Ischemic stroke usually results when an artery to the brain is blocked, often by a blood clot and/or a fatty deposit due to atherosclerosis.
Symptoms occur suddenly and may include muscle weakness, paralysis, lost or abnormal sensation on one side of the body, difficulty speaking, confusion, problems with vision, dizziness, and loss of balance and coordination.
Diagnosis is usually based on symptoms and results of a physical examination and brain imaging.
Other imaging tests (computed tomography and magnetic resonance imaging) and blood tests are done to identify the cause of the stroke.
Treatment may include medications to break up blood clots or to make blood less likely to clot and procedures to physically remove blood clots, followed by rehabilitation.
About one third of people recover all or most of normal function after an ischemic stroke.
Preventive measures include control of risk factors, medications to make blood less likely to clot, and sometimes surgery or angioplasty to open blocked arteries.
(See also Overview of Stroke Overview of Stroke A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction). Symptoms occur suddenly... read more .)
Causes of Ischemic Stroke
An ischemic stroke typically results from blockage of an artery that supplies blood to the brain, most commonly a branch of one of the internal carotid arteries. As a result, brain cells are deprived of blood. Most brain cells die if they are deprived of blood for 4.5 hours.
Supplying the Brain With Blood
Blood is supplied to the brain through two pairs of large arteries:
In the skull, the vertebral arteries unite to form the basilar artery (at the back of the head). The internal carotid arteries and the basilar artery divide into several branches, including the cerebral arteries. Some branches join to form a circle of arteries (circle of Willis) that connect the vertebral and internal carotid arteries. Other arteries branch off from the circle of Willis like roads from a traffic circle. The branches carry blood to all parts of the brain.
When the large arteries that supply the brain are blocked, some people have no symptoms or have only a small stroke. But others with the same sort of blockage have a massive ischemic stroke. Why? Part of the explanation is collateral arteries. Collateral arteries run between other arteries, providing extra connections. These arteries include the circle of Willis and connections between the arteries that branch off from the circle. Some people are born with large collateral arteries, which can protect them from strokes. Then when one artery is blocked, blood flow continues through a collateral artery, sometimes preventing a stroke. Other people are born with small collateral arteries. Small collateral arteries may be unable to pass enough blood to the affected area, so a stroke results.
The body can also protect itself against strokes by growing new arteries. When blockages develop slowly and gradually (as occurs in atherosclerosis), new arteries may grow in time to keep the affected area of the brain supplied with blood and thus prevent a stroke. If a stroke has already occurred, growing new arteries can help prevent a second stroke (but cannot reverse damage that has been done).
Commonly, blockages are blood clots (thrombi) or pieces of fatty deposits (atheromas, or plaques) due to atherosclerosis Atherosclerosis Atherosclerosis is a condition in which patchy deposits of fatty material (atheromas or atherosclerotic plaques) develop in the walls of medium-sized and large arteries, leading to reduced or... read more . Such blockages often occur in the following ways:
By forming in and blocking an artery: An atheroma in the wall of an artery may continue to accumulate fatty material and become large enough to block the artery. Even if the artery is not completely blocked, the atheroma narrows the artery and slows blood flow through it, like a clogged pipe slows the flow of water. Slow-moving blood is more likely to clot. A large clot can block enough blood flowing through the narrowed artery that brain cells supplied by that artery die. Or if an atheroma splits open (ruptures), the material in it can trigger formation of a blood clot that can block the artery (see figure How Atherosclerosis Develops How Atherosclerosis Develops ).
By traveling from another artery to an artery in the brain: A piece of an atheroma or a blood clot in the wall of an artery can break off and travel through the bloodstream (becoming an embolus). The embolus may then lodge in an artery that supplies the brain and block blood flow there. (Embolism refers to blockage of arteries by materials that travel through the bloodstream to another part of the body.) Such blockages are more likely to occur where arteries are already narrowed by fatty deposits.
By traveling from the heart to the brain: Blood clots may form in the heart or on a heart valve, particularly artificial valves and valves that have been damaged by infection of the heart's lining (endocarditis Infective Endocarditis Infective endocarditis is an infection of the lining of the heart (endocardium) and usually also of the heart valves. Infective endocarditis occurs when bacteria enter the bloodstream and travel... read more ). These clots may break off and travel as emboli and block an artery to the brain. Strokes due to such blood clots are most common among people who have recently had heart surgery, who have had a heart attack, or who have a heart valve disorder or an abnormal heart rhythm (arrhythmia), especially a fast, irregular heart rhythm called atrial fibrillation Atrial Fibrillation and Atrial Flutter Atrial fibrillation and atrial flutter are very fast electrical discharge patterns that make the atria (upper chambers of the heart) contract very rapidly, with some of the electrical impulses... read more .
Clogs and Clots: Causes of Ischemic Stroke
When an artery that carries blood to the brain becomes clogged or blocked, an ischemic stroke can occur. Arteries may be blocked by fatty deposits (atheromas, or plaques) due to atherosclerosis. Arteries in the neck, particularly the internal carotid arteries, are a common site for atheromas.
Arteries may also be blocked by a blood clot (thrombus). Blood clots may form on an atheroma in an artery. Clots may also form in the heart of people with a heart disorder. Part of a clot may break off and travel through the bloodstream (becoming an embolus). It may then block an artery that supplies blood to the brain, such as one of the cerebral arteries.
Blood clots in a brain artery do not always cause a stroke. If the clot breaks up spontaneously within less than 15 to 30 minutes, brain cells do not die and people's symptoms resolve. Such events are called transient ischemic attacks Transient Ischemic Attacks (TIAs) A transient ischemic attack (TIA) is a disturbance in brain function that typically lasts less than 1 hour and results from a temporary blockage of the brain’s blood supply. The cause and symptoms... read more (TIAs).
