Stroke Basics – Causes, Signs and symptoms

stroke

Summary

Also known as a cerebrovascular accident (CVA), a stroke is a life-threatening event in which part of the brain is deprived of adequate oxygen. Strokes are extremely dangerous, accounting for more than 160,000 deaths each year in the United States, according to the Centers for Disease Control and Prevention (CDC). Stroke is the third leading cause of death in the United States, behind heart disease and cancer. It is also a leading cause of adult disability and institutionalization.

There are two kinds of strokes. An ischemic stroke occurs when the blood supply to the brain is interrupted, usually by a blood clot. The second kind of stroke is a hemorrhagic stroke, which occurs when there is bleeding in or around the brain. Some people may also experience a “mini-stroke” (also called a transient ischemic attack), where symptoms last for a short period of time. All strokes are considered medical emergencies.

Symptoms of a stroke may include numbness or weakness, confusion, dizziness, trouble speaking or understanding others and paralysis. After a stroke begins, it is imperative that people seek treatment as soon as possible to re-establish the flow of oxygen-rich blood to brain cells before permanent tissue damage or death occurs. Imaging tests may also be performed to confirm that a stroke has occurred, identify any potential causes and determine the extent of brain damage (if any).

People who survive a stroke should begin stroke rehabilitation as soon as possible to regain as many lost functions (e.g., lack of coordination, muscle strength) as possible. There are several risk factors associated with strokes. They include age, high blood pressure, heart disease, smoking and obesity. In general, prevention methods for stroke are aimed at eliminating or treating the risk factors. This can usually be accomplished by making certain lifestyle changes, such as eating a heart-healthy diet and taking medications. A physician might also recommend surgery for some patients.

About stroke

Also known as a cerebrovascular accident (CVA), a stroke is a life-threatening event in which part of the brain is deprived of adequate oxygen. A stroke can cause oxygen-starved brain cells to die. The condition must be treated immediately. According to the American Heart Association, stroke is the third leading cause of death in the United States, behind heart disease and cancer.

A stroke occurs when a blood vessel in the brain bursts or becomes clogged by a blood clot or other mass. This prevents oxygen and nutrients from getting to nerve cells in the affected area of the brain. These nerve cells can die within minutes, and the area of the body that they control may cease to function. This damage can be permanent, especially if the patient is not immediately treated.

There are two main types of strokes: Ischemic strokes and hemorrhagic strokes. An ischemic stroke occurs when the brain is deprived of oxygen. This is usually due to a blood clot in an artery leading to the brain. A hemorrhagic stroke is caused by excessive bleeding in or around the brain. It may be the result of factors such as high blood pressure, cerebral aneurysm or a head injury. In general, older adults are more likely to experience ischemic strokes, and young people are more likely to experience hemorrhagic strokes.  

In some cases, people experience the symptoms of a stroke for a brief period of time. These are called a transient ischemic attack (TIA) – also sometimes referred to as “mini-strokes” – because symptoms are less severe than an acute ischemic stroke, and go away fairly quickly (within minutes, in most cases). However, TIAs may indicate a serious medical complication that may cause another, more serious stroke at some point in the future.

In recent years, rapid treatment of stroke has advanced as physicians have become better at identifying what kind of stroke is occurring and moving quickly to treat it. This has resulted in a higher survival rate, but also a higher rate of hospitalization as more people survive their strokes.

The focus of stroke therapy remains rapid treatment to re-establish blood flow to the brain – but even this carries some risk. When blood flow is restored (a process known as reperfusion) to the affected area of the brain, further damage can occur. Returning blood carries white blood cells that can block smaller blood vessels and release toxins harmful to brain cells. Nevertheless, brain cells deprived of oxygen can die within minutes, causing long–term disability. If the flow of blood is restricted for too long, death could result. Therefore, the benefits of restoring blood flow to the brain are considered by physicians to outweigh the risks.

A stroke may occur in any person, regardless of age. However, strokes are more common in adults than children. When a person under the age of 18 suffers a stroke, it is known as a pediatric stroke. Because they are rare, pediatric strokes are often not recognized and treatment may delayed. This increases the risk of brain damage. Children tend to have different risk factors for stroke than adults, such as congenital heart disease, sickle cell anemia, and other conditions and traumas. It is important that families with children who are at risk of pediatric stroke learn to recognize the signs of stroke.

