What is stroke?
A stroke occurs when a blocked vessel or artery prevents blood from getting to part of the brain, or when a vessel or artery bursts and spills blood into the brain. The blood supplies the brain with the oxygen and nutrients it needs to work properly. When part of the brain cannot get the blood it needs, it becomes damaged or dies. The sudden flooding of blood into the brain also can cause damage or death to the brain cells (neurons).
There are two types of stroke:
- Ischemic stroke
Ischemic (pronounced ih-SKEE-mik) stroke happens when an artery carrying blood to the brain becomes blocked and cannot supply enough blood to the brain. Usually a blood clot causes the blockage. Sometimes the blockage occurs when an artery becomes too narrow for enough blood to pass through it. This narrowing is called stenosis (sti-NOH-sis). Stenosis is caused by a buildup of plaque (plak)—a mixture of fatty substances, including cholesterol—that forms on the inner walls of the artery.
- Hemorrhagic stroke
Hemorrhagic (prounounced hem-uh-RAJ-ik) stroke occurs when an artery bursts and spills blood into part of the brain. In a healthy brain, the blood remains in the arteries and does not come into contact with neurons. When blood bursts into the brain during a hemorrhagic stroke, the normal flow of blood to the brain is upset, and the blood interferes with the normal chemical balance that neurons need to function.
Transient Ischemic Attack
Sometimes called a mini-stroke, a transient ischemic attack (TIA) starts with the same symptoms of a full stroke but does not progress and cause the damage of a full stroke. A TIA is a warning that a person is at risk for a more serious stroke in the future.1