Survival profiles of patients with frontotemporal dementia and motor neuron disease

Predictors of Care Home Admission and Survival Rate in Patients With Syndromes Associated With Frontotemporal Lobar Degeneration in Europe

BACKGROUND AND OBJECTIVES

Data on care home admission and survival rates of patients with syndromes associated with frontotemporal lobar degeneration (FTLD) are limited. However, their estimation is essential to plan trials and assess the efficacy of intervention. Population-based registers provide unique samples for this estimate. The aim of this study was to assess care home admission rate, survival rate, and their predictors in incident patients with FTLD-associated syndromes from the European FRONTIERS register-based study.

METHODS

We conducted a prospective longitudinal multinational observational registry study, considering incident patients with FTLD-associated syndromes diagnosed between June 1, 2018, and May 31, 2019, and followed for up to 5 years till May 31, 2023. We enrolled patients fulfilling diagnosis of the behavioral variant frontotemporal dementia (bvFTD), primary progressive aphasia (PPA), progressive supranuclear palsy (PSP) or corticobasal syndrome (CBS), and FTD with motor neuron disease (FTD-MND). Kaplan-Meier analysis and Cox multivariable regression models were used to assess care home admission and survival rates. The survival probability score (SPS) was computed based on independent predictors of survivorship.

RESULTS

A total of 266 incident patients with FTLD were included (mean age ± SD = 66.7 ± 9.0; female = 41.4%). The median care home admission rate was 97 months (95% CIs 86-98) from disease onset and 57 months (95% CIs 56-58) from diagnosis. The median survival was 90 months (95% CIs 77-97) from disease onset and 49 months (95% CIs 44-58) from diagnosis. Survival from diagnosis was shorter in FTD-MND (hazard ratio [HR] 4.59, 95% CIs 2.49-8.76, p < 0.001) and PSP/CBS (HR 1.56, 95% CIs 1.01-2.42, p = 0.044) compared with bvFTD; no differences between PPA and bvFTD were found. The SPS proved high accuracy in predicting 1-year survival probability (area under the receiver operating characteristic curve = 0.789, 95% CIs 0.69-0.87), when defined by age, European area of residency, extrapyramidal symptoms, and MND at diagnosis.

DISCUSSION

In FTLD-associated syndromes, survival rates differ according to clinical features and geography. The SPS was able to predict prognosis at individual patient level with an accuracy of ∼80% and may help to improve patient stratification in clinical trials. Future confirmatory studies considering different populations are needed.

Clinicopathological correlates in the frontotemporal lobar degeneration-motor neuron disease spectrum

Amyotrophic lateral sclerosis (ALS) is a devastating motor neuron disease (MND) that shares a common clinical, genetic and pathologic spectrum with frontotemporal dementia (FTD). It is highly heterogeneous in its presentation and features. Up to 50% of patients with MND develop cognitive-behavioural symptoms during the course of the disease, meeting criteria for FTD in 10%-15% of cases. In the absence of a precise biomarker, neuropathology is still a valuable tool to understand disease nosology, reach a definite diagnostic confirmation and help define specific subgroups of patients with common phenotypic, genetic and biomarker profiles. However, few neuropathological series have been published, and the frequency of frontotemporal lobar degeneration (FTLD) in MND is difficult to estimate. In this work we describe a large clinicopathological series of MND patients, analysing the frequency of concurrent FTLD changes and trying to define specific subgroups of patients based on their clinical, genetic and pathological characteristics. We performed an observational, retrospective, multicentre case study. We included all cases meeting neuropathological criteria for MND from the Neurological Tissue Bank of the FRCB-IDIBAPS-Hospital Clínic Barcelona Biobank between 1994 and 2022, regardless of their last clinical diagnosis. While brain donation is encouraged in all patients, it is performed in very few, and representativeness of the cohort might not be precise for all patients with MND. We retrospectively reviewed clinical and neuropathological data and describe the main clinical, genetic and pathogenic features, comparing neuropathologic groups between MND with and without FTLD changes and aiming to define specific subgroups. We included brain samples from 124 patients, 44 of whom (35.5%) had FTLD neuropathologic features (i.e. FTLD-MND). Pathologic TDP-43 aggregates were present in 93.6% of the cohort and were more extensive (higher Brettschneider stage) in those with concurrent FTLD (P < 0.001). Motor symptom onset was more frequent in the bulbar region in FTLD-MND cases than in those with isolated MND (P = 0.023), with no differences in survival. We observed a better clinicopathological correlation in the MND group than in the FTLD-MND group (93.8% versus 61.4%; P < 0.001). Pathogenic genetic variants were more common in the FTLD-MND group, especially C9orf72. We describe a frequency of FTLD of 35.5% in our series of neuropathologically confirmed cases of MND. The FTLD-MND spectrum is highly heterogeneous in all aspects, especially in patients with FTLD, in whom it is particularly difficult to define specific subgroups. In the absence of definite biomarkers, neuropathology remains a valuable tool for a definite diagnosis, increasing our knowledge in disease nosology.

