Neuroimaging in frontotemporal dementia

Educational disparities in brain health and dementia across Latin America and the United States

BACKGROUND

Education influences brain health and dementia. However, its impact across regions, specifically Latin America (LA) and the United States (US), is unknown.

METHODS

A total of 1412 participants comprising controls, patients with Alzheimer's disease (AD), and frontotemporal lobar degeneration (FTLD) from LA and the US were included. We studied the association of education with brain volume and functional connectivity while controlling for imaging quality and variability, age, sex, total intracranial volume (TIV), and recording type.

RESULTS

Education influenced brain measures, explaining 24%-98% of the geographical differences. The educational disparities between LA and the US were associated with gray matter volume and connectivity variations, especially in LA and AD patients. Education emerged as a critical factor in classifying aging and dementia across regions.

DISCUSSION

The results underscore the impact of education on brain structure and function in LA, highlighting the importance of incorporating educational factors into diagnosing, care, and prevention, and emphasizing the need for global diversity in research.

HIGHLIGHTS

Lower education was linked to reduced brain volume and connectivity in healthy controls (HCs), Alzheimer's disease (AD), and frontotemporal lobar degeneration (FTLD). Latin American cohorts have lower educational levels compared to the those in the United States. Educational disparities majorly drive brain health differences between regions. Educational differences were significant in both conditions, but more in AD than FTLD. Education stands as a critical factor in classifying aging and dementia across regions.

Differential linguistic features of verbal fluency in behavioral variant frontotemporal dementia and primary progressive aphasia

Frontotemporal dementia (FTD) is an early-onset neurodegenerative disorder with a heterogeneous clinical presentation. Verbal fluency is regularly used as a sensitive measure of language ability, semantic memory, and executive functioning, but qualitative changes in verbal fluency in FTD are currently overlooked. This retrospective study examined qualitative, linguistic features of verbal fluency in 137 patients with behavioral variant (bv)FTD (n = 50), or primary progressive aphasia (PPA) [25 non-fluent variant (nfvPPA), 27 semantic variant (svPPA), and 34 logopenic variant (lvPPA)] and 25 control participants. Between-group differences in clustering, switching, lexical frequency (LF), age of acquisition (AoA), neighborhood density (ND), and word length (WL) were examined in the category and letter fluency with analysis of variance adjusted for age, sex, and the total number of words. Associations with other cognitive functions were explored with linear regression analysis. The results showed that the verbal fluency performance of patients with svPPA could be distinguished from controls and other patient groups by fewer and smaller clusters, more switches, higher LF, and lower AoA (all p < 0.05). Patients with lvPPA specifically produced words with higher ND than the other patient groups (p < 0.05). Patients with bvFTD produced longer words than the PPA groups (p < 0.05). Clustering, switching, LF, AoA, and ND-but not WL-were differentially predicted by measures of language, memory, and executive functioning (range standardized regression coefficient 0.25-0.41). In addition to the total number of words, qualitative linguistic features differ between subtypes of FTD. These features provide additional information on lexical processing and semantic memory that may aid the differential diagnosis of FTD.

Aging and Olfactory Training: A Scoping Review

Background and Objectives

Decreased olfactory function commonly occurs alongside the aging process. Research suggests olfactory training (OT) has the potential to improve olfactory and cognitive function in individuals with and without olfactory dysfunction. The degree to which these benefits extend into older age and among those with cognitive impairment (i.e., people with dementia and mild cognitive impairment) is less clear. The purpose of the current review was to investigate the extent to which OT affects olfactory function, cognition, and well-being among older people.

Research Design and Methods

A scoping review of the literature was conducted in PubMed, Embase, EbscoHost, and SCOPUS. Articles were considered eligible for original research studies with human populations, included adults aged 55 and older, performed any type of OT, and included a form of olfactory testing. The data from the included studies were synthesized and presented narratively.

Results

A total of 23 studies were included. The results suggest that OT provides multiple benefits to older adults, including those with cognitive impairment. Particularly, OT was associated with measurable changes in olfactory function, improved cognitive function, specifically semantic verbal fluency and working memory, reduced depressive symptoms, and protection from cognitive decline.

Discussion and Implications

The findings suggest that benefits from OT extend beyond changes in olfactory function and include improved cognitive function, amelioration of depressive symptoms, and protection from cognitive decline. Future research is needed across specific participant groups, including those with differentiated types of dementia, to investigate the olfactory and cognitive benefits of OT.

Spatial and Temporal Relationships Between Atrophy and Hypometabolism in Behavioral-Variant Frontotemporal Dementia

PURPOSE

Individuals with behavioral-variant frontotemporal dementia (bvFTD) show changes in brain structure as assessed by MRI and brain function assessed by 18FDG-PET hypometabolism. However, current understanding of the spatial and temporal interplay between these measures remains limited.

METHODS

Here, we examined longitudinal atrophy and hypometabolism relationships in 15 bvFTD subjects with 2 to 4 follow-up MRI and PET scans (56 visits total). Subject-specific slopes of atrophy and hypometabolism over time were extracted across brain regions and correlated with baseline measures both locally, via Pearson correlations, and nonlocally, via sparse canonical correlation analyses (SCCA).

RESULTS

Notably, we identified a robust link between initial hypometabolism and subsequent cortical atrophy rate changes in bvFTD subjects. Network-level exploration unveiled alignment between baseline hypometabolism and ensuing atrophy rates in the dorsal attention, language, and default mode networks. SCCA identified 2 significant and highly localized components depicting the connection between baseline hypometabolism and atrophy slope over time. The first centered around bilateral orbitofrontal, frontopolar, and medial prefrontal lobes, whereas the second concentrated in the left temporal lobe and precuneus.

CONCLUSIONS

This study highlights 18FDG-PET as a dependable predictor of forthcoming atrophy in spatially adjacent brain regions for individuals with bvFTD.

Cerebral perfusion using ASL in patients with COVID-19 and neurological manifestations: A retrospective multicenter observational study

BACKGROUND AND PURPOSE

Cerebral hypoperfusion has been reported in patients with COVID-19 and neurological manifestations in small cohorts. We aimed to systematically assess changes in cerebral perfusion in a cohort of 59 of these patients, with or without abnormalities on morphological MRI sequences.

METHODS

Patients with biologically-confirmed COVID-19 and neurological manifestations undergoing a brain MRI with technically adequate arterial spin labeling (ASL) perfusion were included in this retrospective multicenter study. ASL maps were jointly reviewed by two readers blinded to clinical data. They assessed abnormal perfusion in four regions of interest in each brain hemisphere: frontal lobe, parietal lobe, posterior temporal lobe, and temporal pole extended to the amygdalo-hippocampal complex.

RESULTS

Fifty-nine patients (44 men (75%), mean age 61.2 years) were included. Most patients had a severe COVID-19, 57 (97%) needed oxygen therapy and 43 (73%) were hospitalized in intensive care unit at the time of MRI. Morphological brain MRI was abnormal in 44 (75%) patients. ASL perfusion was abnormal in 53 (90%) patients, and particularly in all patients with normal morphological MRI. Hypoperfusion occurred in 48 (81%) patients, mostly in temporal poles (52 (44%)) and frontal lobes (40 (34%)). Hyperperfusion occurred in 9 (15%) patients and was closely associated with post-contrast FLAIR leptomeningeal enhancement (100% [66.4%-100%] of hyperperfusion with enhancement versus 28.6% [16.6%-43.2%] without, p = 0.002). Studied clinical parameters (especially sedation) and other morphological MRI anomalies had no significant impact on perfusion anomalies.

CONCLUSION

Brain ASL perfusion showed hypoperfusion in more than 80% of patients with severe COVID-19, with or without visible lesion on conventional MRI abnormalities.

Advances in the treatment and management of frontotemporal dementia

INTRODUCTION

Frontotemporal dementia (FTD) is a complex neurodegenerative disorder, characterized by a wide range of pathological conditions associated with the buildup of proteins such as tau and TDP-43. With a strong hereditary component, FTD often results from genetic variants in three genes - MAPT, GRN, and C9orf72.

AREAS COVERED

In this review, the authors explore abnormal protein accumulation in FTD and forthcoming treatments, providing a detailed analysis of new diagnostic advancements, including innovative markers. They analyze how these discoveries have influenced therapeutic strategies, particularly disease-modifying treatments, which could potentially transform FTD management. This comprehensive exploration of FTD from its molecular underpinnings to its therapeutic prospects offers a compelling overview of the current state of FTD research.

