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Sub-arachnoid haemorrhage
A guide for patients and carers
What is a sub-arachnoid haemorrhage?
A sub-arachnoid haemorrhage is a sudden leak of blood (haemorrhage) over the surface of the brain. The brain is covered by a series of membranes, one of which is called the arachnoid (see Figure 1 in printed bound booklet or pdf version). A sub-arachnoid haemorrhage occurs beneath this layer. The blood vessels supplying blood to the brain lie in this space, surrounded by clear fluid (cerebro-spinal fluid).
What causes it?
In 75% of cases, there is a weakness in the wall of one of the blood vessels supplying blood to the brain. This balloon-like swelling is called an aneurysm. The haemorrhage occurs when the aneurysm wall tears because of the pressure of blood. When this happens blood bursts into the surrounding tissues.
Aneurysms also occur in vessels in other parts of the body. The reasons why they develop are not fully understood, but there is a greater risk of them occurring in people with high blood pressure and people who smoke. They become more common as people get older. There is no link between aneurysms and stress.
Could I have prevented it?
Although people who smoke and those with high blood pressure have a greater risk of developing aneurysms, not all of them will develop an aneurysm, and aneurysms also occur in people with no known ‘risk factors’.
Sometimes an aneurysm may press on an important part of the brain and signs that this has happened may develop. Usually, however, it goes undetected, causing no symptoms until it bursts.
Why me?
We do not know why it happens and in most cases there is no way of identifying those people who are at risk.
Why now?
There is no reason why the haemorrhage occurs on one day rather than on another. The bleed often, though not always, happens at a time of physical effort such as coughing, going to the toilet, heavy lifting, or straining, or during sex.
Can I pass the risk to my children?
Only in rare cases is the risk of developing aneurysms inherited. Speak to your doctor if you are worried about this.
In 75% of cases, there is a weakness in the wall of one of the blood vessels supplying blood to the brain. This balloon-like swelling is called an aneurysm. The haemorrhage occurs when the aneurysm wall tears because of the pressure of blood. When this happens blood bursts into the surrounding tissues.
Aneurysms also occur in vessels in other parts of the body. The reasons why they develop are not fully understood, but there is a greater risk of them occurring in people with high blood pressure and people who smoke. They become more common as people get older. There is no link between aneurysms and stress.
Could I have prevented it?
Although people who smoke and those with high blood pressure have a greater risk of developing aneurysms, not all of them will develop an aneurysm, and aneurysms also occur in people with no known ‘risk factors’.
Sometimes an aneurysm may press on an important part of the brain and signs that this has happened may develop. Usually, however, it goes undetected, causing no symptoms until it bursts.
Why me?
We do not know why it happens and in most cases there is no way of identifying those people who are at risk.
Why now?
There is no reason why the haemorrhage occurs on one day rather than on another. The bleed often, though not always, happens at a time of physical effort such as coughing, going to the toilet, heavy lifting, or straining, or during sex.
Can I pass the risk to my children?
Only in rare cases is the risk of developing aneurysms inherited. Speak to your doctor if you are worried about this.
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