Dominant CST3 variants cause adult onset leukodystrophy without amyloid angiopathy.

Leukodystrophies are rare genetic white matter disorders that have been regarded as mainly occurring in childhood. This perception has been altered in recent years, as a growing number of leukodystrophies have been described as having an onset in adulthood. Still, many adult patients presenting with white matter changes remain without a specific molecular diagnosis. We describe a novel adult onset leukodystrophy in 16 patients from eight families carrying one of four different stop-gain or frameshift dominant variants in the CST3 gene. Clinical and radiological features differ markedly from the previously described Icelandic cerebral amyloid angiopathy found in patients carrying p.Leu68Asn substitution in CST3. The clinical phenotype consists of recurrent episodes of hemiplegic migraine associated with transient unilateral focal deficits and slowly progressing motor symptoms and cognitive decline in mid to older adult ages. In addition, in some cases acute onset clinical deterioration led to a prolonged episode with reduced consciousness and even early death. Radiologically, pathognomonic changes are found at typical predilection sites involving the deep cerebral white matter sparing a periventricular and directly subcortical rim, the middle blade of corpus callosum, posterior limb of the internal capsule, middle cerebellar peduncles, cerebral peduncles and specifically the globus pallidus. Histopathologic characterization in two autopsy cases did not reveal angiopathy, but instead micro- to macrocystic degeneration of the white matter. Astrocytes were activated at early stages and later displayed severe degeneration and loss. In addition, despite the loss of myelin, elevated numbers of partly apoptotic oligodendrocytes were observed. A structural comparison of the variants in CST3 suggests that specific truncations of cystatin C result in an abnormal function, possibly by rendering the protein more prone to aggregation. Future studies are required to confirm the assumed effect on the protein and to determine pathophysiologic downstream events at the cellular level.

Is CAA a perivascular brain clearance disease? A discussion of the evidence to date and outlook for future studies.

The brain's network of perivascular channels for clearance of excess fluids and waste plays a critical role in the pathogenesis of several neurodegenerative diseases including cerebral amyloid angiopathy (CAA). CAA is the main cause of hemorrhagic stroke in the elderly, the most common vascular comorbidity in Alzheimer's disease and also implicated in adverse events related to anti-amyloid immunotherapy. Remarkably, the mechanisms governing perivascular clearance of soluble amyloid ß-a key culprit in CAA-from the brain to draining lymphatics and systemic circulation remains poorly understood. This knowledge gap is critically important to bridge for understanding the pathophysiology of CAA and accelerate development of targeted therapeutics. The authors of this review recently converged their diverse expertise in the field of perivascular physiology to specifically address this problem within the framework of a Leducq Foundation Transatlantic Network of Excellence on Brain Clearance. This review discusses the overarching goal of the consortium and explores the evidence supporting or refuting the role of impaired perivascular clearance in the pathophysiology of CAA with a focus on translating observations from rodents to humans. We also discuss the anatomical features of perivascular channels as well as the biophysical characteristics of fluid and solute transport.

An electrostatic cluster guides Aß40 fibril formation in sporadic and Dutch-type cerebral amyloid angiopathy.

Cerebral amyloid angiopathy (CAA) is associated with the accumulation of fibrillar Aß peptides upon and within the cerebral vasculature, which leads to loss of vascular integrity and contributes to disease progression in Alzheimer's disease (AD). We investigate the structure of human-derived Aß40 fibrils obtained from patients diagnosed with sporadic or familial Dutch-type (E22Q) CAA. Using cryo-EM, two primary structures are identified containing elements that have not been observed in in vitro Aß40 fibril structures. One population has an ordered N-terminal fold comprised of two ß-strands stabilized by electrostatic interactions involving D1, E22, D23 and K28. This charged cluster is disrupted in the second population, which exhibits a disordered N-terminus and is favored in fibrils derived from the familial Dutch-type CAA patient. These results illustrate differences between human-derived CAA and AD fibrils, and how familial CAA mutations can guide fibril formation.

O-GalNAc glycosylation determines intracellular trafficking of APP and Aß production.

