EEG - Electroencephalogram

Key points about an EEG

• an EEG is a test that records the small electrical signals that the brain is always producing 
• an EEG is painless and harmless
• it will take up to 1 hour and 30 minutes

What does EEG stand for?

EEG stands for electroencephalogram. Electro (electricity); encephalo (brain); gram (recording).

An EEG digitally records the electrical signals from the brain on a special computer.

Who does an EEG?

A special technician, called a neurophysiology technician, will do your child’s EEG. They are specially trained to do EEGs.

Why do an EEG?

How can technicians get the most information from an EEG?

The EEG records brain waves for 20 to 45 minutes, which is only a small amount of time. Abnormalities do not occur all the time but technicians can do things to increase the chances of picking up abnormalities during the recording time. These include:

• sleep deprivation
• deep breathing (hyperventilation)
• flashing lights (photic stimulation)
• opening and closing eyes

Technicians usually video your child during the EEG. This helps the specialist interpret the EEG. Once the specialist has finished the EEG report, they will usually delete the videos unless the video has recorded an event of interest.

Does an EEG hurt?

No. An EEG is painless and harmless.

Where do you go for an EEG?

There are several hospitals in Aotearoa, New Zealand where your child can have an EEG. Your doctor will tell you which hospital to go to. You may need to travel to another centre.

How long does an EEG take?

The EEG technician will usually record the brain waves for 30 minutes. But, the whole EEG procedure takes up to 1 hour and 30 minutes. This includes putting the electrodes on your child’s head and taking them off.

How do I prepare my child for the EEG?

• your child can eat and drink normally and take any usual medicines
• as this test takes a while, be prepared with food and drink for your child 
• if your child has a special toy, book or cuddly please bring this too - this can help reassure and settle your child
• please wash your child's hair the day before the test

Sleep-deprived EEG

Usually, before the EEG, your child needs to have less sleep than usual. This is called a sleep deprived EEG. Sleep deprivation does 2 things:

• it increases the chances that your child will sleep during the EEG
• it increases the chances that if there are any brain wave abnormalities, they will be seen during the recording

The EEG department will let you know if they would like the EEG to be sleep deprived. They will give you information about how to sleep deprive your child.

What happens at the hospital before the EEG?

Please allow plenty of time to find the department so that you arrive at least 5 minutes before your appointment time.

The technician will ask about medicines, the reason your child has been sent for the test and any other relevant information which will help the doctor report the EEG.

What happens during the EEG recording?

You can go with your child into the recording room

As a parent or caregiver, you can go with your child into the recording room. You can help the technologist get your child's full cooperation. It is best that no more than 2 adults are with your child. Generally, it is best if other tamariki do not come as they can distract your child while they are having the test.

Your baby or toddler can sit on your lap and you can feed them. If your child is older, the technician will ask them to lie on a bed.

Tell the technician about any skin allergies

Please tell the technician if your child has any skin condition or has any allergies to skin products.

The technician will attach about 24 small silver discs to your child's head

The technician will measure your child's head. They will then mark the electrode positions with a special crayon. The technician will attach about 24 small silver discs to your child's head using either paste or tape. They place the discs in various positions on your child's head, forehead and earlobes. They will also put one disc on one or both shoulders to record your child's heart. Some EEG departments use a rubber cap (like a net) or some gel to keep the electrodes in place.

It will take about 15 to 20 minutes to put the electrodes on. It is very important that your child stays fairly still during the whole process, as well as during the recording.

You can read to your child while the technician puts the electrodes on, and during the recording.

It is important for your child to lie still

During the recording, the technician will ask your child to keep still and not talk.

Your child needs to open and close their eyes and breathe in and out deeply

The technician will also ask your child to open and close their eyes for short periods. Your child can practise this at home. It is important for your child to lie still and to be relaxed.

The technician will also ask your child to breathe in and out deeply and quickly for 3 to 4 minutes (hyperventilate). Your child may need to do this twice. This deep breathing is very important but is quite difficult for a child, so they need plenty of encouragement. You may need to do it with your child to keep them going. Breathing deeply makes you feel dizzy and lightheaded. This dizzy feeling means your child is doing it well. It may be an idea to practise a little at home for 20 seconds at a time.

Your child will then have a short sleep

After deep breathing, your child may become sleepy. This is good as the technician will dim the lights and encourage your child to sleep.

Finally, after a short sleep, the technician will flash a special light in front of your child. They will ask your child to look at the light while opening and closing their eyes when asked to.

What happens after the EEG recording?

The technician will remove the electrodes as carefully as possible using a cold liquid - it does not smell very nice but evaporates really quickly.

Your child will need another hair wash once they're at home.

How long do the EEG results take?

A neurologist will examine the recording and write a report. They will send a copy of the report to the doctor who requested the EEG as soon as possible. This should happen within several weeks.