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.

Neuronally Derived Soluble Abeta Evokes Cell-Wide Astrocytic Calcium Dysregulation in Absence of Amyloid Plaques in Vivo.

The key pathologic entities driving the destruction of synaptic function and integrity during the evolution of Alzheimer's disease (AD) remain elusive. Astrocytes are structurally and functionally integrated within synaptic and vascular circuitry and use calcium-based physiology to modulate basal synaptic transmission, vascular dynamics, and neurovascular coupling, which are central to AD pathogenesis. We used high-resolution multiphoton imaging to quantify all endogenous calcium signaling arising spontaneously throughout astrocytic somata, primary processes, fine processes, and capillary endfeet in the brain of awake APP/PS1 transgenic mice (11 male and 6 female mice). Endogenous calcium signaling within capillary endfeet, while surprisingly as active as astrocytic fine processes, was reduced ∼50% in the brain of awake APP/PS1 mice. Cortical astrocytes, in the presence of amyloid plaques in awake APP/PS1 mice, had a cell-wide increase in intracellular calcium associated with an increased frequency, amplitude, and duration of spontaneous calcium signaling. The cell-wide astrocytic calcium dysregulation was not directly related to distance to amyloid plaques. We could re-create the cell-wide intracellular calcium dysregulation in the absence of amyloid plaques following acute exposure to neuronally derived soluble Abeta from Tg2576 transgenic mice, in the living brain of male C57/Bl6 mice. Our findings highlight a role for astrocytic calcium pathophysiology in soluble-Abeta mediated neurodegenerative processes in AD. Additionally, therapeutic strategies aiming to protect astrocytic calcium physiology from soluble Abeta-mediated toxicity may need to pharmacologically enhance calcium signaling within the hypoactive capillary endfeet while reducing the hyperactivity of spontaneous calcium signaling throughout the rest of the astrocyte.SIGNIFICANCE STATEMENT Astrocytic calcium signaling is functionally involved in central pathologic processes of Alzheimer's disease. We quantified endogenous calcium signaling arising spontaneously in the brain of awake APP/PS1 mice, as general anesthesia suppressed astrocytic calcium signaling. Cell-wide astrocytic calcium dysregulation was not related to distance to amyloid plaques but mediated in part by neuronally derived soluble Abeta, supporting a role for astrocytes in soluble-Abeta mediated neurodegeneration. Spontaneous calcium signaling is largely compartmentalized and capillary endfeet were as active as fine processes but hypoactive in the presence of amyloid plaques, while the rest of the astrocyte became hyperactive. The cell-wide calcium pathophysiology in astrocytes may require a combination therapeutic strategy for hypoactive endfeet and astrocytic hyperactivity.

Temporal Ordering of Biomarkers in Dutch-Type Hereditary Cerebral Amyloid Angiopathy.

BACKGROUND: The temporal ordering of biomarkers for cerebral amyloid angiopathy (CAA) is important for their use in trials and for the understanding of the pathological cascade of CAA. We investigated the presence and abnormality of the most common biomarkers in the largest (pre)symptomatic Dutch-type hereditary CAA (D-CAA) cohort to date. METHODS: We included cross-sectional data from participants with (pre)symptomatic D-CAA and controls without CAA. We investigated CAA-related cerebral small vessel disease markers on 3T-MRI, cerebrovascular reactivity with functional 7T-MRI (fMRI) and amyloid-ß40 and amyloid-ß42 levels in cerebrospinal fluid. We calculated frequencies and plotted biomarker abnormality according to age to form scatterplots. RESULTS: We included 68 participants with D-CAA (59% presymptomatic, mean age, 50 [range, 26-75] years; 53% women), 53 controls (mean age, 51 years; 42% women) for cerebrospinal fluid analysis and 36 controls (mean age, 53 years; 100% women) for fMRI analysis. Decreased cerebrospinal fluid amyloid-ß40 and amyloid-ß42 levels were the earliest biomarkers present: all D-CAA participants had lower levels of amyloid-ß40 and amyloid-ß42 compared with controls (youngest participant 30 years). Markers of nonhemorrhagic injury (>20 enlarged perivascular spaces in the centrum semiovale and white matter hyperintensities Fazekas score, ≥2, present in 83% [n=54]) and markers of impaired cerebrovascular reactivity (abnormal BOLD amplitude, time to peak and time to baseline, present in 56% [n=38]) were present from the age of 30 years. Finally, markers of hemorrhagic injury were present in 64% (n=41) and only appeared after the age of 41 years (first microbleeds and macrobleeds followed by cortical superficial siderosis). CONCLUSIONS: Our results suggest that amyloid biomarkers in cerebrospinal fluid are the first to become abnormal in CAA, followed by MRI biomarkers for cerebrovascular reactivity and nonhemorrhagic injury and lastly hemorrhagic injury. This temporal ordering probably reflects the pathological stages of CAA and should be taken into account when future therapeutic trials targeting specific stages are designed.

