Stroke

Damage to part of the brain caused by an interruption to its blood supply. The interruption is most often due to the blockage of a cerebral artery by a blood clot, which may have formed within the artery (see thrombosis), or may have been carried into the artery in the circulation from a clot elsewhere in the body (see embolism). Stroke may also result from localized haemorrhage due to rupture of a blood vessel in or near the brain. The incidence of stroke rises with age and is higher in men. Certain factors increase the risk. The most important are hypertension and atherosclerosis (and, by association, factors such as smoking that contribute to these disorders). Other risk factors are atrial fibrillation, a damaged heart valve, and a recent myocardial infarction; these can cause clots in the heart which may migrate to the brain. Symptoms usually develop abruptly and, depending on the site, cause, and extent of brain damage, may include headache, dizziness, visual disturbance, and difficulty in swallowing. Sensation, movement, or function controlled by the damaged area of the brain is impaired. Weakness or paralysis on one side of the body, called hemiplegia, is a common effect of a serious stroke. A stroke that affects the dominant cerebral hemisphere may cause disturbance of language (see aphasia). About a third of major strokes are fatal, a third result in some disability, and a third have no lasting ill effects (see transient ischaemic attack). In some cases, urgent treatment may improve the chances of recovery. ECG, CT scanning, chest X-rays, blood tests, angiography, and MRI may be used to investigate the cause and extent of brain damage. If a stroke is proven by scan to be due to thrombosis, thrombolytic drugs may be given. Anticoagulants may be given if there is an obvious source of an embolism, such as atrial fibrillation or a narrowed carotid artery. In some cases, antiplatelet agents such as aspirin are given. In most cases, attention to hydration and pressure areas, and good nursing care, are the most important influences on outcome. Physiotherapy may restore lost movement or sensation; speech therapy may help language disturbances.