American Medical Association Family Medical Guide - American Medical Association [412]
Stroke
A stroke occurs when blood flow to part of the brain is obstructed, cutting off the supply of oxygen and nutrients and damaging brain tissue, affecting the physical or mental functions that are controlled by the damaged area of the brain. The effects of a stroke may be temporary or permanent, mild or severe. Most strokes, called ischemic strokes, result from a blocked artery. Hemorrhagic strokes result from a ruptured or leaking artery.
Cerebral thrombosis, cerebral embolism, and cerebral hemorrhage are three possible causes of stroke. Cerebral thrombosis occurs when an artery that supplies blood to the brain becomes narrowed, usually as a result of atherosclerosis (see page 557). In atherosclerosis, fatty deposits called plaque build up in artery walls, narrowing the artery. Over time, the surface of a plaque may become roughened or cracked, providing an ideal site for blood cells to clump together and form a clot (thrombus) inside the blood vessel. The clot may continue to grow until it partially or completely blocks blood flow through the artery.
Stroke
When an artery in the brain is blocked, the blood supply to part of the brain is cut off. The lack of blood can damage the area of the brain normally supplied by the artery. An interruption in blood flow to one side of the brain can cause symptoms such as numbness, weakness, or paralysis on the opposite side of the body.
Cerebral embolism occurs when an artery that supplies blood to the brain is blocked by an embolus. An embolus is usually a bit of debris (such as a fragment of plaque) or a blood clot that has traveled through the bloodstream from another part of the body. The embolus becomes wedged in an artery and obstructs blood flow to part of the brain.
Cerebral hemorrhage occurs when an artery ruptures or leaks, and blood seeps into surrounding brain tissue. An artery may leak or rupture as a result of an aneurysm (a weakened area of a blood vessel wall), damage to the artery caused by uncontrolled high blood pressure or diabetes, or an arteriovenous malformation (an abnormal connection between an artery and a vein, which can rupture). Although the initial effects of a hemorrhagic stroke may be more severe than those of an ischemic stroke, the long-term effects of both types of stroke depend on the part of the brain affected and the extent of the lasting damage.
Berry aneurysm
A berry aneurysm results from a congenital (present at birth) defect in an artery wall. It forms at the base of the brain, where an artery branches. When a berry aneurysm ruptures, blood can spurt into surrounding brain tissue and cause brain damage.
Strokes are a leading cause of death and long-term disability in the United States. The effects of a stroke can differ widely from person to person. About one out of three younger people who have a stroke has long-term impairment, while three out of four older people have permanent disability.
Risk Factors
The following factors can increase your risk of stroke. However, most of these factors can be controlled or eliminated through lifestyle changes.
• Heart disease Heart failure (see page 570) and irregular heart rhythms (see page 580) promote blood clot formation.
• High blood pressure Uncontrolled high blood pressure damages blood vessels and promotes atherosclerosis.
• Undesirable cholesterol profile An undesirable cholesterol profile (see page 146) promotes atherosclerosis.
• Lack of exercise Being inactive can lead to weight gain and an undesirable cholesterol profile.
• Being overweight Weighing more than your ideal body weight (see page 11) increases your risk of having an undesirable cholesterol profile, high blood pressure, and type 2 diabetes—all risk factors for stroke.
• Diabetes Uncontrolled diabetes increases blood levels of LDL (bad) cholesterol and promotes atherosclerosis.
• Smoking Smoking (including