Stroke/Transient Ischemic Attacks Diagnosis

  • Diagnosis

    A stroke is a "brain attack," a sudden interruption of bloodflow to the brain that causes brain damage and loss of function. Stroke is a leading cause of disability and death. Stroke develops suddenly, usually in a matter of minutes, and causes symptoms such as paralysis, numbness or weakness that often affects just one side of the body, confusion, dizziness, speech problems, and loss of vision. The blood supply interruption kills brain cells by depriving them of oxygen and other nutrients found in the blood. Brain cells also become damaged if bleeding occurs in or around the brain, which happens in certain types of strokes. As brain cells die, function is lost in the areas of the brain that they control, such as memory, speech, or movement. The specific functions that will be affected depend on which areas of the brain were damaged and the severity of the stroke Figure 01.

    There are two main types of strokes: ischemic and hemorrhagic. An ischemic stroke is by far the more common type, and occurs when a blood clot or other material blocks an artery supplying blood to the brain. A hemorrhagic stroke occurs when an artery in the brain bursts, causing blood to flow into the surrounding tissue. The mortality rate is higher for hemorrhagic stroke than for ischemic stroke, with most deaths occurring within the first 48 hours.

    A transient ischemic attack (TIA) is a type of stroke that usually lasts only a few minutes. TIAs are sometimes considered to be "mini-strokes." While TIAs cause no long–term damage, having a TIA puts you at increased risk of acute stroke.

    Click to enlarge: Sites in the Brain where Stroke Can Affect Function

    Figure 01. Sites in the Brain where Stroke Can Affect Function

    All forms of stroke are caused by a loss of circulation to the brain, disrupting the neurological functions that correspond to the affected area. Blood reaches the brain through two arteries in the front of the neck called the carotid arteries, and two in the back of the neck called the vertebral arteries. Once in the brain, the arteries branch off to different areas that control different neurological functions such as speech, memory, limb movement, eye movement, and coordination. When blood circulation in this network of arteries is diminished or stopped for even a few seconds, brain cells are destroyed by the lack of oxygen and nutrients that the blood normally supplies. This destruction can lead to permanent selective brain damage or death.

    Ischemic strokes account for up to 80% of all strokes, and are usually caused by a blood clot that blocks bloodflow to the brain. This blockage can occur in two ways. The first way involves a clot from another part of the body (often the heart) that travels through the blood vessels to the brain artery. This type of clot is called an embolus, and when it becomes stuck in the brain artery it causes what is known as an embolic stroke.

    The second type of ischemic stroke is called a thrombotic stroke. In this type of stroke, the blood clot remains attached to the artery wall, and grows until it becomes large enough to interfere with bloodflow.

    A buildup of plaque—a mixture of cholesterol and other fatty substances that accumulate in the inner walls of the arteries—can also cause an ischemic stroke. Plaque buildup is known as atherosclerosis, or hardening of the arteries. As artery walls thicken and lose elasticity, blood flow gradually becomes diminished, which can lead to a stroke. However, this hardening does not necessarily mean that a stroke will occur. The arteries can still carry an adequate supply of blood, even when up to 75% of their area has become obstructed. In addition, small connections between the arteries may expand to route blood around the obstruction, thus compensating for the blocked main artery.

    Hemorrhagic strokes, classified as an intracerebral hemorrhage or subarachnoid hemorrhage, occur when a vessel ruptures inside the brain. In an intracerebral hemorrhage, the more common type of hemorrhagic stroke, a vessel inside the brain ruptures, and blood leaks into the surrounding brain tissue. In a subarachnoid hemorrhage, bleeding spreads into the area surrounding the brain. The most common cause of the bleeding is a ruptured bulging of the artery wall (aneurysm). Although hemorrhagic strokes account for only about 20% of all strokes, they are responsible for up to 80% of the deaths from stroke.

