'Hidden Hearing Loss' May Cause Tinnitus: Study

Scientists know that tinnitus, or ringing in the ears, affects 10% of adults worldwide. But they’re not exactly sure what causes the condition.

The traditional belief is that tinnitus happens in people who had already lost hearing. But some people who have tinnitus are still able to perform well on standard hearing tests, according to researchers at the Massachusetts Eye and Ear Infirmary. That happens because the tests don’t pick up auditory nerve loss, sometimes called "hidden hearing loss." 

"Our work reconciles the idea that tinnitus may be triggered by a loss of auditory nerve, including in people with normal hearing," Stéphane F. Maison, PhD, the lead author of a new study on tinnitus, said in a news release about the study.

Tinnitus is sometimes compared to phantom limb syndrome, in which people feel pain in limbs they no longer have. While the study published in Scientific Reports doesn’t refer to phantom limb syndrome, it does talk about "phantom sound."

"In other words, the brain tries to compensate for the loss of hearing by increasing its activity, resulting in the perception of a phantom sound, tinnitus. Until recently though, this idea was disputed as some tinnitus sufferers have normal hearing tests," the researchers explained in the news release. 

Annoyed by the ringing in your ears? What causes tinnitus, and how can you get the sound to buzz off?

The study included 294 adults — 201 who had never reported having tinnitus, 64 who had reported having temporary tinnitus, and 29 who had reported having constant tinnitus for 6 months or more. 

All 294 had performed normally on a pure tone test, in which subjects raise their hands when they hear beeps to measure the quietest sounds they can detect.

In a different kind of test, electrodes measured responses to clicking sounds in the inner ear, the auditory nerve, and the brain. The second test found reduced response in the auditory nerves and increased activity in the brainstem activity among those who had tinnitus.

Maison, a principal investigator at Eaton-Peabody Laboratories at Mass Eye and Ear/Harvard Medical School, called the study "a first step toward our ultimate goal of silencing tinnitus."

"Beyond the nuisance of having persistent ringing or other sounds in the ears, tinnitus symptoms are debilitating in many patients, causing sleep deprivation, social isolation, anxiety and depression, adversely affecting work performance, and reducing significantly their quality of life," he said in the news release. "We won’t be able to cure tinnitus until we fully understand the mechanisms underlying its genesis."

Sources:

NBC News: "Tinnitus may be linked to ‘hidden hearing loss’ missed on common tests, study suggests."

Scientific Reports: "Evidence of cochlear neural degeneration in normal-hearing subjects with tinnitus."

EurekAlert: "Loss of auditory nerve fibers uncovered in individuals with tinnitus."

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Cite this: 'Hidden Hearing Loss' May Cause Tinnitus: Study - Medscape - Dec 04, 2023.