Stroke

MRI of the human brain. Source: WikiMedia Commons.

A stroke is a condition in which the blood supply to part of the brain is interrupted, or when a blood vessel in the brain ruptures causing blood to leak into the surrounding brain tissue. This can result in death of brain cells which can affect the functioning of the brain. Symptoms can include weakness or numbness in the face, arm or leg; confusion, trouble speaking or understanding; loss of vision in one or both eyes; dizziness or difficulty walking; or severe unexplained or unusual headache.

Every year, 780,000 people in the United States have a stroke. Strokes are the most common cause of long-term disability and the third most frequent cause of death in this country.

Types of Strokes

There are two kinds of stroke: ischemic—the result of blockage of a blood vessel supplying the brain, and hemorrhagic—caused by bleeding into or around the brain.

• Ischemic strokes are the most common type. They are caused by blood clots that block flow through an artery. In some instances the clots originate in the blood vessels of the chest (the aorta), the neck (carotid and vertebral arteries) or the arteries in the head and brain. In other instances the clots form in the heart and travel along the arteries to the brain. A clot that occludes the artery where it forms is called a thrombus, and a clot that travels in the blood stream to lodge somewhere else is called an embolus. In rare instances, clots can form within the veins of the brain. When a clot blocks blood flow, cells beyond the clot are deprived of oxygen and nutrients, and as a result stop working and eventually die. The affected area is called an infarct. The death of brain tissue causes the symptoms of a stroke. In some instances the symptoms resolve in the first 24 hours, a phenomenon called a transient ischemic attack (TIA). In the past, it was thought that TIAs were less serious than strokes. Recent data from imaging studies, however, show that in many cases there is permanent damage to the brain even when symptoms resolve. Because it is not possible to predict whether symptoms will resolve on their own, it is important to seek medical attention as soon as these appear and not wait to see if they resolve. In addition, TIAs are warning signs that an irreversible event may occur in the near future. Of the approximately 50,000 Americans who have a TIA each year, about one-third will subsequently have a stroke.

• Hemorrhagic strokes result from bleeding into the brain or surrounding tissues from a leak or tear in a blood vessel. Hemorrhagic strokes can occur within the brain itself or the membranes that surround and protect it. In a subarachnoid hemorrhage a blood vessel leaks into the lining of the brain (the subarachnoid space). Intracranial hemorrhages can be caused by changes in the blood vessels due to hypertension, rupture of an aneurysm or a vascular malformation, brain tumors, and head injuries.

Risk factors for stroke

There are some risk factors that cannot be modified. Gender appears to play a role in the risk for stroke. Men have a higher risk of having a stroke, whereas more women die from a stroke. The stroke risk for men is 1.25 times that for women. Stroke also seems to run in families. This may be a result of genetic tendencies for stroke risk factors such as an inherited disposition for hypertension or diabetes. It could also be a result of a common lifestyle among members of a family. The risk for stroke varies among different ethnic and racial groups. The incidence of stroke in African Americans is almost double that of white Americans, and African Americans between the ages of 45 and 55 have four to five times the stroke death rate of whites. age and ethnicity. Strokes can happen at any age, but they are more common in older people. While stroke is common in all ethnic groups, some are more susceptible, including African-Americans and Latinos. People of Asian descent have a higher risk of hemorrhagic stroke.

Most of the risk factors for stroke, however, are modifiable. this means that life-style and pharmacological interventions can decrease the risk of a stroke. Modifiable risk factors include:

• Hypertension: High blood pressure is the most important modifiable risk factor for ischemic and hemorrhagic stroke.
• Cigarette smoking
• Diabetes mellitus
• High cholesterol
• Poor diet
• Carotid stenosis
• Heart disease including atrial fibrillation, heart failure and coronary artery disease
• Physical inactivity
• Drug abuse, especially cocaine and amphetamines

More information can be found here

Symptoms

The symptoms of stroke depend on the type of stroke, the area of the brain affected, and the severity of the stroke, but they can be grouped in five large categories. Ischemic and hemorrhagic strokes have similar symptoms. It is important to recognize these symptoms (either in yourself or others) as prompt medical attention can help prevent the sequelae of stroke.

