Sporadic cerebral amyloid angiopathy is not a frequent cause of spontaneous brain hemorrhage

Beta-Amyloid Related Neurodegenerative and Neurovascular Diseases: Potential Implications for Transfusion Medicine

Cerebral amyloid angiopathy (CAA) is a progressive cerebrovascular and neurodegenerative disorder that is caused by the aberrant accumulation of soluble beta-amyloid isoforms in the small vessel walls of the cerebral and cerebellar cortices and the leptomeninges. Vascular beta-amyloid deposition increases vulnerability to intracerebral hemorrhage (ICH). Clinically, CAA can be the underlying cause of up to half of spontaneous lobar ICHs and can also present with convexity subarachnoid hemorrhage, transient focal neurologic episodes and progressive cognitive decline leading to dementia. The majority of CAA is sporadic, with increasing prevalence with age and often coexists with Alzheimer's Disease (AD). Genetic and iatrogenic etiologies are rare. Cases of CAA and AD have been linked to the use of cadaveric pituitary hormone and later life iatrogenic CAA has also been described following early-life neurosurgical procedures with cadaveric dura grafts. Together these data suggest a capacity of beta-amyloid transmissibility. A recent study found that in over 1 million transfusion recipients from donors who later developed (i) >1 ICH or (ii) one ICH event and dementia, had an elevated risk of developing future ICH. Considering prior reports of transfusion associated variant-Creutzfeldt Jakob Disease in humans and in vivo evidence in sheep, coupled with emerging data supporting beta-amyloid's prion-like properties, raises the question of whether CAA could be transmissible by blood transfusion. This would also have implications for screening, especially in an era of emerging plasma biomarkers of cerebral amyloidosis. Given the public health concerns raised by this biologically plausible question, there is a need for future studies with well-characterized definitions - and temporal ascertainment - of CAA exposure and outcomes to examine whether CAA is transfusion-transmissible, and, if so, with what frequency and timing of onset.

Neuropathology of Alzheimer's Disease

The key pathological hallmarks-extracellular plaques and intracellular neurofibrillary tangles (NFT)-described by Alois Alzheimer in his seminal 1907 article are still central to the postmortem diagnosis of Alzheimer's disease (AD), but major advances in our understanding of the underlying pathophysiology as well as significant progress in clinical diagnosis and therapy have changed the perspective and importance of neuropathologic evaluation of the brain. The notion that the pathological processes underlying AD already start decades before symptoms are apparent in patients has brought a major change reflected in the current neuropathological classification of AD neuropathological changes (ADNC). The predictable progression of beta-amyloid (Aβ) plaque pathology from neocortex, over limbic structures, diencephalon, and basal ganglia, to brainstem and cerebellum is captured in phases described by Thal and colleagues. The progression of NFT pathology from the transentorhinal region to the limbic system and ultimately the neocortex is described in stages proposed by Braak and colleagues. The density of neuritic plaque pathology is determined by criteria defined by the Consortium to establish a registry for Alzheimer's diseases (CERAD). While these changes neuropathologically define AD, it becomes more and more apparent that the majority of patients present with a multitude of additional pathological changes which are possible contributing factors to the clinical presentation and disease progression. The impact of co-existing Lewy body pathology has been well studied, but the importance of more recently described pathologies including limbic-predominant age-related TDP-43 encephalopathy (LATE), chronic traumatic encephalopathy (CTE), and aging-related tau astrogliopathy (ARTAG) still needs to be evaluated in large cohort studies. In addition, it is apparent that vascular pathology plays an important role in the AD patient population, but a lack of standardized reporting criteria has hampered progress in elucidating the importance of these changes for clinical presentation and disease progression. More recently a key role was ascribed to the immune response to pathological protein aggregates, and it will be important to analyze these changes systematically to better understand the temporal and spatial distribution of the immune response in AD and elucidate their importance for the disease process. Advances in digital pathology and technologies such as single cell sequencing and digital spatial profiling have opened novel avenues for improvement of neuropathological diagnosis and advancing our understanding of underlying molecular processes. Finally, major strides in biomarker-based diagnosis of AD and recent advances in targeted therapeutic approaches may have shifted the perspective but also highlight the continuous importance of postmortem analysis of the brain in neurodegenerative diseases.

Therapeutic Mechanism and Key Alkaloids of Uncaria rhynchophylla in Alzheimer’s Disease From the Perspective of Pathophysiological Processes

Presently, there is a lack of effective disease-modifying drugs for the treatment of Alzheimer’s disease (AD). Uncaria rhynchophylla (UR) and its predominant active phytochemicals alkaloids have been studied to treat AD. This study used a novel network pharmacology strategy to identify UR alkaloids against AD from the perspective of AD pathophysiological processes and identified the key alkaloids for specific pathological process. The analysis identified 10 alkaloids from UR based on high-performance liquid chromatography (HPLC) that corresponded to 127 targets correlated with amyloid-β (Aβ) pathology, tau pathology and Alzheimer disease pathway. Based on the number of targets correlated with AD pathophysiological processes, angustoline, angustidine, corynoxine and isocorynoxeine are highly likely to become key phytochemicals in AD treatment. Among the 127 targets, JUN, STAT3, MAPK3, CCND1, MMP2, MAPK8, GSK3B, JAK3, LCK, CCR5, CDK5 and GRIN2B were identified as core targets. Based on the pathological process of AD, angustoline, angustidine and isocorynoxeine were identified as the key UR alkaloids regulating Aβ production and corynoxine, isocorynoxeine, dihydrocorynatheine, isorhynchophylline and hirsutine were identified as key alkaloids that regulate tau phosphorylation. The findings of this study contribute to a more comprehensive understanding of the key alkaloids and mechanisms of UR in the treatment of AD, as well as provide candidate compounds for drug research and development for specific AD pathological processes.

