Argyrophilic grain disease: neuropathology, frequency in a dementia brain bank and lack of relationship with apolipoprotein E

Clinicopathological study of dementia with grains presenting with parkinsonism compared with a typical case

Argyrophilic grain disease (AGD) is one of the major pathological backgrounds of senile dementia. Dementia with grains refers to cases of dementia for which AGD is the sole background pathology responsible for dementia. Recent studies have suggested an association between dementia with grains and parkinsonism. In this study, we aimed to present two autopsy cases of dementia with grains. Case 1 was an 85-year-old man who exhibited amnestic dementia and parkinsonism, including postural instability, upward gaze palsy, and neck and trunk rigidity. The patient was clinically diagnosed with progressive supranuclear palsy and Alzheimer's disease. Case 2 was a 90-year-old man with pure amnestic dementia, clinically diagnosed as Alzheimer's disease. Recently, we used cryo-electron microscopy to confirm that the tau accumulated in both cases had the same three-dimensional structure. In this study, we compared the detailed clinical picture and neuropathological findings using classical staining and immunostaining methods. Both cases exhibited argyrophilic grains and tau-immunoreactive structures in the brainstem and basal ganglia, especially in the nigrostriatal and limbic systems. However, Case 1 had more tau immunoreactive structures. Considering the absence of other disease-specific structures such as tufted astrocytes, astrocytic plaques and globular glial inclusions, lack of conspicuous cerebrovascular disease, and no history of medications that could cause parkinsonism, our findings suggest an association between AGD in the nigrostriatal system and parkinsonism.

Impact of APOE on amyloid and tau accumulation in argyrophilic grain disease and Alzheimer's disease

Alzheimer's disease (AD), characterized by the deposition of amyloid-β (Aβ) in senile plaques and neurofibrillary tangles of phosphorylated tau (pTau), is increasingly recognized as a complex disease with multiple pathologies. AD sometimes pathologically overlaps with age-related tauopathies such as four repeat (4R)-tau predominant argyrophilic grain disease (AGD). While AGD is often detected with AD pathology, the contribution of APOE4 to AGD risk is not clear despite its robust effects on AD pathogenesis. Specifically, how APOE genotype influences Aβ and tau pathology in co-occurring AGD and AD has not been fully understood. Using postmortem brain samples (N = 353) from a neuropathologically defined cohort comprising of cases with AD and/or AGD pathology built to best represent different APOE genotypes, we measured the amounts of major AD-related molecules, including Aβ40, Aβ42, apolipoprotein E (apoE), total tau (tTau), and pTau181, in the temporal cortex. The presence of tau lesions characteristic of AD (AD-tau) was correlated with cognitive decline based on Mini-Mental State Examination (MMSE) scores, while the presence of AGD tau lesions (AGD-tau) was not. Interestingly, while APOE4 increased the risk of AD-tau pathology, it did not increase the risk of AGD-tau pathology. Although APOE4 was significantly associated with higher levels of insoluble Aβ40, Aβ42, apoE, and pTau181, the APOE4 effect was no longer detected in the presence of AGD-tau. We also found that co-occurrence of AGD with AD was associated with lower insoluble Aβ42 and pTau181 levels. Overall, our findings suggest that different patterns of Aβ, tau, and apoE accumulation mediate the development of AD-tau and AGD-tau pathology, which is affected by APOE genotype.

The unique neuropathological vulnerability of the human brain to aging

Alzheimer's disease (AD)-related neurofibrillary tangles (NFT), argyrophilic grain disease (AGD), aging-related tau astrogliopathy (ARTAG), limbic predominant TDP-43 proteinopathy (LATE), and amygdala-predominant Lewy body disease (LBD) are proteinopathies that, together with hippocampal sclerosis, progressively appear in the elderly affecting from 50% to 99% of individuals aged 80 years, depending on the disease. These disorders usually converge on the same subject and associate with additive cognitive impairment. Abnormal Tau, TDP-43, and α-synuclein pathologies progress following a pattern consistent with an active cell-to-cell transmission and abnormal protein processing in the host cell. However, cell vulnerability and transmission pathways are specific for each disorder, albeit abnormal proteins may co-localize in particular neurons. All these alterations are unique or highly prevalent in humans. They all affect, at first, the archicortex and paleocortex to extend at later stages to the neocortex and other regions of the telencephalon. These observations show that the phylogenetically oldest areas of the human cerebral cortex and amygdala are not designed to cope with the lifespan of actual humans. New strategies aimed at reducing the functional overload of the human telencephalon, including optimization of dream repair mechanisms and implementation of artificial circuit devices to surrogate specific brain functions, appear promising.

Impact of APOE genotype on prion-type propagation of tauopathy

Apolipoprotein (APOE) is a major risk factor of Alzheimer's disease (AD), with the E2, E3 and E4 isoforms differentially regulating the burden of AD-associated neuropathologies, such as amyloid β and tau. In AD, pathological tau is thought to spread along neuroanatomic connections following a prion-like mechanism. To provide insights into whether APOE isoforms differentially regulate the prion properties of tau and determine trans-synaptic transmission of tauopathy, we have generated human P301S mutant tau transgenic mice (PS19) that carry human APOE (APOE2, APOE3 or APOE4) or mouse Apoe allele. Mice received intrahippocamal injections of preformed aggregates of K18-tau at young ages, which were analyzed 5 months post-inoculation. Compared to the parental PS19 mice with mouse Apoe alleles, PS19 mice expressing human APOE alleles generally responded to K18-tau seeding with more intense AT8 immunoreactive phosphorylated tau athology. APOE3 homozygous mice accumulated higher levels of AT8-reactive ptau and microgliosis relative to APOE2 or APOE4 homozygotes (E3 > E4~2). PS19 mice that were heterozygous for APOE3 showed similar results, albeit to a lesser degree. In the timeframe of our investigation, we did not observe significant induction of argentophilic or MC1-reactive neurofibrillary tau tangle in PS19 mice homozygous for human APOE. To our knowledge, this is the first comprehensive study in rodent models that provides neuropathological insights into the dose-dependent effect of APOE isoforms on phosphorylated tau pathology induced by recombinant tau prions.

Evolving concepts in progressive supranuclear palsy and other 4-repeat tauopathies

Tauopathies are classified according to whether tau deposits predominantly contain tau isoforms with three or four repeats of the microtubule-binding domain. Those in which four-repeat (4R) tau predominates are known as 4R-tauopathies, and include progressive supranuclear palsy, corticobasal degeneration, argyrophilic grain disease, globular glial tauopathies and conditions associated with specific MAPT mutations. In these diseases, 4R-tau deposits are found in various cell types and anatomical regions of the brain and the conditions share pathological, pathophysiological and clinical characteristics. Despite being considered 'prototype' tauopathies and, therefore, ideal for studying neuroprotective agents, 4R-tauopathies are still severe and untreatable diseases for which no validated biomarkers exist. However, advances in research have addressed the issues of phenotypic overlap, early clinical diagnosis, pathophysiology and identification of biomarkers, setting a road map towards development of treatments. New clinical criteria have been developed and large cohorts with early disease are being followed up in prospective studies. New clinical trial readouts are emerging and biomarker research is focused on molecular pathways that have been identified. Lessons learned from failed trials of neuroprotective drugs are being used to design new trials. In this Review, we present an overview of the latest research in 4R-tauopathies, with a focus on progressive supranuclear palsy, and discuss how current evidence dictates ongoing and future research goals.

Cellular and pathological heterogeneity of primary tauopathies

Microtubule-associated protein tau is abnormally aggregated in neuronal and glial cells in a range of neurodegenerative diseases that are collectively referred to as tauopathies. Multiple studies have suggested that pathological tau species may act as a seed that promotes aggregation of endogenous tau in naïve cells and contributes to propagation of tau pathology. While they share pathological tau aggregation as a common feature, tauopathies are distinct from one another with respect to predominant tau isoforms that accumulate and the selective vulnerability of brain regions and cell types that have tau inclusions. For instance, primary tauopathies present with glial tau pathology, while it is mostly neuronal in Alzheimer's disease (AD). Also, morphologies of tau inclusions can greatly vary even within the same cell type, suggesting distinct mechanisms or distinct tau conformers in each tauopathy. Neuropathological heterogeneity across tauopathies challenges our understanding of pathophysiology behind tau seeding and aggregation, as well as our efforts to develop effective therapeutic strategies for AD and other tauopathies. In this review, we describe diverse neuropathological features of tau inclusions in neurodegenerative tauopathies and discuss what has been learned from experimental studies with mouse models, advanced transcriptomics, and cryo-electron microscopy (cryo-EM) on the biology underlying cell type-specific tau pathology.

