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

Differential subtypes of diabetic older adults diagnosed with Alzheimer's disease

AIM

The clinical management of diabetic elderly patients with Alzheimer's disease (AD) is hindered by several difficulties. The present study aimed to clarify the clinical characteristics and pathophysiological properties of AD in diabetic older adults.

METHODS

A total of 91 patients with type 2 diabetes mellitus and 161 non-diabetic individuals who were diagnosed with AD were recruited. Diabetic patients were classified into two groups with glycated hemoglobin (HbA1c) < 7.0% or ≥ 7.0%. The demographics, cognition, daily-life function, metabolic changes, treatment, and behavioral and psychological symptoms of dementia (BPSD), as well as brain pathophysiology, were compared among the three groups.

RESULTS

Patients with higher HbA1c had increased diabetic vascular complications and impaired activities of daily living with decreased levels of serum high-molecular-weight adiponectin and 25-hydroxyvitamin D. Although cognitive status was similar among the three groups, BPSD, including apathy, overeating and excessive daytime sleeping appeared to be increased in the patients with HbA1c ≥ 7.0%. The frequency of apolipoprotein E4 carriers and of posterior cerebral hypoperfusion (AD-pattern) on single-photon emission computed tomography in poorly controlled diabetic subjects was similar to that in non-diabetic AD patients, whereas diabetic patients with HbA1c <7.0% included fewer apolipoprotein E4 carriers and fewer patients with an AD pattern on single-photon emission computed tomography.

CONCLUSION

Subtypes of older diabetic patients with AD were identified based on clinical features and brain pathophysiology. Physical and psychological complications of dementia are prevalent in patients with higher HbA1c. It seems likely that difficulties in the management of diabetes with AD are due not only to non-adherence to diabetes treatment, but also several symptoms and pathophysiological characteristics of dementia.

Germline DNA copy number variation in individuals with Argyrophilic grain disease reveals CTNS as a plausible candidate gene

Argyrophilic grain disease (AGD) is a progressive neurodegenerative disease of the human brain that has never been associated to a particular gene locus. In the present study, we report the results of a CNV investigation in 29 individuals whose anatomopathologic investigation of the brain showed AGD. Rare CNVs were identified in six patients (21%), in particular a 40 kb deletion at 17p13.2 encompassing the CTNS gene. Homozygote mutations in CTNS are known to cause cystinosis, a disorder characterized by the intralysosomal accumulation of cystine in all tissues. We present the first CNV results in individuals presenting AGD and a possible candidate gene implicated in the disorder.

Intercellular transfer of tau aggregates and spreading of tau pathology: Implications for therapeutic strategies

Filaments made of hyperphosphorylated tau protein are encountered in a group of neurodegenerative disorders termed tauopathies. The most prevalent tauopathy, Alzheimer's disease (AD), additionally presents with extracellular deposits of the amyloid-β peptide (Aβ). Current symptomatic treatments have shown short term benefits in reducing cognitive symptoms as well as behavioral abnormalities in patients with mild to moderate AD but there is still no effective treatment to prevent or reverse AD. For decades, the amyloid cascade hypothesis of AD dominated basic research and focused pharmaceutical interest on Aβ. However, the existence of tauopathies that are devoid of Aβ deposits, together with the discovery of mutations in the tau gene leading to frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17T), confirmed the importance of tau per se in disease. Tau became an interesting disease target in its own right. We will review here recent research on cell-to-cell propagation of tau pathology, which we believe to be central to disease progression, and discuss tau immunotherapy in the light of these findings. This article is part of the Special Issue entitled 'The Synaptic Basis of Neurodegenerative Disorders'.

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.

Are tau aggregates toxic or protective in tauopathies?

Aggregation of highly phosphorylated tau into aggregated forms such as filaments and neurofibrillary tangles is one of the defining pathological hallmarks of Alzheimer's disease and other tauopathies. Hence therapeutic strategies have focused on inhibition of tau phosphorylation or disruption of aggregation. However, animal models imply that tau-mediated dysfunction and toxicity do not require aggregation but instead are caused by soluble hyper-phosphorylated tau. Over the years, our findings from a Drosophila model of tauopathy have reinforced this. We have shown that highly phosphorylated wild-type human tau causes behavioral deficits resulting from synaptic dysfunction, axonal transport disruption, and cytoskeletal destabilization in vivo. These deficits are evident in the absence of neuronal death or filament/tangle formation. Unsurprisingly, both pharmacological and genetic inhibition of GSK-3β rescue these tau phenotypes. However, GSK-3β inhibition also unexpectedly increases tau protein levels, and produces insoluble granular tau oligomers. As well as underlining the growing consensus that tau toxicity is mediated by a highly phosphorylated soluble tau species, our findings further show that not all insoluble tau aggregates are toxic. Some tau aggregates, in particular tau oligomers, are non-toxic, and may even be protective against tau toxicity in vivo. This has serious implications for emerging therapeutic strategies to dissolve tau aggregates, which might be ineffective or even counter-productive. In light of this, it is imperative to identify the key toxic tau species and to understand how it mediates dysfunction and degeneration so that the effective disease-modifying therapies can be developed.

