Stroke
Stroke is a brain damage caused by a lack of blood flow to part of the brain. In order to perform its many functions and direct activities throughout the body—from walking to seeing to reasoning—the brain requires a constant supply of energy, provided by the oxygen and nutrients that are delivered by the flowing blood. If blood flow is restricted or cut off at any point between the heart and the brain, portions of the brain relying on blood from the obstructed blood vessel become deprived of oxygen. Brain cells are extremely sensitive to such oxygen deprivation, and if they are deprived of oxygen and nutrients for more than several minutes, they, in effect, starve to death. A stroke results in permanent damage to the brain tissue—and in many cases, permanent disability for the patient. For example, a patient who has had a stroke may develop paralysis on one or both sides of the body; have difficulty with walking, eating, or other daily activities; or lose the ability to speak or understand speech.
TYPES OF STROKE
Think of a blood vessel as a flexible, cylindrical tube, like a straw. The flow of liquid through a straw can be impeded in two different ways: by an obstruction within the straw, or by compression or pinching from outside the straw. The flow of blood through a blood vessel can also be blocked in these two ways. The two main types of stroke, ischemic stroke and hemorrhagic stroke, correspond to these two mechanisms of flow interruption.
SYMPTOM AND DIAGNOSIS
A key feature of stroke symptoms is that they are unexpected and develop suddenly, though they may worsen over the next several hours or days. The symptoms often primarily affect only one side of the body because blood flow is cut off to only part of the brain during a stroke. One of the most common symptoms is a sudden weakness or numbness of one side of the face or of one arm or leg. Some stroke sufferers experience a sudden dimness or loss of vision, particularly in only one eye. They may also suddenly become unable to speak or have trouble understanding speech. Sudden, severe headaches with no known cause and sudden, unexplained dizziness, unsteadiness, or falls, can also be warning signs of a stroke. Anyone who experiences one or more of these symptoms should seek medical attention immediately.
The key imaging technique used in diagnosing strokes is computed tomography (also known as CT or CAT scanning), which employs X rays to obtain images of the internal structures of the body. A CT scan can tell a doctor whether or not a stroke is occurring, whether the stroke is ischemic or hemorrhagic, and in most instances, the extent of brain damage caused by the stroke.
Several other imaging techniques are used along with computed tomography to gather more information about specific types of stroke. Magnetic resonance imaging (MRI) uses a magnetic field to generate images of the human body and produces high-resolution images that are particularly useful in diagnosing brain vessel abnormalities that may be involved in a hemorrhagic stroke. In X-ray angiography, a dye injected into the bloodstream is viewed using X rays to provide detailed images of blood vessels, enabling doctors to identify the source and location of an obstruction or gather anatomical information about aneurysms or AVMs. Two other imaging techniques, single photon emission computed tomography (SPECT) and positron emission tomography (PET), involve injecting a radioactive substance into the bloodstream. As the substance travels through the circulatory system, it constantly emits radiation, which is collected by a radiation detector. The images produced enable doctors to see regions of the brain with abnormally low blood flow, indicating brain tissue that has been injured or damaged by a stroke.
TREATMENT AND RECOVERY
Once doctors have established that a patient is having a stroke, the treatment focuses on removing the obstruction, restoring blood flow to the deprived region of the brain, and preventing the development of complications. In the past, doctors could do little to treat stroke patients until the stroke had run its course. However, a promising advance occurred in June 1996, when the Food and Drug Administration (FDA) approved the drug tissue plasminogen activator (t-PA) for use in treating ischemic strokes. The drug is a thrombolytic agent—or clot buster—that can break up blood clots and thereby restore flow through the obstructed blood vessel when administered within the first three hours of a stroke. This small window of effectiveness makes it more critical than ever for patients to seek immediate medical attention when strokelike symptoms develop.
TYPES OF STROKE
Think of a blood vessel as a flexible, cylindrical tube, like a straw. The flow of liquid through a straw can be impeded in two different ways: by an obstruction within the straw, or by compression or pinching from outside the straw. The flow of blood through a blood vessel can also be blocked in these two ways. The two main types of stroke, ischemic stroke and hemorrhagic stroke, correspond to these two mechanisms of flow interruption.
SYMPTOM AND DIAGNOSIS
A key feature of stroke symptoms is that they are unexpected and develop suddenly, though they may worsen over the next several hours or days. The symptoms often primarily affect only one side of the body because blood flow is cut off to only part of the brain during a stroke. One of the most common symptoms is a sudden weakness or numbness of one side of the face or of one arm or leg. Some stroke sufferers experience a sudden dimness or loss of vision, particularly in only one eye. They may also suddenly become unable to speak or have trouble understanding speech. Sudden, severe headaches with no known cause and sudden, unexplained dizziness, unsteadiness, or falls, can also be warning signs of a stroke. Anyone who experiences one or more of these symptoms should seek medical attention immediately.
The key imaging technique used in diagnosing strokes is computed tomography (also known as CT or CAT scanning), which employs X rays to obtain images of the internal structures of the body. A CT scan can tell a doctor whether or not a stroke is occurring, whether the stroke is ischemic or hemorrhagic, and in most instances, the extent of brain damage caused by the stroke.
Several other imaging techniques are used along with computed tomography to gather more information about specific types of stroke. Magnetic resonance imaging (MRI) uses a magnetic field to generate images of the human body and produces high-resolution images that are particularly useful in diagnosing brain vessel abnormalities that may be involved in a hemorrhagic stroke. In X-ray angiography, a dye injected into the bloodstream is viewed using X rays to provide detailed images of blood vessels, enabling doctors to identify the source and location of an obstruction or gather anatomical information about aneurysms or AVMs. Two other imaging techniques, single photon emission computed tomography (SPECT) and positron emission tomography (PET), involve injecting a radioactive substance into the bloodstream. As the substance travels through the circulatory system, it constantly emits radiation, which is collected by a radiation detector. The images produced enable doctors to see regions of the brain with abnormally low blood flow, indicating brain tissue that has been injured or damaged by a stroke.
TREATMENT AND RECOVERY
Once doctors have established that a patient is having a stroke, the treatment focuses on removing the obstruction, restoring blood flow to the deprived region of the brain, and preventing the development of complications. In the past, doctors could do little to treat stroke patients until the stroke had run its course. However, a promising advance occurred in June 1996, when the Food and Drug Administration (FDA) approved the drug tissue plasminogen activator (t-PA) for use in treating ischemic strokes. The drug is a thrombolytic agent—or clot buster—that can break up blood clots and thereby restore flow through the obstructed blood vessel when administered within the first three hours of a stroke. This small window of effectiveness makes it more critical than ever for patients to seek immediate medical attention when strokelike symptoms develop.
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