February 2011

Tinnitus Cure May Lie in the Brain

Scientists were able to eliminate tinnitus—a persistent ringing in the ears—in rats by stimulating a nerve in the neck while playing a variety of tones. The finding gives hope for a future tinnitus cure in humans.

Tinnitus is usually a high-pitched tone in one or both ears, but can also sound like a clicking, roaring or whooshing sound. While tinnitus isn’t fully understood, it’s known to be a sign that something is wrong in the sound processing system. Something as simple as a piece of earwax blocking the ear canal can cause tinnitus, but it can also come from a number of health conditions—for example, from hearing loss after being exposed to loud noise.

There’s no known cure for tinnitus. Current treatments generally involve masking the sound or learning to ignore it. NIH-funded researchers set out to see if they could develop a way to reverse tinnitus by essentially resetting the brain’s sound processing system.

The researchers used vagus nerve stimulation (VNS), a technique known to release chemicals that encourage changes in the brain. They paired it with the playing of different tones other than the tinnitus frequency. This technique, the scientists reasoned, might induce brain cells to tune to frequencies other than the tinnitus one.

The researchers played various tones during VNS to noise-exposed rats with tinnitus 300 times a day for about 3 weeks. Both the rats’ behavior and brain activity tests showed that their tinnitus had disappeared.

“The key is that, unlike previous treatments, we’re not masking the tinnitus,” says Dr. Michael Kilgard of the University of Texas, one of the lead researchers. “We are eliminating the source of the tinnitus.”

VNS is already used to treat people with certain other conditions. The scientists are now planning to conduct clinical studies of VNS paired with tones in tinnitus patients.