Semantic dementia: demography, familial factors and survival in a consecutive series of 100 cases

Incidence of Primary Progressive Apraxia of Speech and Primary Progressive Aphasia in Olmsted County, MN, 2011-2022

BACKGROUND AND OBJECTIVE

No epidemiologic studies have formally assessed the incidence of primary progressive aphasia (PPA) and primary progressive apraxia of speech (PPAOS). Thus, we decided to assess the incidence of these disorders in Olmsted County, MN, between 2011 and 2022, and to characterize clinical, radiographic, and pathologic characteristics of these patients.

METHODS

This was a retrospective examination of data from a population-based cohort of patients with PPA and PPAOS prospectively identified in Olmsted County, MN, from 2011 to 2022. The incidence of PPA among adults (older than 18 years) was calculated for Olmsted County as the number of patients per 100,000 person-years during the study period. The adult population of Olmsted County was determined by the annual catchment population reported by the Rochester Epidemiological Project for each year 2011-2022. A behavioral neurologist verified the clinical diagnoses and determined subtypes.

RESULTS

We identified 10 patients (60% female) within the study period (median age of symptoms onset: 70 years; range: 66-73), 8 with PPA and 2 with PPAOS. Of the 8 patients with PPA (6 female patients, 2 male patients), 2 met criteria for non-fluent variant PPA (nfvPPA), 3 for logopenic variant PPA (lvPPA), and 3 for semantic variant (svPPA). Speech evaluation confirmed the clinical diagnoses in all patients and all showed typical imaging findings consistent with their respective subtype. Six patients (2 PPAOS, 2 nfvPPA, 2 lvPPA) died and 3 underwent autopsy (2 PPAOS, 1 nfvPPA), confirming the pathologic diagnosis of progressive supranuclear palsy. The incidence of PPA + PPAOS was 0.70 persons per 100,000 person-years (95% CI 0.34-1.29 persons per 100,000) during the study period. The incidence of PPAOS was 0.14 persons per 100,000 person-years (95% CI 0.02-0.55 persons per 100,000), whereas for the 8 patients with PPA, the incidence was 0.56 persons per 100,000 person-years (95% CI 0.24-1.10 cases per 100,000). The incidence of nfvPPA was 0.14 persons per 100,000 person-years (95% CI 0.02-0.55), 0.21 persons per 100,000 person-years (95% CI 0.04-0.61) for lvPPA, and 0.21 persons per 100,000 person-years (95% CI 0.04-0.61) for svPPA.

DISCUSSION

As a group, PPA and PPAOS are a relatively rare group of diseases. PPAOS has a slightly lower incidence than PPA as a group but similar incidence to the individual PPA variants.

Association of cortical morphology, white matter hyperintensity, and glymphatic function in frontotemporal dementia variants

INTRODUCTION

Frontotemporal dementia (FTD) can be phenotypically divided into behavioral variant FTD (bvFTD), nonfluent variant primary progressive aphasia (nfvPPA), and semantic variant PPA (svPPA). However, the neural underpinnings of this phenotypic heterogeneity remain elusive.

METHODS

Cortical morphology, white matter hyperintensities (WMH), diffusion tensor image analysis along the perivascular space (DTI-ALPS), and their interrelationships were assessed in subtypes of FTD. Neuroimaging-transcriptional analyses on the regional cortical morphological deviances among subtypes were also performed.

RESULTS

Changes in cortical thickness, surface area, gyrification, WMH, and DTI-ALPS were subtype-specific in FTD. The three morphologic indices are related to whole-brain WMH volume and cognitive performance, while cortical thickness is related to DTI-ALPS. Neuroimaging-transcriptional analyses identified key biological pathways linked to the formation and/or spread of TDP-43/tau pathologies.

DISCUSSION

We found subtype-specific changes in cortical morphology, WMH, and glymphatic function in FTD. Our findings have the potential to contribute to the development of personalized predictions and treatment strategies for this disorder.

HIGHLIGHTS

Cortical morphologic changes, white matter hyperintensities (WMH), and glymphatic dysfunction are subtype-specific. Cortical morphologic changes, WMH, and glymphatic dysfunction are inter-correlated. Cortical morphologic changes and WMH burden contribute to cognitive impairments.

Clinical, Cortical, Subcortical, and White Matter Features of Right Temporal Variant FTD

The distinct clinical and radiological characteristics of right temporal variant FTD have only been recently recognized.

METHODS

Eight patients with right temporal variant FTD were prospectively recruited and underwent a standardised neuropsychological assessment, clinical MRI, and quantitative neuroimaging.

RESULTS

Our voxelwise grey analyses captured bilateral anterior and mesial temporal grey matter atrophy with a clear right-sided predominance. Bilateral hippocampal involvement was also observed, as well as disease burden in the right insular and opercula regions. White matter integrity alterations were also bilateral in anterior temporal and sub-insular regions with a clear right-hemispheric predominance. Extra-temporal white matter alterations have also been observed in orbitofrontal and parietal regions. Significant bilateral but right-predominant thalamus, putamen, hippocampus, and amygdala atrophy was identified based on subcortical segmentation. The clinical profile of our patients was dominated by progressive indifference, decline in motivation, loss of interest in previously cherished activities, incremental social withdrawal, difficulty recognising people, progressive language deficits, increasingly rigid routines, and repetitive behaviours.

CONCLUSIONS

Right temporal variant FTD has an insidious onset and may be mistaken for depression at symptom onset. It manifests in a combination of apathy, language, and behavioural features. Quantitative MR imaging captures a characteristic bilateral but right-predominant temporal imaging signature with extra-temporal frontal and parietal involvement.

Advances in semantic dementia: Neuropsychology, pathology & neuroimaging

Semantic dementia is a kind of neurodegenerative disorder, characterized by prominent semantic impairments and anterior temporal lobe atrophy. Since 2010, more studies have devoted to this rare disorder, revealing that it is more complex than we think. Clinical advances include more specific findings of semantic impairments and other higher order cognitive deficits. Neuroimaging techniques can help revealing the different brain networks affected (both structurally and functionally) in this condition. Pathological and genetic studies have also found more complex situations of semantic dementia, which might explain the huge variance existing in semantic dementia. Moreover, the current diagnosis criteria mainly focus on semantic dementia's classical prototype. We further delineated the features of three subtypes of semantic dementia based on atrophy lateralization with three severity stages. In a broader background, as a part of the continuum of neurodegenerative disorders, semantic dementia is commonly compared with other resembling conditions. Therefore, we summarized the differential diagnosis between semantic dementia and them. Finally, we introduced the challenges and achievements of its diagnosis, treatment, care and cross cultural comparison. By providing a comprehensive picture of semantic dementia on different aspects of advances, we hope to deepen the understanding of semantic dementia and promote more inspirations on both clinical and theoretical studies about it.

Non-pharmacological interventions for improving language and communication in people with primary progressive aphasia

BACKGROUND

Primary progressive aphasia (PPA) accounts for approximately 43% of frontotemporal dementias and is mainly characterised by a progressive impairment of speech and communication abilities. Three clinical variants have been identified: (a) non-fluent/agrammatic, (b) semantic, and (c) logopenic/phonological PPA variants. There is currently no curative treatment for PPA, and the disease progresses inexorably over time, with devastating effects on speech and communication ability, functional status, and quality of life. Several non-pharmacological interventions that may improve symptoms (e.g. different forms of language training and non-invasive brain stimulation) have been investigated in people with PPA.

OBJECTIVES

To assess the effects of non-pharmacological interventions for people with PPA on word retrieval (our primary outcome), global language functions, cognition, quality of life, and adverse events.

