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Evoked Potential Testing
What are Evoked Potential (EP) studies?
This is a test that measures the brain's electrical response to the signals sent by the nerves. The nervous system uses electrical energy to carry messages smoothly along nerve cells to the brain, allowing us to see, hear, feel, smell, taste and move. Damages to the nervous system caused by disease or trauma can affect how well nerves send messages to the brain. Muscle weakness, pain or numbness, vision or hearing problems may arise if nerves are damaged.
There are three major testing locations:
- Brainstem Auditory Evoked Potential (BAEP)
This looks at the pathway from the ear to the brain.
- Visual Evoked Potential (VEP)
This looks at the pathway from the eyes to the brain.
- Somatosensory Evoked Potential (SEP)
This looks at the pathway from the nerves in the limbs to the brain.
This can be an upper or lower extremity exam or the doctor may want both upper and lower exams done at the same time.
What can I expect before the test?
Wash your hair and skin on the day of your test. DO NOT use any oils or lotions.
Eat a normal meal at your usual mealtime before the test. Avoid caffeine.
Take any medications as you usually would.
Bring a list of your medications with you for your test.
Bring your glasses or contact lenses if you are having a Visual EP.
Come to the Heart and Lung Center at Portsmouth Regional Hospital.
Arrive 15 minutes prior to your appointment time for registration.
Try to relax.
What can I expect during the test?
A qualified technologist will perform the test.
Your skin will be prepped with a special cleanser that contains some grit.
You will lie down on a bed or sit in a chair.
Surface electrodes will be attached to the skin in special locations depending on the EP study being performed.
Electrodes will be placed at several locations on your scalp and earlobe.
If you are having a BAEP, earphones will be placed on you and a stimulus will be given, usually into one ear at a time. The computer will record the results of your brain activity responding to the stimulus.
If you are having a VEP, you will be seated in front of a screen and asked to stare at the center. One eye will be covered while the other eye is being tested. The stimulus will be given. This is a flashing checkerboard screen. The computer will record your brain activity responding to the stimulus.
If you are having a SEP, you will lie down. Electrodes will be placed on your neck, shoulder, and wrist for an upper SEP; or the lower back, neck, knee and ankle for a lower SEP. The stimulus will be a painless electrical pulse given to the wrist, knee, or ankle. The computer will record your brain activity responding to the stimulus.
How long will the test take?
A BAEP will take approximately one hour.
A VEP will take approximately one hour.
An SEP will take approximately one hour for an upper or lower test (2 hours for both).
What can I expect after the test?
The electrodes will be removed, and the adhesive paste will be washed off.
You may return home.
You may resume normal activities.
Your test results will be forwarded to your physician, who will discuss them with you at a later date.