18F-MK-6240 uptake in cortical tau and hemorrhagic lesions in a case of Alzheimer’s disease with possible crossed aphasia

Cerebral amyloid angiopathy (CAA) is a common cause of lobar and subarachnoid hemorrhages in the elderly. A diagnosis of CAA requires multiple lobar hemorrhagic lesions (intracerebral hemorrhage and/or cerebral microbleeds) and/or cortical superficial siderosis (cSS). In contrast, hemorrhagic lesions located in the deep structures are the hallmark of hypertensive arteriopathy (HTN-A). They are an exclusion criterion for CAA, and when present with lobar hemorrhagic lesions considered a separate entity: mixed location hemorrhages/microbleeds (MLHs). We compared clinical, radiological, and cerebrospinal fluid (CSF) marker data in patients with CAA, MLH, and Alzheimer's disease (AD), and healthy controls (HCs) and used it to position MLH in the disease spectrum. Retrospective cohort study of consecutive patients with CAA (n = 31), MLH (n = 31), AD (n = 28), and HC (n = 30). Analysis of clinical, radiological, CSF biomarker (Aß42, Aß40, t-tau, and p-tau), and histopathological data in patients each group. cSS was significantly more common in CAA than MLH (45% vs 13%, p = 0.011), and cSS in MLH was associated with intracerebral hemorrhage (ICH) (p = 0.037). Aß42 levels and the Aß42/Aß40 ratio, diagnostic groups followed the order HC > MLH > CAA > AD and the opposite order for t-tau and p-tau. No clear order was apparent forAß40. Aß40 and Aß42 levels as well as the Aß42/Aß40 ratio were lower in both CAA and MLH patients with cSS than in patients without cSS. Aß40 and Aß42 levels were higher in CAA and MLH patients with lacunar infarcts than in those without. Our data suggest that MLH and CAA are mutually not exclusive diagnoses, and are part of a spectrum with variable contributions of both CAA and HTN-A.

Clinical Relevance of Cerebral Small Vessel Diseases.

Background: Cerebral amyloid angiopathy (CAA), in which amyloid-β (Aβ) is deposited in cerebral and meningeal blood vessels, is associated with not only stroke but also cognitive dysfunction. CAA is classified as type 1 with capillary amyloid β (Aβ) or type 2 without capillary Aβ. Although it is known that CAA activates inflammatory responses, acute phase protein orosomucoid (α-1-acid glycoprotein) expression is still unclear. Methods: There were 26 autopsy brains, including 12 with CAA type1 and 10 with CAAtype2, 4 with other neurodegenerative diseases for control. We evaluated the extent of orosomucoid deposition in patients with CAA and control using pathological specimens, and also compared orosomucoid expression in type 1, type 2 CAA and control. Moreover, the relationships between orosomucoid and each clinical finding, such as history of hypertension, presence of lacunar infarct, cortical microinfarct, cortical superficial siderosis, and subcortical hemorrhage, were evaluated in CAA cases. Results: Vascular immunostaining for orosomucoid was identified more in CAA brains than in controls (p < 0.001). In the comparison between the three groups, immunohistochemistry higher expression of orosomucoid in the arteries/ arterioles of CAA type1 than control group. Although there was no relationships between orosomucoid and hypertension, lacunar infarct, cortical superficial siderosis, and subcortical hemorrhage, CAA with cortical microinfarct cases showed higher number of orosomucoid positive vessels than cortical microinfarct negative cases. Conclusion: Recently, we discovered that the levels of orosomucoid in the blood are elevated in patients with CAA. It was suggested that orosomucoid may be involved in the pathogenesis of CAA. Moreover, orosomucoid might be associated with type 1 CAA and cortical microinfact. As a limitation, the number of controls is small, so it is necessary to increase the number of cases.

