Sex-specific differences in rim appearance of multiple sclerosis lesions on quantitative susceptibility mapping.

Background: Susceptibility MRI techniques, such as phase and quantitative susceptibility mapping (QSM) reveal lesion heterogeneity in MS, including the presence of lesions with outer rims suggestive of iron accumulation in macrophages and microglia, indicative of chronic-active inflammatory white matter lesions (WMLs).

Objective: To evaluate the in vivo relationship between chronic-active WMLs (as visualized by rimmed lesions on QSM) and several clinical metrics.

Methods: 39 patients (15 men, 24 women) with MS underwent 7 Tesla brain MRIs and clinical evaluation. Contrast patterns of lesions identified on FLAIR and quantitative susceptibility maps were reviewed and compared to demographic characteristics and disability scores.

Results: 1279 lesions were identified on FLAIR MRI; 846 (66.2%) of these were visible on QSM, 119 (14.1%) of which had visible rims. Lesions visible on QSM were more likely to have rims in men (16.1%, vs 4.9% in women, p=0.009). In a logistic regression model accounting for several factors, male sex conferred a >10-fold risk of having ≥1 rimmed lesion(s) (p=0.026).

Conclusion: Our findings provide in vivo support for the body of histopathologic literature indicating sex-specific differences in MS WML formation and suggest that QSM can be used to study these sex differences in the future.