Although strokes occur with roughly equal frequency in both men and women, women are more likely to die from stroke. This may be due to the fact that women are less likely than men to receive rapid medical assessment and treatment for stroke.

Female stroke victims account for more than 60 percent of the annual deaths due to stroke, according to the American Heart Association. In addition, 25 percent of women who have suffered a stroke will die within a year, and about 50 percent of female stroke survivors will die within eight years. That means that stroke claims more women’s lives than breast cancer. For every American woman who dies of breast cancer, two more die of stroke.

African-Americans have a higher risk of stroke than most other ethnic groups. The reasons for this are poorly understood. However, it is thought to be related to poverty, lack of access to adequate health-care and genetic factors.

Types and differences of stroke

There are two main types of stroke: ischemic and hemorrhagic.

Roughly 80 percent of strokes are ischemic or caused by a severe episode of cerebral ischemia, according to the National Institutes of Health (NIH). During cerebral ischemia, the brain is deprived of oxygen-rich blood. This is usually because a blood clot is blocking an artery leading to the brain. A blood clot that remains in the blood vessel where it originated is called a thrombus. When a thrombus develops in an artery of the brain, it can cause a thrombotic stroke. Alternatively, the blood clot may lodge in the artery after traveling through the bloodstream from another part of the body (an embolism). This results in an embolic stroke.

Embolic strokes are usually the result of blood pooling in the upper chambers of the heart (atria). They are more common in people who have conditions that cause abnormal heart rhythms (arrhythmias), such as atrial fibrillation. This pooling of blood in the heart elevates the risk of a blood clot forming in the atria and traveling through the aorta and up into the carotid arteries. Blood clots may also originate in lower-left chamber of the heart (left ventricle), particularly in patients with a weakened heart muscle.

A hemorrhagic stroke is caused by excessive bleeding (hemorrhaging) within or around the brain. Bleeding within the brain is known as a cerebral hemorrhage, which can be a complication of high blood pressure. Cerebral hemorrhage occurs when blood leaks from the small arteries in the brain and accumulates over the course of minutes or hours. Hemorrhagic strokes account for about 20 percent of all strokes, according to the NIH. About half of these are due to cerebral hemorrhage. Bleeding around the brain is known as a subarachnoid hemorrhage, which can be caused by a ruptured cerebral aneurysm, a head injury or other causes.

Another type of stroke is called a transient ischemic attack (TIA). These are also sometimes referred to as “mini-strokes” because symptoms are less severe than an acute ischemic stroke, and go away fairly quickly (within minutes, in most cases). However, TIAs may indicate a serious medical complication that may cause another, more serious stroke at some point in the future.

Finally, just as some people experience silent heart attacks with no symptoms, people may also experience a silent stroke. A silent stroke is a stroke in which brain damage occurs, but the person does not show any obvious symptoms. Roughly one-third of elderly people may have had a silent stroke, which often damages their cognitive abilities.

Studies have shown that people who experience silent strokes have twice the risk of developing dementia. In addition to the elderly, other people at higher risk of a silent stroke are those who smoke and those with diabetes and high blood pressure.

Risk factors and causes of stroke

Strokes may have a variety of causes depending on the type of stroke involved. For example, ischemic strokes are usually caused by a blood clot that restricts the flow of blood to the brain. They can also be caused by severe atherosclerosis, which can also block the passage of blood to the brain. Hemorrhagic strokes are generally caused by the bursting of an artery within the brain. This can occur when a weak spot on an artery wall expands (cerebral aneurysm) or when artery walls begin to lose elasticity, leaving them brittle, thin and prone to cracks.  

There are several risk factors associated with strokes. In general, risk factors for stroke are the same among adults of both genders and all races and ethnic backgrounds. These risk factors include:

  • Age. While strokes can strike at any age, nearly three-quarters of strokes occur in people older than 65, according to the Centers for Disease Control and Prevention (CDC).

  • Gender. Men have a slightly higher risk for stroke than women, but women are more likely to die from stroke. Men are more likely than women to suffer a second stroke.

