Definition

Stroke is a brain injury. It occurs when the blood supply to the brain is interrupted. Without oxygen and nutrients from blood, brain tissue dies in less than 10 minutes. The tissue death causes a sudden loss in function.

Causes

A stroke occurs when there is a loss of blood flow. It may happen because of a blockage in blood flow, called ischemic stroke, or because of bleeding in the brain, called hemorrhagic stroke.

A sudden decrease in the flow of blood may be caused by:

• A clot that breaks off from another part of the body (such as the heart or neck) and lodges in blood vessel of neck or brain—there are certain conditions which predispose people to form blood clots, such as:
  • Cancer
  • Pregnancy
  • Atrial fibrillation
  • Certain autoimmune diseases
• A blood clot that forms in neck or brain
• Atherosclerosis —a build-up of fatty substances along the inner lining of the artery that gradually decrease the area the blood can flow through
• Inflammatory conditions in the blood vessels (vasculitis)

Hemorrhagic stroke occur when blood vessels break and bleed into or around the brain. This can happen after an injury.

Hemorrhagic vs. Ischemic Stroke Copyright © Nucleus Medical Media, Inc.

Risk Factors    TOP

The following factors can increase your risk of stroke but the risk can be modified with lifestyle changes and proper medical care:

• 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 (specifically, high-LDL [low-density lipoprotein] "bad" 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

Other factors that can increase your risk of stroke but can not be modified include:

• Prior stroke or pre-existing cardiovascular disease, such as heart attack
• Prior transient ischemic attack (TIA) —some people have this a "warning stroke" with symptoms that resolve in short period of time
• Age: 60 or older
• Family members who have had a stroke
• Gender: males are at greater risk
• Race: Black, Asian, Hispanic
• Blood disorders which increase clotting in sickle cell disease and polycythemia
• Valvular heart disease, such as mitral stenosis

Symptoms    TOP

Symptoms occur suddenly. They differ depending on the part of the brain affected. Also, multiple symptoms can happen at the same time. If you notice any of the symptoms below, call emergency help right away. Getting help immediately is important, because brain tissue dies quickly when deprived of oxygen.

• Sudden weakness or numbness of face, arm, or leg, especially on one side of the body
• Sudden confusion
• Sudden trouble speaking or understanding
• Sudden trouble seeing in one or both eyes
• Sudden dizziness, trouble walking, loss of balance, or coordination
• Sudden severe headache with no known cause

Diagnosis    TOP

Having a stroke is an emergency. Tests may include:

• 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:
  • Computed tomography (CT) scan —a type of x-ray that uses a computer to make pictures of the brain, helps doctors identify hemorrhagic versus ischemic stroke
  • Magnetic resonance imaging (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, including cholesterol, homocysteine, prothrombin time, and other coagulation tests

Other tests may include:

• Arteriography (angiography)—a catheter is placed in a blood vessel in the groin and threaded up to the brain, shows 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, gives 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, shows if the clot comes from one of the heart's chambers

Treatment    TOP

Immediate treatment is needed to:

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

Treatment after immediate care will aim to:

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

Supportive care may also include:

• Adequate oxygen
• Precautions to prevent choking

Prevention    TOP

Lifestyle changes that can help reduce your chance of getting a stroke include:

• Exercise regularly.
• Eat more fruits, vegetables, and whole grains. 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.
• Check blood pressure frequently. 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 statins. These types of drugs 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 (eg, cocaine, heroin, marijuana, amphetamines).