Cortical atrophy in patients with cerebral amyloid angiopathy: a case-control study

Cortical thickness and structural covariance network alterations in cerebral amyloid angiopathy: A graph theoretical analysis

AIMS

This study investigates large-scale brain network alterations in cerebral amyloid angiopathy (CAA) using structural covariance network (SCN) analysis and graph theory based on 7 T MRI.

METHODS

We employed structural covariance network (SCN) analysis based on cortical thickness data from ultra-high field 7 T MRI to investigate network alterations in CAA patients. Graph theoretical analysis was applied to quantify topological properties, including small-worldness, nodal centrality, and network efficiency. Between-group differences were assessed using permutation tests and false discovery rate (FDR) correction.

RESULTS

CAA patients exhibited significant alterations in small-world properties, with decreased Gamma (p = 0.002) and Sigma (p < 0.001), suggesting a shift toward a less optimal network configuration. Local efficiency was significantly different between groups (p = 0.045), while global efficiency remained unchanged (p = 0.127), indicating regionally disrupted rather than globally impaired network efficiency. At the nodal level, the right superior frontal gyrus exhibited increased betweenness centrality (p = 0.013), whereas the right banks of the superior temporal sulcus, left postcentral gyrus, and left superior temporal gyrus showed significantly reduced centrality (all p < 0.05). Additionally, nodal degree and efficiency were altered in key memory-related and association regions, including the entorhinal cortex, fusiform gyrus, and temporal pole.

CONCLUSION

SCN analysis combined with graph theory offers a valuable approach for understanding disease-related connectivity disruptions and may contribute to the development of network-based biomarkers for CAA.

Relationship between cerebrospinal fluid circulation markers, brain degeneration, and cognitive impairment in cerebral amyloid angiopathy

Objectives

To investigate whether cerebrospinal fluid (CSF) circulation markers alter in patients with probable cerebral amyloid angiopathy (pCAA) and whether they are associated with brain degeneration and cognitive impairment.

Methods

We screened pCAA patients from the ADNI3 database according to the Boston 2.0 Criteria. Fifty-two patients with cognitive impairment (26 pCAA; 26 age-sex-matched non-pCAA) and 26 age-sex-matched cognitively normal control (NC) were included in this study. All participants underwent neurological MRI and cognitive assessments. Choroid plexus (ChP) was segmented using a deep learning-based method and its volume was extracted. Diffusion tensor imaging analysis along the perivascular space (DTI-ALPS) was used to assess perivenous fluid mobility. AD pathological markers (Aβ and tau) were assessed using positron emission tomography. Brain parenchymal damage markers included white matter hyperintensities (WMH) volume and brain atrophy ratio. All markers were compared among the three groups. Correlations among the ChP volume, DTI-ALPS index, parenchymal damage markers, and cognitive scales were analyzed in the pCAA group.

Results

The three groups exhibited significant differences in cognitive scores, AD biomarkers, and imaging markers. Post hoc analyses showed that patients with pCAA had significantly higher WMH volume, higher Aβ and tau deposition, and lower DTI-ALPS compared to NC. However, no difference in ChPs volume was found among the groups. Controlling for age, sex, and vascular risk factors, partial correlation analyses showed a significant negative correlation between the DTI-ALPS and WMH volume fraction (r = -0.606, p = 0.002). ChP volume was significantly associated with the Montreal cognitive assessment score (r = -0.492, p = 0.028).

Conclusion

CSF circulation markers were associated with elevated WMH burden and cognitive impairments in probable CAA.

Cognitive Impairment in Cerebral Amyloid Angiopathy: A Single-Center Prospective Cohort Study

Background/Objectives: Cognitive impairment represents a core and prodromal clinical feature of cerebral amyloid angiopathy (CAA). We sought to assess specific cognitive domains which are mainly affected among patients with CAA and to investigate probable associations with neuroimaging markers and Cerebrospinal Fluid (CSF) biomarkers. Methods: Thirty-five patients fulfilling the Boston Criteria v1.5 or v2.0 for the diagnosis of probable/possible CAA were enrolled in this prospective cohort study. Brain Magnetic Resonance Imaging and CSF biomarker data were collected. Every eligible participant underwent a comprehensive neurocognitive assessment. Spearman's rank correlation tests were used to identify possible relationships between the Addenbrooke's Cognitive Examination-Revised (ACE-R) sub-scores and other neurocognitive test scores and the CSF biomarker and neuroimaging parameters among CAA patients. Moreover, linear regression analyses were used to investigate the effects of CSF biomarkers on the ACE-R total score and Mini-Mental State Examination (MMSE) score, based on the outcomes of univariate analyses. Results: Cognitive impairment was detected in 80% of patients, and 60% had a coexistent Alzheimer's disease (AD) pathology based on CSF biomarker profiles. Notable correlations were identified between increased levels of total tau (t-tau) and phosphorylated tau (p-tau) and diminished performance in terms of overall cognitive function, especially memory. In contrast, neuroimaging indicators, including lobar cerebral microbleeds and superficial siderosis, had no significant associations with cognitive scores. Among the CAA patients, those without AD had superior neurocognitive test performance, with significant differences observed in their ACE-R total scores and memory sub-scores. Conclusions: The significance of tauopathy in cognitive impairment associated with CAA may be greater than previously imagined, underscoring the necessity for additional exploration of the non-hemorrhagic facets of the disease and new neuroimaging markers.

Caveolin-1 and Aquaporin-4 as Mediators of Fibrinogen-Driven Cerebrovascular Pathology in Hereditary Cerebral Amyloid Angiopathy

Hereditary Cerebral Amyloid Angiopathy (HCAA) is a rare inherited form of CAA, characterized by increased vascular deposits of amyloid peptides. HCAA provides a unique opportunity to study the pathogenic mechanisms linked to CAA, as it is associated with severe cerebrovascular pathology. Some of HCAA-associated amyloid-β (Aβ) mutations significantly enhance the interaction between fibrinogen and Aβ, resulting in altered fibrin structure and co-deposition with Aβ in the perivascular space. However, the mechanisms underlying perivascular fibrinogen deposition and the associated cerebrovascular pathology in HCAA remain unclear. To investigate this, we analyzed TgSwDI transgenic mice carrying HCAA-associated mutations and observed a significant age-dependent increase in fibrin(ogen) extravasation and fibrin(ogen)-Aβ colocalization in the perivascular space. Moreover, Caveolin-1, a protein involved in non-specific transcytosis across the endothelium, significantly increased with age in TgSwDI mice and correlated with fibrin(ogen) extravasation. Additionally, we noted significant aquaporin-4 (AQP4) depolarization in the CAA-laden blood vessels of TgSwDI mice, which also correlated with fibrin(ogen) extravasation and fibrin(ogen)-Aβ colocalization. Given that AQP4 plays a crucial role in Aβ clearance via the glymphatic pathway, its depolarization may disrupt this critical clearance mechanism, thereby exacerbating CAA pathology. To further explore the relationship between fibrin(ogen) and these factors, we depleted fibrinogen in TgSwDI mice using siRNA against fibrinogen. This intervention resulted in decreased CAA, reduced caveolin-1 levels, attenuated microglial activation, restored polarized expression of AQP4, and improved spatial memory in fibrinogen-depleted TgSwDI mice. These findings suggest that targeting fibrinogen could be a promising strategy for mitigating CAA pathology and its associated cerebrovascular pathology.

Significance Statement

Our study reveals the mechanism by which fibrin(ogen)-Aβ colocalization could exacerbates CAA pathology. Our findings highlight that the age-dependent increase of endothelial caveolin-1 could facilitate fibrin(ogen) extravasation, which binds with Aβ in the perivascular space inducing microglial neuroinflammation and AQP4 depolarization, thus exacerbating CAA pathology. Furthermore, fibrinogen depletion could mitigate CAA severity, reduce microglial activation, restore AQP4 polarization and memory impairment. These results suggest that targeting fibrinogen and caveolin-1-mediated transcytosis may offer new strategies to address CAA-associated cerebrovascular pathology.

Targeted TGF-βR2 Silencing in the Retrotrapezoid Nucleus Mitigates Respiratory Dysfunction and Cognitive Decline in a Mouse Model of Cerebral Amyloid Angiopathy with and without Stroke

Cerebral amyloid angiopathy (CAA) is characterized by the deposition of amyloid-beta peptides within cerebral blood vessels, leading to neurovascular complications. Ischemic strokes result from acute disruptions in cerebral blood flow, triggering metabolic disturbances and neurodegeneration. Both conditions often co-occur and are associated with respiratory dysfunctions. The retrotrapezoid nucleus (RTN), which is crucial for CO2 sensing and breathing regulation in the brainstem, may play a key role in breathing disorders seen in these conditions. This study aims to investigate the role of Transforming Growth Factor Beta (TGF-β) signaling in the RTN on respiratory and cognitive functions in CAA, both with and without concurrent ischemic stroke. Adult male Tg-SwDI (CAA model) mice and C57BL/6 wild-type controls underwent stereotaxic injections of lentivirus targeting TGF-βR2 in the RTN. Stroke was induced by middle cerebral artery occlusion using a monofilament. Respiratory functions were assessed using whole-body plethysmography, while cognitive functions were evaluated through the Barnes Maze and Novel Object Recognition Test (NORT). Immunohistochemical analysis was conducted to measure TGF-βR2 and GFAP expressions in the RTN. CAA mice exhibited significant respiratory dysfunctions, including reduced respiratory rates and increased apnea frequency, as well as impaired cognitive performance. TGF-βR2 silencing in the RTN improved respiratory functions and cognitive outcomes in CAA mice. In CAA mice with concurrent stroke, TGF-βR2 silencing similarly enhanced respiratory and cognitive functions. Immunohistochemistry confirmed reduced TGF-βR2 and GFAP expressions in the RTN following silencing. Our findings demonstrate that increased TGF-β signaling and gliosis in the RTN contribute to respiratory and cognitive dysfunctions in CAA and CAA with stroke. Targeting TGF-βR2 signaling in the RTN offers a promising therapeutic strategy to mitigate these impairments. This study is the first to report a causal link between brainstem gliosis and both respiratory and cognitive dysfunctions in CAA and stroke models.

Core CSF Biomarker Profile in Cerebral Amyloid Angiopathy: Updated Meta-Analysis

BACKGROUND AND OBJECTIVES

There is a clear need to characterize and validate molecular biomarkers of cerebral amyloid angiopathy (CAA), in an effort to improve diagnostics, especially in the context of patients with Alzheimer disease (AD) receiving immunotherapies (for whom underlying CAA is the driver of amyloid-related imaging abnormalities). We performed an updated meta-analysis of 5 core CSF biomarkers (Aβ42, Aβ40, Aβ438, total tau [T-tau], and phosphorylated tau [P-tau]) to assess which of these are most altered in sporadic CAA.