The prevalence of cerebral amyloid angiopathy (CAA) has been shown to increase with age, with rates reported to be around 50-60% in individuals over 80 years old who have cognitive impairment. The disease often presents as spontaneous lobar intracerebral hemorrhage (ICH), which carries a high risk of recurrence, along with transient focal neurologic episodes (TFNE) and progressive cognitive decline, potentially leading to Alzheimer's disease (AD). In addition to ICH, neuroradiologic findings of CAA include cortical and subcortical microbleeds (MB), cortical subarachnoid hemorrhage (cSAH) and cortical superficial siderosis (cSS). Non-hemorrhagic pathologies include dilated perivascular spaces in the centrum semiovale and multiple hyperintense lesions on T2-weighted magnetic resonance imaging (MRI). A definitive diagnosis of CAA still requires histological confirmation. The Boston criteria allow for the diagnosis of a probable or possible CAA by considering specific neurological and MRI findings. The recent version, 2.0, which includes additional non-hemorrhagic MRI findings, increases sensitivity while maintaining the same specificity. The characteristic MRI findings of autoantibody-related CAA-related inflammation (CAA-ri) are similar to the so-called "amyloid related imaging abnormalities" (ARIA) observed with amyloid antibody therapies, presenting in two variants: (a) vasogenic edema and leptomeningeal effusions (ARIA-E) and (b) hemorrhagic lesions (ARIA-H). Clinical and MRI findings enable the diagnosis of a probable or possible CAA-ri, with biopsy remaining the gold standard for confirmation. In contrast to spontaneous CAA-ri, only about 20% of patients treated with monoclonal antibodies who show proven ARIA on MRI also experience clinical symptoms, including headache, confusion, other psychopathological abnormalities, visual disturbances, nausea and vomiting. Recent findings indicate that treatment should be continued in cases of mild ARIA, with ongoing MRI and clinical monitoring. This review offers a concise update on CAA and its associated consequences.

Elderly and forgetful with transient neurological spells: A story of two amyloids?

Background: Patients with Cerebral Amyloid Angiopathy (CAA) have posterior vascular amyloid deposition and lower Amyloid Beta (Aβ) levels when compared to Alzheimer’s Disease (AD). We hypothesized that similar findings would be observed in AD patients with strictly lobar microbleeds (LMB) and/or cortical superficial siderosis (cSS) attributable to CAA [CAA-AD], when compared to AD with no hemorrhagic lesion [NH-AD]. Methods: We reviewed brain MRIs of patients with AD who had T2*-, FLAIR and 3D T1-weighted MRI as well as Florbetapir PET, CSF Aβ-42 and tau levels, and APOE status within the ADNI database. We compared the demographics, quantitative imaging and lab findings of CAA-AD to NH-AD. Results: The CAA-AD (n=51) and NH-AD (n=85) groups were balanced for age, gender and history of hypertension (all p>0.2). The APOE4 was more frequently present in the CAA-AD group (78% vs 60%, p=0.038), no difference for APOE2 (p=0.41). Patients with CAA-AD had higher WMH volume (0.73 vs 0.49 % intracranial volume [ICV], p=0.035) and higher occipital-to-global Florbetapir ratio (0.98 vs 0.94, p=0.02) but similar mean cortical Florbetapir uptake (1.38 vs 1.36, p=0.57), cortical thickness (2.22 vs 2.20 mm, p=0.38), and hippocampal volume (0.37 vs 0.38 % of ICV, p=0.24) when compared to NH-AD. In a multivariable regression model that included all variables above, higher occipital-to-global Florbetapir ratio (p=0.009) and presence of APOE4 (p=0.002) were associated with CAA-AD, higher WMH (p=0.097) showed a trend. In 117 patients with CSF data, CAA-AD (n=46) had lower Aβ-42 (127 vs 140 pg/ml, p=0.038) but similar tau levels (131 vs 136 pg/ml, p=0.68) when compared to NH-AD. Lower Aβ-42 was associated with CAA-AD (p=0.024) in the relevant multivariate regression model. Conclusions: Over one-third of patients with AD displayed subtle hemorrhagic lesions in a CAA-pattern on MRI. When compared to NH-AD, they have higher occipital Florbetapir uptake suggesting vascular amyloid binding and lower CSF Aβ-42 levels that might be related to sequestering of amyloid in cortical vessel walls. These results support the possibility that advanced CAA commonly accompanies clinically diagnosed AD, contributing to dementia pathogenesis and potentially affecting clinical treatment decisions.

Haemorrhagic amyloid-related imaging abnormalities on MRI are frequently observed adverse events in the context of amyloid β immunotherapy trials in patients with Alzheimer’s disease. The underlying histopathology and pathophysiological mechanisms of haemorrhagic amyloid-related imaging abnormalities remain largely unknown, although coexisting cerebral amyloid angiopathy may play a key role. Here, we used ex vivo MRI in cases that underwent amyloid β immunotherapy during life to screen for haemorrhagic lesions and assess underlying tissue and vascular alterations. We hypothesized that these lesions would be associated with severe cerebral amyloid angiopathy. Ten cases were selected from the long-term follow-up study of patients who enrolled in the first clinical trial of active amyloid β immunization with AN1792 for Alzheimer’s disease. Eleven matched non-immunized Alzheimer’s disease cases from an independent brain brank were used as ‘controls’. Formalin-fixed occipital brain slices were imaged at 7 T MRI to screen for haemorrhagic lesions (i.e. microbleeds and cortical superficial siderosis). Samples with and without haemorrhagic lesions were cut and stained. Artificial intelligence-assisted quantification of amyloid β plaque area, cortical and leptomeningeal cerebral amyloid angiopathy area, the density of iron and calcium positive cells and reactive astrocytes and activated microglia was performed. On ex vivo MRI, cortical superficial siderosis was observed in 5/10 immunized Alzheimer’s disease cases compared with 1/11 control Alzheimer’s disease cases (κ = 0.5). On histopathology, these areas revealed iron and calcium positive deposits in the cortex. Within the immunized Alzheimer’s disease group, areas with siderosis on MRI revealed greater leptomeningeal cerebral amyloid angiopathy and concentric splitting of the vessel walls compared with areas without siderosis. Moreover, greater density of iron-positive cells in the cortex was associated with lower amyloid β plaque area and a trend towards increased post-vaccination antibody titres. This work highlights the use of ex vivo MRI to investigate the neuropathological correlates of haemorrhagic lesions observed in the context of amyloid β immunotherapy. These findings suggest a possible role for cerebral amyloid angiopathy in the formation of haemorrhagic amyloid-related imaging abnormalities, awaiting confirmation in future studies that include brain tissue of patients who received passive immunotherapy against amyloid β with available in vivo MRI during life.

