Simple treatment may minimize hearing loss triggered by loud noises

May 7, 2018, University of Southern California
A view of a small part of the mammalian cochlea, which features rows of sensory hair cells (cyan) and synaptic sites (small green and yellow dots), where the sensory hair cells communicate to the nerves. Credit: Juemei Wang (Oghalai lab)

It's well known that exposure to extremely loud noises—whether it's an explosion, a firecracker or even a concert—can lead to permanent hearing loss. But knowing how to treat noise-induced hearing loss, which affects about 15 percent of Americans, has largely remained a mystery. That may eventually change, thanks to new research from the Keck School of Medicine of USC, which sheds light on how noise-induced hearing loss happens and shows how a simple injection of a salt- or sugar-based solution into the middle ear may preserve hearing. The results of the study were published today in PNAS.

Deafening sound

To develop a treatment for noise-induced hearing loss, the researchers first had to understand its mechanisms. They built a tool using novel miniature optics to image inside the cochlea, the hearing portion of the inner ear, and exposed mice to a loud noise similar to that of a roadside bomb.

They discovered that two things happen after exposure to a loud noise: , which are the cells that detect sound and convert it to neural signals, die, and the inner ear fills with excess fluid, leading to the death of .

"That buildup of fluid pressure in the inner ear is something you might notice if you go to a loud concert," says the study's corresponding author John Oghalai, MD, chair and professor of the USC Tina and Rick Caruso Department of Otolaryngology - Head and Neck Surgery and holder of the Leon J. Tiber and David S. Alpert Chair in Medicine. "When you leave the concert, your ears might feel full and you might have ringing in your ears. We were able to see that this buildup of fluid correlates with neuron loss."

Both neurons and sensory hair cells play critical roles in hearing.

"The death of sensory hair cells leads to hearing loss. But even if some sensory hair cells remain and still work, if they're not connected to a neuron, then the brain won't hear the sound," Oghalai says.

The researchers found that sensory hair cell death occurred immediately after exposure to loud noise and was irreversible. Neuron damage, however, had a delayed onset, opening a window of opportunity for treatment.

A simple solution

The buildup of fluid in the inner ear occurred over a period of a few hours after exposure and contained high concentrations of potassium. To reverse the effects of the potassium and reduce the fluid buildup, salt- and sugar-based solutions were injected into the middle ear, just through the eardrum, three hours after noise exposure. The researchers found that treatment with these solutions prevented 45-64 percent of neuron loss, suggesting that the treatment may offer a way to preserve hearing function.

The treatment could have several potential applications, Oghalai explains.

"I can envision soldiers carrying a small bottle of this solution with them and using it to prevent hearing damage after exposure to blast pressure from a roadside bomb," he says. "It might also have potential as a treatment for other diseases of the inner ear that are associated with fluid buildup, such as Meniere's disease."

Oghalai and his team plan to conduct further research on the exact sequence of steps between fluid buildup in the inner ear and neuron death, followed by clinical trials of their potential for noise-induced loss.

Explore further: Researchers identify new drugs that could help prevent hearing loss

More information: Jinkyung Kim el al., "Osmotic stabilization prevents cochlear synaptopathy after blast trauma," PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1720121115

Related Stories

Researchers identify new drugs that could help prevent hearing loss

March 7, 2018
Researchers from St. Jude Children's Research Hospital have discovered that inhibiting an enzyme called cyclin-dependent kinase 2 (CDK2) protects mice and rats from noise- or drug-induced hearing loss. The study, which will ...

White noise after loud noise prevents hearing deficits in mice

June 5, 2017
Mild hearing loss from exposure to less than one hour of loud noise leads to a reorganization of circuits in a key midbrain structure of the auditory system in mice, finds new research published in The Journal of Neuroscience. ...

Guard against hearing loss from fireworks

July 4, 2017
(HealthDay)—Watching a fireworks display can be a treat for your eyes, but the noise can be a threat to your ears.

Is your hearing at risk? Protect your ears

June 6, 2016
Hearing loss is a natural part of the aging process. But noise-induced hearing loss is on the rise.

For millions of Americans, everyday life takes toll on their hearing

February 7, 2017
(HealthDay)—The noise of modern life causes permanent hearing damage to many U.S. adults who don't even suspect they've experienced a loss, federal researchers reported Tuesday.

Hearing loss from loud blasts may be treatable, researchers say

July 1, 2013
Long-term hearing loss from loud explosions, such as blasts from roadside bombs, may not be as irreversible as previously thought, according to a new study by researchers at the Stanford University School of Medicine.

Recommended for you

Discovery of inner ear function may improve diagnosis of hearing impairment

October 15, 2018
Results from a research study published in Nature Communications show how the inner ear processes speech, something that has until now been unknown. The authors of the report include researchers from Linköping University, ...

Team's study reveals hidden lives of medical biomarkers

October 12, 2018
What do medical biomarkers do on evenings and weekends, when they might be considered off the clock?

Widespread errors in 'proofreading' cause inherited blindness

October 12, 2018
Mistakes in "proofreading" the genetic code of retinal cells is the cause of a form of inherited blindness, retinitis pigmentosa (RP) caused by mutations in splicing factors.

Researchers create a functional salivary gland organoid

October 11, 2018
A research group led by scientists from Showa University and the RIKEN Center for Biosystems Dynamics Research in Japan have, for the first time, succeeded in growing three-dimensional salivary gland tissue that, when implanted ...

Lassa fever vaccine shows promise and reveals new test for immunity

October 11, 2018
Lassa fever belongs to the same class of hemorrhagic fevers as Ebola. Like Ebola, it has been a major health threat in Western Africa, infecting 100,000-300,000 people and killing 5,000 per year. A new vaccine against both ...

Genetically engineered 3-D human muscle transplant in a murine model

October 10, 2018
A growing need for tissues and organs in surgical reconstruction is addressed by the promising field of tissue engineering. For instance, muscle atrophy results from severe traumatic events including deep burns and cancer, ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

shitcunt
not rated yet May 08, 2018
Wearing ear protection or a needle to the eardrum, which would you choose?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.