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Computed tomography (CT) brain scan
This is a special type of x-ray of your brain, which involves you lying still for a few minutes on a couch inside a hollow tube. Sometimes, a neuroradiologist may give an injection of contrast into one of the veins in your arm to make the appearances on the scan clearer. The CT scanner produces one or two sheets of x-ray film with pictures of your brain shown in horizontal slices. A CT scan may be the first test used to diagnose a vascular malformation, but often one or more of the other tests described below is also required to be sure. CT scanning may also be used after you are diagnosed with a vascular malformation to investigate suspected bleeding in the brain.

Magnetic resonance imaging (MRI) brain scan
Your doctors may recommend that you have an MRI scan, if it is available in your hospital, instead of or as well as a CT scan. An MRI scan involves lying still on your back for several minutes, whilst you are moved into a hollow tube. Some people find it rather noisy and claustrophobic. The main advantage of an MRI scan is that it provides more detailed pictures, especially of the back and base of the brain, and it uses magnetism rather than radiation. It usually gives more information than a CT about brain AVMs, and it is the most accurate test for a cavernous malformation. MRI examination may include magnetic resonance angiography (MRA), which gives detailed information about blood vessels.

Angiogram
Unlike the other tests, an angiogram requires some preparation. The doctors looking after you will take a few blood tests beforehand. A neuroradiologist will explain the risks and benefits of the procedure to you, and you will be asked to sign a "consent form”. The angiogram is performed in a suite in the x-ray department of your hospital. You will be attached to various monitoring leads, and an intravenous line will be placed in your arm. You may be asked to keep still in certain positions during the procedure and you may also be asked to hold your breath or avoid swallowing for a short period of time.

The radiologist passes a fine flexible tube, called a catheter, into an artery in your groin after first numbing the overlying skin with a local anaesthetic. This catheter is guided towards the arteries in your neck, after which the radiologist injects a liquid that can be seen on x-rays, called contrast. The radiologist then takes several x-ray pictures of the blood vessels in your brain as the contrast passes through them. The whole procedure takes 30 to 45 minutes, after which you will need to lie still with pressure firmly applied to the area where the catheter entered your groin.

An angiogram is usually the most accurate test for vascular malformations, although it does not show cavernous malformations at all. Once you have been diagnosed, a "super-selective" angiogram using finer catheters may be required to show the precise structure of an AVM of the brain or dura, and to help plan your treatment.