If an artery narrows very gradually, other arteries (called collateral arteries—see figure Supplying the Brain With Blood Supplying the Brain With Blood ) sometimes enlarge to supply blood to the parts of the brain normally supplied by the clogged artery. Thus, if a clot occurs in an artery that has developed collateral arteries, people may not have symptoms.
The most common causes of ischemic stroke can be classified as
Large-vessel atherosclerosis (the 4th most common cause)
Stroke is classified as cryptogenic when no clear cause is identified despite a complete evaluation.
Blood clots can form in the heart, especially in people who have or have had the following:
Tiny pieces of these blood clots can break off and travel to small arteries in the brain (as emboli).
Lacunar infarction refers to tiny ischemic strokes, typically no larger than about a third of an inch (1 centimeter). In lacunar infarction, one of the small arteries deep in the brain becomes blocked when part of its wall deteriorates and is replaced by a mixture of fat and connective tissue—a disorder called lipohyalinosis. Lipohyalinosis is different from atherosclerosis, but both disorders can cause arteries to be blocked.
Lacunar infarction can also occur when tiny pieces of fatty material that has been deposited in arteries (atheromas or atherosclerotic plaques Plaque formation Atherosclerosis is a condition in which patchy deposits of fatty material (atheromas or atherosclerotic plaques) develop in the walls of medium-sized and large arteries, leading to reduced or... read more ) break off and travel to small arteries in the brain.
Lacunar infarction tends to occur in older people with diabetes or poorly controlled high blood pressure. Only a small part of the brain is damaged in lacunar infarction, and the prognosis is usually good. However, over time, many small lacunar infarcts may develop and cause problems, including problems with thinking and other mental functions (cognitive impairment).
In large-vessel atherosclerosis Atherosclerosis Atherosclerosis is a condition in which patchy deposits of fatty material (atheromas or atherosclerotic plaques) develop in the walls of medium-sized and large arteries, leading to reduced or... read more , atherosclerotic plaques develop in the walls of large arteries, such as those that supply the brain (cerebral arteries).
The plaques can gradually enlarge and cause the artery to narrow. As a result, tissues supplied by the artery may not receive enough blood and oxygen. Plaques tend to split open (rupture). Then material inside the plaque is exposed to the bloodstream. The material triggers the formation of blood clots (called thromboses). These blood clots can suddenly block all blood flow through an artery. Sometimes the blood clots break off, travel through the bloodstream and block an artery that supplies blood to the brain (called emboli). Both thromboses and emboli can cause a stroke by blocking the blood supply to an area of the brain.
Several conditions besides rupture of an atheroma can trigger or promote the formation of blood clots, increasing the risk of blockage by a blood clot. They include the following:
Blood disorders: Some disorders, such as an excess of red blood cells (polycythemia Polycythemia Vera Polycythemia vera is a myeloproliferative neoplasm of the blood-producing cells of the bone marrow that results in overproduction of all types of blood cells. Polycythemia vera is due to mutations... read more ), antiphospholipid syndrome Antiphospholipid Syndrome Autoimmune disorders, including Graves disease, are more common among women, particularly pregnant women. The abnormal antibodies produced in autoimmune disorders can cross the placenta and... read more , and a high homocysteine level in the blood (hyperhomocysteinemia Symptoms Atherosclerosis is a condition in which patchy deposits of fatty material (atheromas or atherosclerotic plaques) develop in the walls of medium-sized and large arteries, leading to reduced or... read more ), make blood more likely to clot. In children, sickle cell disease Sickle Cell Disease Sickle cell disease is an inherited genetic abnormality of hemoglobin (the oxygen-carrying protein found in red blood cells) characterized by sickle (crescent)-shaped red blood cells and chronic... read more can cause ischemic stroke.
Oral contraceptives Oral Contraceptives Contraceptive hormones can be Taken by mouth (oral contraceptives) Inserted into the vagina (vaginal rings) Applied to the skin (patch) Implanted under the skin read more : Taking oral contraceptives, particularly those with a high estrogen dose, increases the risk of blood clots.
An ischemic stroke can also result from any disorder that reduces the amount of blood supplied to the brain. For example,
An ischemic stroke can occur if inflammation of blood vessels (vasculitis Overview of Vasculitis Vasculitic disorders are caused by inflammation of the blood vessels (vasculitis). Vasculitis can be triggered by certain infections or drugs or can occur for unknown reasons. People may have... read more ) or infection (such as herpes simplex Herpes Simplex Virus (HSV) Infections Herpes simplex virus infection causes recurring episodes of small, painful, fluid-filled blisters on the skin, mouth, lips (cold sores), eyes, or genitals. This very contagious viral infection... read more , meningitis Introduction to Meningitis Meningitis is inflammation of the layers of tissue that cover the brain and spinal cord (meninges) and of the fluid-filled space between the meninges (subarachnoid space). Meningitis can be... read more , or syphilis Syphilis Syphilis is a sexually transmitted infection caused by the bacteria Treponema pallidum. It can occur in three stages of symptoms, separated by periods of apparent good health. Syphilis... read more ) narrows blood vessels that supply the brain.
In atrial fibrillation Atrial Fibrillation and Atrial Flutter Atrial fibrillation and atrial flutter are very fast electrical discharge patterns that make the atria (upper chambers of the heart) contract very rapidly, with some of the electrical impulses... read more , the heart does not contract normally, and blood can stagnate and clot. A clot may break loose, then travel to an artery in the brain, and block it.
Sometimes the layers of the walls of an artery that carries blood to the brain (such as arteries in the neck) separate from each other (called dissection) and interfere with blood flow to the brain.
Migraine headaches or drugs such as cocaine and amphetamines can cause spasm of the arteries, which can narrow the arteries supplying the brain long enough to cause a stroke.
Rarely, a stroke results from a general decrease in blood flow, as occurs when people lose a lot of blood, become severely dehydrated, or have very low blood pressure. This type of stroke often occurs when arteries supplying the brain are narrowed but had not previously caused any symptoms and had not been detected.
