Stroke

A stroke occurs when a blood vessel (artery) that supplies blood to the brain burst or blocked by a blood clot. Within minutes, the nerve cells in that area of the brain are damaged, and they die within a few hours. As a result, the part of the body controlled by the damaged section of the brain cannot function properly.

If you have symptoms of a stroke, you need emergency care, just as though you are having a heart attack. If medical treatment begins soon after symptoms are noticed, fewer brain cells may be permanently damaged.

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It's important to know the signs and symptoms of a stroke so that you or someone you know can get prompt treatment. The most common signs and symptoms include:

• Sudden numbness, weakness, or paralysis of the face, arm or leg — usually on one side of the body.

• Loss of speech, or trouble talking or understanding speech (aphasia).

• Sudden blurred, double or decreased vision.

• Dizziness, loss of balance or loss of coordination.

• A sudden, severe "bolt out of the blue" headache or an unusual headache, which may be accompanied by a stiff neck, facial pain, pain between the eyes, vomiting or altered consciousness.

• Confusion, or problems with memory, spatial orientation or perception.

For most people, a stroke gives no warning. But one possible sign of an impending stroke is a transient ischemic attack (TIA). A TIA is a temporary interruption of blood flow to a part of your brain. The signs and symptoms of TIA are the same as for a stroke, but they appear for a shorter period — several minutes to 24 hours — and then disappear, without leaving apparent permanent effects. You may have more than one TIA, and the recurrent signs and symptoms may be similar or different. A TIA indicates a serious underlying risk that a full-blown stroke may follow. People who have had a TIA are nine times as likely to have a stroke as are those who haven't had a TIA.

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A stroke is sometimes called a brain attack. It's caused by a problem with the amount of blood in the brain. One type of stroke — ischemic stroke — is caused by too little blood in the brain. The other main type of stroke — hemorrhagic stroke — is caused by too much blood within the brain cavity.

Ischemic Stroke

About 80 percent of strokes are ischemic strokes. They occur when blood clots or other particles block arteries to your brain and cause severely reduced blood flow (ischemia). This deprives your brain cells of oxygen and nutrients, and cells may begin to die within minutes. The most common ischemic strokes are:

• Thrombotic Stroke. This type of stroke occurs when a blood clot (thrombus) forms in one of the arteries that supply blood to your brain. A clot usually forms in areas damaged by atherosclerosis — a disease in which the arteries are clogged by an accumulation of cholesterol-containing fatty deposits (plaques). This process can occur within one of the two carotid (kuh-ROT-id) arteries of your neck that carry blood to your brain, as well as in other arteries. An ischemic stroke may also be caused by plaques that completely clog or markedly narrow an artery. This narrowing is called stenosis.
• Embolic Htroke. This type of stroke occurs when a blood clot or other particle forms in a blood vessel away from the brain, but is swept through your bloodstream to lodge in narrower brain arteries. This type of blood clot is called an embolus. It's commonly caused by atrial fibrillation, an abnormal heart rhythm caused by irregular beating in the heart's two upper chambers.

Hemorrhagic Stroke

Hemorrhage is the medical word for bleeding. Hemorrhagic stroke occurs when a blood vessel in your brain leaks or ruptures. Hemorrhages can result from a number of conditions that affect your blood vessels, including uncontrolled high blood pressure (hypertension) and weak spots in your blood vessel walls (aneurysms). A less common cause of hemorrhage is the rupture of an arteriovenous malformation (AVM) — a malformed tangle of thin-walled blood vessels, present at birth. There are two types of hemorrhagic stroke:

• Intracerebral Hemorrhage. In this type of stroke, a blood vessel in the brain bursts and spills into the surrounding brain tissue and damages cells. Brain cells beyond the leak are deprived of blood and are also damaged. High blood pressure is the most common cause of this type of hemorrhagic stroke. High blood pressure can cause small arteries inside your brain to become brittle and susceptible to cracking and rupture.

• Subarachnoid Hemorrhage. In this type of stroke, bleeding starts in a large artery on or near the membrane surrounding the brain and spills into the space between the surface of your brain and your skull. A subarachnoid hemorrhage is often signaled by a sudden, severe "thunderclap" headache. This type of stroke is commonly caused by the rupture of an aneurysm, which can develop with age or result from a genetic predisposition. After a subarachnoid hemorrhage, vessels may go into vasospasm, a condition where arteries near the hemorrhage constrict erratically, causing brain cell damage by further restricting or blocking blood flow to portions of the brain.

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Many factors can increase your risk of a stroke. A number of these factors can also increase your chances of having a heart attack. They include:

• Family history. Your risk of stroke is slightly greater if one of your parents or a brother or sister has had a stroke or TIA.
• Age. Your risk of stroke increases as you get older.

• Sex. Stroke affects men and women about equally. But women are more likely to die of stroke than are men.

• Race. Blacks are at greater risk of stroke than are people of other races. This is partly due to a higher prevalence of high blood pressure and diabetes.