SEARCH METHODS

We searched the Cochrane Dementia and Cognitive Improvement Group's trial register, MEDLINE (Ovid SP), Embase (Ovid SP), four other databases and two other trial registers. The latest searches were run on 26 January 2024.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) evaluating the effects of non-pharmacological interventions in people with PPA.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

There were insufficient data available to conduct the network meta-analyses that we had originally planned (due to trial data being insufficiently reported or not reported at all, as well as the heterogeneous content of the included interventions). Therefore, we provide a descriptive summary of the included studies and results. We included 10 studies, with a total of 132 participants, evaluating non-pharmacological interventions. These were: transcranial direct current stimulation (tDCS) or repetitive transcranial magnetic stimulation (rTMS) as stand-alone treatments (used by two and one studies, respectively); tDCS combined with semantic and phonological word-retrieval training (five studies); tDCS combined with semantic word-retrieval training (one study); and tDCS combined with phonological word-retrieval training (one study). Results for our primary outcome of word retrieval were mixed. For the two studies that investigated the effects of tDCS as stand-alone treatment compared to placebo ("sham") tDCS, we rated the results as having very low-certainty evidence. One study found a significant beneficial effect on word retrieval after active tDCS; one study did not report any significant effects in favour of the active tDCS group. Five studies investigated tDCS administered to the dorsolateral prefrontal cortex, inferior frontal cortex, left frontotemporal region, or the temporoparietal cortex, combined with semantic and phonological word-retrieval training. The most consistent finding was enhancement of word-retrieval ability for trained items immediately after the intervention, when behavioural training was combined with active tDCS compared to behavioural training plus sham tDCS. We found mixed effects for untrained items and maintenance of treatment effects during follow-up assessments. We rated the certainty of the evidence as very low in all studies. One study investigated tDCS combined with semantic word-retrieval training. Training was provided across 15 sessions with a frequency of three to five sessions per week, depending on the personal preferences of the participants. tDCS targeted the left frontotemporal region. The study included three participants: two received 1 mA stimulation and one received 2 mA stimulation. The study showed mixed results. We rated it as very low-certainty evidence. One study investigated tDCS combined with phonological word-retrieval training. Training was again provided across 15 sessions over a period of three weeks. tDCS targeted the left inferior frontal gyrus. This study showed a significantly more pronounced improvement for trained and untrained words in favour of the group that had received active tDCS, but we rated the certainty of the evidence as very low. One study compared active rTMS applied to an individually determined target site to active rTMS applied to a control site (vertex) for effects on participants' word retrieval. This study demonstrated better word retrieval for active rTMS administered to individually determined target brain regions than in the control intervention, but we rated the results as having a very low certainty of evidence. Four studies assessed overall language ability, three studies assessed cognition, five studies assessed potential adverse effects of brain stimulation, and one study investigated quality of life.

AUTHORS' CONCLUSIONS

There is currently no high-certainty evidence to inform clinical decision-making regarding non-pharmacological treatment selection for people with PPA. Preliminary evidence suggests that the combination of active tDCS with specific language therapy may improve impaired word retrieval for specifically trained items beyond the effects of behavioural treatment alone. However, more research is needed, including high-quality RCTs with detailed descriptions of participants and methods, and consideration of outcomes such as quality of life, depressive symptoms, and overall cognitive functioning. Moreover, studies assessing optimal treatments (i.e. behavioural interventions, brain stimulation interventions, and their combinations) for individual patients and PPA subtypes are needed. We were not able to conduct the planned (network) meta-analyses due to missing data that could not be obtained from most of the authors, a general lack of RCTs in the field, and heterogeneous interventions in eligible trials. Journals should implement a mandatory data-sharing requirement to assure transparency and accessibility of data from clinical trials.

(What) can patients with semantic dementia learn?

Semantic Dementia (SD) is a neurodegenerative disease characterised by progressive deterioration of semantic knowledge, resulting in diminished understanding of concepts, whether encountered in verbal or non-verbal form. Over the past three decades, a number of studies employing a range of treatment techniques and learning methods have examined whether patients with SD can relearn previously known concepts or learn and retain new information. In this article, we review this research, addressing two main questions: a) Can aspects of semantic knowledge that are 'lost' due to degeneration be re-acquired? b) How much do other memory systems (working and episodic memory) interact with and depend on semantic memory? Several studies demonstrate successful relearning of previously known words and concepts in SD, particularly after regular, prolonged practice; but this success tends to diminish once practice ceases, and furthermore often fails to generalise to other instances of the same object/concept. This pattern suggests that, with impaired semantic knowledge, learning relies to an abnormal extent on perceptual factors, making it difficult to abstract away from the specific visual or other perceptual format in which a given concept has been trained. Furthermore, the impact of semantic 'status' of a word or object on both working and episodic memory indicates pervasive interaction of these other memory systems with conceptual knowledge.

Transcranial direct current stimulation in semantic variant of primary progressive aphasia: a state-of-the-art review

The semantic variant of primary progressive aphasia (svPPA), known also as "semantic dementia (SD)," is a neurodegenerative disorder that pertains to the frontotemporal lobar degeneration clinical syndromes. There is currently no approved pharmacological therapy for all frontotemporal dementia variants. Transcranial direct current stimulation (tDCS) is a promising non-invasive brain stimulation technique capable of modulating cortical excitability through a sub-threshold shift in neuronal resting potential. This technique has previously been applied as adjunct treatment in Alzheimer's disease, while data for frontotemporal dementia are controversial. In this scoped review, we summarize and critically appraise the currently available evidence regarding the use of tDCS for improving performance in naming and/or matching tasks in patients with svPPA. Clinical trials addressing this topic were identified through MEDLINE (accessed by PubMed) and Web of Science, as of November 2022, week 3. Clinical trials have been unable to show a significant benefit of tDCS in enhancing semantic performance in svPPA patients. The heterogeneity of the studies available in the literature might be a possible explanation. Nevertheless, the results of these studies are promising and may offer valuable insights into methodological differences and overlaps, raising interest among researchers in identifying new non-pharmacological strategies for treating svPPA patients. Further studies are therefore warranted to investigate the potential therapeutic role of tDCS in svPPA.

Textural and Volumetric Changes of the Temporal Lobes in Semantic Variant Primary Progressive Aphasia and Alzheimer's Disease

BACKGROUND

Texture analysis may capture subtle changes in the gray matter more sensitively than volumetric analysis. We aimed to investigate the patterns of neurodegeneration in semantic variant primary progressive aphasia (svPPA) and Alzheimer's disease (AD) by comparing the temporal gray matter texture and volume between cognitively normal controls and older adults with svPPA and AD.

METHODS

We enrolled all participants from three university hospitals in Korea. We obtained T1-weighted magnetic resonance images and compared the gray matter texture and volume of regions of interest (ROIs) between the groups using analysis of variance with Bonferroni posthoc comparisons. We also developed models for classifying svPPA, AD and control groups using logistic regression analyses, and validated the models using receiver operator characteristics analysis.

RESULTS

Compared to the AD group, the svPPA group showed lower volumes in five ROIs (bilateral temporal poles, and the left inferior, middle, and superior temporal cortices) and higher texture in these five ROIs and two additional ROIs (right inferior temporal and left entorhinal cortices). The performances of both texture- and volume-based models were good and comparable in classifying svPPA from normal cognition (mean area under the curve [AUC] = 0.914 for texture; mean AUC = 0.894 for volume). However, only the texture-based model achieved a good level of performance in classifying svPPA and AD (mean AUC = 0.775 for texture; mean AUC = 0.658 for volume).

CONCLUSION

Texture may be a useful neuroimaging marker for early detection of svPPA in older adults and its differentiation from AD.

Increased oligomeric TDP-43 in the plasma of Korean frontotemporal dementia patients with semantic dementia

INTRODUCTION

Semantic dementia (SD) is a progressive neurodegenerative disease associated with impaired vocabulary that progresses to memory impairment. Post-mortem immunohistochemical analysis is the current reliable method of differentiating TDP-43 deposits in cortical tissue; no means of antemortem diagnosis exists in biofluids, let alone in plasma.

METHODS

Here the multimer detection system (MDS) was used to quantify the oligomeric TDP-43 (o-TDP-43) concentrations in plasma of Korean SD patients (n = 16, 6 male, 10 female, ages 59-87). The o-TDP-43 concentrations were compared with the total TDP-43 (t-TDP-43) concentrations quantified through conventional enzyme-linked immunosorbent assay (ELISA).

RESULTS AND DISCUSSION

Only MDS showed a significant increase in o-TDP-43 concentrations in the plasma of patients with SD compared to other neurodegenerative disorders and normal controls (p < 0.05). Based on these results, o-TDP-43 concentrations through the application of MDS may be a useful plasma biomarker in SD-FTD (frontotemporal dementia) diagnosis.

