WHAT IS A STROKE?
The Basic Process
Blood Flow Blockage. The brain receives about 25% of the body’s oxygen, but it cannot store it. Brain cells require a constant supply of oxygen to stay healthy and function properly. Therefore, blood needs to be supplied to the brain continuously through two main arterial systems:
- The carotid arteries come up through either side of the front of the neck. (The pulse of a carotid artery can be felt by placing the fingertips gently against either side of the neck right under the jaw.)
- The basilar artery forms at the base of the skull from the vertebral arteries, which run up along the spine, join, and come up through the rear of the neck.
- A reduction of, or disruption in, blood flow to the brain is the primary cause of a stroke. Blockage for even a short period of time can be disastrous and cause brain damage or even death.
- A stroke is usually defined as two types:
- Ischemic (caused by a blockage in an artery).
- Hemorrhagic (caused by a tear in the artery’s wall that produces bleeding in the brain).
The consequences of a stroke, the type of functions affected, and the severity, depend on where in the brain it has occurred and the extent of the damage.
Cell Death. In addition to oxygen cut-off to the brain, other factors are involved in the cycle of events leading to brain cell death after a stroke. The process is not altogether clear, but one hypothesis is as follows:
- When blood is cut off in the brain, proteins known as excitatory amino acids (such as glutamate and glycine) are released. These amino acids literally excite nerve cells and, when over produced, can kill them.
- These proteins open channels in the membranes that cover neurons (brain cells), allowing large amounts of calcium to flow in.
- Calcium reacts within the neurons to release harmful substances that damage cells.
Natural particles released by the body’s chemical processes, called oxygen-free radicals, may also play a role in the cell damage caused by a stroke. (Some oxygen-free radicals under study are called lipid peroxides.)
Another hypothesis focuses on an enzyme called PARP:
- PARP ordinarily makes minor molecular repairs.
- Confronted with substantial injury, however, PARP over-responds and takes up a substance called ATP, the major source of energy in cells.
- The cells die.
- Within minutes of a stroke, the zone of initial cell death is surrounded by additional damaged and dying brain cells. This process can continue for hours, leading to brain damage, perhaps irreversible.
Ischemic strokes are by far the more common type, causing over 80% of all strokes. Ischemia means the deficiency of oxygen in vital tissues. Ischemic strokes are caused by blood clots that are usually one of three types:
- Thrombotic stroke.
- Embolic stroke.
- Lacunar stroke.
Thrombotic or Large-Artery Stroke and Atherosclerosis. A thromboticstroke usually occurs when an artery to the brain is blocked by a blood clot (a thrombi) that forms as the result of atherosclerosis, commonly known as hardening of the arteries. These strokes are also sometimes referred to as large-artery strokes. They account for about 60% of all strokes. The process leading to thrombotic stroke is complex and occurs over time:
- The arterial walls slowly thicken, harden, and narrow until blood flow is reduced, a condition known as stenosis.
- These now abnormal arteries become vulnerable to injury. This initiates a process called the inflammatory response , which may play a significant role in the stroke.
- The injuries to the arteries signal the immune system to release white blood cells (particularly those called neutrophils andmacrophages) at the site.
- Macrophages literally “eat” foreign debris and become foamy cells that attach to smooth muscle cells of blood vessels causing them to build up.
- The immune system, sensing further harm, releases other factors called cytokines, which attract more white blood cells and perpetuate the whole cycle.
- As these processes continue, blood flow slows.
- In addition, injured inner walls fail to produce enough nitric oxide, a substance critical for maintaining blood vessel elasticity. The arteries become calcified and lose elasticity.
- The hardened and rigid arteries are even more susceptible to injury. If they tear, a blood clot, or thrombus, may form.
- The blood clot then completely blocks the already narrowed artery and shuts off oxygen to part of the brain. A stroke occurs.
Embolic Strokes and Atrial Fibrillation. An embolic stroke is usually caused by a dislodged blood clot that has traveled through the blood vessels (an embolus) until it becomes wedged in an artery. Embolic strokes account for about 25% of all strokes and may be due to various conditions:
- In about 15% of embolic strokes, the blood clots originally form as a result of a rhythm disorder known as atrial fibrillation : This abnormal rhythm is a rapid quivering beat in the upper chambers of the heart (the atria). Because of the irregular pumping, some blood may remain in the heart chamber where it forms clots, which can then break off and travel to the brain as emboli.
- Emboli can originate from blood clots that form at the site of artificial heart valves or as a result of heart valve disorders.
- Emboli can also occur after a heart attack or in association with heart failure.
- Rarely, emboli are formed from fat particles, tumor cells, or air bubbles that travel through the blood stream.
Lacunar Strokes. Lacunar infarcts are a series of very tiny, ischemic strokes, which cause clumsiness, weakness, and emotional variability. They are actually a subtype of thrombotic stroke and constitute about 38% of this major group. In some populations, such as among Japanese, they are the most common stroke subtype. They can also sometimes serve as warning signs for a major stroke.
Over 15% of strokes occur from hemorrhage (sudden bleeding) in the brain. In a healthy brain, brain cells called neurons are protected from exposure to blood by the blood-brain barrier , a wall of tiny vessels and structural cells. In a hemorrhagic stroke, however, this barrier is broken.
Hemorrhagic strokes may be categorized by how and where they occur.
- Parenchymal, or cerebral, hemorrhage strokes. These strokes occur within the brain and account for about 10% of all strokes. They are most often the result of hypertension exerting excessive pressure on arterial walls already damaged by atherosclerosis. Heart attack patients who have been given drugs to break up blood clots or blood-thinning drugs have a slightly elevated risk of this type of stroke.
- Subarachnoid hemorrhagic strokes . This other major hemorrhagic stroke accounts for about 5% of all strokes. They occur when a blood vessel on the surface of the brain bursts, and blood leaks into the subarachnoid space , an area between the brain and the skull. They are usually caused by the rupture of an aneurysm, a weakening in the blood vessel wall, which is often an inherited trait.
- Arteriovenous malformation (AVM) is an abnormal connection between arteries and veins. If it occurs in the brain and ruptures, it can also cause a hemorrhagic stroke.
Low Blood Pressure (Hypotension)
Less often, blood pressure that is too low can reduce oxygen supply to the brain and cause a stroke. This can occur from a heart attack, a major bleeding episode, an overwhelming infection, or rarely, from surgical anesthesia or from overtreatment of high blood pressure.
WHAT ARE THE SYMPTOMS OF A STROKE?
People at risk and partners or caretakers of people at risk for stroke should be aware of the general symptoms, and the stroke victim should get to the hospital as soon as after these warning signs appear. Discouragingly, a 2001 study reported that over 30% of patients with either a stroke or TIA who called their primary care physician were neither evaluated nor sent to the hospital within a month after the first event. It is particularly important for people with migraines or frequent severe headaches to understand how to distinguish between their usual headaches and symptoms of stroke.
Transient Ischemic Attacks (TIAs)
TIAs are mini-ischemic strokes, usually caused by tiny emboli (often formed of pieces of calcium and fatty plaque) that lodge in an artery to the brain. They typically break up quickly and dissolve but they do temporarily block the supply of blood to the brain. The mental or physical disturbances resulting from TIAs generally clear up in less than a day, with nearly all symptoms resolving in less than an hour. Because blood supply is quickly restored to the brain, there is no residual damage as there is in a full-blown stroke.
Transient ischemic attacks, however, are the warning signals of ischemic stroke, just as angina (chest pain caused by coronary artery disease) is the red flag for a heart attack. About 5% of those who experience TIAs go on to suffer a stroke within a month, and without treatment, a third will have strokes within five years. (Because of the relationship between atherosclerosis, coronary artery disease, and stroke, TIAs are also warning signs for a heart attack.)
One of two major arteries is usually involved in a transient ischemic attack, either the carotid or basilar arteries:
Symptoms of TIAs in the Carotid Arteries. The carotid arteries stem off of the aorta (the primary artery leading from the heart) and lead up through the neck around the windpipe and on into the brain. When TIAs occur from blockage in the carotid artery, which they often do, symptoms may occur in either the retina of the eye or the cerebral hemisphere (the large top part of the brain):
- When oxygen to the eye is reduced, people describe the visual effect as a shade being pulled down. People may develop poor night vision.
- When the cerebral hemisphere is affected by a TIA, a person can experience problems with speech and partial and temporary paralysis, tingling, and numbness, usually on one side of the body.
Symptoms of TIAs in the Basilar Artery. The other major site of trouble, the basilar artery, is formed at the base of the skull from the vertebral arteries, which run up along the spine and join at the back of the head. When TIAs occur here, both hemispheres of the brain may be affected so that symptoms occur on both sides of the body. Some include the following:
- Temporarily dim, gray, blurry, or lost vision in both eyes.
