Brain aneurysm

What is a brain aneurysm?

Brain aneurysms are like tiny blisters or balloons on the surface of the arteries running through the brain. The outer wall of the vessel has a weakness, and the inner lining (like the inner tube of a tyre) bulges out. In 15 per cent of cases there are multiple aneurysms on different arteries around the brain.

Symptoms

Unfortunately, most people with an aneurysm are unaware they have a problem until it suddenly ruptures, and they're struck down with the most severe headache they've ever known.

This can rapidly progress to coma and death without urgent treatment.

In about one in ten cases there may be subtle signs that something's amiss. As the aneurysm balloons, it may press on important nerves and brain structures, causing problems with eyesight or with muscles of the face. However, these signs may go unnoticed.

Causes and risk factors

Various factors increase your risk of having an aneurysm:

• A family tendency - several different inherited conditions, including a problem with collagen formation in the tissues, can increase the risk of aneurysms forming, but often there's no clear reason why it runs in a family.
• Major infections - especially infection of the heart, known as bacterial endocarditis.
• Atherosclerosis - often called 'hardening of the arteries'.
• High blood pressure - this may not cause an aneurysm but increase the risk that if you have one it will burst.

The main worry with an aneurysm is that it will burst under the pressure of blood pulsing through the artery, causing a brain haemorrhage, which may be fatal.

Each year, many thousands of people around the world, often young or middle-aged, die or are left disabled because of brain aneurysms.

Treatment and recovery

The only way to find out if someone has a brain aneurysm is to examine the blood vessels of the brain with a brain scan, usually an MR (magnetic resonance) scan, or an angiogram (a special X-ray of the blood vessels).

If an aneurysm is found, an operation can be performed to clip it or tie it off. This usually resolves the problem, although the surgery itself is not without risk.

But it would be far too expensive (and possibly too invasive) to do these tests on everyone to screen the whole population for aneurysms. Brain aneurysms are still relatively rare, especially if you have no family history of them.