[Contribution of cognitive evoked potentials for detecting early cognitive disorders in multiple sclerosis]

In Multiple Sclerosis (MS), one of the most frequent neurological diseases in young adults, cognitive dysfunctions have been under considered whereas their evolution may produce a fronto-sous-cortical deterioration and more than half of the MS patients present such dysfunctions. Nevertheless sensory evoked-potentials are classically used in this disease, event-related potentials (ERP) are not included in the clinical exploration of MS. Two studies are presented aimed at further tracking the usefulness of ERP for detecting early cognitive dysfunctions in MS. All of the patients presented a relapsing remitting MS for less than 5 years with a moderate physical handicap and complained from their memory. They performed a neuropsychological set and ERP were elicited using the oddball paradigm in both modalities, visual and auditory. In the first study, 10 patients without cognitive dysfunction at the neuropsychological evaluation and 10 patients with an attention deficit participated with 10 age-matched controls. In the second study, 10 patients with memory impairment at the neuropsychological evaluation and 10 age-matched controls were included. Our data argue for an earlier modification of ERP parameters in the visual modality than in the auditory one, even before the modification of cognitive scores. In both studies, P300 parameters were correlated to neuropsychological performances (and especially to the attention examination in the first study and to memory tests in the second study) in both modalities. Taking into account the clinical usefulness of ERPs, it is nowadays important to include this electrophysiological method in evaluation and follow-up of MS, and not only using the auditory modality but also the visual presentation in order to detect earlier cognitive dysfunctions even before modification of neuropsychological performances.