Traumatic brain injury.

A traumatic brain injury (TBI) is damage to the brain that usually results from an accident. They can be classified according to several different criteria. One common system is to refer to them as either a “penetrating” or “closed-head” TBI. Penetrating head injuries occur when the skull has been compromised by a foreign object, as in the case of a gunshot wound. This type of injury is particularly destructive to the brain because, in addition to the damage to brain cells, it also causes bleeding and the possibility of infection. As a result, penetrating head injuries have the highest morbidity and mortality rates. Closed-head injuries are typically acceleration-deceleration injuries, caused by a person's head suddenly accelerating (such as from a blow to the head) or decelerating (such as in an automobile collision), which results in the brain striking the inside of the skull.