Deep Learning-Based Image Classification in Differentiating Tufted Astrocytes, Astrocytic Plaques, and Neuritic Plaques

This study aimed to develop a deep learning-based image classification model that can differentiate tufted astrocytes (TA), astrocytic plaques (AP), and neuritic plaques (NP) based on images of tissue sections stained with phospho-tau immunohistochemistry. Phospho-tau-immunostained slides from the motor cortex were scanned at 20× magnification. An automated deep learning platform, Google AutoML, was used to create a model for distinguishing TA in progressive supranuclear palsy (PSP) from AP in corticobasal degeneration (CBD) and NP in Alzheimer disease (AD). A total of 1500 images of representative tau lesions were captured from 35 PSP, 27 CBD, and 33 AD patients. Of those, 1332 images were used for training, and 168 images for cross-validation. We tested the model using 100 additional test images taken from 20 patients of each disease. In cross-validation, precision and recall for each individual lesion type were 100% and 98.0% for TA, 98.5% and 98.5% for AP, and 98.0% and 100% for NP, respectively. In a test set, all images of TA and NP were correctly predicted. Only eleven images of AP were predicted to be TA or NP. Our data indicate the potential usefulness of deep learning-based image classification methods to assist in differential diagnosis of tauopathies.

Neuropathological assessment of the Alzheimer spectrum

Alzheimer disease (AD), the most common form of dementia globally, classically defined a clinicopathological entity, is a heterogenous disorder with various pathobiological subtypes, currently referred to as Alzheimer continuum. Its morphological hallmarks are extracellular parenchymal β-amyloid (amyloid plaques) and intraneuronal (tau aggregates forming neurofibrillary tangles) lesions accompanied by synaptic loss and vascular amyloid deposits, that are essential for the pathological diagnosis of AD. In addition to "classical" AD, several subtypes with characteristic regional patterns of tau pathology have been described that show distinct clinical features, differences in age, sex distribution, biomarker levels, and patterns of key network destructions responsible for cognitive decline. AD is a mixed proteinopathy (amyloid and tau), frequently associated with other age-related co-pathologies, such as cerebrovascular lesions, Lewy and TDP-43 pathologies, hippocampal sclerosis, or argyrophilic grain disease. These and other co-pathologies essentially influence the clinical picture of AD and may accelerate disease progression. The purpose of this review is to provide a critical overview of AD pathology, its defining pathological substrates, and the heterogeneity among the Alzheimer spectrum entities that may provide a broader diagnostic coverage of this devastating disorder as a basis for implementing precision medicine approaches and for ultimate development of successful disease-modifying drugs for AD.

Clinical and pathologic features of cognitive-predominant corticobasal degeneration

OBJECTIVE

To describe clinical and pathologic characteristics of corticobasal degeneration (CBD) with cognitive predominant problems during the disease course.

METHODS

In a series of autopsy-confirmed cases of CBD, we identified patients with cognitive rather than motor predominant features (CBD-Cog), including 5 patients thought to have Alzheimer disease (AD) and 10 patients thought to have behavioral variant frontotemporal dementia (FTD). We compared clinical and pathologic features of CBD-Cog with those from a series of 31 patients with corticobasal syndrome (CBD-CBS). For pathologic comparisons between CBD-Cog and CBD-CBS, we used semiquantitative scoring of neuronal and glial lesion types in multiple brain regions and quantitative assessments of tau burden from image analysis.

RESULTS

Five of 15 patients with CBD-Cog never had significant motor problems during their disease course. The most common cognitive abnormalities in CBD-Cog were executive and visuospatial dysfunction. The frequency of language problems did not differ between CBD-Cog and CBD-CBS. Argyrophilic grain disease, which is a medial temporal tauopathy associated with mild cognitive impairment, was more frequent in CBD-Cog. Apathy was also more frequent in CBD-Cog. Tau pathology in CBD-Cog was greater in the temporal and less in perirolandic cortices than in CBD-CBS.

CONCLUSION

A subset of patients with CBD has a cognitive predominant syndrome than can be mistaken for AD or FTD. Our findings suggest that distribution of tau cortical pathology (greater in temporal and less in perirolandic cortices) may be the basis of this uncommon clinical variant of CBD.

The neuropathological diagnosis of Alzheimer's disease

Alzheimer's disease is a progressive neurodegenerative disease most often associated with memory deficits and cognitive decline, although less common clinical presentations are increasingly recognized. The cardinal pathological features of the disease have been known for more than one hundred years, and today the presence of these amyloid plaques and neurofibrillary tangles are still required for a pathological diagnosis. Alzheimer's disease is the most common cause of dementia globally. There remain no effective treatment options for the great majority of patients, and the primary causes of the disease are unknown except in a small number of familial cases driven by genetic mutations. Confounding efforts to develop effective diagnostic tools and disease-modifying therapies is the realization that Alzheimer's disease is a mixed proteinopathy (amyloid and tau) frequently associated with other age-related processes such as cerebrovascular disease and Lewy body disease. Defining the relationships between and interdependence of various co-pathologies remains an active area of investigation. This review outlines etiologically-linked pathologic features of Alzheimer's disease, as well as those that are inevitable findings of uncertain significance, such as granulovacuolar degeneration and Hirano bodies. Other disease processes that are frequent, but not inevitable, are also discussed, including pathologic processes that can clinically mimic Alzheimer's disease. These include cerebrovascular disease, Lewy body disease, TDP-43 proteinopathies and argyrophilic grain disease. The purpose of this review is to provide an overview of Alzheimer's disease pathology, its defining pathologic substrates and the related pathologies that can affect diagnosis and treatment.

Neuropathology and pathogenesis of extrapyramidal movement disorders: a critical update-I. Hypokinetic-rigid movement disorders

Extrapyramidal movement disorders include hypokinetic rigid and hyperkinetic or mixed forms, most of them originating from dysfunction of the basal ganglia (BG) and their information circuits. The functional anatomy of the BG, the cortico-BG-thalamocortical, and BG-cerebellar circuit connections are briefly reviewed. Pathophysiologic classification of extrapyramidal movement disorder mechanisms distinguish (1) parkinsonian syndromes, (2) chorea and related syndromes, (3) dystonias, (4) myoclonic syndromes, (5) ballism, (6) tics, and (7) tremor syndromes. Recent genetic and molecular-biologic classifications distinguish (1) synucleinopathies (Parkinson's disease, dementia with Lewy bodies, Parkinson's disease-dementia, and multiple system atrophy); (2) tauopathies (progressive supranuclear palsy, corticobasal degeneration, FTLD-17; Guamian Parkinson-dementia; Pick's disease, and others); (3) polyglutamine disorders (Huntington's disease and related disorders); (4) pantothenate kinase-associated neurodegeneration; (5) Wilson's disease; and (6) other hereditary neurodegenerations without hitherto detected genetic or specific markers. The diversity of phenotypes is related to the deposition of pathologic proteins in distinct cell populations, causing neurodegeneration due to genetic and environmental factors, but there is frequent overlap between various disorders. Their etiopathogenesis is still poorly understood, but is suggested to result from an interaction between genetic and environmental factors. Multiple etiologies and noxious factors (protein mishandling, mitochondrial dysfunction, oxidative stress, excitotoxicity, energy failure, and chronic neuroinflammation) are more likely than a single factor. Current clinical consensus criteria have increased the diagnostic accuracy of most neurodegenerative movement disorders, but for their definite diagnosis, histopathological confirmation is required. We present a timely overview of the neuropathology and pathogenesis of the major extrapyramidal movement disorders in two parts, the first one dedicated to hypokinetic-rigid forms and the second to hyperkinetic disorders.