A primary pathology of Alzheimer's disease (AD) is amyloid ß (Aß) deposition in brain parenchyma and blood vessels, the latter being called cerebral amyloid angiopathy (CAA). Parenchymal amyloid plaques presumably originate from neuronal Aß precursor protein (APP). Although vascular amyloid deposits' origins remain unclear, endothelial APP expression in APP knock-in mice was recently shown to expand CAA pathology, highlighting endothelial APP's importance. Furthermore, two types of endothelial APP-highly O-glycosylated APP and hypo-O-glycosylated APP-have been biochemically identified, but only the former is cleaved for Aß production, indicating the critical relationship between APP O-glycosylation and processing. Here, we analyzed APP glycosylation and its intracellular trafficking in neurons and endothelial cells. Although protein glycosylation is generally believed to precede cell surface trafficking, which was true for neuronal APP, we unexpectedly observed that hypo-O-glycosylated APP is externalized to the endothelial cell surface and transported back to the Golgi apparatus, where it then acquires additional O-glycans. Knockdown of genes encoding enzymes initiating APP O-glycosylation significantly reduced Aß production, suggesting this non-classical glycosylation pathway contributes to CAA pathology and is a novel therapeutic target.

Identifying diagnostic and prognostic factors in cerebral amyloid angiopathy-related inflammation: A systematic analysis of published and seven new cases.

AIMS: Cerebral amyloid angiopathy (CAA)-related inflammation (CAA-RI) is a potentially reversible manifestation of CAA, histopathologically characterised by transmural and/or perivascular inflammatory infiltrates. We aimed to identify clinical, radiological and laboratory variables capable of improving or supporting the diagnosis of or predicting/influencing the prognosis of CAA-RI and to retrospectively evaluate different therapeutic approaches. METHODS: We present clinical and neuroradiological observations in seven unpublished CAA-RI cases, including neuropathological findings in two definite cases. These cases were included in a systematic analysis of probable/definite CAA-RI cases published in the literature up to 31 December 2021. Descriptive and associative analyses were performed, including a set of clinical, radiological and laboratory variables to predict short-term, 6-month and 1-year outcomes and mortality, first on definite and second on an expanded probable/definite CAA-RI cohort. RESULTS: Data on 205 definite and 100 probable cases were analysed. CAA-RI had a younger symptomatic onset than non-inflammatory CAA, without sex preference. Transmural histology was more likely to be associated with the co-localisation of microbleeds with confluent white matter hyperintensities on magnetic resonance imaging (MRI). Incorporating leptomeningeal enhancement and/or sulcal non-nulling on fluid-attenuated inversion recovery (FLAIR) enhanced the sensitivity of the criteria. Cerebrospinal fluid pleocytosis was associated with a decreased probability of clinical improvement and longer term positive outcomes. Future lobar haemorrhage was associated with adverse outcomes, including mortality. Immunosuppression was associated with short-term improvement, with less clear effects on long-term outcomes. The superiority of high-dose over low-dose corticosteroids was not established. CONCLUSIONS: This is the largest retrospective associative analysis of published CAA-RI cases and the first to include an expanded probable/definite cohort to identify diagnostic/prognostic markers. We propose points for further crystallisation of the criteria and directions for future prospective studies.

Histopathological Correlates of Lobar Microbleeds in False-Positive Cerebral Amyloid Angiopathy Cases.

OBJECTIVE: A definite diagnosis of cerebral amyloid angiopathy (CAA), characterized by the accumulation of amyloid ß in walls of cerebral small vessels, can only be obtained through pathological examination. A diagnosis of probable CAA during life relies on the presence of hemorrhagic markers, including lobar cerebral microbleeds (CMBs). The aim of this project was to study the histopathological correlates of lobar CMBs in false-positive CAA cases. METHODS: In 3 patients who met criteria for probable CAA during life, but showed no CAA upon neuropathological examination, lobar CMBs were counted on ex vivo 3T magnetic resonance imaging (MRI) and on ex vivo 7T MRI. Areas with lobar CMBs were next sampled and cut into serial sections, on which the CMBs were then identified. RESULTS: Collectively, there were 25 lobar CMBs on in vivo MRI and 22 on ex vivo 3T MRI of the analyzed hemispheres. On ex vivo MRI, we targeted 12 CMBs for sampling, and definite histopathological correlates were retrieved for 9 of them, of which 7 were true CMBs. No CAA was found on any of the serial sections. The "culprit vessels" associated with the true CMBs instead showed moderate to severe arteriolosclerosis. Furthermore, CMBs in false-positive CAA cases tended to be located more often in the juxtacortical or subcortical white matter than in the cortical ribbon. INTERPRETATION: These findings suggest that arteriolosclerosis can generate lobar CMBs and that more detailed investigations into the exact localization of CMBs with respect to the cortical ribbon could potentially aid the diagnosis of CAA during life. ANN NEUROL 2023;94:856-870.

