Frontotemporal dementia: clinicopathological correlations

Occupational attainment influences survival in autopsy-confirmed frontotemporal degeneration

OBJECTIVE

To examine the influence of occupational attainment and education on survival in autopsy-confirmed cases of frontotemporal lobar degeneration (FTLD) and Alzheimer disease (AD).

METHODS

We performed a retrospective chart review of 83 demographically matched, autopsy-confirmed FTLD (n = 34) and AD (n = 49) cases. Each patient's primary occupation was classified and ranked. Level of education was recorded in years. Survival was defined as time from symptom onset until death. Linear regression was used to test for associations among occupational attainment, education, and patient survival.

RESULTS

Median survival was 81 months for FTLD and 95 months for AD. Years of education and occupational attainment were similar for both groups. We found that higher occupational attainment was associated with longer survival in FTLD but not AD.

CONCLUSIONS

Our findings suggest that higher occupational attainment is associated with longer survival in autopsy-confirmed FTLD. The identification of protective factors associated with FTLD survival has important implications for estimates of prognosis and longitudinal studies such as treatment trials.

Frontotemporal lobar degeneration: defining phenotypic diversity through personalized medicine

Frontotemporal lobar degeneration (FTLD) comprises two main classes of neurodegenerative diseases characterized by neuronal/glial proteinaceous inclusions (i.e., proteinopathies) including tauopathies (i.e., FTLD-Tau) and TDP-43 proteinopathies (i.e., FTLD-TDP) while other very rare forms of FTLD are known such as FTLD with FUS pathology (FTLD-FUS). This review focuses mainly on FTLD-Tau and FLTD-TDP, which may present as several clinical syndromes: a behavioral/dysexecutive syndrome (behavioral variant frontotemporal dementia); language disorders (primary progressive aphasia variants); and motor disorders (amyotrophic lateral sclerosis, corticobasal syndrome, progressive supranuclear palsy syndrome). There is considerable heterogeneity in clinical presentations of underlying neuropathology and current clinical criteria do not reliably predict underlying proteinopathies ante-mortem. In contrast, molecular etiologies of hereditary FTLD are consistently associated with specific proteinopathies. These include MAPT mutations with FTLD-Tau and GRN, C9orf72, VCP and TARDBP with FTLD-TDP. The last decade has seen a rapid expansion in our knowledge of the molecular pathologies associated with this clinically and neuropathologically heterogeneous group of FTLD diseases. Moreover, in view of current limitations to reliably diagnose specific FTLD neuropathologies prior to autopsy, we summarize the current state of the science in FTLD biomarker research including neuroimaging, biofluid and genetic analyses. We propose that combining several of these biomarker modalities will improve diagnostic specificity in FTLD through a personalized medicine approach. The goals of these efforts are to enhance power for clinical trials focused on slowing or preventing progression of spread of tau, TDP-43 and other FTLD-associated pathologies and work toward the goal of defining clinical endophenotypes of FTD.

The semantic variant of primary progressive aphasia: clinical and neuroimaging evidence in single subjects

BACKGROUND/AIM

We present a clinical-neuroimaging study in a series of patients with a clinical diagnosis of semantic variant of primary progressive aphasia (svPPA), with the aim to provide clinical-functional correlations of the cognitive and behavioral manifestations at the single-subject level.

METHODS

We performed neuropsychological investigations, 18F-FDG-PET single-subject and group analysis, with an optimized SPM voxel-based approach, and correlation analyses. A measurement of white matter integrity by means of diffusion tensor imaging (DTI) was also available for a subgroup of patients.

RESULTS

Cognitive assessment confirmed the presence of typical semantic memory deficits in all patients, with a relative sparing of executive, attentional, visuo-constructional, and episodic memory domains. 18F-FDG-PET showed a consistent pattern of cerebral hypometabolism across all patients, which correlated with performance in semantic memory tasks. In addition, a majority of patients also presented with behavioral disturbances associated with metabolic dysfunction in limbic structures. In a subgroup of cases the DTI analysis showed FA abnormalities in the inferior longitudinal and uncinate fasciculi.

DISCUSSION

Each svPPA individual had functional derangement involving an extended, connected system within the left temporal lobe, a crucial part of the verbal semantic network, as well as an involvement of limbic structures. The latter was associated with behavioral manifestations and extended beyond the area of atrophy shown by CT scan.

CONCLUSION

Single-subject 18F-FDG-PET analysis can account for both cognitive and behavioral alterations in svPPA. This provides useful support to the clinical diagnosis.

18F-florbetapir PET in patients with frontotemporal dementia and Alzheimer disease

Pathologic deposition of amyloid β (Aβ) protein is a key component in the pathogenesis of Alzheimer disease (AD) but not a feature of frontotemporal dementia (FTD). PET ligands for Aβ protein are increasingly used in diagnosis and research of dementia syndromes. Here, we report a PET study using (18)F-florbetapir in healthy controls and patients with AD and FTD.

METHODS

Ten healthy controls (mean age ± SD, 62.5 ± 5.2 y), 10 AD patients (mean age ± SD, 62.6 ± 4.5), and 8 FTD patients (mean age ± SD, 62.5 ± 9.6) were recruited to the study. All patients underwent detailed clinical and neuropsychologic assessment and T1-weighted MR imaging and were genotyped for apolipoprotein E status. All participants underwent dynamic (18)F-florbetapir PET on a high-resolution research tomograph, and FTD patients also underwent (18)F-FDG PET scans. Standardized uptake value ratios (SUVRs) were extracted for predefined gray and white matter regions of interest using cerebellar gray matter as a reference region. Static PET images were evaluated by trained raters masked to clinical status and regional analysis.

RESULTS

Total cortical gray matter (18)F-florbetapir uptake values were significantly higher in AD patients (median SUVR, 1.73) than FTD patients (SUVR, 1.13, P = 0.002) and controls (SUVR, 1.26, P = 0.04). (18)F-Florbetapir uptake was also higher in AD patients than FTD patients and controls in the frontal, parietal, occipital, and cingulate cortices and in the central subcortical regions. Only 1 FTD patient (homozygous for apolipoprotein E ε4) displayed high cortical (18)F-florbetapir retention, whereas (18)F-FDG PET demonstrated mesiofrontal hypometabolism consistent with the clinical diagnosis of FTD. Most visual raters classified 1 control (10%) and 8 AD (80%) and 2 FTD (25%) patients as amyloid-positive, whereas ratings were tied in another 2 FTD patients and 1 healthy control.

CONCLUSION

Cortical (18)F-florbetapir uptake is low in most FTD patients, providing good discrimination from AD. However, visual rating of FTD scans was challenging, with a higher rate of discordance between interpreters than in AD and control subjects.

Dynamic droplets: the role of cytoplasmic inclusions in stress, function, and disease

Neurodegenerative diseases and other proteinopathies constitute a class of several dozen illnesses etiologically linked to pathological protein misfolding and aggregation. Because of this strong association with disease pathology, cell death, and aging, accumulation of proteins in aggregates or aggregation-associated structures (inclusions) has come to be regarded by many as a deleterious process, to be avoided if possible. Recent work has led us to see inclusion structures and disordered aggregate-like protein mixtures (which we call dynamic droplets) in a new light: not necessarily as a result of a pathological breakdown of cellular order, but as an elaborate cellular architecture regulating function and stress response. In this review, we discuss what is currently known about the role of inclusion structures in cellular homeostasis, stress response, toxicity, and disease. We will focus on possible mechanisms of aggregate toxicity, in contrast to the homeostatic function of several inclusion structures.

