Sleep electroencephalogram (EEG)

Introduction

This leaflet is designed to give you some information about the investigation for which you been referred. We hope it reassures you. We have a team experienced in these investigations; you will have the opportunity to discuss further questions or concerns before the start of the investigation.

Consent

We need your consent for any procedure or treatment beforehand. Staff will explain all the risks and benefits before they ask for your written consent. If you are unsure about any aspect of the procedure or treatment proposed, please do not hesitate to ask for more information.

What is an electroencephalogram (EEG)?

The brain works by electrical signals that can be recorded as waveforms (brainwaves) by small discs (called electrodes) positioned on the scalp. These brainwaves are sent to a computer and the resulting EEG is read by a healthcare scientist and doctor. EEG can help the medical team get information about brain activity while at rest, during sleep and during events being experienced. We record video at the same time as the EEG because this allows us to compare any movements with the brainwaves recorded. We will discuss this with you in more detail during the appointment and get you to sign a consent form.

Why am I having a sleep EEG?

There are many reasons for having an EEG. One common reason is to help determine if an event was a seizure, or to help classify the type of seizure. However, the doctor may have requested the test for lots of other reasons, such as for developmental assessment in children, overall function of the brain or as part of a series of investigations.

You, or your child, may have already had an EEG whilst awake. A sleep EEG can be helpful because the brain waves recorded can sometimes be different when we are tired or asleep compared to when we are awake.

How can I prepare for my sleep EEG?

Sleep deprivation

To help improve the chances of recording some sleep during the appointment, we will ask you to sleep deprive yourself or your child. The amount of sleep deprivation will depend on age so please make sure you read this leaflet and have understood all the information before attending the appointment. If there is a history of seizures being caused by sleep deprivation and you are concerned, please contact the referring doctor (do not contact the department of clinical neurophysiology as we will not have the full background information). Please keep taking all your usual prescribed medications.

Adults – We ask that you do not sleep the night before the test. If this is not possible please aim to go to bed at least two hours later than normal the night before the test, and get up at least two hours earlier than you normally would on the morning of the test. If you normally drive you will need someone to drive you to and from the appointment.

Children who don’t nap during the day – We ask that the child stays up about two hours later than normal the night before the test, and is woken two hours earlier than normal on the morning of the test.

Young children who nap during the day – We ask that the child is woken up earlier than normal on the morning of the test, and that their nap time is delayed to coincide with the test. This may mean you are also sleep deprived, so if you do not feel safe to drive please ask someone to drive you and your child to and from the appointment.

For all children, please try and keep your child awake on the way to the hospital – tired children often fall asleep in the car and you may find it helpful to have an extra person travelling with you if possible. It can also be helpful to bring any familiar things which your child usually likes to have when they go to sleep (cuddly toy, special blanket, milk etc).

Melatonin

Some children are prescribed melatonin to help them become drowsy and sleep during the test. This is a very safe medication, commonly taken by both adults and children, and is the same as the chemical produced by the brain when it is dark to help us sleep. The doctor should have discussed this with you and provided a prescription to collect the melatonin before the appointment. If your child has been referred for a melatonin sleep EEG, you will have been sent a pre-appointment information sheet. We ask that you read this in detail to understand how to get the melatonin, how to give the melatonin, including bringing any food or drink items to help, and any risks involved. If you have not received this information sheet, please contact us. It is important that you wait until you have arrived in the department and are told by a healthcare scientist when to give the melatonin.

What else do I need to do before the appointment?

• Please make sure to eat as usual before the test (do not skip a meal).
• It is important that the hair is clean; please do not use mousse, gel, oil or other hair products as this can affect the recording.
• Please continue taking any prescribed medication. It is helpful to bring a list of your current medications with you.
• Please let us know if you have any skin sensitivities or allergies during this appointment, especially any latex allergies.
• If possible, please attend with a witness to your typical events for us to obtain a detailed history.

Where will the EEG be performed?

Neurophysiology have two departments. One of these can be found on level 3 of the Main Outpatients building and the other is located in Clinic 33 of the Addenbrooke’s Treatment Centre. Please check your letter carefully for details on where your appointment will be and use the maps provided in this leaflet to guide you. Additional information on getting to Addenbrooke’s and different modes of transport can be found at Finding us.

Please note: if you arrive more than 30 minutes late for your appointment, you may not be seen.

Please contact us if you are travelling via hospital transport as this may determine the time of your appointment. Unfortunately, we are unable to see patients on beds or on stretchers in our outpatient department; please call us if this affects you.

Who will be present?

There will be a healthcare scientist present setting up the recording. Addenbrooke’s is a teaching hospital and you may be asked if you would consent to trainee staff performing the test under supervision or if you would mind other healthcare professionals/students observing the test. Refusing consent for this will not affect the test.

We have no provision for accompanying children to be looked after whilst you are having your EEG, or additional children during your child’s EEG.

