Evoked potentials (EPs) are a technique designed to pick up the brain’s responses to peripheral stimulation. For instance, visual stimulation with bright lights might be expected to activate the visual portions of the brain (visual cortex), yielding a recordable signal that is informative about the integrity of the visual pathways. Similarly for the somatosensory cortex and peripheral sensory stimulation, or the auditory cortex response to sound.
Our EP service is integrated into outpatient neurodiagnostics, though inpatient studied are also occasionally performed. We carry out visual evoked potentials (VEPs), somatosensory evoked potentials (SSEPs) and brainstem auditory evoked potentials (BAERs). The studies are performed by the more experienced of our EEG technologists, due to the various technicalities and nuances associated with obtain a reliable and diagnostically useful signal.
Information for Patients
We usually recommending avoiding caffeine on the day of the test because it can affect the test results. Routine medications should be taken as usual. We recommend washing hair the night before or the day of the test, but avoiding conditioners, hair creams, sprays or styling gels. Hair products can make it harder for the sticky patches that hold the electrodes to adhere to the scalp. Prior to the stimulation, flat metal discs (electrodes) are attached to the scalp, much like for EEG. The electrodes are connected to the EP machine with wires. The technologist will then perform some type of stimulation. This may be instructions to view a computer screen with a flashing checkerboard pattern for VEPs, or stimulation of the hand or leg nerve for SSEPs, and asking you to listen to clicking sounds through headphones for BAERs. A the end of the test, the physician on service will analyze the recordings and send a report back to your clinic doctor. Your doctor will normally discuss the results of your test at your next scheduled office appointment.