    In addition to atherosclerosis, other health–related conditions or trauma can lead to stroke. High blood pressure, diabetes mellitus, elevated blood cholesterol, carotid artery disease, heart disease, heavy alcohol abuse, cigarette smoking, drug use, and sickle cell disease can all lead to stroke. Head or neck injuries can also produce bleeding similar to that of a hemorrhagic stroke. Neck injuries that put pressure on the carotid or vertebral arteries can trigger a stroke as well.

    Symptoms of stroke occur suddenly, and in clusters Table 01. The most common symptoms of stroke include weakness or paralysis, often on just one side of the body; sudden, severe numbness or loss of sensation; sudden difficulty seeing in one or both eyes; confusion or difficulty speaking or understanding speech (words may be slurred, or you may be unable to speak); a sudden, severe headache with no known cause; difficulty walking; and dizziness or loss of balance or coordination. The symptoms of patients with hemorrhagic stroke are likely to reflect extreme pressure on the brain, and may include sudden, severe headache, nausea, vomiting, seizures, stupor, or coma.

    Table 1.  Symptoms of Stroke

    Sudden weakness or paralysis, especially on one side of the body
    Sudden numbness or loss of sensation
    Sudden difficulty speaking or understanding speech
    Sudden trouble seeing in one or both eyes
    Sudden loss of balance or coordination; dizziness; difficulty walking
    Sudden, severe headache with no known cause
    Sudden nausea and vomiting
    Brief loss of consciousness or period of confusion, fainting, convulsions, or coma

    The numbness or paralysis associated with stroke often affects just one side of the face, or one leg or arm. This unilateral distribution happens because strokes usually damage only one side of the brain. Symptoms tend to appear on the side of the body opposite the affected area of the brain.

    A transient ischemic attack (TIA) starts with the same symptoms as those of stroke. With TIA, however, the symptoms may go away within 10 to 20 minutes, and rarely last longer than an hour. Since it is impossible to determine at the onset whether symptoms will persist or quickly subside, you should always seek immediate medical treatment.

    As TIAs tend to recur, you may have several attacks in a day, or over several days. However, you may also have symptom–free periods for several years.

    High blood pressure is the most significant risk factor for stroke. If you have high blood pressure, your risk of stroke increases four– to sixfold. An estimated 40% to 90% of stroke patients are diagnosed with high blood pressure before their attack. High blood pressure can cause the arteries to narrow so that less blood reaches the brain. It can also make the arteries thick and stiff, conditions that encourage a buildup of fat and cholesterol and can interfere with the flow of blood to the brain.

    Heart disease is a risk factor for stroke. Although several types of heart disease are associated with stroke, atrial fibrillation carries the greatest risk. Overall, an estimated 20% of ischemic strokes are due to brain embolism from the heart. Atrial fibrillation is defined as irregular beating of the upper left chamber of the heart (left atrium). During fibrillation, the left atrium beats up to four times faster than the rest of the heart, causing irregular bloodflow and the potential for blood clots to form. If a clot moves from the heart to the brain, it can cause a stroke. About 15% of stroke patients have atrial fibrillation before their attack; among patients over the age of 80, one in four strokes is caused by atrial fibrillation.

    Disorders of the heart valves or heart muscle can also increase your risk for stroke. Myocardial infarction (heart attack), valve diseases such as mitral valve stenosis, and prosthetic heart valves can increase your risk for stroke. Two heart disorders that can potentially increase stroke risk are patent foramen ovale (PFO) and atrial septal aneurysm (ASA). PFO is a hole in the heart wall that separates the two upper chambers. Blood clots may pass through this hole, enter the arteries, and circulate to the brain. ASA, which is present from birth, is a bulging of the heart wall into one of the chambers. ASA and PFO often occur together, increasing the risk for stroke.

    Two other heart conditions implicated in stroke risk are left ventricular hypertrophy and left atrial enlargement. Left ventricular hypertrophy means a thickening of the wall of the left ventricle. If you have left atrial enlargement, your left atrium is larger than normal. It is unclear precisely how these two malformations affect the risk of stroke.

