Distribution of tangles and threads in the cerebral cortex in progressive supranuclear palsy

In vivo tau imaging: obstacles and progress

The military conflicts of the last decade have highlighted the growing problem of traumatic brain injury in combatants returning from the battlefield. The considerable evidence pointing at the accumulation of tau aggregates and its recognition as a risk factor in neurodegenerative conditions such as Alzheimer's disease have led to a major effort to develop selective tau ligands that would allow research into the physiopathologic underpinnings of traumatic brain injury and chronic traumatic encephalopathy in military personnel and the civilian population. These tracers will allow new insights into tau pathology in the human brain, facilitating research into causes, diagnosis, and treatment of traumatic encephalopathy and major neurodegenerative dementias, such as Alzheimer's disease and some variants of frontotemporal lobar degeneration, in which tau plays a role. The field of selective tau imaging has to overcome several obstacles, some of them associated with the idiosyncrasies of tau aggregation and others related to radiotracer design. A worldwide effort has focused on the development of imaging agents that will allow selective tau imaging in vivo. Recent progress in the development of these tracers is enabling the noninvasive assessment of the extent of tau pathology in the brain, eventually allowing the quantification of changes in tau pathology over time and its relation to cognitive performance, brain volumetrics, and other biomarkers, as well as assessment of efficacy and patient recruitment for antitau therapeutic trials.

Neuropsychological study of amyotrophic lateral sclerosis and parkinsonism-dementia complex in Kii peninsula, Japan

BACKGROUND

The Kii peninsula of Japan is one of the foci of amyotrophic lateral sclerosis and parkinsonism-dementia complex (ALS/PDC) in the world. The purpose of this study is to clarify the neuropsychological features of the patients with ALS/PDC of the Kii peninsula (Kii ALS/PDC).

METHODS

The medical interview was done on 13 patients with Kii ALS/PDC, 12 patients with Alzheimer's disease, 10 patients with progressive supranuclear palsy, 10 patients with frontotemporal lobar degeneration and 10 patients with dementia with Lewy bodies. These patients and their carer/spouse were asked to report any history of abulia-apathy, hallucination, personality change and other variety of symptoms. Patients also underwent brain magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), and neuropsychological tests comprising the Mini Mental State Examination, Raven's Colored Progressive Matrices, verbal fluency, and Paired-Associate Word Learning Test and some of them were assessed with the Frontal Assessment Battery (FAB).

RESULTS

All patients with Kii ALS/PDC had cognitive dysfunction including abulia-apathy, bradyphrenia, hallucination, decrease of extraversion, disorientation, and delayed reaction time. Brain MRI showed atrophy of the frontal and/or temporal lobes, and SPECT revealed a decrease in cerebral blood flow of the frontal and/or temporal lobes in all patients with Kii ALS/PDC. Disorientation, difficulty in word recall, delayed reaction time, and low FAB score were recognized in Kii ALS/PDC patients with cognitive dysfunction.

CONCLUSIONS

The core neuropsychological features of the patients with Kii ALS/PDC were characterized by marked abulia-apathy, bradyphrenia, and hallucination.

The challenges of tau imaging

In vivo imaging of tau pathology will provide new insights into tau deposition in the human brain, thus facilitating research into causes, diagnosis and treatment of major dementias, such as Alzheimer’s disease, or some variants of frontotemporal lobar degeneration, in which tau plays a role. Tau imaging poses several challenges, some related to the singularities of tau aggregation, and others related to radiotracer design. Several groups around the world are working on the development of imaging agents that will allow the in vivo assessment of tau deposition in aging and in neurodegeneration. Development of a tau imaging tracer will enable researchers to noninvasively examine the degree and extent of tau pathology in the brain, quantify changes in tau deposition over time, evaluate its relation to cognition and assess the efficacy of anti-tau therapy.