• Sudden NUMBNESS or weakness of face, arm, or leg, especially on one side of the body
• Sudden TROUBLE SPEAKING, understanding speech, or confusion
• Sudden TROUBLE SEEING in one or both eyes
• Sudden TROUBLE WALKING, dizziness, loss of balance or coordination
• Sudden SEVERE HEADACHE with no known cause

Depending on where the stroke occurs, people experiencing a stroke may be unaware of their symptoms (anosognosia), experience cognitive difficulties (neglect, apraxia), or have seizures.

Diagnosis

The diagnosis of stroke relies on a detailed clinical examination, imaging, and laboratory tests. The clinical examination is important to establish the nature of the symptoms and their evolution over time. Imaging tests are required to identify the pathology. The imaging tests commonly used in the emergency room include:

• CT scan: This is the most commonly available imaging test. It uses x-rays to look at the brain. It is a quick test (it only takes a few minutes) and because blood shows up brightly, it can help differentiate ischemic vs hemorrhagic strokes. It can also help rule out other potential causes for the symptoms such as brain tumors. Sometimes, in addition to the standard CT scan, a CT angiogram is done to see the arteries and veins of the brain. The CT angiogram requires the use of intravenous contrast.

• MRI: This imaging modality relies of the properties of the water molecules in the brain to produce images, and does not use radiation. In contrast to CT scans, it can show brain infarctions early on, and it is also very sensitive to acute blood and other pathological processes in the brain. It can be used to create images of the blood vessels and to evaluate blood flow to the brain. The MRI scan for acute stroke takes more time than a CT scan (15-20 minutes vs. 2-5 minutes) and is less commonly available in emergency settings.

• A blood glucose test will reveal whether a low blood sugar is responsible for the symptoms. Symptoms from a low blood sugar (sudden confusion and weakness) can be similar to those of a stroke.

Once a stroke is diagnosed and treated, it is important to determine its cause and start specific measures to prevent a recurrence. In order to identify the causes of a stroke, several tests may be used:

• An EKG will reveal information about the person's heart, which is important for both diagnosis and treatment. Sometimes stroke accompanies a heart attack. Sometimes a certain irregular heart rhythm called atrial fibrillation is the cause of stroke. Once this rhythm is treated, it can help prevent future strokes. Because the atrial fibrillation may be intermittent (paroxysmal), continuous monitoring of the heart rhythm using telemetry (while the patient is in the hospital) or holter monitor (while at home) is employed.

• An echocardiogram, or ultrasound of the heart, is done to look for structural lesions of the heart wall or heart valves and clots within the heart that can be the cause of the stroke. Most commonly the echocardiogram is done placing an ultrasound probe on the chest wall. Some patients, particularly younger ones, will also have a transesophageal echo in which the probe is placed down the esophagus to look the posterior part of the heart.

• An ultrasound of the arteries in the neck is performed to see if there are any abnormalities such as a narrowing or plaques in the blood vessels. These arteries lead directly to blood vessels that supply the brain, and atherosclerotic plaques in these arteries can break off and travel to the brain. The arteries within the brain can also be studied using ultrasound, with a test called transcranial sonogram (TCD) to look for areas of narrowing and blockage.

• Other tests to look the arteries of the neck and brain include Magnetic Resonance Angiography and CT angiography.

Other blood tests are drawn to check for anemia, disorders in blood coagulation (defects in blood clotting), inflammatory diseases, infections and, if necessary, to check for the existence of drugs of abuse in the blood, or to check for signs of heart damage.

Treatment

Treatment for acute stroke must be started soon after the onset of symptoms. It is therefore very important to call 911 as soon as a stroke is suspected, and not wait to see if the symptoms improve on their own..

Treating ischemic stroke

The goal of acute ischemic stroke treatments is to restore blood flow to the brain. There are several acute therapies.

• Intravenous tissue plasminogen activator (t-PA): This is a thrombolytic, or "clot-busting" medication. By disrupting fibrin, the net that holds it together, t-PA promotes the break up of the clot. This is the only FDA-approved medication for acute treatment of stroke, as long as it is initiated within 3 hours of onset of symptoms. In the landmark study that proved its efficacy, patients treated with tPA were at least 30% more likely to have a good outcome than patients who did not get tPA. Despite an increased risk of death from treatment-associated bleeding in the brain (seen in 3% of treated patients but none of the untreated ones), those who got tPA were more likely to be alive 3 months after their stroke than patients who did not get the treatment. The benefit of treatment is sustained long-term. While the FDA indication for tPA for stroke is limited to patients who can be treated within 3 hours of symptom onset, recent studies show that tPA may be used safely in some patients even later, and that it is beneficial up to 4.5 hours after symptom onset.