Brain homogenates from human tauopathies induce tau inclusions in mouse brain

Filamentous inclusions made of hyperphosphorylated tau are characteristic of numerous human neurodegenerative diseases, including Alzheimer's disease, tangle-only dementia, Pick disease, argyrophilic grain disease (AGD), progressive supranuclear palsy, and corticobasal degeneration. In Alzheimer's disease and AGD, it has been shown that filamentous tau appears to spread in a stereotypic manner as the disease progresses. We previously demonstrated that the injection of brain extracts from human mutant P301S tau-expressing transgenic mice into the brains of mice transgenic for wild-type human tau (line ALZ17) resulted in the assembly of wild-type human tau into filaments and the spreading of tau inclusions from the injection sites to anatomically connected brain regions. Here we injected brain extracts from humans who had died with various tauopathies into the hippocampus and cerebral cortex of ALZ17 mice. Argyrophilic tau inclusions formed in all cases and following the injection of the corresponding brain extracts, we recapitulated the hallmark lesions of AGD, PSP and CBD. Similar inclusions also formed after intracerebral injection of brain homogenates from human tauopathies into nontransgenic mice. Moreover, the induced formation of tau aggregates could be propagated between mouse brains. These findings suggest that once tau aggregates have formed in discrete brain areas, they become self-propagating and spread in a prion-like manner.

"Prion-like" templated misfolding in tauopathies

The soluble microtubule-associated protein tau forms hyperphosphorylated, insoluble and filamentous inclusions in a number of neurodegenerative diseases referred to as "tauopathies." In Alzheimer's disease, tau pathology develops in a stereotypical manner, with the first lesions appearing in the locus coeruleus and entorhinal cortex, from where they appear to spread to the hippocampus and neocortex. Propagation of tau pathology is also a characteristic of argyrophilic grain disease, where the tau lesions spread throughout the limbic system. Significantly, isoform composition and morphology of tau filaments can differ between tauopathies, suggesting the existence of distinct tau strains. Extensive experimental findings indicate that prion-like mechanisms underly the pathogenesis of tauopathies.

Argyrophilic grain disease differs from other tauopathies by lacking tau acetylation

Post-translational modifications play a key role in tau protein aggregation and related neurodegeneration. Because hyperphosphorylation alone does not necessarily cause tau aggregation, other post-translational modifications have been recently explored. Tau acetylation promotes aggregation and inhibits tau's ability to stabilize microtubules. Recent studies have shown co-localization of acetylated and phosphorylated tau in AD and some 4R tauopathies. We developed a novel monoclonal antibody against acetylated tau at lysine residue 274, which recognizes both 3R and 4R tau, and used immunohistochemistry and immunofluorescence to probe 22 cases, including AD and another eight familial or sporadic tauopathies. Acetylated tau was identified in all tauopathies except argyrophilic grain disease (AGD). AGD is an age-associated, common but atypical 4R tauopathy, not always associated with clinical progression. Pathologically, AGD is characterized by neuropil grains, pre-neurofibrillary tangles, and oligodendroglial coiled bodies, all recognized by phospho-tau antibodies. The lack of acetylated tau in these inclusions suggests that AGD represents a distinctive tauopathy. Our data converge with previous findings to raise the hypothesis that AGD could play a protective role against the spread of AD-related tau pathology. Tau acetylation as a key modification for the propagation tau toxicity deserves further investigation.

What is the pathological significance of tau oligomers?

Insoluble aggregates of the microtubule-associated protein tau characterize a number of neurodegenerative diseases collectively termed tauopathies. These aggregates comprise abnormally hyperphosphorylated and misfolded tau proteins. Research in this field has traditionally focused on understanding how hyperphosphorylated and aggregated tau mediates dysfunction and toxicity in tauopathies. Recent findings from both Drosophila and rodent models of tauopathy suggest that large insoluble aggregates such as tau filaments and tangles may not be the key toxic species in these diseases. Thus some investigators have shifted their focus to study pre-filament tau species such as tau oligomers and hyperphosphorylated tau monomers. Interestingly, tau oligomers can exist in a variety of states including hyperphosphorylated and unphosphorylated forms, which can be both soluble and insoluble. It remains to be determined which of these oligomeric states of tau are causally involved in neurodegeneration and which signal the beginning of the formation of inert/protective filaments. It will be important to better understand this so that tau-based therapeutic interventions can target the most toxic tau species.

[Clinicopathologic findings of argyrophilic-grain dementia in a case of mild cognitive impairment converting to dementia]

