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You are here : 3-RX.com > Medical Encyclopedia > Diseases and Conditions > Stroke
      Category : Health Centers > Stroke


Alternate Names : Brain Attack, Cerebrovascular Accident, CVA

Overview, Causes, & Risk Factors | Symptoms & Signs | Diagnosis & Tests | Prevention & Expectations | Treatment & Monitoring

A stroke is the death of brain tissue that occurs when the brain does not get enough blood and oxygen.

What is going on in the body?

Strokes are classified as ischemic strokes or hemorrhagic strokes. Ischemic strokes happen when the blood supply to the brain is interrupted. The brain cells then die from lack of oxygen. Hemorrhagic strokes occur when blood vessels in the brain burst and release blood into the area around the brain cells. The blood then damages the brain cells. The products released when cells die cause swelling in the brain. Since the skull doesn't allow much room for expansion, this swelling can damage the brain tissue even further.

Examples of ischemic strokes are:

  • stroke from atherosclerosis, which occurs when the arteries supplying the brain are narrowed by plaque formation on the vessel walls
  • stroke from carotid stenosis, which is a blockage in one of the carotid arteries in the neck
  • arteritis, or artery inflammation, in an artery that supplies the brain. This may be due to a condition called temporal arteritis, for example.
  • stroke from carotid dissection. A carotid dissection occurs when one of the carotid arteries in the neck is torn by an injury and blood flow to the brain is blocked.
  • polycythemia vera, a blood cancer that causes blood cells to multiply and the blood to thicken. The thickened blood prevents normal oxygenation of brain cells.
  • stroke from cardiogenic embolism, a condition in which blood clots travel from the heart. Blood clots from the heart may be caused by an irregular heartbeat called atrial fibrillation, severe congestive heart failure, and heart attack.
  • stroke caused by cholesterol or plaque from an artery in the neck. When the cholesterol or plaque travels and blocks an artery supplying the brain, a stroke occurs.
  • severe migraine headaches, which cause constriction of the blood vessels within the brain and deprive brain cells of oxygen
  • Hemorrhagic strokes occur when there is bleeding into the brain caused by damage to the blood vessels. A hemorrhagic stroke may be caused by:

  • high blood pressure
  • abnormal bleeding from blood-thinning medications, such as warfarin or heparin
  • hemophilia A or hemophilia B, which are blood disorders that prevent normal blood clotting
  • low numbers of platelets, a type of blood cell involved in blood clotting. Low platelet counts are seen in a number of diseases and conditions, including acute infections and a severe allergic reaction known as anaphylactic shock.
  • rupture of a cerebral aneurysm, or weakened blood vessel wall within the brain
  • sickle cell disease, an inherited condition that results in abnormal red blood cells
  • a group of abnormal blood vessels within the brain known as an arteriovenous malformation, or AVM
  • head injuries
  • eclampsia, a complication of pregnancy that causes high blood pressure in the mother
  • Stroke is the third leading cause of death in the US and many other countries, right after heart disease and cancer.

    What are the causes and risks of the condition?

    Strokes are caused by an interruption of the blood flow to brain cells or by damage to brain cells.

    The American Heart Association has recently issued guidelines for stroke prevention. The guidelines discuss risk factors for stroke in 3 categories: nonmodifiable, well-documented modifiable, and less well-documented or potentially modifiable.

    The nonmodifiable factors are ones that cannot be changed by the individual and include:

  • increasing age. A person's risk of stroke doubles each year after age 55.
  • race. Strokes occur approximately twice as often in blacks and Hispanics as they do in whites.
  • gender. Men have a 50% higher chance of stroke than women do.
  • family history of stroke or transient ischemic attack (TIA). A TIA is a short, reversible form of stroke that may serve as an early warning sign of stroke.
  • Well-documented modifiable risk factors are those that can be changed by the individual in conjunction with his or her healthcare provider. These factors are linked to stroke by strong research findings, and there is documented proof that changing the risk factor lowers a person's risk of stroke. These factors include:

  • high blood pressure
  • smoking
  • diabetes
  • asymptomatic carotid stenosis, or narrowing of one of the arteries in the neck
  • sickle cell anemia, a blood disorder that forms abnormal red blood cells
  • high cholesterol levels in the blood, including total cholesterol and LDL or "bad cholesterol." Low levels of HDL or "good cholesterol" are also cause for concern.
  • atrial fibrillation, an abnormal heart rhythm
  • Less well-documented or potentially modifiable risk factors for stroke are those that have less proof of either a link to stroke or the impact of modifying the risk factor. These factors include:

  • obesity
  • sedentary lifestyle
  • alcohol abuse
  • high blood levels of homocysteine, a blood component sometimes associated with a higher risk of stroke
  • drug abuse
  • blood disorders, such as blood that clots easily or deficiencies of various blood components
  • hormone replacement therapy (HRT). The AHA currently states that the risk of stroke associated with HRT appears low but needs further study.
  • use of birth control pills, or oral contraceptives
  • inflammatory processes, such as a chronic infection with chlamydia
  • Several recent studies have identified factors that seem to increase or decrease the risk of stroke in particular groups of people. These studies, which warrant further investigation, include these findings:

  • People who were treated for high blood pressure with thiazide diuretics, such as hydrochlorothiazide, had a significantly lower stroke risk than people on ACE inhibitors or calcium channel blockers.
  • Women ages 39 to 50 who ate more fish and omega-3 polyunsaturated fatty acids had a reduced risk of ischemic stroke. This was particularly true in women who did not take aspirin regularly.
  • Women ages 15 to 44 who had 2 drinks of wine a day had a 40% to 60% lower risk of stroke than women who did not drink alcohol.
  • Phenylpropanolamine, a compound contained in appetite suppressants and cold remedies, significantly increased the risk of hemorrhagic stroke in women 18 to 49 years of age. The Food and Drug Administration (FDA) has since asked manufacturers to remove phenylpropanolamine from their products.
  • In one study, people who were treated in emergency departments for transient ischemic attacks (TIA) had a 25% chance of having a stroke or other serious health event within the next 90 days.


    Next section


    Stroke: Symptoms & Signs

    Author: Adam Brochert, MD
    Reviewer: Eileen McLaughlin, RN, BSN
    Date Reviewed: 07/13/01

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