A stroke occurs when a part of the brains blood supply is cut off, brain cells cannot receive oxygen and eventually brain cell death occurs. The brain requires a constant blood flow and irreversible damage can occur if the blood supply is interrupted for more than several minutes. Every year about 750,000 people in the United States suffer a stroke. About 150,000 people die annually form a stroke making it the third leading cause of death in the U.S. after heart disease and cancer.

There are several types of stroke:

  • Ischemic stroke occurs when blood clots or fatty deposits block blood vessels that supply the brain. Thrombotic Stroke (or cerebral thrombosis) is the most common type of ischemic stroke. In this type of stroke, a blood clot (thrombus) forms inside an artery in the brain or one of the neck (carotid or vertebral) arteries that transport blood from the heart to the brain.
  • Embolic Stroke (or cerebral embolism) occurs when a piece of clot (an embolus) breaks loose from the heart or from a blood vessel in the neck and is carried by the blood stream to the brain. Traveling through the arteries as they branch into smaller vessels, the clot reaches a point where it can go no further and plugs the vessel, cutting off the blood supply. This sudden blockage is called an embolism.
  • The other main category of stroke, hemorrhagic stroke, occurs when a blood vessel in or around the brain ruptures, spilling blood into the brain or the area surrounding the brain. When this occurs, the cells nourished by the artery fail to get their normal supply of nutrients and cease to function properly. Furthermore, the accumulated blood from the ruptured artery soon clots, displacing normal brain tissue and disrupting brain function.

Risk Factors

There are many contributing factors to stroke . We concentrate on stroke risk factors that can be treated to reduce the risk of stroke recurrence in the future.


  • hypertension (high blood pressure)
  • smoking
  • heart disease
  • high cholesterol level
  • excess alcohol intake
  • obesity
  • sedentary lifestyle
  • diabetes
  • elevated hematocrit (increase in red blood cells)
  • use of oral contraceptives (especially for women who smoke)
  • stress


  • age
  • sex
  • race
  • family or individual history of stroke or TIA


Symptoms of a stroke vary. It is important to be aware of the common symptoms of stroke and report to the closest emergency room if these occur. Effective treatment for stroke works only when given less than 6 hours of stroke onset.


  • Sudden weakness, numbness, or paralysis of the face, arm or leg (especially on one side of the body)
  • Loss of speech or trouble talking or understanding language
  • Sudden loss of vision, particularly in only one eye
  • Sudden, severe headache with no apparent cause
  • Unexplained dizziness, loss of balance or coordination

Seek Help Promptly If you or someone you know experiences any of the warning signs listed above, it is extremely important to seek emergency help right away. Call 911 for urgent transportation to the nearest emergency medical facility.


Diagnosing a stroke is done by physical and neurological examination, computed tomography (CT) scans of the brain, magnetic resonance imaging (MRI), or doppler and ultrasounds of the head or neck.

  • Neurologic exam
  • Brain imaging tests (CT, or computerized tomography scan; MRI, or magnetic resonance imaging) to understand the type, location, and extent of the stroke
  • Tests that show blood flow and bleeding sites (carotid and transcranial ultrasound, CT or MR angiography)
  • Blood tests for bleeding or clotting disorders
  • EKG (electrocardiogram) or an ultrasound examination (echocardiogram) of the heart to identify cardiac sources of blood clots that could travel to the brain
  • Tests that measure mental function


Treatments available for stroke include the use of intra-venous thrombolytic agents that will dissolve the stroke-causing clot. To be effective, thrombolytic agents must administered within 3 hours of the first onset of stroke symptoms. Potential side effects include bleeding into the brain. Other agents such as aspirin and anticoagulant medications can be helpful in selected cases. Other techniques that can be used in selected patients up to 8 hrs after stroke onset include intra-arterial thrombolytic therapy and mechanical clot retrieval available at John Muir Medical Center.