Multiple sclerosis (MS) is a highly heterogeneous disease in its clinical manifestation and progression. Predicting individual disease courses is key for aligning treatments with underlying pathobiology. We developed an unsupervised machine learning model integrating MRI-derived measures with serum neurofilament light chain (sNfL) levels to identify biologically informed MS subtypes and stages. Using a training cohort of patients with relapsing-remitting and secondary progressive MS (n = 189), with validation on a newly diagnosed population (n = 445), we discovered two distinct subtypes defined by the timing of sNfL elevation and MRI abnormalities (early- and late-sNfL types). In comparison to MRI-only models, incorporating sNfL with MRI improved correlations of data-derived stages with the Expanded Disability Status Scale in the training (Spearman's ρ = 0.420 versus MRI-only ρ = 0.231, P = 0.001) and external test sets (ρ = 0.163 for MRI-sNfL, versus ρ = 0.067 for MRI-only). The early-sNfL subtype showed elevated sNfL, corpus callosum injury and early lesion accrual, reflecting more active inflammation and neurodegeneration, whereas the late-sNfL group showed early volume loss in the cortical and deep grey matter volumes, with later sNfL elevation. Cross-sectional subtyping predicted longitudinal radiological activity: the early-sNfL group showed a 144% increased risk of new lesion formation (hazard ratio = 2.44, 95% confidence interval 1.38-4.30, P < 0.005) compared with the late-sNfL group. Baseline subtyping, over time, predicted treatment effect on new lesion formation on the external test set (faster lesion accrual in early-sNfL compared with late-sNfL, P = 0.01), in addition to treatment effects on brain atrophy (early sNfL average percentage brain volume change: -0.41, late-sNfL = -0.31, P = 0.04). Integration of sNfL provides an improved framework in comparison to MRI-only subtyping of MS to stage disease progression and inform prognosis. Our model predicted treatment responsiveness in early, more active disease states. This approach offers a powerful alternative to conventional clinical phenotypes and supports future efforts to refine prognostication and guide personalized therapy in MS.

Pathogenic GAA repeat expansions in FGF14 are an established cause of late-onset cerebellar ataxia, but have not been linked to Parkinson's disease (PD). Given emerging evidence that repeat expansions in ataxia-associated genes like RFC1, can contribute to atypical or familial forms of PD, we investigated whether FGF14 expansions might play a similar role. Using long-read whole-genome sequencing, we analyzed 411 individuals with PD and 197 neurologically healthy controls from the PPMI cohort, together with 1,429 additional controls from the NIH CARD initiative, the 1000 Genomes Project, and the All of Us program, representing globally diverse populations. We identified pathogenic FGF14 GAA repeat expansions in five individuals with PD and one control. All five individuals fit the clinical criteria of PD and showed typical patterns of neurodegeneration on DaTSCAN imaging; α-synuclein aggregation was confirmed by a positive seeding assay among four individuals with available data. These findings broaden the phenotypic spectrum of FGF14 repeat-associated disease and suggest a rare, previously unrecognized genetic contributor to PD. To our knowledge, this is the first report implicating FGF14 in PD and underscores the utility of long-read sequencing for detecting hidden forms of pathogenic variation in unresolved cases.

