A concussion is a mild traumatic brain injury caused by a blow or “ding” to the head. Common in falls, sports, and car crashes, concussions can temporarily affect the brain causing confusion, memory, speech, vision, or balance problems. The person may appear fine at first, but may show symptoms hours or days later. If left undiagnosed, a concussion may place a person at risk of developing second impact syndrome-a potentially fatal injury that occurs when an athlete sustains a second head injury before a previous head injury has healed. The best treatment is time to allow the brain to heal.