Electroencephalogram (EEG)

What is an Electroencephalogram (EEG)?

An EEG is a recording of the electrical activity of the brain. Fluctuating electrical impulses produced by the brain are recorded as wavy lines of various frequencies on either digital CD, or continuous graph paper. The tracings are reviewed by our neurologists, who are specially trained to read and interpret EEGs.

An EEG is an important test in the evaluation of seizure disorders, metabolic disorders (liver or kidney dysfunction), nervous system disorders (encephalitis or abscess), degenerative disorders (Alzheimer's or Parkinson's Disease), head injuries, headaches, brain tumors, brain death, cerebral palsy, strokes and many others.

What happens during an EEG test?

Small metal discs called electrodes are attached to 22 predetermined locations on your scalp with an adhesive. Other methods of electrode application include an electrocap, special conductive paste used with small disc electrodes, or, very rarely, needle electrodes which are placed under the skin. These electrodes "pick up" the electrical activity of your brain. This electrical activity is transmitted through wires to the electroencephalograph machine, where the signals are amplified and recorded as wavy lines on CDs or graph paper.

The test usually takes about 1 to 1 1/2 hours. You may be asked to hyperventilate (breathe through your mouth deeper and faster than normal) during the test. A strobe light, flashing at different speeds, may be shown to you for a brief time.

Your cooperation is essential for accurate test results. Please follow instructions during all phases of the EEG to help ensure an accurate test. Try to relax, breathe normally and hold as still as possible.

If a standard EEG does not verify seizure activity, an ambulatory or extended EEG may be ordered. During an ambulatory EEG, electrodes are applied to your scalp with glue and are connected to a unit worn on a belt while you go about your usual activity. The unit records brain activity for an extended period of time to more thoroughly assess the seizure diagnosis. You will be required to maintain a diary of activities for the duration of the test.

A video EEG is a more involved, comprehensive test in that you are videotaped during an EEG test. The neurologist is then able to correlate your EEG tracing with your activity and behaviors observed on the tape to diagnose your epilepsy and affected brain location. A video EEG test can take anywhere from a few to eight hours and is only performed in the clinic.

Will the EEG test hurt?

Most people find that the EEG test is a painless procedure.

How should I prepare for an EEG?

Instructions will be given to you prior to the test. Be sure to wash and dry your hair and scalp before the test so that they are clean and oil-free. Do not use conditioner or hair spray. Eat a regular meal or snack two hours before your EEG to help stabilize blood sugar, unless you've been instructed not to eat by your physician. If you take any medications, please ask your physician if you should take them as usual. If your physician has ordered a sleep test, you may need to adjust your sleeping schedule.

If you will be having a video EEG test, you will need to bring someone that can stay with you for the duration of the test. You may wish to bring video tapes, books or other items to pass your time, as well as a bag lunch/beverage.

How will I feel after the test?

Our technician will remove the electrodes and cleanse your scalp of the adhesive. You may want to wash your hair again when you get home. Your diet and activities should not be affected. Please feel free to ask our staff at any time, should you have any questions concerning your EEG test, or other aspects of your care.

How will I get the results of my test?

The results will be interpreted by our neurologists and given to your doctor or explained to you at your next appointment.

Which of your locations offer EEG testing?

EEG tests are conducted at our Golden Valley, Edina, Burnsville and Coon Rapids locations.

Ambulatory EEG tests are conducted at our Golden Valley and Coon Rapids locations. Video EEG tests are performed only at our Golden Valley clinic.

Here is an example of what your EEG tracing may look like: