Introduction

This leaflet explains about invasive monitoring for epilepsy and what to expect when your child comes in to Great Ormond Street Children’s Hospital to have this procedure.

What is invasive monitoring?

Invasive monitoring is another way of confirming the area of the brain from which seizures (fits) associated with epilepsy originate. Invasive monitoring involves an operation to place electrodes, in strips or grids, directly over the surface of your child’s brain. These electrodes are then connected to an EEG (electroencephalogram) machine so that technicians can record your child’s brain activity over several days.

Why does my child need this test?

The procedure will be carried out if doctors think that your child’s epilepsy might be relieved by an operation to remove the part of their brain which is causing the problem. Previous tests will have already given the team some idea which area of your child’s brain needs closer observation. This test will confirm which area of your child’s brain is causing seizures.

Invasive monitoring can also allow the epilepsy team to carry out “functional brain mapping.” This mapping allows the team to check exactly which areas of the brain your child needs for essential tasks, like movement or speech. This is important to know, as it indicates whether surgery to help their epilepsy would put these functions at risk.

How do the doctors decide if my child needs this procedure?

Once the epilepsy team has seen all the results from previous tests they will discuss whether invasive monitoring will also help them to decide whether surgery is an option for your child. You will need to attend a joint epilepsy and surgery outpatient clinic to discuss this with the team. You will also be able to meet the surgeon and he or she will explain the risks and benefits of the test to you and your child.

The epilepsy team will then ask you to think about the information given to you and decide whether you want your child to have the test. When you have decided, please ring the Clinical Nurse Specialist - Epilepsy Surgery and write to the neurosurgeon to confirm that you wish to proceed. The team will then decide a date for the test and let you know the date by letter.

What are the risks of this procedure?

Your child will be given a general anaesthetic (which puts them deeply to sleep) for the operation to put the electrodes in place. Healthy children usually cope well with the anaesthetic, but the risk increases if your child has other health problems. However, the specialist doctors (anaesthetists) who look after your child during the operation will keep any risks to a minimum. Your child may feel sleepy, dizzy or sick afterwards but this usually doesn’t last long. They sometimes need medicine to stop the sickness. This operation has a slightly higher risk of infection than others, but again, the doctors and nurses will do all they can to prevent this.

After the operation to put the electrodes in place, it is sometimes necessary to reduce or stop your child’s anticonvulsant (anti-epilepsy) drugs during the days of invasive monitoring. This is so that your child is more likely to have a seizure while in hospital. The doctors will decide this with you when you and your child come into hospital for the test.

If your child has had a number of seizures recently, even though they are taking anticonvulsant drugs, he or she may be able to continue taking them during the test. There is always a risk in reducing or stopping your child’s drugs suddenly for this test, as it may cause your child to have a longer or more intense seizure than usual. However, the doctors and nurses will monitor your child closely to try to stop this happening.

Are there any alternatives to this procedure?

Your child’s doctors can tell a lot from an EEG and other tests and brain scans, but invasive monitoring can help them to be sure exactly which part of your child’s brain is responsible for their epilepsy. This is particularly helpful where brain scans have not shown an abnormality or where the doctors are concerned that seizures may be starting near an area that is also controlling one of your child’s useful functions.

Are there any complications with this procedure?

Your child may feel sleepy after the operation to have the electrodes inserted, but this usually passes. You may notice that your child’s face seems swollen, but this is temporary and will return to normal after the test. Your child may also feel and be sick after the operation to insert the electrodes. He or she may need some medicine to stop this.

What happens before the test?

You will need to bring your child into hospital the day before the operation to put the electrodes in place. This is to make sure that your child is well enough to have the operation. Your child may also need a further MRI scan to help the doctors decide exactly where to put the electrodes.

A doctor will examine your child and take a blood sample to check that his or her blood levels are fine. The doctors will explain about the test in more detail, discuss any worries you may have and ask you to sign a consent form giving permission for your child to have the operation. Another doctor will also visit you to explain about the anaesthetic.

If your child has any medical problems, for instance, allergies, please tell the doctors about these. If your child has had any infectious diseases like chicken pox or head lice recently, please tell the doctors. Please bring any medicines that your child is taking, and show these to the doctors.

The evening or the morning before the operation, your child will need to have a bath and a hair wash with a special soap.

What does the procedure involve?

The operation to insert the electrodes will be carried out under a general anaesthetic. This means that your child will not feel any pain during the operation. If your child needs electrode grids, the surgeon will open up your child’s skull to place the grids over his or her brain. This involves making a small flap to fold the skull back into place and secure it. If your child needs electrode strips, the surgeon will drill small holes in your child’s skull to thread the strips over his or her brain. After the operation, your child will have many wires coming from the wound in his or her head. These wires will be fastened with tape and bandages so that they cannot be pulled out of place while your child is on the ward. Also, your child will have a nurse with them twenty-four hours a day to make sure this does not happen. Your child will usually have a CT scan immediately after the electrodes are inserted to check exactly where they are.

Once the operation to insert the electrodes is over, your child will stay on Churchill Ward in one of the telemetry rooms. He or she will be connected to the EEG and video monitoring equipment for up to ten days, while the technicians confirm which area of the brain is causing your child’s seizures.

The technicians will let you know if they are planning to carry out functional brain mapping. This involves the technicians and doctors stimulating areas of the brain by way of the electrodes. This will make sure that none of the areas of the brain which are planned to be removed have important functions, especially for movement in the hands or legs.

Your child will have their own nurse for this time who will look after and monitor them closely. He or she will take various measurements like blood pressure and heart rate every hour while the electrodes are in place and also take blood samples for testing. Your child will probably have a drip until he or she is drinking enough fluids.

What happens after the procedure?

Once the technicians have carried out all the monitoring, the epilepsy team will discuss the results with you. This will include whether the area responsible for seizures has been located, whether an operation can be offered and what risks there are.

If you, with the team, decide that removing an area of the brain could help your child, this will take place at the same time as removal of the electrodes. If it is felt not to be of benefit to remove any brain tissue, surgery will take place just to remove the electrodes.