Electroencephalography

What is an EEG Examination?

EEG is the abbreviation of ElectroEncephaloGram, which is the recording of electrical activity produced by the brain.

How is it done?

A standard test takes about 45 minutes to one hour. Sleep tests will take longer - check with your own department for more information.

The Clinical Physiologist starts by making measurements of your head, and after gently rubbing over the marks, attaches about 22 small metal discs using a sticky paste. This takes about 20 minutes. The recording itself takes about 30-40 minutes. You will be lying or sitting during this time and the neurophysiologist will ask you to follow instructions, such as to open or close your eyes.
After the test the discs are removed and you will be able to return home or to work/school. Small pieces of sticky paste may be left in your hair - these will wash out with shampoo.

What other measurements are made?

Some of the following may be needed during your test:

• Deep breathing. This may produce changes in your brain wave activity that could help in diagnosis. You will be asked to take deep breaths for about 3 minutes. This often causes a light-headed feeling or tingling of the lips or fingers - this is normal and will pass off when you return to breath normally.
• Photic stimulation. This is an important part of the test for people who may have seizures or blackouts caused by flashing lights. You will be asked to look at a bright flashing light with your eyes open or closed. This may very rarely cause a seizure in people that are very sensitive, but the Physiologist will be looking at the EEG during the test and will stop the flashing light if you appear to be sensitive.
• Sleep test. A recording during sleep or after deprivation of sleep can sometimes be helpful. You will be told in advance if you are to have this type of recording. Lack of sleep can sometimes cause attacks in people prone to epilepsy. A sedative tablet may be given to help you sleep. If you have this, or an EEG recording after deprivation of sleep, you may be still sleepy when you have finished the test. You should not drive at this time and it is advisable to have someone accompany you home.
• Video. It may be helpful to make a video recording of you during the test.

Will I feel anything?

You will feel the skin being rubbed before the discs are put on your head, but the investigation is otherwise painless. No needles are involved.

Can you read my mind?

No - we only record the electrical activity from your brain, and not any thoughts or emotions you may have.

Is this shock treatment?

No - electricity is not used: we only record the signals produced naturally. This is an investigation and not a treatment.

Will there be any after effects?

No - it has no effect on you at all.

What happens if I have a seizure during the test?

You will be checked to make sure you are well enough to go home. It is very unlikely that the investigation will cause an epileptic attack, but if it does, and you hold a driving licence, you will be obliged to inform the DVLA (as for all attacks): this may affect your ability to hold a driving licence.

What preparation is needed?

Please ensure that your hair is clean and free from grease, hair spray and lacquers etc. Loose clothing will be most comfortable. You may wear jewellery but it may have to be removed.

Should I take my tablets before the test?

Yes - continue your treatment at the usual times, and have meals at your usual times.

Will I have to wait long?

You will be given an appointment time and should not have to wait in the department. Departments work to a busy schedule, so it is important that you arrive on time.

Will I get the result the same day?

The results of the investigation need to be analysed afterwards and a full report will be sent to the doctor who referred you for the test.
If you have any questions about the issues raised above, or any other concerns, please talk to the Clinical Physiologist before the start of your test.