Differences in the cerebral amyloid angiopathy proteome in Alzheimer's disease and mild cognitive impairment.

Cerebral amyloid angiopathy (CAA) is characterized by amyloid beta (Aß) deposition in cerebrovasculature. It is prevalent with aging and Alzheimer's disease (AD), associated with intracerebral hemorrhage, and contributes to cognitive deficits. To better understand molecular mechanisms, CAA(+) and CAA(-) vessels were microdissected from paraffin-embedded autopsy temporal cortex of age-matched Control (n = 10), mild cognitive impairment (MCI; n = 4), and sporadic AD (n = 6) cases, followed by label-free quantitative mass spectrometry. 257 proteins were differentially abundant in CAA(+) vessels compared to neighboring CAA(-) vessels in MCI, and 289 in AD (p < 0.05, fold-change > 1.5). 84 proteins changed in the same direction in both groups, and many changed in the same direction among proteins significant in at least one group (p < 0.0001, R2 = 0.62). In CAA(+) vessels, proteins significantly increased in both AD and MCI were particularly associated with collagen-containing extracellular matrix, while proteins associated with ribonucleoprotein complex were significantly decreased in both AD and MCI. In neighboring CAA(-) vessels, 61 proteins were differentially abundant in MCI, and 112 in AD when compared to Control cases. Increased proteins in CAA(-) vessels were associated with extracellular matrix, external encapsulating structure, and collagen-containing extracellular matrix in MCI; collagen trimer in AD. Twenty two proteins were increased in CAA(-) vessels of both AD and MCI. Comparison of the CAA proteome with published amyloid-plaque proteomic datasets identified many proteins similarly enriched in CAA and plaques, as well as a protein subset hypothesized as preferentially enriched in CAA when compared to plaques. SEMA3G emerged as a CAA specific marker, validated immunohistochemically and with correlation to pathology levels (p < 0.0001; R2 = 0.90). Overall, the CAA(-) vessel proteomes indicated changes in vessel integrity in AD and MCI in the absence of Aß, and the CAA(+) vessel proteome was similar in MCI and AD, which was associated with vascular matrix reorganization, protein translation deficits, and blood brain barrier breakdown.

Amyloid-ß peptide signature associated with cerebral amyloid angiopathy in familial Alzheimer's disease with APPdup and Down syndrome.

Alzheimer's disease (AD) is characterized by extracellular amyloid plaques containing amyloid-ß (Aß) peptides, intraneuronal neurofibrillary tangles, extracellular neuropil threads, and dystrophic neurites surrounding plaques composed of hyperphosphorylated tau protein (pTau). Aß can also deposit in blood vessel walls leading to cerebral amyloid angiopathy (CAA). While amyloid plaques in AD brains are constant, CAA varies among cases. The study focuses on differences observed between rare and poorly studied patient groups with APP duplications (APPdup) and Down syndrome (DS) reported to have higher frequencies of elevated CAA levels in comparison to sporadic AD (sAD), most of APP mutations, and controls. We compared Aß and tau pathologies in postmortem brain tissues across cases and Aß peptides using mass spectrometry (MS). We further characterized the spatial distribution of Aß peptides with MS-brain imaging. While intraparenchymal Aß deposits were numerous in sAD, DS with AD (DS-AD) and AD with APP mutations, these were less abundant in APPdup. On the contrary, Aß deposits in the blood vessels were abundant in APPdup and DS-AD while only APPdup cases displayed high Aß deposits in capillaries. Investigation of Aß peptide profiles showed a specific increase in Aßx-37, Aßx-38 and Aßx-40 but not Aßx-42 in APPdup cases and to a lower extent in DS-AD cases. Interestingly, N-truncated Aß2-x peptides were particularly increased in APPdup compared to all other groups. This result was confirmed by MS-imaging of leptomeningeal and parenchymal vessels from an APPdup case, suggesting that CAA is associated with accumulation of shorter Aß peptides truncated both at N- and C-termini in blood vessels. Altogether, this study identified striking differences in the localization and composition of Aß deposits between AD cases, particularly APPdup and DS-AD, both carrying three genomic copies of the APP gene. Detection of specific Aß peptides in CSF or plasma of these patients could improve the diagnosis of CAA and their inclusion in anti-amyloid immunotherapy treatments.

