Treating Tinnitus Through the…Tongue?

It can sound like a soft buzzing in one's ears. Or a sudden hissing. Or a loud roaring. Tinnitus, the sensation of hearing phantom sounds, ranges from annoying to debilitating, and it affects an estimated 10 to 15 percent of the population. Unfortunately, finding relief from these symptoms can be tough.

Doctors and patients may find themselves attempting many treatments for tinnitus, including sound machines to mask the phantom noise, medications to treat underlying anxiety or depression, and investigational brain implants or vagus nerve stimulation. In the United States, there are currently no clinically approved drugs or devices to treat tinnitus.

Now, in a paper published today in the journal Science Translational Medicine, researchers at Dublin-based biotech Neuromod Devices, along with academic collaborators, present positive results from a year-long, randomized clinical trial of a device that pairs sound with gentle electrical tongue stimulation to treat tinnitus. In a group of 326 adults, 12 weeks of treatment with the device significantly reduced tinnitus symptom severity for up to 12 months after treatment.

Illustration: Neuromod Devices

With the technology, we're shifting the brain's focus away from the tinnitus to other sounds, presented by the treatment device and the environment," says Hubert Lim, chief scientific officer of Neuromod and an associate professor of biomedical engineering and otolaryngology at the University of Minnesota. The device has been approved in Europe under the trade name Lenire since 2014, but it is not yet approved by the U.S. Food and Drug Administration.

Some tinnitus cases are caused by actual sounds generated in the ear, such as changes in blood vessels so that a person is literally hearing the blood pumping in their head. These can often be surgically treated. But most cases are caused by altered brain wiring. These cases are often associated with hearing loss and thought to be the result of the brain overcompensating for that loss, leading to hyperactivity and abnormal brain activity patterns, like revving a car engine that you're afraid is about to stall.

While testing brain implants to treat deafness more than a decade ago, Lim noticed that stimulating somatosensory regions of the brain-that is, areas associated with the perception of touch, pressure, temperature, and pain-caused a decrease in tinnitus in patients. When starting his own lab in Minnesota in 2009, Lim began testing different ways to activate somatosensory pathways without a brain implant, by stimulating the ears, neck, limbs, tongue and more.

In a 2015 study on guinea pigs, his lab showed that by stimulating the ear or tongue of an animal, along with playing sound to activate the auditory centers of the brain, they were able to change brain activity patterns in a way that might treat tinnitus or other brain disorders.

Around the same time, Neuromod Devices was pursuing a pilot study of 54 tinnitus patients using sound and electrically stimulating the tongue in parallel. Soon after, a team at the University of Michigan led by Susan Shore came to a similar conclusion, showing combining sound and mild electrical pulses delivered to the cheek or neck helped quiet the phantom sounds of tinnitus in people.

Photo: Neuromod Devices

In 2017, Lim joined Neuromod to help lead a series of large clinical trials using a device based on that concept. Neuromod's three-part device includes a pair of Bluetooth headphones that deliver tones ranging from around 100 hertz (Hz) frequencies, like a deep voice, up to 8,000 Hz frequencies, like bird chirping, accompanied by general background noise. The sounds are paired with gentle electrical pulses delivered to the tongue via a lollipop-like paddle with 32 electrodes that can synchronize with the sound. The pulses tingle like Pop Rocks or a fizzy soda, says Lim. The headphones and paddle are controlled by a handheld device that can be used to change the timing, intensity, and synchronization of the stimuli.

It's musical," says Lim. We're trying to present many different tones and rich sounds that we pair with tongue stimulation to make the brain become more sensitive. Then the brain finds more meaning in other sounds, and is not even paying attention to the tinnitus anymore."

For the trial, 326 participants with chronic tinnitus were asked to use the device for two 30-minute sessions each day for 12 weeks. Participants could do some activity, like walking or cleaning, while using the device, or just sit and relax. Of the participants, 84 percent used the device for the minimum designated amount of time. Of those, across three treatment groups, 75 to 89 percent saw improvements, and for more than 120 individuals, those improvements lasted for a year after the treatment was stopped. But the device was not a cure-all: In about 20 percent of total cases, including those who stopped mid-treatment, patients saw no improvement of symptoms or their symptoms got worse.

What we've definitely been able to show is we can improve the burden of tinnitus symptoms severity with our treatment," says Lim. He declined to comment on whether the company has applied to the FDA for device approval.

Next, the company is planning a follow-on study to try different variations of tones and tongue stimulation to tease out which features are driving the positive effects.