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Stroke

Introduction

More than 2,400 years ago the father of medicine, Hippocrates, recognized and described stroke-the sudden onset of paralysis. Until recently, modern medicine has had very little power over this disease, but the world of stroke medicine is changing and new and better therapies are being developed every day. Today, some people who have a stroke can walk away from the attack with no or few disabilities if they are treated promptly. Doctors can finally offer stroke patients and their families the one thing that until now has been so hard to give: hope.

In ancient times stroke was called apoplexy,* a general term that physicians applied to anyone suddenly struck down with paralysis. Because many conditions can lead to sudden paralysis, the term apoplexy did not indicate a specific diagnosis or cause. Physicians knew very little about the cause of stroke and the only established therapy was to feed and care for the patient until the attack ran its course.

The first person to investigate the pathological signs of apoplexy was Johann Jacob Wepfer. Born in Schaffhausen, Switzerland, in 1620, Wepfer studied medicine and was the first to identify postmortem signs of bleeding in the brains of patients who died of apoplexy. From autopsy studies he gained knowledge of the carotid and vertebral arteries that supply the brain with blood. He also was the first person to suggest that apoplexy, in addition to being caused by bleeding in the brain, could be caused by a blockage of one of the main arteries supplying blood to the brain; thus stroke became known as a cerebrovascular disease ("cerebro" refers to a part of the brain; "vascular" refers to the blood vessels and arteries).

Medical science would eventually confirm Wepfer's hypotheses, but until very recently doctors could offer little in the area of therapy. Over the last two decades basic and clinical investigators, many of them sponsored and funded in part by the National Institute of Neurological Disorders and Stroke (NINDS), have learned a great deal about stroke. They have identified major risk factors for the disease and have developed surgical techniques and drug treatments for the prevention of stroke. But perhaps the most exciting new development in the field of stroke research is the recent approval of a drug treatment that can reverse the course of stroke if given during the first few hours after the onset of symptoms.

Studies with animals have shown that brain injury occurs within minutes of a stroke and can become irreversible within as little as an hour. In humans, brain damage begins from the moment the stroke starts and often continues for days afterward. Scientists now know that there is a very short window of opportunity for treatment of the most common form of stroke. Because of these and other advances in the field of cerebrovascular disease stroke patients now have a chance for survival and recovery.

What is Stroke?

A stroke occurs when the blood supply to part of the brain is suddenly interrupted or when a blood vessel in the brain bursts, spilling blood into the spaces surrounding brain cells. In the same way that a person suffering a loss of blood flow to the heart is said to be having a heart attack, a person with a loss of blood flow to the brain or sudden bleeding in the brain can be said to be having a "brain attack."

Brain cells die when they no longer receive oxygen and nutrients from the blood or when they are damaged by sudden bleeding into or around the brain. Ischemia is the term used to describe the loss of oxygen and nutrients for brain cells when there is inadequate blood flow. Ischemia ultimately leads to infarction, the death of brain cells which are eventually replaced by a fluid-filled cavity (or infarct) in the injured brain.

When blood flow to the brain is interrupted, some brain cells die immediately, while others remain at risk for death. These damaged cells make up the ischemic penumbra and can linger in a compromised state for several hours. With timely treatment these cells can be saved. The ischemic penumbra is discussed in more detail in the Appendix.

Even though a stroke occurs in the unseen reaches of the brain, the symptoms of a stroke are easy to spot. They include sudden numbness or weakness, especially on one side of the body; sudden confusion or trouble speaking or understanding speech; sudden trouble seeing in one or both eyes; sudden trouble walking, dizziness, or loss of balance or coordination; or sudden severe headache with no known cause. All of the symptoms of stroke appear suddenly, and often there is more than one symptom at the same time. Therefore stroke can usually be distinguished from other causes of dizziness or headache. These symptoms may indicate that a stroke has occurred and that medical attention is needed immediately.

There are two forms of stroke: ischemic - blockage of a blood vessel supplying the brain, and hemorrhagic - bleeding into or around the brain. The following sections describe these forms in detail.

Ischemic Stroke

An ischemic stroke occurs when an artery supplying the brain with blood becomes blocked, suddenly decreasing or stopping blood flow and ultimately causing a brain infarction. This type of stroke accounts for approximately 80 percent of all strokes. Blood clots are the most common cause of artery blockage and brain infarction. The process of clotting is necessary and beneficial throughout the body because it stops bleeding and allows repair of damaged areas of arteries or veins. However, when blood clots develop in the wrong place within an artery they can cause devastating injury by interfering with the normal flow of blood. Problems with clotting become more frequent as people age.