- Tingling or numbness in the mouth, cheeks, or gums.
- Headache in the back of the head.
- Nausea and vomiting.
- Difficulty swallowing.
- Inability to speak clearly.
- Weakness in the arms and legs, sometimes causing a sudden fall.
Symptoms of Major Ischemic Stroke
Speed of Symptom Onset. The speed of symptom onset of a major ischemic stroke may indicate its source:
- If the stroke is caused by a large embolus (a clot that has traveled to an artery in the brain), the onset is sudden. Headache and seizures can occur within seconds of the blockage.
- When thrombosis (a blood clot that has formed within the brain) causes the stroke, the onset usually occurs more gradually, over minutes to hours. On rare occasions it progresses over days to weeks.
Symptoms. The symptoms for a major ischemic stroke are extremely variable:
- Early symptoms can be identical to those of a transient ischemic attack, since, in both cases, the clot can produce a blockage in a branch of the carotid or basilar arteries. (In the case of a TIA, however, the symptoms resolve.) [ See above. ]
- The blood clot usually affects the opposite side of the body from its location in the brain, with possible loss of feeling on one side of the face, in an arm or leg, or blindness in one eye.
- Speech problems can occur if the left hemisphere of the brain is involved. (In some people, mostly those who are left-handed, speech can be affected by a clot on the right side of the brain.) The stroke victim may be unable to express thoughts verbally or to understand spoken words.
- Patients may experience major seizures and possibly coma.
Symptoms of Hemorrhagic Stroke
Cerebral Hemorrhage Symptoms. Symptoms of a cerebral, or parenchymal, hemorrhage typically begin very suddenly and evolve over several hours and include:
- Nausea and vomiting.
- Altered mental states.
Subarachnoid Hemorrhage. When the hemorrhage is a subarachnoid type, warning signs may occur from the leaky blood vessel a few days to a month before the aneurysm fully develops and ruptures. Warning signs may include:
- Abrupt headaches.
- Nausea and vomiting.
- Sensitivity to light.
- Various neurologic abnormalities.
When the aneurysm ruptures, the stroke victim may experience the following:
- A terrible headache.
- Neck stiffness.
- Altered states of consciousness.
- The eyes may become fixed in one direction or lose vision.
- Stupor, rigidity, and coma.
Silent Brain Infarctions
As many as 31% of the elderly experience silent brain infarctions, which are small strokes that cause no apparent symptoms but are major contributors to mental impairment in the elderly. Smokers and people with hypertension are at particular risk.
WHAT ARE THE RISK FACTORS FOR A STROKE?
New or recurrent strokes affect about 600,000 people every year. Although incidence of stroke has increased between 1988 and 1998, more people are surviving stroke, and the death rate from this condition fell by about 15% during that period. While age is the major risk factor, in general, people with stroke are likely to have more than one risk factor.
Older Adults. People most at risk for stroke are older adults, particularly those with high blood pressure, who are sedentary, overweight, smoke, or have diabetes. Older age is also linked with higher rates of post-stroke dementia. In the older age groups, studies are mixed on the effects of stroke by gender.
Younger Adults. Younger people are not immune, however; about 28% of stroke victims are under 65. Strokes in younger people affect men and women equally.
Major studies have reported that ischemic strokes are more deadly in women than in men, regardless of ethnic groups. (A 2000 Canadian analysis of nearly 45,000 patient records, however, reported that among elderly stroke sufferers, women had a slight edge in survival a year after a stroke even though older men were more aggressively treated.) Women may have a higher risk for hemorrhagic strokes than men (although this risk is not consistent in all countries). It is not clear why women have a higher mortality rate from stroke. In one study comparing men and women with atherosclerosis (hardening of the arteries), the risk for stroke in women appeared to be higher with less blockage in the blood vessels. Another study also reported that women had a higher risk for fatal strokes after heart surgery. The arteries that lead to the brain may be more vulnerable to the effects of plaque build-up in women than in men.
All minority groups, including Native Americans, Hispanics, and African Americans, face a significantly higher risk for stroke and stroke death than American Caucasians. The risk is also higher in Asian Americans, although some evidence reports a marked decline in incidence in this group over the past decades. The differences in risk among all groups diminish as people age.
The greatest disparity in risk occurs in young adults. Middle aged African-Americans are two to three times more likely to experience a stroke than their Caucasian peers and four times more likely to die from one. (They also face a higher risk for death from heart disease.) Reasons for both of these risks may include the following:
- African Americans have a higher prevalence of diabetes and hypertension than other groups.
- Poorer diets, higher stress levels, and lack of access to health care certainly play a role. It should be that socioeconomic disparities may play a large role in the differences in mortality between all major American minority ethnic groups and Caucasian Americans.
- All African Americans face discrimination, but women may be at particular risk for unequal treatment. (In one study in which female actors portrayed heart patients, African American women were 60% less likely to receive aggressive diagnostic tests than African American men or any Caucasians, even though they presented with similar symptoms.)
- While African Americans comprise 13% of the US population, African Americans have comprised only 2% to 9% of subjects in most of the major research trials, and so knowledge about their specific risks is limited.
- One study found that African Americans produce less nitric oxide in response to stress; this substance is critical for opening blood vessels and increasing blood flow.
People in the Southeastern US have had the highest risk for stroke in the country for some years; those at particular risk live in North Carolina, South Carolina, and Georgia. This risk may be shifting westward so that high stroke rates are also occurring in the lower Mississippi valley and in Southern California. Socioeconomic differences do not fully explain these higher-risk areas.
High Blood Pressure (Hypertension)
High blood pressure (known medically as hypertension) contributes to 70% of all strokes. In fact, researchers have estimated that nearly 40% of strokes could be averted by controlling blood pressure.
Two numbers are used to describe blood pressure phases and may affect stroke risk separately:
The systolic pressure (the higher and first number) is measured as the heart contracts to pump out the blood. Evidence suggests that elevated systolic pressure poses a significant danger for heart events and stroke events when diastolic is normal, a condition called isolated systolic hypertension . The wider the spread between the systolic and diastolic measurements, the greater the danger.
The diastolic pressure (the lower and second number) is measured as the heart relaxes to allow blood to refill the heart between beats. Abnormally higher diastolic pressure is a strong predictor of heart attack and stroke in most people with hypertension. [For more information, see the Well-Connected Report #14, High Blood Pressure .]
About one in six strokes is due to atrial fibrillation. This is a heart rhythm disorder in which the atria (the upper chambers in the heart) beat very quickly and irrhythmically. The blood pools instead of being pumped out, increasing the risk for formation of blood clots that break loose and travel toward the brain. Atrial fibrillation, in fact, poses a six-fold increased risk for stroke and may also pose a higher risk for complications after a stroke.
Atrial fibrillation is uncommon in people under 60 years old, but about 6% of adults over 80 have this heart rhythm disorder. In this patient group, the risk for stroke may be higher or lower with the presence of other risk factors, including having heart failure, high blood pressure, diabetes, and a previous history of stroke, TIA, or rheumatic heart disease. More women than men have AF, but risk for stroke is higher in women with this condition than in men. [ See Box Atrial Fibrillation and Its Treatments.]
People who smoke a pack a day have almost two and a half times the risk for stroke as nonsmokers. Smoking increases both hemorrhagic and ischemic stroke risk. The risk for stroke may remain elevated for as long as 14 years after quitting, so the earlier one quits the better.
Diabetes and Insulin Resistance
Diabetes is a strong risk factor for ischemic stroke, perhaps because of accompanying risk factors, such as obesity and high blood pressure. Studies have also implicated insulin resistance, which is an important disease mechanism in type 2 diabetes, as an independent factor in the development of atherosclerosis and stroke. With this condition, insulin levels are normal to high, but the body is unable to use the insulin normally to metabolize blood sugar. The body compensates by raising the level of insulin (hyperinsulinemia), which can, in turn, increase the risk for blood clots and reduce HDL levels (the beneficial form of cholesterol). Diabetes does not appear to increase the risk for hemorrhagic stroke. [For more information, see the Well-ConnectedReport #60, Diabetes: Type 2 .]
Obesity and Sedentary Lifestyles
Obesity may increase the risk for both ischemic and hemorrhagic stroke independently of other risk factors that often co-exist with excess weight, including insulin resistance and diabetes, high blood pressure, and unhealthy cholesterol level. Weight that is centered around the abdomen (the so-called apple shape) has a particularly high association with stroke, as it does for heart disease, in comparison to weight distributed around hips (pear-shape).
