A stroke is serious, just like a heart attack. A stroke is sometimes called a "brain attack." Most often, stroke occurs when blood flow to the brain stops because it is blocked by a clot. When this happens, the brain cells in the immediate area begin to die.

Some brain cells die because they stop getting the oxygen and nutrients they need to function. Other brain cells die because they are damaged by sudden bleeding into or around the brain.

The brain cells that don't die immediately remain at risk for death. These cells can linger in a compromised or weakened state for several hours. With timely treatment these cells can be saved. Knowing stroke symptoms, calling 911 immediately, and getting to a hospital as quickly as possible are critical.

Stroke occurs in all age groups, in both sexes, and in all races in every country. It can even occur before birth, when the fetus is still in the womb. Nearly three-quarters of all strokes occur in people over the age of 65. And the risk of having a stroke more than doubles each decade after the age of 55.

There are two kinds of stroke. The most common kind of stroke is called ischemic stroke. It accounts for approximately 80 percent of all strokes. An ischemic stroke is caused by a blood clot that blocks or plugs a blood vessel in the brain.

The other kind of stroke is called hemorrhagic stroke. A hemorrhagic stroke is caused by a blood vessel that breaks and bleeds into the brain.

Stroke damage in the brain can affect the entire body -- resulting in mild to severe disabilities. These include paralysis, problems with thinking, problems with speaking, emotional problems, and pain.

Warning signs are clues your body sends to tell you that your brain is not receiving enough oxygen. These are warning signs of a stroke, or brain attack:

• sudden numbness or weakness of the face, arm, or leg, especially on one side of the body
  
  
• sudden confusion, trouble speaking or understanding
  
  
• sudden trouble seeing in one or both eyes

Warning signs of a stroke, or brain attack:

• sudden trouble walking, dizziness, loss of balance or coordination
  
  
• sudden severe headache with no known cause

If you observe one or more of these signs, don't wait. Call a doctor or 911 right away!

Transient ischemic attacks, or TIAs, occur when the warning signs of stroke last only a few moments and then disappear. These brief episodes are also sometimes called "mini-strokes." Although brief, they identify an underlying serious condition that isn't going away without medical help. Unfortunately, since they clear up, many people ignore them. Don't ignore them. Heeding them can save your life.

A risk factor is a condition or behavior that increases your chances of getting a disease. Having a risk factor for stroke doesn't mean you'll have a stroke. On the other hand, not having a risk factor doesn't mean you'll avoid a stroke. But your risk of stroke grows as the number and severity of risk factors increases.

The risk factors for stroke include high blood pressure, diabetes, cigarette smoking, and heart disease. Experiencing warning signs and having a history of stroke are also risk factors for stroke.

Atherosclerosis, also known as hardening of the arteries, is the most common blood vessel disease. It is caused by the buildup of fatty deposits in the arteries, and is a risk factor for stroke.

Yes. Stroke is preventable. A better understanding of the causes of stroke has helped people make lifestyle changes that have cut the stroke death rate nearly in half in the last two decades.

While family history of stroke plays a role in your risk, there are many risk factors you can control:

• If you have high blood pressure, work with your doctor to get it under control. Managing your high blood pressure is the most important thing you can do to avoid stroke.
  
  
• If you smoke, quit.

Risk factors you can control:

• If you have diabetes, learn how to manage it. Many people do not realize they have diabetes, which is a major risk factor for heart disease and stroke.
  
  
• If you are overweight, start maintaining a healthy diet and exercising regularly.

Risk factors you can control:

• If you have high cholesterol, work with your doctor to lower it. A high level of total cholesterol in the blood is a major risk factor for heart disease, which raises your risk of stroke.

Doctors have several techniques and imaging tools to help diagnose stroke quickly and accurately. The first step in diagnosis is a short neurological examination, or an evaluation of the nervous system.

When a possible stroke patient arrives at a hospital, a health care professional, usually a doctor or nurse, will ask the patient or a companion what happened and when the symptoms began. Blood tests, an electrocardiogram, and a brain scan such as computed tomography or CT, or magnetic resonance imaging or MRI, will often be done.

One test that helps doctors judge the severity of a stroke is the standardized NIH Stroke Scale, developed by the National Institute of Neurological Disorders and Stroke at the National Institutes of Health, or NIH.

Health care professionals use the NIH Stroke Scale to measure a patient's neurological deficits by asking the patient to answer questions and to perform several physical and mental tests. Other scales include the Glasgow Coma Scale, the Hunt and Hess Scale, the Modified Rankin Scale, and the Barthel Index.

The most commonly used imaging procedure is the computed tomography or CT scan, also known as a CAT scan. A CT scan creates a series of cross-sectional images of the head and brain. Because it is readily available at all hours at most major hospitals and produces images quickly, CT is often preferred as the diagnostic brain scan for stroke.

A CT scan also has unique diagnostic benefits. It will quickly rule out a hemorrhage, and can occasionally show a tumor that might mimic a stroke. It may even show evidence of early infarction -- an area of tissue that is dead or dying due to a loss of blood supply. Infarctions generally show up on a CT scan about six to eight hours after the start of stroke symptoms.

Another imaging technique used for stroke patients is the magnetic resonance imaging or MRI scan. MRI uses magnetic fields to detect subtle changes in the content of brain tissue.

One effect of stroke is the slowing of water movement, called diffusion, through the damaged brain tissue. An MRI can show this type of damage within the first hour after the stroke symptoms start.

MRI and CT are equally accurate for determining when hemorrhage is present. The benefit of MRI over a CT scan is more accurate and earlier diagnosis of infarction, especially for smaller strokes. Also, MRI is more sensitive than CT for detecting other types of brain disease, such as brain tumor, that might mimic stroke. However, MRI cannot be performed in patients with certain types of metallic or electronic implants, such as pacemakers for the heart. An infarct is an area of tissue that is dead or dying due to a loss of blood supply.

