The glymphatic system and cerebral small vessel disease

OBJECTIVES

Cerebral small vessel disease is a group of pathologies in which alterations of the brain's blood vessels contribute to stroke and neurocognitive changes. Recently, a neurotoxic waste clearance system composed of perivascular spaces abutting the brain's blood vessels, termed the glymphatic system, has been identified as a key player in brain homeostasis. Given that small vessel disease and the glymphatic system share anatomical structures, this review aims to reexamine small vessel disease in the context of the glymphatic system and highlight novel aspects of small vessel disease physiology.

MATERIALS AND METHODS

This review was conducted with an emphasis on studies that examined aspects of small vessel disease and on works characterizing the glymphatic system. We searched PubMed for relevant articles using the following keywords: glymphatics, cerebral small vessel disease, arterial pulsatility, hypertension, blood-brain barrier, endothelial dysfunction, stroke, diabetes.

RESULTS

Cerebral small vessel disease and glymphatic dysfunction are anatomically connected and significant risk factors are shared between the two. These include hypertension, type 2 diabetes, advanced age, poor sleep, obesity, and neuroinflammation. There is clear evidence that CSVD hinders the effective functioning of glymphatic system.

CONCLUSION

These shared risk factors, as well as the model of cerebral amyloid angiopathy pathogenesis, hint at the possibility that glymphatic dysfunction could independently contribute to the pathogenesis of cerebral small vessel disease. However, the current evidence supports a model of cascading dysfunction, wherein concurrent small vessel and glymphatic injury hinder glymphatic-mediated recovery and promote the progression of subclinical to clinical disease.

Early life predictors of late life cerebral small vessel disease in four prospective cohort studies

Development of cerebral small vessel disease, a major cause of stroke and dementia, may be influenced by early life factors. It is unclear whether these relationships are independent of each other, of adult socio-economic status or of vascular risk factor exposures. We examined associations between factors from birth (ponderal index, birth weight), childhood (IQ, education, socio-economic status), adult small vessel disease, and brain volumes, using data from four prospective cohort studies: STratifying Resilience And Depression Longitudinally (STRADL) (n = 1080; mean age = 59 years); the Dutch Famine Birth Cohort (n = 118; mean age = 68 years); the Lothian Birth Cohort 1936 (LBC1936; n = 617; mean age = 73 years), and the Simpson's cohort (n = 110; mean age = 78 years). We analysed each small vessel disease feature individually and summed to give a total small vessel disease score (range 1-4) in each cohort separately, then in meta-analysis, adjusted for vascular risk factors and adult socio-economic status. Higher birth weight was associated with fewer lacunes [odds ratio (OR) per 100 g = 0.93, 95% confidence interval (CI) = 0.88 to 0.99], fewer infarcts (OR = 0.94, 95% CI = 0.89 to 0.99), and fewer perivascular spaces (OR = 0.95, 95% CI = 0.91 to 0.99). Higher childhood IQ was associated with lower white matter hyperintensity burden (OR per IQ point = 0.99, 95% CI 0.98 to 0.998), fewer infarcts (OR = 0.98, 95% CI = 0.97 to 0.998), fewer lacunes (OR = 0.98, 95% CI = 0.97 to 0.999), and lower total small vessel disease burden (OR = 0.98, 95% CI = 0.96 to 0.999). Low education was associated with more microbleeds (OR = 1.90, 95% CI = 1.33 to 2.72) and lower total brain volume (mean difference = -178.86 cm3, 95% CI = -325.07 to -32.66). Low childhood socio-economic status was associated with fewer lacunes (OR = 0.62, 95% CI = 0.40 to 0.95). Early life factors are associated with worse small vessel disease in later life, independent of each other, vascular risk factors and adult socio-economic status. Risk for small vessel disease may originate in early life and provide a mechanistic link between early life factors and risk of stroke and dementia. Policies investing in early child development may improve lifelong brain health and contribute to the prevention of dementia and stroke in older age.