Cholesterol and Other Lipids
Although an unhealthy balance of cholesterol and other lipids (fatty compounds) plays a major role in heart disease, its role in stroke is less clear. Different lipids may have different effects:
Ischemic Stroke. HDL (the so-called good cholesterol) may be the most important lipid for preventing ischemic stroke. The effects of high total cholesterol and LDL levels on stroke are less clear. One study suggested that the risk for ischemic stroke increases when total cholesterol is above 280 mg/dl.
Hemorrhagic Stroke. HDL may also reduce the risk for hemorrhagicstroke. People with overall cholesterol levels below 180 mg/dl, however, may be at risk for hemorrhagic stroke (which is bleeding in the brain), particularly if they also have high blood pressure. This is a far less common stroke, however, than ischemic stroke.
In any case, reducing cholesterol is extremely important in anyone with heart disease and abnormal lipid levels.
Alcohol, Coffee, and Drug Abuse
Alcohol. Heavy alcohol use, particularly a recent history of drinking, is associated with a higher risk of both ischemic and hemorrhagic stroke. Studies have indicated, however, that mild to moderate alcohol use (one to seven drinks a week) is associated with a significantly lower risk for ischemic stroke, although not hemorrhagic stroke.
Coffee. Studies suggest that drinking three or more cups of coffee a day could increase the risk of stroke in older men with hypertension. Coffee does not appear to pose a danger for men with normal blood pressure.
Drug Abuse. Drug abuse, particularly with cocaine and increasingly methamphetamine (an amphetamine), is a major factor in the incidence of stroke in young adults. Steroids used for body-building also increase the risk.
Genetic and Inborn Factors
Genetics may be responsible for many of the causes of stroke. Studies indicate that a family history of stroke, particularly in one’s father, is a strong risk factor for stroke.
Genetics and Subarachnoid Hemorrhage. Genetic factors account for between 7% and 20% of cases of subarachnoid hemorrhage. Ruptured aneurysms that occur in such patients tend to happen at an earlier age, to be smaller, and are more apt to recur than in those without an inherited condition. A study of people who had suffered subarachnoid hemorrhages found that first-degree relatives of these stroke victims had a high lifetime risk of between 2% and 5%. Some experts recommend screening for aneurysms in people with more than one close relative who suffered a hemorrhagic stroke.
Inherited Disorders that Contribute to Stroke. Some cases of atrial fibrillation may be inherited. Genetic disorders that cause connective tissue disorders are also associated with stroke from hemorrhage; they include polycystic kidney disease, Ehlers-Danlos syndrome type IV, neurofibromatosis type 1, Marfans syndrome, and moyamoya disease.
Specific Genetic Factors Under Investigation. Specific genetic factors are under investigation. The following are some examples:
- Inherited deficiencies in factors called protein C and S, which inhibit blood clotting, are strongly suspected of being responsible for certain cases of stroke in young adults, although one study indicated they were not significant.
- A genetic mutation in a factor V Leiden may be related to blood clotting risks.
- People who have inherited a gene called apolipoprotein (Apo) E-4 may be at increased risk of stroke. This gene is also associated with Alzheimer’s disease. More studies are needed.
Heart Disease and its Treatments
Heart disease and stroke are closely tied for many reasons:
- They often have common risk factors, including high blood pressure, atherosclerosis (hardening of the arteries), and diabetes.
- The risk of stroke is increased during surgical procedures involving the coronary arteries, including coronary bypass operations, angioplasty, and coronary atherectomy.
- Thrombolytic (clot-busting) and other anti-clotting drugs used for treatment of heart attacks also slightly increase the risk for hemorrhagic stroke.
- A heart attack itself increases the risk for a stroke. Those at higher risk are older people and patients who also have congestive heart failure.
It had been commonly believed that mitral-valve prolapse is a major cause of stroke in young people, but the connection has not been well researched. A 1999 study found no evidence that this usually mild heart abnormality has any effect on stroke.
Mental and Emotional Factors
Stress. One survey revealed that men who had a more intense response to stressful situations, such as waiting in line or problems at work, were more likely to have strokes than those who did not report such distress. In some people, prolonged or frequent mental stress causes an exaggerated increase in blood pressure. In fact, a 2001 study has linked for the first time a higher risk for stroke and elevated blood pressure during times of stress in adult Caucasian men (particularly those in lower socioeconomic groups).
Depression. Depression has also been linked to a higher risk for having a stroke and lower survival rates after one. In one 2000 study, patients with severe depression had a 73% higher risk for stroke, and those with moderate depression had a 25% higher risk than average. The risk for stroke in depressed African Americans in the study was notable, 160% higher than average.
Migraine and Associated Risk Factors
Studies have found that migraine or severe headache is a risk factor for stroke in both men and women, especially before age 50. In fact, migraine is associated with about 19% of all strokes. It should be pointed out that many people have migraines, and their risk is still low, 2.7% for women and 4.6% for men, according to one study. Women in the study were at greatest risk between ages 45 and 65 and men before age 45. In both genders, the risk diminished with age.
Oral contraceptives add to the risk for stroke in young women with migraines, but only in those who also have auras. Smoking intensifies their risk.
Taking decongestants may also increase the risk for stroke in people with migraines.
Reports have indicated for some time that certain bacteria and viruses may play a role in atherosclerosis and heart disease, generally by provoking an inflammatory response in the arteries. Similar mechanisms may be at work with stroke. Some evidence linking infections with stroke is as follows.
Lung Infections. In two 2000 studies, chronic infection with Chlamydia pneumoniae, a non-bacterial organism that causes mild pneumonia in adults, was linked with a higher risk for stroke. One of the studies reported a thickening of the inner vessel walls of the carotid arteries in patients who carried the organism. Chlamydia has also been linked to heart disease.
A 1998 study found that patients hospitalized for stroke were three times more likely than patients without strokes to have recently been exposed to infections, usually mild ones in the respiratory tract.
Periodontal Disease. Chronic periodontal (gum) disease has been associated with an increased risk for ischemic stroke and heart disease. The bacteria that cause periodontitis may stimulate inflammatory factors that cause blood clots and other proteins that contribute to this higher risk. On the other hand, gum disease may simply be a common risk factor among other known risk factors for stroke, including being poor, African American, older, and overweight.
Varicella Zoster Virus. Varicella zoster virus (the virus that causes chicken pox and shingles) has been associated with cerebral vasculitis, a condition in which blood vessels in the brain become inflamed. It is a very rare cause of stroke in children. The virus has also been associated with some cases of stroke in young adults.
Other Medical or Physical Conditions
A number of medical or physical conditions may contribute to the risk for stroke:
- Sleep apnea, which may contribute to the narrowing of the carotid artery, appears to increase the risk for stroke three- to six-fold.
- Pregnancy carries a very small risk for stroke, mostly in women with pregnancy related high blood pressure and in those with cesarean delivery. The risk appears to be higher in the postpartum (post-delivery) period, perhaps because of the sudden change in circulation and hormone levels.
- Nearly 40% of young people with strokes and 10% of all stroke patients have components of the immune system known as anti-phospholipid antibodies that increase the chance for blood clots.
- People with sickle-cell anemia are at risk for stroke at a young age.
Over-the-counter decongestants contain ingredients that increase the risk of stroke, particularly in people with other risk factors or who have Raynaud’s phenomenon. One study reported a possible increased risk for stroke in older women who regularly took aspirin; more research is needed to determine if there is any causal relationship.
Neck Manipulation with Chiropractic Therapy
Some studies have reported a higher risk for stroke from injury to the carotid artery after neck manipulation by a chiropractor. Other Factors Associated with Stroke Timing. Like heart attack and sudden cardiac death, stroke appears to be more common in the morning hours, perhaps due to a temporary rise in blood pressure at that time. Various studies point to a higher risk for stroke on weekends, Mondays, and holidays. The risk for hemorrhagic stroke may also be higher in the winter, particularly in older hypertensive people.
Height. Shorter people are at higher risk than taller individuals.
Homocysteine and Vitamin B Deficiencies. Abnormally high blood levels of the amino acid homocysteine, which occur with deficiencies of vitamin B6, B12, and folic acid, are strongly linked to an increased risk of coronary artery disease and stroke. Some experts believe that homocysteine is a major risk factor for stroke, second only to high blood pressure. Others believe it may simply be a chemical bystander, which increases in the presence of other risk factors.
HOW SERIOUS ARE STROKES?
A stroke is always serious. Stroke is the third leading cause of death in the US. About 160,000 Americans die of stroke each year. The mortality rates are declining, however, and 80% of patients survive a stroke attack.
