White matter atrophy in cerebral amyloid angiopathy

Amyloid-related imaging abnormalities: manifestations, metrics and mechanisms

Three monoclonal antibodies directed against specific forms of the amyloid-β (Aβ) peptide have been granted accelerated or traditional approval by the FDA as treatments for Alzheimer disease, representing the first step towards bringing disease-modifying treatments for this disease into clinical practice. Here, we review the detection, underlying pathophysiological mechanisms and clinical implications of amyloid-related imaging abnormalities (ARIA), the most impactful adverse effect of anti-Aβ immunotherapy. ARIA appears as regions of oedema or effusions (ARIA-E) in brain parenchyma or sulci or as haemorrhagic lesions (ARIA-H) in the form of cerebral microbleeds, convexity subarachnoid haemorrhage, cortical superficial siderosis or intracerebral haemorrhage. Analysis of the radiographic appearance of ARIA, its clinical risk factors and underlying neuropathology, and results from animal models point to a central role for cerebral amyloid angiopathy - a condition characterized by cerebrovascular Aβ deposits - as a key component, either as a direct target for antibody-mediated inflammation or as recipient of Aβ mobilized from plaques in the Alzheimer brain parenchyma. The great majority of ARIA occurrences are associated with mild or no clinical symptoms. However, ~5% of all ARIA events are severe enough to result in hospitalization, permanent disability or death and thus raise challenging clinical questions regarding patient selection and use of concomitant agents. Therefore, identifying novel approaches to predicting, modelling, preventing and treating ARIA remains a key step towards allowing safe use of anti-Aβ immunotherapy for the world's rapidly ageing population.

Classification of amyloidosis and protein misfolding disorders in animals 2024: A review on pathology and diagnosis

Amyloidosis is a group of diseases in which proteins become amyloid, an insoluble fibrillar aggregate, resulting in organ dysfunction. Amyloid deposition has been reported in various animal species. To diagnose and understand the pathogenesis of amyloidosis, it is important to identify the amyloid precursor protein involved in each disease. Although 42 amyloid precursor proteins have been reported in humans, little is known about amyloidosis in animals, except for a few well-described amyloid proteins, including amyloid A (AA), amyloid light chain (AL), amyloid β (Aβ), and islet amyloid polypeptide-derived amyloid. Recently, several types of novel amyloidosis have been identified in animals using immunohistochemistry and mass spectrometry-based proteomic analysis. Certain species are predisposed to specific types of amyloidosis, suggesting a genetic background for its pathogenesis. Age-related amyloidosis has also emerged due to the increased longevity of captive animals. In addition, experimental studies have shown that some amyloids may be transmissible. Accurate diagnosis and understanding of animal amyloidosis are necessary for appropriate therapeutic intervention and comparative pathological studies. This review provides an updated classification of animal amyloidosis, including associated protein misfolding disorders of the central nervous system, and the current understanding of their pathogenesis. Pathologic features are presented together with state-of-the-art diagnostic methods that can be applied for routine diagnosis and identification of novel amyloid proteins in animals.

Vascular Neurology Considerations for Antiamyloid Immunotherapy: A Science Advisory From the American Heart Association

Antibodies directed at the amyloid-β peptide offer the prospect of disease-modifying therapy for early-stage Alzheimer disease but also carry the risk of brain edema or bleeding events, collectively designated amyloid-related imaging abnormalities. Introduction of the antiamyloid immunotherapies into practice is therefore likely to present a new set of questions for clinicians treating patients with cerebrovascular disease: Which manifestations of cerebrovascular disease should preclude, or permit, antibody treatment? Is it safe to prescribe amyloid immunotherapies to individuals who require antithrombotic treatment, or to administer thrombolysis to antibody-treated individuals with acute stroke? How should severe amyloid-related imaging abnormalities be managed? This science advisory summarizes the data and key considerations to guide these challenging decisions as the medical community collects further data and experience with these groundbreaking agents.