An 84-year-old Japanese woman with no family history of dementia visited our memory clinic complaining of memory disturbance. Neurological examination revealed no apparent motor abnormalities, focal cerebral signs, parkinsonism, or cerebellar dysfunction. Hasegawa's Dementia Scale-Revised (HDS-R) and Mini mental state examination (MMSE) scores were 24 and 23 points, respectively. MRI revealed left-side-dominant dilatation of the inferior horn of the lateral ventricle. Although egocentric behavior was remarkable, no disturbance of intelligence was apparent at the first examination, and she was diagnosed as having mild cognitive impairment. Her memory disturbance and disorientation gradually worsened. Atrophy of the cerebrum and dilatation of the lateral ventricle advanced gradually on MRI. Two years later, she required care to perform activities of daily living. HDS-R and MMSE scores had dropped to 13 and 18 points, respectively, and conversion to dementia was diagnosed. Ability to perform 3D cube-copying was well preserved. The patient died due to acute myocardial infarction at the age of 87. The clinical diagnosis was Alzheimer disease. At autopsy, the brain weighed 1,250g, and argyrophilic grains were widely observed in the limbic system, corresponding to Saito's stage III. Neuron loss, gliosis, spongiform change, and tissue rarefaction were recognized in the superficial layer of the parahippocampal gyrus. Ballooned neurons, pretangles, oligodendroglial coiled bodies, and neuropil threads were also observed. Neurofibrillary tangles and senile plaques, mainly consisting of diffuse plaque, were recognized as corresponding to Braak stage III and CERAD stage B, respectively. Neither Lewy nor Pick bodies were observed. Although mild phosphorylated TDP-43 immunoreactivity was observed, it was suspected to be due to secondary degeneration of tau deposition. The patient was diagnosed pathologically as having argyrophilic grain dementia. The clinical findings of the present patient reveal important observations that help to clinically discriminate between various dementias such as Alzheimer disease and argyrophilic grain dementia.

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.

Cardiovascular diseases and hippocampal infarcts

The prevalence of hippocampal lesions such as hippocampal infarcts have not been studied in detail even though hippocampal alterations are known to be associated with various clinical conditions such as age-related degenerative disorders and epilepsy.

METHODS

Here we defined the hippocampal infarcts and assessed the prevalence of this lesion in large unselected population of 1,245 subjects age ranging from 1 to 99 years (mean age 79 ± 1 S.E.M). Furthermore, we assessed the association of these lesions with various cardio- and cerebro-vascular disorders and other neurodegenerative lesions. The prevalence of hippocampal infarct in the study population of 1,245 subjects was 12%, increasing to 13% when only those with a clinically diagnosed cognitive impairment (n = 311) were analyzed. Large hemispheric brain infarcts were seen in 31% of the study subjects and these lesions were strongly associated with cardiovascular risk factors such as hypertension (43%), coronary disease (32%), myocardial infarct (22%), atrial fibrillation (20%), and heart failure (20%). In contrast, hippocampal infarcts displayed a significant association only with large hemispheric brain infarct, heart failure, and cardiovascular index as assessed postmortem. It is noteworthy that only widespread hippocampal infarcts were associated with clinical symptoms of cognitive impairment or epilepsy. The surprisingly low prevalence of 12% of hippocampal infarcts in aged population found here and the failure to detect an association between this lesion and various cerebro- cardio-vascular lesions is intriguing. Whether susceptibility to ischemia in line with susceptibility to neuronal degeneration in this region is influenced by still undetermined risk- factors need further investigation. Furthermore it should be noted that the size of the hippocampal tissue damage, i.e., small vs. large cystic infarcts is of significance regarding clinical alterations.

Phenotypic variation of autosomal-dominant corticobasal degeneration

Neurodegenerative tauopathies may be inherited as autosomal-dominant disorders with variable clinicopathological phenotypes, and causative mutations in the microtubule-associated protein tau (MAPT) gene are not regularly seen. Herein, we describe a patient with clinically typical and autopsy-proven corticobasal degeneration (CBD). Her mother was diagnosed to have Parkinson's disease, but autopsy showed CBD pathology as in the index patient. The sister of the index patient had the clinical symptoms of primary progressive aphasia (PPA), but no pathology was available to date. Molecular analysis did not reveal any mutation in the MAPT or progranulin (GRN) genes. Our findings illustrate that CBD, progressive supranuclear palsy and PPA may be overlapping diseases with a common pathological basis rather than distinct entities. Clinical presentation and course might be determined by additional, yet unknown, genetic modifying factors.

A peculiar constellation of tau pathology defines a subset of dementia in the elderly

Sporadic tauopathies are characterized by differential cellular and topographical predominance of phospho-tau immunoreactivity and biochemical distinction of the tau protein. Established entities include progressive supranuclear palsy, corticobasal degeneration, Pick's disease, and argyrophilic grain disease. During a community-based longitudinal study on aging, we detected tau pathologies not compatible with these categories. We immunostained for different phospho-tau epitopes, 4R and 3R tau isoforms, α-synuclein, amyloid-β, and phospho-TDP-43, analyzed the MAPT and ApoE genes, and performed western blotting for the tau protein. The mean age of patients (4 women, 3 men) was 83.8 years. Clinical presentations combined dementia with psychiatric symptoms and/or parkinsonism. In addition to neurofibrillary tangles and diffuse neuronal cytoplasmic tau immunoreactivity, the neuropathology was characterized by peculiar cytopathologies (diffuse granular immunopositivity of astrocytic processes and patchy accumulation of thin threads) in a distinctive distribution (frontal and temporal cortices, hippocampus, amygdala, basal ganglia, locus coeruleus, and substantia nigra). Argyrophilic grains were detected in four patients. Few to moderate densities of neuritic plaques but widespread phospho-TDP-43 pathology was observed in five patients. There was variability in the H1/H2 and ApoE alleles and biochemical features of tau protein. We propose these cases as complex tauopathy with a characteristic constellation: some features of primary tauopathies and Alzheimer's disease mixed with additional cytopathologies including a distinctive astrogliopathy, in a characteristic distribution of lesions. These complex tauopathies in the elderly deserve specific diagnostic and eventually therapeutic considerations.

