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Updated: Oct 3, 2025
Magnetic Resonance Imaging of Multiple Sclerosis at 7.0 Tesla
Published on: February 19, 2021
Long-term dynamics of multiple sclerosis iron rim lesions
Claudia E Weber1, Matthias Wittayer1, Matthias Kraemer2
1Department of Neurology, Medical Faculty Mannheim and Mannheim Center of Translational Neurosciences (MCTN), Heidelberg University, Theodor-Kutzer-Ufer 1 - 3, 68167 Mannheim, Germany.
Background:
Several studies have pointed out that seemingly chronic multiple sclerosis (MS) lesions may also be in inflammatory states. In pathological studies, up to 40% of chronic MS lesions are characterized as "chronic active" or "smoldering" lesions that are characterized by a rim of iron-laden proinflammatory macrophages/microglial cells at the lesion edge with low-grade continuous myelin breakdown. In vivo, these lesions can be visualized as "iron rim lesions" (IRLs) on susceptibility-weighted imaging (SWI). The aim of this study was to investigate the long-term dynamics of IRLs in vivo for a more detailed evolution of dynamic lesion volume changes occurring over time.
Methods:
We retrospectively identified patients with MS who were followed for at least 36 months (up to 72 months) and underwent at least an annual MRI on the same 3 Tsystem. Using Voxel-Guided Morphometry (VGM) we investigated regional volume changes within lesions and correlated these findings with SWI for the presence of a characteristic hypointense lesion rim. To estimate tissue damage, apparent diffusion coefficient (ADC) values for every lesion at baseline and follow-up MRIs were determined.
Results:
Forty-three patients were included in the study. Overall, we identified 302 supratentorial non-confluent MS lesions (52 persistent IRLs, nine transient IRLs, 228 non-IRLs and 13 acute contrast-enhancing lesions). During follow-up, persistent IRLs significantly enlarged, whereas non-IRLs showed a tendency to shrink. At baseline MRI, ADC values were significantly higher in persistent IRLs (1.23 × 10-3 mm/s2) compared to non-IRLs (1.01 × 10-3 mm/s2; p < 0.001), but not compared to transient IRLs (1.06 × 10-3 mm/s2; p = 0.15) and contrast-enhancing lesions (1.15 × 10-3 mm/s2; p = 1.0). During follow-up, ADC values significantly increased more often in persistent IRLs compared to all other lesion types (p < 0.0001).
Conclusions:
Our long-term data demonstrate that persistent IRLs enlarge during disease duration, whereas non-IRLs show a tendency to shrink. Furthermore, IRLs are associated with sustained tissue damage, supporting the notion that IRLs could represent a new imaging biomarker in MS.
Insights
Persistent iron rim lesions (IRLs) in multiple sclerosis (MS) enlarge over time, unlike non-IRLs which tend to shrink. These IRLs indicate sustained tissue damage and may serve as a novel imaging biomarker in MS.
Area of Science:
- Neuroimaging
- Radiology
- Neurology
Background:
- Chronic active lesions in multiple sclerosis (MS) exhibit inflammatory characteristics and myelin breakdown.
- These lesions can be visualized in vivo as iron rim lesions (IRLs) using susceptibility-weighted imaging (SWI).
Purpose of the Study:
- To investigate the long-term dynamics and volume changes of IRLs in MS.
- To understand the evolution of IRLs over time using advanced MRI techniques.
Main Methods:
- Retrospective analysis of MS patients with at least 36 months of follow-up and annual MRI scans.
- Voxel-Guided Morphometry (VGM) used to assess regional volume changes and correlate with SWI findings.
- Apparent diffusion coefficient (ADC) values determined for lesions to estimate tissue damage.
Main Results:
- Persistent IRLs significantly enlarged during follow-up, while non-IRLs tended to shrink.
- Baseline ADC values were higher in persistent IRLs compared to non-IRLs.
- ADC values increased significantly more often in persistent IRLs during follow-up, indicating sustained tissue damage.
Conclusions:
- Persistent IRLs in MS demonstrate growth over disease duration, contrasting with shrinking non-IRLs.
- IRLs are associated with ongoing tissue damage, suggesting their potential as a new imaging biomarker for MS.
