Injury to the head may damage the scalp, skull or brain, with results ranging from mild to fatal. Head injuries can be caused by traffic accidents, sports injuries, falls, workplace accidents, assaults, or firearms. About 70% of all accidental deaths are due to head injuries, as are most injury-related disabilities.

The brain can be damaged even if there is no external evidence of damage. A person who has had a head injury and who is experiencing the following symptoms should seek medical care immediately:

• Serious bleeding from the head or face
• Loss of consciousness, however brief
• Confusion and lethargy
• Lack of pulse or breathing
• Clear fluid drainage from the nose or ear.

A head injury may cause damage both from the direct physical injury and from secondary factors such as lack of oxygen, brain swelling, and disturbance of blood flow. It can cause swirling movements throughout the...