Mitochondrial dysfunction and oxidative and endoplasmic reticulum stress in argyrophilic grain disease

Argyrophilic grain disease (AGD) is characterized by the accumulation of hyperphosphorylated 4R tau in dendritic varicosities (i.e."grains") in neurons and pretangles in certain areas of the cerebral cortex and other brain regions. We investigated oxidative and endoplasmic reticulum (ER) stress and dysregulation of mitochondrialbiogenesis as potential mechanisms involved in the AGD pathogenesis. Samples from AGD patients (n = 8) and nonpathologic, age-matched controls (n = 5) were compared using biochemical and immunohistochemical techniques with a panel of antibodies to markers of ER stress responses, stress chaperones, oxidative stress and associated cellular responses, respiratory chain complexes, mitochondrial regulators, and modulators of mitochondrial biogenesis. Because AGD is often associated with other tauopathies, mainly Alzheimer disease (AD), results were also compared with those of a group of similar Braak AD stage cases without grains (n = 5). In both AD and AGD cases, we found activation of key molecules that are involved in the unfolded protein response and lead to elevated ER chaperone levels, increased oxidative stress damage, mainly related to lipoxidation and targeting glycolytic enzymes. Altered expression of components of the respiratory chain markers modulating mitochondrial biogenesis were selectively affected in AGD. The findings suggest that, despite the common pathogenic trends in AD and AGD, there is molecular specificity for AGD.

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.

The propagation of prion-like protein inclusions in neurodegenerative diseases

The most common neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease, are characterized by the misfolding of a small number of proteins that assemble into ordered aggregates in affected brain cells. For many years, the events leading to aggregate formation were believed to be entirely cell-autonomous, with protein misfolding occurring independently in many cells. Recent research has now shown that cell non-autonomous mechanisms are also important for the pathogenesis of neurodegenerative diseases with intracellular filamentous inclusions. The intercellular transfer of inclusions made of tau, alpha-synuclein, huntingtin and superoxide dismutase 1 has been demonstrated, revealing the existence of mechanisms reminiscent of those by which prions spread through the nervous system.

Protein coding of neurodegenerative dementias: the neuropathological basis of biomarker diagnostics

Neuropathological diagnosis of neurodegenerative dementias evolved by adapting the results of neuroanatomy, biochemistry, and cellular and molecular biology. Milestone findings of intra- and extracellular argyrophilic structures, visualizing protein deposition, initiated a protein-based classification. Widespread application of immunohistochemical and biochemical investigations revealed that (1) there are modifications of proteins intrinsic to disease (species that are phosphorylated, nitrated, oligomers, proteinase-resistant, with or without amyloid characteristics; cleavage products), (2) disease forms characterized by the accumulation of a single protein only are rather the exception than the rule, and (3) some modifications of proteins elude present neuropathological diagnostic procedures. In this review, we summarize how neuropathology, together with biochemistry, contributes to disease typing, by demonstrating a spectrum of disorders characterized by the deposition of various modifications of various proteins in various locations. Neuropathology may help to elucidate how brain pathologies alter the detectability of proteins in body fluids by upregulation of physiological forms or entrapment of different proteins. Modifications of at least the five most relevant proteins (amyloid-beta, prion protein, tau, alpha-synuclein, and TDP-43), aided by analysis of further "attracted" proteins, are pivotal to be evaluated simultaneously with different methods. This should complement the detection of biomarkers associated with pathogenetic processes, and also neuroimaging and genetic analysis, in order to obtain a highly personalized diagnostic profile. Defining clusters of patients based on the patterns of protein deposition and immunohistochemically or biochemically detectable modifications of proteins ("codes") may have higher prognostic predictive value, may be useful for monitoring therapy, and may open new avenues for research on pathogenesis.

[Argyrophilic grain disease: synergistic component of dementia?]

INTRODUCTION

Argyrophilic grain disease (AGD) is one cause of neurodegenerative dementia with a variable clinical spectrum. A neuropathology study is required for diagnosis.

CASE REPORT

We report the case of a 68-year-old patient presenting with cognitive decline associating with frontal dysfunction and parkinsonism. Death occurred two years after onset. The neuropathology study revealed a status criblosus in the basal ganglia, neurofibrillary tangles and AGD.

DISCUSSION

We suggest that AGD could explain the atypical course of this dementia considering the fast cognitive decline, the clinical expression and the topography of the lesions.

CONCLUSION

This case illustrates the possible synergistic deleterious effect of this pathology on other causes of dementia.

The progression of cognitive deterioration and regional cerebral blood flow patterns in Alzheimer's disease: a longitudinal SPECT study

BACKGROUND AND PURPOSE

The progression of cognitive deterioration in patients with Alzheimer's disease (AD) is considerably variable. The ability to predict the progression rate is important for clinicians to treat and manage patients with AD. We examined the possible relationship between the rate of cognitive deterioration and regional cerebral blood flow (rCBF) patterns in patients with AD.

METHODS

We followed 48 patients with AD for an average of 37 months. They were subsequently divided into the rapidly progressing group (n=24) and slowly progressing group (n=24) based on an annual Mini-Mental State Examination (MMSE) score change. Initial and follow-up rCBF were assessed using single photon emission CT (SPECT) and the SPECT data were analyzed by 3D-stereotactic surface projections.