Immune dysfunction is implicated in the pathophysiology of schizophrenia. The 18-kDa translocator protein (TSPO), expressed by various cell types including microglia and astrocytes, is widely used as a marker for neuroinflammation and can be quantified in vivo using positron emission tomography (PET). However, findings from TSPO PET studies in recent-onset psychosis have been inconsistent, and it remains unknown whether TSPO levels can be modified in schizophrenia. We addressed these questions with a baseline case-control comparison of patients with a first-episode psychotic disorder who were symptomatic despite antipsychotic treatment and healthy volunteers, and a longitudinal study testing the effects of natalizumab (a monoclonal antibody previously shown to reduce TSPO levels in neuroinflammatory conditions) on TSPO levels and symptoms in patients. Baseline and three-month follow-up brain imaging was carried out using [18F]DPA-714 TSPO PET, quantified as distribution volume ratio (DVR) in total, frontal lobe, and temporal lobe grey matter. A total of 103 volunteers (62 patients, 41 healthy controls) received baseline brain imaging, and 47 patients completed follow-up imaging after receiving natalizumab (n = 31) or placebo (n = 16) infusions. Natalizumab was well tolerated with no serious treatment-related adverse events. The patient group also received clinical assessments with the Positive and Negative Syndrome Scale (PANSS) at baseline and follow-up. At baseline, DVR was significantly higher in patients relative to controls in total (η2 = 0.04) and temporal lobe (η2 = 0.06) grey matter. However, there was no significant change in DVR across these regions following natalizumab or placebo treatment. Mean ± SD cerebrospinal fluid levels of natalizumab after treatment were 10.7 ± 27.2 ng/mL; indicating that the monoclonal antibody crossed the blood brain barrier. Patients receiving natalizumab showed a modest but statistically significant improvement in PANSS total scores (mean ± SD change: -3.7 ± 9.1, Cohen's d = 0.40, P = 0.017), though there was no relationship between change in DVR and change in symptom severity (P > 0.05). These findings are consistent with elevated grey matter TSPO levels in first-episode psychosis relative to healthy controls. Although natalizumab treatment was associated with a modest reduction in symptoms, the absence of corresponding changes in DVR suggests that higher grey matter TSPO may reflect expression by non-microglial cells. The lack of significant changes in the placebo group indicate it is a stable trait biomarker. Further work is needed to clarify the functional relevance and cellular specificity of TSPO alterations in psychosis. ClinicalTrials.gov: NCT03093064.

The brain's white matter is a dynamic and active tissue which coordinates brain function through the transmission and modulation of information between regions via action potentials. While scientific and clinical interest in studying white matter via diffusion imaging has grown rapidly, an electrophysiologic understanding of white matter in healthy and disease states remains elusive. And although human white matter recordings are acquired in intracranial EEG studies in epilepsy, clinical evaluation typically focuses on gray matter structures to understand seizure generation and plan surgical intervention despite the role of white matter in coordinating and propagating epileptic activity. Here, we study white matter recordings in 29 patients with drug-resistant epilepsy who underwent stereo EEG for surgical evaluation. We elucidate properties of both electrical activity and network connectivity within white matter and its relationship to cortical connectivity. We further integrate tractography and stereo EEG recordings to demonstrate that our observed white matter dynamics reflect underlying structural connectivity patterns between gray matter structures, emphasizing white matter's role in information transmission during seizures. Finally, we find that increased white matter connectivity to the presumed seizure onset zone is associated with poor surgical outcome after epilepsy surgery. Our findings support the 'The Distributed Epileptic Network Hypothesis', which states that the true seizure onset zone is not a single focal anatomical location per se (in some cases), but rather a distributed epileptic network where many brain regions interact together, allowing a patient to enter a seizure state. Therefore, we propose that white matter electrophysiology and connectivity may represent information on the spatial distribution of epilepsy and thus its amenability to intervention, whether through focal ablation or modulation through devices. Overall, white matter functional recordings may provide a wealth of currently untapped knowledge about the neurobiology of disease and could guide clinical decision making in treating drug-resistant epilepsy patients.

