Hyperacusis

Definitions and Terminology

Hyperacusis does not refer to the ability to hear very quiet sounds at long distances. Instead, it is the perception of sounds of moderate physical intensity (that are usually well tolerated by people) as being loud, intrusive, and overwhelming. Other terms used to describe this condition include reduced, decreased, or collapsed sound tolerance. The term phonophobia has been used to describe hyperacusis, but now it is generally restricted to the specific noise sensitivity that can occur during a migraine attack. Misophonia is a related but separate condition, wherein a person develops aversion to specific trigger sounds, such as breathing or chewing noises and can experience overwhelming rage when exposed to a trigger sound.

The experience of hyperacusis varies from person to person, and some clinicians and researchers try to subtype and classify hyperacusis to try to make sense of this. The classifications used include hyperacusis where the main feature is either [Page 875]loudness, annoyance, fear, or pain. Although this can be helpful as a framework within which experiences can be classified, in reality, many patients experience several or all of these features, and while one may be slightly more severe than others, to classify them by that one alone does not do justice to their situation.

Epidemiology

Hyperacusis, and the debilitating effects of hyperacusis, can be experienced by adults, adolescents, and children. Knowledge about the prevalence of hyperacusis is limited. One particular problem with research in this area is that each study has asked a differently worded question about decreased sound tolerance, so the estimates cannot be directly compared. The most reliable estimates indicate that about 2% of adults and 3% of children have hyperacusis at any one time. Information about the natural history of hyperacusis (i.e., does it improve, stay the same, or worsen over time or as the person gets older) is scant, but what is clear is that for some people this is a long-term and chronic condition.

In some instances, people report having both hyperacusis and tinnitus. About 40% of people with a primary complaint of tinnitus experience hyperacusis, and almost 90% of people with a primary complaint of hyperacusis experience tinnitus: These figures hold for both adults and children. What is less clear is how severe the secondary symptom is in such cases, which to treat first, and how far this is an indication of a common mechanism. For several years, there has been an assumption that the association between hyperacusis and tinnitus is indicative of some form of commonality, though this idea is increasingly coming into question.

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