Adult Sleep Electroencephalogram (EEG)

  • Reference Number: HEY-791/2016
  • Departments: Neurophysiology


This leaflet has been produced to give you general information about your procedure.  Most of your questions should be answered by this leaflet.  It is not intended to replace the discussion between you and your doctor, but may act as a starting point for discussion.  If after reading it you have any concerns or require further explanation, please discuss this with a member of the healthcare team caring for you.

What is a sleep EEG?

A sleep EEG will be performed by a clinical physiologist. EEG is the abbreviation of electroencephalogram, which is the recording of electrical activity produced by the brain. It can help to explain fits or seizures and is a tool to help your doctor in making a diagnosis. The activity is recorded on a computer and a video recording of you is made at the same time. A sleep study is similar except that we specifically ask you to halve your normal night’s sleep and to take a small dose of melatonin which is a medication designed to help you sleep. We also record for a longer period of time. Together, this can help us learn even more about the health of your brain.

Why do I need a sleep EEG?

A Sleep EEG is commonly performed if you have already had a routine EEG and your doctor requires further information. Occasionally, particularly if your seizures only occur in sleep, this may be the first EEG recording you have.

We may also perform a Sleep EEG if you have any conditions that may make it difficult for you to undertake/co-operate for a routine EEG.

Can there be any complications or risks?

  • As part of a Sleep EEG you may be asked to breathe deeply for a few minutes or look at a flash of light.
  • In some people there is a very small chance that the deep breathing or flashing light could result in a seizure. You will be asked if you are happy to include the deep breathing and flashing lights as part of the test.

How do I prepare for the sleep EEG?

Please read this information leaflet. Share the information it contains with your partner and family (if you wish) so that they can be of help and support. There may be information they need to know, especially if they are taking care of you during/following this examination.

  • Please let us know before your appointment if you are pregnant or breast feeding.
  • If you suffer from any allergies please let us know as soon as possible.
  • You will not be able to drive after your test due to the medication you have been given and it is advisable for you to have someone to accompany you home.
  • The night before the test please try to go to sleep as late as possible ie 2am and wake very early ie 5am.
  • For 24 hours prior to the test please avoid drinking tea, coffee or any beverages containing caffeine (eg energy drinks and some fizzy drinks).
  • Please wash your hair before you come to the hospital and do not use any hair products (gel, hairspray etc).
  • Take your medication as normal unless otherwise directed by your doctor. Please have a light meal prior to your attendance.
  • Please bring a list of any current medication you are taking.

What will happen?

  • On your arrival in the department we will obtain your consent for the procedure before your investigation begins.
  • The clinical physiologist performing the Sleep EEG will explain the test to you and will be happy to answer any questions you may have.
  • Generally we ask people to come into the examination by themselves as experience shows this makes it easier for people to fall asleep. Sometimes we will ask the person accompanying you to come through at the start if they can supply additional information about your condition but we will generally ask them to leave before we start the recording. If this is going to be a problem for you please discuss this with the clinical physiologist.
  • You will be given your dose of Melatonin.
  • You will be asked to sit on a chair and have your head measured and some points will be marked on it with a soft pencil.
  • You will be asked some questions about the condition leading to your referral for a Sleep EEG.
  • You will then move to lie comfortably on a bed and several small electrodes will be placed on your head using sticky paste.
  • The recording will take approximately an hour and during this period there will be time when your eyes are open and times when they are closed.
  • During the test you will be asked to breathe deeply for a short time. Once the deep breathing is finished you will be left with your eyes closed and asked to try and fall asleep.
  • For part of the test you may be asked to watch a flashing light although this may be unnecessary if you have recently had a routine EEG.

What happens afterwards?

  • The electrodes will be removed and your head cleaned with warm water. You may wish to bring a brush or comb with you to tidy your hair. Any residue of paste can be removed by shampooing the hair at home.
  • You may still feel tired or drowsy following the test due to a combination of lack of sleep and the effects of Melatonin. We recommend that you have someone to accompany you home after the test.
  • Under no circumstances should you drive until the following day.
  • Once you have left the department the recording will be reviewed by the Physiologist and then by a member of the medical team or Senior Physiologist who will send a report to the doctor who referred you for the Sleep EEG. This usually takes up to two weeks.

Should you require further advice on the issues contained in this leaflet, please do not hesitate to contact the Neurophysiology Department on tel: (01482) 675339 or 675388.

General Advice and Consent

Most of your questions should have been answered by this leaflet, but remember that this is only a starting point for discussion with the healthcare team.

Consent to treatment

Before any doctor, nurse or therapist examines or treats you, they must seek your consent or permission. In order to make a decision, you need to have information from health professionals about the treatment or investigation which is being offered to you. You should always ask them more questions if you do not understand or if you want more information.

The information you receive should be about your condition, the alternatives available to you, and whether it carries risks as well as the benefits. What is important is that your consent is genuine or valid. That means:

  • you must be able to give your consent
  • you must be given enough information to enable you to make a decision
  • you must be acting under your own free will and not under the strong influence of another person

Information about you

We collect and use your information to provide you with care and treatment. As part of your care, information about you will be shared between members of a healthcare team, some of whom you may not meet. Your information may also be used to help train staff, to check the quality of our care, to manage and plan the health service, and to help with research. Wherever possible we use anonymous data.

We may pass on relevant information to other health organisations that provide you with care. All information is treated as strictly confidential and is not given to anyone who does not need it. If you have any concerns please ask your doctor, or the person caring for you.

Under the General Data Protection Regulation and the Data Protection Act 2018 we are responsible for maintaining the confidentiality of any information we hold about you. For further information visit the following page: Confidential Information about You.

If you or your carer needs information about your health and wellbeing and about your care and treatment in a different format, such as large print, braille or audio, due to disability, impairment or sensory loss, please advise a member of staff and this can be arranged.