Argyrophilic Grain Pathology in Frontotemporal Lobar Degeneration: Demographic, Clinical, Neuropathological, and Genetic Features

Frontotemporal lobar degeneration (FTLD) is a clinically, pathologically, and genetically heterogeneous group of disorders that affect the frontal and temporal lobes of the brain. FTLD classification distinguishes three main neuropathological groups: FTLD-tau, FTLD-TDP, and FTLD-FUS. As a four-repeat tauopathy, argyrophilic grain disease (AGD) is included in the FTLD-tau group. AGD may also appear in association with other neuropathological disorders. We describe the demographic, clinical, neuropathological, and genetic characteristics of a series of FTLD cases presenting with AGD. For this purpose, a clinico-pathological study of 71 autopsy-confirmed FTLD cases from different tissue banks was performed. AGD was found in 52.1% of FTLD cases. The presence of AGD increased with the increasing age (up to 88.9% in cases older than 80 years; p < 0.001) and was associated with higher ages at onset (p < 0.001) and death (p < 0.001). In AGD cases, progressive supranuclear palsy (PSP) was the most frequent clinical diagnosis (29.7%) and gait disturbance was the most common symptom (64.5%); behavioral and language symptoms were less frequent as compared with non-AGD cases (p = 0.055; p = 0.012). PSP was the most frequent neuropathological diagnosis among cases with AGD (32.4%). This group also showed less brain atrophy (p = 0.094) and higher prevalence of Alzheimer (p = 0.002) and vascular pathology (p = 0.047) as compared to the non-AGD group. We also observed that H1/H1 genotype was overrepresented in AGD cases (p = 0.018) and that there was no association with any specific APOE allele. A subanalysis of PSP cases according to the AGD status was carried out, yielding no significant differences.

APOE ε2 is associated with increased tau pathology in primary tauopathy

Apolipoprotein E (APOE) ε4 allele is the strongest genetic risk factor for late-onset Alzheimer’s disease mainly by modulating amyloid-β pathology. APOE ε4 is also shown to exacerbate neurodegeneration and neuroinflammation in a tau transgenic mouse model. To further evaluate the association of APOE genotype with the presence and severity of tau pathology, we express human tau via an adeno-associated virus gene delivery approach in human APOE targeted replacement mice. We find increased hyperphosphorylated tau species, tau aggregates, and behavioral abnormalities in mice expressing APOE ε2/ε2. We also show that in humans, the APOE ε2 allele is associated with increased tau pathology in the brains of progressive supranuclear palsy (PSP) cases. Finally, we identify an association between the APOE ε2/ε2 genotype and risk of tauopathies using two series of pathologically-confirmed cases of PSP and corticobasal degeneration. Our data together suggest APOE ε2 status may influence the risk and progression of tauopathy.

The APOE ε4 allele is a strong genetic risk factor for Alzheimer’s disease, whereas the APOE ε2 allele is protective. Here the authors show that mice expressing the human APOE ε2/ε2 genotype have increased tau pathology and related behavioral deficits; they also find that the APOE ε2 allele is associated with an increased burden of tau pathology in postmortem human brains with progressive supranuclear palsy.

Neuropathological comorbidity associated with argyrophilic grain disease

Argyrophilic grain disease (AGD) is a common four-repeat tauopathy in elderly people. While dementia is a major clinical picture of AGD, recent studies support the possibility that AGD may be a pathological base in some patients with mild cognitive impairment, late-onset psychosis, bipolar disorder and depression. AGD often coexists with various other degenerative changes. The frequency of AGD in progressive supranuclear palsy (PSP) cases was reported to range from 18.8% to 80%. The frequency of AGD in corticobasal degeneration (CBD) cases tends to be higher than that in PSP cases, ranging from 41.2% to 100%. Conversely, in our previous study of the frequencies of mild PSP and CBD pathologies in AGD cases, five of 20 AGD cases (25%) had a few Gallyas-positive tufted astrocytes, six cases (30%) had a few granular/fuzzy astrocytes, and one case (5.0%) had a few Gallyas-positive astrocytic plaques in the putamen, caudate nucleus and/or superior frontal gyrus. Both Gallyas-positive tufted astrocytes and Gallyas-negative tau-positive granular/fuzzy astrocytes preferentially developed in the putamen, caudate nucleus and superior frontal cortex in AGD cases, being consistent with the predilection sites of Gallyas-positive tufted astrocytes in PSP cases. Further, in AGD cases, the quantities of Gallyas-positive tufted astrocytes, overall tau-positive astrocytes, and tau-positive neurons in the subcortical nuclei and superior frontal cortex were significantly correlated with Saito AGD stage, respectively. The frequency of AGD in AD cases was reported to reach up to 25% when using four-repeat tau immunohistochemistry. Pretangles are essential pathologies in AGD; however, the Braak stage of three-repeat tau-positive NFTs, which may indicate mild AD pathology or primary age-related tauopathy, was not correlated with Saito AGD stage. Clinicians should be aware of the possibility that coexisting AGD may impact clinical and radiological features in cases of other degenerative diseases.

Pathology of Neurodegenerative Diseases

Neurodegenerative disorders are characterized by progressive loss of selectively vulnerable populations of neurons, which contrasts with select static neuronal loss because of metabolic or toxic disorders. Neurodegenerative diseases can be classified according to primary clinical features (e.g., dementia, parkinsonism, or motor neuron disease), anatomic distribution of neurodegeneration (e.g., frontotemporal degenerations, extrapyramidal disorders, or spinocerebellar degenerations), or principal molecular abnormality. The most common neurodegenerative disorders are amyloidoses, tauopathies, α-synucleinopathies, and TDP-43 proteinopathies. The protein abnormalities in these disorders have abnormal conformational properties. Growing experimental evidence suggests that abnormal protein conformers may spread from cell to cell along anatomically connected pathways, which may in part explain the specific anatomical patterns observed at autopsy. In this review, we detail the human pathology of select neurodegenerative disorders, focusing on their main protein aggregates.

Overlapping but distinct TDP-43 and tau pathologic patterns in aged hippocampi

Intracellular proteinaceous aggregates (inclusion bodies) are almost always detectable at autopsy in brains of elderly individuals. Inclusion bodies composed of TDP-43 and tau proteins often coexist in the same brain, and each of these pathologic biomarkers is associated independently with cognitive impairment. However, uncertainties remain about how the presence and neuroanatomical distribution of inclusion bodies correlate with underlying diseases including Alzheimer's disease (AD). To address this knowledge gap, we analyzed data from the University of Kentucky AD Center autopsy series (n = 247); none of the brains had frontotemporal lobar degeneration. A specific question for this study was whether neurofibrillary tangle (NFT) pathology outside of the Braak NFT staging scheme is characteristic of brains with TDP-43 pathology but lacking AD, that is those with cerebral age-related TDP-43 with sclerosis (CARTS). We also tested whether TDP-43 pathology is associated with comorbid AD pathology, and whether argyrophilic grains are relatively likely to be present in cases with, vs. without, TDP-43 pathology. Consistent with prior studies, hippocampal TDP-43 pathology was associated with advanced AD - Braak NFT stages V/VI. However, argyrophilic grain pathology was not more common in cases with TDP-43 pathology in this data set. In brains with CARTS (TDP-43[+]/AD[-] cases), there were more NFTs in dentate granule neurons than were seen in TDP-43[-]/AD[-] cases. These dentate granule cell NFTs could provide a proxy indicator of CARTS pathology in cases lacking substantial AD pathology. Immunofluorescent experiments in a subsample of cases found that, in both advanced AD and CARTS, approximately 1% of dentate granule neurons were PHF-1 immunopositive, whereas ∼25% of TDP-43 positive cells showed colocalized PHF-1 immunoreactivity. We conclude that NFTs in hippocampal dentate granule neurons are often present in CARTS, and TDP-43 pathology may be secondary to or occurring in parallel with tauopathy.

Argyrophilic Grain Disease: Demographics, Clinical, and Neuropathological Features From a Large Autopsy Study

Argyrophilic grain disease (AGD) is a frequent late-onset, 4-repeat tauopathy reported in Caucasians with high educational attainment. Little is known about AGD in non-Caucasians or in those with low educational attainment. We describe AGD demographics, clinical, and neuropathological features in a multiethnic cohort of 983 subjects ≥50 years of age from São Paulo, Brazil. Clinical data were collected through semistructured interviews with an informant and included in the Informant Questionnaire on Cognitive Decline in the Elderly, the Clinical Dementia Rating, and the Neuropsychiatric Inventory. Neuropathologic assessment relied on internationally accepted criteria. AGD was frequent (15.2%) and was the only neuropathological diagnosis in 8.9% of all cases (mean, 78.9 ± 9.4 years); it rarely occurred as an isolated neuropathological finding. AGD was associated with older age, lower socioeconomic status (SES), and appetite disorders. This is the first study of demographic, clinical, and neuropathological aspects of AGD in different ethnicities and subjects from all socioeconomic strata. The results suggest that prospective studies of AGD patients include levels of hormones related to appetite control as possible antemortem markers. Moreover, understanding the mechanisms behind higher susceptibility to AGD of low SES subjects may disclose novel environmental risk factors for AGD and other neurodegenerative diseases.

