST and alleviating the effects of hearing loss. High effectiveness of the proposed treatments support the postulated mechanisms.

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Tinnitus retraining therapy (TRT) is a method for treating tinnitus and decreased sound tolerance, based on the neurophysiological model of tinnitus. This model postulates involvement of the limbic and autonomic nervous systems in all cases of clinically significant tinnitus and points out the importance of both conscious and subconscious connections, which are governed by principles of conditioned reflexes. The treatments for tinnitus and misophonia are based on the concept of extinction of these reflexes, labeled as habituation. TRT aims at inducing changes in the mechanisms responsible for transferring signal (i.e., tinnitus, or external sound in the case of misophonia) from the auditory system to the limbic and autonomic nervous systems, and through this, remove signal-induced reactions without attempting to directly attenuate the tinnitus source or tinnitus/misophonia-evoked reactions. As such, TRT is effective for any type of tinnitus regardless of its etiology. TRT consists of: (1) counseling based on the neurophysiological model of tinnitus, and (2) sound therapy (with or without instrumentation). The main role of counseling is to reclassify tinnitus into the category of neutral stimuli. The role of sound therapy is to decrease the strength of the tinnitus signal. It is crucial to assess and treat tinnitus, decreased sound tolerance, and hearing loss simultaneously. Results from various groups have shown that TRT can be an effective method of treatment.

The First International Conference on Hyperacusis gathered over 100 scientists and health care professionals in London, UK. Key conclusions from the conference included: (1) Hyperacusis is characterized by reduced tolerance of sound that has perceptual, psychological and social dimensions; (2) there is a growing awareness that children as well as adults experience symptoms of hyperacusis or misophonia; (3) the exact mechanisms that give rise to hyperacusis are not clear, but the available evidence suggests that functional changes within the central nervous system are important and in particular, hyperacusis may be related to increased gain in the central auditory pathways and to increased anxiety or emotional response to sound; (4) various counseling and sound therapy approaches seem beneficial in the management of hyperacusis, but the evidence base for these remains poor.