A subdural hematoma is bleeding on the surface of the brain. The bleeding occurs under the tough, outer covering of the brain, called the "dura."
An injury to the head causes most subdural hematomas. The most common causes of these injuries include:
- A car crash
- A fall
- A physical attack
There are 2 main types of subdural hematomas:
- Acute – This type happens in the first hours after a head injury. If the bleeding continues, the subdural hematoma can keep growing, days after the injury.
- Chronic – This type happens most often in older people whose brains have shrunk slightly due to age. In these people, a mild head injury causes bleeding on the brain’s surface. The injury can be so mild that the person doesn’t even notice it. The hematoma grows slowly, over several days or weeks.