Clinicopathological characterization of Pick's disease versus frontotemporal lobar degeneration with ubiquitin/TDP-43-positive inclusions

Motor involvement in frontotemporal lobar degeneration with TAR DNA-binding protein of 43 kDa type C

The degeneration of pyramidal tracts has been reported in frontotemporal lobar degeneration with TDP-43 (TAR DNA-binding protein 43) pathology (FTLD-TDP) type C. Herein, we examined the detailed pathology of the primary motor area and pyramidal tracts in the central nervous system in four autopsy cases of FTLD-TDP type C, all of which were diagnosed by neuropathological, biochemical, and genomic analyses. Three patients showed right dominant atrophy of the frontal and temporal lobes, while the other patient showed left dominant atrophy. All four patients showed motor symptoms, and two patients had episodes of repeated aspiration. In the primary motor area, phosphorylated TDP-43 (p-TDP-43) or annexin A11-immunoreactive long dystrophic neurites were observed in all cases, and neuronophagia of the Betz cells was frequently observed in two of four cases. In the lower motor system, p-TDP-43 or annexin A11-positive dystrophic neurites were detected in the anterior horn of the spinal cord. Immuno-electron microscopy of the insoluble fraction extracted from all cases showed p-TDP-43 or annexin A11-labelled filaments. In FTLD-TDP type C, neurodegeneration with TDP and annexin A11 pathology was observed mainly in the upper motor neurons of both patients with right- and left predominant temporal atrophy and a short disease duration. Furthermore, a combination of TDP-43 and annexin A11 pathology was visible in the lower motor neurons, albeit less frequently. In summary, we reported the TDP-43 and annexin A11-associated involvement of anterior horn cells of the spinal cord for the first time. The degeneration of the motor system could contribute to dysphagia and aspiration pneumonia at the late stage of FTLD-TDP type C. Little or no TDP pathology was found in the corticospinal tract, unlike in FTLD-TDP type B, suggesting the occurrence of secondary degeneration in FTLD-TDP type C.

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

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

MAPT H2 haplotype and risk of Pick's disease in the Pick's disease International Consortium: a genetic association study

BACKGROUND

Pick's disease is a rare and predominantly sporadic form of frontotemporal dementia that is classified as a primary tauopathy. Pick's disease is pathologically defined by the presence in the frontal and temporal lobes of Pick bodies, composed of hyperphosphorylated, three-repeat tau protein, encoded by the MAPT gene. MAPT has two distinct haplotypes, H1 and H2; the MAPT H1 haplotype is the major genetic risk factor for four-repeat tauopathies (eg, progressive supranuclear palsy and corticobasal degeneration), and the MAPT H2 haplotype is protective for these disorders. The primary aim of this study was to evaluate the association of MAPT H2 with Pick's disease risk, age at onset, and disease duration.

METHODS

In this genetic association study, we used data from the Pick's disease International Consortium, which we established to enable collection of data from individuals with pathologically confirmed Pick's disease worldwide. For this analysis, we collected brain samples from individuals with pathologically confirmed Pick's disease from 35 sites (brainbanks and hospitals) in North America, Europe, and Australia between Jan 1, 2020, and Jan 31, 2023. Neurologically healthy controls were recruited from the Mayo Clinic (FL, USA, or MN, USA between March 1, 1998, and Sept 1, 2019). For the primary analysis, individuals were directly genotyped for the MAPT H1-H2 haplotype-defining variant rs8070723. In a secondary analysis, we genotyped and constructed the six-variant-defined (rs1467967-rs242557-rs3785883-rs2471738-rs8070723-rs7521) MAPT H1 subhaplotypes. Associations of MAPT variants and MAPT haplotypes with Pick's disease risk, age at onset, and disease duration were examined using logistic and linear regression models; odds ratios (ORs) and β coefficients were estimated and correspond to each additional minor allele or each additional copy of the given haplotype.

FINDINGS

We obtained brain samples from 338 people with pathologically confirmed Pick's disease (205 [61%] male and 133 [39%] female; 338 [100%] White) and 1312 neurologically healthy controls (611 [47%] male and 701 [53%] female; 1312 [100%] White). The MAPT H2 haplotype was associated with increased risk of Pick's disease compared with the H1 haplotype (OR 1·35 [95% CI 1·12 to 1·64], p=0·0021). MAPT H2 was not associated with age at onset (β -0·54 [95% CI -1·94 to 0·87], p=0·45) or disease duration (β 0·05 [-0·06 to 0·16], p=0·35). Although not significant after correcting for multiple testing, associations were observed at p less than 0·05: with risk of Pick's disease for the H1f subhaplotype (OR 0·11 [0·01 to 0·99], p=0·049); with age at onset for H1b (β 2·66 [0·63 to 4·70], p=0·011), H1i (β -3·66 [-6·83 to -0·48], p=0·025), and H1u (β -5·25 [-10·42 to -0·07], p=0·048); and with disease duration for H1x (β -0·57 [-1·07 to -0·07], p=0·026).

INTERPRETATION

The Pick's disease International Consortium provides an opportunity to do large studies to enhance our understanding of the pathobiology of Pick's disease. This study shows that, in contrast to the decreased risk of four-repeat tauopathies, the MAPT H2 haplotype is associated with an increased risk of Pick's disease in people of European ancestry. This finding could inform development of isoform-related therapeutics for tauopathies.

FUNDING

Wellcome Trust, Rotha Abraham Trust, Brain Research UK, the Dolby Fund, Dementia Research Institute (Medical Research Council), US National Institutes of Health, and the Mayo Clinic Foundation.

Creating the Pick's disease International Consortium: Association study of MAPT H2 haplotype with risk of Pick's disease

Background

Pick's disease (PiD) is a rare and predominantly sporadic form of frontotemporal dementia that is classified as a primary tauopathy. PiD is pathologically defined by argyrophilic inclusion Pick bodies and ballooned neurons in the frontal and temporal brain lobes. PiD is characterised by the presence of Pick bodies which are formed from aggregated, hyperphosphorylated, 3-repeat tau proteins, encoded by the MAPT gene. The MAPT H2 haplotype has consistently been associated with a decreased disease risk of the 4-repeat tauopathies of progressive supranuclear palsy and corticobasal degeneration, however its role in susceptibility to PiD is unclear. The primary aim of this study was to evaluate the association between MAPT H2 and risk of PiD.

Methods

We established the Pick's disease International Consortium (PIC) and collected 338 (60.7% male) pathologically confirmed PiD brains from 39 sites worldwide. 1,312 neurologically healthy clinical controls were recruited from Mayo Clinic Jacksonville, FL (N=881) or Rochester, MN (N=431). For the primary analysis, subjects were directly genotyped for MAPT H1-H2 haplotype-defining variant rs8070723. In secondary analysis, we genotyped and constructed the six-variant MAPT H1 subhaplotypes (rs1467967, rs242557, rs3785883, rs2471738, rs8070723, and rs7521).

Findings

Our primary analysis found that the MAPT H2 haplotype was associated with increased risk of PiD (OR: 1.35, 95% CI: 1.12-1.64 P=0.002). In secondary analysis involving H1 subhaplotypes, a protective association with PiD was observed for the H1f haplotype (0.0% vs. 1.2%, P=0.049), with a similar trend noted for H1b (OR: 0.76, 95% CI: 0.58-1.00, P=0.051). The 4-repeat tauopathy risk haplotype MAPT H1c was not associated with PiD susceptibility (OR: 0.93, 95% CI: 0.70-1.25, P=0.65).

Interpretation

The PIC represents the first opportunity to perform relatively large-scale studies to enhance our understanding of the pathobiology of PiD. This study demonstrates that in contrast to its protective role in 4R tauopathies, the MAPT H2 haplotype is associated with an increased risk of PiD. This finding is critical in directing isoform-related therapeutics for tauopathies.