RETRACTED: Wild type and P301L mutant Tau promote neuro-inflammation and α-Synuclein accumulation in lentiviral gene delivery models

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concerns about the article were raised on PubPeer [https://pubpeer.com/publications/DA4525FDCD8F7FEA2E4ACC9EC9322F] namely that in the western blots there are similarities between Fig. 1D and 1E, Fig. 2B duplicates Fig. 3E, Fig. 4L duplicates Fig. 5A and Fig. 4A partly duplicates Fig. 4F, and Figure 2D is the same as Figure 1B in Algarzae, N., Hebron, M., Miessau, M., Moussa, C.E.H., 2012. Parkin prevents cortical atrophy and Ab-induced alterations of brain metabolism: 13C NMR and magnetic resonance imaging studies in AD models. Neuroscience 225, 22-34. The corresponding author was not able to provide the raw data, and therefore requested to retract the article. Authors Charbel E.-H. Moussa, G. William Rebeck and Alexander M. Herman agreed to this retraction, Preeti J. Khandelwal and Sonya B. Dumanis are no longer in science and could not be contacted.

The relationship between clinical and pathological variables in Richardson's syndrome

In order to determine the relationship between regional neuropathology and severity of clinical features in Richardson's syndrome (PSP-RS), the following hypotheses were tested: (1) executive dysfunction relates to prefrontal pathology; (2) language difficulties to pathology in Broca's area and/or the perirhinal cortex; and (3) visuospatial impairment to pathology in the supramarginal region. A prospectively studied case series of brain donors at a specialist clinic in Addenbrooke's Hospital Cambridge, UK, were examined. All those fulfilling postmortem criteria for PSP-RS and their last cognitive assessment within 24 months of death (N = 11/25) were included. The degree of regional neuronal loss and neuronal tau deposition across a number of cortical brain regions was performed and compared to 10 age- and sex-matched controls from the Sydney Brain Bank. Stepwise multiple linear regressions were used to determine the neuropathological correlates to cognitive scores and revealed the following. Executive dysfunction, as indexed by letter fluency, related to the degree of tau deposition in the superior frontal gyrus and supramarginal cortices (p < 0.020), language deficits related to neuron loss in the perirhinal gyrus (p < 0.001) and tau deposition in Broca's area (p = 0.020), while visuospatial dysfunction and global cognitive impairment related to tau deposition in the supramarginal gyrus (p < 0.007). The severity of cognitive deficits relate to regional cortical tau deposition in PSP-RS, although language impairment related to neuronal loss in the perirhinal region. Global cognitive dysfunction related most to the severity of tau deposition in the supramarginal gyrus warranting further research on the role of this brain region in PSP-RS.

β-amyloid triggers ALS-associated TDP-43 pathology in AD models

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease associated with loss of motor neurons in the brain and spinal cord. ALS is occasionally diagnosed with frontotemporal lobar dementia with ubiquitin-positive inclusions (FTLD-U). Alzheimer's disease (AD) is the most common type of age-associated dementia. Abnormal levels of aggregated Tar-DNA binding protein-43 (TDP-43) are detected in the majority of patients with ALS, FTLD and AD. We observed a significant increase (200%) in the levels of TDP-43 in cortical autopsies of late stage AD patients. Lentiviral expression of Aβ(1-42) in the rat motor cortex led to an increase in TDP-43 pathology, including up-regulation of the mature ~44kDa protein, identical to the pathological changes seen in AD. Furthermore, expression of Aβ(1-42) was associated with TDP-43 phosphorylation and accumulation in the cytosol. Clearance of Aβ with parkin prevented TDP-43 pathology. TDP-43 modifications were also observed in 3xTransgenic AD (3xTg-AD) compared to wild type mice, but these changes were attenuated in parkin-injected hippocampi, even in the presence of Tau pathology, suggesting that TDP-43 pathology is triggered by Aβ, independent of Tau. Increased levels of casein kinase (CK1 and CK2), which are associated with TDP-43 phosphorylation, were also observed in Aβ(1-42) expressing brains. These data indicate an overlap in TDP-43 pathology between AD and ALS-FTLD and suggest that Aβ triggers modifications of TDP-43.

