Implantable device treats balance disorder
By Ben Coxworth
October 24, 2010
Meniere's disease is an inner ear disorder that affects about one percent of the U.S. population, and it’s a disabling condition – attacks of vertigo can occur without warning, requiring people to lay still for several hours at a time. This ever-present possibility causes sufferers to avoid certain activities, situations and even careers. Medication and lifestyle changes often alleviate it, but if they don’t then surgery is the next step, which typically depletes the hearing and/or balance functions of the affected ear. Now, a team of scientists from the University of Washington Medical Center are about to try out a new cochlear implant on their first human test subject. Their hope is that it will get rid of his symptoms, while allowing him to retain full use of both ears.
Meniere’s is not fully understood, although its attacks are believed to be caused by the rupture of an inner-ear membrane. This causes fluid to leak out of its vestibular system, which throws off the brain’s sense of balance.
With the new treatment, the implant is surgically placed in a small well created in the skull’s temporal bone, behind the patient’s ear. Three electrodes extend from it, into the canals of the inner ear's bony labyrinth – their exact placement is determined for each patient by neuronal signal testing. The patient also wears a small external processor behind their ear, which lines up directly with the implant.
When the wearer feels an attack coming on, they activate the processor, which in turn sends a signal to the implant, which then transmits electrical impulses through the three electrodes. These impulses override the malfunctions in the inner ear, allowing the patient to maintain balance until the attack passes.
The device took four years to develop, and was recently approved by the U.S. Food and Drug Administration (FDA) for use in a limited human trial. A total of ten patients will receive the implant. The U Washington team based their device on cochlear implants already in use, which they believe greatly accelerated its FDA approval. They hope that it could also be used to treat more common balance disorders.