A raging fire in acute lacunar stroke: Inflammation, blood–brain barrier dysfunction and the origin of cerebral microbleeds

Analysis of the Relationship between Recent Small Subcortical Infarcts and Autonomic Nervous Dysfunction

OBJECTIVE

Autonomic Nervous System (ANS) dysfunction may be involved in the pathogenesis of Cerebral Small Vessel Disease (CSVD). The study aimed to explore the relationship between Recent Small Subcortical Infarct (RSSI) and Blood Pressure Variability (BPV), and Heart Rate Variability (HRV).

METHODS

A total of 588 patients from the CSVD registration research database of Henan Province were included in this study, and were divided into two groups according to the presence of RSSI. Clinical data, including demographic characteristics, disease history, laboratory indexes, 24-hour ambulatory blood pressure and electrocardiogram indicators, and imaging markers of CSVD, were collected. Univariate and binary logistic regression analyses were used to study the relationship between RSSI and indicators of laboratory, HRV and BPV in the CSVD population.

RESULTS

Multivariate analysis showed that higher 24-hour mean Diastolic Blood Pressure (DBP)[Odds Ratios (OR)=1.083,95% Confidence Intervals (CI)=(1.038,1.129), p < 0.001], Standard Deviation (SD) of 24-hour DBP [OR=1.059,95%CI=(1.000,1.121), p = 0.049], nocturnal mean Systolic Blood Pressure (SBP) [OR=1.020,95%CI=(1.004,1.035), p = 0.012], nocturnal mean DBP [OR=1.025,95%CI=(1.009,1.040), p = 0.002] were independent risk factors for RSSI. In contrast, the decrease of the standard deviation of N-N intervals (SDNN) [OR=0.994,95%CI=(0.989,1.000), p = 0.035] was beneficial to the occurrence of RSSI. In addition, neutrophil counts [OR=1.138,95%CI=(1.030,1.258), p = 0.011], total cholesterol (TC) [OR=1.203,95%CI=(1.008,1.437), p = 0.041] and High-Density Lipoprotein (HDL) [OR=0.391, 95%CI=(0.195,0.786), p = 0.008] were also independently associated with the occurrence of RSSI. After adjusting for confounding factors, except for TC, the other factors remained associated with the occurrence of RSSI.

CONCLUSION

Increased 24-hour mean DBP, nocturnal mean SBP and DBP, SD of 24-hour DBP and decreased SDNN were independently correlated with RSSI occurrence, suggesting that sympathetic overactivity plays a role in the pathogenesis of RSSI.

Structure and function of the perivascular fluid compartment and vertebral venous plexus: Illumining a novel theory on mechanisms underlying the pathogenesis of Alzheimer's, cerebral small vessel, and neurodegenerative diseases

Blood dynamically and richly supplies the cerebral tissue via microvessels invested in pia matter perforating the cerebral substance. Arteries penetrating the cerebral substance derive an investment from one or two successive layers of pia mater, luminally apposed to the pial-glial basal lamina of the microvasculature and abluminally apposed to a series of aquaporin IV-studded astrocytic end feet constituting the soi-disant glia limitans. The full investment of successive layers forms the variably continuous walls of the periarteriolar, pericapillary, and perivenular divisions of the perivascular fluid compartment. The pia matter disappears at the distal periarteriolar division of the perivascular fluid compartment. Plasma from arteriolar blood sequentially transudates into the periarteriolar division of the perivascular fluid compartment and subarachnoid cisterns in precession to trickling into the neural interstitium. Fluid from the neural interstitium successively propagates into the venules through the subarachnoid cisterns and perivenular division of the perivascular fluid compartment. Fluid fluent within the perivascular fluid compartment flows gegen the net direction of arteriovenular flow. Microvessel oscillations at the central tendency of the cerebral vasomotion generate corresponding oscillations of within the surrounding perivascular fluid compartment, interposed betwixt the abluminal surface of the vessels and internal surface of the pia mater. The precise microanatomy of this most fascinating among designable spaces has eluded the efforts of various investigators to interrogate its structure, though most authors non-consensusly concur the investing layers effectively and functionally segregate the perivascular and subarachnoid fluid compartments. Enlargement of the perivascular fluid compartment in a variety of neurological disorders, including senile dementia of the Alzheimer's type and cerebral small vessel disease, may alternately or coordinately constitute a correlative marker of disease severity and a possible cause implicated in the mechanistic pathogenesis of these conditions. Venular pressures modulating oscillatory dynamic flow within the perivascular fluid compartment may similarly contribute to the development of a variety among neurological disorders. An intimate understanding of subtle features typifying microanatomy and microphysiology of the investing structures and spaces of the cerebral microvasculature may powerfully inform mechanistic pathophysiology mediating a variety of neurovascular ischemic, neuroinfectious, neuroautoimmune, and neurodegenerative diseases.

