Classification
Head injuries include both injuries to the brain and those to other parts of the head, such as the scalp and skull.
Head injuries can be closed or open. A closed (non-missile) head injury is where the dura mater remains intact. The skull can be fractured, but not necessarily. 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 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 occurs, a hematoma within the skull can put pressure on the brain. Types of intracranial hemorrage 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 (both are contrecoup injuries).
Specific problems after head injury can include:
- Skull fracture
- Lacerations to the scalp and resulting hemorrhage of the skin
- Traumatic subdural hematoma, a bleeding below the dura mater which may develop slowly
- Traumatic extradural, or epidural hematoma, bleeding between the dura mater and the skull
- Traumatic subarachnoid hemorrhage
- Cerebral contusion, a bruise of the brain
- Concussion, a loss of function due to trauma
- Dementia pugilistica, or "punch-drunk syndrome", caused by repetitive head injuries, for example in boxing or other contact sports
- A severe injury may lead to a coma or death
- Shaken Baby Syndrome - a form of child abuse
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