Clinicopathological diversity of semantic dementia: Comparisons of patients with early-onset versus late-onset, left-sided versus right-sided temporal atrophy, and TDP-type A versus type C pathology

Semantic dementia (SD) is a unique clinicopathological entity associated with TDP-type C pathology. We present four cases of SD that illustrate the clinicopathological diversity of TDP-43 pathology, including early-onset cases of TDP-type C with corticospinal tract (CST) and motor neuron pathology and late-onset cases of TDP-type A with combined pathology. Case 1 was a 62-year-old man with semantic variant of primary progressive aphasia (svPPA) with left-predominant temporal atrophy and TDP-type C pathology with low Alzheimer's disease neuropathologic changes (ADNC). Case 2 was a 63-year-old woman with right-predominant temporal atrophy and TDP-type C pathology who had prosopagnosia and personality changes. Phosphorylated(p)-TDP-43-positive long dystrophic neurites (DNs) were observed throughout the cerebral cortex; they were more abundant in the relatively spared cortices and less so in the severely degenerated cortices. We observed CST degeneration with TDP-43 pathology in the upper and lower motor neurons, without apparent motor symptoms, in SD with TDP-type C pathology. Case 3 was a 76-year-old man who had svPPA and personality changes, with left-predominant temporal atrophy and TDP-type A pathology with high ADNC and argyrophilic grain (AG) stage 3. Case 4 was an 82-year-old man who had prosopagnosia and later developed symptoms of dementia with Lewy bodies (DLB) with right-predominant temporal atrophy and TDP-type A pathology with high ADNC, DLB of diffuse neocortical type, and AG stage 3. The distribution of p-TDP-43-positive NCIs and short DNs was localized in the anterior and inferior temporal cortices. An inverse relationship between the extent of TDP pathology and neuronal loss was also observed in SD with TDP-type A pathology. In contrast, the extent of AD, DLB, and AG pathology was greater in severely degenerated regions. CST degeneration was either absent or very mild in SD with TDP-type A. Understanding the clinicopathological diversity of SD will help improve its diagnosis and treatment.

Four-repeat tauopathies and late-onset psychiatric disorders: Etiological relevance or incidental findings?

Argyrophilic grain disease (AGD), progressive supranuclear palsy (PSP) and corticobasal degeneration are four-repeat (4R) tauopathies that develop in the presenium or later. Whether these diseases are associated with the occurrence of late-onset psychiatric disorders remains unclear. To facilitate the accumulation of clinicopathological findings regarding this issue, we here present a selected series of 11 cases that clinically developed psychotic disorder (n = 7; age at onset: 41-75 years), depressive disorder (n = 1; 49 years), bipolar disorder (n = 2; 32 and 37 years) and somatoform disorder (n = 1; 88 years), and had at least one pathological hallmark of these tauopathies. The mean age at death was 74.3 years. No case showed dementia, at least in the early stage of the course. Nine cases had AGD. Granular fuzzy astrocytes in the amygdala were noted in all AGD cases and one non-AGD case. Two AGD cases had tufted astrocytes (TAs) in the amygdala but not in the frontal cortex and striatum. Three AGD and two non-AGD cases had TAs in the frontal cortex and/or striatum but not in the amygdala. One AGD case had a small number of astrocytic plaques in the frontal cortex, striatum and globus pallidus. Only one case was diagnosed as atypical PSP according to the NINDS-PSP neuropathological criteria. No case had high-level Alzheimer's disease pathology, Lewy body disease or limbic-predominant age-related TDP-43 encephalopathy. Two cases had mild neuronal loss in the hippocampus and substantia nigra, respectively. Clinicopathological studies focusing especially on early changes of 4R tauopathies, as well as the development of surrogate markers of these diseases, may be necessary for better understanding of the pathogenic backgrounds of late-onset psychiatric disorders.

Isoform-specific patterns of tau burden and neuronal degeneration in MAPT-associated frontotemporal lobar degeneration

Frontotemporal lobar degeneration with MAPT pathogenic variants (FTLD-MAPT) has heterogeneous tau pathological inclusions postmortem, consisting of three-repeat (3R) or four-repeat (4R) tau isoforms, or a combination (3R + 4R). Here, we studied grey matter tau burden, its relation to neuronal degeneration, and regional patterns of pathology in different isoform groups of FTLD-MAPT. We included 38 FTLD-MAPT autopsy cases with 10 different MAPT pathogenic variants, grouped based on predominant tau isoform(s). In up to eleven regions (ten cortical and one striatal), we quantified grey matter tau burden using digital histopathological analysis and assigned semi-quantitative ratings for neuronal degeneration (i.e. 0-4) and separate burden of glial and neuronal tau inclusions (i.e. 0-3). We used mixed modelling to compare pathology measures (1) across the entire cohort and (2) within isoform groups. In the total cohort, tau burden and neuronal degeneration were positively associated and most severe in the anterior temporal, anterior cingulate and transentorhinal cortices. Isoform groups showed distinctive features of tau burden and neuronal degeneration. Across all regions, the 3R isoform group had lower tau burden compared to the 4R group (p = 0.008), while at the same time showing more severe neuronal degeneration than the 4R group (p = 0.002). The 3R + 4R group had an intermediate profile with relatively high tau burden along with relatively severe neuronal degeneration. Neuronal tau inclusions were most frequent in the 4R group (p < 0.001 vs. 3R), while cortical glial tau inclusions were most frequent in the 3R + 4R and 4R groups (p ≤ 0.009 vs. 3R). Regionally, neuronal degeneration was consistently most severe in the anterior temporal cortex within each isoform group. In contrast, the regions with the highest tau burden differed in isoform groups (3R: striatum; 3R + 4R: striatum, inferior parietal lobule, middle frontal cortex, anterior cingulate cortex; 4R: transentorhinal cortex, anterior temporal cortex, fusiform gyrus). We conclude that FTLD-MAPT isoform groups show distinctive features of overall neuronal degeneration and regional tau burden, but all share pronounced anterior temporal neuronal degeneration. These data suggest that distinct isoform-related mechanisms of genetic tauopathies, with slightly divergent tau distribution, may share similar regional vulnerability to neurodegeneration within the frontotemporal paralimbic networks.

The Diagnostic Patterns of Referring Physicians and Hospital Expert Psychiatrists Regarding Particular Frontotemporal Lobar Degeneration Clinical and Neuropathological Subtypes

BACKGROUND

It is important to make accurate clinical diagnosis of frontotemporal lobar degeneration (FTLD), which in turn, leads to future therapic approaches. The FTLD cases are frequently inaccurately identified, but the frequency of this misidentification according to the underlying pathological subtypes is still unclear.

OBJECTIVE

We aimed to quantify the accuracy of behavioral variant frontotemporal dementia (bvFTD) and semantic variant primary progressive aphasia (svPPA) diagnoses by both the patients' referring physicians and hospital expert psychiatrists, and we investigated whether the physicians' and psychiatrists' diagnostic patterns are associated with a specific neuropathology.

METHODS

We retrospectively analyzed the cases of a series of Japanese patients with pathologically diagnosed FTLD (n = 55): the bvFTD group (n = 47) consisted of patients with FTLD-tau (n = 20), FTLD-TDP (TAR DNA-binding protein of 43-kDA) (n = 19), and FTLD-FUS (fused in sarcoma) (n = 8). The svPPA patients (n = 8) all had FTLD-TDP.

RESULTS

Only 31% of the patients' referring physicians mentioned FTD syndrome. The referring psychiatrists and neurologists showed similar diagnostic accuracy. High diagnostic accuracy was observed for the TDP pathology group (mainly svPPA patients). The FTLD-FUS patients were more likely to be diagnosed as having a psychiatric disorder by referring physicians. The hospital expert psychiatrists' accuracy for identifying FTLD-tau pathology was low.

CONCLUSION

The results of our analyses revealed a specific diagnostic pattern associated with particular FTLD pathological subtypes, which will help to improve non-specialists' diagnostic ability.

