Electroencephalogram (EEG) - what to expect

Before the EEG

  • Please ensure that your hair is clean.
    If you may have head lice, please ensure you treat it beforehand.
    The test will not be done if head lice are present.
  • Please have your meals as normal, preferably two hours before the test
  • Take your medication as normal unless otherwise directed by your doctor
  • It's helpful if you bring a written list of any medication that you may be taking

Attending your appointment

We don't have a receptionist, so please come in and take a seat.

The technician will know you are coming and will be with you as soon as possible.

The department has limited waiting space, so we can only accommodate the patient and one escort, or one child patient and one of their parents.

If you are unable to keep your appointment, please contact us at least 48 hours beforehand.

We need a quiet and peaceful atmosphere in order to get a good sleep record, so no other adults/children are permitted in the recording room.

  • Mobile phones must be switched off when you are in the EEG unit
  • Unaccompanied children must not be left in the waiting area

EEG - general information

The whole test will take approximately an hour, or an hour and a half if a sleep deprived recording is being carried out.

The test is painless, and you will be either lying down or sitting.

The clinical physiologist will make measurements of your head.

To start with, pencil marks may be made; then approximately 21 small metal discs, attached to long wires (electrodes) are attached, using a sticky paste.

The skin on your head will be rubbed before the electrodes are attached to your head.

The recording takes about 30 minutes.  

During the recording you may also be asked to:

  • Open and close your eyes at various times
  • Breathe deeply
    This may produce changes in your brainwave activity that could help with the diagnosis
    You will be asked to take deep breaths for about three minutes
    This often causes a light-headed feeling or tingling of the lips or fingers; this is normal and will pass off when you return to breathing normally.
  • Look at a flashing light (photic stimulation)
    This is an important part of the test, especially for people who may have seizures or blackouts caused by flashing lights or the television.
    You will be asked to look at a bright flashing light with your eyes open and closed.
    This may cause a seizure in people who are very sensitive, but this is rare, and the clinical physiologist who monitors the EEG during the test will stop if you appear sensitive.

Routine EEG (adult)

The test normally takes about an hour.

You may need to be sedated.

All inpatients will be accompanied by a nurse.

Sedation EEG recordings (which are mainly applicable to children aged between eight months and three years) will take up to 2½ hours.

Some patients will sometimes be asked to re-attend for a further test; this would be a sleep deprivation recording to provide more information.

Special instructions 

  • Please do not have anything eat after the specified time on your appointment letter
  • Please ensure you stay awake during the day and on the way to hospital

Routine EEG (child)

The test normally takes one and a half to two hours.

Please wash your child's hair the night before the appointment and please do not apply:

  • Hair oil
  • Hair spray
  • Gel
  • Mousse
  • Wax
  • Etc

Please do not let your child sleep in the morning before the EEG, on the journey here, or in the waiting room on arrival; this will allow us to apply the electrodes and record some wake EEG and then hopefully record drowsiness and sleep.

If children are asleep on arrival, applying the electrodes usually wakes them up and they are upset and it can be difficult to get them to sleep again.

Please bring anything you feel might be helpful, such as a favourite toy, blanket or book, bottle, etc.                                                  

If your child no longer, or rarely sleeps in the day it would be very helpful if you wake him or her earlier than usual on the day of the EEG, so that he or she is more likely to sleep in the department.

We would suggest waking them two hours earlier than usual, but you know your child best, so please use your own judgement.

Sleep deprivation EEG (adult)

You must be tired when you arrive so you fall asleep naturally.

When you go home it is important that you go to sleep for 2-3 hours, then get up, but go to bed early that evening - to help catch up on sleep you missed the night before.

Sleep deprivation EEG (child)

On the night before the EEG, please keep your child up four hours later than usual in the evening and wake him or her four hours earlier than usual the next morning.

It would be helpful if you could wash his or her hair the night before the appointment.

In any event, on the day of the test, please do not apply:

  • Hair oil
  • Hair spray
  • Gel
  • Mousse
  • Wax
  • Etc

Please ensure your child does not fall asleep again during the morning or on the journey here.

We appreciate that this will be difficult, but your child must be tired in order that we can successfully perform the test.

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