Timothy C. Hain, MD Page last modified: February 5, 2013
Hyperacusis defined Causes Diagnosis Treatment
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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.
|The structures of the inner ear.|
What causes hyperacusis ?
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'). However, the evidence is not strong. In our clinical experience, in hyperacusis, inner ear disease is much less common than other disorders that cause hyperacusis (e.g. migraine). Obviously, deaf people can't have hyperacusis (just as people without inner ear function don't experience motion sickness). When hyperacusis is accompanied by hearing loss, the association could be a mistake (i.e. hearing loss due to age or wear/tear), or caused by irritibility of the hair cells (such as in Meniere's disease), an increase in central gain, or a disorder where there is increased sensitivity to sound (e.g. Superior canal dehiscence).
In inner ear disease, loss of hearing at one frequency may be accompanied by increased sensitivity around the area of the hearing loss, resulting in hyperacusis. Thus a focal hearing loss may be more likely to cause hyperacusis due to an overly broad increase in central sensitivity (this is just a conjecture). According to Spyridakou et al (2012), difficulty with hearing speech in noise does not correlate with hyperacusis, but increased suppression of OAE's by noise does. This would support the conjecture that hyperacusis does not correlate with significant hearing loss.
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 is not a problem in completely deaf people (of course). Hyperacusis also sometimes appears after 7th nerve (Bells palsy) injuries, which paralyze one of the two small ear muscles that protect the ear from loud noise.
Hyperacusis for ones own eye movements -- i.e. an ability to hear ones eyes move, can occur after surgery for tumors of the inner ear(Coad, Lockwood et al. 2001; Biggs and Ramsden 2002) as well as in the SCD syndrome(Schmuziger, Allum et al. 2006)
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 (Central hyperacusis):
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). Contralateral suppression deficits have been reported. (Attius, 2005)
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.
How Is Hyperacusis Treated ?
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. There is also evidence that serotonin pathways are implicated in hyperacusis as well as migraine. 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.
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". 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, 2000) TRT is presently a popular approach. 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).
We have encountered a few patients who had hyperacusis after loud noise, respond very well to a PE tube. We think that this is more likely than not due to treatment of an oval window fistula in these patients.
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 plus a few newer ones are listed below. This is a relatively small amount of research effort.
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