The International Advisory Committee on Clinical Trials led a multinational panel updating the McDonald criteria, adding the optic nerve as a fifth anatomical location and allowing specific magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) markers to support diagnosis without mandatory dissemination in time in defined scenarios.

Multiple sclerosis diagnosis has long required proof that lesions occur in different places and at different times, with MRI and CSF biomarkers gradually shortening time to treatment.

Previous revisions improved sensitivity and specificity across ages and regions, yet misdiagnosis risk still persists, especially with overlapping conditions and when access to specialized tests is limited.