  • High blood pressure (hypertension). Studies have shown that people with hypertension are 4 to 6 times more likely to have a stroke than people without hypertension. Hypertension is considered an important risk factor for stroke because it usually presents no symptoms or warning signs.
  • Coronary artery disease (CAD). There is a strong correlation between CAD and ischemic stroke because both are caused by the same underlying process, atherosclerosis. Atherosclerosis occurs when arteries are obstructed by plaque deposits. This may cause the arteries to rupture.

  • Atrial fibrillation. This heart rhythm disorder can cause the blood to clot. If pieces of these clots break off and block an artery, a stroke can occur. Atrial fibrillation can increase a person’s risk of stroke by 4 to 6 percent, according to the National Institutes of Health (NIH). About 15 percent of patients experience this heart rhythm disorder prior to having a stroke, according to NIH.

  • Diabetes. People with diabetes have two to four times the risk of stroke compared to people who do not have the illness, according to the CDC. Having diabetes also appears to worsen the outcome of a stroke in many cases. People with diabetes are more likely to have many of the risk factors for a stroke, including high blood pressure, CAD and atherosclerosis. The risk of stroke may be increased in diabetes patients who are unable to control their blood sugar levels.

  • Smoking. Smoking doubles a person’s risk for ischemic stroke, according to the CDC. Smoking promotes atherosclerosis, in which plaque builds up on the walls of arteries. In addition, smoking increases the levels of certain blood clotting factors, such as fibrinogen. Nicotine also raises blood pressure, and the carbon monoxide in cigarette smoke reduces the amount of oxygen that blood can carry to the brain.

  • Family history of stroke. Stroke risk increases if a person’s parent, grandparent, sister or brother has had a stroke.

  • Low levels of HDL (“good”) cholesterol. Poor levels of good and bad cholesterol can lead to atherosclerosis, which significantly raises the risk of stroke.
  • Obesity (a body mass index of 30 or greater). People who are obese tend to have more risk factors for stroke (e.g., high blood pressure, CAD, poor cholesterol levels). While obesity is a problem among all groups of Americans, it seems to be especially prevalent among African American women.

  • Lack of exercise. Not maintaining a moderate level of physical activity can lead to obesity, which increases the risk of stroke.

  • Carotid artery dissection. A tear in the inner lining of the carotid artery, creating a space between the inner and outer layers that could cause a stroke if blood leaks into it.

Other possible contributors to stroke risk include:

  • Sleep apnea. A condition in which a person’s breathing stops and starts many times during sleep. Interruptions in oxygen to the heart and brain can significantly increase a person’s risk of heart disease, high blood pressure and stroke.

  • Atrial flutter. A type of atrial tachycardia, which is an unusually fast heart rhythm that originates in the upper chambers of the heart (atria). Atrial flutter is characterized by a very rapid but regular electrical signal in the atria, which causes a very rapid heartbeat.

  • Depression. Although the exact mechanism is not clearly understood, studies continue to show an association between chronic depressive symptoms and increased risk of stroke.

  • Loss of estrogen. After menopause, women’s lower estrogen levels can gradually increase their risk of stroke. Unfortunately, however, estrogen replacement therapy has also been tied to an increase in the risk of stroke. Post menopausal women should discuss with their physician about how best to reduce their risk of stroke.

  • Birth control pills. While today’s low-dose oral contraceptives carry a much lower risk than the earlier pill, they still carry an increased risk of stroke for women who use them than for nonusers. The risk is more pronounced among smokers and women over the age of 40.

  • Antiphospholipid syndrome. Some women who have had frequent miscarriages suffer from a condition called antiphospholipid syndrome, which causes an increased risk of stroke.

Other risk factors for stroke include alcohol or drug abuse, injuries to the head and neck and a history of strokes or heart attacks. People also face a risk of stroke during surgeries or catheter-based procedures, which have a high risk of blood clot formation.

Research is beginning to address another potential risk factor for stroke: access to health care based on race/ethnicity. Studies have shown that African Americans are less likely to receive equitable health care to white Americans. In some cases, African Americans were also seen for emergency care later in the course of their disease than whites Americans.

Children tend to have different risk factors for stroke than adults. In addition to congenital heart disease (e.g., aortic stenosis, atrial septal defect, patent ductus arteriosus), which increases the risk of stroke for adults and children alike, a wide range of diseases and conditions may raise a child’s risk for stroke. These include vasospastic diseases, leukemia, sickle cell anemia, and infection with the varicella-zoster virus, which causes chicken pox.

