Having a sleep electroencephalogram (EEG)

This page explains the procedure for a Sleep EEG test and what to expect.

The brain works by a series of electrical signals – also called brainwaves. These signals can be recorded through the scalp. An EEG is a test that records these signals and tells us more about the function of the brain.

Having a sleep EEG means your child will be encouraged to sleep during their EEG test. There are two methods for this that we recommend at GOSH. You can choose to keep your child up late the night before the test and wake them up early in the morning, or we can give them a medicine called melatonin. More information about these methods can be found below.

It is helpful if you make sure that your child’s hair is clean before the test, with no gel, oil, mousse, or hairspray. If your child is taking medicines, you should continue to give them as normal.

There are two methods we suggest for helping ensure your child will sleep during the test:

Sleep deprivation

We will ask you to keep your child up two hours past their usual bedtime the evening before the test and then wake them up two hours earlier on the day of the test. It is also important that you do not let your child fall asleep on the way to the hospital.

Melatonin

This is a naturally occurring hormone found in the brain and is associated with sleep. We use a medicinal form of the hormone that comes as a liquid or tablet to help get your child to fall asleep during the test. It is very safe and there are no known risks associated. If you choose this method, it is still important that you do not let your child fall asleep on the way to the hospital. Melatonin might make your child sleepy for a little while after the test, but this will not last for long.

If you think it will help them sleep, you can bring your child’s favourite blanket/toy/pillow along with you.

The CBeebies “Get Well Soon Hospital” series has an episode about having an EEG – Series 2, Episode 5.

Your child will have a sleep EEG in the Department of Clinical Neurophysiology, which is on Level 4, Southwood Building.

The person bringing your child to their appointment should ideally have ‘Parental Responsibility’ for them. Parental Responsibility refers to the individual who has legal rights, responsibilities, duties, power, and authority to make decisions for a child. This is because the person may need to give consent for your child to have the test. If you are unable to attend with your child but we still need you to give consent, we might need to contact you by phone during the test.

If you have other children, it is better if they could be looked after at home or by another adult if they come with you. We are unable to look after them during the test.

Once you are in the EEG department, check in at the reception desk and a clinical physiologist will come to meet you. They will confirm your and your child’s details and take you to the recording room. They will explain in more detail how the test will take place and discuss any worries you may have. They will also ask you to give permission for video recording by signing a consent form. They might also ask you to give permission for any extra procedures that the doctor has asked for. This could include looking at flashing lights or hyperventilating (‘over-breathing’).

As we are a teaching hospital, on occasion, we might ask you if you would agree for a trainee to perform the test under supervision. Sometimes other healthcare professionals or students might ask to observe the test as well. Saying no to this will not affect your child’s treatment.

The physiologist will attach a number of small silver discs (electrodes) to certain points on your child’s head using a soft past. Sometimes, they will measure their head and mark the points with a soft pencil before attaching the electrodes. Extra electrodes will also be applied on the shoulders to record your child’s heart rate and muscle activity. Sometimes, additional electrodes may be applied to other areas to get more information.

As each electrode is attached, the physiologist will clean the area of the scalp with a cotton bud and some cream. This does not hurt but some children do not like it. This should take around 20 to 30 minutes. While the electrodes are being applied, your child can sit on a chair, the bed, or your lap, and can play with toys – we have many toys in the department but feel free to bring your child’s own favourite book, toy, or comforter.

The electrodes are attached by wires to a ‘headbox’ and then to the recording machine. The physiologist will record your child’s brainwaves on to the computer and monitor them on a screen – they look like wiggly lines. Your child will not feel anything while the EEG is being recorded. At the same time, a video recording of your child will be made – this is helpful for the doctor to see any changes in behaviour or movements that could help interpreting the recording.

The test has two parts:

Wakefulness

We will record for 20 to 30 minutes while your child is awake. During this part of the test, the physiologist may ask your child to lie or sit quietly if they can.

If your child is old enough, we may also ask them to do some tasks, such as closing their eyes for short periods of time, taking deep breaths by blowing on a windmill or looking at flashing lights. Your child will be continuously monitored throughout the test and these tasks will be stopped if necessary.

Sleep

Your child will be encouraged to sleep. We will turn the lights off and they can lie on the bed or on your lap. Once they fall asleep, we will record for 20 to 30 minutes. Your child will be woken up after this. If you choose to use melatonin, this will be given to your child at the start of the test. This is usually given as a liquid by mouth or as a tablet to be swallowed with some water.

The test takes between 90 and 120 minutes. There are plenty of toys to play with and another member of staff to help if needed. A bottle or a drink might be helpful for younger children.

Your child’s safety is our priority – if they have a seizure during the test, we will take care of them, and make sure they are well enough before they go home.

The physiologist will remove the electrodes from your child’s head. This will not hurt as the paste stays soft and is easy to remove. They will also clean your child’s hair, but it may feel a bit sticky to the touch until you wash it. Warm water and soaking is the best way to remove the paste. Once all the electrodes have been removed, you will be free to go if no other tests or appointments have been planned.

If your child took melatonin to help them sleep, it is unlikely that this will cause sleepiness on the way home from hospital. If you have any concerns, please tell us so we can arrange for a doctor to check that your child is well before going home. Your child can go back to school or nursery after the test if you wish.

You will not be given the results during the appointment. A detailed report will be written and sent to your child’s consultant in time for their next appointment. We aim to do this within two weeks.

If you require more information about the test or have any questions, please call the Department of Clinical Neurophysiology.

Telephone: 020 7813 8471

We are open Monday to Friday, 9am to 5pm.

If you are unable to make your appointment, please call us as soon as possible as we may be able to offer the appointment to another child on the waiting list.

The main entrance to GOSH is currently closed due to construction of our new Children’s Cancer Centre.

Please use the Morgan Stanley Clinical Building entrance on Guildford Street.

Follow the signs to the Southwood Building and go to the Level 4.

Find out more information about travelling to GOSH.