METHODS

We systematically searched PubMed for eligible studies reporting data on CSF biomarkers reflecting APP metabolism (Aβ42, Aβ40, Aβ38), neurodegeneration (T-tau), and tangle pathology (P-tau), in symptomatic sporadic CAA cohorts (based on the Boston criteria) vs control groups and/or vs patients with AD. Biomarker performance was assessed in random-effects meta-analysis based on ratio of mean (RoM) biomarker concentrations in (1) patients with CAA to controls and (2) CAA to patients with AD. RoM >1 indicates higher biomarker concentration in CAA vs comparison population, and RoM <1 indicates higher concentration in comparison groups.

RESULTS

8 studies met inclusion criteria: a total of 11 CAA cohorts (n = 289), 9 control cohorts (n = 310), and 8 AD cohorts (n = 339). Overall included studies were of medium quality based on our assessment tools. CAA to controls had lower mean level of all amyloid markers with CSF Aβ42, Aβ40, and Aβ38 RoMs of 0.46 (95% CI 0.38-0.55, p < 0.0001), 0.70 (95% CI 0.63-0.78, p < 0.0001), and 0.71 (95% CI 0.56-0.89, p = 0.003), respectively. CSF T-tau and P-tau RoMs of patients with CAA to controls were both greater than 1: 1.56 (95% CI 1.32-1.84, p < 0.0001) and 1.31 (95% CI 1.13-1.51, p < 0.0001), respectively. Differentiation between CAA and AD was strong for CSF Aβ40 (RoM 0.76, 95% CI 0.69-0.83, p < 0.0001) and Aβ38 (RoM 0.55, 95% CI 0.38-0.81, p < 0.0001), but not Aβ42 (RoM 1.00; 95% CI 0.81-1.23, p = 0.970). For T-tau and P-tau, average CSF ratios in patients with CAA vs AD were 0.64 (95% CI 0.58-0.71, p < 0.0001) and 0.64 (95% CI 0.58-0.71, p < 0.0001), respectively.

DISCUSSION

Specific CSF patterns of Aβ42, Aβ40, Aβ38, T-tau, and P-tau might serve as molecular biomarkers of CAA, in research and clinical settings, offering the potential to improve the clinical diagnostic approach pathway in specific scenarios.

Quantitative electroencephalography in cerebral amyloid angiopathy

OBJECTIVE

We investigated whether quantitative electroencephalography (qEEG) correlates with cognition and cortical superficial siderosis (cSS) in cerebral amyloid angiopathy.

METHODS

We included patients with sporadic (sCAA) and hereditary Dutch-type CAA (D-CAA). Spectral measures and the phase lag index (PLI) were analyzed on qEEG. Cognition was assessed with the MoCA and cSS presence was scored on 3T-MRI. Linear regression analyses were performed to investigate these qEEG measures and cognition. Independent samples T-tests were used to analyze the qEEG measure differences between participants with and without cSS.

RESULTS

We included 92 participants (44 D-CAA; 48 sCAA). A lower average peak frequency (β[95 %CI] = 0.986[0.252-1.721]; P = 0.009) and a higher spectral ratio (β[95 %CI] = -0.918[-1.761--0.075]; P = 0.033) on qEEG correlated with a lower MoCA score, irrespective of a history of symptomatic intracerebral hemorrhage (sICH). The PLI showed no correlation to the MoCA. qEEG slowing was not different in those with or without cSS.

CONCLUSIONS

Spectral qEEG (but not PLI) reflects cognitive performance in patients with CAA with and without a history of sICH. We found no association between qEEG slowing and cSS.

SIGNIFICANCE

qEEG could be a valuable biomarker, especially in challenging cognitive testing situations in CAA, and a potential predictive tool in future studies.

Intermittent Metabolic Switching and Vascular Cognitive Impairment

Intermittent fasting (IF), a dietary pattern alternating between eating and fasting periods within a 24-hour cycle, has garnered recognition for its potential to enhance both healthspan and lifespan in animal models and humans. It also shows promise in alleviating age-related diseases, including neurodegeneration. Vascular cognitive impairment (VCI) spans a severity range from mild cognitive deficits to severe cognitive deficits and loss of function in vascular dementia. Chronic cerebral hypoperfusion has emerged as a significant contributor to VCI, instigating vascular pathologies such as microbleeds, blood-brain barrier dysfunction, neuronal loss, and white matter lesions. Preclinical studies in rodents strongly suggest that IF has the potential to attenuate pathological mechanisms, including excitotoxicity, oxidative stress, inflammation, and cell death pathways in VCI models. Hence, this supports evaluating IF in clinical trials for both existing and at-risk VCI patients. This review compiles existing data supporting IF's potential in treating VCI-related vascular and neuronal pathologies, emphasizing the mechanisms by which IF may mitigate these issues. Hence providing a comprehensive overview of the available data supporting IF's potential in treating VCI by emphasizing the underlying mechanisms that make IF a promising intervention for VCI.

Cerebral Amyloid Angiopathy in Patients with Cognitive Impairment: Cerebrospinal Fluid Biomarkers

INTRODUCTION

Cerebral amyloid angiopathy (CAA) is characterized by amyloid β (Aβ) deposition in brain vessels, leading to hemorrhagic phenomena and cognitive impairment. Magnetic resonance imaging (MRI)-based criteria allow a diagnosis of probable CAA in vivo, but such a diagnosis cannot predict the eventual development of CAA.

METHODS

We conducted a retrospective cohort study of 464 patients with cognitive disorders whose data were included in a brain health biobank. De-identified parameters including sex, age, cognitive score, APOE status, and cerebrospinal fluid (CSF) levels of Aβ 1-40, Aβ 1-42, phosphorylated tau, and total tau were assessed in those with and without CAA. Odds ratios (ORs) and 95% confidence intervals (CIs) were determined.

RESULTS

CAA was present in 53 of 464 (11.5%) patients. P-tau level was significantly higher in those with CAA (115 vs. 84.3 pg/mL p = 0.038). In univariate analyses, the risk of developing CAA was higher with increased age (OR, 1.036; 95% CI: 1.008, 1.064; p = 0.011) and decreased CSF level of Aβ 1-40 (OR, 0.685; 95% CI: 0.534, 0.878; p = 0.003). In multivariate analyses, the risk of CAA remained higher with a decreased CSF level of Aβ 1-40 (OR, 0.681; 95% CI: 0.531, 0.874; p = 0.003).

CONCLUSION

These findings suggest that Aβ 1-40 levels in the CSF might be a useful molecular biomarker of CAA in patients with dementia.

Targeted TGF-βR2 Knockdown in the Retrotrapezoid Nucleus Mitigates Respiratory Dysfunction and Cognitive Decline in a Mouse Model of Cerebral Amyloid Angiopathy with and without Stroke

Introduction

Cerebral amyloid angiopathy (CAA) is characterized by the deposition of amyloid-beta peptides within cerebral blood vessels, leading to neurovascular complications. Ischemic strokes result from acute disruptions in cerebral blood flow, triggering metabolic disturbances and neurodegeneration. Both conditions often co-occur and are associated with respiratory dysfunctions. The retrotrapezoid nucleus (RTN), which is crucial for CO2 sensing and breathing regulation in the brainstem, may play a key role in breathing disorders seen in these conditions. This study aims to investigate the role of Transforming Growth Factor Beta (TGF-β) signaling in the RTN on respiratory and cognitive functions in CAA, both with and without concurrent ischemic stroke.

Methods

Adult male Tg-SwDI (CAA model) mice and C57BL/6 wild-type controls underwent stereotaxic injections of lentivirus targeting TGF-β2R2 in the RTN. Stroke was induced by middle cerebral artery occlusion using a monofilament. Respiratory functions were assessed using whole-body plethysmography, while cognitive functions were evaluated through the Barnes Maze and Novel Object Recognition Test (NORT). Immunohistochemical analysis was conducted to measure TGF-βR2 and GFAP expressions in the RTN.

Results

CAA mice exhibited significant respiratory dysfunctions, including reduced respiratory rates and increased apnea frequency, as well as impaired cognitive performance. TGF-βR2 knockdown in the RTN improved respiratory functions and cognitive outcomes in CAA mice. In CAA mice with concurrent stroke, TGF-βR2 knockdown similarly enhanced respiratory and cognitive functions. Immunohistochemistry confirmed reduced TGF-βR2 and GFAP expressions in the RTN following knockdown.

Conclusions

Our findings demonstrate that increased TGF-β signaling and gliosis in the RTN contribute to respiratory and cognitive dysfunctions in CAA and CAA with stroke. Targeting TGF-βR2 signaling in the RTN offers a promising therapeutic strategy to mitigate these impairments. This study is the first to report a causal link between brainstem gliosis and both respiratory and cognitive dysfunctions in CAA and stroke models.

Cerebral tau pathology in cerebral amyloid angiopathy

Tau, a hallmark of Alzheimer's disease, is poorly characterized in cerebral amyloid angiopathy. We aimed to assess the clinico-radiological correlations between tau positron emission tomography scans and cerebral amyloid angiopathy. We assessed cerebral amyloid and hyperphosphorylated tau in patients with probable cerebral amyloid angiopathy (n = 31) and hypertensive small vessel disease (n = 27) using 11C-Pittsburgh compound B and 18F-T807 positron emission tomography. Multivariable regression models were employed to assess radio-clinical features related to cerebral tau pathology in cerebral amyloid angiopathy. Cerebral amyloid angiopathy exhibited a higher cerebral tau burden in the inferior temporal lobe [1.25 (1.17-1.42) versus 1.08 (1.05-1.22), P < 0.001] and all Braak stage regions of interest (P < 0.05) than hypertensive small vessel disease, although the differences were attenuated after age adjustment. Cerebral tau pathology was significantly associated with cerebral amyloid angiopathy-related vascular markers, including cortical superficial siderosis (β = 0.12, 95% confidence interval 0.04-0.21) and cerebral amyloid angiopathy score (β = 0.12, 95% confidence interval 0.03-0.21) after adjustment for age, ApoE4 status and whole cortex amyloid load. Tau pathology correlated significantly with cognitive score (Spearman's ρ=-0.56, P = 0.001) and hippocampal volume (-0.49, P = 0.007), even after adjustment. In conclusion, tau pathology is more frequent in sporadic cerebral amyloid angiopathy than in hypertensive small vessel disease. Cerebral amyloid angiopathy-related vascular pathologies, especially cortical superficial siderosis, are potential markers of cerebral tau pathology suggestive of concomitant Alzheimer's disease.