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.

A Causal Classification System for Intracerebral Hemorrhage Subtypes.

OBJECTIVE: Determining the underlying causes of intracerebral hemorrhage (ICH) is of major importance, because risk factors, prognosis, and management differ by ICH subtype. We developed a new causal CLASsification system for ICH Subtypes, termed CLAS-ICH, based on recent advances in neuroimaging. METHODS: CLAS-ICH defines 5 ICH subtypes: arteriolosclerosis, cerebral amyloid angiopathy, mixed small vessel disease (SVD), other rare forms of SVD (genetic SVD and others), and secondary causes (macrovascular causes, tumor, and other rare causes). Every patient is scored in each category according to the level of diagnostic evidence: (1) well-defined ICH subtype; (2) possible underlying disease; and (0) no evidence of the disease. We evaluated CLAS-ICH in a derivation cohort of 113 patients with ICH from Massachusetts General Hospital, Boston, USA, and in a derivation cohort of 203 patients from Inselspital, Bern, Switzerland. RESULTS: In the derivation cohort, a well-defined ICH subtype could be identified in 74 (65.5%) patients, including 24 (21.2%) with arteriolosclerosis, 23 (20.4%) with cerebral amyloid angiopathy, 18 (15.9%) with mixed SVD, and 9 (8.0%) with a secondary cause. One or more possible causes were identified in 42 (37.2%) patients. Interobserver agreement was excellent for each category (kappa value ranging from 0.86 to 1.00). Despite substantial differences in imaging modalities, we obtained similar results in the validation cohort. INTERPRETATION: CLAS-ICH is a simple and reliable classification system for ICH subtyping, that captures overlap between causes and the level of diagnostic evidence. CLAS-ICH may guide clinicians to identify ICH causes, and improve ICH classification in multicenter studies. ANN NEUROL 2023;93:16-28.

Decreased Cerebrospinal Fluid Amyloid ß 38, 40, 42, and 43 Levels in Sporadic and Hereditary Cerebral Amyloid Angiopathy.

OBJECTIVE: Vascular amyloid ß (Aß) accumulation is the hallmark of cerebral amyloid angiopathy (CAA). The composition of cerebrospinal fluid (CSF) of CAA patients may serve as a diagnostic biomarker of CAA. We studied the diagnostic potential of the peptides Aß38, Aß40, Aß42, and Aß43 in patients with sporadic CAA (sCAA), hereditary Dutch-type CAA (D-CAA), and Alzheimer disease (AD). METHODS: Aß peptides were quantified by immunoassays in a discovery group (26 patients with sCAA and 40 controls), a validation group (40 patients with sCAA, 40 patients with AD, and 37 controls), and a group of 22 patients with D-CAA and 54 controls. To determine the diagnostic accuracy, the area under the curve (AUC) was calculated using a receiver operating characteristic curve with 95% confidence interval (CI). RESULTS: We found decreased levels of all Aß peptides in sCAA patients and D-CAA patients compared to controls. The difference was most prominent for Aß42 (AUC of sCAA vs controls for discovery: 0.90, 95% CI = 0.82-0.99; for validation: 0.94, 95% CI = 0.89-0.99) and Aß43 (AUC of sCAA vs controls for discovery: 0.95, 95% CI = 0.88-1.00; for validation: 0.91, 95% CI = 0.83-1.0). All Aß peptides except Aß43 were also decreased in sCAA compared to AD (CSF Aß38: AUC = 0.82, 95% CI = 0.71-0.93; CSF Aß40: AUC = 0.88, 95% CI = 0.80-0.96; CSF Aß42: AUC = 0.79, 95% CI = 0.66-0.92). INTERPRETATION: A combined biomarker panel of CSF Aß38, Aß40, Aß42, and Aß43 has potential to differentiate sCAA from AD and controls, and D-CAA from controls. ANN NEUROL 2023;93:1173-1186.

