EEG Test

What is an EEG?

An EEG (electroencephalogram) is a recording of the electrical activity of the brain, and may be useful to diagnose epilepsy, and other problems with the brain. It is sometimes called a brainwave test. Small metal discs and paste are placed on the surface of scalp by parting the hair. No discomfort is felt.  The electrical activity detected by the small metal discs is amplified by the EEG machine and recorded.


You may have a routine awake EEG, or sometimes a sleep EEG. Each test takes about 1 hour.

The sleep deprived EEG test is a way of provoking the brain. If someone has chest pain then the doctor will place them on a treadmill and exercise their heart to see how it functions under load. With the brain waves, the safest and most accurate way to “provoke” the brain is to be sleep deprived.

The recording is performed by a technician, who will ask you about any symptoms you may have as well as the names of any medications you are taking.

During most of the test you will relax in a comfortable position on a couch with your eyes closed. The technician may ask you to open and close your eyes at various times, breathe deeply for a few minutes and to look at a flashing light.


The results will be analysed after you leave and a report is then sent to your doctor, who will discuss the results with you.

Preparation for the EEG

Your hair should be clean (washed and dried before the test) and free from hair spray, gel etc.

You should eat prior to the test and take medications as usual.

For a sleep-deprived EEG:

You should have less than three hours sleep on the night before your EEG, unless instructed otherwise. The sleep component should ideally finish before 3 am so that you are very tired for the test. If you are told to sleep no more than 3 hours, then go to bed at midnight and get up by 3 am. You should avoid stimulants such as coffee, tea or cola for 6 hours prior to the test.   You should not drink alcohol the night before the test.


Sleep deprivation may bring on a seizure, therefore epilepsy safety precautions are indicated before the test during the sleep deprivation and after the test. It is very important that a friend or family member should bring you to and from the test (as you cannot drive a car when sleep deprived), and should stay with you throughout the day following the test. In some patients with low mood or depression, they can feel more unwell when sleep deprived.