Evoked potential (EP) tests measure the speed of messages going through pathways of the nervous system. These tests may be performed to help determine if and where nerve messages are being blocked. These tests may be performed of the visual, sensory, or auditory systems. Electrodes are placed at various points on the head and, for the sensory testing, also over the spine and limbs.
How and where do I schedule EP Testing?
Call EEG at Presbyterian Hospital at (412) 647-5423. Register with admissions on the first floor. The test will take place on the 8th floor in room F-843 near the elevators.
How do I prepare for the EP testing?
To ensure good electrode recording from your scalp we ask that your hair be clean and dry. Wash your hair the night before the test. Do not use any hairspray, gels, or other hair products before the test. Do not wear braids, a hair weave, or a wig to the test. Take your normal medications on the day of the test. You do not need to be fasting and should eat normally on the day of the test.
What happens during the EP testing?
A technician will first measure your head and apply electrodes (small metal disks) to your scalp and body using an adhesive gel or paste. This preparation usually takes about 30 minutes. The type of EP testing determines where the electrodes will be placed.
Visual evoked potential (VEP) is a test in which each eye is stimulated by focusing on a target in the middle of a checkerboard pattern. The computer alternates the pattern background, and measurements are made of the speed at which this message reaches the back of the brain.
Sensory evoked potentials (SEP) test the speed at which messages reach the spinal cord and brain when nerves in the arms or legs are stimulated. The stimulation is given by repeated very small electrical shocks. Most patients find it mildly annoying; it is not usually painful.
Brainstem auditory evoked potentials (BAER) test the hearing pathways. The stimulation is given through some very fast clicking type noise through a headset the patient wears.
What happens after the testing?
After the recording is done, the technician will remove the electrodes and clean off the adhesive. Due to the scalp electrodes placement, your hair may be somewhat disheveled. After the testing is completed, you may go by your normal activity.
When and how are the EP test results interpreted?
A neurologist will look at and interpret the recording after you leave. The results of the test will be sent to your doctor later. Evoked potential abnormalities may arise for a variety of reasons. The results of these studies are considered along with other laboratory and clinical information by your neurologist.