Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system affecting 60.000 persons in France and characterized by widespread inflammation, focal demyelination, and a variable degree of axonal loss. In recent years the concept of MS as an inflammatory neurodegenerative disease has been corroborated by neuropathologic and in vivo MR imaging studies. A number of MR studies show that the principal pathological substrate of permanent disability is axonal loss as detected in MR studies as global atrophy, but also regionally in the white or grey matter, and that atrophy already occurs at early stages of the disease. Though MR imaging is a powerful tool for MS in terms of diagnosis, description of the natural history of the disease and treatment monitoring, the major drawback of MRI in MS is the lack of specificity of the MR findings. Furthermore, with the advent of disease modifying drugs, there is a need for robust and specific MR markers to identify e.g. clinically isolated syndrome (CIS) patients at presentation at high risk to develop MS or a more severe disease course. An increasing body of MRI evidence corroborates that CIS show early and dynamic changes detected by MR imaging, such as global or regional brain atrophy, as a sign of progressive axonal loss, but atrophy is already a late stage sign of the disease, when tissue is lost. Considerable efforts are spent today to identify early and prognostic MR markers for high risk CIS patients.