RESULTS

At initial evaluation, the rapidly progressing group had greater rCBF deficits mainly in the parietotemporal and frontal regions, and left posterior cingulate than did the slowly progressing group. When compared with initial SPECT, follow-up SPECT showed a significant rCBF reduction in widespread regions, including parietotemporal and frontal lobes, of the rapidly progressing group, while showed in the scattered and small regions of hemispheres of the slowly progressing group.

CONCLUSION

Our longitudinal SPECT study suggests a significant association between rCBF deficits in the parietotemporal, posterior cingulate, and frontal regions and subsequent rapid cognitive and rCBF deterioration.

Tau-positive grains are constant in centenarians' hippocampus

The influence of age on the prevalence of argyrophilic grain disease has been analyzed in the hippocampus from 29 centenarians. Argyrophilic grains were detected in 12 cases with Gallyas silver method, in 24 cases with anti-exon 10 (RD4) immunohistochemistry, in all the cases with a phospho-independent anti-tau (piTau) antibody and with a monoclonal antibody against Ser202 of the tau protein (AT8), suggesting a maturation of the grains. Ballooned neurons were found in the hippocampus of 12 cases in which grains were, on average, more abundant. Coiled bodies were found in 26, 15 and 13 cases respectively with piTau antibody, RD4 and Gallyas method. Cases with coiled bodies had a higher density of grains. The mean density of grains did not differ in the patients with or without dementia. The prevalence of tau-positive grains has been underestimated in the very old population. As neurofibrillary tangles, they appear to be a constant accompaniment of age but, contrarily to neurofibrillary tangles, do not seem to be strongly associated with dementia.

Delineation of early changes in cases with progressive supranuclear palsy-like pathology. Astrocytes in striatum are primary targets of tau phosphorylation and GFAP oxidation

Progressive supranuclear palsy (PSP) is a complex tauopathy usually confirmed at post-mortem in advanced stages of the disease. Early PSP-like changes that may outline the course of the disease are not known. Since PSP is not rarely associated with argyrophilic grain disease (AGD) of varible intensity, the present study was focused on AGD cases with associated PSP-like changes in an attempt to delineate early PSP-like pathology in this category of cases. Three were typical clinical and pathological PSP. Another case presented with cognitive impairment, abnormal behavior and two falls in the last three months. One case suffered from mild cognitive impairment, and two had no evidence of neurological abnormality. Neuropathological study revealed, in addition to AGD, increased intensity and extent of lesion in three groups of regions, striatum, pallidus/subthalamus and selected nuclei of the brain stem, correlating with neurological impairment. Biochemical studies disclosed oxidative damage in the striatum and amygdala. Together the present observations suggest (i) early PSP-like lesions in the striatum, followed by the globus pallidus/subthalamus and selected nuclei of the brain stem; (ii) early involvement of neurons and astrocytes, but late appearance of tufted astrocytes; and (iii) oxidative damage of glial acidic protein in the striatum.

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.

A mouse forward genetics screen identifies LISTERIN as an E3 ubiquitin ligase involved in neurodegeneration

A mouse neurological mutant, lister, was identified through a genome-wide N-ethyl-N-nitrosourea (ENU) mutagenesis screen. Homozygous lister mice exhibit profound early-onset and progressive neurological and motor dysfunction. lister encodes a RING finger protein, LISTERIN, which functions as an E3 ubiquitin ligase in vitro. Although lister is widely expressed in all tissues, motor and sensory neurons and neuronal processes in the brainstem and spinal cord are primarily affected in the mutant. Pathological signs include gliosis, dystrophic neurites, vacuolated mitochondria, and accumulation of soluble hyperphosphorylated tau. Analysis with a different lister allele generated through targeted gene trap insertion reveals LISTERIN is required for embryonic development and confirms that direct perturbation of a LISTERIN-regulated process causes neurodegeneration. The lister mouse uncovers a pathway involved in neurodegeneration and may serves as a model for understanding the molecular mechanisms underlying human neurodegenerative disorders.

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.

Age and apoE associations with complex pathologic features in Alzheimer's disease

The risk for Alzheimer's disease (AD) is influenced by both age and ApoE status. The present study addresses the associations of age and ApoE status on complex pathologic features in AD (n=81) including coexistent cerebrovascular disease (CVD), argyrophilic grain disease (AGD), and Lewy body disease (LBD). The frequency of coexistent cerebrovascular disease increased with increasing age. Age and ApoE status were differentially associated with atherosclerosis, lacunar infarctions, and microvascular pathology. Coexistent Lewy body pathology was negatively associated with age, dropping off abruptly after age 90. The presence of an ApoE epsilon4 allele was associated with an increased frequency of coexistent LBD. Logistic regression analyses demonstrated both dependent and independent effects of age and ApoE status on the presence of coexistent Lewy body pathology in AD. While the decreasing frequency of LBD in AD after age 90 could be partly accounted for by a lower probability of an ApoE epsilon4 allele, the independent association with age suggests either 1) a survival effect, 2) decreased incidence with advancing age, or 3) both.