EXPERT OPINION

Notable challenges in FTD management involve identifying reliable biomarkers for early diagnosis and response monitoring. Genetic forms of FTD, particularly those linked to C9orf72 and GRN, show promise, with targeted therapies resulting in substantial progress in disease-modifying strategies. The potential of neuromodulation techniques, like tDCS and rTMS, is being explored, requiring further study. Ongoing trials and multi-disciplinary care highlight the continued push toward effective FTD treatments. With increasing understanding of FTD's molecular and clinical intricacies, the hope for developing effective interventions grows.

Analysis of positron emission tomography hypometabolic patterns and neuropsychiatric symptoms in patients with dementia syndromes

AIMS

To estimate the proportions of specific hypometabolic patterns and their association with neuropsychiatric symptoms (NPS) in patients with cognitive impairment (CI).

METHODS

This multicenter study with 1037 consecutive patients was conducted from December 2012 to December 2019. ¹⁸ F-FDG PET and clinical/demographic information, NPS assessments were recorded and analyzed to explore the associations between hypometabolic patterns and clinical features by correlation analysis and multivariable logistic regression models.

RESULTS

Patients with clinical Alzheimer's disease (AD, 81.6%, 605/741) and dementia with Lewy bodies (67.9%, 19/28) mostly had AD-pattern hypometabolism, and 76/137 (55.5%) of patients with frontotemporal lobar degeneration showed frontal and anterior temporal pattern (FT-P) hypometabolism. Besides corticobasal degeneration, patients with behavioral variant frontotemporal dementia (36/58), semantic dementia (7/10), progressive non-fluent aphasia (6/9), frontotemporal lobar degeneration and amyotrophic lateral sclerosis (3/5), and progressive supranuclear palsy (21/37) also mostly showed FT-P hypometabolism. The proportion of FT-P hypometabolism was associated with the presence of hallucinations (R = 0.171, p = 0.04), anxiety (R = 0.182, p = 0.03), and appetite and eating abnormalities (R = 0.200, p = 0.01) in AD.

CONCLUSION

Specific hypometabolic patterns in FDG-PET are associated with NPS and beneficial for the early identification and management of NPS in patients with CI.

Addition of the FTD Module to the Neuropsychiatric Inventory improves classification of frontotemporal dementia spectrum disorders

Most neuropsychiatric symptoms (NPS) common in frontotemporal dementia (FTD) are currently not part of the Neuropsychiatric Inventory (NPI). We piloted an FTD Module that included eight extra items to be used in conjunction with the NPI. Caregivers of patients with behavioural variant FTD (n = 49), primary progressive aphasia (PPA; n = 52), Alzheimer's dementia (AD; n = 41), psychiatric disorders (n = 18), presymptomatic mutation carriers (n = 58) and controls (n = 58) completed the NPI and FTD Module. We investigated (concurrent and construct) validity, factor structure and internal consistency of the NPI and FTD Module. We performed group comparisons on item prevalence, mean item and total NPI and NPI with FTD Module scores, and multinomial logistic regression to determine its classification abilities. We extracted four components, together explaining 64.1% of the total variance, of which the largest indicated the underlying dimension 'frontal-behavioural symptoms'. Whilst apathy (original NPI) occurred most frequently in AD, logopenic and non-fluent variant PPA, the most common NPS in behavioural variant FTD and semantic variant PPA were loss of sympathy/empathy and poor response to social/emotional cues (part of FTD Module). Patients with primary psychiatric disorders and behavioural variant FTD showed the most severe behavioural problems on both the NPI as well as the NPI with FTD Module. The NPI with FTD Module correctly classified more FTD patients than the NPI alone. By quantifying common NPS in FTD the NPI with FTD Module has large diagnostic potential. Future studies should investigate whether it can also prove a useful addition to the NPI in therapeutic trials.

Differential impairment of cerebrospinal fluid synaptic biomarkers in the genetic forms of frontotemporal dementia

BACKGROUND

Approximately a third of frontotemporal dementia (FTD) is genetic with mutations in three genes accounting for most of the inheritance: C9orf72, GRN, and MAPT. Impaired synaptic health is a common mechanism in all three genetic variants, so developing fluid biomarkers of this process could be useful as a readout of cellular dysfunction within therapeutic trials.

METHODS

A total of 193 cerebrospinal fluid (CSF) samples from the GENetic FTD Initiative including 77 presymptomatic (31 C9orf72, 23 GRN, 23 MAPT) and 55 symptomatic (26 C9orf72, 17 GRN, 12 MAPT) mutation carriers as well as 61 mutation-negative controls were measured using a microflow LC PRM-MS set-up targeting 15 synaptic proteins: AP-2 complex subunit beta, complexin-2, beta-synuclein, gamma-synuclein, 14-3-3 proteins (eta, epsilon, zeta/delta), neurogranin, Rab GDP dissociation inhibitor alpha (Rab GDI alpha), syntaxin-1B, syntaxin-7, phosphatidylethanolamine-binding protein 1 (PEBP-1), neuronal pentraxin receptor (NPTXR), neuronal pentraxin 1 (NPTX1), and neuronal pentraxin 2 (NPTX2). Mutation carrier groups were compared to each other and to controls using a bootstrapped linear regression model, adjusting for age and sex.

RESULTS

CSF levels of eight proteins were increased only in symptomatic MAPT mutation carriers (compared with controls) and not in symptomatic C9orf72 or GRN mutation carriers: beta-synuclein, gamma-synuclein, 14-3-3-eta, neurogranin, Rab GDI alpha, syntaxin-1B, syntaxin-7, and PEBP-1, with three other proteins increased in MAPT mutation carriers compared with the other genetic groups (AP-2 complex subunit beta, complexin-2, and 14-3-3 zeta/delta). In contrast, CSF NPTX1 and NPTX2 levels were affected in all three genetic groups (decreased compared with controls), with NPTXR concentrations being affected in C9orf72 and GRN mutation carriers only (decreased compared with controls). No changes were seen in the CSF levels of these proteins in presymptomatic mutation carriers. Concentrations of the neuronal pentraxins were correlated with brain volumes in the presymptomatic period for the C9orf72 and GRN groups, suggesting that they become abnormal in proximity to symptom onset.

CONCLUSIONS

Differential synaptic impairment is seen in the genetic forms of FTD, with abnormalities in multiple measures in those with MAPT mutations, but only changes in neuronal pentraxins within the GRN and C9orf72 mutation groups. Such markers may be useful in future trials as measures of synaptic dysfunction, but further work is needed to understand how these markers change throughout the course of the disease.

Differential and subtype-specific neuroimaging abnormalities in amnestic and nonamnestic mild cognitive impairment: A systematic review and meta-analysis

While mild cognitive impairment (MCI) has been classified into amnestic MCI (aMCI) and nonamnestic MCI (naMCI), the neuropathological bases of these two subtypes remain elusive. Here, we performed a systematic review and meta-analysis to determine the subtype specificity of neuroimaging abnormalities in MCI and to identify neural features that may differ between aMCI and naMCI. We synthesized 50 studies that used common neuroimaging modalities, including magnetic resonance imaging and positron emission tomography, to compare brain atrophy, white matter abnormalities, cortical thinning, cerebral hypometabolism, amyloid/tau deposition, or other features among aMCI, naMCI, and normal cognition. Compared with normal cognition, aMCI shows diverse neuroimaging abnormalities of large effect sizes. In contrast, naMCI exhibits restricted abnormalities of small effect sizes. Some features, including medial temporal lobe atrophy and white matter abnormalities, are shared by the two MCI subtypes. Overall, brain abnormalities are worse, if not similar, in aMCI than in naMCI. The only neuroimaging abnormality specific to aMCI is increased amyloid burden; no feature specific to naMCI was found. Taken together, our findings have elucidated the neuropathological changes that occur in aMCI and naMCI. Clarifying the neuroimaging profiles of aMCI and naMCI can improve the early identification, differentiation, and intervention of prodromal dementia.

