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*Please note: This slide show represents a visual interpretation and is not intended to provide, nor substitute as, medical and/or clinical advice.

A stroke occurs when the blood supply to the brain is blocked or reduced.

That can happen because of either a blood clot that breaks off and goes to the brain, or sometimes there’s a narrowing in one of the arteries that supplies blood to the brain.

In some cases bleeding in the brain also causes a stroke, but anything where you have interrupted blood supply to the brain can cause a stroke.

When a stroke happens some of the brain tissue dies. How much of the brain tissue depends on how severe the stroke is.

Rapidly seeking medical attention is critical.

A stroke is sometimes called a “brain attack”, which like a “heart attack” is always a medical emergency.

There are two common types of stroke.

One of these types is called hemorrhagic stroke, and it occurs when a weakened blood vessel ruptures in or near the brain, leaking blood into the brain, and causing the brain cells to die.

The second, more common type of stroke, is called ischemic stroke.

It occurs when a blood vessel (an artery) carrying blood to the brain becomes blocked.

Without blood supply, brain cells, deprived of oxygen and nutrients, can start to die within a few minutes.

Ischemic strokes can have thrombotic or embolic causes.

Thrombotic strokes are caused by a blood clot, medically-termed a "thrombus", in an artery supplying blood to the brain.

Blood clots usually form in arteries affected by atherosclerosis, the build up of hardened plaques on the inner walls of arteries.

If an atherosclerotic plaque is disrupted, a thrombus forms on top of it and blocks the vessel, stopping the flow of blood.

In an embolic stroke, a blood clot, called an embolus, forms somewhere else in the body and travels via the bloodstream to the brain.

Eventually, the clot reaches an artery small enough to block its passage.

It lodges there, obstructing the blood flow and causing a stroke.

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Slide Show - Understanding Stroke

This slide show describes that a stroke is a “brain attack” that occurs when the blood supply to the brain is interrupted, causing the affected brain tissue to die. This interruption of blood supply to the brain can be caused by a blood clot that breaks off and goes to the brain, or a narrowing in one of the arteries that supply blood to the brain, or in some cases bleeding in the brain. There are two types of stroke, hemorrhagic stroke and ischemic stroke. Hemorrhagic strokes are less common, and occur when a weakened blood vessel ruptures in­ or near the brain, leaking blood into the brain, and causing the brain cells to die. Ischemic strokes are the more common type of stroke, and occur when a blood vessel carrying blood to the brain becomes blocked by a blood clot, causing blood not to reach the brain. Without blood supply, the brain cells are deprived of oxygen and nutrients, and can start to die within a few minutes. Ischemic strokes can have thrombotic or embolic causes. A stroke is a medical emergency. If you or someone with you experiences any symptoms, call 9-1-1 immediately.

Animation - Understanding Stroke

This animation describes that a stroke is a “brain attack” that occurs when the blood supply to the brain is interrupted, causing the affected brain tissue to die. This interruption of blood supply to the brain can be caused by a blood clot that breaks off and goes to the brain, or a narrowing in one of the arteries that supply blood to the brain, or in some cases bleeding in the brain. There are two types of stroke, hemorrhagic stroke and ischemic stroke. Hemorrhagic strokes are less common, and occur when a weakened blood vessel ruptures in­ or near the brain, leaking blood into the brain, and causing the brain cells to die. Ischemic strokes are the more common type of stroke, and occur when a blood vessel carrying blood to the brain becomes blocked by a blood clot, causing blood not to reach the brain. Without blood supply, the brain cells are deprived of oxygen and nutrients, and can start to die within a few minutes. Ischemic strokes can have thrombotic or embolic causes. A stroke is a medical emergency. If you or someone with you experiences any symptoms, call 9-1-1 immediately.