If you've ever experienced a prolonged ringing in your ears - even when there wasn't anything generating sound in your environment - you've likely had a case of tinnitus, a condition that roughly 10 million Americans seek treatment for each year. While the condition is mildly annoying for some, it can cause fatigue, depression and anxiety for the 24 million Americans who experience it constantly. According to the U.S. Department of Veteran's Affairs, tinnitus was the number one service-connected disability for veterans receiving compensation at the end of the 2012 fiscal year. Current therapies do not cure the condition.
That's why researchers, funded by the National Institutes of Health (NIH), are currently recruiting candidates for a clinical trial through a cooperative agreement with MicroTransponder, Inc, a medical device company based in Dallas. The trial is supported by the National Institute on Deafness and Other Communication Disorders (NIDCD), a part of NIH, because it may mark a change in the way tinnitus is treated.
The year long trial will treat two groups of adults who have had moderate to severe tinnitus for at least one year using a technique known as vagus nerve stimulation (VNS). This kind of nervous system stimulation has already proven effective in treating individuals with epilepsy and depression; a volunteer group of tinnitus volunteers in Europe also reported encouraging results.
What causes tinnitus?
Scientists don't really know why the brain perceives sound that isn't there, but they do know that chronic cases of tinnitus are usually preceded by loss of hearing resulting from old age, prolonged exposure to loud noise, impacted ear wax, or an injury to the head. Other less common causes of tinnitus are Meniere's disease, TMJ disorders, head or neck injuries and acoustic neuroma. In rare cases, tinnitus can be caused by blood vessel disorder resulting from head and neck tumors, atherosclerosis, and high blood pressure. Certain medications, such as antibiotics, cancer medications, aspirin and antidepressants may also cause, or worsen, tinnitus.
Since hearing loss is the loss of the auditory system's ability to process certain frequencies, researchers believe tinnitus may be the brain's way of trying to regain that ability by turning up the signals of neurons in neighboring frequencies. The rapid, frequent firing of these neurons changes brain patterns, which produces the perception of the ringing or buzzing sounds associated with tinnitus.
How is tinnitus currently managed?
Tinnitus that is a symptom of an underlying medical condition, such as a tumor, infection or excessive ear wax, can often be successfully treated with surgery or medication. For many others, the causes of tinnitus cannot be identified. In those cases, the condition is currently managed by using hearing aids, tinnitus maskers, biofeedback, electrical stimulation, relaxation therapy ad counseling. While none of these methods cure tinnitus, they often help patients manage the condition.
Why is this clinical trial significant?
The VNS therapy will take advantage of the brain's ability to reconfigure itself (neuroplasticity) by stimulating the vagus nerve. Participants in the trial will wear headphones and hear a series of single frequency tones, paired with stimulus to the vagus nerve. When stimulated, the vagus nerve releases chemicals that promote neuroplasticity, such as acetylcholine and norepinephrine.
One of the groups in the study will receive VNS and tone test treatment immediately; the other will receive a combination of VNS and tone treatment that is not thought to have therapeutic benefit. Outcomes will be measured over the course of the year by questionnaires the participants complete as well as periodic hearing tests to determine the minimum decibel levels required to eliminate each participant's awareness of their tinnitus.
“This trial has the potential to open up a whole new world of tinnitus management,” says Gordon Hughes, M.D., director of clinical trials at the NIDCD. “Currently, we usually offer patients a hearing aid if they have hearing loss or a masking device if they don’t. None of these treatments cures tinnitus. But this new treatment offers the possibility of reducing or eliminating the bothersome perception of tinnitus in some patients.”
The clinical trial sites are at the University of Texas at Dallas; University at Buffalo (SUNY), Buffalo; and the University of Iowa, Iowa City. An additional site will be added later in the year. More information about the trial and enrollment is available on the study’s website, http://www.tinnitustrial.com.