Redefining multiple sclerosis: 2024 McDonald diagnostic criteria

Abstract

This review aimed to provide a comprehensive summary of the 2024 McDonald diagnostic criteria, emphasizing key innovations in cerebrospinal fluid and imaging biomarkers, and to discuss their clinical relevance in improving diagnostic accuracy and reducing misdiagnosis. The present review synthesized evidence from recent prospective studies, expert panel recommendations, and updated diagnostic algorithms. Each revision was critically appraised in light of supporting literature, including validation studies of biomarkers such as the kappa free light chain index, central vein sign, and paramagnetic rim lesions. The implications of these updates were evaluated for various clinical scenarios, including clinically isolated syndrome, radiologically isolated syndrome, and atypical presentations. The inclusion of the optic nerve as a fifth topographic region for dissemination in space and the recognition of the kappa free light chain index as a quantitative alternative to oligoclonal bands for dissemination in time represent major advancements. Central vein sign and paramagnetic rim lesions have been endorsed as supportive imaging biomarkers with high specificity for multiple sclerosis (MS), although they remain optional. In cases with lesions in four or five topographic regions, a diagnosis can now be made without evidence of dissemination in time. Furthermore, radiologically isolated syndrome with compatible lesions and at least one supportive biomarker may fulfill MS diagnostic criteria. For primary progressive MS, ≥2 characteristic spinal cord lesions may suffice as objective evidence along with positive cerebrospinal fluid findings. The 2024 McDonald criteria refine MS diagnosis by integrating validated fluid and imaging biomarkers, enabling earlier and more accurate diagnosis. These updates are expected to significantly impact clinical decision-making, particularly in atypical presentations and differential diagnoses.

Cite this article as: Manazoğlu HC, Kürtüncü M. Redefining multiple sclerosis: 2024 McDonald diagnostic criteria. Turk J Neurol 2025;31(3):255-269. doi: 10.55697/tnd.2025.500.

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Contributed to the study design, data collection, analysis and interpretation of data, literature review, writing of the manuscript, and preparation of materials and references: H.C.M.; Contributed to the study conception, design, supervision, interpretation of data, and critical revision of the manuscript. Both authors reviewed and approved the final version of the manuscript: M.K.

The authors declared no conflicts of interest with respect to the authorship and/ or publication of this article.

The authors received no financial support for the research and/or authorship of this article.