Ischemic versus Hemorrhagic Stroke. People who suffer ischemicstrokes have a much better chance for survival than those who experience hemorrhagic strokes. Among the ischemic stroke categories, the greatest dangers are posed by embolic strokes, followed by large-artery (thrombotic) and lacunar strokes.Hemorrhagic stroke not only destroys brain cells, but it poses other complications as well, including increased pressure on the brain or spasms in the blood vessels, both of which can be very dangerous. (In one small study, however, survivors of hemorrhagic stroke had a greater chance for recovering function than those who suffered ischemic stroke.)
Factors Affecting Recurrence. The risk for recurring stroke is highest within the first few weeks and months. The risk is about 10% in the first year and 5% thereafter, so preventive measures should be instituted as soon as possible. Some specific risk factors for early recurrence are the following:
• Being older.
- Having evidence of blocked arteries (a history of coronary artery disease, peripheral artery disease, ischemic stroke, or TIA.
- Having had a hemorrhagic or embolic stroke.
- Being diabetic.
- Having alcoholism.
- Having valvular heart disease.
- Having atrial fibrillation.
Long-Term Outlook for Survivors. Over half of stroke victims survive beyond five years. Between 50% and 70% of stroke sufferers regain functional independence. Between 15% and 30% of those who survive either an ischemic or hemorrhage stroke suffer some permanent disability. On the encouraging side, about 90% of stroke survivors experience varying degrees of improvement after rehabilitation. Furthermore, one 1998 study reported that people who survived for many years after a stroke had a chance for independent living that was about the same as for their peers who had not suffered strokes. The stroke patients even appeared to be less depressed than the comparison group.
HOW ARE STROKES AND TRANSIENT ISCHEMIC ATTACKS DIAGNOSED?
Diagnosing Transient Ischemic Attacks (TIAs) and Determining Risk for Stroke
In people who experience transient ischemic attacks or small strokes, it is important to determine the source of these attacks in order to prevent a major stroke. A complete blood count, chest x-ray, and electrocardiogram are usually performed. Discouragingly, a 2001 study reported that over 30% of patients with TIA who called their primary care physician were neither evaluated nor sent to the hospital within the month after a first event.
Examining the Carotid Artery. The physician usually first examines the carotid artery to determine if it is severely narrowed. If it is, the patient is in danger of a major stroke. (The thickness of carotid artery is also proving to be a valuable indicator for long-term risks for stroke, as well as heart disease and mortality rates in general.)
The physician may use a number of approaches to determine the thickness of the artery:
- A clue to a blocked carotid artery is a bruit. This is a whooshing sound caused by blood flow turbulence in the narrowed artery. A physician may be able to hear a bruit using a stethoscope. Occasionally, even a patient can hear the sound. The presence of a bruit, however, is not necessarily a sign of an impending stroke, nor does the absence of a bruit indicate an unblocked artery.
- Carotid ultrasound is a very valuable tool for measuring the width of the artery. At this time, ultrasound is most useful in people between the ages of 40 and 60 years. It should be noted that severely blocked carotid arteries may distort some measurements, so other tests may be required to confirm the results.
- The blood pressure to the eye may also be measured. If blood flow to the eye is reduced, the physician estimates that the carotid artery is probably severely narrowed.
Other Imaging Techniques. Other imaging techniques may be useful for identifying small clots or other indicators of risk in the brain.
- Transcranial duplex sonography is an ultrasound technique that can identify tiny clots in the brain that do not produce symptoms but place patients at higher risk for TIAs or stroke. In one study, the use of this technique to identify blockage in large arteries in the brain was very helpful in predicting the outlook for patients who had experienc ed an ischemic stroke. It may eventually prove to be useful in identifying unruptured aneurysms.
- Α magnetic resonance imaging (MRI) scan is an accurate way of evaluating the blood vessels and the brain’s circulation. This technique can even identify silent brain injuries in elderly patients with neurologic impairment but no symptoms of stroke, but it is very expensive and not routinely used.
Researchers are hoping that advanced imaging techniques may help doctors to predict outlook in stroke patients.
Cerebral Angiography. If less invasive tests indicate a need for surgery, cerebral angiography may be used. (This procedure can also detect aneurysms.) This requires the insertion of a catheter into the groin, which is then threaded up through the arteries to the base of the carotid artery. At this point a dye is injected and x-rays are taken to determine the location and extent of the narrowing, or stenosis, of the artery. It should be noted that the risk of stroke itself increases using this technique, particularly in elderly people with diabetes.
Diagnosing a Major Stroke
To save a patient’s life, a fast diagnosis of both the presence and type of stroke is critical. The first step is to determine whether symptoms actually indicate a stroke. (Simple verbal and physical tests enable emergency teams to identify nearly all stroke patients.) Noninvasive techniques for diagnosing transient ischemic attacks are also used for major strokes.
Determining the Type and Cause of a Stroke. Once a stroke has been determined, the next important step is to determine as quickly as possible whether it is hemorrhagic or ischemic. Clot-busting drug therapies can be life-saving for ischemic stroke patients, but they are effective only in the first three hours. In addition, they cause bleeding and can be lethal if the stroke is actually caused by a hemorrhage. One or more of the following diagnostic tools may be used:
- A computed tomography (CT) scan performed early on is essential in ruling out hemorrhagic stroke. It is accurate for diagnosing about 95% of hemorrhagic strokes. Evidence of ischemic stroke will usually not show up on a CT scan until after a few days. (The ultrasound technique, transcranial duplex sonography, may be sensitive enough to differentiate between hemorrhagic and ischemic strokes if CT scans are not available.)
- If the CT scan is negative, but the physician still suspects a hemorrhagic stroke, a spinal tap may be indicated. Spinal fluid containing significant amounts of blood will usually confirm a hemorrhagic stroke.
- A heart evaluation using an electrocardiogram (a test that records the electrical current in the heart muscle) and usually an echocardiogram (a machine that uses ultrasound to create an image of the chambers and valves of the heart) is always done when an ischemic stroke is suspected. A technique called transesophageal echocardiography is particularly useful for determining causes, such as atrial fibrillation, that in turn lend themselves to targeted treatments.
A number of blood tests may be helpful for predicting the risk for a stroke as well determining the severity and complications of an existing stroke. Some of these are investigatory.
- Some blood tests are used to determine clotting times.
- Blood sugar levels (hyperglycemia) are measured. Elevated levels indicate a worse outcome for some strokes (although not hemorrhagic or lacunar strokes).
- One blood test measures glutamate, an amino acid. High levels indicate a severe stroke.
- The inflammatory response in the brain stimulates the release of certain markers that are used to diagnose a stroke. C-reactive protein, enzymes called troponins, and elevated erythrocyte sedimentation rates (ESR) are also indicators of the inflammatory process and may predict a higher risk for stroke and a poorer outcome in people with existing stroke.
- Elevated levels of lipoprotein (a) may reveal the possibility of an unruptured aneurysm, which can be confirmed with an MRI (magnetic resonance imaging).
WHAT ARE THE INITIAL STEPS IN MANAGING A STROKE?
Until recently, the treatment of stroke was restricted to basic life support at the time of the stroke and rehabilitation later. Now, however, treatments are being used that are proving to be very beneficial when administered as soon as possible after the onset of the stroke. It is critical then to get to the hospital and be diagnosed as soon as possible.
- If significant symptoms appear in people at risk for stroke, calling 911 is critical (as opposed to calling the family doctor or trying to get the patient to the hospital by car). One study reported that patients who went to the emergency room in an ambulance had a much shorter delay in getting treatment than those who went on their own. Receiving treatment early is critical in reducing the damage from a stroke.
- Although administering aspirin within 48 hours may reduce the risk of a recurrent stroke, it should not be taken before the patient has entered the hospital. Aspirin increases the risk for bleeding in patients with hemorrhagic stroke and would preclude important clot-busting drugs in patients with ischemic stroke.
- As soon as the patient enters the hospital, diagnostic tests, particularly a CT scan, should be obtained to help determine whether the stroke is ischemic or hemorrhagic.
- The patient should receive treatment to support basic life functions and to reduce stress, pain, and agitation. Monitoring blood pressure and maintaining a healthy electrolyte balance (the ratio of sodium, calcium, and potassium in the body’s fluids) are critical.
- If the patient is diagnosed with hemorrhagic stroke, blood pressures above 200 (systolic) or 100 (diastolic) should be treated. (Lowering blood pressure too quickly can be dangerous and it should be monitored carefully.)
- Hospital staff should watch carefully for increased pressure on the brain, which is a frequent complication of hemorrhagic strokes. It can also occur a few days after ischemic strokes. A number of medications may be given during a stroke to reduce this risk. Early symptoms of increased brain pressure are drowsiness, confusion, lethargy, weakness, and headache.