COVID-19 Infection and Circulating Microparticles-Reviewing Evidence as Microthrombogenic Risk Factor for Cerebral Small Vessel Disease

Severe acute respiratory syndrome corona virus-2 (SARS-CoV-2) due to novel coronavirus disease 2019 (COVID-19) has affected the global society in numerous unprecedented ways, with considerable morbidity and mortality. Both direct and indirect consequences from COVID-19 infection are recognized to give rise to cardio- and cerebrovascular complications. Despite current limited knowledge on COVID-19 pathogenesis, inflammation, endothelial dysfunction, and coagulopathy appear to play critical roles in COVID-19-associated cerebrovascular disease (CVD). One of the major subtypes of CVD is cerebral small vessel disease (CSVD) which represents a spectrum of pathological processes of various etiologies affecting the brain microcirculation that can trigger subsequent neuroinflammation and neurodegeneration. Prevalent with aging, CSVD is a recognized risk factor for stroke, vascular dementia, and Alzheimer's disease. In the background of COVID-19 infection, the heightened cellular activations from inflammations and oxidative stress may result in elevated levels of microthrombogenic extracellular-derived circulating microparticles (MPs). Consequently, MPs could act as pro-coagulant risk factor that may serve as microthrombi for the vulnerable microcirculation in the brain leading to CSVD manifestations. This review aims to appraise the accumulating body of evidence on the plausible impact of COVID-19 infection on the formation of microthrombogenic MPs that could lead to microthrombosis in CSVD manifestations, including occult CSVD which may last well beyond the pandemic era.

Carotid intima-media thickness and arterial stiffness in relation to cerebral small vessel disease in neurologically asymptomatic individuals with type 1 diabetes

AIMS

To determine if arterial functional and structural changes are associated with underlying cerebral small vessel disease in neurologically asymptomatic individuals with type 1 diabetes.

METHODS

We enrolled 186 individuals (47.8% men; median age 40.0, IQR 33.0-45.0 years) with type 1 diabetes (median diabetes duration of 21.6, IQR 18.2-30.3 years), and 30 age- and sex-matched healthy controls, as part of the Finnish Diabetic Nephropathy (FinnDiane) Study. All individuals underwent a biochemical work-up, brain magnetic resonance imaging (MRI), ultrasound of the common carotid arteries and arterial tonometry. Arterial structural and functional parameters were assessed by carotid intima-media thickness (CIMT), pulse wave velocity and augmentation index.

RESULTS

Cerebral microbleeds (CMBs) were present in 23.7% and white matter hyperintensities (WMHs) in 16.7% of individuals with type 1 diabetes. Those with type 1 diabetes and CMBs had higher median (IQR) CIMT 583 (525 - 663) μm than those without 556 (502 - 607) μm, p = 0.016). Higher CIMT was associated with the presence of CMBs (p = 0.046) independent of age, eGFR, ApoB, systolic blood pressure, albuminuria, history of retinal photocoagulation and HbA_1c. Arterial stiffness and CIMT were increased in individuals with type 1 diabetes and WMHs compared to those without; however, these results were not independent of cardiovascular risk factors.

CONCLUSIONS

Structural, but not functional, arterial changes are associated with underlying CMBs in asymptomatic individuals with type 1 diabetes.

The dynamic change of phenotypic markers of smooth muscle cells in an animal model of cerebral small vessel disease

BACKGROUND

The pathological character of cerebral small vessel disease (CSVD) is the dysfunction of cerebral small arteries caused by risk factors. A switch from the contractile phenotype to the synthetic phenotype of vascular smooth muscle cells (SMCs) can decrease the contractility of arteries. The alteration of the vascular wall extracellular matrix (ECM) is found to regulate the process. We speculated that SMCs phenotype changes may also occur in CSVD induced by hypertension and the alteration of ECM especially fibronectin and laminin may regulate the process.

METHOD

Male spontaneously hypertensive rats (SHR) were used as a CSVD animal model. SMCs phenotypic markers and the ECM expression of the cerebral small arteries of SHR at different ages were evaluated by immunofluorescence. The phenotype changes of primary brain microvascular SMCs cultured on laminin-coating dish or fibronectin-coating dish were evaluated by western blot.

RESULT

A switch from the contractile phenotype to synthetic phenotype in SHR at 10 and 22 weeks of age was observed. Meanwhile, increased expression of fibronectin and a temporary decline of laminin was found in small arteries of SHR at 22 weeks. In vitro experiments also convinced that SMCs cultured on a fibronectin-coating dish failed to maintain contractile phenotype. While at 50 weeks, significant drops of both synthetic and contractile phenotypic markers were witnessed in SHR, with high expressions of four kinds of ECM.

CONCLUSION

SMCs in cerebral small arteries exhibited a switch from the contractile phenotype to synthetic phenotype during the chronic process of hypertension and aging. Moreover, the change of fibronectin and laminin may regulate the process.

