Strokes are disabling in many ways: they can cause physical disability, are the cause of about 20 per cent of all types of dementia and frequently result in depression.

Strokes occur when the blood supply to part of the brain is disrupted and brain cells are deprived of the oxygen and nutrients they need. As a result an area of brain tissue may become damaged or die.

There are two main types of stroke: ischaemic and haemorrhagic. There are also other, more rare, types of stroke.

Most strokes happen when a blood clot blocks one of the arteries carrying blood to the brain. These are called 'ischaemic' strokes - 'ischaemia' meaning 'an inadequate flow of blood'. An ischaemic stroke can result from either a cerebral thrombosis or a cerebral embolism.

In a cerebral thrombosis, a blood clot, known as a 'thrombus' forms in an artery supplying blood to the brain. This is more likely to happen if the lining of the artery has become furred up with fatty deposits over the years. In a cerebral embolism, a blood clot, which has formed elsewhere in the body, is carried by the bloodstream to the brain where it blocks an artery.

Haemorrhagic strokes are caused by the rupture of a blood vessel and bleeding in or around the brain.

What is a mini-stroke?

Mini-strokes, often referred to as 'transient ischaemic attacks' (TIA), occur when the blood supply to the brain is briefly interrupted. The symptoms are very similar to stroke but they last for less than 24 hours and there is always complete recovery. However, people who experience a mini-stroke are at much higher risk of stroke and should see their GP immediately to see what preventative measures they can take.