Lesion Volume in Relapsing Multiple Sclerosis is Associated with Perivascular Space Enlargement at the Level of the Basal Ganglia

Enlarged perivascular space in the temporal lobe as a prognostic marker in temporal lobe epilepsy with hippocampal sclerosis

OBJECTIVE

This study was undertaken to investigate the regional burden of enlarged perivascular spaces (EPVSs) in patients with temporal lobe epilepsy with hippocampal sclerosis (TLE-HS) and explore its prognostic relevance.

METHODS

In this retrospective observational study, EPVSs in the temporal lobe (T-EPVS), centrum semiovale (CS-EPVS), basal ganglia (BG-EPVS), midbrain, and hippocampus were visually rated in 68 treatment-naïve patients with TLE-HS. Regional EPVS burden was dichotomized into high and low degrees (cutoff: >10 for BG-EPVS/T-EPVS; >20 for CS-EPVS). Cox proportional hazards models were used to determine the potential predictors of seizure freedom (SF; no seizure for >1 year) and delayed SF (SF achieved >6 months after initiating antiseizure medication [ASM]). Multivariate logistic regression using stepwise variable selection based on the Akaike information criterion was performed to investigate whether EPVS burden was associated with medical refractoriness (never achieving SF).

RESULTS

Of the 68 patients, 20 were classified into the refractory group (29.4%). The high T-EPVS group had an older epilepsy onset (37.3 ± 12.3 vs. 26.5 ± 13.0 years, p = .005), higher pretreatment seizure density (median = 12.0, interquartile range [IQR] = 5.0-20.0 vs. 4.0, IQR = 2.0-10.5, p = .008), and lower focal to bilateral tonic-clonic seizure prevalence (13.3% vs. 73.6%, p < .001) than the low T-EPVS group. High T-EPVS burden (odds ratio [OR] = 10.908, 95% confidence interval [CI] = 1.895-62.789) was an independent predictor of medial refractoriness, along with female sex (OR = 12.906, 95% CI = 2.214-75.220) and ASM treatment duration (OR = .985, 95% CI = .971-.999). The low T-EPVS group had higher probability of achieving delayed SF than the high T-EPVS group (pLog-rank = .030, pCox regression = .038), whereas the probability of achieving SF was comparable between the two groups (pLog-rank = .053, pCox regression = .146).

SIGNIFICANCE

Increased T-EPVS burden may serve as an imaging marker of unfavorable prognosis in patients with TLE-HS, underscoring the potential role of perivascular dysfunction in diminished ASM response.

Glymphatic system: a gateway for neuroinflammation

The glymphatic system is a relatively recently identified fluid exchange and transport system in the brain. Accumulating evidence indicates that glymphatic function is impaired not only in central nervous system disorders but also in systemic diseases. Systemic diseases can trigger the inflammatory responses in the central nervous system, occasionally leading to sustained inflammation and functional disturbance of the central nervous system. This review summarizes the current knowledge on the association between glymphatic dysfunction and central nervous system inflammation. In addition, we discuss the hypothesis that disease conditions initially associated with peripheral inflammation overwhelm the performance of the glymphatic system, thereby triggering central nervous system dysfunction, chronic neuroinflammation, and neurodegeneration. Future research investigating the role of the glymphatic system in neuroinflammation may offer innovative therapeutic approaches for central nervous system disorders.

Enlarged perivascular spaces are associated with brain microangiopathy and aging in multiple sclerosis

BACKGROUND

Growing evidence links brain-MRI enlarged perivascular spaces (EPVS) and multiple sclerosis (MS), but their role remains unclear.

OBJECTIVE

This study aimed to investigate the cross-sectional associations of EPVS with several neuroinflammatory and neurodegenerative features in a large multicentric-MS cohort.