MAPT S305I mutation: implications for argyrophilic grain disease

Frontotemporal lobar degeneration (FTLD) with mutations in the tau gene (MAPT) causes familial frontotemporal dementia with tau pathology. Many of these mutations result in morphological phenotypes resembling sporadic tauopathies, although, to date, no such cases mimicking argyrophilic grain disease (AgD) have been documented. We now present a case with a novel S305I MAPT mutation and a morphological phenotype showing resemblance to AgD. At the age of 39, the patient developed behavioural and personality changes and lack of verbal fluency with later poor performance on naming tasks and rigidity in the extremities. After a short disease course of 1.5 years, the patient died. A unique neuropathological phenotype with neuronal diffuse cytoplasmic tau immunoreactivity, oligodendroglial-coiled bodies, argyrophilic grains, and non-argyrophilic, but tau-immunopositive and ubiquitin-immunonegative pre-grains were observed, whereas classical neurofibrillary tangles, Pick bodies, and neuritic plaques were absent. The tau-positive abnormal structures were composed only of 4R-tau isoforms and, ultrastructurally, straight filaments. Neuronal loss was greatest in the medial temporal cortex, hippocampus, and amygdala. These pathological features resemble AgD. The novel S305I substitution has a strong effect on MAPT exon 10 splicing, thereby causing a striking increase in 4R-tau isoforms. Our observation not only widens the phenotypic spectrum of FTLD with MAPT mutation but also underpins the notion that the predominance of similar neuropathological findings in sporadic AgD cases may be viewed as features of a distinct disease entity.

Subcortical neurofibrillary tangles and argyrophilic grains in a case of familial frontotemporal dementia with parkinsonism

A case of familial frontotemporal dementia with parkinsonism (FTDP) similar to progressive supranuclear palsy (PSP) was reported. A 58-year-old man developed personality change followed by parkinsonism and dementia. Three family members showed similar symptoms. Cerebral atrophy was marked on the anterior frontotemporal lobes. The substantia nigra, hippocampus, peri-aqueductal gray matter and pontine nucleus were affected with globose neurofibrillary tangles (NFT) and glial tangles. Argyrophilic grains were distributed in the CA1-CA2. NFT, glial tangles and argyrophilic grains expressed four-repeat microtubule-associated protein tau (MAPT). MAPT gene had no mutation. Familial occurrence of FTDP with PSP-like tauopathy is rare.

The validity of clinical diagnoses of dementia in a group of consecutively autopsied memory clinic patients

BACKGROUND

Epidemiological studies show that up to 10% of individuals aged 65 years and older suffer from dementia, most commonly from dementia of the Alzheimer Type (DAT) (1). Clinicopathological studies are critical to our understanding of this disease and improving the accuracy of clinical diagnoses.

OBJECTIVES

Our objectives were to examine the validity of clinical diagnoses of DAT, to determine the prevalence of different forms of dementia in this sample, and to investigate the relationship between age at death and polymorbidity.

SUBJECTS AND METHOD

Clinical data were available from 221 patients who had been examined at the Basel Memory Clinic between 1986 and 1996. From this population, 34% (75 patients) were autopsied in the Department of Pathology, University Hospital Basel, and neuropathological examinations were additionally performed on 62 (83%) of these patients. Clinical and neuropathological data were retrospectively compared.

RESULTS

67.8% of the neuropathologically examined patients received a definitive diagnosis of AD (Alzheimer's disease), vascular dementia (VaD) or mixed dementia (AD and VaD). AD alone or with other histopathological hallmarks of dementia was the most prevalent neuropathological diagnosis (63%). VaD was deemed the only cause of dementia in only 4.8% of patients. The sensitivity for DAT was 75.9%, the specificity 60.6%. Increasing age was associated with an increasing number of clinical and neuropathological diagnoses.

CONCLUSION

The sensitivity and specificity of the clinical diagnoses of DAT found in our study are similar to previous reports (2-5). Older patients had more etiologies of their dementia than younger patients. This study reaffirms the need for internationally accepted criteria for clinical and neuropathological diagnoses, as well as further clinical-neuropathological investigations to further refine the clinical diagnostic process.

Clinical characteristics of dementia associated with argyrophilic grain disease

BACKGROUND/AIMS

We aimed at characterizing the clinical features of dementia associated with argyrophilic grain disease (AgD).

METHODS

Relatives or close friends of 24 individuals with autopsy-confirmed AgD and 29 patients with autopsy-confirmed Alzheimer's disease (AD) were administered a novel Retrospective Dementia Inventory to assess the cognitive, behavioral and affective symptoms of the deceased patients.

RESULTS

AgD patients showed less severe impairments in memory, language, attention and executive function than AD patients.

CONCLUSION

Compared to AD patients, individuals suffering from AgD appear to present with comparable deficits in behavior and affect but relatively spared cognitive functioning.

