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Salt- or Sugar-Based Solution May Diminish Noise-Induced Hearing Loss
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% 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 school announced on its website. The results of the study were published in PNAS.
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: sensory hair cells, 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 neurons.
“That buildup of fluid pressure in the inner ear is something you might notice if you go to a loud concert,” said 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 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% of neuron loss, suggesting that the treatment may offer a way to preserve hearing function.
The treatment could have several potential applications, Oghalai explained.
“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 said. “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.
Original Paper: Kim J, Xia A, Grillet N, Applegate BE, Oghalai JS. Osmotic stabilization prevents cochlear synaptopathy after blast trauma. PNAS. 2018. Available at: http://www.pnas.org/content/early/2018/05/01/1720121115.short?rss=1
Source: Keck School of Medicine of USC, PNAS
Image: Keck School of Medicine of USC
Earwax, also known as cerumen, is a combination of secretions from sweat glands and fatty materials secreted from sebaceous glands. It can have one of two physical types: a wet yellow-brown wax or a dry white wax. For most people it is just regarded as a horrible bodily substance, but could it actually be more useful.
Our earwax could help prove our identity, reveal information about our ethnicity, sexual orientation, health, what we’ve eaten and even where we’ve been. According to senior author George Preti, PhD, an organic chemist at Monell. ‘Our previous research has shown that underarm odors can convey a great deal of information about an individual, including personal identity, gender, sexual orientation, and health status, we think it possible that earwax may contain similar information.’
Researchers theorise that the fatty nature of earwax makes it a likely repository for lipid-soluble odorants produced by certain diseases and the environment. In order to prove this they used analytical organic chemistry to identify the presence of odor-producing chemical compounds in human earwax, which confirmed that the amounts of these compounds differ between individuals. The findings suggest that human earwax, an easily obtained bodily secretion, could be an overlooked source of personal information.
So the future indicates that wax may have a usage, but at the moment it will probably just continue to be a problem for some of our patients. If you suffer from wax problems, we now offer basic earwax removal at Chalfont Hearing Centre. If you have concerns about earwax or hearing hygiene then contact us on 01494 765144.