Diagnostic evolution in multiple sclerosis: A narrative review of the McDonald criteria from 2001 to 2024

The diagnostic criteria for Multiple sclerosis (MS) have undergone several revisions over the past two decades. This narrative review highlights evolution and key changes to the McDonald criteria since its introduction in 2001. This was one of the first criteria to incorporate evidence on MRI to diagnose MS in addition to clinical diagnosis. Subsequent revisions in 2005 and 2010 refined the requirements for lesion dissemination in space and time. The 2017 McDonald criteria improved sensitivity by including cerebrospinal fluid oligoclonal bands as evidence of dissemination in time. The most recent update was proposed in 2024 and presented at the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) Annual Meeting 2024, American Academy of Neurology (AAN) Annual Meeting 2025, and the Consortium of Multiple Sclerosis Centers (CMSC) Annual Meeting 2025, which introduced novel biomarkers such as kappa free light chains, and imaging features such as the central vein sign and paramagnetic rim lesions. Inclusion of the optic nerve as a fifth topography and permitting MS diagnosis in selected cases of radiologically isolated syndrome has expanded diagnostic horizons. These updates aim to facilitate early diagnosis and treatment initiation in MS. However, they also raise concerns about overdiagnosis and the need for careful clinical correlation. Future directions include biomarker standardization and validation across diverse populations.