High Levels of Perivascular Inflammation and Active Demyelinating Lesions at Time of Death Associated with Rapidly Progressive Multiple Sclerosis Disease Course: A Retrospective Postmortem Cohort Study

Intrathecal Inflammatory Profile and Gray Matter Damage Predict Progression Independent of Relapse Activity in Early Multiple Sclerosis

BACKGROUND AND OBJECTIVES

The objective of this study was to determine, at the time of diagnosis, a CSF and MRI profile of intrathecal compartmentalized inflammation predictive of progression independent of relapse activity (PIRA) in early relapsing-remitting multiple sclerosis (RRMS).

METHODS

This five-year prospective study included 80 treatment-naïve patients with RRMS enrolled at time of diagnosis. All patients underwent a lumbar puncture, regular neurologic evaluations including an Expanded Disability Status Scale (EDSS) assessment every 6 months, and an annual 3T brain MRI. PIRA was defined as having a confirmed disability progression independent of relapse activity. CSF levels of 68 inflammatory molecules were evaluated in combination with white matter and cortical lesion number (CLn) and volume, and regional gray matter thickness and volume.

RESULTS

During the follow-up, 23 patients with RRMS (28.8%) experienced PIRA. At diagnosis, participants with PIRA were older (44.0 ± 10.7 vs 37.4 ± 12.4, p = 0.017) and with more disability (median EDSS score [interquartile range] of 3 [range 2-4] for PIRA vs 1.5 [range 1-2] for no PIRA group, p < 0.001). Random forest selected LIGHT, CXCL13, sTNFR1, sTNFR2, CCL7, MIF, sIL6Rbeta, IL35, CCL2, and IFNβ as the CSF markers best associated with PIRA. sTNFR1 (hazard ratio [HR] 10.11 [2.61-39.10], p = 0.001), sTNFR2 (HR 5.05 [1.63-15.64], p = 0.005), and LIGHT (HR 1.79 [1.11-2.88], p = 0.018) were predictors of PIRA at regression analysis. Baseline thalamus volume (HR 0.98 [0.97-0.99], p = 0.005), middle frontal gyrus thickness (HR 0.05 [0.01-0.72], p = 0.028), and CLn (HR 1.15 [1.05-1.25], p = 0.003) were MRI predictors of PIRA.

DISCUSSION

A specific intrathecal inflammatory profile associated with TNF superfamily markers, CLn, and atrophy of several cortical and deep gray matter regions, assessed at time of diagnosis, is predictive of PIRA in early MS.

Recent developments in multiple sclerosis neuropathology

PURPOSE OF REVIEW

Neuropathological studies in human brain tissue are indispensable for our understanding of disease mechanisms in multiple sclerosis (MS). They inform concepts of lesion evolution, tissue regeneration and disease progression, and ideally reveal new disease mechanisms and therapeutic targets. Here we review recent neuropathological studies that have advanced our knowledge of MS pathogenesis.

RECENT FINDINGS

Recent cohort studies support the notion that different clinical MS disease phenotypes share underlying pathological features, and that clinical and pathological heterogeneity is derived from a variable combination of innate and adaptive inflammation, demyelinating activity, and neuroaxonal loss. Importantly, emerging technologies for spatial transcriptome analysis enable an unprecedented glimpse into the cellular composition and molecular mechanisms involved in lesion evolution. These promising technologies will help identify the identification of molecular hubs governing tissue damage and regeneration.

SUMMARY

Recent neuropathological studies helped to identify tissue correlates of disability and disease progression. Substantial progress in molecular brain tissue analysis revealed the complexity of MS-related tissue features. Close collaboration between tissue-based, molecular, bioinformatic, pharmacologic, imaging and clinical experts is needed to continue to advance the field, particularly for the benefit of people with progressive MS.

