Paramagnetic rim lesion formation is predicted by the initial gadolinium-enhancing lesion diameter

Background: Paramagnetic rim lesions (PRLs) are a magnetic resonance imaging (MRI) marker of compartmentalized intraparenchymal inflammation.

Objectives: The primary objective was to investigate clinical, demographic, and MRI factors that may be predictive of the future formation of PRL.

Methods: This is a retrospective analysis of longitudinal data. Patients were included if they had ⩾1 gadolinium-enhancing lesion on any historical MRI and follow-up scan(s) ⩾6 months afterward on a standardized 3T MRI using the filtered phase component of a susceptibility-sensitive sequence ("SWAN"). Regression and machine-learning models were used to identify the predictive ability of demographic, clinical, immunological, treatment-related, and MRI predictors of PRL formation.

Results: A total of 64 patients having 229 contrast-enhancing lesions (CELs) were included. Among all predictors, the diameter of the initial enhancing lesion was the most influential for determining subsequent PRL formation; every millimeter increase in diameter increased the risk of PRL formation by 44%. Other factors did not contribute additional information; the administration of steroids was not associated with any effect.

Conclusions: The long-axis diameter of a CEL is the best translational predictor of subsequent PRL formation at follow-up. This measure holds promise as a method to identify patients at high risk of chronic active lesion formation during the acute inflammatory window.