WHAT ARE THE DRUGS USED TO TREAT STROKE PATIENTS?
Drugs for Initial Treatment of Ischemic Stroke
Intravenous Thrombolytics. Clot-busting, or thrombolytic, drugs, normally used for breaking up existing clots in people who have had heart attacks, are now administered intravenously for ischemic (not hemorrhagic) stroke. The standard thrombolytic drug used for stroke is t-PA or alteplase (Activase). Streptokinase is also sometimes used and others are under investigation. The following steps are critical before administering these agents.
- Before t-PA is given, a CT scan must also first confirm that the stroke is not hemorrhagic.
- Thrombolytics must be administered within three hours of a stroke (but not after that period) to have any effect. Unfortunately, most stroke patients arrive at the hospital more than three hours after an attack and therefore are not eligible for treatment. This delay is the primary reason why only 1% to 2% of stroke patients are receiving these agents.
T-PA itself carries a risk for hemorrhage and they may not be appropriate for patients with existing risk factors for bleeding. The drug may be appropriate in more patients than previously thought, however, including older people, those with a history of stroke, and those with high blood pressure. More research is needed to confirm this. Thrombolytics are used less frequently than they should be in certain groups, particularly African Americans.
Intra-Arterial t-PA . Researchers are investigating a t-PA agents injected directly into an artery in the brain. Early studies suggest this approach may allow effective treatment up to six hours after a stroke and improve recovery in more patients. The risk for bleeding is increased, however.
Ancrod. Ancrod is an agent derived from the venom of a pit viper snake that reduces the amount of a blood clotting factor called fibrinogen. Although it is not actually a clot-busting drug, some experts believe it might be a possible alternative to thrombolytics. Studies are reporting less disability in patients who are given ancrod within three hours of the stroke. (It is not clear yet whether the agent improves survival.) As with all anti-clotting agents, there is a slightly higher risk for hemorrhage.
Medications that prevent blood from coagulating or clotting have been used for years in people at risk for a recurring stroke. They may also be warranted in some patients at high-risk for a first stroke. A major analysis of 17 trials reported that in patients with a history of TIA or stroke antiplatelet treatment reduced the chances of a second stroke, heart attack, and related deaths by 22%. These benefits were evident in men and women of any age, including those with and without hypertension or diabetes. In general, they are initiated within 48 hours of an ischemic stroke and continued as maintenance.
The specific anti-clotting agents are generally recommended in the following order:
Aspirin. A 2000 review of four trials found no evidence that aspirin can prevent a first ischemic stroke (although the studies reviewed in the report had been conducted using subjects at risk for heart disease, not stroke.) Aspirin has some modest effect in preventing a second stroke and is the most widely recommended agent as initial therapy in doses of between 50 and 325 mg. It is not clear if aspirin should be used after a first stroke in patients who have been taking it before the stroke for heart attack prevention or other medical problems.
Aggrenox. Aggrenox is the brand name for a single capsule containing both low-dose aspirin and extended release dipyridamole, an anti-platelet agent. The two agents have complementary actions and are somewhat more effective than ordinary aspirin for preventing a second stroke in high-risk people; the drug also has a good safety profile. Aggrenox is much more expensive than aspirin, however, and is usually recommended only if aspirin does not appear to be helpful.
Thienopyridines. Ticlopidine (Ticlid) or clopidogrel (Plavix) are anti-blood platelet agents known as thienopyridines. They are slightly more protective against stroke than aspirin, but they are costly. Typically, they are options for patients who cannot tolerate or who do not respond to aspirin. These agents however, can have severe side effects. Ticlopidine particularly has been associated with reversible lupus-like symptoms (an autoimmune disease), reversible neutropenia (a drop in white blood cells), and thrombocytopenia (a severe drop in platelet counts). Clopidogrel has been preferred because of its better safety record, but reports of thrombocytopenia in patients taking clopidogrel have created concern.
Warfarin. The anticoagulant warfarin (Coumadin) is a potent anti-clotting agent and needs to be monitored carefully, as it can lead to bleeding. An important study in 2001 suggested, however, that it is no more effective than aspirin in preventing a second stroke. Warfarin may still be useful in certain patients, such as those with atrial fibrillation or high-risk patients who do not respond to other anti-platelet drugs.
All anti-clotting drugs carry a risk for bleeding. Of some concern in this regard are studies reporting a higher than usual risk for hemorrhagic stroke with long-term use of aspirin. Any risk for hemorrhagic stroke is still very low, particularly with low-dose aspirin.
Drugs for Hemorrhagic Stroke
Calcium Channel Blockers. One of the most common and serious dangers after a subarachnoid hemorrhagic stroke is spasm of the blood vessels near the ruptured site, which closes off oxygen to the brain. Calcium causes contraction of the smooth muscles of the blood vessels, and calcium channel blockers are drugs that relax the blood vessels. One, nimodipine (Nimotop), has been tested in a number of trials with considerable success. The drug works best if it is administered within six hours of the stroke. Calcium channel blockers are not useful for ischemic stroke.
Urokinase Irrigation. Introducing irrigation tubes and administering urokinase (a thrombolytic agent) after surgically removing an aneurysm may help prevent spasm.
Investigative Drugs Used to Protect or Restore Nerve Cells after a Stroke
Nerve-Protecting Agents. Researchers are currently working to develop medications that may slow down or prevent the cascading process that destroys nerve cells after a stroke. Many investigative drugs are targeting the excitatory amino acids, such as glycine and glutamate, which are known to destroy nerve cells after a stroke.
Studies to date have been discouraging. Of note, gavestinal, an investigative agent that blocks glycine, produced no significant benefits for stroke patients in two major trials. Other nerve-protecting agents being investigated that have shown some promise include citicoline, clomethiazole, piracetam, and ebselen.
Agents for Nerve Regeneration. It has been thought that when cells in the brain were destroyed, new ones could not grow to replace them. Scientists have now observed, however, that nerve regrowth (neurogenesis) can occur in the adult human brain. This exciting discovery opens the way for new agents that might in the future stimulate nerve growth and repair damage done by many neurologic diseases, including stroke.
One investigative technique involves the transplanting of laboratory-grown nerve cells into the brains of stroke patients in order to improve motor and speech skills. Six of twelve people who had had strokes in years (rather than days) past, and who received such cells appear to improve their motor skills, but the 2000 study was far too small to be definitive.
WHAT ARE THE SURGICAL PROCEDURES FOR PREVENTING OR TREATING STROKE?
Carotid Endarterectomy to Prevent Ischemic Stroke
Carotid endarterectomy is a surgical procedure used to clean out and open up the narrowed carotid artery. It is used to prevent thrombotic (large-artery) strokes caused by blockage in the internal carotid artery, which is responsible for about 9% of ischemic strokes.
Procedure Description. The procedure generally is as follows:
- The patient is usually given general anesthesia, although it has been reported that using local anesthetic is just as safe and reduces the cost of the procedure.
- A by-pass tube is put in place to transport blood around the blocked area during the procedure.
- The surgeon scrapes away the plaque on the arterial wall.
- The artery is sewn back together and blood flow is restored.
- The patient generally stays in the hospital for about two days. There is often a slight aching in the neck for about two weeks, and the patient should refrain as much as possible from turning the head during this period.
Patients who have this procedure after a stroke are usually advised to wait six weeks. Studies are reporting however, that having the procedure earlier does not pose greater risks.
Appropriate Candidates In general, any patients with severe stenosis and symptoms of stroke can benefit from endarectomy. Severe stenosis is defined as over 70% obstruction of the carotid artery. It has not been clear whether the benefits of the procedure outweighs the risk in elderly patients who meet the criteria, although a 2001 study suggested it may be even more advantageous for people over 75 than for young patients. .
And, anyone with mild stenosis (less than 50%), even with symptoms, would do better with medications.
The benefits of endarectomy for people with symptoms and stenosis between 50% to 70% are somewhat unclear, however. The best candidates for preventive corotid enderactomy in such cases iinclude those with all of the following conditions:
- Patients with symptoms that indicate blockage in the brain.
- Male patients. The benefits of this procedure for women are uncertain.
- A history of a stroke that occurred three months earlier or less.
- The medical centers have major complications rates after endarterectomy of less than 3%.
Carotid endarterectomy in patients with stenosis of over 60% but who have no symptoms has been a subject of much controversy. In general, surgery is recommended in asymptomatic patients who have have the following characteristis:
- Are under 79 years old
- Stenosis is at least 60%
- The risks of surgical complications are less than 3%.
