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Timothy C. Hain,
MD 
Page last modified:
January 9, 2008
Hyperacusis defined
Causes
Diagnosis
Treatment
Hyperacusis Defined:
Hyperacusis is an abnormal sensitivity to sound. About 8% of the population report hyperacusis (Andersson, G., N. Lindvall, et al., 2002).
This is a review on hyperacusis written from the perspective of an otoneurologist (Dr. Hain). It emphasizes mechanisms for hyperacusis outside of inner ear disease.
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| The structures of the inner ear. |
There are many causes of hyperacusis (Katznell and Siegel, 2001).
Inner ear: Most hyperacusis is considered to be associated with damage to the inner ear, specifically the cochlea (the snail like thing on the right labelled '9'). Here, the mechanism is probably either irritibility of the hair cells (such as in Meniere's disease), or a disorder where there is increased sensitivity to sound (e.g. Superior canal dehiscence). Inner ear disease is much less common than other disorders that cause hyperacusis (e.g. migraine).
8th nerve: Hyperacusis can also arise from damage to the nerve between the ear and brain (8th nerve, labeled 6, auditory nerve). Examples here might be hyperacusis after a sudden hearing loss (attributed to viral damage to the hearing nerve), or microvascular compression syndrome. Hyperacusis also sometimes appears after 7th nerve (Bells palsy) injuries, which paralyze the small muscles that protect the ear from loud noise.
Brainstem: The next step in the hearing cascade is the cochlear nucleus in the brainstem. Brainstem hearing disorders are rare, and it is also thought that brainstem hyperacusis is exceedingly rare. There have been a few cases reported however (Pfadenhauer, K., H. Weber, et al., 2001).
Brain: Hyperacusis is very often associated with migraine (where it is caused phonophobia). Because migraine is extremely common (10% of the population), it likely accounts for at least 90% of all hyperacusis. Migraine involves serotonin pathways, which are also postulated to be at the root of central hyperacusis (Marriage and Barnes, 1995). In theory, hyperacusis might also be due to an irritibility of central auditory pathways, as for example, in a person with a seizure disorder.
Psychological: In the audiology community, the hypothesis is sometimes advanced that persons with hyperacusis have caused this problem themselves, by avoiding exposure to ordinary sounds. We find this implausible, but avoidance may add to the problem.
Misc: Persons with Williams syndrome all have hyperacusis (Klein). This pediatric syndrome is characterized by cardiac defects, varying degrees of physical and developmental delay, stellate eye pattern, possible elevated serum calcium level, and elfin/pixie facial features.
How is hyperacusis diagnosed ?
Persons with hyperacusis should be evaluated by a physician expert in ear disease, usually an otologist, neurotologist, or otoneurologist. There should be an examination of the ears. If there is also sensitivity to other sensory input (such as bright light, strong smells, motion) and/or headaches, a neurologist or otoneurologist would be the most appropriate as multiple sensory sensitivity is outside the spectrum of disease usually seen by ear doctors.
Hearing should be tested with an audiometer (i.e. not just tuning forks or other screeners), and the "UCL" audiogram should be obtained (uncomfortable loudness levels). Goldstein, B. and A. Shulman (1996). Otoacoustic emmissions may be helpful (OAE's).
Acoustic reflexes may detect persons with paralysis of their stapedius.
A careful history should be taken, especially for migraine. Persons with migraine often have small white matter lesions that may be seen on the MRI. In addition to hyperacusis, persons with migraine often have photophobia (sensitivity to bright light), motion intolerance, sensitivity to strong smells, and sometimes even unusual cutaneous sensitivity (allodynia). The treatment approach for migraine is completely different than that for other types of hyperacusis.
A psychological assessment may detect persons who have associated anxiety, depression or obsessive compulsive personality disorder (OCD). Those with auditory hallucinations may have a psychiatric disorder such as schizophrenia. Finding these things usually does not mean that the person's hyperacusis is caused by psychiatric problems, but rather may indicate a comorbidity. Usually it results in a medication recommendation.
Medications used in treatment of Hyperacusis
Medications may occasionally help lessen the hyperacusis even though no cause can be found. In general, we are not at all enthused about medication treatment as the side effects can be substantial and the results are often unimpressive. Medications to deal with the psychological fallout of hyperacusis is often useful -- antidepressants and anti-anxiety medications can be very helpful.
Comment. Benzodiazepines and and antidepressants probably reduce anxiety, depression, or obsessive thinking about hyperacusis. Any sort of relief, however, is important. Antimigraine drugs act by preventing migraine, which commonly has hyperacusis. Anti-seizure drugs may be effective in persons with hyperacusis due to irritible neural pathways. Baclofen has been suggested to be useful in reducing responses in brainstem hyperacusis (Szczepaniak, W. S. and A. R. Moller, 1996).
Comment: Ear plugs work by decreasing the amount of sound that the person is exposed to. This approach is generally frowned upon, because there is a feeling that wearing ear plugs over the long term will increase hyperacusis. It is thought that exposure to noise is habituating, and reducing the noise reduces the habituation effect. Nevertheless, as is the case with sunglasses when people are bothered by bright light, ear plugs or muffs can be very useful ( Sammeth, C. A., D. A. Preves, et al., 2000). Electronic noise suppression devices are used similarly, but they are less effective in reducing high-frequencies than passive methods.
Maskers/ sound generators work by conditioning the nervous system to tolerate sound. They are similar in appearence to a hearing aid. Examples of maskers include the Starkey Silent-Star, and the GHI "Tranquil". Controlled studies of maskers have shown some small effects on tinnitus (Dobie, 1999). These devices are readjusted every month to gradually accomplish desensitization. (Vernon, J. A, 1987).
TRT (Tinnitus Retraining Therapy) is a mixture of psychotherapy and masking (for tinnitus) or sound generators (for hyperacusis). (Jastreboff, P. J. and M. M. Jastreboff, 2000) TRT is presently a popular approach. This method of habituation of tinnitus is helpful for some (Wang et al, 2003). It requires considerable time commitment
Psychological help: Often, anxiety or depression which accompanies hyperacusis may be as big a problem as the hyperacusis itself. In this instance, consultation with a psychologist or psychiatrist expert in this field may be helpful. If you can ignore hyperacusis rather than obsess about it, this may be the best way to handle it. Medications that help people with obsessive compulsive disorder (such as the SSRI family) may be helpful.
Surgery is rarely used for treatment of hyperacusis. In persons where hearing is unusable, surgery has been reportedly successful. Cherry, J. R. and M. J. Brown (1996).
While seemingly logical, we do not know of any attempts to treatment of hyperacusis via purposeful reduction of hearing via ototoxic medication or surgery to disrupt the ossicular chain. This method of treatment would necessarily sacrifice some hearing.
As of 2005, there were about 45 papers on PUBMED with hyperacusis in their title. The most relevant of this group are listed below. This is a relatively small amount of research effort.
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