A stroke, also called a cerebral vascular accident (CVA), is caused by a disruption in blood flow to a part of the brain. The disruption can happen because of something blocking a cerebral artery, such as a clot, or from a hemorrhage inside the brain. The result is ischemia, which is the death of cells as a result of a lack of circulating blood. Ischemia causes neurological complications resulting in disability.
Ischemia
An ischemic stroke also is called an occlusive stroke. These generally occur because of atherosclerosis, which is a buildup of plaque in blood vessels, primarily arteries. When cerebral arteries (arteries that bring blood to the brain) are affected by atherosclerosis, they become occluded, or blocked, resulting in ischemia. Donna D. Ignatavicius, M.S., R.N., and M. Linda Workman, Ph.D., authors of "Medical-Surgical Nursing: Critical Thinking for Collaborative Care," explain that 80 percent of strokes are ischemic in nature. However, ischemic strokes also can occur because of an embolism.
Embolism
The Mayo Clinic explains that an embolism is something that travels through the vascular system (veins and arteries) and lodges somewhere in the body; in the case of stroke, the embolism travels to the brain. An embolism can be a blood clot, called a thrombus, which commonly breaks loose from its point of origin in a leg. An embolism also can form from fat or infection. A foreign object that enters the bloodsteam, such as a piece of an intravenous catheter, can become an embolism as well. The end result is the same: ischemia of brain tissue.
Hemorrhage
Hemorrhage accounts for 20 percent of cerebral vascular accidents. Barbara McLean, CCNP, and Janice Zimmerman, M.D., authors of "Fundamental Critical Care Support," explain that a hemorrhagic stroke can result from a ruptured aneurysm or arteriovenous malformation. An aneurysm is a weakening in a blood vessel wall. High blood pressure can lead to rupture of an aneurysm. An arteriovenous malformation is an abnormality in the formation of veins and arteries in the brain. Essentially, veins and arteries get tangled up together and merge.
Arterial blood flows through veins; these vessels are not made to handle the higher pressures. Over time, and especially in the case of uncontrolled hypertension, an AVM may rupture. The result is a loss of blood supply to a part of the brain, which causes neurological damage.
References
- "Medical-Surgical Nursing: Critical Thinking for Collaborative Care"; Donna D. Ignatavicius, M.S., R.N., and M. Linda Workman, Ph.D.; 2006
- The Mayo Clinic: Stroke: Causes
- "Fundamental Critical Care Support (4th ed.)"; B. McLean and J.L. Zimmerman; 2007