The ageing central nervous system in multiple sclerosis: the imaging perspective

The interaction between ageing and multiple sclerosis is complex and carries significant implications for patient care. Managing multiple sclerosis effectively requires an understanding of how ageing and multiple sclerosis impact brain structure and function. Ageing inherently induces brain changes, including reduced plasticity, diminished grey matter volume, and ischaemic lesion accumulation. When combined with multiple sclerosis pathology, these age-related alterations may worsen clinical disability. Ageing may also influence the response of multiple sclerosis patients to therapies and/or their side effects, highlighting the importance of adjusted treatment considerations. MRI is highly sensitive to age- and multiple sclerosis-related processes. Accordingly, MRI can provide insights into the relationship between ageing and multiple sclerosis, enabling a better understanding of their pathophysiological interplay and informing treatment selection. This review summarizes current knowledge on the immunopathological and MRI aspects of ageing in the CNS in the context of multiple sclerosis. Starting from immunosenescence, ageing-related pathological mechanisms and specific features like enlarged Virchow-Robin spaces, this review then explores clinical aspects, including late-onset multiple sclerosis, the influence of age on diagnostic criteria, and comorbidity effects on imaging features. The role of MRI in understanding neurodegeneration, iron dynamics and myelin changes influenced by ageing and how MRI can contribute to defining treatment effects in ageing multiple sclerosis patients, are also discussed.

Differential Analysis of Venous Sinus Diameters: Unveiling Vascular Alterations in Patients with Multiple Sclerosis

BACKGROUND

Alterations in the cerebral venous system have been increasingly recognized as a significant component of the pathophysiology of multiple sclerosis (MS). This study aimed to explore the relationship between venous sinus diameter and MS to understand potential vascular alterations in MS patients compared with controls. We sought to determine whether these alterations were correlated with disease characteristics such as duration, lesion type, and disability score.

METHODS

This study included 79 MS patients diagnosed according to the 2017 McDonald criteria and 67 healthy individuals. Magnetic resonance imaging (MRI) scans via a 1.5 Tesla system provided measurements of the superior sagittal sinus, right and left transverse sinus, sinus rectus, and venous structures. Statistical analysis was conducted via SPSS, employing independent sample t tests, ANOVA, chi-square tests, and Pearson correlation analysis, with the significance level set at p < 0.05.

RESULTS

This study revealed significant differences in venous sinus diameter between MS patients and controls, with MS patients exhibiting larger diameters. Specifically, patients with brainstem and spinal lesions had larger diameters in certain sinus regions. No significant correlations were found between venous sinus diameter and demographic factors, expanded disability status scale scores, or lesion counts. However, a significant increase in perivenular lesions was noted in patients with longer disease durations.

CONCLUSIONS

The findings indicate notable vascular alterations in MS patients, particularly in venous sinus diameters, suggesting a potential vascular component in MS pathology. The lack of correlation with conventional clinical and MRI metrics highlights the complexity of MS pathology. These insights underscore the need for further research, particularly longitudinal studies, to elucidate the role of venous changes in MS progression and their potential as therapeutic targets.

Reconciling lesions, relapses and smouldering associated worsening: A unifying model for multiple sclerosis pathogenesis

The failure of relapses and white matter lesions to properly explain long-term disability and progression in multiple sclerosis is compounded by its artificial separation into relapsing remitting, secondary progressive, and primary progressive pigeonholes. The well-known epidemiological disconnection between relapses and long-term disability progression has been rediscovered as "progression independent of relapse activity", i.e. smouldering multiple sclerosis. This smouldering associated worsening proceeds despite early and prolonged use of disease modification therapies, even those that are highly effective at preventing relapses and new/enhancing white matter lesions on MRI. We recognise that smouldering associated worsening and relapse/lesion associated worsening coexist, to varying extents. The extent of cortical demyelination has been shown to correlate significantly with the severity of diffuse injury in normal appearing white matter (post mortem histopathologically (r = 0.55; P = 0.001), and in vivo with MRI (r = -0.6874; P = 0.0006)) and does so independently of white matter lesion burden. Axon loss in the normal appearing white matter explains disability in multiple sclerosis better than focal white matter lesions do. Smouldering associated worsening typically manifests as a length-dependent central axonopathy. We propose a unifying model for multiple sclerosis pathogenesis, wherein accumulation of cortical lesion burden predisposes associated normal appearing white matter to diffuse injury, whilst also intensifying damage within white matter lesions. Our novel two-hit hypothesis implicates cortical disease as a culprit for smouldering multiple sclerosis, abetted by active focal inflammation in the white matter (and vice versa). Substantiation of the two-hit hypothesis would advance the importance of specific therapeutic intervention for (and monitoring of) cortical/meningeal inflammation in people with multiple sclerosis.

