Journal of Cerebral Blood Flow & Metabolism

BackgroundQuantitative cerebral blood flow (CBF) measured with [15O]water positron emission tomography (PET) is the reference standard for quantifying brain perfusion. However, clinical interpretation of individual CBF measurements is limited by the absence of large normative datasets accounting for physiological variability across the adult lifespan. Long-axial field-of-view PET enables high-sensitivity quantitative [15O]water perfusion imaging without arterial blood sampling, allowing normative characterization of cerebral perfusion at unprecedented scale. The aim of this study was to establish normative and covariate-adjusted models of cerebral blood flow across the adult lifespan using total-body [15O]water PET. MethodsQuantitative CBF measurements were obtained in 302 neurologically healthy adults (age 21-86 years) using total-body [15O]water PET. Linear mixed-effects models were used to evaluate the effects of age, sex, body mass index (BMI), and blood hemoglobin concentration on CBF and to generate normative prediction models across the adult lifespan. Between-subject and within-subject variability were estimated from repeated scans in a subset of participants (n=51). ResultsMean grey matter CBF was 46.1 mL/(min*dL), with substantial inter-individual variability but high within-subject reproducibility (intraclass correlation coefficients 0.78-0.89). Advancing age was associated with a decline in CBF of approximately 7% per decade (p_FDR < 10-12). Higher BMI was associated with lower CBF (approximately -6% per 10 kg/m2; p_FDR < 0.01). Women exhibited higher CBF than men (approximately 7.5%), but this difference was largely explained by lower blood hemoglobin concentration in women. Covariate-adjusted models were used to generate normative predictions and prediction intervals describing expected CBF across adulthood. ConclusionThis study establishes a normative database of quantitative cerebral blood flow across the adult lifespan using high-sensitivity [15O]water PET. Age, BMI, and hemoglobin are major determinants of inter-individual variability in CBF. The resulting generative models provide a quantitative reference framework for interpreting cerebral perfusion measurements and may enable automated detection of abnormal brain perfusion in clinical PET imaging.

Intracerebral haemorrhage (ICH) is a severe form of stroke with high morbidity and mortality rates. For survivors, acute haematoma expansion strongly determines neurological outcome. Although blood pressure reduction is widely investigated as a strategy to limit haematoma growth, the haemodynamic mechanisms regulating haemorrhage development remain poorly understood. Zebrafish provide a tractable in vivo model to study cerebrovascular biology and spontaneous ICH, yet the contribution of vascular regulation to haemorrhage onset and expansion has not been explored in this species. Here, we investigated whether pharmacological modulation of vascular dilation influences ICH development in zebrafish larvae. We first characterised vascular changes during the developmental window in which spontaneous ICH occurs and observed increased heart rate and progressive reductions in arterial diameter between 2 and 3 days post-fertilisation, suggesting increased vascular resistance. We then tested whether vasoconstriction promotes haemorrhage using angiotensin II, which induced systemic and cerebrovascular vasoconstriction but did not increase ICH incidence or haematoma size in two independent ICH models. In contrast, pharmacological vasodilation using sodium nitroprusside or isoproterenol significantly reduced haematoma size in a high-incidence model of atorvastatin-induced ICH. Live imaging of cerebral blood flow revealed that vasodilation was associated with the confinement of red blood cells around affected vessels rather than dispersing into the brain ventricles. Together, these findings indicate that vascular dilation modulates haemorrhage progression in zebrafish ICH and establish this model as a platform to investigate haemodynamic mechanisms regulating haematoma expansion.