The tauopathies: Neuroimaging characteristics and emerging experimental therapies

The tauopathies are a heterogeneous group of neurodegenerative disorders in which the prevailing underlying disease process is intracellular deposition of abnormal misfolded tau protein. Diseases often categorized as tauopathies include progressive supranuclear palsy, chronic traumatic encephalopathy, corticobasal degeneration, and frontotemporal lobar degeneration. Tauopathies can be classified through clinical assessment, imaging findings, histologic validation, or molecular biomarkers tied to the underlying disease mechanism. Many tauopathies vary in their clinical presentation and overlap substantially in presentation, making clinical diagnosis of a specific primary tauopathy difficult. Anatomic imaging findings are also rarely specific to a single tauopathy, and when present may not manifest until well after the point at which therapy may be most impactful. Molecular biomarkers hold the most promise for patient care and form a platform upon which emerging diagnostic and therapeutic applications could be developed. One of the most exciting developments utilizing these molecular biomarkers for assessment of tau deposition within the brain is tau‐PET imaging utilizing novel ligands that specifically target tau protein. This review will discuss the background, significance, and clinical presentation of each tauopathy with additional attention to the pathologic mechanisms at the protein level. The imaging characteristics will be outlined with select examples of emerging imaging techniques. Finally, current treatment options and emerging therapies will be discussed. This is by no means a comprehensive review of the literature but is instead intended for the practicing radiologist as an overview of a rapidly evolving topic.

Dopamine Transporter Imaging for Frontotemporal Lobar Degeneration With Motor Neuron Disease

Introduction

Frontotemporal lobar degeneration (FTLD) is a clinical syndrome with pathological heterogeneity, including Pick's disease and trans-activating response region (TAR) DNA-binding protein with a molecular mass of 43 kDa (TDP-43) proteinopathy (FTLD-TDP). A previous study reported abnormal findings on dopamine transporter (DAT) imaging in 30% of patients with frontotemporal dementia (FTD) in FTLD. However, the previous study did not consider the pathological heterogeneity of FTD regarding the pathomechanism leading to abnormal DAT findings. Recently, abnormal DAT findings were reported in two patients with FTLD with motor neuron disease (MND), of which FTLD-TDP type B was the most common pathological presentation. This study investigated the DAT findings of patients with a final diagnosis of FTLD-MND to determine the frequency of occurrence of DAT abnormalities in FTLD-MND.

Methods

Twenty patients with FTLD who underwent DAT single photon emission computed tomography (DAT-SPECT) were screened, and six patients with a final diagnosis of FTLD-MND were ultimately included. The patients' DAT-SPECT findings were analyzed visually and quantitatively. Neuronal loss and astrogliosis in brain regions (substantia nigra, caudate, and putamen) that could possibly affect DAT findings were evaluated in the three pathologically confirmed cases.

Result

All six patients with FTLD-MND showed abnormal visual DAT-SPECT findings. In addition, in a quantitative assessment, the specific binding ratio in the striatum calculated by the Southampton method was below the lower limit of the 95% prediction interval of the healthy controls by age in all the present cases. Interestingly, three of the six patients showed abnormal findings on DAT-SPECT more than half a year before the onset of MND. Neuronal loss and astrogliosis in brain regions that may affect DAT findings were observed in three pathologically confirmed cases.

Conclusion

Dopamine transporter single photon emission computed tomography revealed abnormal findings in patients with FTLD-MND, which may manifest even before the onset of MND symptoms. We believe that the possibility of future development of MND should be considered if DAT-SPECT shows abnormal findings in FTLD.

Clinical, neuroimaging, and neuropathological characterization of a patient with Alzheimer's disease syndrome due to Pick's pathology

The most common neurodegenerative syndrome associated with Pick's disease pathology (PiD) is behavioral variant frontotemporal dementia (bvFTD), which features profound social behavioral changes. Rarely, PiD can manifest as an Alzheimer's disease (AD)-type dementia with early memory impairment. We describe a patient with AD-type dementia and pure PiD pathology who showed slowly progressive memory impairment, early social changes, and paucity of motor symptoms. Atrophy and PiD were found mainly in frontotemporal regions underlying social behavior. This report may help predict the pathology of patients with atypical AD, which will ultimately be critical for enrolling suitable subjects into disease-modifying clinical trials.

Neuropathology of primary lateral sclerosis

Published descriptions of the neuropathology of clinically defined primary lateral sclerosis (PLS) are reviewed in order to clarify the pathogenesis and the relationship between PLS and classical amyotrophic lateral sclerosis (ALS). Degeneration of the primary motor cortex and corticospinal tracts with preservation of lower motor neurons (LMN) has been reported in most cases. Studies that employed immunohistochemistry found ubiquitin and/or TDP-43-positive neuronal inclusions in the motor cortex and often in the extramotor neocortex. Ubiquitin/TDP-43-immunoreactive inclusions in LMN have been reported in just over half of cases; however, these have never been numerous. The finding of TDP-43 pathology in most cases indicates that PLS and ALS are closely related conditions; however, the fact that cases of PLS consistently show minimal involvement of LMN suggests that PLS represents a distinct entity, rather than an early stage of ALS.

Right temporal variant frontotemporal dementia is pathologically heterogeneous: a case-series and a systematic review

Although the right temporal variant frontotemporal dementia (rtvFTD) is characterised by distinct clinical and radiological features, its underlying histopathology remains elusive. Being considered a right-sided variant of semantic variant primary progressive aphasia (svPPA), TDP-43 type C pathology has been linked to the syndrome, but this has not been studied in detail in large cohorts. In this case report and systematic review, we report the autopsy results of five subjects diagnosed with rtvFTD from our cohort and 44 single rtvFTD subjects from the literature. Macroscopic pathological evaluation of the combined results revealed that rtvFTD demonstrated either a frontotemporal or temporal evolution, even if the degeneration started in the right temporal lobe initially. FTLD-TDP type C was the most common underlying pathology in rtvFTD, however, in 64% of rtvFTD, other underlying pathologies than FTLD-TDP type C were present, such as Tau-MAPT and FTLD-TDP type A and B. Additionally, accompanying motor neuron or corticospinal tract degeneration was observed in 28% of rtvFTD patients. Our results show that in contrast to the general assumption, rtvFTD might not be a pure FTLD-TDP type C disorder, unlike its left temporal counterpart svPPA. Large sample size pathological studies are warranted to understand the diverse pathologies of the right and left temporal variants of frontotemporal dementia.

Upper Motor Neuron Disorders: Primary Lateral Sclerosis, Upper Motor Neuron Dominant Amyotrophic Lateral Sclerosis, and Hereditary Spastic Paraplegia

Following the exclusion of potentially reversible causes, the differential for those patients presenting with a predominant upper motor neuron syndrome includes primary lateral sclerosis (PLS), hereditary spastic paraplegia (HSP), or upper motor neuron dominant ALS (UMNdALS). Differentiation of these disorders in the early phases of disease remains challenging. While no single clinical or diagnostic tests is specific, there are several developing biomarkers and neuroimaging technologies which may help distinguish PLS from HSP and UMNdALS. Recent consensus diagnostic criteria and use of evolving technologies will allow more precise delineation of PLS from other upper motor neuron disorders and aid in the targeting of potentially disease-modifying therapeutics.

Frontotemporal lobar degeneration proteinopathies have disparate microscopic patterns of white and grey matter pathology

Frontotemporal lobar degeneration proteinopathies with tau inclusions (FTLD-Tau) or TDP-43 inclusions (FTLD-TDP) are associated with clinically similar phenotypes. However, these disparate proteinopathies likely differ in cellular severity and regional distribution of inclusions in white matter (WM) and adjacent grey matter (GM), which have been understudied. We performed a neuropathological study of subcortical WM and adjacent GM in a large autopsy cohort (n = 92; FTLD-Tau = 37, FTLD-TDP = 55) using a validated digital image approach. The antemortem clinical phenotype was behavioral-variant frontotemporal dementia (bvFTD) in 23 patients with FTLD-Tau and 42 with FTLD-TDP, and primary progressive aphasia (PPA) in 14 patients with FTLD-Tau and 13 with FTLD-TDP. We used linear mixed-effects models to: (1) compare WM pathology burden between proteinopathies; (2) investigate the relationship between WM pathology burden and WM degeneration using luxol fast blue (LFB) myelin staining; (3) study regional patterns of pathology burden in clinico-pathological groups. WM pathology burden was greater in FTLD-Tau compared to FTLD-TDP across regions (beta = 4.21, SE = 0.34, p < 0.001), and correlated with the degree of WM degeneration in both FTLD-Tau (beta = 0.32, SE = 0.10, p = 0.002) and FTLD-TDP (beta = 0.40, SE = 0.08, p < 0.001). WM degeneration was greater in FTLD-Tau than FTLD-TDP particularly in middle-frontal and anterior cingulate regions (p < 0.05). Distinct regional patterns of WM and GM inclusions characterized FTLD-Tau and FTLD-TDP proteinopathies, and associated in part with clinical phenotype. In FTLD-Tau, WM pathology was particularly severe in the dorsolateral frontal cortex in nonfluent-variant PPA, and GM pathology in dorsolateral and paralimbic frontal regions with some variation across tauopathies. Differently, FTLD-TDP had little WM regional variability, but showed severe GM pathology burden in ventromedial prefrontal regions in both bvFTD and PPA. To conclude, FTLD-Tau and FTLD-TDP proteinopathies have distinct severity and regional distribution of WM and GM pathology, which may impact their clinical presentation, with overall greater severity of WM pathology as a distinguishing feature of tauopathies.