Parental influence on intracerebral hemorrhage onset in hereditary Dutch-type cerebral amyloid angiopathy.

Introduction Dutch-type cerebral amyloid angiopathy (D-CAA) is an autosomal dominant hereditary form of CAA causing intracerebral hemorrhage (ICH) and cognitive decline. The age of onset of ICH in D-CAA mutation carriers is strikingly variable and ranges from end thirties up to seventy years. We investigated the presence of genetic anticipation and assessed the influence of parental age at onset and sex on age of ICH onset in offspring. Methods We included (potential) D-CAA mutation-carriers from our prospective D-CAA family database. Participants were sent a questionnaire by mail and asked for the onset age of symptomatic ICH and the onset age of symptomatic ICH of their affected first-degree relative(s); their siblings and affected parent. We used a Cox regression model with the age of onset of the parent as covariate and the sex of the offspring as factor. Next we replaced the sex of the offspring with a factor with four levels: mother/daughter, mother/son, father/daughter and father/son. We used a random effect per household. Results A total of 66 respondents completed the questionnaire. Reported mean age of first symptomatic ICH was similar (both 52 years, p=0.87) for D-CAA parents (n=60) and their offspring (n=100). Offspring with a mother with D-CAA seemed to have an earlier ICH onset (50 years, SD±7) than offspring with a paternal inheritance (54 years, SD±6, p=0.03). There was no association between onset of first ICH of the parent and offspring after adding sex of the offspring to the Cox regression model: hazard ratio (HR) 0.99, 95%CI: 0.94 to 1.03, p=0.51. The interaction between parent's sex and child's sex was not significant (p=0.70). The results with and without random effect were essentially identical. Conclusion We found no indication for genetic anticipation in D-CAA in general, although maternal inheritance seemed to be associated with an earlier ICH onset.

Rationale and Design of the Statins Use in Intracerebral Hemorrhage Patients (SATURN) Trial.

INTRODUCTION: The benefits and risks of HMG-CoA reductase inhibitor (statin) drugs in survivors of intracerebral hemorrhage (ICH) are unclear. Observational studies suggest an association between statin use and increased risk of lobar ICH, particularly in patients with apolipoprotein-E (APOE) ε2 and ε4 genotypes. There are no randomized controlled trials (RCTs) addressing the effects of statins after ICH leading to uncertainty as to whether statins should be used in patients with lobar ICH who are at high risk for ICH recurrence. The SATURN trial aims to evaluate the effects of continuation versus discontinuation of statin on the risk of ICH recurrence and ischemic major adverse cerebro-cardio-vascular events (MACCE) in patients with lobar ICH. Secondary aims include the assessment of whether the APOE genotype modifies the effects of statins on ICH recurrence, functional and cognitive outcomes and quality of life. METHODS: The SATURN trial is a multi-center, pragmatic, prospective, randomized, open-label, Phase III clinical trial with blinded end-point assessment. A planned total of 1456 patients with lobar ICH will be recruited from 140 sites in the United States, Canada and Spain. Patients presenting within seven days of a spontaneous lobar ICH that occurred while taking a statin, will be randomized (1:1) to continuation (control) vs. discontinuation (intervention) of the same statin drug and dose that they were using at ICH onset. The primary outcome is the time to recurrent symptomatic ICH within a two-year follow-up period. The primary safety outcome is the occurrence of ischemic MACCE. CONCLUSION: The results will help to determine the best strategy for statin use in survivors of lobar ICH and may help to identify if there is a subset of patients who would benefit from statins.

Hypertension control after intracerebral hemorrhage among varying small vessel disease etiologies.

