Electroencephalogram (EEG)

Electro refers to electricity; encephalo refers to the brain; gram refers to record.

A doctor may administer an EEG test to determine whether your child has epilepsy and in what form. The EEG allows the doctor see if there are any irregularities electrical activities occurring in the brain that may produce seizures.

An electroencephalogram is a non-invasive diagnostic test. It records electrical activity on the surface of the brain to identify the location of the abnormally firing neurons that cause seizures. An electroencephalograph is the instrument used to register this activity and record it on graph paper. A neurologist uses these recordings to help identify the location, severity and type of seizure disorder. This safe and painless procedure will not affect your child in any way.

It is important to remember that an abnormal EEG does not diagnose epilepsy nor does a normal EEG reading exclude epilepsy. An EEG can only measure abnormal electrical activity that occurs during the test period. Sometimes, the brain of the person with epilepsy functions perfectly normal during the test.

Tests that have been done on people with epilepsy commonly show uneven activity or large changes in the voltage of brain waves (spikes). Different patterns of activity from different spots on the scalp point to different kinds of epilepsy.

Before an EEGExpand Before an EEG Section

  • If the doctor has ordered a sleep test, adjust your child’s sleeping schedule (reduce sleep) according to the doctor’s instructions and avoid caffeine drinks.
  • Wash his/her hair thoroughly. The scalp should be clean and oil-free for the test so that electrodes can stay on your child’s head and work effectively. Do not use any conditioners or hair products.
    • Remove any hair accessories before going to the test centre.
  • Your child should eat before being tested. This will help to stabilize his/her blood sugar level.
  • Your child should take all prescribed medication(s) unless instructed otherwise by your doctor. Be sure the doctor is informed of all medications being taken.
  • Before the test, you may be asked to provide information about your child’s medical history and any medications being taken.
  • Prior to the test, you may want to play games with your child to achieve a degree of relaxation.

During an EEGExpand During an EEG Section

  • The test may be given in a small room separated from the EEG machine and the technologist. This allows your child to take the test in a quiet, relaxing environment.
  • Some clinics may have small TV cameras set up in the test area to videotape your child’s movements during the test. Analyzing this recorded movement along with the EEG recording may help the doctor identify your type of seizure.
  • The technician will assist your child onto a stretcher.
  • The technician will measure your child’s head and mark where the metal discs will be placed. These small metal discs, called electrodes, will be applied to various places on the scalp with a special cream. This process takes 15-20 minutes. It is painless.
  • Your child will be instructed to keep his/her eyes closed and to remain still and relaxed throughout the examination.
    • Inaccurate results can be caused by an irregular heartbeat, sweating, eye movement, eye blinking, muscle tension, sucking movements, chewing or any movement. Therefore, to help ensure accurate results, let your child know that s/he must relax and breath normally, stay quiet and still, and carefully follow the technician’s instructions.
  • Inform your child that s/he may hear slight noises during the test. This is normal.
  • Ensure your child is aware of the various procedures that may be used during the test to stimulate the brain or to trigger certain brain waves and produce clearer wave patterns.
    • Your child may be asked to open and close your eyes several times.
    • Your child may be instructed to breathe deeply through your mouth for short time. This may cause a slight dizzy feeling or numbness in the hands or feet. These are natural reactions and will subside once the deep breathing is over.
    • A bright, flashing light may be placed in front of your child’s eyes which may cause him/her to see different geometric designs and patterns of light.
    • If your doctor ordered a sleep test, your child will be given a mild sedative to help him/her fall asleep during the examination.
    • These different procedures are done in order to compare brain activity under a wide variety of conditions.
  • The entire EEG test takes 60 to 90 minutes.

After an EEGExpand After an EEG Section

  • The electrodes will be removed from your child’s head. There may be some stickiness from the cream used to place the electrodes. Wash your child’s hair when you get home.
  • Your child should be able to resume normal activities, unless told otherwise by the doctor or technician.

PersonnelExpand Personnel Section

EEG Technologists and Technicians
  • help physicians diagnose epilepsy
  • take your medical history
  • prepare the EEG test
  • operate the EEG machine to record electrical impulses transmitted by the brain and nervous system
  • apply electrodes to designated spots on your child’s head
  • prepare data for doctors to interpret
Physicians who specialize in EEGs
  • read and interpret the results of the EEGs
  • supervise the EEG technicians


An EEG test is fully covered by the Ontario Health Insurance Plan (OHIP).

Click here to learn about other types of diagnostic tests.