Research Advancements on the Correlation Between Spontaneous Intracerebral Hemorrhage of Different Etiologies and Imaging Markers of Cerebral Small Vessel Disease

Objective

The purpose of this review is to identify the correlation between ICH and CSVD imaging markers under SMASH-U classification by searching and analyzing a large number of literatures in recent years, laying a theoretical foundation for future clinical research. At the same time, by collecting clinical data to evaluate patient prognosis, analyzing whether there are differences or supplements between clinical trial conclusions and previous theories, and ultimately guiding clinical diagnosis and treatment through the analysis of imaging biomarkers.

Methods

In this review, by searching CNKI, Web of Science, PubMed, FMRS and other databases, the use of "spontaneous intracerebral hemorrhage", "hypertensive hemorrhagic cerebral small vessel disease", "cerebral small vessel disease imaging", "Based cerebral small vessel diseases", "SMASH the -u classification" and their Chinese equivalents for the main search term. We focused on reading and analyzing hundreds of relevant literatures in the last decade from August 2011 to April 2020, and also included some earlier literatures with conceptual data sources. After screening and ranking the degree of relevance to this study, sixty of them were cited for analysis and elaboration.

Results

In patients with ICH, the number of cerebral microbleeds in lobes, basal ganglia, and the deep brain is positively correlated with ICH volume and independently correlated with neurological functional outcomes; white matter hyperintensity severity is positively correlated with ICH recurrence risk; multiple lacunar infarction independently predict the risk of ICH; severe brain atrophy is an independent risk factor for a poor prognosis in the long term in patients diagnosed with ICH; and the number of enlarged perivascular spaces is correlated with ICH recurrence. However, small subcortical infarct and ICH are the subject of few studies. Higher CSVD scores are independently associated with functional outcomes at 90 days in patients diagnosed with ICH.

Association Between Hippocampal Volumes and Cognition in Cerebral Amyloid Angiopathy

BACKGROUND AND OBJECTIVES

Accumulating evidence suggests that gray matter atrophy, often considered a marker of Alzheimer disease (AD), can also result from cerebral small vessel disease (CSVD). Cerebral amyloid angiopathy (CAA) is a form of sporadic CSVD, diagnosed through neuroimaging criteria, that often co-occurs with AD pathology and leads to cognitive impairment. We sought to identify the role of hippocampal integrity in the development of cognitive impairment in a cohort of patients with possible and probable CAA.

METHODS

Patients were recruited from an ongoing CAA study at Massachusetts General Hospital. Composite scores defined performance in the cognitive domains of memory, language, executive function, and processing speed. Hippocampal subfields' volumes were measured from 3T MRI, using an automated method, and multivariate linear regression models were used to estimate their association with each cognitive domain and relationship to CAA-related neuroimaging markers.

RESULTS

One hundred twenty patients, 36 with possible (age mean [range]: 75.6 [65.6-88.9]), 67 with probable CAA (75.9 [59.0-94.0]), and 17 controls without cognitive impairment and CSVD (72.4 [62.5-82.7]; 76.4% female patients), were included in this study. We found a positive association between all investigated hippocampal subfields and memory and language, whereas specific subfields accounted for executive function (CA4 [Estimate = 5.43; 95% CI 1.26-9.61; p = 0.020], subiculum [Estimate = 2.85; 95% CI 0.67-5.02; p = 0.022]), and processing speed (subiculum [Estimate = 1.99; 95% CI 0.13-3.85; p = 0.036]). These findings were independent of other CAA-related markers, which did not have an influence on cognition in this cohort. Peak width of skeletonized mean diffusivity (PSMD), a measure of white matter integrity, was negatively associated with hippocampal subfields' volumes (CA3 [Estimate = -0.012; 95% CI -0.020 to -0.004; p = 0.034], CA4 [Estimate = -0.010; 95% CI -0.020 to -0.0007; p = 0.037], subiculum [Estimate = -0.019; 95% CI -0.042 to -0.0001; p = 0.003]).

DISCUSSION

These results suggest that hippocampal integrity is an independent contributor to cognitive impairment in patients with CAA and that it might be related to loss of integrity in the white matter. Further studies exploring potential causes and directionality of the relationship between white matter and hippocampal integrity may be warranted.

Using Neuroimaging to Study Cerebral Amyloid Angiopathy and Its Relationship to Alzheimer's Disease

Cerebral amyloid angiopathy (CAA) is characterized by amyloid-β aggregation in the media and adventitia of the leptomeningeal and cortical blood vessels. CAA is one of the strongest vascular contributors to Alzheimer's disease (AD). It frequently co-occurs in AD patients, but the relationship between CAA and AD is incompletely understood. CAA may drive AD risk through damage to the neurovascular unit and accelerate parenchymal amyloid and tau deposition. Conversely, early AD may also drive CAA through cerebrovascular remodeling that impairs blood vessels from clearing amyloid-β. Sole reliance on autopsy examination to study CAA limits researchers' ability to investigate CAA's natural disease course and the effect of CAA on cognitive decline. Neuroimaging allows for in vivo assessment of brain function and structure and can be leveraged to investigate CAA staging and explore its associations with AD. In this review, we will discuss neuroimaging modalities that can be used to investigate markers associated with CAA that may impact AD vulnerability including hemorrhages and microbleeds, blood-brain barrier permeability disruption, reduced cerebral blood flow, amyloid and tau accumulation, white matter tract disruption, reduced cerebrovascular reactivity, and lowered brain glucose metabolism. We present possible areas for research inquiry to advance biomarker discovery and improve diagnostics.

Familial cerebral amyloid disorders with prominent white matter involvement

Familial cerebral amyloid disorders are characterized by the accumulation of fibrillar protein aggregates, which deposit in the parenchyma as plaques and in the vasculature as cerebral amyloid angiopathy (CAA). Amyloid β (Aβ) is the most common of these amyloid proteins, accumulating in familial and sporadic forms of Alzheimer's disease and CAA. However, there are also a number of rare, hereditary, non-Aβ cerebral amyloidosis. The clinical manifestations of these familial cerebral amyloid disorders are diverse, including cognitive or neuropsychiatric presentations, intracerebral hemorrhage, seizures, myoclonus, headache, ataxia, and spasticity. Some mutations are associated with extensive white matter hyperintensities on imaging, which may or may not be accompanied by hemorrhagic imaging markers of CAA; others are associated with occipital calcification. We describe the clinical, imaging, and pathologic features of these disorders and discuss putative disease mechanisms. Familial disorders of cerebral amyloid accumulation offer unique insights into the contributions of vascular and parenchymal amyloid to pathogenesis and the pathways underlying white matter involvement in neurodegeneration. With Aβ immunotherapies now entering the clinical realm, gaining a deeper understanding of these processes and the relationships between genotype and phenotype has never been more relevant.

Identifying individuals with non-Alzheimer's disease co-pathologies: A precision medicine approach to clinical trials in sporadic Alzheimer's disease

INTRODUCTION

Biomarkers remain mostly unavailable for non-Alzheimer's disease neuropathological changes (non-ADNC) such as transactive response DNA-binding protein 43 (TDP-43) proteinopathy, Lewy body disease (LBD), and cerebral amyloid angiopathy (CAA).

METHODS

A multilabel non-ADNC classifier using magnetic resonance imaging (MRI) signatures was developed for TDP-43, LBD, and CAA in an autopsy-confirmed cohort (N = 214).

RESULTS

A model using demographic, genetic, clinical, MRI, and ADNC variables (amyloid positive [Aβ+] and tau+) in autopsy-confirmed participants showed accuracies of 84% for TDP-43, 81% for LBD, and 81% to 93% for CAA, outperforming reference models without MRI and ADNC biomarkers. In an ADNI cohort (296 cognitively unimpaired, 401 mild cognitive impairment, 188 dementia), Aβ and tau explained 33% to 43% of variance in cognitive decline; imputed non-ADNC explained an additional 16% to 26%. Accounting for non-ADNC decreased the required sample size to detect a 30% effect on cognitive decline by up to 28%.

DISCUSSION

Our results lead to a better understanding of the factors that influence cognitive decline and may lead to improvements in AD clinical trial design.

Etiology of White Matter Hyperintensities in Autosomal Dominant and Sporadic Alzheimer Disease

Importance

Increased white matter hyperintensity (WMH) volume is a common magnetic resonance imaging (MRI) finding in both autosomal dominant Alzheimer disease (ADAD) and late-onset Alzheimer disease (LOAD), but it remains unclear whether increased WMH along the AD continuum is reflective of AD-intrinsic processes or secondary to elevated systemic vascular risk factors.

Objective

To estimate the associations of neurodegeneration and parenchymal and vessel amyloidosis with WMH accumulation and investigate whether systemic vascular risk is associated with WMH beyond these AD-intrinsic processes.

Design, Setting, and Participants

This cohort study used data from 3 longitudinal cohort studies conducted in tertiary and community-based medical centers-the Dominantly Inherited Alzheimer Network (DIAN; February 2010 to March 2020), the Alzheimer's Disease Neuroimaging Initiative (ADNI; July 2007 to September 2021), and the Harvard Aging Brain Study (HABS; September 2010 to December 2019).

Main Outcome and Measures

The main outcomes were the independent associations of neurodegeneration (decreases in gray matter volume), parenchymal amyloidosis (assessed by amyloid positron emission tomography), and vessel amyloidosis (evidenced by cerebral microbleeds [CMBs]) with cross-sectional and longitudinal WMH.

Results

Data from 3960 MRI sessions among 1141 participants were included: 252 pathogenic variant carriers from DIAN (mean [SD] age, 38.4 [11.2] years; 137 [54%] female), 571 older adults from ADNI (mean [SD] age, 72.8 [7.3] years; 274 [48%] female), and 318 older adults from HABS (mean [SD] age, 72.4 [7.6] years; 194 [61%] female). Longitudinal increases in WMH volume were greater in individuals with CMBs compared with those without (DIAN: t = 3.2 [P = .001]; ADNI: t = 2.7 [P = .008]), associated with longitudinal decreases in gray matter volume (DIAN: t = -3.1 [P = .002]; ADNI: t = -5.6 [P < .001]; HABS: t = -2.2 [P = .03]), greater in older individuals (DIAN: t = 6.8 [P < .001]; ADNI: t = 9.1 [P < .001]; HABS: t = 5.4 [P < .001]), and not associated with systemic vascular risk (DIAN: t = 0.7 [P = .40]; ADNI: t = 0.6 [P = .50]; HABS: t = 1.8 [P = .06]) in individuals with ADAD and LOAD after accounting for age, gray matter volume, CMB presence, and amyloid burden. In older adults without CMBs at baseline, greater WMH volume was associated with CMB development during longitudinal follow-up (Cox proportional hazards regression model hazard ratio, 2.63; 95% CI, 1.72-4.03; P < .001).

