• 03 MAY 15

    Hyperacusis

    Hyperacusis

    Imagine being at a movie where the sound track is turned up all the way. The turning of newspaper pages, running water in the kitchen sink, a family setting the table – are all intolerable to your ears. When a baby cries upstairs and a truck suddenly screeches into view, the sound is so excruciating that before the film has run for even five minutes you and your family leave.

    The person who has hyperacusis cannot simply get up and walk away to escape this scenario. Instead, the volume on the world is turned up to full. Hyperacusis is an unusual hearing condition. The ears lose most of their dynamic loudness range, and everyday ambient noises sound unbearably or painfully loud. Dynamic range is the ability of the ear to deal with a wide range of volume. With hyperacusis, the ear’s “volume control knob” is broken.

    This disorder generally is chronic and often accompanied by tinnitus (head noises), but a charismatic of hyperacusis is that it can occur in patients who have little or no measurable hearing loss. For this reason medical specialists believe hyperacusis differs from recruitment, which is the abnormal growth in the perception of loudness not uncommon in people with hearing loss. For patients with recruitment, loud noises are uncomfortable. With hyperacusis all sounds are.

    A life altering malady

    Hyperacusis makes living the noisy 21st century difficult, and dramatically changes the patient’s pattern of life. Moving about, travelling and communicating with others is difficult. In many cases, ear protection must be worn most or all of the time; ear plugs or industrial ear muffs or both simultaneously. Even then, patients report that maximum protection often is not sufficient to block certain frequencies or intensities.

    The things that most of us do or take for granted, such as driving a car, walking down the street or riding a bicycle, listening to a television, shopping, attending musicals or athletic events, and movies, going out to restaurants or clubs, or participating in group activities often are difficult or impossible with people with hyperacusis. They would normally not be able to use a vacuum, hammer, or a motorboat or motorcycle. Most frightening many hyperacusis patients find their livelihoods threatened by their condition because most jobs involve some level of noise.

    Noise exposure generally makes the condition worse and exacerbates the accompanying tinnitus. Patients report that they perceive sounds – even their own or another person’s voice – as uncomfortably loud, and this not only causes tinnitus to increase but may also cause pain, fullness or a popping reflex in the ear.

    Hyperacusis can come on suddenly or slowly. Many patients say they developed hypersensitivity to sound over many years, observing that using hearing protection helped initially but then became less and less effective as time passed. These people find that their tinnitus is more noticeable because ear protection shuts out many of the ambient sounds that usually help to cover up sounds in their head.

    A puzzling problem

    Hyperacusis is a poorly understood disorder. Doctors who have seen their patients with the symptoms know that trauma such as loud noise, along with other insults to the ear can precipitate hyperacusis. In addition super sensitive hearing is seen medically in post-operative surgical cases involving the jaw or face, Bell’s palsy, Meniere’s disease, Tay-Sachs disease and TMJ syndrome. The appearance of hyperacusic symptoms in these disorders may provide tantalising clues as to the causes of hyperacusis because in the facial/jaw surgery. Bell’s and Meniere’s disease the hypersensitivity seems to disappear once the patient completely heals from the surgery or once Bell’s or Meniere’s goes into remission or resolves itself.

    Presumably the protective mechanisms a normal ear employs to minimise the harmful effects of loud noise are malfunctioning, so noise is harmful to the hyperacusis person when he or she wears hearing protection. For example, in someone with an extreme case, the noise of an air conditioner or dental office music will raise the level of tinnitus even though the person is wearing ear plugs. There is some speculation that the efferent portion of the auditory nerve – efferent meaning fibres that originate in the brain – serves to regulate or inhibit incoming sounds. A breakdown or dysfunction in this system is a possible explanation of this bizarre condition.

    The real puzzle is why hyperacusis most often shows up in patients who have little or no discernible hearing loss. This baffles ear specialists familiar with recruitment, which is associated with hearing loss but which also occurs in normal ears at extremely intense levels of sound. A theory about hyperacusis is that the efferent fibres of the auditory nerve are selectively damaged even while the hair cells that allow us to hear pure tones in an audiometry evaluation remain intact. Even with regular tinnitus, an estimated 10% of all patients with tinnitus have no measurable hearing impairment so that it comes as no surprise that other ear pathologies – hyperacusis, in this case – can occur in the absence of hearing loss.

    Preventing noise damage

    Like tinnitus, hyperacusis may prove to have many causes. Although the disorder has been reported by patients who could not trace a specific causative event, it definitely can be a result of exposure to loud sounds. Musicians and music fans report that their ears became more and more sensitive to sound after prolonged or repeated exposure, but some patients report that they became hyperacusic after a single loud noise exposure, such as a cordless telephone or a gunshot. But loud noise seems particularly associated with presbycusis, perhaps because of music’s broad range of frequencies and the intensity of volume that is common in live performances.

    The progression of hyperacusis is unpredictable and variable. For some, tolerance does improve over time, while for others it grows steadily worse. Again, the only factor that unquestionably affects progression or regression is continued exposure to noise. Although the nature of hyperacusis is that it generally increases in volume whenever damage – such as renewed exposure occurs, the level may rise either temporarily or permanently.

    Several treatment strategies have been tried clinically, though none as yet in a controlled, methodical fashion. Some patients report they have seen improvement in sound tolerance through the use of tinnitus masking devices, instruments similar to a hearing aid, that emit a high frequency band of noise. This is intended to desensitise the ear and is done with the sound gradually increased over a period of time. Among other therapies tried are medications that increase blood flow or circulation; anti-depressant and anti-anxiety drugs such as those used for tinnitus; biofeedback and relaxation therapy and dental treatments for TMJ dysfunction.

    The underlying reasons why some people are more susceptible to ear problems than others are not understood. Not everyone exposed to loud sounds will develop hyperacusis, and all patients who have hyperacusis do not report unusual noise exposure. But one thing is certain; of the various catalysts for the onset of hyperacusis, noise is the most common and the only preventable one. Avoid loud noises whenever possible and ear protection – ear plugs or ear muffs – when loud sounds are unavoidable.

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