Introduction
Paramagnetic rim lesions (PRLs) are a subset of multiple sclerosis (MS) lesions identifiable using susceptibility-weighted MRI sequences (Ng Kee Kwong KC, 2021). PRLs have been associated with chronic active inflammation and may serve as potential diagnostic and prognostic biomarkers (Toru Asahina, 2024). This study investigates the relationship between PRL magnetic susceptibility (χ) and clinical variables in MS patients.

Methods
A cohort of 88 MS patients (38 males, 43±11 years) underwent a 3T MRI protocol, including FLAIR and QSM sequences. PRLs were manually segmented from QSM images to extract χ-metrics, specifically the median and 90th percentile values, the latter intended to capture the paramagnetic contribution of the lesion rim. Clinical characterization included the Expanded Disability Status Scale (EDSS), disease duration, and MS phenotype (relapsing-remitting vs primary progressive). Statistical correlations were assessed using partial Spearman correlation, controlling for sex, age, and disease duration.

Results

Nineteen patients presented with at least one PRL. Neither the presence of PRLs nor their number or total volume correlated with clinical characteristics. However, the median χ-value showed a significant correlation with EDSS (p=0.006), while the 90th percentile χ-value correlated with both EDSS (p=0.008) and MS phenotype (p=0.009). In particular, for phenotype classification, ROC curve analysis yielded an AUC of 0.84 (specificity=0.79, sensitivity=0.80).

Conclusion

While the presence and number of PRLs do not correlate with clinical status, χ-metrics may serve as valuable markers for disease severity and MS phenotype differentiation. These findings highlight the potential of QSM for more precise characterization of chronic active inflammation in MS.