Explanation

EEG stands for electroencephalogram - electro means electricity, encephalo means head, or brain, and gram means recording. So, an electroencephalogram is an electrical brain recording. An EEG records the electrical messages that neurons in your brain send to each other.

The recording gives your doctors information about how your brain works.

Why do I need one?

The reason you will usually need to have an EEG is because you've had a seizure. You might also have an EEG because you've banged your head, you're having sleep problems, your behaviour has changed recently, or you're going to have an operation.

How does it work?

When you have the EEG, small pads called electrodes will be attached to your scalp. Wires from the electrodes will be connected to the EEG machine. The electrodes are extra sensitive, so they can hear your neurons talking to each other, even through your skull! While you are having the EEG, this electrical chatter is recorded by the EEG machine, and the pattern of chatter is shown on paper or a computer the whole time, as pictures of your brain waves.

What does it show?

The EEG recording can show doctors whether your neurons are sending any abnormal messages, and even where in your brain it's happening.

What happens?

You will sit or lie down on a sofa to have the EEG, so you will be comfortable. The electrodes are attached to your head using sticky paste or tape. You should wash your hair thoroughly before you have the EEG to make sure they stick properly.

When the EEG starts, you must keep very still, to make sure that the machine only picks up your brain waves and not any body movements.

The person doing the test will ask you questions, show you pictures, or ask you to do different tasks, to see how your brain responds. If you're having the EEG because you had a seizure, the doctor may 'create' a seizure by showing you flashing lights or making you breathe in a certain way.

You might need to be asleep for part of the test. If so, the doctor will have asked you not to sleep beforehand, and might give you a medicine to help you nod off. EEGs usually take about an hour to do, but you may have to wear an EEG 'hat' that records your brain the whole day while you do normal stuff. This is called EEG telemetry.

Will it hurt?

It will not hurt you at all. An EEG records electrical messages coming from your brain, it doesn't put any electricity into your brain or body.

What happens next?

A neurologist will look at the recording and try to work out what's going on in your brain. It takes a while to read the EEG, so the neurologist will ask you to come back another day to show you what he or she has found.