Specific risk factors for cerebrovascular disorders in patients with chronic kidney disease in the pre-dialysis period

Cerebral vascular disorders are one of the leading causes of disability and mortality in patients with chronic kidney disease (CKD). The article presents the currently available data on risk factors (RF) for the development of cerebrovascular disorders in pre-dialysis patients with CKD. Two groups of RF are identified: traditional and non-traditional (specific). Traditional RF, which include arterial hypertension, diabetes mellitus and hypercholesterolemia, independently affect the cerebral vascular bed and get worse against the background of CKD. Specific RF is associated with features of the CKD pathogenesis. It includes increased blood levels of homocysteine, β2-microglobulin, impaired calcium-phosphorus metabolism, accumulation of uremic toxins and toxins of intestinal bacteria, anemia and other factors. In the present review, special attention is paid to specific RF and pathogenetic mechanisms of the development of cerebrovascular disorders in predialysis patients with CKD. Timely detection of cerebral risk factors may lead to the improvement of early diagnosis and prevention of cerebral vascular disorders, optimization of therapy for patients with CKD.

Impact of Microbleeds on Outcome Following Recanalization in Patients With Acute Ischemic Stroke

Background and Purpose- We analyzed the association between cerebral microbleeds (CMBs) and clinical outcome in acute ischemic stroke patients and especially in a subgroup of patients with successful recanalization. Methods- A total of 1532 acute ischemic stroke patients treated with intravenous thrombolysis or mechanical thrombectomy were enrolled in this prospective cohort study. The primary outcome was measured using the modified Rankin Scale at 3 months, according to the CMB status based on magnetic resonance imaging at admission. Favorable outcome was defined as functional independence with modified Rankin Scale scores of 0 to 2. Secondary outcomes included the occurrence of symptomatic intracranial hemorrhage. Results- There was no statistically significant association between the presence of CMB and favorable outcome at 3 months when considering all patients (44.3% versus 37.6%; P=0.121). In patients with recanalization, the number of patients with favorable outcomes was significantly higher in the CMB-negative than in the CMB-positive group (57.0% versus 36.0%; P<0.001). In the final multivariate analysis, the presence of CMB, and in particular high CMB burden (≥5), and lobar location, were significantly associated with less favorable 3-month outcomes (odds ratio=0.57; 95% CI, 0.33-0.97; P=0.038) and symptomatic intracranial hemorrhage (odds ratio=3.21; 95% CI, 1.37-7.49; P=0.007) in patients with recanalization. In the analysis of subgroups, a statistically significant interaction was found between CMB presence and recanalization in predicting functional outcomes at 3 months. Conclusions- These results indicate that the presence of CMBs, and especially high burden and lobar location, are independent predictors of poor 3-month clinical outcomes and may increase symptomatic intracranial hemorrhage risk in acute ischemic stroke patients with recanalization. Our findings suggest that CMBs lead to more unfavorable effects in patients with recanalization after large vessel occlusion than in those without recanalization.

Aging exacerbates development of cerebral microbleeds in a mouse model

Background

Cerebral microhemorrhages (CMH) are commonly found in the aging brain. CMH are also the neuropathological substrate of cerebral microbleeds (CMB), demonstrated on brain MRI. Recent studies demonstrate the importance of systemic inflammation in CMH development, but the relationships among inflammation, aging, and CMH development are not well-defined. In the current study, we hypothesized that the pathogenesis of inflammation-induced CMH in mice differs by age.