Diffuse white matter loss in a transgenic rat model of cerebral amyloid angiopathy

Diffuse white matter (WM) disease is highly prevalent in elderly with cerebral small vessel disease (cSVD). In humans, cSVD such as cerebral amyloid angiopathy (CAA) often coexists with Alzheimer's disease imposing a significant impediment for characterizing their distinct effects on WM. Here we studied the burden of age-related CAA pathology on WM disease in a novel transgenic rat model of CAA type 1 (rTg-DI). A cohort of rTg-DI and wild-type rats was scanned longitudinally using MRI for characterization of morphometry, cerebral microbleeds (CMB) and WM integrity. In rTg-DI rats, a distinct pattern of WM loss was observed at 9 M and 11 M. MRI also revealed manifestation of small CMB in thalamus at 6 M, which preceded WM loss and progressively enlarged until the moribund disease stage. Histology revealed myelin loss in the corpus callosum and thalamic CMB in all rTg-DI rats, the latter of which manifested in close proximity to occluded and calcified microvessels. The quantitation of CAA load in rTg-DI rats revealed that the most extensive microvascular Aβ deposition occurred in the thalamus. For the first time using in vivo MRI, we show that CAA type 1 pathology alone is associated with a distinct pattern of WM loss.

Significance of cerebral amyloid angiopathy and other co-morbidities in Lewy body diseases

Lewy body dementia (LBD) and Parkinson's disease-dementia (PDD) are two major neurocognitive disorders with Lewy bodies (LB) of unknown etiology. There is considerable clinical and pathological overlap between these two conditions that are clinically distinguished based on the duration of Parkinsonism prior to development of dementia. Their morphology is characterized by a variable combination of LB and Alzheimer's disease (AD) pathologies. Cerebral amyloid angiopathy (CAA), very common in aged persons and particularly in AD, is increasingly recognized for its association with both pathologies and dementia. To investigate neuropathological differences between LB diseases with and without dementia, 110 PDD and 60 LBD cases were compared with 60 Parkinson's disease (PD) cases without dementia (PDND). The major demographic and neuropathological data were assessed retrospectively. PDD patients were significantly older than PDND ones (83.9 vs 77.8 years; p < 0.05); the age of LB patients was in between both groups (mean 80.2 years), while the duration of disease was LBD < PDD < PDND (mean 6.7 vs 12.5 and 14.3 years). LBD patients had higher neuritic Braak stages (mean 5.1 vs 4.5 and 4.0, respectively), LB scores (mean 5.3 vs 4.2 and 4.0, respectively), and Thal amyloid phases (mean 4.1 vs 3.0 and 2.3, respectively) than the two other groups. CAA was more common in LBD than in the PDD and PDND groups (93 vs 50 and 21.7%, respectively). Its severity was significantly greater in LBD than in PDD and PDND (p < 0.01), involving mainly the occipital lobes. Moreover, striatal Aβ deposition highly differentiated LBD brains from PDD. Braak neurofibrillary tangle (NFT) stages, CAA, and less Thal Aβ phases were positively correlated with LB pathology (p < 0.05), which was significantly higher in LBD than in PDD < PDND. Survival analysis showed worse prognosis in LBD than in PDD (and PDND), which was linked to both increased Braak tau stages and more severe CAA. These and other recent studies imply the association of CAA-and both tau and LB pathologies-with cognitive decline and more rapid disease progression that distinguishes LBD from PDD (and PDND).

Lobar intracerebral haematomas: Neuropathological and 7.0-tesla magnetic resonance imaging evaluation

BACKGROUND AND PURPOSE

The Boston criteria for cerebral amyloid angiopathy (CAA) need validation by neuropathological examination in patients with lobar cerebral haematomas (LCHs). In "vivo" 1.5-tesla magnetic resonance imaging (MRI) is unreliable to detect the age-related signal changes in LCHs. This post-mortem study investigates the validity of the Boston criteria in brains with LCHs and the signal changes during their time course with 7.0-tesla MRI.

MATERIALS AND METHODS

Seventeen CAA brains including 26 LCHs were compared to 13 non-CAA brains with 14 LCHs. The evolution of the signal changes with time was examined in 25 LCHs with T2 and T2* 7.0-tesla MRI.

RESULTS

In the CAA group LCHs were predominantly located in the parieto-occipital lobes. Also white matter changes were more severe with more cortical microinfarcts and cortical microbleeds. On MRI there was a progressive shift of the intensity of the hyposignal from the haematoma core in the acute stage to the boundaries later on. During the residual stage the hyposignal mildly decreased in the boundaries with an increase of the superficial siderosis and haematoma core collapse.

CONCLUSIONS

Our post-mortem study of LCHs confirms the validity of the Boston criteria for CAA. Also 7.0-tesla MRI allows staging the age of the LCHs.

Dissecting Alzheimer disease in Down syndrome using mouse models

Down syndrome (DS) is a common genetic condition caused by the presence of three copies of chromosome 21 (trisomy 21). This greatly increases the risk of Alzheimer disease (AD), but although virtually all people with DS have AD neuropathology by 40 years of age, not all develop dementia. To dissect the genetic contribution of trisomy 21 to DS phenotypes including those relevant to AD, a range of DS mouse models has been generated which are trisomic for chromosome segments syntenic to human chromosome 21. Here, we consider key characteristics of human AD in DS (AD-DS), and our current state of knowledge on related phenotypes in AD and DS mouse models. We go on to review important features needed in future models of AD-DS, to understand this type of dementia and so highlight pathogenic mechanisms relevant to all populations at risk of AD.

No neuropathological evidence for a direct topographical relation between microbleeds and cerebral amyloid angiopathy

Introduction

Cerebral microbleeds correspond to blood breakdown products, including hemosiderin-containing macrophages around small vessels on histological examination. Superficial lobar cerebral microbleeds are increasingly recognized on MRI as a biomarker of cerebral amyloid angiopathy but the direct association between amyloid-laden vessels burden and cerebral microbleeds has yet to be validated neuropathologically. To address this issue, we examined the frequency of histopathologically-defined cerebral microbleeds in different brain regions and their relationship with cerebral amyloid angiopathy in a large autopsy population.

