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Home >> Mercy Neurological Institute >> Epilepsy >> Ambulatory EEG

Ambulatory EEG
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A routine EEG, typically done in an EEG Lab, records the brain's electrical activity as it fluctuates from second to second. But routine EEGs provide only a 20- to 40-minute sample of this activity. If abnormal activity occurs in the brain only once every three or four hours, or only after an hour of sleep, a routine EEG may not show it. Doctors may need a longer recording that includes prolonged periods when patients are both awake and asleep. This test, called an Ambulatory EEG, lets patients walk around and carry on normally while recording data. It is both harmless and painless.

Before the test

  • If unable to keep your scheduled appointment, please provide as much notice as possible. For questions or to change an appointment, please call the Neurodiagnostics Office at 916.453.4471 between 8 a.m. and 4 p.m., Monday - Friday.
  • Wash hair the night before using only shampoo and water. Do not use styling aids such as hair gels, mousse, hairspray or oils of any kind. These products can interfere with the electrodes and the test. For long hair, put it into two braids.
  • Go to bed at midnight and wake up at 6 a.m. We want you to be sleep-deprived for the test.
  • Wear shirts that button or zipper so they can be removed without passing over the head. Once the electrodes are in place it will be difficult to remove clothing over your head.
  • Eat normal meals. Have a good breakfast the day of the test.
  • Take regularly scheduled medications as prescribed by your doctor.
  • If desired, bring a hat (without any metal) or scarf to wear once the electrode application has been completed.

Day of the test

  • Please arrive at Mercy General Hospital's Outpatient Registration Department 30 minutes prior to your appointment. Park in the structure next to the hospital. Please bring all insurance information and a complete list of medications and dosages.
  • The electrodes used in this test are small metal disks applied to the skin just like a regular EEG. Because the electrodes must stay on the head longer than for a regular EEG, a special glue called "collodion" is used to keep them in place. A gauze wrap is then used to keep the electrodes and wires together and out of your way. This is a simple and painless procedure, which should take less than an hour.
  • Children should have a parent or guardian with them throughout the entire electrode application procedure.

During the test

The computer - Once the electrodes have been applied to the scalp they will be connected to a small computer that you will take home. The computer, s small enough to be easily carried, is placed in a pack that can be slung over the shoulder. Patients go about their normal 24-hour routine, taking care to note:

  • Do not, under any circumstances, take a shower while the test is in progress. Wash from the neck down with a washcloth, being careful not to get water into the computer.
  • Do not chew gum during the test.
  • Do not tamper in any way with the computer or electrodes.
  • Do not drop the computer.
  • Pay attention to the battery level and text on the screen (the EEG Tech will explain this) and call the technologist if needed.

The patient diary - Patients will be given a diary to track activities or episodes. Recording the date and time of these activities and events, along with a brief description of what occurred, is extremely important. Patients will be asked to write down such things as:

  • Mealtimes and/or snacktime
  • Restroom usage
  • When you go to sleep
  • Time upon waking from sleep
  • When you take any medication
  • Any health symptoms
  • Any events (seizures, heart palpitations or symptoms for which you are being tested)

The event button - A small button on the side of the computer that should be pressed when experiencing any symptoms being tested, such as feeling "spacey" or confused. If unable to press the button during a seizure, someone can do it for you.

When the button is pressed it makes a mark on the recording. The physician reviewing the study will be able to see what changes occurred on the EEG and use them, along with your diary entries, to evaluate your brain activity at this time.

After the test

Return the next day to have your electrodes removed and data downloaded. This takes less than 30 minutes. The patient diary should also be returned at this time. There is no need to check in at patient registration. Come directly to the EEG Department on the second floor at the time assigned by the technologist.
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