The Relationship between Parkin and Protein Aggregation in Neurodegenerative Diseases

The most prominent changes in neurodegenerative diseases are protein accumulation and inclusion formation. Several neurodegenerative diseases, including Alzheimer's, the Synucleinopathies and Tauopathies share several overlapping clinical symptoms manifest in Parkinsonism, cognitive decline and dementia. As degeneration progresses in the disease process, clinical symptoms suggest convergent pathological pathways. Biochemically, protein cleavage, ubiquitination and phosphorylation seem to play fundamental roles in protein aggregation, inclusion formation and inflammatory responses. In the following we provide a synopsis of the current knowledge about protein accumulation and astrogliosis as a common denominator in neurodegenerative diseases, and we propose insights into protein degradation and anti-inflammation. We review the E3-ubiquitin ligase and other possible functions of parkin as a suppressant of inflammatory signs and a strategy to clear amyloid proteins in neurodegenerative diseases.

Leptin regulates tau phosphorylation and amyloid through AMPK in neuronal cells

Leptin, which serves as a lipid-modulating hormone to control metabolic energy availability, is decreased in Alzheimer's disease (AD) patients, and serum levels are inversely correlated to severity of dementia. We have previously described the effects of leptin in reducing amyloid beta protein both in vitro and in vivo, and tau phosphorylation in vitro. Herein, we systematically investigated the signaling pathways activated by leptin, leading to these molecular endpoints, to better understand its mechanism of action. Inhibition of amyloid beta production and tau phosphorylation in leptin-treated human and/or rat neuronal cultures were both dependent on activation of AMP-activated protein kinase (AMPK). Direct stimulation of AMPK with the cell-permeable activator, 5-aminoimidazole-4-carboxyamide ribonucleoside (AICAR), replicated leptin's effects and conversely, Compound C, an inhibitor of AMPK, blocked leptin's action. The data implicate that AMPK is a key regulator of both AD-related pathways.

Astrocytic tau pathology positively correlates with neurofibrillary tangle density in progressive supranuclear palsy

Tufted astrocytes (TAs) are considered reliable, specific markers for the neuropathologic diagnosis of progressive supranuclear palsy (PSP). It is known that neurofibrillary tangles (NFTs) may relate directly to neurodegeneration, but the role of glial tau pathology is not well determined. To examine the hypothesis that TAs are as pathogenic as NFTs and that both might have a common accumulation, we evaluated the topographic relationship between TAs and NFTs in 12 cases of PSP. The sections of 13 different parts of the brain were stained using the Gallyas-Braak method, and TAs and NFTs were counted and compared statistically. The number of TAs significantly correlated with that of NFTs in the central gray matter, pontine nuclei, and tegmentum, which are responsible for the main symptoms in PSP. In the examined allocortex, however, NFTs were abundant without accompanying TAs. Staining with the specific antibody for 4-repeat tau (RD4) and 3-repeat tau (RD3) was performed to clarify this discrepancy from the standpoint of tau isoforms. NFTs in the entorhinal cortex were stained with both RD3 and RD4, but NFTs in the premotor cortex were stained with only RD4. The nature of NFTs in the allocortical area was different from that of the isocortex in PSP. TAs in the isocortex may share the same pathologic cascade with NFTs stained only by RD4. These results suggest that TAs are part of the same pathologic process as NFTs in PSP.