Tumefactive cerebral amyloid angiopathy - related inflammation.

INTRODUCTION: Cerebral amyloid angiopathy-related inflammation (CAA-ri) derives from inflammatory response to ß-amyloid (Aß) protein deposition within the cerebral blood vessel walls. We report a case that accentuates those clinical and imaging features that can contribute to raise suspicion for the condition and lead to early treatment initiation. CASE PRESENTATION: A 72-year-old man was referred with one-month history of cognitive decline along with behavioral alterations. Brain MRI showed fluid attenuated inversion recovery (FLAIR) asymmetrical multifocal white matter hyperintensities (WMHs) along with multiple cerebral microbleeds (CMBs) and cortical superficial siderosis (cSS) on T2*-weighted gradient-recalled echo (T2*-GRE) images. Metabolic, infectious, and neoplastic causes were excluded, and subsequently corticosteroids were administered to the patient resulting in clinical recovery. Imaging on follow-up disclosed remission of WMHs, while CMBs load increased significantly. DISCUSSION: Clinical neurologists' acquaintance with the clinical and imaging features of CAA-ri allows prompt diagnosis and medication initiation, that is essential for a conceivably treatable condition.

Cerebral amyloid angiopathy and the immune system.

Cerebral amyloid angiopathy (CAA) is characterized by the accumulation of amyloid protein in the walls of cerebral blood vessels. This deposition of amyloid causes damage to the cerebral vasculature, resulting in blood-brain barrier disruption, cerebral hemorrhage, cognitive decline, and dementia. The role of the immune system in CAA is complex and not fully understood. While the immune system has a clear role in the rare inflammatory variants of CAA (CAA related inflammation and Abeta related angiitis), the more common variants of CAA also have immune system involvement. In a protective role, immune cells may facilitate the clearance of beta-amyloid from the cerebral vasculature. The immune system can also contribute to CAA pathology, promoting vascular injury, blood-brain barrier breakdown, inflammation, and progression of CAA. In this review, we summarize the role of the immune system in CAA, including the potential of immune based treatment strategies to slow vascular disease in CAA and associated cognitive impairment, white matter disease progression, and reduce the risk of cerebral hemorrhage. HIGHLIGHTS: The immune system has a role in cerebral amyloid angiopathy (CAA) which is summarized in this review. There is an inflammatory response to beta-amyloid that may contribute to brain injury and cognitive impairment. Immune cells may facilitate the clearance of beta-amyloid from the cerebral vasculature. Improved understanding of the immune system in CAA may afford novel treatment to improve outcomes in patients with CAA.

Associations of cortical SPP1 and ITGAX with cognition and common neuropathologies in older adults.

INTRODUCTION: The secreted phosphoprotein 1 (SPP1) gene expressed by CD11c+ cells is known to be associated with microglia activation and neuroinflammatory diseases. As most studies rely on mouse models, we investigated these genes and proteins in the cortical brain tissue of older adults and their role in Alzheimer's disease (AD) and related disorders. METHODS: We leveraged protein measurements, single-nuclei, and RNASeq data from the Religious Orders Study and Rush Memory and Aging Project (ROSMAP) of over 1200 samples for association analysis. RESULTS: Expression of SPP1 and its encoded protein osteopontin were associated with faster cognitive decline and greater odds of common neuropathologies. At single-cell resolution,  integrin subunit alpha X (ITGAX) was highly expressed in microglia, where specific subpopulations were associated with AD and cerebral amyloid angiopathy. DISCUSSION: The study provides evidence of SPP1 and ITGAX association with cognitive decline and common neuropathologies identifying a microglial subset associated with disease.

