The electroencephalogram (EEG) is a noninvasive test that records the brain’s natural electrical activity. It is used to evaluate brain function or disorders.
How to get ready for an EEG
Your hair must be free from gels, mousse or hair spray. Little or no makeup should be used. Eat a normal meal within 2 hours of thee test, since low blood sugar may influence the results. You should continue to take your medications, unless told to do otherwise by your physician. Bring a list of your medications to the lab.
What happens when you come to the laboratory?
A specially trained technician will be with you throughout the test and give you instructions as needed. The following activities will occur during your visit to the laboratory.
The technician will measure your head and put red marks on your scalp with a soft pencil where the electrodes will go. Each spot will be rubbed with a gritty solution and a cotton tipped applicator. The technician will apply 25 metal discs (electrodes) to the cleaned spots on your scalp. The discs are held in place with a sticky cream and covered with a small piece of gauze. You will be asked to lie down.
During the test
During the 20 minute session you must lay still. You will be asked to open and close your eyes. You may be asked to do 3 minutes of deep breathing. There will also be a strobe light that flashes.
After the test
After the test, the electrodes are removed and a wet wash cloth is used to clean the hair and scalp. There will be some cream that will need to be washed out at home.
A neurologist, a doctor who specializes in the nervous system, will read the tracing. A report will be sent to the requesting doctor.
Evoked Potential Testing
An evoked potential test measures the time it takes for nerves to respond to stimulation. The size of the response is also measured. Nerves from different areas of the body may be tested.
Visual Evoked Potential—(VEP)
For this test the patient focuses on a TV screen, which displays a checkerboard patter. The eye not being tested is covered with a patch. Each eye is usually tested two or more times, and the entire procedure takes approximately 30-45 minutes.
Brainstem Auditory Evoked Potential (BAEP)
Small foam amplifiers are placed in the ears to deliver a series of clicks to one ear at a time. A masking or static sound is played into the other ear. Each ear is tested two or more times, and the procedure takes approximately 30-45 minutes.
Somatosensory Evoked Potential SSEP
Mild Electrical shocks are delivered to the arm or leg, This may cause twitching or tingling. The stimulus lasts for about two minutes at a time, and the entire procedure lasts approximately 45-60 minutes.
A neurologist will read the visual and somatosensory tracings. The brainstem auditory tracing is read by an ear, nose and throat specialist. Results from the test can take up to 5-7 business days.
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