Early-Onset Frontotemporal Dementia-Related Semantic Variant of Primary Progressive Aphasia: Multimodal Evaluation With Brain Perfusion SPECT, SPECT/MRI Coregistration, and MRI Volumetry

ABSTRACT

Frontotemporal dementia (FTD) is a neurodegenerative disorder characterized by cortical and subcortical atrophies, with early involvement of the hippocampus and amygdala. A 58-year-old man with clinical presentation of primary progressive aphasia-particularly its svPPA (semantic variant)-and bilateral asymmetric (left-predominant) anterior temporal lobe atrophy on MRI was referred for brain perfusion SPECT. This revealed bilateral hypoperfusion of the anterior temporal lobe (sustained by software-fused SPECT/MRI), pointing toward FTD rather than Alzheimer disease. Furthermore, voxel-based MRI volumetric analysis confirmed bilateral atrophy affecting the hippocampus and amygdala. Combining SPECT with MRI was supportive of the early-onset FTD-related svPPA diagnosis.

Systems biology approaches to unravel the molecular and genetic architecture of Alzheimer's disease and related tauopathies

Over the years, genetic studies have identified multiple genetic risk variants associated with neurodegenerative disorders and helped reveal new biological pathways and genes of interest. However, genetic risk variants commonly reside in non-coding regions and may regulate distant genes rather than the nearest gene, as well as a gene's interaction partners in biological networks. Systems biology and functional genomics approaches provide the framework to unravel the functional significance of genetic risk variants in disease. In this review, we summarize the genetic and transcriptomic studies of Alzheimer's disease and related tauopathies and focus on the advantages of performing systems-level analyses to interrogate the biological pathways underlying neurodegeneration. Finally, we highlight new avenues of multi-omics analysis with single-cell approaches, which provide unparalleled opportunities to systematically explore cellular heterogeneity, and present an example of how to integrate publicly available single-cell datasets. Systems-level analysis has illuminated the function of many disease risk genes, but much work remains to study tauopathies and to understand spatiotemporal gene expression changes of specific cell types.

Modelling the cascade of biomarker changes in GRN-related frontotemporal dementia

OBJECTIVE

Progranulin-related frontotemporal dementia (FTD-GRN) is a fast progressive disease. Modelling the cascade of multimodal biomarker changes aids in understanding the aetiology of this disease and enables monitoring of individual mutation carriers. In this cross-sectional study, we estimated the temporal cascade of biomarker changes for FTD-GRN, in a data-driven way.

METHODS

We included 56 presymptomatic and 35 symptomatic GRN mutation carriers, and 35 healthy non-carriers. Selected biomarkers were neurofilament light chain (NfL), grey matter volume, white matter microstructure and cognitive domains. We used discriminative event-based modelling to infer the cascade of biomarker changes in FTD-GRN and estimated individual disease severity through cross-validation. We derived the biomarker cascades in non-fluent variant primary progressive aphasia (nfvPPA) and behavioural variant FTD (bvFTD) to understand the differences between these phenotypes.

RESULTS

Language functioning and NfL were the earliest abnormal biomarkers in FTD-GRN. White matter tracts were affected before grey matter volume, and the left hemisphere degenerated before the right. Based on individual disease severities, presymptomatic carriers could be delineated from symptomatic carriers with a sensitivity of 100% and specificity of 96.1%. The estimated disease severity strongly correlated with functional severity in nfvPPA, but not in bvFTD. In addition, the biomarker cascade in bvFTD showed more uncertainty than nfvPPA.

CONCLUSION

Degeneration of axons and language deficits are indicated to be the earliest biomarkers in FTD-GRN, with bvFTD being more heterogeneous in disease progression than nfvPPA. Our data-driven model could help identify presymptomatic GRN mutation carriers at risk of conversion to the clinical stage.

Anomaly detection for the individual analysis of brain PET images

Purpose: In clinical practice, positron emission tomography (PET) images are mostly analyzed visually, but the sensitivity and specificity of this approach greatly depend on the observer's experience. Quantitative analysis of PET images would alleviate this problem by helping define an objective limit between normal and pathological findings. We present an anomaly detection framework for the individual analysis of PET images. Approach: We created subject-specific abnormality maps that summarize the pathology's topographical distribution in the brain by comparing the subject's PET image to a model of healthy PET appearance that is specific to the subject under investigation. This model was generated from demographically and morphologically matched PET scans from a control dataset. Results: We generated abnormality maps for healthy controls, patients at different stages of Alzheimer's disease and with different frontotemporal dementia syndromes. We showed that no anomalies were detected for the healthy controls and that the anomalies detected from the patients with dementia coincided with the regions where abnormal uptake was expected. We also validated the proposed framework using the abnormality maps as inputs of a classifier and obtained higher classification accuracies than when using the PET images themselves as inputs. Conclusions: The proposed method was able to automatically locate and characterize the areas characteristic of dementia from PET images. The abnormality maps are expected to (i) help clinicians in their diagnosis by highlighting, in a data-driven fashion, the pathological areas, and (ii) improve the interpretability of subsequent analyses, such as computer-aided diagnosis or spatiotemporal modeling.

Classification using fractional anisotropy predicts conversion in genetic frontotemporal dementia, a proof of concept

Frontotemporal dementia is a highly heritable and devastating neurodegenerative disease. About 10–20% of all frontotemporal dementia is caused by known pathogenic mutations, but a reliable tool to predict clinical conversion in mutation carriers is lacking. In this retrospective proof-of-concept case-control study, we investigate whether MRI-based and cognition-based classifiers can predict which mutation carriers from genetic frontotemporal dementia families will develop symptoms (‘convert’) within 4 years. From genetic frontotemporal dementia families, we included 42 presymptomatic frontotemporal dementia mutation carriers. We acquired anatomical, diffusion-weighted imaging, and resting-state functional MRI, as well as neuropsychological data. After 4 years, seven mutation carriers had converted to frontotemporal dementia (‘converters’), while 35 had not (‘non-converters’). We trained regularized logistic regression models on baseline MRI and cognitive data to predict conversion to frontotemporal dementia within 4 years, and quantified prediction performance using area under the receiver operating characteristic curves. The prediction model based on fractional anisotropy, with highest contribution of the forceps minor, predicted conversion to frontotemporal dementia beyond chance level (0.81 area under the curve, family-wise error corrected P = 0.025 versus chance level). Other MRI-based and cognitive features did not outperform chance level. Even in a small sample, fractional anisotropy predicted conversion in presymptomatic frontotemporal dementia mutation carriers beyond chance level. After validation in larger data sets, conversion prediction in genetic frontotemporal dementia may facilitate early recruitment into clinical trials.

Rates of Brain Atrophy Across Disease Stages in Familial Frontotemporal Dementia Associated With MAPT, GRN, and C9orf72 Pathogenic Variants

Importance

Several clinical trials are planned for familial forms of frontotemporal lobar degeneration (f-FTLD). Precise modeling of brain atrophy in f-FTLD could improve the power to detect a treatment effect.

Objective

To characterize regions and rates of atrophy in the 3 primary f-FTLD genetic groups (MAPT, GRN, and C9orf72) across all disease stages from asymptomatic to dementia.

Design, Setting, and Participants

This investigation was a case-control study of participants enrolled in the Advancing Research and Treatment for Frontotemporal Lobar Degeneration or Longitudinal Evaluation of Familial Frontotemporal Dementia studies. The study took place at 18 North American academic medical centers between January 2009 and September 2018. Participants with f-FTLD (n = 100) with a known pathogenic variant (MAPT [n = 28], GRN [n = 33], or C9orf72 [n = 39]) were grouped according to disease stage (ie, Clinical Dementia Rating [CDR] plus National Alzheimer's Coordinating Center [NACC] FTLD module). Included were participants with at least 2 structural magnetic resonance images at presymptomatic (CDR + NACC FTLD = 0 [n = 57]), mild or questionable (CDR + NACC FTLD = 0.5 [n = 15]), or symptomatic (CDR + NACC FTLD = ≥1 [n = 28]) disease stages. The control group included family members of known pathogenic variant carriers who did not carry the pathogenic variant (n = 60).

Main Outcomes and Measures

This study fitted bayesian linear mixed-effects models in each voxel of the brain to quantify the rate of atrophy in each of the 3 genes, at each of the 3 disease stages, compared with controls. The study also analyzed rates of clinical decline in each of these groups, as measured by the CDR + NACC FTLD box score.

