A sudden loss of the blood supply to a part of the brain causes a stroke, also known as a cerebrovascular accident, or CVA. There are two major types of strokes. Hemorrhagic stroke, the least common, occurs when a blood vessel feeding the brain bursts open, leaking blood into the brain tissue. The more common type of stroke is the ischemic stroke.
Features
When an artery supplying blood to the brain becomes narrowed by plaque buildup, blood flow becomes sluggish, leading to clots that block blood from reaching a part of the brain. When deprived of blood, brain tissue dies. Sometimes clots form in the heart, break off and cause a stroke when they reach the brain.
Significance
A stroke's damage to the brain leads to significant impairment including paralysis, difficulty in understanding or speaking, visual problems, coma or death. Only about 35 percent of people who suffer an ischemic stroke recover all or most of their normal functioning.
Risk Factors
Controlling risk factors for stroke reduces the risk of having one. Age, race and family history of stroke are unalterable risk factors. High blood pressure, diabetes, underlying heart rhythm disorders including atrial fibrillation, smoking, obesity, lack of exercise, and high LDL or low HDL cholesterol levels are modifiable risks.
Pathology
Plaque buildup, or atherosclerosis, leads to obstruction of blood flow in vessels supplying the brain. Plaque is made up of cholesterol, cells, calcium and other substances and forms when there is too much of the bad cholesterol, LDL, in the blood. The presence of other risk factors for stroke accelerates the process. Two clot-forming processes are the significant narrowing of blood vessels and the rupturing of plaque, which releases clot-forming substances.
Considerations
In treating a stroke, it is important to first diagnose the type of stroke. Clot-busting drugs, which dissolve clots, can be used only in ischemic strokes, where a clot is the underlying cause. Use of these drugs in hemorrhagic stroke would worsen bleeding into brain tissue.
