MEDICAL CONDITIONS
Stroke
What is a stroke?
A stroke is the sudden death of brain cells due to a problem with the blood supply. When blood flow to the brain is impaired, oxygen and important nutrients cannot be delivered. The result is abnormal brain function. Blood flow to the brain can be disrupted by either a blockage or rupture of an artery to the brain. There are many causes for a stroke, as shown in the table and discussed below. A stroke is also referred to as a cerebrovascular accident or CVA.
Causes of Stroke
Blockage of artery - Clogging of arteries within the brain (e.g. lacunar stroke)
- Hardening of the arteries leading to the brain (e.g. carotid artery occlusion)
- Embolism to the brain from the heart or an artery
Rupture of an artery (i.e. hemorrhage) - Cerebral hemorrhage (bleeding within the brain substance)
- Subarachnoid hemorrhage (bleeding between the brain and the inside of the skull)
What causes a stroke?
The blockage of an artery in the brain by a clot (thrombosis) is the most common cause of a stroke. The part of the brain that is supplied by the clotted blood vessel is then deprived of blood and oxygen. The cells of that part of the brain die as a result. Typically, a clot forms in a small blood vessel within the brain that has been previously narrowed due to the long-term, damaging effects of high blood pressure (hypertension) or diabetes. The resulting strokes are called lacunar strokes because they look like little lakes. In other situations, usually because of hardening of the arteries (atherosclerosis), a blood clot can obstruct a larger vessel going to the brain, such as the carotid artery in the neck.
Another type of stroke occurs when a blood clot or a piece of atherosclerotic plaque (cholesterol and calcium deposits on the wall of the inside of the heart or artery) breaks loose, travels through open arteries, and lodges in an artery of the brain. When this happens, the flow of oxygen-rich blood to the brain is blocked and a stroke occurs. This type of stroke is referred to as an embolic stroke. For example, a blood clot might originally form in the heart chamber as a result of an irregular heart rhythm, such as occurs in atrial fibrillation . Usually, these clots remain attached to the inner lining of the heart, but occasionally they can break off, travel through the blood stream, form a plug (embolism) in a brain artery, and cause a stroke. An embolism can also originate in a large artery (for example, the carotid artery, a major artery in the neck that supplies blood to the brain) and then travel downstream to clog a small artery within the brain.
A cerebral hemorrhage occurs when a blood vessel in the brain bursts and bleeds into the surrounding brain tissue. A cerebral hemorrhage (bleeding in the brain) can cause a stroke by depriving blood and oxygen to parts of the brain. The accumulation of blood from a cerebral hemorrhage can also press on parts of the brain and cause damage. A subarachnoid hemorrhage is caused by the rupture of a blood vessel that is usually located between the outside of the brain and the inside of the skull. The blood vessel at the point of rupture is often previously abnormal, such as from an aneurysm (an abnormal ballooning out of the wall of the vessel). Subarachnoid hemorrhages usually cause a sudden, severe headache and are often complicated by further neurological problems, such as paralysis, coma, and even death.
Overall, the most common risk factors for stroke are high blood pressure and increasing age. Diabetes and certain heart conditions, such as atrial fibrillation, are other common risk factors. When strokes occur in younger individuals (less than 50 years old), less common risk factors are often involved. These risk factors include drugs, such as cocaine or amphetamines, ruptured aneurysms, and inherited (genetic) predispositions to blood clotting. Another example of a genetic predisposition to stroke occurs in a rare condition called homocystinuria, in which there are excessive levels of the chemical homocystine in the body. Furthermore, scientists are trying to determine whether the non-hereditary occurrence of high levels of homocystine at any age can predispose to stroke. Another rare cause of stroke is vasculitis , a condition in which the blood vessels become inflamed. Finally, there appears to be a very slight increased occurrence of stroke in people with migraine headache .
What is a TIA?
A transient ischemic attack (TIA) is a short-lived episode (less than 24 hours) of temporary impairment to the brain that is caused by a loss of blood supply. A TIA causes a loss of function in the area of the body that is controlled by the portion of the brain affected. The loss of blood supply to the brain is most often caused by a clot that spontaneously forms in a blood vessel within the brain (thrombosis). However, it can also result from a clot that forms elsewhere in the body, dislodges from that location, and travels to lodge in an artery of the brain (emboli). A spasm and, rarely, a bleed are other causes of a TIA. Many people refer to a TIA as a "mini-stroke."
