Haemorrhagic stroke

A stroke can also be caused by bleeding. This is called a haemorrhagic stroke (hemm-orr-ragic). Blood can leak from a burst or broken blood vessel, one of the tubes that carry blood around the body. The leaked blood can injure part of the brain, similar to a bruise. Blood vessels include arteries, which carry blood from the heart to the rest of the body, and veins, which return blood to the heart. There are two types of haemorrhagic stroke: intracerebral haemorrhage (ICH), when an artery inside the brain bursts and bleeds into the brain itself; and subarachnoid haemorrhage (SAH), when there is bleeding on the surface of the brain, between two of the membrane layers that cover it.

High blood pressure

The main cause of haemorrhagic stroke is high blood pressure (hypertension). High pressure can weaken and rupture major arteries deep inside the brain, causing an intracerebral haemorrhage. Managing blood pressure can reduce this risk.

Cerebral amyloid angiopathy (CAA)

When a protein called amyloid builds up in small blood vessels in the brain, it is called cerebral amyloid angiopathy (CAA). This can damage the vessels and lead to bleeding (haemorrhagic stroke). Sometimes the bleeding is very small (“microbleeds”) and may only be detected on brain imaging. CAA is more common in older people and in some people with dementia, but it can also run in families and affect younger people.

Blood-thinning medication

Medicines that reduce the risk of blood clots and ischaemic stroke (blood thinners, including anticoagulants and antiplatelets) can make bleeding more likely. Your doctor will balance the dose to lower the risk of both clotting and bleeding.

Illegal drugs

Some illegal drugs, such as amphetamine and cocaine, can cause sudden, severe rises in blood pressure and increase the risk of haemorrhagic stroke.

Vascular malformations

When blood vessels do not form normally, a vascular malformation can develop. These are usually present from birth and may grow or weaken with age. They can occur anywhere in the body, including the brain. An arteriovenous malformation (AVM) is an abnormal tangle of connections between arteries and veins. A cavernous malformation is a tangle of tiny vessels forming a weak-walled “cavern” of blood. If a malformation in the brain bursts, a haemorrhagic stroke occurs.

Aneurysm

An aneurysm is a weak or thin spot in an artery wall that balloons outward. As it grows, it can become weaker and may burst, causing bleeding. Aneurysms often cause subarachnoid haemorrhage. They usually develop over years, and many people have no symptoms until the aneurysm ruptures. Controlling blood pressure and not smoking help reduce the risk of rupture.