Prolonged EEG

Introduction

This leaflet is designed to give you some information about the investigation for which your child has been referred. We hope it reassures you. We have a team experienced in these investigations and you will have the chance 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 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 physiologist and doctor. EEG can help the medical team get information about brain activity while at rest, during sleep and during events being experienced by your child. We record video at the same time as the EEG, allowing us to compare any movements with the brainwaves recorded. We will discuss this with you in more detail during your appointment and get you to sign a consent form.

Why is my child having an 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, your child’s doctor may have requested the test for lots of other reasons, such as for developmental assessment, overall function of the brain or as part of a series of investigations.

What do I need to do before the appointment?

It is often important for us to try and get some EEG recording whilst your child is asleep. To help us achieve this, we would recommend the following:

• Depending on the age of your child, please try and prevent any naps before your appointment. This includes on the journey to your appointment so we would recommend travelling with two people if coming by car.
• Delaying a feed if still breastfeeding or by bottle. We will get you to give your child their feed during the appointment.
• If your child regularly has only one or two naps per day, please contact us to see if we can offer an appointment around the time of their usual nap time.
• If your child is older and no longer having regular naps or breastfeeding/feeding from a bottle, we would recommend partial sleep deprivation, asking for bedtime to be 1-2 hours later and for wake-up time to be 1-2 hours earlier than normal.
• Please feel free to bring any special blankets, toys or pillows that might comfort your child and help them go to sleep.

Please also take note of the following:

• 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 giving 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.

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 on the CUH website (opens in a new tab).

Please call us if you are running more than 30 minutes late for your appointment.

Who will be present?

There will be a physiologist 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 additional accompanying children to be looked after whilst you are having your EEG.

What happens during the equipment application?

A physiologist 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 to 20 minutes to prepare for the recording. 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.

Some parents worry about co-operation during this part of the test. 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 it would be worth bringing this. Snacks, a bottle or drink might also be helpful for children.

What happens during the recording itself?

The EEG recording, which normally takes around 1 hour, is not painful. 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:

• Photic stimulation - this involves watching a flashing light. Your will be asked to look at a lamp, which 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.
• Hyperventilation – we will perform this depending on the age and co-operation of your child. This involves taking deep breaths with the help of a colourful windmill. Your child may feel light headed or experience tingling in their 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 general health (heart, asthma etc.) to make sure it is safe 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 the diagnosis. Deep breathing provides extra diagnostic information in about 12 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.

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.

What happens afterwards?

The physiologist will remove the electrodes. This is not painful as the special paste stays soft. They will clean the 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 and can return to your normal activities.

When do I get the results?

The results will not be available on the day of the recording. The physiologist 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 08:30-17:00 or by Email.

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

If your appointment is in Neurophysiology in the Main Outpatients building

My Chart

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: My Chart