A stroke happens when blood supply to the brain is interrupted. Blood is carried to the brain by blood vessels called arteries. Blood contains oxygen and important nutrients for your brain cells. Blood may be interrupted or stop moving through an artery, because the artery is blocked (ischaemic stroke) or bursts (haemorrhagic stroke). When brain cells do not get enough oxygen or nutrients, they die. The area of brain damage is called a cerebral infarct.

Brain cells usually die shortly after the stroke starts. However, some can last a few hours, if the blood supply is not cut off completely. If the blood supply can be returned in the minutes and hours after the stroke, some of these cells may recover. If not, they will also die.

A transient ischaemic attack (TIA) happens when there is a temporary interruption to the blood supply to the brain. It causes the same symptoms as a stroke, but these go away completely within 24 hours.

Why is stroke a medical emergency?

Emergency medical treatment is crucial for three reasons:

• Emergency: Only a doctor can decide whether you are suffering a stroke.
• Treatment: Some treatments must be given within three hours of the stroke starting.
• Assessment: You will need to be assessed by a doctor who will look at treatments to prevent another stroke.

If you are suffering a stroke or mini stroke (TIA), emergency medical treatment could save your life and reduce the likelihood of permanent brain damage. The longer a stroke remains untreated, the greater the chance of stroke related brain damage. Emergency medical treatment soon after stroke symptoms begin, improves the chances of survival and successful rehabilitation.