Clinical characteristics of parkinsonism in frontotemporal dementia according to subtypes

Movement disorders are linked to TDP-43 burden in the substantia nigra of FTLD-TDP brain donors

Movement disorders (MD) have been linked to degeneration of the substantia nigra (SN) in Parkinson's disease and include bradykinesia, rigidity, and tremor. They are also present in frontotemporal dementia (FTD), where MD have been linked to frontotemporal lobar degeneration with tau pathology (FTLD-tau). Although MD can also occur in FTLD with TDP-43 pathology (FTLD-TDP), the local pathology in the SN of FTLD-TDP patients with MD is currently unexplored. The aims of this study are to characterize the frequency and the nature of MD in a cohort of FTLD-TDP brain donors and to investigate the relationship between the presence of MD, the nigral neuronal loss, and the TDP-43 burden in the SN. From our cohort of FTLD-TDP patients (n = 53), we included 13 donors who presented with MD (FTLD-MD+), and nine age-sex matched donors without MD (FTLD-MD-) for whom the SN was available. In these donors, the TDP-43 burden and the neuronal density in the SN were assessed with ImageJ and Qupath software. The results were compared between the two groups using T-test. We found that the TDP-43 burden in the SN was higher in FTLD-MD+ (mean 3,43%, SD ± 2,7) compared to FTLD-MD- (mean 1,21%, SD ± 0,67) (p = 0,04), while no significant difference in nigral neuronal density was found between the groups (p = 0,09). 17% of FTLD-TDP patients developed MD, which present as symmetric akinetic-rigid parkinsonism or CBS. Given the absence of a significant nigral neuronal cell loss, TDP-43 induced neuronal dysfunction could be sufficient to cause MD.

Parkinsonism Is Associated with Altered SMA-Basal Ganglia Structural and Functional Connectivity in Frontotemporal Degeneration

BACKGROUND

Patients with frontotemporal degeneration (FTD) often manifest parkinsonism, which likely results from cortical and subcortical degeneration of brain structures involved in motor control. We used a multimodal magnetic resonance imaging (MRI) approach to investigate possible structural and/or functional alterations in FTD patients with and without parkinsonism (Park+ and Park-).

METHODS

Thirty FTD patients (12 Park+, 18 Park-) and 30 healthy controls were enrolled and underwent 3T MRI scanning. MRI analyses included: (1) surface-based morphometry; (2) basal ganglia and thalamic volumetry; (3) diffusion-based probabilistic tractography of fiber tracts connecting the supplementary motor area (SMA) and primary motor cortex (M1) to the putamen, globus pallidus, and thalamus; and (4) resting-state functional connectivity (RSFC) between the aforementioned regions.

RESULTS

Patients in Park+ and Park- groups showed comparable patterns of cortical thinning in frontotemporal regions and reduced thalamic volume with respect to controls. Only Park+ patients showed reduced putaminal volume and reduced fractional anisotropy of the fibers connecting the SMA to the globus pallidus, putamen, and thalamus, with respect to controls. Park+ patients also showed decreased RSFC between the SMA and putamen with respect to both Park- patients and controls.

CONCLUSIONS

The present findings support the hypothesis that FTD patients with parkinsonism are characterized by neurodegenerative processes in specific corticobasal ganglia-thalamocortical motor loops.

Cognitive Impairment in Older Adults: Epidemiology, Diagnosis, and Treatment

Cognitive impairment and dementia affect dozens of millions of people worldwide and cause significant distress to patients and caregivers and a financial burden to families and health care systems. Careful history-taking, cognitive and physical examination, and supplemental neuroimaging and fluid-based biomarkers can accurately diagnose neurocognitive disorders. Management includes non-pharmacological and pharmacological treatments tailored to the etiology and to the individual.

Incongruences Between Facial Expression and Self-Reported Emotional Reactivity in Frontotemporal Dementia and Related Disorders

OBJECTIVE

Emotional reactivity normally involves a synchronized coordination of subjective experience and facial expression. These aspects of emotional reactivity can be uncoupled by neurological illness and produce adverse consequences for patient and caregiver quality of life because of misunderstandings regarding the patient's presumed internal state. Frontotemporal dementia (FTD) is often associated with altered social and emotional functioning. FTD is a heterogeneous disease, and socioemotional changes in patients could result from altered internal experience, altered facial expressive ability, altered language skills, or other factors. The authors investigated how individuals with FTD subtypes differ from a healthy control group regarding the extent to which their facial expressivity aligns with their self-reported emotional experience.

