What is a stroke?
A stroke is caused by an interruption of the blood supply to part of the brain. The medical term for stroke is cerebrovascular accident (CVA). There are mainly two types of strokes: ischaemic strokes and haemorrhagic strokes. Stroke is not a heart attack as often misunderstood.

What causes a stroke?
A stroke is caused, either by a blockage of a cerebral artery by clot (cerebral thrombosis) or a bleed in to the brain from a burst blood vessel (haemorrhage). The most common (about 85 per cent) cause of stroke is cerebral thrombosis. A retrospective study showed 3474 stroke patients admitted in Dhaka Medical College Hospital last ten years. 78 per cent of those patients suffered from ischaemic strokes. Of the stroke patients, 35 per cent die after 'infarction stroke' within a month, while 55 percent die after brain haemorrhage.

What is a mini stroke or TIA?
TIA stands for Transient Ischaemic Attack. It refers to the sudden onset and brief disturbance (usually for few minutes) to any of the many functions of the brain. So TIA may cause brief loss of vision or loss of speech or weakness of one side of the body. Full recovery usually occurs within few minutes and the patient is left with no obvious disability. Usually a third of those who have had a TIA get full-blown stroke within five years.

What increases risk of a stroke?
There are certain established risk factors that put an individual at risk of stroke. The most common is increasing age. Other risk factors involves high blood pressure, high cholesterol, smoking, diabetes, overweight, irregular heartbeat (atrial fibrillation) and prior stroke (CVA) or mini stroke (TIA). Recently arsenic poisoning through contaminated drinking water is an added risk factor for stroke in Bangladesh. Approximately 10 per cent of people who have stroke will get a recurrence, most likely to occur in the first year. With the passage of time the risk of recurrence lessens considerably.

What are the effects of stroke?
When the brain is deprived of oxygen (due to ischaemia or haemorrhage) some cells die, others become damaged. The effects vary widely, depending on what part of the brain and how much brain tissue has been damaged. There may be weakness of an arm or leg, usually occurs about 80% of stroke patients. Other effects are difficulty with sensation, or loss of vision. Other people may develop difficulty with speech or concentration, difficulty in swallowing, bladder problems, or emotional problems such as depression. The majority of people survive after their stroke.

Prevention
Knowing your risk factors and living healthfully are the best steps you can take to prevent a stroke. In general, a healthy lifestyle means control high blood pressure (hypertension), lower blood cholesterol, reduce salt and saturated fat intake, take B complex vitamins B-6, B-12 and folic acid (folate), don't smoke, control diabetes.

Maintain a healthy weight, exercise regularly, eat healthy foods and manage stress. Abide by the doctor's advice if you have already had signs, or a previous stroke.

Dr. Md Habibe Millat MBBS, FRCS(Edin), a Senior Specialist Registrar, Department of Cardiothoracic Surgery, Cork University Hospital, Republic of Ireland.