Stroke, or brain attack, occurs when the brain is damaged due to a disruption of blood supply. The brain requires a constant supply of energy to perform its functions. If blood flow to the brain is restricted or cut off at any point, the brain suffers injury. Should the disruption continue for more than several minutes, the brain cells may become permanently damaged and tissue in the affected region may die.
The resultant loss or alteration of bodily functions due to an inadequate supply of blood to one or several parts of the brain is called a stroke.
There are two main types of stroke – ischaemic and haemorrhagic.
In ischaemic stroke, which accounts for approximately 80% of all strokes, blood supply to the brain is disrupted due to an obstruction in one or more blood vessels. Such obstruction often occurs in one of the two carotid arteries in the neck carrying oxygenated blood from the heart to the brain.
A blood clot may also develop at other locations in the body and travel through the bloodstream until it lodges itself in a blood vessel which is already narrowed by a pre-existing condition such as atherosclerosis. About 10% of ischaemic strokes are preceded by transient ischaemic attacks (TIAs). These are mini strokes arising from a temporary interruption of blood supply to the brain. They usually last for only a few minutes, and most of their symptoms disappear completely within 24 hours.
Less common is haemorrhagic stroke which occurs when one or more blood vessels in the brain rupture. Blood leaking from the ruptured vessel compresses other vessels nearby and eventually forms into a clot, cutting off blood supply to the surrounding brain tissue. In general, a haemorrhagic stroke tends to affect larger areas of the brain than does an ischaemic stroke, resulting in greater impairment of the victim’s bodily functions.
The symptoms of both types of stroke are similar, although those of haemorrhagic stroke may be more sudden and severe.
Common symptoms include:
- Weakness and/or numbness on one side of the body
- Slurred speech;
- Loss of vision in either or both eyes
- Giddiness
- A sudden, severe headache
- Drowsiness, followed in some cases by coma
- Unsteadiness and loss of muscular coordination
The symptoms experienced by a stroke victim vary depending on the size and location of the blood clot which precipitates the stroke. For some patients, the symptoms may occur suddenly; for others, they may develop slowly over the course of several hours or even a few days.
The main risk factors for stroke are:
- Age
- High blood pressure (hypertension)
- High levels of LDL/“bad” cholesterol
- Diabetes mellitus
- Smoking, including passive smoking
- Excessive alcohol consumption
All of these factors contribute to atherosclerosis (hardening of the arteries), which in turn increases the likelihood of an ischaemic stroke. Similarly, these risk factors may cause blood vessels to weaken, resulting in a haemorrhagic stroke.
Fortunately, although some of the risk factors for stroke (for instance, age) cannot be altered, the majority can be reduced by adopting healthy living practices such as:
- Monitoring your blood pressure regularly and seeking prompt medical treatment if you are found to be hypertensive
- Having your blood sugar and cholesterol levels tested periodically
- Maintaining a healthy body weight
- Eating a healthy, well-balanced diet
- Incorporating regular exercise into your daily routine
- If you are a smoker, giving up smoking
- Avoiding or stopping drug and alcohol abuse
Taken together, these measures can go a long way in preventing stroke.
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