Dissemination in time as a requirement for diagnosis of multiple sclerosis: Time for a change?

The requirement to demonstrate dissemination in time (DIT) in order to diagnose multiple sclerosis (MS) has been enshrined in the literature since earliest efforts to establish diagnostic critera. However, various diagnostic criteria over the years, including the 2017 McDonald criteria, have inconsistently utilized this concept. This Viewpoint contends that current criteria for DIT are inadequate and sometimes inappropriate. It recommends continuing to consider DIT in the diagnosis of MS, but advocates utilizing all available information with high specificity for the disease, including the presence of large numbers of typical lesions, to make the diagnosis. This approach enables early initiation of disease-modifying treatment in situations with a favorable risk-benefit ratio.