Abeta is targeted to the vasculature in a mouse model of hereditary cerebral hemorrhage with amyloidosis

The E693Q mutation in the amyloid beta precursor protein (APP) leads to cerebral amyloid angiopathy (CAA), with recurrent cerebral hemorrhagic strokes and dementia. In contrast to Alzheimer disease (AD), the brains of those affected by hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D) show few parenchymal amyloid plaques. We found that neuronal overexpression of human E693Q APP in mice (APPDutch mice) caused extensive CAA, smooth muscle cell degeneration, hemorrhages and neuroinflammation. In contrast, overexpression of human wild-type APP (APPwt mice) resulted in predominantly parenchymal amyloidosis, similar to that seen in AD. In APPDutch mice and HCHWA-D human brain, the ratio of the amyloid-beta40 peptide (Abeta40) to Abeta42 was significantly higher than that seen in APPwt mice or AD human brain. Genetically shifting the ratio of AbetaDutch40/AbetaDutch42 toward AbetaDutch42 by crossing APPDutch mice with transgenic mice producing mutated presenilin-1 redistributed the amyloid pathology from the vasculature to the parenchyma. The understanding that different Abeta species can drive amyloid pathology in different cerebral compartments has implications for current anti-amyloid therapeutic strategies. This HCHWA-D mouse model is the first to develop robust CAA in the absence of parenchymal amyloid, highlighting the key role of neuronally produced Abeta to vascular amyloid pathology and emphasizing the differing roles of Abeta40 and Abeta42 in vascular and parenchymal amyloid pathology.     

Brain amyloid in normal aging and cerebral amyloid angiopathy is antigenically related to Alzheimer''s disease beta-protein.

Amyloid deposition is a prominent feature of a number of brain disorders, in which amyloid fibrils are found within blood vessel walls, the neuropil (neuritic plaques), neurons (neurofibrillary tangles). These include Alzheimer's disease (AD), AD changes associated with Down's syndrome, neurologically asymptomatic amyloidosis, Parkinson dementia of Guam, hereditary cerebral hemorrhage with amyloidosis of Icelandic origin (HCHWA-I), hereditary cerebral hemorrhage with amyloidosis of Dutch origin (HCHWA-D), and sporadic cerebral amyloid angiopathy (SCAA). Recently it was shown that the amyloid deposits in AD, Parkinson dementia of Guam, and HCHWA-D are formed by a similar 4-kd polypeptide called beta-protein. Because the nature of the amyloid deposits in other types of cerebral amyloidosis is not known, we have conducted immunocytochemical studies on brains from autopsy cases of AD, HCHWA-D, SCAA and neurologically asymptomatic elderly individuals. Brains from two subjects without neurologic involvement were used as controls. Sections from these specimens were incubated with rabbit polyclonal antibodies against 1) a synthetic peptide of 28 residues (anti-SP28), homologous to the NH2-terminal sequence of the beta-protein, 2) the main amyloid component of the HCHWA-I, a variant of cystatin C, and 3) purified fraction of neurofibrillary tangles. In all cases, anti-SP28 antibody specifically stained amyloid deposits in leptomeningeal and cortical vessels and neuritic plaques. These findings demonstrate that the amyloid deposits of SCAA and aged brains are composed of a protein antigenically similar to AD, HCHWA-D, and Parkinson dementia of Guam beta-protein, suggesting that all of these clinically and etiologically different morbid conditions are pathogenetically related. On this basis, they can be tentatively grouped as beta-protein deposition diseases. In addition, we found that HCHWA-D and SCAA vessels were mainly affected, while in AD parenchymal involvement predominates. These differences in the localization and extent of beta-protein deposits may account from the predominance of vascular complications in HCHWA-D and SCAA and of dementia in AD.     

