Clues to Blast-Related Brain Injury

New research shows that explosions trigger unique damage to brain tissue.

The blasts caused by improvised explosive devices in Iraq and Afghanistan appear to inflict a fundamentally different type of brain damage than do more traditional sources of concussions, such as blunt trauma. The findings point toward new approaches to diagnosing and monitoring these injuries, which have been a huge concern to the military in recent years. The research also begins to resolve a controversy in brain-injury research--whether soldiers who are near an explosion but don't get hit in the head can still suffer a unique type of brain damage.

Brain blast: Scientists found that people who suffered concussions as the result of a blast had a more diffuse pattern of brain injury (shown in red) than those whose concussions resulted from a blow to the head or an acceleration injury. Credit: David Moore et al.

Regular concussions are typically caused by direct impact to the head, such as in a fall, or acceleration injuries, as in car accidents. In contrast, blast-induced brain injuries can include both of these factors as well as one that is unique to explosions--a rapid pressure wave that may wreak its own havoc on the brain. As a growing number of troops return from Iraq and Afghanistan with signs of brain injury--post-deployment surveys suggest that 10 to 20 percent of all deployed troops have experienced concussions--the military has been under increasing pressure to understand how this pressure wave affects the brain, as well as how best to diagnose and treat the resulting injuries.

Typically, damage from concussions does not show up on traditional medical imaging tests, such as CT scans or MRIs. But scientists have recently begun using a variation of MRI known as diffusion tensor imaging (DTI) to detect damage to the brain's white matter--the neural wiring that connects cells--after mild traumatic brain injury.

In the new study, David Moore, a neurologist and deputy director for research at the Defense and Veterans Brain Injury CenterinWashington, D.C., and colleagues used DTI to assess troops who had been diagnosed with mild traumatic brain injury following a blast, a direct impact, or an acceleration-induced injury several months prior, as well as healthy people who had never suffered a concussion. They found that those with blast-linked trauma had a more diffuse pattern of damage to the white matter, described as a "pepper-spray pattern," than those whose concussions were caused by direct impact or acceleration. The research was presented at the World Congress for Brain Mapping and Image Guided Therapy conference in Boston last month.

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Moore's team also found signs of inflammation in those people's brains several months after they experienced the blast, when most symptoms of concussion have typically faded away. "We see evidence of prolonged subacute to chronic inflammatory effects [in these patients]," says Moore. "It indicates something unique about the blast itself."