    Having a history of TIA or stroke increases your risk of having another stroke. About one in five individuals who have had a TIA will have a stroke within a year. Having had a previous stroke also increases your risk of having another one—about one in four patients who recover from a stroke will have another within five years. However, making lifestyle adjustments such as giving up smoking or adopting a low–fat diet may reduce your risk.

    Cardiac surgery can increase your stroke risk by about 1%. During heart surgery, a plaque can become dislodged and move through the blood to the arteries in the neck and head, causing a blockage that can precipitate a stroke.

    Having diabetes increases your risk for stroke about threefold. There are two ways in which having diabetes affects your risk for stroke. First, high blood sugar levels damage your blood vessels by making the walls thicker and less elastic, which in turn makes it more difficult for blood to circulate. Second, people with diabetes tend to have high levels of fat in their blood that clog the arteries. Keeping your blood sugar and fat levels under control helps to reduce your risk for stroke.

    Your blood cholesterol levels play a major role in your stroke risk. The risk of stroke and heart disease stems mainly from the cholesterol in the foods you eat. Eating a diet high in saturated fat and cholesterol increases the amount of cholesterol in your body, and can cause hardening and thickening of the arteries. Foods such as meat, eggs, and dairy products are primary sources of cholesterol and fat.

    Excessive cholesterol builds up in your arteries, where it is converted into plaque, blocks the blood vessels, and helps form blood clots that can lead to stroke.

    Smoking nearly doubles the risk for ischemic stroke. Cigarette smoking is a strong risk factor for stroke, especially among younger adults. Smoking encourages hardening of the arteries, and promotes growth of blood clots that can cause stroke.

    Heavy alcohol use increases your blood pressure, and therefore also your risk of having either an ischemic or hemorrhagic stroke. However, several scientific studies have suggested that moderate daily alcohol consumption may actually decrease your risk of ischemic stroke, apparently by decreasing blood clotting. Discuss your alcohol consumption with your doctor to determine what amount of alcohol, if any, you can tolerate with your condition.

    Using illicit drugs can be associated with strokes.

    Cocaine and crack cocaine may cause stroke because they suddenly raise the blood pressure and narrow the blood vessels in the brain, reducing blood flow. The amount of narrowing increases with the frequency of drug use. Cocaine can also cause heart rhythm disorders and rapid heart rate, which may cause blood clots to form.Other drugs that have been associated with stroke risk include amphetamines and heroin.

    Stroke can occur as a complication of syphilis. A syphilitic infection may cause blockage of the arteries in the brain, causing decreased blood flow and damage to brain tissue. Successful treatment of syphilis reduces the risk of stroke.

    Certain inherited and congenital conditions also increase the risk of stroke. Fibromuscular dysplasia (FMD) is an arterial disorder that can cause stroke, primarily among women over 50. FMD may cause stroke if it affects the carotid arteries that supply blood to the brain, or arteries within the brain itself. A rare genetic disease called cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is also a risk factor for stroke and dementia.

    Stroke seems to run in some families, even when specific inherited diseases such as FMD are not present. This genetic link may occur because many of the conditions that put a person at risk for stroke such as diabetes or high blood pressure— are heritable disorders. Habits that may be reinforced in families, such as smoking or eating a high–fat diet, also can influence risk for stroke.

    Although a stroke can occur at any age, the risk is highest for older individuals. For every decade after age 55, the risk of stroke doubles: an estimated two–thirds of strokes occur in people over age 65. People in this age group also have a higher risk of dying from stroke than younger individuals.

    Although the risk for men is 1.25 times higher than for women, women are more likely to die from stroke.As women generally live longer than men, they are usually older when they have their first stroke, and are more likely to die as a result. Men tend to be younger and in somewhat better overall health when they have a stroke, and therefore are more likely to survive.

    The incidence of stroke and the death rate among stroke sufferers are approximately twice as high among African–Americans than in white Americans. This racial discrepancy may be related to a higher rate of risk factors such as smoking or high blood pressure among African–Americans. African–Americans also have a higher incidence of genetic diseases such as diabetes and sickle cell anemia, which also increases their likelihood of having a stroke.

