Subtle pupil dilation and changes in expression have been found to be a new way for medical professionals to detect tinnitus. For the first time, it provides a reliable test to help determine the severity of the condition, providing a more accurate means of intervention.
Researchers form Mass General Brigham observed these tinnitus biomarkers after seeing how a patient's face and eyes responded to exposure to unpleasant sounds. Subtle but clear involuntary changes allowed for the patient to have their condition plotted on a scale – something that takes the onus away from less reliable self-reporting.
“Imagine if cancer severity were determined by giving patients a questionnaire – this is the state of affairs for some common neurological disorders like tinnitus,” said corresponding author Daniel Polley, director of the Eaton-Peabody Laboratories at Mass Eye and Ear, part of Mass General Brigham. “For the first time, we directly observed a signature of tinnitus severity. When we began this study, we didn’t know if sounds would elicit facial movements; so, to discover that these movements not only occur, but can provide the most informative measure to date of tinnitus distress, is quite surprising.”
The new method of detection homes in on observing central nervous system stress, in particular the "fight, flight or freeze" trigger in response to unpleasant sounds like loud coughs or a baby's cry. The more pronounced the tinnitus, the more delayed this physical response is as the auditory information is processed and assessed for threat level by the brain.
For those with severe tinnitus, their involuntary facial twitches and pupil dilation occurred in response to pleasant and unpleasant sounds, as their nervous system was unable to differentiate good from bad. People without the condition, or with less problematic and pervasive tinnitus, had a more nuanced response, and only showed these telltale facial cues when exposed to unpleasant sounds.
“What’s really exciting is this vantage point into tinnitus severity didn’t require highly specialized brain scanners; instead, the approach was relatively low-tech.,” said Polley. “If we can adapt this approach to consumer-grade electronics, they could be put to use in hearing health clinics, as objective measures in clinical trials and by the public at large.”
Tinnitus – most often described as an incessant sound in the ears – can vary in severity, from a slight annoyance to hugely invasive and distressing, affecting sleep, mental health and overall quality of life. Around a quarter of adults aged 65 and older are thought to be affected, but until now there hasn't been a way to reliably assess severity.
As the condition becomes more severe, the body becomes increasingly hyper-vigilant in assessing perceived auditory threats – which triggers alertness (pupil dilation) and other detectable involuntary movements. In the study, 50 participants with no hearing issues and 47 with varying degrees of tinnitus severity were exposed to pleasant and unpleasant sounds, with AI assessing these subtle physical responses.
Now, the team hopes to use this novel nervous system intel to develop interventions that use neural stimulation to counter tinnitus "noise" and offer sufferers relief.
“These biomarkers get to the root of the distress,” said Polley. “While imaging might show hyperactive brain regions in tinnitus patients, these biomarkers reveal body-wide threat evaluation systems that are operating outside of their normal range, leading to the distressful symptoms they experience.”
While age-related health issues can make it a little more complicated in isolating the body's "fight or flight" response specifically to tinnitus, this new assessment method is a big step in accurately and objectively diagnosing the condition and then developing a more personalized treatment plan.
The research was published in the journal Science Translational Medicine.
Source: Mass General Brigham