METHODS

Using a compound measure of emotional reactivity to assess reactions to three emotionally provocative videos, the authors explored potential explanations for differences in alignment of facial expressivity with emotional experience, including parkinsonism, physiological reactivity, and nontarget verbal responses.

RESULTS

Participants with the three main subtypes of FTD all tended to express less emotion on their faces than they did through self-report.

CONCLUSIONS

Exploratory analyses suggest that reasons for this incongruence likely differ not only between but also within diagnostic subgroups.

Writing errors in primary progressive aphasia

Peripheral errors in writing, that is errors produced download the spelling, have been occasionally described in primary progressive aphasia (PPA), but the possibility that these errors might be a marker of parkinsonism associated to some subtypes of PPA has not been explored. We investigated whether errors of peripheral nature characterize the writing disorder in PPA when associated with parkinsonian signs (PSs). Subgroups of PPA without PSs and with PSs were studied. The proportion of the central and peripheral errors in writing words and pseudowords was calculated in each group. In writing words, central errors significantly exceeded peripheral errors in subgroups without PSs. The higher the number of peripheral errors, the higher the probability of presenting PSs. No relation emerged between any error and the Unified Parkinson's Disease Rating Scale, but both types of errors correlated with measures of cognitive ability. Peripheral errors emerge when PSs are associated with PPA and may be linked to a decay of the cognitive control on movement, possibly involving the right hemisphere. Peripheral errors have clinical relevance in PPA, to the extent that they may assume the significance of a marker of specific subtypes and can help to outline the specific clinical picture of individual patients.

Survival in Korean Patients with Frontotemporal Dementia Syndrome: Association with Behavioral Features and Parkinsonism

We investigated the survival time of each clinical syndrome of frontotemporal dementia (FTD) and the impacts of behavioral and motor features on survival of FTD. A total of 216 patients with FTD [82 behavioral variant FTD (bvFTD), 78 semantic variant primary progressive aphasia (svPPA), 43 non-fluent/agrammatic variant PPA (nfvPPA), 13 FTD-motor neuron disease (MND)] were enrolled from 16 centers across Korea. Behaviors and parkinsonism were assessed using the Frontal Behavioral Inventory and Unified Parkinson’s Disease Rating Scale Part III, respectively. The Kaplan–Meier method was used for the survival analysis and the Cox proportional hazards model was applied for analysis of the effect of behavioral and motor symptoms on survival, after controlling vascular risk factors and cancer. An overall median survival of FTD was 12.1 years. The survival time from onset was shortest for FTD-MND and longest for svPPA. The median survival time of patients with bvFTD was unavailable but likely comparable to that of patients with nfvPPA. In the bvFTD group, negative behavioral symptoms and akinetic rigidity were significantly associated with survival. In the nfvPPA group, the presence of dysarthria had a negative impact on survival. These findings provide useful information to clinicians planning for care.

Speech and language impairments in behavioral variant frontotemporal dementia: A systematic review

Although behavioral variant frontotemporal dementia (bvFTD) is classically defined by behavioral and socio-emotional changes, impairments often extend to other cognitive functions. These include early speech and language deficits related to the disease's core neural disruptions. Yet, their scope and clinical relevance remains poorly understood. This systematic review characterizes such disturbances in bvFTD, considering clinically, neuroanatomically, genetically, and neuropathologically defined subgroups. We included 181 experimental studies, with at least 5 bvFTD patients diagnosed using accepted criteria, comparing speech and language outcomes between bvFTD patients and healthy controls or between bvFTD subgroups. Results reveal extensive and heterogeneous deficits across cohorts, with (a) consistent lexico-semantic, reading & writing, and prosodic impairments; (b) inconsistent deficits in motor speech and grammar; and (c) relative preservation of phonological skills. Also, preliminary findings suggest that the severity of speech and language deficits might be associated with global cognitive impairment, predominantly temporal or fronto-temporal atrophy and MAPT mutations (vs C9orf72). Although under-recognized, these impairments contribute to patient characterization and phenotyping, while potentially informing diagnosis and management.

