Diagnosing Hidden Hearing Loss | National Institutes of Health (NIH)

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In short

  • Researchers have developed a method, based on word recognition, to estimate the loss of nerve functioning in the inner ear.
  • With further development, the method could be used in hearing tests to determine if hearing problems are due to loss of nerve fibres.

One in eight people nationwide live with hearing loss in both ears. A common cause of hearing loss is damage to the hair cells in the inner ear. These cells detect sound waves and communicate with the cochlear nerve, which carries sound information to the brain. Loud noise, aging, and certain medications can all potentially cause the loss of these delicate hair cells.

Standard hearing tests measure people’s ability to detect certain sound frequencies. Yet some people who have normal scores on standard hearing tests may still have trouble following a conversation in noisy environments. This type of hearing loss is sometimes called “hidden hearing loss” because it is not easily detected with common hearing tests.

NIH-funded researchers led by Dr. Stéphane Maison of the Massachusetts Eye and Ear Infirmary investigated ways to identify cochlear nerve damage, which could be a cause of hidden hearing loss. In their new study, they looked at more than 95,000 word recognition scores from hearing tests. They included scores from people with a wide range of conditions that cause hearing loss. These included aging, overexposure to noise, and conditions known to specifically cause nerve damage.

The team hypothesized that people with cochlear nerve damage would have lower scores on the word recognition task than predicted by their standard hearing tests. This could happen because, although they can hear certain sounds, the nerve damage would prevent these sounds from being processed properly by the brain. The results were published on June 23, 2022 in Scientific reports.

The researchers found that many people had lower word recognition scores than their standard hearing tests predicted. Age-related cognitive decline was not a major factor in these differences. Word recognition deficits were highest in people with conditions known to significantly damage cochlear nerve fibers.

The team then combined the data from this study with previous work that looked at cochlear nerve damage during autopsies in different age groups. They used this information to develop a model that could estimate the amount of nerve or neural fiber loss based on the difference between predicted and measured word recognition scores.

“Now, for the first time, we know how much neural loss must accumulate before clinical word recognition test scores begin to decline. Further work is needed to improve this model and provide ways to assess neural damage in standard hearing exams,” Maison says.

—by Sharon Reynolds

Funding: NIH National Institute on Deafness and Other Communication Disorders (NIDCD).

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