Concussions are the most common form of brain injury.
A concussion can be caused by a direct or indirect hit to the head or body, which causes the brain to suddenly shift or shake inside the skull. This could happen in a car collision, a sports collision or simply slipping on an icy surface.
Concussions are head injuries that can't be seen with the naked eye. You do not need to lose consciousness to have a concussion. Signs and symptoms could be immediate, or they may be delayed and not show for some time, perhaps days or even weeks following a hit.
If you think you may have a concussion, you should stop activities immediately and seek medical attention.