The EEG helps your physician diagnose your condition. It can also help in planning your treatment. An EEG is a test that records brain activity. Brain activity may change with certain conditions or after an injury. The EEG can also show where in the brain these changes occur. This test is safe and painless. A routine EEG typically lasts 60 to 90 minutes; an ambulatory EEG can last up to four days depending on how much information your physician needs.
During a routine EEG, you can lie down on a comfortable bed. The technologist will ask about your medical history, measure your head and clean your scalp. Small metal disks (electrodes) will be placed on your head using a creamy paste to keep them in place. These are connected to the EEG machine.
When the test starts, you will need to keep very still and keep your eyes closed. This makes sure that the machine only picks up brain waves and not other movement. The technologist may ask you to take deep breaths and show you flashing lights. At the end of the test, the electrodes will be removed and the paste wiped off.
A routine EEG lasts about 60 to 90 minutes.
An ambulatory EEG may take one to four days, depending on how much information your physician needs. During an ambulatory EEG, the technologist will put small metal disks on your scalp, held in place by adhesive. Wires connect the disks with a small computer that you will take home. This weighs about three pounds and is carried in a pack. Wear the pack around your waist or over your shoulder.
The technologist will wrap gauze around your head to cover the wires and disks. You may wear a cap or a scarf over this to cover it up. You will receive instructions about what you should and should not do during the test.
The test begins as soon as you leave and lasts until the disks are removed. You will receive a log to write down anything unusual that occurs during the test. It is very important to write the date, time and a brief description of unusual events or symptoms. At the end of the test, electrodes will be removed and the paste wiped off.
How to prepare for an EEG
- Plan to be in the office for up to two hours.
- Remove hairpieces or unbraid hair before the test.
- Bring a cap or scarf to cover your head when you leave (if you wish).
- Wear a shirt that zips or buttons in front. This will make it easier to change clothes when you get home.
- Arrange to come in each day during testing (if your test lasts for more than one day).
Northwestern Memorial Hospital Comprehensive Epilepsy Center259 E. Erie St.Nineteenth FloorChicago, IL 60611