A heterozygous splicing variant IVS9-7A > T in intron 9 of the MAPT gene in a patient with right-temporal variant frontotemporal dementia with atypical 4 repeat tauopathy

Right temporal variant frontotemporal dementia, also called right-predominant semantic dementia, often has an unclear position within the framework of the updated diagnostic criteria for behavioral variant frontotemporal dementia or primary progressive aphasia. Recent studies have suggested that this population may be clinically, neuropathologically, and genetically distinct from those with behavioral variant frontotemporal dementia or left-predominant typical semantic variant primary progressive aphasia. Here we describe a Japanese case of right temporal variant frontotemporal dementia with novel heterozygous MAPT mutation Adenine to Thymidine in intervening sequence (IVS) 9 at position -7 from 3' splicing site of intron 9/exon 10 boundary (MAPT IVS9-7A > T). Postmortem neuropathological analysis revealed a predominant accumulation of 4 repeat tau, especially in the temporal lobe, amygdala, and substantia nigra, but lacked astrocytic plaques or tufted astrocytes. Immunoelectron microscopy of the tau filaments extracted from the brain revealed a ribbon-like structure. Moreover, a cellular MAPT splicing assay confirmed that this novel variant promoted the inclusion of exon 10, resulting in the predominant production of 4 repeat tau. These data strongly suggest that the MAPT IVS9-7 A > T variant found in our case is a novel mutation that stimulates the inclusion of exon 10 through alternative splicing of MAPT transcript and causes predominant 4 repeat tauopathy which clinically presents as right temporal variant frontotemporal dementia.

Frontotemporal Dementia, Where Do We Stand? A Narrative Review

Frontotemporal dementia (FTD) is a neurodegenerative disease of growing interest, since it accounts for up to 10% of middle-age-onset dementias and entails a social, economic, and emotional burden for the patients and caregivers. It is characterised by a (at least initially) selective degeneration of the frontal and/or temporal lobe, generally leading to behavioural alterations, speech disorders, and psychiatric symptoms. Despite the recent advances, given its extreme heterogeneity, an overview that can bring together all the data currently available is still lacking. Here, we aim to provide a state of the art on the pathogenesis of this disease, starting with established findings and integrating them with more recent ones. In particular, advances in the genetics field will be examined, assessing them in relation to both the clinical manifestations and histopathological findings, as well as considering the link with other diseases, such as amyotrophic lateral sclerosis (ALS). Furthermore, the current diagnostic criteria will be explored, including neuroimaging methods, nuclear medicine investigations, and biomarkers on biological fluids. Of note, the promising information provided by neurophysiological investigations, i.e., electroencephalography and non-invasive brain stimulation techniques, concerning the alterations in brain networks and neurotransmitter systems will be reviewed. Finally, current and experimental therapies will be considered.

Distinguishing Semantic Variant Primary Progressive Aphasia from Alzheimer’s Disease

The differentiation of semantic variant primary progressive aphasia from dementia and Alzheimer’s disease can be difficult, particularly when the semantic anomia is pronounced. This report describes a patient who presented with complaints of memory loss and proved to have prominent semantic loss of all types of nouns, common and proper, concrete and abstract, yet continued to live independently and maintain his activities of daily living. The evaluation was consistent for semantic variant primary progressive aphasia with degradation of semantic knowledge and focal anterior temporal atrophy and hypometabolism. This report summarizes the literature and discusses the differential diagnosis of this disorder from Alzheimer’s disease and related dementias.

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

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

Clinical features and biomarkers of semantic variant primary progressive aphasia with MAPT mutation

BACKGROUND

Semantic variant primary progressive aphasia (svPPA) is generally sporadic, with very few reports of tau pathology caused by MAPT mutations.

METHODS

A 64-year-old man was diagnosed with svPPA with MAPT P301L mutation. Clinical information, cognitive and language functions, multimodal magnetic resonance imaging (MRI), blood biomarkers, fluorodeoxyglucose (FDG) imaging and tau positron emission tomography (PET) were obtained.

RESULTS

Semantic memory impairment was the earliest and most prominent symptom in this family. Tau accumulation and hypometabolism were observed prior to brain atrophy in mutation carriers. Plasma NfL and GFAP concentrations were elevated in the two svPPA patients. Some relative decreases and some relative increases in regional cerebral blood flow (CBF) as measured by arterial spin labelling (ASL) were observed in mutation carriers compared to noncarriers.

CONCLUSIONS

This study describes a large svPPA-affected family with the MAPT P301L mutation and provides an ideal model for inferring underlying pathology and pathophysiological processes in svPPA caused by tauopathies.

More extensive hypometabolism and higher mortality risk in patients with right- than left-predominant neurodegeneration of the anterior temporal lobe

BACKGROUND

Left-predominant neurodegeneration of the anterior temporal lobe (ATL) and the associated syndrome termed semantic variant primary progressive aphasia (svPPA) are well characterized. Less is known about right-predominant neurodegeneration of the ATL, which has been associated with the clinical syndrome named right temporal variant of frontotemporal dementia (rtvFTD). Here, we assessed glucose metabolism across the brain, cognitive performance, and mortality in patients with right-predominant neurodegeneration of the ATL.

METHODS

Patients with predominant hypometabolism of the ATL on FDG PET (as a measure of neurodegeneration) were retrospectively identified and categorized into those with asymmetrical right, left, or symmetric bilateral involvement (N = 10, 17, and 8). We compared whole-brain, normalized regional glucose metabolism using SPM12, cognitive performance on the CERAD Neuropsychological Assessment Battery, and mortality risk (age- and sex-adjusted Cox proportional hazard model) between groups.

RESULTS

Hypometabolism was most pronounced and extensive in patients with right-predominant neurodegeneration of the ATL. Beyond the right temporal lobe, right frontal and left temporal lobes were affected in these patients. Cognitive performance was similarly impaired in all three groups, with predominant naming and hippocampal-dependent memory deficits. Mortality risk was 6.1 times higher in patients with right- than left-predominant ATL neurodegeneration (p < 0.05). Median survival duration after PET was shortest in patients with right- and longest in patients with left-predominant ATL neurodegeneration (5.7 vs 8.3 years after examination).

DISCUSSION

More extensive neurodegeneration and shorter survival duration in patients with right- than left-predominant neurodegeneration of the ATL might indicate that the former consult memory clinics at a later disease stage, when symptoms like naming and episodic memory deficits have already emerged. At the time of diagnosis, the shorter survival duration of patients with right- than left-predominant ATL neurodegeneration should be kept in mind when counseling patients and caregivers.

Mapping behavioural, cognitive and affective transdiagnostic dimensions in frontotemporal dementia

Two common clinical variants of frontotemporal dementia are the behavioural variant frontotemporal dementia, presenting with behavioural and personality changes attributable to prefrontal atrophy, and semantic dementia, displaying early semantic dysfunction primarily due to anterior temporal degeneration. Despite representing independent diagnostic entities, mounting evidence indicates overlapping cognitive-behavioural profiles in these syndromes, particularly with disease progression. Why such overlap occurs remains unclear. Understanding the nature of this overlap, however, is essential to improve early diagnosis, characterization and management of those affected. Here, we explored common cognitive-behavioural and neural mechanisms contributing to heterogeneous frontotemporal dementia presentations, irrespective of clinical diagnosis. This transdiagnostic approach allowed us to ascertain whether symptoms not currently considered core to these two syndromes are present in a significant proportion of cases and to explore the neural basis of clinical heterogeneity. Sixty-two frontotemporal dementia patients (31 behavioural variant frontotemporal dementia and 31 semantic dementia) underwent comprehensive neuropsychological, behavioural and structural neuroimaging assessments. Orthogonally rotated principal component analysis of neuropsychological and behavioural data uncovered eight statistically independent factors explaining the majority of cognitive-behavioural performance variation in behavioural variant frontotemporal dementia and semantic dementia. These factors included Behavioural changes, Semantic dysfunction, General Cognition, Executive function, Initiation, Disinhibition, Visuospatial function and Affective changes. Marked individual-level overlap between behavioural variant frontotemporal dementia and semantic dementia was evident on the Behavioural changes, General Cognition, Initiation, Disinhibition and Affective changes factors. Compared to behavioural variant frontotemporal dementia, semantic dementia patients displayed disproportionate impairment on the Semantic dysfunction factor, whereas greater impairment on Executive and Visuospatial function factors was noted in behavioural variant frontotemporal dementia. Both patient groups showed comparable magnitude of atrophy to frontal regions, whereas severe temporal lobe atrophy was characteristic of semantic dementia. Whole-brain voxel-based morphometry correlations with emergent factors revealed associations between fronto-insular and striatal grey matter changes with Behavioural, Executive and Initiation factor performance, bilateral temporal atrophy with Semantic dysfunction factor scores, parietal-subcortical regions with General Cognitive performance and ventral temporal atrophy associated with Visuospatial factor scores. Together, these findings indicate that cognitive-behavioural overlap (i) occurs systematically in frontotemporal dementia; (ii) varies in a graded manner between individuals and (iii) is associated with degeneration of different neural systems. Our findings suggest that phenotypic heterogeneity in frontotemporal dementia syndromes can be captured along continuous, multidimensional spectra of cognitive-behavioural changes. This has implications for the diagnosis of both syndromes amidst overlapping features as well as the design of symptomatic treatments applicable to multiple syndromes.

