Paramagnetic rim lesions on 1.5T and 3.0T MRI in Mexican patients with multiple sclerosis

Introduction: Paramagnetic rim lesions (PRLs) in multiple sclerosis (MS) patients have been described with different magnetic field strengths in magnetic resonance imaging (MRI).This study aimed to identify the characteristics of PRLs in magnitude and filtered phase susceptibility weighted imaging (SWI/SWAN) in 1.5T and 3.0T MRI in Mexican patients with MS and to determine interobserver agreement.Materials and methods: This retrospective cross-sectional study assessed adults with MS who underwent 1.5T or 3.0T MRI with SWI/SWAN.The variables, sex, age, MS duration, annualized relapse rate, the severity of current disability determined by the Expanded Disability Status Scale (EDSS), the MS clinical phenotype, and the presence, number, location, and volume of PRLs were assessed.Cohen's kappa was used to calculate interobserver agreement.Results: A total of 76 patients with MS were included.At least one PRL was found in 60 (78.9%).A total of 375 PRLs were detected: 233 in 42 (76.4%) of 55 patients with 1.5T MRI with a mean of 5.54 per patient and 142 PRLs in 18 (85.7%) of 21 patients with 3.0T MRI with a mean of 7.9 per patient.The most common location was periventricular (n = 49, 81.7%).A significant association was found between PRLs and younger patients (p = 0.017), a shorter disease evolution (p = 0.010), an annualized relapse rate (p = 0.030), and a higher volume of white matter lesions (p = 0.035).Interobserver agreement was good (κ = 0.709, 95% CI, 0.702-0.716).Conclusion: This study is the first in Mexico that characterizes PRLs with 1.5T and 3.0T MRI magnetic fields in patients with MS with good interobserver agreement.