En español | Persistent tinnitus — a hissing or ringing sound in the head that won't go away — can feel like a prison that sufferers have no hope of escaping. It's no wonder some people become depressed or even suicidal.
Some 50 million Americans experience tinnitus, and around 12 million have sought medical help. Two to 3 million are severely disabled, unable to sleep, work or concentrate.
Until recently doctors couldn't do much to help those trying to cope with intrusive tinnitus, other than prescribe antidepressants or suggest "sound therapy" using devices that mask the ringing with white noise.
Now, though, scientists are uncovering the causes of tinnitus — and exploring intriguing new treatments that might lead to a cure.
Tinnitus (pronounced TIN-i-tuss or tin-EYE-tis) often occurs after exposure to very loud noises, although it also can arise from a head injury, certain medications or even age-related hearing loss. But recent research has shown that in most cases the perception of sound occurs not in the ears but in a part of the brain called the auditory cortex.
Michael Kilgard, a scientist at the University of Texas at Dallas, says brain circuits that process sound become hypersensitive to certain frequencies, creating a ringing sensation even when none is present.
In a recent study, Kilgard induced tinnitus in rats by exposing them to loud sounds. Then he used tiny electrodes to stimulate the rats' vagus nerve, a pathway connecting the brain to other organs. Each jolt of micro-current triggered the release of a substance called acetylcholine, which signals the brain to pay attention.
In sync with the stimulation, he played a wide range of tones — all except the one matching the frequency of their tinnitus — and repeated this 300 times a day for three weeks. The tinnitus disappeared in these rats, while a control group still had the condition.
Next: Retraining the brain. >>