Social cognitive deficits and their neural correlates in progressive supranuclear palsy

Hearts and Minds: Emotion Recognition and Mentalizing in Parkinson's Disease and Progressive Supranuclear Palsy

OBJECTIVE

There are scarce data comparing Parkinson's disease (PD) and Progressive Supranuclear Palsy (PSP) in social cognition (SC). We aimed to compare patients with PSP and PD in SC.

METHODS

We included three groups: PD (n = 18), PSP (n = 20) and controls (n = 23). Participants underwent neuropsychological exams, including the mini-version of the Social and Emotional Assessment, which is composed of the facial emotion recognition test (FERT) and the modified faux-pas (mFP) test, which assesses Theory of Mind (ToM).

RESULTS

Patients with PD scored lower than controls in the FERT, but not in the mFP test. Patients with PSP performed worse than controls in both the mFP and FERT. PD and PSP groups did not differ in the FERT, but PSP performed worse than PD in the mFP test. The mFP test distinguished PSP from PD with 89% accuracy.

CONCLUSION

The assessment of ToM may contribute to the differentiation between PD and PSP.

Impulse Control Disorders in Parkinson's Disease and Atypical Parkinsonian Syndromes-Is There a Difference?

BACKGROUND AND OBJECTIVES

Impulse control disorders (ICDs) are characterized by potentially harmful actions resulting from disturbances in the self-control of emotions and behavior. ICDs include disorders such as gambling, hypersexuality, binge eating, and compulsive buying. ICDs are known non-motor symptoms in Parkinson's disease (PD) and are associated primarily with the use of dopaminergic treatment (DRT) and especially dopamine agonists (DA). However, in atypical parkinsonism (APS), such as progressive supranuclear palsy (PSP) or multiple system atrophy (MSA), there are only single case reports of ICDs without attempts to determine the risk factors for their occurrence. Moreover, numerous reports in the literature indicate increased impulsivity in PSP. Our study aimed to determine the frequency of individual ICDs in APS compared to PD and identify potential factors for developing ICDs in APS.

MATERIALS AND METHODS

Our prospective study included 185 patients with PD and 35 with APS (27 patients with PSP and 9 with MSA) hospitalized between 2020 and 2023 at the Neurological Department of University Central Hospital in Katowice. Each patient was examined using the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease (QUIP) to assess ICDs. Additionally, other scales were used to assess the advancement of the disease, the severity of depression, and cognitive impairment. Information on age, gender, age of onset, disease duration, and treatment used were collected from medical records and patient interviews.

RESULTS

ICDs were detected in 23.39% of patients with PD (including binge eating in 11.54%, compulsive buying in 10.44%, hypersexuality in 8.79%, and pathological gambling in 4.40%), in one patient with MSA (hypersexuality and pathological gambling), and in 18.52% of patients with PSP (binge eating in 3.70%, compulsive buying in 7.41%, and hypersexuality in 11.11%). We found no differences in the frequency of ICDs between individual diseases (p = 0.4696). We confirmed that the use of higher doses of DA and L-dopa in patients with PD, as well as a longer disease duration and the presence of motor complications, were associated with a higher incidence of ICDs. However, we did not find any treatment effect on the incidence of ICDs in APS.

CONCLUSIONS

ICDs are common and occur with a similar frequency in PD and APS. Well-described risk factors for ICDs in PD, such as the use of DRT or longer disease duration, are not fully reflected in the risk factors for ICDs in APS. This applies especially to PSP, which, unlike PD and MSA, is a tauopathy in which, in addition to the use of DRT, other mechanisms related to the disease, such as disorders in neuronal loops and neurotransmitter deficits, may influence the development of ICDs. Further prospective multicenter studies recruiting larger groups of patients are needed to fully determine the risk factors and mechanisms of ICD development in APS.

Grey-matter correlates of empathy in 4-Repeat Tauopathies

Loss of empathy is an early and central symptom of frontotemporal lobar degeneration spectrum diseases. We aimed to investigate the topographical distribution of morphometric brain changes associated with empathy in Progressive Supranuclear Palsy (PSP) and Corticobasal Syndrome (CBS) patients. Twenty-seven participants with CBS and 31 with PSP were evaluated using Interpersonal Reactivity Index scales in correlation with gray matter atrophy using a voxel-based morphometry approach. Lower levels of empathy were associated with an increased atrophy in fronto-temporal cortical structures. At subcortical level, empathy scores were positively correlated with gray matter volume in the amygdala, hippocampus and the cerebellum. These findings allow to extend the traditional cortico-centric view of cognitive empathy to the cerebellar regions in patients with neurodegenerative disorders and suggest that the cerebellum may play a more prominent role in social cognition than previously appreciated.

Pathomechanisms of cognitive impairment in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a neurodegenerative disorder characterized by early postural instability and falls, oculomotor dysfunction (vertical supranuclear gaze palsy), parkinsonism with poor response to levodopa, pseudobulbar palsy, and cognitive impairment. This four-repeat tauopathy is morphologically featured by accumulation of tau protein in neurons and glia causing neuronal loss and gliosis in the extrapyramidal system associated with cortical atrophy and white matter lesions. Cognitive impairment being frequent in PSP and more severe than in multiple system atrophy and Parkinson disease, is dominated by executive dysfunction, with milder difficulties in memory, and visuo-spatial and naming dysfunctions. Showing longitudinal decline, it has been related to a variety of pathogenic mechanisms associated with the underlying neurodegenerative process, such as involvement of cholinergic and muscarinergic dysfunctions, and striking tau pathology in frontal and temporal cortical regions associated with reduced synaptic density. Altered striatofrontal, fronto-cerebellar, parahippocampal, and multiple subcortical structures, as well as widespread white matter lesions causing extensive connectivity disruptions in cortico-subcortical and cortico-brainstem connections, support the concept that PSP is a brain network disruption disorder. The pathophysiology and pathogenesis of cognitive impairment in PSP, as in other degenerative movement disorders, are complex and deserve further elucidation as a basis for adequate treatment to improve the quality of life of patients with this fatal disease.

Development of the Basel Version of the Awareness of Social Inference Test - Theory of Mind (BASIT-ToM) in healthy adults

Impairments of Theory of Mind (ToM) abilities occur in a wide range of brain disorders. Therefore, reliable and ecologically valid examination of these abilities is a crucial part of any comprehensive neuropsychological assessment. An established and ecologically valid, English-language test identifying deficits in ToM abilities is "The Awareness of Social Inference Test - Social Inference Minimal (TASIT-SIM)". However, no comparable German-language ToM test currently exists. In this study, we aimed to develop the first German-language adaption of TASIT-SIM in healthy adults. We selected 13 scenes [four scenes per message type (i.e., honesty, simple sarcasm, paradoxical sarcasm) and one practice scene] out of the 30 TASIT-SIM scenes. In collaboration with a film institute, we filmed each scene at three different intensities. These intensity version scenes were then administered to 240 healthy adults, equally distributed in sex and age, ranging from 35 to 92 years. By applying Rasch analysis, we selected intensity versions that showed neither floor nor ceiling effects in the majority of ToM questions in participants whose ToM abilities were in the medium range. In conclusion, we have developed the first German-language adaption of TASIT-SIM, i.e., the "Basel Version of the Awareness of Social Inference Test - Theory of Mind (BASIT-ToM)". The BASIT-ToM incorporates the strengths of TASIT-SIM, while overcoming its limitations such as inconsistencies in cinematic realization and ceiling effects in healthy participants. Next, the BASIT-ToM needs to be validated in healthy people and clinical populations.

The Lived Experiences of People with Progressive Supranuclear Palsy and Their Caregivers

INTRODUCTION

Progressive supranuclear palsy (PSP) is a neurodegenerative disorder initially characterised by disturbances in gait, balance and posture, with death occurring after several years of progressive physical and cognitive decline. This, along with a low index of suspicion, a high degree of diagnostic uncertainty and no approved treatment options, greatly impacts the lives of patients and caregivers. This research was conducted to (i) gain insight into the clinical and emotional journey of patients with PSP, (ii) assess experiences and perspectives, (iii) understand disease impact and (iv) identify key challenges and unmet needs.

METHODS

A literature search and qualitative interviews with six PSP experts were conducted to map the clinical pathway and identify breakpoints. The pathway was validated by key opinion leaders in seven countries. Qualitative research was conducted over 6 months in seven countries with PSP stakeholders (N = 112) to explore the emotional journey. The approach included self-ethnography, 60-min telephone interviews and the completion of 7-day smartphone diaries.

