Traumatic brain injury is usually the result of a sudden, violent blow to the head — which causes the brain to collide with the inside of the skull. This collision can bruise the brain, tear nerve fibers and cause bleeding. The severity of traumatic brain injury can vary greatly. A mild traumatic brain injury may cause temporary confusion and headache, but a serious one can be fatal. The brain is the consistency of gelatin. It's cushioned from everyday jolts and bumps by the cerebrospinal fluid in which it floats inside the skull. A violent blow to the head can cause the brain to slide forcefully against the inner wall of the skull. Even the sudden stop of a car crash can bounce the brain against the skull. This can result in bleeding in or around the brain and the tearing of nerve fibers. If a person has suffered a blow to the head, he/she should always be examined by a physician. Emergency medical care should be sought if signs and symptoms include: convulsions, weakness or numbness in the extremities, repeated vomiting, slurred speech.