Association between periodontal disease due to Campylobacter rectus and cerebral microbleeds in acute stroke patients

Oral health conditions and cerebral small vessel disease, such as white matter lesions or cerebral microbleeds (CMBs), are associated with the incidence of stroke. The purpose of this study was to examine the associations between oral health conditions (serum IgG titers of periodontal pathogens) with the presence or severity of CMBs in acute stroke patients. From January 2013 to April 2016, acute stroke patients were registered in two hospitals. Serum samples were evaluated for antibody titers against 9 periodontal pathogens using the ELISA method. The cut-off points for reactivity (the positive decision point) to each antigen were defined as more than a mean ELISA unit + 1 standard deviation (after logarithmic transformation) in all subjects. CMBs were evaluated on T2*-weighted MRI. In all, 639 patients were evaluated (ischemic, n = 533 and hemorrhagic, n = 106; 73.1 ± 12.9 years old). Among these patients, 627 were available for CMB evaluation. Among the 9 evaluated periodontal pathogens, only Campylobacter rectus (C. rectus) was associated with the presence of CMBs. the prevalence of positive serum antibody titers against C. rectus was higher among patients with CMBs than among those without CMBs (14.6% vs. 8.7%, P = 0.025). In addition, positive serum antibody titers against C. rectus remained one of the factors associated with the presence of CMBs in multivariate logistic analysis (odds ratio 2.03, 95% confidence interval 1.19–3.47, P = 0.010). A positive serum antibody titer against C. rectus was associated with the presence of CMBs in acute stroke patients.

Genetically determined blood pressure, antihypertensive drug classes, and risk of stroke subtypes

OBJECTIVE

We employed Mendelian randomization to explore whether the effects of blood pressure (BP) and BP-lowering through different antihypertensive drug classes on stroke risk vary by stroke etiology.

METHODS

We selected genetic variants associated with systolic and diastolic BP and BP-lowering variants in genes encoding antihypertensive drug targets from genome-wide association studies (GWAS) on 757,601 individuals. Applying 2-sample Mendelian randomization, we examined associations with any stroke (67,162 cases; 454,450 controls), ischemic stroke and its subtypes (large artery, cardioembolic, small vessel stroke), intracerebral hemorrhage (ICH, deep and lobar), and the related small vessel disease phenotype of white matter hyperintensities (WMH).

RESULTS

Genetic predisposition to higher systolic and diastolic BP was associated with higher risk of any stroke, ischemic stroke, and ICH. We found associations between genetically determined BP and all ischemic stroke subtypes with a higher risk of large artery and small vessel stroke compared to cardioembolic stroke, as well as associations with deep, but not lobar ICH. Genetic proxies for calcium channel blockers, but not β-blockers, were associated with lower risk of any stroke and ischemic stroke. Proxies for calcium channel blockers showed particularly strong associations with small vessel stroke and the related radiologic phenotype of WMH.

CONCLUSIONS

This study supports a causal role of hypertension in all major stroke subtypes except lobar ICH. We find differences in the effects of BP and BP-lowering through antihypertensive drug classes between stroke subtypes and identify calcium channel blockade as a promising strategy for preventing manifestations of cerebral small vessel disease.

Stroke and COVID19: Not only a large-vessel disease

Recent evidence has underlined the association between large-vessel stroke and COVID-19, probably due to a proinflammatory and prothrombotic microenvironment induced by SARS-CoV-2. Here, we report the case of a young fit woman affected by COVID-19 without any flu-like symptom, who suffered from speech disorder and left hemiparesis. Brain magnetic resonance evidenced two small acute brain infarctions in right perirolandic cortex without signs of previous ischemic lesions and hemorrhagic infarction. Diagnostic workup excluded cardiac embolic sources, acquired and inherited thrombophilia or autoimmune diseases. Two positive nasopharyngeal swab tests and high titers of serum specific IgA/IgM confirmed COVID-19 diagnosis. In our case stroke seems to be the only manifestation of SARS-COV-2 infection. Therefore the hypothesis of an underlying viral infection, as COVID-19, should be investigated in all the cases of small vessel cryptogenic stroke.

Hypertensive Arteriopathy and Cerebral Amyloid Angiopathy in Patients with Cognitive Decline and Mixed Cerebral Microbleeds

BACKGROUND

Hypertensive arteriopathy (HA) and cerebral amyloid angiopathy (CAA) may contribute to the development of mixed cerebral microbleeds (CMBs). Recently, the total small vessel disease (SVD) scores for HA and CAA were proposed, which are determined by a combination of MRI markers to reflect overall severity of these microangiopathies.

OBJECTIVE

We investigated whether or not total HA-SVD and CAA-SVD scores could be used to predict overlap of HA and CAA in patients with mixed CMBs.

