Real-world detection of paramagnetic rim lesions and their association with disease burden in multiple sclerosis

Paramagnetic rim lesions (PRLs) are an emerging MRI biomarker in multiple sclerosis (MS). On susceptibility-sensitive MRI, PRLs are characterized by a paramagnetic shift at the lesion rim corresponding to iron-laden macrophages and microglia, and PRL detection can hence be viewed as a proxy for lesion-associated smoldering inflammation in MS brain. The aim of this study was to identify PRLs in a standard university hospital setting to explore the associations between PRL burden and MS-related clinical and paraclinical parameters.

We retrospectively reviewed all 3T brain MRI studies performed as part of MS patient management at a tertiary university hospital in Finland between September 2021 and December 2023. PRLs were visually identified on filtered phase images from susceptibility-weighted imaging (SWI) sequences. Brain volumetric data were extracted from post-contrast 3D T1-weighted images using an automated quantification tool (cNeuro® cMRI). Clinical and laboratory variables were obtained by manual chart review from electronic medical records.

The final cohort included 206 patients. 34% of patients had at least one PRL (the PRL1+ group). The median number of PRLs in the PRL1+ group was 2 and the maximum number was 11. Within the PRL1+ group, PRL count correlated positively with Expanded Disability Status Scale (EDSS), Multiple Sclerosis Severity Score (MSSS) and T2 lesion volume. Patients with PRLs had significantly smaller thalami compared to those without PRLs.

Our real-world data reinforce evidence that PRLs are linked to more severe disease and demonstrate that PRL identification using manufacturer-reconstructed SWI filtered phase images provides a feasible imaging parameter to assess progression-associated pathology in MS in a standard clinical setting.