C9orf72 repeat expansions modify risk for secondary motor and cognitive-behavioral symptoms in behavioral-variant frontotemporal degeneration and amyotrophic lateral sclerosis

In behavioral-variant frontotemporal degeneration (bvFTD) and amyotrophic lateral sclerosis (ALS), the presence of secondary motor or cognitive-behavioral symptoms, respectively, is associated with shorter survival. However, factors influencing the risk and hazard of secondary symptom development remain largely unexplored. We performed a retrospective evaluation of the entire disease course of individuals with amyotrophic lateral sclerosis (n=172) and behavioral-variant frontotemporal degeneration (n=69). Only individuals who had neuropathological confirmation of a TDP-43 proteinopathy at autopsy or had a C9orf72 repeat expansion were included for analysis. We examined the odds and hazard of secondary symptom development and assessed whether they were modified by the presence of a C9orf72 repeat expansion or initial clinical syndrome. Binary logistic regression and Cox proportional hazard analyses revealed increased odds (OR=4.25 [1.97-9.14]; p<0.001) and an increased hazard (HR= 4.77 [2.33-9.79], p<0.001) for developing secondary symptoms in C9orf72 expansion carriers compared to noncarriers. Initial clinical syndrome (bvFTD or ALS), age at symptom onset, and sex were not associated with development of secondary motor or cognitive-behavioral symptoms. These findings highlight the need for clinician vigilance to detect the onset of secondary motor symptoms and cognitive-behavioral in patients carrying a C9orf72 repeat expansion, regardless of initial clinical syndrome, and may warrant dual referrals between cognitive and neuromuscular clinics in these cases.

Brain regions show different metabolic and protein arginine methylation phenotypes in frontotemporal dementias and Alzheimer's disease

Frontotemporal dementia (FTD) is a heterogeneous neurodegenerative disease with multiple histopathological subtypes. FTD patients share similar symptoms with Alzheimer's disease (AD). Hence, FTD patients are commonly misdiagnosed as AD, despite the consensus clinical diagnostic criteria. It is therefore of great clinical need to identify a biomarker that can distinguish FTD from AD and control individuals, and potentially further differentiate between FTD pathological subtypes. We conducted a metabolomic analysis on post-mortem human brain tissue from three regions: cerebellum, frontal cortex and occipital cortex from control, FTLD-TDP type A, type A-C9, type C and AD. Our results indicate that the brain subdivisions responsible for different functions show different metabolic patterns. We further explored the region-specific metabolic characteristics of different FTD subtypes and AD patients. Different FTD subtypes and AD share similar metabolic phenotypes in the cerebellum, but AD exhibited distinct metabolic patterns in the frontal and occipital regions compared to FTD. The identified brain region-specific metabolite biomarkers could provide a tool for distinguishing different FTD subtypes and AD and provide the first insights into the metabolic changes of FTLD-TDP type A, type A-C9, type C and AD in different regions of the brain. The importance of protein arginine methylation in neurodegenerative disease has come to light, so we investigated whether the arginine methylation level contributes to disease pathogenesis. Our findings provide new insights into the relationship between arginine methylation and metabolic changes in FTD subtypes and AD that could be further explored, to study the molecular mechanism of pathogenesis.

A Systematic Review of Caregiver Coping Strategies in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia

Caregivers of patients diagnosed with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) often experience distressing symptoms related to their caregiving role. This review evaluates the existing literature on coping and their relationship to ALS and FTD caregiver psychological wellbeing. Published articles were identified via a systematic search of four databases (Cinahl Complete, Medline, Embase and PsycINFO). Overall, problem-focused coping strategies such as active coping and planning was used most often by ALS and FTD caregivers. Positive emotion-focused coping strategies such as acceptance were also frequently used by FTD caregivers. In contrast, dysfunctional coping strategies such as self-oriented reactions including self-blame, denial and self-preoccupation appeared to be the most salient coping strategy negatively impacting on caregiver psychological wellbeing. Six different coping measures were used and their psychometric properties were typically under-reported or satisfactory at best when reported. While coping is as an important aspect of caregivers' experience, it remains unclear how the temporal dimensions of the coping process as well as stressor specificity influences psychological adaptation, and consequently, development of targeted caregiver intervention. The need for future studies to define the coping process more clearly in order to capture the unique stressors encountered by ALS and FTD caregivers throughout the different disease stages is emphasised.

Brain structural and perfusion changes in amyotrophic lateral sclerosis-frontotemporal dementia patients with cognitive and motor onset: a preliminary study

Amyotrophic lateral sclerosis-frontotemporal dementia (ALS-FTD) is rare but exhibits worse prognosis than either ALS or FTD alone. However, cognitive onset ALS-FTD (ALS-FTD-C) confers significantly better patient survival than does motor onset ALS-FTD (ALS-FTD-M), underscoring a meager understanding of pathological group differences. This study aimed to assess disparities in cortical atrophy and perfusion shown by patients with the above disease variants. A total of 38 participants (ALS-FTD-C, 8; ALS-FTD-M, 6; simultaneous-onset ALS-FTD [ALS-FTD-S], 4; healthy controls [HC], 20) qualified for the study and underwent magnetic resonance imaging scan. Three-dimensional T1-weighted structural brain imaging and 3D-pseudocontinuous arterial spin-labeled imaging were routinely collected. Gray matter volume (GMV) and cerebral blood flow (CBF) in ALS-FTD-C and ALS-FTD-M were compared through voxel-based analysis. Correlations between imaging parameters and clinical data were also assessed. Compared with HC, ALS-FTD had significant GMV reduction mainly in bilateral limbic system. GMV reduction in ALS-FTD-C was similar in pattern but less widespread, whereas ALS-FTD-M lacked any significant GMV reduction. In CBF analyses, ALS-FTD displayed hypoperfusion in bilateral motor cortex, frontotemporal lobe, and left basal ganglia. Hypoperfusion involved bilateral temporal lobe, prefrontal cortex, and putamen in ALS-FTD-C but was limited to left parahippocampal gyrus in ALS-FTD-M. Correlations between clinical data and GMV/CBF changes in specific regions were also identified in ALS-FTD. Group-specific patterns of cortical atrophy and perfusion were evident in ALS-FTD-C and ALS-FTD-M. ALS-FTD-C showed pronounced cortical atrophy and hypoperfusion, which were otherwise minimal in ALS-FTD-M. Above findings preliminarily revealed the pathological group differences that may help in classifying patients with ALS-FTD.

