A concussion is a traumatic brain injury, ex. after blow to the head during contact sport, that affects your brain function. What happens is, the head and brain move rapidly back and forth.
This sudden movement can cause the brain to bounce around in the skull, creating chemical changes in the brain and sometimes damaging brain cells. Most people recover fully after a concussion (usually within 14 to 21 days).
Recovery plans are unique to each person, all involve mental and physical rest and a gradual return to activity. A single concussion usually doesn’t cause permanent damage to your brain. Multiple concussions over a lifetime may result in structural changes in your brain.