Signs and symptoms of stroke

Signs and symptoms can vary according to which type of stroke is present. However, the National Institute of Health (NIH) lists several major general signs of strokes. All of these symptoms appear suddenly:

  • Numbness or weakness of the face, arms or legs
  • Confusion
  • Trouble speaking or understanding others
  • Trouble seeing in one or both eyes
  • Difficulty walking
  • Dizziness
  • Loss of balance and coordination
  • Severe headache (without a known cause)
  • Paralysis of part of the body

The onset of symptoms may also vary depending on the type of stroke. For example, the symptoms of an embolic stroke tend to hit suddenly, whereas the symptoms of a thrombotic stroke develop more gradually. A cerebral hemorrhagic stroke tends to produce symptoms that hit suddenly and then continue to worsen. Additional symptoms of stroke that may appear suddenly or gradually include seizures, a stiff neck and pain upon looking up or into a light.

Symptoms that last for a short period of time are usually an indication of a “mini-stroke” or transient ischemic attack (TIA). This is a medical emergency and anyone experiencing the symptoms of a stroke (regardless of the degree or duration) should seek immediate medical assistance.

If a stroke or TIA is suspected, patients should NOT take aspirin. Aspirin could make a stroke worse. If in doubt about whether the symptoms are an indication of a stroke, call a doctor or go to the emergency room. Patients should not attempt to drive themselves or walk to the emergency room. If there is no transport available, call 9-1-1.

Diagnosis of stroke

When a patient shows symptoms of a stroke, the physician will promptly evaluate the patient’s medical history and quickly run tests such as a computed axial tomography (CAT) scan. The CAT scan can help the physician determine whether the patient is having a cerebral hemorrhage or cerebral ischemia. This information determines the course of emergency treatment. The CAT scan may also help the physician locate the exact position of the damage.

Once the patient is stabilized, the complete evaluation can take several days. Tests that may be run during this time include:

  • Physical examination. The carotid arteries will be examined with a stethoscope. If the physician hears an abnormal sound (a carotid bruit), there is a higher chance of finding atherosclerosis or carotid artery disease – conditions that increase the risk of stroke.
  • A carotid ultrasound, or Duplex scanning. A painless strategy for assessing the presence of plaque in the carotid arteries. It uses high-frequency sound waves.
  • Magnetic resonance angiography (MRA). A diagnostic test used to assess the degree of blockage in the carotid arteries. The MRA is a variation of the magnetic resonance imaging (MRI) scan, which is also very important in diagnosing a stroke.
  • An electrocardiogram (EKG). Performed to identify any cardiac problems that may have led to the stroke, such as a prior heart attack.
  • Blood tests, including a complete blood count (CBC) and a lipid profile (cholesterol test). By looking for risk factors that are associated with stroke, such as high cholesterol, the physician can design a long-term therapy that will reduce the risk of recurrent stroke.

Tests may also be done to assess overall brain functions, as measured by electrical activity. These tests can reveal how much neurological damage was inflicted by the stroke. One such test is the electroencephalogram (EEG). During this painless test, small metal devices electrodes are attached to the scalp. The electrodes are connected by wires (leads) to an electroencephalograph machine that charts the electrical activity of the brain. Physicians may also conduct an evoked-potential study where the brain’s response to sight, hearing and touch are tested and measured.

Treatment options for stroke

People who experience the symptoms of a stroke should call 9-1-1 immediately. Upon arriving at the hospital, the hospital staff will attempt to stabilize the patient using information from an emergency computed axial tomography (CAT) scan. Common strategies include:

  • Maintaining breathing in patients who may be losing consciousness. This is done through the use of breathing equipment and/or supplemental oxygen.

  • Reducing fever (if present) with medications.

  • Providing certain medications, depending on stroke type. Patients who have had an ischemic stroke, may be given intravenous thrombolytic medications to dissolve any obstructing blood clots. The drug must be given within three hours of symptoms first appearing, which underscores the need for patients to get to an emergency room quickly.

