According to the Centers of Disease Control and Prevention, since 2006, blasts have been the most common cause of injury among American soldiers treated at Walter Reed National Military Medical Center.
(U.S. Marine Corps photo/Released)
An explosion generates a blast wave traveling faster than sound and creating a surge of high pressure immediately followed by a vacuum. Studies show that the blast wave shoots through armor and soldiers' skulls and brains, even if it doesn't draw blood. While the exact mechanisms by which it damages the brain's cells and circuits are still being studied, the blast wave's pressure has been show to compress the torso, impacting blood vessels, which then send damaging energy pulses into the brain. The pressure can also be transferred partially through the skull, interacting with the brain.
Shrapnel and debris propelled by the blast can strike a soldier's head, causing either a closed-head injury through blunt force or a penetrating head injury that damages brain tissue.
The kinetic energy generated and released by an explosion can accelerate a soldier's body through the air and into the ground or nearby solid object. Once the body stops, the brain continues to move in the direction of the force, hitting the interior of the skull and then bouncing back into the opposite side, causing a coup-contrecoup injury.
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