Results

The sample included 100 participants with f-FTLD with a known pathogenic variant (mean [SD] age, 50.48 [13.78] years; 53 [53%] female) and 60 family members of known pathogenic variant carriers who did not carry the pathogenic variant (mean [SD] age, 47.51 [12.43] years; 36 [60%] female). MAPT and GRN pathogenic variants were associated with increased rates of volume loss compared with controls at all stages of disease. In MAPT pathogenic variant carriers, statistically significant regions of accelerated volume loss compared with controls were identified in temporal regions bilaterally in the presymptomatic stage, with global spread in the symptomatic stage. For example, mean [SD] rates of atrophy in the left temporal were -231 [47] mm3 per year during the presymptomatic stage, -381 [208] mm3 per year during the mild stage, and -1485 [1025] mm3 per year during the symptomatic stage (P < .05). GRN pathogenic variant carriers generally had minimal increases in atrophy rates between the presymptomatic and mild stages, with rapid increases in atrophy rates in the symptomatic stages. For example, in the right frontal lobes, annualized volume loss was -267 [81] mm3 per year in the presymptomatic stage and -182 [90] mm3 per year in the mild stage, but -1169 [555] mm3 per year in the symptomatic stage. Compared with the other groups, C9orf72 expansion carriers showed minimal increases in rate of volume loss with disease progression. For example, the mean (SD) annualized rates of atrophy in the right frontal lobe in C9orf72 expansion carriers was -272 (118) mm3 per year in presymptomatic stages, -310 (189) mm3 per year in mildly symptomatic stages, and -251 (145) mm3 per year in symptomatic stages.

Conclusions and Relevance

These findings are relevant to clinical trial planning and suggest that the mechanism by which C9orf72 pathogenic variants lead to symptoms may be fundamentally different from the mechanisms associated with other pathogenic variants.

Differences in Discriminability and Response Bias on Rey Auditory Verbal Learning Test Delayed Recognition in Behavioral Variant Frontotemporal Dementia and Alzheimer's Disease

OBJECTIVE

Episodic memory is impaired in Alzheimer's disease (AD) dementia but thought to be relatively spared in behavioral variant frontotemporal dementia (bvFTD). This view is challenged by evidence of memory impairment in bvFTD. This study investigated differences in recognition memory performance between bvFTD and AD.

METHOD

We performed a retrospective analysis on the recognition trial of the Rey Auditory Verbal Learning Test in patients with bvFTD (n = 85), AD (n = 55), and control participants (n = 59). Age- and education-adjusted between-group analysis was performed on the total score and indices of discriminative ability and response bias. Correlations between recognition and measures of memory, language, executive functioning, and construction were examined.

RESULTS

Patients with AD had a significantly lower total recognition score than patients with bvFTD (control 28.8 ± 1.5; bvFTD 24.8 ± 4.5; AD 23.4 ± 3.6, p < .01). Both bvFTD and AD had worse discriminative ability than controls (A' control 0.96 ± 0.03; bvFTD 0.87 ± 0.03; AD 0.84 ± 0.10, p < .01), but there was no difference in response bias (B" control 0.9 ± 0.2; bvFTD 1.6 ± 1.47; AD 1.4± 1.4, p < .01). AD had worse discriminability than bvFTD (p < .05). Discriminability was associated with memory for both patient groups (median correlation coefficient r = .34) and additionally associated with language (r = .31), but not executive functioning (r = -.03) in bvFTD. Response bias was unrelated to other cognitive functions (r = -.02).

CONCLUSIONS

Discriminability, but not response bias, differentiated patients with bvFTD from AD. The presence of an impaired discrimination index suggests a "pure" (recognition) memory deficit in bvFTD.

Frontotemporal Dementia: Neuropathology, Genetics, Neuroimaging, and Treatments

Frontotemporal dementia (FTD) encompasses a group of clinical syndromes, including behavioral variant FTD, nonfluent variant primary progressive aphasia, semantic variant primary progressive aphasia, FTD motor neuron disease, progressive supranuclear palsy syndrome, and corticobasal syndrome. Early on in its course, FTD is commonly seen in psychiatric clinics. In this article the authors review the neuroimaging, pathology, genetics, and therapeutic interventions for FTD spectrum disorders.

Baseline MRI associates with later naming status in primary progressive aphasia

Advanced imaging studies in neurodegenerative disease have yielded new insights into subtypes of disease, progression of disease in various brain regions, and changes in structural and functional connectivity between brain regions related to symptom progression. However, few studies have revealed imaging markers at baseline that correlate with rate or degree of decline in function. Here we tested the hypothesis that imaging features at baseline correlate with outcome of naming in primary progressive aphasia. We obtained longitudinal multimodal imaging in 15 individuals with primary progressive aphasia at the same time points as assessment of naming. We found that functional connectivity between particular brain regions (measured with resting state functional connectivity magnetic resonance imaging) is strongly associated with accuracy of naming 21 months later, independently of baseline severity of naming impairment. These data indicate that functional connectivity may carry information about later performance in naming, and is potentially useful for refining prognosis.

New directions in clinical trials for frontotemporal lobar degeneration: Methods and outcome measures

INTRODUCTION

Frontotemporal lobar degeneration (FTLD) is the most common form of dementia for those under 60 years of age. Increasing numbers of therapeutics targeting FTLD syndromes are being developed.

METHODS

In March 2018, the Association for Frontotemporal Degeneration convened the Frontotemporal Degeneration Study Group meeting in Washington, DC, to discuss advances in the clinical science of FTLD.

RESULTS

Challenges exist for conducting clinical trials in FTLD. Two of the greatest challenges are (1) the heterogeneity of FTLD syndromes leading to difficulties in efficiently measuring treatment effects and (2) the rarity of FTLD disorders leading to recruitment challenges.

DISCUSSION

New personalized endpoints that are clinically meaningful to individuals and their families should be developed. Personalized approaches to analyzing MRI data, development of new fluid biomarkers and wearable technologies will help to improve the power to detect treatment effects in FTLD clinical trials and enable new, clinical trial designs, possibly leveraged from the experience of oncology trials. A computational visualization and analysis platform that can support novel analyses of combined clinical, genetic, imaging, biomarker data with other novel modalities will be critical to the success of these endeavors.

Individualized atrophy scores predict dementia onset in familial frontotemporal lobar degeneration

INTRODUCTION

Some models of therapy for neurodegenerative diseases envision starting treatment before symptoms develop. Demonstrating that such treatments are effective requires accurate knowledge of when symptoms would have started without treatment. Familial frontotemporal lobar degeneration offers a unique opportunity to develop predictors of symptom onset.

METHODS

We created dementia risk scores in 268 familial frontotemporal lobar degeneration family members by entering covariate-adjusted standardized estimates of brain atrophy into a logistic regression to classify asymptomatic versus demented participants. The score's predictive value was tested in a separate group who were followed up longitudinally (stable vs. converted to dementia) using Cox proportional regressions with dementia risk score as the predictor.

RESULTS

Cross-validated logistic regression achieved good separation of asymptomatic versus demented (accuracy = 90%, SE = 0.06). Atrophy scores predicted conversion from asymptomatic or mildly/questionably symptomatic to dementia (HR = 1.51, 95% CI: [1.16,1.98]).

DISCUSSION

Individualized quantification of baseline brain atrophy is a promising predictor of progression in asymptomatic familial frontotemporal lobar degeneration mutation carriers.

Inflammatory and Pro-resolving Mediators in Frontotemporal Dementia and Alzheimer's Disease

Chronic inflammation contributes to neuronal death in Alzheimer's disease (AD) and frontotemporal dementia (FTD). Here we evaluated inflammatory and pro-resolving mediators in AD and behavioural variant of FTD (bvFTD) patients compared with controls, since neuroinflamamtion is a common feature in both diseases. Ninety-eight subjects were included in this study, divided into AD (n = 32), bvFTD (n = 30), and control (n = 36) groups. The levels of hsCRP, IL-1β, IL-6, TNF, and TGF-β1, as well as annexin A1 (AnxA1) and lipoxin A4 (LXA4) were measured in blood and cerebrospinal fluid (CSF). The expression profile of AnxA1 was evaluated in peripheral blood mononuclear cells (PBMCs) as well the distribution of ANXA1 rs2611228 polymorphism. We found reduced peripheral levels of hsCRP and TNF in AD compared with bvFTD patients and controls, and increased levels of TGF-β1 in AD compared to controls. Moreover, reduced plasma levels of AnxA1 were observed in bvFTD compared to AD and controls. There was a significant cleavage of AnxA1 in PBMCs in both dementia groups. The results suggest differential regulation of inflammatory and pro-resolving mediators in bvFTD and AD, while AnxA1 cleavage may impair pro-resolving mechanisms in both groups.

