A concussion is a type of traumatic brain injury. The brain is made of soft tissue and is cushioned by spinal fluid. It is encased in the hard, protective skull. The brain can move around inside the skull and even bang against it. If the brain bangs against the skull — for example, due to a fall on a playground or a whiplash-type of injury — blood vessels can be torn and the nerves inside the brain can be injured. These injuries can cause a concussion. Anyone who has a head injury should be watched closely for signs of a concussion, even if the person feels okay. An undiagnosed concussion can put someone at risk for brain damage and even disability. So anyone who has any symptom of a concussion should be examined right away by a doctor or athletic trainer.