Autopsy as Gold Standard in FDG-PET Studies in Dementia

Positron emission tomography (PET) imaging with F18-fluorodeoxyglucose (FDG) is increasingly used as an adjunct to clinical evaluation in the diagnosis of dementia. Considering that most FDG-PET studies in dementia use clinical diagnosis as gold standard and that clinical diagnosis is approximately 80% sensitive or accurate, we aim to review the evidence-based data on the diagnostic accuracy of brain FDG-PET in dementia when cerebral autopsy is used as gold standard. We searched the PubMed and Medline databases for dementia-related articles that correlate histopathological diagnosis at autopsy with FDG-PET imaging and found 47 articles among which there were only 5 studies of 20 patients or more. We were able to conclude that sensitivity and specificity of FDG-PET for Alzheimer's disease are good, but more studies using histopathological diagnosis at autopsy as gold standard are needed in order to evaluate what FDG-PET truly adds to premortem diagnostic accuracy in dementia.

When dementia progresses quickly: a practical approach to the diagnosis and management of rapidly progressive dementia

Making a diagnosis of rapidly progressive dementia requires practical adaptation of the skills used to assess patients with chronic causes of cognitive impairment. An expedited assessment, commensurate with the accelerated pace of the disease, is required to identify the cause of symptoms amidst a myriad of possibilities. Features upon history, physical examination and cognitive assessment that support specific diagnoses are reviewed, and a stratified approach to testing is presented. The use of readily-accessible investigations is prioritized, acknowledging the implications and applications of novel diagnostic tests. The coordinated use of clinical and laboratory measures are promoted as a means of facilitating rapid evaluation, with the ultimate goal of identifying patients with potentially reversible causes of rapidly progressive dementia.

Chronic traumatic encephalopathy in professional sports: retrospective and prospective views

PRIMARY OBJECTIVE

The purposes of this paper are to review: (1) the history of chronic traumatic encephalopathy (CTE) in sports, (2) the similarities and differences between historic and current definitions of CTE, (3) recent epidemiology and cohort studies of CTE and (4) controversies regarding the current CTE positions.

RESEARCH DESIGN

Not applicable.

METHODS AND PROCEDURES

Selective review of published articles relevant to CTE.

MAIN OUTCOME AND RESULTS

The current definitions of CTE have evolved from its original definition and now rely heavily on the post-mortem detection of hyperphosphorylated tau for diagnosis. As of 2013, there is a blended cohort of 110 professional athletes diagnosed with CTE. It is being assumed that concussions and/or sub-concussive impacts in contact sports are the sole cause of CTE.

CONCLUSIONS

There are multiple causes of abnormal tau protein deposition in the human brain and the pathogenesis of CTE may not be related solely to concussion and/or sub-concussive injury. In all likelihood, the causes of CTE are a multivariate, as opposed to a univariate, phenomenon.

Primary progressive aphasia and the evolving neurology of the language network

Primary progressive aphasia (PPA) is caused by selective neurodegeneration of the language-dominant cerebral hemisphere; a language deficit initially arises as the only consequential impairment and remains predominant throughout most of the course of the disease. Agrammatic, logopenic and semantic subtypes, each reflecting a characteristic pattern of language impairment and corresponding anatomical distribution of cortical atrophy, represent the most frequent presentations of PPA. Such associations between clinical features and the sites of atrophy have provided new insights into the neurology of fluency, grammar, word retrieval, and word comprehension, and have necessitated modification of concepts related to the functions of the anterior temporal lobe and Wernicke's area. The underlying neuropathology of PPA is, most commonly, frontotemporal lobar degeneration in the agrammatic and semantic forms, and Alzheimer disease (AD) pathology in the logopenic form; the AD pathology often displays atypical and asymmetrical anatomical features consistent with the aphasic phenotype. The PPA syndrome reflects complex interactions between disease-specific neuropathological features and patient-specific vulnerability. A better understanding of these interactions might help us to elucidate the biology of the language network and the principles of selective vulnerability in neurodegenerative diseases. We review these aspects of PPA, focusing on advances in our understanding of the clinical features and neuropathology of PPA and what they have taught us about the neural substrates of the language network.

Full-length TDP-43 forms toxic amyloid oligomers that are present in frontotemporal lobar dementia-TDP patients

Proteinaceous inclusions are common hallmarks of many neurodegenerative diseases. TDP-43 proteinopathies, consisting of several neurodegenerative diseases, including frontotemporal lobar dementia (FTLD) and amyotrophic lateral sclerosis (ALS), are characterized by inclusion bodies formed by polyubiquitinated and hyperphosphorylated full-length and truncated TDP-43. The structural properties of TDP-43 aggregates and their relationship to pathogenesis are still ambiguous. Here we demonstrate that the recombinant full-length human TDP-43 forms structurally stable, spherical oligomers that share common epitopes with an anti-amyloid oligomer-specific antibody. The TDP-43 oligomers are stable, have exposed hydrophobic surfaces, exhibit reduced DNA binding capability and are neurotoxic in vitro and in vivo. Moreover, TDP-43 oligomers are capable of cross-seeding Alzheimer's amyloid-β to form amyloid oligomers, demonstrating interconvertibility between the amyloid species. Such oligomers are present in the forebrain of transgenic TDP-43 mice and FTLD-TDP patients. Our results suggest that aside from filamentous aggregates, TDP-43 oligomers may play a role in TDP-43 pathogenesis.

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.

(11)C-PIB-PET for the early diagnosis of Alzheimer's disease dementia and other dementias in people with mild cognitive impairment (MCI)

BACKGROUND

According to the latest revised National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (now known as the Alzheimer's Association) (NINCDS-ADRDA) diagnostic criteria for Alzheimer's disease dementia, the confidence in diagnosing mild cognitive impairment (MCI) due to Alzheimer's disease dementia is raised with the application of imaging biomarkers. These tests, added to core clinical criteria, might increase the sensitivity or specificity of a testing strategy. However, the accuracy of biomarkers in the diagnosis of Alzheimer's disease dementia and other dementias has not yet been systematically evaluated. A formal systematic evaluation of the sensitivity, specificity, and other properties of positron emission tomography (PET) imaging with the (11)C-labelled Pittsburgh Compound-B ((11)C-PIB) ligand was performed.

OBJECTIVES

To determine the diagnostic accuracy of the (11)C- PIB-PET scan for detecting participants with MCI at baseline who will clinically convert to Alzheimer's disease dementia or other forms of dementia over a period of time.

SEARCH METHODS

The most recent search for this review was performed on 12 January 2013. We searched MEDLINE (OvidSP), EMBASE (OvidSP), BIOSIS Previews (ISI Web of Knowledge), Web of Science and Conference Proceedings (ISI Web of Knowledge), PsycINFO (OvidSP), and LILACS (BIREME). We also requested a search of the Cochrane Register of Diagnostic Test Accuracy Studies (managed by the Cochrane Renal Group).No language or date restrictions were applied to the electronic searches and methodological filters were not used so as to maximise sensitivity.

SELECTION CRITERIA

We selected studies that had prospectively defined cohorts with any accepted definition of MCI with baseline (11)C-PIB-PET scan. In addition, we only selected studies that applied a reference standard for Alzheimer's dementia diagnosis for example NINCDS-ADRDA or Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) criteria.