Variant-specific vulnerability in metabolic connectivity and resting-state networks in behavioural variant of frontotemporal dementia

Brain connectivity measures represent candidate biomarkers of neuronal dysfunction in neurodegenerative diseases. Previous findings suggest that the behavioural variant of frontotemporal dementia (bvFTD) and its variants (i.e., frontal and temporo-limbic) may be related to the vulnerability of distinct functional connectivity networks. In this study, 82 bvFTD patients were included, and two patient groups were identified as frontal and temporo-limbic bvFTD variants. Two advanced multivariate analytical approaches were applied to FDG-PET data, i.e., sparse inverse covariance estimation (SICE) method and seed-based interregional correlation analysis (IRCA). These advanced methods allowed the assessment of (i) the whole-brain metabolic connectivity, without any a priori assumption, and (ii) the main brain resting-state networks of crucial relevance for cognitive and behavioural functions. In the whole bvFTD group, we found dysfunctional connectivity patterns in frontal and limbic regions and in all major brain resting-state networks as compared to healthy controls (HC N = 82). In the two bvFTD variants, SICE and IRCA analyses identified variant-specific reconfigurations of whole-brain connectivity and resting-state networks. Specifically, the frontal bvFTD variant was characterised by metabolic connectivity alterations in orbitofrontal regions and anterior resting-state networks, while the temporo-limbic bvFTD variant was characterised by connectivity alterations in the limbic and salience networks. These results highlight different neural vulnerabilities in the two bvFTD variants, as shown by the dysfunctional connectivity patterns, with relevance for the different neuropsychological profiles. This new evidence provides further insight in the variability of bvFTD and may contribute to a more accurate classification of these patients.

Issues pertaining to expert evidence and the reasoning about punishment in a neuroscience-based sentencing appeal

In this paper, we focus on, a significant Australian sentencing appeal in which, after hearing expert evidence pertaining to cognitive function, brain scans, and neuropsychological testing, the Court imposed a less severe sentence than that originally imposed. Our aim is to produce an interdisciplinary critical analysis of the decision, and we approach this by analysing the judicial comments on the evidence pertaining to the offender's mental condition, and the reasoning about punishment. We conclude that the Court's inferences about frontal lobe damage and likely dementia are contestable, and the reasoning about mitigation of punishment based on these questionable inferences could have been improved by a focus on sentencing's retributive aim.

Segmentation of medial temporal subregions reveals early right-sided involvement in semantic variant PPA

Background

Semantic variant of primary progressive aphasia (svPPA) is a subtype of frontotemporal dementia characterized by asymmetric temporal atrophy.

Methods

We investigated the pattern of medial temporal lobe atrophy in 24 svPPA patients compared to 72 controls using novel approaches to segment the hippocampal and amygdalar subregions on MRIs. Based on semantic knowledge scores, we split the svPPA group into 3 subgroups of early, middle and late disease stage.

Results

Early stage: all left amygdalar and hippocampal subregions (except the tail) were affected in svPPA (21–35% smaller than controls), together with the following amygdalar nuclei in the right hemisphere: lateral, accessory basal and superficial (15–23%). On the right, only the temporal pole was affected among the cortical regions. Middle stage: the left hippocampal tail became affected (28%), together with the other amygdalar nuclei (22–26%), and CA4 (15%) on the right, with orbitofrontal cortex and subcortical structures involvement on the left, and more posterior temporal lobe on the right. Late stage: the remaining right hippocampal regions (except the tail) (19–24%) became affected, with more posterior left cortical and right extra-temporal anterior cortical involvement.

Conclusions

With advanced subregions segmentation, it is possible to detect early involvement of the right medial temporal lobe in svPPA that is not detectable by measuring the amygdala or hippocampus as a whole.

Electronic supplementary material

The online version of this article (10.1186/s13195-019-0489-9) contains supplementary material, which is available to authorized users.

In vivo hippocampal subfield shape related to TDP-43, amyloid beta, and tau pathologies

Despite advances in the development of biomarkers for Alzheimer's disease (AD), accurate ante-mortem diagnosis remains challenging because a variety of neuropathologic disease states can coexist and contribute to the AD dementia syndrome. Here, we report a neuroimaging study correlating hippocampal deformity with regional AD and transactive response DNA-binding protein of 43 kDA pathology burden. We used hippocampal shape analysis of ante-mortem T1-weighted structural magnetic resonance imaging images of 42 participants from two longitudinal cohort studies conducted by the Rush Alzheimer's Disease Center. Surfaces were generated for the whole hippocampus and zones approximating the underlying subfields using a previously developed automated image-segmentation pipeline. Multiple linear regression models were constructed to correlate the shape with pathology measures while accounting for covariates, with relationships mapped out onto hippocampal surface locations. A significant relationship existed between higher paired helical filaments-tau burden and inward hippocampal shape deformity in zones approximating CA1 and subiculum which persisted after accounting for coexisting pathologies. No significant patterns of inward surface deformity were associated with amyloid-beta or transactive response DNA-binding protein of 43 kDA after including covariates. Our findings indicate that hippocampal shape deformity measures in surface zones approximating CA1 may represent a biomarker for postmortem AD pathology.

Tau PET imaging in neurodegenerative tauopathies-still a challenge

The accumulation of pathological misfolded tau is a feature common to a collective of neurodegenerative disorders known as tauopathies, of which Alzheimer's disease (AD) is the most common. Related tauopathies include progressive supranuclear palsy (PSP), corticobasal syndrome (CBS), Down's syndrome (DS), Parkinson's disease (PD), and dementia with Lewy bodies (DLB). Investigation of the role of tau pathology in the onset and progression of these disorders is now possible due the recent advent of tau-specific ligands for use with positron emission tomography (PET), including first- (e.g., [¹⁸F]THK5317, [¹⁸F]THK5351, [¹⁸F]AV1451, and [¹¹C]PBB3) and second-generation compounds [namely [¹⁸F]MK-6240, [¹⁸F]RO-948 (previously referred to as [¹⁸F]RO69558948), [¹⁸F]PI-2620, [¹⁸F]GTP1, [¹⁸F]PM-PBB3, and [¹⁸F]JNJ64349311 ([¹⁸F]JNJ311) and its derivative [¹⁸F]JNJ-067)]. In this review we describe and discuss findings from in vitro and in vivo studies using both initial and new tau ligands, including their relation to biomarkers for amyloid-β and neurodegeneration, and cognitive findings. Lastly, methodological considerations for the quantification of in vivo ligand binding are addressed, along with potential future applications of tau PET, including therapeutic trials.

Longitudinal multimodal MRI as prognostic and diagnostic biomarker in presymptomatic familial frontotemporal dementia

Developing and validating sensitive biomarkers for the presymptomatic stage of familial frontotemporal dementia is an important step in early diagnosis and for the design of future therapeutic trials. In the longitudinal Frontotemporal Dementia Risk Cohort, presymptomatic mutation carriers and non-carriers from families with familial frontotemporal dementia due to microtubule-associated protein tau (MAPT) and progranulin (GRN) mutations underwent a clinical assessment and multimodal MRI at baseline, 2-, and 4-year follow-up. Of the cohort of 73 participants, eight mutation carriers (three GRN, five MAPT) developed clinical features of frontotemporal dementia ('converters'). Longitudinal whole-brain measures of white matter integrity (fractional anisotropy) and grey matter volume in these converters (n = 8) were compared with healthy mutation carriers ('non-converters'; n = 35) and non-carriers (n = 30) from the same families. We also assessed the prognostic performance of decline within white matter and grey matter regions of interest by means of receiver operating characteristic analyses followed by stepwise logistic regression. Longitudinal whole-brain analyses demonstrated lower fractional anisotropy values in extensive white matter regions (genu corpus callosum, forceps minor, uncinate fasciculus, and superior longitudinal fasciculus) and smaller grey matter volumes (prefrontal, temporal, cingulate, and insular cortex) over time in converters, present from 2 years before symptom onset. White matter integrity loss of the right uncinate fasciculus and genu corpus callosum provided significant classifiers between converters, non-converters, and non-carriers. Converters' within-individual disease trajectories showed a relatively gradual onset of clinical features in MAPT, whereas GRN mutations had more rapid changes around symptom onset. MAPT converters showed more decline in the uncinate fasciculus than GRN converters, and more decline in the genu corpus callosum in GRN than MAPT converters. Our study confirms the presence of spreading predominant frontotemporal pathology towards symptom onset and highlights the value of multimodal MRI as a prognostic biomarker in familial frontotemporal dementia.