Some TIAs develop slowly while others develop rapidly. By definition, all TIAs resolve within 24 hours. Strokes take longer to resolve than TIAs and reflect a more permanent and serious problem. Although TIAs often last only a few minutes and then end, most experts believe TIAs should be evaluated with the same urgency as a stroke in an effort to prevent recurrences and/or strokes. TIAs can occur once, multiple times, or precede a permanent stroke.
A TIA from a clot to the eye can cause temporary visual loss, which is often described as a curtain coming down. A TIA that involves the carotid artery (the largest blood vessel supplying the brain) can produce problems with movement or sensation on one side of the body, which is the side opposite to the actual blockage. An affected patient may experience paralysis of the arm, leg, and face, all on one side. Double vision, dizziness (vertigo) and loss of speech, understanding, and balance can also be symptoms depending on what part of the brain is lacking blood supply.
TIAs are often warnings of an impending, more severe or permanent stroke and must be immediately evaluated by a physician. TIAs can reflect a local problem in the brain, a plugging of the arteries to the brain such as the carotid arteries, or they can reflect a heart problem in which clots dislodge and flow into the brain. Examples of these heart conditions include atrial fibrillation, valve problems, and poorly beating or weak heart walls.
TIAs and hardening of the heart arteries can occur together and can reflect an underlying disease such as diabetes mellitus , high cholesterol, or high blood pressure (hypertension).
What is the impact of strokes?
In the United States, about 400,000 people a year suffer from a stroke, and up to 40% of these strokes may be fatal. The cost of strokes is not just measured in the billions of dollars lost in work, hospitalization, and the care of survivors in nursing homes. The major cost or impact of a stroke is the loss of independence that occurs in 30% of the survivors. What was a self-sustaining and enjoyable lifestyle may lose most of its quality after a stroke and other family members can find themselves in a new role as caregivers.
How is a stroke recognized?
When brain cells are deprived of oxygen, they cease to perform their usual tasks. The symptoms that follow a stroke depend on the area of the brain that has been affected and the amount of brain tissue damage.
Small strokes may not cause any symptoms, but still damage brain tissue. These strokes that do not cause symptoms are referred to as silent strokes. The most common symptom of a stroke is weakness or paralysis on one side of the body or the other. There may be a partial or complete loss of voluntary movement and/or sensation in a leg and/or arm. A stroke can cause speech problems and weak muscles of the face, which can cause drooling. Numbness or tingling in the leg, arm, or face is very common. A stroke involving the base of the brain can affect balance, vision, and swallowing functions. A stroke can cause difficulty breathing and even unconsciousness.
What should be done if you suspect you or someone else is having a stroke?
If any of the symptoms mentioned above suddenly appear, emergency medical attention should be sought. The sooner treatment is started, the better the eventual outcome will be. Therefore, the first action should be to call 911 (or whatever number activates the emergency medical response in your area). The family doctor and/or neurologist should also be contacted. However, the first priority is ensuring that the ambulance arrives as soon as possible. The affected person should lie flat to promote an optimal blood flow to the brain. If drowsiness, unresponsiveness, or nausea are present, the person should lie on one side to prevent choking on his/her vomit. Although aspirin plays a major role in stroke prevention (see below), once the symptoms of a stroke begin, it is generally recommended that additional aspirin not be taken until the patient receives medical attention. If stroke is of the bleeding type, aspirin could theoretically make matters worse.
How is a stroke diagnosed?
A stroke is a medical emergency. Anyone suspected of having a stroke should be taken to a medical facility immediately for evaluation and treatment. Initially, the doctor takes a medical history from the patient if he/she is alert, or others familiar with the patient if they are available, and performs a physical examination. If a person has been seeing a particular doctor, it would be ideal for that doctor to participate in the assessment. Previous knowledge of the patient can improve the accuracy of the evaluation. A neurologist, a doctor specializing in disorders of the nervous system and diseases of the brain, will often be asked to assist in the diagnosis and management of stroke patients.
