A stroke is a brain injury that occurs because the brain's blood supply is interrupted.
The brain's blood supply can be disrupted for different reasons. Doctors generally classify strokes into three categories, depending on the cause:
Hemorrhagic stroke — Bleeding (hemorrhage) causes this type of stroke. Bleeding can occur within the brain or between the brain and the skull. When bleeding occurs, small blood vessels near the hemorrhage tighten in a spasm. As a result, some brain areas get too little blood flow.
A hemorrhagic stroke that occurs within the brain is called an intracerebral hemorrhage. It often is linked to high blood pressure, old age, heavy alcohol use, or the use of cocaine or methamphetamines. A stroke that occurs between the brain and the skull is called a subarachnoid hemorrhage.
Hemorrhagic strokes are much less common than strokes caused by clots.
To continue reading this article, you must login
Subscribe to Harvard Health Online for immediate access to health news and information from Harvard Medical School.