A blow or a jolt to the head can cause a concussion or traumatic brain injury (TBI). An injury to another part of the body that transmits force to the head can also result in concussion. The injury keeps the brain from working normally. Symptoms of a concussion may last less than a day or may linger for months, or longer.
Millions of mild traumatic brain injuries occur in the U.S. each year, but most don't require a visit to the hospital.