An EEG is a simple test which records the electrical impulses from the brain. This test helps us to diagnose neurophysiological disorders. Neurophysiology is the study of brain, spinal cord nerve and muscle function.
A standard EEG takes around 45 minutes to 1 hour and is recorded by video.
A sleep deprived EEG will take around 3 hours.
How to prepare on the day
Preparing for a standard EEG
Before you come for the test you can have your meals as normal and continue taking any medication that you usually take unless you have been advised otherwise by your clinician.
Bring with you a list of your current medication and any allergies you have.
Make sure that your hair is clean and free from grease, hairspray, gel and any other hair care products, including weaves.
We will ask you to sign a consent form before the test.
Preparing for an adult sleep EEG
If you have been sent for a sleep deprived EEG, you should reduce your sleeping hours at least by half, for example: if you normally sleep for 8 hours you should aim for a maximum of 4 hours.
Make sure you go to bed at your usual time. If you have epilepsy, there is always a small risk that you may have a seizure because of sleep deprivation and your doctor will discuss this with you.
If you intend to drive to the appointment, you should be accompanied by a responsible adult as you will be too tired to drive safely and there is also the small possibility you might have a seizure if you are epileptic.
Preparing for a paediatric sleep EEG
If you have been sent for a sleep EEG, you can go to bed and wake up at your usual time.
For paediatric sleep studies your paediatrician may give you a sleep-promoting medicine called melatonin to help you go to sleep. You should not have any after-effects other than drowsiness.
Collect your melatonin (sleep medicine) from Boots Pharmacy in Main Outpatients prior to your EEG Appointment.
During your EEG
The EEG test is not painful.
The test will be carried out by an expert in electroencephalography called a clinical physiologist. They will ask you a few questions.
If you have any questions about the test, please do not hesitate to ask.
You can bring someone to your appointment with you if you wish.
The clinical physiologist will start by measuring your head and drawing some little dots with a marker on the surface of your head. The clinician will then gently rub the marks with some gel, then attach 3 small discs to the surface of your head using a sticky paste. The paste can be easily removed later with water.
We will ask you to relax on a bed and to follow our instructions such as opening and closing your eyes.
You may also be asked to do a deep breathing exercise and to look at a flashing light during the test.
After your EEG
Once the test is complete the discs will be removed and you can return to your normal activities. There should be no side effects after the standard EEG (without sleep deprivation).
Small pieces of sticky paste may be left in your hair which easily wash out with shampoo and warm water.
If you come for a sleep deprived EEG you should be accompanied by a responsible adult as you will not be allowed to drive home after the test.
The results of the tests will take a few weeks to be analysed by the physiologist and consultant. Your hospital clinician will contact you if something of concern is detected by the test, otherwise your hospital clinician or referring doctor will discuss the results with you at the next appointment.
