Magnetic resonance imaging and epilepsy

When a magnetic resonance imaging (MRI) scanner is used to investigate epilepsy, it takes detailed pictures of your head. It can help to find if there is an abnormality that might be causing epilepsy, for example, scar tissue due to a brain injury.

The MRI will send images of your brain to a computer, which will show different types of brain tissue in different colours. The person who does the test is called a radiographer. The radiographer may need to inject you in your hand or arm, with a harmless dye, to make the tissue show up more clearly. This could make you feel hot and flushed, but it will not hurt.

The MRI is the most common scan used for individuals with epilepsy, particularly if any of the following applies to you:

• you developed epilepsy before the age of two years or in adulthood; or
• you could have damage in the brain to cause the seizures; or
• you continue to have seizures despite taking medication.

The MRI will look for an abnormality in a specific area of the brain, which may be the cause of the seizures.

An MRI is not always used for people who have generalised seizures. This is because epilepsy is unlikely to be caused by structural damage, when epileptic activity starts in both sides of the brain. Therefore, the scan is unlikely to add anything to the diagnosis.

Also, an MRI is not usually needed for people with some epilepsy syndromes, such as benign rolandic epilepsy. Again, this is because these types of epilepsy syndromes are not associated with an abnormality in the brain.

The MRI scan can take up to an hour and is very noisy. In the middle of the scanner is a hollow tube. You will be asked to lie on a table which is then moved inside the tube, which will scan your head and take pictures. Some people do not like being in the confined space of the tube and may be worried about the banging noises made by the machine. If this is the case for you, you may be offered medication to help you relax during the scan.

The scanner is operated from behind a window by a radiographer. After the scan a radiologist will interpret the pictures taken by the MRI. These results will then be send to your doctor who arranged the scan. This will usually be the epilepsy specialist.

MRI scans may not be suitable for people who have had a vagus nerve stimulator (VNS) or metallic clips implanted in their brain. There is a risk that the MRI scan could heat up the wires in the VNS or the metallic clips and cause damage to the surrounding tissue.

Some people with a VNS or metallic clips choose to wear identity jewellery, so medical professionals would be aware of this if they ever needed to have an MRI scan.

If you are concerned that there may be a cause for your epilepsy and think that an MRI scan could be helpful, talk to your GP or specialist about this.

The NICE Guideline recommends that the person who needs and MRI should have the test carried out within four weeks of the doctor requesting it.

Epilepsy Action supports this recommendation but knows that currently, due to the lack of MRI scanners and specialist staff, this does not always happen. We are actively campaigning for better services for epilepsy and hope that in the future, waiting times for MRI scans will meet the NICE recommendations.

28 August 2007