Disease correlates of quantitative susceptibility mapping rim lesions in multiple sclerosis

Objective: This study aimed to explore the association between chronic active rim+ lesions, identified as having a hyperintense rim on quantitative susceptibility mapping (QSM), on both clinical disability and imaging measures of neurodegeneration in patients with multiple sclerosis. Methods: The patient cohort was composed of 159 relapsing remitting multiple sclerosis patients aged 42.17 +/- 10.25 years and disease duration of 10.74 +/- 7.51 years. The Brief International Cognitive Assessment for Multiple Sclerosis and Expanded Disability Status Scale (EDSS) were used to assess clinical disability. Cortical thickness and thalamic volume were evaluated as imaging measures of neurodegeneration. Results: A total of 4,469 multiple sclerosis lesions were identified, of which 171 QSM rim+ (3.8%) lesions were identified among 57 patients (35.9%). In a multivariate regression model, as the overall total lesion burden increased, patients with at least one rim+ lesion on QSM performed worse on both physical disability and cognitive assessments, specifically the Symbol Digit Modalities Test (p=0.010), California Verbal Learning Test-II (p=0.030), and EDSS (p=0.001). In a separate univariate regression model, controlling for age (p<0.001), having at least one rim+ lesion was related to more cortical thinning (p= 0.03) in younger patients (< 45 years). Lower thalamic volume was associated with older patients (p=0.038) and larger total lesion burden (p<0.001) however, the association did not remain significant with rim+ lesions (p=0.10). Interpretation: Our findings demonstrate the significant impact of chronic active lesions, as identified on QSM, on both clinical disability and imaging measures of neurodegeneration in patients with multiple sclerosis.