Occasionally, an ischemic stroke occurs when blood flow to the brain is normal but the blood does not contain enough oxygen. Disorders that reduce the oxygen content of blood include a severe deficiency of red blood cells (anemia Overview of Anemia Anemia is a condition in which the number of red blood cells is low. Red blood cells contain hemoglobin, a protein that enables them to carry oxygen from the lungs and deliver it to all parts... read more ), suffocation, and carbon monoxide poisoning Carbon Monoxide Poisoning Carbon monoxide is a colorless, odorless gas that is produced when many materials are burned and can be toxic when breathed in large amounts Carbon monoxide poisoning is common. Symptoms may... read more . Usually, brain damage in such cases is widespread (diffuse), and coma results.
Sometimes a blood clot in a leg vein (deep venous thrombosis Deep Vein Thrombosis (DVT) Deep vein thrombosis is the formation of blood clots (thrombi) in the deep veins, usually in the legs. Blood clots may form in veins if the vein is injured, a disorder causes the blood to clot... read more ) or, rarely, small pieces of fat from the marrow of a broken leg bone move into the bloodstream. Usually, these blood clots and pieces of fat travel to the heart and block an artery in the lungs (called pulmonary embolism Pulmonary Embolism ). However, some people have an abnormal opening between the right and left upper chambers of the heart (called a patent foramen ovale). In such people, the blood clots and pieces of fat may go through the opening and thus bypass the lungs and enter the aorta (the largest artery in the body). If they travel to arteries in the brain, a stroke can result.
Some risk factors for ischemic stroke can be controlled or modified to some extent—for example, by treating the disorder that increases risk.
The major modifiable risk factors for ischemic stroke are
Narrowing (stenosis) of a carotid artery in the neck
Insulin resistance (an inadequate response to insulin), which occurs in type 2 diabetes
Obesity Obesity Obesity is excess body weight. Obesity is influenced by a combination of factors, which usually results in consuming more calories than the body needs. These factors may include physical inactivity... read more , particularly if the excess weight is around the abdomen
Consumption of too much alcohol
Lack of physical activity
Heart disorders that increase the risk of blood clots forming in the heart, breaking off, and traveling through the blood vessels as emboli (such a heart attack or Acute Coronary Syndromes (Heart Attack; Myocardial Infarction; Unstable Angina) Acute coronary syndromes result from a sudden blockage in a coronary artery. This blockage causes unstable angina or a heart attack (myocardial infarction), depending on the location and amount... read more an abnormal heart rhythm called atrial fibrillation Atrial Fibrillation and Atrial Flutter Atrial fibrillation and atrial flutter are very fast electrical discharge patterns that make the atria (upper chambers of the heart) contract very rapidly, with some of the electrical impulses... read more )
Infective endocarditis Infective Endocarditis Infective endocarditis is an infection of the lining of the heart (endocardium) and usually also of the heart valves. Infective endocarditis occurs when bacteria enter the bloodstream and travel... read more (infection of the heart's lining and usually of the heart valves)
Use of cocaine Cocaine Cocaine is an addictive stimulant drug made from leaves of the coca plant. Cocaine is a strong stimulant that increases alertness, causes euphoria, and makes people feel powerful. High doses... read more or amphetamines Amphetamines Amphetamines are stimulant drugs that are used to treat certain medical conditions but are also subject to abuse. Amphetamines increase alertness, enhance physical performance, and produce euphoria... read more
Use of estrogen therapy, including oral contraceptives
Risk factors that cannot be modified include
Having had a stroke previously
Having relatives who have had a stroke
Symptoms of Ischemic Stroke
Usually, symptoms of an ischemic stroke occur suddenly and are often most severe a few minutes after they start because most ischemic strokes begin suddenly, develop rapidly, and cause death of brain tissue within minutes to hours. Then, most strokes become stable, causing little or no further damage. Strokes that remain stable for 2 to 3 days are called completed strokes. Sudden blockage by an embolus is most likely to cause this kind of stroke.
In about 10 to 15% of strokes, damage continues to occur and symptoms continue to worsen for up to 2 days, as a steadily enlarging area of brain tissue dies. Such strokes are called evolving strokes. In some people, symptoms affect one arm, then spread to other areas on the same side of the body. The progression of symptoms and damage usually occurs in steps, interrupted by somewhat stable periods. During these periods, the area temporarily stops enlarging or some improvement occurs. Such strokes are usually due to the formation of clots in a narrowed artery.
Strokes caused by an embolus often occur during the day, and a headache may be the first symptom. Strokes caused by a blood clot in a narrowed artery often occur at night and are first noticed when the person wakes up.
Many different symptoms can occur, depending on which artery is blocked and thus which part of the brain is deprived of blood and oxygen (see Brain Dysfunction by Location Brain Dysfunction by Location Because different areas of the brain control specific functions, the location of brain damage determines the type of dysfunction that results. Which side of the brain is affected is also important... read more ).
When the arteries that branch from the internal carotid artery (which carry blood along the front of the neck to the brain) are affected, the following are most common:
Blindness in one eye
Loss of vision on either the left side or the right side of both eyes
Abnormal sensations, weakness, or paralysis in one arm or leg or on one side of the body
When the arteries that branch from the vertebral arteries (which carry blood along the back of the neck to the brain) are affected, the following are most common:
Generalized weakness on one or both sides of the body
Many other symptoms, such as difficulty speaking (for example, slurred speech), impaired consciousness (such as confusion), loss of coordination, and urinary incontinence, can occur.
Severe strokes may lead to stupor or coma Stupor and Coma Stupor is unresponsiveness from which a person can be aroused only by vigorous, physical stimulation. Coma is unresponsiveness from which a person cannot be aroused and in which the person's... read more . In addition, strokes, even milder ones, can cause depression or an inability to control emotions. For example, people may cry or laugh inappropriately.