Clearance of interstitial fluid (ISF) and CSF (CLIC) group-part of Vascular Professional Interest Area (PIA), updates in 2022-2023. Cerebrovascular disease and the failure of elimination of Amyloid-ß from the brain and retina with age and Alzheimer's disease: Opportunities for therapy.

This editorial summarizes advances from the Clearance of Interstitial Fluid and Cerebrospinal Fluid (CLIC) group, within the Vascular Professional Interest Area (PIA) of the Alzheimer's Association International Society to Advance Alzheimer's Research and Treatment (ISTAART). The overarching objectives of the CLIC group are to: (1) understand the age-related physiology changes that underlie impaired clearance of interstitial fluid (ISF) and cerebrospinal fluid (CSF) (CLIC); (2) understand the cellular and molecular mechanisms underlying intramural periarterial drainage (IPAD) in the brain; (3) establish novel diagnostic tests for Alzheimer's disease (AD), cerebral amyloid angiopathy (CAA), retinal amyloid vasculopathy, amyloid-related imaging abnormalities (ARIA) of spontaneous and iatrogenic CAA-related inflammation (CAA-ri), and vasomotion; and (4) establish novel therapies that facilitate IPAD to eliminate amyloid ß (Aß) from the aging brain and retina, to prevent or reduce AD and CAA pathology and ARIA side events associated with AD immunotherapy.

Lewy body pathology modifies risk factors for cerebral amyloid angiopathy when comorbid with Alzheimer's disease pathology.

INTRODUCTION: Cerebral amyloid angiopathy (CAA) often accompanies dementia-associated pathologies and is important in the context of anti-amyloid monoclonal therapies and risk of hemorrhage. METHODS: We conducted a retrospective neuropathology-confirmed study of 2384 participants in the National Alzheimer Coordinating Center cohort (Alzheimer's disease [AD], n = 1175; Lewy body pathology [LBP], n = 316; and mixed AD and LBP [AD-LBP], n = 893). We used logistic regression to evaluate age, sex, education, APOE ε4, neuritic plaques, and neurofibrillary tangles (NFTs) in CAA risk. RESULTS: APOE ε4 increased CAA risk in all three groups, while younger age and higher NFT stages increased risk in AD and AD-LBP. In AD-LBP, male sex and lower education were additional risk factors. The odds of APOE ε4 carrier homozygosity related to CAA was higher in LBP (25.69) and AD-LBP (9.50) than AD (3.17). DISCUSSION: AD and LBPs modify risk factors for CAA and should be considered in reviewing the risk of CAA. HIGHLIGHTS: Lewy body pathology modifies risk factors for cerebral amyloid angiopathy (CAA) when present along with Alzheimer's disease (AD) neuropathology. In the context of anti-amyloid monoclonal therapies and their associated risks for hemorrhage, the risk of underlying CAA in mixed dementia with Lewy body pathology needs to be considered.

Cortical microinfarcts in adults with Down syndrome assessed with 3T-MRI.

BACKGROUND: Cortical microinfarcts (CMI) were attributed to cerebrovascular disease and cerebral amyloid angiopathy (CAA). CAA is frequent in Down syndrome (DS) while hypertension is rare, yet no studies have assessed CMI in DS. METHODS: We included 195 adults with DS, 63 with symptomatic sporadic Alzheimer's disease (AD), and 106 controls with 3T magnetic resonance imaging. We assessed CMI prevalence in each group and CMI association with age, AD clinical continuum, vascular risk factors, vascular neuroimaging findings, amyloid/tau/neurodegeneration biomarkers, and cognition in DS. RESULTS: CMI prevalence was 11.8% in DS, 4.7% in controls, and 17.5% in sporadic AD. In DS, CMI increased in prevalence with age and the AD clinical continuum, was clustered in the parietal lobes, and was associated with lacunes and cortico-subcortical infarcts, but not hemorrhagic lesions. DISCUSSION: In DS, CMI are posteriorly distributed and related to ischemic but not hemorrhagic findings suggesting they might be associated with a specific ischemic CAA phenotype. HIGHLIGHTS: This is the first study to assess cortical microinfarcts (assessed with 3T magnetic resonance imaging) in adults with Down syndrome (DS). We studied the prevalence of cortical microinfarcts in DS and its relationship with age, the Alzheimer's disease (AD) clinical continuum, vascular risk factors, vascular neuroimaging findings, amyloid/tau/neurodegeneration biomarkers, and cognition. The prevalence of cortical microinfarcts was 11.8% in DS and increased with age and along the AD clinical continuum. Cortical microinfarcts were clustered in the parietal lobes, and were associated with lacunes and cortico-subcortical infarcts, but not hemorrhagic lesions. In DS, cortical microinfarcts are posteriorly distributed and related to ischemic but not hemorrhagic findings suggesting they might be associated with a specific ischemic phenotype of cerebral amyloid angiopathy.

