Diagnosing a subarachnoid haemorrhage 

If you may have a subarachnoid haemorrhage, you'll be referred to hospital to confirm the diagnosis.

A computerised tomography (CT) scan is used to check for signs of a brain haemorrhage. This involves taking a series of X-rays, which a computer then makes into a detailed 3D image.

In some cases, a subarachnoid haemorrhage isn't picked up by a CT scan. If a CT scan is negative, but your symptoms strongly suggest you've had a haemorrhage, a test called a lumbar puncture will usually be carried out.

A lumbar puncture involves a needle being inserted into the lower part of the spine, so a sample of the fluid that surrounds and supports the brain and spinal cord (cerebrospinal fluid) can be taken out. It will then be analysed for signs of bleeding.

Planning treatment

If the results of a CT scan or lumbar puncture confirm you've had a subarachnoid haemorrhage, you'll usually be referred to a specialist neuroscience unit.

Further tests are usually needed to help plan treatment, which may include either:

  • computed tomography angiography (CTA)  using a CT scan
  • magnetic resonance angiography (MRA)  using an MRI scan

Both of these tests are carried out in the same way as a regular scan. However, a special dye is injected into a vein (usually in your arm or hand) which highlights your blood vessels and tissues.

Occasionally, an angiogram may be needed. This involves inserting a thin tube called a catheter into one of your blood vessels (usually in the groin). Local anaesthetic is used where the catheter 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 blood to the brain. Once in place, special dye is injected through the catheter and into the arteries of the brain. This dye casts a shadow on an X-ray, so the outline of the blood vessels can be seen and the exact position of the aneurysm can be identified.

Read more about angiography.


Page last reviewed: 14/01/2016

Next review due: 01/01/2019