Conclusions and Relevance

The findings suggest that increased WMH volume in AD is associated with neurodegeneration and parenchymal and vessel amyloidosis but not with elevated systemic vascular risk. Additionally, increased WMH volume may represent an early sign of vessel amyloidosis preceding the emergence of CMBs.

Associations between neurovascular coupling and cerebral small vessel disease: A systematic review and meta-analysis

PURPOSE

The pathogenesis of cerebral small vessel disease (cSVD) remains elusive despite evidence of an association between white matter hyperintensities (WMH) and endothelial cerebrovascular dysfunction. Neurovascular coupling (NVC) may be a practical alternative measure of endothelial function. We performed a systematic review of reported associations between NVC and cSVD.

METHODS

EMBASE and PubMed were searched for studies reporting an association between any STRIVE-defined marker of cSVD and a measure of NVC during functional magnetic resonance imaging, transcranial Doppler, positron emission tomography, near-infrared spectroscopy or single-photon emission computed tomography, from inception to November 3rd, 2022. Where quantitative data was available from studies using consistent tests and analyses, results were combined by inverse-variance weighted random effects meta-analysis.

FINDINGS

Of 29 studies (19 case-controls; 10 cohorts), 26 reported decreased NVC with increasing severity of cSVD, of which 18 were individually significant. In 28 studies reporting associations with increasing WMH, 25 reported reduced NVC. Other markers of cSVD were associated with reduced NVC in: eight of nine studies with cerebral microbleeds (six showing a significant effect); three of five studies with lacunar stroke; no studies reported an association with enlarged perivascular spaces. Specific SVD diseases were particularly associated with reduced NVC, including six out of seven studies in cerebral amyloid angiopathy and all four studies in CADASIL. In limited meta-analyses, %BOLD occipital change to a visual stimulus was consistently reduced with more severe WMH (seven studies, SMD -1.51, p < 0.01) and increasing microbleeds (seven studies, SMD -1.31, p < 0.01).

DISCUSSION AND CONCLUSION

In multiple, small studies, neurovascular coupling was reduced in patients with increasing severity of all markers of cSVD in sporadic disease, CAA and CADASIL. Cerebrovascular endothelial dysfunction, manifest as impaired NVC, may be a common marker of physiological dysfunction due to small vessel injury that can be easily measured in large studies and clinical practice.

The iron burden of cerebral microbleeds contributes to brain atrophy through the mediating effect of white matter hyperintensity

The goal of this work was to explore the total iron burden of cerebral microbleeds (CMBs) using a semi-automatic quantitative susceptibility mapping and to establish its effect on brain atrophy through the mediating effect of white matter hyperintensities (WMH). A total of 95 community-dwelling people were enrolled. Quantitative susceptibility mapping (QSM) combined with a dynamic programming algorithm (DPA) was used to measure the characteristics of 1309 CMBs. WMH were evaluated according to the Fazekas scale, and brain atrophy was assessed using a 2D linear measurement method. Histogram analysis was used to explore the distribution of CMBs susceptibility, volume, and total iron burden, while a correlation analysis was used to explore the relationship between volume and susceptibility. Stepwise regression analysis was used to analyze the risk factors for CMBs and their contribution to brain atrophy. Mediation analysis was used to explore the interrelationship between CMBs and brain atrophy. We found that the frequency distribution of susceptibility of the CMBs was Gaussian in nature with a mean of 201 ppb and a standard deviation of 84 ppb; however, the volume and total iron burden of CMBs were more Rician in nature. A weak but significant correlation between the susceptibility and volume of CMBs was found (r = -0.113, P < 0.001). The periventricular WMH (PVWMH) was a risk factor for the presence of CMBs (number: β = 0.251, P = 0.014; volume: β = 0.237, P = 0.042; total iron burden: β = 0.238, P = 0.020) and was a risk factor for brain atrophy (third ventricle width: β = 0.325, P = 0.001; Evans's index: β = 0.323, P = 0.001). PVWMH had a significant mediating effect on the correlation between CMBs and brain atrophy. In conclusion, QSM along with the DPA can measure the total iron burden of CMBs. PVWMH might be a risk factor for CMBs and may mediate the effect of CMBs on brain atrophy.

Clinical considerations in early-onset cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) is an important cerebral small vessel disease associated with brain haemorrhage and cognitive change. The commonest form, sporadic amyloid-β CAA, usually affects people in mid- to later life. However, early-onset forms, though uncommon, are increasingly recognized and may result from genetic or iatrogenic causes that warrant specific and focused investigation and management. In this review, we firstly describe the causes of early-onset CAA, including monogenic causes of amyloid-β CAA (APP missense mutations and copy number variants; mutations of PSEN1 and PSEN2) and non-amyloid-β CAA (associated with ITM2B, CST3, GSN, PRNP and TTR mutations), and other unusual sporadic and acquired causes including the newly-recognized iatrogenic subtype. We then provide a structured approach for investigating early-onset CAA, and highlight important management considerations. Improving awareness of these unusual forms of CAA amongst healthcare professionals is essential for facilitating their prompt diagnosis, and an understanding of their underlying pathophysiology may have implications for more common, late-onset, forms of the disease.

Sex-Specific Patterns of Cerebral Atrophy and Enlarged Perivascular Spaces in Patients with Cerebral Amyloid Angiopathy and Dementia

BACKGROUND AND PURPOSE

Cerebral amyloid angiopathy is characterized by amyloid β deposition in leptomeningeal and superficial cortical vessels. Cognitive impairment is common and may occur independent of concomitant Alzheimer disease neuropathology. It is still unknown which neuroimaging findings are associated with dementia in cerebral amyloid angiopathy and whether they are modulated by sex. This study compared MR imaging markers in patients with cerebral amyloid angiopathy with dementia or mild cognitive impairment or who are cognitively unimpaired and explored sex-specific differences.

MATERIALS AND METHODS

We studied 58 patients with cerebral amyloid angiopathy selected from the cerebrovascular and memory outpatient clinics. Clinical characteristics were collected from clinical records. Cerebral amyloid angiopathy was diagnosed on MR imaging on the basis of the Boston criteria. Visual rating scores for atrophy and other imaging features were independently assessed by 2 senior neuroradiologists.

RESULTS

Medial temporal lobe atrophy was higher for those with cerebral amyloid angiopathy with dementia versus those cognitively unimpaired (P = .015), but not for those with mild cognitive impairment. This effect was mainly driven by higher atrophy in men with dementia, compared with women with and without dementia (P = .034, P = .012; respectively) and with men without dementia (P = .012). Enlarged perivascular spaces in the centrum semiovale were more frequent in women with dementia versus men with and without dementia (P = .021, P = .011; respectively) and women without dementia (P = .011).

CONCLUSIONS

Medial temporal lobe atrophy was more prominent in men with dementia, whereas women showed a higher number of enlarged perivascular spaces in the centrum semiovale. Overall, this finding suggests differential pathophysiologic mechanisms with sex-specific neuroimaging patterns in cerebral amyloid angiopathy.

CKD, Brain Atrophy, and White Matter Lesion Volume: The Japan Prospective Studies Collaboration for Aging and Dementia

Rationale & Objective

Chronic kidney disease, defined by albuminuria and/or reduced estimated glomerular filtration rate (eGFR), has been reported to be associated with brain atrophy and/or higher white matter lesion volume (WMLV), but there are few large-scale population-based studies assessing this issue. This study aimed to examine the associations between the urinary albumin-creatinine ratio (UACR) and eGFR levels and brain atrophy and WMLV in a large-scale community-dwelling older population of Japanese.

Study Design

Population-based cross-sectional study.

Setting & Participants

A total of 8,630 dementia-free community-dwelling Japanese aged greater than or equal to 65 years underwent brain magnetic resonance imaging scanning and screening examination of health status in 2016-2018.

Exposures

UACR and eGFR levels.

Outcomes

The total brain volume (TBV)-to-intracranial volume (ICV) ratio (TBV/ICV), the regional brain volume-to-TBV ratio, and the WMLV-to-ICV ratio (WMLV/ICV).

Analytical Approach

The associations of UACR and eGFR levels with the TBV/ICV, the regional brain volume-to-TBV ratio, and the WMLV/ICV were assessed by using an analysis of covariance.

Results

Higher UACR levels were significantly associated with lower TBV/ICV and higher geometric mean values of the WMLV/ICV (P for trend = 0.009 and <0.001, respectively). Lower eGFR levels were significantly associated with lower TBV/ICV, but not clearly associated with WMLV/ICV. In addition, higher UACR levels, but not lower eGFR, were significantly associated with lower temporal cortex volume-to-TBV ratio and lower hippocampal volume-to-TBV ratio.

Limitations

Cross-sectional study, misclassification of UACR or eGFR levels, generalizability to other ethnicities and younger populations, and residual confounding factors.

Conclusions

The present study demonstrated that higher UACR was associated with brain atrophy, especially in the temporal cortex and hippocampus, and with increased WMLV. These findings suggest that chronic kidney disease is involved in the progression of morphologic brain changes associated with cognitive impairment.

Neuroimaging biomarkers of small vessel disease in cerebral amyloid angiopathy-related intracerebral hemorrhage

AIMS

The significance of the correlation of computed tomography (CT)-based cerebral small vessel disease (SVD) markers with the clinical outcomes in patients with cerebral amyloid angiopathy (CAA)-related intracerebral hemorrhage (ICH) remains uncertain. Thus, this study aimed to explore the relationship between SVD markers and short-term outcomes of CAA-ICH.

METHODS

A total of 183 patients with CAA-ICH admitted to the Xuanwu Hospital, and Beijing Fengtai You'anmen Hospital, from 2014 to 2021 were included. The multivariate logistic regression analysis was performed to identify the correlation between SVD markers based on CT and clinical outcomes at 7-day and 90-day.

RESULTS

Of the 183 included patients, 66 (36%) were identified with severe SVD burden. The multivariate analysis showed that the total SVD burden, white matter lesion (WML) grade, and brain atrophy indicator were independent risk factors for unfavorable outcomes at 90-day. The brain atrophy indicator was independently associated with mortality at 90-day. Severe cortical atrophy was significantly associated with early neurological deterioration.

CONCLUSIONS

The neuroimaging profiles of SVD based on CT in patients with CAA-ICH might predict the short-term outcome more effectively. Further studies are required to validate these findings and identify modifiable factors for preventing CAA-ICH development.

