Irreversible Hearing Damage Caused By Noise Is Expected To Be Treated
It is well known that exposure to very large noise, whether it is an explosion, firecrackers, or a concert, can cause permanent hearing loss, which affects about 15% of Americans. However, how to treat the hearing loss caused by noise is still a large mystery. This situation maybe will change, thanks to a new study published by Peck School of Medicine at the University of Southern California at PNAS, which reveals how noise-induced hearing loss occurs and shows How to maintain hearing in a simple injection of a salt or a sugar-based solution in the middle ear.
In order to develop a method for treating noise-induced hearing loss, researchers must understand the mechanism firstly. They used a new micro-optical instrument to create a tool to image the inside of the cochlea (the auditory part of the inner ear) and expose the mouse to the huge noise of a roadside bomb.They found that when exposed to loud noise, two things happen: sensory hair cells, cells that detect sound and convert it into nerve signals, die, so the inner ear is filled with excess fluid, causing neuronal death. .
The researchers explained that if you go to a loud concert, you may notice an increase in fluid pressure in the inner ear. When you leave the concert, your ears may feel uncomfortable and will ring. We can see that the accumulation of this fluid is related to the loss of neurons.
Neurons and sensory hair cells play a key role in hearing, and sensory hair cell death leads to hearing loss. But even if some of the hair cells are still working, if they are not connected to the neurons, then the brain will not hear the sound. The researchers found that sensory hair cell death occurs after exposure to loud noise and is irreversible. However, neuronal damage has a delayed onset, opening the window of opportunity for treatment.
Accumulation of fluid in the ear occurs within a few hours after exposure to loud noise and contains high concentrations of potassium. In order to reverse the action of potassium and reduce the accumulation of liquid, after 3 hours of noise exposure, the salt and sugar-based solution was injected into the middle ear, passing only through the tympanic membrane. The researchers found that treatment with these solutions prevented 45-64% of neuronal loss, suggesting that this treatment can provide a means of maintaining hearing function.