Long-latency cerebral event-related potentials in multiple sclerosis

The objective of this study was to characterize electrophysiologic ally the basis of the cognitive dysfunction in multiple sclerosis. The cognitive dy sfunction experienced by patients with multiple sclerosis has recently beco me more widely appreciated, but the best means of monitoring such function is unknown. Long-latency cerebral event-related potentials were recorded in a group of patients with relapsing/remitting or secondarily progressive mu ltiple sclerosis and in a group of age-matched normal control subjects. Sub jects were presented a series of auditory tones, with one (1,000 Hz) occurr ing during 86% of the trials (frequent tone) and the other (2,000 Hz) occur ring during 14% of the trials (rare tone). Subjects were required to listen to the stimuli and count the occurrence of the rare tones. Cerebral respon ses recorded from the scalp were averaged separately for the rare and frequ ent tones. The NI, P2, N2, and P3 components of the long-latency response w ere all prolonged in latency in patients with MS, as were the N1-N2 and N1- P3 interpeak latencies. In addition, the amplitude of the P2 and P3 peaks w as diminished in patients compared with control subjects. Significant corre lations were found between the changes in both interpeak latency peak ampli tude and the scores on the Mini-Mental State Examination. Electrophysiologi c changes occur in MS that are the result of central disease (as opposed to involvement of primary afferent pathways) and correlate with cognitive sta tus. The recording of event-related potentials may thus provide a useful to ol, not only as an objective measure of cognitive function in patients with MS, but also as an aid in the evaluation of response to treatment.