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A stroke happens when the blood supply to part of the brain is interrupted. As a result brain cells get less of the oxygen and nutrients that they need. Some brain cells can become damaged and others can die. This can cause different effects depending on where it happens in your brain.

There are two types of stroke:

• Ischaemic stroke - this type of stroke occurs when a blood clot blocks one of the arteries that carries blood to the brain. About 85 in every 100 strokes are ischaemic.

• Haemorrhagic stroke - this type of stroke occurs as a result of bleeding from a burst blood vessel, in or around the brain. About 15 in every 100 strokes are haemorrhagic.

A transient ischaemic attack (TIA) is similar to a stroke, but the symptoms do not last longer than 24 hours. See the section 'What is a TIA?' for more information about transient ischaemic attacks.

What are the signs and symptoms of a stroke?

A stroke is a medical emergency. Urgent treatment is essential because the sooner a person receives treatment for a stroke, the better the outcome is likely to be.

If you think that you or someone else is having a stroke phone 999 immediately and ask for an ambulance.

The signs and symptoms of stroke include:

• Sudden weakness or numbness, especially on one side of the body. It could be the face, arm, leg or a combination of these.
• Sudden blurred vision or loss of sight in part of the eye, one eye or both eyes.
• Sudden confusion, difficulty speaking or understanding.
• Sudden dizziness, loss of balance or lack of co-ordination.
• Sudden severe headache with no known cause.
• Sudden change to facial expression or inability to smile.

If you have any of these symptoms, even for just a short amount of time, call 999 and ask for for an ambulance.