METHODS

Fifty-three subjects with mixed CMBs were retrospectively analyzed. MRI markers (CMBs, lacunes, perivascular space, white matter hyperintensity [WMH] and cortical superficial siderosis [cSS]) were assessed. The HA-SVD score and CAA-SVD score were obtained for each subject. Anterior or posterior WMH was also assessed using the age-related white matter changes scale.

RESULTS

The two scores were positively correlated (ρ= 0.449, p < 0.001). The prevalence of lobar dominant CMB distribution (p < 0.001) and lacunes in the centrum semiovale (p < 0.001) and the severity of WMH in the parieto-occipital lobes (p = 0.004) were significantly higher in the high CAA-SVD score group. cSS was found in four patients with high CAA-SVD score who showed lobar-dominant CMB distribution and severe posterior WMH.

CONCLUSION

Mixed CMBs are mainly due to HA. Assessing both two scores may predict the overlap of HA and CAA in individuals with mixed CMBs. Patients with a high CAA-SVD score may have some degree of advanced CAA, especially when lobar predominant CMBs, severe posterior WMH, lobar lacunes, or cSS are observed.

Nonarteritic anterior ischemic optic neuropathy is associated with cerebral small vessel disease

We investigated the presence of cerebral small vessel disease (SVD) in patients with nonarteritic anterior ischemic optic neuropathy (NAION) compared to control subjects without NAION to identify the association between NAION and cerebral SVD. We retrospectively reviewed the cases of 63 patients with NAION and 2749 control subjects without any neurologic and ocular diseases including NAION who underwent careful medical interviews, ophthalmic examinations, and magnetic resonance imaging (MRI) studies of the brain. We assessed and compared the degree of cerebral SVD on the MRIs. The patients with NAION presented with cerebral SVD more frequently than controls (68% versus 37%, respectively, p<0.001), which was also observed after adjusting for age, sex, comorbid conditions including hypertension, diabetes, and dyslipidemia, and smoking using the standardized mortality ratio (68% vs. 37%, p<0.001). A multivariate logistic regression analysis showed that the odds of cerebral SVD were 4.86 (95% CI, 2.10 to 11.24, p<0.001) times higher in patients with NAION than in the controls. We found that there was an association between cerebral SVD and NAION even after adjusting for age, sex, and medical histories. Clinicians should consider brain MRI scans in patients with NAION to prevent neurological impairment after cerebral SVD.

Inflammation and cerebral small vessel disease: A systematic review

Inflammation is increasingly implicated as a risk factor for dementia, stroke, and small vessel disease (SVD). However, the underlying mechanisms and causative pathways remain unclear. We systematically reviewed the existing literature on the associations between markers of inflammation and SVD (i.e., white matter hyperintensities (WMH), lacunes, enlarged perivascular spaces (EPVS), cerebral microbleeds (CMB)) in cohorts of older people with good health, cerebrovascular disease, or cognitive impairment. Based on distinctions made in the literature, markers of inflammation were classified as systemic inflammation (e.g. C-reactive protein, interleukin-6, fibrinogen) or vascular inflammation/endothelial dysfunction (e.g. homocysteine, von Willebrand factor, Lp-PLA2). Evidence from 82 articles revealed relatively robust associations between SVD and markers of vascular inflammation, especially amongst stroke patients, suggesting that alterations to the endothelium and blood-brain barrier may be a driving force behind SVD. Conversely, cross-sectional findings on systemic inflammation were mixed, although longitudinal investigations demonstrated that elevated levels of systemic inflammatory markers at baseline predicted subsequent SVD severity and progression. Importantly, regional analysis revealed that systemic and vascular inflammation were differentially related to two distinct forms of SVD. Specifically, markers of vascular inflammation tended to be associated with SVD in areas typical of hypertensive arteriopathy (e.g., basal ganglia), while systemic inflammation appeared to be involved in CAA-related vascular damage (e.g., centrum semiovale). Nonetheless, there is insufficient data to establish whether inflammation is causal of, or secondary to, SVD. Findings have important implications on interventions, suggesting the potential utility of treatments targeting the brain endothelium and blood brain barrier to combat SVD and associated neurodegenerative diseases.