Fluid biomarkers to diagnose frontotemporal lobar degeneration (FTLD) are currently lacking. In this study, we aimed to identify proteomic changes in cerebrospinal fluid (CSF) associated with FTLD pathogenesis, focusing on signatures unique to different genetic groups. Additionally, we sought proteins distinguishing FTLD-spectrum disorders from controls. To this end, we measured a comprehensive library of over 2900 proteins in CSF using proximity extension assay technology in two well-characterized FTLD cohorts. The discovery cohort, selected from the GENFI cohort, included 47 symptomatic pathogenic variant carriers (22 C9orf72, 14 GRN, 10 MAPT and 1 TARDBP), 124 presymptomatic pathogenic variant carriers (55 C9orf72, 44 GRN, 24 MAPT and 1 TARDBP) and 57 healthy non-carriers. The validation cohort comprised individuals clinically diagnosed with an FTLD-spectrum disorder (n = 132) and cognitively intact controls (n = 32). We assessed differentially abundant proteins using linear regression, adjusting for age and sex. Overrepresentation analysis was conducted for the three genetic groups using Gene Ontology Biological Processes as ontology source. To develop diagnostic tools, we applied a LASSO regression, establishing two types of panels: one to distinguish individuals with an FTLD-spectrum disorder from controls (FTLD panel) and another to differentiate individuals with underlying TDP pathology from controls (TDP panel). We observed 23 dysregulated proteins in symptomatic carriers. Of these, four were also significantly dysregulated (NEFL, TPM3, MSLN and DNM3) in the validation cohort. When focusing on genetic subgroups, 63 upregulated proteins were observed in symptomatic MAPT carriers, with enriched biological pathways linked to immune function. In symptomatic C9orf72 carriers, four proteins - related to energy metabolism - were upregulated. When limiting symptomatic carriers to GRN, six proteins were dysregulated, with enriched pathways involved in neuronal development and projection. Notably, NEFL and TPM3 were consistently significant in all comparisons across both cohorts. We developed two diagnostic panels: one for FTLD and one for FTLD-TDP. The FTLD panel consisted of six proteins (NEFL, RBFOX3, NPTX1, TFF1, ENTPD5, and CNP). The TDP panel was made up of seven proteins (NEFL, RBFOX3, CBLN4, ENTPD5, CCL25, CNP, and MMP1). Both panels were successfully replicated in the validation cohort (AUC of 0.94 and 0.96 respectively). This study highlights distinct proteomic signatures across FTLD genetic subgroups and their associated pathologies using a targeted proteomic approach. Additionally, we present two diagnostic panels-comprising both established and novel proteins-that effectively differentiate individuals with FTLD-spectrum disorders from healthy controls, offering promising avenues for improved clinical diagnosis.

Despite the universal need for sleep across animal species, the biological mechanisms underlying the restorative aspects of sleep remain poorly understood. While sleep architecture is traditionally evaluated using EEG, multiple studies have shown a mismatch between EEG-defined parameters and subjective sleep quality. In particular, slow-wave activity - a hallmark of non-REM (NREM) sleep - does not consistently align with perceptions of sleep depth or subsequent well-being. This discrepancy suggests that core physiological processes beyond neuronal activity contribute to the restorative value of sleep. Recent discoveries have identified the glymphatic system as a brain-wide clearance pathway that facilitates the removal of metabolic waste during sleep. In rodents, glymphatic activity is driven by a complex interplay between norepinephrine oscillations, vascular dynamics, and cerebrospinal fluid (CSF) flow - particularly during NREM sleep. Human imaging studies have revealed parallel signatures, including large-scale CSF pulsations and inverse coupling between blood and CSF volumes during sleep. Disruption of these infraslow dynamics has been observed in conditions such as insomnia, chronic fatigue, and sleep misperception, suggesting a potential link between impaired glymphatic function and non-restorative sleep. This review synthesizes the current evidence for glymphatic clearance as a contributor to sleep's restorative function, discusses emerging biomarkers, such as cyclic alternating patterns (CAP) and pupil-based proxies of noradrenergic tone, and highlights the need for improved methods to evaluate glymphatic function in humans. We propose that brain clearance may represent a key physiological determinant of restorative sleep and suggest future directions to test this hypothesis across health and disease.

Neurons rely on finely tuned RNA regulatory mechanisms to sustain their specialized functions, with heterogeneous nuclear ribonucleoproteins (hnRNPs) emerging as key regulators of these processes. hnRNPs exert multilayered control over synaptic plasticity, axonal function, and neurodevelopmental gene expression by dynamically coordinating mRNA splicing, stability, transport, and local translation. Given their pivotal role in neuronal RNA metabolism, recent discoveries have highlighted how hnRNP dysfunction drives pathological RNA dysregulation across a spectrum of neurological disorders. This review provides insights into hnRNP-mediated RNA regulation in the brain, examines their contributions to neurological diseases, and explores how targeting these proteins could pave the way for novel therapeutic strategies to preserve neuronal integrity across diverse neurological conditions.