Results

The frontal, parietal and occipital cortex as well as the adjacent white matter and basal ganglia of 113 consecutive autopsies were examined. Cerebral microbleedss were identified on haematoxylin-eosin-stained histological slides, cerebral amyloid angiopathy using anti-amyloid antibody. Cerebral microbleeds were present in 92.9 % of the cases and cerebral amyloid angiopathy in 44.3 % of them. Cerebral microbleeds were more frequent in parietal and frontal lobes followed by the occipital region and basal ganglia. In contrast, cerebral amyloid angiopathy was most frequent in the occipital lobe. There was no significant topographical association between cerebral amyloid angiopathy presence or severity and cerebral microbleeds in any brain region. In lobar areas, cerebral amyloid angiopathy was found in the cortex, predominantly affecting pial arteries and their superficial cortical branches, in contrast to microbleeds which were mainly in the white matter and occurred around deeper arteries and arterioles, including the subcortical segment of long penetrating branches of pial vessels.

Conclusions

Our study does not support a direct relation between cerebral microbleeds and cerebral amyloid angiopathy burden at the neuropathological level, raising intriguing questions on the potential pathophysiological mechanisms of cerebral microbleeds in the context of cerebral amyloid angiopathy or other small vessel disease pathology.

The overlap between vascular disease and Alzheimer's disease--lessons from pathology

Recent epidemiological and clinico-pathological data indicate considerable overlap between cerebrovascular disease (CVD) and Alzheimer's disease (AD) and suggest additive or synergistic effects of both pathologies on cognitive decline. The most frequent vascular pathologies in the aging brain and in AD are cerebral amyloid angiopathy and small vessel disease. Up to 84% of aged subjects show morphological substrates of CVD in addition to AD pathology. AD brains with minor CVD, similar to pure vascular dementia, show subcortical vascular lesions in about two-thirds, while in mixed type dementia (AD plus vascular dementia), multiple larger infarcts are more frequent. Small infarcts in patients with full-blown AD have no impact on cognitive decline but are overwhelmed by the severity of Alzheimer pathology, while in early stages of AD, cerebrovascular lesions may influence and promote cognitive impairment, lowering the threshold for clinically overt dementia. Further studies are warranted to elucidate the many hitherto unanswered questions regarding the overlap between CVD and AD as well as the impact of both CVD and AD pathologies on the development and progression of dementia.

The relationship between cerebral amyloid angiopathy and cortical microinfarcts in brain ageing and Alzheimer's disease

AIMS

Cerebral amyloid angiopathy (CAA) represents the deposition of amyloid β protein (Aβ) in the meningeal and intracerebral vessels. It is often observed as an accompanying lesion of Alzheimer's disease (AD) or in the brain of elderly individuals even in the absence of dementia. CAA is largely age-dependent. In subjects with severe CAA a higher frequency of vascular lesions has been reported. The goal of our study was to define the frequency and distribution of CAA in a 1-year autopsy population (91 cases) from the Department of Internal Medicine, Rehabilitation, and Geriatrics, Geneva.

MATERIALS AND METHODS

Five brain regions were examined, including the hippocampus, and the inferior temporal, frontal, parietal and occipital cortex, using an antibody against Aβ, and simultaneously assessing the severity of AD-type pathology with Braak stages for neurofibrillary tangles identified with an anti-tau antibody. In parallel, the relationships of CAA with vascular brain lesions were established.

RESULTS

CAA was present in 53.8% of the studied population, even in cases without AD (50.6%). The strongest correlation was seen between CAA and age, followed by the severity of amyloid plaques deposition. Microinfarcts were more frequent in cases with CAA; however, our results did not confirm a correlation between these parameters.

CONCLUSION

The present data show that CAA plays a role in the development of microvascular lesions in the ageing brain, but cannot be considered as the most important factor in this vascular pathology, suggesting that other mechanisms also contribute importantly to the pathogenesis of microvascular changes.

Cerebral Amyloidal Angiopathy--a disease with implications for neurology and psychiatry

Cerebral Amyloidal Angiopathy (CAA), which occurs sporadically in most cases but can also occur hereditarily, belongs to the group amyloidoses and is characterized by the deposition and accumulation of beta-amyloid (Aβ) in smaller arterial vessels of the brain. The deposition of Aβ leads to degenerative changes in the cerebral vessel system (thickening of the vessel wall, microaneurysm, constriction of vascular lumen, dissection), which favour the development of the clinical symptomatology most often associated with CAA. Besides haemorrhages, cerebral ischaemia, transient neurological symptoms, leukoencephalopathy as well as cognitive decline and even dementia may appear in connection with CAA. A definite diagnosis of CAA can only be made on the basis of a pathological assessment, even though diagnostic findings of cerebral neuroimaging and clinical symptoms allow the diagnosis of a probable CAA. At present, no causal therapy options are available. Although CAA is placed within the range of neurological illnesses, psychiatric symptoms such as cognitive impairment, personality change or behavioural problems as well as depression are plausible clinical manifestations of CAA and may even dominate the clinical picture. Apart from epidemiological, pathogenetical, clinical and diagnostical aspects, possible psychiatric implications of CAA are discussed in the review article.

Pathology and pathogenesis of vascular cognitive impairment-a critical update

Vascular cognitive impairment (VCI) [vascular cognitive disorder (VCD), vascular dementia] describes a continuum of cognitive disorders ranging from mild cognitive impairment (MCI) to dementia, in which vascular brain injury involving regions important for memory, cognition and behavior plays an important role. Clinical diagnostic criteria show moderate sensitivity (ca 50%) and variable specificity (range 64-98%). In Western clinical series, VaD is suggested in 8-10% of cognitively impaired elderly subjects. Its prevalence in autopsy series varies from 0.03 to 58%, with means of 8 to 15% (in Japan 22-35%). Major types of sporadic VaD are multi-infarct encephalopathy, small vessel and strategic infarct type dementias, subcortical arteriosclerotic leukoencephalopathy (SAE) (Binswanger), multilacunar state, mixed cortico-subcortical type, granular cortical atrophy (rare), postischemic encephalopathy, and a mixture of cerebrovascular lesions (CVLs). They result from systemic, cardiac and local large or small vessel disease (SVD); their pathogenesis is multifactorial. Hereditary forms of VaD caused by gene mutations are rare. Cognitive decline is commonly associated with widespread small ischemic vascular lesions involving subcortical brain areas (basal ganglia and hemispheral white matter). The lesions affect neuronal networks involved in cognition, memory, and behavior (thalamo-cortical, striato-subfrontal, cortico-subcortical, limbic systems). CVLs often coexist with Alzheimer-type lesions and other pathologies; 25-80% of elderly demented show mixed pathologies. The lesion pattern of "pure" VaD differs from that in mixed dementia (AD + CVLs) suggesting different pathogenesis of both phenotypes. Minor CVLs, except for severe amyloid angiopathy, appear not essential for cognitive impairment in full-blown AD, while both mild AD-type pathology and SVD may interact synergistically in promoting dementia. However, in a large percentage of non-demented elderly individuals, both AD-related and vascular brain pathologies have been reported. Despite recent suggestions for staging and grading CVLs in specific brain areas, due to the high variability of CVLs associated with cognitive impairment, no validated neuropathological criteria are currently available for VaD and mixed dementia. Further clinico-pathological studies and harmonization of neuropathological procedures are needed to validate the diagnostic criteria for VaD and mixed dementia in order to clarify the impact of CVLs and other coexistent pathologies on cognitive impairment as a basis for further successful therapeutic options.