Experiences of families of people living with frontotemporal dementia: a qualitative systematic review

Frontotemporal dementia (FTD) is characterised by atrophy of the frontal and/or temporal lobes. People with FTD show language and emotional disturbances from onset, and communication problems usually affect people with FTD and their families even before diagnosis. These unique characteristics of FTD are not well understood and create substantial problems for people living with FTD and their families. This review explores the experiences of families of people living with FTD. Studies were selected and screened according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched four bibliographic databases for articles up to February 2021 to identify qualitative data on the experiences of families. The Critical Appraisal Skills Programme checklist for qualitative studies was used to assess all included studies. Of 235 identified articles, we included six studies in the qualitative synthesis. Meta-ethnography was conducted to interpret families' experiences of people living with FTD. The emergent concepts were synthesised into five themes: Something is wrong with my loved one; No one fully understands; Existential pain of caring for a loved one with FTD; Increased burden owing to specific FTD symptoms; and Forced to adapt to new and unique ways of living with a loved one with FTD. This review highlighted families' confusion and suffering (which began in the early stages of the disease, and sometimes before diagnosis) and the difficulty of communicating with people with FTD. These findings have implications for future practice, as they demonstrate the positive effect on family life of appropriate support that is provided early, rather than after the disease has progressed.

When words first fail: Predicting the emergence of primary progressive aphasia variants from unclassifiable anomic performance in early disease

Background

The majority of patients with primary progressive aphasia (PPA) can be distinguished into one of three variants: semantic, non-fluent/agrammatic, or logopenic. However, many do not meet criteria for any one variant.

Aim

To identify aspects of cognitive-linguistic performance that yield an early unclassifiable PPA designation that predicted the later emergence of a given variant.

Methods & Procedures

Of 256 individuals with PPA evaluated, 19 initially were unclassifiable and later met criteria for a variant. Receiver operating characteristic curves were used to evaluate the binary ability of a given task to predict eventual classification as a given variant. Tasks with a high area under the curve were examined using regression analyses to determine their ability to predict variant.

Outcomes & Results

High mean predictive value was observed for multiple naming assessments targeting nouns and verbs. The Boston Naming Test (BNT) was the only test that, in isolation, resulted in a significant model and high classification accuracy.

Conclusions

Although naming impairment is common across PPA variants, very low initial BNT scores emerged as a uniquely accurate basis for predicting eventual semantic variant, and normal BNT scores predicted eventual nonfluent/agrammatic variant. High performance on picture-verb verification was useful in identifying future lvPPA.

Mapping cortical disease-burden at individual-level in frontotemporal dementia: implications for clinical care and pharmacological trials

Imaging studies of FTD typically present group-level statistics between large cohorts of genetically, molecularly or clinically stratified patients. Group-level statistics are indispensable to appraise unifying radiological traits and describe genotype-associated signatures in academic studies. However, in a clinical setting, the primary objective is the meaningful interpretation of imaging data from individual patients to assist diagnostic classification, inform prognosis, and enable the assessment of progressive changes compared to baseline scans. In an attempt to address the pragmatic demands of clinical imaging, a prospective computational neuroimaging study was undertaken in a cohort of patients across the spectrum of FTD phenotypes. Cortical changes were evaluated in a dual pipeline, using standard cortical thickness analyses and an individualised, z-score based approach to characterise subject-level disease burden. Phenotype-specific patterns of cortical atrophy were readily detected with both methodological approaches. Consistent with their clinical profiles, patients with bvFTD exhibited orbitofrontal, cingulate and dorsolateral prefrontal atrophy. Patients with ALS-FTD displayed precentral gyrus involvement, nfvPPA patients showed widespread cortical degeneration including insular and opercular regions and patients with svPPA exhibited relatively focal anterior temporal lobe atrophy. Cortical atrophy patterns were reliably detected in single individuals, and these maps were consistent with the clinical categorisation. Our preliminary data indicate that standard T1-weighted structural data from single patients may be utilised to generate maps of cortical atrophy. While the computational interpretation of single scans is challenging, it offers unrivalled insights compared to visual inspection. The quantitative evaluation of individual MRI data may aid diagnostic classification, clinical decision making, and assessing longitudinal changes.

Characterizing Differences in Functional Connectivity Between Posterior Cortical Atrophy and Semantic Dementia by Seed-Based Approach

Background

Posterior cortical atrophy (PCA) and semantic dementia (SD) are focal syndromes involving different cerebral regions. This study aimed to demonstrate the existence of abnormal functional connectivity (FC) with an affected network in PCA and SD.

Methods

A total of 10 patients with PCA, 12 patients with SD, and 11 controls were recruited to undergo a detailed clinical history interview and physical examination, neuropsychological assessments, and PET/MRI scan. Seed-based FC analyses were conducted to construct FC in language network, visual network, and salience network. The two-sample t-test was performed to reveal distinct FC patterns in PCA and SD, and we further related the FC difference to cognition. Meanwhile, the uptake value of fluorodeoxyglucose in regions with FC alteration was also extracted for comparison.

Results

We found a global cognitive impairment in patients with PCA and SD. The results of FC analyses showed that patients with PCA present decreased FC in left precentral gyrus to left V1 and increased FC in right inferior frontal gyrus to right V1 in the visual network, right medial frontal gyrus and left fusiform to left anterior temporal lobe and post-superior temporal gyrus in the language network, and left superior temporal gyrus to left anterior insula in the salience network, which were related to cognitive function. Patients with SD had decreased FC from right superior frontal gyrus, right middle frontal gyrus and right superior frontal gyrus to left anterior temporal lobe, or post-superior temporal gyrus in the language network, as well as left superior frontal gyrus to right anterior insula in the salience network, positively relating to cognitive function, but increased FC in the right superior temporal gyrus to left anterior temporal lobe in the language network, and right insula and left anterior cingulum to right anterior insula in the salience network, negatively relating to cognitive function. Most of the regions with FC change in patients with PCA and SD had abnormal metabolism simultaneously.

Conclusion

Abnormal connectivity spread over the cortex involving language and salience networks was common in patients with PCA and SD, whereas FC change involving the visual network was unique to patients with PCA. The FC changes were matched for cognitive deficits.

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.

Frontotemporal dementia: A unique window on the functional role of the temporal lobes

Frontotemporal dementia (FTD) is an umbrella term covering a plethora of progressive changes in executive functions, motor abilities, behavior, and/or language. Different clinical syndromes have been described in relation to localized atrophy, informing on the functional networks that underlie these specific cognitive, emotional, and behavioral processes. These functional declines are linked with the underlying neurodegeneration of frontal and/or temporal lobes due to diverse molecular pathologies. Initially, the accumulation of misfolded proteins targets specifically susceptible cell assemblies, leading to relatively focal neurodegeneration that later spreads throughout large-scale cortical networks. Here, we discuss the most recent clinical, neuropathological, imaging, and genetics findings in FTD-spectrum syndromes affecting the temporal lobe. We focus on the semantic variant of primary progressive aphasia and its mirror image, the right temporal variant of FTD. Incipient focal atrophy of the left anterior temporal lobe (ATL) manifests with predominant naming, word comprehension, reading, and object semantic deficits, while cases of predominantly right ATL atrophy present with impairments of socioemotional, nonverbal semantic, and person-specific knowledge. Overall, the observations in FTD allow for crucial clinical-anatomic inferences, shedding light on the role of the temporal lobes in both cognition and complex behaviors. The concerted activity of both ATLs is critical to ensure that percepts are translated into concepts, yet important hemispheric differences should be acknowledged. On one hand, the left ATL attributes meaning to linguistic, external stimuli, thus supporting goal-oriented, action-related behaviors (e.g., integrating sounds and letters into words). On the other hand, the right ATL assigns meaning to emotional, visceral stimuli, thus guiding socially relevant behaviors (e.g., integrating body sensations into feelings of familiarity).

