Serious medical condition caused by the loss of blood supply to part of the brain. The two main types of stroke are ischaemic and haemorrhagic. Ischaemic strokes, caused by blockage of blood vessels due to blood clots, occur in around 80% of all cases. Haemorrhagic strokes, more commonly known as cerebral haemorrhages, occur when a blood vessel in the brain ruptures and bleeds into the brain (an intracelebral haemorrhage) or onto the surface of the brain (a subarachnoid haemorrhage). A stroke can cause permanent brain damage or even death very quickly after the onset of symptoms, and the condition is always regarded as a medical emergency.
Symptoms The characteristic symptoms of a stroke are muscle weakness and slurred or incomprehensible speech. Muscle weakness usually occurs only on one side of the face, with the mouth or eye dropping on the affected side and the loss of ability to smile. It may also be difficult to raise one or both arms due to weakness or numbing. Speech becomes garbled and can be lost completely. Transient ischaemic attacks (‘mini strokes’), with effects lasting less than 24 hours, still require investigation, as they tend to be precursors to a full-blown stroke.
Causes Strokes can be caused by any condition that physically affects blood vessels, especially those that reduce wall strength and size (such as aneurysms or atherosclerosis) or produce blood clots (such as sickle cell disease). The risk of strokes increases with the age of the individual, those over 65 years being most at risk. However, strokes can occur at any stage of life and around 25% of cases occur in those under 65. High blood pressure, heart disease, obesity, smoking, and high cholesterol are known risk factors, and strokes also commonly occur in patients with irregular heartbeats (see fibrillation).
Treatment Speed of treatment is critical, as brain damage continues until the blood supply is restored. Many hopsitals have specialist stroke units, which provide faster diagnosis and treatment. Initially the type of stroke that has occurred is determined by conducting a brain scan. If caught within a few hours, ischaemic strokes can be treated by using ‘clot-busting’ drugs, such as alteplase, to break up the blockage. Anticoagulants, such as aspirin and warfarin, are administered to restrict blood clotting and help prevent further strokes. Treatment for haemorrhagic strokes usually requires neurosurgery, which takes signficantly longer to stop the damage, leading to higher rates of mortality and permanent disability.
Long-term health problems are a common consequence of strokes. Left-brain strokes affect the right-hand side of the body, while right-brain strokes affect the left-hand side of the body. Loss of facial and limb muscle control, paralysis, speech difficulties, and impaired mental function are common. Not all effects are permanent, and functionality can be restored by various courses of rehabilitation tailored to the patient's symptoms. Treatments include physiotherapy, psychology, and speech therapy.
Prevention Strokes can sometimes be prevented by surgery (as in the case of some aneurysms) or by use of anticoagulant drugs, vitamin E, or daily aspirin to minimize the risk of stroke due to blood clots. Lifestyle changes, especially reduction of smoking and drinking, weight reduction, and regular exercise, are known to reduce an individual's risk of stroke.
American Heart Association
Brain Basics: Preventing Stroke
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The verb stroke [OE] and the noun stroke  are different words, but they come ultimately from the same source - the prehistoric Germanic...