After a concussion, the brain may no longer make sense of sounds

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Researchers are studying athletes and military personnel to learn more about how a concussion can affect the brain’s ability to understand sound.

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Concussion from bomb blasts

The military has been studying the link between head injury and sound processing since about 2005, says Melissa Papesh, a research investigator at the Veterans Affairs National Center for Rehabilitative auditory research in Portland, Ore.

During the wars in Iraq and Afghanistan, she says, the VA began to see something odd in military personnel.

«We have all of a sudden this large influx of relatively young and middle aged people,» she says. «They’re coming into our audiology clinics and saying, ‘hey, I’m having problems hearing.'»

Except when Papesh runs tests on their hearing, it looks «essentially normal.» Surprisingly, their ears are fine. But their brains can’t process what they’re hearing.

Like athletes with concussions, these patients have trouble separating speech from background noise. Many also have problems processing rapidly spoken speech, she says.

VA scientists knew that the blast wave from a roadside bomb could cause a concussion without leaving any visible sign of injury. So they took a closer look at the patients who had trouble processing sounds, and found that many had been exposed to one or more blasts.

Some veterans still have auditory symptoms more than a decade after being exposed to a bomb blast, Papesh says.

Now that most military personnel have left the battlefield, the VA is looking at another potential source of brain injury. It involves exposure to lots of smaller blast waves that pass through the brains of people who fire high-powered weapons or use explosives in training exercises.

«That will be a big area of research in the future,» Papesh says. The military «wants to prevent this kind of stuff before it becomes a chronic problem for veterans.»