DATA COLLECTION AND ANALYSIS

We screened all titles generated by electronic database searches. Two review authors independently assessed the abstracts of all potentially relevant studies. The identified full papers were assessed for eligibility and data were extracted to create two by two tables. Two independent assessors performed quality assessment using the QUADAS 2 tool. We used the hierarchical summary receiver operating characteristic (ROC) model to produce a summary ROC curve.

MAIN RESULTS

Conversion from MCI to Alzheimer's disease dementia was evaluated in nine studies. The quality of the evidence was limited. Of the 274 participants included in the meta-analysis, 112 developed Alzheimer's dementia. Based on the nine included studies, the median proportion converting was 34%. The studies varied markedly in how the PIB scans were done and interpreted.The sensitivities were between 83% and 100% while the specificities were between 46% and 88%. Because of the variation in thresholds and measures of (11)C-PIB amyloid retention, we did not calculate summary sensitivity and specificity. Although subject to considerable uncertainty, to illustrate the potential strengths and weaknesses of (11)C-PIB-PET scans we estimated from the fitted summary ROC curve that the sensitivity was 96% (95% confidence interval (CI) 87 to 99) at the included study median specificity of 58%. This equated to a positive likelihood ratio of 2.3 and a negative likelihood ratio of 0.07. Assuming a typical conversion rate of MCI to Alzheimer's dementia of 34%, for every 100 PIB scans one person with a negative scan would progress and 28 with a positive scan would not actually progress to Alzheimer's dementia.There were limited data for formal investigation of heterogeneity. We performed two sensitivity analyses to assess the influence of type of reference standard and the use of a pre-specified threshold. There was no effect on our findings.

AUTHORS' CONCLUSIONS

Although the good sensitivity achieved in some included studies is promising for the value of (11)C-PIB-PET, given the heterogeneity in the conduct and interpretation of the test and the lack of defined thresholds for determination of test positivity, we cannot recommend its routine use in clinical practice.(11)C-PIB-PET biomarker is a high cost investigation, therefore it is important to clearly demonstrate its accuracy and standardise the process of the (11)C-PIB diagnostic modality prior to it being widely used.

Neurodegenerative disease phenotypes in carriers of MAPT p.A152T, a risk factor for frontotemporal dementia spectrum disorders and Alzheimer disease

Recently, Coppola and colleagues demonstrated that a rare microtubule-associated protein tau (MAPT) sequence variant, c.454G>A (p.A152T) significantly increases the risk of frontotemporal dementia (FTD) spectrum disorders and Alzheimer disease (AD) in a screen of 15,369 subjects. We describe clinical features of 9 patients with neurodegenerative disease (4 women) harboring p.A152T, aged 51 to 79 years at symptom onset. Seven developed FTD spectrum clinical syndromes, including progressive supranuclear palsy syndrome (n=2), behavioral variant FTD (bvFTD, n=1), nonfluent variant primary progressive aphasia (nfvPPA, n=2), and corticobasal syndrome (n=2); 2 patients were diagnosed with clinical AD. Thus, MAPT p.A152T is associated with a variety of FTD spectrum clinical presentations, although patients with clinical AD are also identified. These data warrant larger studies with clinicopathologic correlation to elucidate the influence of this genetic variant on neurodegenerative disease.

Myelin oligodendrocyte basic protein and prognosis in behavioral-variant frontotemporal dementia

OBJECTIVE

To determine the prognostic utility of tauopathy-associated single nucleotide polymorphisms (SNPs) in sporadic behavioral-variant frontotemporal dementia (bvFTD).

METHODS

Eighty-one patients with sporadic bvFTD were genotyped for tauopathy-associated SNPs at rs8070723 (microtubule-associated protein tau [MAPT]) and rs1768208 (myelin-associated oligodendrocyte basic protein [MOBP]). We performed a retrospective case-control study comparing age at onset and disease duration between carriers of ≥1 polymorphism allele and noncarriers for these SNPs. Subanalyses were performed for autopsied subgroups with tauopathy (n = 20) and TDP-43 proteinopathy (n = 12). To identify a potential biological basis for disease duration, neuroimaging measures of white matter integrity were evaluated (n = 37).

RESULTS

Carriers of risk allele (T) in rs1768208 (i.e., MOBP RA+) had a shorter median disease duration (TC/TT = 5.5 years, CC = 9.5 years; p = 0.02). This was also found in the subset of cases with autopsy-confirmed tauopathies (p = 0.04) but not with TDP-43 proteinopathies (p > 0.1). By comparison, polymorphisms at rs8070723 (MAPT) had no effect on disease duration (p > 0.1), although carriers of protective allele (G) in rs8070723 had a younger median age at onset (AG/GG = 54.5 years, AA = 58 years; p < 0.01). MOBP RA+ patients had increased radial diffusivity in the superior corona radiata and midbrain, and reduced fractional anisotropy in the superior corona radiata as well as superior and inferior longitudinal fasciculi compared with noncarriers (p < 0.01).

CONCLUSIONS

The rs1768208 risk polymorphism in MOBP may have prognostic value in bvFTD. MOBP RA+ patients have more severe white matter degeneration in bvFTD that may contribute to shorter disease duration. Future studies are needed to help confirm these findings.

Amyloid imaging in atypical presentations of Alzheimer's disease

Alzheimer's disease (AD) is thought to progress in a fairly stereotyped manner, with episodic memory loss being the first and most salient domain of impairment, reflecting the early disease in structures supporting this function. However, there is considerable heterogeneity in the relative involvement of different cognitive domains, and at the extreme are three syndromes associated with AD: (1) logopenic progressive aphasia, (2) posterior cortical atrophy, and (3) frontal variant of AD. As each of these syndromes is variably associated with non-AD dementia and clinically overlaps with other presentations more commonly associated with different causes of neurodegeneration (e.g., progressive nonfluent aphasia), the use of amyloid imaging for detection of the molecular pathologic features of AD is of significant clinical value. This article reviews several amyloid imaging studies of these populations which support autopsy case series and reveal a dissociation between the spatial distribution of amyloid plaques and clinical phenotype.

Three-Class Differential Diagnosis among Alzheimer Disease, Frontotemporal Dementia, and Controls

Biomarkers derived from brain magnetic resonance (MR) imaging have promise in being able to assist in the clinical diagnosis of brain pathologies. These have been used in many studies in which the goal has been to distinguish between pathologies such as Alzheimer's disease and healthy aging. However, other dementias, in particular, frontotemporal dementia, also present overlapping pathological brain morphometry patterns. Hence, a classifier that can discriminate morphometric features from a brain MRI from the three classes of normal aging, Alzheimer's disease (AD), and frontotemporal dementia (FTD) would offer considerable utility in aiding in correct group identification. Compared to the conventional use of multiple pair-wise binary classifiers that learn to discriminate between two classes at each stage, we propose a single three-way classification system that can discriminate between three classes at the same time. We present a novel classifier that is able to perform a three-class discrimination test for discriminating among AD, FTD, and normal controls (NC) using volumes, shape invariants, and local displacements (three features) of hippocampi and lateral ventricles (two structures times two hemispheres individually) obtained from brain MR images. In order to quantify its utility in correct discrimination, we optimize the three-class classifier on a training set and evaluate its performance using a separate test set. This is a novel, first-of-its-kind comparative study of multiple individual biomarkers in a three-class setting. Our results demonstrate that local atrophy features in lateral ventricles offer the potential to be a biomarker in discriminating among AD, FTD, and NC in a three-class setting for individual patient classification.