Some people have a seizure Seizure Disorders In seizure disorders, the brain's electrical activity is periodically disturbed, resulting in some degree of temporary brain dysfunction. Many people have unusual sensations just before a seizure... read more when the stroke begins. Seizures may also occur months to years later. Late seizures result from scarring or materials that are deposited from blood in the damaged brain tissue.
Occasionally, fever develops. It may be caused by the stroke or another disorder.
If symptoms, particularly impaired consciousness, worsen during the first 2 to 3 days, the cause is often swelling due to excess fluid (edema) in the brain. In large strokes, the swelling in the brain is typically at its worst about 3 days after the stroke begins. Symptoms usually lessen within a few days, as the fluid is absorbed. Nonetheless, the swelling is particularly dangerous because the skull does not expand. The resulting increase in pressure can cause the brain to shift, further impairing brain function, even if the area directly damaged by the stroke does not enlarge. If the pressure becomes very high, the brain may be forced sideways and downward in the skull, through the rigid structures that separate the brain into compartments. The resulting disorder is called herniation Herniation: The Brain Under Pressure , which can be fatal.
Complications of stroke
Strokes can lead to other problems (complications):
If swallowing is difficult, people may not eat enough and become malnourished and dehydrated.
Food, saliva, or vomit may be inhaled (aspirated) into the lungs, resulting in aspiration pneumonia Aspiration Pneumonia and Chemical Pneumonitis Aspiration pneumonia is lung infection caused by inhaling mouth secretions, stomach contents, or both. Chemical pneumonitis is lung irritation caused by inhalation of substances irritating or... read more .
Being in one position too long can result in pressure sores Pressure Sores Pressure sores are areas of skin damage resulting from a lack of blood flow due to prolonged pressure. Pressure sores often result from pressure combined with pulling on the skin, friction,... read more and lead to muscle loss, deconditioning, urinary tract infections, and permanent shortening of muscles (contractures).
Not being able to move the legs can result in the formation of blood clots in deep veins of the legs and groin (deep vein thrombosis Deep Vein Thrombosis (DVT) Deep vein thrombosis is the formation of blood clots (thrombi) in the deep veins, usually in the legs. Blood clots may form in veins if the vein is injured, a disorder causes the blood to clot... read more ).
Clots in the deep veins of the legs can break off, travel through the bloodstream, and block an artery to a lung (a disorder called pulmonary embolism Pulmonary Embolism (PE) Pulmonary embolism is the blocking of an artery of the lung (pulmonary artery) by a collection of solid material brought through the bloodstream (embolus)—usually a blood clot (thrombus) or... read more ).
People may have difficulty sleeping.
The losses and problems resulting from the stroke may make people depressed.
Diagnosis of Ischemic Stroke
A doctor's evaluation
Computed tomography and sometimes magnetic resonance imaging
Laboratory tests, including those to measure blood sugar
Doctors can usually diagnose an ischemic stroke based on the history of events and results of a physical examination. Doctors can usually identify which artery in the brain is blocked based on symptoms. For example, weakness or paralysis of the left leg suggests blockage of the artery supplying the area on the right side of the brain that controls the left leg’s muscle movements.
Doctors often use a standardized set of questions and commands to determine how severe the stroke is, how well people are functioning, and how symptoms are changing over time. These test helps doctors evaluate the person's level of consciousness, ability to answer questions, ability to obey simple commands, vision, arm and leg function, and speech.
When Specific Areas of the Brain Are Damaged
Different areas of the brain control specific functions. Consequently, where the brain is damaged determines which function is lost.
Doctors measure the blood sugar level. A low blood sugar level (hypoglycemia Hypoglycemia Hypoglycemia is abnormally low levels of sugar (glucose) in the blood. Hypoglycemia is most often caused by medications taken to control diabetes. Much less common causes of hypoglycemia include... read more ) can cause similar symptoms.
Computed tomography (CT) is usually done next. CT helps distinguish an ischemic stroke from a hemorrhagic stroke, a brain tumor, an abscess, and other structural abnormalities. However, during the first hours after some strokes, the CT scan may be normal or show only subtle changes. As a result, diagnosis may be delayed. So if available, diffusion-weighted magnetic resonance imaging Diffusion-weighted MRI In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (MRI), which can detect ischemic strokes within minutes of their start, may be done next.
As soon as possible, doctors may also do other imaging tests (CT angiography CT angiography In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more or magnetic resonance angiography Magnetic resonance angiography (MRA) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more ) to check for blockages in large arteries. Prompt treatment of these blockages can sometimes limit the amount of brain damage caused by the stroke.
Tests to identify the cause
Identifying the precise cause of an ischemic stroke is important. If the blockage is a blood clot, another stroke may occur unless the underlying disorder is corrected. For example, if blood clots result from an abnormal heart rhythm, treating that disorder can prevent new clots from forming and causing another stroke.
