Implementing the 2017 McDonald criteria for the diagnosis of multiple sclerosis.

The latest revision of the McDonald criteria for the diagnosis of multiple sclerosis (MS) was published online in 2017. New features of the criteria, which were designed to facilitate earlier diagnosis of MS, include the recognition of oligoclonal bands in the cerebrospinal fluid as a possible marker of dissemination of MS pathology in time, the introduction of symptomatic lesions as a parameter to demonstrate spatial or temporal pathology dissemination, and the use of cortical lesions to demonstrate dissemination in space. In this Viewpoint, a panel of world-renowned MS specialists share their personal experiences of the new criteria to date.