This information is for people who want to know more about brain scans. On this page we briefly describe each of the brain scans you might have if your doctor thinks you have epilepsy. We talk about the most common types of scans, as well as the referral and follow-up procedures.
Use this page as a general guide and speak to a health professional for more information and support.
Brain scans play an important role in diagnosing the specific causes of epilepsy.
This page covers the most common types of scans used, as well as referral and follow-up procedures.
Types of neuroimaging (brain scans)
Neuroimaging (a brain scan) gives a detailed picture of the brain.
Brain scans can help to identify an area of the brain that has not developed properly, or an area of the brain that is damaged through a lack of oxygen or a bleed, for example.
There are different types of brain scans. The most common types used to help diagnose epilepsy are:
- Magnetic resonance imaging (MRI) scans
- Functional magnetic resonance imaging (fMRI) scans
- Computerised tomography (CT) scans
We describe some of these common types of scans in more detail below.
A magnetic resonance imaging (MRI) scan uses magnetic fields to take a clear and detailed image of the brain’s structure. Sometimes epilepsy can be caused by structural changes in the brain, so this test can help doctors find out if that’s what is causing your seizures.
3T MRI has a stronger magnet and makes better images of organs and soft tissue than other types of MRI.
An MRI scan with functional imaging (fMRI) provides images of the brain’s structures, irregularities in the brain and blood flow in a specific area of the brain.
When we think, speak, move or use our senses, there’s an increased blood flow to the area of the brain that we’re using.
This makes an fMRI scan very useful for seeing which parts of the brain control different parts of the body and seeing where seizures start.
A computerised tomography (CT) scan [link to https://www.nhs.uk/conditions/ct-scan/] records very detailed cross-sectioned images of the brain onto a computer. The image is taken from side to side, to see the inside structure of the brain. The images are not as clear or detailed as an MRI scan.
A CT scan is safe and painless. CT scans show both bone and soft issues, including the various parts of the brain.
A CT scan may reveal an obvious structural abnormality or damage to the brain.
CT scans are not routinely offered for people with established epilepsy who visit an emergency department after a typical seizure, unless there are other concerns.
First scan
The first scan you will normally be offered is an MRI scan. Unless you have idiopathic generalised epilepsy, or you have self-limited epilepsy with centrotemporal spikes (SeLECTS). You should have your first MRI scan within six weeks of being referred for one.
Because MRI scans involve having to lie still for some time in an enclosed and noisy space, they can be unsettling for children. So, some children may be given a sedative (drug) to help them sleep or stay calm before an MRI scan.
If an MRI scan is not suitable for you, you will be offered a CT scan. As part of an MRI or CT scan, sometimes children will be given an injection of dye into the blood, through the hand or foot. This helps to highlight the blood vessels in the brain. This is called ‘MRI with contrast’.
With MRI and CT scans, the advantages and disadvantages should be discussed with you and your family or carers. This is especially important if a general anaesthetic or sedation is needed for the scan. It’s important you have all the information you need to help you decide.
If you have had treatment and your seizures still continue, and there’s still no clear diagnosis, your MRI scans might be sent for further review by a hospital specialist.
Repeat scans
You might need a repeat scan if:
- the quality of the first scan wasn’t clear enough to get an accurate diagnosis
- your epilepsy has developed new features
- you have idiopathic generalised epilepsy, or you have self-limited epilepsy with centrotemporal spikes (SeLECTS), and have not responded to initial treatment
- you are being considered for surgery.
Other types of scans
Other types of scans are available. These include:
With a single photon emission computed tomography (SPECT) scan of the brain,
a computer gathers the images and shows them in cross-sections (images from side to side). These images can be added together to form a 3D image.
When there’s brain injury, there’s reduced blood flow to the specific part of the brain that’s been damaged. During a SPECT scan, dye is injected into the bloodstream, allowing the scan to trace and identify areas of reduced blood flow in the brain.
If a SPECT scan is done during a seizure, it will show where in the brain the seizure started. Find out more about epileptic seizures.
Positive emission tomography (PET) scans are more precise than SPECT scans.
They show how tissues in the brain are working and show structural abnormalities that cannot be seen on an MRI scan.
PET scans are not widely available. Sometimes they are used to help plan operations, for example brain surgery for epilepsy.
Find out more about PET scans.
