Many bumps and bruises to the head are minor, but a severe injury carries the risk of brain damage and may even be fatal. A blow to the head may shake or bruise the brain, and if the skull is fractured, material may enter the brain and cause infection. A blow or penetrating injury may cause swelling of the brain or bleeding in or around the brain.
If a head injury is minor, there may only be a headache, or sometimes a concussion (brief unconsciousness due to disturbance of brain function).
A more severe injury may result in significant brain damage, prolonged unconsciousness or coma, and may potentially be fatal.
After a severe injury, there may be muscular weakness or paralysis and loss of sensation. There may also be memory loss (amnesia). A serious head injury may require surgery and may result in long-term disability