Cerebral small vessel disease (cSVD) is a leading cause of stroke and vascular cognitive impairment, yet the cellular mechanisms underlying microvascular dysfunction in human disease remain incompletely understood. In particular, the relationship between pericyte alterations and endothelial activation, two key features of blood-brain barrier dysfunction, remains unresolved. Here, we performed a quantitative single-vessel analysis of the human cortical microvasculature across increasing cSVD severity and ageing. Using multiplex immunohistochemistry combined with spectral unmixing and automated image analysis, we analysed 11,409 microvascular fragments from post-mortem brain tissue derived from 20 cases. Endothelial cells, pericytes, and endothelial activation were assessed using PECAM-1, PDGFR{beta}, and VCAM-1, respectively. Microvascular density and diameter differed between cortical grey matter and the underlying white matter, with white matter vessels being less dense and wider in controls. While vessel diameter remained stable across disease stages, microvascular density increased with cSVD severity and age in the white matter. At the molecular level, PDGFR{beta} signal decreased markedly with increasing cSVD severity, consistent with progressive pericyte loss. This reduction was observed in both grey and white matter and correlated with disease severity and age. Notably, intermediate disease groups displayed marked heterogeneity, with vessels exhibiting either preserved or near-complete pericyte coverage, suggesting a potentially bimodal transition. In parallel, endothelial markers PECAM-1 and VCAM-1 increased significantly with disease severity, reflecting endothelial activation. Unsupervised Gaussian mixture clustering of marker expression identified three vascular states characterised by (i) preserved pericytes with low endothelial activation, (ii) marked pericyte loss without endothelial activation, and (iii) combined pericyte depletion and endothelial activation. These clusters broadly aligned with clinical severity but revealed intermediate states not captured by post-mortem diagnosis alone. Together, these findings suggest that pericyte loss and endothelial activation are partially dissociated processes that occur in a sequential progression in human cSVD, supporting pericyte dysfunction as an early event and highlighting it as a potential therapeutic target in microvascular disease.

IntroductionNeuroinflammation is increasingly implicated in age-related cognitive decline, neurodegeneration and neuropsychiatric disorders. During systemic inflammation, microglia are rapidly activated, simultaneously changing their shape and releasing cytokines that perturb neuronal function. This change in glial morphology alters their intracellular diffusion properties and provides a potentially measurable signature of their activation state. Diffusion-weighted magnetic resonance spectroscopy (dMRS) shows promise in detecting these changes. Here, we combined IFN-{beta} challenge with dMRS to assess changes in metabolite diffusion in healthy young and older adults. We hypothesised that IFN-{beta} would increase diffusion of choline-containing compounds (tCho) but not N-acetylaspartate + N-acetylaspartylglutamate (tNAA), age would be associated with an increase in tCho diffusion and concentration, lower tNAA concentration and increased effects of IFN-{beta}. MethodsWe recruited 15 young (mean 25.2 {+/-} 5.1 years, 6 male) and 15 older (mean 62.6 {+/-} 4.1 years, 5 male) healthy volunteers, each tested twice, once after IFN-{beta} and once after placebo. Physiological and behavioural responses were recorded hourly, and blood samples taken at baseline, 4 and 6.5 hours post-injection. dMRS occurred at [~]4.5 hours at 3T, using a semi-LASER sequence with four diffusion weightings (b = 0 and 3 x 3500 s/mm{superscript 2}), in 4.5 cm3 VOIs in the left thalamus and corona radiata. Apparent Diffusion Coefficients (ADCs) of tCho, tNAA and creatine+phosphocreatine (tCr) were calculated from averaged spectra using custom MATLAB software. ResultsIFN-{beta} administration produced a significant increase in thalamic tCho diffusivity compared with placebo (t(28) = -2.15, p = 0.040), with no change in tNAA or tCr ADC, or tCho concentrations. IFN-{beta}-related increases in tCho ADC positively correlated with increases in circulating IL-6 (R{superscript 2} = 0.14, p = 0.040). Age-related effects were also evident during the placebo condition, with older participants showing lower thalamic tNAA diffusivity (t(27) = 2.86, p = 0.008), lower tNAA/tCr in both grey and white matter (grey: t(27) = 2.49, p = 0.023; white: t(27) = 2.94, p = 0.007), and higher white-matter tCho/tCr (t(27) = -2.23, p = 0.034). ConclusiondMRS detected IFN-{beta}-induced increases in thalamic tCho diffusivity corresponding with peripheral inflammation, supporting its sensitivity to acute inflammation-induced changes in glial morphology. Age-related differences in tNAA diffusion and concentrations further highlight metabolite-specific ageing effects. HighlightsO_LIdMRS detects increased thalamic total choline diffusivity following IFN-{beta}-induced inflammation. C_LIO_LIIFN-{beta}-related changes in total choline diffusivity are associated with peripheral IL-6 responses. C_LIO_LIAgeing is linked to reduced NAA diffusion and higher white-matter tCho/tCr C_LIO_LIdMRS is sensitive to inflammation- and age-related neurochemical changes in vivo. C_LI

