The efficacy of oral corticosteroids for the treatment of relapses of multiple sclerosis has not been proved. French neurologists treat such patients with intravenous corticosteroids. The aim of the study is to check if the efficacy of high dose oral methylprednisolone is similar to the efficacy intravenous (IV) prednisolone. The main criteria of efficacy is symptom recovery within 28 days after inclusion.