RESULTS

The current PSP clinical journey can take many different pathways, with patients cycling through the healthcare system before a correct referral is made and a possible/probable diagnosis received. Breakpoints contribute to delays in accessing appropriate clinical care, a high degree of diagnostic divergence and suboptimal management of the disease. The emotional journey is dominated by negative feelings, although some moments of positivity were noted. The research highlighted a lack of disease understanding amongst all stakeholders and a lack of support for patients/caregivers. The authors make a number of recommendations for care improvements, including longer consultation times, closer collaboration among healthcare professionals and patient organisations, and more varied support and information for patients/caregivers.

CONCLUSION

This work represents a major collaborative effort to understand the lived experience of PSP. The research illustrates that a coordinated effort from all stakeholders is required to address ongoing needs and challenges within PSP.

Clinical Spectrum of Tauopathies

Tauopathies are both clinical and pathological heterogeneous disorders characterized by neuronal and/or glial accumulation of misfolded tau protein. It is now well understood that every pathologic tauopathy may present with various clinical phenotypes based on the primary site of involvement and the spread and distribution of the pathology in the nervous system making clinicopathological correlation more and more challenging. The clinical spectrum of tauopathies includes syndromes with a strong association with an underlying primary tauopathy, including Richardson syndrome (RS), corticobasal syndrome (CBS), non-fluent agrammatic primary progressive aphasia (nfaPPA)/apraxia of speech, pure akinesia with gait freezing (PAGF), and behavioral variant frontotemporal dementia (bvFTD), or weak association with an underlying primary tauopathy, including Parkinsonian syndrome, late-onset cerebellar ataxia, primary lateral sclerosis, semantic variant PPA (svPPA), and amnestic syndrome. Here, we discuss clinical syndromes associated with various primary tauopathies and their distinguishing clinical features and new biomarkers becoming available to improve in vivo diagnosis. Although the typical phenotypic clinical presentations lead us to suspect specific underlying pathologies, it is still challenging to differentiate pathology accurately based on clinical findings due to large phenotypic overlaps. Larger pathology-confirmed studies to validate the use of different biomarkers and prospective longitudinal cohorts evaluating detailed clinical, biofluid, and imaging protocols in subjects presenting with heterogenous phenotypes reflecting a variety of suspected underlying pathologies are fundamental for a better understanding of the clinicopathological correlations.

Resting state functional brain networks associated with emotion processing in frontotemporal lobar degeneration

This study investigated the relationship between emotion processing and resting-state functional connectivity (rs-FC) of the brain networks in frontotemporal lobar degeneration (FTLD). Eighty FTLD patients (including cases with behavioral variant of frontotemporal dementia, primary progressive aphasia, progressive supranuclear palsy syndrome, motor neuron disease) and 65 healthy controls underwent rs-functional MRI. Emotion processing was tested using the Comprehensive Affect Testing System (CATS). In patients and controls, correlations were investigated between each emotion construct and rs-FC changes within critical networks. Mean rs-FC of the clusters significantly associated with CATS scoring were compared among FTLD groups. FTLD patients had pathological CATS scores compared with controls. In controls, increased rs-FC of the cerebellar and visuo-associative networks correlated with better scores in emotion-matching and discrimination tasks, respectively; while decreased rs-FC of the visuo-spatial network was related with better performance in the affect-matching and naming. In FTLD, the associations between rs-FC and CATS scores involved more brain regions, such as orbitofrontal and middle frontal gyri within anterior networks (i.e., salience and default-mode), parietal and somatosensory regions within visuo-spatial and sensorimotor networks, caudate and thalamus within basal-ganglia network. Rs-FC changes associated with CATS were similar among all FTLD groups. In FTLD compared to controls, the pattern of rs-FC associated with emotional processing involves a larger number of brain regions, likely due to functional specificity loss and compensatory attempts. These associations were similar across all FTLD groups, suggesting a common physiopathological mechanism of emotion processing breakdown, regardless the clinical presentation and pattern of atrophy.

Measuring social cognition in frontotemporal lobar degeneration: a clinical approach

Alterations in social cognition, a broad term indicating our ability to understand others and adapt our behavior accordingly, have been the focus of growing attention in the past years. Some neurological conditions, such as those belonging to the frontotemporal lobar degeneration (FTLD) spectrum, are associated to varying degrees with social cognition deficits, encompassing problems with theory of mind (ToM), empathy, perception of social stimuli, and social behavior. In this review, we outline a clinical framework for the evaluation of social cognition and discuss its role in the assessment of patients affected by a range of FTLD conditions.

Social cognition in the FTLD spectrum: evidence from MRI

Over the past few years, there has been great interest in social cognition, a wide term referring to the human ability of understanding others' emotions, thoughts, and intentions, to empathize with them and to behave accordingly. While there is no agreement on the classification of social cognitive processes, they can broadly be categorized as consisting of theory of mind, empathy, social perception, and social behavior. The study of social cognition and its relative deficits is increasingly assuming clinical relevance. However, the clinical and neuroanatomical correlates of social cognitive alterations in neurodegenerative conditions, such as those belonging to the frontotemporal lobar (FTLD) spectrum, are not fully established. In this review, we describe the current understanding of social cognition impairments in different FTLD conditions with respect to MRI.

Salience driven attention is pivotal to understanding others' intentions

Interpreting others' beliefs, desires and intentions is known as "theory of mind" (ToM), and is often evaluated using simplified measurement tools, which may not correctly reflect the brain circuits that are required for real-life ToM functioning. We aimed to identify the brain structures necessary to correctly infer intentions from realistic scenarios by administering The Awareness of Social Inference Test, Enriched subtest to 47 patients with behavioural variant frontotemporal dementia, 24 patients with progressive supranuclear palsy syndrome, 31 patients with Alzheimer's syndrome, and 77 older healthy controls. Neuroimaging data was analyzed using voxel based morphometry, and participants' understanding of intentions was correlated with voxel-wise and region-of interest data. We found that structural integrity of the cinguloinsular cortex in the salience network (SN) was more pivotal for accurate ToM than previously described, emphasizing the importance of the SN for selectively recognizing and attending to social cues during ToM inferences.

Abnormal structural connectivity in progressive supranuclear palsy-Richardson syndrome

OBJECTIVES

Progressive supranuclear palsy-Richardson syndrome (PSP-RS) is characterized by symmetrical parkinsonism with postural instability and frontal dysfunction. This study aims to use the whole brain structural connectome (SC) to gain insights into the underlying disconnectivity which may be implicated in the clinical features of PSP-RS.

METHODS

Sixteen patients of PSP-RS and 12 healthy controls were recruited. Disease severity was quantified using PSP rating scale (PSPRS), and mini-mental scale was applied to evaluate cognition. Thirty-two direction diffusion MRIs were acquired and used to compute the structural connectome of the whole brain using deterministic fiber tracking. Group analyses were performed at the edge-wise, nodal, and global levels. Age and gender were used as nuisance covariates for all the subsequent analyses, and FDR correction was applied.

RESULTS

Network-based statistics revealed a 34-edge network with significantly abnormal edge-wise connectivity in the patient group. Of these, 25 edges were cortical connections, of which 68% were frontal connections. Abnormal deep gray matter connections were predominantly comprised of connections between structures of the basal ganglia. The characteristic path length of the SC was lower in PSP-RS, and nodal analysis revealed abnormal degree, strength, local efficiency, betweenness centrality, and participation coefficient in several nodes.

CONCLUSIONS

Significant alterations in the structural connectivity of the whole brain connectome were observed in PSP-RS. The higher degree of abnormality observed in nodes belonging to the frontal lobe and basal ganglia substantiates the predominant frontal dysfunction and parkinsonism observed in PSP-RS. The findings of this study support the concept that PSP-RS may be a network-based disorder.

