Vestibular Prosthesis May Treat Balance Disorders
by James Cavuoto, editor
The market for treating vestibular disorders may be a potential area of growth for the neurotechnology industry. There is significant unmet medical need for inner ear disorders such as Meniere’s disease, which produces vertigo, tinnitus, and other symptoms. Although there is medication which can help once an attack is underway, there is currently no long-term therapy which can resolve the disease completely.
The vestibular system’s proximity to the cochlea—both are in the inner ear—causes it to be compromised in a number of hearing-impaired patients. The National Institute on Deafness and Other Communication Disorders estimates that up to two-thirds of children with acquired deafness have severe vestibular deficits. Balance disorders also constitute a major health concern for older persons. According to the Centers for Disease Control and Prevention, balance disorders are causally related to some 200,000 hip fractures that occur annually in Americans over the age of 65.
Over the years, there have been several efforts to develop a vestibular prosthesis, including research at Harvard University, University of California, Irvine, and Washington University. One promising new effort to stimulate the vestibular nerve is underway at the University of Washington in Seattle. Christopher Phillips and colleagues reported their findings recently in Experimental Brain Research.
The UW team has developed a vestibular prosthesis which delivers electrical stimulation to the fluid inside the semicircular canals of the ear. In effect, the stimulation of the fluid makes the brain believe that the body is moving or swaying in a certain direction. This then causes a compensatory postural reflex to stabilize the posture thereby helping to restore balance.
For their study, the prosthesis was inserted into the ears of four subjects all suffering from long-term Meniere’s disease and differing degrees of hearing loss which was resistant to other management strategies. After a full evaluation of each participant’s vestibular function, their eye function was measured in response to electrical stimulation along with their postural response both with their eyes open and closed.
The researchers found that electrical stimulation of the fluid in the semicircular canals of the affected ear did result in a change in posture, the direction of which was dependent on which ear was stimulated.
However, each subject had different sway responses to the stimulation given. The authors believe this could be caused by small differences in the location of the electrode between subjects. Thus fine tuning and individual calibration for each electrode implant would be required for it to be effective.
Overall, the results illustrate that this type of prosthesis may eventually be a possible treatment for balance issues caused by Meniere’s disease. However, there are a large number of matters which would need resolving before it is ready for use. The lack of consistency in direction and magnitude of sway response would require further study to ensure that any prosthesis developed could give reliable results for different individuals.
The authors conclude: “Taken together, our findings support the feasibility of a vestibular prosthesis for the control of balance and illustrate new challenges for the development of this technology. This study is a first step in that direction.”