Microstructural white matter damage on MRI is associated with disease severity in Dutch-type cerebral amyloid angiopathy

Peak width of skeletonized mean diffusivity (PSMD) is an emerging diffusion-MRI based marker to study subtle early alterations to white matter microstructure. We assessed PSMD over the clinical continuum in Dutch-type hereditary CAA (D-CAA) and its association with other CAA-related MRI-markers and cognitive symptoms. We included (pre)symptomatic D-CAA mutation-carriers and calculated PSMD from diffusion-MRI data. Associations between PSMD-levels, cognitive performance and CAA-related MRI-markers were assessed with linear regression models. We included 59 participants (25/34 presymptomatic/symptomatic; mean age 39/58 y). PSMD-levels increased with disease severity and were higher in symptomatic D-CAA mutation-carriers (median [range] 4.90 [2.77-9.50]mm2/s × 10-4) compared with presymptomatic mutation-carriers (2.62 [1.96-3.43]mm2/s × 10-4) p = <0.001. PSMD was positively correlated with age, CAA-SVD burden on MRI (adj.B [confidence interval] = 0.42 [0.16-0.67], p = 0.002), with number of cerebral microbleeds (adj.B = 0.30 [0.08-0.53], p = 0.009), and with both deep (adj.B = 0.46 [0.22-0.69], p = <0.001) and periventricular (adj.B = 0.38 [0.13-0.62], p = 0.004) white matter hyperintensities. Increasing PSMD was associated with decreasing Trail Making Test (TMT)-A performance (B = -0.42 [-0.69-0.14], p = 0.04. In D-CAA mutation-carriers microstructural white matter damage is associated with disease phase, CAA burden on MRI and cognitive impairment as reflected by a decrease in information processing speed. PSMD, as a global measure of alterations to the white matter microstructure, may be a useful tool to monitor disease progression in CAA.

Non-hemorrhagic imaging markers of cerebral amyloid angiopathy in memory clinic patients

INTRODUCTION

The Boston criteria v2.0 for cerebral amyloid angiopathy (CAA) incorporated non-hemorrhagic imaging markers. Their prevalence and significance in patients with cognitive impairment remain uncertain.

METHODS

We studied 622 memory clinic patients with available magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) biomarkers. Two raters assessed non-hemorrhagic markers, and we explored their association with clinical characteristics through multivariate analyses.

RESULTS

Most patients had mild cognitive impairment; median age was 71 years and 50% were female. Using the v2.0 criteria, possible or probable CAA increased from 75 to 383 patients. Sixty-eight percent of the sample had non-hemorrhagic CAA markers, which were independently associated with age (odds ratio [OR] = 1.04, 95% confidence interval [CI] = 1.01-1.07), female sex (OR = 1.68, 95% CI = 1.11-2.54), and hemorrhagic CAA markers (OR = 2.11, 95% CI = 1.02-4.35).

DISCUSSION

Two-thirds of patients from a memory clinic cohort had non-hemorrhagic CAA markers, increasing the number of patients meeting the v2.0 CAA criteria. Longitudinal approaches should explore the implications of these markers, particularly the hemorrhagic risk in this population.

HIGHLIGHTS

The updated Boston criteria for cerebral amyloid angiopathy (CAA) now include non-hemorrhagic markers. The prevalence of non-hemorrhagic CAA markers in memory clinic patients is unknown. Two-thirds of patients in our memory clinic presented non-hemorrhagic CAA markers. The presence of these markers was associated with age, female sex, and hemorrhagic CAA markers. The hemorrhagic risk of patients presenting these type of markers remains unclear.

Serum and cerebrospinal fluid neurofilament light chain and glial fibrillary acid protein levels in early and advanced stages of cerebral amyloid Angiopathy

BACKGROUND

Neurofilament light chain (NFL) is a biomarker for neuroaxonal damage and glial fibrillary acidic protein (GFAP) for reactive astrocytosis. Both processes occur in cerebral amyloid angiopathy (CAA), but studies investigating the potential of NFL and GFAP as markers for CAA are lacking. We aimed to investigate NFL and GFAP as biomarkers for neuroaxonal damage and astrocytosis in CAA.

