Animation: stroke
Take a look at this animation to see what happens to your brain if you have a stroke.
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The brain controls all your bodily functions — including your breathing, consciousness, communication and movement.
Blood flows to the brain through a network of arteries supplying vital nutrients and oxygen.
A stroke happens when blood supply to part of the brain is interrupted.
If the blood supply is cut off for more than a few minutes, brain cells start to die. The affected area stops working properly.
There are 2 types of stroke.
- Ischaemic stroke: blockage of an artery by a blood clot (about 85 per cent of all strokes).
- Haemorrhagic stroke: rupture of an artery causing bleeding into or around the brain (about 15 per cent of all strokes).
Ischaemic stroke
In an ischaemic stroke, an artery supplying part of the brain becomes blocked.
This can be due to atherosclerosis — build up of fatty deposits in the inner wall of arteries over many years. One of these fatty deposits may rupture and a blood clot may form at the site, blocking the artery.
Ischaemic stroke can also be caused by a blood clot that forms elsewhere in the body and then dislodges. The clot may be carried in the bloodstream and lodge in an artery supplying the brain. This process is called embolism.
Haemorrhagic stroke
The second type of stroke is haemorrhagic stroke, caused by rupture of an artery supplying the brain.
This is most likely to happen if there is uncontrolled high blood pressure, an aneurysm (ballooning of an artery) or a malformation of the brain blood vessels (arteriovenous malformation).
Because arterial blood is at high pressure, rupture of an artery tends to cause severe bleeding (haemorrhage) within or around the brain. This puts pressure on the delicate brain tissue, causing death of brain cells.
Symptoms
Because one side of the brain controls the opposite side of the body, a stroke on the right side of the brain will generally cause symptoms on the left side of the body and vice versa.
Symptoms of stroke usually come on suddenly — any of the following can occur:
- difficulty understanding speech;
- blurred or double vision, visual loss;
- loss of balance or coordination;
- difficulty speaking;
- weakness, paralysis or drooping of the face;
- severe headache; or
- weakness, paralysis or numbness — usually of one arm or leg, or all of one side of the body.
Stroke is a medical emergency — it can be fatal or cause permanent disability. Call 000 if you or someone you know suddenly experiences any of the above symptoms. Rapid hospital treatment makes a full recovery more likely.
Other, less common symptoms of stroke are nausea and vomiting, drowsiness or unconsciousness, seizures and loss of control of the bladder or bowel.
Transient ischaemic attack
Some people have warning signs of a stroke. These are called transient ischaemic attacks (TIAs) or mini-strokes and are due to a temporary disruption of blood supply to the brain.
The symptoms of TIA are the same as those of a stroke, except they go away within 24 hours — sometimes lasting only a few minutes.
About one in 5 people who have a TIA develop a major stroke in the next 3 months. So it is important that you seek medical help immediately if you have stroke symptoms, even if they are fleeting.
Last Reviewed: 24 April 2007
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