Hyperacusis
Hyperacusis is a health condition characterized by an over-sensitivity to all or certain frequencies 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. Others feel hyperacusis is a brain 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 of sound (industrial hearding trauma, rock concert, personal hearing device). Hyperacusis is also common in advanced Lyme disease due to nerve inflamation 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)
- Adverse drug reaction
- Williams Syndrome
- Autism
- Bell's palsy
- Ménière’s disease
- Superior Canal Dehiscence Syndrome
- Chronic ear infections
Treatment
The most common treatment (therapy) for hyperacusis is sound retraining therapy which utilizes broadband sound. By listening to broadband sound at soft levels for a disciplined period of time each day the patient can rebuild (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 evoke response) or other diagnostic tests which involve loud noise (MRI) do not collapse (worsen) the patients tolerance to sound.