A concussion is an injury to the brain caused by a blow to the head. A concussion may cause you to become temporarily confused or disoriented, have memory loss (amnesia), or become unconscious. Concussions are the most common head injuries in sports.

A concussion occurs when a blow to the head causes shaking, jarring, stretching, swelling, or tearing of brain tissue and delicate nerve fibers.
The sports in which concussions most commonly occur are football, gymnastics, ice hockey, and wrestling. However, concussions can occur in any sport or activity where you may get hit in the head.

If you have had a concussion you may have any of the following symptoms:

• headache
• confusion
• memory loss (amnesia)
• loss of consciousness
• sleepiness
• nausea or vomiting
• trouble concentrating
• dizziness
• weakness
• seizures
• loss of balance.

You may have these symptoms, called post-concussive syndrome, for several days or weeks after the injury.