Methods

We studied young (3 months, n = 20) and old (18 months, n = 25) C57BL/6 mice injected with low-dose lipopolysaccharide (LPS; 1 mg/kg, i.p.) or saline at 0, 6, and 24 h. Seven days after the first LPS/saline injection, brains were harvested, sectioned, and stained with hematoxylin and eosin (H&E) and Prussian blue (PB) to estimate acute/fresh and sub-acute CMH development, respectively. The relationships between microglial/macrophage activation (ionized calcium-binding adapter molecule-1), astrocyte activation (glial fibrillary acidic protein), blood-brain barrier (BBB) disruption (brain immunoglobulin G), aging, and CMH development were examined using immunohistochemistry.

Results

Aging alone did not increase spontaneous H&E-positive CMH development but significantly increased the number, size, and total area of LPS-induced H&E-positive CMH in mice. LPS- and saline-treated aged mice had significantly larger PB-positive CMH compared with young mice, but the total area of PB-positive CMH was increased only in LPS-treated aged mice. Aged mice had significantly increased microglial/macrophage activation, which correlated with H&E- and PB-positive CMH development. Aged mice treated with LPS had significantly increased astrocyte activation and BBB disruption compared with young LPS-treated mice.

Conclusions

Aging makes the brain more susceptible to inflammation-induced CMH in mice, and this increase in CMH with aging is associated with microglial/macrophage activation.

Serum Lipid Fractions and Cerebral Microbleeds in a Healthy Japanese Population

Background: Cerebral microbleeds (CMBs) are associated with focal hemosiderin deposits and represent a form of cerebral small vessel disease. To date, indefinite and inconsistent reports are available regarding the association between serum lipid fractions and CMBs. In addition, these previous studies did not include Asian populations, who may have a higher risk of cerebral hemorrhage. The purpose of this study was to examine the associations between serum lipid fractions and CMBs in healthy Japanese subjects. Methods: We performed a cross-sectional study involving 4,024 neurologically normal Japanese subjects (mean age 61.6 years). All the participants underwent 1.5-Tesla magnetic resonance imaging scan, and CMBs were classified into 3 groups based on their locations. The concentrations of lipid fractions were categorized into quartiles and the association between the lipid fractions and CMBs were investigated using logistic regression analysis. Results: CMBs were observed in 164 (4.1%) of participants. Of these participants with CMBs, 33 (20.1%) had lobar CMBs and 91 (55.5%) had deep CMBs. Subjects with deep CMBs had lower total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) levels. After adjusting for confounding factors, lower TC and HDL-C levels were still associated with the presence of deep CMBs (OR for the highest vs. the lowest quartiles of TC and HDL-C was 2.28 [95% CI 1.05-4.94], and 1.93 [95% CI 1.02-3.65], respectively). The presence of subcortical infarcts and periventricular hyperintensities was more frequently observed in deep CMBs, whereas white matter hyperintensities were more frequently observed in lobar CMBs. Conclusions: Our results suggest that low serum TC and HDL-C levels are closely associated with deep CMBs.

The Cerebrovascular-Chronic Kidney Disease Connection: Perspectives and Mechanisms

Chronic kidney disease (CKD) is an independent risk factor for the development of cerebrovascular disease, particularly small vessel disease which can manifest in a variety of phenotypes ranging from lacunes to microbleeds. Small vessel disease likely contributes to cognitive dysfunction in the CKD population. Non-traditional risk factors for vascular injury in uremia include loss of calcification inhibitors, hyperphosphatemia, increased blood pressure variability, elastinolysis, platelet dysfunction, and chronic inflammation. In this review, we discuss the putative pathways by which these mechanisms may promote cerebrovascular disease and thus increase risk of future stroke in CKD patients.