In brain-heart interactions, several pathways have been proposed to mediate feedback loops between systems. Among these, cerebrovascular dynamics operate at their interface. However, how cardiovascular control, ventilation mechanisms, and cerebral autoregulation interact is not well characterized, especially in ageing and post-stroke conditions, where perfusion can be compromised. In a cohort of 57 elderly participants, including 30 stroke survivors, we investigated the relationship between cardiac sympathetic activity and both, cerebral blood flow regulation and ventilatory status. Sympathetic reflexes, assessed via cardiac sympathetic index (CSI) during sit-to-stand transitions, were preserved across all participants, with marginal group differences between stroke and non-stroke populations. However, among individuals with constrained ventilation, indexed by reduced end-tidal CO2 at baseline, we identified a more elevated CSI following postural change, scaling with the degree of CO2 dysregulation. Furthermore, transcranial Doppler measurements revealed exaggerated changes in mean flow velocity (MFV) within the right middle cerebral artery in most participants. These MFV shifts significantly correlated with the magnitude of cardiac sympathetic change under orthostatic stress, suggesting that CSI can capture maladaptive cerebrovascular responses. Together, these findings highlight a distinct cardiac-cerebrovascular crosstalk in elderly individuals, revealing patterns consistent with compensatory or maladaptive sympathetic overactivation under conditions of impaired cerebrovascular control.

Background Intracranial aneurysm rupture is the leading cause of spontaneous subarachnoid hemorrhage and is associated with substantial mortality and long term neurological disability. Emerging evidence suggests that the gut microbiome may influence vascular inflammation and endothelial integrity through immune and metabolic pathways, yet human evidence linking gut microbial alterations to intracranial aneurysm remains fragmented and inconsistent. Objective This systematic review and meta analysis aimed to synthesize available human evidence on the association between gut microbiome alterations and intracranial aneurysm formation or rupture, with a primary focus on microbial dysbiosis and differences in gut microbial alpha diversity. Methods This study was conducted according to PRISMA 2020 guidelines and the protocol was prospectively registered in PROSPERO (CRD420261360785). A comprehensive search of PubMed, Scopus, Web of Science, Embase, and Cochrane CENTRAL was performed from database inception until April 1, 2026, with additional screening of grey literature sources. Observational human studies evaluating gut microbiome characteristics in patients with intracranial aneurysm were included. Mendelian randomization (MR) studies investigating genetically predicted microbial taxa and aneurysm outcomes were also reviewed. Random effects meta analysis using standardized mean differences (SMD) was performed for alpha diversity outcomes. MR taxa reported in at least two independent studies were quantitatively synthesized using inverse variance weighting of log odds ratios. Results The systematic search identified 396 records. After removal of duplicates and eligibility screening, 20 studies met inclusion criteria, including 12 observational clinical studies and 8 Mendelian randomization analyses. Meta analysis of three microbiome sequencing studies demonstrated significantly reduced gut microbial alpha diversity in patients with ruptured intracranial aneurysms compared with controls. Sensitivity analyses confirmed the robustness of pooled estimates. In addition, MR evidence identified several microbial taxa, including Ruminococcus1, Bilophila, Fusicatenibacter, and Porphyromonadaceae, as potentially protective factors against aneurysm related outcomes. Across observational studies, gut dysbiosis was frequently associated with inflammatory pathways and alterations in microbial metabolites implicated in vascular dysfunction. Conclusion Current human evidence suggests a potential association between gut microbiome dysbiosis and intracranial aneurysm pathophysiology, particularly in relation to aneurysm rupture. Reduced microbial diversity and specific microbial taxa may influence vascular inflammation and aneurysm wall stability. However, existing evidence remains limited and heterogeneous. Large prospective cohorts and mechanistic studies are required to clarify causal relationships and evaluate whether microbiome targeted interventions could contribute to aneurysm risk stratification or prevention strategies.