Towards a clearer definition of logopenic progressive aphasia

Logopenic progressive aphasia is the most recently described clinical variant of primary progressive aphasia (PPA), defined by impairment of lexical retrieval and sentence repetition. Unlike other PPA variants, the logopenic variant of PPA (lv-PPA) is commonly associated with Alzheimer's disease (AD), a fact that is relevant to the selection of patients for clinical trials and disease-modifying therapies. Despite the straightforward definition and coherent pathological association, the existence of lv-PPA has been challenged, as its distinction from AD or other PPA variants can be difficult. Despite these issues, lv-PPA patients display characteristic linguistic deficits, a pattern of brain atrophy, and possibly genetic susceptibility, which warrant considering this variant as a discrete AD endophenotype. More specific clinical and anatomical markers can strengthen the consistency of this syndrome.

Sequential distribution of pTDP-43 pathology in behavioral variant frontotemporal dementia (bvFTD)

We examined regional distribution patterns of phosphorylated 43-kDa TAR DNA-binding protein (pTDP-43) intraneuronal inclusions in frontotemporal lobar degeneration (FTLD). Immunohistochemistry was performed on 70 μm sections from FTLD-TDP autopsy cases (n = 39) presenting with behavioral variant frontotemporal dementia. Two main types of cortical pTDP-43 pathology emerged, characterized by either predominantly perikaryal pTDP-43 inclusions (cytoplasmic type, cFTLD) or long aggregates in dendrites (neuritic type, nFTLD). Cortical involvement in nFTLD was extensive and frequently reached occipital areas, whereas cases with cFTLD often involved bulbar somatomotor neurons and the spinal cord. We observed four patterns indicative of potentially sequential dissemination of pTDP-43: cases with the lowest burden of pathology (pattern I) were characterized by widespread pTDP-43 lesions in the orbital gyri, gyrus rectus, and amygdala. With increasing burden of pathology (pattern II) pTDP-43 lesions emerged in the middle frontal and anterior cingulate gyrus as well as in anteromedial temporal lobe areas, the superior and medial temporal gyri, striatum, red nucleus, thalamus, and precerebellar nuclei. More advanced cases showed a third pattern (III) with involvement of the motor cortex, bulbar somatomotor neurons, and the spinal cord anterior horn, whereas cases with the highest burden of pathology (pattern IV) were characterized by pTDP-43 lesions in the visual cortex. We interpret the four neuropathological patterns in bvFTD to be consistent with the hypothesis that pTDP-43 pathology can spread sequentially and may propagate along axonal pathways.

Asymmetry and heterogeneity of Alzheimer's and frontotemporal pathology in primary progressive aphasia

Fifty-eight autopsies of patients with primary progressive aphasia are reported. Twenty-three of these were previously described (Mesulam et al., 2008) but had their neuropathological diagnoses updated to fit current criteria. Thirty-five of the cases are new. Their clinical classification was guided as closely as possible by the 2011 consensus guidelines (Gorno-Tempini et al., 2011). Tissue diagnoses included Alzheimer's disease in 45% and frontotemporal lobar degeneration (FTLD) in the others, with an approximately equal split between TAR DNA binding protein 43 proteinopathies and tauopathies. The most common and distinctive feature for all pathologies associated with primary progressive aphasia was the asymmetric prominence of atrophy, neuronal loss, and disease-specific proteinopathy in the language-dominant (mostly left) hemisphere. The Alzheimer's disease pathology in primary progressive aphasia displayed multiple atypical features. Males tended to predominate, the neurofibrillary pathology was more intense in the language-dominant hemisphere, the Braak pattern of hippocampo-entorhinal prominence was tilted in favour of the neocortex, and the APOE e4 allele was not a risk factor. Mean onset age was under 65 in the FTLD as well as Alzheimer's disease groups. The FTLD-TAR DNA binding protein 43 group had the youngest onset and fastest progression whereas the Alzheimer's disease and FTLD-tau groups did not differ from each other in either onset age or progression rate. Each cellular pathology type had a preferred but not invariant clinical presentation. The most common aphasic manifestation was of the logopenic type for Alzheimer pathology and of the agrammatic type for FTLD-tau. The progressive supranuclear palsy subtype of FTLD-tau consistently caused prominent speech abnormality together with agrammatism whereas FTLD-TAR DNA binding protein 43 of type C consistently led to semantic primary progressive aphasia. The presence of agrammatism made Alzheimer's disease pathology very unlikely whereas the presence of a logopenic aphasia or word comprehension impairment made FTLD-tau unlikely. The association of logopenic primary progressive aphasia with Alzheimer's disease pathology was much more modest than has been implied by results of in vivo amyloid imaging studies. Individual features of the aphasia, such as agrammatism and comprehension impairment, were as informative of underlying pathology as more laborious subtype diagnoses. At the single patient level, no clinical pattern was pathognomonic of a specific neuropathology type, highlighting the critical role of biomarkers for diagnosing the underlying disease. During clinical subtyping, some patients were unclassifiable by the 2011 guidelines whereas others simultaneously fit two subtypes. Revisions of criteria for logopenic primary progressive aphasia are proposed to address these challenges.

Neuropsychiatric symptom profile differs based on pathology in patients with clinically diagnosed behavioral variant frontotemporal dementia

BACKGROUND

Behavioral variant frontotemporal dementia (bvFTD) is pathologically heterogeneous. With emerging therapeutics, determining underlying pathology during life is increasingly important. Neuropsychiatric symptoms are prevalent and diagnostic in bvFTD.

METHODS

We assessed the neuropsychiatric profile of patients with clinically diagnosed bvFTD as a function of pathology at autopsy. Patients with a clinical diagnosis of bvFTD at the initial visit were selected from the National Alzheimer's Coordinating Center (NACC) database. Neuropsychiatric symptoms endorsed on the Neuropsychiatric Inventory Questionnaire (NPI-Q) were analyzed.

RESULTS

Of 149 patients with clinically diagnosed bvFTD, pathology was primarily Alzheimer's disease (AD) in 20.5%. These patients differed from those with underlying frontotemporal lobar degeneration: patients with AD pathology (plaques and tangles) were more likely to have hallucinations, delusions, or agitation. Patients were further differentiated into tau-positive (30% of cases, including Pick's disease, FTD and parkinsonism with tau-positive or argyrophilic inclusions, and other tauopathies) or tau-negative cases (70% of cases, including bvFTD tau-negative ubiquitin-positive inclusions). These patients also differed in some of the neuropsychiatric symptoms seen. Tau-negative cases were more likely to demonstrate depression, delusions, and changes in appetite and eating.

CONCLUSIONS

These preliminary findings contribute to our increasing ability to predict, using simple clinical tools, the neuropathological underpinnings of bvFTD during life.

Reduced CSF p-Tau181 to Tau ratio is a biomarker for FTLD-TDP

OBJECTIVES

To validate the ability of candidate CSF biomarkers to distinguish between the 2 main forms of frontotemporal lobar degeneration (FTLD), FTLD with TAR DNA-binding protein 43 (TDP-43) inclusions (FTLD-TDP) and FTLD with Tau inclusions (FTLD-Tau).