Frontotemporal dementia

Frontotemporal dementia (FTD) is the second commonest cause of young onset dementia. Our understanding of FTD and its related syndromes has advanced significantly in recent years. Among the most prominent areas of progress is the overlap between FTD, MND, and other neurodegenerative conditions at a clinicopathologic and genetic level. In parallel major advances in neuroimaging techniques, the discovery of new genetic mutations as well as the development of potential biomarkers may serve to further expand knowledge of the biologic processes at play in FTD and may in turn propel research toward identifying curative and preventative pharmacologic therapies. The aim of this chapter is to discuss the clinical, pathologic, and genetic complexities of FTD and related disorders.

Uncovering the heterogeneity and temporal complexity of neurodegenerative diseases with Subtype and Stage Inference

The heterogeneity of neurodegenerative diseases is a key confound to disease understanding and treatment development, as study cohorts typically include multiple phenotypes on distinct disease trajectories. Here we introduce a machine-learning technique—Subtype and Stage Inference (SuStaIn)—able to uncover data-driven disease phenotypes with distinct temporal progression patterns, from widely available cross-sectional patient studies. Results from imaging studies in two neurodegenerative diseases reveal subgroups and their distinct trajectories of regional neurodegeneration. In genetic frontotemporal dementia, SuStaIn identifies genotypes from imaging alone, validating its ability to identify subtypes; further the technique reveals within-genotype heterogeneity. In Alzheimer’s disease, SuStaIn uncovers three subtypes, uniquely characterising their temporal complexity. SuStaIn provides fine-grained patient stratification, which substantially enhances the ability to predict conversion between diagnostic categories over standard models that ignore subtype (p = 7.18 × 10⁻⁴) or temporal stage (p = 3.96 × 10⁻⁵). SuStaIn offers new promise for enabling disease subtype discovery and precision medicine.

Progressive diseases tend to be heterogeneous in their underlying aetiology mechanism, disease manifestation, and disease time course. Here, Young and colleagues devise a computational method to account for both phenotypic heterogeneity and temporal heterogeneity, and demonstrate it using two neurodegenerative disease cohorts.

Meta-analytic Review of Memory Impairment in Behavioral Variant Frontotemporal Dementia

OBJECTIVES

A meta-analysis of the extent, nature and pattern of memory performance in behavioral variant frontotemporal dementia (bvFTD). Multiple observational studies have challenged the relative sparing of memory in bvFTD as stated in the current diagnostic criteria.

METHODS

We performed a meta-analytic review covering the period 1967 to February 2017 of case-control studies on episodic memory in bvFTD versus control participants (16 studies, 383 patients, 603 control participants), and patients with bvFTD versus those with Alzheimer's disease (AD) (20 studies, 452 bvFTD, 874 AD). Differences between both verbal and non-verbal working memory, episodic memory learning and recall, and recognition memory were examined. Data were extracted from the papers and combined into a common metric measure of effect, Hedges' d.

RESULTS

Patients with bvFTD show large deficits in memory performance compared to controls (Hedges' d -1.10; 95% confidence interval [CI] [-1.23, -0.95]), but perform significantly better than patients with AD (Hedges' d 0.85; 95% CI [0.69, 1.03]). Learning and recall tests differentiate best between patients with bvFTD and AD (p<.01). There is 37-62% overlap in test scores between the two groups.

CONCLUSIONS

This study points to memory disorders in patients with bvFTD, with performance at an intermediate level between controls and patients with AD. This indicates that, instead of being an exclusion criterion for bvFTD diagnosis, memory deficits should be regarded as a potential integral part of the clinical spectrum. (JINS, 2018, 24, 593-605).

Qualitative Assessment of Verbal Fluency Performance in Frontotemporal Dementia

BACKGROUND/AIMS

Verbal fluency is impaired in patients with frontotemporal dementia (FTD) and primary progressive aphasia (PPA). This study explored qualitative differences in verbal fluency (clustering of words, switching between strategies) between FTD and PPA variants.

METHODS

Twenty-nine patients with behavioral variant FTD (bvFTD) and 50 with PPA (13 nonfluent/agrammatic, 14 semantic, and 23 logopenic) performed a semantic and letter fluency task. Clustering (number of multiword strings) and switching (number of transitions between clustered and nonclustered words) were recorded by two independent raters. Between-group differences, associations with memory, language, and executive functioning, and longitudinal change (subsample) in clustering and switching were examined.

RESULTS

Interrater reliability was high (median 0.98). PPA patients generated (a) smaller (number of) clusters on semantic and letter fluency than bvFTD patients (p < 0.05). Semantic variant patients used more switches than nonfluent/agrammatic or logopenic variant patients (p < 0.05). Clustering in semantic fluency was significantly associated with memory and language (range standardized regression coefficients 0.24-0.38). Switching in letter fluency was associated with executive functioning (0.32-0.35).

CONCLUSION

Clustering and switching in verbal fluency differed between patients with subtypes of FTD and PPA. Qualitative aspects of verbal fluency provide additional information on verbal ability and executive control which can be used for clinically diagnostic purposes.

Functional Connectivity Changes in Behavioral, Semantic, and Nonfluent Variants of Frontotemporal Dementia

Frontotemporal dementia (FTD) affects behavior, language, and personality. This study aims to explore functional connectivity changes in three FTD variants: behavioral (bvFTD), semantic (svPPA), and nonfluent variant (nfvPPA). Seventy-six patients diagnosed with FTD by international criteria and thirty-two controls were investigated. Functional connectivity from resting functional magnetic resonance imaging (fMRI) was estimated for the whole brain. Two types of analysis were done: network basic statistic and topological measures by graph theory. Several hubs in the limbic system and basal ganglia were compromised in the behavioral variant apart from frontal networks. Nonfluent variants showed a major disconnection with respect to the behavioral variant in operculum and parietal inferior. The global efficiency had lower coefficients in nonfluent variants than behavioral variants and controls. Our results support an extensive disconnection among frontal, limbic, basal ganglia, and parietal hubs.

Longitudinal diffusion imaging across the C9orf72 clinical spectrum

INTRODUCTION

Discrepancies between diffusion tensor imaging (DTI) findings and functional rating scales in amyotrophic lateral sclerosis (ALS) may be due to symptom heterogeneity, particularly coexisting cognitive-behavioural dysfunction affecting non-motor regions of the brain. Carriers of expansion mutations in the C9orf72 gene, whose motor and cognitive-behavioural symptoms span a range from ALS to frontotemporal dementia, present an opportunity to evaluate the relationship between symptom heterogeneity and DTI changes.

METHODS

Twenty-eight C9orf72 mutation carriers with varied cognitive and motor symptoms underwent clinical evaluation and DTI imaging. Twenty returned for two or more follow-up evaluations. Each evaluation included motor, executive and behavioural scales and disease staging using the King's college staging system.

RESULTS

Widespread reduction of white matter integrity occurred in C9orf72 mutation carriers compared with 28 controls. The ALS Functional Rating Scale (ALSFRS-R) and King's stage correlated with DTI measures of the corticospinal tract and mid-callosum. Cognitive and behavioural scores correlated with diffusion measures of frontal white matter. King's stage, but not ALSFRS-R, correlated with anterior callosum DTI measures. Over a 6-month follow-up, DTI changes spread from anterior to posterior, and from deep to superficial subcortical white matter. In C9orf72 carriers with ALS or ALS-FTD, changes in corticospinal tractography measures correlated with changes in ALSFRS-R.

CONCLUSION

Discrepancies between DTI findings and clinical measures of disease severity in ALS may partly be accounted for by cognitive-behavioural deficits affecting extramotor white matter tracts. Both ALSFRS-R and King's stage correlated with corticospinal DTI measures. Group-level DTI changes could be detected over 6 months.