Prevalence of cerebrovascular lesions in patients with Lewy body dementia: a neuropathological study

BACKGROUND

The co-existence of vascular pathology in patients with Lewy body dementia (LBD) is still a matter of debate. This study analyses the prevalence and the severity of cerebrovascular lesions in post-mortem brains of patients with LBD.

PATIENTS AND METHODS

Twenty brains of demented patients with autopsy-proven Lewy body disease were compared to 14 brains of age-matched controls.

RESULTS

Associated Alzheimer disease (AD) features, stages I-IV, were present in 70% of the LBD brains and in 7% of the controls (P<0.001). Cerebral amyloid angiopathy (CAA) was only present in 30% and lipohyalinosis in 10%. A semi-quantitative analysis, performed on a coronal section of a whole cerebral hemisphere and on a horizontal section through the pons and the cerebellum, revealed significantly more mini-bleeds in the LBD brains (P=0.007), predominantly in the cerebral cortex (P=0.03). Other cerebrovascular lesions were only rarely observed. Comparison of the LDB brains, with and without moderate AD features and CAA, showed no difference in the severity of the cerebrovascular lesions including mini-bleeds.

CONCLUSIONS

The prevalence of mini-bleeds in LBD brains appears to be independent from the co-existence of moderate AD pathology and CAA. It is more probably due to disturbances of the blood-brain barrier, related to the neurodegenerative process itself.

Etiologies of intracerebral hematomas

Intracerebral hemorrhage (ICH) remains a life-threatening disease that carries significant morbidity and mortality despite recent diagnostic and management advances. Various conditions are associated with increased risk of intracerebral hemorrhage. Understanding the etiology of these conditions and their pathophysiological contribution to ICH will likely lead to better therapeutic and preventative measures and improve the morbidity and mortality associated with intracerebral hemorrhage. We will review the current literature regarding important etiologies/risk factors of intracerebral hemorrhage.

Cerebral amyloid angiopathy impact on endothelium

Cerebral amyloid angiopathy (CAA) is an age-associated disease characterized by amyloid deposition in cerebral and meningeal vessel walls. CAA is detected in the majority of the individuals with dementia and also in a large number of non-demented elderly individuals. In addition, CAA is strongly associated with Alzheimer's disease (AD) pathology. Mechanical consequences including intra-cerebral or subarachnoid hemorrhage remains CAA most feared complication, but only a small fraction of CAA results in severe bleeding. On the hand the non-mechanical consequences in cerebrovascular regulation are prevalent and may be even more deleterious. Studies of animal models have provided strong evidence linking the vasoactive Aβ 1-40, the main species found in CAA, to disturbances in endothelial-dependent factors, disrupting cerebrovascular regulation Here, we aimed to review experimental findings regarding the non-mechanical consequences of CAA for cerebrovascular regulation and discuss the implications of these results to clinical practice.

Histopathological analysis of intracerebral hemorrhage: implications for clinical management

BACKGROUND

The clinical impact of routine neuropathologic examination of samples from patients with intracerebral hemorrhage (ICH) is unclear.

METHODS

Therefore, we evaluated a consecutive series of 378 surgical specimens from patients with ICH concerning demographic data, localization of hemorrhage, preoperative clinical diagnosis and neuropathological diagnosis.

RESULTS

Histological examination revealed the putative origin of ICH in 143 cases (37.8%). Vascular pathologies were detected in 127 patients (33.6%), while tumors were identified in 9 patients (2.4%), infarction in 6 patients (1.6%) and abscess in 1 patient (0.3%). Preoperatively, tumor was considered in 65 patients (17.2%), while vascular malformations were supposed in 94 patients (24.9%), infarction in 18 cases (4.8%) and abscess in 3 cases (0.8%). In 198 patients (52.4%) no specific assumption was made.

CONCLUSIONS

Comparing preoperative assumptions and histological diagnoses, tumor, vascular malformations and infarctions were clinically overestimated, while arteriolosclerosis and amyloid angiopathy were underestimated. In conclusion, we found that histological findings potentially affecting clinical management and prognosis were obtained in 37.8% of cases. Our data suggest that histopathological examination of intracerebral hemorrhage provides important information for patient management and should be routinely performed.

Detection of cerebral microbleeds with quantitative susceptibility mapping in the ArcAbeta mouse model of cerebral amyloidosis

Cerebral microbleeds (CMBs) are findings in patients with neurological disorders such as cerebral amyloid angiopathy and Alzheimer's disease, and are indicative of an underlying vascular pathology. A diagnosis of CMBs requires an imaging method that is capable of detecting iron-containing lesions with high sensitivity and spatial accuracy in the presence of potentially confounding tissue abnormalities. In this study, we investigated the feasibility of quantitative magnetic susceptibility mapping (QSM), a novel technique based on gradient-recalled echo (GRE) phase data, for the detection of CMBs in the arcAβ mouse, a mouse model of cerebral amyloidosis. Quantitative susceptibility maps were generated from phase data acquired with a high-resolution T(2)(*)-weighted GRE sequence at 9.4 T. We examined the influence of different regularization parameters on susceptibility computation; a proper adjustment of the regularization parameter minimizes streaking artifacts and preserves fine structures. In the present study, it is shown that QSM provides increased detection sensitivity of CMBs and improved contrast when compared with GRE magnitude imaging. Furthermore, QSM corrects for the blooming effect observed in magnitude and phase images and depicts both the localization and spatial extent of CMBs with high accuracy. Therefore, QSM may become an important tool for diagnosing CMBs in neurological diseases.