Over the past century, studying the human brain has been one of the most complex and enduring biological challenges. Initial approaches, ranging from gross neural anatomy to cellular subtype organization, have significantly advanced our understanding of the intricate structure of the human brain. Recent innovations in spatial transcriptomic technologies offer high-resolution insights into mRNA expression at single-cell or even subcellular resolution. Developing a greater understanding of the spatial expression of genes in specific cell types in the human brain can provide additional insights into their functions and underlying mechanisms that influence neurological disease states. Whilst these tools have been highly successful in rodent and non-human primate brains, analysis of the human brain has several specific challenges. In this review, we first provide a comparison of spatial transcriptomics tools, followed by a summary of studies using these tools in human brains, and finally, discuss the challenges and opportunities associated. The guidelines should enable researchers to address the challenges of using new spatial transcriptomics technologies to analyse complex organs like the human brain.

Sporadic Alzheimer's disease (sAD) is marked by dysregulated lipid metabolism, prominently involving apolipoprotein E (ApoE). MicroRNA-33 (miR-33) has emerged as a key regulator of lipid homeostasis, yet its role in sAD remains unclear. This study investigated miR-33 dysregulation in APOE ε4 allele (ApoE4)-associated sAD and explored its therapeutic potential using clustered regulatory interspaced short palindromic repeats (CRISPR)-mediated gene editing. Elevated miR-33 expression was observed in both AD patients, particularly those with ApoE4-associated sAD, and in the ApoE4 mouse model, implicating its role in AD pathology. Using CRISPR/Cas9, we modulated miR-33 expression in astrocytes to regulate ApoE lipidation and ameliorate AD-related pathology. Our results show that targeted miR-33 regulation in astrocytes via CRISPR/Cas9 restores ApoE lipidation and mitigates AD pathology in both in vitro and in vivo AD mice. Additionally, applying this gene therapy approach in ApoE4 sAD patient cell lines highlights its translational potential for therapeutic intervention. In conclusion, our findings elucidate miR-33's role in AD pathogenesis and underscore the therapeutic promise of CRISPR-mediated miR-33 targeting for restoring lipid homeostasis and ameliorating AD pathology. This study provides valuable insights into developing miRNA-based gene therapy strategies for treating sAD.

Frontotemporal dementia (FTD) shows autosomal dominant transmission in up to a third of families, enabling the study of presymptomatic and prodromal phases. Despite self-reported well-being and normal daily cognitive functioning, brain structural changes are evident a decade or more before the expected onset of disease. This divergence between cognitive function and brain structure contrasts with the coupling of structural and functional decline after symptom onset. In healthy ageing, it has been shown that functional connectivity is a better predictor of cognitive function than volumetric structural imaging. We previously proposed that in the presymptomatic phase of genetic FTD, the maintenance of brain functional network integrity enables carriers of pathogenic variants to sustain cognitive performance. However, prior work has focused on a small number of, often predefined, networks. This provides a limited and potentially biased characterisation of the substrates and moderators of brain network integration. Here, we test the hypothesis that brain-wide functional integration in FTD determines resilience to progressive pathology before symptom onset. We assess functional connectome integration in 289 presymptomatic carriers of pathogenic variants associated with FTD using functional magnetic resonance imaging in relation to cognition and contrast with 271 family members without pathogenic variants. Because structural atrophy, functional integration and cognitive profiles are multivariate, we used canonical correlation models, supplemented by multiple linear regression models for each imaging modality. We confirmed progressive atrophy and normal cognitive function in presymptomatic carriers compared to non-carriers. Notably, functional integration was preserved in presymptomatic carriers across age, while it declined in familial non-carriers. The strongest effects were observed in cognitive control networks. The changes in functional integration in presymptomatic carriers were behaviourally relevant and independent of the severity of atrophy, suggesting a resilience mechanism in those at risk of dementia. To generate hypotheses about the genetic and neurometabolic basis of resilience, we assessed the spatial overlap between behaviourally-relevant functional integration maps and gene transcription profiles. These spatial correlations suggested resilience signatures to glial cell composition (astrocytes, microglia, oligodendrocytes), revealing cellular mechanisms inaccessible to standard neuroimaging. Our findings suggest that resilience to atrophy is associated with enhanced functional integration, protecting against clinical conversion for many years in individuals at risk of dementia. This result has implications for the design of presymptomatic disease-modifying therapy trials and gives hope for therapeutic strategies aimed at enhancing resilience and ability to maintain function despite the presence of genetically determined neuropathology.