Background. Carotid webs (CaWs) are shelf-like protrusions in carotid bifurcation recognized as a potential cause of ischemic stroke. However, their impact on wall-based hemodynamic metrics (TAWSS, OSI, RRT) in distinguishing from normal bifurcations remains unclear. Methods. Carotid geometries were reconstructed from CT angiography in patients with CaWs, classified as symptomatic (with ischemic stroke) or asymptomatic (incidentally detected), and controls with normal bifurcations. Influence of three blood viscosity models (Newtonian, Carreau-Yasuda, Casson) was evaluated. Metrics were quantified using a Gaussian-weighted spatial averaging method and compared between groups. Results. CFD simulations were performed in 22 CaW cases (16 symptomatic, 6 asymptomatic) and 6 normal bifurcations. Simulations predicted recirculation corresponding to delayed contrast clearance on DSA. Viscosity models had minimal influence on flow patterns (<2% differences). CaWs showed greater inter-patient variability than normal bifurcations, but overlap remained (e.g., TAWSS 3.39 (2.72-8.96) vs 4.18 (3.09-4.56) Pa, p = 0.858). Symptomatic CaWs showed lower TAWSS and higher OSI and RRT than asymptomatic CaWs (TAWSS 3.39 vs 6.63 Pa), although did not reach statistical significance (p > 0.25). Conclusion. Symptomatic CaWs show lower shear stress and stronger oscillations than asymptomatic CaWs. However, wall-based hemodynamic metrics alone may not distinguish CaWs from normal carotid geometries.

The coupling between brain excitatory activity and positive blood oxygen level-dependent (BOLD) responses is well-established. Although often associated with inhibition, negative BOLD remains partially understood. Moving away from neurovascular coupling, apparent diffusion coefficient (ADC)-fMRI provides a more direct measure of excitatory activity, possibly mediated by transient cellular deformations. While decreases in ADC align with positive BOLD, the possible translation of negative BOLD into positive ADC has not been investigated in humans. Diffusion-weighted fMRI (dfMRI) combines vascular and microstructural contributions. Using interleaved subthreshold transcranial magnetic stimulation (TMS)-fMRI on the primary motor cortex (M1), we induced negative BOLD responses in contralateral M1 and primary somatosensory cortex (S1). This was accompanied by a negative dfMRI response, but no ADC-fMRI response, indicating minimal microstructural fluctuations. In ipsilateral M1/S1, no BOLD response was detected while dfMRI revealed a positive cluster, suggesting sensitivity to subtle neural activity. These findings provide new insights into vascular and neuronal responses underlying subthreshold TMS and negative BOLD.

Atherosclerosis is linked to an increased risk of cognitive decline, with chronic inflammation being a common feature of both pathologies. IL-12 activates STAT4 to regulate myeloid cell functions, and blockade of this pathway alleviates cognitive impairment in Alzheimers models. However, the mechanisms connecting vascular pathology to neuroinflammation remain unclear. Here, we examine whether STAT4 functions as a common mediator of neuroinflammation in atherosclerosis. We demonstrate that LysMCre-specific STAT4 deficiency ameliorates deficits in long-term memory in low-density lipoprotein-deficient (Ldlr-/-) mice fed a high-fat diet (HFD-C). STAT4 deficiency moderately reduces Ser199-phosphorylated Tau burden. Atherosclerosis alters brain immune composition, characterized by increased numbers of CD45+ leukocytes, activated microglia, and activated T and B cells, whereas STAT4 deficiency attenuates these effects. Nanostring gene-expression pathway analysis further highlights the importance of STAT4 in regulating multiple neuroinflammatory pathways and the Rhodopsin-like receptor signaling, which is associated with synaptic plasticity. LysMCre-specific STAT4 deficiency supports microglial efferocytosis in atherosclerotic Ldlr-/- mice and increases the number of efferocytotic macrophages. Accordingly, STAT4 deficiency also reduced neuronal death. Overall, our data reveal an important role for myeloid-driven STAT4 expression in the pathogenesis of cognitive decline associated with atherosclerosis, mediated through impaired efferocytosis and enhanced leukocyte activation, leading to increased brain neuroinflammation.