Brain MRI Pattern Recognition Translated to Clinical Scenarios

We explored the performance of structure-based computational analysis in four neurodegenerative conditions [Ataxia (AT, n = 16), Huntington's Disease (HD, n = 52), Alzheimer's Disease (AD, n = 66), and Primary Progressive Aphasia (PPA, n = 50)], all characterized by brain atrophy. The independent variables were the volumes of 283 anatomical areas, derived from automated segmentation of T1-high resolution brain MRIs. The segmentation based volumetric quantification reduces image dimensionality from the voxel level [on the order of O(10⁶)] to anatomical structures [O(10²)] for subsequent statistical analysis. We evaluated the effectiveness of this approach on extracting anatomical features, already described by human experience and a priori biological knowledge, in specific scenarios: (1) when pathologies were relatively homogeneous, with evident image alterations (e.g., AT); (2) when the time course was highly correlated with the anatomical changes (e.g., HD), an analogy for prediction; (3) when the pathology embraced heterogeneous phenotypes (e.g., AD) so the classification was less efficient but, in compensation, anatomical and clinical information were less redundant; and (4) when the entity was composed of multiple subgroups that had some degree of anatomical representation (e.g., PPA), showing the potential of this method for the clustering of more homogeneous phenotypes that can be of clinical importance. Using the structure-based quantification and simple linear classifiers (partial least square), we achieve 87.5 and 73% of accuracy on differentiating AT and pre-symptomatic HD patents from controls, respectively. More importantly, the anatomical features automatically revealed by the classifiers agreed with the patterns previously described on these pathologies. The accuracy was lower (68%) on differentiating AD from controls, as AD does not display a clear anatomical phenotype. On the other hand, the method identified PPA clinical phenotypes and their respective anatomical signatures. Although most of the data are presented here as proof of concept in simulated clinical scenarios, structure-based analysis was potentially effective in characterizing phenotypes, retrieving relevant anatomical features, predicting prognosis, and aiding diagnosis, with the advantage of being easily translatable to clinics and understandable biologically.

Mistakes, Too Few to Mention? Impaired Self-conscious Emotional Processing of Errors in the Behavioral Variant of Frontotemporal Dementia

Anosognosia, or lack of awareness of one's deficits, is a core feature of the behavioral variant of frontotemporal dementia (bvFTD). We hypothesized that this deficit has its origins in failed emotional processing of errors. We studied autonomic and facial emotional reactivity to errors in patients with bvFTD (n = 17), Alzheimer's disease (AD, n = 20), and healthy controls (HC, n = 35) during performance of a timed two-alternative-choice button press task. Performance-related behavioral responses to errors were quantified using rates of error correction and post-error slowing of reaction times. Facial emotional responses were measured by monitoring facial reactivity via video and subsequently coding the type, duration and intensity of all emotional reactions. Skin conductance response (SCR) was measured via noninvasive sensors. SCR and total score for each facial emotion expression were quantified for each trial. Facial emotions were grouped into self-conscious (amusement, embarrassment) and negative (fear, sadness, anger, disgust, contempt) emotions. HCs corrected 99.4% of their errors. BvFTD patients corrected 94% (not statistically different compared with HC) and AD corrected 74.8% of their errors (p < 0.05 compared with HC and bvFTD). All groups showed similar post-error slowing. Errors in HCs were associated with greater facial reactivity and SCRs compared with non-error trials, including both negative and self-conscious emotions. BvFTD patients failed to produce self-conscious emotions or an increase in SCR for errors, although they did produce negative emotional responses to a similar degree as HCs. AD showed no deficit in facial reactivity to errors. Although, SCR was generally reduced in AD during error trials, they showed a preserved increase in SCR for errors relative to correct trials. These results demonstrate a specific deficit in emotional responses to errors in bvFTD, encompassing both physiological response and a specific deficit in self-conscious emotions, despite intact awareness and correction of errors. The findings provide a potential mechanism for anosognosia and possibly other behavioral abnormalities in bvFTD and highlight the importance of studying multiple channels of reactivity to errors, including performance related responses and emotional responses, in order to understand how impaired error processing could influence behavior.

Neuroimaging in Dementia

Although the diagnosis of dementia still is primarily based on clinical criteria, neuroimaging is playing an increasingly important role. This is in large part due to advances in techniques that can assist with discriminating between different syndromes. Magnetic resonance imaging remains at the core of differential diagnosis, with specific patterns of cortical and subcortical changes having diagnostic significance. Recent developments in molecular PET imaging techniques have opened the door for not only antemortem but early, even preclinical, diagnosis of underlying pathology. This is vital, as treatment trials are underway for pharmacological agents with specific molecular targets, and numerous failed trials suggest that earlier treatment is needed. This article provides an overview of classic neuroimaging findings as well as new and cutting-edge research techniques that assist with clinical diagnosis of a range of dementia syndromes, with an emphasis on studies using pathologically proven cases.

In vivo tau PET imaging in dementia: Pathophysiology, radiotracer quantification, and a systematic review of clinical findings

In addition to the deposition of β-amyloid plaques, neurofibrillary tangles composed of aggregated hyperphosphorylated tau are one of the pathological hallmarks of Alzheimer's disease and other neurodegenerative disorders. Until now, our understanding about the natural history and topography of tau deposition has only been based on post-mortem and cerebrospinal fluid studies, and evidence continues to implicate tau as a central driver of downstream neurodegenerative processes and cognitive decline. Recently, it has become possible to assess the regional distribution and severity of tau burden in vivo with the development of novel radiotracers for positron emission tomography (PET) imaging. In this article, we provide a comprehensive discussion of tau pathophysiology, its quantification with novel PET radiotracers, as well as a systematic review of tau PET imaging in normal aging and various dementia conditions: mild cognitive impairment, Alzheimer's disease, frontotemporal dementia, progressive supranuclear palsy, and Lewy body dementia. We discuss the main findings in relation to group differences, clinical-cognitive correlations of tau PET, and multi-modal relationships among tau PET and other pathological markers. Collectively, the small but growing literature of tau PET has yielded consistent anatomical patterns of tau accumulation that recapitulate post-mortem distribution of neurofibrillary tangles which correlate with cognitive functions and other markers of pathology. In general, AD is characterised by increased tracer retention in the inferior temporal lobe, extending into the frontal and parietal regions in more severe cases. It is also noted that the spatial topography of tau accumulation is markedly distinct to that of amyloid burden in aging and AD. Tau PET imaging has also revealed characteristic spatial patterns among various non-AD tauopathies, supporting its potential role for differential diagnosis. Finally, we propose novel directions for future tau research, including (a) longitudinal imaging in preclinical dementia, (b) multi-modal mapping of tau pathology onto other pathological processes such as neuroinflammation, and (c) the need for more validation studies against post-mortem samples of the same subjects.

Imaging and fluid biomarkers in frontotemporal dementia

Frontotemporal dementia (FTD), the second most common type of presenile dementia, is a heterogeneous neurodegenerative disease characterized by progressive behavioural and/or language problems, and includes a range of clinical, genetic and pathological subtypes. The diagnostic process is hampered by this heterogeneity, and correct diagnosis is becoming increasingly important to enable future clinical trials of disease-modifying treatments. Reliable biomarkers will enable us to better discriminate between FTD and other forms of dementia and to predict disease progression in the clinical setting. Given that different underlying pathologies probably require specific pharmacological interventions, robust biomarkers are essential for the selection of patients with specific FTD subtypes. This Review emphasizes the increasing availability and potential applications of structural and functional imaging biomarkers, and cerebrospinal fluid and blood fluid biomarkers in sporadic and genetic FTD. The relevance of new MRI modalities - such as voxel-based morphometry, diffusion tensor imaging and arterial spin labelling - in the early stages of FTD is discussed, together with the ability of these modalities to classify FTD subtypes. We highlight promising new fluid biomarkers for staging and monitoring of FTD, and underline the importance of large, multicentre studies of individuals with presymptomatic FTD. Harmonization in the collection and analysis of data across different centres is crucial for the implementation of new biomarkers in clinical practice, and will become a great challenge in the next few years.