Distinct early symptoms in neuropathologically proven frontotemporal lobar degeneration

OBJECTIVES

Frontotemporal lobar degeneration (FTLD) is associated with accumulation of neurodegeneration-related protein, such as tau, TAR DNA-binding protein 43 (TDP-43), or fused in sarcoma protein (FUS). There have been very few systematic studies of the early symptoms of clinical phenotypes: behavioral variant frontotemporal dementia (bvFTD), semantic variant primary progressive aphasia (svPPA). Clinical subtypes and the patterns of atrophy reflect protein-accumulation patterns, but the relationship between early symptoms and pathological findings remains unclear.

METHODS

We retrospectively investigated the clinical records and examined the neuropathology of 39 bvFTD and 6 svPPA patients to identify symptoms appearing within 2 years of the first clinically apparent changes.

RESULTS

The bvFTD group consisted of 13 FTLD-tau, 18 FTLD-TDP, and 8 FTLD-FUS, and the svPPA group consisted of 6 FTLD-TDP. Age at death is significantly younger in FTLD-FUS (52.8 ± 12.6; P = 0.0104 < 0.05). Over 50% of bvFTD patients show apathy or inertia, and distinct language features appear early in svPPA. Interestingly, bvFTD and svPPA frequently present additional symptoms, not included in the diagnostic criteria, such as physical signs, reticence, dazed condition, and delusions. Stereotyped behaviors, hyperorality and dietary changes are prominent in FTLD-FUS, while linguistic deficits are greater in FTLD-TDP.

CONCLUSIONS

Specific symptoms tend to appear in the early stage of FTLD in each pathological background. They might reflect the morphological features and pathological progression, and should be helpful in the stratification of patients for future therapeutic trials based on the proteinopathies.

TDP-43 pathology in primary lateral sclerosis

Primary lateral sclerosis (PLS) is a controversial form of motor neuron disease (MND), with uncertainty whether it represents a distinct clinico-pathological entity or is simply a variant of classical amyotrophic lateral sclerosis (ALS). Neuropathological studies provide an opportunity to investigate these issues; however, there have been very few published descriptions of postmortem findings in clinically defined PLS, using modern techniques. Here, we report the neuropathological features of seven cases of PLS with age at onset ranging from 47 to 73 years and disease duration from 3.5 to 35 years. All cases showed chronic degeneration of the primary motor cortex and/or the corticospinal tracts with preservation of lower motor neurons (LMN). All five cases, in which motor cortex was available, had TDP-43 immunoreactive (TDP-ir) cortical pathology. In all seven cases, TDP-ir inclusions were also present in LMN; however, these were always rare, averaging less than one inclusion per tissue section. The finding of TDP-ir pathology in all our cases suggests that PLS and ALS are closely related conditions. Importantly however, the extremely minor involvement of LMN, even after very long disease duration in some cases, suggests that PLS is a distinct form of MND in which LMN are spared or protected.

Factors associated with development and distribution of granular/fuzzy astrocytes in neurodegenerative diseases

Granular/fuzzy astrocytes (GFAs), a subtype of “aging‐related tau astrogliopathy,” are noted in cases bearing various neurodegenerative diseases. However, the pathogenic significance of GFAs remains unclear. We immunohistochemically examined the frontal cortex, caudate nucleus, putamen and amygdala in 105 cases composed of argyrophilic grain disease cases (AGD, N = 26), and progressive supranuclear palsy (PSP, N = 10), Alzheimer’s disease (AD, N = 20) and primary age‐related tauopathy cases (PART, N = 18) lacking AGD, as well as 31 cases bearing other various neurodegenerative diseases to clarify (i) the distribution patterns of GFAs in AGD, and PSP, AD and PART lacking AGD, (ii) the impacts of major pathological factors and age on GFA formation and (iii) immunohistochemical features useful to understand the formation process of GFAs. In AGD cases, GFAs consistently occurred in the amygdala (100%), followed by the putamen (69.2%) and caudate nucleus and frontal cortex (57.7%, respectively). In PSP cases without AGD, GFAs were almost consistently noted in all regions examined (90–100%). In AD cases without AGD, GFAs were less frequent, developing preferably in the putamen (35.0%) and caudate nucleus (30.0%). PART cases without AGD had GFAs most frequently in the amygdala (35.3%), being more similar to AGD than to AD cases. Ordered logistic regression analyses using all cases demonstrated that the strongest independent factor of GFA formation in the frontal cortex and striatum was the diagnosis of PSP, while that in the amygdala was AGD. The age was not significantly associated with GFA formation in any region. In GFAs in AGD cases, phosphorylation and conformational change of tau, Gallyas‐positive glial threads indistinguishable from those in tufted astrocytes, and the activation of autophagy occurred sequentially. Given these findings, AGD, PSP, AD and PART cases may show distinct distributions of GFAs, which may provide clues to predict the underlying processes of primary tauopathies.

Classification of primary progressive aphasia: challenges and complexities

Primary progressive aphasia (PPA) is classified into three variants, logopenic variant PPA (lvPPA), nonfluent agrammatic PPA (nfaPPA), and semantic variant PPA (svPPA), based on clinical (syndromic) characteristics with support from neuroimaging and/or underlying neuropathology. Classification of PPA variants provides information valuable to disease management. International consensus criteria are widely employed to identify PPA subtypes; however, classification is complex, and some individuals do not fit neatly into the subtyping scheme. In this review, diagnostic challenges and their implications are discussed, possible explanations for these challenges are explored, and approaches to address PPA classification are considered.

Cellular and regional vulnerability in frontotemporal tauopathies

The frontotemporal tauopathies all deposit abnormal tau protein aggregates, but often of only certain isoforms and in distinguishing pathologies of five main types (neuronal Pick bodies, neurofibrillary tangles, astrocytic plaques, tufted astrocytes, globular glial inclusions and argyrophilic grains). In those with isoform specific tau aggregates glial pathologies are substantial, even though there is limited evidence that these cells normally produce tau protein. This review will assess the differentiating features and clinicopathological correlations of the frontotemporal tauopathies, the genetic predisposition for these different pathologies, their neuroanatomical selectivity, current observations on how they spread through the brain, and any potential contributing cellular and molecular changes. The findings show that diverse clinical phenotypes relate most to the brain region degenerating rather than the type of pathology involved, that different regions on the MAPT gene and novel risk genes are associated with specific tau pathologies, that the 4-repeat glial tauopathies do not follow individual patterns of spreading as identified for neuronal pathologies, and that genetic and pathological data indicate that neuroinflammatory mechanisms are involved. Each pathological frontotemporal tauopathy subtype with their distinct pathological features differ substantially in the cell type affected, morphology, biochemical and anatomical distribution of inclusions, a fundamental concept central to future success in understanding the disease mechanisms required for developing therapeutic interventions. Tau directed therapies targeting genetic mechanisms, tau aggregation and pathological spread are being trialled, although biomarkers that differentiate these diseases are required. Suggested areas of future research to address the regional and cellular vulnerabilities in frontotemporal tauopathies are discussed.