Tests for causes may include the following:
Continuous ECG monitoring Continuous Ambulatory Electrocardiography A standard electrocardiograph (ECG) records the heart's electrical activity for only a few seconds. This can detect abnormalities that are constant; however, sometimes abnormal heart rhythms... read more (done at home or in the hospital) to record the heart rate and rhythm continuously for 24 hours (or more), which may detect abnormal heart rhythms that occur unpredictably or briefly
Echocardiography Echocardiography and Other Ultrasound Procedures Ultrasonography uses high-frequency (ultrasound) waves bounced off internal structures to produce a moving image. It uses no x-rays. Ultrasonography of the heart (echocardiography) is one of... read more to check the heart for blood clots, pumping or structural abnormalities, and valve disorders
Imaging tests— color Doppler ultrasonography Color Doppler ultrasonography Ultrasonography uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. A device called a transducer converts electrical current into sound waves... read more , magnetic resonance angiography Magnetic resonance angiography (MRA) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more , CT angiography CT angiography In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more (CT done after a contrast agent is injected into a vein), or cerebral angiography Angiography In angiography, x-rays are used to produce detailed images of blood vessels. It is sometimes called conventional angiography to distinguish it from computed tomography (CT) angiography and magnetic... read more (done using a catheter inserted into an artery to inject the contrast agent)—to determine whether arteries, especially the internal carotid arteries, are blocked or narrowed
Blood tests to check for anemia Overview of Anemia Anemia is a condition in which the number of red blood cells is low. Red blood cells contain hemoglobin, a protein that enables them to carry oxygen from the lungs and deliver it to all parts... read more , polycythemia Polycythemia Vera Polycythemia vera is a myeloproliferative neoplasm of the blood-producing cells of the bone marrow that results in overproduction of all types of blood cells. Polycythemia vera is due to mutations... read more , blood clotting disorders Overview of Blood Clotting Disorders Blood clots help stop bleeding. Blood clotting (coagulation) disorders are dysfunctions in the body's ability to control the formation of blood clots. These dysfunctions may result in Too little... read more , vasculitis Overview of Vasculitis Vasculitic disorders are caused by inflammation of the blood vessels (vasculitis). Vasculitis can be triggered by certain infections or drugs or can occur for unknown reasons. People may have... read more , and some infections (such as heart valve infections Infective Endocarditis Infective endocarditis is an infection of the lining of the heart (endocardium) and usually also of the heart valves. Infective endocarditis occurs when bacteria enter the bloodstream and travel... read more and syphilis Syphilis Syphilis is a sexually transmitted infection caused by the bacteria Treponema pallidum. It can occur in three stages of symptoms, separated by periods of apparent good health. Syphilis... read more ) and for risk factors such as high cholesterol levels or diabetes
Urine drug screen for cocaine and amphetamines
Imaging tests enable doctors to determine how narrowed the carotid arteries are and thus to estimate the risk of a subsequent stroke or transient ischemic attack Transient Ischemic Attacks (TIAs) A transient ischemic attack (TIA) is a disturbance in brain function that typically lasts less than 1 hour and results from a temporary blockage of the brain’s blood supply. The cause and symptoms... read more (TIA). Such information helps determine which treatments are needed.
For cerebral angiography, a thin, flexible tube (catheter) is inserted into an artery, usually in the groin, and threaded through the aorta to an artery in the neck. Then, a substance that can be seen on x-rays (radiopaque contrast agent) is injected to outline the artery. Thus, this test is more invasive than other tests that provide images of the brain’s blood supply. However, it provides more information. Cerebral angiography is done before any endovascular procedure that uses a catheter to treat a blocked or narrowed arteries. Cerebral angiography is also done when vasculitis Overview of Vasculitis Vasculitic disorders are caused by inflammation of the blood vessels (vasculitis). Vasculitis can be triggered by certain infections or drugs or can occur for unknown reasons. People may have... read more is suspected.
Because CT angiography is less invasive, it has largely replaced cerebral angiography done with a catheter. The exceptions are when endovascular procedures are planned. These procedures involve using instruments threaded through a catheter to physically remove a clot (mechanical thrombectomy Mechanical thrombectomy An ischemic stroke is death of an area of brain tissue (cerebral infarction) resulting from an inadequate supply of blood and oxygen to the brain due to blockage of an artery. Ischemic stroke... read more ), to widen a narrowed artery (angioplasty), and/or to place a tube made of wire mesh (a stent) to keep the artery open.
Treatment of Ischemic Stroke
Measures to support vital functions, such as breathing
Medications to break up blood clots or make blood less likely to clot
Sometimes surgery to remove a blockage or angioplasty with a stent
Measures to manage problems that stroke can cause, such as difficulty swallowing
Measures to prevent blood clots in the legs
When a stroke occurs, minutes matter. The longer blood flow to the brain is reduced or stopped, the more brain damage there will be. People who have any symptom suggesting an ischemic stroke should immediately call 911 and go to an emergency department.
Treatment to remove or break up clots is most effective when done as soon as possible. For some medications (thrombolytic therapy) to be effective, they must be started within 4.5 hours of when the stroke began. Procedures to remove clots through a catheter (mechanical thrombectomy) can be effective up to 6 hours after a stroke began and sometimes even later. Starting treatment as soon as possible is crucial because the earlier blood flow is restored to the brain, the less brain damage there is and the better are the chances for recovery. Thus, doctors try to rapidly determine when the stroke began and confirm that the stroke is an ischemic stroke, not a hemorrhagic stroke, which is treated differently.
Another priority is to restore the person’s breathing, heart rate, blood pressure (if low), and temperature to normal. An intravenous line is inserted to provide medications and fluids when needed. If the person has a fever, it may be lowered using acetaminophen, ibuprofen, or a cooling blanket because brain damage is worse when body temperature is elevated.
Generally, doctors do not immediately treat high blood pressure Treatment High blood pressure (hypertension) is persistently high pressure in the arteries. Often no cause for high blood pressure can be identified, but sometimes it occurs as a result of an underlying... read more unless it is very high (over 220/120 mm Hg) because when arteries are narrowed, blood pressure must be higher than normal to push enough blood through them to the brain. However, very high blood pressure can injure the heart, kidneys, and eyes and must be lowered.
If a stroke is very severe and affects a large area of the brain, medications such as mannitol may be given to reduce swelling and the increased pressure in the brain. Some people need a ventilator to breathe adequately.