Background and Objectives: Normal appearing white matter (NAWM) may already harbor subtle microstructural alterations not yet visible on conventional MRI. Quantitative Multi-Parametric Mapping (qMPM) such as Magnetization Transfer saturation (MTsat), longitudinal relaxation rate (R1), and Proton Density (PD) offer new possibilities for analyzing NAWM which are sensitive to demyelination, axonal loss, and edema. We aimed to characterize these alterations within white matter hyperintensities (WMH) and the perilesional NAWM (pNAWM), to gain insights into the underlying process of lesion progression. We also investigated their association with cerebrovascular risk factors (CVRF) and long-term cognitive performance. Methods: This investigation included the cerebral MRI data of 245 participants from the prospective Berlin Longterm Observation of Vascular Events (BeLOVE) study. Furthermore, 121 participants cognitive performance was evaluated at baseline and longitudinally at 2 years follow-up using Montreal Cognitive Assessment (MoCA). Regions of interest (ROIs) of WMH, pNAWM at 1, 2, 3 mm were assessed in comparison to the mirrored contralesional white matter (cWM). Linear mixed effects models were employed to demonstrate the pairwise comparisons between each region using estimated marginal means and the association of MPM metrics with CVRFs. Linear regression was used to assess the association with cognitive performance. Results: In 245 participants, (mean age 62 years, SD: 12 years; 29.8% females), MPM metrics demonstrated a clear spatial gradient of microstructural injury. MTsat and R1 values were lower in WMH compared to cWM (lower case Greek beta = -0.48 (-0.52 - -0.44) and lower case Greek beta = -0.07 (-0.08 - -0.06), p<0.001, respectively) and showed gradual recovery with increasing distance indicating a microstructural gradient in pNAWM. Conversely, PD values were higher in WMH and decreased peripherally (lower case Greek beta = 2.32 (2.05 - 2.61, p<0.001). No substantial associations were found between MPM parameters and CVRFs in our cohort. At baseline and 2-year follow-up, cognitive performance was associated with higher pNAWM R1 values, whereas MTsat were only moderately associated. Discussion: Quantitative MPM reliably detects microstructural alterations not only within WMH, but also in pNAWM, confirming the high sensitivity of qMPM to subtle tissue pathology and support its utility as a promising biomarker for longitudinal studies and monitoring therapeutic effects.

Hypoxic-ischemic encephalopathy (HIE) is a neonatal brain injury in which a definitive diagnosis within the first 6 hours of life is essential for initiating therapeutic hypothermia and improving neurological outcomes. However, early clinical evaluation and currently available biomarkers lack quantitative specificity during this narrow therapeutic window. We are providing insights into how rapid disturbances in systemic metabolites that regulate cerebral energy metabolism, neurotransmitter cycling, redox balance, and membrane integrity generate a definitive biochemical signature of HIE immediately after birth. We performed quantitative blood-based 1H NMR metabolomics on collected blood samples within [~]1 hour of birth from 81 neonates (HIE, n = 42; non-HIE, n = 39), under optimized handling conditions to preserve metabolic integrity. Metabolite analysis revealed a distinct HIE-associated profile characterized by elevated lactate, alanine, succinate, glutamate, taurine, glycine, choline, and pyroglutamate, alongside significant depletion of glucose and glutamine compared with non-HIE controls (p < 0.05). These coordinated metabolic shifts reflect impaired mitochondrial respiration, enhanced anaerobic glycolysis, excitotoxic amino acid accumulation, altered membrane phospholipid turnover, and oxidative stress. Multivariate analysis demonstrated clear separation between groups (PLS-DA accuracy = 0.83, R{superscript 2}Y = 0.46, Q{superscript 2} = 0.82), with glutamine, lactate, glutamate, and pyroglutamate as key discriminators. Pathway enrichment highlighted perturbations in glycolysis, the glucose-alanine cycle, glutamate-glutamine metabolism, Warburg effect like metabolic reprogramming, and redox homeostasis. Integration into supervised machine-learning models (Random Forest, XGBoost, SVM, KNN) achieved strong diagnostic performance (AUC = 0.97 {+/-} 0.03; sensitivity {approx} 87%). Collectively, this minimally invasive NMR-to-machine-learning framework enables early, mechanistically grounded risk stratification of neonatal HIE within the therapeutic window.

Angiogenesis, the formation of new vessels from pre-existing ones, is essential for embryonic development and tightly regulated by VEGFA signaling. However, the contribution of additional modulators remains poorly defined. The co-receptor NRP1 is crucial for hindbrain vascularization, yet how its activity is spatiotemporally controlled is unclear. We identify the glycosylphosphatidylinositol (GPI)-anchored protease MT4-MMP as a key regulator of developmental angiogenesis. Endothelial cell-specific, inducible deletion of MT4-MMP (Mt4-mmpi{Delta}EC mice) causes an exacerbated vascular plexus in the E11.5 embryonic hindbrains. In vitro, loss of MT4-MMP in endothelial cells disrupts cell polarization and migration and enhances VEGFA-induced ERK signaling. Consistently, pERK levels are increased in hindbrain vessels from Mt4-mmpi{Delta}EC embryos, whereas they are reduced in mice with constitutive and global MT4-MMP deficiency. By combining co-expression analysis in cultured cells and embryonic hindbrains with proteomics, in silico protein modeling, and in vitro digestion assays, we identify NRP1 as a previously unrecognized MT4-MMP substrate in this context. Accordingly, inhibition of VEGFA binding to NRP1 partially rescues the aberrant angiogenic phenotype in the embryonic hindbrain of Mt4-mmpi{Delta}EC mice. Our findings reveal that MT4-MMP shapes developing brain vasculature by modulating NRP1-dependent VEGFA/ERK signaling. This newly identified MT4-MMP/NRP1 axis may have potential relevance in CNS vascular abnormalities in development and disease, as well as other pathophysiological contexts.

Background: Unruptured intracranial aneurysms (UIAs) pose a significant risk of subarachnoid hemorrhage. Both hypertension and hyperhomocysteinemia are recognized as independent risk factors for vascular disease; however, their combined impact (H-type hypertension) on aneurysm instability and rupture remains unclear. Methods: We analyzed a prospective cohort of 358 adults with UIAs (475 aneurysms) using high-resolution vessel-wall MRI (HRVWI) for cross-sectional and longitudinal assessment. H-type hypertension was defined as hypertension with plasma homocysteine ?10 ?mol/L. Multivariable logistic regression assessed associations with AWE and aneurysm growth (longitudinal sub-cohort: n = 82, 89 aneurysms). Mendelian randomization (MR) analyses evaluated the causal role of homocysteine in hypertension and aSAH. Proteomic profiling identified potential molecular mechanisms. Results: AWE occurred in 33.7% of aneurysms, which were larger, irregular, and had higher PHASES scores. Elevated homocysteine (10.3 vs 9.5 ?mol/L, p = 0.004) and H-type hypertension (43.8% vs 28.3%, p < 0.001) were associated with AWE. After adjustment, H-type hypertension independently predicted AWE (OR = 3.18) and aneurysm growth (OR = 3.63). MR analyses showed homocysteine increased aSAH (OR = 1.39) and hypertension risk (OR = 1.10), while hypertension increased aSAH risk (OR = 1.58). Mediation analysis did not support hypertension as a mediator (p = 0.20). Proteomic analyses identified key pathways related to inflammation?immune dysregulation, extracellular matrix remodeling, and signaling activation as potential mediators. Conclusions: H-type hypertension amplifies aneurysmal-wall instability and growth. Combined control of blood pressure and homocysteine merits prospective evaluation for UIA prevention.

PURPOSEGlycolytic production of HDO from the metabolism of perdeuterated glucose provides a means for metabolic imaging with 2H MRI. The present study compared HDO production from a cost-efficient [2,3,4,6,6-2H5]glucose with [2H7]glucose in vitro and in vivo. METHODS2H NMR spectroscopy was performed to measure glucose consumption, lactate, and HDO production in the SFxL glioblastoma cell line. In vivo studies in healthy mice using 2H magnetic resonance spectroscopy were performed at 11.1 T after administering a bolus of either metabolic contrast agent. In vivo metabolite levels were quantified using unlocalized and slice-selective localized spectra. RESULTSOur in vitro results demonstrated similar glucose consumption and HDO production kinetics, although significant differences in lactate labeling were observed. The in vivo study showed comparable glucose consumption and HDO production kinetics following tail-vein bolus administration of either metabolic contrast agent, while lactate was not detected in the brain. CONCLUSION[2,3,4,6,6-2H5]glucose shows comparable HDO production to [2H7]glucose, while offering lower cost and reduced spectral complexity. These findings place [2,3,4,6,6-2H5]glucose as an alternative to [2H7]glucose for HDO-based DMI studies.

Cerebrovascular reactivity (CVR), the ability of cerebral blood vessels to dilate or constrict in response to a vasoactive stimulus, is an important measure of cerebrovascular health. Accurate CVR estimation requires accounting for the time required for the vasoactive stimulus to reach each brain region and the time it takes for local arterioles to modulate cerebral blood flow. The temporal search range used to calculate this spatially varying offset can substantially impact CVR estimates, and the appropriate search range may vary across populations, acquisition protocols, and even brain regions. Here, we present an iterative approach for automatically determining the appropriate maximum shift, using breath-hold fMRI data acquired in a cohort of stroke survivors. This approach selectively expands the delay search range only for voxels with estimated delays at the boundary (i.e., near the minimum or maximum shift) until the estimated delay is no longer constrained or a predefined value is reached. In the context of stroke, this approach significantly increased the number of voxels with statistically significant CVR among those initially at the boundary. It also resulted in CVR polarity reversals in voxels originally at the early-response boundary and amplified negative CVR values in voxels originally at the late-response boundary, suggesting that using an iterative maximum shift can critically impact CVR interpretation. This approach is broadly applicable beyond stroke, but careful parameter tuning is required, as illustrated by our demonstration of the parameter tuning process for a participant with Moyamoya disease. Together, these findings suggest that iterative delay correction allows for improved CVR assessments in clinical populations.

Migraine is a common and disabling neurological disorder linked to alterations in neuronal activity and waste clearance in the brain. MRI-visible perivascular spaces (PVS) are key components of the glymphatic system which may serve as imaging biomarker of such disorder. We hypothesised that higher frequency of migraine episodes would be associated with increased PVS burden, reflecting greater levels of impaired glymphatic clearance. In this retrospective case-control study of 90 participants (20 episodic migraineurs, 18 chronic migraineurs, and 52 age- and sex-matched healthy controls; 58 females, median [Q1, Q3] age=28.6 [25.1, 39.4] years) we investigated PVS alterations in episodic migraineurs (n=20) and 18 chronic migraineurs (n=18). PVS volumes and cluster counts were quantified in the white matter (WM), basal ganglia (BG), midbrain, and hippocampus. We stratified PVS metrics by white matter lobes and arterial vascular territories. After adjusting for age, sex, and total brain volume, episodic migraineurs exhibited significantly lower BG-PVS volumes (exp({beta})=0.76, 95%CI [0.61, 0.94], p=0.01) compared to controls. Chronic migraineurs exhibited significantly lower PVS cluster counts in the parietal (exp({beta})=0.8, 95%CI [0.68, 0.94], p=0.01) and temporal lobes (exp({beta})=0.72, 95%CI [0.53, 0.96], p=0.03) and middle cerebral artery territory (exp({beta})=0.82, 95%CI [0.68, 0.97], p=0.03) compared to healthy controls. Within migraineurs, those with aura (n=20) exhibited significantly lower PVS burden in all brain regions, vascular territories, and across the frontal, parietal, and temporal lobes (all pFDR<0.05). Our findings suggest that the aura symptom, rather than the migraine disorder itself, may primarily drive changes in perivascular spaces, with effects varying across brain regions.

BackgroundNeonatal global hypoxic-ischemic cerebral injury is a leading cause of infant mortality and lifelong disability. Current rodent models do not replicate neonatal global cerebral ischemia (nGCI) and reperfusion injury. Here, we developed and characterized a rodent model of cardiac arrest and cardiopulmonary reperfusion (CA/CPR) to induce nGCI, producing acute systemic ischemia, mild neuronal injury, white matter alterations, and motor and memory deficits. MethodsRat pups underwent CA/CPR or sham procedure on postnatal day 9-11. CA/CPR in rat pups was performed under anesthesia while intubated. Asystole was induced with intravenous (IV) KCl and maintained for 10-14 minutes. Resuscitation included oxygen ventilation, chest compressions, and IV epinephrine. ResultsTwelve minutes of asystole provided an optimal balance between survival and systemic injury. Behavioral testing on postoperative day (POD) 7 revealed memory impairments. Despite the absence of overt neuronal death in the hippocampus or cerebellum, we observed evidence of glial activation and white matter alterations. ConclusionThis novel rodent model of nGCI addresses limitations in existing models while offering clinically relevant features to support future mechanistic and translational research. ImpactO_LIThis study validates cardiac arrest and cardiopulmonary resuscitation (CA/CPR) as a novel model for neonatal global cerebral ischemia (nGCI), complementing existing rodent models of unilateral and permanent injury by enabling investigation of both global ischemia and reperfusion injury. C_LIO_LInGCI results in memory impairment in the absence of overt neuronal cell death. Functional deficits are associated with neuroinflammatory responses in the hippocampus, white matter, and cerebellum. C_LIO_LINeonatal CA/CPR induces global cerebral ischemia which uniquely allows investigation of hindbrain structures, such as cerebellum, which are typically spared in existing rodent models of neonatal hypoxia-ischemia. C_LI

ObjectiveImpaired blood flow has recently been recognized as a critical contributor to cognitive impairment and dementia. It was reported that cerebral distal arterial flow measured from Simultaneous Non-contrast Angiography and Intraplaque Hemorrhage (SNAP) MRI is associated with post-treatment cognitive function improvement in carotid atherosclerosis patients. In this study, we aim to evaluate the value of SNAP-based measurements in assessing cerebrovascular function in an aging population. Materials and MethodsNeurovascular MRI data were collected on 36 aging participants (22 cognitively unimpaired and 14 impaired; 9 mild cognitive impairment (MCI) and 5 Alzheimers Disease (AD)). Neurovascular MRI measurements, including white matter hyperintensities (WMH) volumes, cerebral blood flow (CBF), and SNAP-based distal cerebral arterial flow (dCAF) index, were quantified. Cognitive function was assessed using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). ResultsSignificant differences in the dCAF index were observed between cognitively unimpaired and impaired groups, and the dCAF index was significantly correlated with the RBANS total score. While CBF was significantly associated with dCAF index, there is no significant correlation of CBF or WMH with the RBANS score in this population. ConclusionOur findings suggest that the dCAF measured with SNAP MRI is valuable for evaluating the cognition-related cerebrovascular condition in an aging population.

Body fat distribution is a strong predictor of cardiometabolic disease risk. Gene-environment and gene-gene interactions can affect body fat distribution, resulting in differential phenotypic variance across genotype groups that can be detected through variance quantitative trait loci (vQTLs). Using UK Biobank MRI data in conjunction with genetic data, we explored evidence for vQTLs for body fat distribution phenotypes aiming to uncover potential genetic interactions. We identified three vQTLs for liver fat distribution, including rs738408 (PNPLA3), rs4293458 (APOE), and rs58542926 (TM6SF2), and one vQTL region (FTO) for abdominal subcutaneous adipose tissue. To dissect putative gene-environment and gene-gene interactions underlying these signals, we identified multiple vQTL-environment interactions and one epistatic effect (rs58542926*rs429358) for liver fat. The vQTLs and interaction results were validated in multiple UK Biobank and external replication cohort datasets (Framingham Heart Study, All of Us, and TwinsUK), showing replication of the three liver vQTLs with the greatest reproducibility for vQTL rs738408. Our findings uncover vQTLs and underlying interaction effects on body fat distribution, especially liver fat, that may be useful for the development of precision medicine approaches.

The SAFE MRI ECMO (NCT05469139) study established the safety of ultra-low-field 64mT MRI in patients receiving extracorporeal membrane oxygenation (ECMO) in the setting of intensive care and demonstrated that these images were highly sensitive in detecting acquired brain injuries. This retrospective analysis of prospectively collected observational data sought to expand on these findings in light of the crucial need for neurological monitoring while patients receive ECMO by evaluating the feasibility of volumetric analyses derived from ultra-low-field MR images. T2-weighted scans from thirty patients who received ultra-low-field MRI while undergoing ECMO at Johns Hopkins Hospital were analyzed using a volumetric pipeline to determine whole brain volume and volumes of total grey matter, total white matter, subcortical grey matter, ventricles, left hemisphere, right hemisphere, telencephalon, left and right lateral ventricles, the total intracranial volume, and the cerebellum. Segmented brain volumes in patients undergoing ECMO were comparable to measurements obtained using conventional field and ultra-low-field MRI in the absence of ECMO instrumentation. The subgroup analysis demonstrated subtle volumetric differences between patients supported with venoarterial ECMO and those receiving venovenous ECMO. These data provide the first evidence that ultra-low-field MRI provides volumetric measurements comparable to conventional field-strength MRI, even in the presence of ECMO circuitry, supporting its feasibility for neuroimaging in critically ill patients.