Having Electroencephalography (EEG)

An electroencephalogram (EEG) is a test to detect abnormalities in the electrical activity of the brain.  Brain cells (or neurons) communicate by producing electrical signals. These signals are measured by the EEG and any abnormalities are detected.

You will sit in a reclining chair or lie down on an exam table in a softly lighted room. The technologist will measure certain points on your head. He or she will use a special pencil to mark the spots where electrodes will be placed on your scalp. Your scalp will be rubbed with a mild abrasive, and electrodes (15 to 30) will be attached using tape or an adhesive.

This test is safe and painless. Avoid all foods containing caffeine for 8 hours before the test. You may also be instructed to avoid prescription medicines that affect the nervous system.

Most tests are done as an outpatient and may take up to an hour. Some tests are looking for existing seizure activity and you may need to stay overnight at the hospital and remain connected to the electrodes for a longer period of time.


  • Try to relax and remain still.

  • Avoid talking during the test.

During the test

You will be asked to do any of the following:

  • Relax, and open and close your eyes when the technician asks you to do so.

  • Breathe rapidly and deeply (hyperventilate) for a few minutes.

  • Sense a flashing light through your closed eyes.

  • Relax and go to sleep.

  • Respond to questions.

After your test

When your test is done, all of the electrodes will be removed. At home, wash your hair to remove any remaining glue, gel, or paste. You can get right back to your normal routine. Your doctor will let you know when your test results are ready.