METHODS

Antemortem CSF samples were collected from 30 patients with FTLD in a single-center validation cohort, and CSF levels of 5 putative FTLD-TDP biomarkers as well as levels of total Tau (t-Tau) and Tau phosphorylated at threonine 181 (p-Tau181) were measured using independent assays. Biomarkers most associated with FTLD-TDP were then tested in a separate 2-center validation cohort composed of subjects with FTLD-TDP, FTLD-Tau, Alzheimer disease (AD), and cognitively normal subjects. The sensitivity and specificity of FTLD-TDP biomarkers were determined.

RESULTS

In the first validation cohort, FTLD-TDP cases had decreased levels of p-Tau181 and interleukin-23, and increased Fas. Reduced ratio of p-Tau181 to t-Tau (p/t-Tau) was the strongest predictor of FTLD-TDP pathology. Analysis in the second validation cohort showed CSF p/t-Tau ratio <0.37 to distinguish FTLD-TDP from FTLD-Tau, AD, and healthy seniors with 82% sensitivity and 82% specificity.

CONCLUSION

A reduced CSF p/t-Tau ratio represents a reproducible, validated biomarker for FTLD-TDP with performance approaching well-established CSF AD biomarkers. Introducing this biomarker into research and the clinical arena can significantly increase the power of clinical trials targeting abnormal accumulations of TDP-43 or Tau, and select the appropriate patients for target-specific therapies.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that the CSF p/t-Tau ratio distinguishes FTLD-TDP from FTLD-Tau.

Disruption of large-scale neural networks in non-fluent/agrammatic variant primary progressive aphasia associated with frontotemporal degeneration pathology

Non-fluent/agrammatic primary progressive aphasia (naPPA) is a progressive neurodegenerative condition most prominently associated with slowed, effortful speech. A clinical imaging marker of naPPA is disease centered in the left inferior frontal lobe. We used multimodal imaging to assess large-scale neural networks underlying effortful expression in 15 patients with sporadic naPPA due to frontotemporal lobar degeneration (FTLD) spectrum pathology. Effortful speech in these patients is related in part to impaired grammatical processing, and to phonologic speech errors. Gray matter (GM) imaging shows frontal and anterior-superior temporal atrophy, most prominently in the left hemisphere. Diffusion tensor imaging reveals reduced fractional anisotropy in several white matter (WM) tracts mediating projections between left frontal and other GM regions. Regression analyses suggest disruption of three large-scale GM-WM neural networks in naPPA that support fluent, grammatical expression. These findings emphasize the role of large-scale neural networks in language, and demonstrate associated language deficits in naPPA.

Acetylated tau neuropathology in sporadic and hereditary tauopathies

We have recently shown acetylation of tau at lysine residue 280 (AC-K280) to be a disease-specific modification in Alzheimer disease (AD), corticobasal degeneration, and progressive supranuclear palsy, likely representing a major regulatory tau modification. Herein, we extend our observations using IHC with a polyclonal antibody specific for AC-K280. Thirty brain regions were examined in argyrophilic grain disease (AGD; n = 5), tangle-predominant senile dementia (TPSD; n = 5), Pick disease (n = 4), familial AD (FAD; n = 2; PSEN1 p.G206A and p.S170P), and frontotemporal dementia with parkinsonism linked to chromosome-17 (FTDP-17; n = 2; MAPT p.P301L and IVS10 + 16). All AGD, TPSD, FAD, and FTDP-17 cases had significant AC-K280 reactivity that was similar in severity and distribution to phosphorylated tau. AC-K280 robustly labeled grain pathological characteristics in AGD and was predominantly associated with thioflavin-S-positive neurofibrillary tangles and less reactive in neuropil threads and extracellular tangles in TPSD and FAD. Thioflavin-S-negative neuronal and glial inclusions of patients with FTDP-17 were robustly AC-K280 reactive. A low degree of AC-K280 was found in a subset of 4-repeat tau-containing lesions in Pick disease. AC-K280 is a prominent feature of both neuronal and glial tau aggregations in tauopathies of various etiologies. The close association of AC-K280 with amyloid and pre-amyloid conformations of tau suggests a potential role in tangle maturation and, thus, could serve as a useful biomarker or therapeutic target in a variety of tauopathies.

Cerebrospinal fluid tau levels predict prognosis in non-inherited frontotemporal dementia

BACKGROUND

The course of frontotemporal dementia (FTD) is heterogeneous and no predictors of survival are currently available. Cerebrospinal fluid (CSF) tau dosage has been demonstrated to be useful in predicting outcome over time in a number of neurological disorders.

OBJECTIVE

To assess CSF tau levels in FTD and to evaluate their prognostic value.

METHODS

Seventy-seven FTD patients with no mutations in known causative genes were consecutively enrolled, and CSF tau and phospho-tau levels analysed. Each patient was reassessed over time, and survival (i.e. death/bedridden and otherwise) was evaluated. The survival analysis was carried out by Cox proportional hazards regression models.

RESULTS

Patients with high CSF tau levels (≥400 pg/ml) had shorter survival than those with low CSF tau levels [hazard ratio (HR) = 3.406; 95% CI: 1.151-10.077; Wald χ(2) = 4.902; d.f. = 1; p = 0.027]. The association between tau levels and survival probability was confirmed after adjusting for age, gender, clinical phenotype and FTD clinical dementia rating at enrolment (HR = 3.769; 95% CI: 1.143-12.433; Wald χ(2) = 4.748; d.f. = 1; p = 0.029). Neither demographic or clinical characteristics nor CSF phospho-tau levels or apolipoprotein E genotype were significantly associated with prognosis.

CONCLUSIONS

This study argues that CSF tau levels may be considered in FTD to predict patients' outcome. Establishing in vivo prognostic biomarkers is mandatory to define homogeneous groups for inclusion in future clinical trials and to monitor the effectiveness of future therapeutic approaches.

Progranulin peripheral levels as a screening tool for the identification of subjects with progranulin mutations in a Portuguese cohort

BACKGROUND

Progranulin (PGRN) mutations are associated with different clinical phenotypes, including frontotemporal lobar degeneration (FTLD), corticobasal syndrome (CBS) and Alzheimer's disease (AD). As all pathogenic PGRN mutations identified so far cause disease through haploinsufficiency, determination of PGRN levels has been proposed as a reliable method to identify mutation carriers.

OBJECTIVE

To evaluate the accuracy of peripheral PGRN levels in the identification of the PGRN mutation carriers detected thus far in our Portuguese cohort.

METHODS

Serum PGRN levels were measured in 244 subjects (124 patients in the spectrum of FTLD, 2 asymptomatic descendants of a FTLD patient, 56 AD patients and 64 controls) by a novel commercial ELISA kit.

RESULTS

Low PGRN levels were detected in 7 individuals (5 behavioral variant frontotemporal dementia, 1 CBS, and 1 still clinically unaffected) that constituted the group of the null PGRN mutation carriers previously identified in our molecular diagnostic laboratory. The pathogenic mutations found consisted of 4 insertion-deletions, causing frameshifts resulting in premature stop codons, 3 of which were novel. In addition, a normal PGRN level was found in a patient harboring a novel missense variant. For this novel ELISA kit, we established a PGRN cut-off level that identified with 100% accuracy the pathogenic mutation carriers.

