Strokes caused by a break in the wall of a blood vessel in the brain are called haemorrhagic strokes (hemm-orr-ragic).
This causes blood to leak into the brain, stopping the delivery of oxygen and nutrients.
Types of haemorrhagic stroke
Haemorrhagic strokes are described by their location in the brain. There are two types:
- Intracerebral haemorrhage occurs when an artery inside the brain bursts and bleeds into the brain. The most common cause is high blood pressure (hypertension).
- Subarachnoid haemorrhage (SAH) is bleeding on the surface of the brain. There are 3 layers of membrane (or meninges) that cover the brain. A subarachnoid haemorrhage is a bleed that happens between the layer closest to the brain and the second layer.
Causes of haemorrhagic stroke
Haemorrhagic stroke can be caused by a number of disorders that affect the blood vessels.
High blood pressure
The main cause of haemorrhagic stroke is high blood pressure (hypertension).
This is a weak or thin spot in the wall of an artery that balloons out. As the aneurysm gets bigger, it gets weaker and can burst. If the aneurysm bursts, it leaks blood into the brain.
The weak spots that cause aneurysms are usually present at birth. Aneurysms develop over a number of years, and usually don't cause detectable problems until they break.
A burst aneurysm is usually caused by high blood pressure or trauma (a sudden injury to the head).
Vascular malformations are defects of blood vessels (arteries, veins, and capillaries).
A vascular malformation is usually present at birth. It may be that as you get older the blood vessels get bigger and weaker. It can occur anywhere in the body, including the brain.
An arteriovenous malformation (AVM) is an abnormal tangled connection between arteries and veins.
A cavernous malformation is rare. It is a tangle of tiny blood vessels creating a weak walled ‘cavern’ of blood.
If the vascular malformation is in the brain and the blood vessel walls burst, then you will have a haemorrhagic stroke.
Cerebral amyloid angiopathy (CAA)
This is a build-up of a protein called amyloid in small blood vessels in the brain. The protein can damage the blood vessels and lead to bleeding.
Often the bleeding from CAA is very small and known as “microbleeds”. You might not know you have had microbleeds until they are picked up by brain imaging.
CAA is more common in older people and in people who have dementia, but sometimes it can be inherited.
Medications including anticoagulants and antiplatelets, which are taken to lower the risk of blood clots and ischaemic stroke, can increase your risk of haemorrhagic stroke.
Your doctor will make sure you take the right amount of blood thinner to reduce your risk of both kinds of stroke.
Some illegal drugs such as cocaine can also increase the risk of haemorrhagic stroke.
If you or a loved one has had a stroke, there is support available. See our help after stroke section for more information.