• Electroencephalogram



    Electroencephalogram (EEG) is a test used to look at the electrical activity in the brain.
    Placement of Sensors for an EEG
    Copyright © Nucleus Medical Media, Inc.

    Reasons for Test

    An EEG may be done to:
    • Help diagnose seizures
    • Assess if brain function has been affected by certain conditions and diseases, such as:

    Possible Complications

    There are no major complications associated with this test.

    What to Expect

    Prior to Test

    Depending on the reason for your EEG, you may be given some of the following instructions:
    • Ask your doctor whether you need to stop any medications, such as stimulants, prior to the test.
    • Avoid caffeine for eight hours before the test.
    • Shampoo your hair the day of the test. Do not use hair styling products.
    • If you are having a sleep-deprived EEG, you may need to stay awake the night before the test. You should also arrange for a ride to and from the test.
    • If you are prone to seizures, arrange for a ride to and from the test.

    Description of Test

    You will sit in a chair or lie on a bed. Electrodes will be placed on your scalp with special gel or paste. The electrodes will record the brain's electrical activity. You will be asked to close your eyes and be still for most of the test. Depending on the reason for the test, there may be other steps such as:
    • You may be asked to breathe deeply and rapidly.
    • A strobe light may be turned on. It sends fast pulses of light.
    In some cases, a video recording of the test will be made.

    After Test

    The technician will remove the electrodes and you will be able to go home.
    Talk to your doctor about restarting any medications that you may have stopped.

    How Long Will It Take?

    The test may take about one hour. In some cases, an EEG is done overnight or over a number of days. The test may be done at home or in the hospital.

    Will It Hurt?

    No, an EEG is painless.


    Your test results will be reviewed. Your doctor will get a report within 1-2 weeks and will talk to you about the results.

    Call Your Doctor

    Call your doctor if you have a seizure disorder and your regular seizure pattern changes when you restart your anti-seizure medication.


    Epilepsy Foundation http://www.epilepsyfoundation.org

    National Institute of Neurological Disorders and Stroke http://www.ninds.nih.gov


    Canadian Neurological Sciences Federation http://www.cnsfederation.org

    Epilepsy Canada http://www.epilepsy.ca


    EEG (electroencephalogram). Nemours Kid's Health website. Available at: http://kidshealth.org/parent/general/sick/eeg.html. Updated September 2013. Accessed February 13, 2014.

    Seizure in adults. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T114746/Seizure-in-adults. Updated April 11, 2016. Accessed October 10, 2016.

    Seizure in children. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T550165/Seizure-in-children. Updated April 11, 2016. Accessed October 10, 2016.

    Shevell M, Ashwal S, et al. Practice parameter: Evaluation of the child with global developmental delay: Report of the Quality Standards Subcommittee of the American Academy of Neurology and The Practice Committee of the Child Neurology Society. Neurology. 2003;60:367-380.

    Revision Information

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