Реферат: Stroke Essay Research Paper Stroke an injury
Stroke Essay, Research Paper
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, although Americans managed to cut the stroke death rate nearly in half during the 1970’s and 1980’s the 1990’s is the Decade of the Brain. The nonfatal strokes, which have been decreasing along with the stroke death rate, now appear to be increasing for unknown causes. Of the more than three million Americans who have survived a stroke, more than two million end 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 effects the persons’ outcome.
A stroke or “brain attack” 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. While not usually fatal, 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, is 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 haemorrhagic 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 either cerebral infarction or intracerebral hemorrhage, subarachniod hemorrhage can frequently lead to death. Many strokes could be prevented by paying attention to the waring signs and risk factors.
Having a risk factor for stroke doesn’t necessarily foretell a stroke. Conversely, not having a risk factor doesn’t mean a stroke can’t occur. But 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.
* 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
* HIGH BLOOD PRESSURE
* CIGARETTE SMOKING
* HEART DISEASE
* TRANSIENT ISCHEMIC ATTACKS
A person who has had a stroke appears, literally, to be stricken down. He or she may be partially paralysed, 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 centre 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 too fat, but 20 percent of them are over their desired weight. 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.
To show some hope for these risk factor minorities, Dr. Ralph Sacco at Columbia University in New York City is investigating stroke recurrences in African-Americans and Hispanics. There is little data contrasting stroke incidence, risk, and prognosis in black, Hispanics and white in the same population living in the same environment, and area using the same methods. Dr. Sacco’s study will determine the incidence of a stroke, assess the effect of stroke risk factors, and the following participants for up to four years looking for stroke recurrence or death.
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 paralysed. 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.
The effects of a stroke can be devastating to their family and themselves. From my personal experience, my aunt’s friend who is 93 and my girl friend’s grandfather who is 76, has noticeable change the way I act around them and talk to them.
In my aunts friends’ case, he has not fully recovered from his stroke about three weeks ago, although this is only a short time for recovery, I feel that he will never regain what he has lost. He has lost short term memory, some sight and his speech are somewhat slurred. It funny, if you ask him how much a bag of groceries were in England 70 years ago, he would tell “you it to the penny.” But he still calls me Chris, my brother, every time I see him.
My girl friend Tracy’s, grandfathers’ case, he has recovered fully. When he was in the hospital, he called his great-grandson the name of his grandson and vis-versa. The family thinks that, that is what pushed his fully recovery. The surrounding of family members can trigger the brain’s memory to start thinking and comprehending clearly. The only thing that has change about him is that he swears now!
One day physicians hope to be able to treat patients having a stroke by halting the damaging effects of the everyday chemicals process. These effects result in the process of brain injury which 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, but can recover, back to full functioning cells. 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 weren’t even 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 been supported by the NINED (National Institute of Neurological Disorders and Stroke) have solved many of the mechanisms involved in this cascade. A great deal of effort has been focussed on three key mechanisms or otherwise known as the “fearsome threesome.” Scientists have notified many drugs which can interfere with these links, which inturn 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 helps 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.
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 defences. 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, neutralzes free radicals which may help short-circuit lipid peroxidation.
Glutamate an amino acid, is a prime culprit in the releasing of excessive amounts during a stroke. In a break through finding, NINDS grantee Dr. Charles F. Stevens, has shown that the nerve cell releasing glutamate rather than the cell activated by glutamate regulates long-term potential. This finding creates new ways for therapeutic interventions that may eventually maintain the normal function of glutamate, help preserve brain cells and retain memory threatened during a stroke.
Modern technology such as ultrasound and magnetic resonance angiography (MRA) coupled with clear clinical symptoms may eventually replace many X-rays. These modern imaging methods are not only noninvasive and essentially risk-free but much, much cheaper.
Stroke patients recovering from impaired language function may benefit from the research of scientists. They discovered that certain parts of the brain, using a postron emission tomography (PET) are activated when people read groups of letters that obey spelling rules but are not activated when people are shown nonsense groups. Since many stroke patients lose their ability to use or understand language, these findings will be a basis for developing better methods to help restore language skills.
While modifying lifestyles, exercising, not smoking, eating healthy foods, and recognizing stroke warning signs many 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 trails as you are reading this.
After years of discouraging results, the positive results will lead to renewed efforts to make even more progress in treating and preventing the devastating consequences of a stroke.