Parkinson's disease is a progressive neurodegenerative disorder characterized by motor dysfunction, dopaminergic neuronal loss in the substantia nigra and abnormal accumulation of α-synuclein Lewy bodies. Research suggests that the cerebrovascular system plays a role in fluid dynamics, waste clearance and removal of abnormal proteins. Imaging studies show that this waste clearance system, known as the glymphatic system, is disrupted in Parkinson's disease, highlighting its involvement in the disease. This immunohistochemical human brain tissue study quantified changes in the cerebrovascular system (perivascular space, string vessels, pericytes, aquaporin-4 and astrocytes) in Parkinson's disease (n = 18) cases with variable disease durations (median = 14 years, range = 19 years) compared with age- and post-mortem-matched (P > 0.05) control cases (n = 7). Analysis was carried out in brain regions variably affected by cell loss (substantia nigra) and protein deposition (substantia nigra and medial temporal cortex). The occipital cortex was included because this region is not affected by cell loss or protein deposition. Group differences were analysed, and the relationship with protein deposition (Lewy body stage, amyloid score and neurofibrillary tangle score) was assessed. Although total astrocyte density did not change (P > 0.05), Parkinson's disease cases exhibited reduced aquaporin-4 in astrocytic endfeet and enlargement of the arteriolar and venular perivascular space. Significant changes in the capillary network were also observed, with increased presence of string vessels (P < 0.001) and pericyte loss (P < 0.001), changes likely to impact blood flow and its regulation. The increased presence of string vessels was significantly correlated with disease duration (P < 0.05), especially in the occipital cortex. The occipital cortex demonstrated the greatest decreases in pericytes (P < 0.001) and aquaporin-4 mislocalization (P < 0.05), and changes in pericyte density were also significant in the substantia nigra. In contrast, these changes were not significant in the medial temporal cortex despite protein deposition in this region. Although no Lewy pathology was detected in the occipital cortex, there was a positive relationship between Lewy body stage and perivascular space size (ρ = 0.6, P < 0.05). These findings reveal progressive, region-specific alterations in the cellular components of the glymphatic system and vascular integrity in Parkinson's disease. Notably, the correlation between increased presence of string vessels and disease duration, even in a region unaffected by protein deposition, suggests that vascular changes might play an important role in disease progression. These results emphasize the need for further investigation into the interplay between regional vascular changes and Parkinson's disease progression, which might offer new insights for therapeutic strategies.

Gait disturbance in individuals with spinal cord injury (SCI) at levels rostral to the lumbar locomotor centre results from disconnection between the supraspinal system and the spinal locomotor centre. Here, we present a non-invasive volition-controlled spinal stimulation paradigm that empowers paraplegic individuals to regain stepping control in their impaired legs. Using hand muscle-controlled magnetic stimulation targeting the lumbar spinal motor circuits in the preserved lumber cord, individuals with chronic SCI achieved control of start-stop motion, step length and cadence of bilateral cyclic stepping in paralysed legs. Stimulus-induced cyclic stepping with leg muscle EMG activity was evoked in all participants with complete or incomplete SCI, regardless of the lesion site between the thoracic and lumbar spinal cord. Combining voluntary gait effort with closed-loop stimulation further enhanced leg movements. Repeated application of this closed-loop stimulation led to progressive improvement in stimulus-induced stepping and muscle responses, particularly in participants with thoracic SCI, and in stimulus-free stepping, particularly in participants with incomplete SCI. Our findings indicate that the preserved lumbar spinal motor circuit plays a crucial role in improving stimulus-induced stepping, whereas the preserved descending pathway is required for improving stimulus-free stepping. This non-invasive closed-loop spinal stimulation paradigm bypasses the lesion site on the spinal cord and strengthens both the preserved spinal circuits and the descending pathways to allow bilateral stepping control to be regained after SCI. This approach holds great promise for SCI-related gait rehabilitation because it has the potential to lead to functional recovery. Furthermore, this approach offers a viable alternative for individuals with contraindications to invasive procedures or those who do not consent to surgical treatments.