Illness Cognitions in ALS: New Insights Into Clinical Management of Behavioural Symptoms

Timely management of frontotemporal dysfunction associated with amyotrophic lateral sclerosis (ALS) has important prognostic and therapeutic implications. However, there remains a paucity of research on best practise recommendations to guide the development of interventions for cognitive and behavioural symptoms as part of ALS care. Accordingly, a focus on illness perceptions may provide a preliminary framework for managing cognitive and behavioural symptoms. The aim of the present study was to explore the nature of illness perceptions among ALS patients with cognitive and behavioural symptoms. A total of 39 patients were recruited from a specialised ALS clinic. Factor analysis showed three independent and clinically interpretable factors corresponding to “cognitive and emotion related ALS perceptions,” “cognitive- specific ALS perceptions” and “ALS coherence”. Of these factors, greater perceived cognitive and emotional impacts of ALS were associated with an approximate 4-fold increased risk of behavioural changes (p < 0.05). Greater perceived cognitive and emotional impacts of ALS was also associated with more rapid disease progression (p < 0.001). As such, timely provision of intervention addressing perceptions about the impact of ALS on functioning as well as associated emotional distress may optimise clinical management of cognitive and behavioural symptoms of ALS.

Common genetic variation is associated with longitudinal decline and network features in behavioral variant frontotemporal degeneration

The T allele in rs1768208 located in or near the myelin oligodendrocyte basic protein gene (MOBP) is a risk factor for frontotemporal degeneration pathology. We evaluated the hypothesis that the presence of a T allele in rs1768208 will be associated with rate of cognitive decline in behavioral variant frontotemporal degeneration (bvFTD) related to compromised frontal networks. We studied 81 individuals clinically diagnosed with bvFTD who were genotyped for rs1768208 and coded using a dominant model reflecting the presence (i.e., MOBP +) or absence (MOBP -) of the T risk allele. Linear mixed-effects models assessed the association of genotype on neuropsychological performance over time. Regression analyses examined differences in network structure by MOBP genotype. We found a genotype by time interaction for declining cognitive performance, whereby MOBP + individuals demonstrated faster rates of decline in executive function. The presence of a MOBP risk allele was associated with degradation of white matter network features in the frontal lobe. These findings suggest that individual genetic variation may contribute to heterogeneity in clinical progression.

Motor neuron disease beginning with frontotemporal dementia: clinical features and progression

Objective: To study disease characteristics, progression and outcome in a group of motor neuron disease (MND) patients beginning with frontotemporal dementia (FTD) by comparing them with patients with the typical motor-onset. Methods: 849 patients recruited from tertiary centers were studied according to FTD-onset and motor-onset. We studied clinical data, functional decline and survival. Results: Twenty six patients (3.1%) had FTD-onset of whom seven (26.9%) had coincident motor dysfunction. In those with isolated FTD-onset, motor symptoms developed after a median of 12 months (IQR: 4-18). FTD-onset patients were older at presentation; the bulbar-region was more frequently first affected than in the motor-onset group; there was a predominant upper motor neuron (UMN) phenotype; fasciculations were less common than in motor onset disease but facial and upper limb apraxia was more frequent; as well as ALS and FTD familial history. No differences were observed for gender, frequency of C9orf72 hexanucleotide repeat expansion, family history of Alzheimer's and Parkinson's diseases, median delay from motor symptoms to diagnosis, median ALSFRS-R rate of change, handedness, emotional lability, depression, weight loss, resting tremor, bradykinesia, sensory changes or neuropathy. Clinical and demographic features were similar between FTD-onset patients developing bulbar MND and bulbar-onset ALS patients. Once bulbar symptoms manifested functional progression and survival were similar to those of bulbar-onset ALS patients. Conclusions: MND patients with FTD-onset have a distinctive phenotype characterized by predominant UMN presentation and rapid progression to bulbar involvement. The main factor impacting functional decline and survival is the onset of bulbar dysfunction.

Predicting loss of independence and mortality in frontotemporal lobar degeneration syndromes

OBJECTIVE

To test the hypothesis that in syndromes associated with frontotemporal lobar degeneration, behavioural impairment predicts loss of functional independence and motor clinical features predict mortality, irrespective of diagnostic group.

