Cognitive dysfunction in multiple sclerosis patients: electrophysiological and psychometrical assessment in 46 patients

Jung, J.1, Morlet, D.1, Confavreux, C.2, and Fischer, C.2
1Inserm U280, Processus mentaux et activation cérébrale, Lyon, France; 2Hopital Neurologique P. Wertheimer, Lyon, France

Background: Multiple sclerosis (MS) is a major cause of physical disability in young adults. Moreover neuropsychological deficits are frequent in MS. Several studies have shown attentional deficits, particularly involving controlled information processing. Little is known about automatic information processing. Mismatch Negativity (MMN) is classically assumed to be a neurophysiological index of automatic information detection.

Goal of the study: The aim of our study was to assess automatic information processing in MS using ERPs and to evaluate MMN as a putative index of global cognitive dysfunction.

Subjects and methods: Our study included 46 MS patients assessed with a passive oddball paradigm using duration deviants, compared to a group of 46 healthy subjects. Measurements included latencies and amplitudes of the N1P2 complex, MMN wave and P3 wave. 18 of the 46 patients underwent psychometrical evaluation including global intellectual functioning test (Mattis), attentional skills test (TEA), verbal memory test and information processing speed test (PASAT).

Results: N1P2 complex amplitude, MMN and P3 areas were reduced in MS patients. MMN and P3 latencies were shortened in our patients. Neuropsychological testing showed attentional deficits and global intellectual deficits at a group level. MMN area and N1P2 complex amplitude reduction was more pronounced in cognitively impaired patients.

Conclusion: Automatic information processing as indexed by MMN is altered in MS patients, and MMN area may be even more critically reduced in cognitively impaired patients. We speculate that MMN could represent an objective index of cognitive dysfunction in MS.