[Cerebral amyloid angiopathy is difficult to diagnose in the intensive care unit]

Cerebral amyloid angiopathy is a common cause of intracerebral haemorrhage in elderly patients. The diagnosis of cerebral amyloid angiopathy is based on the Boston criteria combining clinical and radiological criteria with no other cause of intracerebral haemorrhage. We describe the case of a 60-year-old female admitted to the intensive care unit for agitation and spatial disorientation. She had multiple intracerebral haematomas on brain CT scan. Typical cerebral microbleeds using MRI and the absence of other cause of intracerebral haemorrhage argued in favour of the diagnosis of cerebral amyloid angiopathy. The patient outcome was favourable with a discharge from the intensive care unit on day 16.

Review: sporadic cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) may result from focal to widespread amyloid-β protein (Aβ) deposition within leptomeningeal and intracortical cerebral blood vessels. In addition, pericapillary Aβ refers to Aβ depositions in the glia limitans and adjacent neuropil, whereas in capillary CAA Aβ depositions are present in the capillary wall. CAA may cause lobar intracerebral haemorrhages and microbleeds. Hypoperfusion and reduced vascular autoregulation due to CAA might cause infarcts and white matter lesions. CAA thus causes vascular lesions that potentially lead to (vascular) dementia and may further contribute to dementia by impeding the clearance of solutes out of the brain and transport of nutrients across the blood brain barrier. Severe CAA is an independent risk factor for cognitive decline. The clinical diagnosis of CAA is based on the assessment of associated cerebrovascular lesions. In addition, perivascular spaces in the white matter and reduced concentrations of both Aβ(40) and Aβ(42) in cerebrospinal fluid may prove to be suggestive for CAA. Transgenic mouse models that overexpress human Aβ precursor protein show parenchymal Aβ and CAA, thus corroborating the current concept of CAA pathogenesis: neuronal Aβ enters the perivascular drainage pathway and may accumulate in vessel walls due to increased amounts and/or decreased clearance of Aβ, respectively. We suggest that pericapillary Aβ represents early impairment of the perivascular drainage pathway while capillary CAA is associated with decreased transendothelial clearance of Aβ. CAA plays an important role in the multimorbid condition of the ageing brain but its contribution to neurodegeneration remains to be elucidated.

Perivascular drainage of solutes is impaired in the ageing mouse brain and in the presence of cerebral amyloid angiopathy

The deposition of amyloid-β (Aβ) peptides in the walls of leptomeningeal and cortical blood vessels as cerebral amyloid angiopathy (CAA) is present in normal ageing and the majority of Alzheimer's disease (AD) brains. The failure of clearance mechanisms to eliminate Aβ from the brain contributes to the development of sporadic CAA and AD. Here, we investigated the effects of CAA and ageing on the pattern of perivascular drainage of solutes in the brains of naïve mice and in the Tg2576 mouse model of AD. We report that drainage of small molecular weight dextran along cerebrovascular basement membranes is impaired in the hippocampal capillaries and arteries of 22-month-old wild-type mice compared to 3- and 7-month-old animals, which was associated with age-dependent changes in capillary density. Age-related alterations in the levels of laminin, fibronectin and perlecan in vascular basement membranes were also noted in wild-type mice. Furthermore, dextran was observed in the walls of veins of Tg2576 mice in the presence of CAA, suggesting that deposition of Aβ in vessel walls disrupts the normal route of elimination of solutes from the brain parenchyma. These data support the hypothesis that perivascular solute drainage from the brain is altered both in the ageing brain and as a consequence of CAA. These findings have implications for the success of therapeutic strategies for the treatment of AD that rely upon the health of the ageing cerebral vasculature.

The impact of cerebral amyloid angiopathy on the occurrence of cerebrovascular lesions in demented patients with Alzheimer features: a neuropathological study

OBJECTIVE

The aim of this neuropathological study was to determine the prevalence of the different cerebrovascular lesions to be attributed to cerebral amyloid angiopathy (CAA) and of those associated with the severity of the Alzheimer dementia (AD) itself.

PATIENTS AND METHODS

The cerebrovascular lesions were compared separately in 40 brains of patients with mild and 50 with severe AD features. In the two groups, the number of lesions were compared between the brains with severe and those with mild of absent CAA.

RESULTS

The age of the patients, the vascular risk factors and antithrombotic treatment were similar in all the compared groups. The brains with mild and severe AD features and with CAA contained more haematomas, cortical micro-infarcts and micro-bleeds, and more severe white matter changes, and cortico-subcortical and white matter mini-bleeds. In the CAA brains with severe AD features, also more cortical territorial infarcts were observed, compared to those with mild AD features.

CONCLUSIONS

The increase in cortical infarcts cannot be attributed to the CAA alone, but also to the severity of the degenerative features, implying additional vascular factors in the pathogenesis of AD.

Cerebral amyloid angiopathy in East and West

Cerebral amyloid angiopathy, a vasculopathy characterised by the deposition of amyloid fibrils in the arteries and arterioles in the cerebral cortex and meninges, has been reported to be associated with intracerebral haemorrhage and cognitive impairment in the elderly. Advances in neuroimaging and validation of the clinical diagnostic criteria aid in making a correct clinical diagnosis. Associations with Alzheimer's disease, asymptomatic microbleeds and white matter changes on neuroimaging have an influence on the clinical treatment for patients with probable cerebral amyloid angiopathy. Reviewing the reports from Asian countries, we found that patients with cerebral amyloid angiopathy have a strong age-related prevalence and a consistent association with dementia, but a weaker correlation with intracerebral haemorrhage, most likely due to a higher incidence of hypertensive intracerebral haemorrhage. Involvement of the occipital lobe arteries by CAA is common in all races and ethnicities, while frontal lobe arteries may be more frequently involved in the East compared to the West. The clinical impact of cerebral amyloid angiopathy on intracerebral haemorrhage and cognitive impairment could be increasingly obvious in Asian countries with ageing populations, especially with improving control of hypertension, the leading cause of intracerebral haemorrhage.

