The term concussion describes an injury to the brain resulting from an impact to the head. By definition, a concussion is not a life-threatening injury, but it can cause both short-term and long-term problems. A concussion results from a closed-head type of injury and does not include injuries in which there is bleeding under the skull or into the brain Concussions are usually caused by a blow to the head. Violently shaking the head and upper body also can cause concussions.
Some concussions cause you to lose consciousness, but most do not. It’s possible to have a concussion and not realize it Concussions are particularly common if you play a contact sport, such as football. Most people usually recover fully after a concussion.