Clinical and neuroimaging characteristics of primary progressive aphasia

The chapter covers the clinical syndrome of a primary progressive aphasia (PPA), the demographics of this rare neurodegenerative disease, defining clinical and neuroanatomic characteristics of each PPA variant, disease progression, and behavioral features. The chapter begins with a brief introduction that includes references to seminal papers that defined this clinical syndrome and its three variants. The classic PPA subtypes discussed in the chapter are semantic variant PPA (svPPA), nonfluent/agrammatic PPA (nfaPPA), and logopenic variant PPA (lvPPA). The key language and cognitive characteristics, and language tasks that can elicit these language impairments, are detailed. Overlap in the clinical profiles of the PPA variants, which make differential diagnosis challenging, are explained. Disease progression is described, revealing that the PPA variants become more similar over time. Although PPA is language-predominant dementia, there are behavioral manifestations, particularly in svPPA. Changes in behavior in this variant are addressed as well as behavioral changes in nfaPPA and lvPPA that are less well recognized. The patterns of atrophy in the left temporal, parietal, and/or frontal cortices unique to each PPA variant are described. The underlying neuropathologies of the PPA variants are discussed, specifically tauopathies and non-tauopathies associated with svPPA and nfaPPA and Alzheimer's disease pathology in lvPPA.

Semantic Variant Primary Progressive Aphasia: Practical Recommendations for Treatment from 20 Years of Behavioural Research

People with semantic variant primary progressive aphasia (svPPA) present with a characteristic progressive breakdown of semantic knowledge. There are currently no pharmacological interventions to cure or slow svPPA, but promising behavioural approaches are increasingly reported. This article offers an overview of the last two decades of research into interventions to support language in people with svPPA including recommendations for clinical practice and future research based on the best available evidence. We offer a lay summary in English, Spanish and French for education and dissemination purposes. This paper discusses the implications of right- versus left-predominant atrophy in svPPA, which naming therapies offer the best outcomes and how to capitalise on preserved long-term memory systems. Current knowledge regarding the maintenance and generalisation of language therapy gains is described in detail along with the development of compensatory approaches and educational and support group programmes. It is concluded that there is evidence to support an integrative framework of treatment and care as best practice for svPPA. Such an approach should combine rehabilitation interventions addressing the language impairment, compensatory approaches to support activities of daily living and provision of education and support within the context of dementia.

Two Rare Variants in PLAU and BACE1 Genes-Do They Contribute to Semantic Dementia Clinical Phenotype?

We have performed whole-genome sequencing to identify the genetic variants potentially contributing to the early-onset semantic dementia phenotype in a patient with family history of dementia and episodic memory deficit accompanied with profound semantic loss. Only very rare variants of unknown significance (VUS) have been identified: a nonsense variant c.366C>A/p.Cys122* in plasminogen activator, urokinase (PLAU) and a missense variant c.944C>T/p.Thr315Met in β-site APP-cleaving enzyme 1 (BACE1)-along with known disease-modifying variants of moderate penetrance. Patient-derived fibroblasts showed reduced PLAU and elevated BACE1 mRNA and protein levels compared to control fibroblasts. Successful rescue of PLAU mRNA levels by nonsense-mediated mRNA decay (NMD) inhibitor (puromycin) confirmed NMD as the underlying mechanism. This is the first report of the PLAU variant with the confirmed haploinsufficiency, associated with semantic dementia phenotype. Our results suggest that rare variants in the PLAU and BACE1 genes should be considered in future studies on early-onset dementias.

Considering Hemispheric Specialization in Emotional Face Processing: An Eye Tracking Study in Left- and Right-Lateralised Semantic Dementia

Face processing relies on a network of occipito-temporal and frontal brain regions. Temporal regions are heavily involved in looking at and processing emotional faces; however, the contribution of each hemisphere to this process remains under debate. Semantic dementia (SD) is a rare neurodegenerative brain condition characterized by anterior temporal lobe atrophy, which is either predominantly left- (left-SD) or right-lateralised (right-SD). This syndrome therefore provides a unique lesion model to understand the role of laterality in emotional face processing. Here, we investigated facial scanning patterns in 10 left-SD and 6 right-SD patients, compared to 22 healthy controls. Eye tracking was recorded via a remote EyeLink 1000 system, while participants passively viewed fearful, happy, and neutral faces over 72 trials. Analyses revealed that right-SD patients had more fixations to the eyes than controls in the Fear (p = 0.04) condition only. Right-SD patients also showed more fixations to the eyes than left-SD patients in all conditions: Fear (p = 0.01), Happy (p = 0.008), and Neutral (p = 0.04). In contrast, no differences between controls and left-SD patients were observed for any emotion. No group differences were observed for fixations to the mouth, or the whole face. This study is the first to examine patterns of facial scanning in left- versus right- SD, demonstrating more of a focus on the eyes in right-SD. Neuroimaging analyses showed that degradation of the right superior temporal sulcus was associated with increased fixations to the eyes. Together these results suggest that right lateralised brain regions of the face processing network are involved in the ability to efficiently utilise changeable cues from the face.

Disease Progression in Frontotemporal Dementia and Alzheimer Disease: The Contribution of Staging Scales

INTRODUCTION

There is a shortage of validated instruments to estimate disease progression in frontotemporal dementia (FTD).

OBJECTIVES

To evaluate the ability of the FTD Rating Scale (FTD-FRS) to detect functional and behavioral changes in patients diagnosed with the behavioral variant of FTD (bvFTD), primary progressive aphasia (PPA), and Alzheimer disease (AD) after 12 months of the initial evaluation, compared to the Clinical Dementia Rating scale-frontotemporal lobar degeneration (CDR-FTLD) and the original Clinical Dementia Rating scale (CDR).

METHODS

The sample consisted of 70 individuals, aged 40+ years, with at least 2 years of schooling, 31 with the diagnosis of bvFTD, 12 with PPA (8 with semantic variant and 4 with non-fluent variant), and 27 with AD. The FTD-FRS, the CDR, and the 2 additional CDR-FTLD items were completed by a clinician, based on the information provided by the caregiver with frequent contact with the patient. The Addenbrooke Cognitive Examination-Revised was completed by patients. After 12 months, the same protocol was applied.

RESULTS

The FTD-FRS, CDR-FTLD, and CDR detected significant decline after 12 months in the 3 clinical groups (exception: FTD-FRS for PPA). The CDR was less sensitive to severe disease stages.

CONCLUSIONS

The FTD-FRS and the CDR-FTLD are especially useful tools for dementia staging in AD and in the FTD spectrum.

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

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

Speech and language therapy in primary progressive aphasia: a critical review of current practice

INTRODUCTION

Primary progressive aphasia (PPA) is a complex language-led dementia syndrome whereby disproportionate deterioration of speech and language occurs subsequent to neurodegenerative disease in the early to mid-stages of the condition. As no effective pharmacotherapies are currently available, speech and language therapies are the optimum treatment to maximize communication for as long as possible.

AREAS COVERED

The authors present an overview of current speech-language therapy practices in PPA, highlighting recent research on effective treatments.

EXPERT OPINION

The challenges in this complex field of practice are described. We highlight the challenge of improving access to speech-language therapy by advocating for increased referral rates. The authors also suggest effective incorporation of innovative technologies in treatment and an enhanced evidence base for the utility of lexical retrieval treatment in improving everyday communication as challenges for the future. Finally, increased provision of PPA-specific education and support for individuals and their families is required.

Neuroinflammation is highest in areas of disease progression in semantic dementia

Despite epidemiological and genetic data linking semantic dementia to inflammation, the topography of neuroinflammation in semantic dementia, also known as the semantic variant of primary progressive aphasia, remains unclear. The pathology starts at the tip of the left temporal lobe where, in addition to cortical atrophy, a strong signal appears with the tau PET tracer 18F-flortaucipir, even though the disease is not typically associated with tau but with TDP-43 protein aggregates. Here, we characterized the topography of inflammation in semantic variant primary progressive aphasia using high-resolution PET and the tracer 11C-PBR28 as a marker of microglial activation. We also tested the hypothesis that inflammation, by providing non-specific binding targets, could explain the 18F-flortaucipir signal in semantic variant primary progressive aphasia. Eight amyloid-PET-negative patients with semantic variant primary progressive aphasia underwent 11C-PBR28 and 18F-flortaucipir PET. Healthy controls underwent 11C-PBR28 PET (n = 12) or 18F-flortaucipir PET (n = 12). Inflammation in PET with 11C-PBR28 was analysed using Logan graphical analysis with a metabolite-corrected arterial input function. 18F-flortaucipir standardized uptake value ratios were calculated using the cerebellum as the reference region. Since monoamine oxidase B receptors are expressed by astrocytes in affected tissue, selegiline was administered to one patient with semantic variant primary progressive aphasia before repeating 18F-flortaucipir scanning to test whether monoamine oxidase B inhibition blocked flortaucipir binding, which it did not. While 11C-PBR28 uptake was mostly cortical, 18F-flortaucipir uptake was greatest in the white matter. The uptake of both tracers was increased in the left temporal lobe and in the right temporal pole, as well as in regions adjoining the left temporal pole such as insula and orbitofrontal cortex. However, peak uptake of 18F-flortaucipir localized to the left temporal pole, the epicentre of pathology, while the peak of inflammation 11C-PBR28 uptake localized to a more posterior, mid-temporal region and left insula and orbitofrontal cortex, in the periphery of the damage core. Neuroinflammation, greatest in the areas of progression of the pathological process in semantic variant primary progressive aphasia, should be further studied as a possible therapeutic target to slow disease progression.