Mediation of Reduced Hippocampal Volume by Cerebral Amyloid Angiopathy in Pathologically Confirmed Patients with Alzheimer's Disease

BACKGROUND

Hippocampal atrophy in cerebral amyloid angiopathy (CAA) has been reported to be similar to that in Alzheimer's disease (AD).

OBJECTIVE

To evaluate if CAA pathology partly mediates reduced hippocampal volume in patients with AD.

METHODS

Patients with a clinical diagnosis of AD and neuropathological confirmation of AD+/-CAA in the National Alzheimer's Coordinating Center database were included in the study. The volumes of temporal lobe structures were calculated on T1-weighted imaging (T1-MRI) using automated FreeSurfer software, from images acquired on average 5 years prior to death. Multivariate regression analysis was performed to compare brain volumes in four CAA groups. The hippocampal volume on T1-MRI was correlated with Clinical Dementia Rating sum of boxes (CDRsb) score, apolipoprotein E (APOE) genotype, and hippocampal atrophy at autopsy.

RESULTS

The study included 231 patients with no (n = 45), mild (n = 70), moderate (n = 67), and severe (n = 49) CAA. Among the four CAA groups, patients with severe CAA had a smaller mean left hippocampal volume (p = 0.023) but this was not significant when adjusted for APOE ɛ4 (p = 0.07). The left hippocampal volume on MRI correlated significantly with the hippocampal atrophy grading on neuropathology (p = 0.0003). Among patients with severe CAA, the left hippocampal volume on T1-MRI: (a) decreased with an increase in the number of APOE ɛ4 alleles (p = 0.04); but (b) had no evidence of correlation with CDRsb score (p = 0.57).

CONCLUSION

Severe CAA was associated with smaller left hippocampal volume on T1-MRI up to five years prior to death among patients with neuropathologically confirmed AD. This relationship was dependent on APOE ɛ4 genotype.

Subcortical volumes in cerebral amyloid angiopathy compared with Alzheimer's disease and controls

Background

Previous reports have suggested that patients with cerebral amyloid angiopathy (CAA) may harbor smaller white matter, basal ganglia, and cerebellar volumes compared to age-matched healthy controls (HC) or patients with Alzheimer's disease (AD). We investigated whether CAA is associated with subcortical atrophy.

Methods

The study was based on the multi-site Functional Assessment of Vascular Reactivity cohort and included 78 probable CAA (diagnosed according to the Boston criteria v2.0), 33 AD, and 70 HC. Cerebral and cerebellar volumes were extracted from brain 3D T1-weighted MRI using FreeSurfer (v6.0). Subcortical volumes, including total white matter, thalamus, basal ganglia, and cerebellum were reported as proportion (%) of estimated total intracranial volume. White matter integrity was quantified by the peak width of skeletonized mean diffusivity.

Results

Participants in the CAA group were older (74.0 ± 7.0, female 44%) than the AD (69.7 ± 7.5, female 42%) and HC (68.8 ± 7.8, female 69%) groups. CAA participants had the highest white matter hyperintensity volume and worse white matter integrity of the three groups. After adjusting for age, sex, and study site, CAA participants had smaller putamen volumes (mean differences, -0.024% of intracranial volume; 95% confidence intervals, -0.041% to -0.006%; p = 0.005) than the HCs but not AD participants (-0.003%; -0.024 to 0.018%; p = 0.94). Other subcortical volumes including subcortical white matter, thalamus, caudate, globus pallidus, cerebellar cortex or cerebellar white matter were comparable between all three groups.

Conclusion

In contrast to prior studies, we did not find substantial atrophy of subcortical volumes in CAA compared to AD or HCs, except for the putamen. Differences between studies may reflect heterogeneity in CAA presenting syndromes or severity.

Long-term outcome of cerebral amyloid angiopathy-related hemorrhage

OBJECT

The long-term functional outcome of cerebral amyloid angiopathy-related hemorrhage (CAAH) patients is unclear. We sought to assess the long-term functional outcome of CAAH and determine the prognostic factors associated with unfavorable outcomes.

METHODS

We enrolled consecutive CAAH patients from 2014 to 2020 in this observational study. Baseline characteristics and clinical outcomes were presented. Multivariable logistic regression analysis was performed to identify the prognostic factors associated with long-term outcome.

RESULTS

Among the 141 CAAH patients, 76 (53.9%) achieved favorable outcomes and 28 (19.9%) of them died at 1-year follow-up. For the longer-term follow-up with a median observation time of 19.0 (interquartile range, 12.0-26.5) months, 71 (50.4%) patients obtained favorable outcomes while 33 (23.4%) died. GCS on admission (OR, 0.109; 95% CI, 0.021-0.556; p = 0.008), recurrence of ICH (OR, 2923.687; 95% CI, 6.282-1360730.14; p = 0.011), WML grade 3-4 (OR, 31.007; 95% CI, 1.041-923.573; p = 0.047), severe central atrophy (OR, 4220.303; 95% CI, 9.135-1949674.84; p = 0.008) assessed by CT was identified as independent predictors for long-term outcome.

INTERPRETATION

Nearly 50% of CAAH patients achieved favorable outcomes at long-term follow-up. GCS, recurrence of ICH, WML grade and cerebral atrophy were identified as independent prognostic factors of long-term outcome.

Measures of intracranial compartments in acute intracerebral haemorrhage: data from the Rapid Intervention with Glyceryl Trinitrate in Hypertensive Stroke-2 Trial (RIGHT-2)

BACKGROUND AND PURPOSE

Intracerebral haemorrhage volume (ICHV) is prognostically important but does not account for intracranial volume (ICV) and cerebral parenchymal volume (CPV). We assessed measures of intracranial compartments in acute ICH using computerised tomography scans and whether ICHV/ICV and ICHV/CPV predict functional outcomes. We also assessed if cistern effacement, midline shift, old infarcts, leukoaraiosis and brain atrophy were associated with outcomes.

METHODS

Data from 133 participants from the Rapid Intervention with Glyceryl Trinitrate in Hypertensive Stroke-2 Trial trial were analysed. Measures included ICHV (using ABC/2) and ICV (XYZ/2) (by independent observers); ICHV, ICV and CPV (semiautomated segmentation, SAS); atrophy (intercaudate distance, ICD, Sylvian fissure ratio, SFR); midline shift; leukoaraiosis and cistern effacement (visual assessment). The effects of these measures on death at day 4 and poor functional outcome at day 90 (modified Rankin scale, mRS of >3) was assessed.

RESULTS

ICV was significantly different between XYZ and SAS: mean (SD) of 1357 (219) vs 1420 (196), mean difference (MD) 62 mL (p<0.001). There was no significant difference in ICHV between ABC/2 and SAS. There was very good agreement for ICV measured by SAS, CPV, ICD, SFR, leukoaraiosis and cistern score (all interclass correlations, n=10: interobserver 0.72-0.99, intraobserver 0.73-1.00). ICHV/ICV and ICHV/CPV were significantly associated with mRS at day 90, death at day 4 and acute neurological deterioration (all p<0.05), similar to ICHV. Midline shift and cistern effacement at baseline were associated with poor functional outcome but old infarcts, leukoaraiosis and brain atrophy were not.

CONCLUSIONS

Intracranial compartment measures and visual estimates are reproducible. ICHV adjusted for ICH and CPV could be useful to prognosticate in acute stroke. The presence of midline shift and cistern effacement may predict outcome but the mechanisms need validation in larger studies.

Effect of vascular amyloid on white matter disease is mediated by vascular dysfunction in cerebral amyloid angiopathy

We postulated that vascular dysfunction mediates the relationship between amyloid load and white matter hyperintensities (WMH) in cerebral amyloid angiopathy (CAA). Thirty-eight cognitively healthy patients with CAA (mean age 70 ± 7.1) were evaluated. WMH was quantified and expressed as percent of total intracranial volume (pWMH) using structural MRI. Mean global cortical Distribution Volume Ratio representing Pittsburgh Compound B (PiB) uptake (PiB-DVR) was calculated from PET scans. Time-to-peak [TTP] of blood oxygen level-dependent response to visual stimulation was used as an fMRI measure of vascular dysfunction. Higher PiB-DVR correlated with prolonged TTP (r = 0.373, p = 0.021) and higher pWMH (r = 0.337, p = 0.039). Prolonged TTP also correlated with higher pWMH (r = 0.485, p = 0.002). In a multivariate linear regression model, TTP remained independently associated with pWMH (p = 0.006) while PiB-DVR did not (p = 0.225). In a bootstrapping model, TTP had a significant indirect effect (ab = 0.97, 95% CI: 0.137-2.461), supporting that the association between PiB-DVR and pWMH is mediated by TTP response. There was no longer a direct effect independent of the hypothesized pathway. Our study suggests that the effect of vascular amyloid load on white matter disease is mediated by vascular dysfunction in CAA. Amyloid lowering strategies might prevent pathophysiological processes leading to vascular dysfunction, therefore limiting ischemic brain injury.

Diffusion tensor tractography of the fornix in cerebral amyloid angiopathy, mild cognitive impairment and Alzheimer's disease

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The fornix was delineated with deterministic tractography from diffusion tensor images (DTI).

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Fornix diffusion changes were found in the fornix in CAA, AD and MCI compared to controls.

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Higher fornix diffusivity correlated with smaller hippocampal volume and larger ventricles.

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Fornix diffusion measures correlated with cognitive measures in the combined disease groups.

Purpose

Cerebral amyloid angiopathy (CAA) is a common neuropathological finding and clinical entity that occurs independently and with co-existent Alzheimer’s disease (AD) and small vessel disease. We compared diffusion tensor imaging (DTI) metrics of the fornix, the primary efferent tract of the hippocampus between CAA, AD and Mild Cognitive Impairment (MCI) and healthy controls.

Methods

Sixty-eight healthy controls, 32 CAA, 21 AD, and 26 MCI patients were recruited at two centers. Diffusion tensor images were acquired at 3 T with high spatial resolution and fluid-attenuated inversion recovery (FLAIR) to suppress cerebrospinal fluid (CSF) and minimize partial volume effects on the fornix. The fornix was delineated with deterministic tractography to yield mean diffusivity (MD), axial diffusivity (AXD), radial diffusivity (RD), fractional anisotropy (FA) and tract volume. Volumetric measurements of the hippocampus, thalamus, and lateral ventricles were obtained using T1-weighted MRI.

