A concussion is a brain injury that may result in a bad headache or unconsciousness.

See also: Concussion - first aid

There are more than a million cases of concussion each year in the United States.

A concussion may result when the head hits an object or a moving object strikes the head. A concussion can result from a fall, sports activities, and car accidents. Significant movement of the brain (jarring) in any direction can cause unconsciousness. How long a person remains unconscious may indicate the severity of the concussion.

Often victims have no memory of events preceding the injury, or immediately after regaining consciousness. More severe head injuries can cause longer periods of memory loss (amnesia).

Usually, a person has the most memory loss immediately after getting hurt. Some of the memory comes back as time goes by. However, complete memory recovery for the event may not occur.

Bleeding into or around the brain can occur with any blow to the head, whether or not unconsciousness occurs. If someone has received a blow to the head, they should be watched closely for signs of possible brain damage.

Things to watch for include repeated vomiting, unequal pupils, confused mental state or varying levels of consciousness, seizure-like activity, weakness on one side of the body, or the inability to wake up (coma). If any of these signs are present, immediately call 911.

A concussion results from a significant blow to the head. Symptoms can range from mild to severe. They can include:

• Headache
• Loss of consciousness
• Memory loss (amnesia) of events surrounding the injury

Emergency signs:

• Altered level of consciousness (drowsy, hard to arouse, or similar changes)
• Convulsions
• Muscle weakness on one or both sides
• Persistent confusion
• Persistent unconsciousness (coma)
• Repeated vomiting
• Unequal pupils
• Unusual eye movements
• Walking problems

A neurological examination may show abnormalities.

Tests that may be performed include:

• Head CT
• MRI of the head

An initial "baseline" neurological evaluation by a health care worker determines appropriate treatment for an uncomplicated concussion. If a blow to the head during athletics leads to a bad headache, a feeling of being confused (dazed), or unconsciousness, a trained person must determine when the person can return to playing sports.

If a child or young adult has lost consciousness, that person should not play sports for a period of 3 months. Studies have shown that there is an increased rate of brain injury and occasionally death in people who have had a previous concussion with unconsciousness.

Concussion complicated by bleeding or brain damage must be treated in a hospital.

Full recovery is expected from an uncomplicated concussion, although prolonged dizziness, irritability, headaches, and other symptoms may occur.

• Brain injury
• Intracerebral hemorrhage

Call your health care provider if anyone has a head injury that produces unconsciousness, or a head injury without unconsciousness that produces symptoms that cause concern.

Call 911 or go the emergency room if emergency signs develop.

Attention to safety, including the use of appropriate athletic gear, such as bike helmets and seat belts, reduces the risk of head injury.

Ropper, AH, Gorson, KC. Clinical Practice; Concussion. N Engl J Med. 2007; 356: 166-172.