Definition

Stroke is a brain injury. It occurs when the brain's blood supply is interrupted. Without oxygen and nutrients from blood, brain tissue dies quickly (less than 10 minutes). This causes a sudden function loss.

Causes

A stroke occurs when blood flow to the brain is blocked (called ischemic stroke). This is caused by one of the following:

• Sudden decreased blood flow
  • Damage to a blood vessel supplying blood to the brain can occur suddenly from either:
    • Injury
    • A clot that forms and breaks off from another part of 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
      • Certain autoimmune diseases
• Local blood clot
  • A build-up of fatty substances ( atherosclerotic plaque ) along the inner lining of the artery causes:
    • Narrowing of artery
    • Reduced elasticity
    • Local inflammation
    • Blood protein defects leading to increased clotting tendency
    • Decreased blood flow in the artery
• Clot in an artery supplying the brain
• Inflammatory conditions in the blood vessels (vasculitis)

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

© 2009 Nucleus Medical Media, Inc.

Risk Factors

These risk factors increase your chance of developing a stroke. Tell your doctor if you have any of these risk factors.

Risk factors you can affect:

• 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 or impaired glucose tolerance
• Atrial fibrillation (abnormality of heart rhythm)
• Use of birth control pills if you are over 35 years old and smoke
• Long-term use of hormone replacement therapy

Risk factors you cannot affect:

• Prior stroke or pre-existing cardiovascular disease such as heart attack
• Prior transient ischemic attack (TIA)
  • Some people experience a "warning stroke" or TIA. This is a temporary interruption of the brain's blood supply (mini-stroke). These are stroke symptoms that resolve completely within minutes. There may be a very high risk of having a full-blown stroke 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. They differ depending on the part of the brain affected. Multiple symptoms arise at the same time. Call emergency help right away. Brain tissue dies quickly when deprived of oxygen.

Symptoms:

• 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 by:
  • 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
  • Ultrasonography—a test that uses sound waves to examine the blood vessels feeding the brain
• Blood tests especially homocysteine, prothrombin time , and other coagulation tests

Some tests may include:

• Arteriography (angiography)—a catheter is placed in a blood vessel in the groin and threaded up to the brain; to show arteries in the brain
• Magnetic resonance angiography (MRA)—shows brain blood vessels by mapping blood flow
• CT angiogram (CTA)—this test uses a CT scanner and can give images of the blood vessels inside the brain, after a dye is injected into the veins
• Functional MRI—shows brain activity by picking up signals from oxygenated blood
• Doppler ultrasound —shows narrowing of the arteries (carotid and vertebral) supplying the brain; evaluates flow of blood in brain
• Echocardiography —a test that uses high-frequency sound waves (ultrasound) to examine the size, shape, and motion of the heart; to show 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 later strokes
• Improve functioning
• Overcome disabilities

Prevention

To help reduce your chance of getting a stroke, take the following steps:

• Exercise regularly.
• Eat more fruits and vegetables . Limit dietary salt and fat .
• Stop smoking .
• Increase your consumption of fish
• Drink alcohol only in moderation (1-2 drinks per day).
• Maintain a healthy weight.
• Frequently check blood pressure . Follow your doctor's recommendations for keeping it in a safe range.
• Take a low dose of aspirin (50-325 milligrams per day) if your doctor says it is safe.
• Keep chronic medical conditions under control. This includes high cholesterol and diabetes.
• Talk to your doctor about the use of a ‘statin’ drug. It may help prevent certain kinds of strokes in some people.
• Seek medical care if you have symptoms of a stroke, even if symptoms stop.
• Stop the use of recreational drugs (cocaine, heroin, marijuana, amphetamines).