Relationship between neuronal loss and tangle formation in neurons and oligodendroglia in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a progressive degenerative disorder characterized by neuronal loss, gliosis and abnormal fibril formation of abnormally phosphorylated tau protein in neurons and glia cells, but the cause is not clear at present. For the purpose of clarifying the pathological significance of accumulation of tau protein in neurons and oligodendroglia in PSP, we morphologically classified neurofibrillary tangles (NFT) and coiled bodies (CB) in oligodendroglia in three PSP brains into four stages, using double staining for immunohistochemistry with AT8 antibody and modified Gallyas-Braak (GB) staining. AT8-positive neurons without abnormal fibril structure with GB staining were classified as stage I, AT8-positive neurons containing a few fibril structures with GB staining were classified stage II, AT8-positive neurons containing mature fibril structures were classified as stage III, and AT8 negative neurons containing abnormal fibril structures stained only with GB staining were classified as stage IV (ghost tangles). These stages were also assessed for CB. Then we counted the number of cells of each stage in various brain regions to investigate the relationship of NFT and CB with neuronal loss and gliosis. The results showed that there were very few stage IV NFT and CB, which reflect cell death, but that stage III NFT and CB were abundant. Moreover, CB were abundant in regions with severe neuronal loss. These results suggest that appearance of CB is closely associated with degenerative regions.

Corticobasal ganglionic degeneration and progressive supranuclear palsy presenting with cognitive decline

Corticobasal ganglionic degeneration (CBGD) and progressive supranuclear palsy (PSP) were originally described in the sixties as predominantly motor syndromes. Over the years, the detailed study of additional cases of CBGD has shown that it is a distinctive histological entity which can often present as dementia or aphasia. Although some pathological features of CBGD overlap with those of other forms of non-Alzheimer non-Lewy body dementia, the distribution and relative number of these abnormalities and the distinctive pattern of tau immunodeposits allows the distinction of CBGD from Pick's disease and fronto-temporal dementia. In contrast, PSP only rarely presents with prominent dementia or behavioral changes. In these unusual PSP cases, care must be taken to exclude the diagnoses of CBGD and familial tangle-only dementia.

Tau-positive glial inclusions in progressive supranuclear palsy, corticobasal degeneration and Pick's disease

The presence of tau-positive glial inclusions has been recently found a consistent feature in the brains of patients with progressive supranuclear palsy (PSP), corticobasal degeneration (CBD) and Pick's disease (PiD). These inclusions are classified based on cellular origin as tau-positive astrocytes, presumably either fibrillary or protoplasmic, coiled bodies and glial threads. Immunohistochemically, their major structural component is abnormal tau proteins, similar to those found in Alzheimer's disease. Nevertheless, their morphology, including ultrastructural profile, has been suggested to be distinctive for each disease. The profile and extent of particular glial inclusions correlate well with disease phenotype. Highly characteristic correlations include tufts of abnormal fibers in PSP, astrocytic plaques and dense glial threads in CBD and ramified astrocytes and small Pick body-like inclusions in PiD. The significance of the inclusions in disease pathogenesis and their biochemical characteristics remain to be clarified. Nevertheless, these distinctive glial lesions most likely reflect fundamental alterations in isoform composition of tau as well as its specific cellular and regional expression in sporadic tauopathies.

Individual and regional variations of phospho-tau species in progressive supranuclear palsy

The purpose of this study was to learn about possible variations in phospho-tau profiles in terms of case-to-case differences, regional modifications and diversification of tau phosphorylation sites in five PSP cases with moderate to severe frontosubcortical dysfunction. Gel electrophoresis of sarkosyl-insoluble fractions and Western blotting with five anti-tau phospho-specific antibodies directed to phosphorylation sites Thr181, Ser202, Ser214, Ser396 and Ser422 were used to study four brain regions including frontal cortex, area 8, subcortical white matter of the frontal lobe, caudate/putamen: striatum, and basis pontis: pons. Although two bands of 66 and 62 kDa were observed in almost every region in each case, the intensity of the bands depends on the anti-tau phospho-specific antibody. More importantly, bands of 72, 50/55 and 37 kDa were commonly found in PSP brains, whereas other bands of about 60, 42, 33 and 29 kDa were irregularly observed. The pattern of bands differed slightly from one case to another and from one region to another. Moreover, the phospho-tau profile differed depending on the anti-tau phospho-specific antibody used. These data suggest that several species of tau are variably phosphorylated at a given time in a given region (and probably in a given cell), and that tau aggregates are composed of several phosphorylated truncated or cleaved tau molecules, in addition to phosphorylated complete tau isoforms.

