Stroke.
Publié le 11/05/2013
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IV DIAGNOSIS
The symptoms typical of a stroke can also be caused by other conditions, including brain tumors, various infections, and overdoses of certain drugs.
A patient that hasstrokelike symptoms may undergo a battery of imaging techniques to rule out other medical problems and confirm that a stroke has occurred.
The key imagingtechnique 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 ofthe 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 braindamage 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 vesselabnormalities 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 detailedimages of blood vessels, enabling doctors to identify the source and location of an obstruction or gather anatomical information about aneurysms or AVMs.
Two otherimaging techniques, single photon emission computed tomography (SPECT) and positron emission tomography (PET), involve injecting a radioactive substance into thebloodstream.
As the substance travels through the circulatory system, it constantly emits radiation, which is collected by a radiation detector.
The images producedenable doctors to see regions of the brain with abnormally low blood flow, indicating brain tissue that has been injured or damaged by a stroke.
V 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 thebrain, 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, apromising advance occurred in June 1996, when the Food and Drug Administration (FDA) approved the drug tissue plasminogen activator (t-PA) for use in treatingischemic 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 whenadministered 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 attentionwhen strokelike symptoms develop.
After a patient is stabilized, recovery and rehabilitation begins.
Along with the stroke survivor, family, friends, support groups, and a variety of health-care professionalsare involved in this long and often difficult process.
In some cases an undamaged portion of a patient’s brain is able to take over the functions that were previouslyperformed by the damaged portion of the brain, and the patient regains the functions that were lost due to the stroke.
Rehabilitation can also help restore lostfunctions.
Physical therapy helps patients regain the use of their limbs and the ability to walk, and helps prevent muscle stiffening in patients who are paralyzed.
Speechtherapy can help patients regain the ability to speak.
Occupational therapy improves patients’ hand-eye coordination and helps them relearn basic activities, such asdressing, cooking, and writing.
VI RISK FACTORS AND PREVENTION
Scientists have identified a number of factors that increase a person’s risk for stroke.
The probability of stroke increases as people get older, with those over age 65 atgreatest risk.
The incidence of stroke in males and females is about equal, although females are more likely to die from stroke than males.
As is the case with manydiseases and medical conditions, people with a family history of stroke are more likely to have a stroke themselves.
Finally, a person who has already had a stroke orTIA is at greater risk of having another stroke in the future.
Fortunately, a healthy lifestyle can help minimize some risk factors for stroke, such as high blood pressure, smoking, and high blood cholesterol.
High blood pressureplaces abnormally high stress on the walls of blood vessels which, over time, weakens and damages the vessels.
Certain chemicals found in cigarette smoke can affectthe properties of the blood, making it more prone to forming clots.
In addition, the nicotine in cigarette smoke damages blood vessel walls and makes them moresusceptible to atherosclerosis.
And when excess cholesterol is present in the bloodstream, it accumulates along the walls of blood vessels, accelerating the progressionof atherosclerosis and thereby increasing the risk of a stroke.
Quitting smoking, controlling high blood pressure through diet or medication, eating a low-fat, healthydiet, and becoming physically active can greatly decrease a person’s risk of having a stroke.
For people who have blood vessel abnormalities that can lead to a stroke, or who have already had a stroke or TIA, a variety of steps can be taken to prevent a first orsecond stroke from occurring.
To prevent the blood vessel obstructions that cause ischemic strokes, physicians try to maximize blood flow through a narrowed vesseland minimize the risk of clotting.
One common treatment is carotid endarterectomy, a surgical procedure that removes an atherosclerotic deposit from a diseasedcarotid artery.
Sometimes anticoagulant drugs such as aspirin and warfarin are prescribed to prevent the formation of clots in patients at risk for thrombus or embolismformation.
To prevent rupture of the weakened blood vessels that cause hemorrhagic stroke, physicians try to provide an obstruction to protect a weakened vessel from furtherdamage and redirect blood flow through normal vessels feeding the same regions of the brain.
An aneurysm can be treated surgically by placing a metal clip at its baseto seal off the weakened vessel.
An AVM, on the other hand, is cut away from the normal brain tissue and removed.
An alternative to surgery, which attempts to treatthe diseased blood vessel from the outside, is endovascular therapy, which addresses the problem from within the vessel.
In a typical endovascular procedure, acatheter—a long, thin, flexible tube—is inserted into a major artery, usually in the thigh, and guided through the blood vessels to the location of the aneurysm or AVM.Tiny platinum coils are then deposited from the end of the catheter into the diseased vessel, providing a physical barrier to prevent the forces exerted by blood flowfrom further damaging the weakened vessel.
These treatments can be beneficial even when performed after a hemorrhagic stroke because they can prevent ananeurysm or AVM from rupturing a second time and causing another stroke.
Contributed By:George James HademenosMicrosoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation.
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