METHODS

We used a transdiagnostic approach to survival in an epidemiological cohort in the UK, testing the association between clinical features, independence and survival in patients with clinical diagnoses of behavioural variant frontotemporal dementia (bvFTD n=64), non-fluent variant primary progressive aphasia (nfvPPA n=36), semantic variant primary progressive aphasia (svPPA n=25), progressive supranuclear palsy (PSP n=101) and corticobasal syndrome (CBS n=68). A principal components analysis identified six dimensions of clinical features. Using Cox proportional hazards and logistic regression, we identified the association between each of these dimensions and both functionally independent survival (time from clinical assessment to care home admission) and absolute survival (time to death). Analyses adjusted for the covariates of age, gender and diagnostic group. Secondary analysis excluded specific diagnostic groups.

RESULTS

Behavioural disturbance, including impulsivity and apathy, was associated with reduced functionally independent survival (OR 2.46, p<0.001), even if patients with bvFTD were removed from the analysis. Motor impairments were associated with reduced absolute survival, even if patients with PSP and CBS were removed from the analysis.

CONCLUSION

Our results can assist individualised prognostication and planning of disease-modifying trials, and they support a transdiagnostic approach to symptomatic treatment trials in patients with clinical syndromes associated with frontotemporal lobar degeneration.

Clinical Determinants of Disease Progression in Amyotrophic Lateral Sclerosis-A Retrospective Cohort Study

Background: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that is ultimately fatal but characterized by substantial phenotypic heterogeneity, which is known to impact long-term course and survival. This study investigated clinical determinants of disease progression and outcome in a large cohort of patients with ALS. Methods: Retrospective analysis included comprehensive data from 625 patients who attended a tertiary ALS centre at least twice. Patients were stratified according to five distinct clinical phenotypes: classical ALS; bulbar ALS; ALS with frontotemporal dementia (ALS-FTD); upper motor neuron predominant (UMNP); and lower motor neuron predominant (LMNP). Results: This study confirmed higher age at symptom onset, shorter latency to diagnosis and more rapid decline in the revised ALS Functional Rating Scale sum score as predictors of poor prognosis. Hazard ratios for shorter survival were higher in patients with ALS-FTD versus classical ALS, and in patients with versus without chronic obstructive pulmonary disease (COPD). Mean survival was longest in the UMNP phenotype group. Conclusions: This study confirmed established predictors of shorter survival in ALS and showed that concomitant COPD in particular relates to poor outcome.

Cognitive network hyperactivation and motor cortex decline correlate with ALS prognosis

We aimed to quantitatively characterize progressive brain network disruption in Amyotrophic Lateral Sclerosis (ALS) during cognition using the mismatch negativity (MMN), an electrophysiological index of attention switching. We measured the MMN using 128-channel EEG longitudinally (2-5 timepoints) in 60 ALS patients and cross-sectionally in 62 healthy controls. Using dipole fitting and linearly constrained minimum variance beamforming we investigated cortical source activity changes over time. In ALS, the inferior frontal gyri (IFG) show significantly lower baseline activity compared to controls. The right IFG and both superior temporal gyri (STG) become progressively hyperactive longitudinally. By contrast, the left motor and dorsolateral prefrontal cortices are initially hyperactive, declining progressively. Baseline motor hyperactivity correlates with cognitive disinhibition, and lower baseline IFG activities correlate with motor decline rate, while left dorsolateral prefrontal activity predicted cognitive and behavioural impairment. Shorter survival correlates with reduced baseline IFG and STG activity and later STG hyperactivation. Source-resolved EEG facilitates quantitative characterization of symptom-associated and symptom-preceding motor and cognitive-behavioral cortical network decline in ALS.

Heterogeneity of behavioural and language deficits in FTD-MND

OBJECTIVE

To comprehensively examine the clinical presentation of patients diagnosed with frontotemporal dementia-motor neuron disease (FTD-MND) compared to FTD subtypes. To clarify the heterogeneity of behavioural and language deficits in FTD-MND using a data-driven approach.

METHODS

Patients with FTD-MND (n = 31), behavioural variant FTD (n = 119), non-fluent variant primary progressive aphasia (n = 47), semantic variant primary progressive aphasia (n = 42), and controls (n = 127) underwent comprehensive clinical, cognitive and behavioural assessments. Two-step cluster analysis examined patterns of behavioural and language impairment. Voxel-based morphometry and tract-based spatial statistics were used to investigate differences across the subgroups that emerged from cluster analysis.

RESULTS

More than half of FTD-MND patients initially presented with variable combinations of deficits (e.g., mixed behaviour/cognitive, mixed behaviour/cognitive/motor deficits), with 74% of them meeting criteria for FTD-MND within 24 months with a median of 12 months. The frequency and severity of behavioural and language abnormalities in FTD-MND lie between that seen in the three FTD phenotypes. Cluster analysis identified three patterns of behavioural and language impairment in FTD-MND. The three FTD-MND subgroups demonstrated different profiles of white matter tract disruption, but did not differ in age at onset, disease duration or patterns of cortical atrophy.

CONCLUSIONS

While highly heterogeneous, in terms of behavioural and language deficits, and disease severity, the presentation of FTD-MND may be distinct to that of FTD. Distinct white matter degeneration patterns may underpin heterogeneous clinical profiles in FTD-MND. FTD presenting with mixed behavioural-language disturbances should be monitored closely for at least 12-24 months for the emergence of MND symptoms/signs.

Survival and Prognostic Factors in C9orf72 Repeat Expansion Carriers: A Systematic Review and Meta-analysis

Importance

The c9orf72 repeat expansion (c9 or c9orf72RE) confers a survival disadvantage in amyotrophic lateral sclerosis (ALS); its effect on prognosis in frontotemporal dementia (FTD) remains uncertain. Data on prognostic factors in c9orf72RE disorders could inform patient care, genetic counseling, and trial design.