Although increasingly used in the emergency diagnosis of stroke, MRI is not immediately available at all hours in most hospitals, where CT is used for acute stroke diagnosis. Also, MRI takes longer to perform than CT, and may not be performed if it would significantly delay treatment.

With stroke, treatment depends on the stage of the disease. There are three treatment stages for stroke: prevention, therapy immediately after stroke, and rehabilitation after stroke. Stroke treatments include medications, surgery, and rehabilitation.

In treating a stroke that has just occurred, every minute counts. Ischemic strokes -- the most common kind -- can be treated with thrombolytic drugs. These drugs halt the stroke by dissolving the blood clot that is blocking blood flow to the brain. But a person needs to be at the hospital as soon as possible after symptoms start to be evaluated and receive treatment.

A thombolytic drug known as t-PA can be effective if a person receives it intravenously within 3 hours after his or her stroke symptoms have started. Since thrombolytic drugs can increase bleeding, t-PA should be used only after the doctor is certain that the patient has suffered an ischemic and not a hemorrhagic stroke.

Medication or drug therapy is the most common treatment for stroke. The most popular kinds of drugs to prevent or treat stroke are antithrombotics -- which include antiplatelet agents and anticoagulants -- and thrombolytics.

Antithrombotics prevent the formation of blood clots that can become stuck in an artery of the brain and cause strokes. In the case of stroke, doctors prescribe antiplatelet drugs mainly for prevention. The most widely known and used antiplatelet drug is aspirin. Other antiplatelet drugs include clopidogrel, ticlopidine, and dipyridamole.

Anticoagulants reduce the risk of stroke by reducing the clotting property of the blood. The most commonly used anticoagulants include warfarin, also known as Coumadin®, heparin, and enoxaparin, also known as Lovenox.

Neuroprotectants are medications that protect the brain from secondary injury caused by stroke. Although the Food and Drug Administration has not approved any neuroprotectants for use in stroke at this time, many are being tested in clinical trials.

Surgery can be used to prevent stroke, treat stroke, repair damage to the blood vessels, or correct malformations in and around the brain. The two most common types of surgery for stroke are carotid endarterectomy and extracranial/intracranial bypass, or EC/IC bypass. Extracranial refers to the area outside the cranium, or skull, and intracranial refers to the area inside the skull.

Carotid endarterectomy is a surgical procedure in which a doctor removes fatty deposits, or plaque, from the inside of one of the carotid arteries. The procedure is performed to prevent stroke. The carotid arteries are located in the neck and are the main suppliers of blood to the brain.

EC/IC bypass surgery is a procedure that restores blood flow to a blood-deprived area of brain tissue. The surgeon reroutes a healthy artery in the scalp to the area of brain tissue affected by a blocked artery.

For most stroke patients, rehabilitation mainly involves physical therapy. The aim of physical therapy is to have the stroke patient relearn simple motor activities such as walking, sitting, standing, lying down, and the process of switching from one type of movement to another.

Another type of therapy to help patients relearn daily activities is occupational therapy. This type of therapy also involves exercise and training. Its goal is to help the stroke patient relearn everyday activities such as eating, drinking and swallowing, dressing, bathing, cooking, reading and writing, and toileting.

Speech therapy helps stroke patients relearn language and speaking skills, or learn other forms of communication. It is appropriate for patients who have no deficits in cognition or thinking, but have problems understanding speech or written words, or problems forming speech.

Talk therapy, along with the right medication, can help ease some of the mental and emotional problems that result from stroke.

The National Institute of Neurological Disorders and Stroke sponsors a wide range of basic and clinical research aimed at finding better ways to prevent, diagnose, and treat stroke, and to restore functions lost as a result of stroke.

Currently, scientists are conducting stroke studies in animals. One promising area of animal research involves hibernation. If scientists can discover how animals hibernate without experiencing brain damage, they may discover ways to stop the brain damage associated with decreased blood flow in stroke patients.

Scientists are also working to develop new and better ways to help the brain repair itself to restore important functions to stroke patients. New advances in imaging and rehabilitation have shown that the brain can compensate for functions lost as a result of stroke.

Clinical trials -- another avenue of stroke research -- give scientists a way to test new treatments in humans. Clinical trials test surgical devices and procedures, medications, and rehabilitation therapies. They also test methods to improve lifestyles and mental and social skills. The goal of clinical trials is to find safe and effective treatments and to establish the right levels of treatment.

Scientists are using clinical trials to study ways of restoring blood flow to the brain. They hope to find methods that are safer, more effective, and available to more stroke victims. Some of these studies are testing new types of thrombolytic drugs -- drugs that halt the stroke by dissolving the blood clot that is blocking blood flow to the brain.

Other studies are testing techniques such as combining thrombolytic drugs with other drugs or with ultrasound, delivering clot dissolving drugs directly into the clot, and pulling the clot out with a device unaided by drugs.

Researchers are also testing the use of brain imaging to identify patients who may benefit from treatment even beyond three hours, since many have their strokes in their sleep or are brought to the hospital too late for standard therapy.

Brain plasticity is the brain's ability to learn and change, allowing it to adapt to deficits and injury and to take over the functions of damaged cells. When cells in an area of the brain responsible for a particular function die after a stroke, the patient becomes unable to perform that function. However, the brains ability to rewire the connections between its nerve cells allows it to compensate for lost functions.

For more information on stroke, including research sponsored by the National Institute of Neurological Disorders and Stroke, call 1-800-352-9424 or visit the Web site: www.ninds.nih.gov.