GABAergic cortical network physiology in frontotemporal lobar degeneration

The clinical syndromes caused by frontotemporal lobar degeneration are heterogeneous, including the behavioural variant frontotemporal dementia (bvFTD) and progressive supranuclear palsy. Although pathologically distinct, they share many behavioural, cognitive and physiological features, which may in part arise from common deficits of major neurotransmitters such as γ-aminobutyric acid (GABA). Here, we quantify the GABAergic impairment and its restoration with dynamic causal modelling of a double-blind placebo-controlled crossover pharmaco-magnetoencephalography study. We analysed 17 patients with bvFTD, 15 patients with progressive supranuclear palsy, and 20 healthy age- and gender-matched controls. In addition to neuropsychological assessment and structural MRI, participants undertook two magnetoencephalography sessions using a roving auditory oddball paradigm: once on placebo and once on 10 mg of the oral GABA reuptake inhibitor tiagabine. A subgroup underwent ultrahigh-field magnetic resonance spectroscopy measurement of GABA concentration, which was reduced among patients. We identified deficits in frontotemporal processing using conductance-based biophysical models of local and global neuronal networks. The clinical relevance of this physiological deficit is indicated by the correlation between top-down connectivity from frontal to temporal cortex and clinical measures of cognitive and behavioural change. A critical validation of the biophysical modelling approach was evidence from parametric empirical Bayes analysis that GABA levels in patients, measured by spectroscopy, were related to posterior estimates of patients’ GABAergic synaptic connectivity. Further evidence for the role of GABA in frontotemporal lobar degeneration came from confirmation that the effects of tiagabine on local circuits depended not only on participant group, but also on individual baseline GABA levels. Specifically, the phasic inhibition of deep cortico-cortical pyramidal neurons following tiagabine, but not placebo, was a function of GABA concentration. The study provides proof-of-concept for the potential of dynamic causal modelling to elucidate mechanisms of human neurodegenerative disease, and explains the variation in response to candidate therapies among patients. The laminar- and neurotransmitter-specific features of the modelling framework, can be used to study other treatment approaches and disorders. In the context of frontotemporal lobar degeneration, we suggest that neurophysiological restoration in selected patients, by targeting neurotransmitter deficits, could be used to bridge between clinical and preclinical models of disease, and inform the personalized selection of drugs and stratification of patients for future clinical trials.

Phonemic fluency quantity and quality: Comparing patients with PSP, Parkinson's disease and focal frontal and subcortical lesions

Progressive supranuclear palsy (PSP) can be difficult to distinguish from Parkinson's disease (PD), but has a much graver prognosis. PSP is characterised severely reduced output on measures of phonemic fluency, suggesting that it may be a specific marker of PSP. However, reduced phonemic fluency has also been noted in PD, and very few studies have actually compared phonemic fluency in PSP and PD. Although anecdotal reports suggest that phonemic fluency output in PSP may have specific characteristics, with more low-frequency words and perseverative errors, no study to date has formally explored this. Further investigation into phonemic fluency output and its cognitive and neuroanatomical correlates is now critical for improving our understanding of the verbal fluency in PSP. In this study, we compared phonemic fluency characteristics (including quantity, frequency and error rates) in patients with PSP, PD and focal frontal or subcortical lesions, and age- and education-matched healthy controls. We then compared these characteristics with performance on extensive neuropsychological testing. We found that PSP patients generated significantly fewer words than patients with PD and patients with right frontal focal lesions, and healthy controls. Phonemic fluency was also significantly reduced in patients with left frontal and subcortical focal lesions. However, there were no significant group differences in word frequency or error rates. Phonemic fluency was best predicted by performance on the Vocabulary and Hayling neuropsychological tests. We argue that these findings provide important evidence that reduced phonemic fluency is a hallmark of PSP and argue that the specificity of this impairment betrays an underlying impairment in energization, reflecting dysfunction of left frontal and subcortical networks.

Spatial attention and spatial short term memory in PSP and Parkinson's disease

Progressive Supranuclear Palsy (PSP) is a neurodegenerative disorder characterised by deterioration in motor, oculomotor and cognitive function. A key clinical feature of PSP is the progressive paralysis of eye movements, most notably for vertical saccades. These oculomotor signs can be subtle, however, and PSP is often misdiagnosed as Parkinson's disease (PD), in its early stages. Although some of the clinical features of PD and PSP overlap, they are distinct disorders with differing underlying pathological processes, responses to treatment and prognoses. One key difference lies in the effects the diseases have on cognition. The oculomotor system is tightly linked to cognitive processes such as spatial attention and spatial short-term memory (sSTM), and previous studies have suggested that PSP and PD experience different deficits in these domains. We therefore hypothesised that people with PSP (N = 15) would experience problems with attention (assessed with feature and conjunction visual search tasks) and sSTM (assessed with the Corsi blocks task) compared to people with PD (N = 16) and Age Matched Controls (N = 15). As predicted, feature and conjunction search were sgnificantly slower in the PSP group compared to the other groups, and this deficit was significantly worse for feature compared to conjunction search. The PD group did not differ from AMC on feature search but were significantly impaired on the conjunction search. The PSP group also had a pronounced vertical sSTM impairment that was not present in PD or AMC groups. It is argued that PSP is associated with specific impairment of visuospatial cognition which is caused by degeneration of the oculomotor structures that support exogenous spatial attention, consistent with oculomotor theories of spatial attention and memory.

Characteristics and progression of patients with frontotemporal dementia in a regional memory clinic network

Background

Due to heterogeneous clinical presentation, difficult differential diagnosis with Alzheimer’s disease (AD) and psychiatric disorders, and evolving clinical criteria, the epidemiology and natural history of frontotemporal lobar degeneration (FTD) remain elusive. In order to better characterize FTD patients, we relied on the database of a regional memory clinic network with standardized diagnostic procedures and chose AD patients as a comparator.

Methods

Patients that were first referred to our network between January 2010 and December 2016 and whose last clinical diagnosis was degenerative or vascular dementia were included. Comparisons were conducted between FTD and AD as well as between the different FTD syndromes, divided into language variants (lvFTD), behavioral variant (bvFTD), and FTD with primarily motor symptoms (mFTD). Cognitive progression was estimated with the yearly decline in Mini Mental State Examination (MMSE).

Results

Among the patients that were referred to our network in the 6-year time span, 690 were ultimately diagnosed with FTD and 18,831 with AD. Patients with FTD syndromes represented 2.6% of all-cause dementias. The age-standardized incidence was 2.90 per 100,000 person-year and incidence peaked between 75 and 79 years. Compared to AD, patients with FTD syndromes had a longer referral delay and delay to diagnosis. Patients with FTD syndromes had a higher MMSE score than AD at first referral while their progression was similar. mFTD patients had the shortest survival while survival in bvFTD, lvFTD, and AD did not significantly differ. FTD patients, especially those with the behavioral variant, received more antidepressants, anxiolytics, and antipsychotics than AD patients.

Conclusions

FTD syndromes differ with AD in characteristics at baseline, progression rate, and treatment. Despite a broad use of the new diagnostic criteria in an organized memory clinic network, FTD syndromes are longer to diagnose and account for a low proportion of dementia cases, suggesting persistent underdiagnosis. Congruent with recent publications, the late peak of incidence warns against considering FTD as being exclusively a young-onset dementia.

Neuroinflammation and Tau Colocalize in vivo in Progressive Supranuclear Palsy

OBJECTIVE

We examined the relationship between tau pathology and neuroinflammation using [11 C]PK11195 and [18 F]AV-1451 PET in 17 patients with progressive supranuclear palsy (PSP) Richardson's syndrome. We tested the hypothesis that neuroinflammation and tau protein aggregation colocalize macroscopically, and correlate with clinical severity.

METHODS

Nondisplaceable binding potential (BPND ) for each ligand was quantified in 83 regions of interest (ROIs). The [11 C]PK11195 and [18 F]AV-1451 BPND values were correlated across all regions. The spatial distributions of [11 C]PK11195 and [18 F]AV-1451 binding were determined by principal component analyses (PCAs), and the loading of each spatial component compared against the patients' clinical severity (using the PSP rating scale).

RESULTS

Regional [11 C]PK11195 and [18 F]AV-1451 binding were positively correlated (R = 0.577, p < 0.0001). The PCA identified 4 components for each ligand, reflecting the relative expression of tau pathology or neuroinflammation in distinct groups of brain regions. Positive associations between [11 C]PK11195 and [18 F]AV-1451 components' loadings were found in both subcortical (R = 0.769, p < 0.0001) and cortical regions (R = 0.836, p < 0.0001). There were positive correlations between clinical severity and both subcortical tau pathology (R = 0.667, p = 0.003) and neuroinflammation (R = 0.788, p < 0.001).

INTERPRETATION

We show that tau pathology and neuroinflammation colocalize in PSP, and that individual differences in subcortical tau pathology and neuroinflammation are linked to clinical severity. Although longitudinal studies are needed to determine causal associations between these molecular pathologies, we suggest that the combination of tau- and immune-oriented strategies may be useful for effective disease-modifying treatments in PSP. ANN NEUROL 2020;88:1194-1204.