Objective

To examine prognostic factors in c9ALS, c9FTD, c9ALS-FTD, and atypical phenotypes.

Data Sources

The MEDLINE, Embase, Amed, ProQuest, PsychINFO, CINAHL, and LILACS databases were searched between January 2011 and January 2019. Keywords used were c9orf72 and chromosome 9 open reading frame 72. Reference lists, citations of eligible studies, and review articles were also searched by hand.

Study Selection

Studies reporting disease duration for patients with a confirmed c9orf72RE and a neurological and/or psychiatric disorder were included. A second author independently reviewed studies classified as irrelevant by the first author. Analysis began in January 2019.

Data Extraction and Synthesis

Data were extracted by 1 author; a further author independently extracted 10% of data. Data were synthesized in univariate and multivariable Cox regression and are displayed as hazard ratios (HR) and 95% confidence intervals.

Main Outcomes and Measures

Survival after symptom onset.

Results

Overall, 206 studies reporting on 1060 patients were included from 2878 publications identified (c9ALS: n = 455; c9FTD: n = 296; c9ALS-FTD: n = 198; atypical phenotypes: n = 111); 197 duplicate cases were excluded. The median (95% CI) survival (in years) differed significantly between patients with c9ALS (2.8 [2.67-3.00]), c9FTD (9.0 [8.09-9.91]), and c9ALS-FTD (3.0 [2.73-3.27]); survival in atypical phenotypes varied substantially. Older age at onset was associated with shorter survival in c9ALS (HR, 1.03; 95% CI, 1.02-1.04; P < .001), c9FTD (HR, 1.04; 95% CI, 1.02-1.06; P < .001), and c9ALS-FTD (HR, 1.02; 95% CI, 1.004-1.04; P = .016). Bulbar onset was associated with shorter survival in c9ALS (HR, 1.64; 95% CI, 1.27-2.08; P < .001). Age at onset and bulbar onset ALS remained significant in multivariable regression including variables indicating potential diagnostic ascertainment bias, selection bias, and reporting bias. Family history, sex, study continent, FTD subtype, or the presence of additional pathogenic sequence variants were not significantly associated with survival. Clinical phenotypes in patients with neuropathologically confirmed frontotemporal lobar degeneration-TDP-43, motor neuron disease-TDP-43 and frontotemporal lobar degeneration-motor neuron disease-TDP-43 were heterogenous and impacted on survival.

Conclusions and Relevance

Several factors associated with survival in c9orf72RE disorders were identified. The inherent limitations of our methodological approach must be considered; nonetheless, the reported prognostic factors were not significantly associated with the bias indicators examined.

Predictors of survival in frontotemporal lobar degeneration syndromes

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

Behavioural Variant Frontotemporal Dementia: Recent Advances in the Diagnosis and Understanding of the Disorder

Frontotemporal dementia (FTD), particularly the behavioural variant (bvFTD) form, has fascinated researchers. Recent years have seen an increasing interest in aspects of bvFTD that extend beyond the initial focus on cognitive changes and frontal executive dysfunction. Changes have been identified in aspects including fundamental changes in physiology and metabolism, and cognitive domains such as episodic memory. Work on social cognition has emphasised the importance of a breakdown in interpreting and expressing emotions, while the overlap between psychiatric disorders and bvFTD has been brought into focus by the finding of high rates of psychotic features in carriers of the c9orf72 gene expansion. We review these aspects in the chapter " Behavioural variant frontotemporal dementia: Recent advances in diagnosis and understanding of the disorder" and also potential markers of disease progression and early diagnosis that may aid in the development of treatment options, which have thus far eluded us.

Frontotemporal dementia-linked P112H mutation of TDP-43 induces protein structural change and impairs its RNA binding function

TDP‐43 forms the primary constituents of the cytoplasmic inclusions contributing to various neurodegenerative diseases, including amyotrophic lateral sclerosis and frontotemporal dementia (FTD). Over 60 TDP‐43 mutations have been identified in patients suffering from these two diseases, but most variations are located in the protein's disordered C‐terminal glycine‐rich region. P112H mutation of TDP‐43 has been uniquely linked to FTD, and is located in the first RNA recognition motif (RRM1). This mutation is thought to be pathogenic, but its impact on TDP‐43 at the protein level remains unclear. Here, we compare the biochemical and biophysical properties of TDP‐43 truncated proteins with or without P112H mutation. We show that P112H‐mutated TDP‐43 proteins exhibit higher thermal stability, impaired RNA‐binding activity, and a reduced tendency to aggregate relative to wild‐type proteins. Near‐UV CD, 2D‐nuclear‐magnetic resonance, and intrinsic fluorescence spectrometry further reveal that the P112H mutation in RRM1 generates local conformational changes surrounding the mutational site that disrupt the stacking interactions of the W113 side chain with nucleic acids. Together, these results support the notion that P112H mutation of TDP‐43 contributes to FTD through functional impairment of RNA metabolism and/or structural changes that curtail protein clearance.

Metabolic brain changes across different levels of cognitive impairment in ALS: a 18F-FDG-PET study

OBJECTIVE

To identify the metabolic changes related to the various levels of cognitive deficits in amyotrophic lateral sclerosis (ALS) using 18F-2-fluoro-2-deoxy-D-glucose positron emission tomography (18F-FDG-PET) imaging.

