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.

Carmen's Story

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.

What Is Stroke?

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.

In a transient ischemic attack (TIA), blood clots inhibit blood flow to the brain, causing symptoms similar to those of a stroke.

In a transient ischemic attack (TIA), blood clots inhibit blood flow to the brain, causing symptoms similar to those of a stroke.
IIllustration by Electronic Illustrators Group. © 2016 Cengage Learning®.
Stroke in the United States and the World

According to the World Health Organization, 15 million people around the world have a stroke each year. Of these, five million die and another five million are permanently disabled.

Ischemic Strokes

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 clots

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.

Transient ischemic attacks

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

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.


How Do People Know They Are Having a Stroke?

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.

How Do Doctors Diagnose and Treat Stroke?

Strokes can affect many different parts of the brain.

Strokes can affect many different parts of the brain.
IIllustration by Frank Forney. © 2016 Cengage Learning®.

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 *

  • There are two broad categories of aphasia: fluent and nonfluent.
  • Fluent aphasia is the result of damage to the temporal lobe (the side portion) of the brain. This is called Wernicke's (VER-nik-ahs) aphasia. People with Wernicke's aphasia may speak in long sentences that have no meaning, add unnecessary words, and even create madeup words. These people usually have great difficulty understanding speech, and they are often unaware of their mistakes. Physically these individuals usually have no body weakness because their brain injury is not near the parts of the brain that control movement.
  • Nonfluent aphasia is caused by damage to the frontal lobe of the brain. This is called Broca's aphasia. People with Broca's aphasia frequently speak in short phrases that make sense but are produced with great effort. They often omit small words such as “is,” “and,” and “the” but typically understand the speech of others. They are often aware of their difficulties and can become easily frustrated. Physically, these people have right-sided weakness or paralysis of the arm and leg because the frontal lobe is also important for motor movements.
  • Another type of nonfluent aphasia is called global aphasia and is caused by damage to extensive portions of the language areas of the brain. Individuals with global aphasia have severe communication difficulties and may be extremely limited in their ability to speak or comprehend language.

Imaging tests also help healthcare professionals to evaluate stroke. The CT scan may rule out a hemorrhage or may show evidence of early infarction. If the stroke is caused by a hemorrhage, a CT scan can reveal any bleeding into the brain. CT scans and other early steps are critical in determining the cause of the stroke and emergency treatment. MRIs * may be taken to detect subtler changes in brain tissue or areas of dead tissue soon after a stroke.

Stroke treatment varies depending on the whether the stroke is hemorrhagic or ischemic. Treatment most often involves medication and rehabilitation. Acute stroke therapy uses medication to stop a stroke while it is happening by either quickly dissolving the blood clot that is causing the stroke or by stopping the bleeding of a hemorrhagic stroke. Surgery is almost never used for acute stroke treatment. Very rarely, and only in hemorrhagic stroke, a neurosurgeon may consider placing a drain into an area of the brain to remove some blood and relieve pressure on the brain. Carotid endarterectomy (kar-OT-id en-DAR-ta-rek-to-ME) (surgery to remove plaque buildup in carotid arteries) may be indicated to prevent an ischemic stroke from happening, although it is rarely performed as an emergency procedure.

Medication and surgery

Various medications can be used to treat stroke:

Surgery is not used to treat an ischemic stroke, but it is sometimes used to treat a hemorrhagic stroke. An attempt to surgically remove accumulated blood and intracranial pressure caused by a hemorrhagic stroke is a delicate procedure, as the surgery itself may generate additional bleeding, thereby causing more harm. Surgery is sometimes used to repair aneurysms or vascular malformations in and around the brain.


Post-stroke rehabilitation helps people overcome the disabilities that result from stroke damage. For some people, such as Carmen's grandfather, acute stroke treatment and poststroke therapy lead to a full recovery. For others, recovery is only partial.

Dwight D. Eisenhower

Dwight D. Eisenhower (1890–1969) was a U.S. Army general and the 34th president of the United States. “Ike,” as he was known, had a meteoric rise as a military commander during World War II. In 1953 he was elected to his first term in the White House. Despite having had a heart attack in 1955 and a stroke in 1957, he was elected to a second term. Eisenhower completed his presidency in 1961, when John F. Kennedy was sworn in as 35th president.

Although strokes occur in the brain, they may affect the entire body and all activities of daily living. Some of the disabilities that may result from a stroke include paralysis (or partial paralysis) of different parts of the body, difficulties with memory and concentration, speech problems, and emotional distress as people cope with their changed circumstances. Rehabilitation may involve several different forms of therapy:

Psychotherapy often is useful following a stroke because depression, anxiety, frustration, and anger are common poststroke symptoms.

Preventing Stroke

The most important risk factors * for stroke are hypertension (high blood pressure), heart disease, diabetes, and smoking. Others factors that increase the risk of having a stroke are heavy alcohol consumption, high cholesterol levels, and genetic or congenital conditions, such as vascular (blood vessel) abnormalities.