Small Vessel Disease Is Associated with Tissue Inhibitor of Matrix Metalloproteinase-4 After Ischaemic Stroke

Small vessel disease (SVD) is frequent in aging and stroke patients. Inflammation and remodeling of extracellular matrix have been suggested as concurrent mechanisms of SVD. We investigated the relationship between imaging features of SVD and circulating metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in patients with ischaemic stroke. In patients treated with intravenous thrombolysis, we took blood samples before intravenous thrombolysis and 90 days after the acute stroke and analysed levels of MMPs and TIMPs. We assessed leukoaraiosis, number of lacunes and brain atrophy on pre-treatment CT scan and graded global SVD burden combining such features. We investigated associations between single features, global SVD and MMPs and TIMPs at baseline and at follow-up, retaining univariate statistically significant associations in multivariate linear regression analysis and adjusting for clinical confounders. A total of 255 patients [mean (±SD) = 68.6 (± 12.7) years, 154 (59%) males] were included, 107 (42%) had no signs of SVD; 47 (19%) had from moderate to severe SVD burden. A total of 107 (42%) patients had no signs of SVD; 47 (19%) had from moderate to severe SVD burden. After adjustment, only TIMP-4 proved associations with SVD features. Brain atrophy was associated with baseline TIMP-4 (β = 0.20;p = 0.019) and leukoaraiosis with 90 days TIMP-4 (β = 0.19; p = 0.013). Global SVD score was not associated with baseline TIMP-4 levels (β = 0.10; p = 0.072), whereas was associated with 90 days TIMP-4 levels (β = 0.21; p = 0.003). Total SVD burden was associated with higher TIMP-4 levels 90 days after stroke, whereas was not during the acute phase. Our results support a biological relationship between SVD grade and TIMP-4.

Doppler Resistivity and Cerebral Small Vessel Disease: Hemodynamic Structural Correlation and Usefulness for the Etiological Classification of Acute Ischemic Stroke

INTRODUCTION AND GOAL

Lacunar stroke is defined as an <1.5 cm diameter infarct located in the territory of a perforating artery, that is not accessible for direct study using conventional imaging techniques. Diagnosis requires exclusion of other causes. It usually occurs in the context of chronic cerebral small vessel disease, which can be suspected during the neurosonography study in the form of high pulsatility [PI] or resistance index [RI]. Clinical research was performed to confirm that PI and RI correlate with cerebral small vessel lesion burden and to determine whether these parameters are useful for supporting a lacunar origin (LO) in acute stroke.

MATERIAL AND METHODS

We prospectively recorded internal carotid artery resistivity and the Fazekas score for all patients with acute ischemic stroke who met inclusion but not exclusion criteria over a 6-month period.

RESULTS

The study population comprised 74 patients. A correlation was observed between the Fazekas score and resistivity. Both parameters predicted a LO, with an area under the curve of .78 and .696, respectively. The optimal cut-offs were PI = .96/RI = .58 for screening (sensitivity, 96%) and PI = 1.46/RI = .83 for confirmation (specificity, 89%).

CONCLUSIONS

Doppler ultrasound is a useful technique for determining the LO of acute stroke.

Cerebral small vessel disease: neuroimaging markers and clinical implication

Cerebral small vessel disease (CSVD) is a broad category of cerebrovascular diseases which primarily affect the perforating arterioles, capillaries and venules with multiple distinct etiologies. In spite of distinctive pathogenesis, CSVD shares similar neuroimaging markers, including recent small subcortical infarct, lacune of presumed vascular origin, white matter hyperintensity of presumed vascular origin, perivascular space and cerebral microbleeds. The radiological features of neuroimaging markers are indicative for etiological analysis. Furthermore, in sporadic arteriosclerotic pathogenesis associated CSVD, the total CSVD burden is a significant predictor for stroke events, global cognitive impairment, psychiatric disorders and later life quality. This review aims to summarize the radiological characteristics as well as the clinical implication of CSVD markers and neuroimaging interpretation for CSVD symptomatology.

Doppler Resistivity and Cerebral Small Vessel Disease: Hemodynamic Structural Correlation and Usefulness for the Etiological Classification of Acute Ischemic Stroke

INTRODUCTION AND GOAL

Lacunar stroke is defined as an <1.5 cm diameter infarct located in the territory of a perforating artery, that is not accessible for direct study using conventional imaging techniques. Diagnosis requires exclusion of other causes. It usually occurs in the context of chronic cerebral small vessel disease, which can be suspected during the neurosonography study in the form of high pulsatility [PI] or resistance index [RI]. Clinical research was performed to confirm that PI and RI correlate with cerebral small vessel lesion burden and to determine whether these parameters are useful for supporting a lacunar origin (LO) in acute stroke.

MATERIAL AND METHODS

We prospectively recorded internal carotid artery resistivity and the Fazekas score for all patients with acute ischemic stroke who met inclusion but not exclusion criteria over a 6-month period.

RESULTS

The study population comprised 74 patients. A correlation was observed between the Fazekas score and resistivity. Both parameters predicted a LO, with an area under the curve of .78 and .696, respectively. The optimal cut-offs were PI = .96/RI = .58 for screening (sensitivity, 96%) and PI = 1.46/RI = .83 for confirmation (specificity, 89%).

