A brain aneurysm is usually diagnosed using a magnetic resonance imaging (MRI) scan and angiography (MRA), or a computerised tomography (CT) scan and angiography (CTA).
An MRI scan is usually used to look for aneurysms in the brain that haven't ruptured. This type of scan uses strong magnetic fields and radio waves to produce detailed images of your brain.
A CT scan is usually preferred if it's thought the aneurysm has ruptured and there's bleeding on the brain (subarachnoid haemorrhage).
This type of scan takes a series of X-rays, which are then assembled by a computer into a detailed three-dimensional image.
In some cases, a ruptured aneurysm is not picked up by a CT scan. If a CT scan is negative but your symptoms strongly suggest you have a ruptured aneurysm, a test called a lumbar puncture will usually be carried out.
A lumbar puncture is a procedure where a needle is inserted into the lower part of the spine to remove a sample of the fluid (cerebrospinal fluid) that surrounds and supports the brain and spinal cord. This fluid can be analysed for signs of bleeding.
If the results of scans or a lumbar puncture suggest you've either had a brain haemorrhage or have an unruptured brain aneurysm, a further test called an angiogram or arteriogram may be carried out to help plan treatment.
An angiogram or arteriogram involves inserting a needle, usually in the groin, through which a narrow tube called a catheter can be guided into one of your blood vessels.
Local anaesthetic is used where the needle is inserted, so you won't feel any pain.
Using a series of X-rays displayed on a monitor, the catheter is guided into the blood vessels in the neck that supply the brain with blood.
Once in place, special dye is injected into the arteries of the brain through the catheter. This dye casts a shadow on an X-ray, so the outline of the blood vessels can be seen and an aneurysm can be recognised if one is present.
There's no routine screening programme for brain aneurysms and it's unlikely that one will be introduced in future.
This is because researchers have calculated routine screening would do little to prevent deaths, but would place a significant drain on NHS resources.
Screening is only recommended for people thought to have a significant risk of having a brain aneurysm that could rupture at some point in future.
This would usually only apply to you if you had two or more first-degree relatives (father, mother, sister or brother) who had experienced a subarachnoid haemorrhage.
If this applies to you, contact your GP. They'll be able to refer you to a specialist clinic for further assessment.
Discovering you have an aneurysm unsuitable for surgical treatment can cause worry and distress, even though the risk of it rupturing is small. Some people have reported regret at getting screened.
There are no right or wrong answers, but it's important you discuss the potential implications of screening with the staff at the clinic.
Screening may also be recommended if you have a condition that increases your chances of developing a brain aneurysm, such as autosomal dominant polycystic kidney disease.