Hyperaucusis
Have you ever heard a sound so loud it hurt your ears, and made you emotionally upset? How about dozens of times a day---and nobody understands you, because they don't hear it? (at least not as loud as you do) That's what patients with hyperacusis endure day after day after day, feeling isolated and misunderstood because too often, even their doctors have never heard of their condition.
Hyperacusis is the scientific name for extreme sensitivity to sound. It is a condition so rare that it strikes only one person in 50,000. It is caused by ear trauma (exposure to extremely loud sounds, head injuries, epilepsy, ear infections, allergies, Bell's Palsy, and certain drugs). It can make a person's life a living hell, where they can't carry on a normal conversation, take a shower, ride in a car, or many other normal activities because they can't tolerate the sounds involved, because they seem so loud. Ninety percent of hyperacusis victims also have tinnitus (ringing in the ears) and each exposure to a loud noise makes the condition worse--necessitating constant protection of the ears, meaning a secluded life, often on disability, as victims can't tolerate noise in the workplace. There are other, related disorders, hyperacute hearing, which is almost identical to hyperacusis, except the victim is born with it and it usually accompanies autism, and recruitment, a more common type of sound sensitivity that usually strikes the elderly. The thing that all these hearing disorders have in common is that sounds that fail to cause discomfort to normal ears can cause pain to the ears of their victims.
There are treatments--white noise earphones for hyperacusis (both normal sound and complete silence worsens the condition) and Auditory Integration Therapy for hyperacute hearing (which consists of listening to specially filtered music--usually Mozart-- for two hours a day for ten consecutive days). But treatment is often very expensive--up to $ 600.00 for a course of AIT. And while the treatments help some people--they are not a panacea. There are many ways to cope. Using earplugs in noisy situations, and avoiding noisy places. Eating in a restaurant away from peak hours and away from the dish-clattering kitchen is one simple example. Watching religious services on TV at home instead of going to services where there is loud clapping and singing is another. Staying away from loud appliances, using electric lawnmowers, or even paying someone else to do the job is another.
Hyperacusis is used to describe a high level of sensitivity to sound. It is also known as dysacusis, oxylacusis, hypersensitive hearing, or phonophobia. Persons with hyperacusis do not show abnormal loudness growth but an abnormal discomfort for suprathreshold sound. Audiograms for hyperacusis sufferers are typically normal. They show normal sound thresholds but the sensitivity level is above normal. The comfort level for most people is below 100 decibels. People with hyperacusis can experience discomfort at 40 to 50 decibels or lower. The disorder may be frequency-specific. Not all sounds of the same loudness (number of decibels) cause discomfort, but only sounds within a certain range, thus a small change of frequency may cause discomfort at low volume.
The prevalence rate of hyperacusis is unknown. It frequently occurs with tinnitus, which afflicts approximately 40 million poeple in the United States. A questionnaire in a clinic population by Sanchez and Stephens (1997) found that eight percent of tinnitus sufferers have hyperacusis. These two studies would suggest about 3 million people in the United States have hyperacusis. Further a survey conducted by the Autism Research Institute found up to 40% of children with autism to be affected by hyperacusis. Hyperacusis also has an occurence rate of 95% in children with Williams syndrome. These facts plus its comorbidity with many other diseases leads one to believe hyperacusis is not an extremely rare disease.
Hyperacusis is a poorly understood disorder resulting in many theories of etiology and prognosis. Hyperacusis can occur alone or in conjunction with other disorders. A sudden single burst of noise, a head injury, or surgery to the face or jaw can result in hyperacusis. There are two types of hyperacusis, peripheral and central.
Peripheral hyperacusis is when the ears built in mechanism against loud or sharp sound seems to have been turned off. Absence of acoustic reflexes, positive history of vestibular disorders, Meniere's disease, or perilymph fistula account for peripheral hyperacusis. Hyperacusis co-occurring with Bell's palsy, Ramsey Hunt syndrome, and myasthenia gravis is also considered to be peripheral hyperacusis. Hyperacusis is also an otological complication of herpes zoster and craniomandibular disorders.
NOTE: for more updated information, please also check out www.hyperacusis.net.
For more information, call the Hyperacusis Network at: 1--920--468--4667 or the American Tinnitus Association at: 1--503--248--9985
Here is another link for more information:
The Canadian Tinnitus & Hyperacusis Centre
Recruitment
A normal ear is able not only to hear extremely quiet sounds (between 0 and 20dB hearing level) but can also tolerate very loud sound without discomfort (up to levels of 115dB hearing level). With hearing loss an inability to hear quiet sounds may be coupled with a paradoxical intolerance for loud sounds due to recruitment. An ear with recruitment might well be unable to hear sounds, particularly high frequency sounds, below 50dB, but find any sounds above 80dB not only uncomfortable but liable to produce distortion.
Recruitment is due to a reduction in neural elements in the inner ear (usually the hair cells), so that a small change in stimulus intensity produces a bigger change in response of the inner ear. More nerve fibres are switched on or 'recruited', for a corresponding sound stimulus. Another way to look at this problem is to consider the ear rather like a musical instrument. Nevertheless many people, perhaps the majority, who have hypersensitivity and hearing loss, have hyperacusis rather than recruitment, or may have some degree of both. Even if recruitment exists it is possible to retrain the brain (central processing) to alter its appreciation of loudness and accommodate the smaller dynamic range of the hearing impaired, and recruiting cochlea. Where the hearing is normal, or near normal , hypersensitivity is always due to hyperacusis (plus or minus phonophobia) and NEVER due to recruitment. This concept may represent a fundamental change of thinking to traditional views given by many health care professionals.
Treatment of Hyperacusis With Hearing Loss
With hearing lossWhere there is a hearing loss and a need for a hearing aid fitting, this must be done without overloading the ear with amplified sound. Many hearing aids have some form of compression which stops loud sounds entering the hearing aid from being over-amplified. Automatic volume control is available on most hearing aids and non-linear compression is a more advanced type, that may help some hearing impaired people with hyperacusis and/or recruitment. Programmable hearing aids frequently make the task of appropriate hearing aid fitting easier.
In fitting hearing aids to sensitive ears, it is best to leave the ear canal as un-occluded as possible, particularly to begin with. Where there is simply a relatively small high frequency hearing loss, an "open" mould should be used. Where more amplification is needed, the mould should be vented to allow the escape of unwanted high levels of low frequency sound. Trials with different sorts of ear moulds can often be very helpful.