Advances in neuroimaging in frontotemporal dementia

Frontotemporal dementia (FTD) is a clinically and neuroanatomically heterogeneous neurodegenerative disorder with multiple underlying genetic and pathological causes. Whilst initial neuroimaging studies highlighted the presence of frontal and temporal lobe atrophy or hypometabolism as the unifying feature in patients with FTD, more detailed studies have revealed diverse patterns across individuals, with variable frontal or temporal predominance, differing degrees of asymmetry, and the involvement of other cortical areas including the insula and cingulate, as well as subcortical structures such as the basal ganglia and thalamus. Recent advances in novel imaging modalities including diffusion tensor imaging, resting-state functional magnetic resonance imaging and molecular positron emission tomography imaging allow the possibility of investigating alterations in structural and functional connectivity and the visualisation of pathological protein deposition. This review will cover the major imaging modalities currently used in research and clinical practice, focusing on the key insights they have provided into FTD, including the onset and evolution of pathological changes and also importantly their utility as biomarkers for disease detection and staging, differential diagnosis and measurement of disease progression. Validating neuroimaging biomarkers that are able to accomplish these tasks will be crucial for the ultimate goal of powering upcoming clinical trials by correctly stratifying patient enrolment and providing sensitive markers for evaluating the effects and efficacy of disease-modifying therapies. This review describes the key insights provided by research into the major neuroimaging modalities currently used in research and clinical practice, including what they tell us about the onset and evolution of FTD and how they may be used as biomarkers for disease detection and staging, differential diagnosis and measurement of disease progression. This article is part of the Frontotemporal Dementia special issue.

Frontotemporal Dementia

Frontotemporal dementia (FTD) is a heterogeneous disorder with distinct clinical phenotypes associated with multiple neuropathologic entities. Presently, the term FTD encompasses clinical disorders that include changes in behavior, language, executive control, and often motor symptoms. The core FTD spectrum disorders include behavioral variant FTD, nonfluent/agrammatic variant primary progressive aphasia, and semantic variant PPA. Related FTD disorders include frontotemporal dementia with motor neuron disease, progressive supranuclear palsy syndrome, and corticobasal syndrome. In this article, the authors discuss the clinical presentation, diagnostic criteria, neuropathology, genetics, and treatments of these disorders.

Weighted Protein Interaction Network Analysis of Frontotemporal Dementia

The genetic analysis of complex disorders has undoubtedly led to the identification of a wealth of associations between genes and specific traits. However, moving from genetics to biochemistry one gene at a time has, to date, rather proved inefficient and under-powered to comprehensively explain the molecular basis of phenotypes. Here we present a novel approach, weighted protein–protein interaction network analysis (W-PPI-NA), to highlight key functional players within relevant biological processes associated with a given trait. This is exemplified in the current study by applying W-PPI-NA to frontotemporal dementia (FTD): We first built the state of the art FTD protein network (FTD-PN) and then analyzed both its topological and functional features. The FTD-PN resulted from the sum of the individual interactomes built around FTD-spectrum genes, leading to a total of 4198 nodes. Twenty nine of 4198 nodes, called inter-interactome hubs (IIHs), represented those interactors able to bridge over 60% of the individual interactomes. Functional annotation analysis not only reiterated and reinforced previous findings from single genes and gene-coexpression analyses but also indicated a number of novel potential disease related mechanisms, including DNA damage response, gene expression regulation, and cell waste disposal and potential biomarkers or therapeutic targets including EP300. These processes and targets likely represent the functional core impacted in FTD, reflecting the underlying genetic architecture contributing to disease. The approach presented in this study can be applied to other complex traits for which risk-causative genes are known as it provides a promising tool for setting the foundations for collating genomics and wet laboratory data in a bidirectional manner. This is and will be critical to accelerate molecular target prioritization and drug discovery.

Frontotemporal Dementias

PURPOSE OF REVIEW

This article reviews the common behavioral and cognitive features of frontotemporal dementia (FTD) and related disorders as well as the distinguishing clinical, genetic, and pathologic features of the most common subtypes.

RECENT FINDINGS

Advances in clinical phenotyping, genetics, and biomarkers have enabled improved predictions of the specific underlying molecular pathology associated with different presentations of FTD. Evaluation of large international cohorts has led to recent refinements in diagnostic criteria for several of the FTD subtypes.

SUMMARY

The FTDs are a group of neurodegenerative disorders featuring progressive deterioration of behavior or language and associated pathology in the frontal or temporal lobes. Based on anatomic, genetic, and neuropathologic categorizations, the six clinical subtypes of FTD or related disorders are: (1) behavioral variant of FTD, (2) semantic variant primary progressive aphasia, (3) nonfluent agrammatic variant primary progressive aphasia, (4) corticobasal syndrome, (5) progressive supranuclear palsy, and (6) FTD associated with motor neuron disease. Recognition and accurate diagnoses of FTD subtypes will aid the neurologist in the management of patients with FTD.

Longitudinal imaging in C9orf72 mutation carriers: Relationship to phenotype

Expansion mutations in the C9orf72 gene may cause amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), or mixtures of the two clinical phenotypes. Different imaging findings have been described for C9orf72-associated diseases in comparison with sporadic patients with the same phenotypes, but it is uncertain whether different phenotypes have a common genotype-associated imaging signature. To address this question, 27 unrelated C9orf72 expansion mutation carriers (C9 +) with varied phenotypes, 28 age-matched healthy controls and 22 patients with sporadic ALS (sALS) underwent 3T MRI scanning and clinical phenotyping. Measures of brain volumes and cortical thickness were extracted from T1 images. Compared to healthy controls and sALS patients, symptomatic C9 + subjects had greater ventricular volume loss and thalamic atrophy for age, with diffuse, patchy cortical thinning. Asymptomatic carriers did not differ from controls. C9 + ALS and ALS-FTD patients had less thinning of the motor cortex than sALS patients, but more thinning in extramotor regions, particularly in frontal and temporal lobes. C9 + ALS patients differed from sporadic ALS patients in the thickness of the superior frontal gyrus and lateral orbitofrontal cortex. Thickness of the precentral gyrus was weakly correlated with the revised ALS functional rating scale. Thickness of many cortical regions, including several frontal and temporal regions, was moderately correlated with letter fluency scores. Letter fluency scores were weakly correlated with ventricular and thalamic volume. To better understand how imaging findings are related to disease progression, nineteen C9 + subjects and 23 healthy controls were scanned approximately 6 months later. Ventricular volume increased in C9 + patients with FTD and ALS-FTD phenotypes and remained stable in asymptomatic C9 + subjects. We conclude that diffuse atrophy is a common underlying feature of disease associated with C9orf72 mutations across its clinical phenotypes. Ventricular enlargement can be measured over a 6-month time frame, and appears to be faster in patients with cognitive impairment.

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Patchy cortical thinning and diffuse atrophy are a hallmark of symptomatic ALS and FTD C9orf72 mutation carriers.

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Symptomatic C9orf72 carriers have more atrophy and diffuse thinning than sporadic ALS patients and healthy controls.

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Ventricular enlargement can be detected over a 6-month interval in symptomatic C9orf72 carriers.

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Impaired letter fluency is associated with diffuse cortical thinning.

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Changes in letter fluency, but not ALSFRS-R are correlated with 6-month ventricular enlargement.

Past, present, and prospects: Reflections 40 years on from the selective impairment of semantic memory (Warrington, 1975)

We summarize the main findings and conclusions of Warrington's (1975) paper, The Selective Impairment of Semantic memory, a neuropsychological paper that described three cases with degenerative neurological conditions [Warrington, E. K. (1975). The selective impairment of semantic memory. The Quarterly Journal of Experimental Psychology, 27, 635–657]. We consider the developments that have followed from its publication and give a selective overview of the field in 2014. The initial impact of the paper was on neuropsychological investigations of semantic loss followed some 14 years later by the identification of Semantic Dementia (the condition shown by the original cases) as a distinctive form of degenerative disease with unique clinical and pathological characteristics. We discuss the distinction between disorders of semantic storage and refractory semantic access, the evidence for category- and modality-specific impairments of semantics, and the light that has been shed on the structure and organization of semantic memory. Finally we consider the relationship between semantic memory and the skills of reading and writing, phonological processing, and autobiographical memory.

Frontotemporal Dementia: An Updated Clinician's Guide

Today, frontotemporal dementia (FTD) remains one of the most common forms of early-onset dementia, that is, before the age of 65, thus posing several diagnostic challenges to clinicians since symptoms are often mistaken for psychiatric or neurological diseases causing a delay in correct diagnosis, and the majority of patients with FTD present with symptoms at ages between 50 and 60. Genetic components are established risk factors for FTD, but the influence of lifestyle, comorbidity, and environmental factors on the risk of FTD is still unclear. Approximately 40% of individuals with FTD have a family history of dementia but less than 10% have a clear autosomal dominant pattern of inheritance. Lack of insight is often an early clue to FTD. A tailored treatment option at an early phase can mitigate suffering and improve patients' and caregivers' quality of life.