Patterns of hippocampal tau pathology differentiate neurodegenerative dementias

BACKGROUND/AIMS

Deposits of phosphorylated tau protein and convergence of pathology in the hippocampus are the hallmarks of neurodegenerative tauopathies. Thus we aimed to evaluate whether regional and cellular vulnerability patterns in the hippocampus distinguish tauopathies or are influenced by their concomitant presence.

METHODS

We created a heat map of phospho-tau (AT8) immunoreactivity patterns in 24 hippocampal subregions/layers in individuals with Alzheimer's disease (AD)-related neurofibrillary degeneration (n = 40), Pick's disease (n = 8), progressive supranuclear palsy (n = 7), corticobasal degeneration (n = 6), argyrophilic grain disease (AGD, n = 18), globular glial tauopathy (n = 5), and tau-astrogliopathy of the elderly (n = 10). AT8 immunoreactivity patterns were compared by mathematical analysis.

RESULTS

Our study reveals disease-specific hot spots and regional selective vulnerability for these disorders. The pattern of hippocampal AD-related tau pathology is strongly influenced by concomitant AGD. Mathematical analysis reveals that hippocampal involvement in primary tauopathies is distinguishable from early-stage AD-related neurofibrillary degeneration.

CONCLUSION

Our data demonstrate disease-specific AT8 immunoreactivity patterns and hot spots in the hippocampus even in tauopathies, which primarily do not affect the hippocampus. These hot spots can be shifted to other regions by the co-occurrence of tauopathies like AGD. Our observations support the notion that globular glial tauopathies and tau-astrogliopathy of the elderly are distinct entities.

A novel tau mutation, p.K317N, causes globular glial tauopathy

Globular glial tauopathies (GGTs) are 4-repeat tauopathies neuropathologically characterized by tau-positive, globular glial inclusions, including both globular oligodendroglial inclusions and globular astrocytic inclusions. No mutations have been found in 25 of the 30 GGT cases reported in the literature who have been screened for mutations in microtubule associated protein tau (MAPT). In this report, six patients with GGT (four with subtype III and two with subtype I) were screened for MAPT mutations. They included 4 men and 2 women with a mean age at death of 73 years (55-83 years) and mean age at symptomatic onset of 66 years (50-77 years). Disease duration ranged from 5 to 14 years. All were homozygous for the MAPT H1 haplotype. Three patients had a positive family history of dementia, and a novel MAPT mutation (c.951G>C, p.K317N) was identified in one of them, a patient with subtype III. Recombinant tau protein bearing the lysine-to-asparagine substitution at amino acid residue 317 was used to assess functional significance of the variant on microtubule assembly and tau filament formation. Recombinant p.K317N tau had reduced ability to promote tubulin polymerization. Recombinant 3R and 4R tau bearing the p.K317N mutation showed decreased 3R tau and increased 4R tau filament assembly. These results strongly suggest that the p.K317N variant is pathogenic. Sequencing of MAPT should be considered in patients with GGT and a family history of dementia or movement disorder. Since several individuals in our series had a positive family history but no MAPT mutation, genetic factors other than MAPT may play a role in disease pathogenesis.

Neuropathologic features of suicide victims who presented with acute poststroke depression: significance of association with neurodegenerative disorders

To investigate the neuropathologic characteristics of poststroke depression (PSD) leading to suicide, we retrospectively selected deceased subjects who had been diagnosed as having early PSD. Cases were divided into subjects who had committed suicide and those who had not. Neuropathologic examinations, including immunohistochemistry, were conducted. Twenty-four subjects fulfilled criteria for early PSD; 11 of these had committed suicide, and the other 13 had not. Lesion type, size of stroke, and location of stroke were variable but did not differ significantly between the groups. Alzheimer disease-related pathology stages also did not differ between the groups. Argyrophilic grain disease was found in both the suicide group (6 of 11) and the nonsuicide group (2 of 13); there were 2 highly possible cases of early progressive supranuclear palsy in the suicide group. Together, argyrophilic grain disease and progressive supranuclear palsy were found significantly more frequently in suicide cases than in nonsuicide cases (p = 0.01). These data suggest that overlapping 4-repeat tauopathies, which include argyrophilic grain disease and progressive supranuclear palsy, might be an important aggravating factor of PSD that could lead to suicide. The presence of other neurodegenerative diseases does not preclude PSD because the prevalence of these diseases in older persons suggests that they might often occur concomitantly.

Medial temporal regional argyrophilic grain as a possible important factor affecting dementia in Parkinson's disease

Argyrophilic grain (ArG) is the main pathological feature of argyrophilic grain disease (AGD) and is clinically characterized by cognitive impairment, behavioral abnormalities, personality changes, and emotional imbalances. However, ArG can not only be found in AGD but also in various other neurological disorders, including Parkinson's disease (PD). The association of ArG with psychosis and/or dementia in various neurological disorders remains unknown; in this study, we have investigated this in PD. The distribution and degree of ArG deposition, spongiform change in the transentorhinal cortex (TER SpC), and phosphorylated alpha-synuclein-positive neurites in CA2/3 were assessed, and we used formalin-fixed, paraffin-embedded specimens obtained from the anterior/posterior medial temporal region of 20 autopsy cases diagnosed as PD. These cases were clinically divided into two groups: PD without dementia (PDND) and PD with dementia (PDD). Most PDD cases revealed scattered to numerous ArG or moderate to severe TER SpC, both of which were rarely observed in the PDND group. Furthermore, by the degree of ArG density and TER SpC, the PDD group was further divided into three subtypes: PDD with ArG, with TER SpC and without ArG/TER SpC. Scattered-to-numerous ArG and/or moderate-to-severe TER SpC were observed only in PDD, which suggested that both ArG and TER SpC could be important factors affecting dementia in PD and that their distribution and degree are equally important.

Argyrophilic grain disease: An underestimated tauopathy

Argyrophilic grain disease (AGD) is an under-recognized, distinct, highly frequent sporadic tauopathy, with a prevalence reaching 31.3% in centenarians. The most common AGD manifestation is slowly progressive amnestic mild cognitive impairment, accompanied by a high prevalence of neuropsychiatric symptoms. AGD diagnosis can only be achieved postmortem based on the finding of its three main pathologic features: argyrophilic grains, oligodendrocytic coiled bodies and neuronal pretangles. AGD is frequently seen together with Alzheimer's disease-type pathology or in association with other neurodegenerative diseases. Recent studies suggest that AGD may be a defense mechanism against the spread of other neuropathological entities, particularly Alzheimer's disease. This review aims to provide an in-depth overview of the current understanding on AGD.

APOE2 enhances neuroprotection against Alzheimer's disease through multiple molecular mechanisms

The common APOE2 gene variant is neuroprotective against Alzheimer's disease (AD) and reduces risk by nearly 50%. However, the mechanisms by which APOE2 confers neuroprotection are largely unknown. Here we showed that ApoE protein abundance in human postmortem cortex follows an isoform-dependent pattern (E2>E3>E4). We also identified a unique downstream transcriptional profile determined by microarray and characterized by downregulation of long-term potentiation (LTP) related transcripts and upregulation of extracellular matrix (ECM)/integrin-related transcripts in E2 cases and corroborated this finding at the protein level by demonstrating increases in ECM collagens and laminins. In vivo studies of healthy older individuals demonstrated a unique and advantageous biomarker signature in E2 carriers. APOE2 also reduced the risk of mild cognitive impairment to AD conversion by half. Our findings suggest that ApoE2 protein abundance, coupled with its inability to bind to LDLRs, may act to increase amyloid-beta (Ab) clearance. In addition, increased ECM and reduced LTP-related expression results in diminished activity-dependent Ab secretion and/or excitotoxicity, and thus also promotes neuroprotection.