Just because a person has slurred speech or weakness on one side of the body does not necessarily signal the occurrence of a stroke. There are many other possibilities that can be responsible for these symptoms. Other conditions that can mimic a stroke include brain tumors, a brain abscess (a collection of pus in the brain caused by bacteria or a fungus), and subdural hematomas. A subdural hematoma is a collection of mostly clotted blood that accumulates between the brain and the skull. This produces a mass that can enlarge and press against the brain. In contrast, in a subarachnoid hemorrhage, blood spills out into the space between the brain and the skull and causes more sudden and catastrophic effects. Viral encephalitis can also produce symptoms similar to those of a stroke, as can an overdose of certain medications. An imbalance of sodium, calcium, or glucose in the body can also cause changes in the nervous system that can mimic a stroke. CAT Scan : In order to help determine the cause of a suspected stroke, a special x-ray test called a CAT scan (also called a CT scan), of the brain is often performed. A CAT scan can show bleeding into the brain, which is treated differently than a stroke that is caused by blockage of the blood supply. A CAT scan also rules out many of the other causes of neurological conditions mentioned above that can mimic a stroke. For more information, please see the CAT Scan article.
MRI Scan: A newer method of viewing the brain is Magnetic Resonance Imaging (MRI), which uses harmless magnetic waves rather than X-rays. The major advantage of an MRI is that the pictures it takes of the brain are much more detailed than with CAT scans. Nonetheless, a CAT scan is often the first brain scan performed on a stroke patient because it can detect the presence of an early hemorrhage better than an MRI. This is a critical piece of information that is needed for immediate treatment. An MRI can be performed afterwards if finer details are required for further medical decision making. People with certain medical devices (e.g. pacemakers) cannot be subjected to the powerful magnetic field of an MRI. Other people with fear of closed spaces (claustrophobia) find the long tube of the MRI scanner just too confining, although many centers offer "open" MRIs that are less uncomfortable for those with claustrophobia. For more information, please see the MRI article.
Other methods of MRI technology: An MRI scan can also be used to specifically view the blood vessels non-invasively (without using tubes or injections), a procedure called an MRA (Magnetic Resonance Angiogram). An exciting new MRI method called Diffusion Weighted Imaging (DWI) is being offered in some medical centers. This technique can detect the area of abnormality minutes after the blood flow to a part of the brain has ceased whereas a conventional MRI may not detect a stroke until up to 6 hours after it has started and a CAT scan sometimes cannot detect it until it is 12 to 24 hours old.
Conventional Angiogram: An angiogram is another test that is sometimes used to view the blood vessels. A long catheter tube is inserted into an artery (usually in the groin area) and dye is injected while X-rays are simultaneously taken. While an angiogram delivers some of the most detailed images of the blood vessel anatomy, it is also an invasive procedure and is used only when absolutely needed. For example, an angiogram is done after a hemorrhage when the precise source of bleeding needs to be identified. It also is sometimes performed to accurately evaluate the condition of a carotid artery when surgery to unblock that blood vessel is contemplated.
Carotid Doppler Ultrasound : A carotid doppler ultrasound is a non-invasive (without injections or placing tubes) method that uses sound waves to screen for narrowings and decreased blood flow in the carotid artery (the major artery in the neck that supplies blood to the brain).
Heart Tests: Certain tests to evaluate heart function are often performed in stroke patients to search for the source of an embolism. An echocardiogram is a sound wave test that is done by placing a microphone device on the chest or down the food pipe (transesophageal echocardiogram) in order to view the heart chambers. A Holter monitor is similar to a regular electrocardiogram (EKG), but the electrode stickers remain on the chest for 24 hours or longer in order to identify a faulty heart rhythm.
Blood Tests: Blood tests (such as a sedimentation rate) are done to look for signs of inflammation that can suggest inflamed arteries. Certain blood proteins that can increase the chance of stroke by thickening the blood are measured. These tests are performed to identify treatable causes of a stroke or to help prevent further injury.
What is the treatment of a stroke?
TPA: One of the most important new treatments over the last few years for the immediate treatment of a stroke is a medicine called tPA (which stands for tissue plasminogen activator). TPA is a very powerful "clot-buster" that is infused through the veins. If given within the first three hours after the onset of symptoms, tPA can significantly improve the patient's outcome from the stroke over the long term. The sooner tPA is started, the better the outcome, so time is of the essence.
Early use of Heparin and Aspirin: Drugs to thin the blood (anticoagulation; for example, heparin) are also sometimes used in treating stroke patients in the hopes of improving the patient's recovery. It is unclear, however, whether the use of anticoagulation improves the outcome from the current stroke or simply helps to prevent subsequent strokes (see below). In certain patients, aspirin given after the onset of a stroke does have a small, but measurable effect on recovery. The treating doctor can best determine which of the agents mentioned above is the most appropriate option, based on the results of tests done.
