Stroke

A stroke is the sudden destruction of brain cells when blood flow to the brain is disrupted, usually by a blockage in a blood vessel. It is a medical emergency that can cause weakness, speech problems, paralysis * , and death, although most people survive.

While eating lunch with her grandfather on a sunny afternoon, 14-year-old Carmen was in the midst of describing her summer camp plans when suddenly one side of her grandfather's face went slack. He tried to speak, but he was slurring his words. Without warning, he clutched the picnic table, and the drinking glass he held crashed to the ground.

“Grandma,” Carmen called. As her grandmother rushed to dial for emergency aid, Carmen held her grandfather's trembling hand.

A stroke occurs when the blood supply to part of the brain is suddenly interrupted, or when a blood vessel in the brain bursts, spilling blood into the spaces surrounding neurons (nerve cells). Like other cells, brain cells die when they no longer receive oxygen and nutrients from the bloodstream, or when they are damaged by sudden bleeding into or around the brain.

There are two major types of strokes. Ischemic strokes involve a reduced blood flow to the brain. Hemorrhagic (hem-o-RAJ-ik) strokes involve bleeding in the brain. Ischemia (is-KEY-me-a) is the term used to describe the loss of oxygen and nutrients when there is inadequate blood flow. If ischemia is left untreated, it can lead to infarction (in-FARK-shun), or cell and tissue death in the surrounding area.

Ischemic strokes occur when a blood vessel to the brain becomes blocked, suddenly decreasing or stopping blood flow and ultimately causing an infarction. Ischemic strokes account for approximately 87 percent of all strokes. A blood clot (also called a thrombus) is the most common cause of vessel blockage and brain infarction.

Blood clotting is necessary in the body to stop bleeding and allow repair of damaged areas, but when blood clots develop in the wrong place within an artery, they can cause injury by stopping the normal flow of blood. The chance of clots developing increases as people age.

An embolus (EM-bowl-us) is a clot that has formed in a blood vessel somewhere in the body, often in the heart. It can break away from the wall of the vessel where it was formed, travel through the circulatory system, and become wedged in the brain, causing an embolic stroke. Ischemic strokes also can be caused by the formation of a blood clot in one of the cerebral arteries (arteries supplying blood to the brain). If the clot grows large enough, it will block blood flow.

Stenosis (ste-NO-sis), or a narrowing of the arteries, also can cause ischemia. Occurring in large arteries or small arteries, stenosis is called blood vessel disease or small vessel disease. The most common blood vessel disease that causes stenosis is atherosclerosis (ath-ER-ohskler-OH-sis). Deposits of plaque (a mixture of cholesterol and other fatty substances) build up along the inner walls of larger and medium-sized arteries, causing thickening, hardening, and loss of elasticity of the artery walls. Small pieces of plaque can break off from the blood vessel walls and form a clot.

Some people get a warning that they may be headed for a future stroke. A transient ischemic attack (TIA) is a very small stroke caused by a temporarily blocked blood vessel. Unlike a full stroke, a TIA leaves no permanent damage. Symptoms are similar to those of a full stroke, but they usually last 24 hours or less. It is impossible to know whether the symptoms are caused by a stroke or by a TIA, so any symptoms should receive immediate medical attention. Having a TIA increases the risk of having a full stroke in the future, and medical attention can sometimes prevent or lessen the severity of the stroke.

Hemorrhagic strokes are caused by burst blood vessels. In a healthy brain, the neurons do not come into direct contact with blood. Oxygen and nutrients move across a membrane from the blood vessel to the brain cells. Neuroglial (noo-ro-GLEE-al) cells help control which fluids and nutrients reach the neurons of the brain. When an artery in the brain bursts, blood spills out into the surrounding tissue, overriding the control of neuroglial cells and disrupting the delicate chemical balance of the brain.

Hemorrhagic strokes may occur in several ways. Aneurysms, or weak spots on artery walls, can stretch or “balloon” until eventually they break and spill blood into surrounding brain cells. Hemorrhages can also happen when plaque-encrusted arteries lose their elasticity and become brittle and thin enough to crack. Hypertension (high blood pressure) increases the risk that a brittle artery wall will give way and release blood into surrounding brain tissue.

Individuals who have an arteriovenous (ar-TEER-ee-o-VEN-us) malformation (a tangle of defective blood vessels and capillaries within the brain that can rupture) can also be at increased risk of hemorrhagic stroke. Although hemorrhagic strokes are less common than ischemic strokes, they have a much higher fatality rate because more brain tissue can be damaged more quickly.

Symptoms of stroke, such as those experienced by Carmen's grandfather, appear suddenly. They may include:

Strokes are medical emergencies and require immediate medical attention.

Doctors have diagnostic techniques and imaging tools to help diagnose strokes quickly and accurately. When a person with signs and symptoms of stroke arrives at the hospital, the first diagnostic step is a physical examination and a medical history. Often, an electrocardiogram * and a CT scan *

• Tissue plasminogen activator (t-PA) is most effective if given intravenously within three hours of the onset of stroke symptoms when a CT scan confirms that a person has suffered an ischemic stroke. However, t-PA increases the risk of major bleeding, so it can be used only when a patient fully meets the established guidelines, including the onset of symptoms less than three hours in duration.
• Antiplatelet drugs prevent clotting by decreasing the activity of cells that contribute to the clotting properties of blood. They can reduce the risk of ischemic stroke.
• Anticoagulants reduce the risk of stroke by thinning the blood and reducing its clotting properties.
• Thrombolytic agents can sometimes be used to treat an ongoing stroke. These drugs work by dissolving the blood clot that is blocking the blood vessel supplying the brain.

• Physical therapy helps people regain movement, balance, and coordination, and reestablish skills such as sitting, walking, and moving from one activity to another.
• Occupational therapy helps people who have had strokes readapt to everyday life by relearning practical skills needed at home, such as dressing, eating, bathing, reading, and writing.
• Speech therapy addresses the speech and language problems that arise when a stroke causes brain damage in the language parts of the brain. Speech therapy helps people who have no deficits in thinking but have problems either understanding written words or forming speech. One common problem for people who have had a stroke is aphasia (a-FAY-zha), a condition in which comprehension or expression of words is impaired. Speech therapists help stroke patients by working with them to improve language skills, develop alternative ways of communicating, and develop coping skills to deal with the frustration of not being able to communicate easily.

Preventing Stroke