Studies Associate Noisy Inner Ear Nerve Injury with Endolymphatic Hydrops

Exposure to loud sounds such as firecrackers and deafening concerts is the most common preventable cause of deafness. According to a survey, more than 12% of the world’s population is at risk for noise-induced hearing loss.

Loud sounds can cause loss of auditory nerve cells in the inner ear. The inner ear is responsible for transmitting acoustic information to the brain, causing hearing loss. However, the mechanism behind this deafness is not fully understood.

A new study by USC’s Keck Medicine now links this type of inner ear nerve injury to a condition known as endolymphatic hydrops, an accumulation of fluid in the inner ear, both of which are routinely encountered by people. Life has shown to occur at noise exposure levels that may occur.

In addition, researchers have found that treating the resulting fluid accumulation with readily available saline reduces nerve damage to the inner ear.

This study provides clues to better understand when and how noise-induced deafness occurs and proposes new ways to detect and prevent deafness. “

Dr. John Ogarai, Otorhinolaryngologist at Keck Medicine, Chairman of USC Caruso Otorhinolaryngology – Leading Author of Head and Neck Surgery and Research

A previous study by Oghalai in mice exposed to blast pressure waves simulating a bomb explosion linked nerve damage to fluid accumulation in the inner ear.

In this study, Oghalai et al. Wanted to investigate the effects of common loud sounds in the range of 80-100 decibels on the ears. After exposure, they used an imaging technique known as optical coherence tomography to measure the level of cochlear inner ear fluid, a hollow spiral bone found in the inner ear.

Moisture levels in the inner ear remained normal until exposed to the sound of 95 decibels. However, researchers found that after exposure to 100 decibels-; this corresponds to the sound of power lawnmowers, chainsaws, motorcycles, etc.-; mice developed inner ear fluid accumulation within hours. One week after this exposure, the animals were found to have lost auditory neurons.

However, when researchers apply hypertonic saline, a salt-based solution used to treat human nasal congestion, to affected ears one hour after noise exposure, immediate fluid accumulation and long-term fluid accumulation occur. Both nerve damage in the body is reduced, which means deafness can be prevented at least partially.

According to Oghalai, these findings have some important implications. In particular, the loss of nerve cells in the inner ear is known as “hidden hearing loss” because hearing tests cannot detect damage.

“First, you can scan the human ear exposed to loud noises, such as deploying sirens and airbags, to determine the level of fluid accumulation. This technology has already been tested. Medical professionals have already tested it. You may have a way to diagnose an imminent nerve. Damage. ” “Second, if the scan finds water buildup, people can be treated with hypertonic saline and possibly protect their hearing.”

He also believes that this study opens a new window for understanding the disorders of the inner ear that cause Meniere’s disease, dizziness, tinnitus (tinnitus), and deafness.

“”Previously, the accumulation of inner ear fluid was thought to be primarily associated with Meniere’s disease. This study shows that people exposed to loud noises experience similar changes, “he said.

Oghalai hopes that this study will lead to further research into why ear fluid accumulation occurs and will facilitate the development of better treatments for Meniere’s disease.

This study was supported by the National Institute for Deafness and Other Communication Disorders.