Managing other Medical Problems: Treatment of blood pressure that is too high or too low may be necessary in treating a stroke. Currently, lowering an elevated blood pressure into the normal range is no longer recommended during the first few days following a stroke. Doing so might compromise the blood flow through narrowed or nearly closed arteries, which could make the stroke worse or lessen the chance of recovery. In patients with diabetes , the blood sugar (glucose) level is often quite high after a stroke. Controlling the glucose level in these patients may minimize the size of a stroke. Finally, oxygen may administered to stroke patients when necessary.
Rehabilitation: When a patient is no longer acutely ill after a stroke, the health care staff focuses maximizing the patient's functional abilities. This is most often done in an inpatient rehabilitation hospital or in a special area of a general hospital. Rehabilitation can also take place at a nursing facility. The rehabilitation process can include some or all of the following: (1) speech therapy to relearn talking and swallowing; (2) occupational therapy to regain dexterity in the arms and hands; (3) physical therapy to improve strength and walking; and (4) family education to orient them in caring for their loved one at home and the challenges they will face. The goal is for the patient to resume as many, if not all, of their pre-stroke activities and functions. Since a stroke involves the permanent loss of brain cells, a total return to the patient's pre-stroke status is, unfortunately, not a realistic goal in many cases.
When a stroke patient is ready to go home, a nurse may come to the home for a period of time until the family is familiar with caring for the patient and how to give various medications. Physical therapy may continue at home. Eventually, the patient is usually left at home with one or more caregivers, who now find their lives have changed in major ways. Caring for the stroke patient at home may be easy or very nearly impossible. At times, it becomes apparent that the patient must be placed in a board and care home or a skilled nursing facility because adequate care cannot be given at home despite the good intentions of the family.
What complications can occur after a stroke?
A stroke can become worse despite an early arrival at the hospital, and appropriate medical treatment. It is not unusual for a stroke and a heart attack to occur at the same time or in very close proximity to each other. It may be the weakening of the heart that is the last straw for a narrowed brain artery, which then closes and leads to a stroke.
During the acute illness, swallowing is often affected. The weakness that affects the arm, leg, and side of the face can also impact the muscles of swallowing. A stroke that causes slurred speech seems to predispose the patient to abnormal swallowing mechanics and the development of pneumonia when food or saliva go into the wind pipe. Abnormal swallowing can also occur independently of slurred speech. Because a stroke often results in immobility, blood clots can develop in a leg vein. This poses a risk for a clot to travel upwards to and lodge in the lungs - a potentially life-threatening situation. There are a number of ways in which the treating physician can help prevent these leg vein clots. (Please see the article on Deep Vein Thrombosis and Pulmonary Embolism.) Prolonged immobility can also lead to pressure sores (a breakdown of the skin, called decubitus ulcers), which can be prevented by frequent repositioning of the patient by the nurse or other caretakers. Stroke patients often have some problem with depression as part of the recovery process, which needs to be recognized and treated. The prognosis following a stroke is related to the severity of the stroke and how much of the brain has been damaged. Some patients return to a near-normal condition with minimal awkwardness or speech defects. Many stroke patients are left with permanent problems such as hemiplegia (weakness on one side of the body), aphasia (difficulty or the inability to speak), or incontinence of the bowel and/or bladder. A significant number of persons become unconscious and die following a major stroke.
If a stroke has been massive or devastating to a person's ability to think or function, the family is left with some very difficult decisions. In these cases, it is sometimes advisable to limit further medical intervention. It is often appropriate for the doctor and the patient's family to discuss and implement orders to not resuscitate the patient in the case of a cardiac arrest, since the quality of life for the patient would be so poor. In many cases, this decision is made somewhat easier if the patient has made such a request when well.
What can be done to prevent a stroke?
The following information is based on the National Stroke Association guidelines for stroke prevention (JAMA. 1999 Dec 1;282(21):1999-2000; discussion 2000-1.)
Risk Factor Reduction: The possibility of suffering a stroke can be markedly decreased by controlling the risk factors. The most important risk factor for stroke is high blood pressure. When a person's blood pressure is persistently too high, roughly greater than 140/90, the risk of a stroke increases in proportion to the degree by which the blood pressure is elevated. Controlling blood pressure in the normal range decreases the chances of a stroke. Another important risk factor is cigarette or other tobacco use. Cigarettes cause the carotid arteries to develop severe atherosclerosis, which can lead to their closure and block the blood flow to the brain. Atherosclerosis in general, including involvement of the arteries that supply blood to the heart, is accelerated by smoking . So, when an individual smokes, the main question becomes - which will occur first; a stroke, heart attack, or lung cancer?
