Damage to part of the brain caused by an interruption in its blood supply, sometimes called a brain attack
- More common over the age of 70
- More common in males
- Smoking and a high-fat diet are risk factors
- Genetics as risk factor depends on the cause
If the blood supply to part of the brain is interrupted, the affected region no longer functions normally. This condition is called a stroke, although it is often described as a “brain attack” to highlight the need for urgent medical attention. A stroke may be due to either a blockage or bleeding from one of the arteries supplying the brain.
There is usually little or no warning of a stroke. Immediate admission to hospital for assessment and treatment is essential if there is to be a chance of preventing permanent brain damage. The after effects of a stroke vary depending on the location and extent of the brain tissue affected. They range from mild, temporary symptoms, such as blurred vision, to lifelong disability or death.
If the symptoms disappear within 24 hours, the condition is known as a transient ischaemic attack, which is a warning sign of a possible future stroke.
How common is it?
Each year, about 120,000 people in the UK have a stroke. The condition is more common in men and in older people. A 70-year-old living in the UK is about 100 times more likely to have a stroke than a 40-year-old. Although the number of deaths from stroke has fallen over the last 50 years, stroke is still the third most common cause of death in the UK after heart attacks and cancer.
What are the causes?
About 80 per cent of all strokes are due to blockage of an artery supplying the brain; these are known as ischaemic strokes. This type of stroke occurs as a result of cerebral thrombosis or cerebral embolism. In cerebral thrombosis, a blood clot forms in an artery in the brain. In cerebral embolism, a fragment of a blood clot that has formed in another part of the body, such as the heart or the main arteries of the neck, travels in the blood and lodges in an artery supplying the brain.
The remaining 20 per cent of strokes are due to bleeding from an artery supplying the brain (cerebral haemorrhage); these are known as haemorrhagic strokes. Cerebral haemorrhage occurs when an artery supplying the brain ruptures, causing blood to leak out into the surrounding tissue.
The blood clots that lead to cerebral thrombosis and cerebral embolism are more likely to form in an artery that has been damaged by atherosclerosis, a condition in which fatty deposits build up in artery walls. Factors that increase the risk of atherosclerosis developing are high blood pressure (see Hypertension), a high-fat diet, smoking, diabetes mellitus, and high levels of lipids in the blood (see Inherited hyperlipidaemias).
Cerebral embolism may be a complication of heart rhythm disorders (see Arrhythmias), heart valve disorders, and recent myocardial infarction, all of which can cause blood clots to form in the heart. The risk of cerebral embolism, thrombosis, or haemorrhage is increased by high blood pressure. Sickle-cell disease, an abnormality of the red blood cells, also increases the risk of cerebral thrombosis because abnormal blood cells tend to clump together and block blood vessels. Less commonly, thrombosis occurs as a result of the cerebral arteries becoming narrowed due to inflammation of the arteries, a condition called vasculitis. This inflammation may, in turn, be due to various underlying conditions, such as the autoimmune disorder polyarteritis nodosa.
What are the symptoms?
In most people the symptoms develop rapidly over a matter of seconds or minutes. The exact symptoms depend on the area of the brain affected. The symptoms may include:
Facial weakness, which may cause drooping of the face, mouth, or eye on one side, drooling, and the inability to smile.
Arm weakness or numbness, causing the inability to raise both arms and keep them raised.
Speech problems, such as slurred speech.
Weakness, numbness, or paralysis on one side of the body.
Visual disturbances, such as loss of part of the field of vision or loss of vision in one eye.
Difficulty in finding words and in understanding what others are saying.
If the stroke is severe, areas of the brain that control breathing and blood pressure may be affected or the person may lose consciousness or even lapse into a coma. in these circumstances, the outcome may be fatal.
How is it diagnosed?
If you suspect that a person has had a stroke, get emergency medical help.
Imaging of the brain, such as CT scanning or MRI, may be used to find out whether the stroke was caused by bleeding or a blockage in a vessel. Cerebral angiography, MRA (magnetic resonance angiography, a form of MRI), or carotid Doppler scanning may be performed to help identify narrowed arteries that can be corrected by surgery. Further tests may be carried out to look for the source of an embolus. These tests may include echocardiography to assess the heart valves and heart monitoring (see ECG) to check the heart rhythm.
What is the treatment?
The initial treatment following a stroke is close monitoring and nursing care to protect the person’s airways during recovery. If CT scanning reveals a clot in a blood vessel, immediate treatment with a thrombolytic drug to dissolve the clot may be given. This treatment may improve the outcome and is now used increasingly. However, the drug increases the risk of bleeding within the brain and must be given within a few hours of the onset of symptoms.
Long-term treatment to reduce the risk of further strokes will depend on the cause of the stroke. If the cause was a cerebral embolism, you may be given drugs such as aspirin, clopidogrel, or warfarin, which act on clotting factors in the blood to reduce the risk of further clots (see Drugs that prevent blood clotting). If a narrowed artery has been identified, it may be widened surgically. After a cerebral haemorrhage, treatment may be focused on the underlying cause, although in a few cases, surgery to remove a clot from the brain is carried out first. Long-term treatment may include antihypertensive drugs to lower blood pressure and a statin (see Lipid-lowering drugs) to reduce blood cholesterol levels. If the stroke is the result of inflammation of the arteries, corticosteroids may be given. Depression is quite common after a stroke and may need treatment.
In all cases of stroke, rehabilitative therapies, such as physiotherapy, occupational therapy, and speech therapy are essential. Lifestyle changes, such as reducing fat in your diet and giving up smoking, can reduce the risk of another stroke.
What is the prognosis?
The outlook after a stroke is often difficult to predict at first and depends to some extent on the cause. About one-third of people make a full or almost full recovery. Another third have some disability, and may need long-term care in a nursing home. Symptoms that persist for more than 6 months are likely to be permanent. About 1 in 5 people dies within a month of the stroke.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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