CONCLUSION

This study supports the use of a novel assay for the determination of PGRN levels as a screening procedure to identify patients harboring null PGRN mutations. This approach would significantly decrease the required PGRN mutation analysis workload and should be extended to other clinical phenotypes than behavioral variant frontotemporal dementia and to apparently sporadic cases.

Brain site-specific proteome changes in aging-related dementia

This study is aimed at gaining insights into the brain site-specific proteomic senescence signature while comparing physiologically aged brains with aging-related dementia brains (for example, Alzheimer's disease (AD)). Our study of proteomic differences within the hippocampus (Hp), parietal cortex (pCx) and cerebellum (Cb) could provide conceptual insights into the molecular mechanisms involved in aging-related neurodegeneration. Using an isobaric tag for relative and absolute quantitation (iTRAQ)-based two-dimensional liquid chromatography coupled with tandem mass spectrometry (2D-LC-MS/MS) brain site-specific proteomic strategy, we identified 950 proteins in the Hp, pCx and Cb of AD brains. Of these proteins, 31 were significantly altered. Most of the differentially regulated proteins are involved in molecular transport, nervous system development, synaptic plasticity and apoptosis. Particularly, proteins such as Gelsolin (GSN), Tenascin-R (TNR) and AHNAK could potentially act as novel biomarkers of aging-related neurodegeneration. Importantly, our Ingenuity Pathway Analysis (IPA)-based network analysis further revealed ubiquitin C (UBC) as a pivotal protein to interact with diverse AD-associated pathophysiological molecular factors and suggests the reduced ubiquitin proteasome degradation system (UPS) as one of the causative factors of AD.

White matter imaging helps dissociate tau from TDP-43 in frontotemporal lobar degeneration

BACKGROUND

Frontotemporal lobar degeneration (FTLD) is most commonly associated with TAR-DNA binding protein (TDP-43) or tau pathology at autopsy, but there are no in vivo biomarkers reliably discriminating between sporadic cases. As disease-modifying treatments emerge, it is critical to accurately identify underlying pathology in living patients so that they can be entered into appropriate etiology-directed clinical trials. Patients with tau inclusions (FTLD-TAU) appear to have relatively greater white matter (WM) disease at autopsy than those patients with TDP-43 (FTLD-TDP). In this paper, we investigate the ability of white matter (WM) imaging to help discriminate between FTLD-TAU and FTLD-TDP during life using diffusion tensor imaging (DTI).

METHODS

Patients with autopsy-confirmed disease or a genetic mutation consistent with FTLD-TDP or FTLD-TAU underwent multimodal T1 volumetric MRI and diffusion weighted imaging scans. We quantified cortical thickness in GM and fractional anisotropy (FA) in WM. We performed Eigenanatomy, a statistically robust dimensionality reduction algorithm, and used leave-one-out cross-validation to predict underlying pathology. Neuropathological assessment of GM and WM disease burden was performed in the autopsy-cases to confirm our findings of an ante-mortem GM and WM dissociation in the neuroimaging cohort.

RESULTS

ROC curve analyses evaluated classification accuracy in individual patients and revealed 96% sensitivity and 100% specificity for WM analyses. FTLD-TAU had significantly more WM degeneration and inclusion severity at autopsy relative to FTLD-TDP.

CONCLUSIONS

These neuroimaging and neuropathological investigations provide converging evidence for greater WM burden associated with FTLD-TAU, and emphasise the role of WM neuroimaging for in vivo discrimination between FTLD-TAU and FTLD-TDP.

TREM2 in neurodegeneration: evidence for association of the p.R47H variant with frontotemporal dementia and Parkinson's disease

BACKGROUND

A rare variant in the Triggering Receptor Expressed on Myeloid cells 2 (TREM2) gene has been reported to be a genetic risk factor for Alzheimer's disease by two independent groups (Odds ratio between 2.9-4.5). Given the key role of TREM2 in the effective phagocytosis of apoptotic neuronal cells by microglia, we hypothesized that dysfunction of TREM2 may play a more generalized role in neurodegeneration. With this in mind we set out to assess the genetic association of the Alzheimer's disease-related risk variant in TREM2 (rs75932628, p.R47H) with other related neurodegenerative disorders.

RESULTS

The study included 609 patients with frontotemporal dementia, 765 with amyotrophic lateral sclerosis, 1493 with Parkinson's disease, 772 with progressive supranuclear palsy, 448 with ischemic stroke and 1957 controls subjects free of neurodegenerative disease. A significant association was observed for the TREM2 p.R47H substitution in susceptibility to frontotemporal dementia (OR = 5.06; p-value = 0.001) and Parkinson's disease (OR = 2.67; p-value = 0.026), while no evidence of association with risk of amyotrophic lateral sclerosis, progressive supranuclear palsy or ischemic stroke was observed.

CONCLUSIONS

Our results suggest that the TREM2 p.R47H substitution is a risk factor for frontotemporal dementia and Parkinson's disease in addition to Alzheimer's disease. These findings suggest a more general role for TREM2 dysfunction in neurodegeneration, which could be related to its role in the immune response.

Multimodal comparative studies of neurodegenerative diseases

Here we provide a brief description of our program to improve diagnostic accuracy in cases with phenotypically similar presentations that are due to distinct histopathologic abnormalities. We propose a staged approach to diagnosis, beginning with a screening assessment of specific, quantitative neuropsychological measures, and followed by assessments of imaging and biofluid biomarkers. Our goal is to determine the specific histopathologic abnormalities contributing to an individual's neurodegenerative condition.

Caring for loved ones with frontotemporal degeneration: the lived experiences of spouses

There is an abundant literature about the experience of caregiving for a spouse living with Alzheimer's disease (AD), but there are very few qualitative studies about caregiving for persons living with Frontotemporal Degeneration (FTD). FTD causes a change in personality and affected persons may lose the ability to adhere to social norms. Thus, the emotional loss caregivers experience is often confounded by anger in response to embarrassing and socially inappropriate behaviors. In this paper, we offer a glimpse of this lived experience through the voices of two spouses whom we interviewed, each with experience caring for persons living with FTD. We suggest that FTD caregivers experience a loss of emotional attachment to their spouse because of their partner's behavioral symptoms. This loss gives rise to feelings of isolation and anger as caregivers assume new roles and reimagine their future. The findings from these interviews illuminate the need for more research and greater attention and support for FTD caregivers early in the disease trajectory.

New perspective on parkinsonism in frontotemporal lobar degeneration

Frontotemporal dementia (FTD) is the second most common type of presenile dementia. Three clinical prototypes have been defined; behavioral variant FTD, semantic dementia, and progressive nonfluent aphasia. Progressive supranuclear palsy, corticobasal degeneration, and motor neuron disease may possess clinical and pathological characteristics that overlap with FTD, and it is possible that they may all belong to the same clinicopathological spectrum. Frontotemporal lobar degeneration (FTLD) is a clinicopathological syndrome that encompasses a heterogenous group of neurodegenerative disorders. Owing to the advancement in the field of molecular genetics, diagnostic imaging, and pathology, FTLD has been the focus of great interest. Nevertheless, parkinsonism in FTLD has received relatively less attention. Parkinsonism is found in approximately 20–30% of patients in FTLD. Furthermore, parkinsonism can be seen in all FTLD subtypes, and some patients with familial and sporadic FTLD can present with prominent parkinsonism. Therefore, there is a need to understand parkinsonism in FTLD in order to obtain a better understanding of the disease. With regard to the clinical characteristics, the akinetic rigid type of parkinsonism has predominantly been described. Parkinsonism is frequently observed in familial FTD, more specifically, in FTD with parkinsonism linked to chromosome 17q (FTDP-17). The genes associated with parkinsonism are microtubule associated protein tau (MAPT), progranulin (GRN or PGRN), and chromosome 9 open reading frame 72 (C9ORF72) repeat expansion. The neural substrate of parkinsonism remains to be unveiled. Dopamine transporter (DAT) imaging revealed decreased uptake of DAT, and imaging findings indicated atrophic changes of the basal ganglia. Parkinsonism can be an important feature in FTLD and, therefore, increased attention is needed on the subject.

