Brain Injury

Head injury is a trauma to the head, that may or may not include injury to the brain. The incidence (number of new cases) of head injury is 300 per 100,000 per year (0.3% of the population), with a mortality of 25 per 100,000 in North America and 9 per 100,000 in Britain. Head trauma is a common cause of childhood hospitalization.

Causes
Common causes of head injury are auto accidents, home and occupational accidents, falls, and assaults. Bicycle accidents are also a common cause of head injury-related death and disability, especially among children. [1]

Types of head injury
Head injuries include both injuries to the brain and those to other parts of the head, such as the scalp and skull.

Head injuries may be closed or open. A closed (non-missile) head injury is one in which the skull is not broken. A penetrating head injury occurs when an object pierces the skull and breaches the dura mater. Brain injuries may be diffuse, occurring over a wide area, or focal, located in a small, specific area.

A head injury may cause a skull fracture, which may or may not be associated with injury to the brain. Some patients may have linear or depressed skull fractures.

If intracranial hemorrhage, or bleeding within the brain occurs, a hematoma within the skull can put pressure on the brain. Types of intracranial hematoma include subdural, subarachnoid, extradural, and intraparenchymal hematoma. Craniotomy surgeries are used in these cases to lessen the pressure by draining off blood.

Brain injury can be at the site of impact, but can also be at the opposite side of the skull due to a contrecoup effect (the impact to the head can cause the brain to move within the skull, causing the brain to impact the interior of the skull opposite the head-impact).

If the impact causes the head to move, the injury may be worsened, because the brain may ricochet inside the skull (causing additional impacts), or the brain may stay relatively still (due to inertia) but be hit by the moving skull.