    The Southeast has the highest stroke mortality rate in the US, and is sometimes called the "Stroke Belt." Three states within this region—Georgia, North Carolina, and South Carolina—have mortality rates that are approximately twice as high as that of the US as a whole. While the reasons for these differences in stroke incidence and mortality are unclear, possible factors include higher rates of cigarette smoking and a regional preference for salty, high–fat foods, both of which can contribute to hypertension.

    Your doctor will take a medical history to learn about your symptoms. Your doctor will ask you about your health history and risk factors, such as high blood pressure, high cholesterol, smoking, diabetes, and previous incidents of stroke or TIA. If you are having difficulty speaking, have fainted, or are in a coma, a family member or other caregiver will be asked to provide information. The doctor will examine you for the symptoms of a stroke, including paralysis, numbness, vision problems, dizziness, difficulty walking, and slurred speech, and will check your temperature, pulse, respiration, and blood pressure. The doctor's main objectives are to learn whether you have had a stroke, or if you have a condition that may cause similar symptoms, such as a tumor or an abscess.

    If you are diagnosed with stroke, the doctor must determine whether you had an ischemic or hemorrhagic stroke before he or she can recommend an appropriate course of treatment.

    In most cases you will undergo a computed tomography (CT) or magnetic resonance imaging (MRI) test. The CT scan produces a series of cross–sectional images of the head and brain that help the doctor determine the cause, location, and extent of the injury. You may also undergo a magnetic resonance imaging (MRI ) diagnostic test, which is more sensitive than a CT scan. The CT scan is more commonly used as a preliminary diagnostic tool, because it is faster and less expensive than an MRI, and can more readily detect bleeding in the brain at an early stage.

    Other diagnostic tests that may be ordered include a chest x–ray, carotid ultrasound, cerebral angiography, electrocardiogram (ECG), or echocardiogram. The carotid or neck ultrasound is used to determine if the neck arteries have narrowed significantly; if so, a follow–up test known as a magnetic resonance angiography (MRA) or cerebral angiography may be conducted. These studies provide more details about the severity of the arterial narrowing. The ECG is used to detect abnormal heart rhythms or other underlying heart disorders. The echocardiogram is used to look at the structure of your heart and the movement of its valves, which may reveal an embolus or a blood clot.

    You may also undergo tests to evaluate the brain's electrical activity. These tests include the electroencephalogram (EEG), in which the brain's electrical signals are picked up by electrodes and printed on paper as brain waves. The other test you may receive is an evoked response test, which measures how the brain handles sensory information that may have been affected during the stroke, such as hearing or vision.

    The doctor will order a series of blood or laboratory tests to look for underlying conditions that may increase your risk for stroke. The doctor will run tests to look for diabetes or high cholesterol, two conditions that increase your risk for stroke. The doctor may also analyze your spinal fluid for blood or blood products, which would help determine whether you had a hemorrhagic stroke. Changes in the spinal fluid may indicate that tumor, infection, or inflammation are responsible for the stroke–like symptoms.

    If you smoke, cut back or quit Table 02. Your risk of stroke will decline significantly in two to four years after quitting, although it will take several decades for you to return to the risk level of someone who has never smoked.

    Do not use cocaine, crack cocaine, heroin, amphetamines, or other illicit drugs.

    If you have diabetes, regularly monitor your blood sugar level, follow your recommended diet, and use insulin as directed.

    Have your blood pressure checked regularly. If your blood pressure reading is consistently normal, you should be rechecked every two years. If your blood pressure is in the high to normal range, have it rechecked once a year. If you have been diagnosed with hypertension, follow your doctor's recommendations for rechecks. Depending on the situation, you may need to be rechecked anywhere from several days to two months after your previous evaluation.