INTRODUCTION: Intracerebral hemorrhage (ICH) is attributable to cerebral small vessel disease (cSVD), which includes cerebral amyloid angiopathy (CAA) and hypertensive-cSVD (HTN-cSVD). HTN-cSVD includes patients with strictly deep ICH/microbleeds and mixed location ICH/microbleeds, the latter representing a more severe form of HTN-cSVD. We test the hypothesis that more severe forms of HTN-cSVD are related to worse hypertension control in long-term follow-up after ICH. METHODS: From consecutive non-traumatic ICH patients admitted to a tertiary care center, we classified the ICH as CAA, strictly deep ICH/microbleeds, and mixed-location ICH/microbleeds. CSVD burden was quantified using a validated MRI-based score (range: 0-6 points). We created a multivariable (linear mixed effects) model adjusting for age, sex, race, year of inclusion, hypertension, and antihypertensive medication usage to investigate the association of average systolic blood pressure (SBP) during follow-up with cSVD etiology/severity. RESULTS: 796 ICH survivors were followed for a median of 48.8 months (IQR 41.5-60.4). CAA-related ICH survivors (n = 373) displayed a lower median SBP (138 mmHg, IQR 133-142 mmHg) compared to those of strictly deep ICH (n = 222, 141 mmHg, IQR 136-143 mmHg, p = 0.04), and mixed location ICH/microbleeds (n = 201, 142 mmHg, IQR 135-144 mmHg, p = 0.02). In the multivariable analysis, mixed location ICH/microbleeds (effect: + 3.8 mmHg, SE: 1.3 mmHg, p = 0.01) and increasing cSVD severity (+ 1.8 mmHg per score point, SE: 0.8 mmHg, p = 0.03) were associated with higher SBP in follow-up. CONCLUSION: CSVD severity and subtype predicts long-term hypertension control in ICH patients.

Cerebrovascular reactivity MRI as a biomarker for cerebral small vessel disease-related cognitive decline: Multi-site validation in the MarkVCID Consortium.

INTRODUCTION: Vascular contributions to cognitive impairment and dementia (VCID) represent a major factor in cognitive decline in older adults. The present study examined the relationship between cerebrovascular reactivity (CVR) measured by magnetic resonance imaging (MRI) and cognitive function in a multi-site study, using a predefined hypothesis. METHODS: We conducted the study in a total of three analysis sites and 263 subjects. Each site performed an identical CVR MRI procedure using 5% carbon dioxide inhalation. A global cognitive measure of Montreal Cognitive Assessment (MoCA) and an executive function measure of item response theory (IRT) score were used as outcomes. RESULTS: CVR and MoCA were positively associated, and this relationship was reproduced at all analysis sites. CVR was found to be positively associated with executive function. DISCUSSION: The predefined hypothesis on the association between CVR and a global cognitive score was validated in three independent analysis sites, providing support for CVR as a biomarker in VCID. HIGHLIGHTS: This study measured a novel functional index of small arteries referred to as cerebrovascular reactivity (CVR). CVR was positively associated with global cognition in older adults. This finding was observed in three independent cohorts at three sites. Our statistical analysis plan was predefined before beginning data collection.

Antiplatelet Agent Use After Stroke due to Intracerebral Hemorrhage.

This focused update about antiplatelet agents to reduce the high risk of major adverse cardiovascular events after stroke due to spontaneous (nontraumatic) intracerebral hemorrhage (ICH) complements earlier updates about blood pressure-lowering, lipid-lowering, and oral anticoagulation or left atrial appendage occlusion for atrial fibrillation after ICH. When used for secondary prevention in people without ICH, antiplatelet agents reduce the risk of major adverse cardiovascular event (rate ratio, 0.81 [95% CI, 0.75-0.87]) and might increase the risk of ICH (rate ratio, 1.67 [95% CI, 0.97-2.90]). Before 2019, guidance for clinical decisions about antiplatelet agent use after ICH has focused on estimating patients' predicted absolute risks and severities of ischemic and hemorrhagic major adverse cardiovascular event and applying the known effects of these drugs in people without ICH to estimate whether individual ICH survivors in clinical practice might be helped or harmed by antiplatelet agents. In 2019, the main results of the RESTART (Restart or Stop Antithrombotics Randomized Trial) randomized controlled trial including 537 survivors of ICH associated with antithrombotic drug use showed, counterintuitively, that antiplatelet agents might not increase the risk of recurrent ICH compared to antiplatelet agent avoidance over 2 years of follow-up (12/268 [4%] versus 23/268 [9%]; adjusted hazard ratio, 0.51 [95% CI, 0.25-1.03]; P=0.060). Guidelines in the United States, Canada, China, and the United Kingdom and Ireland have classified the level of evidence as B and indicated that antiplatelet agents may be considered/reasonable after ICH associated with antithrombotic agent use. Three subsequent clinical trials have recruited another 174 participants with ICH, but they will not be sufficient to determine the effects of antiplatelet therapy on all major adverse cardiovascular events reliably when pooled with RESTART. Therefore, ASPIRING (Antiplatelet Secondary Prevention International Randomized Study After Intracerebral Hemorrhage) aims to recruit 4148 ICH survivors to determine the effects of antiplatelet agents after ICH definitively overall and in subgroups.

