Severe involvement of the ambient gyrus in a case of dementia with argyrophilic grain disease

Pure argyrophilic grain disease revisited: independent effects on limbic, neocortical, and striato-pallido-nigral degeneration and the development of dementia in a series with a low to moderate Braak stage

Agyrophilic grains (AGs) are age-related limbic-predominant lesions in which four-repeat tau is selectively accumulated. Because previous methodologically heterogeneous studies have demonstrated inconsistent findings on the relationship between AGs and dementia, whether AGs affect cognitive function remains unclear. To address this question, we first comprehensively evaluated the distribution and quantity of Gallyas-positive AGs and the severity of neuronal loss in the limbic, neocortical, and subcortical regions in 30 cases of pure argyrophilic grain disease (pAGD) in Braak stages I-IV and without other degenerative diseases, and 34 control cases that had only neurofibrillary tangles with Braak stages I-IV and no or minimal Aβ deposits. Then, we examined whether AGs have independent effects on neuronal loss and dementia by employing multivariate ordered logistic regression and binomial logistic regression. Of 30 pAGD cases, three were classified in diffuse form pAGD, which had evident neuronal loss not only in the limbic region but also in the neocortex and subcortical nuclei. In all 30 pAGD cases, neuronal loss developed first in the amygdala, followed by temporo-frontal cortex, hippocampal CA1, substantia nigra, and finally, the striatum and globus pallidus with the progression of Saito AG stage. In multivariate analyses of 30 pAGD and 34 control cases, the Saito AG stage affected neuronal loss in the amygdala, hippocampal CA1, temporo-frontal cortex, striatum, globus pallidus, and substantia nigra independent of the age, Braak stage, and limbic-predominant age-related TDP-43 encephalopathy (LATE-NC) stage. In multivariate analyses of 23 pAGD and 28 control cases that lacked two or more lacunae and/or one or more large infarctions, 100 or more AGs per × 400 visual field in the amygdala (OR 10.02, 95% CI 1.12-89.43) and hippocampal CA1 (OR 12.22, 95% CI 1.70-87.81), and the presence of AGs in the inferior temporal cortex (OR 8.18, 95% CI 1.03-65.13) affected dementia independent of age, moderate Braak stages (III-IV), and LATE-NC. Given these findings, the high density of limbic AGs and the increase of AGs in the inferior temporal gyrus may contribute to the occurrence of dementia through neuronal loss, at least in cases in a low to moderate Braak stage.

Different cohort, disparate results: Selection bias is a key factor in autopsy cohorts

INTRODUCTION

Research-oriented autopsy cohorts provide critical insights into dementia pathobiology. However, different studies sometimes report disparate findings, partially because each study has its own recruitment biases. We hypothesized that a straightforward metric, related to the percentage of research volunteers cognitively normal at recruitment, would predict other inter-cohort differences.

METHODS

The National Alzheimer's Coordinating Center (NACC) provided data on N = 7178 autopsied participants from 28 individual research centers. Research cohorts were grouped based on the proportion of participants with normal cognition at initial clinical visit.

RESULTS

Cohorts with more participants who were cognitively normal at recruitment contained more individuals who were older, female, had lower frequencies of apolipoprotein E ε4, Lewy body disease, and frontotemporal dementia, but higher rates of cerebrovascular disease. Alzheimer's disease (AD) pathology was little different between groups.

DISCUSSION

The percentage of participants recruited while cognitively normal predicted differences in findings in autopsy research cohorts. Most differences were in non-AD pathologies.

HIGHLIGHTS

Systematic differences exist between autopsy cohorts that serve dementia research. We propose a metric to use for gauging a research-oriented autopsy cohort. It is essential to consider the characteristics of autopsy cohorts.

Voxel-Based and Surface-Based Morphometry Analysis in Patients with Pathologically Confirmed Argyrophilic Grain Disease and Alzheimer’s Disease