Utility of cerebrovascular imaging biomarkers to detect cerebral amyloidosis.

INTRODUCTION: The relationship between cerebrovascular disease (CVD) and amyloid beta (Aß) in Alzheimer's disease (AD) is understudied. We hypothesized that magnetic resonance imaging (MRI)-based CVD biomarkers-including cerebral microbleeds (CMBs), lacunar infarction, and white matter hyperintensities (WMHs)-would correlate with Aß positivity on positron emission tomography (Aß-PET). METHODS: We cross-sectionally analyzed data from the Alzheimer's Disease Neuroimaging Initiative (ADNI, N = 1352). Logistic regression was used to calculate odds ratios (ORs), with Aß-PET positivity as the standard-of-truth. RESULTS: Following adjustment, WMHs (OR = 1.25) and superficial CMBs (OR = 1.45) remained positively associated with Aß-PET positivity (p < 0.001). Deep CMBs and lacunes exhibited a varied relationship with Aß-PET in cognitive subgroups. The combined diagnostic model, which included CVD biomarkers and other accessible measures, significantly predicted Aß-PET (pseudo-R2 = 0.41). DISCUSSION: The study highlights the translational value of CVD biomarkers in diagnosing AD, and underscores the need for more research on their inclusion in diagnostic criteria. CLINICALTRIALS: gov: ADNI-2 (NCT01231971), ADNI-3 (NCT02854033). HIGHLIGHTS: Cerebrovascular biomarkers linked to amyloid beta (Aß) in Alzheimer's disease (AD). White matter hyperintensities and cerebral microbleeds reliably predict Aß-PET positivity. Relationships with Aß-PET vary by cognitive stage. Novel accessible model predicts Aß-PET status. Study supports multimodal diagnostic approaches.

Temporal Characterization of the Amyloidogenic APPswe/PS1dE9;hAPOE4 Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is a devastating disorder with a global prevalence estimated at 55 million people. In clinical studies administering certain anti-beta-amyloid (Aß) antibodies, amyloid-related imaging abnormalities (ARIAs) have emerged as major adverse events. The frequency of these events is higher among apolipoprotein ε4 allele carriers (APOE4) compared to non-carriers. To reflect patients most at risk for vascular complications of anti-Aß immunotherapy, we selected an APPswe/PS1dE9 transgenic mouse model bearing the human APOE4 gene (APPPS1:E4) and compared it with the same APP/PS1 mouse model bearing the human APOE3 gene (APOE ε3 allele; APPPS1:E3). Using histological and biochemical analyses, we characterized mice at three ages: 8, 12, and 16 months. Female and male mice were assayed for general cerebral fibrillar and pyroglutamate (pGlu-3) Aß deposition, cerebral amyloid angiopathy (CAA), microhemorrhages, apoE and cholesterol composition, astrocytes, microglia, inflammation, lysosomal dysfunction, and neuritic dystrophy. Amyloidosis, lipid deposition, and astrogliosis increased with age in APPPS1:E4 mice, while inflammation did not reveal significant changes with age. In general, APOE4 carriers showed elevated Aß, apoE, reactive astrocytes, pro-inflammatory cytokines, microglial response, and neuritic dystrophy compared to APOE3 carriers at different ages. These results highlight the potential of the APPPS1:E4 mouse model as a valuable tool in investigating the vascular side effects associated with anti-amyloid immunotherapy.