Slowed information processing speed has long been considered the principal cognitive deficit in multiple sclerosis, with slowed cognitive speed presumed responsible for downstream deficits in other functions, including memory. This speed-centric model was established over three decades ago before disease-modifying therapies were available, and contrasts with our current clinical experience, but nonetheless remains dominant and unquestioned. We re-evaluated this model among current patients with multiple sclerosis diagnosed and cared for within the modern diagnostic and treatment era (2001-2025). Within a case-control cohort, persons with early relapsing-remitting disease (≤5.0 years since diagnosis, n=170) performed worse than neurologically-healthy controls (n=45) on memory but not cognitive speed, and cognitive speed among patients remained normal and stable over the next six years despite subtle memory decline. Relative to four historical studies of early relapsing-remitting disease (diagnosed using older criteria), effect sizes for case-control differences in our cohort were much lower for cognitive speed, but comparable for memory. An independent clinical cohort of 1004 consecutive patients aged 18-65 years with relapse-onset multiple sclerosis completed standard-of-care cognitive screenings between 2018 and 2025. We captured data from three independent periods. During the first period (n=642), rates of poor performance (≤7.5th percentile) did not differ from normative expectations for cognitive speed (8.4%) or attention (9.0%), but were nonetheless elevated for verbal memory (23.8%) and visuospatial memory (14.8%). Patients during the second (n=123) and third (n=239) periods demonstrated memory deficits despite normal cognitive speed on co-normed tasks. Objective cognitive speed among current patients was remarkably similar to healthy normative expectations (z-score: mean [sd], 0.03[1.14]; median [IQR], 0.00[-0.67, 0.67]), and was much better than across several historical comparisons from 20-25 years ago. Self-reported cognitive deficits within the total clinical cohort versus control respondents indicated worst disease-related difficulties in expressive language (e.g., word-finding), followed by working memory and episodic memory, with a small difference in executive/speed that was fully explained by mood in relapsing-remitting disease. Current patient-reported attention/executive deficits were lower than 35 years ago, despite comparable memory difficulties. As an exception, attention/executive and cognitive speed deficits were observed in secondary-progressive disease. The speed-centric model of cognitive dysfunction in multiple sclerosis is inaccurate within the modern diagnostic and treatment era. Memory deficits remain prevalent, and we highlight working memory maintenance as an important target for further investigation. The field requires testable models of memory dysfunction informed by contemporary cognitive neuroscience, with the goal of developing heretofore elusive treatments for memory deficits.

