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What is stroke? [Index]


For the human brain to function at peak levels, blood must flow through its many vessels.  If blood flow is obstructed to any part, the brain loses its energy supply and becomes injured.  If blood is obstructed for more than several minutes, the brain cells' injury becomes permanent and tissue dies in the affected region.  The loss or alteration of bodily function that results from an insufficient supply of blood to part of the brain is called a stroke.


Stroke is the third leading cause of death in the United States after diseases of the heart and all forms of cancer.  About 600,000 Americans have strokes each year.  Someone has a stroke every 53 seconds.

Someone dies of a stroke every 3.3 minutes.

What are the types of stroke? [Index]

If we consider an isolated blood vessel, blood flow to the brain tissue can be hampered in two ways:

1.  the vessel clogs within (ischemic stroke)

2.  the vessel ruptures, causing blood to leak into the brain (hemorrhagic stroke)

Ischemic stroke accounts for about 83 percent of all cases.  It results from an obstruction, typically a blood clot.   These clots are called a cerebral thrombus or cerebral embolism.

Hemorrhagic stroke accounts for about 17 percent of stroke cases.  It results from a weakened vessel that ruptures and bleeds into the surrounding brain.  The blood accumulates and compresses the surrounding brain tissue.  The two types of hemorrhagic strokes are intracerebral hemorrhage or subarachnoid hemorrhage.

Ischemic strokes occur as a result of an obstruction within a blood vessel supplying blood to the brain.  The underlying condition for this type of obstruction is the development of fatty deposits lining the vessel walls.  This condition is called atherosclerosis.  These fatty deposits can cause two types of obstruction:

Cerebral thrombosis refers to a thrombus (blood clot) that develops at the clogged part of the vessel.

Cerebral embolism refers generally to a blood clot that forms at another location in the circulatory system, usually the heart and large arteries of the upper chest and neck.  A portion of the blood clot breaks loose, enters the bloodstream and travels through the brain's blood vessels until it reaches vessels too small to let it pass.  A second important cause of embolism is an irregular heartbeat, known as atrial fibrillation.  It creates conditions where clots can form in the heart, dislodge and travel to the brain.

Hemorrhagic stroke occurs when a weakened blood vessel ruptures.  Two types of weakened blood vessels usually cause hemorrhagic stroke:  aneurysms and arteriovenous malformations (AVMs).

An aneurysm is a ballooning of a weakened region of a blood vessel.  If left untreated, the aneurysm continues to weaken until it ruptures and bleeds into the brain.

An arteriovenous malformation (AVM) is a cluster of abnormally formed blood vessels.  Any one of these vessels can rupture, also causing bleeding into the brain.

Transient ischemic attacks, also called TIAs, are minor or warning strokes.  In a TIA, conditions indicative of an ischemic stroke are present and the typical stroke warning signs develop.   However, the obstruction (blood clot) occurs for a short time and tends to resolve itself through normal mechanisms.

Even though the symptoms disappear after a short time, TIAs are strong indicators of a possible major stroke.  Steps should be taken immediately to prevent a stroke.

What are the effects of stroke? [Index]

The brain is an extremely complex organ that controls various body functions.  If a stroke occurs and blood flow can't reach the region that controls a particular body function, that part of the body won't work as it should.

If the stroke occurs toward the back of the brain, for instance, it's likely that some disability involving vision will result.  The effects of a stroke depend primarily on the location of the obstruction and the extent of brain tissue affected.

The effects of a stroke depend on a number of factors including the location of the obstruction and how much brain tissue is affected.  However, because one side of the brain controls the opposite side of the body, a stroke affecting one side will result in neurological complications on the side of the body it affects.
Left Brain

If the stroke occurs in the left side of the brain, the right side of the body (and the left side of the face) will be affected, producing some or all of the following:

  • Paralysis on the right side of the body
  • Speech/language problems
  • Slow, cautious behavioral style
  • Memory loss
lkjklj Right Brain

If the stroke occurs in the brain's right side, the left side of the body (and the right side of the face) will be affected, which could produce any or all of the following:

  • Paralysis on the left side of the body
  • Vision problems
  • Quick, inquisitive behavioral style
  • Memory loss

What are the risk factors of stroke? [Index]

The American Stroke Association has identified several factors that increase the risk of stroke.  The more risk factors a person has, the greater the chance that he or she will have a stroke.  Some of these you can't control, such as increasing age, family health history, race and gender.  But you can change, treat or modify most other risk factors to lower your risk.  Factors resulting from lifestyle or environment can be modified with a healthcare provider's help.

What other factors can affect the risk of stroke? [Index]

How are heart disease risk factors related to stroke? [Index]

Other risk factors are secondary risk factors for stroke.  They affect the risk of stroke indirectly by increasing the risk of heart disease:

Know the warning signs of stroke[Index]

If you notice one or more of these signs in another person or yourself, don't wait.  Call 9-1-1 or your local emergency medical services number immediately and get the person to a hospital right away!  Treatment can be more effective if given quickly.  Every second counts!

The signs are:

Not all of these signs occur with every stroke.  Sometimes they go away and return.  If some occur, get help fast.  If you notice one or more of these signs in another person, don't wait.  Call 9-1-1 and get them to a hospital right away!

What is a TIA (transient ischemic attack)?[Index]

A TIA is a "mini-stroke" with the same signs as a stroke, only the signs last only a few minutes.

About 10 percent of strokes are preceded by TIAs.  However, of those who have had one TIA or more, about 36 percent will later have a stroke.  A person who has had one or more TIAs is 9.5 times more likely to have a stroke than someone of the same age and sex who has not.

Chain of Survival[Index]

Every stroke or TIA must be treated as a life-threatening emergency.   Time is very important.  A stroke in progress must be diagnosed.  If you are going to receive tPA, a "clot-busting" drug treatment, or other appropriate therapy, you must get to a hospital quickly so a doctor can diagnose your stroke and treat you within 3 hours of the time symptoms begin.  In the hospital emergency room, tests will determine if a TIA, stroke or another medical problem caused your symptoms.

Treatment for stroke will be different if an artery is blocked (ischemic stroke) or a blood vessel has ruptured (hemorrhagic stroke).  To increase your chances of surviving a stroke, take these 5 steps in the Stroke Chain of Survival within three hours of the onset of symptoms:

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Material taken from the American Heart Association.