Salience Network Atrophy Links Neuron Type-Specific Pathobiology to Loss of Empathy in Frontotemporal Dementia

Each neurodegenerative syndrome reflects a stereotyped pattern of cellular, regional, and large-scale brain network degeneration. In behavioral variant of frontotemporal dementia (bvFTD), a disorder of social-emotional function, von Economo neurons (VENs), and fork cells are among the initial neuronal targets. These large layer 5 projection neurons are concentrated in the anterior cingulate and frontoinsular (FI) cortices, regions that anchor the salience network, a large-scale system linked to social-emotional function. Here, we studied patients with bvFTD, amyotrophic lateral sclerosis (ALS), or both, given that these syndromes share common pathobiological and genetic factors. Our goal was to determine how neuron type-specific TAR DNA-binding protein of 43 kDa (TDP-43) pathobiology relates to atrophy in specific brain structures and to loss of emotional empathy, a cardinal feature of bvFTD. We combined questionnaire-based empathy assessments, in vivo structural MR imaging, and quantitative histopathological data from 16 patients across the bvFTD/ALS spectrum. We show that TDP-43 pathobiology within right FI VENs and fork cells is associated with salience network atrophy spanning insular, medial frontal, and thalamic regions. Gray matter degeneration within these structures mediated loss of emotional empathy, suggesting a chain of influence linking the cellular, regional/network, and behavioral levels in producing signature bvFTD clinical features.

Comparing two facets of emotion perception across multiple neurodegenerative diseases

Deficits in emotion perception (the ability to infer others' emotions accurately) can occur as a result of neurodegeneration. It remains unclear how different neurodegenerative diseases affect different forms of emotion perception. The present study compares performance on a dynamic tracking task of emotion perception (where participants track the changing valence of a film character's emotions) with performance on an emotion category labeling task (where participants label specific emotions portrayed by film characters) across seven diagnostic groups (N = 178) including Alzheimer's disease (AD), behavioral variant frontotemporal dementia (bvFTD), semantic variant primary progressive aphasia (svPPA), non-fluent variant primary progressive aphasia (nfvPPA), progressive supranuclear palsy (PSP), corticobasal syndrome and healthy controls. Consistent with hypotheses, compared to controls, the bvFTD group was impaired on both tasks. The svPPA group was impaired on the emotion labeling task, whereas the nfvPPA, PSP and AD groups were impaired on the dynamic tracking task. Smaller volumes in bilateral frontal and left insular regions were associated with worse labeling, whereas smaller volumes in bilateral medial frontal, temporal and right insular regions were associated with worse tracking. Findings suggest labeling and tracking facets of emotion perception are differentially affected across neurodegenerative diseases due to their unique neuroanatomical correlates.

Redefining the multidimensional clinical phenotypes of frontotemporal lobar degeneration syndromes

The syndromes caused by frontotemporal lobar degeneration have highly heterogeneous and overlapping clinical features. There has been great progress in the refinement of clinical diagnostic criteria in the past decade, but we propose that a better understanding of aetiology, pathophysiology and symptomatic treatments can arise from a transdiagnostic approach to clinical phenotype and brain morphometry. In a cross-sectional epidemiological study, we examined 310 patients with a syndrome likely to be caused by frontotemporal lobar degeneration, including behavioural variant frontotemporal dementia, non-fluent, and semantic variants of primary progressive aphasia (PPA), progressive supranuclear palsy and corticobasal syndrome. We included patients with logopenic PPA and those who met criteria for PPA but not a specific subtype. To date, 49 patients have a neuropathological diagnosis. A principal component analysis identified symptom dimensions that broadly recapitulated the core features of the main clinical syndromes. However, the subject-specific scores on these dimensions showed considerable overlap across the diagnostic groups. Sixty-two per cent of participants had phenotypic features that met the diagnostic criteria for more than one syndrome. Behavioural disturbance was prevalent in all groups. Forty-four per cent of patients with corticobasal syndrome had progressive supranuclear palsy-like features and 30% of patients with progressive supranuclear palsy had corticobasal syndrome-like features. Many patients with progressive supranuclear palsy and corticobasal syndrome had language impairments consistent with non-fluent variant PPA while patients with behavioural variant frontotemporal dementia often had semantic impairments. Using multivariate source-based morphometry on a subset of patients (n = 133), we identified patterns of covarying brain atrophy that were represented across the diagnostic groups. Canonical correlation analysis of clinical and imaging components found three key brain-behaviour relationships, with a continuous spectrum across the cohort rather than discrete diagnostic entities. In the 46 patients with follow-up (mean 3.6 years) syndromic overlap increased with time. Together, these results show that syndromes associated with frontotemporal lobar degeneration do not form discrete mutually exclusive categories from their clinical features or structural brain changes, but instead exist in a multidimensional spectrum. Patients often manifest diagnostic features of multiple disorders while deficits in behaviour, movement and language domains are not confined to specific diagnostic groups. It is important to recognize individual differences in clinical phenotype, both for clinical management and to understand pathogenic mechanisms. We suggest that a transdiagnostic approach to the spectrum of frontotemporal lobar degeneration syndromes provides a useful framework with which to understand disease aetiology, progression, and heterogeneity and to target future treatments to a higher proportion of patients.

Towards accurate and unbiased imaging-based differentiation of Parkinson's disease, progressive supranuclear palsy and corticobasal syndrome

The early and accurate differential diagnosis of parkinsonian disorders is still a significant challenge for clinicians. In recent years, a number of studies have used magnetic resonance imaging data combined with machine learning and statistical classifiers to successfully differentiate between different forms of Parkinsonism. However, several questions and methodological issues remain, to minimize bias and artefact-driven classification. In this study, we compared different approaches for feature selection, as well as different magnetic resonance imaging modalities, with well-matched patient groups and tightly controlling for data quality issues related to patient motion. Our sample was drawn from a cohort of 69 healthy controls, and patients with idiopathic Parkinson’s disease (n = 35), progressive supranuclear palsy Richardson’s syndrome (n = 52) and corticobasal syndrome (n = 36). Participants underwent standardized T1-weighted and diffusion-weighted magnetic resonance imaging. Strict data quality control and group matching reduced the control and patient numbers to 43, 32, 33 and 26, respectively. We compared two different methods for feature selection and dimensionality reduction: whole-brain principal components analysis, and an anatomical region-of-interest based approach. In both cases, support vector machines were used to construct a statistical model for pairwise classification of healthy controls and patients. The accuracy of each model was estimated using a leave-two-out cross-validation approach, as well as an independent validation using a different set of subjects. Our cross-validation results suggest that using principal components analysis for feature extraction provides higher classification accuracies when compared to a region-of-interest based approach. However, the differences between the two feature extraction methods were significantly reduced when an independent sample was used for validation, suggesting that the principal components analysis approach may be more vulnerable to overfitting with cross-validation. Both T1-weighted and diffusion magnetic resonance imaging data could be used to successfully differentiate between subject groups, with neither modality outperforming the other across all pairwise comparisons in the cross-validation analysis. However, features obtained from diffusion magnetic resonance imaging data resulted in significantly higher classification accuracies when an independent validation cohort was used. Overall, our results support the use of statistical classification approaches for differential diagnosis of parkinsonian disorders. However, classification accuracy can be affected by group size, age, sex and movement artefacts. With appropriate controls and out-of-sample cross validation, diagnostic biomarker evaluation including magnetic resonance imaging based classifiers may be an important adjunct to clinical evaluation.

Central auditory processing in parkinsonian disorders: A systematic review

Altered auditory processing has been increasingly recognized as a non-motor feature in parkinsonian disorders. This systematic review provides an overview of behavioral and electrophysiological literature on central auditory processing in patients with Parkinson's disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). A systematic database search was conducted and yielded 88 studies that met the intelligibility criteria. The collected data revealed distinct impairments in a range of central auditory processes in PD, including altered deviance detection of basic auditory features, auditory brainstem processing, auditory gating and selective auditory attention. In contrast to PD, literature on central auditory processing in atypical parkinsonian disorders was relatively scarce, but provided some evidence for impaired central auditory processing in MSA and PSP. The interpretation of these findings is discussed and suggestions for further research are offered.

The Progressive Supranuclear Palsy: Past and Present Aspects

Objectives: Recently, new criteria for sensitive and specific clinical diagnosis of progressive supranuclear palsy (PSP) have been addressed while distinct clinical phenotypes of the disorder have been increasingly described in the literature. This study aimed to describe past and present aspects of the disease as well as to highlight the cognitive and behavioral profile of PSP patients in relation to the underlying pathology, genetics and treatment procedures.Methods: A Medline and Scopus search was performed to identify articles published on this topic. Articles published solely in English were considered.Results: The most common clinical characteristics of PSP included early postural instability and falls, vertical supranuclear gaze palsy, parkinsonism with poor response to levodopa and pseudobulbar palsy. Frontal dysfunction and verbal fluency deficits were the most distinct cognitive impairments in PSP while memory, visuospatial and social cognition could also be affected. Apathy and impulsivity were also present in PSP patients and had significant impact on relatives and caregivers.Conclusions: PSP is a neurodegenerative disorder with prominent tau neuropathology. Movement, motivation and communication impairments in patients with PSP may limit participation in everyday living activities. Comprehensive neuropsychological assessments are of significant importance for PSP cognitive evaluation. Pharmacologic and non-pharmacologic approaches could be applied in order to relieve patients and improve quality of life.Clinical Implications: Executive dysfunction is the most notable cognitive impairment and dominates the neuropsychological profile of patients with PSP.

