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About Your EEG:

An EEG or electroencephalogram is a completely safe and painless procedure for recording the electrical activity produced by the brain. Patterns of the brain's electrical activity provide information about specific brain functions. This information is used to help identify a wide variety of neurological problems. The test usually takes 1 to 1½ hours to perform. Part of this time is spent in applying the electrodes. The actual recording time varies but usually lasts about 30 minutes.

Prior to the Test:

1. To make application of the electrodes to your scalp easier, please shampoo your hair the night before the test and do not use hair treatment products, such as hair spray, or fix you hair in tight braids or other styles which may interfere with the test.

2. Continue to take your prescription medicine unless specifically instructed by your physician to discontinue use. The technician needs to know what medicines you are taking, so if you take several medications you may want to bring a list of them to the test.

3. Unless you are instructed otherwise, you should eat normally. However, avoid coffee, tea, coca-cola, and other drinks and food that contain caffeine.

4. If possible, please arrive a few minutes early for your test. The quality of the test will improve if you have a chance to relax for a few minutes beforehand.

5. A special cream is used to attach the electrodes to your scalp during this test. While the technician will clean most of this paste from your hair following the test, you may want to bring a scarf or hat with you as well.

During the Test:

The most important things to do during the test are to relax and follow the technician's instructions. Please feel free to ask the technician questions at any time during the test.

1. We ask that all family and friends, except those who need to translate for the patient, wait in the reception area during the test.

2. While your doctor has provided information concerning your specific problem, the technician will also ask you for certain information that will be helpful to the physician who will interpret your test results.

3. The technician will then measure and mark the places on your scalp where the electrodes are to be applied. This is done with a special washable crayon.

4. Next, the technician will scrub each spot with a cleansing solution to ensure proper contact for the electrode. The electrodes will then be attached with a water soluble paste.

5. During the recording, you will be asked to lie down on an examination table. We will try to make you as comfortable as possible in order to help you relax.

6. The technician will ask you to open and close your eyes several times during the recording. You might also be asked to perform some special breathing and visual exercises that provide additional information.

After the Test:

1. When the recording is complete, the technician will remove the electrodes and clean the paste from your scalp. A little residue might remain, although the technician will try to remove as much of the paste as possible. The residue will not harm your scalp and will wash away with shampoo.

2. Your physician will tell you how to obtain your test results. You may resume normal activities immediately.

The ambulatory EEG

If someone will actually have a seizure during the EEG recording this can confirm the diagnosis of epilepsy and the type of seizure which has occurred. However, during most routine EEGs people frequently do not have seizures. This is referred to as an ‘inter-ictal EEG’ - that is, an EEG between (inter) attacks (ictal).  

An inter-ictal EEG will often be normal, even in someone who definitely has epilepsy. This is because the electrical disturbance in the brain which occurs in epilepsy comes and goes, and since a routine EEG only gives quite a short sample of what is happening in the brain over 30 minutes or so, any abnormalities could very well fail to show up in the recording. 

If a routine EEG has been normal or has shown features which are suspicious but not definite enough to support a diagnosis of epilepsy, your doctor may ask for an ambulatory EEG. 

What is an ambulatory EEG?

The limitations of routine EEG recordings in detecting the often intermittent abnormalities seen in epilepsy have already been explained. One way to improve the information gained is to perform what is known as an ambulatory (‘walking’) EEG recording. This involves recording the brainwaves of someone who is walking around, freely mobile and not confined to the testing room in an EEG department.

Standard EEG electrodes are placed on the scalp, but a smaller number than with a routine recording. The wires from these electrodes are plugged into a small portable relay box and the EEG signals are recorded on a standard cassette tape or disc in a battery-operated recorder worn around the chest or waist.

Once the ambulatory EEG recorder has been fitted and tested, the person goes home and carries on with normal daily activities, returning about 24 hours later to have the device removed. If a longer recording is needed, the tape or disc can be changed and the batteries and scalp electrodes checked before the person returns home for a further period of recording. It may seem a little odd to be walking around with EEG electrodes on the head, but most people quickly adapt to this and are able to carry on with their normal daily lives. This technique is used with both adults and children.

There are two advantages to ambulatory EEG recording. First of all, it allows the EEG to be recorded over a much longer period than a routine EEG - for several days if need be. This greatly increases the chances of detecting abnormalities.

The second advantage is that it may be possible to actually record the EEG during an attack, particularly if these are occurring quite often. This may allow doctors to distinguish whether the attacks are epileptic or not. The recording may also give a very clear picture of how often attacks are occurring in someone who is known to have epilepsy.

People having this type of EEG will be asked to keep a record of any attacks that occur during the recording, noting the time and a short description of what occurred.

You may review or print out the Patient’s Guide to Ambulatory EEG, explaining the test procedure in details and specifying all the DO’s and DONT’s.

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    Mission Viejo, CA 92691
    Tel: (949) 586-5500