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July 01, 2013

Researchers Say Hearing Loss from IEDs May Be Treatable

by Jessica Berman

Victims of improvised explosive devices, or IEDs, in war zones often suffer hearing loss, but a new study suggests that the deafness may not be permanent.  The findings suggest that the inner ear structures that are damaged in such roadside bomb blasts may recover with the proper treatment.  

Soldiers who survive the explosion of a roadside bomb, are usually deafened in addition to sustaining other physical injuries, according to John Oghalai, a specialist in diseases of the ear at Stanford University in California.  

He says that’s because the blast caused by IEDs produces an airwave of extreme force, and the inner ear structures cannot withstand the massive air pressure. He says hearing aids do not help in cases of explosion-related deafness, and being deaf can have a devastating impact on peoples’ lives.

“It takes you away from communication.  It takes you away from society.  When you can’t communicate with people, even if you could see them and whatever, it’s not the same as being an active participant in communication.  So people become isolated and they become depressed," said Oghalai.

There is currently no cure for blast-related deafness.  But Oghalai says researchers now know what causes it, so they can begin to develop biological cures.

He says earlier research indicated that the intense pressure wave obliterates the cochlea - the snail-shaped structure deep inside the inner ear that converts sound vibrations into the electrical impulses that the brain interprets as hearing.
 
But researchers led by Oghalai studied the effect of loud blasts in a mouse model, and they discovered that was not the case.  

When the anesthetized rodents were exposed to noise of the same intensity produced by an IED, tiny hair and nerve cells inside the cochlea became severely damaged and died, but not the critical cochlea itself.

“The cochlea looks almost like it’s just been subjected to a lot of repetitive noise trauma, rather than any type severe trauma.  So that’s good [because] as we develop treatments for one, it will work for the other," he said.

Oghalai theorizes that treating the ear immediately after the damage could limit the extent of hearing loss.  He hopes researchers will have therapies available for clinical human trials in 10 years.

A study by John Oghalai and colleagues identifying the cause of IED-related deafness is published in the journal PLoS ONE.