Specific treatment of stroke may include medications to break up blood clots (thrombolytic therapy) and medications to make blood less likely to clot (antiplatelet medications and anticoagulants), followed by rehabilitation. At some specialized centers, blood clots are physically removed from arteries in the brain (mechanical thrombectomy). Or angioplasty Carotid artery angioplasty and stenting An ischemic stroke is death of an area of brain tissue (cerebral infarction) resulting from an inadequate supply of blood and oxygen to the brain due to blockage of an artery. Ischemic stroke... read more is done to widen the artery. For angioplasty, a catheter with a balloon at its tip is threaded into the narrowed artery (see figure ). The balloon is then inflated for several seconds to widen the artery. To keep the artery open, doctors insert a tube made of wire mesh (a stent) into the artery.
Thrombolytic (fibrinolytic) medications
In certain circumstances, a medication called tissue plasminogen activator (tPA) is given intravenously to break up clots and help restore blood flow to the brain. Two tPAs are available: alteplase and tenecteplase.
Because tPA can cause bleeding in the brain and elsewhere, it usually should not be given to people with certain conditions, such as the following:
Bleeding within the brain or a very large area of dead brain tissue detected by CT or MRI
A suspected hemorrhagic stroke Overview of Hemorrhagic Stroke Hemorrhagic strokes include bleeding within the brain (intracerebral hemorrhage) and bleeding between the inner and outer layers of the tissue covering the brain (subarachnoid hemorrhage). ... read more , even if CT does not detect evidence of one
A tendency to bleed (indicated by a low platelet count or abnormal results of other blood tests)
Internal bleeding (hemorrhage)
A brain disorder that may increase the risk of bleeding, such as some cancers, an arteriovenous malformation Brain Arteriovenous Malformations (AVMs) An arteriovenous malformation is a tangle of dilated blood vessels that directly connect arteries and veins, bypassing the capillaries (which normally connect arteries and veins). Brain arteriovenous... read more (an abnormal connection between arteries and veins), or a cerebral aneurysm Brain Aneurysms An aneurysm is a bulge (dilation) in the wall of an artery. Aneurysms that occur in the arteries of the brain (cerebral arteries) are called cerebral aneurysms. Aneurysms may occur in any artery... read more (a bulge in the wall of an artery)
Blood pressure that remains high after treatment with an antihypertensive medication
Brain or spinal surgery within the past 3 months
A tendency to bleed or bruise easily
Before tPA is given, CT is done to rule out bleeding in the brain. To be effective and safe, tPA, given intravenously, must be started within 3 hours of the beginning of an ischemic stroke. Some experts recommend using tPA up to 4.5 hours after an ischemic stroke begins.
But when tPA is given between 3 and 4.5 hours, additional conditions may prohibit its use. These conditions include
Being over age 80
Taking an anticoagulant by mouth (regardless of its effect on clotting)
Having a severe stroke that resulted in substantial loss of function
Having a history of both stroke and diabetes mellitus
After 4.5 hours, giving tPA intravenously increases the risk of bleeding.
Pinpointing when the stroke began may be difficult. So doctors assume that the stroke began the last time a person was known to be well. For example, if a person awakens with symptoms of a stroke, doctors assume the stroke began when the person was last seen awake and well. Thus, tPA can be used in only some people who have had a stroke. If advanced imaging identifies undamaged brain tissue, people may be given tPA even if doctors cannot determine when the stroke began—for example, if people wake up and have had a stroke sometime during the night.
For mechanical thrombectomy, doctors use a device to physically remove the blood clot in large cerebral arteries. This procedure is often done when people have had a severe stroke. New evidence suggests that mechanical thrombectomy can effectively treat people who have a stroke, regardless of its severity.
Mechanical thrombectomy is traditionally done within 6 hours of when symptoms began. However, the procedure can be done up to 24 hours after symptoms began if imaging tests show undamaged brain tissue. Thus, at some stroke centers, doctors are starting to use a special type of CT or MRI (perfusion imaging Perfusion MRI In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more ) and other imaging tests to determine how much a stroke has progressed, rather than going strictly by time. These tests can show how much blood flow has been reduced and indicate how much brain tissue may be saved. This approach (based on brain tissue status, not time) is especially useful when doctors are unsure of when the stroke began—for example, when people wake up in the morning and have symptoms of a stroke. If imaging tests show that blood flow is only somewhat reduced, treatment with mechanical thrombectomy up to 24 hours after symptoms start may still be able to save brain tissue. But if blood flow has been greatly reduced or has stopped, treatment after only 1 hour may be unable to save any brain tissue.
Different types of devices can be used. For example, the stent retriever may be used. It resembles a tiny wire cage. It can be attached to a catheter, which is inserted through an incision, often in the groin, and threaded to the clot. The cage is opened up, then closed around the clot, which is drawn out through a larger catheter. If done within 6 hours of the stroke's start, mechanical thrombectomy with a stent retriever can dramatically improve outcomes in people with a large blockage. Devices can restore blood flow in 90 to 100% of people.
Mechanical thrombectomy is done only in stroke centers.
Antiplatelet medications and anticoagulants
If a thrombolytic medication cannot be used, most people are given aspirin (an antiplatelet medication) as soon as they get to the hospital. Antiplatelet medications make platelets less likely to clump and form clots. (Platelets are tiny cell-like particles in the blood that help it clot in response to damaged blood vessels.) Taking aspirin plus clopidogrel (another antiplatelet medication) is slightly more effective than aspirin alone for reducing the risk of another stroke, but only if given within 24 hours after stroke symptoms began. It is given only for first 3 weeks after the stroke and reduces the risk of recurrence only for the first 3 months after a stroke. After that, the combination has no advantage over aspirin alone. Also, taking clopidogrel plus aspirin for more than 3 weeks increases the risk of bleeding by a small amount. However, the combination is sometimes given for 3 months in certain circumstances—for example, when people have a partial blockage of a large artery.
If symptoms seem to be worsening despite other treatments, anticoagulants such as heparin and warfarin are used. They may also be used to treat specific types of strokes (such as those due to a blood clot in a vein in the brain, or atrial fibrillation, or dissection of an artery in the neck). Anticoagulants inhibit proteins in blood that help it to clot (clotting factors).
