It turns out that long-term hearing loss from loud blasts from roadside bombs and other deafening explosions could be treatable, according to a new study by researchers at the Stanford University School of Medicine.
The study, which used mice, found that the loud explosions caused hair-cell and nerve-cell damage, as opposed to structural damage as previously thought. Damage is, in fact, primarily done to the cochlea, the inner ear's auditory portion. This discovery is good news for millions of soldiers and civilians suffering from long-term hearing loss from explosions.
John Oghalai, M.D., Stanford's associate professor of otalyngology and the study's senior author, comments in July's issue of PLOS ONE that the study's findings mean that researchers could attempt to successfully reduce this hearing loss from explosions.
New Hearing Loss Findings
The damage would be irreversible if the cochlea had been ripped apart by the explosion, as earlier studies found, but the new discovery suggests that the hearing loss is, in fact, treatable. Earlier studies' findings may have been due to the use of older, less sophisticated imaging techniques, according to researchers.
Oghalai, who treats patients at Stanford Hospital and Clinics and directs the hearing center at the Lucile Packard Children's Hopsital, claims that veterans' most common health issue is hearing loss, whether it be minor ringing from gunfire, for example, or hearing loss from explosions and loud machinery.
The U.S. Department of Defense funded Stanford's study, after recognizing the increasingly prevalent global use of improvised explosive devices (IEDs). Tinnitus, a constant ringing in the ears, is the most common condition for veterans with service-connected disabilities, while hearing loss falls in second place. Aside from veterans, the study's results hold true for anyone exposed to loud noises from jet engines, air bags or gunfire.
More Than 60% of Wounded Soldiers Experience Hearing Loss
More than 60 percent of wounded-in-action military personnel have eardrum injuries, tinnitus or hearing loss, according to the study. Twenty-eight percent of all service members experience post-deployment hearing loss. While the cause is not well-understood, permanent hearing loss tends to occur after a blast injury to the ear leads to cochlea trauma.
Researchers used a micro-CT scanner to observe the mice's ears, imaging the ears' workings after dissection. They noticed hair cell loss and auditory nerve cell loss when they looked inside the cochlea, according to Oghalai.
Oghalai claims that with one loud blast, you could lose a huge number of hair cells and auditory nerve cells but not immediately, meaning that the damage could be diminished if the ear is treated with certain medications right after the blast.
Blast-causing hearing loss is caused by the body's immune response to the injured cells, Oghalai says. The body creates scar tissue to heal the injury, but this tissue damages the ear's ability to vibrate and therefore its hearing mechanism.
Oghalai adds that determining the window in which doctors can stop the body's inflammatory response, immediately after a loud blast, could lead to further research.
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