Stroke

A stroke, sometimes called a brain attack, is a medical emergency in which part of the brain loses its blood supply. Without oxygen and glucose, brain cells begin to die within minutes, so a stroke can cause lasting disability or death. Its effects depend on which area of the brain is damaged.

Most strokes, around four in five, are ischemic: a blood clot or fatty plaque blocks an artery to the brain, often in someone with atherosclerosis or the irregular heart rhythm atrial fibrillation. Hemorrhagic strokes happen when a weakened artery leaks or ruptures, often because of high blood pressure or an aneurysm, and the escaping blood damages and compresses brain tissue. A transient ischemic attack, or mini-stroke, is a brief blockage that clears without permanent damage but signals a high risk of a full stroke.

Signs come on suddenly: weakness or numbness, usually on one side of the body, a drooping face, slurred or confused speech, loss of vision or balance, and sometimes a severe headache. Speed matters, because treatments that dissolve or remove a clot work only within a window of a few hours. High blood pressure is the most important risk factor that can be changed.