Cerebral microbleeds in early Alzheimer's disease

We hypothesize that cerebral microbleeds (CMB) in patients with different neuropsychological profiles (amnestic or non-amnestic) and MRI features of vascular damage could provide important information on the underlying pathological process in early Alzheimer's disease. The study was performed at two trial sites. We studied 136 outpatients with cognitive decline. MRI was performed using a magnetic field of 1.5 and 3 T. Neuropsychological assessment included Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment scale (MoCA), Addenbrooke's Cognitive Examination (ACE-R), Cambridge Cognitive Examination battery (CAMCOG) (Part 3), Clock Drawing Test, fluency test and the visual memory test (SCT). CSF was examined for standard parameters such as tau, phosphorylated tau, amyloid-β 1-40 and 42 and Qalbumin, in accordance with established protocols and genotype. In 61 patients (45 %), at least 1 CMB was found. Most of the CMBs were described in the amnestic profile (67 %). In 86 % of the cases, multiple CMB were observed. The ratio of Aβ1-40/42 in non-amnestic patients with CMB was significantly lower (mean 0.6) than in patients without CMB (mean 1.2). A notable difference in the albumin ratio as an indicator of the BBB was observed between groups with and without CMB. In the CMP-positive group, the E2 genotype was observed more frequently, and the E4 genotype less frequently, than in the CMB-negative group. Based on the cerebrospinal fluid-serum albumin ratio, we were able to show that patients with CMB present several features of BBB dysfunction. According to logistic regression, the predictive factors for CMB in patients with cognitive decline were age, WMHs score and albumin ratio. We found a significant reduction in the Aβ-amyloid ratio in the non-amnestic profile group with CMB (particularly in the cortical region) in comparison to those without CMB. While this is an interesting finding, its significance needs to be assessed in a prospective follow-up.

Experimental microembolism induces localized neuritic pathology in guinea pig cerebrum

Microbleeds are a common finding in aged human brains. In Alzheimer's disease (AD), neuritic plaques composed of β-amyloid (Aβ) deposits and dystrophic neurites occur frequently around cerebral vasculature, raising a compelling question as to whether, and if so, how, microvascular abnormality and amyloid/neuritic pathology might be causally related. Here we used a guinea pig model of cerebral microembolism to explore a potential inductive effect of vascular injury on neuritic and amyloid pathogenesis. Brains were examined 7-30 days after experimental microvascular embolization occupying ~0.5% of total cortical area. Compared to sham-operated controls, glial fibrillary acidic protein immunoreactivity was increased in the embolized cerebrum, evidently around intracortical vasculature. Swollen/sprouting neurites exhibiting increased reactivity of nicotinamide adenine dinucleotide phosphate diaphorase, parvalbumin, vesicular glutamate transporter 1 and choline acetyltransferase appeared locally in the embolized brains in proximity to intracortical vasculature. The embolization-induced swollen/sprouting neurites were also robustly immunoreactive for β-amyloid precursor protein and β-secretase-1, the substrate and initiating enzyme for Aβ genesis. These experimental data suggest that microvascular injury can induce multisystem neuritic pathology associated with an enhanced amyloidogenic potential in wild-type mammalian brain.

The Significance of Cortical Cerebellar Microbleeds and Microinfarcts in Neurodegenerative and Cerebrovascular Diseases

Background: As cortical microbleeds and microinfarcts in neurodegenerative and cerebrovascular diseases have been studied predominantly at the level of the cerebral hemispheres and linked to the presence of cerebral amyloid angiopathy (CAA), we aimed at determining with 7.0-tesla magnetic resonance imaging (MRI) whether the causes and the frequency of cortical cerebellar microbleeds (CCeMBs) and microinfarcts (CCeMIs) are the same. Materials and Methods: Hundred and four postmortem brains, composed of 29 with pure Alzheimer's disease (AD), 9 with AD associated to CAA, 10 with frontotemporal lobar degeneration, 9 with amyotrophic lateral sclerosis, 10 with Lewy body disease, 12 with progressive supranuclear palsy, 9 with vascular dementia (VaD), and 16 controls, were examined. On a horizontal section of a cerebellar hemisphere examined with 7.0-tesla MRI, the number CCeMBs and CCeMIs were compared between the different disease groups and the control group. The MRI findings were also compared with the corresponding mean values observed on histological examination of a separate standard horizontal section of a cerebellar hemisphere, used for diagnostic purpose. Results: CCeMBs and CCeMIs were only significantly increased in the VaD group. When comparing the diseased patients with and without CAA mutually and with those with arterial hypertension and severe atherosclerotic cerebrovascular disease, only in the latter an increase of CCeMBs and CCeMIs was observed. There was an excellent correlation between the MRI and the neuropathological findings. Conclusions: CCeMBs and CCeMIs are mainly due to atherosclerotic cerebrovascular disease and not due to CAA. Their increased presence cannot be included to the Boston diagnostic criteria for CAA.