Questions and Answers About Stroke

What is a stroke?

A stroke occurs when blood flow to the brain is interrupted. When a stroke occurs, brain cells in the immediate area begin to die because they no longer receive the oxygen and nutrients they need to function.

What are the types of strokes?

A stroke can occur in two ways. In an ischemic stroke, a blood clot blocks or plugs a blood vessel or artery in the brain. About 80 percent of all strokes are ischemic. In an hemorrhagic stroke, a blood vessel in the brain breaks and bleeds into the brain. About 20 percent of strokes are hemorrhagic.

What are the symptoms of stroke?

What makes stroke symptoms distinct is their sudden onset:

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

Why can't some victims identify stroke symptoms?

Because stroke injures the brain, one is not able to perceive one's own problems correctly. To a bystander, the stroke patient may seem unaware or confused. A stroke victim's best chance is if someone around her recognizes the stroke and acts quickly.

What should a bystander do?

Bystanders should know the signs and act in time. If you believe someone is having a stroke — if they lose the ability to speak, or move an arm or leg on one side, or experience facial paralysis on one side — call 911 immediately. Stroke is a medical emergency. Immediate treatment may save someone's life and enhance his or her chances for successful rehabilitation and recovery.

Why is there a need to act fast?

Ischemic strokes, the most common strokes, can be treated with a drug called t-PA which dissolves artery-obstructing clots. The window of opportunity to use t-PA to treat stroke patients is three hours, but to be evaluated and receive treatment, patients need to get to the hospital within 60 minutes. A five-year clinical trial conducted by NINDS found that selected stroke patients who received t-PA within three hours of the onset of stroke symptoms were at least 30 percent more likely than placebo patients to recover from their stroke with little or no disability after three months.

What are the risk factors for stroke?

There are things you can do to prevent stroke. High blood pressure increases your risk of stroke four to six times. Heart disease, especially a condition known as atrial fibrillation or AF, can double your risk of stroke. Your risk also increases if you smoke, have diabetes, sickle cell disease, high cholesterol, or a family history of stroke.

What can you do to reduce your risk of stroke?

To reduce your risk of stroke monitor your blood pressure, track your cholesterol level, stop smoking, exercise regularly and find out if you should be taking a drug to reduce blood clotting.

What is the toll on Americans?

Stroke is a leading cause of serious, long-term adult disability. Four million Americans are living with the effects of stroke. The length of time to recover from a stroke depends on its severity. Fifty to 70 percent of stroke survivors regain functional independence, but 15 to 30 percent are permanently disabled.

What is the cost of stroke for our nation?

Stroke places a major health burden on our society in terms of mortality, morbidity and economic costs. The National Stroke Association estimates stroke costs the U.S. about $43 billion a year. Direct costs for medical care and therapy average $28 billion a year. The average cost per patient for the first 90 days after a stroke is $15,000 although 10 percent of those cases exceed $35,000.


National Institutes of Health, NINDS, "Stroke: Hope Through Research.", 1999

NINDS rt-PA Study Group. Tissue plasminogen activator for acute ischemic stroke. New Eng J Med. 1995;333(24): 1851-1587

National Stroke Association, The Stroke/Brain Attack Reporter's Handbook, 2000

Framingham Heart Study, NHLBI

National Stroke Association, The Stroke Brain Attack Briefing, 1999

National Stroke Association, The Stroke/Brain Attack Reporter's Handbook, 2000


NINDS health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Institute of Neurological Disorders and Stroke or any other Federal agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history.

All NINDS-prepared information is in the public domain and may be freely copied. Credit to the NINDS or the NIH is appreciated.

Last Modified March 29, 2016