  • Some strokes that result from blood clots may be treated with emergency catheter procedures, where a catheter is inserted in the leg and maneuvered to the brain. A contrast dye is injected to better locate the blockage. In some cases a corkscrew-type catheter can be used to remove the blood clot.

  • Some patients with stroke due to hemorrhage may be treated with blood clotting factors to promote clotting. After patients have stabilized, they may be treated with a procedure where a catheter is inserted in the leg and advanced to the brain. Contrast dye is injected to locate the aneurysm. In some cases a coil can then be placed in the aneurysm causing it to clot and prevent further bleeding.
  • Special attention may be given to maintaining nutritional needs intravenously or through the mouth and preventing pneumonia, a common complication after a stroke.

In cases where the stroke was caused by a partial blockage of a carotid artery in the neck, a surgery called carotid endarterectomy might be used to remove the accumulated plaque. In other cases, a cerebral angioplasty may be used to treat problems with the brain’s blood vessels. This procedure commonly uses balloons and stents.

People who survive a stroke will often need to undergo treatment to deal with some of the long-term effects of the event. The goal of the treatment is to minimize as much neurological damage as possible, such as impaired movement or speech. The sooner that treatment is begun, the more likely it is that patients will regain significant functions. Individuals may experience depression, which may be related to damage in certain parts of the brain or frustration at the loss of basic functions. If this should occur, patients are urged to seek the help of a qualified counselor for support and treatment.

After a stroke

According to the American Heart Association, stroke is a leading cause of long-term disability in the United States. Most survivors are able to recover enough to remain independent, although others become permanently disabled. Some survivors may require institutional care after a stroke.

In general, a more severe stroke will require more time in post-stroke rehabilitation to bring back as much of the patient’s functioning as possible. Changes in functioning that may be addressed in rehabilitation include:

  • Confusion or dementia
  • Difficulty swallowing/eating
  • Drooping on one side of the face/mouth
  • Lack of balance/coordination
  • Paralysis on one side of the body
  • Trouble controlling one’s bladder or bowels (incontinence)
  • Trouble seeing or hearing clearly
  • Trouble speaking clearly
  • Weakness (e.g., being unable to make a strong fist with both hands)

Depression in both the patient and family members is also common after having a stroke. Increasing numbers of people are facing these post-stroke challenges as death rates from stroke drop and survival rates climb.

A small percentage of stroke survivors may experience pain in those areas that lost sensation following their stroke. The cause of this condition, called central poststroke pain, is unknown and can be difficult to treat. Several drugs are being studied to help relieve poststroke pain.

Prevention methods for stroke

Preventive measures do not fully protect an individual from having a stroke but can go far to reduce the risks of such an event. Many of the preventive measures involve lifestyle changes and are similar to those that can help prevent heart disease. Lifestyle measures include:

  • Controlling high blood pressure (hypertension). Blood pressure abnormalities must be continually monitored and controlled because they are a chief contributor to strokes.
  • Getting treatment for conditions that increase the risk of stroke, such as atrial fibrillation, atrial flutter, sleep apnea and diabetes.
  • Learning stress management techniques and seeking help for depression or drug abuse. Cocaine, especially, has been linked to hemorrhagic stroke.
  • Reducing cholesterol levels, by making lifestyle changes and taking cholesterol-reducing drugs.
  • Living a healthy life, including increasing exercise level, maintaining an ideal weight and quitting smoking.
  • Limiting use of alcohol to about one glass of wine or one beer per day.
  • Eating a heart-healthy diet. Findings from a number of studies have illustrated how a heart-healthy diet can decrease stroke risk. For example, in one study, women who ate fish more than five times a week were found to have a significantly lower risk of stroke than women who ate fish less than once a month. Fish is rich in omega-3 fatty acids. In another study, people in rural Japan with the highest levels of vitamin C in their blood (from eating large amounts of fruits and vegetables) were found to be significantly less likely to have a stroke than those with the lowest levels. It is important to note that taking vitamin C supplements has not shown the same protective effect as eating a diet rich in vitamin C.

People may be advised by their physician to take aspirin or other antiplatelet agents to help prevent the formation of blood clots. However, aspirin should not be used as a first aid remedy for people who are having a stroke because they can make some types of stroke worse.

For patients with a blockage of 80 percent or greater, there is a significant risk of stroke even in the absence of symptoms. These patients often need more invasive treatments such as an angioplasty and stent.

