Accelerating to get through a traffic light before it turned red, jason was hit broadside by a car coming from the right and flipped. three backseat passengers were treated and hospitalized for injuries. one backseat passenger lost consciousness at the scene of the accident. however, by the time he arrived at the hospital one hour later, he had regained consciousness and was coherent. no neurologic deficits were noted after a 24-hour observation period. this type of head injury is called a: