USC Center for Stroke and Cerebrovascular Disorders

Defining the Brain Attack

Clogged Blood Vessel

When a blood clot becomes lodged in one of the major blood vessels near the base of the brain, the brain normally supplied by this vessel becomes injured, causing a stroke.

A stroke is an attack of the brain. It occurs when there is interruption of normal blood flow to the brain causing brain cell death and the impairm

ent of functions such as speech, vision, or movement. A brain attack may also cause coma and death. Stroke is the third leading cause of death in the United States after heart disease and cancer. Each year, stroke will strike 500,000 Americans killing 150,000 of them and disabling more adults than any other disease. Although stroke affects more men than women, still more women die each year from stroke than from breast cancer.

Every minute, another American will suffer a brain attack. Four out of five American families will be touched by stroke at some time. Annually, stroke costs the United States $30 billion dollars in medical costs and lost productivity. The risk of African-Americans having a stroke as well as dying from stroke is almost twice that for Caucasians and Hispanics.

Just as a heart attack occurs when an artery to the heart muscle is obstructed, a brain attack or stroke occurs when an artery leading to or within the brain becomes obstructed or ruptures. These brain arteries can be blocked by blood clots (formed in the heart or elsewhere in the body or by the gradual buildup of fatty plaques or deposits, a process known as atherosclerosis. A brain artery ruptures when a weak spot on the blood vessel wall breaks. When the blood supply to a portion of the brain is interrupted, even for a few minutes, brain cells begin to die.

Major Causes of Stroke

Carotid Artery

On the left is a normal carotid artery supplying blood to the brain. On the right, there is obstruction of the carotid artery by fatty deposits.

The carotid artery in the neck is one of the major sources of blood supply to the brain. Due to a variety of causes, including high blood pressure, high blood fat and cholesterol levels, diabetes, smoking and hereditary factors, fatty deposits or plaques may gradually build up within the carotid artery. Eventually, this can obstruct the normal flow of blood to the brain. A special ultrasound examination of the neck can help detect this problem.

Blood clots may develop in the heart because of an abnormal heart rhythm, especially in the condition known as atrial fibrillation. Once a small blood clot is formed, it can leave the heart and enter one of the arteries traveling to the brain, causing a stroke. Blood-thinning medications help reduce the risk of this type of stroke.

In addition to aneurysms, brain blood vessels may burst and bleed as a result of high blood pressure or hypertension, or in some cases, due to collections of abnormal tangled blood vessels known as arteriovenous malformations, or AVMs.

A brain aneurysm is a protruding bubble or sac on a blood vessel caused by a weak spot in the vessel wall that balloons out over time. Aneurysms have thin, weak walls and have a tendency to rupture causing hemorrhage into and around vital brain structures, frequently resulting in a stroke or death.

Method of Treatment

Carotid Therapies:

One method of removing a blood clot obstructing a brain artery is to advance a tiny tube or catheter through the affected blood vessel to the site of obstruction. Through this catheter, a "clot busting' medicine (thrombolytic agent) can be directly applied to the clot to dissolve it (above left). Once the blockage is relieved and normal blood flow is restored, the brain damage may reverse and a stroke can be avoided (above right). However, this form of therapy, to be effective, needs to be instituted wifhin 6 hours of the onset of stroke symptoms.

• Hypertension or high blood pressure
• Cigarette smoking
• High blood cholesterol levels, obesity, physical inactivity
• Heart disease, especially an irregular heartbeat called atrial fibrillation
• Diabetes
• Transient ischemic attacks (TIAs). These are brief attacks that can cause neurologic deficits which resolve over a short period of time, such as temporary blindness in one eye.
• Prior stroke
• Aging
• The incidence of stroke is about 30% higher in men than women
• A family history of stroke
• African-American men and women have a significantly increased risk of
• stroke compared to Caucasians and Hispanics.

• Numbness, weakness or paralysis of the face, arm or leg, especially on one side of the body.
• Sudden blurred or decreased vision in one or both eyes.
• Sudden and severe headache with no apparent cause, often described as the worst headache of your life.
• Difficulty speaking or understanding simple statements.
• Dizziness, loss of balance, or loss in coordination, especially when combined with another symptom.

If you experience any of these symptoms yourself, or recognize them in someone else, CALL 911 immediately, even if the symptoms only last for a short time. Early treatment ensures the best chance of recovery from stroke. Remember, every minute counts.

• Control your blood pressure.
• Find out if you have heart disease, especially an irregular heartbeat known as atrial fibrillation, and follow your doctor's advice for treatment of your heart disease.
• Find out if you have carotid artery disease. This condition may be treated using either surgery or balloon angioplasty.
• Find out if you have diabetes and follow your doctor's advice on controlling this disease. If you smoke, stop. If you don't smoke, don't start.
• Lower your cholesterol level.
• Limit your alcohol consumption.
• Control your weight.

By following your doctor's advice and controlling your risk factors, approximately 80% of strokes can be prevented.