METHODS

For this cross-sectional study serum and cerebrospinal fluid (CSF) samples were collected between 2010 and 2020 from controls, (pre)symptomatic Dutch-type hereditary (D-CAA) mutation-carriers and participants with sporadic CAA (sCAA) from two prospective CAA studies at two University hospitals in the Netherlands. NFL and GFAP levels were measured with Simoa-assays. The association between NFL and GFAP levels and age, cognitive performance (MoCA), CAA-related MRI markers (CAA-CSVD-burden) and Aβ40 and Aβ42 levels in CSF were assessed with linear regression adjusted for confounders. The control group was divided in age < 55 and ≥55 years to match the specific groups.

RESULTS

We included 187 participants: 28 presymptomatic D-CAA mutation-carriers (mean age 40 years), 29 symptomatic D-CAA participants (mean age 58 years), 59 sCAA participants (mean age 72 years), 33 controls < 55 years (mean age 42 years) and 38 controls ≥ 55 years (mean age 65 years). In presymptomatic D-CAA, only GFAP in CSF (7.7*103pg/mL vs. 4.4*103pg/mL in controls; P<.001) was increased compared to controls. In symptomatic D-CAA, both serum (NFL:26.2pg/mL vs. 12.5pg/mL; P=0.008, GFAP:130.8pg/mL vs. 123.4pg/mL; P=0.027) and CSF (NFL:16.8*102pg/mL vs. 7.8*102pg/mL; P=0.01 and GFAP:11.4*103pg/mL vs. 7.5*103pg/mL; P<.001) levels were higher than in controls and serum levels (NFL:26.2pg/mL vs. 6.7pg/mL; P=0.05 and GFAP:130.8pg/mL vs. 66.0pg/mL; P=0.004) were higher than in pre-symptomatic D-CAA. In sCAA, only NFL levels were increased compared to controls in both serum (25.6pg/mL vs. 12.5pg/mL; P=0.005) and CSF (20.0*102pg/mL vs 7.8*102pg/mL; P=0.008). All levels correlated with age. Serum NFL correlated with MoCA (P=0.008) and CAA-CSVD score (P<.001). NFL and GFAP in CSF correlated with Aβ42 levels (P=0.01/0.02).

CONCLUSIONS

GFAP level in CSF is an early biomarker for CAA and is increased years before symptom onset. NFL and GFAP levels in serum and CSF are biomarkers for advanced CAA.

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.

Imaging of Amyloid-beta-related Arteritis

Cerebral amyloid angiopathy (CAA) is a cerebrovascular disorder marked by the accumulation of amyloid-beta peptide (Aβ) within the leptomeninges and smaller blood vessels of the brain. CAA can be both noninflammatory and inflammatory, and the inflammatory version includes Aβ-related angiitis (ABRA). ABRA is a vasculitis of the central nervous system related to an inflammatory response to Aβ in the vascular walls, which necessitates differentiating ABRA from noninflammatory CAA, as ABRA may require immunosuppressive treatment. MR imaging is typically the most effective imaging modality of choice to screen for these conditions, and they should be obtained at varying time points to track disease progression.

Association of Kidney Function With Dementia and Structural Brain Differences: A Large Population-Based Cohort Study

BACKGROUND

The association between kidney function and dementia risk and the mechanisms underlying this relationship remain unclear.

METHODS

Within the UK Biobank, 191 970 dementia-free participants aged ≥60 (mean age: 64.1 ± 2.9 years) were followed for 16 years to detect incident dementia. Serum creatinine and Cystatin C were measured at baseline to calculate estimated glomerular filtration rate (eGFR, mL/min/1.73 m2). Kidney function was categorized as normal (eGFR ≥ 90), mildly impaired (60 ≤ eGFR < 90), or moderately to severely impaired (eGFR < 60). Dementia was assessed based on self-reported medical history and medical records. During the follow-up, a subsample of 12 637 participants underwent brain MRI scans. Volumes of total brain, gray matter, white matter, hippocampus, and white matter hyperintensities were assessed.

