2024 McDonald Criteria Revisions Published in The Lancet Neurology

The 2024 revisions to the McDonald criteria for the diagnosis of multiple sclerosis (MS) have been published in The Lancet Neurology in September 2025, marking the first major update since 2017. The criteria were updated to reflect significant changes in the field, including an evolving understanding of MS and recognition of disease biomarkers. Notably, the optic nerve is now recognized as a fifth anatomical region for demonstrating dissemination in space. In addition, imaging and laboratory markers—including the central vein sign, paramagnetic rim lesions, and the kappa free-light chain index in cerebrospinal fluid—are recognized as supportive tools to assist in diagnostic decision making.

The criteria were developed by the International Advisory Committee on Clinical Trials, convened by the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) and the National Multiple Sclerosis Society. The process included multiple expert meetings and a consensus conference with global representation, with a discussion of the existing evidence base and structured voting methods to achieve agreement.

Key updates include:

• Optic nerve involvement can now be used to demonstrate dissemination in space.
• Dissemination in time is no longer mandatory in certain scenarios if other supportive evidence is present.
• Central vein sign and paramagnetic rim lesions on MRI may improve diagnostic specificity.
• The kappa free-light chain index is accepted as an alternative to oligoclonal bands to demonstrate dissemination in time.
• The revisions include provisions for a ‘biological diagnosis’ of MS in which MRI findings suggestive of MS are reported along with other findings that may not be representative of a typical MS attack or relapse.

These revisions provide a unified diagnostic approach across relapsing and progressive MS, aiming to reduce misdiagnosis and expedite treatment initiation across the lifespan.

Source: Montalban X, Lebru-Frénay C, Oh J, et al. Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteria. Lancet Neurol. 2025;24(10):850-865. doi:10.1016/S1474-4422(25)00270-4