Hyperacusis

Hyperacusis is a health condition characterized by an over-sensitivity to certain frequency ranges of sound (a collapsed tolerance to normal environmental sound). A person with hyperacusis has difficulty tolerating everyday sounds, some of which may seem unpleasantly 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 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. 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, 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). Some come down with hyperacusis suddenly by firing a gun, having an airbag deploy in their car, experiencing any extremely loud sound, taking ear sensitive drugs, Lyme's disease, Meniere’s, TMJ (Temporo-Mandibular Joint – jaw disorder), head injury, or surgery. Others are born with sound sensitivity (Superior Canal Dehiscence Syndrome), have had a history of ear infections, or come from a family that has had hearing problems. The causes include, but are not limited to:
 * Severe head trauma
 * Facial nerve dysfunction (to Stapedius)
 * 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
 * A vestibular disorder: see below.

Symptoms
In cochlear hyperacusis (the most common form of hyperacusis), the symptoms are ear pain, annoyance, and general intolerance to any sounds that most people don't notice or consider unpleasant. Crying spells or panic attacks may result from cochlear hyperacusis. As many as 86% of hyperacusis sufferers also have tinnitus.

In vestibular hyperacusis, the sufferer may experience feelings of dizziness, nausea, or a loss of balance when certain pitched sounds are present. For instance, someone with vestibular hyperacusis may feel like they are falling and as a result involuntarily grimace and clutch for something to brace themselves with.

Anxiety, stress, and/or phonophobia may be present in both types of hyperacusis. Someone with either form of hyperacusis may develop avoidant behavior in order to try to avoid a stressful sound situation or to avoid embarrassing themself in a social situation that might involve noise.

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.

People

 * Stephen Merritt, of The Magnetic Fields, suffers from this condition.