Prevalence of small cerebral bleeds in patients with a neurodegenerative dementia: a neuropathological study

BACKGROUND

Small cerebral bleeds are frequently observed on magnetic resonance imaging in patients with Alzheimer dementia (AD). Histological confirmations in post-mortem brains are scarce. This study describes the prevalence of cerebrovascular lesions and the quantification of the "bleeding load" in post-mortem brains of patients with neurodegenerative dementias.

PATIENTS AND METHODS

Forty-five brains of AD patients, 8 of dementia with Lewy bodies (DLB) and 12 of fronto-temporal dementia (FTD) were compared to 10 controls. Histological examination was performed for the evaluation of cerebral amyloid angiopathy (CAA), white matter changes (WMCs), micro-infarcts, and cerebral micro- and mini-bleeds (MnBs). The latter were evaluated semi-quantitatively on a coronal section of a whole cerebral hemisphere and on a horizontal section through the pons and cerebellum.

RESULTS

Arterial hypertension (AH) was the main vascular risk factor in the patients with AD and DLB (P<0.05). MnBs, consisting of small perivascular bleeds, were significantly more frequent (P<0.001) in AD brains. They were mainly and equally present in the cerebral cortex of AD and DLB brains (P=0.04). Combined AD and DLB pathologies were present in 15%. CAA and WMCs occurred more frequently in AD brains (P<0.001). Occasional MnBs were observed in 60% of the controls.

CONCLUSIONS

This neuropathological study confirms the frequent presence of MnBs and WMCs in AD brains. The relative high incidence of cortical MnBs in DLB brains is probably due to the high incidence of AH and the frequent association with AD and CAA.

MRI markers of small vessel disease in lobar and deep hemispheric intracerebral hemorrhage

BACKGROUND AND PURPOSE

MRI evidence of small vessel disease is common in intracerebral hemorrhage (ICH). We hypothesized that ICH caused by cerebral amyloid angiopathy (CAA) or hypertensive vasculopathy would have different distributions of MRI T2 white matter hyperintensity (WMH) and microbleeds.

METHODS

Data were analyzed from 133 consecutive patients with primary supratentorial ICH and adequate MRI sequences. CAA was diagnosed using the Boston criteria. WMH segmentation was performed using a validated semiautomated method. WMH and microbleeds were compared according to site of symptomatic hematoma origin (lobar versus deep) or by pattern of hemorrhages, including both hematomas and microbleeds, on MRI gradient recalled echo sequence (grouped as lobar only-probable CAA, lobar only-possible CAA, deep hemispheric only, or mixed lobar and deep hemorrhages).

RESULTS

Patients with lobar and deep hemispheric hematoma had similar median normalized WMH volumes (19.5 cm versus 19.9 cm(3), P=0.74) and prevalence of >or=1 microbleed (54% versus 52%, P=0.99). The supratentorial WMH distribution was similar according to hemorrhage location category; however, the prevalence of brain stem T2 hyperintensity was lower in lobar hematoma versus deep hematoma (54% versus 70%, P=0.004). Mixed ICH was common (23%). Patients with mixed ICH had large normalized WMH volumes and a posterior distribution of cortical hemorrhages similar to that seen in CAA.

CONCLUSIONS

WMH distribution is largely similar between CAA-related and non-CAA-related ICH. Mixed lobar and deep hemorrhages are seen on MRI gradient recalled echo sequence in up to one fourth of patients; in these patients, both hypertension and CAA may be contributing to the burden of WMH.

Imaging cerebral microbleeds using susceptibility weighted imaging: one step toward detecting vascular dementia

PURPOSE

To monitor changes in the number of cerebral microbleeds (CMBs) in a longitudinal study of healthy controls (HC) and mild-cognitively impaired (MCI) patients using susceptibility weighted imaging (SWI).

MATERIALS AND METHODS

SWI was used to image 28 HC and 75 MCI patients annually at 1.5 Tesla over a 4-year period. Magnitude and phase data were used to visualize CMBs for the first and last scans of 103 subjects.

RESULTS

Preliminary analysis revealed that none of the 28 HC had more than three CMBs. In the 75 MCI patients, five subjects had more than three CMBs in both first and last scans, while one subject had more than three bleeds only in the last scan. In five of these six MCI patients, the number of CMBs increased over time and all six went on to develop progressive cognitive impairment (PCI). Of the 130 total CMBs seen in the last scans of the six MCI cases, most were less than 4 mm in diameter.

CONCLUSION

SWI can reveal small CMBs on the order of 1 mm in diameter and this technique can be used to follow their development longitudinally. Monitoring CMBs may be a means by which to evaluate patients for the presence of microvascular disease that leads to PCI.

Correlation of hypointensities in susceptibility-weighted images to tissue histology in dementia patients with cerebral amyloid angiopathy: a postmortem MRI study

Neuroimaging with iron-sensitive MR sequences [gradient echo T2* and susceptibility-weighted imaging (SWI)] identifies small signal voids that are suspected brain microbleeds. Though the clinical significance of these lesions remains uncertain, their distribution and prevalence correlates with cerebral amyloid angiopathy (CAA), hypertension, smoking, and cognitive deficits. Investigation of the pathologies that produce signal voids is necessary to properly interpret these imaging findings. We conducted a systematic correlation of SWI-identified hypointensities to tissue pathology in postmortem brains with Alzheimer’s disease (AD) and varying degrees of CAA. Autopsied brains from eight AD patients, six of which showed advanced CAA, were imaged at 3T; foci corresponding to hypointensities were identified and studied histologically. A variety of lesions was detected; the most common lesions were acute microhemorrhage, hemosiderin residua of old hemorrhages, and small lacunes ringed by hemosiderin. In lesions where the bleeding vessel could be identified, β-amyloid immunohistochemistry confirmed the presence of β-amyloid in the vessel wall. Significant cellular apoptosis was noted in the perifocal region of recent bleeds along with heme oxygenase 1 activity and late complement activation. Acutely extravasated blood and hemosiderin were noted to migrate through enlarged Virchow–Robin spaces propagating an inflammatory reaction along the local microvasculature; a mechanism that may contribute to the formation of lacunar infarcts. Correlation of imaging findings to tissue pathology in our cases indicates that a variety of CAA-related pathologies produce MR-identified signal voids and further supports the use of SWI as a biomarker for this disease.

