Inclusion Criteria :  Patient older than 18 years old. With Multiple Sclerosis according to Mc Donald 2017 criteria or with clinically isolated syndrome and included with OFSEP cohort. Phenotype known (RR, SP, PP or CIS). Date of diagnosis known. With at least one MRI that includes 3D T1 and FLAIR at 1.5T or 3T.  Exclusion Criteria :  Stroke Other causes of dementia not caused by Multiple Sclerosis (Alzheimer's disease, Parkinsonian syndromes…)