A surgery known as a carotid endarterectomy is considered the standard treatment for severe blockages. This surgery is effective in preventing stroke for patients who either have significant blockage of a carotid artery or who have already experienced a stroke or transient ischemic attack (TIA). A carotid endarterectomy involves the removal of fatty build-up from the carotid arteries supplying blood to the brain. While the person is under general anesthesia, the plaque from the artery is removed along with the entire inner lining of the artery

For patients who are not good candidates for surgery, a physician may choose to further reduce the risk of stroke by recommending a procedure called carotid artery stenting. The Food and Drug Administration (FDA) approved carotid artery stents in September 2004 for use in certain patients. Like other stents, carotid artery stents are tiny mesh tubes that work by crushing arterial plaque against the wall of the artery and holding it in place. This prevents pieces from breaking off and traveling downstream, causing a stroke.

A cerebral aneurysm that has not yet ruptured may be diagnosed early, particularly if it was causing warning signs that led the patient to seek treatment. Surgery may be necessary to repair the aneurysm and prevent a hemorrhagic stroke. This surgery is sometimes called “clipping.” It involves snipping off the aneurysm before it can rupture. Another technique that is gaining attention is called the detachable coil technique. In this minimally invasive procedure, a small coil is implanted into the bulge in the arterial wall. The coil provokes an immune response from the body, which produces a blood clot inside the aneurysm that strengthens the arterial walls and reduces the risk of a rupture.

Ongoing research for stroke

Surgery, medications, hospital care and rehabilitation are all considered accepted methods of treating a patient who has suffered a stroke. Scientists are also continuously exploring new methods of treating strokes and preventing recurrent strokes. Research is ongoing in several areas, including:

  • Antibiotics. Studies have found that atherosclerotic plaque can harbor bacteria, which, in turn, may increase the tendency for arterial rupture. Researchers are investigating whether antibiotics can exert any effects against such bacteria, thereby increasing the plaque’s stability and reducing the risk of it breaking off and causing a stroke.
  • Mechanical thrombolysis. These are devices that use catheter-delivered tools to break up or remove blood clots. Currently, clot-busting drugs are the only method available to break up a blood clot in the brain. However, they can take up to an hour to be effective. Devices being tested use lasers, sound waves, suction, spinning blades or snares to remove clots.
  • Neuroprotective agents. Neuroprotective agents represent another avenue of stroke treatment. These agents attempt to rescue brain cells from injury caused by an ischemic stroke. Some agents attempt to increase the flow of blood to the region of brain experiencing stroke. Other agents may prevent damage caused by blood returning to the affected area of the brain. Still other agents seek to limit the damage caused by dying brain cells, which release a chemical as they die that kills surrounding brain cells.
  • Stem cell transplants. Stem cells are basic cells that have the ability to develop into many different types of cells. They start out very similar to each other, but depending on where they develop, the cells become highly specialized to their individual functions. Researchers are investigating a variety of methods in which stem cell transplants could be used as a treatment for stroke damage and other conditions involving damaged brain cells.
  • Hypothermia. Researchers are studying whether lowering a patient’s body temperature can decrease the amount of damage that occurs during a severe stroke by lowering the brain’s demand for oxygen.
  • Cholesterol-lowering drugs. Recent studies indicate that statins may decrease a patient’s stroke risk.

More investigation is needed to determine the safety and effectiveness of these potential treatments, and to determine the best method of administering these treatments to patients.

Questions for your doctor about stroke

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about stroke:

  1. How likely am I to have a stroke? Why?
  2. What symptoms may indicate I am having a stroke?
  3. How will I know if I have a “silent stroke”?
  4. Are there any tests available to me that would indicate whether or not I have had a stroke? How do I prepare for these tests?
  5. What type of testing will you need to perform after I have had a stroke? What information will this tell you?
  6. What type of stroke did I have? What was the extent of brain damage? Was there any permanent damage?
  7. What treatment options are available to me?
  8. Do any of my current medications or medical conditions interfere with these treatments, or affect my risk of stroke?
  9. Do you recommend that I undergo any type of physical therapy, occupational therapy or speech therapy?
  10. How can I protect myself against future strokes?
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