An EEG is the recording of the electrical activity produced by the brain
About your EEG?
It is not painful and has no after-effects. The purpose of a sleep EEG is to record this activity when you are drowsy/asleep. The test is performed by a physiologist.
Preparation for the test
- So that you are more likely to fall asleep during this test, we request that you take about half the usual amount of sleep that you normally do on the night before this recording.
- For example, if you normally sleep for 8 hours then halve your sleep time to four hours. If you normally go to bed at 11.00 pm then you would need to get up at 3.00 am. We ask that you get out of bed and perform some absorbing task, like some (quiet) housework. Please be aware that if you stay in bed you could easily fall asleep again.
Please note sleep deprivation can increase the risk of seizures.
- You may wish for someone to accompany you, as you may still feel tired.
- Please have something to eat prior to the appointment.
- Continue to take medications as prescribed.
- It is essential that we can get access to your scalp. Please avoid top knots, backcombing etc hair should be clean and dry. Please do not use any hair products i.e. gel or hairspray.
- If you have a weave or complex braids or have any doubts about your hair please call the department before your appointment as it may affect the test.
How is it done?
The test is performed by a physiologist and takes approximately two hours. The test involves attaching approximately 23 electrodes to the surface of the head. The area beneath the electrodes is rubbed with a cotton bud and the electrodes are applied using a sticky paste. This takes approximately 10-15 minutes. Some minor skin irritation may occur. Please make staff aware if you have a skin complaint or allergy. The electrodes are then connected to the EEG machine.
You will then be asked to relax on a bed, the lights will be dimmed and you will be left to fall asleep.
We will record for at least 20 minutes even if you do not fall asleep. If you do sleep, we will record for approximately one hour. A video recording will be made during this time. This allows the doctors to see what you are doing and it will record any symptoms you may have.
Viewing the video as well as your electrical activity can help the doctors make a diagnosis. The video recording will form part of your confidential medical records. A copy of the recording may be saved and made available to the medical staff involved in your care.
If your video recording is not deemed to be helpful it will be erased, You may be asked to consent for the video to be used for teaching purposes.
Some of the following may be required during the test:
- Deep breathing (this may produce changes in the electrical activity, which can help with the diagnosis). You will be asked to take deep breaths for approximately three minutes. This can cause a feeling of light headedness and some slight tingling in the lips and fingertips. This is normal and will pass when you return to normal breathing.
- Flashing lights. You may be asked to watch a flashing light. This will flash at different speeds for short periods of time and will last for 2-3 minutes in total.
This may, in rare circumstances, cause a seizure in some patients. However, the physiologist will be closely monitoring you throughout and will try to limit this occurring.
Once the recording is finished the electrodes and paste are removed. You may wish to wash your hair when you get home.
Test results
All results will be analysed by a consultant who specialises in neurophysiology. The report will not be available immediately but should reach your GP/Consultant within 7-14 days.
How can I prepare my child for an EEG?
- We need you child to have clean and dry hair with no extra products such as oil, gel, mousse or hair spray. This will help stick the electrodes on your child’s head.
- Continue to give your child’s medication as normal prior to the investigation unless instructed by your doctor. Your child should also eat and drink as normal. Melatonin tablets or liquid is usually prescribed for your child before the sleep EEG. This is used to promote sleep for your child.
- Wait until you come to our department before administering Melatonin.
- Arrange for someone to look after your other children if possible. It is better if they could be looked after at home or by another adult if they come with you.
- It is important for your child to be quiet and relaxed during the test.
- Bring toys/anything that your child likes to create some familiarity and help to distract during appointment.
Some questions that your child might ask about an EEG
Q: Does it hurt?
A: No, the test does not hurt. We will place small sticky disks on your hair. It may only feel a bit cold and sticky. You won’t feel anything during the test apart from the wires on your head. You will feel the same after the recording as you did before it.
Q: Can it read my mind?
A: No, your thoughts are private and cannot be discovered by this test.
Q: Will they give me a needle?
A: No, we do not use any needles, only small metal disks which sits on your head.
Q: Will they give me an electric shock?
A: No. The metal discs record electricity coming from your brain but you do not feel this.
What if my child has special and complex needs?
If your child has special needs or you think they may not be able to cooperate with the procedure you can contact our EEG staff to discuss your concerns and the best course of action.
You can also discuss this with your child’s doctor if you think more support is required. You can contact the Learning Disability Team for more support ([email protected]) so that they can help us preparing your child for the test.
If your child has an Hospital Passport you can send it to us so we can make the necessary adjustments and help your child having the best hospital experience possible. See contact details and opening hours of the Neurophysiology department in this leaflet.
Students and trainees
As we are a teaching hospital, on occasion you might be asked if you would agree to a trainee to perform the test under supervision. Saying no to this will not affect your child’s treatment. It is entirely your decision.
We welcome feedback about our services. Please tell a member of staff if you felt this service was good or otherwise.
Further Information about EEG’s is available from numerous organisations including
UK Epilepsy Helpline
Helpline (freephone)
Further information
If you have any queries or questions regarding the information in this leaflet, please contact the Neurophysiology Department on:
Large print copies are also available on request from the department on the number above.
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