RESULTS

Over the follow-up, 5 327 (2.8%) participants developed dementia. Compared to normal kidney function, there was an increased risk of dementia with moderate to severely impaired kidney function (hazard ratio = 1.53, 95% confidence interval [CI]: 1.32-1.76) but not mildly impaired kidney function. In Laplace regression, dementia onset among people with moderate to severely impaired kidney function occurred 1.53 (95% CI: 0.98-2.08) years earlier than those with normal kidney function. Moderate to severely impaired kidney function was related to significantly lower gray matter volume (β = -0.11, 95% CI: -0.19 to -0.03), but not to other brain magnetic resonance imaging measures.

CONCLUSIONS

Impaired kidney function is associated with about 50% increased risk of dementia and anticipates dementia onset by more than 1.5 years. Brain neurodegeneration may underlie the kidney function-dementia association.

Clinical Characteristics, Neuroimaging Markers, and Outcomes in Patients with Cerebral Amyloid Angiopathy: A Prospective Cohort Study

Background and purpose: Sporadic cerebral amyloid angiopathy (CAA) is a small vessel disease, resulting from progressive amyloid-β deposition in the media/adventitia of cortical and leptomeningeal arterioles. We sought to assess the prevalence of baseline characteristics, clinical and radiological findings, as well as outcomes among patients with CAA, in the largest study to date conducted in Greece. Methods: Sixty-eight patients fulfilling the Boston Criteria v1.5 for probable/possible CAA were enrolled and followed for at least twelve months. Magnetic Resonance Imaging was used to assess specific neuroimaging markers. Data regarding cerebrospinal fluid biomarker profile and Apolipoprotein-E genotype were collected. Multiple logistic regression analyses were performed to identify predictors of clinical phenotypes. Cox-proportional hazard regression models were used to calculate associations with the risk of recurrent intracerebral hemorrhage (ICH). Results: Focal neurological deficits (75%), cognitive decline (57%), and transient focal neurological episodes (TFNEs; 21%) were the most common clinical manifestations. Hemorrhagic lesions, including lobar cerebral microbleeds (CMBs; 93%), cortical superficial siderosis (cSS; 48%), and lobar ICH (43%) were the most prevalent neuroimaging findings. cSS was independently associated with the likelihood of TFNEs at presentation (OR: 4.504, 95%CI:1.258-19.088), while multiple (>10) lobar CMBs were independently associated with cognitive decline at presentation (OR:5.418, 95%CI:1.316-28.497). cSS emerged as the only risk factor of recurrent ICH (HR:4.238, 95%CI:1.509-11.900) during a median follow-up of 20 months. Conclusions: cSS was independently associated with TFNEs at presentation and ICH recurrence at follow-up, while a higher burden of lobar CMBs with cognitive decline at baseline. These findings highlight the prognostic value of neuroimaging markers, which may influence clinical decision-making.

Regional contribution of vascular dysfunction in white matter dementia: clinical and neuropathological insights

The maintenance of adequate blood supply and vascular integrity is fundamental to ensure cerebral function. A wide range of studies report vascular dysfunction in white matter dementias, a group of cerebral disorders characterized by substantial white matter damage in the brain leading to cognitive impairment. Despite recent advances in imaging, the contribution of vascular-specific regional alterations in white matter dementia has been not extensively reviewed. First, we present an overview of the main components of the vascular system involved in the maintenance of brain function, modulation of cerebral blood flow and integrity of the blood-brain barrier in the healthy brain and during aging. Second, we review the regional contribution of cerebral blood flow and blood-brain barrier disturbances in the pathogenesis of three distinct conditions: the archetypal white matter predominant neurocognitive dementia that is vascular dementia, a neuroinflammatory predominant disease (multiple sclerosis) and a neurodegenerative predominant disease (Alzheimer's). Finally, we then examine the shared landscape of vascular dysfunction in white matter dementia. By emphasizing the involvement of vascular dysfunction in the white matter, we put forward a hypothetical map of vascular dysfunction during disease-specific progression to guide future research aimed to improve diagnostics and facilitate the development of tailored therapies.