Novel TUBA4A Variant Associated With Familial Frontotemporal Dementia

OBJECTIVE

Despite the strong genetic component of frontotemporal dementia (FTD), a substantial proportion of patients remain genetically unresolved. We performed an in-depth study of a family with an autosomal dominant form of FTD to investigate the underlying genetic cause.

METHODS

Following clinical and pathologic characterization of the family, genetic studies included haplotype sharing analysis and exome sequencing. Subsequently, we performed immunohistochemistry, immunoblotting, and a microtubule repolymerization assay to investigate the potential impact of the candidate variant in tubulin alpha 4a (TUBA4A).

RESULTS

The clinical presentation in this family is heterogeneous, including behavioral changes, parkinsonian features, and uncharacterized dementia. Neuropathologic examination of 2 patients revealed TAR DNA binding protein 43 (TDP-43) pathology with abundant dystrophic neurites and neuronal intranuclear inclusions, consistent with frontotemporal lobar degeneration-TDP type A. We identified a likely pathogenic variant in TUBA4A segregating with disease. TUBA4A encodes for α-tubulin, which is a major component of the microtubule network. Variants in TUBA4A have been suggested as a rare genetic cause of amyotrophic lateral sclerosis (ALS) and have sporadically been reported in patients with FTD without supporting genetic segregation. A decreased trend of TUBA4A protein abundance was observed in patients compared with controls, and a microtubule repolymerization assay demonstrated disrupted α-tubulin function. As opposed to variants found in ALS, TUBA4A variants associated with FTD appear more localized to the N-terminus, indicating different pathogenic mechanisms.

CONCLUSIONS

Our findings support the role of TUBA4A variants as rare genetic cause of familial FTD.

Recommendations to distinguish behavioural variant frontotemporal dementia from psychiatric disorders

The behavioural variant of frontotemporal dementia (bvFTD) is a frequent cause of early-onset dementia. The diagnosis of bvFTD remains challenging because of the limited accuracy of neuroimaging in the early disease stages and the absence of molecular biomarkers, and therefore relies predominantly on clinical assessment. BvFTD shows significant symptomatic overlap with non-degenerative primary psychiatric disorders including major depressive disorder, bipolar disorder, schizophrenia, obsessive-compulsive disorder, autism spectrum disorders and even personality disorders. To date, ∼50% of patients with bvFTD receive a prior psychiatric diagnosis, and average diagnostic delay is up to 5-6 years from symptom onset. It is also not uncommon for patients with primary psychiatric disorders to be wrongly diagnosed with bvFTD. The Neuropsychiatric International Consortium for Frontotemporal Dementia was recently established to determine the current best clinical practice and set up an international collaboration to share a common dataset for future research. The goal of the present paper was to review the existing literature on the diagnosis of bvFTD and its differential diagnosis with primary psychiatric disorders to provide consensus recommendations on the clinical assessment. A systematic literature search with a narrative review was performed to determine all bvFTD-related diagnostic evidence for the following topics: bvFTD history taking, psychiatric assessment, clinical scales, physical and neurological examination, bedside cognitive tests, neuropsychological assessment, social cognition, structural neuroimaging, functional neuroimaging, CSF and genetic testing. For each topic, responsible team members proposed a set of minimal requirements, optimal clinical recommendations, and tools requiring further research or those that should be developed. Recommendations were listed if they reached a ≥ 85% expert consensus based on an online survey among all consortium participants. New recommendations include performing at least one formal social cognition test in the standard neuropsychological battery for bvFTD. We emphasize the importance of 3D-T1 brain MRI with a standardized review protocol including validated visual atrophy rating scales, and to consider volumetric analyses if available. We clarify the role of 18F-fluorodeoxyglucose PET for the exclusion of bvFTD when normal, whereas non-specific regional metabolism abnormalities should not be over-interpreted in the case of a psychiatric differential diagnosis. We highlight the potential role of serum or CSF neurofilament light chain to differentiate bvFTD from primary psychiatric disorders. Finally, based on the increasing literature and clinical experience, the consortium determined that screening for C9orf72 mutation should be performed in all possible/probable bvFTD cases or suspected cases with strong psychiatric features.

