RESUMEN
BACKGROUND AND PURPOSE: McDonald criteria for multiple sclerosis diagnosis have been revised over the years, diagnostic procedures have been simplified and earlier diagnosis facilitated. The new 2017 revision introduces other important changes, with a further simplification for the diagnosis. Oligoclonal bands reassume a more relevant role in the workup. METHODS: We describe 3 typical cases of patients admitted for clinically isolated syndrome and illustrate how the application of the new criteria can change the diagnostic approach with respect to the previous criteria. RESULTS: In two of the three cases a diagnosis of multiple sclerosis is now possible. CONCLUSIONS: The new 2017 Multiple Sclerosis criteria may have an important impact in clinical practice with an earlier treatment to avoid the risk of disease dissemination. Their application requires a careful assessment to avoid misdiagnosis and mistreatments.