Myelin in Alzheimer's disease: culprit or bystander?

Alzheimer's disease (AD) is a neurodegenerative disorder with neuronal and synaptic losses due to the accumulation of toxic amyloid β (Αβ) peptide oligomers, plaques, and tangles containing tau (tubulin-associated unit) protein. While familial AD is caused by specific mutations, the sporadic disease is more common and appears to result from a complex chronic brain neuroinflammation with mitochondriopathies, inducing free radicals' accumulation. In aged brain, mutations in DNA and several unfolded proteins participate in a chronic amyloidosis response with a toxic effect on myelin sheath and axons, leading to cognitive deficits and dementia. Αβ peptides are the most frequent form of toxic amyloid oligomers. Accumulations of misfolded proteins during several years alters different metabolic mechanisms, induce chronic inflammatory and immune responses with toxic consequences on neuronal cells. Myelin composition and architecture may appear to be an early target for the toxic activity of Aβ peptides and others hydrophobic misfolded proteins. In this work, we describe the possible role of early myelin alterations in the genesis of neuronal alterations and the onset of symptomatology. We propose that some pathophysiological and clinical forms of the disease may arise from structural and metabolic disorders in the processes of myelination/demyelination of brain regions where the accumulation of non-functional toxic proteins is important. In these forms, the primacy of the deleterious role of amyloid peptides would be a matter of questioning and the initiating role of neuropathology would be primarily the fact of dysmyelination.

Mendelian Randomization Analyses Accounting for Causal Effect of COVID-19 on Brain Imaging-Derived Phenotypes

BACKGROUND

The coronavirus disease 2019 (COVID-19) has been a major challenge to global health and a financial burden. Little is known regarding the possible causal effects of COVID-19 on the macro- and micro-structures of the human brain.

OBJECTIVE

To determine the causal links between susceptibility, hospitalization, and the severity of COVID-19 and brain imaging-derived phenotypes (IDPs).

METHODS

Mendelian randomization (MR) analyses were performed to investigate the causal effect of three COVID-19 exposures (SARS-CoV-2 infection, hospitalized COVID-19, and critical COVID-19) on brain structure employing summary datasets of genome-wide association studies.

RESULTS

In terms of cortical phenotypes, hospitalization due to COVID-19 was associated with a global decrease in the surface area (SA) of the cortex structure (β= -624.77, 95% CI: -1227.88 to -21.66, p = 0.042). At the regional level, SARS-CoV-2 infection was found to have a nominally causal effect on the thickness (TH) of the postcentral region (β= -0.004, 95% CI: -0.007 to -0.001, p = 0.01), as well as eight other IDPs. Hospitalized COVID-19 has a nominally causal relationship with TH of postcentral (β= -0.004, 95% CI: -0.007 to -0.001, p = 0.01) and other 6 IDPs. The nominally causal effects of critical COVID-19 on TH of medial orbitofrontal (β=0.004, 95% CI: 0.001to 0.007, p = 0.004) and other 7 IDPs were revealed.

CONCLUSIONS

Our study provides compelling genetic evidence supporting causal relationships between three COVID-19 traits and brain IDPs. This discovery holds promise for enhancing predictions and interventions in brain imaging.

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.

Mapping the current trends and hotspots of vascular cognitive impairment from 2000-2021: A bibliometric analysis

AIMS

To visualize the trends and hotspots in the scientific research related to vascular cognitive impairment (VCI) quantitatively and qualitatively.

METHODS

Cross-sectional bibliometric analysis of publications that related to VCI was conducted. Publications were found by searching in the Web of Science Core Collection database (WoSCC) - Edition: Science Citation Index Expanded (SCI-Expanded) from January 2000 to December 2021. Publication type was restricted to article and review in the English language. The downloaded data were screened and analyzed in January 2022.