Hippocampal sclerosis dementia: a reappraisal

Hippocampal sclerosis (HpScl) is characterized by neuronal loss and gliosis in CA1 and subiculum of the hippocampus, and may be one contributing factor to dementia in old age. The term hippocampal sclerosis dementia (HpSclD) designates the presence of both hippocampal sclerotic lesions and a dementia syndrome. In the present review, we outline the pathological heterogeneity underlying HpSclD and discuss related disorders due to tau protein pathology and frontotemporal dementia with ubiquitin positive inclusions (FTLD-U). We also provide a detailed morphological description of ten of our own autopsied HpSclD cases, and compare these pathological findings with those reported in the literature. The lateralization of HpScl and the atrophy of the mammillary bodies were striking features in most of our cases. The main pathology consisted of tau positive lesions with a predominance of neuronal and glial pretangles in Ammon's horn and the dentate gyrus. Neurofibrillary and ghost tangles in CA1 and the subiculum were scarce and thus insufficient to explain the hippocampal pyramidal cell loss. In some cases, tau pathology in the hippocampal formation coexisted with glial tau pathology in the frontal cortex. The most striking finding besides the tau pathology was the presence of concomitant neuronal cytoplasmic inclusions and neurites immunoreactive for the transactive response DNA-binding protein-43 (TDP-43) in the dentate gyrus and temporal neocortex, similar to those found in FTLD-U. Taken together, the pathology of HpSclD is indicative of a degenerative rather than a hypoxic/ischemic etiology of HpSclD. Presently, HpSclD may best be deemed a disorder with various neurodegenerative etiologies, most notably tauopathy and TDP-43 proteinopathy (i.e. FTLD-U). Each of these disease processes could either independently or concertedly account for the dementia syndrome in HpSclD.

Silver diagnosis in neuropathology: principles, practice and revised interpretation

Silver-staining methods are helpful for histological identification of pathological deposits. In spite of some ambiguities regarding their mechanism and interpretation, they are widely used for histopathological diagnosis. In this review, four major silver-staining methods, modified Bielschowsky, Bodian, Gallyas (GAL) and Campbell–Switzer (CS) methods, are outlined with respect to their principles, basic protocols and interpretations, thereby providing neuropathologists, technicians and neuroscientists with a common basis for comparing findings and identifying the issues that still need to be clarified. Some consider “argyrophilia” to be a homogeneous phenomenon irrespective of the lesion and the method. Thus, they seek to explain the differences among the methods by pointing to their different sensitivities in detecting lesions (quantitative difference). Comparative studies, however, have demonstrated that argyrophilia is heterogeneous and dependent not only on the method but also on the lesion (qualitative difference). Each staining method has its own lesion-dependent specificity and, within this specificity, its own sensitivity. This “method- and lesion-dependent” nature of argyrophilia enables operational sorting of disease-specific lesions based on their silver-staining profiles, which may potentially represent some disease-specific aspects. Furthermore, comparisons between immunohistochemical and biochemical data have revealed an empirical correlation between GAL+/CS-deposits and 4-repeat (4R) tau (corticobasal degeneration, progressive supranuclear palsy and argyrophilic grains) and its complementary reversal between GAL-/CS+deposits and 3-repeat (3R) tau (Pick bodies). Deposits containing both 3R and 4R tau (neurofibrillary tangles of Alzheimer type) are GAL+/CS+. Although no molecular explanations, other than these empiric correlations, are currently available, these distinctive features, especially when combined with immunohistochemistry, are useful because silver-staining methods and immunoreactions are complementary to each other.

Neurofibrillary tangle-predominant dementia: comparison with classical Alzheimer disease

Neurofibrillary tangle predominant dementia (NFTPD) is a subset of late onset dementia, clinically different from traditional "plaque and tangle" Alzheimer disease (AD): later onset, shorter duration, less severe cognitive impairment, and almost absence of ApoE epsilon4. Neuropathology reveals abundant allocortical neurofibrillary pathology with no or few isocortical tau lesions, absence of neuritic plaques, absence or scarcity of amyloid deposits, but neurofibrillary changes comprising both 3 and 4 repeat (3R and 4R) tau immunohistochemistry are not significantly different from those in classical AD. Comparing 51 autopsy cases of NFTPD with 244 classical AD subjects, the nosology of NFTPD and its differences from AD are discussed.

Frontotemporal dementia

Frontotemporal dementia (FTD) and related conditions are often considered daunting because of the numerous inter-related clinical syndromes and their apparently heterogeneous pathologic substrates. Although the labyrinthine complexity of the disease seemingly continues to grow, recent discoveries have made the maze of FTD somewhat more navigable, spurring new interest in the field. This review begins by surveying the fascinating clinical presentations of these conditions and the few currently available treatments, then turns to recent progress in understanding the pathophysiology of FTD. Among the important advances surveyed are clinicopathologic correlations that enable prediction of the pathologic substrate of certain clinical subtypes, and genetic studies that have been particularly fruitful in identifying new causes of FTD.

Argyrophilic grain disease in demented subjects presenting initially with amnestic mild cognitive impairment

A previous autopsy study of patients with amnestic-type mild cognitive impairment (MCI) suggested an overrepresentation of argyrophilic grain disease (AGD). We studied 34 patients who had diagnoses of amnestic MCI during progression to dementia and who came to autopsy. Neuropathologic evaluation included routine histochemical and immunohistochemical methods, including a 4-repeat tau-specific marker (ET3). AGD was found in association with a variety of neuropathologic diseases in 18 (53%) cases but was the primary pathologic finding in only one (3%) case. ET3 allowed the detection of AGD in 5 additional cases missed using standard techniques. Cases with AGD were significantly older than those without (mean, 94 vs 84 years; p < 0.004, rank sum test). No significant differences were found between groups for other demographic variables, association of AGD with neuropathologic findings of Alzheimer disease, Lewy body, or cerebrovascular disease, or global measures of cognitive function, although there was a nonsignificant trend towards worsening cognitive status in cases with AGD. AGD is a common pathologic finding in subjects who have been diagnosed with amnestic MCI.

