Stroke

What is a stroke?

A stroke, or cerebrovascular accident (CVA), occurs when blood supply to part of the brain is disrupted, causing brain cells to die. When blood flow to the brain is impaired, oxygen and glucose cannot be delivered to the brain. Blood flow can be compromised by a variety of mechanisms.

Blockage of an artery

  • Narrowing of the small arteries within the brain can cause a so-called lacunar stroke, (lacune=empty space). Blockage of a single arteriole can affect a tiny area of brain causing that tissue to die (infarct).
  • Hardening of the arteries (atherosclerosis) leading to the brain. There are four major blood vessels that supply the brain with blood. The anterior circulation of the brain that controls most motor, activity, sensation, thought, speech, and emotion is supplied by the carotid arteries. The posterior circulation, which supplies the brainstem and the cerebellum, controlling the automatic parts of brain function and coordination, is supplied by the vertebrobasilar arteries.

If these arteries become narrow as a result of atherosclerosis, plaque or cholesterol, debris can break off and float downstream, clogging the blood supply to a part of the brain. As opposed to lacunar strokes, larger parts of the brain can lose blood supply, and this may produce more symptoms than a lacunar stroke.

  • Embolism to the brain from the heart. In situations in which blood clots form within the heart, the potential exists for small clots to break off and travel (embolize) to the arteries in the brain and cause a stroke.

Rupture of an artery (hemorrhage)

  • Cerebral hemorrhage (bleeding within the brain substance). The most common reason to have bleeding within the brain is uncontrolled high blood pressure. Other situations include aneurysms that leak or rupture or arteriovenous malformations (AVM) in which there is an abnormal collection of blood vessels that are fragile and can bleed.

What causes a stroke?

Blockage of an artery

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. As a result of the deprived blood and oxygen, the cells of that part of the brain die. Typically, a clot forms in a small blood vessel within the brain that has been previously narrowed due to a variety of risk factors including:

  • high blood pressure (hypertension),
  • high cholesterol,
  • diabetes, and
  • smoking.

Embolic stroke

Another type of stroke may occur 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.

Cerebral hemorrhage

A cerebral hemorrhage occurs when a blood vessel in the brain ruptures 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. Blood is also very irritating to the brain and can cause swelling of brain tissue (cerebral edema). Edema and the accumulation of blood from a cerebral hemorrhage increases pressure within the skull and causes further damage by squeezing the brain against the bony skull.

Subarachnoid hemorrhage

In a subarachnoid hemorrhage, blood accumulates in the space beneath the arachnoid membrane that lines the brain. The blood originates from an abnormal blood vessel that leaks or ruptures. Often this is from an aneurysm (an abnormal ballooning out of the wall of the vessel). Subarachnoid hemorrhages usually cause a sudden, severe headache and stiff neck. If not recognized and treated, major neurological consequences, such as coma, and brain death will occur.

Vasculitis

Another rare cause of stroke is vasculitis, a condition in which the blood vessels become inflamed.

Migraine headache

There appears to be a very slight increased occurrence of stroke in people with migraine headache. The mechanism for migraine or vascular headaches includes narrowing of the brain blood vessels. Some migraine headache episodes can even mimic stroke with loss of function of one side of the body or vision or speech problems. Usually, the symptoms resolve as the headache resolves.

What are the risk factors for stroke?

Overall, the most common risk factors for stroke are:

  • high blood pressure,
  • high cholesterol,
  • smoking,
  • diabetes and
  • increasing age.

Heart rhythm disturbances like atrial fibrillation, patent foramen ovale, and heart valve disease can also be the cause.

When strokes occur in younger individuals (less than 50 years old), less common risk factors are considered including illicit drugs, such as cocaine or amphetamines, ruptured aneurysms, and inherited (genetic) predispositions to blood clotting.

An 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. Scientists are trying to determine whether the non-hereditary occurrence of high levels of homocystine at any age can predispose to stroke.

