Table of Contents
What is Stroke and Definition
An interruption of BLOOD flow and oxygen supply to the BRAIN, sometimes called a brain attack. Stroke strikes about 700,000 Americans each year. For two thirds of them the stroke is a second or subsequent stroke. About 85 percent of strokes are ischemic; they result from blockage of an arterial pathway in the brain. The remaining 15 percent are hemorrhagic; they result from bleeding into the brain, typically from a blood vessel that ruptures. About 90 percent of people survive a first ischemic stroke, though a third of them experience permanent disability of varying severity as a consequence of the damage to the brain. The risk for death rises with each subsequent stroke. Hemorrhagic strokes are more likely to be fatal, claiming the lives of nearly half of those who have them. In 2000, about 2.4 million Americans were stroke survivors.
HYPERTENSION (high BLOOD PRESSURE) is the leading cause of stroke. Unfortunately, hypertension has no symptoms and many people do not know they have it until they suffer stroke or HEART ATTACK. Chronically elevated blood pressure stresses blood vessels, causing them to stiffen and thicken to help protect against the constant pounding of blood. This response (ARTERIOSCLEROSIS) makes the arteries vulnerable to INFLAMMATION and accumulations of debris (ATHEROSCLEROTIC PLAQUE), resulting in ATHEROSCLEROSIS. The high pressure of blood rushing through the arteries causes tiny fragments of the plaque to break free. The fragments float through the blood circulation until they lodge in a blood vessel, blocking the further flow of blood. When this occlusion happens in the heart, it causes a MYOCARDIAL INFARCTION or heart attack. In the brain, the occlusion causes stroke.
Brain cells require a constant supply of oxygen to meet their energy needs. Deprivation of oxygen for as little as 30 seconds causes them to begin shutting down. Lack of oxygen for two to three minutes causes brain cells to begin dying. After five minutes, enough brain cells can die to cause permanent loss of function in the affected area. This loss may involve cognitive function, memory, speech and language processing, and physical movement. The brain’s correlation to the body is ipsilateral. Damage to the right brain may result in weakness or paralysis on the left side of the body; damage to the left brain may affect the right side of the body.
Time is crucial. Treatment for ischemic stroke that begins within four hours can incorporate drugs to dissolve the blocking blood clot, minimizing or preventing damage to the brain.
Symptoms of Stroke and Diagnostic Path
Symptoms of stroke may be subtle or pronounced. The main symptoms of stroke include
- numbness or tingling on one side of the face or body
- difficulty speaking (including slurred speech) or swallowing
- drooping of facial features on one side
- weakness or PARALYSIS on one side of the body
- loss of vision or change in vision, particularly in only one EYE
It is important to seek medical attention without delay at the first indication that a stroke may be occurring. Early treatment with THROMBOLYTIC THERAPY can dissolve developing blood clots, mitigating or preventing the stroke. The diagnostic path typically includes COMPUTED TOMOGRAPHY (CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI) to visualize the location and extent of the stroke, and to determine whether the stroke is ischemic or hemorrhagic. ELECTROENCEPHALOGRAM (EEG), which measures the brain’s electrical activity, and a comprehensive NEUROLOGIC EXAMINATION can help assess the extent of damage the stroke has caused.
Stroke Treatment Options and Outlook
Immediate treatment focuses on minimizing damage to the brain. Optimally, early intervention permits thrombolytic therapy, which must begin within four hours of the stroke’s onset. Treatment beyond this window of opportunity typically includes ANTICOAGULATION THERAPY for ischemic stroke to prevent further clots from forming and supportive measures to maintain cardiovascular stability. Most people who experience strokes have hypertension, so subsequent treatment includes measures to bring blood pressure under control through medications and lifestyle changes.
People who receive thrombolytic therapy often have no residual effects from their strokes and can return to their regular activities within a few weeks. People who experience permanent disability as a result of stroke may require inpatient or outpatient rehabilitation. The level of recovery depends on the extent of damage. Many people with serious disabilities are able to learn methods for adapting to their limitations, allowing them to return to some activities and perhaps independent living. About 70 percent of people who experience strokes are able to return to functional independence and often many of their regular activities, within three to six months.
Risk Factors and Preventive Measures
The key risk factors for stroke are hypertension and atherosclerosis. Cardiovascular conditions involving clot formation present a high risk for stroke. These include DEEP VEIN THROMBOSIS (DVT), ATRIAL FIBRILLATION, CAROTID STENOSIS, and VALVULAR HEART DISEASE. DIABETES also raises the risk for stroke. Other risk factors are those for all forms of CARDIOVASCULAR DISEASE (CVD): smoking, physical inactivity, and diet high in saturated fats and excessive calories. Stroke also becomes more likely with advancing age.
The most effective preventive measure is maintaining a healthy blood pressure. All adults over age 50 should have annual blood pressure checks, with more frequent checks when blood pressure is elevated or risk factors for hypertension are present. Efforts to maintain good cardiovascular health, such as daily physical exercise and WEIGHT LOSS AND WEIGHT MANAGEMENT, help lower the risk for subsequent stroke as well as for other forms of cardiovascular disease.
See also CALORIE; CARDIOVASCULAR DISEASE PREVENTION; COGNITIVE FUNCTION AND DYSFUNCTION; ENDARTERECTOMY; HEALTH RISK FACTORS; RISK FACTORS FOR CARDIOVASCULAR DISEASE; SPEECH DISORDERS; SWALLOWING DISORDERS; TRANSIENT ISCHEMIC ATTACK (TIA).