The 2024 revised McDonald criteria for multiple sclerosis recognize the optic nerve as a topography for dissemination in space. Optical coherence tomography-derived inter-eye differences in peri-papillary retinal nerve fiber layer or ganglion cell-inner plexiform layer thicknesses (≥6μm or ≥4μm, respectively) are proposed for identifying unilateral optic nerve involvement. However, the value of combining inter-eye difference measures and optimal temporal-quadrant peri-papillary retinal nerve fiber layer inter-eye differences remains unclear. We investigated the diagnostic performance of combined inter-eye differences, optimal temporal-quadrant peri-papillary retinal nerve fiber layer inter-eye differences, and examined the effects of time, prior optic neuritis frequency, sex, and race on inter-eye differences. Retinal optical coherence tomography images from all study participants underwent rigorous quality control. Receiver operating characteristic analyses and area under the receiver operating characteristic curves (AUC) were used to determine optimal inter-eye differences of individual and combined measures to distinguish eyes with, from without, prior optic neuritis in people with multiple sclerosis. Mixed-effects models were used to assess impact of time, prior optic neuritis events, sex, and race on inter-eye differences. An independent multiple sclerosis cohort from a second center was examined for external validation. Among 1854 people with multiple sclerosis, optimal inter-eye difference thresholds for identifying unilateral optic nerve involvement were 6μm for peri-papillary retinal nerve fiber layer (AUC=0.80), 4μm for ganglion cell-inner plexiform layer (AUC=0.83), and 8μm for temporal-quadrant peri-papillary retinal nerve fiber layer (AUC=0.71) thicknesses. Peri-papillary retinal nerve fiber layer inter-eye differences ≥6μm or ganglion cell-inner plexiform layer inter-eye differences ≥4μm yielded 87.6% sensitivity, 70.0% specificity, and 64.0% positive predictive value. Concurrent inter-eye differences at lower thresholds (≥5μm peri-papillary retinal nerve fiber layer, ≥3μm ganglion cell-inner plexiform layer) reduced sensitivity to 72.5%, but improved specificity (86.6%) and positive predictive value (76.7%), while maintaining accuracy and negative predictive value. Temporal-quadrant peri-papillary retinal nerve fiber layer inter-eye differences did not improve diagnostic performance. Over a median of 5.1 years, ganglion cell-inner plexiform layer and peri-papillary retinal nerve fiber layer inter-eye differences remained stable. Prior optic neuritis counts and sex did not affect inter-eye differences. Although Black Americans had higher inter-eye differences than White Americans, optimal thresholds were comparable across races. The validation cohort comprising 254 people with multiple sclerosis confirmed these findings. In conclusion, concurrent peri-papillary retinal nerve fiber layer (≥5μm) and ganglion cell-inner plexiform layer inter-eye differences (≥3μm) improve unilateral optic nerve involvement detection versus either alone (≥6μm or ≥4μm, respectively), while temporal-quadrant peri-papillary retinal nerve fiber layer inter-eye differences offer limited benefit. Inter-eye differences remain stable longitudinally and unaffected by prior optic neuritis frequency.

The discovery of the glymphatic system and meningeal lymphatic vessels revolutionized the understanding of brain waste clearance. These findings challenged the long-held notion of central nervous system (CNS) immune privilege and provided insights into how the brain maintains homeostasis despite lacking conventional lymphatic drainage. However, the impact of pathological conditions, particularly CNS cancers, on the glymphatic system and vice versa remains underexplored. Glioblastoma (GBM) is the most common and aggressive primary adult CNS cancer. Its presence results in glymphatic dysfunction with significant clinical implications. Recent studies suggest that the glymphatic system interacts with GBM to influence immunity, drug delivery, fluid regulation, and tumor progression, stressing its significant role in GBM biology and potentially treatment response. This review highlights the evidence for glymphatic dysfunction in GBM and its consequences. Furthermore, we discuss the potential to harness the power of the glymphatic system to improve patient outcomes in this terrible disease.

Multiple sclerosis is a disorder of the central nervous system (CNS) in which autoreactive immune cells migrate through a damaged blood brain barrier, resulting in focal demyelinating lesions. Beyond focal lesions, there are also diffuse surface-in gradients of pathology in MS, wherein damage is most severe directly adjacent to cerebrospinal fluid (CSF)-contacting surfaces, such as the subpial and periventricular areas. This observation suggests that toxic factors within MS CSF contribute to the emergence and/or evolution of surface-in gradients. Directly separating the CSF from the periventricular parenchyma are ependymal cells - a glial epithelium that are equipped with tufts of motile cilia which are critical for circulating CSF solutes and regulating local fluid flow. While damage to ependymal cilia has the potential to drastically modify CSF homeostasis and thus contribute to the damage of CSF exposed regions, these motile cellular structures have yet to be investigated in the context of MS. We first conducted single cell RNA sequencing of fresh human periventricular brain tissue containing ependymal cells from MS patients and non-MS disease controls. We subsequently collected CSF from MS patients and exposed cultured rodent ependymal cells to this CSF to evaluate impact on ependymal ciliary function. To complement our direct evaluation of cilia in the context of MS, we also confirmed whether cilia were altered in an animal model of MS, experimental autoimmune encephalomyelitis (EAE), and designed a novel transgenic animal model to evaluate the cellular and behavioural effect(s) of adult ependymal ciliary disruption. Single cell RNA sequencing analysis of human ependymal cells in MS demonstrated largescale dysregulation of ciliary genes and in situ stains of MS brain tissue confirmed a loss of ependymal cilia. Exposure of ependymal cells to MS CSF led to transcriptional modification of ciliary gene and protein expression and reduced ciliary beating frequency. Likewise, analysis of ependymal cells in EAE also demonstrated altered cilia gene and protein expression. We showed that IFNγ, which is elevated in MS CSF, could alter cilia protein expression and motility. Lastly, conditional knockout in adult mice of Ccdc39 in ependymal cells led to transient ventricular enlargement, increased periventricular microglial density, and alterations in nesting behaviour. These data suggest that motile cilia in ependymal cells are dysregulated in CNS autoimmunity. More importantly, they suggest that ependymal cilia disruption could play a role periventricular pathology formation in MS and can lead to behavioural deficits underlying non-motor MS symptomatology.