METHODS

274 ALS patients underwent neuropsychological assessment and brain 18F-FDG-PET at diagnosis. According to the criteria published in 2017, cognitive status was classified as ALS with normal cognition (ALS-Cn, n=132), ALS with behavioural impairment (ALS-Bi, n=66), ALS with cognitive impairment (ALS-Ci, n=30), ALS with cognitive and behavioural impairment (ALS-Cbi, n=26), ALS with frontotemporal dementia (ALS-FTD, n=20). We compared each group displaying some degree of cognitive and/or behavioural impairment to ALS-Cn patients, including age at PET, sex and ALS Functional Rating Scale-Revised as covariates.

RESULTS

We identified frontal lobe relative hypometabolism in cognitively impaired patients that resulted more extensive and significant across the continuum from ALS-Ci, through ALS-Cbi, to ALS-FTD. ALS-FTD patients also showed cerebellar relative hypermetabolism. ALS-Bi patients did not show any difference compared with ALS-Cn.

CONCLUSIONS

These data support the concept that patients with cognitive impairment have a more widespread neurodegenerative process compared with patients with a pure motor disease: the more severe the cognitive impairment, the more diffuse the metabolic changes. Otherwise, metabolic changes related to pure behavioural impairment need further characterisation.

Phenotypic variability in ALS-FTD and effect on survival

OBJECTIVE

To determine if survival and cognitive profile is affected by initial presentation in amyotrophic lateral sclerosis-frontotemporal dementia (ALS-FTD) (motor vs cognitive), we compared survival patterns in ALS-FTD based on initial phenotypic presentation and their cognitive profile compared to behavioral variant FTD (bvFTD).

METHODS

Cognitive/behavioral profiles were examined in 98 patients (59 ALS-FTD and 39 bvFTD). The initial presentation of ALS-FTD was categorized into either motor or cognitive. Survival was calculated from initial symptom onset. MRI brain atrophy patterns were examined using a validated visual rating scale.

RESULTS

In the ALS-FTD group, 41 (69%) patients were categorized as having an initial cognitive presentation and 18 (31%) a motor presentation. Patients with motor presentation experienced a significantly shorter median survival of 2.7 years compared to 4.4 years (p < 0.001) in those with a cognitive presentation. No differences between motor vs cognitive onset ALS-FTD were found on cognitive testing. When compared to bvFTD, ALS-FTD-cognitive presentation was characterized by reduced language function (p < 0.001), verbal fluency (p = 0.001), and naming (p = 0.007). Both motor and cognitive onset ALS-FTD showed reduced emotion processing (p = 0.01) and exhibited greater motor cortex and dorsal lateral prefrontal cortex atrophy than bvFTD. Increased motor cortex atrophy was associated with 1.5-fold reduction in survival.

CONCLUSIONS

Initial motor presentation in ALS-FTD leads to faster progression than in those with a cognitive presentation, despite similar overall cognitive deficits. These findings suggest that disease progression in ALS-FTD may be critically linked to physiologic and motor changes.

Development of the MiNDToolkit for management of cognitive and behavioral impairment in motor neuron disease

Aim: To develop structured guidance, recommendations and techniques for nonpharmacological management of cognitive and behavioral impairments in motor neuron disease, called the MiNDToolkit. Methods: A four-round-modified Delphi method was utilized (online and face-to-face meeting), supplemented by recent research, recommendations, expertise from allied health professionals, clinicians, researchers and clients. Results: Round 1 (N = 47) identified allied health professionals techniques. Round 2 (N = 23) and 3 (N = 19) used expert consensus, refining general focus, specific elements and techniques. Round 4 (N = 8) applied personal, lived and occupational experience, finalizing the general structure and content of specific techniques. Conclusion: The MiNDToolkit is composed of multiple tools to structure decision-making through flowcharts, decision trees and checklists, provide information about impairments, assessment recommendations and techniques or strategies for nonpharmacological management cognitive or behavioral impairments in motor neuron disease.

Genetic predictors of survival in behavioral variant frontotemporal degeneration

OBJECTIVE

To determine autosomal dominant genetic predictors of survival in individuals with behavioral variant frontotemporal degeneration (bvFTD).

METHODS

A retrospective chart review of 174 cases with a clinical phenotype of bvFTD but no associated elementary neurologic features was performed, with diagnosis either autopsy-confirmed (n = 57) or supported by CSF evidence of non-Alzheimer pathology (n = 117). Genetic analysis of the 3 most common genes with pathogenic autosomal dominant mutations associated with frontotemporal degeneration was performed in all patients, which identified cases with C9orf72 expansion (n = 28), progranulin (GRN) mutation (n = 12), and microtubule-associated protein tau (MAPT) mutation (n = 10). Cox proportional hazards regressions were used to test for associations between survival and mutation status, sex, age at symptom onset, and education.

RESULTS

Across all patients with bvFTD, the presence of a disease-associated pathogenic mutation was associated with shortened survival (hazard ratio [HR] 2.164, 95% confidence interval [CI] 1.391, 3.368). In separate models, a GRN mutation (HR 2.423, 95% CI 1.237, 4.744), MAPT mutation (HR 8.056, 95% CI 2.938, 22.092), and C9orf72 expansion (HR 1.832, 95% CI 1.034, 3.244) were each individually associated with shorter survival relative to sporadic bvFTD. A mutation on the MAPT gene results in an earlier age at onset than a C9orf72 expansion or mutation on the GRN gene (p = 0.016).

