EVENT-RELATED AUDITORY-EVOKED POTENTIALS AND MULTIPLE-SCLEROSIS

Long latency event-related auditory evoked potentials, particularly th e P300 wave, constitute an objective electrophysiological index of cog nitive function. For this reason, these potentials have been studied i n a series of 101 patients with multiple sclerosis (MS), classified ac cording to McAlpine's criteria into definite, probable and possible ca ses. The patients were also classified as depressed or non-depressed a ccording to the DSM-III and Research Diagnostic Criteria. They were al so subjected to a battery of psychometric tests. In the patient popula tion the N200 and P300 latencies were increased, as were the P200 late ncies, when compared with a control population. This electrophysiologi cal pattern had previously been observed in other conditions character ised by subcortical lesions. Partial correlations (at constant disease duration) between the disability score and the cognitive deficit were found to be significant. Patients with an increased P300 latency had a greater disability and the P300 latency was significantly correlated with the duration of the illness. The N200 and P300 latencies were in creased in depressed MS subjects, but this increase did not reach the level of significance. Depression was more frequent in the more severe ly handicapped patients. This suggests that the origin of the depressi on seen in multiple sclerosis is only partly organic, and that it is o ne of the factors contributing to the subcortical cognitive deficit in multiple sclerosis. Progressive forms of the disease exhibited the mo st profound cognitive deficit, and the most marked increase in P300 la tency.