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Stroke



Stroke, an injury to the brain from failure in blood flow or bleeding, leaves millions of human beings disabled. This is one of the most devastating and costly health problems that society faces. It affects more than 500,000 Americans each year.

Of the more than three million Americans who have survived a stroke, more than two million ended up with crippling disabilities, including paralysis, loss of speech, and lapses of memory.

Stroke (cerebrovascular accident, CVA) is a broad term, since it refers to almost any occurrence that prevents adequate amounts of blood from reaching a portion of the brain, which in turn causes brain cells to die. This may happen either over a period of time or quite suddenly, depending on the cause. The number of cells involved affects the outcome.

A stroke is usually the result of progressive disease that develops over many years. A stroke occurs when brain cells die because of inadequate blood flow. When blood flow fails, brain cells are robbed of vital supplies of oxygen and nutrients. Some strokes have little recognizable effect. Other can quickly cause death.

A blockage of a blood vessel in the brain or neck is the most frequent cause of a stroke. It can leave a portion of dead tissue in the brain, called a cerebral infarction, which can result in a disability. These blockages come from three different conditions:
  • thrombosis, the formation of a clot within a blood vessel of the brain or neck.
  • Embolism, the movement of a clot from another part of the body to the neck or brain.
  • Stenosis, a severe narrowing of an artery to the brain.

About 80 percent of all strokes are caused by blockage and the other 20 percent from bleeding. A hemorrhagic stroke can result from bleeding into the brain called intracerebral hemorrhage or into the space surrounding the brain called subarachnoid hemorrhage. While, less common than cerebral infarction or intracerebral hemorrhage, subarachniod hemorrhage can frequently lead to death.

Many strokes could be prevented by one’s paying attention to the warning signs and risk factors. The risk of a stroke goes up as both the number and the severity of risk factors increase. A physician can identify and help treat and monitor the progress of many of these warning signs and risk factors.

WARNING SIGNS:

* SUDDEN WEAKNESS, NUMBNESS OF THE FACE ARM AND/OR LEG
* TEMPORARY DIFFICULTY OR LOSS OF SPEECH, OR TROUBLE UNDERSTANDING SPEECH
* UNEXPLAINED HEADACHES OR CHANGE IN THE PATTER OF HEADACHES
* DOUBLE VISION WHICH LASTS FOR A SHORT TIME
* TEMPORARY UNSTEADINESS OR DIZZINESS

RISK FACTORS:

* HIGH BLOOD PRESSURE
* CIGARETTE SMOKING
* HEART DISEASE
* DIABETES
* TRANSIENT ISCHEMIC ATTACKS

A person who has had a stroke appears, literally, to be stricken down. He or she may be partially paralyzed, speechless, and sometimes, unconscious. If cells that control the movements of the arm are involved, the person will be unable to move his or her arm. However, if the cells that are destroyed only carry instruction from the controlling center to the muscles, new pathways many are made that utilize other nerves which bypass the damaged area or areas.

In such a case although the patient may be unable to move his arm at first, he will gradually regain control of the muscles used in the arm movements. The disturbance in circulation maybe due to any one of the following factors:

1) A small percentage of strokes are caused by a cerebral embolism which is a small clot of blood circulating in the bloodstream, lodges in one of the tiny blood vessels in the brain. Since blood cannot pass this plug, the nerve cell that the small vessel normally supplies with blood will die. The number of cells that die will depend on the size of the plugged vessel.
2) A more common cause of a stroke is a cerebral thrombosis, which is a stationary blood clot that forms in the blood vessel and closes it. The result is the same as in case of a cerebral embolism.
3) A stroke is also caused by hemorrhage from a broken blood vessel. The cells beyond the break are deprived of oxygen, and there is pressure on cells in the area surrounding the break. Some of these cells may be able to function again after the blood is absorbed and the pressure relieved. When blood escapes from a vessel, it quickly forms a clot using thrombin and myosin, which closes the break and stops the hemorrhage. Later the clot is absorbed, thus removing the pressure.
4) Any accident that causes physical damage to the brain may produce the same results as a stroke. In general, the symptoms will be similar; and the person may be treated in the same way as on whose disability is cause by a stroke.

