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What causes a stroke?

There are two main types of stroke, and each has different causes. The first type, an ischaemic stroke, occurs when a blood clot blocks an artery serving the brain, disrupting blood supply. Very often an ischaemic stroke is the end result of a build up of cholesterol and other debris in the arteries (atherosclerosis) over many years.


An ischaemic stroke may be due to:

Blood clot:
A blood clots get stuck in an artery and blocks the blood flow.

The second main type of stroke is a haemorrhagic stroke, when a blood vessel in or around the brain bursts, causing a bleed or hemorrhage. Long-standing, untreated high blood pressure places a strain on the artery walls, increasing their risk of bursting and bleeding.


A haemorrhagic stroke may be due to:

Haemorrhagic stroke:
When an artery bursts blood is forced into the brain tissue, damaging cells so that area of the brain can't function.

1. An intracerebral haemorrhage, in which a blood vessel bursts within the brain itself.
2. A subarachnoid haemorrhage,in which a blood vessel on the surface of the brain bleed into the area between the brain and the skull, known as the subarachnoid space.

**Aknowledgement:
Diagrams used with permission from Stroke Foundation of New Zealand

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