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.

A case of TDP-43 type C pathology presenting as nonfluent variant primary progressive aphasia

We report a case of rapidly progressive nonfluent variant PPA (nfvPPA), age at onset 77 years old and disease duration 3.3 years, who came to post mortem and was found to have TDP-43 type C pathology, an unusual finding for nfvPPA. All prior TDP-43 type C cases from the UCL FTD cohort (n=25) had a semantic variant PPA (svPPA) phenotype, with all having a younger age at onset and longer disease duration than the nfvPPA case. Volumetric analysis of MRI from the nfvPPA case, twelve of the svPPA cases and ten age-matched controls was performed. Whilst left frontal and insular volumes were lower in the nfvPPA case compared with svPPA, cortical and medial temporal lobe volumes were lower (particularly on the right) in the svPPA group compared with the nfvPPA patient. Such anatomical involvement is likely to be consistent with the presence of a nonfluent aphasia (left frontal lobe and insula), and only mild semantic deficit early in the illness (left but not right temporal lobe). Such unique cases add to the heterogeneity of the FTD spectrum.

Lysosomal Dysfunction at the Centre of Parkinson's Disease and Frontotemporal Dementia/Amyotrophic Lateral Sclerosis

Parkinson's disease (PD) and frontotemporal dementia/amyotrophic lateral sclerosis (FTD/ALS) are insidious and incurable neurodegenerative diseases that represent a significant burden to affected individuals, caregivers, and an ageing population. Both PD and FTD/ALS are defined at post mortem by the presence of protein aggregates and the loss of specific subsets of neurons. We examine here the crucial role of lysosome dysfunction in these diseases and discuss recent evidence for converging mechanisms. This review draws upon multiple lines of evidence from genetic studies, human tissue, induced pluripotent stem cells (iPSCs), and animal models to argue that lysosomal failure is a primary mechanism of disease, rather than merely reflecting association with protein aggregate end-points. This review provides compelling rationale for targeting lysosomes in future therapeutics for both PD and FTD/ALS.

The role of 18F-FP-CIT PET in differentiation of progressive supranuclear palsy and frontotemporal dementia in the early stage

PURPOSE

The purpose of this study was to evaluate whether the pattern of striatal dopamine transporter (DAT) availability could differentiate between progressive supranuclear palsy (PSP) and frontotemporal dementia (FTD) in the first few years of the disease.

METHODS

We enrolled patients who had Parkinsonism and frontal dysfunction and/or language deficit, visited the clinic within 2 years of the onset of symptoms, and had been followed-up for longer than 5 years; thus resulting in 26 patients with PSP and 24 patients with FTD. By quantitatively analyzing N-(3-[¹⁸F]fluoropropyl)-2β-carbon ethoxy-3β-(4-iodophenyl) nortropane PET, we compared the pattern of DAT availability at the time of the baseline evaluation between the two groups. The discriminatory power of variables including DAT activity and clinical parameters was investigated by receiver operating characteristics (ROC) analyses. Additionally, we analyzed the correlation between striatal subregional DAT availability and cognitive profiles.

RESULTS

Patients with PSP and FTD had significantly lower DAT availability than normal controls in the whole striatum and in each striatal subregion. When comparing the two groups, DAT availability was significantly lower in patients with PSP than those with FTD in all striatal subregions. The PSP and FTD groups had generally similar subregional patterns of DAT activity in terms of the anteroposterior and ventrodorsal gradients and asymmetry, except for a different preferential involvement in the caudate. The ROC analysis showed that the DAT activity of the whole striatum had an excellent discriminatory power relative to Parkinsonism or neurocognitive profiles. Correlation analysis showed that verbal memory was significantly correlated with DAT availability in the whole striatum and the putaminal subregion only in patients with PSP.

CONCLUSIONS

DAT scans have prognostic value in determining whether patients with Parkinsonism and behavioral and/or language dysfunction will develop features of PSP or FTD later in the disease course.