Paramagnetic rim lesions in adult and pediatric patients: marker of diagnosis and disability

Introduction: On magnetic resonance imaging (MRI), the iron-enriched macrophages and microglia at lesion edges create a paramagnetic effect, enabling the identification of certain chronic active lesions as paramagnetic rim lesions (PRLs) on Susceptibility Weighted Imaging (SWI) scans. PRLs are a recognized marker of disability in adult multiple sclerosis (MS) patients, detectable in approximately 60% of patients and accounting for about 10% of total lesions, serving as a radiological marker for disability and differential diagnosis. Methods: We conducted a retrospective study on both adult and pediatric patients who had at least one SWI MRI scan for PRL detection. Lesions were identified on T2-weighted and Fluid-Attenuated Inversion Recovery (FLAIR) sequences, with SWI sequences used specifically for PRL identification. Clinical features, including age, sex, intracranial volume, and Expanded Disability Status Scale (EDSS) scores, were evaluated. Statistical analysis employed linear correlation, the Mann-Whitney U test, and the Kruskal-Wallis test. Results: A total of 212 adult patients were included, with a median age of 43.0 years (IQR 32.9–51.6) and a median disease duration of 8.0 years (IQR 2.9–16). PRLs comprised 13.9% of all lesions (652 out of 4,675), with 70.3% of patients showing at least one PRL. PRL presence was significantly correlated with EDSS scores (p=0.009) and MRI measures, including cortical lesions (p<0.001) and black holes. Patients with four or more PRLs had higher disability scores. PMS patients exhibited a higher number of PRLs. Among 52 pediatric MS patients, PRLs correlated with total lesion load but showed no link with clinical measures. In contrast, 66 pediatric patients with myelin oligodendrocyte glycoproteinassociated disease (MOGAD) had no PRLs. Conclusion: This study confirms a high prevalence of PRLs in all MS subtypes, particularly in PMS, where PRLs correlate with greater disability. PRLs were also associated with cortical lesions and observed as T1 black holes in 25% 4 of cases, suggesting significant tissue destruction. In pediatric MS, PRLs were common but did not correlate with clinical outcomes, while no PRLs were found in MOGAD cases, underscoring PRLs’ potential role in distinguishing MS subtypes. Limitations, such as the small sample size and absence of postcontrast imaging, highlight the need for further longitudinal research to clarify PRLs' role in MS progression and guide treatment strategies. Introduction: On magnetic resonance imaging (MRI), the iron-enriched macrophages and microglia at lesion edges create a paramagnetic effect, enabling the identification of certain chronic active lesions as paramagnetic rim lesions (PRLs) on Susceptibility Weighted Imaging (SWI) scans. PRLs are a recognized marker of disability in adult multiple sclerosis (MS) patients, detectable in approximately 60% of patients and accounting for about 10% of total lesions, serving as a radiological marker for disability and differential diagnosis. Methods: We conducted a retrospective study on both adult and pediatric patients who had at least one SWI MRI scan for PRL detection. Lesions were identified on T2-weighted and Fluid-Attenuated Inversion Recovery (FLAIR) sequences, with SWI sequences used specifically for PRL identification. Clinical features, including age, sex, intracranial volume, and Expanded Disability Status Scale (EDSS) scores, were evaluated. Statistical analysis employed linear correlation, the Mann-Whitney U test, and the Kruskal-Wallis test. Results: A total of 212 adult patients were included, with a median age of 43.0 years (IQR 32.9–51.6) and a median disease duration of 8.0 years (IQR 2.9–16). PRLs comprised 13.9% of all lesions (652 out of 4,675), with 70.3% of patients showing at least one PRL. PRL presence was significantly correlated with EDSS scores (p=0.009) and MRI measures, including cortical lesions (p<0.001) and black holes. Patients with four or more PRLs had higher disability scores. PMS patients exhibited a higher number of PRLs. Among 52 pediatric MS patients, PRLs correlated with total lesion load but showed no link with clinical measures. In contrast, 66 pediatric patients with myelin oligodendrocyte glycoprotein-associated disease (MOGAD) had no PRLs. Conclusion: This study confirms a high prevalence of PRLs in all MS subtypes, particularly in PMS, where PRLs correlate with greater disability. PRLs were also associated with cortical lesions and observed as T1 black holes in 25% of cases, suggesting significant tissue destruction. In pediatric MS, PRLs were common but did not correlate with clinical outcomes, while no PRLs were found in MOGAD cases, underscoring PRLs’ potential role in distinguishing MS subtypes. Limitations, such as the small sample size and absence of post-contrast imaging, highlight the need for further longitudinal research to clarify PRLs' role in MS progression and guide treatment strategies.