Known treatable risk factors may explain the higher rates of death and disability from strokes among African-Americans and Hispanics. The proportion of people with theses risk factors is predominantly higher in African-Americans and other minorities. For example, about 33 percent of white adult American men have high blood pressure compared to 38 percent of African-American adult men and 25 percent of white adult American women have high blood pressure compared to 39 percent of adult African-American women. Smoking among white men at 28 percent and among white women at 28 percent; among African-American the figures are 33 percent for man and 22 percent for women.

Nearly 50 million American adults are overweight or obese. Primarily as a result of more risk factors, African-Americans experience more strokes, have more severe strokes, and are twice as likely to die of a stroke as white Americans. Risk factors conditions are frequently worse among some minorities and may lead to stroke recurrence, which is an important contributor to increased disabilities.

There are many effects that a stroke can have on an individual. The immediate physical effects of a stroke are that half the person’s body becomes paralyzed. He has no control over it and often cannot even that is it there. It can affect the arm and leg, but also the face, mouth, tongue, and eye. The other half of his body appears to be relatively normal.

Mentally, the person has received a sever shock. At first, he is sure he will be well in a few days or weeks. When he discovers that such is hot the case, his personality may change and he may seem to become an entirely different person. Patience and understanding are needed by anyone who will work with him at the extremely difficult times.

During recent years, interest in rehabilitation has increased greatly, especially with regard to people who have had strokes. Most hospitals have a "stroke team" that functions whenever a patient requires the teams help.

One day, physicians hope to be able to treat patients having a stroke by halting the damaging effects of chemicals processes -- processes of brain injury that last for several hours. Scientists know that not all of the brain damage occurs at the beginning of the symptoms. At the onset of a stroke, brain cells instantly decrease in activity. Some of the cells appear to be undamaged, potentially able to return to full functioning.

Within hours after a stroke a second phase sets in. At this point the brain swells and brain damage starts. This event of process can last several hours or even days. It is an unregulated chemical chain of reactions that feeds on itself. It can cause the death of cells in different areas that were not involved in the original stroke. Due to the biological process of this time lagging event, specific interventions will disturb the cascade, and the depressed brain cells can rejuvenate.

Over the past decade, scientists have solved many of the mechanisms involved in this cascade. A great deal of effort has been focused on three key mechanisms or otherwise known as the "fearsome threesome." Scientists have notified many drugs that can interfere with these links, which in turn protects the cells from the chemical processes. The fearsome threesome is: calcium influx, excitatory amino acids, and free radicals.

Calcium is normally maintained at low levels inside the brain cells and at high levels in the surrounding fluids. When a injury occurs too much calcium enters the cells, thus causing it to swell, quit working correctly and eventually burst.

Excitatory amino acids help brain cells communicate. They are tightly regulated within the brain cell and only released in small amounts. When a brain cell dies, the total amount of these chemicals is released at once. Releasing of glutamate, an amino acid, is a prime example of the releasing of excessive amounts of a chemical during a stroke.

Free radicals, which are extremely destructive molecules that are unneeded byproducts of normal metabolism. During injury, excess amounts of free radicals are generated which overwhelm the natural defenses. Free radicals attack membrane lipids. When the outer cells wall degrades and bursts, the cell dies, releasing its contents and beginning the cycle of destruction over again. Tirilazad mesylate, used in one clinical trail, neutralizes free radicals which may help short-circuit lipid peroxidation.

Exercising, not smoking, eating healthy foods, and recognizing stroke warning signs can save lives. Scientists are learning more about the complex mechanisms of stroke damage and how to prevent it. Modern brain imaging technologies are mapping functions to anatomy and pointing the direction to specific therapies. Promising drugs and rehabilitation strategies are being tested in clinical trials.


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The information presented here is not meant to be medical advice nor to act as a substitute for medical advice. Serious side-effects, including death, could result if one were to take any prescription medicine without the supervision of a physician.



Copyright 2003, Thomas Manaugh, PhD