[Diagnosis of Multiple Sclerosis: Revision of the McDonald Criteria 2017]

Multiple sclerosis (MS) is the most common chronic autoimmune disorder of the central nervous system (CNS) largely affecting young adults. The diagnosis of MS is based on two pillars: 1) detection of the spatial and temporal dissemination of focal neurological deficits and 2) exclusion of important differential diagnoses. The current revision of the diagnostic criteria (McDonald 2017) also follows these principles, takes new data on magnetic resonance imaging (MRI) into account and reintroduces the role of cerebrospinal fluid (CSF) diagnostics for relapsing-remitting forms. The main priority is a reliable diagnosis as early as possible with the aim of a timely initiation of course-adapted treatment. Some of the concrete innovations are the consideration of cortical MRI lesions (equivalent to juxtacortical foci), the elimination of a distinction between asymptomatic and symptomatic MRI lesions and consideration of characteristic CSF findings for the criterion of temporal dissemination. Relapsing MS can be diagnosed at the time of the first attack by the detection of CSF-specific oligoclonal bands and the MRI detection of a typical local lesion distribution (even without simultaneous detection of a contrast-enhancing lesion). For the primary progressive course, for which a first treatment option has recently been approved, the known definition remains unaltered. With respect to the differential diagnosis there is a clear demarcation from Devic's syndrome, now known as neuromyelitis optica spectrum disorders (NMOSD), as recent insights indicate a separate disease entity caused by an autoimmune response against the astrocytic aquaporin 4 (AQP4) water channel. Finally, future studies will have to provide a definition for secondary progressive MS courses and clarify how to handle diseases characterized by antibodies against myelin oligodendrocyte glycoprotein (MOG) or patients with radiologically isolated syndrome (RIS), i. e. incidental MRI-based detection of CNS lesions in the absence of any clinical event. In summary, McDonald 2017 is within the conceptual structure of its predecessor and simplifies an early diagnosis, thus paving the way to early treatment of MS.