A concussion is a blow or jolt to the head that can change the way your brain normally works. Also called a mild traumatic brain injury, a concussion can result from a car crash, a sports injury, or from a seemingly innocuous fall. Concussion recovery times can vary greatly. Most people who sustain a concussion or mild TBI are back to normal by three months or sooner. But others have long-term problems remembering things and concentration. Accidents can be so minor that neither doctor nor patient makes the connection.