The atrophy pattern in Alzheimer-related PPA is more widespread than that of the frontotemporal lobar degeneration associated variants

Objective

The three recognized variants of primary progressive aphasia (PPA) are associated with different loci of degeneration—left posterior perisylvian in logopenic variant (lvPPA), left frontal operculum in non-fluent variant (nfvPPA), and left rostroventral-temporal in semantic variant (svPPA). Meanwhile, it has become apparent that patients with lvPPA, in which Alzheimer pathology is the norm, frequently have more extensive language deficits—namely semantic and grammatical problems—than is captured in the strict diagnostic recommendations for this variant. We hypothesized that this may be because the degeneration in AD-related PPA typically extends beyond the left posterior perisylvian region.

Methods

Magnetic resonance images from 25 PPA patients (9AD-related PPA, 10 svPPA, 6 nfvPPA) and a healthy control cohort were used to calculate cortical thickness in three regions of interest (ROIs). The three ROIs being the left-hemispheric loci of maximal reported degeneration for each of the three variants of PPA.

Results

Consistent with past studies, the most severe cortical thinning was in the posterior perisylvian ROI in AD-related PPA; the ventral temporal ROI in svPPA; and the frontal opercular ROI in nfvPPA. Significant cortical thinning in AD-related PPA, however, was evident in all three ROIs. In contrast, thinning in svPPA and nfvPPA was largely restricted to their known peak loci of degeneration.

Conclusions

Although cortical degeneration in AD-related PPA is maximal in the left posterior perisylvian region, it extends more diffusely throughout the left hemisphere language network offering a plausible explanation for why the linguistic profile of lvPPA so often includes additional semantic and grammatic deficits.

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lvPPA is associated with AD pathology.

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AD-PPA present with more extensive deficits than lvPPA.

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Atrophy in AD-PPA encompasses the peak atrophy sites of the other PPA subtypes.

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The extended atrophy in AD-PPA explains the heterogeneity of linguistic deficits.

Subarachnoid hemorrhage enhances the expression of TDP-43 in the brain of experimental rats and human subjects

The transactive response DNA-binding protein of 43 (TDP-43) may be involved in neurodegenerative disease and in the response to brain injury; however, alterations in the expression of TDP-43 following subarachnoid hemorrhage (SAH) require further investigation. The present study reported a notable elevation in the expression of TDP-43 within the cerebrospinal fluid (CSF) of patients with aneurysmal SAH and increased brain expression of TDP-43 in a rat model of SAH. The TDP-43 protein and a derivative migrated at 43 and 24 kDa, respectively, as observed via the immunoblotting of concentrated CSF samples obtained from patients with SAH; no signal was detected in the CSF from healthy controls. SAH in rats was induced by intravascular suture puncture. The expression levels of TDP-43 in rat cortical lysates following SAH were increased at 0.5 h, peaked at 48 h and remained significantly elevated at 72 h post-injury, compared with sham controls. TDP-43 immunolabeling indication localization within neurons, astrocytes and microglia in the experimental rats. Collectively, the findings of the present study indicated the early involvement of TDP-43 in the brain in response to SAH, and that expression levels of TDP-43 in the CSF may serve as a prognostic biomarker among patients with this condition.

Clinical features of the behavioural variant of frontotemporal dementia that are useful for predicting underlying pathological subtypes of frontotemporal lobar degeneration

BACKGROUND

The behavioural variant of frontotemporal dementia (bvFTD) is the most common phenotype of frontotemporal lobar degeneration (FTLD). FTLD is divided into three main pathological subtypes: tau-positive FTLD (FTLD-tau), FTLD-TAR DNA-binding protein (TDP), and FTLD-Fused in sarcoma (FUS). At present, it is difficult to predict the underlying pathological subtypes of sporadic bvFTD before a patient's death.

METHODS

We retrospectively investigated the clinical features of 34 Japanese patients with sporadic bvFTD, with or without motor neuron disease (MND), who had been pathologically diagnosed with FTLD. We examined whether, and how, the clinical features differed among Pick's disease, FTLD-TDP, and FTLD-FUS patients.

RESULTS

Six of the 34 patients developed MND during the course of bvFTD. These six bvFTD-MND patients were all pathologically diagnosed with FTLD-TDP. The other 28 patients were composed of 12 FTLD-tau patients including 11 Pick's disease patients, 8 FTLD-TDP patients, and 8 FTLD-FUS patients. A comparison of the clinical features of the three pathological subtypes of the 33 patients demonstrated that the age at onset was significantly younger in FTLD-FUS patients than in Pick's disease or FTLD-TDP patients. Furthermore, while hyperorality and dietary changes in the early stage of the disease were present in approximately 40% of Pick's disease and FTLD-FUS patients, they were absent in FTLD-TDP patients.

CONCLUSION

The comorbidity of MND, a younger age at onset, and hyperorality and dietary changes in the early stage may be useful clinical features for predicting underlying pathological subtypes of sporadic bvFTD. The results of our study should be confirmed by prospective studies employing a larger number of cases.

Retiring the term FTDP-17 as MAPT mutations are genetic forms of sporadic frontotemporal tauopathies

See Josephs (doi:10.1093/brain/awx367) for a scientific commentary on this article.In many neurodegenerative disorders, familial forms have provided important insights into the pathogenesis of their corresponding sporadic forms. The first mutations associated with frontotemporal lobar degeneration (FTLD) were found in the microtubule-associated protein tau (MAPT) gene on chromosome 17 in families with frontotemporal degeneration and parkinsonism (FTDP-17). However, it was soon discovered that 50% of these families had a nearby mutation in progranulin. Regardless, the original FTDP-17 nomenclature has been retained for patients with MAPT mutations, with such patients currently classified independently from the different sporadic forms of FTLD with tau-immunoreactive inclusions (FTLD-tau). The separate classification of familial FTLD with MAPT mutations implies that familial forms cannot inform on the pathogenesis of the different sporadic forms of FTLD-tau. To test this assumption, this study pathologically assessed all FTLD-tau cases with a known MAPT mutation held by the Sydney and Cambridge Brain Banks, and compared them to four cases of four subtypes of sporadic FTLD-tau, in addition to published case reports. Ten FTLD-tau cases with a MAPT mutation (K257T, S305S, P301L, IVS10+16, R406W) were screened for the core differentiating neuropathological features used to diagnose the different sporadic FTLD-tau subtypes to determine whether the categorical separation of MAPT mutations from sporadic FTLD-tau is valid. Compared with sporadic cases, FTLD-tau cases with MAPT mutations had similar mean disease duration but were younger at age of symptom onset (55 ± 4 years versus 70 ± 6 years). Interestingly, FTLD-tau cases with MAPT mutations had similar patterns and severity of neuropathological features to sporadic FTLD-tau subtypes and could be classified into: Pick's disease (K257T), corticobasal degeneration (S305S, IVS10‰+‰16, R406W), progressive supranuclear palsy (S305S) or globular glial tauopathy (P301L, IVS10‰+‰16). The finding that the S305S mutation could be classified into two tauopathies suggests additional modifying factors. Assessment of our cases and previous reports suggests that distinct MAPT mutations result in particular FTLD-tau subtypes, supporting the concept that they are likely to inform on the varied cellular mechanisms involved in distinctive forms of sporadic FTLD-tau. As such, FTLD-tau cases with MAPT mutations should be considered familial forms of FTLD-tau subtypes rather than a separate FTDP-17 category, and continued research on the effects of different mutations more focused on modelling their impact to produce the very different sporadic FTLD-tau pathologies in animal and cellular models.