Association of Depression Onset and Treatment With Blood Pressure Control After Intracerebral Hemorrhage.

BACKGROUND: Blood pressure (BP) control represents a crucial intervention to improve long-term outcomes following spontaneous intracerebral hemorrhage (ICH). However, fewer than half of ICH survivors achieve target treatment goals. ICH survivors are also at very high risk for poststroke depression, which may contribute to inadequate BP control. We, therefore, sought to determine whether depressive symptoms after ICH are associated with inadequate BP control. We also investigated whether associations between depression after ICH and BP measurements were mediated by treatment with selective serotonin reuptake inhibitors or norepinephrine-serotonin reuptake inhibitors antidepressants. METHODS: We leveraged data from a single-center longitudinal study of ICH conducted at Massachusetts General Hospital (Boston, MA) between 2006 and 2018. We collected data from semiautomated review of electronic health records, baseline and follow-up interviews, and computed tomography imaging. Information on BP measurements, depression diagnoses, antidepressants medication use, and medical visits were collected longitudinally and analyzed using mixed effects models. Primary outcomes included systolic and diastolic BP measurements during long-term follow-up after ICH. RESULTS: We included 1243 consecutive ICH patients without pre-stroke depression history. Of these, 721 (58%) were diagnosed with incident depression over a median follow-up time of 52.8 months (interquartile range, 42.1-60.5). Depression onset was associated with subsequent increase in systolic (+8.3 mm Hg, SE, 2.4 mm Hg, P=0.012) and diastolic (+4.4 mm Hg, SE, 1.2 mm Hg) BP measurements. Resolution of depressive symptoms was associated with subsequent decrease in systolic (-5.9 mm Hg, SE, 1.4 mm Hg, P=0.031) and diastolic (-3.4 mm Hg, SE, 1.1 mm Hg, P=0.041) BP measurements. We also found associations between higher systolic BP measurements and use of selective serotonin reuptake inhibitor and noradrenaline-serotonin reuptake inhibitor antidepressants, independent of whether depression symptoms were active or not (all P<0.05). CONCLUSIONS: ICH survivors displayed increasing BP values after receiving a diagnosis of depression, followed by decreasing values among those experiencing resolution of depressive symptoms. Use of selective serotonin reuptake inhibitor and noradrenaline-serotonin reuptake inhibitor antidepressants was independently associated with higher systolic BP measurements. Clinicians ought to closely monitor BP for ICH survivors being treated for depression, especially using selective serotonin reuptake inhibitor and noradrenaline-serotonin reuptake inhibitor. Future studies will also be required to investigate the mechanisms underlying these associations.

Blood Pressure Control Targets and Risk of Cardiovascular and Cerebrovascular Events After Intracerebral Hemorrhage.

