Stroke

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Definition | Causes | Risk Factors | Symptoms | Diagnosis | Treatment | Prevention | Organizations

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Definition

Stroke is a brain injury that occurs when the brain's blood supply is interrupted. Without oxygen and nutrients from blood, brain tissue starts to die rapidly, resulting in a sudden loss of function.

(Also called brain attack or cerebrovascular accident)

Causes

A stroke most often occurs when blood flow to the brain becomes blocked (called ischemic stroke). One of the following problems may cause this blockage:

• A build-up of fatty substances (atherosclerotic plaque) along an artery's inner lining causes it to narrow, reduces its elasticity, and decreases its blood flow.
• A clot forms in an artery supplying the brain.
• A clot forms somewhere in the body (often the heart) and breaks free, traveling to and becoming lodged in an artery supplying the brain.

A stroke may also occur if a blood vessel breaks and bleeds into or around the brain, this is called hemorrhagic stroke.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

Modifiable risk factors:

• High blood pressure
• Narrowing of arteries supplying the brain due to atherosclerosis
• High cholesterol levels, particularly LDL (low density lipoprotein) cholesterol
• Smoking
• Obesity
• Lack of exercise
• Drinking excessive amounts of alcohol
• Diabetes mellitus
• Atrial fibrillation (abnormality of heart rhythm) that is treatable

Non-modifiable risk factors:

• A prior stroke or pre-existing cardiovascular disease other than stroke
• A prior transient ischemic attack (a temporary interrupting of the brain's blood supply, often called a mini-stroke)
• Age: 60 or older
• Family members who have had a stroke
• Race: Black

Some patients experience a "warning stroke" or transient ischemic attack (TIA). These are symptoms of a stroke that resolve completely, usually within hours. Such patients are at a significantly increased risk of having a full-blown stroke sometime in the near future.

Symptoms

Symptoms occur suddenly and differ depending on the part of the brain affected. Multiple symptoms generally arise simultaneously. Do not delay calling for emergency medical help. Brain tissue dies quickly when deprived of oxygen.

Symptoms include:

• Weakness or numbness on one side of the body
• Blurry, dimming, or no vision
• Difficulty swallowing, talking, or comprehending others
• Dizziness, falling, or loss of balance
• Severe or unusual headache

Diagnosis

Having a stroke is an emergency situation. Diagnosis includes:

• Neurological exams
• Blood tests
• Imaging scans
• Other tests to quickly determine the cause, location, and amount of damage

Tests may include:

CT Scan - a type of x-ray that uses a computer to make pictures of the brain

MRI Scan - a test that uses magnetic waves to make pictures of the brain

Arteriography (Angiography) - shows arteries in the brain

Magnetic Resonance Angiography (MRA) - shows brain blood vessels by mapping blood flow

Functional MRI - shows brain activity by picking up signals from oxygenated blood

Doppler Ultrasound - shows narrowing of the arteries supplying the brain

Treatment

Immediate treatment is needed to:

• Dissolve a clot causing an ischemic stroke
• Stop the bleeding during a hemorrhagic stroke

Other stroke care aims to:

• Reduce the chance of subsequent strokes
• Improve functioning
• Overcome disabilities

Medications

Medications include:

• Clot-dissolving drugs - given within three hours of the onset of symptoms. (Note: only in carefully selected patients.) Tissue plasminogen activator (tPA) is given through a vein after the doctor has confirmed the stroke's cause and there is no evidence of bleeding.
• Nerve-protecting drugs - help prevent additional nerve-cell damage caused by the chemicals released from dying brain cells. These drugs are promising but not yet routinely used.

Other drugs are used to:

• Control blood pressure
• Reduce chance of additional clot formation (aspirin or similar medications)
• Reduce brain swelling
• Correct irregular heart rhythm

Other interventions during an acute stroke include:

• Providing adequate oxygen
• Administering glucose
• Taking precautions to prevent choking

Surgery

Surgery may be performed following a stroke or TIA to prevent a recurrence. Surgical techniques include:

Carotid endarterectomy - fatty deposits are removed from a carotid artery (major arteries in the neck that lead to the brain)

Extracranial/intracranial bypass - reroutes the blood supply around a blocked artery using a healthy scalp artery

Rehabilitation

Rehabilitation may include:

• Physical therapy
• Occupational therapy
• Speech therapy

Prevention

The following may help prevent a stroke:

• Exercise regularly.
• Increase intake of fruits and vegetables and limit dietary salt and fat.
• Stop smoking.
• Drink alcohol only in moderation (1-2 drinks per day).
• Maintain a healthy weight.
• Frequently check blood pressure and follow physician recommendations for keeping it in a safe range.
• Consider taking a low dose of aspirin (75 mg/day) if your physician determines it is safe.
• Keep chronic medical conditions under control (such as high cholesterol and diabetes).
• Seek medical care if you have symptoms of a stroke, even if symptoms stop.

Organizations

American Heart Association
http://www.americanheart.org

National Stroke Association
http://www.stroke.org/

SOURCES:

National Institute of Neurological Disorders and Stroke

American Heart Association

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Last reviewed June 2001 by Medical Review Board