Coexistence of Alzheimer's amyloid precursor protein and amyloid protein in cerebral vessel walls

Polyclonal antibodies to synthetic peptides homologous to amino acid residues 45-62, 597-624, and 676-695 of the predicted sequence of Alzheimer's amyloid precursor protein (APP) were used to investigate the site of origin of APP, and the relationship between APP and amyloid protein in Alzheimer's disease (AD) and hereditary cerebral hemorrhage with amyloidosis, Dutch type (HCHWA-D). Cortical sections as well as homogenates of isolated leptomeningeal and cortical microvessels from three patients with AD, two patients with HCHWA-D, and two nondemented controls were probed. In vessel extracts of both groups of patients and the controls, APP was detected as a set of proteins with electrophoretic mobility of 105 to 135 kilodaltons. In cortical sections of all subjects, APP immunoreactivity was found in leptomeningeal and cortical vessel walls. In patients with AD and HCHWA-D, APP and amyloid fibrils coexisted in the same vessels. Moreover, APP immunoreactivity was found in association with 50% of senile plaques in AD brains, but was not evidenced in parenchymal amyloid deposits in patients with HCHWA-D. These data suggest that the vascular system is a source of APP and that the processing of APP into insoluble fibrils in AD and HCHWA-D may take place in situ.     

Small heat shock proteins associated with cerebral amyloid angiopathy of hereditary cerebral hemorrhage with amyloidosis (Dutch type) induce interleukin-6 secretion

In hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D), severe cerebral amyloid angiopathy (CAA) is associated with an inflammatory reaction. Small heat shock proteins (sHsps) are molecular chaperones and association of HspB8 with CAA in HCHWA-D has been observed. The aims of this study were to investigate (1) if other sHsps are associated with the pathological lesions in HCHWA-D brains, (2) if the amyloid-beta protein (A beta) increases production of sHsps in cultured cerebral cells and (3) if sHsps are involved in the cerebral inflammatory processes in both Alzheimer's disease (AD) and HCHWA-D. We conclude that Hsp20, HspB8 and HspB2 are present in CAA in HCHWA-D, and that A beta did not affect cellular sHsps expression in cultured human brain pericytes and astrocytes. In addition, we demonstrated that Hsp20, HspB2 and HspB8 induced interleukin-6 production in cultured pericytes and astrocytes, which could be antagonized by dexamethasone, whereas other sHsps and A beta were inactive, suggesting that sHsps may be among the key mediators of the local inflammatory response associated with HCHWA-D and AD lesions.     

Preliminary observations of increased diffusional kurtosis in human brain following recent cerebral infarction

By application of the MRI method of diffusional kurtosis imaging, a substantially increased diffusional kurtosis was observed within the cerebral ischemic lesions of three stroke subjects, 13–26 h following the onset of symptoms. This increase is interpreted as probably reflecting a higher degree of diffusional heterogeneity in the lesions when compared with normal‐appearing contralateral tissue. In addition, for two of the subjects with white matter infarcts, the increase had a strong fiber tract orientational dependence. It is proposed that this effect is consistent with a large drop in the intra‐axonal diffusivity, possibly related to either axonal varicosities or alterations associated with the endoplasmic reticulum. Copyright © 2010 John Wiley & Sons, Ltd.     

Cerebral amyloid angiopathy: major contributor or decorative response to Alzheimer's disease pathogenesis

Amyloid deposition within cerebral vessels, or cerebral amyloid angiopathy (CAA), is common in advanced age and even more common in Alzheimer's disease. CAA may be complicated by lobar intracerebral hemorrhage, while rare kindreds of autosomal dominant CAA also show propensity for intracerebral hemorrhage, due to germline mutations in specific amyloidogenic precursor proteins and apparent compromise of structural integrity of the blood vessel wall due to marked amyloid deposition. The relationship between cerebral amyloid angiopathy and cognitive dysfunction, however, is less clear. While cognitive dysfunction in familial CAA is likely related to prodigious amyloid deposits and vascular luminal compromise (e.g., hereditary cerebral hemorrhage with angiopathy-Dutch type (HCHWA-D)), cerebral amyloid angiopathy with intracerebral hemorrhage often presents sporadically in cognitively intact elderly patients. Moreover, while about 80% of subjects with Alzheimer's disease have demonstrable amyloid beta within blood vessel walls at autopsy, the vast majority of these fail to suffer clinically relevant intracerebral hemorrhage during life. The remaining 20% manage to progress and die of their disease with virtual no amyloid within blood vessels. Thus, the role of amyloid beta deposits in cerebral vessels as regards cognitive function on the one hand, and tendency for hemorrhage on the other, remain to be resolved for sporadic late onset Alzheimer's disease and CAA. Recent studies on transgenic APP23 mice suggest a relationship between passive immunization and amyloid angiopathy-associated cerebral hemorrhage, although the mechanism of hemorrhage was unclear from the data presented. We suggest that amyloid accumulation represents a response to chronic stress, and that the neurodegenerative process occurs at the neuronal level, encompassing oxidative stress and aberrant cell cycle activation. As such, CAA represents tissue homeostasis, such that an abrupt perturbation of this balance (e.g., amyloid beta immunization) is deleterious.     

Hereditary Cerebral Hemorrhage with Amyloidosis-Dutch type (HCHWA-D): II - A Review of Histopathological Aspects

Cerebral amyloid-β (Aβ) angiopathy is the histopathological hallmark of hereditary cerebral hemorrhage with amyloidosis (Dutch) (HCHWA-D). Aβ deposits are found mainly in the cerebral and cerebellar meningocortical blood vessels and as plaques throughout the cerebrocortical gray matter. Aβ deposition in arteries and arterioles starts at the junction of media and adventitia and proceeds to involve the media causing degeneration of the vascular smooth muscle cells. Cerebrocortical arterioles often show one or two layers of radial Aβ around a layer of homogenous Aβ that replaces the media. Degenerating neurites, reactive astrocytes and microglial cells may surround cerebrocortical angiopathic arterioles and capillaries, probably in reaction to invasion of the perivascular neuropil by Aβ fibrils. Furthermore, clusters of coarse extracellular matrix deposits may be found near Aβ-laden cerebrocortical arterioles. The amyloid-associated proteins, cystatin C, and βPP colocalize diffusely with Dutch vascular Aβ, whereas HLA-DR immunoreactivity is found only in the periphery of the diseased vessel wall. The latter phenomenon may be related to the presence of perivascular cells. Angiopathic blood vessels frequently show structural changes. The relation of the described pathology to the development of hemorrhage, infarction and leukoencephalopathy needs further elucidation.     

The cerebral beta-amyloid angiopathies: hereditary and sporadic

We review the clinical, radiologic, and neuropathologic features of the hereditary and sporadic forms of cerebral amyloid angiopathy (CAA) associated with vascular deposition of the beta-amyloid peptide. Amino acid substitutions at 4 sites in the beta-amyloid precursor protein, all situated within the beta-amyloid peptide sequence itself, have been shown to cause heritable forms of CAA. The vascular diseases caused by these mutations are associated primarily with cerebral hemorrhages, white matter lesions, and cognitive impairment, and only variable extents of the plaque and neurofibrillary pathologies characteristic of Alzheimer disease. Sporadic CAA typically presents 20 or more years later than hereditary CAA, but is otherwise characterized by a comparable constellation of recurrent cerebral hemorrhages, white matter lesions, and cognitive impairment. The clinical, radiologic and pathologic similarities between hereditary and sporadic CAA suggest that important lessons for this common age-related process can be learned from the mechanisms by which mutation makes beta-amyloid tropic or toxic to vessels.     

White Matter Changes in Dementia: Role of Impaired Drainage of Interstitial Fluid

White matter abnormalities on magnetic resonance imaging (MRI) are associated with dementia and include white matter hyperintensities (WMH; also termed leukoaraiosis) and visible perivascular spaces (PVS). We review the potential role of impaired drainage of interstitial fluid in the pathogenesis of WMH and PVS. Whereas the volume of extracellular space in the grey matter is tightly controlled, fluid accumulates and expands the extracellular spaces of the white matter in acute hydrocephalus, vasogenic edema and WMH. Although there are no conventional lymphatic vessels in the brain, there is very effective lymphatic drainage for fluid and solutes along restricted pathways in the basement membranes of cerebral capillaries and arteries in young individuals. Lymphatic drainage of the brain is impaired with age and in association with apolipoprotein E ε4, risk factors for Alzheimer's disease and cerebral amyloid angiopathy (CAA). Deposition of proteins in the lymphatic drainage pathways in the walls of cerebral arteries with age is recognized as protein elimination failure angiopathy (PEFA), as in CAA and cerebral autosomal dominant arteriopathy and leukoencephalopathy (CADASIL). Facilitating perivascular lymphatic drainage from the aging brain may play a significant role in the prevention of CAA, WMH and Alzheimer's disease and may enhance the efficacy of immunotherapy for Alzheimer's disease.     

