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:
A blood clots get stuck in an artery and blocks the blood flow.
- A cerebral thrombosis, in which a blood clot (thrombus) forms in a main artery leading to the brain, cutting off body supply.
- A cerebral embolism, in which a blood clot forms in a blood vessel elsewhere in the body, for instance in the neck or the heart, and is carried in the bloodstream to the brain.
- A lacunar stroke, in which in the blockage is in the small blood vessels deep within the brain.
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:
When an artery bursts blood is forced into the brain tissue, damaging cells so that area of the brain can't function.
- An intracerebral haemorrhage, in which a blood vessel bursts within the brain itself.
- 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.
Diagrams used with permission from Stroke Foundation of New Zealand
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