An important 2000 study reported that over half of the strokes that occurred in patients with asymptomatic stenosis were caused by embolisms (traveling clots) or lacunar infarcts (very tiny, ischemic strokes). Only 3.5% of the strokes were due to blockage in the carotid arteries, which is the only condition that is benefited by carotid endarterectomy. Given these results, the experts in the study could not recommend the procedure for even asymptomatic patients with severestenosis (narrowing of 70% to 99%) of carotid arteries until more studies define which patients would benefit. (Other experts disagree and still believe that many asymptomatic patients with severe stenosis are good candidates, regardless of whether they have symptoms or not.)
Benefits after a Stroke. The long-term benefits of surgery include improvements in vision, speech, swallowing, functioning of arms and legs, and general quality of life. It should be noted that the studies showing such high benefit of surgery versus drug therapy were done in institutions whose surgeons are experienced with such operations.
Complications. There is a risk of a heart attack or even stroke from the procedure. Studies have reported, in fact, that strokes occur during or immediately after the operation in up to 9% of these operations. The other overall risk of death from postoperative stroke was 2.8%. Women appear to have a significantly higher risk for postoperative stroke than men have. Doctors are researching the utility of an emergency procedure that places a stent (a circular wire mesh) to open the carotid artery in the event of such a stroke.
A 2000 study reported that older surgeons had a worse record than younger ones, possibly because they relied on residents or were less likely to adopt new procedures. Patients should be sure the surgeon has recent experience in the procedure and has a history of complication rates of no more than 4%.
Carotid angioplasty is being investigated as an alternative to carotid endarterectomy. It is based on the same principles as angiography done for heart disease.
- An extremely thin catheter tube is inserted into an artery in the groin.
- It is threaded through the circulatory system until it reaches the blocked area in the brain carotid artery.
- The physician either breaks up the clot or inflates a tiny balloon against the blood vessel walls (angioplasty). Or, after temporarily inflating the balloon, the doctor may leave a circular wire mesh (stent) inside the vessel to keep it open.
This procedure carries a risk for an embolic stroke. In fact, recent studies report very high complications, and in one study, results with angioplasty were worse compared to carotid endarterectomy. At this time, angioplasty is not recommended except for highly selected patients. More experience with the procedure may improve results.
Extracranial-Intracranial (EC-IC) bypass has been under investigation for decades for ischemic stroke, but has had very mixed results, some extremely negative. With this procedure a healthy artery in the scalp is rerouted to an area of the brain that was deprived of blood because of a blocked artery. This procedure is now sometimes used for patients with aneurysms. Some experts hope, however, that, in specific cases chosen via careful imaging and using the latest surgical techniques, EC-IC may prove to be helpful for some stroke patients.
Surgery for Preventing and Treating Hemorrhagic Strokes
Surgical Intervention of Unruptured Aneurysms. If an unruptured aneurysm is detected, patients should discuss all options with their physician, including surgical repair. Unruptured aneurysms occur in between 1% and 6% of the general population, however, and controversy exists over when to operate and on which patients. In general, the decision rests on the size of the aneurysm, but uncertainty still exists:
- One study reported that in patients with aneurysms smaller than 10 mm the risk for rupture was only .05% per year (which is far greater than the risks from surgery). Even people with a history of subarachnoid hemorrhage had only a 0.5% annual risk for recurrence when aneurysms were that small.
- For aneurysms between 10 and 25 mm, the risk of rupture was still quite low, slightly less than 1 percent per year for both groups.
- Aneurysms over 25 mm had a 6% chance of rupturing within a year.
Aneurysms can often cause symptoms, however, even if they do not rupture. Patients should discuss their particular risk factors carefully with their physicians. Individuals with arteriovenous malformation, a condition caused by abnormal associations between arteries and veins, should be monitored for the development of aneurysm.
Clipping the Aneurysm. If is it possible, the standard surgical procedure for treating a ruptured aneurysm is to place a clip across the neck of the aneurysm, which blocks off bleeding. It is usually performed within the first three days. Getting to the aneurysm is often extremely difficult. Deep cooling of the body to stop circulation may be used to allow more time for the operation. Procedures that remove large portions of the bone in the skull are being developed to allow fast access. One long-term 2001 study indicated that there is a relatively high risk for newly formed aneurysms, particularly after nine years. Patients may want to discuss follow-up angiography to detect any new aneurysms nine or ten years after the procedure.
Transcatheter Embolization for Sealing off the Aneurysm. In a technique called transcatheter embolization, surgeons thread a thin tube through the artery leading to the aneurysm through which materials are passed to plug or obstruct the aneurysm. In one version of this procedure, the following occurs:
- A tiny platinum coil is inserted through the tube and positioned into the aneurysm.
- An electric charge is passed through the coil to form blood clots.
- In this case, blood clots benefit the patient by using the coil as a scaffold and sealing off the aneurysm.
- In small trials using the coil, only 3.7% of patients suffered a second stroke after seven months compared to the usual re-rupture rate of 30% to 40%.
Clipping the aneurysm appears to produce better results, but embolization is less invasive and may be suitable for selected patients. More comparative studies are needed.
Emergency Surgery for Hemorrhagic Strokes. Emergency surgery for a hemorrhagic stroke usually involves locating and removing large blood clots. In the past, such procedures had little effect on survival. Advances, however, are improving outcome when surgery is performed very early.
WHAT ARE THE MEDICAL AND LIFE-STYLE MEASURES FOR PREVENTING A STROKE?
A healthy diet rich in fruits and vegetables and low in salt and saturated fats may significantly lower the risk for a first ischemic stroke. (The protective effects of diet on a second stroke are less clear.)
Fruits and Vegetables. Diets rich in fruits (particularly citrus) and vegetables (particularly those that are green, leafy or cruciferous, such as broccoli and kale) are particularly protective against a first ischemic and possibly hemorrhagic stroke. Foods such as apples and tea, which are high in food chemicals called flavonoids, may also be very beneficial. Foods high in potassium (bananas, oranges, and potatoes) may be particularly protective in people with high blood pressure.
Whole Grains. A 2000 study reported a lower incidence in stroke in women who had a high intake of whole-grain foods.
Calcium, Potassium, and Magnesium. Calcium, magnesium, and potassium serve as electrolytes in the body and may play a role in stroke:
A major 1999 study reported that calcium intake is associated with a lower risk for stroke in women, which supports an earlier study reporting a lower risk for stroke in men who drank more milk.
Some evidence suggests that diets rich in potassium may protect against stroke, mostly by reducing blood pressure but also possibly because of other mechanisms. Low potassium levels may also increase the risk for stroke in certain people. In a 2000 study, potassium-poor diets were associated with a higher risk for stroke only in men with hypertension.
Magnesium deficiencies may increase the risk for atrial fibrillation. No evidence yet exists, however, that taking magnesium supplements is protective.
Fats and Oils. Although saturated fats, found in animal products, are known risk factors for heart disease, the effects of fats and oils on stroke are less clear. In fact, some fat may be important for stroke protection:
- One study indicated that middle-aged men without heart disease who had the highest intake of monounsaturated or saturated fat (not polyunsaturated oils) also had the lowest risk for stroke. Monounsaturated oils, obtained in olive and canola oils, however, may have protective benefits against both heart disease and stroke.
- A fatty acid called alpha-linolenic acid found in canola oil, soybeans, and walnuts, may have particular benefits against stroke by helping to prevent the formation of blood clots. (High amounts of saturated fats, found in animal products, are not recommended since they increase the risk for heart disease.)
- Omega-3 fatty acids, which are found in certain oily fish and may be obtained in supplements, may reduce risks for ischemic stroke, Omega-3 fatty acids are further categorized as docosahexaenoic (DHA) and eicosapentaenoic acids (EPA). These compounds have anti-inflammatory and anti-blood clotting effects and may be significantly beneficial to the heart. Consuming fish two or three times a week, in any case, helps the heart and may also reduce the risk of stroke.
- Studies suggest that the low intake of animal protein and saturated fats increases the risk of hemorrhagic stroke (which is, however, a much lower risk than ischemic stroke.
Vitamins. The effects of vitamins on stroke, dementia, or both are being studied. Studies are conflicting, however. A 2000 study on people with type 2 diabetes has suggested that high-dose supplements of vitamin E may protect the brain. On the other hand, a 2000 study reported no protective association from supplements but did report a slightly lower risk of death from stroke in people who had a high intake of foods rich in vitamin E. Yet another 2000 study offered some additional information. Men who took either vitamin E or C or who took them both for less than three or four years experienced no protection against dementia associated with stroke. However, men who took both for the full eight years of the study reported an 88% reduced risk for dementia from stroke or blocked blood vessels. (They had no effect on Alzheimer’s.) Supplement dosages were not reported. High doses of vitamin E may increase the risk for bleeding and therefore hemorrhagic stroke. Studies have suggested that people who have higher blood levels of folic acid have a lower than average risk for stroke.
