Invasive monitoring with Stereoelectroencephalography (sEEG)

This page explains invasive monitoring with steroelectroencephalography (sEEG) for epilepsy and what to expect when your child comes into Birmingham Children’s Hospital (BCH) to have this procedure.

What is invasive monitoring?

Invasive monitoring is a very specialised and detailed way of confirming the exact area of the brain causing your child’s seizures (fits) and the exact areas of the brain being used for important tasks such as speech or movement. sEEG involves an operation to insert electroencephalogram (EEG) electrodes into the brain. These EEG electrodes are then connected to an EEG (electroencephalogram) monitor so that clinical physiologists 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 part of their brain but previous tests have not been able to determine the exact area or we believe the area involved may have an important function. Previous tests will have already given the team some idea which area of your child’s brain needs closer observation. This test will help to confirm which area of your child’s brain is causing seizures. sEEG, together with other tests, can sometimes also help the epilepsy 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 sEEG will help them to decide whether surgery is an option for your child. You will be asked to attend the epilepsy surgery clinic to discuss this with the team. At this clinic, you will meet both a neurologist and a neurosurgeon and we will explain fully the risks and benefits of the test to you and your child. We will send you a letter following your epilepsy surgery clinic appointment summarising the benefits and risks of surgery for 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 this procedure. If you decide to proceed, the team will then plan a date for the procedure and offer you 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. Children are routinely given medicine for sickness and for pain. There is a small chance of bleeding (about one per cent) within the brain. Occasionally, if this bleeding is putting pressure on the brain, a further operation may be needed to remove the blood, but this is very rare.

There is also a very small chance of surgery causing damage to the brain. After the operation to put the electrodes in place, it is often necessary to reduce or stop your child’s antiepileptic drugs while they are having sEEG. 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 procedure.

If your child has had a number of seizures recently, even though they are taking antiepileptic drugs, they 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 procedure, 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 and an emergency medication plan will be in place to ensure your child’s safety.

What happens before the operation?

You will need to come to Ward 10 the day before the operation. This is to make sure that your child is well enough to have the operation. A doctor will examine your child and may take a repeat blood sample to check that his or her blood parameters (for example, clotting tests, full blood count) are fine.

The neurosurgeon will explain about the surgery in more detail, discuss any worries you may have and ask your permission for the operation, by signing a consent form. Another doctor will also visit you to explain about the anaesthetic.

Occasionally, some children need neuropsychology testing and a further scan before the operation, but we will let you know if this is likely before you come into hospital.

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.

The procedure may be cancelled if head lice have not been treated successfully before admission. Before the operation, your child will need to have a bath and a hair wash with a special soap.

What does sEEG surgery the 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. Part of your child’s head will be shaved to allow the surgeon to see clearly where the electrodes will go. This will be done while your child is under the anaesthetic.

The procedure involves applying a Leksell stereotactic frame followed by a CT scan which is fused to the MRI scan used to plan the position of the SEEG electrodes. This enables us to precisely insert the electrodes to the planned predetermined points and avoid the brain’s blood vessels. The electrodes are inserted with the aid of a surgical robot. The electrodes themselves are very small (0.8mm diameter), the surgeon will drill a number of small holes (just over 1mm in diameter) in your child’s skull to thread the electrodes into his or her brain and a small metal holder is attached to secure each electrode in place.

After the operation, your child will have many wires coming from 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 an allocated nurse with them 24 hours a day to make sure this does not happen.

What happens following surgery?

Once the operation to insert the electrodes is over, your child will stay on Ward 10 in one of the telemetry beds. He or she will be connected to the EEG and video monitoring equipment, usually for seven days, while the epilepsy team confirm which area of the brain is causing your child’s seizures.

We need 3 clear examples of a seizure to clarify the areas where the seizures start. Your child will have to remain in the bed space 4 during this time attached to the monitors which means you will need to use the commode or urinal bottles at the bedside. 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 have a CT the day after implantation to check the position of the electrodes and to make sure that nothing has occurred (like bleeding etc.) You may notice that your child’s face is a little swollen. This is temporary and will begin to improve after two to three days. Your child may also feel, or be, sick after the operation to insert the electrodes and may need some medicine to treat this.

What happens after the procedure?

Your child’s stay in hospital is likely to last between around 7 days, although it may be a little longer. The electrodes are usually removed in the operating theatre with a general anaesthetic after seven days, but sometimes a longer period of recording is needed. The length of recording depends on what happens in the first few days of the test and we will keep you and your child updated during the monitoring.

Once the neurophysiology team have carried out all the monitoring, the epilepsy team will discuss the results with you. This may include whether the area responsible for seizures has been located, whether an operation can be offered and what risks there are. Sometimes more analysis of the results will be needed after your child has had their test and if this is the case for your child, the results will be discussed with you in clinic after the test. In 20 per cent of cases, despite invasive monitoring, it is still not possible to identify the area where the seizures are starting.

Stimulation Studies

The epilepsy team will let you know if they are planning to carry out stimulation studies. This involves the doctors using the electrodes to stimulate parts of the brain. In some children having sEEG, the stimulation may be used to try to find out more about the activity which occurs when a seizure is happening. The team will also sometimes use stimulation to test if the areas of the brain where seizures start are also important for other functions such as moving arms or legs Your child will probably have an intravenous drip via a cannula until he or she is drinking enough fluids.

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 sEEG 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, but is also useful if your child has a large abnormality on their brain scan or may have seizures starting near an area that is also controlling one of your child’s useful functions.