| Definition: |
Loss of neurologic functions (brain attack) which occurs suddenly or in a step-wise fashion, caused by complications of atherosclerosis.
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| Causes, incidence, and risk factors: |
Stroke secondary to atherosclerosis affects about 2 out of 1,000 people, or approximately 50% of all those who have strokes. Strokes are the third leading cause of death in most developed countries, including the U.S. Stroke secondary to atherosclerosis is most common in people over 50 years old. The incidence of stroke rises dramatically with age, with the risk doubling with each decade after 35 years old. About 5% of people over 65 years old have had at least one stroke. The disorder occurs in men more often than women.
Atherosclerosis (hardening of the arteries) is a condition where fatty deposits occur in the inner lining of the arteries, and atherosclerotic plaque (a mass consisting of fatty deposits and blood platelets) develops. The plaque may obstruct (occlude) the artery by itself, or may trigger a clot (thrombus) at that location, causing cerebral thrombosis (thrombotic stroke). The occlusion of the artery develops slowly.
Atherosclerotic plaque does not necessarily cause stroke. There are many small connections among the various brain arteries. If blood flow gradually decreases, these small connections will increase in size and "by-pass" the obstructed area (collateral circulation). If there is enough collateral circulation, even a totally blocked artery may not cause neurologic deficits. A second safety mechanism within the brain is that the arteries are large enough that 75% of the blood vessel can be occluded, and there will still be adequate blood flow to that area of the brain.
Atherosclerosis occludes the blood vessels, causing ischemia (reduced tissue oxygenation associated with insufficient blood flow) and infarction (tissue death associated with ischemia).
Pieces of atherosclerotic plaque or clot may travel in the bloodstream (embolism). However, strokes caused by embolism are most commonly strokes secondary to cardiogenic embolism (clots that develop because of heart disorders, which then travel to the brain). Whatever the source of the embolism, the clot travels through the bloodstream and becomes stuck in a small artery in the brain. This stroke occurs suddenly with immediate maximum neurologic deficit (loss of brain function).
Risks for stroke secondary to atherosclerosis include: a history of high blood pressure (hypertension is present in about 70% of all victims of stroke); peripheral vascular disease; smoking; transient ischemic attacks or other cerebrovascular disease; high blood lipids; high levels of homocysteine; diabetes mellitus; obesity; sedentarism, and kidney disease requiring dialysis.
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| Treatment: |
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Go to the emergency room as quickly as possible if you believe you have had or may be having a stroke. Stroke is an acute, serious condition that should be treated immediately. Strokes are now called "brain attacks" to stress that time is of the essence in treating this condition.
The most effective treatment for stroke (intravenous rtPA), which works to dissolve the offending clot and prevent permanent deficits, can only be given before three hours have elapsed since the onset of the deficits. There is risk of serious bleeding with this treatment so it cannot be used in all cases, but the most important factor in effective treatment for stroke is arriving at the hospital as early as possible from the onset of symptoms. For virtually all strokes, there is a need for hospitalization, possibly including intensive care and life support.
For patients who can't be treated with clot-busting drugs, treatment will be based on the type of stroke they may have had, however, the focus will be supportive (i.e., blood pressure control, adequate fluid management, and prevention of complications such as infections). Rehabilitation is important following stroke to maximize function in affected areas. Treatment is also aimed at prevention of future strokes. Recovery may occur as other areas of the brain take over functioning for the damaged areas. The goal of treatment is to prevent spread (extension) of the stroke and to maximize the ability of the person to function (see stroke).
Special treatment (in addition to treatment for stroke in general) may include medications to control blood cholesterol levels.
A special diet often follows the American Heart Association recommendations for people with hyperlipidemia (increased fats/lipids in the bloodstream). This may include restriction of fat, especially saturated fat. It may also include restriction of salt/sodium if stroke is accompanied by high blood pressure.
A carotid endarterectomy (removal of plaque from the carotid arteries) may be needed by some people to prevent new strokes from occurring.
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| Expectations (prognosis): |
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Stroke is the third leading cause of death in developed countries. About one-fourth of the sufferers die as a result of the stroke or its complications, about one-half have some degree of recovery but are left with variable disability and about one-fourth recover most or all function. There are three important signs occurring at the onset of the stroke that predict best who will recover to a lesser extent in the convalescence phase: low-grade temperature or fever, high blood sugar (hyperglycemia), and low blood pressure (hypotension). People with these symptoms are less likely to make a full recovery. Contrary to common belief, recurrence of stroke is only around 2% within the first 14 days.
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| Calling your health care provider: |
Go to the emergency room or call the local emergency number (such as 911) if symptoms occur indicating a stroke.
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| Prevention: |
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The prevention of stroke secondary to atherosclerosis includes control of risk factors. Hypertension, diabetes, heart disease, and other risk factors should be treated as appropriate. Smoking should be minimized or, preferably, stopped.
Treatment of TIA can prevent some strokes.
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Review Date: 5/12/2002
Reviewed By: Alberto Espay, M.D., Department of Neurology, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada. Review provided by VeriMed Healthcare Network.
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