CONCLUSIONS

Our findings suggest that autosomal dominantly inherited mutations, modulated by age at symptom onset, associate with shorter survival among patients with bvFTD. We suggest that clinical trials and clinical management should consider mutation status and age at onset when evaluating disease progression.

Occupational attainment influences longitudinal decline in behavioral variant frontotemporal degeneration

To evaluate whether occupational attainment influences the trajectory of longitudinal cognitive decline in behavioral variant frontotemporal degeneration (bvFTD). Single-center, retrospective, longitudinal study. Sixty-three patients meeting consensus criteria for bvFTD underwent evaluation at the University of Pennsylvania Frontotemporal Degeneration Center. All patients were studied longitudinally on letter-guided fluency, category-naming fluency and Boston Naming Test (BNT). Occupational attainment was defined categorically by assigning each individual's occupation to a professional or non-professional category. Linear mixed-effects models evaluated the interaction of neuropsychological performance change with occupational status. Regression analyses were used to relate longitudinal decline in executive function to baseline MRI grey matter atrophy. Higher occupational status was associated with a more severe slope of cognitive decline on letter-guided fluency and category-naming fluency, but not BNT. Faster rates of longitudinal decline on letter-guided and category-naming fluency were associated with more severe baseline grey matter atrophy in right dorsolateral and inferior frontal regions. Our longitudinal findings suggest that bvFTD individuals with higher lifetime cognitive experience demonstrate more rapid decline on measures of executive function. This finding converges with cross-sectional evidence suggesting that lifetime cognitive experiences contribute to heterogeneity in clinical progression in bvFTD.

Machine Learning in Amyotrophic Lateral Sclerosis: Achievements, Pitfalls, and Future Directions

Background: Amyotrophic Lateral Sclerosis (ALS) is a relentlessly progressive neurodegenerative condition with limited therapeutic options at present. Survival from symptom onset ranges from 3 to 5 years depending on genetic, demographic, and phenotypic factors. Despite tireless research efforts, the core etiology of the disease remains elusive and drug development efforts are confounded by the lack of accurate monitoring markers. Disease heterogeneity, late-stage recruitment into pharmaceutical trials, and inclusion of phenotypically admixed patient cohorts are some of the key barriers to successful clinical trials. Machine Learning (ML) models and large international data sets offer unprecedented opportunities to appraise candidate diagnostic, monitoring, and prognostic markers. Accurate patient stratification into well-defined prognostic categories is another aspiration of emerging classification and staging systems. Methods: The objective of this paper is the comprehensive, systematic, and critical review of ML initiatives in ALS to date and their potential in research, clinical, and pharmacological applications. The focus of this review is to provide a dual, clinical-mathematical perspective on recent advances and future directions of the field. Another objective of the paper is the frank discussion of the pitfalls and drawbacks of specific models, highlighting the shortcomings of existing studies and to provide methodological recommendations for future study designs. Results: Despite considerable sample size limitations, ML techniques have already been successfully applied to ALS data sets and a number of promising diagnosis models have been proposed. Prognostic models have been tested using core clinical variables, biological, and neuroimaging data. These models also offer patient stratification opportunities for future clinical trials. Despite the enormous potential of ML in ALS research, statistical assumptions are often violated, the choice of specific statistical models is seldom justified, and the constraints of ML models are rarely enunciated. Conclusions: From a mathematical perspective, the main barrier to the development of validated diagnostic, prognostic, and monitoring indicators stem from limited sample sizes. The combination of multiple clinical, biofluid, and imaging biomarkers is likely to increase the accuracy of mathematical modeling and contribute to optimized clinical trial designs.

Predicting Development of Amyotrophic Lateral Sclerosis in Frontotemporal Dementia

BACKGROUND

A proportion of patients with frontotemporal dementia (FTD) also develop amyotrophic lateral sclerosis (ALS).

OBJECTIVE

We aimed to establish the risk of developing ALS in patients presenting with FTD and to identify the relevant clinical variables associated with progression from FTD to FTD-ALS.

METHODS

Of 218 consecutive patients with FTD, 10.1% had a dual FTD-ALS diagnosis at presentation. The remaining 152 FTD patients with follow-up of at least 12 months were included in the present study. We calculated the rate of progression to FTD-ALS and compared the baseline characteristics of FTD patients who developed ALS to those who did not develop ALS.

RESULTS

Five percent of FTD patients developed ALS. The incidence rate of ALS was 6.7/100 patient-years in patients with FTD symptoms since 1 year, which declined with duration of FTD symptoms. No FTD patients developed ALS after 5 years. Five out of 8 FTD patients who developed ALS had presented with a mixed behavioral variant FTD and progressive non-fluent aphasia (bvFTD+PNFA) phenotype, 2 with bvFTD, and 1 with PNFA. Progression to FTD-ALS was significantly more frequent in patients with bvFTD+PNFA compared to those without this phenotype (p < 0.0001, OR 38.3, 95% CI: 7.3 to 199.2), and in FTD patients who carried the C9orf72 repeat expansion compared to those without the repeat expansion (p = 0.02, OR 8.0, 95% CI: 1.7 to 38.6).