Frontotemporal dementia with trans-activation response DNA-binding protein 43 presenting with catatonic syndrome

Catatonia is a clinical syndrome characterized by symptoms such as immobility, mutism, stupor, stereotypy, echophenomena, catalepsy, automatic obedience, posturing, negativism, gegenhalten and ambitendency. This syndrome occurs mostly in mood disorder and schizophrenic patients, and is related to neuronal dysfunction involving the frontal lobe. Some cases of frontotemporal dementia (FTD) with catatonia have been reported, but these cases were not examined by autopsy. Here, we report on a FTD case which showed catatonia after the first episode of brief psychotic disorder. At the age of 58, the patient had a sudden onset of disorganized behavior and meaningless speech. Psychotropic drugs were effective for catatonic symptoms. However, after remission apathy, hyperorality, socially inappropriate behavior, hoarding, and an instinctive grasp reaction appeared and persisted. Brain MRI showed significant atrophy of the bilateral fronto-temporal lobes. A neuropathological examination revealed extensive trans-activation response DNA-binding protein 43 (TDP-43) positive neurocytoplasmic inclusions and dystrophic neurites in the brain, including the cerebral cortex, basal ganglia, and brainstem. Pathological diagnosis was frontotemporal lobar degeneration (FTLD) with TDP-43 (FTLD-TDP) type C, which was also confirmed by the band pattern of C-terminal fragments of TDP-43 on western blotting of sarkosyl-insoluble fractions extracted from the frozen brain. Dysfunction of the thalamus, globus pallidus, supplementary motor area, amygdala and cingulate cortex have been said to be related to the catatonic syndrome. In this case, these areas were affected, showing abnormal TDP-43-positive structures. Further studies are expected to confirm further clinical - pathological correlations to FTLD.

Pathologic Involvement of Glutamatergic Striatal Inputs From the Cortices in TAR DNA-Binding Protein 43 kDa-Related Frontotemporal Lobar Degeneration and Amyotrophic Lateral Sclerosis

In frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS), recent studies have presumed relationships between cognitive declines and striatal dysfunctions. The striatum contributes to socio-cognitive functions by receiving glutamatergic inputs from the cerebral cortices. However, the vulnerability of these cortico-striatal inputs is unclear in these diseases. This study aimed to evaluate the glutamatergic inputs to the striatum from the cerebral cortices in patients with sporadic TDP-43-related FTLD (FTLD-TDP) and ALS (ALS-TDP). We examined 46 consecutively autopsied patients (31 FTLD-TDP and 15 ALS patients) and 10 normal controls. The axon terminals of the glutamatergic cortico-striatal projection neurons were quantified at the striatum using antivesicular glutamate transporter-1 (VGLUT-1) immunohistochemistry. In results, all FTLD-TDP patients displayed marked depletion of VGLUT-1-positive axon terminals in the caudate head and putamen. Particularly, the patients with type C pathology showed a severe loss. The nondemented ALS patients displayed loss of VGLUT-1-positive axon terminals in the putamen, but those were relatively spared in the caudate head. Confocal microscopy revealed TDP-43 aggregations within VGLUT-1-positive axon terminals in a subset of the patients. Our results indicate marked involvement of glutamatergic striatal inputs from the cerebral cortices in association with socio-cognitive declines in a disease spectrum of TDP-43 proteinopathy.

Neuropathological comorbidity associated with argyrophilic grain disease

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

Degradomics in Neurotrauma: Profiling Traumatic Brain Injury

Degradomics has recently emerged as a subdiscipline in the omics era with a focus on characterizing signature breakdown products implicated in various disease processes. Driven by promising experimental findings in cancer, neuroscience, and metabolomic disorders, degradomics has significantly promoted the notion of disease-specific "degradome." A degradome arises from the activation of several proteases that target specific substrates and generate signature protein fragments. Several proteases such as calpains, caspases, cathepsins, and matrix metalloproteinases (MMPs) are involved in the pathogenesis of numerous diseases that disturb the physiologic balance between protein synthesis and protein degradation. While regulated proteolytic activities are needed for development, growth, and regeneration, uncontrolled proteolysis initiated under pathological conditions ultimately culminates into apoptotic and necrotic processes. In this chapter, we aim to review the protease-substrate repertoires in neural injury concentrating on traumatic brain injury. A striking diversity of protease substrates, essential for neuronal and brain structural and functional integrity, namely, encryptic biomarker neoproteins, have been characterized in brain injury. These include cytoskeletal proteins, transcription factors, cell cycle regulatory proteins, synaptic proteins, and cell junction proteins. As these substrates are subject to proteolytic fragmentation, they are ceaselessly exposed to activated proteases. Characterization of these molecules allows for a surge of "possible" therapeutic approaches of intervention at various levels of the proteolytic cascade.

The Relationship Between Development of Neuronal and Astrocytic Tau Pathologies in Subcortical Nuclei and Progression of Argyrophilic Grain Disease

Progressive supranuclear palsy (PSP) cases frequently have argyrophilic grain disease (AGD). However, the PSP-like tau pathology in AGD cases has not been fully clarified. To address this, we examined tau pathologies in the subcortical nuclei and frontal cortex in 19 AGD cases that did not meet the pathological criteria of PSP or corticobasal degeneration, nine PSP cases and 20 Braak NFT stage-matched controls. Of the 19 AGD cases, five (26.3%) had a few Gallyas-positive tau-positive tufted astrocytes (TAs) and Gallyas-negative tau-positive TA-like astrocytic inclusions (TAIs), and six (31.6%) had only TAIs in the striatum and/or frontal cortex. Subcortical tau pathology was sequentially and significantly greater in AGD cases lacking these tau-positive astrocytic lesions, AGD cases having them, and PSP cases than in controls. There was a significant correlation between three histologic factors, including the AGD stage and the quantities of subcortical neuronal and astrocytic tau pathologies. Tau immunoblotting demonstrated 68- and 64-kDa bands and 33-kDa low-molecular mass tau fragments in PSP cases, and although with lesser intensity, in AGD cases with and without TAs and TAIs also. Given these findings, the progression of AGD may be associated with development of the neuronal and astrocytic tau pathologies characteristic of PSP.

Marked Involvement of the Striatal Efferent System in TAR DNA-Binding Protein 43 kDa-Related Frontotemporal Lobar Degeneration and Amyotrophic Lateral Sclerosis

Recent pathological studies indicate that neuronal loss and/or TAR DNA-binding protein-43 kDa (TDP-43) inclusions are frequent in the striatum of patients with TDP-43-related frontotemporal lobar degeneration (FTLD-TDP) and amyotrophic lateral sclerosis (ALS-TDP). However, no investigations have clarified the impact of such pathological changes on striatal neuronal outputs in these diseases. We analyzed pathological changes in the striatal efferent system of 59 consecutively autopsied patients with sporadic FTLD-TDP or ALS-TDP. The axon terminals of striatal efferent neurons were immunohistochemically assessed in the substantia nigra pars reticulata (SNr) and globus pallidus (GP). All of the FTLD-TDP patients exhibited a marked depletion of axon terminals, irrespective of disease duration. In particular, losses of substance-P-positive projections to the SNr and internal segment of GP were consistently severe. Similar findings were also observed in 69.0% of the ALS-TDP patients, although the severity was much less than that in the FTLD-TDP patients (p < 0.001). The accumulation of phosphorylated TDP-43 was observed in the striatal efferent neurons, efferent tracts, or their axon terminals in the SNr and GP in both groups. Thus, striatal efferent projections are essentially and commonly involved in the TDP-43-related FTLD/ALS disease spectrum.

Behavioral variant of frontotemporal dementia: Fundamental clinical issues associated with prediction of pathological bases

Behavioral variant of frontotemporal dementia (bvFTD) is a clinical syndrome characterized mainly by behavioral symptoms due to frontal dysfunction. Major neurodegenerative bases of bvFTD include Pick's disease, frontotemporal lobar degeneration with trans-activation response DNA protein 43-positive inclusions, corticobasal degeneration, and progressive supranuclear palsy. Early disinhibition characterized by socially inappropriate behaviors, loss of manners, and impulsive, rash and careless actions is the most important clinical feature of bvFTD. On the other hand, it was reported that clinical presentations of some Alzheimer's disease cases and patients with psychiatric disorders (e.g., addictive disorders, gambling disorder and kleptomania) often resemble that of bvFTD. Although clinical differentiation of 'true' bvFTD cases with frontotemporal lobar degeneration (FTLD) pathology from mimicking cases without it is not always easy, evaluation of the following features, which were noted in autopsy-confirmed FTLD cases and/or clinical bvFTD cases with circumscribed lobar atrophy, may often provide clues for the diagnosis. (i) The initial symptoms frequently develop at 65 years or younger, and (ii) 'socially inappropriate behaviors' can be frequently interpreted as contextually inappropriate behaviors prompted by environmental visual and auditory stimuli. Taking a detailed history usually reveals various kinds of such behaviors in various situations in everyday life rather than the repetition of a single kind of behavior (e.g., repeated shoplifting). (iii) A correlation between the distribution of cerebral atrophy and neurological and behavioral symptoms is usually observed, and the proportion of FTLD cases with right side-predominant cerebral atrophy may be higher in a psychiatric setting than a neurological setting. Finally, (iv) whether the previous course and the combination of symptoms observed at the first medical visit can be explained by major evolution patterns of clinical syndromes in pathologically confirmed FTLD cases should be considered. These views may provide clues to differentiate FTLD from Alzheimer's disease and to predict a subsequent clinical course and therapeutic interventions needed in the future.

