How It Is Done
An electroencephalogram (EEG) may be
done in a hospital or in a doctor's office by an EEG technologist. The EEG
record is read by a doctor who is specially trained to diagnose and treat
disorders affecting the nervous system (neurologist).
You will be asked to lie on
your back on a bed or table or relax in a chair with your eyes closed. The EEG
technologist will attach several flat metal discs (electrodes) to different
places on your head, using a sticky paste to hold the electrodes in place. A
cap with fixed electrodes may be placed on your head instead of individual
electrodes. In rare cases, these electrodes may be attached to the scalp with
The electrodes are hooked by wires to a computer
that records the electrical activity inside the brain. A machine can show the
activity as a series of wavy lines drawn by a row of pens on a moving piece of
paper or as an image on the computer screen.
Lie still with your
eyes closed during the recording, and do not talk to the technologist unless
you need to. The technologist will watch you directly or through a window
during the test. The recording may be stopped from time to time to allow you to
stretch and reposition yourself.
The technologist may ask you to
do different things during the test to record what activity your brain does at
- You may be asked to breathe deeply and rapidly (hyperventilate).
Usually you will take 20 breaths a minute for 3 minutes.
- You may be asked to look at a bright, flashing light called a
strobe. This is called photic or stroboscopic stimulation.
- You may be asked to go to sleep. If you can't fall asleep, you
may be given a sedative to help you fall asleep. If an EEG is being done to
check a sleep problem, an all-night recording of your brain's electrical
activity may be done.
An EEG takes 1 to 2 hours. After the test, you may do your
normal activities. But if you were sleep-deprived or given a sleep medicine,
have someone drive you home after the test.