Understanding the different causes and types of stroke

Each year 780,000 Americans are victims of stroke. However, 500,000 of those strokes could be prevented. In the United States, stroke is the third leading cause of death, killing 160,000 people each year and the leading cause of adult disability. These sobering statistics reveal a need for increased awareness about stroke – what it is, and how to identify and prevent stroke.

What is stroke and how many types are there?

A stroke occurs when a blood vessel to the brain becomes blocked or when a vessel ruptures. A blockage is called an ischemic stroke and a ruptured blood vessel is called a hemorrhagic stroke. When either of these things happens, brain cells begin to die and brain damage occurs. When brain cells die during a stroke, abilities controlled by that area of the brain are lost. These abilities include speech, movement and memory. How a stroke patient is affected depends on where the stroke occurs in the brain and how much the brain is damaged.

Ischemic stroke

In some areas of the human body, blood clotting can be good. For instance, when someone is bleeding from a wound, a blood clot works to slow and eventually stop the bleeding. In the case of stroke, however, blood clots are dangerous because they block arteries and cut off blood flow, a process called ischemia.

Ischemic stroke occurs when arteries are blocked by blood clots or by the gradual build-up of plaque and other fatty deposits. Almost 85 percent of all strokes are ischemic. An ischemic stroke can occur in two ways: embolic and thrombotic strokes. Watch the simulation.

Hemorrhagic stroke

Strokes caused by the breakage or "blowout" of a blood vessel in the brain are called hemorrhagic strokes. The medical term for this type of breakage is hemorrhage. Hemorrhages can be caused by a number of disorders, which affect the blood vessels, including long-standing high blood pressure and cerebral aneurysms. An aneurysm is a weak or thin spot on a blood vessel wall. These weak spots are usually present at birth. Aneurysms develop over a number of years and usually don't cause detectable problems until they break. Watch the simulation.

Videos: Copyright 2008 National Stroke Association.

For more information, go to the National Stroke Association Website.

Next week: Top ten ways to prevent stroke.