Specific profile of tau isoforms in argyrophylic grain disease

Argyrophylic grain disease (AGD) is a neurodegenerative condition that has been classified among the sporadic tauopathies. Entities in this group present intracellular aggregates of hyperphosphorylated tau, giving rise to characteristic neuronal and glial inclusions. In different tauopathies, the proportion of several tau isoforms present in the aggregates shows specific patterns. AGD has been tentatively classified in the 4R group (predominance of 4R tau isoforms) together with progressive supranuclear palsy and corticobasal degeneration. Pick's disease is included in the 3R group (predominance of 3R isoforms), whereas tau pathology of Alzheimer's disease represents and intermediate group (3 or 4 repeats [3R plus 4R, respectively] isoforms). In this work, we have analyzed tau present in aggregates isolated from brain samples of patients with argyrophylic grain disease. Our results indicate that the main tau isoform present in aggregates obtained from patients with AGD is a hyperphosphorylated isoform containing exons 2 and 10 but lacking exon 3.

Corticobasal degeneration with olivopontocerebellar atrophy and TDP-43 pathology: an unusual clinicopathologic variant of CBD

Corticobasal degeneration (CBD) is a disorder affecting cognition and movement due to a progressive neurodegeneration associated with distinctive neuropathologic features, including abnormal phosphorylated tau protein in neurons and glia in cortex, basal ganglia, diencephalon, and brainstem, as well as ballooned neurons and astrocytic plaques. We identified three cases of CBD with olivopontocerebellar atrophy (CBD-OPCA) that did not have α-synuclein-positive glial cytoplasmic inclusions of multiple system atrophy (MSA). Two patients had clinical features suggestive of progressive supranuclear palsy (PSP), and the third case had cerebellar ataxia thought to be due to idiopathic OPCA. Neuropathologic features of CBD-OPCA are compared to typical CBD, as well as MSA and PSP. CBD-OPCA and MSA had marked neuronal loss in pontine nuclei, inferior olivary nucleus, and Purkinje cell layer. Neuronal loss and grumose degeneration in the cerebellar dentate nucleus were comparable in CBD-OPCA and PSP. Image analysis of tau pathology showed greater infratentorial tau burden, especially in pontine base, in CBD-OPCA compared with typical CBD. In addition, CBD-OPCA had TDP-43 immunoreactive neuronal and glial cytoplasmic inclusions and threads throughout the basal ganglia and in olivopontocerebellar system. CBD-OPCA met neuropathologic research diagnostic criteria for CBD and shared tau biochemical characteristics with typical CBD. These results suggest that CBD-OPCA is a distinct clinicopathologic variant of CBD with olivopontocerebellar TDP-43 pathology.

Tau pathology in frontotemporal lobar degeneration with C9ORF72 hexanucleotide repeat expansion

An expanded GGGGCC hexanucleotide repeat in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal lobar degeneration associated with TDP-43 pathology (FTLD-TDP). In addition to TDP-43-positive neuronal and glial inclusions, C9ORF72-linked FTLD-TDP has characteristic TDP-43-negative neuronal cytoplasmic and intranuclear inclusions as well as dystrophic neurites in the hippocampus and cerebellum. These lesions are immunopositive for ubiquitin and ubiquitin-binding proteins, such as sequestosome-1/p62 and ubiquilin-2. Studies examining the frequency of the C9ORF72 mutation in clinically probable Alzheimer's disease (AD) have found a small proportion of AD cases with the mutation. This prompted us to systematically explore the frequency of Alzheimer-type pathology in a series of 17 FTLD-TDP cases with mutations in C9ORF72 (FTLD-C9ORF72). We identified four cases with sufficient Alzheimer-type pathology to meet criteria for intermediate-to-high-likelihood AD. We compared AD pathology in the 17 FTLD-C9ORF72 to 13 cases of FTLD-TDP linked to mutations in the gene for progranulin (FTLD-GRN) and 36 cases of sporadic FTLD (sFTLD). FTLD-C9ORF72 cases had higher Braak neurofibrillary tangle stage than FTLD-GRN. Increased tau pathology in FTLD-C9ORF72 was assessed with thioflavin-S fluorescent microscopy-based neurofibrillary tangle counts and with image analysis of tau burden in temporal cortex and hippocampus. FTLD-C9ORF72 had significantly more neurofibrillary tangles and higher tau burden compared with FTLD-GRN. The differences were most marked in limbic regions. On the other hand, sFTLD and FTLD-C9ORF72 had a similar burden of tau pathology. These results suggest FTLD-C9ORF72 has increased propensity for tau pathology compared to FTLD-GRN, but not sFTLD. The accumulation of tau as well as lesions immunoreactive for ubiquitin and ubiquitin-binding proteins (p62 and ubiquilin-2) suggests that mutations in C9ORF72 may involve disrupted protein degradation that favors accumulation of multiple different proteins.

Vascular dementia: different forms of vessel disorders contribute to the development of dementia in the elderly brain

The diagnosis of vascular dementia (VaD) describes a group of various vessel disorders with different types of vascular lesions that finally contribute to the development of dementia. Most common forms of VaD in the elderly brain are subcortical vascular encephalopathy, strategic infarct dementia, and the multi infarct encephalopathy. Hereditary forms of VaD are rare. Most common is the cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). Sporadic forms of VaD are caused by degenerative vessel disorders such as atherosclerosis, small vessel disease (SVD) including small vessel arteriosclerosis, arteriolosclerosis, and lipohyalinosis, and cerebral amyloid angiopathy (CAA). Less frequently inflammatory vessel disorders and tumor-associated vessel lesions (e.g. angiocentric T-cell or angiotropic large cell lymphoma) can cause symptoms of dementia. Here, we review and discuss the impact of vessel disorders to distinct vascular brain tissue lesions and to the development of dementia in elderly individuals. The impact of coexisting neurodegenerative pathology in the elderly brain to VaD as well as the correlation between SVD and CAA expansion in the brain parenchyma with that of Alzheimer's disease (AD)-related pathology is highlighted. We conclude that "pure" VaD is rare and most frequently caused by infarctions. However, there is a significant contribution of vascular lesions and vessel pathology to the development of dementia that may go beyond tissue damage due to vascular lesions. Insufficient blood blow and alterations of the perivascular drainage mechanisms of the brain may also lead to a reduced protein clearance from extracellular space and subsequent increase of proteins in the brain parenchyma, such as the amyloid β-protein, and foster, thereby, the development of AD-related neurodegeneration. As such, it seems to be important for clinical practice to consider treatment of potentially coexisting AD pathology in cognitively impaired patients with vascular lesions.

Co-occurrence of argyrophilic grain disease in sporadic amyotrophic lateral sclerosis

AIMS

Phosphorylated TDP-43 (pTDP-43) is the pathological protein responsible for amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease. Recently, it has been reported that accumulation of pTDP-43 can occur in the brains of patients with argyrophilic grain disease (AGD), in which phosphorylated 4-repeat tau is the pathological protein. To elucidate the association of ALS with AGD, we examined the brains from 37 consecutively autopsied patients with sporadic ALS (age range 45-84 years, mean 71.5 ± 9.0 years).

METHODS

Sections from the frontotemporal lobe were stained with the Gallyas-Braak method and also immunostained with antibodies against phosphorylated tau, 4-repeat tau and pTDP-43.

RESULTS

Fourteen (38%) of the 37 ALS patients were found to have AGD. With regard to staging, 5 of these 14 cases were rated as I, 4 as II and 5 as III. pTDP-43 immunohistochemistry revealed the presence of positive neuronal and glial cytoplasmic inclusions in the affected medial temporal lobe in many cases (93% and 64%, respectively). On the other hand, pTDP-43-positive small structures corresponding to argyrophilic grains were observed only in one case. A significant correlation was found between AGD and the Braak stage for neurofibrillary pathology (stage range 0-V, mean 2.1). However, there were no significant correlations between AGD and any other clinicopathological features, including dementia.

CONCLUSIONS

The present findings suggest that co-occurrence of AGD in ALS is not uncommon, and in fact comparable with that in a number of diseases belonging to the tauopathies or α-synucleinopathies.

