Frequently asked questions: EEG & EP

Please find below answers to questions about electroencephalograms (EEG) and evoked potentials (EP) tests

Who performs the test?

A registered technologist with the Canadian Board of Registration of Electroencephalograph Technologists, Inc. will perform the EEG or EP test.

A neurologist (someone who specializes in nervous system disorders) interprets the recordings taken from the EEG or EP and then sends the results to your doctor within one to two weeks. Your doctor may schedule an appointment to go over the test results with you.

Electroencephalograms (EEG) tests

Three types of EEG testing may be performed:

  1. Routine EEG
    Allow one hour for this test.

  2. Sleep Deprived EEG
    Allow for 1.5 hours for this test. Awake, drowsy and sleep states will be monitored. Please deprive yourself of sleep by remaining awake the night prior to your test. You may eat and drink, but avoid caffeinated beverages. 

    It is strongly recommended that you do not drive to and from this procedure.

  3. Prolonged EEG
    Video monitoring with partial sleep deprivation of four hours. You will be monitored for three hours with digital video during awake, drowsy and sleep states. Allow 3.5 hours for this test. You may eat and drink, but please avoid caffeinated beverages.

Evoked Potential (EP) tests

Three types of EP testing may be performed:

  1. Visual Evoked Potentials (VEP)
    The patient sits before a screen on which an alternating checkerboard pattern is displayed. If you wear glasses, bring them to this procedure. Allow 30 minutes for the test.

  2. Brainstem Auditory Evoked Potentials (BAEP)
    The patient hears a series of clicks in each ear. Allow 30 minutes for the test.

  3. Sensory Evoked Potentials (SEP)
    Short electrical impulses are administered to the arms or legs. Please wear comfortable clothing and pants that roll up above the knee. Allow one to 1.5 hours for the test.

What you should do to prepare

  • Continue taking all medications prescribed by your doctor, unless instructed otherwise.
  • Please bring a list of current medications.
  • Wear comfortable clothing. You may be sitting and or lying on a bed during the test.
  • Shampoo your hair the day before your test. DO NOT use any hair gels, hairsprays, conditioners or lotions.
  • Hair extensions, hairpieces or wigs must be removed.

EEG and EP testing is harmless, generally painless, and is a very sensitive technique for detecting neurological abnormalities.

Location and Contact

Electroencephalogram and Evoked Potentials

Sunnybrook Health Sciences Centre
2075 Bayview Avenue
M-wing, first floor
Room M1 600
Toronto, ON M4N 3M5

Phone: 416-480-4475
Fax: 416-480-4674


Monday - Friday
7:30 a.m. - 5:00 p.m.


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