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Stroke

Definition :
A stroke occurs when the blood supply to a part of your brain is interrupted or severely reduced, depriving brain tissue of oxygen and nutrients. Within a few minutes, brain cells begin to die.

Stroke is a medical emergency. Prompt treatment of a stroke could mean the difference between life and death. Early treatment can also minimize damage to your brain and potential disability.

In the United States, stroke is a leading cause of adult disability and the third-leading cause of death; only heart disease and cancer cause more deaths annually.

The good news is that many fewer Americans now die of strokes than was the case 20 or 30 years ago. Improvement in the control of major risk factors for stroke — smoking, high blood pressure and high cholesterol — is likely responsible for the decline.

Causes :
A stroke is sometimes called a brain attack. The problem is with the amount of blood in your brain. The cause of one type of stroke — ischemic stroke — is too little blood in the brain. The cause of the other main type of stroke — hemorrhagic stroke — is too much blood within the skull.

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 stroke. An embolic stroke occurs when a blood clot or other particle forms in a blood vessel away from your brain — commonly in your heart — and is swept through your bloodstream to lodge in narrower brain arteries. This type of blood clot is called an embolus. It's often caused by irregular beating in the heart's two upper chambers (atrial fibrillation). This abnormal heart rhythm can lead to poor blood flow and the formation of a blood clot.

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, damaging 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 in which arteries near the hemorrhage constrict erratically, causing brain cell damage by further restricting or blocking blood flow to portions of the brain.

Risk Factor :
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, a blood fat, also may increase your risk of atherosclerosis. 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 your 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 glucose appropriately, but it 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 your risk of a stroke.
  • 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 much more 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 and hormone therapy. The risk of stroke is higher among women who take birth control pills, especially among smokers and those older than 35. However, today's low-dose pills carry a much lower risk than their earlier counterparts. Hormone therapy for menopause also carries a slightly increased risk of stroke.

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.

When to seek medical advice :
If you notice any signs or symptoms of a stroke or TIA, get medical help right away. A TIA may seem like a passing event. But it is 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 or TIA. Don't wait to see if the signs and symptoms go away. 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.

Symptoms :
Knowing the signs and symptoms of a stroke may make it possible for you or someone you know to get prompt treatment. The signs and symptoms of stroke usually occur suddenly; frequently there's more than one. Signs and symptoms include :
  • Sudden numbness, weakness, or paralysis of your face, arm or leg — usually on one side of your body
  • Sudden difficulty speaking or understanding speech (aphasia)
  • Sudden blurred, double or decreased vision
  • Sudden 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 your 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 last 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 much more likely to have a stroke as are those who haven't had a TIA.

Diagnosis :
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. Your doctor may check for risk factors of stroke, including high blood pressure, high cholesterol levels, diabetes and elevated levels of the amino acid homocysteine. Your doctor may also use a stethoscope to listen for a whooshing sound (bruit) over your arteries that may indicate atherosclerosis.
  • 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. Doctors use CTA to look for aneurysms or arteriovenous malformations and to evaluate arteries for narrowing. CT scanning, which is done without dye, can provide images of your brain and show hemorrhages, 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). During this procedure, a flexible probe with a transducer built into it is placed in your esophagus — the tube that connects the back of your mouth to your stomach. Because your esophagus is directly behind your heart, very clear, detailed ultrasound images can be created, allowing a better view of some things, such as blood clots, that might not be seen clearly in a traditional echocardiography exam.

Treatment:
Getting prompt medical treatment for stroke is of utmost importance. Treatment itself depends on the type of stroke.

Ischemic stroke
To treat an ischemic stroke, doctors must remove any obstruction and restore blood flow to your brain.

Emergency treatment. Therapy with clot-busting drugs must start within three hours. Quick treatment not only improves your chances of survival, but may also reduce the amount of disability resulting from the stroke.

Injection of a clot-busting (thrombolytic) drug — such as a tissue plasminogen activator (TPA) — into your veins to dissolve a blood clot may be more effective in increasing your chances of a full recovery, compared with other treatment methods. Currently, though, only a small proportion of Americans who have had a stroke receive thrombolytic therapy. Reasons for this include :

  • A limited time window. Three hours has long been considered the window within which clot-busting drugs should be administered intravenously. Whether people can still gain some benefit from receiving clot-busting drugs beyond three hours is uncertain. After too much time has passed, the risks of bleeding or other complications from this type of therapy begin to outweigh the potential benefits.
  • A limited group of people who benefit from this therapy. TPA-type therapy doesn't treat hemorrhagic stroke. In fact, it may dramatically worsen a hemorrhagic stroke. Also, not everyone who has had an ischemic stroke is an ideal candidate for thrombolytic therapy. The ability of TPA-type agents to dissolve blood clots carries with it a risk of brain hemorrhage and bleeding elsewhere. With the diagnosis of an acute stroke, you and your doctor can work together to weigh the risks versus benefits of thrombolytic therapy in your individual case. Your doctor may not give you clot-busting medications if your blood pressure isn't controllable at the time when the TPA is being considered.

