Hyperacusis
| Hyperacusis | |
|---|---|
| Classification and external resources | |
| Specialty | otolaryngology |
| ICD-10 | H93.2 |
| ICD-9-CM | 388.42 |
| DiseasesDB | 29099 |
| MeSH | D01200178 |
Hyperacusis (also spelled hyperacousis) is a health condition characterized by an increased sensitivity to certain frequency and volume ranges of sound (a collapsed tolerance to usual environmental sound). A person with severe hyperacusis has difficulty tolerating everyday sounds, some of which may seem unpleasantly or painfully loud to that person but not to others.
It can be acquired as a result of damage sustained to the hearing apparatus, or inner ear. There is speculation that the efferent portion of the auditory nerve (olivocochlear bundle) has been affected (efferent meaning fibers that originate in the brain which serve to regulate hearing). This theory suggests that the efferent fibers of the auditory nerve are selectively damaged, while the hair cells that allow the hearing of pure tones in an audiometric evaluation remain intact. In cases not involving aural trauma to the inner ear, hyperacusis can also be acquired as a result of damage to the brain or the neurological system. In these cases, hyperacusis can be defined as a cerebral processing problem specific to how the brain perceives sound. In rare cases, hyperacusis may be caused by a vestibular disorder. This type of hyperacusis, called vestibular hyperacusis, is caused by the brain perceiving certain sounds as motion input as well as auditory input.
Although severe hyperacusis is rare, a lesser form of hyperacusis affects musicians, making it difficult for them to play in the very loud environment of a rock band or orchestra which previously gave them no problems. It also makes attendance at loud discos or live events difficult for a portion of the population, given that sound levels at such events usually exceed recommended safe levels of exposure. This is a problem which may be caused by genetic differences, stress or ill-health, or by abnormal responses in the tensor tympani (tonic tensor tympani syndrome) and stapedius muscles, which function in the normal acoustic reflex response that protects the inner ear from loud sounds.
25% of people with tinnitus report mild hyperacusis.
In cochlear hyperacusis (the most common form of hyperacusis), the symptoms are ear pain, annoyance, and general intolerance to any sounds that most people do not notice nor consider unpleasant. Crying spells or panic attacks may result from cochlear hyperacusis. As many as 86% of people with hyperacusis also have tinnitus.
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