What is a transient ischemic attack (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 with strokes, complete function may never return and reflect a more permanent and serious problem. Although most TIAs often last only a few minutes, all 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 transient ischemic attack should be considered an emergency because there is no guarantee that the situation will resolve and function will return.

A TIA from a clot to the eye can cause temporary visual loss (amaurosis fugax), which is often described as the sensation of 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.

What is the impact of strokes?

In the United States, stroke is the third largest cause of death (behind heart disease and all forms of cancer). 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.

What are stroke symptoms?

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 can still damage brain tissue. These strokes that do not cause symptoms are referred to as silent strokes. According to The U.S. National Institute of Neurological Disorders and Stroke (NINDS), these are the five major signs of stroke:

  • 1. Sudden numbness or weakness of the face, arm or leg, especially on one side of the body. The loss of voluntary movement and/or sensation may be complete or partial. There may also be an associated tingling sensation in the affected area.
  • 2. Sudden confusion or trouble speaking or understanding. Sometimes weakness in the muscles of the face can cause drooling.
  • 3. Sudden trouble seeing in one or both eyes
  • 4. Sudden trouble walking, dizziness, loss of balance or coordination
  • 5. Sudden, severe headache with no known cause

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. 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 be placed in the rescue position on their side to prevent choking should vomiting occur.
  • 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.

Cincinnati Prehospital Stroke Scale (CPSS)

According to a study by the University of North Carolina, three commands may be used to assess whether a person may be experiencing a stroke. Lay persons can command a potential stroke victim to:

  • 1. Smile
  • 2. Raise both arms
  • 3. Speak a simple sentence

The three commands, known as the Cincinnati Prehospital Stroke Scale (CPSS), are used by health professionals as a simple first step in the assessment process for signs of stroke. If a person has trouble with any of these simple commands, emergency services (911) should be called immediately with a description of the situation, noting that you suspect the individual is having a stroke.

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 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),
  • migraine headache,
  • bleeding in the brain either spontaneously or from trauma,
  • meningitis or encephalitis,
  • an overdose of certain medications, or
  • an imbalance of sodium, calcium, or glucose in the body can also cause changes in the nervous system that can mimic a stroke.

In the acute stroke evaluation, many things will occur at the same time. As the physician is taking the history and performing the physical examination, nursing staff will begin monitoring the patient’s vital signs, getting blood tests, and performing an electrocardiogram (EKG or ECG).

Part of the physical examination that is becoming standardized is the use of a stroke scale. The American Heart Association has published a guide to the examination of the nervous system to help care providers determine the severity of a stroke and whether aggressive intervention may be warranted.

There is a narrow time frame to intervene in an acute stroke with medications to reverse the loss of blood supply to part of the brain (please see TPA below). The patient needs to be appropriately evaluated and stabilized before any clot-busting drugs can be potentially utilized.

Computerized tomography: In order to help determine the cause of a suspected stroke, a special x-ray test called a CT scan of the brain is often performed. A CT scan is used to look for bleeding or masses within the brain, a much different situation than stroke that is also treated differently.

MRI scan: Magnetic resonance imaging (MRI) uses magnetic waves rather than x-rays to image the brain. The MRI images are much more detailed than those from CT, but this is not a first line test in stroke. While a CT scan may be completed within a few minutes, an MRI may take more than an hour to complete. An MRI may be performed later in the course of patient care if finer details are required for further medical decision making. People with certain medical devices (for example, pacemakers) or other metals within their body, cannot be subjected to the powerful magnetic field of an MRI.

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). Another 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 six hours after it has started, and a CT scan sometimes cannot detect it until it is 12 to 24 hours old. Again, this is not a first line test in the evaluation of a stroke patient, when time is of the essence.

Computerized tomography with angiography: Using dye that is injected into a vein in the arm, images of the blood vessels in the brain can give information regarding aneurysms or arteriovenous malformations. As well, other abnormalities of brain blood flow may be evaluated. With increasingly sophisticated technology, CT angiography has supplanted conventional angiograms.