Blood clots can cause ischemia and infarction in two ways. A clot that forms in a part of the body other than the brain can travel through blood vessels and become wedged in a brain artery. This free-roaming clot is called an embolus and often forms in the heart. A stroke caused by an embolus is called an embolic stroke. The second kind of ischemic stroke, called a thrombotic stroke, is caused by thrombosis, the formation of a blood clot in one of the cerebral arteries that stays attached to the artery wall until it grows large enough to block blood flow.

Ischemic strokes can also be caused by stenosis, or a narrowing of the artery due to the buildup of plaque (a mixture of fatty substances, including cholesterol and other lipids) and blood clots along the artery wall. Stenosis can occur in large arteries and small arteries and is therefore called large vessel disease or small vessel disease, respectively. When a stroke occurs due to small vessel disease, a very small infarction results, sometimes called a lacunar infarction, from the French word "lacune" meaning "gap" or "cavity."

The most common blood vessel disease that causes stenosis is atherosclerosis. In atherosclerosis, deposits of plaque build up along the inner walls of large and medium-sized arteries, causing thickening, hardening, and loss of elasticity of artery walls and decreased blood flow.

Hemorrhagic Stroke

In a healthy, functioning brain, neurons do not come into direct contact with blood. The vital oxygen and nutrients the neurons need from the blood come to the neurons across the thin walls of the cerebral capillaries. The glia (nervous system cells that support and protect neurons) form a blood-brain barrier, an elaborate meshwork that surrounds blood vessels and capillaries and regulates which elements of the blood can pass through to the neurons.

When an artery in the brain bursts, blood spews out into the surrounding tissue and upsets not only the blood supply but the delicate chemical balance neurons require to function. This is called a hemorrhagic stroke. Such strokes account for approximately 20 percent of all strokes.

Hemorrhage can occur in several ways. One common cause is a bleeding aneurysm, a weak or thin spot on an artery wall. Over time, these weak spots stretch or balloon out under high arterial pressure. The thin walls of these ballooning aneurysms can rupture and spill blood into the space surrounding brain cells.

Hemorrhage also occurs when arterial walls break open. Plaque-encrusted artery walls eventually lose their elasticity and become brittle and thin, prone to cracking. Hypertension, or high blood pressure, increases the risk that a brittle artery wall will give way and release blood into the surrounding brain tissue.

A person with an arteriovenous malformation (AVM) also has an increased risk of hemorrhagic stroke. AVMs are a tangle of defective blood vessels and capillaries within the brain that have thin walls and can therefore rupture.

Bleeding from ruptured brain arteries can either go into the substance of the brain or into the various spaces surrounding the brain. Intracerebral hemorrhage occurs when a vessel within the brain leaks blood into the brain itself. Subarachnoid hemorrhage is bleeding under the meninges, or outer membranes, of the brain into the thin fluid-filled space that surrounds the brain.

The subarachnoid space separates the arachnoid membrane from the underlying pia mater membrane. It contains a clear fluid (cerebrospinal fluid or CSF) as well as the small blood vessels that supply the outer surface of the brain. In a subarachnoid hemorrhage, one of the small arteries within the subarachnoid space bursts, flooding the area with blood and contaminating the cerebrospinal fluid. Since the CSF flows throughout the cranium, within the spaces of the brain, subarachnoid hemorrhage can lead to extensive damage throughout the brain. In fact, subarachnoid hemorrhage is the most deadly of all strokes.

Transient Ischemic Attacks

A transient ischemic attack (TIA), sometimes called a mini-stroke, starts just like a stroke but then resolves leaving no noticeable symptoms or deficits. The occurrence of a TIA is a warning that the person is at risk for a more serious and debilitating stroke. Of the approximately 50,000 Americans who have a TIA each year, about one-third will have an acute stroke sometime in the future. The addition of other risk factors compounds a person's risk for a recurrent stroke. The average duration of a TIA is a few minutes. For almost all TIAs, the symptoms go away within an hour. There is no way to tell whether symptoms will be just a TIA or persist and lead to death or disability. The patient should assume that all stroke symptoms signal an emergency and should not wait to see if they go away.

Recurrent Stroke

Recurrent stroke is frequent; about 25 percent of people who recover from their first stroke will have another stroke within 5 years. Recurrent stroke is a major contributor to stroke disability and death, with the risk of severe disability or death from stroke increasing with each stroke recurrence. The risk of a recurrent stroke is greatest right after a stroke, with the risk decreasing with time. About 3 percent of stroke patients will have another stroke within 30 days of their first stroke and one-third of recurrent strokes take place within 2 years of the first stroke.

How Do You Recognize Stroke?

Symptoms of stroke appear suddenly. Watch for these symptoms and be prepared to act quickly for yourself or on behalf of someone you are with:

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

If you suspect you or someone you know is experiencing any of these symptoms indicative of a stroke, do not wait. Call 911 emergency immediately. There are now effective therapies for stroke that must be administered at a hospital, but they lose their effectiveness if not given within the first 3 hours after stroke symptoms appear. Every minute counts!