BACKGROUND: Intracerebral hemorrhage (ICH) survivors are at high risk for recurrent stroke and cardiovascular events. Blood pressure (BP) control represents the most potent intervention to lower these risks, but optimal treatment targets in this patient population remain unknown. We sought to determine whether survivors of ICH achieving more intensive BP control than current guideline recommendations (systolic BP <130 mmHg and diastolic BP <80 mmHg) were at lower risk of major adverse cardiovascular and cerebrovascular events and mortality. METHODS: We analyzed data for 1828 survivors of spontaneous ICH from 2 cohort studies. Follow-up BP measurements were recorded 3 and 6 months after ICH, and every 6 months thereafter. Outcomes of interest were major adverse cardiovascular and cerebrovascular events (recurrent ICH, incident ischemic stroke, myocardial infarction), vascular mortality (defined as mortality attributed to recurrent ICH, ischemic stroke, or myocardial infarction), and all-cause mortality. RESULTS: During a median follow-up of 46.2 months, we observed 166 recurrent ICH, 68 ischemic strokes, 69 myocardial infarction, and 429 deaths. Compared with survivors of ICH with systolic BP 120 to 129 mmHg, participants who achieved systolic BP <120 mmHg displayed reduced risk of recurrent ICH (adjusted hazard ratio [AHR], 0.74 [95% CI, 0.59-0.94]) and major adverse cardiovascular and cerebrovascular events (AHR, 0.69 [95% CI, 0.53-0.92]). All-cause mortality (AHR, 0.76 [95% CI, 0.57-1.03]) and vascular mortality (AHR, 0.68 [95% CI, 0.45-1.01]) did not differ significantly. Among participants aged >75 years or with modified Rankin Scale score 4 to 5, systolic BP <120 mmHg was associated with increased all-cause mortality (AHR, 1.38 [95% CI, 1.02-1.85] and AHR, 1.36 [95% CI, 1.03-1.78], respectively), but not vascular mortality. We found no differences in outcome rates between survivors of ICH with diastolic BP <70 versus 70 to 79 mmHg. CONCLUSIONS: Targeting systolic BP <120 mmHg in select groups of survivors of ICH could result in decreased major adverse cardiovascular and cerebrovascular events risk without increasing mortality. Our findings warrant investigation in dedicated randomized controlled trials.

Sex Differences in Onset and Progression of Cerebral Amyloid Angiopathy.

BACKGROUND: Cerebral Amyloid Angiopathy (CAA) disease course is highly variable even in hereditary forms. Sex may be a possible modifying factor. We investigated biological sex differences in clinical disease course and magnetic resonance imaging-markers in sporadic (sCAA) and Dutch-type hereditary CAA (D-CAA). METHODS: Patients with D-CAA and sCAA were included from hospital and research databases of the Leiden University Medical Center (2012-2020) and Massachusetts General Hospital (1994-2012). Key outcomes were: sex differences in symptomatic intracerebral hemorrhage (sICH) onset, recurrence and survival (analyzed using Kaplan Meier survival and regression analyses), and sex differences in magnetic resonance imaging-markers in D-CAA (explored using scatterplots), and in sCAA (investigated using regression analysis). RESULTS: We included 136 patients with D-CAA (mean age 57 years, 56% women, 64% with previous sICH) and 370 patients with sCAA (mean age 76 years, 51% women, all with previous sICH). Men and women with D-CAA did not differ for sICH onset (median age 54 in men and 56 in women [P=0.13]). Men with D-CAA had a slightly higher number of sICH compared with women (median 2 versus 1; adjusted RR, 1.5 [95% CI, 1.1-1.9]) and a shorter interval between the first and second sICH (median 1.8 years for men and 3.1 years for women, P=0.02). Men with sCAA had their first sICH at an earlier age (median 75 versus 78 years, respectively, P=0.003) and more lobar microbleeds (median 1 versus 0, P=0.022) compared with women with sCAA. No substantial differences were found in the other magnetic resonance imaging markers. Survival after first sICH was comparable between sexes for D-CAA (P=0.12) and sCAA (P=0.23). CONCLUSIONS: Men with CAA seem to have an earlier onset (sCAA) and more hemorrhagic disease course (sCAA and D-CAA) compared with women. Future studies are necessary to confirm these findings and determine the underlying role of sex-related factors.

Using Noncontrast Computed Tomography to Improve Prediction of Intracerebral Hemorrhage Expansion.