Caffeine Intake, Alcohol, and Smoking
Everyone should quit smoking and, if they drink alcohol at all, should do so in moderation. In healthy people with normal blood pressure, drinking a couple of cups of coffee a day is unlikely to do any harm. Caffeine drinkers, however, would do better to choose tea, which may have beneficial nutrients, and people with existing hypertension should avoid caffeine altogether (since caffeine may increase the risk for stroke in this group).
The benefits of exercise on stroke are less established than on heart disease, but recent studies are suggesting a positive association:
- According to one analysis of a group of 11,000 men, those who burned between 2,000 and 3,000 calories a week (about an hour of brisk walking five days a week) cut their risk of stroke in half. Groups who burned between 1,000 and 2,000 calories or more than 3,000 calories per week also gained some protection against stroke but to a lesser degree. In the same study, exercise that involved recreation was more protective than exercise routines consisting simply of walking or climbing.
A 2000 study of women also found substantial protection from brisk walking or striding (rather than casual walking).
Blood-Pressuring Lowering Agents in Patients with or without Hypertension
Drug therapy is always recommended for people with hypertension where there is evidence that it is affecting the organs. Reducing even mild to moderate high blood pressure using drug therapy (primarily diuretics, ACE inhibitors, and beta-blockers) has been shown to lower the risk of stroke by as much as 42%. ACE inhibitors may be particularly protective against stroke in many patients, including those with diabetes.
Importantly, one 2001 study suggested that taking anti-hypertensive agents can reduce the risk for a stroke even in patients with a history of TIA or a first stroke even if they have normal blood pressure. In the study the patients took a diuretic plus an ACE inhibitor. Results were particularly impressive with patients who had a history of hemorrhagic stroke. [For more information on these agents, see the Well-ConnectedReport, High Blood Pressure .]
Cholesterol Lowering Drugs
Statins. The cholesterol-managing HMG-CoA reductase inhibitors, commonly called statins, such as lovastatin (Mevacor), pravastatin (Pravachol), and simvastatin (Zocor), reduce the risk of a second stroke in people with high cholesterol levels and heart disease. These agents lower LDL (the so-called bad cholesterol) and raise HDL (the so-called good cholesterol) levels and help open up arteries. Having taken statins may help stroke sufferers recover more quickly, although more research is needed to confirm this. It is not clear if they are helpful for people with a prior stroke but no history of heart disease.
Fibrates. Fibrates are other agents used to improve cholesterol levels. They tend to increase HDL (the good cholesterol) and reduce levels of triglycerides (which are now believed to be important health risk factors). Fibrates include gemfibrozil (Lopid), fenofibrate (Tricor), and bezafibrate (under investigation). In one trial, men with heart disease and low HDL levels had a 31% lower risk of ischemic stroke after taking gemfibrozil than did men who took a placebo. (These drugs may not provide the same benefits in people with higher HDL.)
Hormone Replacement Therapy
The beneficial effects of estrogen on blood vessels that open blood flow to the heart should also serve the same purpose in the brain and protect against stroke. The effect of HRT on stroke has been controversial, however. There have been many contradictory studies, some showing a reduction in risk, some an increase, and many showing no effect.
Major studies on women and hormone replacement therapy have reported in 2001 little or no protection against stroke in postmenopausal women who took hormone replacement therapy.
- One of the studies known as the Women’s Estrogen for Stroke Trial (WEST) reported a slightly increased risk for heart attack and stroke in postmenopausal women taking HRT within the first two years of treatment.
- In the Heart and Estrogen Replacement Study (HERS) there was no difference in stroke risk between those taking or not taking HRT.
|Atrial Fibrillation and Its Treatments
The object of treatment for atrial fibrillation is to prevent blood clots from forming by first restoring and then maintaining normal heart rhythm and function. To initially restore heart rhythm, anti-arrhythmic drugs are usually used first. If they fail to restore normal rhythm, a procedure known as cardioversion is often effective. Even if a steady rhythm is restored by drugs or cardioversion, however, it often cannot be sustained for prolonged periods, so long-term maintenance therapy using anti-arrhythmic drugs may be required.
Anti-Clotting Drugs. After a diagnosis of atrial fibrillation, patients usually need to take drugs to reduce blood clotting, usually warfarin (an anticoagulant) or aspirin.
Electrical Cardioversion. Electrical cardioversion is mild shock therapy and is the current standard treatment used to restore normal heart rhythm. It is conducted as follows:
Although the stabilizing effect is usually only temporary, some evidence suggests that a series of cardioversions may succeed in maintaining normal rhythm in young healthy patients without the need for antiarrhythmic medications.
Implanted cardioverters (eg, Atrioverter, Jewel AF) are being investigated for maintenance. Studies are very promising.
Drugs used to Restore Normal Rhythm . Before any antiarrhythmic agent is used, conditions that might be causing the atrial fibrillation should be addressed first. In some cases, medications rather than electric cardioversion may be used for restoring normal rhythm.
They include intravenous beta-blockers (such as propranolol) or calcium channel blockers. Digitalis, an older drug, is not used as often but is proving to be very effective in combination with a beta-blocker. These agents are used to reduce heart rate at the onset of atrial fibrillation. None of them, however, are able to convert an abnormal heart rhythm to a normal one and are not useful for rhythm maintenance.
Drugs Used for Maintaining Normal Heart Rhythm. For maintaining a stable rhythm, the following drugs may used. The specific choices typically depend on whether the patient has existing heart disease or not:
Many of these drugs carry a small but significant increased risk, however, for a life-threatening arrhythmia called torsades de pointes and so should be avoided by people with certain heart conditions.
Surgical Procedures for Complex AF. In some difficult cases, surgery may be recommended. The options and candidates depend on other complicating factors. The following are some examples:
HOW IS STROKE RECOVERY MANAGED?
Reducing Risk Factors for Another Stroke
Patients should begin all measures, including any medications and life-style changes needed to prevent another stroke. [ See What Are the Nonsurgical Measures for Preventing a Stroke?] For those whose stroke was ischemic, aspirin, warfarin, or both will usually be prescribed. Using a neurologist as the primary physician after a stroke, rather than some other specialist or primary care doctor, significantly increases the chance for survival. In any case, patients or their families should be persistent in requesting the best care possible during this important early period. Being treated initially in a stroke unit instead of a general ward appears to play a strong role for better long-term quality of life. Unfortunately, Medicare has cut back reimbursing rehabilation from three weeks a few years ago to a current low level of about 11 days.
Reducing the Risk for Non-Neurologic Complications after a Stroke
In addition to problems brought on by neurologic damage, stroke patients are also at risk for other serious problems that reduce their chances for survival. They include the following:
- Blood clots in the legs (deep vein thrombosis).
- Pulmonary embolism (a blood clot that travels to the lungs).
- Widespread infection.
- Heart problems.
- Urinary tract infections.
Measures should be taken to monitor and treat patients for these important problems.
Candidates for Rehabilitation
In all, 90% of stroke survivors experience varying degrees of improvement after rehabilitation. With current cost cutting, there is pressure to send elderly stroke victims directly to a nursing home rather than try rehabilitation first, although one study found that patients were three times more likely to return home from rehab units than from nursing homes. Not all patients, however, need or benefit from formal rehabilitation:
- If the stroke is severe, intensive training would not be very helpful
- If the stroke is mild, patients often improve on their own.
Positive factors that help predict good candidates for rehabilitation:
- A patient should be able to sit up for at least an hour.
- The patients should be able to learn and be aware.
- Spasticity may be a good sign, because it indicates live nerve action.
- Patients who are able to move their shoulders or fingers within the first three weeks after having a stroke are more likely to recover the use of their hands than patients who cannot perform these movements. The ability to feel light pressure on the affected hand, however, makes no difference for future hand movement.
- Family members or close friends should be active participants in the rehabilitation process.
Factors that might predict a poor response to rehabilitation:
- Dysphagia (the inability to swallow) is associated with a higher mortality rate, possibly because of increased risk for infection and malnutrition. (Dysphagic patients who are given nutrition using a stomach tube may improve more than those who are fed using a feeding tube inserted down through the nose.)
- The inability to recognize nonspeech sounds that occur right after a stroke.
- A poor hand grip that is still present after three weeks is an indicator of severe problems.
- Having had very severe seizures after the stroke.
Factors that do not rule out rehabilitation:
- About 30% of patients experience aphasia (an impaired ability to speak), which is particularly distressing. It is necessary to understand that this disability does not necessarily impair the ability to think.
