Treating tinnitus: could neuromodulation provide a long-term solution?

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erived from the Latin word for ringing, tinnitus is the perception of noises in the head or the ear that have no real external source. Although usually associated with ringing, it can be more like a buzzing, whistling or hissing sound — and for some, it is constant.

For many, this incessant phantom noise dramatically affects their overall quality of life, particularly interfering with the sufferer’s ability to work and socialise. Moreover, Tinnitus is associated with mood swings, lack of concentration, sleep deprivation, as well as depression and anxiety.

But despite the severe impact it can have on people’s day-to-day lives, most of the ways that tinnitus is managed are inadequate for sufferers particularly in the long-term. One option is being prescribed a hearing aid with a tinnitus noise masker to help cushion the sounds, thereby reducing associated distress. Another option is cognitive behavioural therapy, either in individual or group counselling sessions.

Although the British Tinnitus Association (BTA) regard both as safe, they note there is no evidence of effectiveness for hearing aids and only recommend them for tinnitus patients who also have hearing loss. The BTA adds that while CBT is regarded to be effective at reducing distress and making the tinnitus less bothersome, more and larger studies would be needed to prove its efficacy.

As a result of this clear unmet need, while doing his PhD at University College Dublin, Dr Ross O’Neill decided to look at the interaction between tinnitus and the nervous system. O’Neill found it to be a stimulation problem in the somatic nervous system. “There was a growing body of evidence that shows if you stimulate that nerve, it can suppress this neural hyperactivity that seems to give rise to tinnitus,” explains O’Neill.

He then stumbled across the work of Professor Hubert Lim at the University of Minnesota who was exploring “what was happening mechanistically in the hearing parts of the brain if you use this bimodal stimulation approach”. Consequently, O’Neill reached out to Lim and proposed that the two join forces. The result was Irish-headquartered Neuromod – with O’Neill as CEO and Lim as chief scientific officer – and its bimodal stimulation device Lenire.

Lim’s work identified the tongue as “one of the key drives of changes in the auditory brain relevant for tinnitus treatment”. However, as this approach involves bimodal stimulation, Neuromod’s device has a secondary sensory input, the ears, and the aim is to make “the brain more sensitive to things other than the tinnitus”, explains Lim.

Through the Lenire’s three components – a handheld controller to operate the stimuli, the tongue tip to deliver energy pulses to the trigeminal nerve in the somatic nervous system through the tip of the tongue, and Bluetooth headphones to deliver the paired sound stimuli to the auditory nerve – “we are presenting diverse stimuli along the tongue and sounds with a lot of richness and at different tones that are changing frequency”, Lim notes.

Starting with one kilohertz combined with electrical stimulation on the tongue, Lim explains that this makes the brain wonder “why one kilohertz and what is this tongue stimulation?” and therefore decide “this must be important because my tongue is being stimulated at the same time as one kilohertz sounds are coming in.” The brain then pays attention to the one kilohertz sounds, rather than the tinnitus. Next, the Lenire introduces different sound frequencies, including eight kilohertz and 50 hertz, to further distract the brain from the tinnitus.

Neuromod’s Lenire uses a combination of two different types of stimuli to counter tinnitus symptoms. Credit: Neuromod

It is the combination of these two different types of stimuli that makes Neuromod’s Lenire effective at both reducing the volume of the tinnitus and helping individuals to detach from the tinnitus.

Lim notes it works in the same way as Pavlovian conditioning. During research in the late 19^th century, Russian physiologist Ivan Pavlov realised that his dogs were salivating not only in response to food being placed in front of them, as he predicted, but also when they heard the footsteps of his assistant who brought them the food.

He then tested this by introducing a metronome sound just before giving food to the dogs. After a few trials, when Pavlov clicked the metronome, the dogs began salivating even when no food was delivered. This was because the dogs had associated the metronome sound with food.

Further research showed that paired stimuli inputs changed the coding of the brain in the long-term, according to Lim. In the case of Lenire, the tongue acts as a reinforcer, like the food in Pavlov’s experiment, of the desired changes from stimulating the auditory nerve. By stimulating both the tongue and ears, your brain “changes its circuitry on a long-term scale”; “whereas if you just presented the sound, it may only change temporarily”, notes Lim.

Lenire’s ability to treat tinnitus in the long-term is not just theoretical, it has been proven in Neuromod’s clinical trials of the device in tinnitus patients.

In October last year, Neuromod published data from its Phase IIA TENT-A1 study, which enrolled 326 patients in Ireland and Germany and evaluated them over a 12-week treatment period and a 12-month post-treatment follow-up period.

Of the 84% of enrolled patients who completed the trial, 86.2% experienced improvement in tinnitus severity after 12 weeks of treatment, while 80.1% experienced continued improvement 12 months post-treatment based on two outcome questionnaires: the tinnitus handicap inventory and tinnitus functional index.

Neuromod plans to confirm these findings in an ongoing B phase of its Phase II trial, TENT-A2.

Already approved in the EU, Neuromod is now looking to expand into the US market. Credit: Neuromod

Already approved and being prescribed to patients for use for 30 to 60 minutes a day over ten weeks in Europe, Neuromod recently closed a €10.5m Series B round to support approval and commercialisation of Lenire in the US.

O’Neill explains that Neuromod is working on its US regulatory submission. The company will be submitting Lenire through the Food and Drug Administration (FDA)’s De Novo pathway and hopes to have approval next year.

Neuromod is interested in the US market partly because it is the one of the “largest single currency, single language market in the world”, according to O’Neill. This gives it an advantage over Europe where there is neither one currency nor one language. This means that “once we get FDA approval, the entire market is open to us.”

Another reason for O’Neill and Neuromod’s interest in the US is the country has the world’s single largest customer for hearing instruments: the US Department of Veterans Affairs (USVA).

Linked to this, O’Neill notes, “tinnitus is the largest and fastest growing service-connected disability among US veterans”, as the USVA’s 2019 annual benefits report suggests.

Therefore, once Neuromod receives FDA approval, the next step will be to launch Lenire in the US market and pursue the USVA as a customer.