A head injury is any trauma that leads to injury of the scalp, skull, or brain. The injuries can range from a minor bump on the skull to serious brain injury.

Head injury is classified as either closed or open (penetrating).

• A closed head injury means you received a hard blow to the head from striking an object.
• An open, or penetrating, head injury means you were hit with an object that broke the skull and entered the brain. This usually happens when you move at high speed, such as going through the windshield during a car accident. It can also happen from a gunshot to the head.

There are several types of brain injuries. Two common types of head injuries are:

• Concussion, the most common type of traumatic brain injury
• Contusion, which is a bruise on the brain

See also:

• Subarachnoid hemorrhage
• Subdural hematoma

Every year, millions of people sustain a head injury. Most of these injuries are minor because the skull provides the brain with considerable protection. The symptoms of minor head injuries usually go away on their own. More than half a million head injuries a year, however, are severe enough to require hospitalization.

Learning to recognize a serious head injury, and implementing basic first aid, can make the difference in saving someone's life.

In patients who have suffered a severe head injury, there is often one or more other organ systems injured. For example, a head injury is sometimes accompanied by a spinal injury.

Common causes of head injury include traffic accidents, falls, physical assault, and accidents at home, work, outdoors, or while playing sports.

Some head injuries result in prolonged or non-reversible brain damage. This can occur as a result of bleeding inside the brain or forces that damage the brain directly. These more serious head injuries may cause:

• Changes in personality, emotions, or mental abilities
• Speech and language problems
• Loss of sensation, hearing, vision, taste, or smell
• Seizures
• Paralysis
• Coma

The signs of a head injury can occur immediately or develop slowly over several hours. Even if the skull is not fractured, the brain can bang against the inside of the skull and be bruised. (This is called a concussion.) The head may look fine, but complications could result from bleeding inside the skull.

When encountering a person who just had a head injury, try to find out what happened. If he or she cannot tell you, look for clues and ask witnesses. In any serious head trauma, always assume the spinal cord is also injured.

The following symptoms suggest a more serious head injury -- other than a concussion or contusion -- and require emergency medical treatment:

• Loss of consciousness, confusion, or drowsiness
• Low breathing rate or drop in blood pressure
• Convulsions
• Fracture in the skull or face, facial bruising, swelling at the site of the injury, or scalp wound
• Fluid drainage from nose, mouth, or ears (may be clear or bloody)
• Severe headache
• Initial improvement followed by worsening symptoms
• Irritability (especially in children), personality changes, or unusual behavior
• Restlessness, clumsiness, lack of coordination
• Slurred speech or blurred vision
• Inability to move one or more limbs
• Stiff neck or vomiting
• Pupil changes
• Inability to hear, see, taste, or smell