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In the study, researchers at Boston University and the Veterans Affairs Boston Healthcare System analyzed brain tissue from four U.S. military personnel who were known to have been close to explosions.
The results, published online May 16 in Science Translational Medicine, showed that exposure to a single blast -- equivalent to the force from a typical improvised explosive device (IED) -- results in chronic traumatic encephalopathy and long-term brain impairments associated with the condition.
Chronic traumatic encephalopathy, a progressive brain disorder that can only be diagnosed after death, has been reported in athletes with multiple concussions. Chronic traumatic encephalopathy and traumatic brain injury share common features, including psychiatric symptoms and long-term memory and learning problems.
Traumatic brain injury can occur in people exposed to blasts and may affect about 20 percent of the 2.3 million U.S. military personnel deployed in Iraq and Afghanistan since 2001, according to the researchers.
The investigators also concluded that the blast wind, not the shock wave, from an IED explosion leads to traumatic brain injury and long-term consequences such as chronic traumatic encephalopathy.
Explosions lead to dramatic changes in pressure in the air around the blast. In addition to injuries caused by debris and shrapnel, the blast forces themselves can lead to devastating injuries.
A shock wave occurs right after an explosion, when the air around the explosion becomes overpressurized; a blast wind follows the shock wave, when the air around the explosion gets sucked back in to fill the void created by the blast. A blast wind can reach a velocity of up to 330 miles per hour.
"The force of the blast wind causes the head to move so forcefully that it can result in damage to the brain," study co-leader Dr. Lee Goldstein, an associate professor at Boston University School of Medicine and Boston University College of Engineering, said in a university news release.
The researchers also found that immobilizing the head during blast exposure can prevent the learning and memory deficits associated with chronic traumatic encephalopathy.
"Our study provides compelling evidence that blast TBI [traumatic brain injury] and CTE [chronic traumatic encephalopathy] are structural brain disorders that can emerge as a result of brain injury on the battlefield or playing field," Goldstein said. "Now that we have identified the mechanism responsible for CTE, we can work on developing ways to prevent it so that we can protect athletes and our military service personnel."
-- Robert Preidt
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