Traumatic brain injury occurs when a sudden physical assault on the head causes damage to the brain. The damage can be focal, confined to one area of the brain, or diffuse, involving more than one area of the brain. Traumatic brain injury can result from a closed head injury or a penetrating head injury.

A closed head injury occurs when the head suddenly and violently hits an object, but the object does not break through the skull. A penetrating head injury occurs when an object pierces the skull and enters the brain tissue.   More detail...