Background: Due to clinicoradiological similarities, including amnestic cognitive impairment and limbic atrophy, differentiation of argyrophilic grain disease (AGD) from Alzheimer’s disease (AD) is often challenging. Minimally invasive biomarkers, especially magnetic resonance imaging (MRI), are valuable in routine clinical practice. Although it is necessary to explore radiological clues, morphometry analyses using new automated analytical methods, including whole-brain voxel-based morphometry (VBM) and surface-based morphometry (SBM), have not been sufficiently investigated in patients with pathologically confirmed AGD and AD. Objective: This study aimed to determine the volumetric differences in VBM and SBM analyses between patients with pathologically confirmed AGD and AD. Methods: Eight patients with pathologically confirmed AGD with a lower Braak neurofibrillary tangle stage (<III), 11 patients with pathologically confirmed AD without comorbid AGD, and 10 healthy controls (HC) were investigated. Gray matter volumetric changes in VBM and cortical thickness changes in SBM were compared between the two patient groups (i.e., AGD and AD) and the HC group. Results: In contrast to widespread gray matter volume or cortical thickness loss in the bilateral limbic, temporoparietal, and frontal lobes of the AD group, these were limited, especially in the limbic lobes, in the AGD group, compared with that of the HC group. Although bilateral posterior dominant gray matter volume loss was identified in the AD group compared with the AGD group on VBM, there was no significant cluster between these patient groups on SBM. Conclusion: VBM and SBM analyses both showed a different distribution of atrophic changes between AGD and AD.

Macroscopic findings of brain with dementia

In this paper, we have described the points to be noted when examining the macroscopic findings of the brain of patients with dementia. The characteristics of the macroscopic findings of the brain of patients with dementia are shown in the figure of the outer surface and the cut surface. Gross findings in the brain of patients with Alzheimer's disease should consider, in addition to the degree of limbic changes, whether the atrophy is diffuse, the degree of ventricular enlargement, and the complications of vascular changes. The macroscopic findings of the brain of patients with dementia with Lewy bodies are characterized by the absence of notable abnormal findings other than the depigmentation of the substantia nigra and locus coeruleus. In dementia with Lewy bodies, other types of dementia complications should be considered if abnormal findings are present. It should be noted that accurate diagnosis of argyrophilic grain dementia and senile dementia of neurofibrillary tangle type by macroscopic findings alone is often difficult to distinguish from a mild case of Alzheimer's disease and change by physiological aging in particular. In frontotemporal lobar degeneration, changes in the basal ganglia, brain stem, cerebellum and motor neurons should be observed to make a differential diagnosis of various types of frontotemporal lobar degeneration. It is important to understand the areas that are often damaged in different types of dementia and the extent of lesions, and to distinguish each type of dementia. Care should be taken as macroscopic findings are more complex when several types of dementia are mixed. It was shown that accurate understanding of macroscopic findings is essential for understanding clinical symptoms, imaging findings, differential diagnosis of dementia and disease pathogenesis.

A biomarker study in long-lasting amnestic mild cognitive impairment

Background

Mild cognitive impairment (MCI) is a heterogeneous syndrome resulting from Alzheimer’s disease (AD) as well as to non-AD and non-neurodegenerative conditions. A subset of patients with amnestic MCI (aMCI) present with an unusually long-lasting course, a slow rate of clinical neuropsychological progression, and evidence of focal involvement of medial temporal lobe structures. In the present study, we explored positron emission tomography (PET) and cerebrospinal fluid (CSF) biomarkers in a sample of subjects with aMCI with such clinical features in order to provide in vivo evidence to improve disease characterisation in this subgroup.

Methods

Thirty consecutive subjects with aMCI who had long-lasting memory impairment (more than 4 years from symptom onset) and a very slow rate of cognitive progression were included. All subjects underwent fluorodeoxyglucose-positron emission tomography (FDG-PET) metabolic imaging. A measure of cerebral amyloid load, by PET and/or CSF, was obtained in 26 of 30 subjects. The mean clinical follow-up was 58.3 ± 10.1 months.

Results

No patient progressed to dementia during the follow-up. The typical AD FDG-PET pattern of temporoparietal hypometabolism was not present in any of the subjects. In contrast, a selective medial temporal lobe hypometabolism was present in all subjects, with an extension to frontolimbic regions in some subjects. PET imaging showed absent or low amyloid load in the majority of samples. The values were well below those reported in prodromal AD, and they were slightly elevated in only two subjects, consistent with the CSF β-amyloid (1–42) protein values. Notably, no amyloid load was present in the hippocampal structures.

Conclusions

FDG-PET and amyloid-PET together with CSF findings questioned AD pathology as a unique neuropathological substrate in this aMCI subgroup with long-lasting disease course. The possibility of alternative pathological conditions, such as argyrophilic grain disease, primary age-related tauopathy or age-related TDP-43 proteinopathy, known to spread throughout the medial temporal lobe and limbic system structures should be considered in these patients with MCI.

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.

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.

