Stroke, called a cerebral vascular accident, or CVA, is a disruption in blood flow to the brain. The third leading cause of death in the United States, the American Stroke Association reports that stroke is also the primary cause of disability among American adults. Although there are many risk factors for stroke, there are three causes of stroke.
Ischemia
Ischemia is a lack of oxygen-rich blood flow to cells. According to Donna D. Ignatavicius, MS, RN, and M. Linda Workman, Ph.D, authors of "Medical-Surgical Nursing: Critical Thinking for Collaborative Care", ischemia accounts for 80 percent of strokes. Ischemia is caused by anything that interrupts oxygenation of cells. In the case of stroke, arteriosclerosis is a the most common cause of ischemia. Arteriosclerosis is a buildup of plaque inside the body's blood vessels, primarily the arteries. As the plaque buildup increases, the lumen, or inside space, of the arteries narrows. When the arteries of the brain are affected by arteriosclerosis, cerebral blood flow is diminished, which causes ischemia or damaged to brain cells. Ischemia produces mild and sometimes vague symptoms of stroke. Eventually the arteries become completely blocked and cause a stroke capable of permanent and debilitating damage.
Brain tumors cause a small percentage of ischemic strokes. In the case of brain tumors, as the tumor grows it compresses blood vessels in the area of the brain where it is located, causing ischemia.
Embolism
Another cause of having a stroke is an embolism. An embolism is a blood clot, called a thrombus, or other substance, like a piece of intravenous tubing, that travels through the veins and arteries, called the vascular system, and lodges at some point in the body. The Mayo Clinic explains that in the case of stroke the embolism travels to the brain. Embolic strokes frequently result from a thrombus that breaks loose from its point of origin in a lower extremity. When the thrombus lodges in the brain, it blocks blood flow to cerebral tissue, causing cerebral cell damage and cell death.
Brain Hemorrhage
Brain hemorrhage is bleeding inside the brain. This type of stroke accounts for 20 percent of cerebral vascular accidents. Barbara McLean, CCNP, and Janice Zimmerman, M.D., authors of "Fundamental Critical Care Support," explain that causes of a hemorrhagic stroke can be a ruptured aneurysm--weakened blood vessel--or an arteriovenous malformation, which is an abnormal interconnected cluster of veins and arteries. When an artery ruptures, there is a loss of blood flow to a portion of the brain. The brain cells in this area get damaged from ischemia, or lack of oxygen. In addition, the blood that leaks from the ruptured artery into surrounding tissues irritates the tissues, causing vasoconstriction. Vasoconstriction is narrowing of blood vessels, which increases ischemia and enlarges the area of brain damage.
References
- American Stroke Association: Learn About Stroke
- "Medical-Surgical Nursing: Critical Thinking for Collaborative Care"; Donna D. Ignatavicius MS RN, & M. Linda Workman Ph.D; 2006
- The Mayo Clinic: Stroke: Causes
- "Fundamental Critical Care Support (4th ed.)"; McLean, B. & Zimmerman, J. L.; 2007