Risk Factors for a Stroke

Stroke prevention is still the best medicine. The most important treatable conditions linked to stroke are:

  • High blood pressure.Treat it. Eat a balanced diet, maintain a healthy weight, and exercise to reduce blood pressure. Drugs are also available.
  • Cigarette smoking. Quit. Medical help is available to help quit.
  • Heart disease. Manage it. Your doctor can treat your heart disease and may prescribe medication to help prevent the formation of clots. If you are over 50, NINDS scientists believe you and your doctor should make a decision about aspirin therapy.
  • Diabetes. Control it. Treatment can delay complications that increase the risk of stroke.
  • Transient ischemic attacks (TIAs). Seek help. TIAs are small strokes that last only for a few minutes or hours. They should never be ignored and can be treated with drugs or surgery.
     

What Stroke Therapies are Available?

Physicians have a wide range of therapies to choose from when determining a stroke patient's best therapeutic plan. The type of stroke therapy a patient should receive depends upon the stage of disease. Generally there are three treatment stages for stroke: prevention, therapy immediately after stroke, and post-stroke rehabilitation. Therapies to prevent a first or recurrent stroke are based on treating an individual's underlying risk factors for stroke, such as hypertension, atrial fibrillation, and diabetes, or preventing the widespread formation of blood clots that can cause ischemic stroke in everyone, whether or not risk factors are present. Acute stroke therapies try to stop a stroke while it is happening by quickly dissolving a blood clot causing the stroke or by stopping the bleeding of a hemorrhagic stroke. The purpose of post-stroke rehabilitation is to overcome disabilities that result from stroke damage.

Therapies for stroke include medications, surgery, or rehabilitation.

Medications

Medication or drug therapy is the most common treatment for stroke. The most popular classes of drugs used to prevent or treat stroke are antithrombotics (antiplatelet agents and anticoagulants) and thrombolytics.

Antithrombotics prevent the formation of blood clots that can become lodged in a cerebral artery and cause strokes. Antiplatelet drugs prevent clotting by decreasing the activity of platelets, blood cells that contribute to the clotting property of blood. These drugs reduce the risk of blood-clot formation, thus reducing the risk of ischemic stroke. In the context of stroke, physicians prescribe antiplatelet drugs mainly for prevention. The most widely known and used antiplatelet drug is aspirin. Other antiplatelet drugs include clopidogrel, ticlopidine, and dipyridamole. The NINDS sponsors a wide range of clinical trials to determine the effectiveness of antiplatelet drugs for stroke prevention.

Anticoagulants reduce stroke risk 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). The NINDS has sponsored several trials to test the efficacy of anticoagulants versus antiplatelet drugs. The Stroke Prevention in Atrial Fibrillation (SPAF) trial found that, although aspirin is an effective therapy for the prevention of a second stroke in most patients with atrial fibrillation, some patients with additional risk factors do better on warfarin therapy. Another study, the Trial of Org 10127 in Acute Stroke Treatment (TOAST), tested the effectiveness of low-molecular weight heparin (Org 10172) in stroke prevention. TOAST showed that heparin anticoagulants are not generally effective in preventing recurrent stroke or improving outcome.

Thrombolytic agents are used to treat an ongoing, acute ischemic stroke caused by an artery blockage. These drugs halt the stroke by dissolving the blood clot that is blocking blood flow to the brain. Recombinant tissue plasminogen activator (rt-PA) is a genetically engineered form of t-PA, a thombolytic substance made naturally by the body. It can be effective if given intravenously within 3 hours of stroke symptom onset, but it should be used only after a physician has confirmed that the patient has suffered an ischemic stroke. Thrombolytic agents can increase bleeding and therefore must be used only after careful patient screening. The NINDS rt-PA Stroke Study showed the efficacy of t-PA and in 1996 led to the first FDA-approved treatment for acute ischemic stroke. Other thrombolytics are currently being tested in clinical trials.

Neuroprotectants are medications that protect the brain from secondary injury caused by stroke. Although no neuroprotectants are FDA-approved for use in stroke at this time, many are in clinical trials. There are several different classes of neuroprotectants that show promise for future therapy, including glutamate antagonists, antioxidants, apoptosis inhibitors, and many others.

Surgery

Surgery can be used to prevent stroke, to treat acute stroke, or to repair vascular damage or malformations in and around the brain. There are two prominent types of surgery for stroke prevention and treatment: carotid endarterectomy and extracranial/intracranial (EC/IC) bypass.