White matter involvement in mitochondrial diseases

White matter involvement is recently being realized as a common finding in mitochondrial disorders. It is considered an inherent part of the classical mitochondrial syndromes which are usually associated with alterations in the mitochondrial DNA such as: Leigh disease, Kearns-Sayre syndrome, mitochondrial encephalomyopathy lactic acidosis, and stroke like episodes, mitochondrial neuro-gastro-intestinal encephalomyopathy and Leber's hereditary optic neuropathy. White matter involvement is also described in mitochondrial disorders due to mutations in the nuclear DNA which are transmitted in an autosomal pattern. MRI findings suggestive of a mitochondrial disease are: small cyst-like lesions in abnormal white matter, involvement of both cerebral and cerebellar white matter, and a combination of a leukoencephalopathy with bilateral basal ganglia lesions. The clinical manifestations may be disproportionate to the extent of white matter involvement. Other organs may frequently be involved. The onset is often in infancy with a neurodegenerative course. The finding of a leukoencephalopathy in a patient with a complex neurologic picture and multisystem involvement should prompt a thorough mitochondrial evaluation.     

常染色体显性遗传病伴皮质下梗死和白质脑病的临床研究进展

常染色体显性遗传病伴皮质下梗死和白质脑病(cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy,CADASIL)是一种临床上罕见的以中年人发病的遗传性微小动脉疾病,由19号染色体上Notch3基因突变所致的遗传性卒中疾病.该病患者初期多有偏头痛发作史,中年时反复发作短暂性脑缺血发作(transient ischemic attack, TIA)或缺血脑卒中,病程晚期患者可出现进行性加重的痴呆及精神症状.头颅磁共振成像(magnetic resonance imaging,MRI)检查显示双侧大脑半球多发的白质病变,为本病特征性的影像学表现.本文总结了该病临床研究进展,包括临床表现、神经影像学表现、CADASIL量表、病理学及分子遗传学,以加深对该病的认识,从而有助于早期诊断,减少误诊和漏诊.     

Tooth Loss Is Associated with Brain White Matter Change and Silent Infarction among Adults without Dementia and Stroke

Periodontal disease is a predictor of stroke and cognitive impairment. The association between the number of lost teeth (an indicator of periodontal disease) and silent infarcts and cerebral white matter changes on brain CT was investigated in community-dwelling adults without dementia or stroke. Dental examination and CT were performed in 438 stroke- and dementia-free subjects older than 50 yr (mean age, 63 ± 7.9 yr), who were recruited for an early health check-up program as part of the Prevention of Stroke and Dementia (PRESENT) project between 2009 and 2010. In unadjusted analyses, the odds ratio (OR) for silent cerebral infarcts and cerebral white matter changes for subjects with 6-10 and > 10 lost teeth was 2.3 (95% CI, 1.38-4.39; P = 0.006) and 4.2 (95% CI, 1.57-5.64; P < 0.001), respectively, as compared to subjects with 0-5 lost teeth. After adjustment for age, education, hypertension, diabetes mellitus, hyperlipidemia, and smoking, the ORs were 1.7 (95% CI, 1.08-3.69; P = 0.12) and 3.9 (95% CI, 1.27-5.02; P < 0.001), respectively. These findings suggest that severe tooth loss may be a predictor of silent cerebral infarcts and cerebral white matter changes in community-dwelling, stroke- and dementia-free adults.     

The role of cerebral ischemia in Alzheimer's disease

The Alzheimer type of dementia and stroke are known to increase at comparable rates with age. Recent advances suggest that vascular risk factors linked to cerebrovascular disease and stroke in the elderly significantly increase the risk of developing Alzheimer's disease (AD). These include atherosclerosis, atrial fibrillation, coronary artery disease, hypertension, and diabetes mellitus. Moreover, review of various autopsy series shows that 60-90% of AD cases exhibit variable cerebrovascular pathology. Although some vascular lesions such as cerebral amyloid angiopathy, endothelial degeneration, and periventricular white matter lesions are evident in most cases of AD, a third will exhibit cerebral infarction. Despite the interpretation of pathological evidence, longitudinal clinical studies suggest that the co-existence of stroke and AD occurs more than by chance alone. Strokes known to occur in patients with Alzheimer syndrome and most frequently in the oldest old substantially worsen cognitive decline and outcome, implicating some interaction between the disorders. Nevertheless, the nature of a true relationship between the two disorders seems little explored. What predisposes to strokes in underlying cognitive decline or AD? Is it possible that cerebral ischemia is a causal factor for AD? I examined several vascular factors and the vascular pathophysiology implicated in stroke and AD, and propose that cerebral ischemia or oligemia may promote Alzheimer type of changes in the aging brain. Irrespective of the ultimate pathogenetic mechanism, these approaches implicate that management of peripheral vascular disease is important in the treatment or prevention of Alzheimer's disease or mixed dementia.     

