Common loud noises cause fluid buildup in the inner ear, study finds
Research has implications for detecting and treating hearing loss

Date:
November 11, 2021
Source:
Keck Medicine of USC
Summary:
A new study reveals that common loud noises cause fluid buildup
in the inner ear and suggests a simple possible treatment for
noise-induced hearing loss.



FULL STORY ========================================================================== Exposure to loud noise, such as a firecracker or an ear-splitting concert,
is the most common preventable cause of hearing loss. Research suggests
that 12% or more of the world population is at risk for noise-induced
loss of hearing.


==========================================================================
Loud sounds can cause a loss of auditory nerve cells in the inner ear,
which are responsible for sending acoustic information to the brain,
resulting in hearing difficulty. However, the mechanism behind this
hearing loss is not fully understood.

Now, a new study from Keck Medicine of USC links this type of inner ear
nerve damage to a condition known as endolymphatic hydrops, a buildup of
fluid in the inner ear, showing that these both occur at noise exposure
levels people might encounter in their daily life.

Additionally, researchers found that treating the resulting fluid buildup
with a readily available saline solution lessened nerve damage in the
inner ear.

"This research provides clues to better understand how and when
noise-induced damage to the ears occurs and suggests new ways to detect
and prevent hearing loss," said John Oghalai, MD, an otolaryngologist with
Keck Medicine, chair of the USC Caruso Department of Otolaryngology --
Head and Neck Surgery and lead author of the study.

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



==========================================================================
For this study, Oghalai and colleagues wanted to explore the effect of
common loud sounds ranging from 80 to 100 decibels on the ear. After the exposure, they used an imaging technique known as an optical coherence tomography to measure the level of inner ear fluid in the cochlea,
the hollow, spiral-shaped bone found in the inner ear.

Up until exposure to 95 decibels of sound, the inner ear fluid level
remained normal. However, researchers discovered that after exposure to
100 decibels - - which is equivalent to sounds such as a power lawn mower, chain saw or motorcycle -- mice developed inner ear fluid buildup within
hours. A week after this exposure, the animals were found to have lost
auditory nerve cells.

However, when researchers applied hypertonic saline, a salt-based solution
used to treat nasal congestions in humans, into affected ears one hour
after the noise exposure, both the immediate fluid buildup and the
long-term nerve damage lessened, implying that the hearing loss could
be at least partially prevented.

These study results have several important implications, according to
Oghalai, especially as the loss of nerve cells in the inner ear is known
as "hidden hearing loss" because hearing tests are unable to detect
the damage.

"First, if human ears exposed to loud noise, such as a siren or airbag deployment, can be scanned for a level of fluid buildup -- and this
technology is already being tested out -- medical professionals may have
a way of diagnosing impending nerve damage," he said. "Secondly, if the
scan discovered fluid buildup, people could be treated with hypertonic
saline and possibly save their hearing." He also believes the study opens
a new window into understanding Meniere's disease, a disorder of the inner
ear that causes vertigo, ringing in the ears (tinnitus) and hearing loss.

"Previously, inner ear fluid buildup was thought to be primarily linked
to Meniere's disease. This study indicates that people exposed to loud
noises experience similar changes," he said.

Oghalai hopes this study will lead to further research on the reasons ear
fluid buildup occurs, and encourage the development of better treatments
for Meniere's disease.

The study was supported by the National Institute on Deafness and Other Communication Disorders.

========================================================================== Story Source: Materials provided by Keck_Medicine_of_USC. Note: Content
may be edited for style and length.


========================================================================== Journal References:
1. Ido Badash, Patricia M. Quin~ones, Kevin J. Oghalai, Juemei Wang,
Christopher G. Lui, Frank Macias-Escriva, Brian E. Applegate,
John S.

Oghalai. Endolymphatic Hydrops is a Marker of Synaptopathy Following
Traumatic Noise Exposure. Frontiers in Cell and Developmental
Biology, 2021; 9 DOI: 10.3389/fcell.2021.747870
2. Jinkyung Kim, Anping Xia, Nicolas Grillet, Brian E. Applegate,
John S.

Oghalai. Osmotic stabilization prevents cochlear synaptopathy after
blast trauma. Proceedings of the National Academy of Sciences,
2018; 115 (21): E4853 DOI: 10.1073/pnas.1720121115 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211111080420.htm

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