Normative data for Emotion Hexagon test and frequency of impairment in behavioral variant frontotemporal dementia, Alzheimer's disease and Huntington's disease

Social cognitive functions such as Theory of Mind, empathy and emotion recognition can be impaired in dementia spectrum disorders, especially in diseases with prominent frontal dysfunction. The Emotion Hexagon test (EHT) is a short test of basic emotion recognition. As with other social cognitive tests, normative data for this test is sparse. The aim of this study was to present regression-based normative data for the EHT. Further, we wished to investigate the frequency of impairment in patients with the behavioral variant of frontotemporal dementia (bvFTD, N = 11), Alzheimer's disease (AD, N = 44) and Huntington's disease (HD, N = 52) when using regression-based normative data. The results documented that age (but not gender or education) had a significant effect on EHT score. The effect of age had numerical impact on expected scores in persons older than 60 years. Normative data (including percentile estimates) are presented. The EHT is sensitive to impairment in both bvFTD and HD, where more than 80% of patients had lower scores than expected. In both groups, 54% of patients fell below the 5th percentile-estimate, and in HD 65% fell below the 10th percentile-estimate. In the AD group 25% fell below the 10th percentile-estimate, and 14% fell below the 5th percentile-estimate. In conclusion, very low scores are typically associated with HD and bvFTD, but very poor performances can also be found in other diseases such like AD. Hopefully, the normative data presented and the documentation of their validity in clinical practice is a useful tool for clinicians.

Neuropathologic basis of frontotemporal dementia in progressive supranuclear palsy

BACKGROUND

Progressive supranuclear palsy (PSP) is a neurodegenerative disorder characterized by neuronal loss in the extrapyramidal system with pathologic accumulation of tau in neurons and glia. The most common clinical presentation of PSP, referred to as Richardson syndrome, is that of atypical parkinsonism with vertical gaze palsy, axial rigidity, and frequent falls. Although cognitive deficits in PSP are often ascribed to subcortical dysfunction, a subset of patients has dementia with behavioral features similar to the behavioral variant of frontotemporal dementia. In this study we aimed to identify the clinical and pathological characteristics of PSP presenting with frontotemporal dementia.

METHODS

In this study, we compared clinical and pathologic characteristics of 31 patients with PSP with Richardson syndrome with 15 patients with PSP with frontotemporal dementia. For pathological analysis, we used semiquantitative methods to assess neuronal and glial lesions with tau immunohistochemistry, as well image analysis of tau burden using digital microscopic methods.

RESULTS

We found greater frontal and temporal neocortical neuronal tau pathology in PSP with frontotemporal dementia compared with PSP with Richardson syndrome. White matter tau pathology was also greater in PSP with frontotemporal dementia than PSP with Richardson syndrome. Genetic and demographic factors were not associated with atypical distribution of tau pathology in PSP with frontotemporal dementia.

CONCLUSIONS

The results confirm the subset of cognitive-predominant PSP mimicking frontotemporal dementia in PSP. PSP with frontotemporal dementia has distinct clinical features that differ from PSP with Richardson syndrome, as well as differences in distribution and density of tau pathology. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Prognostic importance of apathy in syndromes associated with frontotemporal lobar degeneration

Objective

To determine the influence of apathy, impulsivity, and behavioral change on survival in patients with frontotemporal dementia, progressive supranuclear palsy, and corticobasal syndrome.

Methods

We assessed 124 patients from the epidemiologic PiPPIN (Pick's Disease and Progressive Supranuclear Palsy, Prevalence and Incidence) study. Patients underwent detailed baseline cognitive and behavioral assessment focusing on apathy, impulsivity, and behavioral change. Logistic regression identified predictors of death within 2.5 years from assessment, including age, sex, diagnosis, cognition, and 8 neurobehavioral profiles derived from a principal component analysis of neuropsychological and behavioral measures.

Results

An apathetic neurobehavioral profile predicted death (Wald statistic = 8.119, p = 0.004, Exp(B) = 2.912, confidence interval = >1 [1.396–6.075]) and was elevated in all patient groups. This profile represented apathy, weighted strongly to carer reports from the Apathy Evaluation Scale, Neuropsychiatric Inventory, and Cambridge Behavioral Inventory. Age at assessment, sex, and global cognitive impairment were not significant predictors. Differences in mortality risk across diagnostic groups were accounted for by their neuropsychiatric and behavioral features.

Conclusions

The relationship between apathy and survival highlights the need to develop more effective and targeted measurement tools to improve its recognition and facilitate treatment. The prognostic importance of apathy suggests that neurobehavioral features might be useful to predict survival and stratify patients for interventional trials. Effective symptomatic interventions targeting the neurobiology of apathy might ultimately also improve prognosis.

Reduced capacity for empathy in corticobasal syndrome and its impact on carer burden

Corticobasal syndrome (CBS) is clinically characterised by a wide range of motor, cognitive, and behavioural features but remains challenging to diagnose accurately. Despite recent evidence supporting the presence of social cognition and emotion processing disturbances, few studies have explored the nature of empathic ability in CBS. This study aimed to (a) investigate the extent to which cognitive and affective dimensions of empathy are affected in CBS and (b) to determine the impact of such changes on carer burden. Empathic capacity was assessed in 29 CBS patients and 28 matched healthy controls. We employed the Interpersonal Reactivity Index (IRI), an instrument measuring: (a) perspective taking, (b) fantasy, (c) empathic concern, and (d) personal distress. A significant change in both perspective taking and empathic concern was observed in CBS following disease onset. Furthermore, affective empathy deficits in CBS patients predicted higher levels of carer burden. Disturbances in both cognitive and affective empathy are present in CBS and lead to increased levels of carer burden.

Neurocognitive mechanisms of theory of mind impairment in neurodegeneration: a transdiagnostic approach

Much of human interaction is predicated upon our innate capacity to infer the thoughts, beliefs, emotions, and perspectives of others, in short, to possess a "theory of mind" (ToM). While the term has evolved considerably since its inception, ToM encompasses our unique ability to apprehend the mental states of others, enabling us to anticipate and predict subsequent behavior. From a developmental perspective, ToM has been a topic of keen research interest, with numerous studies seeking to explicate the origins of this fundamental capacity and its disruption in developmental disorders such as autism. The study of ToM at the opposite end of the lifespan, however, is paradoxically new born, emerging as a topic of interest in its own right comparatively recently. Here, we consider the unique insights afforded by studying ToM capacity in neurodegenerative disorders. Arguing from a novel, transdiagnostic perspective, we consider how ToM vulnerability reflects the progressive degradation of neural circuits specialized for an array of higher-order cognitive processes. This mechanistic approach enables us to consider the common and unique neurocognitive mechanisms that underpin ToM dysfunction across neurodegenerative disorders and for the first time examine its relation to behavioral disturbances across social, intimate, legal, and criminal settings. As such, we aim to provide a comprehensive overview of ToM research in neurodegeneration, the resultant challenges for family members, clinicians, and the legal profession, and future directions worthy of exploration.

Atrophy in midbrain & cerebral/cerebellar pedunculi is characteristic for progressive supranuclear palsy - A double-validation whole-brain meta-analysis

OBJECTIVE

Progressive supranuclear palsy (PSP) is an atypical parkinsonian syndrome characterized by vertical gaze palsy and postural instability. Midbrain atrophy is suggested as a hallmark, but it has not been validated systematically in whole-brain imaging.

METHODS

We conducted whole-brain meta-analyses identifying disease-related atrophy in structural MRI. Eighteen studies were identified (N = 315 PSP, 393 controls) and separated into gray or white matter analyses (15/12). All patients were diagnosed according to the National Institute of Neurological Disorders and Stroke and the Society for PSP (NINDS-SPSP criteria, Litvan et al. (1996a)), which are now considered as PSP-Richardson syndrome (Höglinger et al., 2017). With overlay analyses, we double-validated two meta-analytical algorithms: anatomical likelihood estimation and seed-based D mapping. Additionally, we conducted region-of-interest effect size meta-analyses on radiological biomarkers and subtraction analyses differentiating PSP from Parkinson's disease.

