Smoldering lesions in MS: if you like it then you should put a rim on it.

Purpose: In multiple sclerosis (MS), chronic active/smoldering white matter lesions presenting with hypointense rims on susceptibility-weighted imaging (SWI) of the brain have been recognized as an important radiological feature. The aim of this work was to study the prevalence of paramagnetic rim lesions (RLs) in MS patients in a clinical setting and to assess differences in demographic and clinical variables regarding the presence of RLs.

Methods: All 3 T brain magnetic resonance (MR) studies performed in MS patients between July 2020 and January 2021 were reviewed. In all patients, RLs were assessed on three-dimensional (3D) SWI images and the T2 FLAIR lesion load volume was assessed. Demographic, laboratory (oligoclonal bands in CSF), and clinical data, including functional status with Expanded Disability Status Scale (EDSS), were retrieved from the clinical files.

Results: Of the 192 patients, 113 (59%) presented with at least 1 RL. In the RL-positive group, the mean RL count was 4.81 ranging from 1 to 37. There was no significant difference in the number of RLs between the different types of MS (p = 0.858). Regarding the presence of RLs, there were no significant differences based on gender (p = 0.083), disease duration (p = 0.520), treatment regime (p = 0.326), EDSS score (p = 0.103), and the associated T2 FLAIR lesion load volume.

Conclusion: SWI RLs were frequently detected in our cohort regardless of the MS type, T2 FLAIR lesion load volume, demographic features, disease duration, or clinical score. Our results suggest that RLs are not associated with more severe forms of the disease. Today, RLs can be seen on 3 T 3D SWI, although this is not a clinical standard sequence yet. Therefore, it should be considered an additional helpful MR sequence in the diagnostic workup of MS, although more studies are warranted to establish the role of RLs as prognostic markers.