• High blood pressure (hypertension). High blood pressure is a risk factor for both ischemic and hemorrhagic strokes. It can weaken and damage blood vessels in and around your brain, leaving them vulnerable to atherosclerosis and hemorrhage.

• Undesirable levels of blood cholesterol. High levels of low-density lipoprotein (LDL) cholesterol, the "bad" cholesterol, may increase your risk of atherosclerosis. In excess, LDLs and other materials build up on the lining of artery walls, where they may harden into plaques. High levels of triglycerides, another blood fat, also may increase your atherosclerosis risk. In contrast, high levels of high-density lipoprotein (HDL) cholesterol, the "good" cholesterol, reduce your risk of atherosclerosis by escorting cholesterol out of your body through the liver.

• Cigarette smoking. Smokers have a much higher risk of stroke than do nonsmokers. Smoking contributes to plaques in your arteries. Nicotine makes your heart work harder by increasing your heart rate and blood pressure. The carbon monoxide in cigarette smoke replaces oxygen in your blood, decreasing the amount of oxygen delivered to the walls of your arteries and your tissues, including the tissues in your brain.

• Diabetes. Diabetes is a major risk factor for stroke. When you have diabetes, your body not only can't handle sugar appropriately but also can't process fats efficiently, and you're at greater risk of high blood pressure. These diabetes-related effects increase your risk of developing atherosclerosis. Diabetes also interferes with your body's ability to break down blood clots, increasing your risk of ischemic stroke.

• Obesity. Being overweight increases your chance of developing high blood pressure, heart disease, atherosclerosis and diabetes — all of which increase stroke risk.

• Cardiovascular disease. Several cardiovascular diseases can increase your risk of a stroke, including congestive heart failure, a previous heart attack, an infection of a heart valve (endocarditis), a particular type of abnormal heart rhythm (atrial fibrillation), aortic or mitral valve disease, valve replacement, or a hole in the upper chambers of the heart known as patent foramen ovale. Atrial fibrillation is the most common condition associated with strokes caused by embolic clots. In addition, atherosclerosis in blood vessels near your heart may indicate that you have atherosclerosis in other blood vessels — including those in and around your brain.

• Previous stroke or TIA. If you've already had a stroke, your risk of having another one increases. In addition, people who have had a TIA are nine times as likely to have a stroke as are those who haven't had a TIA.

• Elevated homocysteine level. This amino acid, a building block of proteins, occurs naturally in your blood. But people with elevated levels of homocysteine have a higher risk of heart and blood vessel damage.

• Use of birth control pills. The risk of stroke is higher among women who take birth control pills, especially among smokers and women older than 35. However, today's low-dose pills carry a much lower risk than their earlier counterparts.

Other factors that can increase your risk of stroke include heavy or binge drinking, the use of illicit drugs such as cocaine, and uncontrolled stress.

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If you notice any signs of a stroke or TIA, get medical help right away. A TIA may seem like a passing event. But it can be an important warning sign — and a chance to take steps that may prevent a stroke.
If someone appears to be having a stroke, watch the person carefully while waiting for an ambulance. You may need to take additional actions in the following situations:

• If breathing ceases, begin resuscitation.

• If vomiting occurs, turn the person's head to the side. This can prevent choking.

• Don't let the person eat or drink anything.

Every minute counts when it comes to treating a stroke. The longer a stroke goes untreated the greater the damage and potential disability. The success of most treatments depends on how soon a person is seen by a doctor in a hospital emergency room after signs and symptoms begin.

If you've had a previous stroke or TIA or think you're at risk of stroke, talk with your doctor about screening and diagnostic tests.

Before treating a stroke, your doctor must diagnose the type of stroke and its location. Other possible causes of your symptoms, such as a tumor, also need to be excluded.

The following are most often used as screening tools to determine your risk, but they may also be used as diagnostic tools if you're having a stroke:

• Physical examination and tests

• Carotid ultrasonography. In this procedure, a wand-like device (transducer) sends high-frequency sound waves into your neck. The sound waves pass through tissue and then return, creating on-screen images that delineate any narrowing or clotting in your carotid arteries.

• Arteriography. This procedure gives a view of arteries in your brain not normally seen in X-rays. Your doctor inserts a thin, flexible tube (catheter) through a small incision, usually in your groin. The catheter is manipulated through your major arteries and into your carotid or vertebral artery. Then your doctor injects a dye through the catheter to provide X-ray images of your arteries.

• Computerized tomography (CT). In computerized tomographic angiography (CTA), a dye is injected into your vein and X-ray beams create a three-dimensional image of the blood vessels in your neck and brain. CTA is used to look for aneurysms or arteriovenous malformations and to evaluate for artery narrowing. CT scanning, which is done without dye, can provide images of your brain, but without as much detailed information about the blood vessels.

