Visual evoked potentials - current concepts and future perspectives

Sensory evoked potentials (EPs) represent changes in electrical activity of the nervous system, triggered by stimulating sensory receptors or peripheral nerves or either an external or internal impulse. Although every sensory modality can be investigated, sensory EPs mostly used in clinical practice are the following three types: visual evoked potentials (VEP), short latency brainstem auditory evoked potentials (BAEP) and somatosensory evoked potentials (SSEP) . The above EPs modalities are commonly used in combination, as complementary methods in clinical neurophysiology, so they are called multimodal EPs . EPs can also represent brain response as a result of cognitive activity (event related response – ERP) . EPs are recorded in different clinical contexts. They may be used to assess peripheral sensory function, to evaluate the functional integrity of sensory projection pathways in the central nervous system (CNS), and cerebral cortical sensory areas . EPs are recorded by using scalp electrodes for standard electroencephalography (EEG) . Due to low amplitudes of EPs, computer summation or averaging is necessary to isolate them from the background “noise” consisting of spontaneous electrical brain activity on which EPs are superimposed 1, 3, . EPs were introduced in the early years of clinical EEG within 1930s. The first device for signal processing in the field of EPs using signal averaging method was introduced by Dawson in 1951, while widespread use was enabled in 1970s . Non-invasiveness and harmlessness both represent the clear advantages of EPs, as well as their repeatability, objectivity and resistance to drugs and anaesthetics. On the other hand, the disadvantage of EPs is their low disease specificity 2, .