CONCLUSIONS

Doppler ultrasound is a useful technique for determining the LO of acute stroke.

Small vessels, dementia and chronic diseases - molecular mechanisms and pathophysiology

Cerebral small vessel disease (SVD) is a major contributor to stroke, cognitive impairment and dementia with limited therapeutic interventions. There is a critical need to provide mechanistic insight and improve translation between pre-clinical research and the clinic. A 2-day workshop was held which brought together experts from several disciplines in cerebrovascular disease, dementia and cardiovascular biology, to highlight current advances in these fields, explore synergies and scope for development. These proceedings provide a summary of key talks at the workshop with a particular focus on animal models of cerebral vascular disease and dementia, mechanisms and approaches to improve translation. The outcomes of discussion groups on related themes to identify the gaps in knowledge and requirements to advance knowledge are summarized.

Sex differences in associations between blood lipids and cerebral small vessel disease

BACKGROUND AND AIMS

Dyslipidemia predicts higher risk of coronary events and stroke and might be associated with cerebral small vessel disease (SVD). Previous studies linking blood lipids and SVD have yielded inconsistent results, which may be attributable to sex differences in lipids metabolism. The aim of this study was to investigate the relationships between blood lipids and SVD in neurologically healthy men and women.

METHODS AND RESULTS

Consecutive 817 people aged 50 years or more were enrolled and underwent magnetic resonance imaging scans to evaluate the periventricular white matter lesions (PVWMLs), deep white matter lesions (DWMLs) and silent brain infarction (SBI). Fasting total cholesterol, triglyceride, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol, apolipoprotein A-1 (apoA-1) and apolipoprotein B were assessed. Multivariable logistic regression analyses were performed to determine the associations of blood lipids with PVWMLs, DWMLs and SBI. HDL-C (for PVWMLs: OR 0.36, 95% CI 0.19-0.71; for DWMLs: OR 0.35, 95% CI 0.20-0.63) and apoA-1 (for PVWMLs: OR 0.27, 95% CI 0.11-0.66; for DWMLs: OR 0.22, 95% CI 0.10-0.48) were inversely associated with the severity of PVWMLs and DWMLs in women but not in men after adjustment for age, hypertension, diabetes, current smoking, daily drinking, body mass index and uric acid. Additionally, no blood lipids were significantly associated with SBI.

CONCLUSIONS

Our findings demonstrate that sex differences may exist in the associations between lipids and SVD. HDL-C and apoA-1 levels were inversely associated with the severity of PVWMLs and DWMLs in women.

Total Magnetic Resonance Imaging Burden of Small Vessel Disease in Cerebral Amyloid Angiopathy: An Imaging-Pathologic Study of Concept Validation

IMPORTANCE

Cerebral amyloid angiopathy (CAA) is characteristically associated with magnetic resonance imaging (MRI) biomarkers of small vessel brain injury, including strictly lobar cerebral microbleeds, cortical superficial siderosis, centrum semiovale perivascular spaces, and white matter hyperintensities. Although these neuroimaging markers reflect distinct pathophysiologic aspects in CAA, no studies to date have combined these structural imaging features to gauge total brain small vessel disease burden in CAA.

OBJECTIVES

To investigate whether a composite score can be developed to capture the total brain MRI burden of small vessel disease in CAA and to explore whether this score contributes independent and complementary information about CAA severity, defined as intracerebral hemorrhage during life or bleeding-related neuropathologic changes.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective, cross-sectional study examined a single-center neuropathologic CAA cohort of eligible patients from the Massachusetts General Hospital from January 1, 1997, through December 31, 2012. Data analysis was performed from January 2, 2015, to January 9, 2016. Patients with pathologic evidence of CAA (ie, any presence of CAA from routinely collected brain biopsy specimen, biopsy specimen at hematoma evacuation, or autopsy) and available brain MRI sequences of adequate quality, including T2-weighted, T2*-weighted gradient-recalled echo, and/or susceptibility-weighted imaging and fluid-attenuated inversion recovery sequences, were considered for the study.

MAIN OUTCOMES AND MEASURES

Brain MRIs were rated for lobar cerebral microbleeds, cortical superficial siderosis, centrum semiovale perivascular spaces, and white matter hyperintensities. All 4 MRI lesions were incorporated into a prespecified ordinal total small vessel disease score, ranging from 0 to 6 points. Associations with severity of CAA-associated vasculopathic changes (fibrinoid necrosis and concentric splitting of the wall), clinical presentation, number of intracerebral hemorrhages, and other imaging markers not included in the score were explored using logistic and ordinal regression.

