A stroke, or “brain attack,” occurs when blood circulation to the brain fails. Brain cells can die from decreased blood flow and the resulting lack of oxygen. There are two broad categories of stroke: those caused by a blockage of blood flow and those caused by bleeding into the brain. A blockage of a blood vessel in the brain or neck, called an ischemic stroke, is the most frequent cause of stroke and is responsible for about 80 percent of strokes. These blockages stem from three conditions: the formation of a clot within a blood vessel of the brain or neck, called thrombosis; the movement of a clot from another part of the body such as the heart to the brain, called embolism; or a severe narrowing of an artery in or leading to the brain, called stenosis. Bleeding into the brain or the spaces surrounding the brain causes the second type of stroke, called hemorrhagic stroke.
The most common symptoms of a stroke are:
- Weakness or numbness of the face, arm, or leg on one side of the body
- Loss of vision or dimming (like a curtain falling) in one or both eyes
- Loss of speech, difficulty talking, or understanding what others are saying
- Sudden, severe headache with no known cause
- Loss of balance or unstable walking, usually combined with another symptom
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