PRL
Paramagnetic Rim Lesions (Chronic Active Smoldering MS Lesions)
常磁性リム病変（PRL：慢性活動性・くすぶり型脱髄病変）
1. Biological & Technical Mechanism
Paramagnetic Rim Lesions (PRLs) represent the in vivo neuroimaging signature of chronic active ('smoldering') Multiple Sclerosis plaques. After blood-brain barrier closure, a subset of white matter lesions fails to resolve; instead, a rim of iron-enriched, C1q-expressing proinflammatory microglia (MIMS-iron) and reactive astrocytes persists at the lesion edge for years, driving slow radial expansion, ongoing axonal transection, and remyelination failure. Because intracellular ferric iron induces local magnetic field inhomogeneities, PRLs appear as hyperintense rings on Quantitative Susceptibility Mapping (QSM) or hypointense rims on unwrapped T2*-weighted phase and Susceptibility-Weighted Imaging (SWI).
常磁性リム病変（PRL）は、血液脳関門の破綻が収束した後も鎮静化せず、病変の辺縁（Rim）に鉄を豊富に含む炎症性ミクログリア（MIMS-iron）および反応性アストロサイトが数年間にわたり集簇し続ける「慢性活動性病変（Chronic Active Lesion）」をMRI上で直接可視化したものです。ミクログリア内の常磁性鉄イオンが局所磁場の位相シフトを引き起こすため、3T/7TのT2*位相画像や磁化率強調画像（SWI）では低信号リング、定量的磁化率マッピング（QSM）では高磁化率リングとして描出されます。
2. Open Science & Clinical Trial Significance
PRLs are incorporated into the revised 2024 McDonald diagnostic criteria as a specificity marker for MS and serve as a key imaging endpoint in trials evaluating microglia-targeting therapies (such as BTK inhibitors) and single-nucleus spatial transcriptomics.
PRLを1個以上有する患者はPIRA（再発非依存性進行）および脳実質・視床萎縮の進行リスクが有意に高いことが示されており、2024年改訂マクドナルド診断基準における疾患特異的バイオマーカーとして採用されたほか、OpenNeuro等の7T/3T BIDSデータセットを用いた自動セグメンテーション研究が活発に行われています。
Related Neuroscience Terms & Standards
Irreversible accumulation of neurological disability occurring outside of clinical relapses, driven by diffuse smoldering neuroinflammation, chronic active lesions, and neuroaxonal loss in MS.
MRI finding showing a small thin vein running centrally through a white matter hyperintense lesion on T2*-weighted / FLAIR* imaging, reflecting the perivenular pathology of Multiple Sclerosis.
International consensus diagnostic framework integrating clinical attacks, MRI topography (Dissemination in Space/Time, optic nerve, CVS, PRLs), and CSF oligoclonal bands to diagnose MS.
Oral small-molecule therapeutics crossing the blood-brain barrier to simultaneously inhibit B-cell receptor signaling and FcγR-mediated proinflammatory microglial activation in Multiple Sclerosis.
High-throughput transcriptomic profiling at individual cell or nucleus resolution, enabling identification of disease-associated microglia (DAM), astrocytes, and vulnerable neuronal subtypes.
Subcellular-resolution spatial transcriptomics imaging hundreds to thousands of RNA species in intact brain tissue sections while preserving cytoarchitecture.
Open Datasets & Research Publications Related to PRL
Spatial Transcriptomics of Chronic Active Multiple Sclerosis Lesions Reveals Iron-Laden MIMS Microglia Driving OPC Differentiation Arrest
Subcellular MERFISH and single-nucleus RNA sequencing across human post-mortem white matter lesions map complement C1q signaling and interferon-responsive oligodendrocyte states at paramagnetic lesion rims.
Combined Serum GFAP and Neurofilament Light Chain (NfL) Stratifies Progression Independent of Relapse Activity (PIRA) in Multiple Sclerosis
Prospective multi-center validation across 1,420 MS patients demonstrating that elevated serum GFAP paired with paramagnetic rim lesions (PRLs) predicts 24-week confirmed PIRA independent of acute gadolinium-enhancing relapses.
OpenNeuro BIDS Repository: 3T/7T 3D-FLAIR, MP2RAGE & Quantitative Susceptibility Mapping (QSM) of Paramagnetic Rim Lesions in Multiple Sclerosis
High-resolution structural MRI, T2*-weighted phase/QSM, and multi-shell diffusion tensor imaging (DTI) dataset with manual expert lesion masks for white matter lesions, paramagnetic rim lesions (PRLs), and central vein sign (CVS) assessment.
MSDA: COVID19 GDSI LocalDashboard - Federated MS Data Toolkit
Official open-source repository and tool for Multiple Sclerosis federated research and data harmonization under MS-DATA-ALLIANCE.
Global Data Sharing Initiative (GDSI): Containerized Federated Analysis Pipeline for MS Registries
International federated research initiative and containerized query framework allowing participating national MS registries to analyze disease-modifying therapy (DMT) safety, anti-CD20 outcomes, and PIRA progression without transferring identifiable patient data.
Multiple Sclerosis and Viruses: « Liaisons Dangereuses ».
Multiple sclerosis (MS) is a complex, multifactorial neurodegenerative disease with an aetiology that is still partially elusive. Several risk factors are associated with MS development including genetic predisposition and various environmental stressors; however, recently, viral infections have gained significant attention as a crucial environmental trigger. Despite the well-established link between Epstein-Barr virus (EBV) and MS susceptibility, a single-pathogen model fails to clearly characterise the molecular cascades driving the disease, suggesting that the transition from infection to autoimmune response involves more than one viral agent. In this review we examine the speculation that the interactions among different neurotropic viruses could serve a collective causative role in MS, which is under-researched in the literature at present. We summarise contradictory evidence on the role of different viral agents, including the Herpesviridae family (Human Cytomegalovirus, EBV, Herpes Simplex Viruses HSV-1 and HSV-2, and Varicella Zoster Virus), Paramyxoviridae family (Measles Virus and Rubella Virus), Influenza virus, SARS-CoV-2, and Human Endogenous Retroviruses (HERVs). Through interplay within shared molecular pathways, immune modulation, and activation of latent infections, these viruses may collectively influence the inflammatory and demyelinating processes that characterise MS. This review evaluates the etiological role of viral interplay in MS through the cumulative and interactive effects of these pathogens. The available epidemiological, immunological, and experimental data converge on the concept that viral co-exposures act synergistically to shape MS susceptibility in genetically predisposed individuals. Characterising these viral interactions presents a new research direction for the identification of novel biomarkers and the development of preventative strategies through the targeted control of viral networks.
Disclaimer: This encyclopedia entry is intended for academic neuroscience research and data science reference only, and does not constitute medical advice.