If people have been given a thrombolytic medication, doctors usually wait at least 24 hours before antiplatelet medications or anticoagulants are started because these medications add to the already increased risk of bleeding in the brain. Anticoagulants are not given to people who have uncontrolled high blood pressure or who have had a hemorrhagic stroke.
Carotid artery surgery
Once an ischemic stroke is completed, surgical removal of fatty deposits (atheromas, or plaques) due to atherosclerosis or clots in an internal carotid artery may be done (see figure ). This procedure, called carotid endarterectomy, can help if all of the following are present:
The stroke resulted from narrowing of a carotid artery by more than 70% (more than 60% in people who have been having transient ischemic attacks).
Some brain tissue supplied by the affected artery still functions after the stroke.
The person’s life expectancy is at least 5 years.
In such people, carotid endarterectomy may reduce the risk of subsequent strokes. This procedure also reestablishes the blood supply to the affected area, but it cannot restore lost function because some brain tissue is dead.
For carotid endarterectomy, a general anesthetic is used. The surgeon makes an incision in the neck over the area of the artery that contains the blockage, then an incision in the artery. The blockage is removed, and the incisions are closed. For a few days afterwards, the neck may hurt, and swallowing may be difficult. Most people stay in the hospital 1 or 2 days. Heavy lifting should be avoided for about 3 weeks. After several weeks, people can resume their usual activities.
Carotid endarterectomy can trigger a stroke because the operation may dislodge clots or other material that can then travel through the bloodstream and block an artery. However, after the operation, the risk of stroke is lower than it is when medications are used, and this risk is lower for several years. The procedure can result in a heart attack because people who have this procedure often have risk factors for coronary artery disease Overview of Coronary Artery Disease (CAD) Coronary artery disease is a condition in which the blood supply to the heart muscle is partially or completely blocked. The heart muscle needs a constant supply of oxygen-rich blood. The coronary... read more .
People should find a surgeon who is experienced doing this operation and who has a low rate of serious complications (such as heart attack, stroke, and death) after the operation. If people cannot find such a surgeon, the risks of endarterectomy may outweigh its expected benefits.
Carotid artery angioplasty and stenting
If endarterectomy is too risky or cannot be done because of the artery's anatomy, a less invasive procedure (carotid artery angioplasty) can be done to widen the artery.
For this procedure, a local anesthetic is given. Then a catheter with an umbrella filter at its tip is inserted through a small incision into a large artery near the groin or in the arm, and the catheter is threaded to the internal carotid artery in the neck. A substance that can be seen on x-rays (radiopaque contrast agent) is injected, and x-rays are taken so that the narrowed area can be located. Doctors use the catheter to widen the carotid artery, then insert a tube made of wire mesh (a stent) into the artery. Once in place, the stent is expanded to help keep the artery open. The filter catches any debris that may break off during the procedure.
After the stent is placed, the catheter and the filter at its tip are removed. People remain awake for the procedure, which usually takes 1 to 2 hours.
Placement of a stent appears to be as safe and as effective in preventing strokes and death as endarterectomy Carotid artery surgery An ischemic stroke is death of an area of brain tissue (cerebral infarction) resulting from an inadequate supply of blood and oxygen to the brain due to blockage of an artery. Ischemic stroke... read more . For younger people and people who do not have risk factors for heart or blood vessel disorders (such as high blood pressure High Blood Pressure High blood pressure (hypertension) is persistently high pressure in the arteries. Often no cause for high blood pressure can be identified, but sometimes it occurs as a result of an underlying... read more , high cholesterol levels Dyslipidemia Dyslipidemia is a high level of cholesterol and/or triglycerides or a low level of high-density lipoprotein (HDL) cholesterol. Lifestyle, genetics, disorders (such as low thyroid hormone levels... read more , diabetes Diabetes Mellitus (DM) Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more , and smoking Smoking Smoking tobacco is harmful to almost every organ in the body. Smoking increases the risk of heart attack, lung cancer, chronic obstructive pulmonary disease (COPD), and other disorders. Nicotine... read more ), carotid endarterectomy is usually done.
A similar procedure can be done for other types of large blocked arteries (see figure ).
Long-term treatment of strokes
Long-term treatment of stroke includes measures to do the following:
Control problems that can make the effects of stroke worse
Prevent or treat problems caused by strokes
Prevent future strokes
Treat any disorders that are also present
During the recovery period, high blood sugar (hyperglycemia) and fever can make brain damage worse after a stroke. Lowering them limits the damage and results in better functioning.
Before people who have had a stroke start to eat, drink, or take medications by mouth, they are checked for problems with swallowing. Problems with swallowing can lead to aspiration pneumonia Aspiration Pneumonia and Chemical Pneumonitis Aspiration pneumonia is lung infection caused by inhaling mouth secretions, stomach contents, or both. Chemical pneumonitis is lung irritation caused by inhalation of substances irritating or... read more . Measures to prevent this problem are started early. If problems are detected, a therapist can teach people how to swallow safely. Sometimes people need to be fed through a tube (tube feeding Tube Feeding Tube feeding may be used to feed people whose digestive tract is functioning normally but who cannot eat enough to meet their nutritional needs. Such people include those with the following... read more ).
If people cannot move on their own or have difficulty moving, they are at risk of developing blood clots in their legs (deep vein thrombosis Prevention Deep vein thrombosis is the formation of blood clots (thrombi) in the deep veins, usually in the legs. Blood clots may form in veins if the vein is injured, a disorder causes the blood to clot... read more ) and pressure sores Prevention Pressure sores are areas of skin damage resulting from a lack of blood flow due to prolonged pressure. Pressure sores often result from pressure combined with pulling on the skin, friction,... read more . Pneumatic compression stockings may be used to prevent blood clots. Powered by an electric pump, these stockings repeatedly squeeze the calves and move blood into and through the veins. People at high risk of developing blood clots may also be given an anticoagulant (such as heparin), injected under the skin of the abdomen or arm. Often, an anticoagulant is given by mouth.