Diagnostic Performance of RO948 F 18 Tau Positron Emission Tomography in the Differentiation of Alzheimer Disease From Other Neurodegenerative Disorders

Question

How does RO948 F 18 positron emission tomographic scanning discriminate between Alzheimer disease and other neurodegenerative disorders in comparison with magnetic resonance imaging and cerebrospinal fluid measures?

Findings

In this diagnostic study including 613 patients from the Swedish BioFINDER-2 clinical trial, standard uptake value ratios of RO948 F 18 were higher in patients with Alzheimer disease dementia compared with cognitively unimpaired controls and patients with other neurodegenerative disorders; furthermore, RO948 F 18 outperformed magnetic resonance imaging and cerebrospinal fluid measures. Generally, tau positron emission tomographic positivity was confined to amyloid β–positive cases or MAPT R406W mutation carriers in this cohort; in patients with semantic variant primary progressive aphasia, RO948 F 18 retention was lower than that for flortaucipir F 18.

Meaning

These findings suggest that RO948 F 18 has a high specificity for Alzheimer disease–type tau and highlight its potential as a diagnostic marker in the workup of patients treated in memory clinics.

Importance

The diagnostic performance of second-generation tau positron emission tomographic (PET) tracers is not yet known.

Objective

To examine the novel tau PET tracer RO948 F 18 ([¹⁸F]RO948) performance in discriminating Alzheimer disease (AD) from non-AD neurodegenerative disorders.

Design, Setting, and Participants

In this diagnostic study, 613 participants in the Swedish BioFINDER-2 study were consecutively enrolled in a prospective cross-sectional study from September 4, 2017, to August 28, 2019. Participants included 257 cognitively unimpaired controls, 154 patients with mild cognitive impairment, 100 patients with AD dementia, and 102 with non-AD neurodegenerative disorders. Evaluation included a comparison of tau PET tracer [¹⁸F]RO948 with magnetic resonance imaging (MRI) and cerebrospinal fluid and a head-to-head comparison between [¹⁸F]RO948 and flortaucipir F 18 ([¹⁸F]flortaucipir) in patients with semantic variant primary progressive aphasia (svPPA).

Exposures

[¹⁸F]RO948 (all patients) and [¹⁸F]flortaucipir (3 patients with svPPA) tau PET; MRI (hippocampal volume, composite temporal lobe cortical thickness, whole-brain cortical thickness) and cerebrospinal fluid measures (p-tau181 and amyloid Aβ42 and Aβ40 ratio[Aβ42/Aβ40], and Aβ42/p-tau181 ratio).

Main Outcomes and Measures

Standard uptake value ratios (SUVRs) in 4 predefined regions of interest (ROIs) reflecting Braak staging scheme for tau pathology and encompass I-II (entorhinal cortex), III-IV (inferior/middle temporal, fusiform gyrus, parahippocampal cortex, and amygdala), I-IV, and V-VI (widespread neocortical areas), area under the receiver operating characteristic curve (AUC) values, and subtraction images between [¹⁸F]RO948 and [¹⁸F]flortaucipir.

Results

Diagnostic groups among the 613 participants included cognitively unimpaired (mean [SD] age, 65.8 [12.1] years; 117 men [46%]), mild cognitive impairment (age, 70.8 [8.3] years; 82 men [53%]), AD dementia (age, 73.5 [6.7] years; 57 men [57%]), and non-AD disorders (age, 70.5 [8.6] years; 41 men [40%]). Retention of [¹⁸F]RO948 was higher in AD dementia compared with all other diagnostic groups. [¹⁸F]RO948 could distinguish patients with AD dementia from individuals without cognitive impairment and those with non-AD disorders, and the highest AUC was obtained using the I-IV ROI (AUC = 0.98; 95% CI, 0.96-0.99 for AD vs no cognitive impairment and AUC = 0.97; 95% CI, 0.95-0.99 for AD vs non-AD disorders), which outperformed MRI (highest AUC = 0.91 for AD vs no cognitive impairment using whole-brain thickness, and AUC = 0.80 for AD vs non-AD disorders using temporal lobe thickness) and cerebrospinal fluid measures (highest AUC = 0.94 for AD vs no cognitive impairment using Aβ42/p-tau181, and AUC = 0.93 for AD vs non-AD disorders using Aβ42/Aβ40). Generally, tau PET positivity using [¹⁸F]RO948 was observed only in Aβ-positive cases or in MAPT R406W mutation carriers. Retention of [¹⁸F]RO948 was not pronounced in patients with svPPA, and head-to-head comparison revealed lower temporal lobe uptake than with [¹⁸F]flortaucipir.

Conclusions and Relevance

In this study, elevated [¹⁸F]RO948 SUVRs were most often seen among Aβ-positive cases, which suggests that [¹⁸F]RO948 has high specificity for AD-type tau and highlights its potential as a diagnostic marker in the differential diagnosis of AD.

Beyond language impairment: Profiles of apathy in primary progressive aphasia

Primary progressive aphasia (PPA) is characterised by predominant language and communication impairment. However, behavioural changes, such as apathy, are increasingly recognised. Apathy is defined as a reduction in motivation and goal-directed behaviour. Recent theoretical models have suggested that apathy can be delineated into multiple dimensions: executive apathy (i.e., deficits in maintaining goals and organisation), emotional apathy (i.e., emotional blunting and indifference) and initiation apathy (i.e., reduced self-initiation). Whether the nature of apathy differs between clinical variants of PPA, and across early and late disease stages, remains to be established. Here, carers/informants of 20 semantic variant PPA (svPPA), 15 non-fluent variant PPA (nfvPPA), 16 logopenic variant PPA (lvPPA) and 25 healthy older controls completed the Dimensional Apathy Scale to quantify executive, emotional and initiation apathy. Voxel-based morphometry was used to identify associations between dimensions of apathy and regions of grey matter intensity decrease. Our behavioural results showed greater executive and initiation apathy in late svPPA than in late nfvPPA patients, while late svPPA had greater emotional apathy than both late nfvPPA and late lvPPA groups. Executive and initiation apathy were significantly higher than premorbid levels in all PPA subtypes, while elevated emotional apathy was only seen in early and late svPPA. Distinct neural correlates were identified across apathy dimensions. Executive apathy correlated with grey matter intensity of the left dorsolateral prefrontal and inferior parietal cortices; emotional apathy with the left medial prefrontal, insular and cerebellar regions; and initiation apathy with right parietal areas. Our findings are the first to reveal evidence of the dimensional nature of apathy in PPA, with different clinical signatures observed for each subtype. From a clinical standpoint, these results will inform the development of targeted interventions for specific aspects of apathy which emerge in PPA.

Language impairment in progressive supranuclear palsy and corticobasal syndrome

Although commonly known as movement disorders, progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS) may present with changes in speech and language alongside or even before motor symptoms. The differential diagnosis of these two disorders can be challenging, especially in the early stages. Here we review their impact on speech and language. We discuss the neurobiological and clinical-phenomenological overlap of PSP and CBS with each other, and with other disorders including non-fluent agrammatic primary progressive aphasia and primary progressive apraxia of speech. Because language impairment is often an early and persistent problem in CBS and PSP, there is a need for improved methods for language screening in primary and secondary care, and more detailed language assessments in tertiary healthcare settings. Improved language assessment may aid differential diagnosis as well as inform clinical management decisions.

