While significant progress has been made on medical imagery in recent years in the individualization of different lesions in the nervous system for demyelination, axonal loss, atrophy, little progress has been made in the specific recognition the inflammatory process. Yet this point is essential since the currently available treatments have a partial impact mainly on the inflammatory component and that many uncertainties remain about the links between inflammation and tissue destruction affecting myelin and axons. The recent discovery of a macrophage cell marker in the CNS, more specific (USPIO) of inflammation gives us the opportunity to answer important questions which one can sense that this could have a significant impact on therapeutic drug monitoring of these patients. This study will involve 50 patients recruited in five French centers (Marseille, Paris, Reims, Rennes, Toulouse) from the earliest manifestations of the disease with clinical and MRI scheduled for the first 3 years of their disease.