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 necessary. 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 esophagus (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 and C-reactive protein 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. Screening blood tests looking for potential infection, anemia, kidney function, and electrolyte abnormalities may also be considered.

What is the treatment of a stroke?

Tissue plasminogen activator (TPA)

There is opportunity to use alteplase (TPA) as a clot-buster drug to dissolve the blood clot that is causing the stroke. There is a narrow window of opportunity to use this drug. The earlier that it is given, the better the result and the less potential for the complication of bleeding into the brain.

Present American Heart Association guidelines recommend that if used, TPA must be given within three hours after the onset of symptoms. Normally, TPA is injected into a vein in he arm. The time frame for use can be extended to six hours if it is dripped directly into the blood vessel that is blocked. This is usually performed by an interventional radiologist, and not all hospitals have access to this technology.

For posterior circulation strokes that involve the vertebrobasilar system, the time frame for treatment with TPA may be extended even further to 18 hours.

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 will determine the medications to be used based upon a patient’s specific needs.

Managing other Medical Problems

Blood pressure and cholesterol control are key to prevention of future stroke events. In transient ischemic attacks, the patient may be discharged with medications even if the blood pressure and cholesterol levels are acceptable. In an acute stroke, blood pressure will be tightly controlled to prevent further damage.

In patients with diabetes, the blood sugar (glucose) level is often elevated 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 healthcare staff focuses on 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 the procedures for giving 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.

During the acute illness, swallowing may be 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. Should food and saliva enter the trachea instead of the esophagus when eating or swallowing, pneumonia or a lung infection can occur. Abnormal swallowing can also occur independently of slurred speech.

Because a stroke often results in immobility, blood clots can develop in a leg vein (deep vein thrombosis). This poses a risk for a clot to travel upwards to and lodge in the lungs – a potentially life-threatening situation (pulmonary embolism). There are a number of ways in which the treating physician can help prevent these leg vein clots. 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?

Risk factor reduction

High blood pressure: 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 130/85, 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.

Smoking: 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?

Diabetes: 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 healthy diet and medications can help normalize an elevated blood cholesterol level.

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. 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, newer antiplatelet preparations can be used [clopidogrel (Plavix), dipyridamole (Persantine).

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 At A Glance
  • 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.
  • 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.
  • Any person suspected of having a stroke or TIA should present for emergency care immediately
  • Clot-busting drugs like TPA can be used to reverse a stroke, but the time frame for their use is very narrow. Patients need to present for care as soon as possible so that TPA therapy can be considered.
  • Stroke prevention involves minimizing risk factors, such as controlling high blood pressure, elevated cholesterol, tobacco abuse, and diabetes.

References: Johnston SC, Nguyen-Huynh MN, Schwarz ME, Fuller K, Williams CE, Josephson SA, Hankey GJ, Hart RG, Levine SR, Biller J, Brown RD Jr, Sacco RL, Kappelle LJ, Koudstaal PJ, Bogousslavsky J, Caplan LR, van Gijn J, Algra A, Rothwell PM, Adams HP, Albers GW.; “National Stroke Association guidelines for the management of transient ischemic attacks.” Ann Neurol. 2006 Sep;60(3):301-13. “Primary prevention of ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council: cosponsored by the Atherosclerotic Peripheral Vascular Disease Interdisciplinary Working Group; Cardiovascular Nursing Council; Clinical Cardiology Council; Nutrition, Physical Activity, and Metabolism Council; and the Quality of Care and Outcomes Research Interdisciplinary Working Group: the American Academy of Neurology affirms the value of this guideline.” Stroke. 2006 Jun;37(6):1583-633. Epub 2006 May 4. Liferidge AT, Brice JH, Overby BA, Evenson KR. “Ability of laypersons to use the Cincinnati Prehospital Stroke Scale.” Prehosp Emerg Care. 2004 Oct-Dec:8(4):384-7.
Last Editorial Review: 7/7/2008

MedicineNet

%d bloggers like this: