Project description:The perivascular space (PVS) surrounds cerebral blood vessels and plays an important role in clearing waste products from the brain. Their anatomy and function have been described for arteries, but PVS around veins remain poorly characterized. Using in vivo 2-photon imaging in mice, we determined the size of the PVS around arteries and veins, and their connection with the subarachnoid space. After infusion of 70 kD FITC-dextran into the cerebrospinal fluid via the cisterna magna, labeled PVS were evident around arteries, but veins showed less frequent labeling of the PVS. The size of the PVS correlated with blood vessel size for both pial arteries and veins, but not for penetrating vessels. The PVS around pial arteries and veins was separated from the subarachnoid space by a thin meningeal layer, which did not form a barrier for the tracer. In vivo, FITC-dextran signal was observed adjacent to the vessel wall, but minimally within the wall itself. Post-mortem, there was a significant shift in the tracer's location within the arterial wall, extending into the smooth muscle layer. Taken together, these findings suggest that the PVS around veins has a limited role in the exchange of solutes between CSF and brain parenchyma.
Project description:Background and aimsEnlarged perivascular spaces (also known as Virchow-Robin spaces) on T2-weighted brain magnetic resonance imaging are common, but their etiology, and specificity to small vessel as opposed to general cerebrovascular disease or ageing, is unclear. We tested the association between enlarged perivascular spaces and ischemic stroke subtype, other markers of small vessel disease, and common vascular risk factors.MethodsWe prospectively recruited patients with acute stroke, diagnosed and subtyped by a stroke physician using clinical features and brain magnetic resonance imaging. A neuroradiologist rated basal ganglia and centrum semiovale enlarged perivascular spaces on a five-point scale, white matter lesions, recent and old infarcts, and cerebral atrophy. We assessed associations between basal ganglia-, centrum semiovale- and total (combined basal ganglia and centrum semiovale) enlarged perivascular spaces, stroke subtype, white matter lesions, atrophy, and vascular risk factors.ResultsAmong 298 patients (mean age 68 years), after adjusting for vascular risk factors and white matter lesions, basal ganglia-enlarged perivascular spaces were associated with increasing age (P = 0.001), centrum semiovale-enlarged perivascular spaces (P < 0.001), cerebral atrophy (P = 0.03), and lacunar stroke subtype (P = 0.04). Centrum semiovale-enlarged perivascular spaces were associated mainly with basal ganglia-enlarged perivascular spaces. Total enlarged perivascular spaces were associated with increasing age (P = 0.01), deep white matter lesions (P = 0.005), and previous stroke (P = 0.006).ConclusionsEnlarged perivascular spaces are associated with age, lacunar stroke subtype and white matter lesions and should be considered as another magnetic resonance imaging marker of cerebral small vessel disease. Further evaluation of enlarged perivascular spaces in studies of ageing, stroke, and dementia is needed to determine their pathophysiological importance.
Project description:Perivascular spaces, also known as Virchow-Robin spaces, are usually considered as a normal, asymptomatic finding. However, this finding can occasionally demonstrate an atypical appearance and can be symptomatic. We report herein a rare case of cognitive impairment associated with extremely enlarged perivascular spaces. A 68-year-old Japanese woman visited our hospital with a 1-year history of progressive memory impairment. In addition to temporal disorientation and short-term memory impairment, neuropsychological testing showed frontal lobe-related symptoms such as slowed thinking processes, reduced verbal fluency, attention deficit, and reduced working memory. Magnetic resonance imaging of the brain showed widespread enlarged perivascular spaces almost symmetrically in the subcortical white matter of bilateral hemispheres, prominently in bilateral insulas, and frontal opercula. On 99mTc-ethyl cysteinate dimer single photon emission computed tomography, hypoperfusion was apparent in bilateral insulas and frontal opercula where enlarged periventricular spaces were prominent, whereas cerebral perfusion was preserved in areas where enlargement of perivascular spaces was mild or absent. Because symptoms were consistent with the distribution of the enlarged perivascular spaces and hypoperfusion in the brain, cognitive impairment due to enlarged perivascular spaces was diagnosed. Clinicians should note enlarged perivascular spaces as a potential cause of neurological deficits including cognitive impairment.
Project description:BackgroundPerivascular spaces on brain magnetic resonance imaging (MRI) may indicate poor fluid drainage in the brain and have been associated with numerous neurological conditions. Cerebrovascular reactivity (CVR) is a marker of cerebrovascular function and represents the ability of cerebral blood vessels to regulate cerebral blood flow in response to vasodilatory or vasoconstrictive stimuli. We aimed to examine whether pathological widening of the perivascular space in older adults may be associated with deficits in CVR.MethodsIndependently living older adults free of dementia or clinical stroke were recruited from the community and underwent brain MRI. Pseudo-continuous arterial spin labeling MRI quantified whole brain cerebral perfusion at rest and during CVR to hypercapnia and hypocapnia induced by visually guided breathing exercises. Perivascular spaces were visually scored using existing scales.ResultsThirty-seven independently living older adults (mean age = 66.3 years; SD = 6.8; age range 55-84 years; 29.7% male) were included in the current analysis. Multiple linear regression analysis revealed a significant negative association between burden of perivascular spaces and global CVR to hypercapnia (B = -2.0, 95% CI (-3.6, -0.4), p = .015), adjusting for age and sex. Perivascular spaces were not related to CVR to hypocapnia.DiscussionPerivascular spaces are associated with deficits in cerebrovascular vasodilatory response, but not vasoconstrictive response. Enlargement of perivascular spaces could contribute to, or be influenced by, deficits in CVR. Additional longitudinal studies are warranted to improve our understanding of the relationship between cerebrovascular function and perivascular space enlargement.
Project description:Perivascular Spaces (PVS) are a feature of Small Vessel Disease (SVD), and are an important part of the brain's circulation and glymphatic drainage system. Quantitative analysis of PVS on Magnetic Resonance Images (MRI) is important for understanding their relationship with neurological diseases. In this work, we propose a segmentation technique based on the 3D Frangi filtering for extraction of PVS from MRI. We used ordered logit models and visual rating scales as alternative ground truth for Frangi filter parameter optimization and evaluation. We optimized and validated our proposed models on two independent cohorts, a dementia sample (N?=?20) and patients who previously had mild to moderate stroke (N?=?48). Results demonstrate the robustness and generalisability of our segmentation method. Segmentation-based PVS burden estimates correlated well with neuroradiological assessments (Spearman's ??=?0.74, p?<?0.001), supporting the potential of our proposed method.
Project description:Perivascular space (PVS) is a crevice between two slices of cerebral pia maters, filled with tissue fluid, which be formed by pia mater emboling in the surrounding of cerebral perforating branch (excluding micrangium). Normal PVS (diameter < 2 mm) can be found in almost all healthy adults; however enlarged PVS (diameter > 2 mm) has correlation with neurological disorders probably. The article reviews the formation mechanism, imageology characteristics and the relation with neurological disorders of PVS, which is beneficial to the research of some neurological disorders etiopathogenesis and treatment.
Project description:Diffusion within the extracellular and perivascular spaces of the brain plays an important role in biological processes, therapeutic delivery, and clearance mechanisms within the central nervous system. Recently, ultrasound has been used to enhance the dispersion of locally administered molecules and particles within the brain, but ultrasound-mediated effects on the brain parenchyma remain poorly understood. We combined an electron microscopy-based ultrastructural analysis with high-resolution tracking of non-adhesive nanoparticles in order to probe changes in the extracellular and perivascular spaces of the brain following a non-destructive pulsed ultrasound regimen known to alter diffusivity in other tissues. Freshly obtained rat brain neocortical slices underwent sham treatment or pulsed, low intensity ultrasound for 5min at 1MHz. Transmission electron microscopy revealed intact cells and blood vessels and evidence of enlarged spaces, particularly adjacent to blood vessels, in ultrasound-treated brain slices. Additionally, ultrasound significantly increased the diffusion rate of 100nm, 200nm, and 500nm nanoparticles that were injected into the brain slices, while 2000nm particles were unaffected. In ultrasound-treated slices, 91.6% of the 100nm particles, 20.7% of the 200nm particles, 13.8% of the 500nm particles, and 0% of the 2000nm particles exhibited diffusive motion. Thus, pulsed ultrasound can have meaningful structural effects on the brain extracellular and perivascular spaces without evidence of tissue disruption.
Project description:Background and Purpose- Perivascular spaces (PVS) around venules may help drain interstitial fluid from the brain. We examined relationships between suspected venules and PVS visible on brain magnetic resonance imaging. Methods- We developed a visual venular quantification method to examine the spatial relationship between venules and PVS. We recruited patients with lacunar stroke or minor nondisabling ischemic stroke and performed brain magnetic resonance imaging and retinal imaging. We quantified venules on gradient echo or susceptibility-weighted imaging and PVS on T2-weighted magnetic resonance imaging in the centrum semiovale and then determined overlap between venules and PVS. We assessed associations between venular count and patient demographic characteristics, vascular risk factors, small vessel disease features, retinal vessels, and venous sinus pulsatility. Results- Among 67 patients (69% men, 69.0±9.8 years), only 4.6% (range, 0%-18%) of venules overlapped with PVS. Total venular count increased with total centrum semiovale PVS count in 55 patients after accounting for venule-PVS overlap (?=0.468 [95% CI, 0.187-0.750]) and transverse sinus pulsatility (?=0.547 [95% CI, 0.309-0.786]) and adjusting for age, sex, and systolic blood pressure. Conclusions- Despite increases in both visible PVS and suspected venules, we found minimal spatial overlap between them in patients with sporadic small vessel disease, suggesting that most magnetic resonance imaging-visible centrum semiovale PVS are periarteriolar rather than perivenular.
Project description:ObjectiveTo examine the association between enlarged perivascular spaces (EPVS) and the prevalence and extent of small acute diffusion-weighted imaging (DWI) lesions (SA-DWIL) in patients with spontaneous supratentorial intracerebral hemorrhage (ICH).MethodsWe conducted a retrospective review of a consecutive cohort of 201 patients with spontaneous supratentorial ICH who had brain MRI with DWI within 1 month of ICH onset. We compared the clinical and imaging characteristics, including EPVS, of patients with and without SA-DWIL. We used univariate and multivariate logistic regression analyses to determine the variables associated with SA-DWIL.ResultsSmall acute DWI lesions were detected in 27.9% (n = 56) of patients. Intraventricular and subarachnoid extension of ICH (p ≤ 0.001), high centrum semiovale (CSO)-EPVS (p < 0.001), high basal ganglia-EPVS (p = 0.007), overall extent of white matter hyperintensity (p = 0.018), initial ICH volume (p < 0.001), and mean change in mean arterial blood pressure (δ MAP = MAP at admission - the lowest MAP before MRI scan) (p = 0.027) were associated with SA-DWIL on univariate analyses. On multivariate logistic regression analyses, larger ICH volume (odds ratio [OR] 1.03; 95% confidence interval [CI] 1.01-1.06; p = 0.006) and high CSO-EPVS (OR 12.56; 95% CI 4.40-35.85; p < 0.001) were independently associated with the presence of SA-DWIL.ConclusionsIn our cohort, high EPVS, in particular CSO-EPVS, and larger hematoma volume emerged as independent predictors for SA-DWIL after ICH. Our findings might provide a new explanation for the pathophysiologic mechanisms predisposing to SA-DWIL after ICH.