A comparison of degeneration in motor thalamus and cortex between progressive supranuclear palsy and Parkinson's disease

Changes in motor cortical activation are associated with the major symptoms observed in both Parkinson's disease and progressive supranuclear palsy (PSP). While research has concentrated on basal ganglia abnormalities as central to these cortical changes, several studies in both disorders have shown pathology in the thalamus and motor cortices. In particular, we recently reported an 88% loss of corticocortical projection neurones in the pre-supplementary motor (pre-SMA) cortex in Parkinson's disease. Further analysis of the degree of neuronal loss and pathology in motor cortices and their thalamocortical relays in Parkinson's disease and PSP is warranted. Six cases with PSP, nine cases with Parkinson's disease and nine controls were selected from a prospectively studied brain donor cohort. alpha-Synuclein, ubiquitin and tau immunohistochemistry were used to identify pathological lesions. Unbiased stereological methods were used to analyse atrophy and neuronal loss in the motor thalamus [ventral anterior, ventrolateral anterior and ventrolateral posterior (VLp) nuclei] and motor cortices (primary motor, dorsolateral premotor and pre-SMA cortices). Analysis of variance and post hoc testing was used to determine differences between groups. In Parkinson's disease, the motor thalamus and motor cortices (apart from the pre-SMA) were preserved containing only rare alpha-synuclein-positive and ubiquitin-positive Lewy bodies. In contrast, patients with PSP had significant atrophy and neuronal loss in VLp (22 and 30%, respectively), pre-SMA (21 and 51%, respectively) and primary motor cortices (33 and 54%, respectively). In the primary motor cortex of PSP cases, neuronal loss was confined to inhibitory interneurones, whereas in the pre-SMA both interneurones (reduced by 26%) and corticocortical projection neurones (reduced by 82%) were affected. Tau-positive neurofibrillary and glial tangles were observed throughout the motor thalamus and motor cortices in PSP. These non-dopaminergic lesions in motor circuits are likely to contribute to the pathogenesis of both PSP and Parkinson's disease. The selective involvement of the VLp and primary motor cortex in PSP implicates these cerebellothalamocortical pathways as differentiating this disease, possibly contributing to the early falls.

Tuft-shaped astrocytes in Lewy body disease

We investigated the occurrence and distribution of tuft-shaped astrocytes (TuSAs) in 60 brains from patients with Lewy body disease (LBD), which were clinically diagnosed as Parkinson's disease (PD) or dementia with Lewy bodies (DLB), and 85 brains from control subjects. TuSAs have been documented as a neuropathological hallmark of progressive supranuclear palsy (PSP). We found phosphorylated tau (p-tau)-positive and alpha-synuclein-negative TuSAs in 10 of 60 patients with LBD and 3 of 85 control cases. TuSAs were mainly located within the precentral and premotor gyri of the frontal lobe cortex. There were only few TuSAs, but the distribution pattern and morphological and immunohistological features were similar to that in PSP. Furthermore, other p-tau positive structures, including aggregates in neurons, coiled-like glial cells and threads showed a similar distribution to those in PSP; mainly in the hippocampus, striatum, subthalamic nucleus, precentral and premotor gyri, brainstem nucleus, and dentate nucleus. In these cases, however, neuronal loss and gliosis were not seen in the regions involved in PSP, such as the subthalamic nucleus, pallidum, inferior olivary, cerebellar dentate nuclei, and periaqueductal gray matter. Clinical features were indistinguishable between the LBD with and without TuSAs. The appearance of TuSAs was not related to the frequency of Lewy bodies, neurofibrillary tangles, and senile plaques, but was significantly more pronounced with advancing age in both LBD and controls. These findings suggest that in a subgroup of elderly individual cases, especially associated with LB pathology, the glial and neuronal p-tau accumulation is increased and has a distributional pattern similar to PSP.

