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Electroencephalogram (EEG)

How It Is Done continued...

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 tiny needles.

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 that time.

  • 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.

How It Feels

There is no pain with an electroencephalogram (EEG).

If paste is used to hold the electrodes, some paste may stay in your hair after the test, so you will have to wash your hair to remove it. If needle electrodes are used (which is rare), you will feel a brief, sharp prick (about like having a hair pulled out) when each electrode is inserted. If electrodes are placed in your nose, they may cause a tickling feeling and, rarely, some soreness or a small amount of bleeding for 1 to 2 days after the test.

If you are asked to breathe rapidly, you may feel lightheaded or have some numbness in your fingers. This reaction is normal. It will go away a few minutes after you start breathing normally again.

WebMD Medical Reference from Healthwise

Last Updated: October 10, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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