• Magnetic resonance imaging (MRI). Using a strong magnetic field, an MRI can generate a three-dimensional view of your brain. This test is sensitive for detecting an area of brain tissue damaged by an ischemic stroke. Magnetic resonance angiography (MRA) uses this magnetic field and a dye injected into your veins to evaluate arteries in your neck and brain.

• Echocardiography. Your doctor can use this ultrasound technology to compose images of your heart. He or she may also use transesophageal echocardiography (TEE) to create clear and detailed ultrasound images with a better view of some things, such as blood clots, that might not be clearly visible on a traditional echocardiogram.

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Prompt treatment of stroke and medical problems related to stroke, such as pneumonia, high blood sugar, and pressure on the brain, may minimize brain damage and improve the chances of survival. Starting a rehabilitation program as soon as possible after a stroke greatly increases your chances of recovering some of the abilities you lost.

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Knowing your risk factors and living healthfully are the best steps you can take to prevent a stroke. In general, a healthy lifestyle means that you:

• Control high blood pressure (hypertension). One of the most important things you can do to reduce your stroke risk is to keep your blood pressure under control. If you've had a stroke, lowering your blood pressure can help prevent a subsequent transient ischemic attack or stroke. Exercising, managing stress, maintaining a healthy weight, and limiting sodium and alcohol intake are all ways to keep hypertension in check. In addition to recommendations for lifestyle changes, your doctor may prescribe medications to reduce hypertension, such as diuretics, angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers.

• Lower your cholesterol and saturated fat intake. Eating less cholesterol and fat, especially saturated fat, may reduce the plaques in your arteries. If you can't control your cholesterol through dietary changes alone, your doctor may prescribe a cholesterol-lowering medication.

• Take B vitamins. B complex vitamins — B-6, B-12 and folic acid (folate) — can work together to reduce blood levels of homocysteine, thereby lowering your risk of a stroke.

• Don't smoke. Quitting smoking reduces your risk of stroke. Several years after quitting, a former smoker's risk of stroke is the same as that of a nonsmoker.

• Control diabetes. You can manage diabetes with diet, exercise, weight control and medication. Strict control of your blood sugar may reduce damage to your brain if you do have a stroke.

• Maintain a healthy weight. Being overweight contributes to other risk factors for stroke such as high blood pressure, cardiovascular disease and diabetes. Weight loss of as little as 10 pounds may lower your blood pressure and improve your cholesterol levels

• Exercise regularly. Aerobic exercise reduces your risk of stroke in many ways. Exercise can lower your blood pressure, increase your level of HDL cholesterol, and improve the overall health of your blood vessels and heart. It also helps you lose weight and control diabetes, and can reduce stress. Gradually work up to 30 minutes of activity — such as walking, jogging, swimming or bicycling — on most, if not all, days of the week.

• Manage stress. Stress can cause a temporary spike in your blood pressure — a risk factor for brain hemorrhage — or long-lasting hypertension. It can also increase your blood's tendency to clot, which may elevate your risk of ischemic stroke. Simplifying your life, exercising and using relaxation techniques are all approaches that you can learn to reduce stress.

• Drink alcohol in moderation, if at all. Alcohol can be both a risk factor and a preventive measure for stroke. Binge drinking and heavy alcohol consumption increase your risk of high blood pressure and of ischemic and hemorrhagic strokes. However, drinking small to moderate amounts of alcohol can increase your HDL cholesterol and decrease your blood's clotting tendency. Both factors can contribute to a reduced risk of ischemic stroke.

• Don't use illicit drugs. Many street drugs, such as cocaine, are associated with a definite risk of a TIA or a stroke.

In addition, eat healthy foods. A brain-healthy diet should include:

• Five or more daily servings of fruits and vegetables, which contain nutrients such as potassium, folate and antioxidants that may protect you against stroke.

• Foods rich in soluble fiber, such as oatmeal and beans.

• Foods rich in calcium, a mineral found to reduce stroke risk.

• Soy products such as tempeh, miso, tofu and soy milk, which can reduce your LDL cholesterol and raise your HDL cholesterol level.

• Foods rich in omega-3 fatty acids, including cold-water fish, such as salmon, mackerel and tuna. However, pregnant women and women who plan to become pregnant in the next several years should limit their weekly intake of cold-water fish because of the potential for mercury contamination.

You obviously can't change some risk factors for a stroke — family history, age, sex and race. But knowing you're at risk can motivate you to change your lifestyle to reduce other risks. First-time heart attacks and strokes are often fatal or disabling; therefore prevention is critical. The American Heart Association (AHA) recommends:

• Early risk factor screening. The AHA recommends that all people, beginning at age 20, undergo risk factor screening that includes recording blood pressure, body mass index, waist circumference and pulse at least every two years, and cholesterol and glucose testing at least every five years.

• Risk estimation. The AHA recommends that doctors estimate each person's percentage risk of developing cardiovascular disease within the next 10 years. The estimate would be based on the risk factor screening. The AHA recommends estimation of risk every five years for people age 40 or older, or for anyone with two or more risk factors.

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* Text Resources: The Mayo Clinic Staff