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.

Oxidative stress, accumulation of biological 'garbage', and aging

Normal metabolism is associated with unavoidable mild oxidative stress resulting in biomolecular damage that cannot be totally repaired or removed by cellular degradative systems, including lysosomes, proteasomes, and cytosolic and mitochondrial proteases. Consequently, irreversibly damaged and functionally defective structures (biological 'garbage') accumulate within long-lived postmitotic cells, such as cardiac myocytes and neurons, leading to progressive loss of adaptability and increased probability of death and characterizing a process called aging, or senescence. Intralysosomal 'garbage' is represented by lipofuscin (age pigment), an undegradable autophagocytosed material, while extralysosomal 'garbage' involves oxidatively modified cytosolic proteins, altered biomembranes, defective mitochondria and other organelles. In aged postmitotic cells, heavily lipofuscin-loaded lysosomes perform poorly, resulting in the enhanced accumulation of defective mitochondria, which in turn produce more reactive oxygen species causing additional damage (the mitochondrial-lysosomal axis theory). Potential anti-aging strategies may involve not only overall reduction of oxidative stress, but also the use of intralysosomal iron chelators hampering Fenton-type chemistry as well as the stimulation of cellular degradative systems.

Tau-Positive Fine Granules in the Cerebral White Matter: A Novel Finding Among the Tauopathies Exclusive to Parkinsonism-Dementia Complex of Guam

We examined the autopsied brains of cases of 6 types of tauopathy: parkinsonism-dementia complex of Guam (PDC), corticobasal degeneration (CBD), progressive supranuclear palsy (PSP), Pick disease, Alzheimer disease (AD), and myotonic dystrophy together with Guamanian controls. Light microscopy sections of these brains were examined using anti-tau antibodies. Tau-positive fine granules (TFGs) were globe-shaped, and 3 to 6 mum in diameter, were observed predominantly in the frontal white matter in 30 of the 35 patients with PDC. However, no TFGs were found in association with PSP, myotonic dystrophy, Pick disease, AD, or CBD. Western blot analysis of frozen brain tissue taken from the PDC cases revealed that the frontal cortex was hyperphosphorylated and contained 6 tau isoforms (3R+4R tau). However, in the present study, it was revealed that the novel TFGs in the white matter of patients with PDC was composed of 4R tau. Western blot analysis of sarkosyl-insoluble tau from the white matter of the PDC cases showed 2 major bands of 60 and 64 kDa and one minor band of 67 kDa. After dephosphorylation, these bands resolved into one major band of 4-repeat (4R) tau isoform and 3 minor bands of 3-repeat (3R) and 4R tau isoforms. Moreover, the TFGs observed in cases in which the number of neurofibrillary tangles (NFTs) was higher than the threshold level were not correlated with the presence of cortical NFTs. In conclusion, these novel TFGs were found almost exclusively in PDC brains and could therefore be considered as a characteristic neuropathologic marker of this particular tauopathy. The TFGs were hyperphosphorylated tau-positive structures that may be formed by a different mechanism from that used to produce cortical NFTs.

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.

Tau protein aggregation in the frontal and entorhinal cortices as a function of aging

OBJECTIVES

The abnormal accumulation of tau protein is increasingly recognized as the neuropathological hallmark of a number of dementing illness in which frontotemporal lobar degeneration occurs. In this paper we examined the age-dependant deposition of tau protein in the frontal and entorhinal neocortices.

METHODS

We examined autopsy records from 1997 to 2002 and selected 87 cases (10 in each decade from 0 to 79 years of age, 7 in 80-89 decade) with no history of dementia or other neurodegenerative diseases, and for which neurodegenerative diseases were excluded neuropathologically. Archival paraffin-embedded frontal and entorhinal cortices were examined by both Gallyas-Braak silver staining and a panel of antibodies recognizing tau protein accumulation.

RESULTS

Tau neuronal aggregates were observed in both frontal and entorhinal cortices in the third decade. While the frontal neuronal tau aggregates remained infrequent in the remaining decades, the number and extent ofneuronal tau aggregates in the entorhinal cortex increased such that by the 7th decade the majority of cases showed extensive tau aggregate formation. The most consistent morphological observation was of dense, perikaryal neuronal tau-immunoreactive aggregates, similar to the total tau distribution, firstly presenting in cortical layers II and III and subsequently involving in layers IV-VI. Neuropil threads became maximal in the 9th decade in both frontal and entorhinal cortices. Astrocytic tau accumulation was first observed in both frontal and entorhinal cortices in the 6th decade, predominantly in layer I and subcortical white matter, and increased in number with aging. Extraneuronal tau reactive aggregates and coiled bodies were rarely observed in the entorhinal cortex, and when present, were scattered through layer II to VI.

CONCLUSIONS

We have observed an age-dependant pattern of neuronal, extraneuronal and glial tau protein accumulation in the entorhinal cortex in individuals without neurodegenerative diseases. In contrast, tau protein aggregation is infrequently observed in the frontal cortex as a function of aging.