Neuropathological features of corticobasal degeneration presenting as corticobasal syndrome or Richardson syndrome

Patients with corticobasal degeneration can present with several different clinical syndromes, making ante-mortem diagnosis a challenge. Corticobasal syndrome is the clinical phenotype originally described for corticobasal degeneration, characterized by asymmetric rigidity and apraxia, cortical sensory deficits, dystonia and myoclonus. Some patients do not develop these features, but instead have clinical features consistent with the Richardson syndrome presentation of progressive supranuclear palsy, characterized by postural instability, early unexplained falls, vertical supranuclear gaze palsy, symmetric motor disability and dysphagia. The aim of this study was to identify differences in corticobasal degeneration presenting with corticobasal syndrome (n = 11) or Richardson syndrome (n = 15) with respect to demographic, clinical and neuropathological features. Corticobasal degeneration cases were also compared with patients with pathologically proven progressive supranuclear palsy with Richardson syndrome (n = 15). Cases with corticobasal degeneration, regardless of presentation, shared histopathological and tau biochemical characteristics, but they had differing densities of tau pathology in neuroanatomical regions that correlated with their clinical presentation. In particular, those with corticobasal syndrome had greater tau pathology in the primary motor and somatosensory cortices and putamen, while those with Richardson syndrome had greater tau pathology in limbic and hindbrain structures. Compared with progressive supranuclear palsy, patients with corticobasal degeneration and Richardson syndrome had less neuronal loss in the subthalamic nucleus, but more severe neuronal loss in the medial substantia nigra and greater atrophy of the anterior corpus callosum. Clinically, they had more cognitive impairment and frontal behavioural dysfunction. The results suggest that Richardson syndrome can be a clinicopathological presentation of corticobasal degeneration. Atrophy of anterior corpus callosum may be a potential neuroimaging marker to differentiate corticobasal degeneration from progressive supranuclear palsy in patients with Richardson syndrome.

Neuropathological findings of PSP in the elderly without clinical PSP: possible incidental PSP?

AIMS

We aimed to describe cases with incidental neuropathological findings of progressive supranuclear palsy (PSP) from the Banner Sun Health Research Institute Brain and Body Donation Program.

METHODS

We performed a retrospective review of 277 subjects with longitudinal motor and neuropsychological assessments who came to autopsy. The mean Gallyas-positive PSP features grading for subjects with possible incidental neuropathological PSP was compared to those of subjects with clinically manifest disease.

RESULTS

There were 5 cases with histopathological findings suggestive of PSP, but no parkinsonism, dementia or movement disorder during life. Cognitive evaluation revealed 4 of the 5 cases to be cognitively normal; one case had amnestic mild cognitive impairment (MCI) in her last year of life. The mean age at death of the 5 cases was 88.9 years (range 80-94). All 5 individuals had histopathologic microscopic findings suggestive of PSP. Mean Gallyas-positive PSP features grading was significantly lower in subjects with possible incidental neuropathological PSP than subjects with clinical PSP, particularly in the subthalamic nucleus.

CONCLUSIONS

We present 5 patients with histopathological findings suggestive of PSP, without clinical PSP, dementia or parkinsonism during life. These incidental neuropathological PSP findings may represent the early or pre-symptomatic stage of PSP. The mean Gallyas-positive PSP features grading was significantly lower in possible incidental PSP than in clinical PSP, thus suggesting that a threshold of pathological burden needs to be reached within the typically affected areas in PSP before clinical signs and symptoms appear.

Neuropathological asymmetry in argyrophilic grain disease

The presence of argyrophilic grains in the neuropil is associated with a form of dementia. We investigated morphological asymmetry in 653 consecutive autopsy patients from a general geriatric hospital (age [mean +/- SD] = 81.1 +/- 8.9 years), focusing on those from patients with advanced argyrophilic grain disease. Paraffin sections of the bilateral posterior hippocampi were immunostained with anti-phosphorylated tau and anti-4-repeat tau antibodies and by the Gallyas-Braak method. In a side-to-side comparison, asymmetry was defined when either the extent or the density of argyrophilic grains was different. Of the 653 subjects, 65 (10%) had Stage 3 argyrophilic grain disease, and 59 (90.8%) showed histopathological asymmetry. Antemortem computed tomographic images (n = 24), magnetic resonance imaging scans (n = 8), and combined computed tomographic and magnetic resonance images (n = 15) were available; images from 20 of the 47 subjects showed asymmetry that correlated with the histopathological asymmetry. Cerebral cortical asymmetry consistent with the histopathology was also visible in N-isopropyl-123I-p-iodoamphetamine single photon emission computed tomographic images from 6 patients and 18F-labeled fluorodeoxyglucose positron emission tomographic images from 2 patients. Thus, asymmetric involvement of the medial temporal lobe in patients with advanced argyrophilic grain disease may represent a diagnostic feature and contribute to distinguishing dementia with grains from Alzheimer disease.

Argyrophilic grain disease with delusions and hallucinations: a pathological study

No clear clinical syndrome for argyrophilic grain disease (AGD) has yet been identified. Previous studies have documented its clinical features, namely, personality changes characterized by emotional disorder involving aggression or ill temper and relatively well-preserved cognitive function, but the clinical manifestations of delusions and hallucinations as they appear in AGD have not been thoroughly described. Here, we report on a 72-year-old Japanese AGD patient who showed psychiatric symptoms, memory impairment and emotional change. He perceived and described a person who was not present and tried to grasp things on the floor though nothing was there. He also insisted that somebody was watching him and consequently always kept his curtains closed. These psychiatric symptoms were observed at an early stage in the patient's disease course. Serial neuroradiological examination showed progressive atrophy of the bilateral temporal lobes. The patient died at 79 years-of-age. Microscopic neuropathological examination showed transactivation responsive region (TAR)-DNA-binding protein of 43 kDa (TDP-43) positive structures in addition to widespread argyrophilic grains and coiled bodies. According to recent recommendations for pathological diagnosis, this case corresponds to AGD with limbic TDP-43 pathology. This case shows that patients with AGD that is eventually confirmed through autopsy can present with delusions and hallucinations early in the course of their disease. The clinical significance of TDP-43 pathology in the brains of patients with AGD remains uncertain.

Correlation of clinical features with argyrophilic grains at autopsy

Argyrophilic grains (AGs) are a pathologic feature found in association with neurodegenerative disease. Some have suggested that these features may occur as a distinctive condition. We reviewed 80 subjects from our tissue bank with pathologically confirmed AGs and identified their clinical features. We compared these subjects' features to the features of subjects with matched clinical diagnoses but without AGs. Subjects with AGs represented 21.7% of the entire autopsy sample from 1999 to 2005 (80 out of 367). Of Alzheimer disease (AD) subjects, 43 out of 233 had AGs (18.4% of AD subjects); 11 out of 42 Parkinson disease with dementia subjects had AGs (26.1% of Parkinson disease with dementia subjects); 2 out of 9 dementia with Lewy bodies subjects had AGs (22.2% of dementia with Lewy bodies subjects); 4 out of 15 mild cognitive impairment subjects had AGs (26.7% of mild cognitive impairment subjects); and 20 out of 68 cognitively normal subjects had AGs (29.4% of cognitively normal). Subjects with AGs tended to be older but only significantly so in AD. Many comorbid non-neurologic health conditions were seen in cases of AGs without any single predilection emerging. AGs occur in approximately 22% of the entire autopsy cohort and are likely associated with advanced age. No distinctive antemortem clinical features were over represented in the AG cases. AGs can occur with or without neurodegenerative conditions and can occur in the absence of significant cognitive decline. AGs are not clearly associated with any single comorbid health condition.

