Ambulatory Electroencephalogram (EEG)

Explanation of the test

This test measures the electrical activity of the brain over a 24- hour period. The test shows areas of the brain that are not functioning correctly either because of too little or too much electrical activity and can identify mild brain seizures.

The EEG is recorded on a small computer disk inserted into a case and worn by the patient around the waist. EEG signals are transmitted to the disk by means of small electrodes attached to the scalp with special fast drying glue. The patient is given a dairy to enter symptoms, the times of meals and the time he goes to sleep. When symptoms occur, the patient is to push a button on the recorder, which notates the time of the event. He may perform his usually daily activities.

The patient returns to the department the following day to have the electrodes removed. A solvent, similar to nail polish remover is used. Neither the glue used to apply the electrodes nor the solvent are damaging to the hair or scalp.

The small computer disk containing the information is removed from the case at the conclusion of the testing period. The information it contains is transferred to a large computer where it can be read and interpreted by a neurologist.


  • Hair washed with shampoo (no conditioners may be applied) night before or day of test.
  • Hair must be dry.
  • Must wear a garment that buttons down the front: either a blouse, shirt or dress.

General information

  • Total time to apply the equipment is 90 - 120 minutes.
  • Total time to remove the equipment is 20 - 30 minutes.
  • A button-down-the-front garment must be worn so that it can be removed at bedtime.
  • The patient may not shower or bathe while wearing this equipment.
  • There is no radiation (x-ray) involved with this test.
  • Any further questions about how the test is performed should be asked of the technologist when you arrive for the test or you can call the Neurodiagnostics Department at 773-665-3195.
  • Your doctor will receive the final results after a neurologist interprets the test, usually within 3 business days.
  • If you are unable to keep your appointment please call Central Scheduling at 773-665-3060. If you will be late, call Neurodiagnostics at 773-665-3195.
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