Results

Diffusivity (MD, AXD, and RD) of the fornix was highest in AD followed by CAA compared to controls; the MCI group was not significantly different from controls. FA was similar between groups. Fornix tract volume was ∼ 30% lower for all three patient groups compared to controls, but not significantly different between the patient groups. Thalamic and hippocampal volumes were preserved in CAA, but lower in AD and MCI compared to controls. Lateral ventricular volumes were increased in CAA, AD and MCI. Global cognition, memory, and executive function all correlated negatively with fornix diffusivity across the combined clinical group.

Conclusion

There were significant diffusion changes of the fornix in CAA, AD and MCI compared to controls, despite relatively intact thalamic and hippocampal volumes in CAA, suggesting the mechanisms for fornix diffusion abnormalities may differ in CAA compared to AD and MCI.

Cerebellar atrophy and its implications on gait in cerebral amyloid angiopathy

OBJECTIVE

Recent data suggest that cerebral amyloid angiopathy (CAA) causes haemorrhagic lesions in cerebellar cortex as well as subcortical cerebral atrophy. However, the potential effect of CAA on cerebellar tissue loss and its clinical implications have not been investigated.

METHODS

Our study included 70 non-demented patients with probable CAA, 70 age-matched healthy controls (HCs) and 70 age-matched patients with Alzheimer's disease (AD). The cerebellum was segmented into percent of cerebellar subcortical volume (pCbll-ScV) and percent of cerebellar cortical volume (pCbll-CV) represented as percent (p) of estimated total intracranial volume. We compared pCbll-ScV and pCbll-CV between patients with CAA, HCs and those with AD. Gait velocity (metres/second) was used to investigate gait function in patients with CAA.

RESULTS

Patients with CAA had significantly lower pCbll-ScV compared with both HC (1.49±0.1 vs 1.73±0.2, p<0.001) and AD (1.49±0.1 vs 1.66±0.24, p<0.001) and lower pCbll-CV compared with HCs (6.03±0.5 vs 6.23±0.6, p=0.028). Diagnosis of CAA was independently associated with lower pCbll-ScV compared with HCs (p<0.001) and patients with AD (p<0.001) in separate linear regression models adjusted for age, sex and presence of hypertension. Lower pCbll-ScV was independently associated with worse gait velocity (β=0.736, 95% CI 0.28 to 1.19, p=0.002) in a stepwise linear regression analysis including pCbll-CV along with other relevant variables.

INTERPRETATION

Patients with CAA show more subcortical cerebellar atrophy than HC or patients with AD and more cortical cerebellar atrophy than HCs. Reduced pCbll-ScV correlated with lower gait velocity in regression models including other relevant variables. Overall, this study suggests that CAA causes cerebellar injury, which might contribute to gait disturbance.

Cerebral Microbleeds, Cerebral Amyloid Angiopathy, and Their Relationships to Quantitative Markers of Neurodegeneration

BACKGROUND AND OBJECTIVES

Age-related cognitive impairment is driven by the complex interplay of neurovascular and neurodegenerative disease. There is a strong relationship between cerebral microbleeds (CMBs), cerebral amyloid angiopathy (CAA), and the cognitive decline observed in conditions such as Alzheimer disease. However, in the early, preclinical phase of cognitive impairment, the extent to which CMBs and underlying CAA affect volumetric changes in the brain related to neurodegenerative disease remains unclear.

METHODS

We performed cross-sectional analyses from 3 large cohorts: The Northern Manhattan Study (NOMAS), Alzheimer's Disease Neuroimaging Initiative (ADNI), and the Epidemiology of Dementia in Singapore study (EDIS). We conducted a confirmatory analysis of 82 autopsied cases from the Brain Arterial Remodeling Study (BARS). We implemented multivariate regression analyses to study the association between 2 related markers of cerebrovascular disease-MRI-based CMBs and autopsy-based CAA-as independent variables and volumetric markers of neurodegeneration as dependent variables. NOMAS included mostly dementia-free participants age 55 years or older from northern Manhattan. ADNI included participants living in the United States age 55-90 years with a range of cognitive status. EDIS included community-based participants living in Singapore age 60 years and older with a range of cognitive status. BARS included postmortem pathologic samples.

RESULTS

We included 2,657 participants with available MRI data and 82 autopsy cases from BARS. In a meta-analysis of NOMAS, ADNI, and EDIS, superficial CMBs were associated with larger gray matter (β = 4.49 ± 1.13, p = 0.04) and white matter (β = 4.72 ± 2.1, p = 0.03) volumes. The association between superficial CMBs and larger white matter volume was more evident in participants with 1 CMB (β = 5.17 ± 2.47, p = 0.04) than in those with ≥2 CMBs (β = 1.97 ± 3.41, p = 0.56). In BARS, CAA was associated with increased cortical thickness (β = 6.5 ± 2.3, p = 0.016) but not with increased brain weight (β = 1.54 ± 1.29, p = 0.26).

DISCUSSION

Superficial CMBs are associated with larger morphometric brain measures, specifically white matter volume. This association is strongest in brains with fewer CMBs, suggesting that the CMB/CAA contribution to neurodegeneration may not relate to tissue loss, at least in early stages of disease.

Pathological changes within the cerebral vasculature in Alzheimer's disease: New perspectives

Cerebrovascular disease underpins vascular dementia (VaD), but structural and functional changes to the cerebral vasculature contribute to disease pathology and cognitive decline in Alzheimer's disease (AD). In this review, we discuss the contribution of cerebral amyloid angiopathy and non‐amyloid small vessel disease in AD, and the accompanying changes to the density, maintenance and remodelling of vessels (including alterations to the composition and function of the cerebrovascular basement membrane). We consider how abnormalities of the constituent cells of the neurovascular unit – particularly of endothelial cells and pericytes – and impairment of the blood‐brain barrier (BBB) impact on the pathogenesis of AD. We also discuss how changes to the cerebral vasculature are likely to impair Aβ clearance – both intra‐periarteriolar drainage (IPAD) and transport of Aβ peptides across the BBB, and how impaired neurovascular coupling and reduced blood flow in relation to metabolic demand increase amyloidogenic processing of APP and the production of Aβ. We review the vasoactive properties of Aβ peptides themselves, and the probable bi‐directional relationship between vascular dysfunction and Aβ accumulation in AD. Lastly, we discuss recent methodological advances in transcriptomics and imaging that have provided novel insights into vascular changes in AD, and recent advances in assessment of the retina that allow in vivo detection of vascular changes in the early stages of AD.

Emergent White Matter Degeneration in the rTg-DI Rat Model of Cerebral Amyloid Angiopathy Exhibits Unique Proteomic Changes

Cerebral amyloid angiopathy (CAA), characterized by cerebral vascular amyloid accumulation, neuroinflammation, microbleeds, and white matter (WM) degeneration, is a common comorbidity in Alzheimer disease and a prominent contributor to vascular cognitive impairment and dementia. WM loss was recently reported in the corpus callosum (CC) in the rTg-DI rat model of CAA. The current study shows that the CC exhibits a much lower CAA burden compared with the adjacent cortex. Sequential Window Acquisition of All Theoretical Mass Spectra tandem mass spectrometry was used to show specific proteomic changes in the CC with emerging WM loss and compare them with the proteome of adjacent cortical tissue in rTg-DI rats. In the CC, annexin A3, heat shock protein β1, and cystatin C were elevated at 4 months (M) before WM loss and at 12M with evident WM loss. Although annexin A3 and cystatin C were also enhanced in the cortex at 12M, annexin A5 and the leukodystrophy-associated astrocyte proteins megalencephalic leukoencephalopathy with subcortical cysts 1 and GlialCAM were distinctly elevated in the CC. Pathway analysis indicated neurodegeneration of axons, reflected by reduced expression of myelin and neurofilament proteins, was common to the CC and cortex; activation of Tgf-β1 and F2/thrombin was restricted to the CC. This study provides new insights into the proteomic changes that accompany WM loss in the CC of rTg-DI rats.

Role of White Matter Abnormalities in the Relationship Between Microbleed Burden and Cognitive Impairment in Cerebral Amyloid Angiopathy

Background: Cerebral amyloid angiopathy (CAA) often presents as cognitive impairment, but the mechanism of cognitive decline is unclear. Recent studies showed that number of microbleeds were associated with cognitive decline. Objective: We aimed to investigate how microbleeds contribute to cognitive impairment in association with white matter tract abnormalities or cortical thickness in CAA. Methods: This retrospective comparative study involved patients with probable CAA according to the Boston criteria (Aβ  + CAA) and patients with Alzheimer’s disease (Aβ  + AD), all of whom showed severe amyloid deposition on amyloid PET. Using mediation analysis, we investigated how FA or cortical thickness mediates the correlation between the number of lobar microbleeds and cognition. Results: We analyzed 30 patients with Aβ  + CAA (age 72.2±7.6, female 53.3%) and 30 patients with Aβ  + AD (age 71.5±7.6, female 53.3%). The two groups showed similar degrees of cortical amyloid deposition in AD-related regions. The Aβ  + CAA group had significantly lower FA values in the clusters of the posterior area than did the Aβ  + AD group (family-wise error-corrected p <  0.05). The correlation between the number of lobar microbleeds and visuospatial function was indirectly mediated by white matter tract abnormality of right posterior thalamic radiation (PTR) and tapetum, while lobar microbleeds and language function was indirectly mediated by the abnormality of left PTR and sagittal stratum. Cortical thickness did not mediate the association between lobar microbleeds and cognition. Conclusion: This result supports the hypothesis that microbleeds burden leads to white matter tract damage and subsequent cognitive decline in CAA.

Recurrent intracerebral hemorrhage in patients with cerebral amyloid angiopathy: a propensity-matched case-control study

OBJECTIVE

Cerebral amyloid angiopathy (CAA) can present with intracerebral hemorrhage (ICH), convexity subarachnoid hemorrhage (SAH), and rarely acute ischemic stroke (AIS). The objective of our study was to compare the readmission rates for recurrent ICH, SAH, and AIS among patients admitted for ICH with and without CAA.

METHODS

Using the National Readmissions Database 2016-2018 we identified patients admitted for ICH with and without a concomitant diagnosis of CAA. Primary outcome of the study was readmission due to ICH. Secondary outcomes included readmissions due to AIS and SAH. Survival analysis was performed, and Kaplan-Meier curves were created to assess for readmissions.