• Intraarterial use of thrombolytics: In some instances, "clot-busting" medications may be applied directly at the site of occlusion, theoretically leading to greater concentrations of the drug at the clot and less exposure elsewhere in the body. The drug is administered via a catheter inserted into the groin and threaded up the arteries into the blood vessels of the brain. While this technique is not FDA approved, it is used routinely at some hospitals for patients who are outside the usual time-window for intravenous tPA.

• Other intravascular procedures: In some instances, interventional neurologists and radiologists may use other procedures to remove blood clots. These devices are also threaded through the arteries into the brain and placed close to the blood clot. They are useful for people with severe stroke who may not be treated with thrombolytics. Research is ongoing to evaluate their efficacy for treating stroke.

• Some patients with severe stroke may require life-saving neurosurgical procedures including removal of part of the skull (hemicraniectomy).

• All patients with stroke, whether or not they receive the treatments detailed above, should be carefully monitored. The judicious management of blood pressure, temperature, and blood glucose can decrease the disability after a stroke. Simple measures such as using blood thinners to prevent blood clots in the legs, and correct positioning to prevent pneumonia and bed sores, can reduce the risk of death in patients with stroke.

• Measures to prevent recurrent stroke (see below) should be instituted as soon as possible.

Treating hemorrhagic stroke

The goal of treatment in patients with hemorrhagic stroke is to prevent complications and neurological deterioration: monitoring and managing blood pressure, blood glucose and temperature and preventing pneumonia and blood clots in the legs. Some patients with intracerebral hemorrhage may require neurosurgical interventions to remove the blood and to decrease the pressure within the skull. These patients are often treated in an intensive care unit.

Physical therapies and rehabilitation

With any type of stroke, patients often will require rehabilitation services following the event. Physical therapists and occupational therapists are usually involved in the care plan. Activities can include range of motion exercises, help with activities of daily living (dressing, washing, eating), exercises and aids to improve walking, and speech therapy. Improvements can be seen in most people who undergo continued rehabilitation services.

Prevention

Therapies to prevent a first or recurrent stroke are based on treating an individual's underlying risk factors for stroke, such as hypertension, atrial fibrillation, and diabetes.

Smoking, high alcohol consumption and the use of illicit drugs can all increase the risk of having a stroke. Stopping these activities is one of the best ways to help prevent a stroke. Diets with lots of fruits, vegetables, legumes and grains and low in fat and an active life style can help reduce the risk of a stroke.

After someone has a stroke, many tests are done to identify potential risk factors, as detailed in the studies section. Specific preventive measures depend on which risks factors are identified. Some of the most common groups of medications used to prevent a stroke include:

• Antiplatelet agents: Medications such as aspirin, clopidogrel and dypiridamole are used to keep the platelets from forming clots. Antiplatelet drugs are the most commonly employed medications for stroke preventions, and are prescribed for most people with stroke, unless they require treatment with an anticoagulant. An important question has emerged recently regarding the variability in the interindividual response to clopidogrel due to genetic variations in the hepatic isoenzyme CYP2C19 of the P450 cytochrome . This affects the way how to achieve effective antiagregation in patients who need this drug as an alternative to aspirin and in patients undergoing coronary percutaneous procedures. Moreover a significant interaction has been described with omeprazole and other proton-pump inhibitors, as to an increase in 27% of relative risk in coronary events in patients with acute coronary syndrome (Ho PM et al. JAMA 2009;30: 937-944).

• Anticoagulants: Drugs such as warfarin, heparin and low molecular weight heparins keep the blood from clotting. These medications are prescribed for patients with atrial fibrillation and sometimes for people with other cardiac conditions such as heart failure. The dose of coumadin is different for every person, and it requires frequent monitoring via blood tests adjustments. There are also some dietary restrictions. While coumadin increases the risk of bleeding, it is a very effective medication to prevent stroke in people with atrial fibrillation in whom it decreases the risk of stroke by almost 70%.