Distribution of tuft-shaped astrocytes in the cerebral cortex in progressive supranuclear palsy

The deposition of abnormal levels of tau protein is a major neuropathological feature of progressive supranuclear palsy (PSP), and the presence of tuft-shaped astrocytes is a neuropathological hallmark of PSP. We examined the topographic distribution of tuft-shaped astrocytes in the cerebral hemisphere by Gallyas-Braak silver staining in three Japanese autopsy cases of typical PSP. The distribution of tuft-shaped astrocytes was relatively uniform between cases. Tuft-shaped astrocytes were identified predominantly in posterior frontal areas such as the precentral gyrus and premotor and supplementary motor areas (Brodmann areas 4, 6 and 8). Tuft-shaped astrocytes were most dense in areas of cortical convexity, and they were more abundant in the crests of the cerebral gyri than in the valleys of the cerebral sulci. The temporal, parietal and occipital cortices, including the hippocampal formation and cingulate gyrus, were relatively free of tuft-shaped astrocytes. We confirmed involvement of the cerebral cortex in the pathology of PSP, and showed the widespread presence of tuft-shaped astrocytes, particularly in the precentral gyrus and premotor and supplementary motor areas, to be an essential neuropathological feature of PSP. The extra-pyramidal and pyramidal signs, supranuclear oculomotor abnormalities and other cortical signs associated with PSP may be related to the high density of tuft-shaped astrocytes in the precentral gyrus and premotor and supplementary motor areas. Dementia, apraxia, aphasia and frontal lobe signs may also result, at least in part, from this cortical involvement.

Staging disease severity in movement disorder tauopathies: Brain atrophy separates progressive supranuclear palsy from corticobasal degeneration

The movement disorders progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) both deposit tau in degenerating neurons and are considered to be tauopathies. The recently developed scheme for staging tissue degeneration in another tauopathy, frontotemporal dementia [Broe et al., Neurology 2003;60:1005-1011] was applied to pathologically confirmed PSP (n = 24) and CBD (n = 9) cases and correlated with clinical indices. In contrast to frontotemporal dementia, the majority of PSP cases had limited or no visible atrophy, while the pattern of atrophy in CBD cases conformed to the existing staging scheme (all but one case exhibiting substantial visible tissue atrophy). Despite similar clinical severity and disease duration between groups, there was a marked difference between the PSP and CBD cases in pathological disease stage (chi(2) = 8.86; P = 0.03). The degree of global atrophy in PSP appears to be distinct from other tauopathies, while CBD fits the same pattern as other pathological forms of frontotemporal dementia.

Frontal atrophy correlates with behavioural changes in progressive supranuclear palsy

Regional brain volumes were measured in 21 patients with progressive supranuclear palsy (PSP), 17 patients with Parkinson's disease and 23 controls using 3D MRI-based volumetry. Cortical, subcortical and ventricular volume measures were correlated with global indices of motor disability and cognitive disturbance. All MRI measures, including hippocampal volume, were preserved in Parkinson's disease. Patients with PSP could be distinguished from both Parkinson's disease and controls by whole brain volume loss, ventricular dilatation and disproportionate atrophy of the frontal cortex. Caudate nucleus volume loss additionally differentiated PSP from controls, but was modest in severity and proportionate to whole brain volume loss. The present study identifies disease-specific differences in the topography of brain atrophy between PSP and Parkinson's disease, and has potential implications for the in vivo radiological differentiation of these two disorders. In PSP, the variance in frontal grey matter volume related to measures of behavioural disturbance, confirming the use of behavioural tests for ante-mortem case differentiation and suggesting that intrinsic cortical deficits contribute to these clinical disturbances.