Clinical features of non-hypertensive lobar intracerebral hemorrhage related to cerebral amyloid angiopathy

BACKGROUND AND PURPOSE

The present study aims to clarify the clinical features of non-hypertensive cerebral amyloid angiopathy-related lobar intracerebral hemorrhage (CAA-L-ICH).

METHODS

We investigated clinical, laboratory, and neuroimaging findings in 41 patients (30, women; 11, men) with pathologically supported CAA-L-ICH from 303 non-hypertensive Japanese patients aged >OR=55, identified via a nationwide survey as symptomatic CAA-L-ICH.

RESULTS

The mean age of patients at onset of CAA-L-ICH was 73.2 +/- 7.4 years; the number of patients increased with age. The corrected female-to-male ratio for the population was 2.2, with significant female predominance. At onset, 7.3% of patients received anti-platelet therapy. In brain imaging studies, the actual frequency of CAA-L-ICHs was higher in the frontal and parietal lobes; however, after correcting for the estimated cortical volume, the parietal lobe was found to be the most frequently affected. CAA-L-ICH recurred in 31.7% of patients during the average 35.3-month follow-up period. The mean interval between intracerebral hemorrhages (ICHs) was 11.3 months. The case fatality rate was 12.2% at 1 month and 19.5% at 12 months after initial ICH. In 97.1% of patients, neurosurgical procedures were performed without uncontrollable intraoperative or post-operative hemorrhage.

CONCLUSIONS

Our study revealed the clinical features of non-hypertensive CAA-L-ICH, including its parietal predilection, which will require further study with a larger number of patients with different ethnic backgrounds.

Genetics and molecular pathogenesis of sporadic and hereditary cerebral amyloid angiopathies

In cerebral amyloid angiopathy (CAA), amyloid fibrils deposit in walls of arteries, arterioles and less frequently in veins and capillaries of the central nervous system, often resulting in secondary degenerative vascular changes. Although the amyloid-beta peptide is by far the commonest amyloid subunit implicated in sporadic and rarely in hereditary forms of CAA, a number of other proteins may also be involved in rare familial diseases in which CAA is also a characteristic morphological feature. These latter proteins include the ABri and ADan subunits in familial British dementia and familial Danish dementia, respectively, which are also known under the umbrella term BRI2 gene-related dementias, variant cystatin C in hereditary cerebral haemorrhage with amyloidosis of Icelandic-type, variant transthyretins in meningo-vascular amyloidosis, disease-associated prion protein (PrP(Sc)) in hereditary prion disease with premature stop codon mutations and mutated gelsolin (AGel) in familial amyloidosis of Finnish type. In this review, the characteristic morphological features of the different CAAs is described and the implication of the biochemical, genetic and transgenic animal data for the pathogenesis of CAA is discussed.

Hereditary and sporadic forms of abeta-cerebrovascular amyloidosis and relevant transgenic mouse models

Cerebral amyloid angiopathy (CAA) refers to the specific deposition of amyloid fibrils in the leptomeningeal and cerebral blood vessel walls, often causing secondary vascular degenerative changes. Although many kinds of peptides are known to be deposited as vascular amyloid, amyloid-beta (Abeta)-CAA is the most common type associated with normal aging, sporadic CAA, Alzheimer's disease (AD) and Down's syndrome. Moreover, Abeta-CAA is also associated with rare hereditary cerebrovascular amyloidosis due to mutations within the Abeta domain of the amyloid precursor protein (APP) such as Dutch and Flemish APP mutations. Genetics and clinicopathological studies on these familial diseases as well as sporadic conditions have already shown that CAA not only causes haemorrhagic and ischemic strokes, but also leads to progressive dementia. Transgenic mouse models based on familial AD mutations have also successfully reproduced many of the features found in human disease, providing us with important insights into the pathogenesis of CAA. Importantly, such studies have pointed out that specific vastopic Abeta variants or an unaltered Abeta42/Abeta40 ratio favor vascular Abeta deposition over parenchymal plaques, but higher than critical levels of Abeta40 are also observed to be anti-amyloidogenic. These data would be important in the development of therapies targeting amyloid in vessels.

[Amyloidoses in neuropathology]

Amyloidoses play an important role in neuropathology, both in autopsies and biopsy specimens. Cerebral amyloidoses are typically characterized by the deposition of beta-amyloid and mostly affect patients >60 years. The cardinal symptom of cerebral amyloid angiopathy (CAA) is spontaneous intracerebral hemorrhage, whereas the clinical presentation of Alzheimer's disease is dementia. Rare familial forms of amyloidoses may affect young patients and need thorough neuropathological assessment, similar to the relatively infrequent prion diseases. Amyloidoses within neuromuscular tissues mainly occur in the setting of systemic amyloid diseases. Detailed evaluation including thorough characterisation of amyloid is essential for ensuring the neuropathological diagnosis.

Population studies of sporadic cerebral amyloid angiopathy and dementia: a systematic review

BACKGROUND

Deposition of amyloid-beta (Abeta) in vessel walls of the brain as cerebral amyloid angiopathy (CAA) could be a major factor in the pathogenesis of dementia. Here we investigate the relationship between dementia and the prevalence of CAA in older populations. We searched the literature for prospective population-based epidemiological clinicopathological studies, free of the biases of other sampling techniques, which were used as a comparison.

METHODS

To identify population-based studies assessing CAA and dementia, a previous systematic review of population-based clinicopathological studies of ageing and dementia was employed. To identify selected-sample studies, PsychInfo (1806-April Week 3 2008), OVID MEDLINE (1950-April Week 2 2008) and Pubmed (searched 21 April 2008) databases were searched using the term "amyloid angiopathy". These databases were also employed to search for any population-based studies not included in the previous systematic review. Studies were included if they reported the prevalence of CAA relative to a dementia classification (clinical or neuropathological).

