What is the purpose of an ambulatory EEG?
A routine EEG provides a 20 to 40 minute sample of brain electrical activity, which is often sufficient. An ambulatory EEG, on the other hand, can record up to 72 hours of EEG activity with a special recorder that is slightly larger than a portable cassette player. This recorder allows you to go about your normal routine while the EEG is being recorded.
Why do I need the test?
Your doctor may order an ambulatory EEG for you for a number of reasons: To diagnose epilepsy and determine what type of seizures are occurring. EEG is the most useful and important test in confirming a diagnosis of epilepsy.
- Distinguish fainting spells from seizures.
- To quantify the number of abnormal discharges or seizures in patients with epilepsy.
- Evaluate periods of unconsciousness or memory loss.
- Monitor how effective medications are.
- Study events that occur sporadically.
How is the test done?
The first day of your Ambulatory appointment is the EEG set-up procedure which lasts two hours. The EEG technologist will attach 16 to 26 flat metal discs called electrodes to different places on your head, using special glue called collodion to keep them in place. The electrodes are connected by wires to a small recorder that amplifies and records the electrical activity inside the brain. You can wear the recorder on your waist, with the wire running either under or outside of their shirt.
You will be asked to keep a diary of activities during the day. Most recorders have an “event” button for patients to press if they experience any of the symptoms for which they are being tested, such as episodes of feeling “spacey” or confused. A family member should press the button if the patient is unable to do it.
An ambulatory EEG test may last anywhere from 24 to 72 hours. Please do not take a shower during this time as water will damage the machine.
An appointment will be made for the technologist to remove the electrodes from your scalp with acetone or similar solutions at the end of the test. You still may wish to wash your hair when returning home to remove any remaining paste.