Recent advances in dementia research in Japan: non-Alzheimer-type degenerative dementias

In this article, we review recent reports by Japanese researchers on non-Alzheimer-type degenerative dementias. These dementias can be classified into the following subtypes: dementias with Lewy bodies, including diffuse Lewy body disease, dementias with neurofibrillary tangles, dementias with glial tangles, including progressive supranuclear palsy and corticobasal degeneration, argyrophilic grain dementia, frontotemporal dementias including Pick's disease; dementias with degeneration of subcortical nuclei, including Huntington's disease and, last, unclassified dementias. Recently, these various forms of dementia have received much attention in Japan, as elsewhere.

Regional quantitative analysis of tau-positive neurons in progressive supranuclear palsy: comparison with Alzheimer's disease

In patients with progressive supranuclear palsy (PSP), various tau-positive abnormal structures are found in the cerebral cortex as well as in the subcortical nuclei. Similar tau-positive abnormalities are also identified in cortico-basal degeneration (CBD). It is therefore questionable as to whether PSP can be neuropathologically differentiated from CBD. It also remains nuclear whether neurofibrillary tangles (NFT) in the cerebral cortex of PSP patients consist of PSP-NFT or concomitant Alzheimer's disease (AD)-NFT, although there have been some reports suggesting that PSP- and AD-NFT are different with respect to distribution pattern and biochemical character. In this study, a regional quantitative analysis of the distribution and antigenicity of tau-positive neurons (TPN) was performed in PSP cases and compared with that in AD cases. TPN consisted of NFT with tangle-formation and pretangle neurons (PN) without tangle-formation. In addition, NFT were subdivided into mature and immature NFT according to the difference of staining properties with anti-tau-related antibodies. The comparison of the TPN of the PSP cases with those of the AD cases revealed that the degree of tangle-formation in the TPN of AD was similar in all of the examined regions, while that in the TPN of PSP varied according to the region and case. Moreover, the NFT in the PSP and AD cases had different distributions according to the cortical layer and subnucleus, even in the common predilection sites of PSP and AD, suggesting that NFT in these regions of the PSP cases consist mainly of PSP-NFT. In addition, the PSP cases could be divided into two groups according to the difference of the tangle-formation of TPN; group I with typical PSP pathology and group II with atypical PSP pathology similar to CBD. This suggests that there is a continuity between PSP and CBD with respect to the distribution and antigenicity of TPN.

Proposals for re-evaluation of current autopsy criteria for the diagnosis of Alzheimer's disease

Defining criteria for the postmortem diagnosis of Alzheimer's disease (AD) has proven difficult due to the phenotypical heterogeneity of the disease, the absence of a specific disease marker and an overlap of AD neuropathology with that observed in a number of nondemented aged individuals. Even though the role of plaques and tangles in the pathogenesis of AD remains undetermined, a host of clinicopathological correlative studies have shown that both lesions, if present in sufficient numbers-particularly in the neocortex-are still to be considered the best morphological signposts for the disease. All currently used criteria for the neuropathologic diagnosis of AD have some weaknesses and need to be reestablished and revalidated. Multivariant analysis in a personal autopsy series of elderly subjects revealed significant correlations between psychostatus and both the CERAD criteria and Braak staging of neuritic Alzheimer-type lesions, and less concordance with the National Institutes of Aging and Tierney criteria. We propose a set of histopathologic diagnostic criteria for both definite and preclinical AD that rely on various constellations of both different types of plaques, except diffuse amyloid deposits, and neurofibrillary tangles, in allocortical and isocortical areas considering their topographic pattern. This set of criteria encompasses phenotypic variations of the pathology and takes into account the chronic, progressive course of AD. It allows the detection of preclinical disease in subjects in whom dementia is not reported and includes those cases in the morphological gray zone between "normal" aging and full-fledged AD that practicing neuropathologists consider the most problematic. The set of criteria includes guidelines concerning tissue sampling and processing, and standardized staining methods that should allow neurologists to minimize interrater and interlaboratory variability in the assessment of morphologic lesions and the diagnosis of AD.