What happens during the equipment application?

A healthcare scientist will measure the head using a soft pencil, like a crayon, and a tape measure. They will then use a cotton bud and gritty paste, like an exfoliator, to clean small areas of the scalp, which is not painful, but does involve some rubbing. Small silver discs with wires on will then be attached to the scalp using a special sticky paste, a bit like Vaseline®. There will also be some discs applied to the shoulders and the upper parts of both arms in the same way to record heart rate and any movements. All the wires will be tied together and connected to a small box that records all the data. It takes between 15 and 20 minutes to prepare for the recording.

For children, we have a small selection of toys available, but please feel free to bring your own items or a device to keep your child entertained.

What happens after the equipment is applied?

The EEG recording, which normally takes around 60 minutes, is not painful. During the test we would like you to be as comfortable as possible so will ask you to lie down on a bed in a darkened room. The healthcare scientist will sit in an adjoining room.

Many parents worry that their child will not sit still or lie down for this length of time. A lot of our recordings are performed on children, and we have an expert team who are experienced at distracting or occupying children to enable a good recording. If your child has a favourite toy, pillow or blanket, it would be worth bringing this. Snacks, a bottle or drink might also be helpful for children.

What happens during the recording itself?

It is important that we record some rest but we might also ask to perform some special procedures that might help to add some additional information. These include:

• Hyperventilation - this involves taking deep breaths as if you are blowing up a balloon or blowing out a candle. You may feel lightheaded or experience tingling in your fingers, toes or face. These are normal side effects which will pass within a few minutes of stopping the deep breathing. We will ask you about your general health (heart, asthma etc.) to make sure it is safe for you to do the deep breathing. The breathing causes a change in blood flow which may change your brain waves and provide extra information to help with your diagnosis. Deep breathing provides extra diagnostic information in about 12 per 100 patients.
• Photic stimulation - this involves watching a flashing light. You will be asked to look at a lamp, which is placed in front of you and flashes on and off at different rates. In a small percentage of people, flashing lights may increase the risk of a seizure (photosensitivity). If a brain response is seen, the light is turned off quickly and reducing the risk of having a seizure. Stimulation with flashing lights provides extra diagnostic information in about 3 per 100 patients.

Risks

There are no risks or side effects with the EEG test. Occasionally there can be slight redness or skin irritation where the electrodes are on the scalp. The recording itself is painless.

There is a low risk that sleep deprivation might cause an event when compared to having a full nights sleep. Please contact us if you have a history of seizures caused by sleep deprivation. We advise that a friend or family member sleep in the room with you the night after sleep deprivation as you may be more susceptible to seizures whilst in this state.

The flashing lights or deep breathing may cause you to have one of your events, but this may help with getting the right diagnosis.

• Hyperventilation is associated with triggering a seizure in 2 per 100 patients, and infrequent other types of event. It is associated with a more severe generalised tonic-clonic seizure in approximately 3 in 10,000 patients.
• Photic stimulation is associated with triggering a seizure in less than 1 in 100 patients, and a more severe generalised tonic-clonic seizure in approximately 4 in 10,000 patients.

You will be asked to give your consent to performing hyperventilation and photic stimulation. They help provide more accurate diagnosis and treatment, and there are no alternative methods. If you have a seizure you will legally be required to inform the DVLA; and may be required to surrender your driving licence.

What happens afterwards?

The healthcare scientist will remove the electrodes. This is not painful as the special paste stays soft. They will clean your hair, but it will feel a little sticky until it is washed with shampoo. Once the electrodes are removed you will be free to go home. We advise that you do not drive following sleep deprivation.

When do I get the results?

The results will not be available on the day of the recording. The healthcare scientist and doctor will review the test and will prepare a detailed report for the consultant that referred you. The results will be sent to your referring consultant within 2 weeks, sooner if urgent. It is best to discuss these results with the consultant that referred you as they will need to be explained alongside any other tests that have been performed.

Contacts / further information

If you need any further information or have any other queries please contact the neurophysiology administrator by phone on 01223 217136 Monday to Friday 09:00-16:00 or by email

If your appointment is in Clinic 33 of the Addenbrooke’s Treatment Centre

We are on level 3 in the Addenbrooke’s Treatment Centre (ATC). We are at the end of the corridor, just before the double doors to Papworth Hospital. You will find us next to the Endoscopy department.

If your appointment is in Neurophysiology in the Main Outpatients building

We are on level 3 in the Outpatients building area. You will find us in-between ward A3 and the Ultrasound department.

CUH Directions App:

For both apple and android phones. Find in your app store:

CUH Directions

MyChart

We would encourage you to sign up for MyChart. This is the electronic patient portal at Cambridge University Hospitals that enables patients to securely access parts of their health record held within the hospital’s electronic patient record system (Epic). It is available via your home computer or mobile device.

More information is available on our website: MyChart