Prepulse inhibition reflects subcortical sensory integration, where a low-intensity peripheral stimulus (prepulse) reduces the amplitude of a reflex response to a subsequent high-intensity stimulus. As a measure of pre-attentive sensory gating, prepulse inhibition has been found to be altered in small cohorts of patients with functional disorders, including functional motor disorder and fibromyalgia, suggesting a shared deficit in sensory information processing. However, prior studies have not demonstrated consistent associations between prepulse inhibition abnormalities and clinical measures. We hypothesized that widespread pain and somatic symptoms in somatic symptom disorders may result from a general deficit in the interpretation of bodily signals, potentially linked to abnormalities in sensory filtering as measured by prepulse inhibition. In this study, we examined 140 participants across four age- and sex-matched groups: 35 patients clinically categorized with functional motor disorder without fibromyalgia, 35 with both functional motor disorder and fibromyalgia, 35 with fibromyalgia only, and 35 healthy controls. A weak electrical stimulus to the index finger served as the prepulse, delivered 100 ms before supraorbital nerve stimulation to elicit the R2 component of the blink reflex. Prepulse inhibition was calculated as the percent reduction in R2 amplitude. Across all groups, lower prepulse was significantly associated with higher scores on the Fibromyalgia Severity Scale, consisting of Widespread Pain Index and Symptom Severity Scale. In patients with functional motor disorder, no association was found between prepulse inhibition size and objectively rated motor symptom severity. These findings suggest that impaired early sensory processing at subcortical level is related to "fibromyalgianess" in people with functional motor disorder and fibromyalgia. Abnormal prepulse inhibition may serve as an objective transdiagnostic marker of fibromyalgia symptomatology or fibromyalgianess, including widespread pain and other non-motor symptoms in functional disorders, highlighting a potential role of sensory gating deficits in the pathophysiology of fibromyalgia-spectrum manifestations.

The recent introduction of immunotherapeutic agents targeting amyloid-β (Aβ) has advanced the pharmacological treatment of Alzheimer's disease (AD). Although several anti-Aβ antibodies have dramatically reduced cerebral amyloid plaques, this has not translated into major cognitive or clinical benefits, thus questioning the clinical relevance of these biomarker changes. Indeed, there is an ongoing debate over whether amyloid reduction alone constitutes sufficient evidence of disease modification to justify regulatory approval. Against this backdrop, we propose a third pathway that transcends the binary framework of molecular versus clinical end points by positioning brain connectivity as a system-level intermediate phenotype. This approach is supported by a growing body of evidence. Alterations in brain networks are early, sensitive, and modifiable markers of AD pathology. Connectivity metrics capture the dynamic interplay between genetic and environmental factors, offering a unified model of disease. Advances in precision medicine, such as individualized connectivity 'fingerprints' and the emergence of digital twins, further position brain connectivity as a powerful platform for therapeutic innovation. We argue that adopting brain network analysis as a key outcome measure enables a shift beyond isolated biomarker achievements toward a more integrated, biologically grounded, and clinically meaningful framework for disease modification in AD, bridging the gap between molecular advances and real-world impact.