The four main types of head injuries are:
- Concussion: a mild brain injury that is usually temporary.
- Contusion: a bruise on the brain.
- Fracture: broken skull bones.
- Hematoma: a blood clot caused by a blow to the brain.
The head and brain can be injured whether or not the skull is actually damaged. A hard knock or jolt, even with no external sign of injury, is enough to cause a brain injury.