Carotid endarterectomy is a surgical procedure in which a doctor removes fatty deposits (plaque) from the inside of one of the carotid arteries, which are located in the neck and are the main suppliers of blood to the brain. As mentioned earlier, the disease atherosclerosis is characterized by the buildup of plaque on the inside of large arteries, and the blockage of an artery by this fatty material is called stenosis. The NINDS has sponsored two large clinical trials to test the efficacy of carotid endarterectomy: the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the Asymptomatic Carotid Atherosclerosis Trial (ACAS). These trials showed that carotid endarterectomy is a safe and effective stroke prevention therapy for most people with greater than 50 percent stenosis of the carotid arteries when performed by a qualified and experienced neurosurgeon or vascular surgeon.

Currently, the NINDS is sponsoring the Carotid Revascularization Endarterectomy vs. Stenting Trial (CREST), a large clinical trial designed to test the effectiveness of carotid endarterectomy versus a newer surgical procedure for carotid stenosis called stenting. The procedure involves inserting a long, thin catheter tube into an artery in the leg and threading the catheter through the vascular system into the narrow stenosis of the carotid artery in the neck. Once the catheter is in place in the carotid artery, the radiologist expands the stent with a balloon on the tip of the catheter. The CREST trial will test the effectiveness of the new surgical technique versus the established standard technique of carotid endarterectomy surgery.

EC/IC bypass surgery is a procedure that restores blood flow to a blood-deprived area of brain tissue by rerouting a healthy artery in the scalp to the area of brain tissue affected by a blocked artery. The NINDS-sponsored EC/IC Bypass Study tested the ability of this surgery to prevent recurrent strokes in stroke patients with atherosclerosis. The study showed that, in the long run, EC/IC does not seem to benefit these patients. The surgery is still performed occasionally for patients with aneurysms, some types of small artery disease, and certain vascular abnormalities.

One useful surgical procedure for treatment of brain aneurysms that cause subarachnoid hemorrhage is a technique called "clipping." Clipping involves clamping off the aneurysm from the blood vessel, which reduces the chance that it will burst and bleed.

A new therapy that is gaining wide attention is the detachable coil technique for the treatment of high-risk intracranial aneurysms. A small platinum coil is inserted through an artery in the thigh and threaded through the arteries to the site of the aneurysm. The coil is then released into the aneurysm, where it evokes an immune response from the body. The body produces a blood clot inside the aneurysm, strengthening the artery walls and reducing the risk of rupture. Once the aneurysm is stabilized, a neurosurgeon can clip the aneurysm with less risk of hemorrhage and death to the patient.

Rehabilitation Therapy

Stroke is the number one cause of serious adult disability in the United States. Stroke disability is devastating to the stroke patient and family, but therapies are available to help rehabilitate post-stroke patients.

For most stroke patients, physical therapy (PT) is the cornerstone of the rehabilitation process. A physical therapist uses training, exercises, and physical manipulation of the stroke patient's body with the intent of restoring movement, balance, and coordination. The aim of PT 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 involving relearning daily activities is occupational therapy (OT). OT also involves exercise and training to help the stroke patient relearn everyday activities such as eating, drinking, dressing, bathing, cooking, reading and writing, and toileting. The goal of OT is to help the patient become independent or semi-independent.

Speech and language problems arise when brain damage occurs in the language centers of the brain. Due to the brain's great ability to learn and change (called brain plasticity), other areas can adapt to take over some of the lost functions. Speech language pathologists help stroke patients relearn language and speaking skills, including swallowing, or learn other forms of communication. Speech therapy is appropriate for any patients with problems understanding speech or written words, or problems forming speech. A speech therapist helps stroke patients help themselves by working to improve language skills, develop alternative ways of communicating, and develop coping skills to deal with the frustration of not being able to communicate fully. With time and patience, a stroke survivor should be able to regain some, and sometimes all, language and speaking abilities.

Many stroke patients require psychological or psychiatric help after a stroke. Psychological problems, such as depression, Anxiety, frustration, and anger, are common post-stroke disabilities. Talk therapy, along with appropriate medication, can help alleviate some of the mental and emotional problems that result from stroke. Sometimes it is also beneficial for family members of the stroke patient to seek psychological help as well.

References:

National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892

Nutritional and Herbal Therapy for Stroke

There are number of food and herbal choices that can help prevent a stroke.

  • Omega-3 fatty acids from salmon, tuna or trout or a fish oil concentrate (4-10 capsules daily) can inhibit blood clots and reduce inflammation. They also have a hypotensive effect.
  • Calcium and magnesium help lower blood pressure. Magnesium can improve circulation.
  • Garlic prevents blood clots and can lower blood pressure.
  • Green Tea extract can also prevent blood clots, lowers LDL cholesterol levels and lowers blood pressure.
  • Ginkgo Biloba (120-240 mg a day) improves circulation and memory and prevents blood clots.

 


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