Stroke results from the sudden loss of blood flow to the brain, usually a specific part of the brain (see fig. 1). The brain needs a constant supply oxygen and nutrition so when blood flow is interrupted, that part of the brain begins to die. Blood flow can be interrupted by either a blockage, often associated with a blood clot that has traveled to the brain or formed within the brain’s blood vessel, or by a ruptured blood vessel that results in bleeding into the brain. When part of the brain is injured in this way it no longer functions normally. There are many symptoms of stroke but common symptoms include weakness or numbness involving parts of the body, slurred speech, partial or complete loss of vision and loss of balance.
Examples of some of the risk factors for stroke include high blood pressure, high cholesterol, smoking, diabetes, and severe carotid artery disease (the arteries in the neck through which blood flows to the brain). Atrial fibrillation, an abnormal heart rhythm, is also a common risk factor for stroke. Stroke due to atrial fibrillation is thought to result from blood clots that form in the heart and travel to the brain.
Symptoms of stroke can be brief and reversible. This is often called a TIA (transient ischemic attack). TIA’s are considered a “warning” stroke and indicate a need to evaluate for causes of stroke and begin treatment to prevent stroke that might be permanent.
Many people that have a stroke will be found to have carotid artery narrowing from atherosclerosis . The carotid arteries, which travel through the neck, supply blood to much of the brain. The atherosclerotic plaque in the carotid arteries can rupture, cause a blood clot and either interrupt blood flow, or, more commonly, cause small amounts of debris and blood clots associated with a rupture to travel through the circulation to the brain. Rupture of plaque and blood clots within the brain itself can have a similar effect.
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