• Statin agents: These medications can lower cholesterol, but recent studies show that they may also decrease the risk of recurrent stroke through other mechanisms. People with a history of stroke are often prescribed these medications even when their cholesterol levels are normal.

• Blood pressure medications: Maintaining a normal blood pressure is one of the most important interventions to prevent a stroke. Exercise and diet are important to keep blood pressure low, but when these are not enough, different kinds of blood pressure medications can be used. In particular, diuretics and a group of medications called ACE-inhibitors are very effective for decreasing the risk of recurrent stroke.

People with diabetes mellitus must follow a strict diet and use insulin or oral medications to keep their blood glucose stable.

Patients with severe (>70%) narrowing of the arteries in the neck (carotid stenosis) and a history of stroke or TIA may decrease their risk of recurrent stroke with a carotid endarterectomy, a surgical procedure to remove plaque from the artery. The role of this surgery in patients with less severe narrowing, or in those without a prior stroke or TIA (asymptomatic carotid stenosis) is less clear, as the risk of a stroke is less.

Living with the Effects of a Stroke

For more information on living with the effects of a stroke, visit the American Stroke Association's website Life After Stroke.

Research and clinical trials

The National Institute of Neurological Disorders and Stroke (NINDS) conducts stroke research and clinical trials at its laboratories and clinics at the National Institutes of Health (NIH), and through grants to major medical institutions across the country. Currently, NINDS researchers are studying the mechanisms of stroke risk factors and the process of brain damage that results from stroke. Basic research has also focused on the genetics of stroke and stroke risk factors. Scientists are working to develop new and better ways to help the brain repair itself to restore important functions. New advances in imaging and rehabilitation have shown that the brain can compensate for function lost as a result of stroke.

A list of current clinical research trials on stroke can be found at Internet Stroke Center of Washington University and here.

Expected Outcome

Although stroke is a disease of the brain, it can affect the entire body. A common disability that results from stroke is complete paralysis on one side of the body, called hemiplegia. Stroke can also cause a less severe form called hemiparesis which is weakness in the muscles on one side of the body.

A stroke may cause problems with thinking, awareness, attention, learning, judgment, and memory. Stroke survivors often have problems understanding or forming speech. A stroke can lead to emotional problems. Stroke patients may have difficulty controlling their emotions or may express inappropriate emotions. Many stroke patients experience depression. Stroke survivors may also have numbness or strange sensations in the hands, arms, feet, legs, or other parts of the body. The pain is often worse in the hands and feet and is made worse by movement and temperature changes, especially cold temperatures.

Recurrent stroke is frequent; about 25 percent of people who recover from their first stroke will have another stroke within 5 years. Recurrent stroke is a major contributor to stroke disability and death, with the risk of severe disability or death from stroke increasing with each stroke recurrence. The risk of a recurrent stroke is greatest right after a stroke, with the risk decreasing with time. About 3 percent of stroke patients will have another stroke within 30 days of their first stroke and one-third of recurrent strokes take place within 2 years of the first stroke.

Epidemiology

Statistics

Source: American Stroke Association

• Stroke is the third leading cause of death in the United States.
• As of 2005, some 5,800,000 people in the United States had suffered a stroke.
• Every 40 seconds, someone in the US suffers a stroke, and every 3 to 4 minutes, someone dies of one.
• African-Americans have twice the risk of first-ever strokes compared with whites.
• Smokers have twice the risk of ischemic stroke compared with non-smokers.
• People with average blood pressure less than 120/80 have half the risk of stroke compared with people with high blood pressure.
• 15% of strokes are preceded by a mini-stroke, or TIA.

References

Stroke Prevention

Treatment of acute stroke

Use of tPA within 3 hours of onset of symptoms

Thrombolysis at 3-4.5 hours after onset of symptoms

Experimental treatments for acute stroke

External Links

• The Internet Stroke Center - Washington University in St. Louis
  • Warning Signs of Stroke
  • Stroke support groups

• American Stroke Association

• National Institute of Neurological Disorders and Stroke (NINDS):
  • Post-Stroke Rehabilitation
  • Stroke Diagnostics and Therapeutics Section

• National Institutes of Health (NIH):
  • Know Stroke

• American Physical Therapy Association: Stroke Resources

• Interactive tutorial on arteriovenous malformations

• Interactive tutorial on brain aneurysms