BACKGROUND: Noncontrast computed tomography hypodensities are a validated predictor of hematoma expansion (HE) in intracerebral hemorrhage and a possible alternative to the computed tomography angiography (CTA) spot sign but their added value to available prediction models remains unclear. We investigated whether the inclusion of hypodensities improves prediction of HE and compared their added value over the spot sign. METHODS: Retrospective analysis of patients admitted for primary spontaneous intracerebral hemorrhage at the following 8 university hospitals in Boston, US (1994-2015, prospective), Hamilton, Canada (2010-2016, retrospective), Berlin, Germany (2014-2019, retrospective), Chongqing, China (2011-2015, retrospective), Pavia, Italy (2017-2019, prospective), Ferrara, Italy (2010-2019, retrospective), Brescia, Italy (2020-2021, retrospective), and Bologna, Italy (2015-2019, retrospective). Predictors of HE (hematoma growth >6 mL and/or >33% from baseline to follow-up imaging) were explored with logistic regression. We compared the discrimination of a simple prediction model for HE based on 4 predictors (antitplatelet and anticoagulant treatment, baseline intracerebral hemorrhage volume, and onset-to-imaging time) before and after the inclusion of noncontrast computed tomography hypodensities, using receiver operating characteristic curve and De Long test for area under the curve comparison. RESULTS: A total of 2465 subjects were included, of whom 664 (26.9%) had HE and 1085 (44.0%) had hypodensities. Hypodensities were independently associated with HE after adjustment for confounders in logistic regression (odds ratio, 3.11 [95% CI, 2.55-3.80]; P<0.001). The inclusion of noncontrast computed tomography hypodensities improved the discrimination of the 4 predictors model (area under the curve, 0.67 [95% CI, 0.64-0.69] versus 0.71 [95% CI, 0.69-0.74]; P=0.025). In the subgroup of patients with a CTA available (n=895, 36.3%), the added value of hypodensities remained statistically significant (area under the curve, 0.68 [95% CI, 0.64-0.73] versus 0.74 [95% CI, 0.70-0.78]; P=0.041) whereas the addition of the CTA spot sign did not provide significant discrimination improvement (area under the curve, 0.74 [95% CI, 0.70-0.78]). CONCLUSIONS: Noncontrast computed tomography hypodensities provided a significant added value in the prediction of HE and appear a valuable alternative to the CTA spot sign. Our findings might inform future studies and suggest the possibility to stratify the risk of HE with good discrimination without CTA.

Peak Width of Skeletonized Mean Diffusivity: A Neuroimaging Marker for White Matter Injury.

A leading cause of white matter (WM) injury in older individuals is cerebral small vessel disease (SVD). Cerebral SVD is the most prevalent vascular contributor to cognitive impairment and dementia. Therapeutic progress for cerebral SVD and other WM disorders depends on the development and validation of neuroimaging markers suitable as outcome measures in future interventional trials. Diffusion-tensor imaging (DTI) is one of the best-suited MRI techniques for assessing the extent of WM damage in the brain. But the optimal method to analyze individual DTI data remains hindered by labor-intensive and time-consuming processes. Peak width of skeletonized mean diffusivity (PSMD), a recently developed fast, fully automated DTI marker, was designed to quantify the WM damage secondary to cerebral SVD and reflect related cognitive impairment. Despite its promising results, knowledge about PSMD is still limited in the radiologic community. This focused review provides an overview of the technical details of PSMD while synthesizing the available data on its clinical and neuroimaging associations. From a critical expert viewpoint, the authors discuss the limitations of PSMD and its current validation status as a neuroimaging marker for vascular cognitive impairment. Finally, they point out the gaps to be addressed to further advance the field.

Cortical superficial siderosis is associated with reactive astrogliosis in cerebral amyloid angiopathy.

BACKGROUND: Cortical superficial siderosis (cSS) has recently emerged as one of the most important predictors of symptomatic intracerebral hemorrhage and is a risk factor for post-stroke dementia in cerebral amyloid angiopathy (CAA). However, it remains unknown whether cSS is just a marker of severe CAA pathology or may itself contribute to intracerebral hemorrhage risk and cognitive decline. cSS is a chronic manifestation of convexal subarachnoid hemorrhage and is neuropathologically characterized by iron deposits in the superficial cortical layers. We hypothesized that these iron deposits lead to local neuroinflammation, a potentially contributory pathway towards secondary tissue injury. METHODS: Accordingly, we assessed the distribution of inflammatory markers in relation to cortical iron deposits in post-mortem tissue from CAA cases. Serial sections from the frontal, parietal, temporal, and occipital lobes of nineteen autopsy cases with CAA were stained with Perls' Prussian blue (iron) and underwent immunohistochemistry against glial fibrillary acidic protein (GFAP, reactive astrocytes) and cluster of differentiation 68 (CD68, activated microglia/macrophages). Digitized sections were uploaded to the cloud-based Aiforia® platform, where deep-learning algorithms were utilized to detect tissue, iron deposits, and GFAP-positive and CD68-positive cells. RESULTS: We observed a strong local relationship between cortical iron deposits and reactive astrocytes. Like cSS-related iron, reactive astrocytes were mainly found in the most superficial layers of the cortex. Although we observed iron within both astrocytes and activated microglia/macrophages on co-stains, there was no clear local relationship between the density of microglia/macrophages and the density of iron deposits. CONCLUSION: Iron deposition resulting from cSS is associated with local reactive astrogliosis.