METHODS

In total, 207 patients underwent 3T axial-T2-weighted brain-MRI for EPVS assessment (EPVS dichotomized into high/low according to ⩾ 2/< 2 rating categories). MRI biomarkers included brain-predicted age and brain-predicted age difference (brain-PAD), central vein sign (CVS)-positive lesion percentage (CVS%), paramagnetic rim and cortical lesions, T2-lesion load, and brain volumetry. The variable relative importance for EPVS-category prediction was explored using a classification random forest approach.

RESULTS

High EPVS patients were older (49 vs 44 years, p = 0.003), had ⩾ 1 vascular risk factors (VRFs; p = 0.005), lower CVS% (67% vs 78%, p < 0.001), reduced brain volumes (whole brain: 0.63 vs 0.73, p = 0.01; gray matter: 0.36 vs 0.40; p = 0.002), and older brain-predicted age (58 vs 50 years, p < 0.001). No differences were found for neuroinflammatory markers. After adjusting for age and VFRs (multivariate analyses), the high EPVS category correlated with lower CVS% (odds ratio (OR) = 0.98, 95% confidence interval (CI) = 0.96-0.99; p = 0.02), lower whole brain (OR = 0.01, 95% CI = 0.0003-0.5; p = 0.02), gray matter (OR = 0.0004, 95% CI = 0.0000004-0.4; p = 0.03) volumes, and higher brain-PAD (OR = 1.05, 95% CI = 1.01-1.09; p = 0.02). Random forest identified brain-PAD as the most important predictor of high EPVS.

CONCLUSION

EPVS in MS likely reflect microangiopathic disease rather than neuroinflammation, potentially contributing to accelerated neurodegeneration.

Noninvasive Magnetic Resonance Imaging Measures of Glymphatic System Activity

The comprehension of the glymphatic system, a postulated mechanism responsible for the removal of interstitial solutes within the central nervous system (CNS), has witnessed substantial progress recently. While direct measurement techniques involving fluorescence and contrast agent tracers have demonstrated success in animal studies, their application in humans is invasive and presents challenges. Hence, exploring alternative noninvasive approaches that enable glymphatic research in humans is imperative. This review primarily focuses on several noninvasive magnetic resonance imaging (MRI) techniques, encompassing perivascular space (PVS) imaging, diffusion tensor image analysis along the PVS, arterial spin labeling, chemical exchange saturation transfer, and intravoxel incoherent motion. These methodologies provide valuable insights into the dynamics of interstitial fluid, water permeability across the blood-brain barrier, and cerebrospinal fluid flow within the cerebral parenchyma. Furthermore, the review elucidates the underlying concept and clinical applications of these noninvasive MRI techniques, highlighting their strengths and limitations. It addresses concerns about the relationship between glymphatic system activity and pathological alterations, emphasizing the necessity for further studies to establish correlations between noninvasive MRI measurements and pathological findings. Additionally, the challenges associated with conducting multisite studies, such as variability in MRI systems and acquisition parameters, are addressed, with a suggestion for the use of harmonization methods, such as the combined association test (COMBAT), to enhance standardization and statistical power. Current research gaps and future directions in noninvasive MRI techniques for assessing the glymphatic system are discussed, emphasizing the need for larger sample sizes, harmonization studies, and combined approaches. In conclusion, this review provides invaluable insights into the application of noninvasive MRI methods for monitoring glymphatic system activity in the CNS. It highlights their potential in advancing our understanding of the glymphatic system, facilitating clinical applications, and paving the way for future research endeavors in this field. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 5.

The relationship between inflammation, impaired glymphatic system, and neurodegenerative disorders: A vicious cycle