Clinical, Neuroimaging, and Genetic Markers in Cerebral Amyloid Angiopathy-Related Inflammation: A Systematic Review and Meta-Analysis.

BACKGROUND: There are limited data regarding the prevalence of distinct clinical, neuroimaging and genetic markers among patients diagnosed with cerebral amyloid angiopathy-related inflammation (CAA-ri). We sought to determine the prevalence of clinical, radiological, genetic and cerebrospinal fluid biomarker findings in patients with CAA-ri. METHODS: A systematic review and meta-analysis of published studies including patients with CAA-ri was conducted to determine the prevalence of clinical, neuroimaging, genetic and cerebrospinal fluid biomarker findings. Subgroup analyses were performed based on (1) prospective or retrospective study design and (2) CAA-ri diagnosis with or without available biopsy. We pooled the prevalence rates using random-effects models and assessed the heterogeneity using Cochran-Q and I2-statistics. RESULTS: We identified 4 prospective and 17 retrospective cohort studies comprising 378 patients with CAA-ri (mean age, 71.5 years; women, 52%). The pooled prevalence rates were as follows: cognitive decline at presentation 70% ([95% CI, 54%-84%]; I2=82%), focal neurological deficits 55% ([95% CI, 40%-70%]; I2=82%), encephalopathy 54% ([95% CI, 39%-68%]; I2=43%), seizures 37% ([95% CI, 27%-49%]; I2=65%), headache 31% ([95% CI, 22%-42%]; I2=58%), T2/fluid-attenuated inversion recovery-hyperintense white matter lesions 98% ([95% CI, 93%-100%]; I2=44%), lobar cerebral microbleeds 96% ([95% CI, 92%-99%]; I2=25%), gadolinium enhancing lesions 54% ([95% CI, 42%-66%]; I2=62%), cortical superficial siderosis 51% ([95% CI, 34%-68%]; I2=77%) and lobar macrohemorrhage 40% ([95% CI, 11%-73%]; I2=88%). The prevalence rate of the ApoE (Apolipoprotein E) ε4/ε4 genotype was 34% ([95% CI, 17%-53%]; I2=76%). Subgroup analyses demonstrated no differences in these prevalence rates based on study design and diagnostic strategy. CONCLUSIONS: Cognitive decline was the most common clinical feature. Hyperintense T2/fluid-attenuated inversion recovery white matter lesions and lobar cerebral microbleeds were by far the most prevalent neuroimaging findings. Thirty-four percent of patients with CAA-ri have homozygous ApoE ε4/ε4 genotype and scarce data exist regarding the cerebrospinal fluid biomarkers and its significance in these patients.

Etiology of Primary Cerebellar Intracerebral Hemorrhage Based on Topographic Localization.

BACKGROUND: Cerebellar intracerebral hemorrhage (cICH) is often attributed to hypertension or cerebral amyloid angiopathy (CAA). However, deciphering the exact etiology can be challenging. A recent study reported a topographical etiologic relationship with superficial cICH secondary to CAA. We aimed to reexamine this relationship between topography and etiology in a separate cohort of patients and using the most recent Boston criteria version 2.0. METHODS: We performed a retrospective analysis of consecutive patients with primary cICH admitted to a tertiary academic center between 2000 and 2022. cICH location on brain computed tomography/magnetic resonance imaging scan(s) was divided into strictly superficial (cortex, surrounding white matter, vermis) versus deep (cerebellar nuclei, deep white matter, peduncular region) or mixed (both regions). Magnetic resonance imaging was rated for markers of cerebral small vessel disease. We assigned possible/probable versus absent CAA using Boston criteria 2.0. RESULTS: We included 197 patients; 106 (53.8%) were females, median age was 74 (63-82) years. Fifty-six (28%) patients had superficial cICH and 141 (72%) deep/mixed cICH. Magnetic resonance imaging was available for 112 (57%) patients (30 [26.8%] with superficial and 82 [73.2%] with deep/mixed cICH). Patients with superficial cICH were more likely to have possible/probable CAA (48.3% versus 8.6%; odds ratio [OR], 11.43 [95% CI, 3.26-40.05]; P<0.001), strictly lobar cerebral microbleeds (51.7% versus 6.2%; OR, 14.18 [95% CI, 3.98-50.50]; P<0.001), and cortical superficial siderosis (13.8% versus 1.2%; OR, 7.70 [95% CI, 0.73-80.49]; P=0.08). Patients with deep/mixed cICH were more likely to have deep/mixed cerebral microbleeds (59.2% versus 3.4%; OR, 41.39 [95% CI, 5.01-341.68]; P=0.001), lacunes (54.9% versus 17.2%; OR, 6.14 [95% CI, 1.89-19.91]; P=0.002), severe basal ganglia enlarged perivascular spaces (36.6% versus 7.1%; OR, 7.63 [95% CI, 1.58-36.73]; P=0.01), hypertension (84.4% versus 62.5%; OR, 3.43 [95% CI, 1.61 to -7.30]; P=0.001), and higher admission systolic blood pressure (172 [146-200] versus 146 [124-158] mm Hg, P<0.001). CONCLUSIONS: Our results suggest that superficial cICH is strongly associated with CAA whereas deep/mixed cICH is strongly associated with hypertensive arteriopathy.