RESULTS

In total, 105 patients with pathologically defined CAA were included: 52 with autopsies, 22 with brain biopsy specimens, and 31 with pathologic samples from hematoma evacuations. The mean (range) age of the patients was 73 (71-74) years, and 55 (52.4%) were women. In multivariable ordinal regression analysis, severity of CAA-associated vasculopathic changes (odds ratio, 2.40; 95% CI, 1.06-5.45; P = .04) and CAA presentation with symptomatic intracerebral hemorrhage (odds ratio, 2.23; 95% CI, 1.07-4.64; P = .03) were independently associated with the total MRI small vessel disease score. The score was associated with small, acute, diffusion-weighted imaging lesions and posterior white matter hyperintensities in adjusted analyses.

CONCLUSIONS AND RELEVANCE

This study provides evidence of concept validity of a total MRI small vessel disease score in CAA. After further validation, this approach can be potentially used in prospective clinical studies.

[Clinical relevance of cerebral microbleeds--update]

Cerebral microbleeds (CMBs) on paramagnetic-sensitive magnetic resonance sequences correspond pathologically to clusters of hemosiderin-laden macrophages and have emerged as an important new imaging marker of cerebral small vessel disease (SVD), including intracerebral hemorrhage (ICH). The prevalence of CMBs varies according to the specific disease settings (stroke subtypes and demented disorders) and is highest in ICH patients. The associations of CMBs with aging, hypertension and apolipoprotein E genotype are consistent with the two major underlying pathogenesis of CMBs: hypertensive arteriopathy and cerebral amyloid angiopathy (CAA). The distributional patterns of CMBs might help us understand the predominant SVD pathogenesis of the brain; the strictly lobar type of CMBs often reflects the presence of advanced CAA, while the other types of CMBs, such as "deep or infratentorial CMBs", including the mixed type, are strongly associated with hypertension.

Brain Activation and Psychomotor Speed in Middle-Aged Patients with Type 1 Diabetes: Relationships with Hyperglycemia and Brain Small Vessel Disease

Slower psychomotor speed is very common in patients with type 1 diabetes mellitus (T1D), but the underlying mechanisms are not clear. We propose that hyperglycemia is associated with slower psychomotor speed via disruption of brain activation. Eighty-five adults (48% women, mean age: 49.0 years, mean duration: 40.8) with childhood onset T1D were recruited for this cross-sectional study. Median response time in seconds (longer = worse performance) and brain activation were measured while performing a psychomotor speed task. Exposure to hyperglycemia, measured as glycosylated hemoglobin A1c, was associated with longer response time and with higher activation in the inferior frontal gyrus and primary sensorimotor and dorsal cingulate cortex. Higher activation in inferior frontal gyrus, primary sensorimotor cortex, thalamus, and cuneus was related to longer response times; in contrast, higher activation in the superior parietal lobe was associated with shorter response times. Associations were independent of small vessel disease in the brain or other organs. In this group of middle-aged adults with T1D, the pathway linking chronic hyperglycemia with slower processing speed appears to include increased brain activation, but not small vessel disease. Activation in the superior parietal lobe may compensate for dysregulation in brain activation in the presence of hyperglycemia.

Diffuse Proliferative Cerebral Angiopathy: A case report and review of the literature

Diffuse proliferative cerebral angiopathy is a distinct entity from cerebral arterio-venous malformations; characterized by multiple small arterial feeders and draining veins with normal brain parenchyma seen in-between the abnormal vessels. It is usually seen in younger age group. Here we report a case of diffuse cerebral proliferative angiopathy in a 78-year-old female patient along with discussion of the neuro-imaging findings and review of the literature. It is important to recognize this entity to avoid aggressive surgery or intervention and thus preventing permanent damage to the normal intermingled brain tissue.

[Pathogenesis and clinical manifestations of sporadic cerebral small vessel disease]

Sporadic small vessel disease (sSVD) is one of the most common vascular disease of the central nervous system (CNS). It is the main cause of lacunar stokes, hemorrhages to deep brain regions and chronic CNS diseases such as vascular parkinsonism and dementia. Beside a high and growing incidence of sSVD especially in the elderly population, the knowledge of ethiopathogenesis and optimal treatment of sSVD have not been established. The article summarizes different clinical manifestations (acute and chronic) as well as heterogenous radiologic changes found in CNS neuroimaging.

