Two main forms of stroke exist:

• Ischemic stroke is caused by blockage of a blood vessel.
• Hemorrhagic stroke is caused by bleeding.

Ischemic Stroke

This type of stroke accounts for about 70 percent to 80 percent of all strokes and occurs when a blood clot forms and blocks blood flow in an artery bringing blood to part of the brain. Blood clots usually form in arteries damaged by fatty buildups. A wandering clot or some other particle that forms away from the brain, usually in the heart, may also cause an ischemic stroke. This is called cerebral embolism. The clot is carried by the bloodstream until it lodges in an artery leading to or in the brain, blocking the flow of blood. The most common cause of these emboli is blood clots that form during atrial fibrillation (AF). AF is a disorder found in about 2.2 million Americans.

Hemorrhagic Stroke

Hemorrhage (bleeding) strokes may be caused by a head injury or a burst aneurysm (blood-filled pouch). When hemorrhage occurs, blood flow is disrupted and some of the brain cells can no longer work. The amount of bleeding determines the severity of cerebral hemorrhages in terms of post-stroke side effects.

It is critical to get help immediately if you suspect a stroke. Health care professionals cannot treat stroke until they know what type of stroke it is.

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