The term "glymphatic" emerged roughly a decade ago, marking a pivotal point in neuroscience research. The glymphatic system, a glial-dependent perivascular network distributed throughout the brain, has since become a focal point of investigation. There is increasing evidence suggesting that impairment of the glymphatic system appears to be a common feature of neurodegenerative disorders, and this impairment exacerbates as disease progression. Nevertheless, the common factors contributing to glymphatic system dysfunction across most neurodegenerative disorders remain unclear. Inflammation, however, is suspected to play a pivotal role. Dysfunction of the glymphatic system can lead to a significant accumulation of protein and waste products, which can trigger inflammation. The interaction between the glymphatic system and inflammation appears to be cyclical and potentially synergistic. Yet, current research is limited, and there is a lack of comprehensive models explaining this association. In this perspective review, we propose a novel model suggesting that inflammation, impaired glymphatic function, and neurodegenerative disorders interconnected in a vicious cycle. By presenting experimental evidence from the existing literature, we aim to demonstrate that: (1) inflammation aggravates glymphatic system dysfunction, (2) the impaired glymphatic system exacerbated neurodegenerative disorders progression, (3) neurodegenerative disorders progression promotes inflammation. Finally, the implication of proposed model is discussed.

The glymphatic system and multiple sclerosis: An evolving connection

Multiple sclerosis (MS) is a complex autoimmune disorder that affects the central nervous system, resulting in demyelination and an array of neurological manifestations. Recently, there has been significant scientific interest in the glymphatic system, which operates as a waste-clearance system for the brain. This article reviews the existing literature, and explores potential links between the glymphatic system and MS, shedding light on its evolving significance in the context of MS pathogenesis. The authors consider the pathophysiological implications of glymphatic dysfunction in MS, the impact of disrupted sleep on glymphatic function, and the bidirectional relationship between MS and sleep disturbances. By offering an understanding of the intricate interplay between the glymphatic system and MS, this review provides valuable insights which may lead to improved diagnostic techniques and more effective therapeutic interventions.

Imaging of brain barrier inflammation and brain fluid drainage in human neurological diseases

The intricate relationship between the central nervous system (CNS) and the immune system plays a crucial role in the pathogenesis of various neurological diseases. Understanding the interactions among the immunopathological processes at the brain borders is essential for advancing our knowledge of disease mechanisms and developing novel diagnostic and therapeutic approaches. In this review, we explore the emerging role of neuroimaging in providing valuable insights into brain barrier inflammation and brain fluid drainage in human neurological diseases. Neuroimaging techniques have enabled us not only to visualize and assess brain structures, but also to study the dynamics of the CNS in health and disease in vivo. By analyzing imaging findings, we can gain a deeper understanding of the immunopathology observed at the brain-immune interface barriers, which serve as critical gatekeepers that regulate immune cell trafficking, cytokine release, and clearance of waste products from the brain. This review explores the integration of neuroimaging data with immunopathological findings, providing valuable insights into brain barrier integrity and immune responses in neurological diseases. Such integration may lead to the development of novel diagnostic markers and targeted therapeutic approaches that can benefit patients with neurological disorders.

Promises of Lipid-Based Nanocarriers for Delivery of Dimethyl Fumarate to Multiple Sclerosis Brain

Multiple sclerosis (MS) is a neurodegenerative autoimmune disorder of the central nervous system (CNS) infecting 2.5 million people worldwide. It is the most common nontraumatic neurological impairment in young adults. The blood-brain barrier rupture for multiple sclerosis pathogenesis has two effects: first, during the onset of the immunological attack, and second, for the CNS self-sustained "inside-out" demyelination and neurodegeneration processes. In addition to genetic variations, environmental and lifestyle variables can also significantly increase the risk of developing MS. Dimethyl fumarate (DMF) and sphingosine-1-phosphate (S1P) receptor modulators that may pass the blood-brain barrier and have positive direct effects in the CNS with quite diverse mechanisms of action raise the possibility that a combination therapy could be successful in treating MS. Lipid nanocarriers are recognized as one of the best drug delivery techniques to the brain for effective brain delivery. Numerous scientific studies have shown that lipid nanoparticles can enhance the lipid solubility, oral bioavailability, and brain availability of the drugs. Nanolipidic carriers for DMF delivery could be derived through vitamin D, tocopherol acetate, stearic acid, quercetin, cell-mimicking platelet-based, and chitosan-alginate core-shell-corona-shaped nanoparticles. Clinical and laboratory diagnosis of MS can be performed mainly through magnetic resonance imaging. The advancements in nanotechnology have enabled the clinicians to cross the blood-brain barrier and to target the brain and central nervous system of the patient with multiple sclerosis.

