A stroke is a sudden episode that may affect consciousness, sensation, and movement, which results from a blockage or rupture of a blood vessel in the brain. It causes symptoms that last for at least 24 hours. A stroke (known medically as a cerebrovascular accident or CVA) occurs when the blood supply to part of the brain is suddenly interrupted or when a blood vessel in the brain bursts, spilling blood into the spaces surrounding brain cells. Brain cells die when they no longer receive oxygen and nutrients from the blood or there is sudden bleeding into or around the brain.
There are two main types -- ischemic and hemorrhagic. The ischemic type occurs when there is a lack of oxygen- or nutrient-rich blood to a part of the brain for a long enough period of time that brain tissue dies. This lack of blood flow occurs because of a severely narrowed or blocked artery in the neck or brain. The ischemic type makes up 80 percent of all cases.
The second type is a hemorrhagic stroke. This type occurs because of bleeding in the brain from a broken blood vessel. For each type -- ischemic and hemorrhagic -- the causes can vary.