Imaging of cerebrovascular disease in sickle cell anemia

Cerebral vascular disease is a common and serious complication of sickle cell disease that mainly involves the large blood vessels of the skull base. Because recurrences are common and residual deficits severe, attention has turned to detection of preclinical cerebral involvement with the goal of preventing clinical damage. Magnetic resonance imaging (MRI), an extremely sensitive tool for detecting cerebral infarction/ischemia, has shown that 10% of asymptomatic patients exhibit white matter lesions that seem to be associated with impaired cognitive function and may be predictive of stroke; magnetic resonance angiography demonstrates occlusions of skull base arteries but is not reliable for the diagnosis of stenosis because of artifacts generated by rapid turbulent flow. Transcranial Doppler is sensitive and specific for the detection of arterial stenosis and occlusion, even in asymptomatic patients. Digitized cerebral angiography remains the gold standard investigation for pretreatment confirmation of lesions detected by Doppler and/or MRI.     

Genetic prion disease with codon 196 PRNP mutation: clinical and pathological findings

Ten percent to 15% of all human transmissible spongiform encephalopathy are characterized by a mutation in prion protein gene (PRNP). They are distinct with respect to clinical signs, disease onset, disease duration, and diagnostic findings. During our surveillance activities in Germany, we identified 7 patients with the rare mutation E196K in PRNP gene, thereof 4 patients belonging to 2 families. The clinical syndromes were characterized by nonspecific and psychiatric symptoms at disease onset and progressed to predominant motor signs. These patients showed a late median disease onset of 71 years and short disease duration of 6.5 months. In absence of family history, they mimicked sporadic Creutzfeldt-Jakob disease (CJD). In clinical tests they were 100% positive for 14-3-3 protein detection in cerebrospinal fluid and less sensitive for magnetic resonance imaging (MRI) and electroencephalogram (EEG) abnormalities. As a secondary magnetic resonance imaging (MRI) abnormality, we have seen conspicuous common involvement of the subcortical white matter in 57%. Four patients underwent autopsy—pathological lesions revealed striking similarity to sporadic Creutzfeldt-Jakob disease but also involvement of the white matter.     

Decreased cortical gray and cerebral white matter in male patients with familial bipolar I disorder

BACKGROUND: Previous MRI studies of bipolar disorder have failed to consistently demonstrate cortical gray or cerebral white matter tissue loss, as well as sulcal or ventricular enlargement. The inconsistencies are most likely due to the clinical and gender heterogeneity of the study populations as well as the different MRI acquisition and processing techniques. The objective of this study was to determine if there was a cortical gray matter and cerebral white matter deficit as well as sulcal and ventricular enlargement in a homogeneous sample of euthymic male patients with familial bipolar I disorder. METHODS: MRI tissue segmentation was utilized to obtain cortical gray matter, cerebral white matter, ventricular cerebrospinal fluid (CSF), and sulcal CSF volumes in 22 euthymic males with familial bipolar I disorder and 32 healthy male control subjects. RESULTS: Relative to the controls, the familial bipolar I patients demonstrated: (1) significant reductions of both cortical gray matter and cerebral white matter volumes; and (2) significant increases in both sulcal and ventricular CSF volumes. In the bipolar group, there was a significant negative correlation between cortical gray matter volume and sulcal CSF volume. LIMITATIONS: Small sample size, retrospective interviews, possible medication effects. CONCLUSIONS: These results provide evidence for significant cortical gray matter and cerebral white matter deficits and associated sulcal and ventricular enlargement in euthymic males with familial bipolar I disorder.     

Detection of HLA-DR on microglia in the human brain is a function of both clinical and technical factors.