    If your blood pressure is high, your doctor may recommend that you lose weight; a reduction of as little as 10 pounds can be beneficial. You should also exercise regularly; following a routine of 30 to 45 minutes of brisk walking several days a week is a good start. You should cut back on your sodium intake; however, the body's response to salt and its influence on blood pressure can vary significantly, so talk to your doctor about how much salt is best for you. You can also reduce your risk of high blood pressure and stroke by eating a healthy, balanced diet. Your doctor may also advise you to limit your alcohol intake.

    You can lower your risk of stroke by improving your cholesterol level. Eating a healthy diet, which includes ample servings of fruits and vegetables and low–fat foods, is one way to lower your cholesterol. Regular exercise also helps. If these steps do not cause a drop in your cholesterol level, your doctor may recommend cholesterol–lowering medication.

    Table 2.  Stroke Prevention Steps

    If you smoke, stop. If you are unable to stop on your own, seek medical help.
    Know your blood pressure and have it checked regularly. If it is high, follow your doctor's advice to keep it at a normal level. High blood pressure is treatable, but not curable?stay on your medications.
    If you have atrial fibrillation, follow your doctor's advice about how to prevent the formation of new blood clots that can travel to your brain.
    If you drink, limit daily alcohol intake to no more than two beers or the equivalent.
    If you have high cholesterol, follow your doctor's recommendations about how to keep it under control.
    Exercise daily?just walking for half an hour daily is helpful.
    If you have a circulatory problem that increases your risk for stroke, follow your doctor's advice closely to treat the problem and to prevent blood clots from forming.
    If you have diabetes, follow your doctor's advice closely to keep your blood sugar normal.
    If you have heart disease, follow your doctor's advice about treating it and preventing new blood clots from forming.
  • Prevention and Screening

    If you smoke, cut back or quit Table 02. Your risk of stroke will decline significantly in two to four years after quitting, although it will take several decades for you to return to the risk level of someone who has never smoked.

    Do not use cocaine, crack cocaine, heroin, amphetamines, or other illicit drugs.

    If you have diabetes, regularly monitor your blood sugar level, follow your recommended diet, and use insulin as directed.

    Have your blood pressure checked regularly. If your blood pressure reading is consistently normal, you should be rechecked every two years. If your blood pressure is in the high to normal range, have it rechecked once a year. If you have been diagnosed with hypertension, follow your doctor's recommendations for rechecks. Depending on the situation, you may need to be rechecked anywhere from several days to two months after your previous evaluation.

    If your blood pressure is high, your doctor may recommend that you lose weight; a reduction of as little as 10 pounds can be beneficial. You should also exercise regularly; following a routine of 30 to 45 minutes of brisk walking several days a week is a good start. You should cut back on your sodium intake; however, the body's response to salt and its influence on blood pressure can vary significantly, so talk to your doctor about how much salt is best for you. You can also reduce your risk of high blood pressure and stroke by eating a healthy, balanced diet. Your doctor may also advise you to limit your alcohol intake.

    You can lower your risk of stroke by improving your cholesterol level. Eating a healthy diet, which includes ample servings of fruits and vegetables and low–fat foods, is one way to lower your cholesterol. Regular exercise also helps. If these steps do not cause a drop in your cholesterol level, your doctor may recommend cholesterol–lowering medication.

    Table 2.  Stroke Prevention Steps

    If you smoke, stop. If you are unable to stop on your own, seek medical help.
    Know your blood pressure and have it checked regularly. If it is high, follow your doctor's advice to keep it at a normal level. High blood pressure is treatable, but not curable?stay on your medications.
    If you have atrial fibrillation, follow your doctor's advice about how to prevent the formation of new blood clots that can travel to your brain.
    If you drink, limit daily alcohol intake to no more than two beers or the equivalent.
    If you have high cholesterol, follow your doctor's recommendations about how to keep it under control.
    Exercise daily?just walking for half an hour daily is helpful.
    If you have a circulatory problem that increases your risk for stroke, follow your doctor's advice closely to treat the problem and to prevent blood clots from forming.
    If you have diabetes, follow your doctor's advice closely to keep your blood sugar normal.
    If you have heart disease, follow your doctor's advice about treating it and preventing new blood clots from forming.

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