Tinnitus Market Offers New Neurotech Opportunity

by James Cavuoto, editor

The market for treating tinnitus, a complex auditory condition often associated with ringing in the ears, may represent one of the newest opportunities for neurotechnology vendors. About 50 million Americans are believed to suffer from some form of the condition, and about 12 million of these are characterized as severe enough to require medical treatment. Currently, there is no single treatment regimen that has proven successful, perhaps owing to the multiplicity of possible causes—from noise-induced hearing loss to ototoxic medications to sinus infection—and the differing degrees of disability.

One of the first neurotech firms to target this market is a Valencia, CA startup called NeuroSystec Inc. An offshoot of the Alfred Mann Foundation, NeuroSystec has devised a therapy that inhibits spontaneous firing of the spiral ganglion, which is thought to be the source of the erroneous perception of sound arriving at the auditory cortex.

NeuroSystec CEO Stephen McCormack described the company’s technology and licensing strategies at the recent SoCalBio Investor Conference in Los Angeles. The company has licensed an osmotic pump from Durect Corp. and plans to target the NMDA receptor with nanoliter delivery of an NMDA antagonist. They have also licensed technology from cochlear implant manufacturer Advanced Bionics, the Boston Scientific unit recently acquired from Mann.

There is a potentially symbiotic, though complex, relationship between tinnitus and cochlear implants. Many studies have shown that cochlear implants reduce severity of tinnitus and the condition represents a secondary target market besides profound deafness. But in some cases, cochlear implants have induced tinnitus, or exacerbated it, so there is clearly cause for neural prosthesis vendors to learn more about the potential interaction.

Because electrode implantation destroys whatever healthy hair cells are left inside the cochlea, cochlear implants are prescribed to deaf or near-deaf patients only. In one study, half of those who’d had tinnitus before their cochlear implants experienced tinnitus relief after their cochlear implants.

There are two possible explanations for why cochlear implants produce relief from tinnitus. First, the tinnitus might be masked by the ambient sounds that the implants bring back. Alternatively, the tinnitus might be suppressed by the electrical stimulation sent through the auditory nerve by the implant. Some forms of electrical stimulation to the ear can stop tinnitus briefly.

The Hertie Institute for Clinical Brain Research at the University of Tubingen in Germany has been investigating neurostimulation of the auditory cortex as a potential treatment for chronic tinnitus. Researchers there are testing the hypothesis that an initial disturbance of the inner ear or cochlear nerve induces “maladaptive” plasticity in the auditory cortex. This maladaptive plasticity causes pertinent overactivity of certain auditory areas and produces the sensation of tinnitus.

Another German team headed by B. Langguth, published a report in the journal Neuroreport in 2003 that showed promising results for treating tinnitus using repetitive transcranial magnetic stimulation. And the American Tinnitus Association has funded several research programs looking at neurostimulation, including a grant to Wayne State University in Michigan investigating electrical stimulation to suppress dorsal cochlear nucleus hyperactivity.

Another approach to treatment relies on masking. The Aurex-3 device developed by ADM Tronics in New Jersey and marketed by CarePoint Group in the U.K., consists of an applicator and probe placed against the mastoid bone behind the ear. The device uses audio and vibratory frequencies that the user can tune to match the frequency of the tinnitus.

Treatment sessions of 10-minute duration are self administered three times a day over the first couple of weeks and then on demand as the tinnitus condition changes. Many report a change in the quality of their tinnitus that is steadily progressive, changes that are described as moving from a debilitating high-pitched sound, such as escaping high-pressure steam, to that of a waterfall, and then on to a sensation of running water as the treatment progresses.