Contribution of new imaging sequences to the diagnosis of multiple sclerosis

The 2024 revision of the McDonald criteria reinforces the central role of magnetic resonance imaging (MRI) in diagnosing multiple sclerosis (MS). Key updates include the addition of the optic nerve as a fifth typical region for dissemination in space (DIS), requiring dedicated orbital MRI with high-resolution coronal fat-suppressed T2/STIR sequences. The central vein sign (CVS), defined as a vein traversing a T2/FLAIR lesion, offers high diagnostic specificity and can substitute for dissemination in time (DIT) or cerebrospinal fluid analysis. Paramagnetic rim lesions (PRLs), although not necessarily seen in every person with MS, indicate chronic active lesions and carry prognostic significance, correlating with greater disability over time, and supporting the diagnosis of MS in some specific cases. Consensus protocols now advocate baseline whole-brain and whole-spinal cord imaging, optimized 3D T2-FLAIR for lesion detection, and susceptibility-weighted imaging for CVS and PRLs, ideally at 3T but feasible at 1.5T with protocol optimization. These advances align imaging with MS pathobiology, reduce misdiagnosis risk - particularly in older patients or those with vascular comorbidities - and support differential diagnosis from mimics such as MOG-antibody disease and neuromyelitis optica spectrum disorder. While CVS and PRLs remain adjunctive due to limited availability in some settings, their integration into routine practice enhances diagnostic confidence and prognostic stratification. Overall, the 2024 McDonald criteria promote a flexible, yet biology-informed framework, combining clinical aspects with imaging to guide early diagnosis.