A severe blow to the head can cause cerebral contusion, or bruising of the brain tissue. More serious than a concussion, contusion disrupts normal nerve functions in the bruised area and may cause loss of consciousness, hemorrhage, edema, and even death.
Cerebral contusion results from acceleration-deceleration or coup-contrecoup injuries. Such injuries can occur directly beneath the site of impact when the brain rebounds against the skull from the force of a blow (a beating with a blunt instrument, for example), when the force of the blow drives the brain against the opposite side of the skull, or when the head is hurled forward and stopped abruptly (as in an automobile accident when a driver’s head strikes the windshield).
When these injuries occur, the brain continues moving and slaps against the skull (acceleration), then rebounds (deceleration). These injuries can also cause the brain to strike against bony prominences inside the skull (especially the sphenoidal ridges), causing intracranial hemorrhage or hematoma that may result in tentorial herniation.