[Diagnostic criteria of multiple sclerosis in neuroimaging].

Although sensitivity of MRI to MS is high, its specificity is limited and requires the use of criteria such as Paty's, Fazekas's and then Barkhof's, taking successively into account the technical progress and the use of contrast agents. In the later the confidence level brought by contrast enhancement is equivalent to that of 9 hyperintense lesions seen on T2-weighted imaging. Therefore MRI is now the first paraclinical test to perform for MS suspicion and is aimed at the diagnosis MS from the first clinical event, without need to wait for the second relapse for temporal dissemination confirmation. The goal is to be able to discuss early treatment if it becomes clear that it could prevent disease progression. The early evidence of spatial and temporal dissemination of the disease takes equally into account the clinical and MRI information and eliminates the previous terminology of "clinically defined MS". Presently the diagnosis is either confirmed or ruled out and in a limited number of cases or before the completion of the work up phase the category of "possible MS" is used. Although progress were also made in the field of prognosis evaluation of MS with MRI, it still brings less definitive information to predict individually the evolution of each form of the disease. This opens a large place for new techniques such as magnetisation transfer, spectroscopy and diffusion imaging which are already able to help pathophysiological understanding and which may play an increased role even at the individual level in the future.