Balance Booster

Almost ten years ago the chicken pox he had suffered as a kid came back in the form of shingles. The virus that lay dormant for all those years in his nerves attacked the vestibular nerves of Kawabata's the inner ear, leaving him rather unsteady on his feet because of a balance disorder.

"Human beings, in order to maintain balance, need to rely on three main sources of information. These three main senses are vision, the sense of gravity from the inner ear, and what we call somatosensory, which is the pressure information you get from below your feet," explains Dozza, whose work is part of a collaboration between the Department of Electronics, Computer science and Systems at the University of Bologna, Italy and the Balance Disorder Laboratory at OHSU's Neurological Sciences Institute. "What the brain normally does is get information from vision, inner ear, and from your feet. It is continuously integrating this information to have the best estimation of your position and movement, in order to apply the best strategy to keep balance. When one of these senses is not there, balance is more challenging and the chance of falling increases."

Loss of balance or vestibular disorders are a fairly common result of ototoxicity, often from common infections and side effects to antibiotics, and can affect people of all ages and all walks of life — according to studies from the National Institutes of Health, 90 million Americans (40 percent of the population) will complain to their doctors of dizziness at least once in their lifetime.

This dizziness could indicate damage to the inner ear of both ears that results in bilateral vestibular loss. Sufferers may also notice visual problems and imbalance, particularly in the dark.

"What is bad about vestibular loss is that it doesn't happen gradually. You can't compensate while the disease… is impairing you more and more," Dozza explains. "It happens mainly suddenly. One day you'll wake up and you'll have no clear idea where the vertical is."

So Dozza and his colleagues produced a device, kind of like an MP3 music player, to help sufferers stay on the straight and narrow by giving the wearer's brain more balance input. Worn on the belt, it contains sensors that detect when the person sways outside a vertical "safe zone." A computer then converts that information into musical tones played through headphones, which get louder the further they sway from vertical and using stereo sound to indicate the direction of the sway. Patients learn that different tones correspond to different directions of sway, so they can correct their posture before falling over. With enough training, the tones replace missing balance information that the brain normally receives from a nerve in the inner ear.

"What we are trying to do with this device is give to these subjects some additional information about their movement, which their brain can integrate with the other information it is using in order to improve balance," Dozza says.

"I didn't have to concentrate… and after a number of minutes it felt very natural," says Kawabata. "Because of the character of the tone they've chosen, it was quite intuitive to determine my position. The left and right was indicated by the stereo effect and the forward and back had a different characteristic. It was very easy to learn quickly."

More testing and development is needed, but Dozza hopes that the device will let people with balance disorders manage their condition themselves. "We believe there is a chance that people will only need to wear it once a day or once a week. We don't know for sure yet," he says.

The researcher's plan to work on making the device much smaller certainly appeals to those who would benefit from it. "I look forward to something that is small, like an iPod, that I could wear unobtrusively," Kawabata says.

Dozza says the device also improves balance in healthy people and could someday be used to train athletes helping to improve their performance.