RESULTS

The study consisted of 194,290 patients with ICH, 8247 with CAA and 186,043 without CAA as a concomitant diagnosis. After propensity matching, we identified 7857 hospitalizations with CAA and 7874 without CAA. Patients with CAA had higher risk of readmission due to ICH as compared to those without CAA [hazards ratio (HR) 3.44, 95% confidence interval (CI) 2.55-4.64, P < 0.001] during the mean follow-up period of 181.4 (SD ± 106.4) days. Patients with CAA were also more likely to be readmitted due to SAH (HR 2.52, 95% CI 1.18-5.37, P 0.017) but not due to AIS (HR 0.74, 95% CI 0.54-1.01, P 0.061). Age (HR 0.96 per year increase in age, 95% CI 0.94-0.98, P < 0.001) and Medicare payer (HR 3.31; 95% CI 1.89-5.78, P < 0.001) were independently associated with readmissions due to ICH.

DISCUSSION

Patients admitted for ICH with a concomitant diagnosis of CAA are three times more likely to have readmissions for recurrent ICH compared to patients without CAA.

Main features of hereditary cerebral amyloid angiopathies: A systematic review

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Cerebral Amyloid Angiopathy (CAA) is a major contributor to stroke risk, cognitive decline, as well as multiple neurobehavioral and neuropsychiatric disturbances.

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Most CAA cases are sporadic, but many hereditary forms exist and present as familial monogenic disorders with early-onset hemorrhagic stroke and dementia.

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Hereditary CAA is usually characterized by earlier age at onset and more severe course when compared to sporadic CAA.

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Most forms of hereditary CAA are caused by APP mutations, leading to accumulation of amyloid beta in vascular deposits within the small vessels of the central nervous system.

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Cognitive decline is a common manifestation of hereditary CAA, either due to recurrent hemorrhagic stroke events or as chronic progression of small vessel vasculopathy.

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Recent studies highlighted increased risk for behavioral and psychiatric disorders among individuals affect by sporadic CAA, thus warranting similarly focused future investigations for hereditary CAA.

The term Cerebral Amyloid Angiopathy (CAA) refers to a group of neurovascular disorders characterized by amyloid deposition within the walls of leptomeningeal and cortical blood vessels of the brain, with specific predilection for arterioles, and (less often) capillaries and veins. Most CAA cases in the general population are sporadic in nature, and represent primarily an age-related condition affecting individuals in the fifth decade of life and beyond. Sporadic CAA is caused by deposition of amyloid-β (Aβ), originating from proteolytic cleavage of the Amyloid Precursor Protein (APP), within the walls of cerebral small caliber vessels. However, hereditary forms of CAA have also been described, generally presenting as rare familial disorder with monogenic (predominantly autosomal dominant) inheritance patterns. Hereditary CAA forms tend to affect younger individuals, and their course and clinical progression is more severe. Studies to date primarily focused on the vascular manifestations of sporadic and hereditary CAA, chiefly symptomatic lobar Intracerebral Hemorrhage (ICH). However, in the past decade sporadic CAA has also been consistently linked to progressive neurocognitive, neurobehavioral, and neuropsychiatric symptoms. This systematic review focuses on the genetics, pathogenesis, neuroimaging, neuropathology, and clinical manifestations of hereditary CAA with specific emphasis on previously overlooked cognitive, behavioral, and psychiatric symptoms.

Current Clinical Applications of Intracranial Vessel Wall MR Imaging

Intracranial vessel wall MR imaging (VWI) is increasingly being used as a valuable adjunct to conventional angiographic imaging techniques. This article will provide an updated review on intracranial VWI protocols and image interpretation. We review VWI technical considerations, describe common VWI imaging features of different intracranial vasculopathies and show illustrative cases. We review the role of VWI for differentiating among steno-occlusive vasculopathies, such as intracranial atherosclerotic plaque, dissections and Moyamoya disease. We also highlight how VWI may be used for the diagnostic work-up and surveillance of patients with vasculitis of the central nervous system and cerebral aneurysms.

Endovascular Treatment for Acute Stroke in Cerebral Amyloid Angiopathy

Background and Purpose

We aimed to compare outcome of endovascular thrombectomy in acute ischemic stroke in patients with and without cerebral amyloid angiopathy (CAA).

Methods

We included patients with and without possible or probable CAA based on the modified Boston criteria from an observational multicenter cohort of patients with acute ischemic stroke and endovascular thrombectomy, the German Stroke Registry Endovascular Treatment trial. We analyzed baseline characteristics, procedural parameters, and functional outcome after 90 days.

Results

Twenty-eight (17.3%) of 162 acute ischemic stroke patients were diagnosed with CAA based on iron-sensitive magnetic resonance imaging performed before endovascular thrombectomy. CAA patients were less likely to have a good 90-day outcome (14.3 versus 37.8%). National Institutes of Health Stroke Scale score (adjusted odds ratio, 0.88; P<0.001), successful recanalization (adjusted odds ratio 6.82; P=0.005), and CAA (adjusted odds ratio 0.28; P=0.049) were independent outcome predictors. Intravenous thrombolysis was associated with an increased rate of good outcome (36.3% versus 0%, P=0.031) in CAA.

Conclusions

Endovascular thrombectomy with or without thrombolysis appears beneficial in acute ischemic stroke patients with possible or probable CAA, but is associated with a worse functional outcome.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03356392.

Cortical Thickness and Its Association with Clinical Cognitive and Neuroimaging Markers in Cerebral Amyloid Angiopathy

BACKGROUND

Cerebral amyloid angiopathy (CAA) contributes to brain neurodegeneration and cognitive decline, but the relationship between these two processes is incompletely understood.

OBJECTIVE

The purpose of this study is to examine cortical thickness and its association with cognition and neurodegenerative biomarkers in CAA.

METHODS

Data were collected from the Functional Assessment of Vascular Reactivity study and the Calgary Normative Study. In total, 48 participants with probable CAA, 72 cognitively normal healthy controls, and 24 participants with mild dementia due to AD were included. Participants underwent an MRI scan, after which global and regional cortical thickness measurements were obtained using FreeSurfer. General linear models, adjusted for age and sex, were used to compare cortical thickness globally and in an AD signature region.

RESULTS

Global cortical thickness was lower in CAA compared to healthy controls (mean difference (MD) -0.047 mm, 95% confidence interval (CI) -0.088, -0.005, p = 0.03), and lower in AD compared to CAA (MD -0.104 mm, 95% CI -0.165, -0.043, p = 0.001). In the AD signature region, cortical thickness was lower in CAA compared to healthy controls (MD -0.07 mm, 95% CI -0.13 to -0.01, p = 0.02). Within the CAA group, lower cortical thickness was associated with lower memory scores (R2 = 0.10; p = 0.05) and higher white matter hyperintensity volume (R2 = 0.09, p = 0.04).

CONCLUSION

CAA contributes to neurodegeneration in the form of lower cortical thickness, and this could contribute to cognitive decline. Regional overlap with an AD cortical atrophy signature region suggests that co-existing AD pathology may contribute to lower cortical thickness observed in CAA.

Vessel Wall Enhancement on Black-Blood MRI Predicts Acute and Future Stroke in Cerebral Amyloid Angiopathy

BACKGROUND AND PURPOSE

Cerebral amyloid angiopathy (CAA) is a known risk factor for ischemic stroke though angiographic imaging is often negative. Our goal was to determine the relationship between vessel wall enhancement (VWE) in acute and future ischemic stroke in CAA patients.

MATERIALS AND METHODS

This was a retrospective study of patients with new-onset neurologic symptoms undergoing 3T vessel wall MR imaging from 2015 to 2019. Vessel wall enhancement was detected on pre- and postcontrast flow-suppressed 3D T1WI. Interrater agreement was evaluated in cerebral amyloid angiopathy-positive and age-matched negative participants using a prevalence- and bias-adjusted kappa analysis. In patients with cerebral amyloid angiopathy, multivariable Poisson and Cox regression were used to determine the association of vessel wall enhancement with acute and future ischemic stroke, respectively, using backward elimination of confounders to P < .20.

RESULTS

Fifty patients with cerebral amyloid angiopathy underwent vessel wall MR imaging, including 35/50 (70.0%) with ischemic stroke and 29/50 (58.0%) with vessel wall enhancement. Prevalence- and bias-corrected kappa was 0.82 (95% CI, 0.71-0.93). The final regression model for acute ischemic stroke included vessel wall enhancement (prevalence ratio = 1.5; 95% CI, 1.1-2.2; P = .022), age (prevalence ratio = 1.02; 95% CI, 1.0-1.05; P = .036), time between symptoms and MR imaging (prevalence ratio = 0.9; 95% CI, 0.8-0.9; P < .001), and smoking (prevalence ratio = 0.7; 95% CI, 0.5-1.0; P = .042) with c-statistic = 0.92 (95% CI, 0.84-0.99). Future ischemic stroke incidence with cerebral amyloid angiopathy was 49.7% (95% CI, 34.5%-67.2%) per year over a total time at risk of 37.5 person-years. Vessel wall enhancement-positive patients with cerebral amyloid angiopathy demonstrated significantly shorter stroke-free survival with 63.9% (95% CI, 43.2%-84.0%) versus 32.2% (95% CI, 14.4%-62.3%) ischemic strokes per year, chi-square = 4.9, P = .027. The final model for future ischemic stroke had a c-statistic of 0.70 and included initial ischemic stroke (hazard ratio = 3.4; 95% CI, 1.0-12.0; P = .053) and vessel wall enhancement (hazard ratio = 2.5; 95% CI, 0.9-7.0; P = .080).

CONCLUSIONS

Vessel wall enhancement is associated with both acute and future stroke in patients with cerebral amyloid angiopathy.

A practical approach to the management of cerebral amyloid angiopathy

Cerebral amyloid angiopathy is a common small vessel disease in the elderly involving vascular amyloid-β deposition. Cerebral amyloid angiopathy is one of the leading causes of intracerebral hemorrhage and a significant contributor to age-related cognitive decline. The awareness of a diagnosis of cerebral amyloid angiopathy is important in clinical practice as it impacts decisions to use lifelong anticoagulation or nonpharmacological alternatives to anticoagulation such as left atrial appendage closure in patients who have concurrent atrial fibrillation, another common condition in older adults. This review summarizes the latest literature regarding the management of patients with sporadic cerebral amyloid angiopathy, including diagnostic criteria, imaging biomarkers for cerebral amyloid angiopathy severity, and management strategies to decrease intracerebral hemorrhage risk. In a minority of patients, the presence of cerebral amyloid angiopathy triggers an autoimmune inflammatory reaction, referred to as cerebral amyloid angiopathy-related inflammation, which is often responsive to immunosuppressive treatment in the acute phase. Diagnosis and management of cerebral amyloid angiopathy-related inflammation will be presented separately. While there are currently no effective therapeutics available to cure or halt the progression of cerebral amyloid angiopathy, we discuss emerging avenues for potential future interventions.