Decreased striatal dopamine transporter uptake in the non-fluent/agrammatic variant of primary progressive aphasia

BACKGROUND AND PURPOSE

Patients with the non-fluent/agrammatic variant of primary progressive aphasia (nfvPPA) may develop atypical parkinsonian syndromes. However, there is no current biomarker to assess which patients are at high risk of developing parkinsonism. 123I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane (123I-FP-CIT)-SPECT detects striatal dopamine dysfunction in vivo. The objective of the present study was to study whether non-fluent/agrammatic patients without parkinsonism at baseline present decreased striatal 123I-FP-CIT uptake.

METHODS

Visual and semi-quantitative assessments of the striatal 123I-FP-CIT uptake ratio were carried out in 15 patients with nfvPPA, eight patients with the logopenic variant of PPA (lvPPA) and 18 controls. To rule out progranulin mutations or underlying Alzheimer's disease (AD), serum progranulin levels and cerebrospinal fluid (CSF) biomarkers of AD (Aβ42 , total-tau, phosphorylated-tau181 ) were determined. A second 123I-FP-CIT-SPECT analysis in the biomarker-enriched groups was also carried out.

RESULTS

Patients with nfvPPA presented reduced striatal 123I-FP-CIT binding, especially in the left hemisphere (P = 0.002), compared with controls. All lvPPA patients had normal striatal 123I-FP-CIT uptake. 123I-FP-CIT striatal binding in nfvPPA patients with normal progranulin and CSF biomarker levels (nfvPPA/bio-) was also significantly reduced (P < 0.05) compared with lvPPA patients with positive AD biomarkers. Sixty-four per cent (9/14) of nfvPPA patients and 80% of nfvPPA/bio- patients (8/10) showed a diminished individual left striatal 123I-FP-CIT uptake ratio. On follow-up, seven nfvPPA/bio- patients developed parkinsonism (median 1.9 years; range 1.2-2.9), six of them with baseline reduced 123I-FP-CIT uptake.

CONCLUSIONS

Reduced striatal tracer uptake in nfvPPA patients prior to clinical parkinsonism can be detected by 123I-FP-CIT-SPECT, especially in those with nfvPPA/bio-, suggesting subclinical nigrostriatal degeneration. Decreased striatal 123I-FP-CIT binding might identify PPA patients at increased risk of developing atypical parkinsonian syndromes, probably related to tau-pathology.

From frontotemporal lobar degeneration pathology to frontotemporal lobar degeneration biomarkers

Frontotemporal dementia (FTD) is an increasingly recognized cause of dementia. This review discusses the different FTD clinical syndromes and frontotemporal lobar degeneration (FTLD) pathological correlates as well as new genetic and proteomic findings that have added to our understanding of FTLD pathogenesis. Various diagnostic modalities including the use of biomarkers will also be addressed. Finally we will highlight future directions in the FTD field. More research is needed to elucidate the cellular mechanisms of neurodegeneration in FTLD and improve clinical diagnostic capabilities.

Using Pittsburgh Compound B for in vivo PET imaging of fibrillar amyloid-beta

The development of Aβ-PET imaging agents has allowed for detection of fibrillar Aβ deposition in vivo and marks a major advancement in understanding the role of Aβ in Alzheimer's disease (AD). Imaging Aβ thus has many potential clinical benefits: early or perhaps preclinical detection of disease and accurately distinguishing AD from dementias of other non-Aβ causes in patients presenting with mild or atypical symptoms or confounding comorbidities (in which the distinction is difficult to make clinically). From a research perspective, imaging Aβ allows us to study relationships between amyloid pathology and changes in cognition, brain structure, and function across the continuum from normal aging to mild cognitive impairment (MCI) to AD; and to monitor the effectiveness of anti-Aβ drugs and relate them to neurodegeneration and clinical symptoms. Here, we will discuss the application of one of the most broadly studied and widely used Aβ imaging agents, Pittsburgh Compound-B (PiB).

Cerebrospinal fluid biomarkers for differentiation of frontotemporal lobar degeneration from Alzheimer's disease

Accurate ante mortem diagnosis in frontotemporal lobar degeneration (FTLD) is crucial to the development and implementation of etiology-based therapies. Several neurodegenerative disease-associated proteins, including the major protein constituents of inclusions in Alzheimer's disease (AD) associated with amyloid-beta (Aβ(1-42)) plaque and tau neurofibrillary tangle pathology, can be measured in cerebrospinal fluid (CSF) for diagnostic applications. Comparative studies using autopsy-confirmed samples suggest that CSF total-tau (t-tau) and Aβ(1-42) levels can accurately distinguish FTLD from AD, with a high t-tau to Aβ(1-42) ratio diagnostic of AD; however, there is also an urgent need for FTLD-specific biomarkers. These analytes will require validation in large autopsy-confirmed cohorts and face challenges of standardization of within- and between-laboratory sources of error. In addition, CSF biomarkers with prognostic utility and longitudinal study of CSF biomarker levels over the course of disease are also needed. Current goals in the field include identification of analytes that are easily and reliably measured and can be used alone or in a multi-modal approach to provide an accurate prediction of underlying neuropathology for use in clinical trials of disease modifying treatments in FTLD. To achieve these goals it will be of the utmost importance to view neurodegenerative disease, including FTLD, as a clinicopathological entity, rather than exclusively a clinical syndrome.

Atypical motor and behavioral presentations of Alzheimer disease: a case-based approach

BACKGROUND

The correlation of clinical presentation to pathology in dementia syndromes is important to correctly classify and ultimately treat these conditions. However, despite careful clinical characterization, it remains difficult to accurately predict an underlying causative pathology in some cases. Alzheimer disease is a well-defined clinical entity having established diagnostic criteria and characteristic neuropathologic findings. Alzheimer pathology, however, can cause varying clinical syndromes, including both atypical motor and behavioral presentations.

REVIEW SUMMARY

Atypical clinical presentations of Alzheimer disease are reviewed in a case-based format. Corticobasal syndrome, with asymmetric Parkinsonism, dystonia, and apraxia, is increasingly recognized as a presentation of Alzheimer pathology. Frontal variant Alzheimer, clinically indistinguishable from behavioral variant frontotemporal dementia (bv-FTD), can present with difficulties in executive function, poor attention, and behavioral issues. Posterior cortical atrophy (the "visual variant" of Alzheimer) has predominant visuospatial dysfunction and can be an Alzheimer presentation. Finally, Alzheimer can present as logopenic progressive aphasia with word-finding difficulty.

CONCLUSIONS

Clinicopathologic correlation may be more complex than previously realized, and the location of the microscopic changes may have as much to do with the clinical presentation as the nature of the changes themselves. Recognizing these clinical syndromes can lead to greater accuracy in diagnosis and treatment.

