Hyperacusis and Tinnitus

One well-accepted definition of hyperacusis is that it is a general hypersensitivity or hyper-reactivity to sounds, which are well-tolerated by other people or by the person itself in the past. The major impact is on the level of the behavioural response, as patients with hyperacusis are likely to avoid loud sounds due to their subjective aversiveness, which again leads to avoidance of normal sounds as well because of the increased sensitization of their hearing system. For the assessment of hyperacusis, psychoacoustic measurements (uncomfortable loudness levels (ULLs)) and different questionnaires for the various psychological symptoms are available. Animal and human neuroscience studies of hyperacusis (in tinnitus) mostly affirm the prominent model of increased central neural gain (increased sensitization of the hearing system). This fits well with the most prominent treatment of desensitization to avoided sounds as implemented in psychology-based interventions such as cognitive behavioural therapy (CBT). This sounds like a success story. However, open issues are related to hyperacusis subtyping, overcoming the limited validity and small correlation of audiological measures and questionnaires, disentangling mechanisms of hyperacusis and tinnitus from those of other conditions, transferring neuroscience data to personalized treatment regimens and, overall, affirming the proposed concepts with experimental data. Thus, more research is needed, as can be seen in the available literature, which shows that hyperacusis is the smaller and later-born sibling of tinnitus.