Clinical Neurophysiology and Epilepsy


South East of England and London

Electroencephalography (EEG)


EEG is the recording of the brain electrical activity using electrodes placed on the scalp.

It is performed by a trained technician. A routine EEG recording is done either while sitting up in a chair or lying down on a couch. The whole procedure takes about an hour and you will be asked to close and open your eyes from time to time and encouraged to relax and drop off to sleep. It is harmless and painless.


During the recording the technician may carry out some activation procedures to reveal extra information and bring out abnormalities not otherwise seen.


These include:


-Hyperventilation (over breathing) when the technician will ask you to take regular deep breaths in and out for 3 minutes. Don’t worry if you feel light headed, occasionally over breathing may provoke a seizure but the technician is fully aware of this possibility and will keep a close eye on you and the EEG trace.


-Photic stimulation is performed by using a bright strobe light flashing in front of your eyes at various frequencies.

It will be done with your eyes open and closed.

Like hyperventilation photic stimulation may trigger a seizure if you are photosensitive but again the technician will be closely monitoring you and your EEG.