Measures to prevent pressure sores Prevention Pressure sores are areas of skin damage resulting from a lack of blood flow due to prolonged pressure. Pressure sores often result from pressure combined with pulling on the skin, friction,... read more are started early. For example, staff members periodically change the person's position in bed to help prevent pressure sores from forming. They also regularly inspect the skin for any sign of pressure sores.
Controlling or treating risk factors for stroke (such as high blood pressure, diabetes, smoking, consumption of too much alcohol, high cholesterol levels, and obesity) can help prevent future strokes.
Statins Lipid-lowering drugs Dyslipidemia is a high level of cholesterol and/or triglycerides or a low level of high-density lipoprotein (HDL) cholesterol. Lifestyle, genetics, disorders (such as low thyroid hormone levels... read more (such as atorvastatin) are medications that lower levels of cholesterol and other fats (lipids). They are often given when strokes result from the buildup of fatty deposits in an artery (atherosclerosis Atherosclerosis Atherosclerosis is a condition in which patchy deposits of fatty material (atheromas or atherosclerotic plaques) develop in the walls of medium-sized and large arteries, leading to reduced or... read more ). Such therapy can help prevent strokes from recurring.
Antiplatelet medications, taken by mouth, may be used to reduce the risk of blood clots and thus help prevent strokes due to atherosclerosis. One of the following can be used:
A combination tablet of low-dose aspirin plus dipyridamole
Clopidogrel plus aspirin
Clopidogrel is indicated for people who are allergic to aspirin.
Taking clopidogrel plus aspirin appears to reduce the risk of future strokes more than taking aspirin alone, but only for the first 3 months after a stroke. After that, the combination has no advantage over aspirin alone. Also, taking clopidogrel plus aspirin for a long time increases the risk of bleeding by a small amount. Usually, antiplatelet medications are not given to people who are taking warfarin because antiplatelet medications add to the risk of bleeding, but, occasionally, there are exceptions.
Anticoagulants (such as warfarin), taken by mouth, may be used to prevent strokes due to blood clots. When people are taking warfarin, blood tests are done regularly to measure how long it takes for blood to clot. Regular testing is needed to make sure the dose of warfarin is not too high. If the dose is too high, the risk of bleeding is increased.
Dabigatran, apixaban, and rivaroxaban are newer anticoagulants that are often used instead of warfarin. These newer anticoagulants are more convenient to use because they, unlike warfarin, do not require regular monitoring with blood tests to measure how long it takes for blood to clot. Also, they are not affected by foods and are unlikely to interact with other medications. But the new anticoagulants have some disadvantages. Dabigatran and apixaban must be taken twice a day (warfarin is taken once a day). Also, people must not miss any doses of the newer medications for the medications to be effective. Also, these medications are significantly more expensive than warfarin.
People who have atrial fibrillation Atrial Fibrillation and Atrial Flutter Atrial fibrillation and atrial flutter are very fast electrical discharge patterns that make the atria (upper chambers of the heart) contract very rapidly, with some of the electrical impulses... read more or a heart valve disorder Overview of Heart Valve Disorders Heart valves regulate the flow of blood through the heart's four chambers—two small, round upper chambers (atria) and two larger, cone-shaped lower chambers (ventricles). Each ventricle has... read more are given anticoagulants (such as warfarin) instead of antiplatelet medications, which do not seem to prevent blood clots from forming in the heart.
Occasionally, people at high risk of another stroke (such as people who have had a minor stroke) are given aspirin plus an anticoagulant.
If other disorders such as heart failure Heart Failure (HF) Heart failure is a disorder in which the heart is unable to keep up with the demands of the body, leading to reduced blood flow, back-up (congestion) of blood in the veins and lungs, and/or... read more , abnormal heart rhythms, Overview of Abnormal Heart Rhythms Abnormal heart rhythms (arrhythmias) are sequences of heartbeats that are irregular, too fast, too slow, or conducted via an abnormal electrical pathway through the heart. Heart disorders are... read more and lung infections are present, they must be treated.
Because a stroke often causes mood changes, especially depression Depression Depression is a feeling of sadness and/or a decreased interest or pleasure in activities that becomes a disorder when it is intense enough to interfere with functioning. It may follow a recent... read more , family members or friends should inform the doctor if the person seems depressed. Depression can be treated with antidepressants Drug therapy for depression Depression is a feeling of sadness and/or a decreased interest or pleasure in activities that becomes a disorder when it is intense enough to interfere with functioning. It may follow a recent... read more and psychotherapy Psychotherapy Depression is a feeling of sadness and/or a decreased interest or pleasure in activities that becomes a disorder when it is intense enough to interfere with functioning. It may follow a recent... read more .
Prognosis for Ischemic Stroke
The sooner a stroke is treated with a medication that breaks up blood clots (thrombolytic medication), the less severe brain damage is likely to be and the better the chances for recovery.
During the first few days after an ischemic stroke, doctors usually cannot predict whether a person will improve or worsen. Younger people and people who start improving quickly are likely to recover more fully.
About 50% of people with one-sided paralysis and most of those with less severe symptoms recover some function by the time they leave the hospital, and they can eventually take care of their basic needs. They can think clearly and walk adequately, although use of the affected arm or leg may be limited. Use of an arm is more often limited than use of a leg.
About 10% of people who have an ischemic stroke recover all normal function.
Some people are physically and mentally devastated and unable to move, speak, or eat normally.
About 20% of people who have an ischemic stroke die within 28 days. The proportion is higher among older people. About 25% of people who recover from a first stroke have another stroke within 5 years. Subsequent strokes impair function further.
Most impairments still present after 12 months are permanent.