RESULTS

Four population-based studies were identified. They showed that on average 55-59% of those with dementia displayed CAA (of any severity) compared to 28-38% of the non-demented. 37-43% of the demented displayed severe CAA in contrast to 7-24% of the non-demented. There was no overlap in the range of these averages and they were less variable and lower than those reported in 38 selected sample studies (demented v non-demented: 32-100 v 0-77% regardless of severity; 0-50 v 0-11% for severe only).

CONCLUSION

CAA prevalence in populations is consistently higher in the demented as compared to the non-demented. This supports a significant role for CAA in the pathogenesis of dementia.

Cerebral amyloid angiopathy: pathogenetic mechanisms and link to dense amyloid plaques

Cerebral amyloid angiopathy (CAA) of the amyloid-beta (Abeta) type is the most common form of sporadic CAA and is now also accepted as an early and integral part of Alzheimer's disease (AD) pathogenesis. Cerebral amyloid angiopathy is a risk factor for haemorrhagic stroke and is believed to independently contribute to dementia. Rare forms of hereditary cerebral amyloidosis caused by mutations within the Abeta domain of amyloid precursor protein (APP) have been identified, where mutant Abeta preferably deposits in vessels because of a decreased fibrillogenic potential and/or increased vasotopicity. A review of factors involved in CAA caused by wild-type Abeta suggests that increased Abeta levels in brain without an increased Abeta42/Abeta40 ratio is one of the most important prerequisites for vascular amyloidosis. This is exemplified by CAA observed in APP duplication and Down's syndrome patients, neprilysin polymorphism patients and knockout mice and Swedish APP (KM670/671NL) mice. Select presenilin mutations also lead to a prominent CAA, and importantly, presenilin mutations are shown to have varied effects on the production of Abeta40, the predominant amyloid found in CAA. Conversely, APP mutations such as Austrian APP (T714I) drastically decrease Abeta40 production and are deficient in CAA. Apolipoprotein E-epsilon4 is also shown to be a risk factor for CAA, and this might be because of its specific role in the aggregation of Abeta40. Recent data also suggest that dense-core senile plaques in humans and dense plaques in transgenic mice, composed predominantly of Abeta40, associate with vessels. This review highlights some of these aspects of genetics and biochemistry of CAA and pathological descriptions linked to a prominent CAA and/or dense plaques in humans and relevant mouse models and discusses how this knowledge has led to a better understanding of the processes involved in vascular amyloidosis, and in causing dementia, and thus has important therapeutic implications.

Cerebral amyloid angiopathy in Lewy body disease

While Alzheimer and Lewy body pathologies are discussed as major substrates of dementia in Parkinson's disease (PD/Lewy body disease of brainstem type), the incidence and impact of cerebral amyloid angiopathy (CAA) and its association with cognitive decline in PD and dementia with Lewy bodies (DLB) are unknown. The severity of CAA and other Alzheimer lesions were assessed in 68 cases of autopsy-confirmed PD, 32 of them with dementia (PDD), and in 20 cases of DLB. PDD patients were significantly older than those without dementia (mean age 84.5 vs 77.6 years; p < 0.01), the age of DLB patients was in between both groups (mean 80.0 years), while duration of disease was DLB < PDD < PD (mean 6.5 vs 8.5 and 14.3 years). PDD patients had a significantly higher neuritic Braak stage (mean 4.2 vs 2.4, p < 0.01), significantly higher cortical amyloid beta (Abeta) load, capillary cerebral amyloid angiopathy (CapCAA) and generalized CAA than those without dementia (mild CapCAA in 22% vs moderate to severe CapCAA in 87%; mild generalized CAA in 5.5% vs moderate to severe generalized CAA in 82%). Mean PD stage was higher in both DLB and PDD than in PD (mean 5.2 vs 4.5 and 4.0, respectively): Mean neuritic Braak stage in DLB was 3.4, severe Abeta plaque load was seen in 95%, moderate to severe CapCAA in 90% and mild to severe generalized CAA in 70%. This and other recent studies imply an association of CAA with cognitive decline in both PD/PDD and DLB, particularly in cases with concomitant AD-type pathology.

Unexpectedly low prevalence of intracerebral hemorrhages in sporadic cerebral amyloid angiopathy: an autopsy study

In a retrospective study of a consecutive autopsy series of 2060 elderly subjects (mean age 78.5 +/- 6.8 SD years), sporadic cerebral amyloid angiopathy (CAA) of various degrees was detected in 73.2% and in 98.5% of autopsy-confirmed cases of typical (plaque and tangle) Alzheimer disease (AD). Spontaneous (non-traumatic) intracerebral hemorrhages (ICH) (excluding microbleeds) were seen in 5.6% of the total cohort and in 7.2% of definite AD cases; CAA was found in 49% of brains without and in 48.7% with ICH which was not significantly different. The latter groups showed a significantly higher frequency of severe degrees of CAA than those without ICH (80.4 vs 30.9%, p < 0.001). Patients with CAA were older than those without CAA, showing a higher frequency of clinical dementia and pathologically confirmed AD, but signs of hypertension (history and/or autopsy) were seen in 41 and 33.6% of these cases, respectively, compared to 70-75% in patients with non-CAA related ICHs. CAA-related ICH much more frequently involved cerebral lobes or hemispheres, while non-CAA related lesions were more often located in basal ganglia and brainstem. The data of a lower prevalence of CAA in cases without than with ICH, but a similar prevalence of ICH with and without CAA do not support the concept that CAA represents the most evident risk factor for ICH in the aged. While severe degrees of CAA were indeed associated with ICH, the general prevalence of large ICH in this autopsy cohort was much higher in cases without CAA, probably due to other risk factors including hypertension, which was documented in around 40% of cases with CAA-related ICH. APOE epsilon3/4 and epsilon4/4 were significantly more frequent in AD (n = 163) than in age-matched controls (n = 47) and were associated with more severe degrees of CAA, but no general genotyping in ICHs with and without CAA was performed. Hence, the role of APOE in the pathogenesis of ICH with and without CAA needs further elucidation.