Longitudinal clinical study of patients with white matter iron rims lesions in multiple sclerosis

Introduction Identifying accurate prognostic imaging biomarkers in multiple sclerosis (MS) is crucial. Iron rims (IR) surrounding white matter lesions (WML) are suggested to predict a more severe disease course. Only small longitudinal cohorts of patients with and without IRL have been reported so far. Objective To assess if the presence and number of IRL in patients with CIS and MS are associated with worse long-term clinical disability. Methods Ninety-one CIS/MS patients were recruited between 2008 and 2013 and scanned with 7T MRI. Age-Related Multiple Sclerosis Score (ARMSS), a validated measure of disease severity, was calculated for patients at the time of scan and at the latest clinical follow-up after 9 years. WMLs were assessed for the presence of IRL using SWI-filtered phase images. Results 132 IRLs were detected in 42 patients (46%). 9% of WMLs had IR. 54% of the cohort had no rims, 30% had 1-3 rims and 16% had ≥4. Patients with IRL at baseline had a higher EDSS and ARMSS. Presence of IRL was also a predictor of long-term disability especially in those patients with ≥4 IRL. The effect of IRL on disability was greater than the baseline WML numbers, another known prognostic biomarker. Conclusion The presence and number of perilesional IR at a baseline scan hold prognostic value for long term clinical disability in MS.