This page explains about EEGs and what to expect when your child comes to Great Ormond Street Hospital (GOSH) to have this procedure.
What is an electroencephalogram?
An electroencephalogram is a test that looks at the function of the brain.
The brain works by a series of nerve impulses, which cause electrical signals within the brain. These signals (also called brainwaves) can be recorded through the scalp. A digital video recording will be made during the test. This enables the doctors to compare your child’s brainwaves with his or her movement and/or behaviour at the time. More information about how we use these video recordings is available in the accompanying information sheet.
An EEG is a safe method of recording your brain’s function without the need for sedation or an anaesthetic. This makes it a good way to get an overall view of the function of the brain and can indicate stages of development. It is helpful as part of general investigations and also if there are more specific problems, such as seizures.
What happens before the test?
If your child is having an EEG as an outpatient, the <%$Linker: Internal <?xml version="1.0" encoding="utf-16"?><dictionary /> 2 254519 0 oLinkInternal EEG department About us false /medical-conditions/clinical-specialties/neurophysiology-information-for-parents-and-visitors/about-us-cs/ true false%> (also called the Department of Clinical Neurophysiology) will send you an appointment letter. If your child is having an EEG during his or her hospital stay as an inpatient or day case patient, the ward will arrange the test and let you know when it will happen.
It is helpful if you could make sure that your child’s hair is clean before the test, with no mousse, gel, oil or hairspray. If your child is taking medicines, you should continue to give them as normal.The doctor will explain about the test in more detail, discuss any worries you may have and ask you to give permission for both the EEG test, any stimulus (activation procedures) used, such as a flashing light or over breathing, and video recording by signing a consent form.
What does the test involve?
The clinical physiologist will attach small silver discs (electrodes) to certain points on your child’s scalp using a soft paste. Sometimes, they will measure your child’s head beforehand and mark the points with a soft pencil before attaching the electrodes.
As each electrode is attached, the clinical physiologist will clean the area of the scalp with a cotton bud and some cream. This does not hurt but some children do not like it. While all the electrodes are applied, your child can sit on a chair, the bed or your lap, and can play with toys.
The electrodes are attached by wires to a ‘headbox’ and then to the recording machine. The clinical physiologist will record your child’s brainwaves on to the recording machine connected to a computer and monitor them on a screen. At the same time the digital video recording of your child will be made.
During the test, the clinical physiologist may ask your child to lie or sit quietly if possible or continue to play. He or she may also ask your child to do some breathing exercise or be shown a flashing light during the test. Your child will be closely monitored throughout the test and these stimuli will be stopped at the first sign of a seizure.
How long does the test last?
The test takes between 45 and 90 minutes, depending on the information required. Many parents worry that their child will not sit still for this long, but most children cope with the test as there are plenty of toys to play with and sometimes another member of staff to help too. A bottle or a drink might be helpful for younger children.
Are there any risks or complications with the test?
There are no risks of complications associated with an EEG.
What happens after the test?
The clinical physiologist will remove the electrodes from your child’s scalp. This will not hurt as the paste stays soft and so is easy to remove. They will also clean your child’s hair but it may feel a bit sticky to the touch until you wash it. Once all the electrodes have been removed, you will be free to go home if no other tests or appointments have been planned.
How long until we get the results?
You will not be given the results during the appointment. The doctors in the EEG department will write a detailed report of the test results and send them to your child’s doctor. The results will usually be ready in time for your child’s next appointment.
Last reviewed by Great Ormond Street Hospital: February 2008
Ref: 07F094 © GOSH Trust February 2008
Compiled by the Department of Clinical Neurophysiology in collaboration with the Child and Family Information Group.
This information does not constitute health or medical advice and will not necessarily reflect treatment at other hospitals. If you have any questions, please ask your doctor. No liability can be taken as a result of using this information.