Modeling the association between 43 different clinical and pathological variables and the severity of cognitive impairment in a large autopsy cohort of elderly persons

We evaluated the association between mini-mental status examination (MMSE) scores proximal to death and the values of 43 different clinical and pathological parameters. Studies were performed using data from 334 elderly, longitudinally evaluated research subjects who had undergone autopsy and satisfied inclusion criteria from an initial study group of 501. Interindividual variance in MMSE scores was used as a surrogate for the severity of cognitive impairment linked to aging (CILA). A statistical linear regression-based model provided a framework for assessing the parameters with significant, direct impact on CILA severity. Strong association between CILA and Alzheimer's disease (AD) pathology, especially isocortical neurofibrillary tangles, was evident. The pattern of association between AD lesion densities with cognitive impairment severity was biologically informative, with neuritic plaques having more impact in relatively high-functioning individuals. Abundant isocortical Lewy bodies tended to be an additive pathology correlating with final MMSE scores approximately 10 points lower. In a subset of cases we found evidence for association between TDP-43-related pathology and CILA severity, independent of AD or hippocampal sclerosis. There was no support for independent association between CILA severity and most evaluated indices including diffuse plaques, argyrophilic grains, heart disease, education level, apolipoprotein E alleles or diabetes.

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.

Quantitative MR imaging in Alzheimer disease

Alzheimer disease (AD) is the most common type of dementia. It currently affects approximately 4 million people in the United States. AD is a progressive neurodegenerative disorder characterized by the gradual deposition of neuritic plaques and neurofibrillary tangles in the brain, which is thought to occur decades before the onset of clinical symptoms. Identification of people at risk before the clinical appearance of dementia has become a priority due to the potential benefits of therapeutic intervention. Although atrophy of medial temporal lobe structures has been shown to correlate with progression of AD, a growing number of recent reports have indicated that such atrophy may not be specific to AD. To improve diagnostic specificity, new quantitative magnetic resonance (MR) imaging methods are being developed that exploit known pathogenic mechanisms exclusive to AD. This article reviews the MR techniques that are currently available for the diagnostic assessment of AD.

Argyrophilic grain disease: frequency and neuropathology in centenarians

Argyrophilic grain disease (AGD) is a progressive degenerative disease of the human brain, the prevalence of which increases with advancing age. The features of AGD in autopsied brains from 32 centenarians were studied using phosphorylated tau (AT8) immunostaining combined with Gallyas-Braak staining and 4R tau-specific antibody (RD4) immunostaining. Ten of 32 centenarians were diagnosed as AGD, yielding an overall frequency of 31.3%. In the demented group, nine (39.1%) of 23 cases were found with argyrophilic grains (AGs), while in the non-demented group, AGs were found in only one (11.1%) of nine cases, the difference between them being significant (P<0.05). Among the cases with Alzheimer's disease (AD), five (41.7%) of 12 were found with AGs. One (25%) of four cases with senile dementia with tangles (SDT) also suffered from AGD. Dementia caused by "pure" AGD accounted for 13% (3/23) among demented subjects. Our findings indicated that there is a high frequency of AGD in centenarians. In agreement with previous studies, we favor the view that age may be one of the risk factors for AGD.

Argyrophilic grains are not always argyrophilic--distinction from neurofibrillary tangles of diffuse neurofibrillary tangles with calcification revealed by comparison between Gallyas and Campbell-Switzer methods

Silver staining profiles of argyrophilic grains (AGs) and of neurofibrillary tangles (NFTs) of diffuse neurofibrillary tangles with calcification (DNTC, collectively as DNTC-NFTs) were examined for their relation to tau- and ubiquitin-like immunoreactivity (IR). Pairs of mirror sections were triple-fluorolabeled with an anti-PHF tau (AT8) antibody, an anti-ubiquitin antibody and thiazin red (TR), a fluorochrome that identifies fibrillary structures such as NFTs of Alzheimer's disease (AD). One of the paired sections was subsequently stained with Gallyas method (GAL), and the other with Campbell-Switzer method (CS). Comparison of the same microscopic field on the paired fluorolabeled sections, subsequently silver-stained with either GAL or CS enabled the determination of five different profiles of each structure: AT8-IR, ubiquitin-like-IR, affinity to TR, argyrophilia with GAL or CS staining. AGs, mainly composed of four-repeat (4R) tau, were argyrophilic with GAL but not with CS, and their affinity to TR and ubiquitin-like-IR was not intense. This staining profile of AGs is identical with those of tau-positive structures in the cortex of progressive supranuclear palsy/corticobasal degeneration, both composed of 4R tau. This selective affinity of AGs to GAL is in sharp contrast with Pick bodies, composed of three-repeat (3R) tau, that are positive for CS but not for GAL, as we reported previously. This contrast is explainable if the argyrophilia with CS is related to deposits containing 3R tau, while that with GAL is linked to those containing 4R tau. Indeed, DNTC-NFTs, that contain both 3R and 4R tau, were argyrophilic with CS and GAL, and their affinity to TR and ubiquitin-like-IR were consistent, as we reported previously for NFTs of AD and of Down's syndrome, both similarly composed of 3R and 4R tau. Taken together, differences in molecular composition of tau protein in these deposits are linked to their argyrophilic properties dependent on the staining method in these sporadic tauopathies. Although explanations for these empirical differences are not yet available, awareness of this clear distinction is potentially of diagnostic and pathological significance.