Detection of HLA-DR, a class II major histocompatibility antigen, on glial cells is dependent not only on duration and type of tissue fixation and processing, but also on clinical factors. Glial cells labeled by anti-HLA-DR were consistent with microglia by light microscopic and ultrastructural criteria, and were colabeled with other microglial markers, including LN-1, Leu-M5, and leukocyte common antigen (LCA). In young and elderly subjects who died suddenly, anti-HLA-DR labeled microglia in the white matter, but far fewer cells in the gray matter. In subjects who died of chronic debilitating illness, such as Alzheimer's disease and carcinomatosis, anti-HLA-DR labeled numerous microglia throughout both the gray and white matter. In Alzheimer's disease, microglia were aggregated in compact senile plaques, but loosely associated with diffuse amyloid deposits. These results suggest that HLA-DR may be constitutively expressed in white matter, but induced in gray matter microglia in chronic disease states or in association with amyloid deposits.     

Mechanisms regulating cerebral hypoperfusion in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy

Cerebral small vessel disease (CSVD) is a leading cause of stroke and dementia. As the most common type of inherited CSVD, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized by the NOTCH3 gene mutation which leads to Notch3 ectodomain deposition and extracellular matrix aggregation around the small vessels. It further causes smooth muscle cell degeneration and small vessel arteriopathy in the central nervous system. Compromised cerebral blood flow occurs in the early stage of CADASIL and is associated with white matter hyperintensity, the typical neuroimaging pathology of CADASIL. This suggests that cerebral hypoperfusion may play an important role in the pathogenesis of CADASIL. However, the mechanistic linkage between NOTCH3 mutation and cerebral hypoperfusion remains unknown. Therefore, in this mini-review, it examines the cellular and molecular mechanisms contributing to cerebral hypoperfusion in CADASIL.     

TAY-SACHS DISEASE WITH CONSPICUOUS CRANIAL COMPUTERIZED TOMOGRAPHIC APPEARANCES

An autopsy case of a 3-year-old female infant with Tay- Sachs disease was presented. A cherry red spot in the fundus and a deficiency of N-acetyl-β-hexosaminidase A in the white blood cells were revealed soon after admission at the age of one year. Her parents and sister were found to be healthy carriers. The patient showed a typical clinical course with marked cranial swelling. In addition to the marked ballooning of neurons on light microscope, membranous cytoplasmic body (MCB) on electron microscope and abnormal accumulation of GM₂ ganglioside in the cerebral cortex by thin layer chromatography were confirmed in the autopsy specimens. In the late stage of her clinical course, the cranial computerized tomography (CT) demonstrated symmetric and deep-wavy hyperdense cerebral cortical zones, diffuse hypoden-sity and diminished volume of cerebral white matter, mild to moderate ventricular dilatation, and a small cerebellum and brainstem. These conspicuous appearances of the cranial CT seem to be characteristic of Tay-Sachs disease in the late stage, and they are derived from abnormal accumulation of GM₂ ganglioside in the cerebral cortex, and diffuse intense demyelination (dysmyelinating demyelination) of the cerebral white matter. ACTA PATHOL. JPN. 35: 1521–1532, 1985.     

Immunohistochemical study of cerebral amyloid angiopathy. II. Enhancement of immunostaining using formic acid pretreatment of tissue sections.

Cerebral amyloid angiopathy (CAA) is a biochemically heterogeneous entity most commonly associated with stroke syndromes, Alzheimer's disease (AD), Down's syndrome, and miscellaneous neurologic conditions. The authors have applied and extended (using formic acid pretreatment of histologic sections) an immunocytochemical technique that used antibody to a synthetic 28-amino acid peptide representing a segment of the AD amyloid precursor, to study CAA and related parenchymal amyloid deposits in brain tissues originally derived from: 1) patients with CAA with or without typical clinicopathologic features of AD, cerebral hemorrhage, and infarcts; 2) a young boy with angiocentric brain amyloid; 3) patients with familial (Icelandic, Dutch) forms of cerebral hemorrhage caused by CAA; and 4) Japanese patients with nonfamilial CAA-related brain hemorrhage, sometimes associated with histopathology characteristic of AD. Formic acid pretreatment of sections resulted in markedly enhanced staining of senile plaque core and microvascular, especially capillary, amyloid, and some apparent staining of the neuritic component of senile plaques. Perivascular halos of immunoreactive material were observed frequently. Neurofibrillary tangles were not immunolabeled, nor were blood vessels or any parenchymal components within cerebral white matter. CAA in Japanese patients with nonfamilial encephalic hemorrhages appeared immunocytochemically identical to AD-related CAA. Arterioles in brains that had severe CAA frequently showed significant stenosis of their lumina by nonamyloid hyaline or cellular material.