There are three types of strokes a person can have. An ischaemic stroke occurs when the artery supplying blood to the brain becomes blocked, an intracerebral haemorrhage occurs when a weakened artery ruptures and begins to bleed into the brain, and a subarachnoid haemorrhage occurs when an artery on the brain’s surface bursts. All types can lead to an area of the brain dying and are often accompanied by sudden impairment of a number of brain functions.
An ischaemic stroke is caused by a blood clot blocking an artery supplying blood to the brain. Approximately 4 out of 5 strokes are ischaemic.
There are two main types of ischaemic strokes that can occur.
- Embolic Stroke
This occurs if a blood clot forms somewhere in the body, usually from the heart or the blood vessels in the neck and it travels through the bloodstream up to the brain. Once the clot is in the brain it will travel through blood vessels until it reaches one that is too small for it to pass through. It can get stuck and stop the blood from getting through.
- Thrombotic Stroke
Blood flow through the artery may leave behind cholesterol-laden ‘plaques’ that can stick to the inner artery wall. These plaques can rupture over time, which causes a clot to form on its surface, blocking it completely, and stopping blood from getting through.
An intracerebral haemorrhage occurs when a weakened artery ruptures and bleeds into the brain. Intracerebral haemorrhages make up 15% of all strokes. There are two main ways that blood vessels can be weakened, causing this type of stroke:
- Arteriolosclerosis: age, high blood pressure, smoking and heavy alcohol intake can cause thickening, fragility and small out-pouches (aneurysms) of small arteries in the brain. If these vessels burst, this commonly causes a bleed deep within the brain.
- Cerebral amyloid angiopathy: In this condition a protein called amyloid builds up within vessel walls, causing weakness and fragility. If these vessels burst, they usually cause bleeding deep within the brain, although they can sometimes cause bleeding on the surface (subarachnoid haemorrhage).
A subarachnoid haemorrhage occurs when there is bleeding on the surface of the brain and is usually caused by bursting of an aneurysm – a swelling of a weakened part of a blood vessel. The outside of the brain is covered by three layers of membrane and this type of haemorrhage is a bleed between the layer closest to the brain and the second layer. The larger and more irregular the aneurysm is the more likely it is to burst, however not all aneurysms require treatment.
- Subarachnoid haemorrhages make up around 5% of all strokes. They most commonly present with sudden headache and reduced consciousness, but can present similarly to other forms of stroke.
A transient ischaemic attack (TIA) or ‘mini-stroke’ is a condition that relates to stroke but results in a temporary blockage of the blood supply to the brain, lasting a few minutes up to several hours. TIAs can produce similar signs and symptoms to a stroke but that disappear within 24 hours, and do not leave any signs of damage on a follow-up scan. Having a TIA is a vital warning sign that a person is at a very high risk of having a major stroke and they should seek medical attention immediately. Many conditions can mimic TIA and proper diagnosis is important, to ensure proper preventative treatment. Proper treatment can reduce the risk of subsequent stroke by about 80%.
Stroke in Australia
In Australia, it is estimated that one person has a stroke every 10 minutes. Stroke affects approximately 37,000 people each year, resulting in around 8,000 deaths. Stroke is the leading cause of adult disability in Australia and it is estimated that up to 400,000 Australians live with their disability with untold family and community consequences (NSF 2014).
 AIHW, Australia’s Health Report, 2016.