Cerebrovascular Accident Health Article

Definition

Cerebrovascular accident (CVA) is the medical term for what is commonly termed a stroke. It refers to the injury to the brain that occurs when flow of blood to brain tissue is interrupted by a clogged or ruptured artery, causing brain tissue to die because of lack of nutrients and oxygen.

Description

The severity associated with cerebrovascular accident can best be demonstrated by the following facts:

• CVA is the leading cause of adult disability in the world.
• Worldwide, one-quarter of all strokes are fatal.
• Stroke is the third leading cause of death in the United States and the leading cause of disability.
• It is estimated that four of every five families in the United States will be affected by stroke in their lifetime,
• More than half a million people in the United States experience a new or recurrent stroke each year.
• Stroke kills about 150,000 Americans each year, or almost one out of three stroke victims.
• Three million Americans are currently permanently disabled from stroke.
• In the United States, stroke costs about $43 billion per year in direct costs and loss of productivity.
• Two-thirds of strokes occur in people over the age of 65.
• Strokes affect men more often than women, although women are more likely to die from a stroke.
• Strokes affect African Americans more often than Caucasians, and are more likely to be fatal among African Americans.
• The incidence of strokes among people ages 30 to 60 is less than 1%. This figure triples by the age of 80.
• The rate of occurrence for strokes in the United States fell by 15.52% between 1988 and 1998. But the number of deaths from stroke actually rose by 5%.

Causes and symptoms

Arterial blood carries oxygen and nutrients to the cells of the body. When arteries are unable to carry out this function due to rupture, constriction, or obstruction, the cells nourished by these arteries die. There are two forms of stroke, ischemic, which is caused by a blocked blood vessel that supplies blood to the brain, and hemorrhagic, which is bleeding into or around the brain.

The most common type of stroke is ischemic, which refers to the loss of oxygen and nutrients for brain cells that occurs because the blood supply to a portion of the brain has been cut off. Ischemic strokes account for approximately 80% of all strokes, and can be further broken down into two subtypes: thrombotic, also called cerebral thrombosis, and embolic, also termed cerebral embolism.

Thrombotic strokes are by far the more prevalent of ischemic strokes, and can be seen in nearly all aging populations worldwide. As people grow older, atherosclerosis, or hardening of the arteries, occurs. This results in a buildup of a waxy, cholesterol-laden substance in the arteries, which eventually narrows the interior space, or lumen, of the artery. This arterial narrowing occurs in all parts of the body, including the brain. As the process continues, the occlusion, or shutting off, of the artery eventually becomes complete so that no blood supply can pass through. Usually the occurrence of the symptoms of a thrombotic stroke are much more gradual and less dramatic than other strokes due to the slow, ongoing process that produces it.

Transient ischemic attacks (TIAs) are one form of thrombotic stroke, and usually the least serious. TIAs represent the occlusion of a very small artery, or arteriole. This blockage affects only a small portion of brain tissue and does not leave noticeable permanent ill effects. These transient ischemic attacks last only a matter of minutes, but are a forewarning that part of the brain is not receiving its necessary supply of blood, and, consequently, an insufficient amount of oxygen and nutrients.

Embolic strokes are usually a more spectacular, emergency event. They take place when the heart's rhythm is changed for a number of reasons, and blood clot formation takes place. Such a blood clot can move through the circulatory system until it blocks a blood vessel and stops the blood supply to cells in a specific portion of the body. If the blood clot occludes an artery that nourishes heart muscle, it causes myocardial infarction, or heart attack. If it blocks off a vessel that feeds brain tissue, it is termed an embolic stroke. Normally, these blockages occur in the brain itself, as when arteries directly feeding portions of brain tissue are blocked by a clot. But occasionally, the obstruction is found in the arteries of the neck, especially the carotid artery.

Approximately 20% of cerebrovascular accidents are termed hemorrhagic strokes, and are generally classified as subarachnoid hemorrhage or intracerebral hemorrhage, depending upon the location of the hemorrhage. Hemorrhagic strokes occur when an artery to the brain has a weakness and balloons outward, producing an aneurysm. Such an aneurysm often ruptures due to this inflation and thinning of the arterial wall, causing a hemorrhage in the affected portion of the brain.

Both ischemic and hemorrhagic strokes display similar symptoms. However, which symptoms appear depends upon which portion of the brain is cut off from its supply of oxygen and nourishment. The brain is divided into left and right hemispheres, which control bodily movement on opposing sides of the body. For example, the left hemisphere of the brain is responsible for both motor control of the right side of the body, and its sensory discrimination, just as the right hemisphere is responsible for body movements and feeling on the left side. Deeper brain tissue in the left hemisphere of the brain directs muscle tone and coordination for both the right arm and leg. As the communication and speech centers for the brain are also located in the left hemisphere of the brain, interruption of blood supply to that area can also affect the person's ability to speak.

Besides age, high blood pressure (hypertension) is one of the foremost causes of thrombotic stroke. Heart disease, obesity, diabetes, smoking, oral contraceptives in women, polycythemia (an increased number of red blood cells), and sleep apnea are also risk factors for thrombotic stroke, as is a diet high in cholesterol-producing, or fatty, foods.

The risk factors for hemorrhagic stroke include high blood pressure that can, over a period of time, cause the ballooning out of arteries known as aneurysm, and also causes the hereditary malformation that produces defective and weakened veins and arteries. Substance abuse is another major cause of hemorrhagic stroke. Cocaine, stimulants such as amphetamine drugs, and chronic alcoholism can cause a weakening of blood vessels that can result in hemorrhagic stroke.

The symptoms of stroke depend upon the part of the brain that is affected, and how large a portion of brain tissue has been damaged by the CVA. Unconsciousness and even seizures can be initial components of a stroke. Other effects materialize over a time period ranging from minutes to hours, and even, in some rare instances, over several days. Headache, mental confusion, vertigo, vision problems, difficulty speaking and communicating, including slurring of words (aphasia), and weakness or paralysis of one side of the body (hemiplegia) are all symptoms of stroke that are frequently observed. Stroke victims often have facial drooping, or slackness of the facial muscles, on the affected side, as well as difficulty swallowing. The severity of these symptoms will depend upon the amount of brain tissue that has been damaged and its location in the brain.