MRI-Based Lesion Differentiation in Older Patients With Multiple Sclerosis

Magnetic resonance imaging (MRI) is central to the diagnosis and monitoring of multiple sclerosis (MS). In individuals above 50 years of age, interpretation of white matter lesions becomes increasingly complex because lesions visible on conventional T2-weighted and FLAIR MRI may reflect MS-related demyelination, chronic cerebral small vessel disease (cSVD), or nonspecific age-related white matter changes. Conventional MRI has limited specificity in differentiating between these entities, which may complicate assessment of disease activity and progression. Quantitative Susceptibility Mapping (QSM) is an advanced MRI technique that quantifies tissue magnetic susceptibility and provides complementary information to conventional imaging. Differences in susceptibility characteristics may reflect underlying tissue composition and microstructural properties, potentially allowing improved differentiation between demyelinating and vascular white matter lesions. This prospective observational cohort study includes individuals aged 50-70 years with established MS undergoing routine clinical MRI follow-up, as well as an age-comparable cohort with clinical and radiological evidence of cSVD. Participants with MS will undergo longitudinal follow-up through routine clinical MRI and clinical assessments, whereas participants in the cSVD cohort will undergo a single study visit including MRI and standardized clinical testing. MRI examinations include standard clinical sequences with the addition of a short QSM acquisition. Clinical assessment includes brief standardized measures of cognitive processing speed, executive function, and physical function performed in conjunction with clinical visits. Imaging analyses will focus on lesion-level and participant-level susceptibility characteristics and their distribution patterns across cohorts. Associations between QSM-derived measures and clinical function will be explored. The study is designed to evaluate the diagnostic utility and clinical relevance of QSM-based lesion characterization in older individuals with MS.