Argyrophilic grain disease: A late-onset dementia with distinctive features among tauopathies

Argyrophilic grain disease (AgD) is a late-onset dementia morphologically characterized by the presence of abundant spindle-shaped argyrophilic grains (ArG) in neuronal processes and coiled bodies in oligodendrocytes. AgD changes consist of the microtubule-associated protein tau in an abnormally and hyperphosphorylated state and are mainly found in limbic regions, for example, in the hippocampus, the entorhinal and transentorhinal cortices and the amygdala. AgD shows a significant correlation with advancing age, and it became apparent from recent clinicopathological studies that it might account for approximately 5% of all dementia cases. Further immunohistochemical and biochemical studies revealed that AgD is a four-repeat (4R) tauopathy similar to PSP and corticobasal degeneration (CBD), but distinct from Alzheimer's disease (AD) and Pick's disease. Moreover, a common genetic background regarding the tau gene haplotype has been suggested for AgD, PSP and CBD. However, although there are currently only limited data available, AgD seems to be clinically distinct from PSP and CBD and shares rather features of (mild) AD or other forms of 'limbic' dementias, among them senile dementia with tangles and the localized form of AD.

Staging of Argyrophilic Grains: An Age-Associated Tauopathy

We have reported that the ambient gyrus is the site with the greatest accumulation of argyrophilic grains (AGs) and that the degeneration of the ambient gyrus is responsible for dementia with grains. Here we analyzed 1,405 serial autopsy cases from 2 hospitals and detected AGs only in cases older than 56 years of age. The distribution of AGs followed a stereotypic regional pattern. Thus, we propose the following staging paradigm: stage I: AGs restricted to the ambient gyrus and its vicinity; stage II: AGs more apparent in the anterior and posterior medial temporal lobe, including the temporal pole, as well as the subiculum and entorhinal cortex; and stage III: abundant AGs in the septum, insular cortex, and anterior cingulate gyrus, accompanying spongy degeneration of the ambient gyrus. Sixty-three of 65 (96.9%) argyrophilic grain stage III cases without other dementing pathology were classified as 0.5 or higher in the clinical dementia rating. Forty-seven of 50 dementia with grains cases (94%) were stage III and 3 were stage II. No association with apoE genotyping was detected. Our study further confirms that dementia with grains is an age-associated tauopathy with relatively uniform distribution and may independently contribute to cognitive decline in the elderly.

Severe involvement of ambient gyrus in dementia with grains

Argyrophilic grains are detected as punctate or filiform structures in the neuropil of the medial temporal lobe, and dementia with grains (DG) is defined as a form of dementia with argyrophilic grains as the only explainable cause. We found argyrophilic grains in 43.2% of our 190 serial autopsy brains (mean age, 79.7 yr) from a community-based geriatric hospital, but only 20% of these argyrophilic grain-positive brains fulfilled the criteria for DG. To determine if there are structural differences between cognitively normal cases with argyrophilic grains (CNG) and DG, we studied 14 brains with CNG and 15 brains with DG. All cases of DG had severe atrophy of the ambient gyrus (the junction between temporal lobe and amygdala) with spongiosis, neuronal loss, and gliosis, as well as many grains, pretangles, coiled bodies, and tau-immunoreactive astrocytes. Comparable changes were not present in the ambient gyrus of CNG brains. The temporal neocortex and hippocampus were relatively spared in DG, in contrast to Alzheimer disease. Our study suggests that selective severe involvement of the ambient gyrus may explain the clinical manifestations of a limbic-type dementia in DG.