Large Subcortical Intracerebral Hemorrhage Because of Reversible Cerebral Vasoconstriction Syndrome: A Case Study.

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

Inflammation Complicates an ‘Age-Related’ Cerebral Microangiopathy

BackgroundCerebral amyloid angiopathy (CAA) diagnostic is of special interest due to its association with cognitive impairment, Alzheimer disease (AD) and Amyloid‐Related Imaging Abnormalities (ARIA) in trials with anti‐amyloid immunotherapies. We aimed to assess the frequency of CAA diagnosis and associated lesions in subjects with cognitive complaint and normal cognition enrolled in the INSIGHT‐preAD study.MethodCognitively normal elderly with memory complaint included in the INSIGHT‐preAD study were assessed with multimodal explorations for 5 years follow‐up. 3T MRI‐scans were performed at baseline and during follow‐up at 2 and 4 years. Lobar cerebral microbleeds (CMB), cortical superficial siderosis (CSS), enlarged perivascular spaces (EPVS) and white matter hyperintensities (WMH) were rated according to validated scales and guidelines. Boston criteria V2.0 were applied to diagnose possible and probable CAA.ResultAmong the 318 subjects (median [Q1, Q3] age: 76.4 [74.1, 78.5] years, 201 (63.2%) women) enrolled at baseline, 41 (12.9%) had at least one lobar CMB, 4 (1.3%) CSS, 68 (21.7%) severe EPVS in the centrum semi‐ovale and 245 (77%) WMH with a spot pattern ≥10. The median FAZEKAS score was 2.0 [1.0, 2.0]. At baseline, 251 (78.9%) subjects had CAA: 218 (68.5%) possible CAA and 33 (10.4%) probable CAA with a median number of CMB of 1.0 [1.0, 1.0]. Compared to non‐CAA subjects (n = 67), those with probable CAA at baseline were not different on demographics and vascular risk factor, had more executive dysfunction, and tended to be associated with Apoe4 status and lower hippocampal volume. After 2‐ and 4‐ years of follow‐up, 81.2% and 81.3% of the subjects still in the study had CAA, with 13.3% and 14.1% of probable CAA respectively, and the number of subjects with CMB increased to 15.9% and 18.3%.ConclusionIn the INSIGHT‐preAD study, the high frequence of CAA, with minimal change after 4 years follow‐up, was essentially due to the non‐hemorrhagic lesions. The hemorrhagic lesions (CMB and CSS) were uncommon, probably underestimated by the MRI T2* sequence. These results have implications in clinical setting and could be useful in pre‐symptomatic AD anti‐amyloid immunotherapy trial.

Clinical and neuropathologic analysis of intracerebral hemorrhage in patients with cerebral amyloid angiopathy

To investigate the relationship between cerebral amyloid angiopathy and subcortical (lobar) hemorrhage, we examined the severity of amyloid deposition in the leptomeningeal, cortical and subcortical arteries in 28 autopsied elderly patients with cerebral amyloid angiopathy with subcortical hemorrhage, deep cerebral hemorrhage or without hemorrhage. The severity was evaluated in terms of the frequency of amyloid-laden arteries and the degree of amyloid deposition within the arteries. The frequency of amyloid-laden arteries, especially among arteries over 200 microns in diameter, was higher in subcortical hemorrhage group than in the deep hemorrhage group and the non-hemorrhage group, and when the degree of amyloid deposition in the arteries was divided into four grades (none, mild, moderate or severe), the severity was higher in the subcortical hemorrhage group than in the deep cerebral hemorrhage group and the non-hemorrhage group. These results suggest that severe cerebral amyloid angiopathy is related to non-traumatic subcortical hemorrhage in elderly persons.

