A concussion is a type of traumatic brain injury—or TBI—caused by a bump, blow, or jolt to the head or by a hit to the body that causes the head and brain to move rapidly back and forth. This sudden movement can cause the brain to bounce around or twist in the skull, stretching and damaging the brain cells and creating chemical changes in the brain.
A person with a severe brain injury will need to be hospitalized and may have long-term problems affecting things such as:
Coordination and balance
Speech, hearing or vision
A severe brain injury can affect all aspects of people’s lives, including relationships with family and friends, as well as their ability to work or be employed, do household chores, drive, and/or do other normal daily activities. (http://www.cdc.gov/headsup/basics/severe_brain_injury.html)