Many products, from vitamin concoctions to acoustic devices, claim to cure tinnitus, but scientific evidence doesn't support those claims, says Timothy C. Hain, MD, professor emeritus at Northwestern University Medical School in Chicago. And no medications are known to be effective, he says. Dr. Hain also thinks it's unlikely that one pill will cure tinnitus—and even if it could, it would be unlikely to work for all patients because the condition has different underlying causes.

Researchers continue to explore the link between hearing loss and tinnitus, speculating that preventing hearing loss might also prevent tinnitus. Unfortunately, though, much hearing loss is due to damage to fine hairs in the inner cochlea that detect vibrations and translate them into electrical impulses. In mammals, these hairs, once damaged, cannot regenerate. Although researchers are trying to regenerate these hairs, nothing at the moment shows signs of providing clinical benefit.

Phantom Sounds

Some investigators, like Michael P. Kilgard, PhD, professor of neuroscience at the School of Behavioral and Brain Sciences at the University of Texas at Dallas, believe tinnitus is caused by neurons remapping after hearing loss. Each neuron coming from the ear to the brain represents a sound frequency, and the brain interprets that neuron's firing as that sound, he explains. When hearing is damaged, some neurons no longer receive stimuli from the ear. Instead of lying idle or atrophying, the neurons tend to react to stimuli in nearby neurons and fire spontaneously. When they fire, the brain translates them as the sound frequencies they used to represent and hears sounds that are not there.

The phenomenon is similar to feeling pain after a limb has been amputated, says Dr. Kilgard. The nerves that used to come from the limb are still there, he explains, they've just been amputated at the stump. So when nerve activity happens near or at the stump, these nerves may fire, and the brain interprets them as pain in the limb.

Nerve Stimulation

Dr. Kilgard's research focuses on redirecting the brain's attention from the tinnitus frequencies to other frequencies within hearing range. He theorizes that in the process of retraining the brain, the neurons will remap to different frequencies. Over time, the brain will learn that these neurons represent new frequencies, and will no longer generate tinnitus.

Dr. Kilgard, his team at the University of Texas, and MicroTransponder Inc., a company in Dallas specializing in implantable neurostimulation, have developed a small electrical device that is implanted in a patient's chest and connected to the vagus nerve in the neck—which, among other things, sends signals to and from the digestive system. The patient then listens through earphones to a range of sounds from a laptop. As each sound is played, the vagal nerve stimulator, connected via Bluetooth, sends electrical impulses to the vagus nerve. The patient doesn't feel any conscious sensations, but the theory is that the brain is getting a signal to pay attention to something, and through repeating the electrical stimulus and sound, it learns that certain frequencies are more important than the tinnitus one and moves its resources to these more "important" frequencies. The hope is that the neurons will remap to express more of the desired frequencies and less of the tinnitus frequency, and that this change may be permanent.

This device was successfully tested and found to be safe in a small study of 10 patients in Belgium; the results were published in the Journal of the International Neuromodulation Society in 2014. The device is currently undergoing larger Food and Drug Administration–approved trials in the United States to see if it is effective.

More Research Needed

Scientists have looked at other ways to stimulate nerves, including deep brain stimulation and magnetic stimulation. Nerve stimulation offers hope for treating the underlying cause of tinnitus, says Terry D. Fife, MD, FAAN, FANS, director of neuro-otology and balance disorders at the Barrow Neurological Institute and professor of neurology at the University of Arizona College of Medicine in Tucson. He cautions, however, that clinical trials for these approaches are still in the early stages and the evidence for their effectiveness is not yet convincing.

A cure is a long way off, agrees Richard S. Tyler, PhD, an audiologist and professor of otolaryngology at the University of Iowa, whose department is participating in a phase 3 trial of Dr. Kilgard's device. But, he says, if one of these approaches benefits even 20 or 30 percent of tinnitus patients, it will represent a great leap forward.