Digital Pathology Identifies Associations between Tissue Inflammatory Biomarkers and Multiple Sclerosis Outcomes

BACKGROUND

Multiple sclerosis (MS) is a clinically heterogeneous disease underpinned by inflammatory, demyelinating and neurodegenerative processes, the extent of which varies between individuals and over the course of the disease. Recognising the clinicopathological features that most strongly associate with disease outcomes will inform future efforts at patient phenotyping.

AIMS

We used a digital pathology workflow, involving high-resolution image acquisition of immunostained slides and opensource software for quantification, to investigate the relationship between clinical and neuropathological features in an autopsy cohort of progressive MS.

METHODS

Sequential sections of frontal, cingulate and occipital cortex, thalamus, brain stem (pons) and cerebellum including dentate nucleus (n = 35 progressive MS, females = 28, males = 7; age died = 53.5 years; range 38-98 years) were immunostained for myelin (anti-MOG), neurons (anti-HuC/D) and microglia/macrophages (anti-HLA). The extent of demyelination, neurodegeneration, the presence of active and/or chronic active lesions and quantification of brain and leptomeningeal inflammation was captured by digital pathology.

RESULTS

Digital analysis of tissue sections revealed the variable extent of pathology that characterises progressive MS. Microglia/macrophage activation, if found at a higher level in a single block, was typically elevated across all sampled blocks. Compartmentalised (perivascular/leptomeningeal) inflammation was associated with age-related measures of disease severity and an earlier death.

CONCLUSION

Digital pathology identified prognostically important clinicopathological correlations in MS. This methodology can be used to prioritise the principal pathological processes that need to be captured by future MS biomarkers.

The prevalence and topography of spinal cord demyelination in multiple sclerosis: a retrospective study

Spinal cord pathology is a major determinant of irreversible disability in progressive multiple sclerosis. The demyelinated lesion is a cardinal feature. The well-characterised anatomy of the spinal cord and new analytic approaches allows the systematic study of lesion topography and its extent of inflammatory activity unveiling new insights into disease pathogenesis. We studied cervical, thoracic, and lumbar spinal cord tissue from 119 pathologically confirmed multiple sclerosis cases. Immunohistochemistry was used to detect demyelination (PLP) and classify lesional inflammatory activity (CD68). Prevalence and distribution of demyelination, staged by lesion activity, was determined and topographical maps were created to identify patterns of lesion prevalence and distribution using mixed models and permutation-based voxelwise analysis. 460 lesions were observed throughout the spinal cord with 76.5% of cases demonstrating at least 1 lesion. The cervical level was preferentially affected by lesions. 58.3% of lesions were inflammatory with 87.9% of cases harbouring at least 1 inflammatory lesion. Topographically, lesions consistently affected the dorsal and lateral columns with relative sparing of subpial areas in a distribution mirroring the vascular network. The presence of spinal cord lesions and the proportion of active lesions related strongly with clinical disease milestones, including time from onset to wheelchair and onset to death. We demonstrate that spinal cord demyelination is common, highly inflammatory, has a predilection for the cervical level, and relates to clinical disability. The topography of lesions in the dorsal and lateral columns and relative sparing of subpial areas points to a role of the vasculature in lesion pathogenesis, suggesting short-range cell infiltration from the blood and signaling molecules circulating in the perivascular space incite lesion development. These findings challenge the notion that end-stage progressive multiple sclerosis is 'burnt out' and an outside-in lesional gradient predominates in the spinal cord. Taken together, this study provides support for long-term targeting of inflammatory demyelination in the spinal cord and nominates vascular dysfunction as a potential target for new therapeutic approaches to limit irreversible disability.