The 2024 Update to the McDonald Criteria for Multiple Sclerosis Diagnosis: A Guide for Radiologists

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the CNS. The McDonald criteria serve as the primary framework for MS diagnosis, integrating clinical, imaging, and laboratory findings to enable timely and accurate diagnoses. Towards these goals, the 2024 update of the McDonald criteria introduced key changes, incorporating the optic nerve as a fifth topographic site for dissemination in space, recognizing an additional CSF biomarker that can substitute for dissemination in time, and allowing radiologically isolated syndrome to be classified as MS under specific conditions. Furthermore, the updated criteria integrate two high-specificity markers identified on susceptibility-sensitive MRI sequences-namely the central vein sign and paramagnetic rim lesion-as optional diagnostic tools. Additionally, the revised criteria incorporate stricter diagnostic thresholds for patients over age 50, patients with vascular risk factors or headache disorders, and children, to mitigate the risk of misdiagnoses. As MRI remains central to MS diagnosis, radiologists must remain proficient in identifying the new imaging markers and appropriately applying the revised criteria. This review provides a radiology-focused overview of the 2024 updates to the McDonald criteria for MS diagnosis, highlighting the revised criteria's imaging and clinical implications and providing practical guidance for optimizing MS diagnoses in daily practice.