Clinicopathologic differences among patients with behavioral variant frontotemporal dementia

OBJECTIVE

To characterize the presenting symptoms and signs of patients clinically diagnosed with behavioral variant frontotemporal dementia (bvFTD) and who had different neuropathologic findings on autopsy.

METHODS

This study reviewed all patients entered as clinical bvFTD in the National Alzheimer's Coordinating Center's database and who had both clinical and neuropathologic data from 2005 to 2011. Among the 107 patients identified, 95 had unambiguous pathologic findings, including 74 with frontotemporal lobar degeneration (bvFTD-FTLD) and 21 with Alzheimer disease (bvFTD-AD). The patients with bvFTD-FTLD were further subdivided into τ-positive (n = 23) or τ-negative (n = 51) histopathology subgroups. Presenting clinical signs and symptoms were compared between these neuropathologic groups.

RESULTS

The patients with bvFTD-FTLD were significantly more likely than patients with bvFTD-AD to have initially predominant personality changes and poor judgment/decision-making. In contrast, patients with bvFTD-AD were more likely than patients with bvFTD-FTLD to have memory difficulty and delusions/hallucinations and agitation. Within the bvFTD-FTLD group, the τ-positive subgroup had more patients with initial behavioral problems and personality change than the τ-negative subgroup, who, in turn, had more patients with initial cognitive impairment and speech problems.

CONCLUSION

During life, patients with AD pathology may be misdiagnosed with bvFTD if they have an early age at onset and prominent neuropsychiatric features despite having greater memory difficulties and more intact personality and executive functions than patients with bvFTD-FTLD. Among those with FTLD pathology, patients with τ-positive bvFTD were likely to present with behavior/personality changes. These findings offer clues for antemortem recognition of neuropathologic subtypes of bvFTD.

Cognitive decline and reduced survival in C9orf72 expansion frontotemporal degeneration and amyotrophic lateral sclerosis

BACKGROUND

Significant heterogeneity in clinical features of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS) cases with the pathogenic C9orf72 expansion (C9P) have been described. To clarify this issue, we compared a large C9P cohort with carefully matched non-expansion (C9N) cases with a known or highly-suspected underlying TAR DNA-binding protein 43 (TDP-43) proteinopathy.

METHODS

A retrospective case-control study was carried out using available cross-sectional and longitudinal clinical and neuropsychological data, MRI voxel-based morphometry (VBM) and neuropathological assessment from 64 C9P cases (ALS=31, FTLD=33) and 79 C9N cases (ALS=36, FTLD=43).

RESULTS

C9P cases had an earlier age of onset (p=0.047) and, in the subset of patients who were deceased, an earlier age of death (p=0.014) than C9N. C9P had more rapid progression than C9N: C9P ALS cases had a shortened survival (2.6 ± 0.3 years) compared to C9N ALS (3.8 ± 0.4 years; log-rank λ2=4.183, p=0.041), and C9P FTLD showed a significantly greater annualised rate of decline in letter fluency (4.5 ± 1.3 words/year) than C9N FTLD (1.4 ± 0.8 words/year, p=0.023). VBM revealed greater atrophy in the right frontoinsular, thalamus, cerebellum and bilateral parietal regions for C9P FTLD relative to C9N FTLD, and regression analysis related verbal fluency scores to atrophy in frontal and parietal regions. Neuropathological analysis found greater neuronal loss in the mid-frontal cortex in C9P FTLD, and mid-frontal cortex TDP-43 inclusion severity correlated with poor letter fluency performance.

CONCLUSIONS

C9P cases may have a shorter survival in ALS and more rapid rate of cognitive decline related to frontal and parietal disease in FTLD. C9orf72 genotyping may provide useful prognostic and diagnostic clinical information for patients with ALS and FTLD.

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.

'Limits and current knowledge of Pick's disease: its differential diagnosis'. A translation of the 1957 Delay, Brion, Escourolle article

This article is a translation of a French article by Delay, Brion, and Escourolle. In a seminal article published in French in 1957 these authors summarized the work of previous researchers and reviewed a wide sample of frontotemporal dementia (FTD) cases formerly referred to as Pick's disease. The authors were among the first to define the critical clinical and anatomical differences between Alzheimer's disease (AD) and FTD and they even delineated distinctive FTD subtypes making possible the advances that now constitute the base of our studies. Reviewing their work allows us to appreciate the progress research has made.

Asparaginyl endopeptidase cleaves TDP-43 in brain

TAR DNA-binding protein 43 (TDP-43) is a nuclear protein involved in RNA splicing and a major protein component in ubiquitin-positive, tau-negative inclusions of frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Under disease conditions, TDP-43 redistributes to the cytoplasm where it can be phosphorylated, ubiquitinated, and proteolytically cleaved. Enzymes responsible for TDP-43 proteolytic processing in brain remain largely unreported. Using a MS approach, we identified two truncated TDP-43 peptides, terminating C-terminal to asparagines 291 (N291) and 306 (N306). The only documented mammalian enzyme capable of cleaving C-terminal to asparagine is asparaginyl endopeptidase (AEP). TDP-43-immunoreactive fragments (~35 and 32 kDa) predicted to be generated by AEP cleavage at N291 and N306 were observed by Western blot analyses of postmortem frontotemporal lobar degeneration brain tissue and cultured human cells over-expressing TDP-43. Studies in vitro determined that AEP can directly cleave TDP-43 at seven sites, including N291 and N306. Western blots of brain homogenates isolated from AEP-null mice and wild-type littermate controls revealed that TDP-43 proteolytic fragments were substantially reduced in the absence of AEP in vivo. Taken together, we conclude that TDP-43 is cleaved by AEP in brain. Moreover, these data highlight the utility of combining proteomic strategies in vitro and in vivo to provide insight into TDP-43 biology that will fuel the design of more detailed models of disease pathogenesis.

Category-specific semantic memory: converging evidence from bold fMRI and Alzheimer's disease

Patients with Alzheimer's disease have category-specific semantic memory difficulty for natural relative to manufactured objects. We assessed the basis for this deficit by asking healthy adults and patients to judge whether pairs of words share a feature (e.g. "banana:lemon-COLOR"). In an fMRI study, healthy adults showed gray matter (GM) activation of temporal-occipital cortex (TOC) where visual-perceptual features may be represented, and prefrontal cortex (PFC) which may contribute to feature selection. Tractography revealed dorsal and ventral stream white matter (WM) projections between PFC and TOC. Patients had greater difficulty with natural than manufactured objects. This was associated with greater overlap between diseased GM areas correlated with natural kinds in patients and fMRI activation in healthy adults for natural kinds. The dorsal WM projection between PFC and TOC in patients correlated only with judgments of natural kinds. Patients thus remained dependent on the same neural network as controls during judgments of natural kinds, despite disease in these areas. For manufactured objects, patients' judgments showed limited correlations with PFC and TOC GM areas activated by controls, and did not correlate with the PFC-TOC dorsal WM tract. Regions outside of the PFC-TOC network thus may help support patients' judgments of manufactured objects. We conclude that a large-scale neural network for semantic memory implicates both feature knowledge representations in modality-specific association cortex and heteromodal regions important for accessing this knowledge, and that patients' relative deficit for natural kinds is due in part to their dependence on this network despite disease in these areas.