RESULTS

In total, 16,264 publications were identified, with a steady increase in annual publications. The United States was the leading country in VCI research regarding publication numbers and national influence. National Institute of Aging had the highest influence among all the institutes in the field of VCI. Philip Scheltens was the most active author. The top five active authors' publications focused on pathobiology, neuroimaging standards, risk factors, prevention, and the standard diagnosis of vascular dementia (VaD). A co-cited publication clustering resulted in 19 main clusters, and the prevention, blood-brain barrier, cholesterol, cerebral amyloid angiopathy, and VaD were the top 5 clusters. Moreover, burst keywords detection revealed that the "small vessel disease" is the current hotspot in the field of VCI.

CONCLUSIONS

This bibliometric analysis mapped the overall research structure of VCI and analyzed the current research trends and hotspots for future studies orientation. Neuroimaging, risk factors detection, and pathobiology are the current trends in VCI research. Small vessel disease and its mechanisms are the current hotspots of VCI research.

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.

Pamiparib Induces Neurodevelopmental Defects and Cerebral Haemorrhage in Zebrafish Embryos via Inhibiting Notch Signalling

Pamiparib is a poly ADP-ribose polymerase (PARP) inhibitor used in clinical studies, which can penetrate the blood-brain barrier efficiently. At present, there are few studies on its effect on vertebrate neurodevelopment. In this study, we exposed zebrafish embryos to 1, 2 and 3 µM of Pamiparib from 6 to 72 h post-fertilisation (hpf). Results showed that pamiparib can specifically induce cerebral haemorrhage, brain atrophy and movement disorders in fish larvae. In addition, pamiparib exposure leads to downregulation of acetylcholinesterase (AChE) and adenosine triphosphate (ATPase) activities, and upregulation of oxidative stress which then leads to apoptosis and disrupts the gene expression involved in the neurodevelopment, neurotransmitter pathways and Parkinson's disease (PD) like symptoms. Meanwhile, astaxanthin can partially rescue neurodevelopmental defects by downregulating oxidative stress. After exposure to pamiparib, the Notch signalling is downregulated, and the use of an activator of Notch signalling can partially rescue neurodevelopmental toxicity. Therefore, our research indicates that pamiparib may induce zebrafish neurotoxicity by downregulating Notch signalling and provides a reference for the potential neurotoxicity of pamiparib during embryonic development.

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.

Corpus callosum lesions are associated with worse cognitive performance in cerebral amyloid angiopathy

The impact of vascular lesions on cognition is location dependent. Here, we assessed the contribution of small vessel disease lesions in the corpus callosum to vascular cognitive impairment in cerebral amyloid angiopathy, as a model for cerebral small vessel disease. Sixty-five patients with probable cerebral amyloid angiopathy underwent 3T magnetic resonance imaging, including a diffusion tensor imaging scan, and neuropsychological testing. Microstructural white-matter integrity was quantified by fractional anisotropy and mean diffusivity. Z-scores on individual neuropsychological tests were averaged into five cognitive domains: information processing speed, executive functioning, memory, language and visuospatial ability. Corpus callosum lesions were defined as haemorrhagic (microbleeds or larger bleeds) or ischaemic (microinfarcts, larger infarcts and diffuse fluid-attenuated inversion recovery hyperintensities). Associations between corpus callosum lesion presence, microstructural white-matter integrity and cognitive performance were examined with multiple regression models. The prevalence of corpus callosum lesions was confirmed in an independent cohort of memory clinic patients with and without cerebral amyloid angiopathy (n = 82). In parallel, we assessed corpus callosum lesions on ex vivo magnetic resonance imaging in cerebral amyloid angiopathy patients (n = 19) and controls (n = 5) and determined associated tissue abnormalities with histopathology. A total number of 21 corpus callosum lesions was found in 19/65 (29%) cerebral amyloid angiopathy patients. Corpus callosum lesion presence was associated with reduced microstructural white-matter integrity within the corpus callosum and in the whole-brain white matter. Patients with corpus callosum lesions performed significantly worse on all cognitive domains except language, compared with those without corpus callosum lesions after correcting for age, sex, education and time between magnetic resonance imaging and neuropsychological assessment. This association was independent of the presence of intracerebral haemorrhage, whole-brain fractional anisotropy and mean diffusivity, and white-matter hyperintensity volume and brain volume for the domains of information processing speed and executive functioning. In the memory clinic patient cohort, corpus callosum lesions were present in 14/54 (26%) patients with probable and 2/8 (25%) patients with possible cerebral amyloid angiopathy, and in 3/20 (15%) patients without cerebral amyloid angiopathy. In the ex vivo cohort, corpus callosum lesions were present in 10/19 (53%) patients and 2/5 (40%) controls. On histopathology, ischaemic corpus callosum lesions were associated with tissue loss and demyelination, which extended beyond the lesion core. Together, these data suggest that corpus callosum lesions are a frequent finding in cerebral amyloid angiopathy, and that they independently contribute to cognitive impairment through strategic microstructural disruption of white-matter tracts.

