Routine EEG
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What is an EEG?
EEG Brochure - What does the EEG show?
- Does an abnormal EEG confirm epilepsy?
- How does the EEG help?
- What happens before the EEG?
- What happens during the EEG?
- How long will it take?
- Obtaining the results of the test
- Some questions that your child might ask about an EEG
What is an EEG?
An electroencephalogram (EEG) is a recording of the brain's electrical activity. The brain produces small electrical signals which the EEG machine is able to pick up and reproduce as a record on paper or on a computer screen. The EEG is an important part of the evaluation of children and adults with seizure disorders.
What does the EEG show?
The EEG recording shows rhythmical electrical activity, often called brain waves. The brain waves may be normal or show abnormalities in certain regions. In people with epilepsy, there may be "epileptic activity" on the EEG indicating their predisposition to seizures. This epileptic activity can take several forms and be either generalised (recorded over all regions) or focal (recorded in one or more localised regions).
Many types of childhood epilepsy have characteristic epileptic activity on the EEG that leads to a specific diagnosis and treatment. Focal abnormalities seen on an EEG occasionally warrant a child having a brain scan.
Does an abnormal EEG confirm epilepsy?
Minor irregularities of no significance are frequently seen in EEG recordings of normal children, especially infants and young children. Non-epileptic abnormalities and even epileptic activity may be recorded in children with neurological and behavioural problems (eg. cerebral palsy, autism, speech delay) and do not mean that the child has epilepsy. Furthermore, about 2% of normal school-age children who do not have seizures have epileptic activity on EEG.
Conversely, a normal EEG does not exclude epilepsy. Many types of epilepsy may be associated with a normal EEG between seizures. A normal EEG during a "seizure" usually excludes epilepsy as the cause.
The interpretation of EEG findings in children can be difficult and it is recommended that EEGs in children are recorded and interpreted by clinicians experienced in paediatric EEG.
How does the EEG help?
The main roles of EEG in the evaluation of children with epilepsy are to:
- help distinguish focal from generalised seizures and epilepsies
- help make a specific (syndrome) diagnosis in a child with epilepsy.
EEG is occasionally used to:
- help confirm or exclude epilepsy, following a thorough clinical evaluation (usually with EEG recording during episodes)
- monitor treatment in some types of epilepsy
- help localise the site of seizure activity in a child with focal epilepsy
An EEG can occasionally lead to confusion, especially if non-specific abnormalities or epileptic activity is seen in a child without seizures.
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What happens before the EEG?
To help reduce the amount of natural oil in the hair it is important to thoroughly wash your child's hair the night before the EEG recording.
Before the recording, the EEG technologist will ask you a few questions, even though you may have given this information to your doctor.
For the EEG to be successful, a child needs to be relaxed and remain fairly still during the recording. The EEG technologist will help to relax your child, but babies and young children may need dummies, bottles or other comforters.
It is often desirable for infants and children to sleep during the EEG recording. To achieve this, morning or afternoon sleeps should be postponed until you reach the EEG department and the test has commenced. Do not let your child sleep on the journey to the hospital.
Sometimes a child needs sedation before the recording, to facilitate application of electrodes or recording during sleep. If so, you should have been informed of this by your child's doctor prior to your appointment. Your child's doctor will normally prescribe the sedation on the EEG request form. The staff in the EEG department will discuss with you whether or not to give the sedation, depending on your child's age and how sleepy they seem.
Some children cooperate better if their parents are present during the recording. Others cooperate better if their parents wait outside the recording room. It is important to arrange for another adult to look after your other children while the recording is being done, as they will have to wait outside.
What happens during the EEG?
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Your child will either sit in a reclining chair or be nursed by you. After explaining the procedure, the technologist will measure your child's head and mark the scalp with a soft pencil. The technologist will then put a little fluid on these areas and rub the scalp lightly with a cotton bud, to prevent the natural oils from the hair from interfering with the recording. They will then put several (usually 23) small metal disk electrodes with wires onto the scalp, keeping them in place with a "sticky" cream and some tape. The cream is easy to wash out of the hair after the test is completed. After the electrodes have been applied, your child needs only to rest.
Children old enough to cooperate will be asked to open and close their eyes a number of times. Later in the recording they may be asked to do some deep breathing. The deep breathing will continue for a few minutes and may make your child feel tingly or dizzy. Your child will usually be asked to look at a flashing light. The deep breathing and flashing lights sometimes activate epileptic activity on the EEG that is helpful in making a correct diagnosis.
Where possible, we try to also record the EEG during sleep. Fortunately, young children often doze briefly during the EEG recording.
How long will it take?
The test usually takes 50-60 minutes, 20 minutes to set up and 30-40 minutes to record. Sometimes it takes longer, especially if a sleep recording is needed.
Obtaining the results of the test
The EEG technologist has been specially trained for this work and will be pleased to answer any questions about the procedure. However, the technologist will not be able to give you the results of the test. The EEG recording will be interpreted later by a neurologist and the results will be sent to your child's doctor. Results are usually available to your doctor within 24-48 hours. Please check with the EEG staff that they have the correct details for your child's doctor and let them know what arrangements were made for you to obtain the result.
Cartoons of EEG
 normal EEG (cartoon) |
 absence seizure EEG (cartoon) |
Some questions that your child might ask about an EEG
Q: Does it hurt?
A: No. Some children might find the procedure irritating, but it does not hurt.
Q: Do they cut my hair?
A: No. The metal disk electrodes are put on the scalp between the hair.
Q: Will they give me a needle?
A: No. You might be given a medicine to drink to make you sleepy but there are no needles.
Q: Will they give me an electric shock?
A: No. The metal discs record electricity coming from the brain but you do not feel this.
Q: Are there any after effects?
A: No. You will feel the same after the recording as you did before it.
Q: Can it read my mind?
A: No. Your thoughts are private and cannot be discovered by this test.
Remember
- Wash your child's hair the night before
- Do not let your child sleep on the way to hospital
- Please arrange babysitting for your other children as they can not be present when the test is done.
For more information
| Contact: |
Department of Neurology (03) 9345 5661 |
| or | |
| Children's Epilepsy Program |
See also information on
Acknowledgement
Digital EEG is recorded on a special unit made for the Royal Children's Hospital by Compumedics, and purchased with a generous donation from Tattersalls.