Predictors of survival in frontotemporal lobar degeneration syndromes

After decades of research, large-scale clinical trials in patients diagnosed with frontotemporal lobar degeneration (FTLD) are now underway across multiple centres worldwide. As such, refining the determinants of survival in FTLD represents a timely and important challenge. Specifically, disease outcome measures need greater clarity of definition to enable accurate tracking of therapeutic interventions in both clinical and research settings. Multiple factors potentially determine survival, including the clinical phenotype at presentation; radiological patterns of atrophy including markers on both structural and functional imaging; metabolic factors including eating behaviour and lipid metabolism; biomarkers including both serum and cerebrospinal fluid markers of underlying pathology; as well as genetic factors, including both dominantly inherited genes, but also genetic modifiers. The present review synthesises the effect of these factors on disease survival across the syndromes of frontotemporal dementia, with comparison to amyotrophic lateral sclerosis, progressive supranuclear palsy and corticobasal syndrome. A pathway is presented that outlines the utility of these varied survival factors for future clinical trials and drug development. Given the complexity of the FTLD spectrum, it seems unlikely that any single factor may predict overall survival in individual patients, further suggesting that a precision medicine approach will need to be developed in predicting disease survival in FTLD, to enhance drug target development and future clinical trial methodologies.

Temporal variant of frontotemporal dementia in C9orf72 repeat expansion carriers: two case studies

The temporal variant of frontotemporal dementia (tv-FTD) is a progressive neurodegenerative disease with a complex clinical picture mainly characterized by behavioral and language disorders. In this work, we describe clinical, genetic, neuroanatomical and neuropathological (only in one case) features of two patients with tv-FTD carrying C9orf72 repeat expansion. The first patient (AB) presented with a 1-year disease duration showing focal right anterior temporal lobe (ATL) atrophy on magnetic resonance imaging (MRI). The second patient (BC) came to medical attention 13 years after disease onset and showed a prominent bilateral ATL involvement. Both patients showed naming deficits, impairment in identifying known faces and proper names, and personality changes with new onset behavioral rigidity, and progressing language difficulties to single-word and sentence comprehension difficulties. They were classified as tv-FTD. Clinical, cognitive and MRI follow-up were performed. As cognitive impairment progressed, MRI atrophy worsened in ATL and frontotemporal areas in both patients. Both cases had clear family histories of neurological and/or psychiatric disease. Genetic testing revealed a C9orf72 hexanucleotide repeat expansion in both cases. BC passed away after 15 years of disease and autopsy showed the expected TDP-type B pathology. These genetic cases of tv-FTD highlight the susceptibility of ATL to C9orf72-related pathology and emphasize the importance of genetical testing in FTD-spectrum disorders, regardless of the clinical phenotype.

Frontotemporal Dementia: A Window to Alexithymia

Alexithymia is pervasive among psychiatric patients, but its neurobiological mechanism is unclear. Patients with alexithymia cannot "read emotions," a process involving interoception, or the perception of the body's internal state, primarily in the insulae. The frontotemporal dementias are also associated with inability to correctly read emotions; hence, these dementias can provide a window into the mechanism of alexithymia. Patients with behavioral variant frontotemporal dementia (bvFTD) have a weak emotional signal with impaired emotional recognition, hypoemotionality, and decreased physiological arousal. bvFTD affects the insulae, and the weak emotional signal facilitates impaired interoceptive accuracy, resulting in an overreliance on cognitive appraisal rather than on internal sensations. In contrast, patients with semantic dementia, another frontotemporal dementia syndrome, can have intact interoception, but they have disturbed cognitive appraisal of the meaning of their bodily sensations. This "alexisomia" in semantic dementia can lead to misinterpreted somatic symptoms. Together, the findings in alexithymic patients and frontotemporal dementia syndromes support the model of impaired interoceptive accuracy as the mechanism of alexithymia, possibly from dysfunction in the insulae.

Somatic TARDBP variants as a cause of semantic dementia

The aetiology of late-onset neurodegenerative diseases is largely unknown. Here we investigated whether de novo somatic variants for semantic dementia can be detected, thereby arguing for a more general role of somatic variants in neurodegenerative disease. Semantic dementia is characterized by a non-familial occurrence, early onset (<65 years), focal temporal atrophy and TDP-43 pathology. To test whether somatic variants in neural progenitor cells during brain development might lead to semantic dementia, we compared deep exome sequencing data of DNA derived from brain and blood of 16 semantic dementia cases. Somatic variants observed in brain tissue and absent in blood were validated using amplicon sequencing and digital PCR. We identified two variants in exon one of the TARDBP gene (L41F and R42H) at low level (1-3%) in cortical regions and in dentate gyrus in two semantic dementia brains, respectively. The pathogenicity of both variants is supported by demonstrating impaired splicing regulation of TDP-43 and by altered subcellular localization of the mutant TDP-43 protein. These findings indicate that somatic variants may cause semantic dementia as a non-hereditary neurodegenerative disease, which might be exemplary for other late-onset neurodegenerative disorders.

Diagnostic Assessment in Primary Progressive Aphasia: An Illustrative Case Example

Purpose Diagnosis and classification of primary progressive aphasia (PPA) requires confirmation of specific speech and language symptoms, highlighting the important role of speech-language pathologists in the evaluation process. The purpose of this case report is to inform speech-language pathologists regarding current practices for diagnostic assessment in PPA, describing standard approaches as well as complementary, state-of-the-art procedures that may improve diagnostic precision. Method We describe the diagnostic evaluation of a 49-year-old woman with complaints of progressive word-finding difficulty. She completed standard neurological, neuropsychological, and speech-language evaluations, as well as magnetic resonance and positron emission tomography imaging of her brain. In addition, a history of developmental speech, language, and learning abilities was obtained, as well as genetic testing and assessment of cerebrospinal fluid biomarkers. We discuss the evaluation results in the context of the most current research related to PPA diagnosis. Conclusion Detailed behavioral assessment, thorough intake of symptom history and neurodevelopmental differences, multimodal neuroimaging, and comprehensive examination of genes and biomarkers are of paramount importance for detecting and characterizing PPA, with ramifications for early behavioral and/or pharmacological intervention. Supplemental Material https://doi.org/10.23641/asha.12771113.

Distinct performance profiles on the Brixton test in frontotemporal dementia

The Brixton Spatial Anticipation Test is a well-established test of executive function that evaluates the capacity to abstract, follow, and switch rules. There has been remarkably little systematic analysis of Brixton test performance in the prototypical neurodegenerative disorder of the frontal lobes: behavioural variant frontotemporal dementia (bvFTD) or evaluation of the test's ability to distinguish frontal from temporal lobe degenerative disease. We carried out a quantitative and qualitative analysis of Brixton performance in 76 patients with bvFTD and 34 with semantic dementia (SD) associated with temporal lobe degeneration. The groups were matched for demographic variables and illness duration. The bvFTD group performed significantly more poorly (U = 348, p < .0001, r = .58), 53% of patients scoring in the poor-impaired range compared with 6% of SD patients. Whereas bvFTD patients showed problems in rule acquisition and switching, SD patients did not, despite their impaired conceptual knowledge. Error analysis revealed more frequent perseverative errors in bvFTD, particularly responses unconnected to the stimulus, as well as random responses. Stimulus-bound errors were rare. Within the bvFTD group, there was variation in performance profile, which could not be explained by demographic, neurological, or genetic factors. The findings demonstrate sensitivity and specificity of the Brixton test in identifying frontal lobe degenerative disease and highlight the clinical value of qualitative analysis of test performance. From a theoretical perspective, the findings provide evidence that semantic knowledge and the capacity to acquire rules are dissociable. Moreover, they exemplify the separable functional contributions to executive performance.

Clinical Features of Late-onset Semantic Dementia

BACKGROUND

Semantic dementia (SD) is characterized by progressive semantic anomia extending to a multimodal loss of semantic knowledge. Although often considered an early-onset dementia, SD also occurs in later life, when it may be misdiagnosed as Alzheimer disease (AD).

OBJECTIVE

To evaluate late-onset SD in comparison to early-onset SD and to AD.

METHODS

We identified 74 individuals with SD and then compared those with late-onset SD (≥65 years of age) to those with early-onset SD (<65) on demographic and clinical features. We also compared a subgroup of 23 of the late-onset SD individuals with an equal number of individuals with clinically probable AD.

