The cause of intracranial bleeding (hemorrhage) is an injury to the head, often as a result of an automobile or motorcycle accident or even a seemingly trivial event, such as bumping your head. Mild head trauma is more likely to cause a hematoma if you're an older adult, especially if you're taking an anticoagulant or anti-platelet drugs, such as aspirin. A serious injury may have occurred even if there's no open wound, bruise or other outward sign of damage.

If a hematoma results from the injury to your head, it may occur as a subdural hematoma, an epidural hematoma or an intraparenchymal hematoma.

Subdural hematoma

This occurs when blood vessels — usually veins — rupture between your brain and the outermost of three membrane layers that cover your brain (dura mater). The leaking blood forms a hematoma that compresses the brain tissue. If the hematoma keeps enlarging, a progressive decline in consciousness occurs, possibly even resulting in death.

The three types of subdural hematomas include:

  • Acute. This type is the most dangerous. It's generally caused by a severe head injury, and signs and symptoms usually appear immediately.
  • Subacute. In subacute subdural hematoma, signs and symptoms take longer to appear, sometimes days or weeks after your injury.
  • Chronic. Less severe head injuries may cause a chronic subdural hematoma. Bleeding from a chronic subdural hematoma may be much slower, and symptoms can take weeks to appear. You may not even recall injuring your head.

All three types require medical attention as soon as signs and symptoms are apparent, or permanent brain damage may result.

The risk of subdural hematoma is greater for people who:

  • Take aspirin or anticoagulants daily
  • Abuse alcohol
  • Are elderly

Epidural hematoma

Also called an extradural hematoma, this type occurs when a blood vessel — usually an artery — ruptures between the outer surface of the dura mater and the skull. Blood then leaks between the dura mater and the skull to form a mass that compresses the brain tissue.

Some people with this type of injury may remain conscious, but most become drowsy or comatose from the moment of trauma. An epidural hematoma that affects an artery in your brain can be deadly unless you get prompt treatment.

Intraparenchymal hematoma

This type of hematoma, also known as intracerebral hematoma, occurs when blood pools in the brain. After a head trauma, there may be multiple severe intraparenchymal hematomas.

The trauma that causes intraparenchymal hematomas often is responsible for so-called white matter shear injuries — torn axons in the brain's white matter. Axons are connections that carry electrical impulses, or messages, from the neurons in the brain to the rest of the body. When this connection is sheared, serious brain damage can result because the neurons can no longer communicate.

Trauma isn't the only cause of intraparenchymal hematoma. Nontraumatic causes, which are rare, may include:

  • Blood vessel disorders, such as arteriovenous malformation (AVM) or aneurysm
  • Long-term hypertension
  • Neurological conditions, such as cerebral amyloid angiopathy
  • Brain tumors
  • Use of blood thinners
  • Certain autoimmune diseases
  • Bleeding disorders, such as hemophilia, leukemia and sickle cell anemia
  • Central nervous system infection, such as encephalitis
  • Drugs, such as cocaine or amphetamines
Jun. 25, 2011