Arteriolar neuropathology in cerebral microvascular disease.

Cerebral microvascular disease (MVD) is an important cause of vascular cognitive impairment. MVD is heterogeneous in aetiology, ranging from universal ageing to the sporadic (hypertension, sporadic cerebral amyloid angiopathy [CAA] and chronic kidney disease) and the genetic (e.g., familial CAA, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy [CADASIL] and cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy [CARASIL]). The brain parenchymal consequences of MVD predominantly consist of lacunar infarcts (lacunes), microinfarcts, white matter disease of ageing and microhaemorrhages. MVD is characterised by substantial arteriolar neuropathology involving ubiquitous vascular smooth muscle cell (SMC) abnormalities. Cerebral MVD is characterised by a wide variety of arteriolar injuries but only a limited number of parenchymal manifestations. We reason that the cerebral arteriole plays a dominant role in the pathogenesis of each type of MVD. Perturbations in signalling and function (i.e., changes in proliferation, apoptosis, phenotypic switch and migration of SMC) are prominent in the pathogenesis of cerebral MVD, making 'cerebral angiomyopathy' an appropriate term to describe the spectrum of pathologic abnormalities. The evidence suggests that the cerebral arteriole acts as both source and mediator of parenchymal injury in MVD.

Past antihypertensive medication use is associated with lower levels of small vessel disease and lower Aß plaque stage in the brains of older individuals.

AIMS: This study assesses the association of antihypertensive medication use on the severities of neuropathological cerebrovascular disease (CVD excluding lobar infarction) in older individuals. METHODS: Clinical and neuropathological data were retrieved for 149 autopsy cases >75 years old with or without CVD or Alzheimer's disease and no other neuropathological diagnoses. Clinical data included hypertension status, hypertension diagnosis, antihypertensive medication use, antihypertensive medication dose (where available) and clinical dementia rating (CDR). Neuropathological CVD severity was evaluated for differences with anti-hypertensive medication usage. RESULTS: Antihypertensive medication use was associated with less severe white matter small vessel disease (SVD, mainly perivascular dilatation and rarefaction), with a 5.6-14.4 times greater likelihood of less severe SVD if medicated. No significant relationship was detected between infarction (presence, type, number and size), lacunes or cerebral amyloid angiopathy and antihypertensive medication use. Only increased white matter rarefaction/oedema and not perivascular dilation was associated with Alzheimer's pathology, with a 4.3 times greater likelihood of reduced Aß progression through the brain if white matter rarefaction severity was none or mild. Antihypertensive medication use was associated with reduced Aß progression but only in those with moderate to severe white matter SVD. CONCLUSIONS: This histopathological study provides further evidence that antihypertensive medication use in older individuals is associated with white matter SVD and not with other CVD pathologies. This is mainly due to a reduction in white matter perivascular dilation and rarefaction/oedema. Even in those with moderate to severe white matter SVD, antihypertensive medication use reduced rarefaction and Aß propagation through the brain.