What is a stroke?

A stroke is a brain attack. It happens when the blood supply to part of the brain is cut off, killing brain cells.

Ischaemic stroke

Most strokes happen because of a blockage in an artery leading to the brain. This is called an ischaemic stroke.

An ischaemic stroke happens when a blockage cuts off the blood supply to the brain. You may also hear it referred to as a clot.

In ischaemic stroke, the blockage can be caused by a blood clot forming in an artery leading to the brain, or within one of the small vessels deep inside the brain.

A transient ischaemic attack (TIA or mini-stroke), is the same as a stroke but the symptoms only last for a short amount of time. It is a major warning sign of a stroke and should always be taken seriously.

Find out more about what causes an ischaemic stroke.

Haemorrhagic stroke

If blood leaks from a blood vessel in or around the brain, this is called a haemorrhagic stroke. You may also hear it called a brain haemorrhage or a brain bleed.

In the UK, around 15% of strokes are haemorrhagic (due to a bleed), and about 85% are ischaemic (due to a blockage to the blood supply in the brain).

Haemorrhagic stroke tends to affect younger people than ischaemic stroke and is most common in people aged between 45 and 70. Most strokes in the UK happen over the age of 70.

There are two main types of haemorrhagic stroke:

  1. Bleeding within the brain: called an intracerebral haemorrhage, or intracranial haemorrhage (ICH).
  2. Bleeding on the surface of the brain: called a subarachnoid haemorrhage (SAH).

Bleeding within the brain

When an artery inside the brain bursts it is called an intracerebral haemorrhage. About 10% of all strokes are of this type. The blood leaks out into the brain tissue at high pressure, killing brain cells and causing brain swelling.

Bleeding on the surface of the brain

The brain sits inside a fluid-filled cushion of membranes that protects it from the skull, called the subarachnoid space. If blood vessels near the surface of the brain burst and blood leaks into the subarachnoid space, this is called a subarachnoid haemorrhage (SAH).

SAH accounts for around 5% of all strokes, and it is most often caused by a burst aneurysm (a bulging of the wall of an artery).

Subarachnoid haemorrhage (SAH) can run in families. If you have had a SAH and are concerned that this might affect your own family, speak to your GP. They can help you understand the causes of your stroke and the risks for your family members.

Find out more about haemorrhagic stroke.

Transient ischaemic attack (TIA or mini-stroke)

A TIA is the same as a stroke, but the symptoms last a short time. You get stroke symptoms because a clot is blocking the blood supply in your brain. When the clot moves away, the stroke symptoms stop.

Why is it urgent?

Having a TIA is a warning that you are at risk of having a stroke. The risk is greatest in the first days and weeks after a TIA.

Why did it happen?

Clots in the brain can happen for different reasons, and doctors treat you to reduce the risk of another clot happening. Doctors also look for risk factors like high blood pressure or smoking. They will give you the treatment and advice you need.

Will I have a stroke?

It’s difficult to tell for sure if someone is going to have a stroke after a TIA. But having a TIA is a major sign that you have a much higher than normal risk of having a stroke. That’s why doctors work so hard to find out what caused it and help you improve your health. And by following treatments and making healthy lifestyle changes, you can actively reduce your risk of a stroke.

Spot the signs of a stroke and TIA

A TIA has the same main symptoms as a stroke. Use the FAST test:

FAST test

There are other common signs of TIA and stroke. They include:

  • Sudden weakness on one side in your arms, hands or legs.

  • Sudden blurred vision or loss of sight in one or both eyes.

  • Sudden memory loss or confusion.

  • Dizziness or a sudden fall.

A TIA is a medical emergency, the same as a stroke. If you spot the signs of a TIA or stroke, call 999. Don’t wait to see if the symptoms pass.

If you didn’t get medical help right away, get an urgent appointment with your GP or go to an NHS urgent treatment centre. You need to get your symptoms checked as soon as possible.

Find out more about what causes a TIA.

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