Against the noise

Minimizing hearing loss triggered by loud noises

Research reveals how traumatic noise damages hearing and identifies a potential way to preserve it

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 in PNAS.

A deafening sound

Photo
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.
Source: Juemei Wang (Oghalai lab)

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. “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.

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

John Oghalai

The buildup of fluid in the inner ear occurred over a period of a few hours after loud noise 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 treatment for noise-induced hearing loss.


Source: Keck Medicine of USC

08.05.2018

Read all latest stories

Related articles

Radiation protection

Using skin creams during radiation therapy: Is it safe?

Nearly two-thirds of all cancer patients in the United States will undergo radiation therapy as part of their treatment, and as many as 90 percent of those patients will experience radiation…

Cause and effect

Diabetes and heart failure: discovering the connection

Men with diabetes are 2.4 times more likely than non-diabetics to suffer heart failure and women are five times more likely. But why? A new Loyola University Chicago Stritch School of Medicine study…

Research

Non-small cell lung cancer: women live longer than men

Women diagnosed with non-small cell lung cancers (NSCLC) live longer than their male counterparts, according to results of a SWOG study presented by Loyola Medicine researcher Kathy Albain, MD, at…

Related products

Research use only (RUO)

Eppendorf - Mastercycler nexus X2

Eppendorf AG

Research use only (RUO)

SARSTEDT - Low DNA Binding Micro Tubes

SARSTEDT AG & CO.

Research use only (RUO)

Shimadzu - CLAM-2000

Shimadzu Europa GmbH