Research Traces Area Of The Brain That May Be Source Of Ear Ringing

Brain scans of people with ringing in the ears have found a clue to what causes the buzzing, roaring, whistling and other phantom noise affecting some 50 million Americans.

One expert called the work a breakthrough toward finding the cause of the problem, called tinnitus, and perhaps better treatments. The scans found abnormally high activity in a pecan-sized area that helps the brain process sounds.

Within that area, “there may be one spot that’s triggering off all that activity,” said Dr. Alan Lockwood of the State University of New York at Buffalo and the Veterans Affairs Medical Center in that city.

He and others report the work in January’s issue of Neurology.

For most people, tinnitus is just annoying. But an estimated 12 million Americans have it bad enough to seek medical help or to be considered disabled, according to the American Tinnitus Association.

No cure is known. Patients can learn to cope and use noise-producing devices to distract them or cover their phantom sound.

Scientists already knew that tinnitus can be triggered by loud noise, some medications and blows to the head. But they don’t know what goes wrong within a person to keep the phantom sound going.

Recent studies have implicated the brain in most cases. The new work studied people with tinnitus in one ear, and it found abnormally high activity in an area on the opposite side of the brain.

“It’s a very significant breakthrough” toward understanding what brain structures are involved in tinnitus, said James Kaltenbach of Wayne State University in Detroit, who wasn’t involved in the new study.

“Until now we haven’t really had a good handle on what structures are involved,” Kaltenbach said. Once researchers find that out, they can begin exploring what goes wrong to produce tinnitus, and “you can begin custom-designing drugs that target those mechanisms.”

Lockwood’s work found the abnormal activity in a cluster of sites within the auditory cortex, which is one of a chain of brain centers that process signals from the ears.

While the new work implicates the auditory cortex, “it doesn’t say the problem begins there,” Kaltenbach said. So sites that communicate with it must be investigated, he said.

The scans were performed on four people with severe tinnitus and the unusual ability to adjust the volume of the phantom sounds by tightening their jaws. The study compared their brain activity with jaws relaxed and jaws clenched, and found that made a difference in the auditory cortex.

Lockwood and Kaltenbach cautioned that because the participants had an unusual form of tinnitus, it’s not clear that the result will apply to the disorder in general. Other patients will have to be studied.

Lockwood said, however, that the participants’ tinnitus was typical in ways other than the volume control.

The researchers also had the patients listen to real noise through the ear affected by tinnitus. That turned on much more of their sound-processing brain circuitry than was seen in six people without tinnitus. So a “wiring” abnormality might be one reason for the disorder, Lockwood said.

There may also be a link between the real noise and the brain’s limbic system, which plays a role in emotion. That could explain why tinnitus is so distressing, Lockwood said.

“We don’t have a cure for tinnitus,” Lockwood said. “What we have … is precise information about the areas of the brain affected and some ideas that can be tested by further experimentation that may hopefully, eventually lead to a cure.”