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.

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.

Cerebral white matter vasculature: still uncharted?

White matter vasculature plays a major role in the pathophysiology of permanent neurological deficits following a stroke or progressive cognitive alteration related to small vessel disease. Thus, knowledge of the complex vascularization and functional aspects of the deep white matter territories is paramount to comprehend clinical manifestations of brain ischemia. This review provides a structured presentation of the existing knowledge of the vascularization of the human cerebral white matter from seminal historical studies to the current literature. First, we revisit the highlights of prenatal development of the endoparenchymal telencephalic vascular system that are crucial for the understanding of vessel organization in the adult. Second, we reveal the tangled history of debates on the existence, clinical significance, and physiological role of leptomeningeal anastomoses. Then, we present how conceptions on white matter vascularization transitioned from the mixed ventriculopetal/ventriculofugal theory, in which a low-flow area was interposed in between concurrent arterial flows, to the purely ventriculopetal theory. The latter model explains variable white matter sensitivity to ischemia by various organizations of ventriculopetal vessel terminals having different origin/length properties and interconnection patterns. Next, arteries supplying primarily the white matter are described according to their length and overall structure. Furthermore, the known distribution territories, to date, are studied in relation to primary anatomical structures of the human cerebral white matter, emphasizing the sparsity of the "ground-truth" data available in the literature. Finally, the implications for both large vessel occlusion and chronic small vessel disease are discussed, as well as the insights from neuroimaging. All things considered, we identify the need for further research on deep white matter vascularization, especially regarding the arterial supply of white matter fiber tracts.

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.

Emerging Concepts in Vascular Dementia: A Review

OBJECTIVE

Vascular dementia (VaD) is the second most common cause of dementia and a major health concern worldwide. A comprehensive review on VaD is warranted for better understanding and guidance for the practitioner. We provide an updated overview of the epidemiology, pathophysiological mechanisms, neuroimaging patterns as well as current diagnostic and therapeutic approaches.

MATERIALS AND METHODS

A narrative review of current literature in VaD was performed based on publications from the database of PubMed, Scopus and Google Scholar up to January, 2021.

RESULTS

VaD can be the result of ischemic or hemorrhagic tissue injury in a particular region of the brain which translates into clinically significant cognitive impairment. For example, a cerebral infarct in the speech area of the dominant hemisphere would translate into clinically significant impairment as would involvement of projection pathways such as the arcuate fasciculus. Specific involvement of the angular gyrus of the dominant hemisphere, with resultant Gerstman's syndrome, could have a pronounced effect on functional ability despite being termed a "minor stroke". Small vessel cerebrovascular disease can have a cumulate effect on cognitive function over time. It is unfortunately well recognized that "good" functional recovery in acute ischemic or haemorrhagic stroke, including subarachnoid haemorrhage, does not necessarily translate into good cognitive recovery. The victim may often be left unable to have gainful employment, drive a car safely or handle their affairs independently.

CONCLUSIONS

This review should serve as a compendium of updated information on VaD and provide guidance in terms of newer diagnostic and potential therapeutic approaches.