PurposeFamilial cerebral cavernous malformation syndrome (FCCM) is characterized by multiple hemorrhagic lesions and is sometimes mistaken for cerebral amyloid angiopathy (CAA).MethodsWe compared clinical and radiologic characteristics in patients with definite (N = 32) and presumed FCCM (n = 76) to patients with definite (N = 29) and probable CAA (N = 21).ResultsPatients with CAA were older (78.6 years CAA vs. 43.4 FCCM; p < 0.0001), had cognitive complaints (66.0% CAA vs. 8.3% FCCM; p < 0.0001), and less likely to have a family history (4.0% CAA vs. 50.9% FCCM; p < 0.0001). FCCM patients were more likely to have at least 1 Zabramski type 2 lesion (0 CAA vs. 79.6% FCCM; p < 0.0001). Presence of any subcortical white matter hemorrhagic lesion (23.0% CAA vs. 99.1% FCCM; p < 0.0001), a lesion in either the basal ganglia, internal capsule or cerebellum (28.0% CAA vs 79.6% FCCM; p < 0.0001) and a subcortical white matter to cortical ribbon distribution of hemorrhagic lesions ≥ 1.0 was predictive of FCCM (6.0% CAA vs 83.9% FCCM; p < 0.0001). CAA patients more commonly had white matter disease, sulcal subarachnoid hemorrhage, and severely enlarged perivascular spaces in the centrum. However, none of the latter features were unique to CAA. FCCM patients meeting Boston 2.0 criteria for CAA (n = 14) had additional factors that helped distinguish them from CAA.ConclusionsPatients with FCCM can be reliably distinguished from CAA by accurately applying the Boston 2.0 criteria, assessing hemorrhagic lesion distribution and types, and assessing for clinical features unique to FCCM. FCCM criteria are proposed. The frequent finding of leukoaraiosis and enlarged perivascular spaces in the centrum semiovale in FCCM patients deserves further investigation.

Cortical superficial siderosis is an established haemorrhagic neuroimaging marker of cerebral amyloid angiopathy. In fact, cortical superficial siderosis is emerging as a strong independent risk factor for future lobar intracerebral haemorrhage. However, the underlying neuropathological correlates and pathophysiological mechanisms of cortical superficial siderosis remain elusive. Here we use an in vivo MRI, ex vivo MRI, histopathology approach to assess the neuropathological correlates and vascular pathology underlying cortical superficial siderosis. Fourteen autopsy cases with cerebral amyloid angiopathy (mean age at death 73 years, nine males) and three controls (mean age at death 91 years, one male) were included in the study. Intact formalin-fixed cerebral hemispheres were scanned on a 3 T MRI scanner. Cortical superficial siderosis was assessed on ex vivo gradient echo and turbo spin echo MRI sequences and compared to findings on available in vivo MRI. Subsequently, 11 representative areas in four cases with available in vivo MRI scans were sampled for histopathological verification of MRI-defined cortical superficial siderosis. In addition, samples were taken from predefined standard areas of the brain, blinded to MRI findings. Serial sections were stained for haematoxylin and eosin and Perls' Prussian blue, and immunohistochemistry was performed against amyloid-β and GFAP. Cortical superficial siderosis was present on ex vivo MRI in 8/14 cases (57%) and 0/3 controls (P = 0.072). Histopathologically, cortical superficial siderosis corresponded to iron-positive haemosiderin deposits in the subarachnoid space and superficial cortical layers, indicative of chronic bleeding events originating from the leptomeningeal vessels. Increased severity of cortical superficial siderosis was associated with upregulation of reactive astrocytes. Next, cortical superficial siderosis was assessed on a total of 65 Perls'-stained sections from MRI-targeted and untargeted sampling combined in cerebral amyloid angiopathy cases. Moderate-to-severe cortical superficial siderosis was associated with concentric splitting of the vessel wall (an advanced form of cerebral amyloid angiopathy-related vascular damage) in leptomeningeal vessels (P < 0.0001), but reduced cerebral amyloid angiopathy severity in cortical vessels (P = 0.048). In terms of secondary tissue injury, moderate-to-severe cortical superficial siderosis was associated with the presence of microinfarcts (P = 0.025), though not microbleeds (P = 0.973). Collectively, these data suggest that cortical superficial siderosis on MRI corresponds to iron-positive deposits in the superficial cortical layers, representing the chronic manifestation of bleeding episodes from leptomeningeal vessels. Cortical superficial siderosis appears to be the result of predominantly advanced cerebral amyloid angiopathy of the leptomeningeal vessels and may trigger secondary ischaemic injury in affected areas.