Deep clinical and neuropathological phenotyping of Pick disease

OBJECTIVE

To characterize sequential patterns of regional neuropathology and clinical symptoms in a well-characterized cohort of 21 patients with autopsy-confirmed Pick disease.

METHODS

Detailed neuropathological examination using 70μm and traditional 6μm sections was performed using thioflavin-S staining and immunohistochemistry for phosphorylated tau, 3R and 4R tau isoforms, ubiquitin, and C-terminally truncated tau. Patterns of regional tau deposition were correlated with clinical data. In a subset of cases (n = 5), converging evidence was obtained using antemortem neuroimaging measures of gray and white matter integrity.

RESULTS

Four sequential patterns of pathological tau deposition were identified starting in frontotemporal limbic/paralimbic and neocortical regions (phase I). Sequential involvement was seen in subcortical structures, including basal ganglia, locus coeruleus, and raphe nuclei (phase II), followed by primary motor cortex and precerebellar nuclei (phase III) and finally visual cortex in the most severe (phase IV) cases. Behavioral variant frontotemporal dementia was the predominant clinical phenotype (18 of 21), but all patients eventually developed a social comportment disorder. Pathological tau phases reflected the evolution of clinical symptoms and degeneration on serial antemortem neuroimaging, directly correlated with disease duration and inversely correlated with brain weight at autopsy. The majority of neuronal and glial tau inclusions were 3R tau-positive and 4R tau-negative in sporadic cases. There was a relative abundance of mature tau pathology markers in frontotemporal limbic/paralimbic regions compared to neocortical regions.

INTERPRETATION

Pick disease tau neuropathology may originate in limbic/paralimbic cortices. The patterns of tau pathology observed here provide novel insights into the natural history and biology of tau-mediated neurodegeneration.

Pathology in primary progressive aphasia syndromes

'Primary progressive aphasia' (PPA) refers to core linguistic disorders caused by neurodegenerative disease. Three main PPA variants are recognized: nonfluent/agrammatic, semantic and logopenic. Correctly classifying patients during life according to the underlying histopathology will become increasingly important as cause-specific treatments become available. This article reviews clinical and histopathological studies of PPA, with particular reference to updated PPA classifications. Currently, one-to-one relationships do not exist within PPA subtypes. The semantic variant has the best correspondence between the clinical syndrome and the underlying pathological cause and the logopenic variant the worst correspondence. The use of future biomarkers should facilitate accurate clinicopathological correlation of patients during life.

Significance and limitation of the pathological classification of TDP-43 proteinopathy

Based on the cerebral tans-activation response DNA protein 43 (TDP-43) immunohistochemistry, frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP) is classified into four subtypes: type A has numerous neuronal cytoplasmic inclusions (NCIs) and dystrophic neurites (DNs); type B has numerous NCIs with few DNs; type C is characterized by DNs which are often longer and thicker than DNs in type A, with few NCIs; and type D has numerous neuronal intranuclear inclusions and DNs with few NCIs. The relevance of this classification system is supported by clinical, biochemical and genetic correlations, although there is still significant heterogeneity, especially in cases with type A pathology. The subtypes of TDP-43 pathology should be determined in cases with other neurodegenerative disorders, including Alzheimer's disease and dementia with Lewy bodies, to evaluate the pathological significance of TDP-43 abnormality in them. The results of the biochemical analyses of the diseased brains and the cellular models suggest that different strains of TDP-43 with different conformations may determine the clinicopathological phenotypes of TDP-43 proteinopathy, like prion disease. Clarifying the mechanism of the conformational changes of TDP-43 leading to the formation of multiple abnormal strains may be important for differential diagnosis and developing disease-modifying therapy for TDP-43 proteinopathy.

Frontal white matter tracts sustaining speech production in primary progressive aphasia

In primary progressive aphasia (PPA), speech and language difficulties are caused by neurodegeneration of specific brain networks. In the nonfluent/agrammatic variant (nfvPPA), motor speech and grammatical deficits are associated with atrophy in a left fronto-insular-striatal network previously implicated in speech production. In vivo dissection of the crossing white matter (WM) tracts within this "speech production network" is complex and has rarely been performed in health or in PPA. We hypothesized that damage to these tracts would be specific to nfvPPA and would correlate with differential aspects of the patients' fluency abilities. We prospectively studied 25 PPA and 21 healthy individuals who underwent extensive cognitive testing and 3 T MRI. Using residual bootstrap Q-ball probabilistic tractography on high angular resolution diffusion-weighted imaging (HARDI), we reconstructed pathways connecting posterior inferior frontal, inferior premotor, insula, supplementary motor area (SMA) complex, striatum, and standard ventral and dorsal language pathways. We extracted tract-specific diffusion tensor imaging (DTI) metrics to assess changes across PPA variants and perform brain-behavioral correlations. Significant WM changes in the left intrafrontal and frontostriatal pathways were found in nfvPPA, but not in the semantic or logopenic variants. Correlations between tract-specific DTI metrics with cognitive scores confirmed the specific involvement of this anterior-dorsal network in fluency and suggested a preferential role of a posterior premotor-SMA pathway in motor speech. This study shows that left WM pathways connecting the speech production network are selectively damaged in nfvPPA and suggests that different tracts within this system are involved in subcomponents of fluency. These findings emphasize the emerging role of diffusion imaging in the differential diagnosis of neurodegenerative diseases.

Corticobasal degeneration initially developing motor versus non-motor symptoms: a comparative clinicopathological study

BACKGROUND

Clinical presentations of pathologically confirmed corticobasal degeneration (CBD) vary, and the heterogeneity makes its clinical diagnosis difficult, especially when a patient lacks any motor disturbance in the early stage.

METHODS

We compared clinical and pathological features of four pathologically confirmed CBD cases that initially developed non-motor symptoms, including behavioural and psychiatric symptoms but without motor disturbance (CBD-NM), and five CBD cases that initially developed parkinsonism and/or falls (CBD-M). The age range at death for the CBD-NM and CBD-M subjects (58-85 years vs 45-67 years) and the range of disease duration (2-18 years vs 2-6 years) did not significantly differ between the groups.

RESULTS

Prominent symptoms in the early stage of CBD-NM cases included self-centred behaviours such as frontotemporal dementia (n = 1), apathy with and without auditory hallucination (n = 2), and aggressive behaviours with delusion and visual hallucination (n = 1). Among the four CBD-NM cases, only one developed asymmetric motor disturbance, and two could walk without support throughout the course. Final clinical diagnoses of the CBD-NM cases were frontotemporal dementia (n = 2), senile psychosis with delirium (n = 1), and schizophrenia (n = 1). Neuronal loss was significantly less severe in the subthalamic nucleus and substantia nigra in the CBD-NM cases than in the CBD-M cases. The severity of tau pathology in all regions examined was comparable in the two groups.

CONCLUSION

CBD cases that initially develop psychiatric and behavioural changes without motor symptoms may have less severe degenerative changes in the subthalamic nucleus and substantia nigra, and some CBD cases can lack motor disturbance not only in the early stage but also in the last stage of the course.

