What is a Brain Injury?

An acquired brain injury is a sudden and often accidental injury that results from bleeding, trauma, swelling, or shearing of brain tissue. An acquired brain injury does not include mental conditions present at birth or caused by a health condition, such as Alzheimer’s disease. The primary brain injury can be either traumatic or non-traumatic:

Traumatic brain injury

Traumatic brain injury (also called TBI) is caused by trauma to the head from a hard blow, fall, car accident, or gunshot or knife wound.

- A closed head injury is when the brain is injured, but the skull is not broken. Common causes of closed head injuries are car accidents, falls, and hard blows to the head.

- An open head injury is when the skull is broken or dented and the brain is injured. Loose bone fragments can put pressure on the brain. Common causes of open head injuries are skull fractures and gunshot or knife wounds.

Non-traumatic brain injury

Non-traumatic brain injury is caused by:
• anoxia—a complete lack of oxygen to tissues in the brain (such as from a heart attack or carbon monoxide poisoning). Anoxia causes problems with the cells chemical activity and then cell death within a few minutes unless oxygen is restored. Anoxia is rare. Hypoxia is a reduction of the oxygen supply to the tissues and is more common.
• brain infection; cancer or tumor
• toxic drugs or chemicals
• complications of liver disease, kidney disease, diabetes
• aneurysm or a stroke (a blockage or rupture of a blood vessel in the brain, also called cerebral vascular accident).

Causes of Brain Injury

Both traumatic and non-traumatic brain injury can result in the following:

- A diffuse injury which affects several areas of the brain and can result from the brain twisting or rebounding (bouncing) inside the skull.

- A focal injury which is limited to one area or one side of the brain.

- A contusion which is a blow to the head hard enough to bruise the brain.

- Bleeding inside the skull, called a hemorrhage, which can result from either a traumatic brain injury, aneurysm, or stroke.