Sleep Duration, Kidney Function, and Their Effects on Cerebral Small Vessel Disease in Elderly Hypertensive Patients

BACKGROUND

Short sleep duration has been shown to be associated with cardio/cerebrovascular disease. White matter hyperintensities (WMH) have been associated with an increased risk of stroke. In addition to high ambulatory blood pressure (BP), chronic kidney disease (CKD) is a risk for WMH. In this study, we investigated the relationships among sleep duration, CKD, and WMH in elderly hypertensives.

METHODS

Ambulatory BP monitoring and brain magnetic resonance imaging were performed in 514 Japanese elderly hypertensives (mean age 72.3 years, males 37%). WMH cases were further divided into deep subcortical white matter lesion or periventricular hyperintensity (PVH). CKD (n = 193) was defined as estimated glomerular filtration rate less than 60 ml/min/1.73 m(2).

RESULTS

According to sleep duration (<7.5, ≥7.5 to <9.5, and ≥9.5 hour per night), significant associations of sleep duration were observed with WMH and PVH. In the regression analysis including age, gender, smoking, antiplatelet agents use, 24-hour systolic BP, nondipper, white coat hypertension and CKD, short sleep duration was significantly positively associated with WMH and PVH when subjects with mid-range sleep duration were used as a reference group. A significant interaction was found between short sleep duration and CKD for PVH. In the non-CKD group, short sleep duration had strong significant positive associations with WMH and PVH.

CONCLUSIONS

In the present study, short sleep duration was a positive significant determinant for WMH and PVH in elderly hypertensives. Sleep duration might serve as a strong determinant for white matter lesions especially in those without CKD.

ASCO classification in clinical practice

ASCO (Atherosclerosis, Small vessel disease, Cardiac source, Other cause) is a new of classification of ischemic cerebrovascular diseases. This classification categorizes the data of the patients according to all underlying diseases and allows the clinician to grade the severity of cause (Each of the four phenotypes can be graded 1, 2, or 3). It is suggested to use ASCO classification in large epidemiologic studies but this classification may be used in daily practice. In this study we aimed to analyze the clinical features of patients with ischemic stroke and to investigate results of ASCO classification of these patients and data of 35 patients with ischemic stroke is analyzed. Use of ASCO classification is discussed with the special example cases. Patients' etiology of stroke was classified according to ASCO as known, unknown, completely unknown and unclassifiable group. Percentile of the patients classified as "known" was 71.4% (n = 25), "unknown" was 17.1% (n = 6), "completely unknown" was 5.7% (n = 2) and "unclassifiable group" was 5.7% (n = 2). We think that the ASCO classification which is thought to be more useful in large epidemiologic studies may be used in clinical follow-up period of the stroke patients. Further studies, from different neurology centers and stroke units, are needed to expand our experiences about use of ASCO classification in clinical practice.

Kidney pathology precedes and predicts the pathological cascade of cerebrovascular lesions in stroke prone rats

Introduction

Human cerebral small vessel disease (CSVD) has been hypothesized to be an age-dependent disease accompanied by similar vascular changes in other organs. SHRSP feature numerous vascular risk factors and may be a valid model of some aspects of human CSVD. Here we compare renal histopathological changes with the brain pathology of spontaneously hypertensive stroke-prone rats (SHRSP).

Material and Methods

We histologically investigated the brains and kidneys of 61 SHRSP at different stages of age (12 to 44 weeks). The brain pathology (aggregated erythrocytes in capillaries and arterioles, microbleeds, microthromboses) and the kidney pathology (aggregated erythrocytes within peritubular capillaries, tubular protein cylinders, glomerulosclerosis) were quantified separately. The prediction of the brain pathology by the kidney pathology was assessed by creating ROC-curves integrating the degree of kidney pathology and age of SHRSP.

Results

Both, brain and kidney pathology, show an age-dependency and proceed in definite stages whereas an aggregation of erythrocytes in capillaries and arterioles, we parsimoniously interpreted as stases, represent the initial finding in both organs. Thus, early renal tubulointerstitial damage characterized by rather few intravasal erythrocyte aggregations and tubular protein cylinders predicts the initial step of SHRSPs' cerebral vascular pathology marked by accumulated erythrocytes. The combined increase of intravasal erythrocyte aggregations and protein cylinders accompanied by glomerulosclerosis and thrombotic renal microangiopathy in kidneys of older SHRSP predicts the final stages of SHRSPs' cerebrovascular lesions marked by microbleeds and thrombotic infarcts.

Conclusion

Our results illustrate a close association between structural brain and kidney pathology and support the concept of small vessel disease to be an age-dependent systemic pathology. Further, an improved joined nephrologic and neurologic diagnostic may help to identify patients with CSVD at an early stage.