Dual vulnerability of TDP-43 to calpain and caspase-3 proteolysis after neurotoxic conditions and traumatic brain injury

Transactivation response DNA-binding protein 43 (TDP-43) proteinopathy has recently been reported in chronic traumatic encephalopathy, a neurodegenerative condition linked to prior history of traumatic brain injury (TBI). While TDP-43 appears to be vulnerable to proteolytic modifications under neurodegenerative conditions, the mechanism underlying the contribution of TDP-43 to the pathogenesis of TBI remains unknown. In this study, we first mapped out the calpain or caspase-3 TDP-43 fragmentation patterns by in vitro protease digestion. Concurrently, in cultured cerebrocortical neurons subjected to cell death challenges, we identified distinct TDP-43 breakdown products (BDPs) of 35, 33, and 12 kDa that were indicative of dual calpain/caspase attack. Cerebrocortical culture incubated with calpain and caspase-fragmented TDP-43 resulted in neuronal injury. Furthermore, increased TDP-43 BDPs as well as redistributed TDP-43 from the nucleus to the cytoplasm were observed in the mouse cortex in two TBI models: controlled cortical impact injury and overpressure blast-wave-induced brain injury. Finally, TDP-43 and its 35 kDa fragment levels were also elevated in the cerebrospinal fluid (CSF) of severe TBI patients. This is the first evidence that TDP-43 might be involved in acute neuroinjury and TBI pathology, and that TDP-43 and its fragments may have biomarker utilities in TBI patients.

Biomarkers in the primary progressive aphasias

BACKGROUND

Primary progressive aphasia (PPA) is a progressive disorder of language that is increasingly recognised as an important presentation of a specific spectrum of neurodegenerative conditions.

AIMS

In an era of etiologically specific treatments for neurodegenerative conditions, it is crucial to establish the histopathologic basis for PPA. In this review, I discuss biomarkers for identifying the pathology underlying PPA.

MAIN CONTRIBUTION

Clinical syndromes suggest a probabilistic association between a specific PPA variant and an underlying pathology, but there are also many exceptions. A considerable body of work with biomarkers is now emerging as an important addition to clinical diagnosis. I review genetic, neuroimaging and biofluid studies that can help determine the pathologic basis for PPA.

CONCLUSIONS

Together with careful clinical examination, there is great promise that supplemental biomarker assessments will lead to accurate diagnosis of the pathology associated with PPA during life and serve as the basis for clinical trials in this spectrum of disease.

Argyrophilic grain disease as a neurodegenerative substrate in late-onset schizophrenia and delusional disorders

To study the relationship between neurodegenerative diseases including argyrophilic grain disease (AGD) and late-onset schizophrenia and delusional disorders (LOSD; onset ≥40 years of age), we pathologically examined 23 patients with LOSD, 71 age-matched normal controls, and 22 psychiatric disease controls (11 depression, six personality disorder, two bipolar disorders, and three neurotic disorders cases). In all LOSD cases (compared to age-matched normal controls), the frequencies of Lewy body disease (LBD), AGD, and corticobasal degeneration (CBD) were 26.1 % (11.3 %), 21.7 % (8.5 %), and 4.3 % (0.0 %), respectively. There was no case of pure Alzheimer's disease (AD). The total frequency of LBD, AGD, and CBD was significantly higher in LOSD cases than in normal controls. Argyrophilic grains were significantly more severe in LOSD than in controls, but were almost completely restricted to the limbic system and adjacent temporal cortex. In LOSD patients whose onset occurred at ≥65 years of age (versus age-matched normal controls), the frequencies of LBD and AGD were 36.4 % (19.4 %) and 36.4 % (8.3 %), respectively, and AGD was significantly more frequent in LOSD patients than in normal controls. In LOSD patients whose onset occurred at <65 years of age, the frequencies of LBD, AGD, and CBD were 16.7, 8.3, and 8.3 %, comparable to those of age-matched normal controls (10.2, 5.1, and 0.0 %). In all psychiatric cases, delusion was significantly more frequent in AGD cases than in cases bearing minimal AD pathology alone. Given these findings, LOSD patients may have heterogeneous pathological backgrounds, and AGD may be associated with the occurrence of LOSD especially after 65 years of age.

An autopsy case of incipient Pick's disease: immunohistochemical profile of early-stage Pick body formation

There is little immunohistochemical information about the early stage of Pick body formation, due to the extremely limited opportunities of studying Pick's disease at the incipient or subclinical stage. We report a 62-year-old man without any clinical manifestations of Pick's disease, who died of B-cell lymphoma of the brainstem. Post mortem examination revealed many Pick bodies without obvious neuronal loss mainly in the left frontal and temporal lobes. Three brains of patients with typical Pick's disease (disease duration: 7, 11 and 16 years) were also examined. Pick bodies were immunopositive for phosphorylated tau and 3-repeat tau, and less consistently for p62 in both incipient and typical cases. In the incipient case, borderline positivity for ubiquitin was evident in only a few Pick bodies, whereas in the typical cases many Pick bodies showed obvious positivity for ubiquitin. These findings suggest that Pick bodies are rarely ubiquitinated in the early stage of Pick body formation.

Senile onset frontotemporal lobar degeneration with TAR-DNA binding protein 43 proteinopathy primarily presenting with wasteful habits

We present an autopsied case of a senile Japanese woman with sporadic frontotemporal lobar degeneration (FTLD) presenting as frontotemporal dementia. Disease onset was at the age of 70 and presented as a behaviour disorder, particularly involving wasteful habits. The patient had repeated incidents of making expensive purchases and then had difficulty making payments. Following these symptoms, she showed other changes of character such as lethargy and apathy. She gradually showed signs of parkinsonism including rigidity and bradykinesia, and in the terminal stage, an akinetic mutism state with quadriplegia in flexion was observed. Head magnetic resonance imaging revealed severe frontotemporal lobe atrophy with severe lateral ventricular dilatation and frontal white matter degeneration. At autopsy, the brain weighed 930 g and the frontotemporal cerebral cortex showed neuron loss with gliosis, tissue rarefaction and spongiform change, particularly in the superficial layers. Pathologic degeneration was more severe in the anterior portion of the frontal lobe with extensive white matter degeneration. Immunostaining for phosphorylated TAR-DNA binding protein 43 (TDP-43) revealed numerous neuronal cytoplasmic inclusions and extensive short dystrophic neuritis, particularly in the frontotemporal cortex. Many TDP-43-positive cytoplasmic inclusions were also observed in the dentate gyrus of the hippocampus. The patient was pathologically diagnosed with FTLD with TDP-43-positive inclusions (FTLD-TDP) without motor neuron disease. The immunohistochemical findings corresponded to type A of the FTLD-TDP pathology classification system.

Presenting neuropsychological testing profile of autopsy-confirmed frontotemporal lobar degeneration

AIMS

We aimed to investigate how neuropsychological test measures at presentation might differentiate frontotemporal lobar degeneration (FTLD) from Alzheimer's disease (AD).

METHODS

We compared autopsy-confirmed FTLD and definite AD with Clinical Dementia Rating ≤1. Factor scores and t values of each neuropsychological test measure were compared between FTLD and AD patients. Logistic regression analyses were applied to identify independent predictors within test measures for the differentiation of FTLD from AD.

RESULTS

Factor analyses showed that the memory domain was more severely impaired in AD than in FTLD, whereas the language and attention domains were more severely impaired in FTLD than in AD. Multiple logistic regression analysis showed that Letter Fluency, Boston Naming Test and delayed memory recall remained independent predictors of FTLD compared to AD. However, test measures did not discriminate between FTLD-tau and FTLD-ubiquitin.

CONCLUSION

We confirm that memory and language function tests discriminate between FTLD and AD.

The non-fluent/agrammatic variant of primary progressive aphasia

The non-fluent/agrammatic variant of primary progressive aphasia (naPPA) is a young-onset neurodegenerative disorder characterised by poor grammatical comprehension and expression and a disorder of speech sound production. In an era of disease-modifying treatments, the identification of naPPA might be an important step in establishing a specific cause of neurodegenerative disease. However, difficulties in defining the characteristic language deficits and heterogeneity in the anatomical distribution of disease in naPPA have led to controversy. Findings from imaging studies have linked an impairment of this uniquely human language capacity with disruption of large-scale neural networks centred in left inferior frontal and anterior superior temporal regions. Accordingly, the pathological burden of disease in naPPA is anatomically focused in these regions. Most cases of naPPA are associated with the spectrum of pathological changes found in frontotemporal lobar degeneration involving the microtubule-associated protein tau. Knowledge of these unique clinical-pathological associations should advance care for patients with this important class of neurodegenerative diseases while supplementing our knowledge of human cognitive neuroscience.