Hyperacusis

Hyperacusis is a health condition characterized by an over-sensitivity to certain frequency ranges of sound (a collapsed tolerance to normal environmental sound).

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 has been affected (efferent meaning fibers that originate in the brain which serve to regulate sounds). This theory also suggests that the efferent fibers of the auditory nerve are selectively damaged, while the hair cells that allow us to hear 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.

Although severe hyperacusis is rare, 40% of tinnitus patients complain of mild hyperacusis.

Causes
The most common cause of hyperacusis is overexposure to excessively high decibel levels (or sound pressure levels). Hyperacusis is also common in advanced Lyme disease due to nerve inflammation and the neurotoxic nature of the spirochetal bacteria. If successfully treated, many lyme patients' noise tolerance returns to normal. Other causes include, but are not limited to:
 * Severe head trauma
 * Surgery
 * Ear irrigation
 * TMJ (Temporomandibular joint disorder)
 * Adverse drug reaction
 * Williams Syndrome
 * Autism
 * Bell's palsy
 * Ménière’s disease
 * Asperger syndrome
 * Superior Canal Dehiscence Syndrome
 * Chronic ear infections
 * Minor Head Injury

Treatment
The most common treatment for hyperacusis is retraining therapy which uses broadband noise. Tinnitus Retraining Therapy (TRT), a treatment originally used to treat tinnitus, uses broadband noise to treat hyperacusis. Pink noise can also be used to treat hyperacusis. By listening to broadband noise at soft levels for a disciplined period of time each day, patients can rebuild (i.e., re-establish) their tolerances to sound. When seeking treatment, it is important that the physician determine the patient's [Loudness Discomfort Levels]] (LDL) so that hearing tests (brainstem auditory evoke response) or other diagnostic tests which involve loud noise (MRI) do not worsen the patient's tolerance to sound.