Symmetry differences of structural connectivity in multiple sclerosis and healthy state

Focal and diffuse cerebral damages occur in Multiple Sclerosis (MS) that promotes profound shifts in local and global structural connectivity parameters, mainly derived from diffusion tensor imaging. Most of the reconstruction analyses have applied conventional tracking algorithms largely based on the controversial streamline count. For a more credible explanation of the diffusion MRI signal, we used convex optimization modeling for the microstructure-informed tractography2 (COMMIT2) framework. All multi-shell diffusion data from 40 healthy controls (HCs) and 40 relapsing-remitting MS (RRMS) patients were transformed into COMMIT2-weighted matrices based on the Schefer-200 parcels atlas (7 networks) and 14 bilateral subcortical regions. The success of the classification process between MS and healthy state was efficiently predicted by the left DMN-related structures and visual network-associated pathways. Additionally, the lesion volume and age of onset were remarkably correlated with the components of the left DMN. Using complementary approaches such as global metrics revealed differences in WM microstructural integrity between MS and HCs (efficiency, strength). Our findings demonstrated that the cutting-edge diffusion MRI biomarkers could hold the potential for interpreting brain abnormalities in a more distinctive way.

The etiology and evolution of magnetic resonance imaging-visible perivascular spaces: Systematic review and meta-analysis

Objectives

Perivascular spaces have been involved in neuroinflammatory and neurodegenerative diseases. Upon a certain size, these spaces can become visible on magnetic resonance imaging (MRI), referred to as enlarged perivascular spaces (EPVS) or MRI-visible perivascular spaces (MVPVS). However, the lack of systematic evidence on etiology and temporal dynamics of MVPVS hampers their diagnostic utility as MRI biomarker. Thus, the goal of this systematic review was to summarize potential etiologies and evolution of MVPVS.

Methods

In a comprehensive literature search, out of 1,488 unique publications, 140 records assessing etiopathogenesis and dynamics of MVPVS were eligible for a qualitative summary. 6 records were included in a meta-analysis to assess the association between MVPVS and brain atrophy.

Results

Four overarching and partly overlapping etiologies of MVPVS have been proposed: (1) Impairment of interstitial fluid circulation, (2) Spiral elongation of arteries, (3) Brain atrophy and/or perivascular myelin loss, and (4) Immune cell accumulation in the perivascular space. The meta-analysis in patients with neuroinflammatory diseases did not support an association between MVPVS and brain volume measures [R: −0.15 (95%-CI −0.40–0.11)]. Based on few and mostly small studies in tumefactive MVPVS and in vascular and neuroinflammatory diseases, temporal evolution of MVPVS is slow.

Conclusion

Collectively, this study provides high-grade evidence for MVPVS etiopathogenesis and temporal dynamics. Although several potential etiologies for MVPVS emergence have been proposed, they are only partially supported by data. Advanced MRI methods should be employed to further dissect etiopathogenesis and evolution of MVPVS. This can benefit their implementation as an imaging biomarker.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=346564, identifier CRD42022346564.

Potential application of hydrogel to the diagnosis and treatment of multiple sclerosis

Abstract

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system. This disorder may cause progressive and permanent impairment, placing significant physical and psychological strain on sufferers. Each progress in MS therapy marks a significant advancement in neurological research. Hydrogels can serve as a scaffold with high water content, high expansibility, and biocompatibility to improve MS cell proliferation in vitro and therapeutic drug delivery to cells in vivo. Hydrogels may also be utilized as biosensors to detect MS-related proteins. Recent research has employed hydrogels as an adjuvant imaging agent in immunohistochemistry assays. Following an overview of the development and use of hydrogels in MS diagnostic and therapy, this review discussed hydrogel’s advantages and future opportunities in the diagnosis and treatment of MS.

Graphical abstract