- Although confusion is common among people who have had strokes, partial or even complete recovery is very possible.
Some Rehabilitation Approaches
Physical therapy should be started as soon as the patient is stable, as early as two days after the stroke. Some patients will experience the fastest recovery in the first few days but many will continue to improve for about six months or longer. Because stroke affects different parts of the brain, specific approaches to managing rehabilitation vary widely among individual patients:
- Retraining Muscles. One approach is based on training different muscles to replace those that have been impaired by damaged brain cells. In one small but important 2000 study, 13 stroke victims who had right-side paralysis had their non-paralyzed arm immobilized so that they were forced to use their paralyzed arm. Eleven of the patients experienced improvement in their impaired arms. The affected side of their brains also appeared to become more active. More studies are necessary. Physical exercise relating to the disability caused by the stroke is, in any case, important and may actually help repair the brain.
- Speech therapy and sign language. While professional speech therapy progresses, the patient’s caregivers should use and encourage the patient in non-verbal communications, such as pantomime, facial expressions, and pen and paper. Learning and using the sign-language alphabet may be helpful both in communicating and improving small-motor dexterity.
- Biofeedback techniques combined with physical therapy. This combination has been beneficial in certain cases. Electrical stimulation of the throat, for example, may help patients with dysphagia recover their ability to swallow faster. Stimulation of the wrist and finger is also showing promise for improving motor capabilities.
- Attention Training. Problems in attention are very common after strokes. Direct retraining teaches patients to perform specific tasks using repetitive drills in response to certain stimuli. (For example, they are told to press a buzzer each time they hear a specific number.) A variant of this approach trains patients to relearn real-life skills, such as driving, carrying on a conversation, or other daily skills. For example, in one study, small electric cars were used in a lab to teach driving.
Drug Therapy for Rehabilitation
Drug therapy can sometimes help relieve specific effects of stroke:
- Dantrolene (Dantrium), baclofen, and injections of the deadly bacterial toxin botulism have shown some promise in relieving spasticity.
- In one small study, the drug bromocriptine (Parlodel), normally used for Parkinson’s disease, was helpful for patients with severe speech problems, improving their ability to pronounce multi-syllable words and to form sentences.
- Some patients experience intractable hiccups, which can be very serious. Among the drugs used for this condition are chlorpromazine or baclofen.
- The use of amphetamines may help improve speech and motor skills when combined with physical therapy. Studies have reported that dextroamphetamine or methylphenidate (Ritalin), an amphetamine used in attention deficit disorder, may help patients recover function after a stroke.
Certain drugs commonly taken for conditions associated with stroke may actually slow recovery. They include drugs used for high blood pressure, including clonidine and prazosin, anticonvulsant drugs, the antipsychotic drug haloperidol, and the common anti-anxiety drugs benzodiazepines.
Managing the Emotional Consequences
The Emotional State of the Patients. Strong motivation with the goal of independence after rehabilitation is important for recovery. Unfortunately, depression is very common after a stroke, both as a direct and indirect result of the stroke:
- Strokes that affect the right hemisphere in the brain particularly increase the risk for depression.
- Patients can certainly become depressed by the great changes in their ability to function.
- A peculiar stroke-induced condition, known as post-stroke crying or neurologic emotionalism, is a neurologic not a psychologic disorder.
If depression is prolonged, it can impair recovery. One study showed that people who suffered strokes and became depressed were three times more likely to die within ten years than stroke victims who were not depressed. There is a significantly increased risk of suicide in patients with stroke, especially in women and those under age 60.
Antidepressants, particularly fluoxetine (Prozac) and similar so-called SSRI drugs, have been beneficial in relieving post-stroke crying and to improve recovery in general, and mood in particular, in patients who are depressed. Antidepressants may also help restore mental abilities.
Some physicians also recommend agents called tricyclic antidepressants, including amitriptyline (Elavil) and nortriptyline (Pamelor). In one 2000 study nortriptyline (Pamelor) not only improved mood but also had positive effects on mental functioning, suggesting perhaps that some dementia associated with stroke may actually be due to depression. Tricyclics may also be useful for neurologic emotionalism.
Anxiety disorder is also common and debilitating. Some research, in fact, indicates that many patients suffer from feelings identical to post-traumatic stress syndrome. The two disorders often overlap, but drug treatments for each differ and may offset the other.
It should be noted that many drugs for psychologic disorders affect the central nervous system and can actually delay rehabilitation. Skilled professional help is needed to determine the most effective and safest treatments.
The Emotional State of the Caregiver. The caregiver’s emotions and responses to the patient are critical. Patients do worse when caregivers are depressed, over-protective, and not knowledgeable about the stroke. Unfortunately, in one study, over half of the caregivers themselves were depressed, particularly if the stroke victims were left with dementia or abnormal behavior.
WHERE ELSE CAN HELP BE OBTAINED FOR STROKES?
National Stroke Association 9707 East Eastern Lane, Englewood, Colorado 80112 (800-787-6537) or (303-649-9299) or (303-649-0122 for hearing impaired) on the Internet (http://www.stroke.org/) This organization offers a number of informational services, including treatment and prevention options.
National Institute of Neurological Disorders and Stroke, Building 31, Room 8A16, 31 Center Drive, MSC 2540, National Institutes of Health, Bethesda, MD 20892-2540. Call (301-496-5751) or (800-352-9424) or on the Internet (http://www.ninds.nih.gov/) This organization is a good resource for information about major US centers for stroke research and clinical trials.
National Rehabilitation Information Center (NARIC), 1010 Wayne Avenue, Suite 800 Silver Spring, MD 20910. Call (301-562-2400 ) or (800-346-2742) or on the Internet (http://www.naric.com/) NARIC is a research referral and information center that distributes information regarding the rehabilitation, products, and technology for people with disabilities; it provides a resource package for stroke.
National Aphasia Association, 156 Fifth Ave., Suite 707, New York, NY 10010. Call (800-922-4622) or on the Internet (http://www.aphasia.org/)
American Academy of Neurology, 1080 Montreal Avenue, St. Paul, Minnesota 55116. Call (651-695-1940) or on the Internet (http://www.aan.com/)
The American Association of Neurological Surgeons and Congress of Neurological Surgeons (http://www.neurosurgery.org/) Will help find neurosurgeon in local areas.
Agency for Health Care Policy and Research, PO Box 8547, Silver Spring, MD 20907. Call (301-594-2800) or (800-358-9295) or on the Internet (http://text.nlm.nih.gov/) This agency provides guidelines on rehabilitation based on extensive research by the US Public Health Service. Request Post-Stroke Rehabilitation: Assessment, Referral, and Patient Management. Guidelines are also available by fax. Individuals must use a fax machine with a telephone handset.
Website with description of carotid endarterectomy
A nicely done student website providing clear anatomical images and descriptions of the brain (http://library.thinkquest.org/26463/default.shtml)
An online catalog that offer kitchen products, bathroom helpers and daily living products for people of all ages and abilities or disabilities (http://www.dynamic-living.com)
GUIDELINES FOR STROKE
Well-Connected reports are written and updated by experienced medical writers and reviewed and edited by the in-house editors and a board of physicians, including faculty at Harvard Medical School and Massachusetts General Hospital. The reports are distinguished from other information sources available to patients and health care consumers by their quality, detail of information, and currency. These reports are not intended as a substitute for medical professional help or advice but are to be used only as an aid in understanding current medical knowledge. A physician should always be consulted for any health problem or medical condition. The reports may not be copied without the express permission of the publisher.
Board of Editors
Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital
Stephen A. Cannistra, MD, Oncology, Associate Professor of Medicine, Harvard Medical School; Director, Gynecologic Medical Oncology, Beth Israel Deaconess Medical Center
Masha J. Etkin, MD, PhD, Gynecology, Harvard Medical School; Physician, Massachusetts General Hospital
John E. Godine, MD, PhD, Metabolism, Harvard Medical School; Associate Physician, Massachusetts General Hospital
Edwin Huang, MD, Gynecology, Harvard Medical School, Physician, Massachusetts General Hospital
Daniel Heller, MD, Pediatrics, Harvard Medical School; Associate Pediatrician, Massachusetts General Hospital; Active Staff, Children’s Hospital
Paul C. Shellito, MD, Surgery, Harvard Medical School; Associate Visiting Surgeon, Massachusetts General Hospital
Theodore A. Stern, MD, Psychiatry, Harvard Medical School; Psychiatrist and Chief, Psychiatric Consultation Service, Massachusetts General Hospital
Nidus Information Services
Cynthia Chevins, Publisher
Bruce Carlson, Business Development Manager
Carol Peckham, Editorial Director
Eliza McCarty, Update Editor