People with hypertension (high blood pressure) have a risk of stroke that is four to six times greater than those without hypertension. One-third of adults in the United States have high blood pressure. Antihypertensive drugs and attention to diet can decrease a person's risk of stroke.

Heart disease

After hypertension, the second most powerful risk factor for stroke is heart disease, particularly the condition known as atrial fibrillation * Diabetes

People with diabetes have three times the risk of stroke as those without diabetes. The relative risk is highest in the fifth and sixth decades of life and decreases after that. People with diabetes who control their blood sugar level well, who avoid smoking, and who avoid or control hypertension are less likely to have strokes.

Cigarette smoking

Smokers have a 40 to 60 percent greater chance of having a stroke than nonsmokers. Smoking increases a person's chance of ischemic stroke, independent of all other risk factors.

Blood cholesterol levels

High cholesterol levels can contribute to the risk of stroke. Too much cholesterol in the blood is associated with plaque developing in the walls of arteries (atherosclerosis), leading to stenosis of blood vessels. By lowering cholesterol through diet and exercise, a person can lower the risk of atherosclerosis and stroke. Doctors may prescribe cholesterol-lowering medication for people with high cholesterol levels.

Lifestyle changes

Many strokes can be prevented with changes in lifestyle. These changes include:

Medical measures

To prevent stroke, doctors may prescribe medications to lower blood pressure and cholesterol levels. In some cases, particularly if a person has atrial fibrillation, doctors may prescribe regular doses of aspirin, Coumadin (an anticoagulant medication that stops the formation of clots), or other medications that prevent blood clotting. If carotid (ka-ROT-id) arteries (arteries supplying the brain) are partially blocked by plaque, surgery can clear them and prevent strokes in many cases.

Strokes can happen to people of either sex no matter what their age or racial background. Transient ischemic attacks (TIAs) multiply a person's risk of having a full stroke and should receive immediate medical attention.

See also Aging • Alcoholism • Aneurysm • Diabetes • Embolism • Genetic Disease: Overview • Heart Disease: Overview • Hypertension • Tobacco-Related Diseases: Overview • Vascular Diseases: Overview


Books and Articles

Grotta, James. C., Gregory W. Albers, and Joseph P. Broderick. Stroke: Pathophysiology, Diagnosis, and Management, 6th ed. Atlanta, GA: Elsevier, Inc., 2015.

Jacobs, Anne Burleigh. Highs, Lows, and Plateaus: A Path to Recovery. Bloomington, IN: AuthorHouse, 2014.


MedlinePlus. “Aphasia.” U.S. National Library of Medicine. (accessed July 13, 2016).

MedlinePlus. “Stroke.” U.S. National Library of Medicine. (accessed July 13, 2016).

National Heart, Lung, and Blood Institute. “How Is a Stroke Treated?” (accessed July 13, 2016).


American Heart Association. 7272 Greenville Ave., Dallas, TX 752314596. Toll-free: 800-242-8721. Website: (accessed July 13, 2016).

Heart and Stroke Foundation of Canada. 222 Queen St., Suite 1402, Ottawa, ON K1P 5V9, Canada. Telephone: 613-569-4361. Website: (accessed July 13, 2016).

National Institute on Deafness and Other Communication Disorders. 1 Communication Ave., Bethesda, MD 20892-3456. Toll-free: 800-241-1044. Website: (accessed July 13, 2016).

National Institute of Neurological Disorders and Stroke. PO Box 5801, Bethesda, MD 20824. Telephone: 301-496-5751. Website: (accessed July 13, 2016).

National Stroke Association. 9707 E. Easter Ln., Suite B, Centennial, CO 80112. Toll-free: 800-787-6537. Website: (accessed July 13, 2016).

* paralysis (pah-RAH-luh-sis) is the loss or impairment of the ability to move some part of the body.

* ischemia (is-KEY-me-a) is the loss of oxygen and nutrients when there is inadequate blood flow to an organ or tissue.

* infarction (in-FARK-shun) is cell and tissue death resulting from oxygen deprivation caused by blockage of the tissue's blood supply.

* electrocardiogram (e-lek-tro-KAR-dee-o-gram), also known as an EKG, is a test that records and displays the electrical activity of the heart.

* CT scans are the shortened name for computed tomography (to-MOG-ra-fee), which uses computers to view structures inside the body. Formerly called computerized axial tomography (CAT).

* MRI, which is short for magnetic resonance imaging, produces computerized images of internal body tissues based on the magnetic properties of atoms within the body.

* risk factors are any factors that increase the chance of developing a disease.

* atrial fibrillation (AY-tree-al fib-ri-LAY-shun) is the arrhythmic or irregular beating of the left upper chamber of the heart. This irregular heartbeat leads to an irregular flow of blood and to the formation of blood clots that can leave the heart and travel to the brain, causing a stroke.

  This information is not a tool for self-diagnosis or a substitute for professional care.