RESULTS

Whole brain meta-analyses revealed consistent gray matter atrophy in bilateral thalamus, anterior insulae, midbrain, and left caudate nucleus. White matter alterations were consistently detected in bilateral superior/middle cerebellar pedunculi, cerebral pedunculi, and midbrain atrophy. Region-of-interest meta-analyses demonstrated that midbrain metrics generally perform very well in distinguishing PSP from other parkinsonian syndromes with strong effect sizes. Subtraction analyses identified the midbrain as differentiating between PSP and Parkinson's disease.

CONCLUSIONS

Our meta-analyses identify gray matter atrophy of the midbrain and white matter atrophy of the cerebral/cerebellar pedunculi and midbrain as characteristic for PSP. Results support the incorporation of structural MRI data, and particularly these structures, into the revised PSP diagnostic criteria.

Diminished positive affect and traumatic stress: A biobehavioral review and commentary on trauma affective neuroscience

Post-traumatic stress manifests in disturbed affect and emotion, including exaggerated severity and frequency of negative valence emotions, e.g., fear, anxiety, anger, shame, and guilt. However, another core feature of common post-trauma psychopathologies, i.e. post-traumatic stress disorder (PTSD) and major depression, is diminished positive affect, or reduced frequency and intensity of positive emotions and affective states such as happiness, joy, love, interest, and desire/capacity for interpersonal affiliation. There remains a stark imbalance in the degree to which the neuroscience of each affective domain has been probed and characterized in PTSD, with our knowledge of post-trauma diminished positive affect remaining comparatively underdeveloped. This remains a prominent barrier to realizing the clinical breakthroughs likely to be afforded by the increasing availability of neuroscience assessment and intervention tools. In this review and commentary, the author summarizes the modest extant neuroimaging literature that has probed diminished positive affect in PTSD using reward processing behavioral paradigms, first briefly reviewing and outlining the neurocircuitry implicated in reward and positive emotion and its interrelationship with negative emotion and negative valence circuitry. Specific research guidelines are then offered to best and most efficiently develop the knowledge base in this area in a way that is clinically translatable and will exert a positive impact on routine clinical care. The author concludes with the prediction that the development of an integrated, bivalent theoretical and predictive model of how trauma impacts affective neurocircuitry to promote post-trauma psychopathology will ultimately lead to breakthroughs in how trauma treatments are conceptualized mechanistically and developed pragmatically.

Structural Imaging in Atypical Parkinsonism

Qualitative and quantitative structural magnetic resonance imaging offer objective measures of the underlying neurodegeneration in atypical parkinsonism. Regional changes in tissue volume, signal changes and increased deposition of iron as assessed with different structural MRI techniques are surrogate markers of underlying neurodegeneration and may reflect cell loss, microglial proliferation and astroglial activation. Structural MRI has been explored as a tool to enhance diagnostic accuracy in differentiating atypical parkinsonian disorders (APDs). Moreover, the longitudinal assessment of serial structural MRI-derived parameters offers the opportunity for robust inferences regarding the progression of APDs. This review summarizes recent research findings as (1) a diagnostic tool for APDs as well as (2) as a tool to assess longitudinal changes of serial MRI-derived parameters in the different APDs.

Neurophysiological signatures of Alzheimer's disease and frontotemporal lobar degeneration: pathology versus phenotype

The disruption of brain networks is characteristic of neurodegenerative dementias. However, it is controversial whether changes in connectivity reflect only the functional anatomy of disease, with selective vulnerability of brain networks, or the specific neurophysiological consequences of different neuropathologies within brain networks. We proposed that the oscillatory dynamics of cortical circuits reflect the tuning of local neural interactions, such that different pathologies are selective in their impact on the frequency spectrum of oscillations, whereas clinical syndromes reflect the anatomical distribution of pathology and physiological change. To test this hypothesis, we used magnetoencephalography from five patient groups, representing dissociated pathological subtypes and distributions across frontal, parietal and temporal lobes: amnestic Alzheimer's disease, posterior cortical atrophy, and three syndromes associated with frontotemporal lobar degeneration. We measured effective connectivity with graph theory-based measures of local efficiency, using partial directed coherence between sensors. As expected, each disease caused large-scale changes of neurophysiological brain networks, with reductions in local efficiency compared to controls. Critically however, the frequency range of altered connectivity was consistent across clinical syndromes that shared a likely underlying pathology, whilst the localization of changes differed between clinical syndromes. Multivariate pattern analysis of the frequency-specific topographies of local efficiency separated the disorders from each other and from controls (accuracy 62% to 100%, according to the groups' differences in likely pathology and clinical syndrome). The data indicate that magnetoencephalography has the potential to reveal specific changes in neurophysiology resulting from neurodegenerative disease. Our findings confirm that while clinical syndromes have characteristic anatomical patterns of abnormal connectivity that may be identified with other methods like structural brain imaging, the different mechanisms of neurodegeneration also cause characteristic spectral signatures of physiological coupling that are not accessible with structural imaging nor confounded by the neurovascular signalling of functional MRI. We suggest that these spectral characteristics of altered connectivity are the result of differential disruption of neuronal microstructure and synaptic physiology by Alzheimer's disease versus frontotemporal lobar degeneration.

Sensitivity and Specificity of the ECAS in Parkinson's Disease and Progressive Supranuclear Palsy

Disentangling Parkinson's disease (PD) and progressive supranuclear palsy (PSP) may be a diagnostic challenge. Cognitive signs may be useful, but existing screens are often insufficiently sensitive or unsuitable for assessing people with motor disorders. We investigated whether the newly developed ECAS, designed to be used with people with even severe motor disability, was sensitive to the cognitive impairment seen in PD and PSP and able to distinguish between these two disorders. Thirty patients with PD, 11 patients with PSP, and 40 healthy controls were assessed using the ECAS, as well as an extensive neuropsychological assessment. The ECAS detected cognitive impairment in 30% of the PD patients, all of whom fulfilled the diagnostic criteria for mild cognitive impairment. The ECAS was also able to detect cognitive impairment in PSP patients, with 81.8% of patients performing in the impaired range. The ECAS total score distinguished between the patients with PSP and healthy controls with high sensitivity (91.0) and specificity (86.8). Importantly, the ECAS was also able to distinguish between the two syndromes, with the measures of verbal fluency offering high sensitivity (82.0) and specificity (80.0). In sum, the ECAS is a quick, simple, and inexpensive test that can be used to support the differential diagnosis of PSP.

Social Cognition Dysfunctions in Neurodegenerative Diseases: Neuroanatomical Correlates and Clinical Implications

Social cognitive function, involved in the perception, processing, and interpretation of social information, has been shown to be crucial for successful communication and interpersonal relationships, thereby significantly impacting mental health, well-being, and quality of life. In this regard, assessment of social cognition, mainly focusing on four key domains, such as theory of mind (ToM), emotional empathy, and social perception and behavior, has been increasingly evaluated in clinical settings, given the potential implications of impairments of these skills for therapeutic decision-making. With regard to neurodegenerative diseases (NDs), most disorders, characterized by variable disease phenotypes and progression, although similar for the unfavorable prognosis, are associated to impairments of social cognitive function, with consequent negative effects on patients' management. Specifically, in some NDs these deficits may represent core diagnostic criteria, such as for behavioral variant frontotemporal dementia (bvFTD), or may emerge during the disease course as critical aspects, such as for Parkinson's and Alzheimer's diseases. On this background, we aimed to revise the most updated evidence on the neurobiological hypotheses derived from network-based approaches, clinical manifestations, and assessment tools of social cognitive dysfunctions in NDs, also prospecting potential benefits on patients' well-being, quality of life, and outcome derived from potential therapeutic perspectives of these deficits.

Characterisation of meta-analytical functional connectivity in progressive supranuclear palsy

AIM

To characterise the meta-analytical functional connectivity patterns in progressive supranuclear palsy (PSP) and compare them to idiopathic Parkinson's disease (IPD).

MATERIALS AND METHODS

It was previously reported that PSP and IPD showed distinct regions of brain atrophy based on voxel-based morphometry (VBM) meta-analysis. Using these regions as seeds, healthy control data were referenced to create and statistically compare meta-analytical functional connectivity maps of PSP and IPD.

RESULTS

Some overlap was noted between the two diseases, including within the thalamus, striatum, and prefrontal cortex; however, the PSP seeds demonstrated more extensive functional co-activity throughout the brain, particularly within the midbrain, precentral gyrus, parietal cortex, basal ganglia, and cerebellum.

CONCLUSION

These findings may help guide future longitudinal studies in the development of new functional imaging biomarkers for diagnosis and assessing treatment response.

White matter change with apathy and impulsivity in frontotemporal lobar degeneration syndromes

Objective

To identify the white matter correlates of apathy and impulsivity in the major syndromes associated with frontotemporal lobar degeneration, using diffusion-weighted imaging and data from the PiPPIN (Pick's Disease and Progressive Supranuclear Palsy: Prevalence and Incidence) study. We included behavioral and language variants of frontotemporal dementia, corticobasal syndrome, and progressive supranuclear palsy.

