Efficacy of Cholecalciferol (Vitamin D3) for Delaying the Diagnosis of MS After a Clinically Isolated Syndrome

Inclusion Criteria: * The patient must have given his/her informed and signed consent * The patient must be insured or beneficiary of a health insurance plan * The patient is available for 24 months of follow-up * The patient has had a classic CIS with the past 90 days * Reference cerebro-medullary MRI scheduled within the 90 days after the beginning of symptoms * With MRI (cerebro ± medullary) showing demyelination according to spatial spread criteria by Swanton (2006): * At least 1 lesion in at least 2 of the 4 following territories: (1) Peri-ventricular; (2) Juxta-cortical; (3) Sub-tentorial; (4) Medullary * No other suspected pathology * Vitamin D level in blood less than 100 nmol / l at the pre-inclusion visit * Women of childbearing potential must use very effective contraception for the duration of the study. A very effective contraceptive method is defined as a method resulting in a low failure rate (that is to say less than 1% per year) when used consistently and correctly, such as implants, injectables, combined oral contraceptives, IUDs, sexual abstinence, or partner with a vasectomy. Randomisation stratification criteria: * The patient can also also meet the temporal dissemination criteria defined according to McDonald criteria 2010 (Polman et al., 2011), because this condition is currently not sufficient for prescribing a background treatment: Simultaneous presence of at least one asymptomatic lesion taking on contrast and at least one asymptomatic lesion not …