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 (usually in less than 10 minutes), resulting in a sudden loss of function.

This condition is also known "brain attack" or cerebrovascular accident (CVA).

Causes

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

• Sudden decreased blood flow—Damage to a blood vessel supplying blood to the brain can occur suddenly from injury or from a clot that forms and breaks off from another location in the body, such as the heart or neck. There are certain conditions which predispose people to form blood clots, such as cancer, pregnancy, atrial fibrillation, and certain autoimmune diseases.
• Local blood clot—A build-up of fatty substances (atherosclerotic plaque) along the inner lining of the artery causes it to narrow, reduces its elasticity, causes local inflammation, and decreases the blood flow in the artery.
• A clot forms in an artery supplying the brain.
• Inflammation of blood vessels—Inflammatory conditions in the blood vessels (vasculitis) can interrupt blood flow.

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

	Hemorrhagic vs. Ischemic Stroke
	Copyright © 2005 Nucleus Communications, Inc. All rights reserved. www.nucleusinc.com

Risk Factors

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

Risk factors include:

Modifiable risk factors:

• High blood pressure (the number one risk factor for ischemic stroke)
• High blood homocysteine level
• Drug abuse (heroin, cocaine, amphetamines)
• Narrowing of arteries supplying the brain due to atherosclerosis
• High cholesterol levels, particularly low-density lipoprotein (LDL) cholesterol
• Smoking
• Diabetes mellitus
• Atrial fibrillation (abnormality of heart rhythm)
• Use of birth control pills if you are over 35 years old and smoke

Nonmodifiable risk factors:

• Prior stroke or pre-existing cardiovascular disease such as heart attack
• Prior transient ischemic attack (TIA)
  • Some patients experience a "warning stroke" or TIA, a temporary interruption of the brain's blood supply, often called a mini-stroke. These are symptoms of a stroke that resolve completely, usually within minutes. Such patients are at a significantly increased risk of having a full-blown stroke sometime in the near future.
• Age: 60 or older
• Family members who have had a stroke
• Gender: males are at greater risk than females
• Race: Black, Asian, Hispanic
• Blood disorders which increase clotting in sickle cell disease and polycythemia
• Valvular heart disease such as mitral stenosis

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, including the face
• Seizures
• Confusion
• Nausea and vomiting of sudden onset
• Blurry, dimming, double vision, 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
• Electrocardiogram (ECG, EKG)—a test that records the heart's activity by measuring electrical currents through the heart muscle
• Brain and blood vessel imaging via CT scan, MRI scan, and/or ultrasonography
• Blood tests especially homocysteine, prothrombin time, and other coagulation tests
• Other tests to quickly determine the cause, location, and amount of damage

Some tests may include:

• CT scan—a type of x-ray that uses a computer to make pictures of the brain. This test helps doctors identify hemorrhagic versus ischemic stroke.
• 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
• Echocardiography—a test that uses high-frequency sound waves (ultrasound) to examine the size, shape, and motion of the heart. This test shows if the clot comes from one of the heart's chambers.

Treatment

Immediate treatment is needed to:

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

Other treatment aims to:

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

Medications

Medications include:

• Clot-dissolving drugs—These are given within three hours of the onset of symptoms. (Note: These drugs are only used 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.
• Blood-thinning drugs (anticoagulants)—Heparin is given by vein (along with tPA, if indicated) and an oral medication (warfarin) is sometimes started if long-term treatment with a blood-thinner is anticipated.
• Antiplatelet drug—Aspirin is the most common, but clopidogrel (Plavix), dipyridamole (Persantine), and ticlopidine (Ticlid) are also sometimes used.

Other drugs are used to:

• Control blood pressure (Labetalol, the first-line drug, or sodium nitroprusside)
• Reduce chance of additional clot formation (aspirin or similar medications)
• Reduce brain swelling
• Correct irregular heart rhythm (such as atrial fibrillation)

Other interventions during an acute stroke include:

• Providing adequate oxygen
• Taking precautions to prevent choking
• Frequent neurological examinations

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).
• Carotid angioplasty and stenting—In a less invasive procedure than carotid endarterectomy, the carotid artery is widened, and a metallic mesh tube is inserted into the artery to help keep it open.
• Extracranial/intracranial bypass—This surgery reroutes the blood supply around a blocked artery using a healthy scalp artery.
• Craniotomy—In the case of a hemorrhagic stroke, this surgery may be performed to relieve pressure buildup in the brain caused by swelling.

A study was conducted comparing endarterectomy and stenting in 527 patients who recently suffered a minor stroke or TIA and had severe carotid artery narrowing (at least 60%). Even though endarterectomy is more invasive (and dangerous) than stenting, endarterectomy led to fewer deaths and repeat strokes than stenting within the first six months.*

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.
• If you drink alcohol, 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 milligrams per 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.
• Stop the use of recreational drugs (cocaine, heroin, marijuana, amphetamines)

RESOURCES:

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

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

CANADIAN RESOURCES:

Heart and Stroke Foundation of Canada
http://ww2.heartandstroke.ca

Prevent Stroke
http://www.preventstroke.ca/

References:

Adams H, Adams R, Del Zoppo G, Goldstein LB. Guidelines for the early management of patients with ischemic stroke: 2005 guidelines update: a scientific statement from the Stroke Council of the American Heart Association/American Stroke Association. Stroke. 2005;36:916-923.

American Heart Association website. Available at: http://www.americanheart.org.

Duncan PW, Zorowitz R, Bates B, et al. AHA/ASA. Management of adult stroke rehabilitation care: a clinical practice guideline. Stroke. 2005;36:100-143.

Merritt's Neurology. 11th ed. Lippincott Williams & Wilkins; 2005.

National Institute of Neurological Disorders and Stroke website. Available at: http://www.ninds.nih.gov/.

National Stroke Association website. Available at: http://www.stroke.org.

Sacco RL, Adams R, Albers G, et al. Guidelines for prevention of stroke in patients with ischemic stroke or transient ischemic attack: a statement for healthcare professionals from the AHA/ASA Council on Stroke: co-sponsored by the Council on Cardiovascular Radiology and Intervention. Stroke. 2006;37:577-617.

Silver B. Ischemic stroke. In: Gilman S, editor. MedLink Neurology website. Available at: http://www.medlink.com. Accessed February 23, 2008.

Stroke (acute management). EBSCO Publishing Dynamed website.Available at: http://www.ebscohost.com/dynamed. Updated February 21, 2008. Accessed Feb 23, 2008.

*Updated section on Surgery on 11/20/06 according to the following study, as cited by DynaMed's Systematic Literature Surveillance : Mas JL, Chatellier G, Beyssen B, et al. Endarterectomy versus stenting in patients with symptomatic severe carotid stenosis. N Engl J Med. 2006;355:1726-1729.

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