Methods

Seventy patients and 30 controls underwent diffusion tensor imaging at 3-tesla after detailed assessment of apathy and impulsivity. We used tract-based spatial statistics of fractional anisotropy and mean diffusivity, correlating with 8 orthogonal dimensions of apathy and impulsivity derived from a principal component analysis of neuropsychological, behavioral, and questionnaire measures.

Results

Three components were associated with significant white matter tract abnormalities. Carer-rated change in everyday skills, self-care, and motivation correlated with widespread changes in dorsal frontoparietal and corticospinal tracts, while carer observations of impulsive–apathetic and challenging behaviors revealed disruption in ventral frontotemporal tracts. Objective neuropsychological tests of cognitive control, reflection impulsivity, and reward responsiveness were associated with focal changes in the right frontal lobe and presupplementary motor area. These changes were observed across clinical diagnostic groups, and were not restricted to the disorders for which diagnostic criteria include apathy and impulsivity.

Conclusion

The current study provides evidence of distinct structural network changes in white matter associated with different neurobehavioral components of apathy and impulsivity across the diverse spectrum of syndromes and pathologies associated with frontotemporal lobar degeneration.

Association Between Poor Cognitive Functioning and Risk of Incident Parkinsonism: The Rotterdam Study

Importance

Cognitive dysfunction is a common feature among patients with parkinsonism, including Parkinson disease (PD). However, there is a scarcity of data on cognitive functioning before parkinsonism diagnosis, a stage at which patients may still respond to putative disease-modifying interventions.

Objective

To assess whether poor cognitive functioning is associated with an increased risk of parkinsonism.

Design, Setting, and Participants

Between January 8, 2002, and December 14, 2008, baseline cognitive function was assessed in 7386 participants of the Rotterdam Study who were free of parkinsonism and dementia. Four tests were administered (Stroop color word test, letter-digit substitution, verbal fluency, and word learning) and a global cognition score was derived from principal component analysis. Subsequently, participants were followed up until January 1, 2015, for the onset of parkinsonism through serial in-person examinations and complete access to medical records. Parkinsonism was defined as the (1) presence of hypokinesia or bradykinesia plus at least 1 other cardinal sign and/or (2) clinical diagnosis by a neurologist or geriatrician. Patients with dementia diagnosis before parkinsonism diagnosis were considered to have probable PD.

Main Outcomes and Measures

Hazard ratios (HRs) for incident parkinsonism per SD decrease in global cognition, adjusted for age, sex, and study subcohort.

Results

A total of 7386 patients were included in the analysis; of these, 4236 (57.4%) were women and mean (SD) age was 65.3 (10.2) years. During follow-up (median, 8.3 years; range, 0-15 years), 79 (1.1%) individuals received a diagnosis of incident parkinsonism; of these, 57 (72.2%) received a diagnosis of probable PD. Among patients with incident parkinsonism, 24 (30.4%) also developed dementia (10 before and 14 after parkinsonism onset). Poor global cognition at baseline was associated with a higher hazard of incident parkinsonism (hazard ratio [HR], 1.79; 95% CI, 1.37-2.33). The association remained robust beyond the first 8 years (HR, 1.59; 95% CI, 1.01-2.59) and after removing individuals with dementia onset before parkinsonism (HR, 1.72; 95% CI, 1.28-2.27). Poor global cognition at baseline was also associated with incident probable PD (HR, 1.52; 95% CI, 1.11-2.08). Letter-digit substitution (HR, 1.59; 95% CI, 1.22-2.04), verbal fluency (HR, 1.61; 95% CI, 1.23-2.08), and inverted interference task Stroop color word test (HR, 1.56; 95% CI, 1.25-1.96) scores were each associated with incident parkinsonism, whereas the association with word learning delayed-task scores was weaker (HR, 1.18; 95% CI, 0.92-1.52).

Conclusions and Relevance

Poor cognitive functioning is associated with an increased risk of incident parkinsonism, including probable PD. Cognition indicates the probability of parkinsonism over long intervals and extends beyond patients with onset of parkinsonism after dementia. The findings suggest that cognitive dysfunction can be considered a sign of prodromal PD.

Structural connections support emotional connections: Uncinate Fasciculus microstructure is related to the ability to decode facial emotion expressions

The Uncinate Fasciculus (UF) is an association fibre tract connecting regions in the frontal and anterior temporal lobes. UF disruption is seen in several disorders associated with impaired social behaviour, but its functional role is unclear. Here we set out to test the hypothesis that the UF is important for facial expression processing, an ability fundamental to adaptive social behaviour. In two separate experiments in healthy adults, we used high-angular resolution diffusion-weighted imaging (HARDI) and constrained spherical deconvolution (CSD) tractography to virtually dissect the UF, plus a control tract (the corticospinal tract (CST)), and quantify, via fractional anisotropy (FA), individual differences in tract microstructure. In Experiment 1, participants completed the Reading the Mind in the Eyes Task (RMET), a well-validated assay of facial expression decoding. In Experiment 2, a different set of participants completed the RMET, plus an odd-emotion-out task of facial emotion discrimination. In both experiments, participants also completed a control odd-identity-out facial identity discrimination task. In Experiment 1, FA of the right-, but not the left-hemisphere, UF was significantly correlated with performance on the RMET task, specifically for emotional, but not neutral expressions. UF FA was not significantly correlated with facial identity discrimination performance. In Experiment 2, FA of the right-, but not left-hemisphere, UF was again significantly correlated with performance on emotional items from the RMET, together with performance on the facial emotion discrimination task. Again, no significant association was found between UF FA and facial identity discrimination performance. Our findings highlight the contribution of right-hemisphere UF microstructure to inter-individual variability in the ability to decode facial emotion expressions, and may explain why disruption of this pathway affects social behaviour.

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We studied white matter microstructure correlates of facial emotion decoding skills.

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Focused on the role of a key limbic tract, the Uncinate Fasciculus (UF).

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Right UF microstructure linked to facial expression decoding skills.

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UF microstructure not related to facial identity discrimination skills.

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Right UF has a distinct role in the processing of facial expressions of emotion.

Brain gray matter abnormalities in progressive supranuclear palsy revisited

Whole-brain voxel-based morphometry (VBM) studies of progressive supranuclear palsy (PSP) have demonstrated heterogeneous findings regarding gray matter (GM) abnormalities. Here, we used Seed-based d Mapping, a coordinate-based meta-analytic approach to identify consistent regions of GM anomalies across studies of PSP. Totally, 18 original VBM studies, comprising 284 patients with PSP and 367 healthy controls were included. As compared to healthy controls, patients with PSP demonstrated significant GM reductions in both cortical and subcortical regions, including the frontal motor cortices, medial (including anterior cingulate cortex) and lateral frontal cortices, insula, superior temporal gyrus, striatum (putamen and caudate nucleus), thalamus, midbrain, and anterior cerebellum. Our study further suggests that many confounding factors, such as age, male ratio, motor severity, cognitive impairment severity, and illness duration of PSP patients, and scanner field-strength, could contribute to the heterogeneity of GM alterations in PSP across studies. Our comprehensive meta-analysis demonstrates a specific neuroanatomical pattern of GM atrophy in PSP with the involvement of the cortical-subcortical circuitries that mediate vertical supranuclear gaze palsy, motor disabilities (postural instability with falls and parkinsonism), and cognitive-behavioral disturbances. Confounding factors merit attention in future studies.

Advancing functional dysconnectivity and atrophy in progressive supranuclear palsy

Progressive supranuclear palsy syndrome (PSP-S) results from neurodegeneration within a network of brainstem, subcortical, frontal and parietal cortical brain regions. It is unclear how network dysfunction progresses and relates to longitudinal atrophy and clinical decline. In this study, we evaluated patients with PSP-S (n = 12) and healthy control subjects (n = 20) at baseline and 6 months later. Subjects underwent structural MRI and task-free functional MRI (tf-fMRI) scans and clinical evaluations at both time points. At baseline, voxel based morphometry (VBM) revealed that patients with mild-to-moderate clinical symptoms showed structural atrophy in subcortex and brainstem, prefrontal cortex (PFC; supplementary motor area, paracingulate, dorsal and ventral medial PFC), and parietal cortex (precuneus). Tf-fMRI functional connectivity (FC) was examined in a rostral midbrain tegmentum (rMT)-anchored intrinsic connectivity network that is compromised in PSP-S. In healthy controls, this network contained a medial parietal module, a prefrontal-paralimbic module, and a subcortical-brainstem module. Baseline FC deficits in PSP-S were most severe in rMT network integrative hubs in the prefrontal-paralimbic and subcortical-brainstem modules. Longitudinally, patients with PSP-S had declining intermodular FC between the subcortical-brainstem and parietal modules, while progressive atrophy was observed in subcortical-brainstem regions (midbrain, pallidum) and posterior frontal (perirolandic) cortex. This suggested that later-stage subcortical-posterior cortical change may follow an earlier-stage subcortical-anterior cortical disease process. Clinically, patients with more severe baseline impairment showed greater subsequent prefrontal-parietal cortical FC declines and posterior frontal atrophy rates, while patients with more rapid longitudinal clinical decline showed coupled prefrontal-paralimbic FC decline. VBM and FC can augment disease monitoring in PSP-S by tracking the disease through stages while detecting changes that accompany heterogeneous clinical progression.