Progressive White Matter Injury in Preclinical Dutch Cerebral Amyloid Angiopathy.

Autosomal-dominant, Dutch-type cerebral amyloid angiopathy (D-CAA) offers a unique opportunity to develop biomarkers for pre-symptomatic cerebral amyloid angiopathy (CAA). We hypothesized that neuroimaging measures of white matter injury would be present and progressive in D-CAA prior to hemorrhagic lesions or symptomatic hemorrhage. In a longitudinal cohort of D-CAA carriers and non-carriers, we observed divergence of white matter injury measures between D-CAA carriers and non-carriers prior to the appearance of cerebral microbleeds and >14 years before the average age of first symptomatic hemorrhage. These results indicate that white matter disruption measures may be valuable cross-sectional and longitudinal biomarkers of D-CAA progression. ANN NEUROL 2022;92:358-363.

Impact of region of interest definition on visual stimulation-based cerebral vascular reactivity functional MRI with a special focus on applications in cerebral amyloid angiopathy.

Cerebral vascular reactivity quantified using blood oxygen level-dependent functional MRI in conjuncture with a visual stimulus has been proven to be a potent and early marker for cerebral amyloid angiopathy. This work investigates the influence of different postprocessing methods on the outcome of such vascular reactivity measurements. Three methods for defining the region of interest (ROI) over which the reactivity is measured are investigated: structural (transformed V1), functional (template based on the activation of a subset of subjects), and percentile (11.5 cm3 most responding voxels). Evaluation is performed both in a test-retest experiment in healthy volunteers (N = 12), as well as in 27 Dutch-type cerebral amyloid angiopathy patients and 33 age- and sex-matched control subjects. The results show that the three methods select a different subset of voxels, although all three lead to similar outcome measures in healthy subjects. However, in (severe) pathology, the percentile method leads to higher reactivity measures than the other two, due to circular analysis or "double dipping" by defining a subject-specific ROI based on the strongest responses within each subject. Furthermore, while different voxels are included in the presence of lesions, this does not necessarily result in different outcome measures. In conclusion, to avoid bias created by the method, either a structural or a functional method is recommended. Both of these methods provide similar reactivity measures, although the functional ROI appears to be less reproducible between studies, because slightly different subsets of voxels were found to be included. On the other hand, the functional method did include fewer lesion voxels than the structural method.

Vascular Contributions to Brain Health: Cross-Cutting Themes.

As life expectancy grows, brain health is increasingly seen as central to what we mean by successful aging-and vascular brain health as central to overall brain health. Cerebrovascular pathologies are highly prevalent independent contributors to age-related cognitive impairment and at least partly modifiable with available treatments. The current Focused Update addresses vascular brain health from multiple angles, ranging from pathophysiologic mechanisms and neuroimaging features to epidemiologic risk factors, social determinants, and candidate treatments. Here we highlight some of the shared themes that cut across these distinct perspectives: (1) the lifetime course of vascular brain injury pathogenesis and progression; (2) the scientific and ethical imperative to extend vascular brain health research in non-White and non-affluent populations; (3) the need for improved tools to study the cerebral small vessels themselves; (4) the potential role for brain recovery mechanisms in determining vascular brain health and resilience; and (5) the cross-pathway mechanisms by which vascular and neurodegenerative processes may interact. The diverse perspectives featured in this Focused Update offer a sense of the multidisciplinary approaches and collaborations that will be required to launch our populations towards improved brain health and successful aging.