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Tests before epilepsy brain surgery for children

These pages are about surgery in the UK. If you are looking for information about surgery in another country, please contact your local epilepsy organisation.

To find out if your child will be suitable for surgery, the epilepsy team at the CESS centre will thoroughly assess them. As part of the assessment, the CESS team will ask for your child to have a number of tests, which could include:

Electroencephalogram (EEG)/video telemetry

The EEG tells the doctors about the electrical activity in the brain. During this test, your child will sit or lie down. The person doing the test will attach the electrodes to your child’s head with a sticky gel. They may ask them to breathe deeply for some minutes and also to look at a flashing light. These activities can change the electrical activity in your child’s brain, and this will show on the computer.

In video telemetry, a video recording is done at the same time as the EEG. This means that if your child has a seizure, doctors can see exactly what happens. It will help to show exactly which part of the  brain the seizures are coming from. An EEG/video telemetry can be done while your child is awake or asleep, or both.

Invasive EEG telemetry

Some children might need to have more detailed EEG telemetry. This is called invasive EEG telemetry. This can be done with subdural grids/strip electrodes or stereo-EEG.

Subdural grids/strip electrodes

These are placed directly on the surface of the brain. They are good for showing seizures starting on the surface of the brain, but not as good for showing seizures in deeper parts of the brain. They are also good for ‘cortical mapping’. Cortical mapping shows which part of the brain controls a person’s speech and hand or leg functions. Cortical mapping is done to reduce the risk of any complications after the surgery.


This is good for looking deeper into the brain, and also for seeing what is happening in both sides of the brain. After some careful planning, the neurosurgeon identifies the areas of the brain where stereo-EEG electrodes need to be placed. They then place the electrodes in the brain, through small holes in the skull.

The information from invasive EEG telemetry will be reviewed and a decision made about whether epilepsy surgery should go ahead

Are there any risks in having invasive EEG telemetry?

There are some risks from both types of invasive EEG monitoring. These are not common, but can include a loss of speech or paralysis down one side of the body. 

Magnetic resonance imaging (MRI scan)

MRI stands for magnetic resonance imaging. An MRI scan uses a strong magnetic field and radio waves to create pictures on a computer, of tissues, organs and other structures inside your child’s body.

Functional MRI scan (fMRI)

This is similar to the MRI scan but, during the scan, your child will be asked to do something, such as:

  • Tap their thumb against their fingers or do other more difficult finger movements
  • Look at pictures
  • Answer questions on a computer screen

These activities increase the flow of oxygen-rich blood to a particular part of the brain. From these activities it will be possible to see which part of the brain manages important tasks such as thought, speech and language, movement and sensation.

Positron emission tomography (PET scan)

This scan uses a radioactive substance, called a tracer, to look for information about how the brain is working. It can also show if there’s a structural cause for the epilepsy.

Single-photon emission computed tomography (SPECT scan)

This scan shows different parts of the brain in different colours. Your child will be given an injection of a radioactive dye, which will go to their brain. The different colours show how much blood flow is in each part of the brain. Usually, blood flow is highest in the part of the brain where seizures start.

There are 2 sorts of SPECT scans: one is the inter-ictal and the other is the ictal. ‘Inter’ means between and so the inter-ictal SPECT scan is done between seizures. Ictal means seizure, so the ictal SPECT scan is done just after a child has had a seizure.

Magnetoencephalography (MEG scan)

This is a newer type of scan, and is only available in very special circumstances. The scanner sits outside your child’s head and measures their brain activity. It can tell which parts of your child’s brain are active during a certain task.

Neuropsychology tests

These are tests that show if your child has any memory or learning problems. They can take up to 6, or sometimes 8 hours, split into 2 or 3 different sessions, and involve a number of games and puzzles.

The results of the tests may help the surgeon to plan the type of surgery your child might need. They can also show whether the surgery will affect any functions that can’t be taken over by other parts of the brain. This is to try to make sure your child will not have any problems after surgery that they didn’t have before.

Neuropsychiatry assessment

Your child will see a psychiatrist with experience of epilepsy brain surgery as part of their initial assessment. They will check whether they have any emotional and behaviour problems, as these can affect some children with epilepsy. And they will be able to suggest any treatment your child needs.

The psychiatrist will also be one of the people who checks with you and your child what your aims and expectations are for surgery.

Other assessments

Your child might have some other types of assessments, depending on the type of epilepsy, and problems they have. These assessments might include some of the following:

  • Speech and language
  • Development
  • Vision, particularly peripheral vision
  • The need for occupational therapy
  • The need for physiotherapy

If you would like to see this information with references, visit the Advice and Information references section of our website. If you are unable to access the internet, please contact our Epilepsy Action Helpline freephone on 0808 800 5050.


Epilepsy Action wishes to thank Prof. Richard Appleton, honorary professor in paediatric neurology and Dr Tim Martland, consultant paediatric neurologist at Royal Manchester Children’s Hospital and Lead Clinician for NorCESS for their contributions.

Prof. Appleton and Dr Martland have declared no conflict of interest.

This information has been produced under the terms of The Information Standard.

  • Updated May 2017
    To be reviewed May 2020

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