Mild cognitive impairment associated with limbic and neocortical Lewy body disease: a clinicopathological study

There are little data on the relationship between Lewy body disease and mild cognitive impairment syndromes. The Mayo Clinic aging and dementia databases in Rochester, Minnesota, and Jacksonville, Florida were queried for cases who were diagnosed with mild cognitive impairment between 1 January 1996 and 30 April 2008, were prospectively followed and were subsequently found to have autopsy-proven Lewy body disease. The presence of rapid eye movement sleep behaviour disorder was specifically assessed. Mild cognitive impairment subtypes were determined by clinical impression and neuropsychological profiles, based on prospective operational criteria. The diagnosis of clinically probable dementia with Lewy bodies was based on the 2005 McKeith criteria. Hippocampal volumes, rate of hippocampal atrophy, and proton magnetic resonance spectroscopy were assessed on available magnetic resonance imaging and spectroscopy scans. Eight subjects were identified; six were male. Seven developed dementia with Lewy bodies prior to death; one died characterized as mild cognitive impairment. The number of cases and median age of onset (range) for specific features were: seven with rapid eye movement sleep behaviour disorder-60 years (27-91 years), eight with cognitive symptoms-69 years (62-89 years), eight with mild cognitive impairment-70.5 years (66-91 years), eight with parkinsonism symptoms-71 years (66-92 years), six with visual hallucinations-72 years (64-90 years), seven with dementia-75 years (67-92 years), six with fluctuations in cognition and/or arousal-76 years (68-92 years) and eight dead-76 years (71-94 years). Rapid eye movement sleep behaviour disorder preceded cognitive symptom onset in six cases by a median of 10 years (2-47 years) and mild cognitive impairment diagnosis by a median of 12 years (3-48 years). The mild cognitive impairment subtypes represented include: two with single domain non-amnestic mild cognitive impairment, three with multi-domain non-amnestic mild cognitive impairment, and three with multi-domain amnestic mild cognitive impairment. The cognitive domains most frequently affected were attention and executive functioning, and visuospatial functioning. Hippocampal volumes and the rate of hippocampal atrophy were, on average, within the normal range in the three cases who underwent magnetic resonance imaging, and the choline/creatine ratio was elevated in the two cases who underwent proton magnetic resonance spectroscopy when they were diagnosed as mild cognitive impairment. On autopsy, six had neocortical-predominant Lewy body disease and two had limbic-predominant Lewy body disease; only one had coexisting high-likelihood Alzheimer's disease. These findings indicate that among Lewy body disease cases that pass through a mild cognitive impairment stage, any cognitive pattern or mild cognitive subtype is possible, with the attention/executive and visuospatial domains most frequently impaired. Hippocampal volume and proton magnetic resonance spectroscopy data were consistent with recent data in dementia with Lewy bodies. All cases with rapid eye movement sleep behaviour disorder and mild cognitive impairment were eventually shown to have autopsy-proven Lewy body disease, indicating that rapid eye movement sleep behaviour disorder plus mild cognitive impairment probably reflects brainstem and cerebral Lewy body disease.

Evaluation of subcortical pathology and clinical correlations in FTLD-U subtypes

Frontotemporal lobar degeneration (FTLD) can be classified as tau-positive (FTLD-tau) and tau-negative FTLD. The most common form of tau-negative FTLD is associated with neuronal inclusions that are composed of TAR DNA-binding protein 43 (TDP-43) (FTLD-TDP). Recent evidence suggests that FTLD-TDP can be further subdivided into at least three major histologic variants based on patterns of TDP-43 immunoreactive neuronal cytoplasmic inclusions (NCI) and dystrophic neurites (DN) in neocortex and hippocampus. The aim of this study was to extend the histologic analysis to other brain regions and to determine if there were distinct clinical and pathologic characteristics of the FTLD-TDP subtypes. Thirty-nine FTLD-TDP cases were analyzed (Mackenzie type 1 n = 24, Mackenzie type 2 n = 9, Mackenzie type 3 n = 6). There was a highly significant association between clinical syndrome and FTLD-TDP subtype, with progressive non-fluent aphasia associated with type 1, semantic dementia with type 2, and behavioral variant frontotemporal dementia with types 1, 2 and 3. Semi-quantitative analysis of NCI and DN demonstrated different patterns of involvement in cortical, subcortical and brainstem areas that were characteristic for each of the three types of FTLD-TDP. Type 1 had a mixture of NCI and DN, as well as intranuclear inclusions in most cases and TDP-43 pathology at all levels of the neuraxis, but less in brainstem than supratentorial structures. Type 2 cases were characterized by predominance of long, thick DN in the cortex, as well as numerous NCI in hippocampus, amygdala and basal ganglia, but virtually no NCI and only sparse DN in diencephalon and brainstem. Type 3 had a paucity of DN at all levels of the neuraxis and significantly more NCI in the hypoglossal nucleus than the other types. These findings extend previously described clinicopathological associations of FTLD-TDP subtypes and support the notion that FTLD-TDP subtypes may be distinct clinicopathologic disorders.

Neuropathology of non-Alzheimer degenerative disorders

Neurodegenerative diseases are characterized by selective and progressive loss of specific populations of neurons, which determines the clinical presentation. The same neuronal populations can be affected in a number of different disorders. Given that the clinical presentation reflects the particular population of neurons that are targets of the disease process, it is clear that for any given clinical syndrome, more than one neurodegenerative disease can account for the clinical syndrome. Because of this clinical ambiguity, for the purpose of this brief review neurodegenerative disorders are classified according to the underlying molecular pathology rather than their clinical presentation. The major neurodegenerative diseases can be classified into amyloidoses, tauopathies, alpha-synucleinopathies and TDP-43 proteinopathies.

Argyrophilic grain disease: an update about a frequent cause of dementia

Argyrophilic grain disease (AGD) is a sporadic, very late-onset tauopathy, accounting for approximately 4–13% of neurodegenerative dementias. AGD may manifest with a range of symptoms such as cognitive decline and behavioral abnormalities. To date, no study has been able to demonstrate a distinct clinical syndrome associated with AGD. The diagnosis is exclusively based on postmortem findings, the significance of which remains controversial because up to 30% of AGD cases are diagnosed in subjects without any cognitive impairment, while AGD findings often overlap with those of other neurodegenerative processes. Nevertheless, the presence of AGD is likely to have a significant effect on cognitive decline. The neuropathological hallmarks of AGD are argyrophilic grains, pre-neurofibrillary tangles in neurons and coiled bodies in oligodendrocytes found mainly in the entorhinal cortex and hippocampus. This review aims to provide an up-to-date overview of AGD, emphasizing pathological aspects. Additionally, the findings of a Brazilian case series are described.

Accumulation of phosphorylated TDP-43 in brains of patients with argyrophilic grain disease

To determine whether TAR-DNA binding protein 43 (TDP-43) immunoreactivity was present in brains of argyrophilic grain disease (AGD), we immunohistochemically examined 15 cases of AGD (mean age at death: 84 years) using a panel of anti-TDP-43 antibodies, including both phosphorylation-independent and -dependent ones. Nine AGD cases (60%) showed TDP-43 immunoreactivities mainly in the limbic regions and lateral occipitotemporal cortex. TDP-43 positive structures included neuronal cytoplasmic inclusions, dystrophic neurites, glial cytoplasmic inclusions, grain-like dot-shaped structures, and neurofibrillary tangle (NFT)-like structures. The distribution of these TDP-43 positive structures was largely consistent with that of argyrophilic grains. Double-labeling confocal microscopy revealed, however, that many of phospho-TDP-43 positive structures were not colocalized with phospho-tau staining. Colocalization of phospho-TDP-43 and phospho-tau was observed only in part of neuronal cytoplasmic inclusions, grain-like structures and NFT-like structures. There were no differences in demographics, disease duration, brain weight, NFT Braak stage, or severity of amyloid burden between AGD cases with and without TDP-43-immunoreactivity. However, cases of AGD with TDP-43-immunoreactivity were assigned to higher AGD stages than those without TDP-43-immunoreactivity (P < 0.05). Furthermore, the TDP-43 pathology tended to be prominent in cases with severe grain pathology. The results of the present study indicate for the first time a high frequency of concomitant TDP-43 pathology in AGD, and suggest that abnormal accumulation of TDP-43 may be involved in the pathological process and disease progression of AGD.

Cortical Alzheimer type pathology does not influence tau pathology in progressive supranuclear palsy

Alzheimer disease (AD) is characterized by numerous senile plaques (SP) in addition to widespread neocortical neurofibrillary tangles (NFT). Some elderly have pathologic aging (PA), which is characterized by numerous SP composed of diffuse amyloid deposits with few or no NFT confined to the limbic lobe. Both AD and PA represent a range of Alzheimer type pathology (ATP). Some cases of progressive supranuclear palsy (PSP) have concurrent ATP, but the relationship between ATP and PSP has not been addressed. In this study, a consecutive series of PSP cases were divided into three groups according to the degree of concurrent ATP - pure PSP, PSP/PA and PSP/AD. Braak NFT stage was significantly greater in PSP/AD compared with both PSP/PA and PSP. Among the pathologic variables studied in middle frontal, superior temporal and motor cortices, there were no differences between PSP and PSP/PA except for SP. In PSP/AD, there was greater neuronal tau pathology (pretangles, NFT and neuropil threads) in middle frontal and superior temporal cortices, probably a reflection of ATP since there was no comparable increase in PSP-related glial tau pathology in these regions. The APOEvarepsilon4 allele frequency was significantly higher in PSP/PA and PSP/AD than in PSP. These results strongly argue that ATP in PSP represents independent disease processes even when present in the same brain.

