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Fri 1 Jun 2007 12:00 AM

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An earful that nobody wants

Exploring the various methods that are being used to reduce the impact of tinnitus - ringing in ears without an outside sound.

William Leighton heard hundreds, if not thousands, of fire alarms and sirens in his 27 years as a Bangor, Me., firefighter. But they didn't bother the semi-retired lieutenant nearly so much as the sound he hears now when it's dead quiet. "It's a metallic ringing," says Leighton, 59. "It's like the noise you hear when you stand under high-tension wires, but this is in my head."

Leighton has tinnitus: the perception of sound without an external source. We've all had ringing in our ears at one time or another, but usually temporarily after, say, a loud concert. But for tinnitus (pronounced tin-NIGHT-us or TIN-it-us) sufferers like Leighton, the sound often seems to start for no reason - and then won't go away. He had been retired from active firefighting for over a decade when his tinnitus started. Ringing is common, but people also experience relentless buzzing, cricket-like noises, hissing, or humming. Men experience it more than women, and like so many other conditions, it becomes more common with age.

Ringing is common, but people also experience relentless buzzing, cricket-like noises, hissing, or humming.

By some accounts, up to 90% of all tinnitus patients have some level of noise-related hearing loss. Tinnitus is a problem for rock 'n' roll musicians (most famously, Peter Townshend of the Who, but also reportedly members of Pearl Jam, and others), other performers who have been exposed to loud noises, hunters, military veterans, and firefighters like Leighton who didn't wear the ear protection now required by federal safety regulations. Beethoven is the most famous tinnitus sufferer, although his case was probably not related to damage from loud noises. He complained about a continual "whistle and buzz" in his ears as his hearing worsened in his 30s before he went completely deaf at age 44.

Tinnitus is strongly associated with hearing loss, but it's unclear why. One hypothesis is that brain cells in the regions of the brain that ordinarily process sound become disinhibited and spontaneously active when they aren't receiving enough input from the ear and its auditory nerves. For that reason, tinnitus has been compared to the phantom limb pain experienced by amputees.

Doctors don't have any surefire surgical or pharmaceutical treatments for many cases of tinnitus, so often there's a great deal of trial and error - with no guarantee of success. Leighton, a lifetime firefighter, said his doctor told him that he was going to have to assume a new role when it comes to his tinnitus: "He explained to me that you need to be your own detective."

Causes

Tinnitus is often divided into objective and subjective cases. The cochlea (pronounced COKE-lee-ah) is the coiled structure inside the ear that contains the hair cells that vibrate and translate sound vibrations into nerve signals. In objective tinnitus, the cochlea is being stimulated, but from within the body, not by sound waves arriving from elsewhere. The classic example is a pulsatile tinnitus caused by turbulent blood flow through the blood vessels near the cochlea. Sometimes the hair cells spontaneously vibrate on their own, creating noise that can be heard with special instruments. Objective tinnitus can also be caused by twitches in the muscles near or within the ear that cause a clicking sound.

Subjective tinnitus is an unfortunate term because it suggests that the problem is a matter of opinion or just in the person's mind. Doctors have used it to highlight the lack of any objective sound stimulus. The vast majority of people with tinnitus have subjective tinnitus. Sometimes it's also called "tinnitus originating from the auditory system" - with the auditory system comprising the cochlea, the nerves that project from it, the brainstem, and the auditory centers of the brain. It's not an elegant phrase, but it does paint a more accurate picture.

There are many causes of so-called subjective tinnitus. The unifying theme is some kind of damage to the ear, the auditory centers of the brain, or both.

Diagnosis

Tinnitus is really a symptom, so as you might expect, treatment choices hinge on the underlying cause. For that reason, experts say it's especially important for doctors to ask patients a lot of questions. Does the sound seem to come from one ear or both? Is it high- or low-pitched? (Low-pitched is often seen in patients with Ménière's disease.) Have you been exposed to loud noises or taken medications that might have been ototoxic (harmful to the ears)? Some physicians might ask patients about their social lives and mental health. Tinnitus is often worse for people who are isolated, depressed, anxious, not able to move about easily, or in pain from other conditions.


The physical examination focuses on the head, neck, and, of course, the ears. A thorough hearing test is important because of the association between hearing loss and tinnitus. Depending on the results from all of the above, an MRI or some other imaging test may be needed.

Treatments

The kinks and bulges in blood vessels that cause turbulent blood flow can be repaired surgically. If the problem is twitchy muscles, some research has shown that injections of botulinum toxin (Botox), the muscle relaxant, will help. Operations to cut part of the auditory nerve, or take pressure off of it, have been tried, and a few success stories have been reported. But this approach is controversial and should be avoided.

Some therapies aim to get people to ignore — or at least be less annoyed by tinnitus.

Many medications have been studied, but none has emerged as reliably effective. Some experts say clinical trials have been difficult to interpret because the placebo effect is stronger than usual in tinnitus trials.

Lidocaine, familiar as a topical pain reliever, does seem to be effective against low-pitched tinnitus. But the treatment involves intravenous administration of the drug, so it's not widely used. Side effects are a problem, too. Unfortunately, oral medications similar to lidocaine haven't worked.

When people are depressed they tend to focus more on problems like tinnitus, and antidepressants sometimes help by relieving the underlying depression and thus the tinnitus. But there's also a theory that tinnitus is caused by imbalances of some of the same neurotransmitters (serotonin and gamma-aminobutyric acid, or GABA) that cause depression. If that's true, then antidepressants may be influencing brain chemistry causing tinnitus, not simply the depression that makes people more aware of the problem.

Other approaches

Some therapies aim to get people to ignore - or at least be less annoyed by - tinnitus instead of trying to attack the cause. Masking devices, which look like hearing aids, produce a low-level sound. By tuning into the masking device, the ear and the brain seem to forget about tinnitus - at least temporarily. But the devices don't work for everybody, and for some, they make it worse. Tinnitus retraining programs combine counseling with low-level noise generators similar in principle to the masking devices. Proponents claim a 75% success rate, but the programs can take a long time (1½ years by some accounts) to complete. Critics say the favourable studies are seriously flawed. Whenever conventional medicine lacks answers, particularly to a troubling chronic condition, people turn to alternative medicine. Tinnitus is no exception. Many of the usual suspects are involved: acupuncture, ginkgo biloba, various vitamins and minerals. They don't hold up well under the scrutiny of studies, but doctors tend to be tolerant of experimentation as long as no harm is done.

Hearing protection is important

Leighton thought his detective work was paying off. When he restarted his B vitamins, the tinnitus went away: "I called my son Scott and told him I think I have got the answer." A few days later, though, the metallic ringing came back. He copes by staying active (the noise goes away when he goes kayaking) and keeping the television on in the evening when there isn't much noise or activity. Leighton knows that his tinnitus is related to hearing loss from the high-decibel sirens and alarms that bombarded his ears on the job. Now he does what he can to protect them from loud noises. Tinnitus does tend to get worse with further hearing loss. Leighton looks forward to the occasional "quiet days" and dreads the noisy ones.

This article is provided courtesy of Harvard Medical International. © 2007 President and Fellows of Harvard College

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