RESULTS

Twenty-six (35.1%) of the SD individuals were late onset, and 48 (64.9%) were early onset. There were no differences between the two groups on clinical measures, although greater asymmetry of temporal involvement trended to significance in the late-onset SD group. Compared to the 23 AD individuals, the subgroup of 23 late-onset SD individuals had worse performance on confrontational naming, irregular word reading, and face recognition; however, this subgroup displayed better verbal delayed recall and constructions. The late-onset SD individuals also experienced early personality changes at a time when most individuals with AD had not yet developed behavioral changes.

CONCLUSIONS

Approximately one-third of SD individuals may be late onset, and the differentiation of late-onset SD from AD can lead to better disease management, education, and prognosis. SD may be distinguished by screening for disproportionate changes in reading, face recognition, and personality.

Regional and hemispheric susceptibility of the temporal lobe to FTLD-TDP type C pathology

Post-mortem studies show that focal anterior temporal lobe (ATL) neurodegeneration is most often caused by frontotemporal lobar degeneration TDP-43 type C pathology. Clinically, these patients are described with different terms, such as semantic variant primary progressive aphasia (svPPA), semantic dementia (SD), or right temporal variant frontotemporal dementia (FTD) depending on whether the predominant symptoms affect language, semantic knowledge for object or people, or socio-emotional behaviors. ATL atrophy presents with various degrees of lateralization, with right-sided cases considered rarer even though estimation of their prevalence is hampered by the paucity of studies on well-characterized, pathology-proven cohorts. Moreover, it is not clear whether left and right variants show a similar distribution of atrophy within the ATL cross-sectionally and longitudinally. Here we study the largest cohort to-date of pathology-proven TDP-43-C cases diagnosed during life as svPPA, SD or right temporal variant FTD. We analyzed clinical, cognitive, and neuroimaging data from 30 cases, a subset of which was followed longitudinally. Guided by recent structural and functional parcellation studies, we constructed four bilateral ATL regions of interest (ROIs). The computation of an atrophy lateralization index allowed the comparison of atrophy patterns between the two hemispheres. This led to an automatic, imaging-based classification of the cases as left-predominant or right-predominant. We then compared the two groups in terms of regional atrophy patterns within the ATL ROIs (cross-sectionally) and atrophy progression (longitudinally). Results showed that 40% of pathology proven cases of TDP-43-C diagnosed with a temporal variant presented with right-lateralized atrophy. Moreover, the findings of our ATL ROI analysis indicated that, irrespective of atrophy lateralization, atrophy distribution within both ATLs follows a medial-to-lateral gradient. Finally, in both left and right cases, atrophy appeared to progress to the contralateral ATL, and from the anterior temporal pole to posterior temporal and orbitofrontal regions. Taken together, our findings indicate that incipient right predominant ATL atrophy is common in TDP-43-C pathology, and that distribution of damage within the ATLs appears to be the same in left- and right- sided variants. Thus, regardless of differences in clinical phenotype and atrophy lateralization, both temporal variants of FTD should be viewed as a spectrum presentation of the same disease.

Longitudinal flortaucipir ([18F]AV-1451) PET uptake in semantic dementia

To assess volume loss and flortaucipir uptake in patients with semantic dementia (SD) over time. Eight SD patients (3 female) underwent clinical evaluations, flortaucipir positron emission tomography, and brain magnetic resonance imaging at 2 visits. Voxel-level comparisons of magnetic resonance imaging gray and white matter volume loss and flortaucipir positron emission tomography uptake were performed in SPM12, comparing SD patients to controls at each visit. T-tests on difference images and paired t-tests of flortaucipir uptake were also performed. At the voxel level, SD patients showed asymmetric, bilateral gray volume loss in the temporal lobes, which, via visual inspection, extended posteriorly at follow-up. White matter loss and flortaucipir uptake were noted in SD patients in the left temporal lobe only, which appeared to extend posteriorly, without involvement of the right hemisphere at follow-up. Longitudinal analyses did not support significant changes in flortaucipir uptake between visits. The biological mechanisms of flortaucipir signal in suspected underlying TAR-DNA binding protein 43 pathology are unknown. A 1-year interval is not sufficient time to demonstrate significant longitudinal flortaucipir uptake changes in SD.

Distinct Interplay Between Atrophy and Hypometabolism in Alzheimer's Versus Semantic Dementia

Multimodal neuroimaging analyses offer additional information beyond that provided by each neuroimaging modality. Thus, direct comparisons and correlations between neuroimaging modalities allow revealing disease-specific topographic relationships. Here, we compared the topographic discrepancies between atrophy and hypometabolism in two neurodegenerative diseases characterized by distinct pathological processes, namely Alzheimer's disease (AD) versus semantic dementia (SD), to unravel their specific influence on local and global brain structure-function relationships. We found that intermodality topographic discrepancies clearly distinguished the two patient groups: AD showed marked discrepancies between both alterations, with greater hypometabolism than atrophy in large posterior associative neocortical regions, while SD showed more topographic consistency between atrophy and hypometabolism across brain regions. These findings likely reflect the multiple pathologies versus the relatively unitary pathological process underlying AD versus SD respectively. Our results evidence that multimodal neuroimaging-derived indexes can provide clinically relevant information to discriminate the two diseases, and potentially reveal distinct neuropathological processes.

Multimodal semantic battery to monitor progressive loss of concepts in the semantic variant of primary progressive aphasia (svPPA): an innovative proposal

Semantic variant primary progressive aphasia (svPPA) is a rare neurodegenerative disease characterized by a progressive loss of semantic knowledge. Patients with svPPA show anomia, impaired word comprehension, poor object recognition, and difficulties in retrieving semantic information. svPPA is also a unique "natural" model that allows clinicians and cognitive neuroscientists to study the organization of semantic memory because only semantic knowledge is affected in the initial period of the disease, with relative sparing of other cognitive domains. In the clinical practice, semantic memory is commonly tested only with verbal tests. The aim of the present study was to preliminary test a new Multimodal Semantic Battery developed in our laboratory, which comprised 11 subtests designed to assess the semantic knowledge of multiple items via all input modalities. The battery was administered twice, over four years, to a patient diagnosed with svPPA. We found that when extensively tested with multiple tests, in some cases, he was still able to recall semantic features of the items that otherwise would not have emerged with standard semantic tests. These results are discussed for the clinical practice: monitoring semantic memory through all modalities in a practical and reliable way could be useful for both clinicians and experimental researchers to better investigate the breakdown of semantic knowledge.

A unified neurocognitive model of semantics language social behaviour and face recognition in semantic dementia

The anterior temporal lobes (ATL) have become a key brain region of interest in cognitive neuroscience founded upon neuropsychological investigations of semantic dementia (SD). The purposes of this investigation are to generate a single unified model that captures the known cognitive-behavioural variations in SD and map these to the patients' distribution of frontotemporal atrophy. Here we show that the degree of generalised semantic impairment is related to the patients' total, bilateral ATL atrophy. Verbal production ability is related to total ATL atrophy as well as to the balance of left > right ATL atrophy. Apathy is found to relate positively to the degree of orbitofrontal atrophy. Disinhibition is related to right ATL and orbitofrontal atrophy, and face recognition to right ATL volumes. Rather than positing mutually-exclusive sub-categories, the data-driven model repositions semantics, language, social behaviour and face recognition into a continuous frontotemporal neurocognitive space.

Anterior temporal lobe is necessary for efficient lateralised processing of spoken word identity

In the healthy human brain, the processing of language is strongly lateralised, usually to the left hemisphere, while the processing of complex non-linguistic sounds recruits brain regions bilaterally. Here we asked whether the anterior temporal lobes, strongly implicated in semantic processing, are critical to this special treatment of spoken words. Nine patients with semantic dementia (SD) and fourteen age-matched controls underwent magnetoencephalography and structural MRI. Voxel based morphometry demonstrated the stereotypical pattern of SD: severe grey matter loss restricted to the anterior temporal lobes, with the left side more affected. During magnetoencephalography, participants listened to word sets in which identity and meaning were ambiguous until word completion, for example PLAYED versus PLATE. Whereas left-hemispheric responses were similar across groups, patients demonstrated increased right hemisphere activity 174-294 msec after stimulus disambiguation. Source reconstructions confirmed recruitment of right-sided analogues of language regions in SD: atrophy of anterior temporal lobes was associated with increased activity in right temporal pole, middle temporal gyrus, inferior frontal gyrus and supramarginal gyrus. Overall, the results indicate that anterior temporal lobes are necessary for normal and efficient lateralised processing of word identity by the language network.

Classification of primary progressive aphasia: challenges and complexities

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