Vertigo, dizziness and balance disorders can literally make a person's head spin. Almost as unsettling is the long and frustrating odyssey through the healthcare system to seek treatment for these conditions. The balance system is distributed throughout our bodies and is therefore not limited to any single medical specialty. Often specialists only appreciate their piece of the problem and, like the story of the blind men and the elephant, no one sees the "big picture" of dizziness.
Balance disorders can arise from a disturbance of sensory input from the inner ear, vision or muscles and joints. They can arise from a disturbance of central processing of balance signals that arrive in the brain and they can arise from a disturbance of outgoing signals to eye muscles or muscles of posture and gait. Doctors use a combination of detailed medical history, physical examination and diagnostic tests to determine the most likely cause of dizziness, or vertigo.
If the problem stems from the inner ear, it may be benign paroxysmal positional vertigo (BPPV), the most common inner ear cause of acute vertigo. This condition arises when small crystals that are normally embedded in the gelatinous wall of the inner ear break loose and move freely in the inner ear fluid. People with this condition experience brief, intense spinning vertigo when changing positions. BPPV can be cured by a treatment called the Epley particle repositioning maneuver that relocates the loose crystal particles to an area of the inner ear where they cannot bump into the balance organs and trigger a vertigo attack. Unfortunately, about 50 percent of people with BPPV have relapsing episodes and although the Epley maneuver can clear the acute symptoms, it cannot prevent relapses.
For chronic dizziness that stems from the inner ear, there are only three treatment options: medicine, surgery and physical therapy. Although medications can suppress symptoms of nausea and can occasionally reduce vertigo, it is rare that medications cure dizziness. Surgical treatments for inner ear disease fall into two broad categories: those that treat or cure an underlying ear disorder (for example mastoid surgery to treat chronic infection) and those that disable the ear so it sends less of a balance signal into the brain. In the latter, the rationale for surgery is that having no balance signal is preferable to having a fluctuating or unstable signal that actually disrupts balance and causes vertigo. The third treatment for chronic dizziness caused in the inner ear is a physical therapy called vestibular rehabilitation. It has two complementary strategies. One strategy is to determine what movements or actions most provoke a person's symptoms and then practice them akin to a figure skater practicing her spins every day so she can stand still at the end of the performance instead of falling over. The other strategy, called sensory substitution, is to teach a person to depend on the reliable parts of the balance system and neglect faulty information coming from the parts of the system that aren't functioning properly. For example, a person with a damaged inner ear could be trained to pay particular attention to visual cues of spatial orientation to help him maintain his balance.
In the last 10 years, technology has been developed that may soon offer new treatment options to people with balance disorders. The new technology uses micromechanical motion sensors to detect motions of the head and body. The motion sensor information is then fed to a computer chip for processing. The output of the computer chip is delivered to the person with dizziness to aid their balance. There are two methods for delivering the computer output. The more invasive way is to deliver the output as electric signals to the vestibular nerves via a surgically implanted electrode array within the inner ear. This is exactly analogous to the way a cochlear implant delivers electrical signals to the auditory nerve to restore hearing. The feasibility of this approach has been demonstrated in the research lab but it will be some time before such implants are available for wider use. The other method uses "sensory substitution." Actions that would normally stimulate the "motion" sense in the inner ear are detected by the micromechanical sensors, processed by the computer chip and rerouted to the affected person as hearing or touch sensations. In one version of this approach, the motion signals are converted to sounds. Variations in loudness or pitch indicate different directions of motion. In another version of sensory substitution, the motion signals are sent to an array of small electrodes placed on the surface of the tongue. When the person moves forward, the front of the tongue is stimulated and when the person moves backward, the back of the tongue is stimulated. In yet another version of sensory substitution, the motion information is delivered as vibrations against the skin of their torso. The dizzy person wears a belt or vest lined with an array of small vibrating buttons around the torso. Leaning or tilting in any direction activates the vibrators on the corresponding side of the torso, alerting the person wearing the vest that they are leaning and need to correct their position. Each of these sensory feedback devices is in a different stage of development.
Our research team at the Massachusetts Eye and Ear Infirmary has been developing the vibrating device worn around the torso. We have done a series of experiments to determine the most informative way to provide this vibrotactile information to patients. We have designed the vest to have columns of vibrators. A small tilt activates the lowest vibrator in the column. A medium tilt activates the middle vibrator, and so on. We use a training task called the BalanceMaster™ to train our dizzy research patients to use the vibrotactile vest in 15 to 30 minutes. After training, we test their ability to balance. We test postural stability by having them try to stand on a floating posture test platform with their eyes closed and we test gait stability by having them walk down a runway that suddenly jerks to one side or the other, causing them to stumble. People who are unable to stand on a floating posture test platform without the vest are able to do this task when they wear the vest. They also have improved stability on the runway and recover from stumbles better.
Besides these objective measures of improved performance, people who have used the vibrotactile vest report that they can sense an improvement when they wear the vest. They have told us that they find it moderately or very useful in helping them walk or stand. Others have said that the device could help them expand the scope of their daily activities that have been limited by their balance problems. One person who suffers from Mal de Debarquement Syndrome reported that the vibrotactile vest reduced her feeling of constant motion when she was standing still.
Today the vibrotactile vest is only used in the research laboratory. In the future it will be possible to use it in rehabilitation clinics or as a permanent treatment for people who can walk. It has potential applications for people with inner ear problems and many others with other causes of dizziness or who walk unsteadily all with the objective of increasing a person's ability to do things on their own that their current balance problem makes difficult and to reduce their risk of falling. Greater ability increases confidence and, ultimately, quality of life.
Conrad Wall III, Ph.D., received his B.S. and M.S. degrees in physics from Tulane University and his Ph.D. in bioengineering from Carnegie-Mellon University. He is an associate professor of otology and laryngology at Harvard Medical School and in the joint Harvard-MIT Whitaker College of Health Sciences Technology. Dr. Wall is the founder and director of the Jenks Vestibular Diagnostic Laboratory at the Massachusetts Eye and Ear Infirmary, where he also participates in sponsored research. Dr. Wall is project lead of the Balance Project on the Infirmary's Neural Prosthesis Research Center and principal investigator of a National Institutes of Health-funded project to develop and validate motion sensors for balance aids. He chairs the working group in charge of the American National Standards Institute standard on the vestibular function test battery.
Steven D. Rauch, M.D., is associate professor of otology and laryngology at Harvard Medical School and a member of the Otology Service of the Massachusetts Eye and Ear Infirmary. He received his B.A. cum laude from Amherst College and M.D. from University of Cincinnati. He took his otolaryngology training at Massachusetts Eye and Ear Infirmary where he joined the faculty in 1984. Dr. Rauch divides his time between his clinical practice of otology and his research.