Validation of the neuropathologic criteria of the third consortium for dementia with Lewy bodies for prospectively diagnosed cases

There is limited information on the validity of the pathologic criteria of the Third Consortium on Dementia with Lewy bodies (CDLB), and none are based on prospectively diagnosed cases. In this study, the core clinical features of dementia with Lewy bodies (DLB) and the suggestive clinical feature of rapid eye movement sleep behavior disorder were assessed using a battery of standardized clinical instruments in 76 patients with the clinical diagnosis of either DLB or Alzheimer disease. At autopsy, 29 patients had high-likelihood, 17 had intermediate-likelihood, and 6 had low-likelihood DLB pathology. The frequency of core clinical features and the accuracy of the clinical diagnosis of probable DLB were significantly greater in high-likelihood than in low-likelihood cases. This is consistent with the concept that the DLB clinical syndrome is directly related to Lewy body pathology and inversely related to Alzheimer pathology. Thus, the Third Consortium on DLB neuropathologic criteria scheme performed reasonably well and are useful for estimating the likelihood of the premortem DLB syndrome based on postmortem findings. In view of differences in the frequency of clinically probable DLB in cases with Braak neurofibrillary tangle stages V (90%) and VI (20%) and diffuse cortical Lewy bodies, a possible modification of the scheme is to consider cases with neurofibrillary tangle stage VI to be low-likelihood DLB.

Glial cytoplasmic inclusions in neurologically normal elderly: prodromal multiple system atrophy?

In this study, we used immunohistochemistry to screen for alpha-synuclein pathology in the brains of 241 individuals without clinical evidence of neurologic disease, and discovered 36 cases (15%) with incidental Lewy bodies (LBs) and one case, a 96-year-old woman (0.4%), with inclusions similar to those seen in multiple system atrophy (MSA), a non-familial neurodegenerative disorder characterized by parkinsonism, cerebellar ataxia and autonomic dysfunction and alpha-synuclein immunoreactive glial cytoplasmic inclusions (GCI). In a routine hospital autopsy series of 125 brains, we detected GCI in a neurologically normal 82-year-old man (0.8%). Both cases showed widespread GCI in the central nervous system, as well as a few neuronal cytoplasmic inclusions, but no neuronal loss or gliosis in vulnerable brain regions, including the substantia nigra, putamen, inferior olive and pontine base. Applying a recently proposed grading scale for MSA, the two cases showed pathology far below that detected in patients with clinically overt MSA, suggesting the possibility that these two individuals had preclinical MSA. The prevalence of clinically overt MSA is estimated to be about 4 per 100,000 persons (0.004%), which is far less than the frequency of GCI in this series (0.4-0.8%). Further studies are needed to determine if GCI in neurologically normal elderly represents prodromal MSA or a rare non-progressive age-related alpha-synucleinopathy.

Clinical, neuropathological and genotypic variability in SNCA A53T familial Parkinson's disease. Variability in familial Parkinson's disease

Individuals with familial Parkinson's disease (PD) due to a monogenic defect can show considerable clinical and neuropathological variability. To identify factors underlying this variability, histopathological analysis was performed in two clinically different A53T alpha-synuclein heterozygotes from Family H, a multigenerational alpha-synuclein A53T kindred. To determine whether additional genetic factors could contribute to phenotypic variability, Family H and another multigenerational A53T kindred were analyzed for parkin polymorphisms. We identified a previously described variant in parkin exon 4 associated with increased PD risk (S167N). The two A53T heterozygotes had markedly different neuropathology and different parkin genotypes: A N167 homozygote had early onset rapidly progressive disease, early dementia, myoclonus and sleep disorder, while a S167 homozygote had late onset, slowly progressive disease and late dementia. Both had brainstem, cortical, and intraneuritic Lewy bodies (LB). The N167 individual had widespread cortical neurofibrillary degeneration, while the S167 individual had only medial temporal lobe neurofibrillary degeneration. The N167 individual had severe neuronal loss in CA2 associated with Lewy neurites (LN), while the S167 individual had severe neuronal loss in CA1 associated with TDP-43 immunoreactive neuronal inclusions. These findings implicate TDP-43 in the pathology of familial PD and suggest that parkin may act as a modifier of the A53T alpha-synuclein phenotype of familial PD. Furthermore, they suggest a mechanism by which a rare genetic variant that is associated with a minor increase of PD risk in the heterozygous state may, in the homozygous state, exacerbate a disease phenotype associated with a highly penetrant dominant allele.

Co-localization of tau and alpha-synuclein in the olfactory bulb in Alzheimer's disease with amygdala Lewy bodies

We recently reported that Alzheimer's disease (AD) with amygdala Lewy bodies (ALB) is a distinct form of alpha-synucleinopathy that occurs in advanced AD. In AD/ALB the alpha-synuclein pathology correlated with tau pathology, but not amyloid plaques, and there was often co-localization of tau and alpha-synuclein in the same neuron. Given the anatomical connectivity of the anterior olfactory nucleus and the amygdala, which receives axonal projections from the olfactory bulb, we hypothesized that there might be a relationship between tau and alpha-synuclein pathology in the olfactory bulb and the amygdala in AD. We screened for alpha-synuclein pathology in the olfactory bulb in AD with and without ALB, and investigated its relationship with tau pathology. In 38 of 41 (93%) AD/ALB cases and 4 of 21 (19%) AD cases without ALB (AD/non-ALB), alpha-synuclein pathology was detected in the olfactory bulb. Double immunolabeling at the light and electron microscopic levels revealed co-localization of tau and alpha-synuclein in the olfactory bulb neurons and neurites. The severity of tau pathology correlated with alpha-synuclein pathology in the olfactory bulb. In addition, alpha-synuclein pathology in the olfactory bulb correlated with alpha-synuclein pathology in amygdala. Tau pathology was greater in both the olfactory bulb and amygdala in AD/ALB than in AD/non-ALB, but there was no difference in tau pathology between the two groups in other brain regions assessed. The present study shows that in AD/ALB, the olfactory bulb is nearly equally vulnerable to tau and alpha-synuclein pathology as the amygdala and suggests that neurodegeneration in these two anatomical regions is linked.

Coexistence of amyotrophic lateral sclerosis and argyrophilic grain disease: a non-demented autopsy case showing circumscribed temporal atrophy and involvement of the amygdala

We report a case of a 68-year-old right-handed man with sporadic amyotrophic lateral sclerosis (ALS) and argyrophilic grain disease (AGD) having a 22-month duration. His initial symptoms were dysarthria and swallowing difficulty at the age of 67. Subsequently bulbar palsy and pyramidal signs developed. His cognitive functions including face recognition, personality, and behavior were not changed compared with that of before the disease onset. However, magnetic resonance imaging disclosed severe right side-predominant temporal atrophy. The neurological diagnosis was bulbar type ALS. Pathological examination disclosed histological evidence of ALS, including loss of Betz cells and lower motor neurons, corticospinal tract degeneration, and Bunina bodies. In addition, severe neuronal loss in the bilateral temporal cortex with an anterior gradient was found. Ubiquitin-positive inclusions were encountered in the spinal anterior horn cells and hippocampal dentate gyrus, while few ubiquitin-positive inclusions were noted in the affected temporal cortex. The amygdala, especially the basolateral nuclear group, was severely affected by neuronal loss with tissue rarefaction. Moderate neuronal loss was encountered in the parahippocampal gyrus, and to a lesser degree, in the ambient gyrus. Unexpectedly, many argyrophilic grains, coiled bodies, tau-positive bush-like astrocytes, pretangles, and ballooned neurons were found in the limbic system and temporal cortex. In the hippocampus, selective tau accumulation with minor neurofibrillary changes was observed in CA2 neurons. The present case suggests that (i) ALS and AGD do rarely coexist, and (ii) when ALS patients have severe temporal atrophy, not only ALS with dementia but also concurrent AGD should be considered in the differential diagnosis.