Brain Can Generate Unexplained Noise In Ears

"Controlled clinical trials are now necessary to evaluate whether this method can permanently reduce and thus cure tinnitus," said senior author Christian Gerloff, M.D, of the University of Tuebingen in Germany.

Many people experience tinnitus, defined as the perception of sound in the absence of an obvious source, at some point in their lives. For most of us, it is a temporary and benign oddity with a host of causes, such as ear infection, blockage of the ear canal, or medications such as antibiotics.

For more than forty million Americans, however, tinnitus is an ongoing problem. It is especially prevalent among the elderly and those with some degree of hearing loss. According to the American Tinnitus Association, a patient advocacy group, some twelve million Americans seek medical attention for the disorder, and about one million are affected to the point of disability.

In some cases a mechanical sound source, such as a damaged artery or other blood vessel disorder, can be identified and treated, but for most forms of tinnitus there is little effective treatment.

"Recently, neuroscientists have brought forward a new concept which postulates similarities between tinnitus and chronic pain. According to this concept, sounds that only the patient can detect might be some sort of 'phantom' auditory perception similar to phantom pain," said Gerloff.

By this theory, abnormal brain activity is creating the illusion of sound in the absence of acoustic stimuli.

In order to investigate this possibility, Gerloff and his colleagues used focused magnetic stimulation to temporarily interfere with the activity of specific brain regions in 14 patients with intractable, chronic tinnitus. They focused their attention on auditory association areas, regions of the brain known to specialize in the processing of auditory input.

The researchers found that when they stimulated a region called the left temporoparietal cortex, which contains several auditory association areas, tinnitus was temporarily reduced in most of the patients. There was no statistically significant reduction when other brain areas were stimulated.

The authors note that only 8 of the 14 patients experienced tinnitus relief during more than one of the five stimulations of the left temporoparietal cortex. Indeed, one patient reported a slight temporary worsening of the tinnitus, which suggests that the situation is not as simple as the nerve cells in the temporoparietal cortex being the source of all tinnitus sounds. However, the findings do provide clues for further research.

"Knowing that these brain areas are functionally relevant for tinnitus makes them a primary target for modern therapeutic approaches based on brain stimulation methods," said Gerloff.