Electroencephalogram (EEG)

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An Electroencephalogram or EEG records electrical impulses from the brain. The EEG is performed to determine if there is any change in the brain cell function. The results often depend on brain function at the time of the recording. Therefore, epileptic patients who are not having seizures during the recording may have a normal record.

EEG, or electroencephalogram, is a tool we use to image the brain while it is performing a cognitive task. This allows us to detect the location and magnitude of brain activity involved in the various types of cognitive functions we study. EEG allows us to view and record the changes in your brain activity during the time you are performing the task. Images are acquired by using electrodes to monitor the amount of electrical activity at different points on your scalp.

All of our EEG Technical Staff are certified by the Canadian Board of Registration of Electroencephalograph Technologists.





How do I prepare for my appointment?

Your hair must be clean and dry when the EEG recording is being done. You must wash your hair either the night before or the morning of your test and your hair must be completely dry before the EEG is started. After your hair has been washed and dried, do not use hair spray, mousse, cream, etc. on your hair. These cause disturbance in the recording.

Sometimes, your physician will order a sleep-activated (also called sleep-deprived) EEG. This is to try and get you to sleep during the test. It is our policy that you sleep naturally rather than with the aid of a hypnotic (sleeping pill). Therefore, if your test is in the morning, you should go to bed no earlier than 10 pm and awake at 2 a.m. You should remain awake until the test that morning. If your test is scheduled for the afternoon, you should go to bed no earlier than midnight and awake at 4 a.m., and stay awake until the test. You may have your meals as usual but do not have caffeine (tea, coffee, pop, etc.)

Hyperventilation and strobe lights (photic stimulation) are commonly used activation methods during an EEG. Sometimes, these procedures can induce seizures, which the technologist can manage.

How long will the test take?

  • A regular EEG test will take 1-1½ hours.
  • A sleep-deprived EEG test will take 1-2 hours.

What should I expect during the test?

A specially trained registered technologist performs the test in the E EG laboratory. Designated areas of the head are wiped with a skin cleanser and button-like electrodes are applied, using a paste and secured lightly with paper tape. The electrodes are connected to the EEG machine through many small wires. The preparation takes approximately 20 minutes. You will be lying down, relaxing, while the recording is being done. There is absolutely no pain or other sensation involved. You will not feel any electrical currents. Recording time is a minimum of 20 minutes and often as long as 1 hour.

Once the test begins, the electrodes send electrical impulse data from your brain to the recording machine. This machine converts electrical impulses into visual patterns that can be seen on a screen and are saved to a computer. On the screen, the electrical impulses look like wavy lines with peaks and valleys. You may be directed by the technologist to do certain things while the test is in progress, such as lie still, close your eyes, breathe deeply, or quickly, or look at stimuli like a flashing light or a picture.



Sarah George
Manager, Diagnostic Imaging
519-254-5577, ext. 52231

Colleen Nelson
Director, Diagnostic Imaging, Nuclear Medicine, Cardiopulmonary, EEG, and PFT
519-254-5577, ext. 52444