Hope for individuals impacted by ‘hidden’ tinnitus disorder

Researchers are uncovering fresh perspectives on the “hidden” condition tinnitus, whose illusory ringing, hissing, and other sounds are frequently associated with auditory damage, yet for which healthcare professionals have lacked an objective gauge, until now.

This development, published in late April in the journal Science Translational Medicine and supported by the National Institute of Deafness and Other Communication Disorders, holds the potential to offer healthcare providers and investigators a method to assess tinnitus intensity beyond the subjective patient surveys currently employed. Moreover, it may assist in the formulation of more effective treatments.

In this revised dialogue, Daniel Polley, head of the Eaton-Peabody Laboratories at Harvard-associated Massachusetts Eye and Ear and educator in otolaryngology and head and neck surgery at Harvard Medical School, shares insights from research conducted with MEE colleagues that investigates involuntary pupil dilation and facial reactions to sound in patients with differing degrees of tinnitus.

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What exactly is tinnitus? Is it simply ringing in the ears?

Most instances of tinnitus share one characteristic: the conscious perception of a sound that does not exist in the tangible environment, an illusory sound.

I experience tinnitus, and it resembles a nonstop radio session — a singular note — that I can generally dismiss. Nevertheless, it’s always present if I choose to focus on it.

It’s remarkably prevalent, affecting around 12 percent of individuals. Among those aged 65 and older, that figure rises to 25 percent and beyond.

For many, this illusory sound poses a mild inconvenience, but for others it can be crippling. It transcends a mere auditory issue; it encapsulates a life-altering challenge and affects mental well-being. The severity of tinnitus is not inherently louder, as most individuals perceive their tinnitus at a relatively low volume when compared to actual sounds.

However, what differentiates individuals with tinnitus disorders is the way it intrudes on emotional and arousal systems. A prevalent grievance among those experiencing severe tinnitus is difficulty falling asleep and waking more easily.

Frequently, individuals with tinnitus disorders exhibit an aversion or heightened sensitivity to sound. There’s significant co-occurrence with depression, anxiety, and social isolation, representing a spectrum of neurological and psychological complications that accompany it.

So, for those genuinely struggling, it’s not necessarily due to the volume, but because they simply cannot ignore it?

Exactly, they can’t filter it out. Perhaps the neurological profile of more severe tinnitus distinguishes it from milder cases; the very brain systems intended to eliminate irrelevant stimuli are co-opted in generating the tinnitus experience. This hypothesis fueled our investigation and led us down this path.

And you think your research could facilitate a better understanding and study of this condition?

Improved treatments for tinnitus are essential. That is the primary focus for the field — and for me personally. However, attempting treatments without first establishing a solid foundation is unlikely to yield significant results.

It’s relatively easy to assert that a treatment is effective when its success hinges solely on subjective assessments and lacks controls for placebo effects. To be persuasive, forthcoming studies must illustrate enhancements in physiological indications of tinnitus distress — transformations that are not likely to derive solely from placebo effects.

This research assists in laying that groundwork. Initially, it provides a method to visualize different tinnitus types. Secondly, it connects those types to an intervention and asks, “Did it work?” based not merely on subjective patient feedback, but on whether an objective physiological change occurred as well. That’s how we can validate that we’re genuinely advancing.

So, what distinguishes tinnitus from ailments like the common cold or cancer is that, prior to now, we lacked a physiological method to discern what’s occurring? It’s subjective and based on self-reports?

Exactly. It transports us back to the 18th or 19th century. With any other neurological condition, such as epilepsy, one can quantify a seizure or assess a stroke. For Parkinson’s, neuroimaging enables objective measurement of motor functions.

Very few disorders are genuinely hidden, where you cannot utilize outputs or inputs to illuminate the specter within the system. Chronic pain mainly falls into this category — it’s actually more prevalent than tinnitus.

For both conditions, an objective measure is essential. In chronic pain, all that exists is, “How intense is your pain today, on a scale of one to ten?” This metric’s value is that it forecasts the individual severity scores derived from questionnaires.

Can you elaborate on the measure you’ve documented?

The study offers a novel approach to conceptualizing…
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what’s leading to tinnitus. We aimed to develop an indicator that would relate to an individual’s severity and not merely differentiate them from someone without tinnitus.

We also sought to circumvent a measurement that could solely be conducted in a specific research hospital utilizing costly devices. Our goal is to assess these elements with apparatus that could practically be found in an ordinary hearing health clinic.

Our concept is that as you or I go about our daily activities, our brain continuously monitors the surroundings for possible dangers so we can protect ourselves, escape, or remain immobile. These systems are structured to capture your conscious attention since awareness of potential threats is crucial.

If these systems are commandeered within the tinnitus-generating network, that might clarify why it’s challenging to push it from your thoughts: because you’ve integrated the mechanism that is intended to always provoke conscious awareness. If these networks detect a danger, they engage the sympathetic nervous system — fight, flight, or freeze — leading to physiological responses such as pupil dilation and heightened galvanic skin response.

Thus, if individuals with intense tinnitus have their auditory threat assessment system stuck in overdrive, we could present emotionally charged sounds across a spectrum: neutral sounds, like a typewriter; upbeat sounds, like a laughing baby; and sounds that most people find distressing, like a severe coughing fit.

We anticipated that individuals with more intense tinnitus would exhibit an exaggerated response to a wide array of sounds, with their sympathetic nervous system perceiving all these sounds as potential threats.

How do you connect that to an objective measurement?

Clearly, we control our facial expressions to convey our emotional state, but our faces also involuntarily react to reflect our assessment of situations — whether pleasant or unpleasant — and our internal emotional state — whether sad or joyous. Numerous studies have investigated facial expressions when presented with images meant to evoke happiness or fear, yet no one has examined facial expressions in response to auditory stimuli. We did and determined that sounds indeed provoke facial movements.

If the sound is enjoyable, a neurotypical individual shows more movement around the mouth. Conversely, if the sound is unpleasant, there is movement in the brow and tightening of the eyes.

Upon examining individuals with significant tinnitus and sound sensitivity, we found a stark contrast. Their facial expressions exhibited little movement. They displayed a muted response across all sounds, whether pleasant, neutral, or unpleasant.

No one has ever quantified this before. No one has ever considered the face and its connection to tinnitus. Yet that turned out to be, by far, the most insightful measurement for predicting an individual’s tinnitus severity.

Was there a pupil reaction as well?

Indeed, the pupil is part of the sympathetic nervous system. It’s interconnected with the fight, flight, or freeze mechanism. The pupil expands when the sympathetic nervous system is activated, and in our study, the pupil dilated excessively to the sounds that the face was responding minimally to.

They are complementary to each other. They provided distinct insights into an individual’s severity. When utilized together, they enhance the prediction of a person’s tinnitus intensity compared to using just one of them. The facial movements are significantly more informative.

How might this be utilized as a tool?

The first FDA-approved device for tinnitus is available by prescription, though its efficacy is debated. One of the challenges is that they employ the same subjective questionnaires to assess outcomes. With every tinnitus intervention developed, individuals question, “Is it a placebo?”

My laboratory is dedicated to generating novel therapies, so these findings represent a crucial achievement. We can incorporate them into our interventional research. We aim to transition to a video-based system to facilitate high-quality measurements more swiftly and with less specialized apparatus. We may achieve clinical application if physicians can categorize a tinnitus patient as severe or mild in their practice using an objective measure.

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