[Retrochiasmatic lesions in multiple sclerosis. Demonstration by visual evoked potentials. Correlation with magnetic resonance imaging].

Monocular stimulation of each visual hemifield can show an interhemispheric asymmetry of VEP. Validity of this test needs a reproducibility of responses and exclusion of stimulation induced by eye movements. In a prospective study of 22 MS cases, it appeared that interhemispheric asymmetry was a criterion of dissemination is space and had a good diagnostic value: MS became clinically definite in 10/12 cases; in 10 other cases in which a correlative MRI-VEP study was possible, there were disseminated high signal areas in T2 weighted sequences on hemispheric MRI. In 7/10 cases, these areas were located on retrochiasmatic visual pathways. With MRI, VEP are the most performant tests for early diagnosis in MS. Technical progress will improve its fiability. Prospective correlative clinical, electrophysiological and MRI studies are necessary on a larger number of MS patients.