Surgical and other procedures. Your doctor may recommend a procedure to open up an artery that's moderately to severely narrowed by plaques. This may include :

  • Carotid endarterectomy. Your surgeon makes an incision in your neck to expose your carotid artery. The artery is opened, the plaques are removed, and your surgeon closes the artery. In people with marked blockages in the carotid artery who are candidates for the surgery, the procedure may reduce the risk of ischemic stroke. However, in addition to the usual risks associated with any surgery, a carotid endarterectomy itself can also trigger a stroke or heart attack by releasing a blood clot or fatty debris, although surgeons now place filters (distal protection devices) at strategic points in your bloodstream to "catch" any material that may break free during the procedure.
  • Angioplasty. Used less commonly than carotid endarterectomy, angioplasty can widen the inside of an artery leading to your brain, usually the carotid artery. In this procedure, a balloon-tipped catheter is maneuvered into the obstructed area of your artery. The balloon is inflated, compressing the plaques against your artery walls. A metallic mesh tube (stent) is usually left in the artery to prevent recurrent narrowing. Distal protection devices also may be used with angioplasty.
  • Other techniques. Doctors are also exploring new ways to remove clots. In a catheter embolectomy, a catheter is threaded into one of the arteries that lead to the brain and used to remove clots. You may also receive thrombolytic drugs directly into these arteries, via a catheter.

Preventive medications. If you've had an ischemic stroke, it's important to determine why the stroke occurred and to prevent another. Your doctor may recommend medications to help reduce your risk of having a TIA or stroke. These include :

  • Anti-platelet drugs. Platelets are cells in your blood that initiate clots. Anti-platelet drugs make your platelets less sticky and less likely to clot. The most frequently used anti-platelet medication is aspirin. Your doctor may also consider prescribing Aggrenox, a combination of low-dose aspirin and the anti-platelet drug dipyridamole, to reduce blood clotting. If aspirin doesn't prevent your TIA or stroke or if you can't take aspirin, your doctor may instead prescribe an anti-platelet drug such as clopidogrel (Plavix) or ticlopidine (Ticlid).
  • Anticoagulants. These drugs include heparin and warfarin (Coumadin). They affect the clotting mechanism in a different manner than do anti-platelet medications. Heparin is fast acting and is used over the short term in the hospital. Slower acting warfarin is used over a longer term. These drugs have a profound effect on blood clotting and require that you work with your doctor to monitor them closely. Your doctor may prescribe these drugs if you have certain blood-clotting disorders, certain arterial abnormalities, an abnormal heart rhythm, such as atrial fibrillation, or other heart problems.

Hemorrhagic stroke
Surgery may be used to treat a hemorrhagic stroke or prevent another one. The most common procedures — aneurysm clipping and arteriovenous malformation (AVM) removal — carry some risks. Your doctor may recommend one of these procedures if you're at high risk of spontaneous aneurysm or AVM rupture :

  • Aneurysm clipping. A tiny clamp is placed at the base of the aneurysm, isolating it from the circulation of the artery to which it's attached. This can keep the aneurysm from bursting, or it can prevent re-bleeding of an aneurysm that has recently hemorrhaged.
  • Coiling (aneurysm embolization). In an embolization procedure, a catheter is maneuvered into the aneurysm. A tiny platinum coil is pushed through the catheter and positioned inside the aneurysm. The coil fills the aneurysm, causing clotting and sealing the aneurysm off from connecting arteries.
  • Surgical AVM removal. It's not always possible to remove an AVM if it's too large or if it's located deep within the brain. Surgical removal of a smaller AVM from a more accessible portion of the brain, though, can eliminate the risk of rupture, lowering the overall risk of hemorrhagic stroke. Other treatment options for AVMs include focused radiation or embolization, in which the small arteries supplying the blood to the AVM are blocked, shrinking the AVM.

Recovery and rehabilitation
Stroke survivors who can go home to a healthy spouse or other companion are more likely to become independent and productive again. Encouragement and early treatment are important.

Recovery and rehabilitation depend on the area of the brain involved and the amount of tissue damaged. Harm to the right side of the brain may impair movement and sensation on the left side of the body. Damage to brain tissue on the left side may affect movement on the right side; this damage may also cause speech and language disorders. In addition, people who've had a stroke may have problems with breathing, swallowing, balancing and hearing, and loss of vision and bladder or bowel function.

Because numerous impairments may be involved, rehabilitation is facilitated by a diverse team, which may include a :

  • Rehabilitation doctor (physiatrist)
  • Nurse
  • Dietitian
  • Physical therapist
  • Occupational therapist
  • Recreational therapist
  • Speech therapist
  • Social worker
  • Psychologist or psychiatrist
  • Chaplain

The goal of rehabilitation is to help you recover as much of your independence and functioning as possible. Much of rehabilitation involves relearning skills you may have lost, such as walking or communicating.

With advances in research and brain-imaging techniques, doctors are gaining a new understanding of how brain systems adapt after stroke to regain function (brain plasticity). Research suggests that normal brain cells are highly adaptable and can undergo changes in function and shape that allow them to take on the functions of nearby damaged cells. As a result, rehabilitation efforts are being geared toward retraining unaffected brain tissue to compensate for the lost functions of damaged tissue.

Prevention:
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 treat 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.
  • 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, control diabetes and 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 and crack cocaine, are established risk factors for a TIA or a stroke.

Follow a healthy diet
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.
 
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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