Corticobasal degeneration: widespread argentophilic threads and glia in addition to neurofibrillary tangles. Similarities of cytoskeletal abnormalities in corticobasal degeneration and progressive supranuclear palsy

A 57-year-old man had exhibited cortical sensory disturbance, rigidity, spasticity, dementia, alien hand, grasp reflex, supranuclear ophthalmoplegia, pseudobulbar palsy, and neck dystonia for 4 years. Histological examination of autopsied specimens revealed neuronal loss in the cerebral cortex, with ballooned neurons, subthalamic nucleus, substantia nigra, basal ganglia, midbrain tegmentum, and the thalamus. There were neurofibrillary tangles in the subthalamic nucleus and the substantia nigra. Gallyas-Braak silver impregnation demonstrated numerous argentophilic tangles, threads, and a few argentophilic glia in the cerebral cortex, subcortical white matter, particularly in the precentral gyrus, subcortical nuclei, and the brainstem. These argentophilic structures were largely positive for tau, and negative for ubiquitin, paired helical filaments, and phosphorylated neurofilament. Ultrastructurally, 15-nm-wide straight tubules were observed in the neurons of the substantia nigra, globus pallidus, and the precentral cortex, coexisting with a few twisted tubules periodically constricted at 160- to 230-nm intervals. It was conclusively shown that Gallyas- and tau-positive cytoskeletal abnormalities occurred widely in brain of corticobasal degeneration. Both distribution and morphology of abnormal phosphorylated tau protein in corticobasal degeneration appear to resemble these features in progressive supranuclear palsy. These findings suggest a common cytoskeletal etiopathological significance in corticobasal degeneration and progressive supranuclear palsy.

Structural basis of dementia in neurodegenerative disorders

Progressive dementia syndromes in adults are caused by a number of conditions associated with different structural lesions of the brain. In most clinical and autopsy series, senile dementia of the Alzheimer type is the most common cause of mental decline in the elderly accounting for up to 90%, whereas degenerative non-Alzheimer dementias range from 7 to 30% (mean 8-10%). They include a variety of disorders featured morphologically by neuron and synapse loss and gliosis, often associated with cytopathological changes involving specific cortical and subcortical circuits. These neuronal/glial inclusions and neuritic alterations show characteristic immunoreactions and ultrastructure indicating cytoskeletal mismetabolism. They are important diagnostic sign posts that, in addition to the distribution pattern of degenerative changes, indicate specific vulnerability of neuronal populations, but their pathogenic role and contribution to mental decline are still poorly understood. In some degenerative disorders no such cytopathological hallmarks have been observed; a small number is genetically determined. While in Alzheimer's disease (AD) mental decline is mainly related to synaptic and neuritic pathologies, other degenerative disorders show variable substrates of dementia involving different cortical and/or subcortical circuits which may or may not be superimposed by cortical Alzheimer lesions. In most demented patients with Lewy body disorders (Parkinson's disease, Lewy body dementia), they show similar distribution as in AD, while in Progressive Supranuclear Palsy (PSP), mainly prefrontal areas are involved. Lobar atrophies, increasingly apparent as causes of dementia, show fronto-temporal cortical neuron loss, spongiosis and gliosis with or without neuronal inclusions (Pick bodies) and ballooned cells, while dementing motor neuron disease and multisystem atrophies reveal ubiquitinated neuronal and oligodendroglial inclusions. There are overlaps or suggested relationships between some neurodegenerative disorders, e.g. between corticobasal degeneration, PSP and Pick's atrophy. In many of these disorders with involvement of the basal ganglia, degeneration of striatofrontal and hippocampo-cortical loops are important factors of mental decline which may be associated with isocortical neuronal degeneration and synapse loss or are superimposed by cortical AD pathology.