Another risk factor for developing a stroke is diabetes mellitus . Diabetes causes the small vessels to close prematurely. When these blood vessels close in the brain, small (lacunar) strokes may occur. Good control of blood sugar is important in decreasing the risk of stroke in diabetic patients. An elevated level of blood cholesterol is also a risk factor for a stroke due to the eventual blockage of blood vessels (atherosclerosis). A low cholesterol diet and medications can help normalize an elevated blood cholesterol level. For more information, please read the Cholesterol article. Blood Thinner/Warfarin: An irregular heart beat (atrial fibrillation in particular) is associated with an increased risk of an embolic stroke, in which the blood clot travels from the heart, through the bloodstream, and into the brain. Warfarin (Coumadin) is a blood "thinner" that prevents the blood from clotting. This medication is often used in patients with atrial fibrillation to decrease this risk. For more information, please see the Atrial Fibrillation article. Warfarin is also sometimes used to prevent the recurrence of a stroke in other situations, such as with certain other heart conditions and conditions in which the blood has a tendency to clot on its own (hypercoagulable states). Patients taking warfarin need to have periodic blood checks to make sure that their current dose is producing the desired effect. Patients on warfarin also need to know that they are at increased risk for bleeding, either externally or internally.
Aspirin and other Antiplatelet Therapy: Many stroke patients who do not require warfarin can use another class of medicines called "antiplatelet" drugs to reduce their risk of suffering another stroke. These medicines reduce the tendency of the blood to clot (clog) in the arteries. As a side effect, patients on these medicines usually have a higher likelihood of bleeding, but this risk is less than when taking an anticoagulant like warfarin. The most commonly prescribed first-choice antiplatelet agent for preventing a stroke recurrence is aspirin. If the patient has an adverse reaction to aspirin or has a stroke despite being on aspirin, three newer antiplatelet preparations can be used. These medications are clopidogrel (Plavix), aspirin/extended release dipyridamole (Aggrenox), and ticlopidine (Ticlid).
Carotid Endarterectomy: In many cases, a person may suffer a TIA or a stroke that is caused by the narrowing or ulceration (sores) of the carotid arteries (the major arteries in the neck that supply blood to the brain). If left untreated, patients with these conditions have a high risk of experiencing a major stroke in the future. An operation that cleans out the carotid artery and restores normal blood flow is known as a carotid endarterectomy. This procedure has been shown to markedly reduce the incidence of a subsequent stroke. In patients who have a narrowed carotid artery, but no symptoms, this operation may be indicated in order to prevent the occurrence of a first stroke.
What is in the future for stroke treatment?
Currently, studies are being done on additional drugs that dissolve clots. These drugs are administered either in the veins (like tPA) or directly into the clogged artery. The goal of these studies is to determine which stroke patients might benefit from this new and aggressive form of treatment. New medications are also being tested that help slow the degeneration of the nerve cells that are deprived of oxygen during a stroke. These drugs are referred to as "neuroprotective" agents, an example of which is sipatrigine. Another example is chlormethiazole, which works by modifying the expression of genes within the brain. (Genes produce proteins that determine an individual's makeup.) Finally, stem cells, which have the potential to develop into a variety of different organs, are being used to try to replace brain cells damaged by a previous stroke. In many academic medical centers, some of these experimental agents may be offered in the setting of a clinical trial. While new therapies for the treatment of patients after a stroke are on the horizon, they are not yet perfect and may not restore complete function to a stroke victim. - Stroke is the sudden death of brain cells due to lack of oxygen.
- Stroke is caused by the blockage of blood flow or rupture of an artery to the brain.
- Any person suspected of having a stroke or TIA should be sent to an emergency room immediately for further management and treatment.
- Sudden tingling, weakness, or paralysis on one side of the body or difficulty with balance, speaking, swallowing, or vision can be a symptom of a stroke.
- A suspected stroke can be confirmed by scanning the brain with special x-ray tests, such as a CAT scan.
- Stroke prevention involves minimizing risk factors, such as controlling high blood pressure, elevated cholesterol, and diabetes.
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