Decreased Basal Ganglia Volume in Cerebral Amyloid Angiopathy

Background and Purpose

Cerebral amyloid angiopathy (CAA) is a common pathology of the leptomeningeal and cortical small vessels associated with hemorrhagic and non-hemorrhagic brain injury. Given previous evidence for CAA-related loss of cortical thickness and white matter volume, we hypothesized that CAA might also cause tissue loss in the basal ganglia.

Methods

We compared basal ganglia volumes expressed as a percentage of total intracranial volume (pBGV) of non-demented patients with sporadic and hereditary CAA to age-matched healthy control (HC) and Alzheimer’s disease (AD) cohorts.

Results

Patients with sporadic CAA had lower pBGV (n=80, 1.16%±0.14%) compared to HC (n=80, 1.30%±0.13%, P<0.0001) and AD patients (n=80, 1.23%±0.11%, P=0.001). Similarly, patients with hereditary CAA demonstrated lower pBGV (n=25, 1.26%±0.17%) compared to their matched HC (n=25, 1.36%±0.15%, P=0.036). Using a measurement of normalized basal ganglia width developed for analysis of clinical-grade magnetic resonance images, we found smaller basal ganglia width in patients with CAA-related lobar intracerebral hemorrhage (ICH; n=93, 12.35±1.47) compared to age-matched patients with hypertension-related deep ICH (n=93, 13.46±1.51, P<0.0001) or HC (n=93, 15.45±1.22, P<0.0001). Within the sporadic CAA research cohort, decreased basal ganglia volume was independently correlated with greater cortical gray matter atrophy (r=0.45, P<0.0001), increased basal ganglia fractional anisotropy (r=–0.36, P=0.001), and worse performance on language processing (r=0.35, P=0.003), but not with cognitive tests of executive function or processing speed.

Conclusions

These findings suggest an independent effect of CAA on basal ganglia tissue loss, indicating a novel mechanism for CAA-related brain injury and neurologic dysfunction.

Classification differentiates clinical and neuroanatomic features of cerebral small vessel disease

Age-related cerebral small vessel disease involves heterogeneous pathogenesis, such as arteriosclerosis/lipohyalinosis and cerebral amyloid angiopathy. MRI can visualize the brain lesions attributable to small vessel disease pathologies, including white-matter hyperintensities, lacune and cerebral microbleeds. However, these MRI markers usually coexist in small vessel disease of different aetiologies. Currently, there is no available classification integrating these neuroimaging markers for differentiating clinical and neuroanatomic features of small vessel disease yet. In this study, we tested whether our proposed stratification scheme could characterize specific clinical, neuroanatomic and potentially pathogenesis/aetiologies in classified small vessel disease subtypes. Cross-sectional analyses from a community-based non-demented non-stroke cohort consisting of ≥50 years old individuals were conducted. All participants were scanned 3T brain MRI for small vessel disease detection and neuroanatomic measurements and underwent physical and cognitive assessments. Study population were classified into robust and four small vessel disease groups based on imaging markers indicating (i) bleeding or non-bleeding; (ii) specific location of cerebral microbleeds; and (iii) the severity and combination of white-matter hyperintensities and lacune. We used whole-brain voxel-based morphometry analyses and tract-based spatial statistics to evaluate the regional grey-matter volume and white-matter microstructure integrity for comparisons among groups. Among the 735 participants with eligible brain MRI images, quality screening qualified 670 for grey-matter volume analyses and 617 for white-matter microstructural analyses. Common and distinct patterns of the clinical and neuroimaging manifestations were found in the stratified four small vessel disease subgroups. Hierarchical clustering analysis revealed that small vessel disease type 4 had features distinct from the small vessel disease types 1, 2 and 3. Abnormal white-matter microstructures and cognitive function but preserved physical function and grey-matter volume were found in small vessel disease type 4. Among small vessel disease types 1, 2 and 3, there were similar characteristics but different severity; the clinical features showed both physical frail and cognitive impairment and the neuroanatomic features revealed frontal–subcortical white-matter microstructures and remote, diffuse cortical abnormalities. This novel stratification scheme highlights the distinct clinical and neuroanatomic features of small vessel disease and the possible underlying pathogenesis. It could have potential application in research and clinical settings.

Cerebrospinal Fluid Biomarkers in Cerebral Amyloid Angiopathy

Background:

There is limited data on cerebrospinal fluid (CSF) biomarkers in sporadic amyloid-β (Aβ) cerebral amyloid angiopathy (CAA).

Objective:

To determine the profile of biomarkers relevant to neurodegenerative disease in the CSF of patients with CAA.

Methods:

We performed a detailed comparison of CSF markers, comparing patients with CAA, Alzheimer’s disease (AD), and control (CS) participants, recruited from the Biomarkers and Outcomes in CAA (BOCAA) study, and a Specialist Cognitive Disorders Service.

Results:

We included 10 CAA, 20 AD, and 10 CS participants (mean age 68.6, 62.5, and 62.2 years, respectively). In unadjusted analyses, CAA patients had a distinctive CSF biomarker profile, with significantly lower (p < 0.01) median concentrations of Aβ₃₈, Aβ₄₀, Aβ₄₂, sAβPPα, and sAβPPβ. CAA patients had higher levels of neurofilament light (NFL) than the CS group (p < 0.01), but there were no significant differences in CSF total tau, phospho-tau, soluble TREM2 (sTREM2), or neurogranin concentrations. AD patients had higher total tau, phospho-tau and neurogranin than CS and CAA groups. In age-adjusted analyses, differences for the CAA group remained for Aβ₃₈, Aβ₄₀, Aβ₄₂, and sAβPPβ. Comparing CAA patients with amyloid-PET positive (n = 5) and negative (n = 5) scans, PET positive individuals had lower (p < 0.05) concentrations of CSF Aβ₄₂, and higher total tau, phospho-tau, NFL, and neurogranin concentrations, consistent with an “AD-like” profile.

Conclusion:

CAA has a characteristic biomarker profile, suggestive of a global, rather than selective, accumulation of amyloid species; we also provide evidence of different phenotypes according to amyloid-PET positivity. Further replication and validation of these preliminary findings in larger cohorts is needed.

Neuropathological Correlates of Cumulative Benzodiazepine and Anticholinergic Drug Use

BACKGROUND

Benzodiazepines and anticholinergic drugs have been implicated in causing cognitive decline and potentially increasing dementia risk. However, evidence for an association with neuropathology is limited.

OBJECTIVE

To estimate the correlation between neuropathology at death and prior use of benzodiazepines and anticholinergic drugs.

METHODS

We categorized 298 brain donors from the population-based Medical Research Council Cognitive Function and Ageing Study, according to their history of benzodiazepine (including Z-drugs) or anticholinergic medication (drugs scoring 3 on the Anticholinergic Cognitive Burden scale) use. We used logistic regression to compare dichotomized neuropathological features for those with and without history of benzodiazepine and anticholinergic drug use before dementia, adjusted for confounders.

RESULTS

Forty-nine (16%) and 51 (17%) participants reported benzodiazepine and anticholinergic drug use. Alzheimer's disease neuropathologic change was similar whether or not exposed to either drug, for example 46% and 57% had intermediate/high levels among those with and without anticholinergic drug use. Although not significant after multiple testing adjustments, we estimated an odds ratio (OR) of 0.40 (95% confidence interval [95% CI] 0.18-0.87) for anticholinergic use and cortical atrophy. For benzodiazepine use, we estimated ORs of 4.63 (1.11-19.24) and 3.30 (1.02-10.68) for neuronal loss in the nucleus basalis and substantial nigra. There was evidence of neuronal loss in the nucleus basalis with anticholinergic drug use, but the association reduced when adjusted for confounders.

CONCLUSIONS

We found no evidence that benzodiazepine or anticholinergic drug use is associated with typical pathological features of Alzheimer's disease; however, we cannot rule out effects owing to small numbers.

Neuropsychological and neuroimaging characteristics of classical superficial siderosis

OBJECTIVE

To define the neuropsychological and neuroimaging characteristics of classical infratentorial superficial siderosis (iSS), a rare but disabling disorder defined by hemosiderin deposition affecting the superficial layers of the cerebellum, brainstem and spinal cord, usually associated with a slowly progressive neurological syndrome of deafness, ataxia and myelopathy.

METHODS

We present the detailed neuropsychological and neuroimaging findings in 16 patients with iSS (mean age 57 years; 6 female).

RESULTS

Cognitive impairment was present in 8/16 (50%) of patients: executive dysfunction was the most prevalent (44%), followed by impairment of visual recognition memory (27%); other cognitive domains were largely spared. Disease symptom duration was significantly correlated with the number of cognitive domains impaired (r = 0.59, p = 0.011). Mood disorders were also common (anxiety 62%, depression 38%, both 69%) but not associated with disease symptom duration. MRI findings revealed siderosis was not only in infratentorial brain regions, but also in characteristic widespread symmetrical supratentorial brain regions, independent of disease duration and degree of cognitive impairment. The presence of small vessel disease markers was very low and did not account for the cognitive impairment observed.

CONCLUSION

Neuropsychological disturbances are common in iSS and need to be routinely investigated. The lack of association between the anatomical extent of hemosiderin and cognitive impairment or disease duration suggests that hemosiderin itself is not directly neurotoxic. Additional biomarkers of iSS disease severity and progression are needed for future research and clinical trials.

Current Management and Therapeutic Strategies for Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is characterized by accumulation of amyloid β (Aβ) in walls of leptomeningeal vessels and cortical capillaries in the brain. The loss of integrity of these vessels caused by cerebrovascular Aβ deposits results in fragile vessels and lobar intracerebral hemorrhages. CAA also manifests with progressive cognitive impairment or transient focal neurological symptoms. Although development of therapeutics for CAA is urgently needed, the pathogenesis of CAA remains to be fully elucidated. In this review, we summarize the epidemiology, pathology, clinical and radiological features, and perspectives for future research directions in CAA therapeutics. Recent advances in mass spectrometric methodology combined with vascular isolation techniques have aided understanding of the cerebrovascular proteome. In this paper, we describe several potential key CAA-associated molecules that have been identified by proteomic analyses (apolipoprotein E, clusterin, SRPX1 (sushi repeat-containing protein X-linked 1), TIMP3 (tissue inhibitor of metalloproteinases 3), and HTRA1 (HtrA serine peptidase 1)), and their pivotal roles in Aβ cytotoxicity, Aβ fibril formation, and vessel wall remodeling. Understanding the interactions between cerebrovascular Aβ deposits and molecules that accumulate with Aβ may lead to discovery of effective CAA therapeutics and to the identification of biomarkers for early diagnosis.