Magnetic resonance imaging for the diagnosis of Parkinson's disease

The differential diagnosis of parkinsonian syndromes is considered one of the most challenging in neurology and error rates in the clinical diagnosis can be high even at specialized centres. Despite several limitations, magnetic resonance imaging (MRI) has undoubtedly enhanced the diagnostic accuracy in the differential diagnosis of neurodegenerative parkinsonism over the last three decades. This review aims to summarize research findings regarding the value of the different MRI techniques, including advanced sequences at high- and ultra-high-field MRI and modern image analysis algorithms, in the diagnostic work-up of Parkinson's disease. This includes not only the exclusion of alternative diagnoses for Parkinson's disease such as symptomatic parkinsonism and atypical parkinsonism, but also the diagnosis of early, new onset, and even prodromal Parkinson's disease.

Radiological biomarkers for diagnosis in PSP: Where are we and where do we need to be?

PSP is a pathologically defined neurodegenerative tauopathy with a variety of clinical presentations including typical Richardson's syndrome and other variant PSP syndromes. A large body of neuroimaging research has been conducted over the past two decades, with many studies proposing different structural MRI and molecular PET/SPECT biomarkers for PSP. These include measures of brainstem, cortical and striatal atrophy, diffusion weighted and diffusion tensor imaging abnormalities, [18F] fluorodeoxyglucose PET hypometabolism, reductions in striatal dopamine imaging and, most recently, PET imaging with ligands that bind to tau. Our aim was to critically evaluate the degree to which structural and molecular neuroimaging metrics fulfill criteria for diagnostic biomarkers of PSP. We queried the PubMed, Cochrane, Medline, and PSYCInfo databases for original research articles published in English over the past 20 years using postmortem diagnosis or the NINDS-SPSP criteria as the diagnostic standard from 1996 to 2016. We define a five-level theoretical construct for the utility of neuroimaging biomarkers in PSP, with level 1 representing group-level findings, level 2 representing biomarkers with demonstrable individual-level diagnostic utility, level 3 representing biomarkers for early disease, level 4 representing surrogate biomarkers of PSP pathology, and level 5 representing definitive PSP biomarkers of PSP pathology. We discuss the degree to which each of the currently available biomarkers fit into this theoretical construct, consider the role of biomarkers in the diagnosis of Richardson's syndrome, variant PSP syndromes and autopsy confirmed PSP, and emphasize current shortfalls in the field. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Apathy and impulsivity in frontotemporal lobar degeneration syndromes

Apathy and impulsivity are common and disabling consequences of frontotemporal lobar degeneration. They cause substantial carer distress, but their aetiology remains elusive. There are critical limitations to previous studies in this area including (i) the assessment of either apathy or impulsivity alone, despite their frequent co-existence; (ii) the assessment of behavioural changes within single diagnostic groups; and (iii) the use of limited sets of tasks or questions that relate to just one aspect of these multifactorial constructs. We proposed an alternative, dimensional approach that spans behavioural and language variants of frontotemporal dementia, progressive supranuclear palsy and corticobasal syndrome. This accommodates the commonalities of apathy and impulsivity across disorders and reveals their cognitive and anatomical bases. The ability to measure the components of apathy and impulsivity and their associated neural correlates across diagnostic groups would provide better novel targets for pharmacological manipulations, and facilitate new treatment strategies and strengthen translational models. We therefore sought to determine the neurocognitive components of apathy and impulsivity in frontotemporal lobar degeneration syndromes. The frequency and characteristics of apathy and impulsivity were determined by neuropsychological and behavioural assessments in 149 patients and 50 controls from the PIck's disease and Progressive supranuclear palsy Prevalence and INcidence study (PiPPIN). We derived dimensions of apathy and impulsivity using principal component analysis and employed these in volumetric analyses of grey and white matter in a subset of 70 patients (progressive supranuclear palsy, n = 22; corticobasal syndrome, n = 13; behavioural variant, n = 14; primary progressive aphasias, n = 21) and 27 control subjects. Apathy and impulsivity were present across diagnostic groups, despite being criteria for behavioural variant frontotemporal dementia alone. Measures of apathy and impulsivity frequently loaded onto the same components reflecting their overlapping relationship. However, measures from objective tasks, patient-rated questionnaires and carer-rated questionnaires loaded onto separate components and revealed distinct neurobiology. Corticospinal tracts correlated with patients' self-ratings. In contrast, carer ratings correlated with atrophy in established networks for goal-directed behaviour, social cognition, motor control and vegetative functions, including frontostriatal circuits, orbital and temporal polar cortex, and the brainstem. Components reflecting response inhibition deficits correlated with focal frontal cortical atrophy. The dimensional approach to complex behavioural changes arising from frontotemporal lobar degeneration provides new insights into apathy and impulsivity, and the need for a joint therapeutic strategy against them. The separation of objective tests from subjective questionnaires, and patient from carer ratings, has important implications for clinical trial design.awx101media15448041163001.

Disease-Specific Regions Outperform Whole-Brain Approaches in Identifying Progressive Supranuclear Palsy: A Multicentric MRI Study

To identify progressive supranuclear palsy (PSP), we combined voxel-based morphometry (VBM) and support vector machine (SVM) classification using disease-specific features in multicentric magnetic resonance imaging (MRI) data. Structural brain differences were investigated at four centers between 20 patients with PSP and 20 age-matched healthy controls with T1-weighted MRI at 3T. To pave the way for future application in personalized medicine, we applied SVM classification to identify PSP on an individual level besides group analyses based on VBM. We found a major decline in gray matter density in the brainstem, insula, and striatum, and also in frontomedian regions, which is in line with current literature. Moreover, SVM classification yielded high accuracy rates above 80% for disease identification in imaging data. Focusing analyses on disease-specific regions-of-interest (ROI) led to higher accuracy rates compared to a whole-brain approach. Using a polynomial kernel (instead of a linear kernel) led to an increased sensitivity and a higher specificity of disease detection. Our study supports the application of MRI for individual diagnosis of PSP, if combined with SVM approaches. We demonstrate that SVM classification provides high accuracy rates in multicentric data—a prerequisite for potential application in diagnostic routine.

Managing cognition in progressive supranuclear palsy

Cognitive impairment is integral to the syndrome of progressive supranuclear palsy. It is most commonly described as a frontal dysexecutive syndrome but other impairments include apathy, impulsivity, visuospatial and memory functions. Cognitive dysfunction may be exacerbated by mood disturbance, medication and communication problems. In this review we advocate an individualized approach to managing cognitive impairment in progressive supranuclear palsy with the education of caregivers as a central component. Specific cognitive and behavioral treatments are complemented by treatment of mood disturbances, rationalizing medications and a patient-centered approach to communication. This aims to improve patients’ quality of life, reduce carer burden and assist people with progressive supranuclear palsy in decisions about their life and health, including discussions of feeding and end-of-life issues.

Neuronal network disintegration: common pathways linking neurodegenerative diseases

Neurodegeneration refers to a heterogeneous group of brain disorders that progressively evolve. It has been increasingly appreciated that many neurodegenerative conditions overlap at multiple levels and therefore traditional clinicopathological correlation approaches to better classify a disease have met with limited success. Neuronal network disintegration is fundamental to neurodegeneration, and concepts based around such a concept may better explain the overlap between their clinical and pathological phenotypes. In this Review, promoters of overlap in neurodegeneration incorporating behavioural, cognitive, metabolic, motor, and extrapyramidal presentations will be critically appraised. In addition, evidence that may support the existence of large-scale networks that might be contributing to phenotypic differentiation will be considered across a neurodegenerative spectrum. Disintegration of neuronal networks through different pathological processes, such as prion-like spread, may provide a better paradigm of disease and thereby facilitate the identification of novel therapies for neurodegeneration.