Contrast Evoked Potentials and Psychophysics in Multiple Sclerosis Patients

Abstract

Visual evoked potentials (VEPs) have become widely accepted in recent years in diagnostic schemes for the assessment of multiple sclerosis (MS). It has been shown that for this purpose a deviation in latency is a better criterion than a deviation in amplitude, since amplitude varies widely among subjects, whereas EP latency, especially with contrast stimulation, remains restricted to a rather narrow range. The latency of the EP to stimulation with a reversing checkerboard pattern appears to be increased in 268 out of 393 (= 68%) MS patients (Halliday et al., 1973: 49/51 = 96%; Asselman et al., 1975: 34/51 = 61%; Mastaglia et al., 1976: 34/68 = 50%; Regan et al., 1976: 6/13 = 46%; Lowitsch et al., 1976: 98/135 = 73%; Hennerici et al., 1977: 35/57 = 61%; Duwaer and Spekreijse, 1978: 12/18 = 67%). However, latency increases are not specific for multiple sclerosis since they have also been observed in patients with a variety of other pathologies (Assesman et al., 1975; Halliday et al., 1976). Furthermore, an increased EP latency cannot always be ascribed to an increased conductance time due to demyelination of the optic nerve fibers since a variety of modifications in the stimulus situation — modifications which might also be induced by the presence of pathologies in the subject — may result in an increased EP latency (Duwaer and Spekreijse, 1978).Some examples are given in Fig. 1.