CONCLUSIONS

FTD patients with a mixed bvFTD+PNFA phenotype and with a C9orf72 repeat expansion should be closely monitored for the possible development of ALS. The risk of developing ALS in FTD appears to decline with the duration of FTD symptoms.

Population Base Rates and Disease Course of Common Psychiatric and Neurodegenerative Disorders

Knowledge of population base rates of neurological and psychiatric disorders is fundamental for diagnostic decision making. Consideration of relevant probabilistic information can improve diagnostic efficiency and accuracy. However, such data continue to be misused or underutilized, which can lead to misdiagnoses and negative patient outcomes. The aim of the current review is to create an easily accessible and comprehensive reference of existing age of onset as well as prevalence and incidence data for common neurodegenerative and psychiatric disorders in adults. Relevant epidemiological data were compiled from well-respected and frequently-cited textbooks and scholarly studies. Reviews were collected from PubMed, and publicly-available sources were gathered from Google Scholar. Results are organized and presented in several tables and a figure, which can be used as a diagnostic guide for students and clinicians across healthcare disciplines.

Amyotrophic lateral sclerosis: moving towards a new classification system

Amyotrophic lateral sclerosis is a progressive adult-onset neurodegenerative disease that primarily affects upper and lower motor neurons, but also frontotemporal and other regions of the brain. The extent to which each neuronal population is affected varies between individuals. The subsequent patterns of disease progression form the basis of diagnostic criteria and phenotypic classification systems, with considerable overlap in the clinical terms used. This overlap can lead to confusion between diagnosis and phenotype. Formal classification systems such as the El Escorial criteria and the International Classification of Diseases are systematic approaches but they omit features that are important in clinical management, such as rate of progression, genetic basis, or functional effect. Therefore, many neurologists use informal classification approaches that might not be systematic, and could include, for example, anatomical descriptions such as flail-arm syndrome. A new strategy is needed to combine the benefits of a systematic approach to classification with the rich and varied phenotypic descriptions used in clinical practice.

Survival in Frontotemporal Dementia Phenotypes: A Meta-Analysis

BACKGROUND

Survival in frontotemporal dementia (FTD) is not well understood. We conducted a mixed effects meta-analysis of survival in FTD to examine phenotype differences and contributory factors.

METHODS

The PubMed, Medline, EMBASE, CINAHL, PsycINFO and Cochrane databases were searched for studies describing survival or natural history of behavioral variant FTD (bvFTD), progressive non-fluent aphasia (PNFA), semantic dementia (SD), FTD with amyotrophic lateral sclerosis (FTD-ALS), progressive supranuclear palsy and corticobasal degeneration. There were no language restrictions.

RESULTS

We included 27 studies (2,462 subjects). Aggregate mean and median survival were derived for each phenotype and, for comparison, Alzheimer's disease (AD) (using data from the selected studies). Survival was shortest in FTD-ALS (2.5 years). Mean survival was longest in bvFTD and PNFA (8 years) and median survival in SD (12 years). AD was comparable in survival to all except FTD-ALS. Age and sex did not affect survival; the education effect was equivocal. Heterogeneity in FTD survival was largely, but not wholly, explained by phenotypes.

CONCLUSIONS

Survival differs for FTD phenotypes but, except for FTD-ALS, compares well to AD survival. Elucidating the potential causes of within-phenotype heterogeneity in survival (such as complicating features and comorbidities) may open up opportunities for tailored interventions.

What can imaging tell us about cognitive impairment and dementia?

Dementia is a contemporary global health issue with far reaching consequences, not only for affected individuals and their families, but for national and global socio-economic conditions. The hallmark feature of dementia is that of irreversible cognitive decline, usually affecting memory, and impaired activities of daily living. Advances in healthcare worldwide have facilitated longer life spans, increasing the risks of developing cognitive decline and dementia in late life. Dementia remains a clinical diagnosis. The role of structural and molecular neuroimaging in patients with dementia is primarily supportive role rather than diagnostic, American and European guidelines recommending imaging to exclude treatable causes of dementia, such as tumor, hydrocephalus or intracranial haemorrhage, but also to distinguish between different dementia subtypes, the commonest of which is Alzheimer’s disease. However, this depends on the availability of these imaging techniques at individual centres. Advanced magnetic resonance imaging (MRI) techniques, such as functional connectivity MRI, diffusion tensor imaging and magnetic resonance spectroscopy, and molecular imaging techniques, such as 18F fluoro-deoxy glucose positron emission tomography (PET), amyloid PET, tau PET, are currently within the realm of dementia research but are available for clinical use. Increasingly the research focus is on earlier identification of at risk preclinical individuals, for example due to family history. Intervention at the preclinical stages before irreversible brain damage occurs is currently the best hope of reducing the impact of dementia.

Semi-automated quantification of C9orf72 expansion size reveals inverse correlation between hexanucleotide repeat number and disease duration in frontotemporal degeneration

We investigated whether chromosome 9 open reading frame 72 hexanucleotide repeat expansion (C9orf72 expansion) size in peripheral DNA was associated with clinical differences in frontotemporal degeneration (FTD) and amyotrophic lateral sclerosis (ALS) linked to C9orf72 repeat expansion mutations. A novel quantification workflow was developed to measure C9orf72 expansion size by Southern blot densitometry in a cross-sectional cohort of C9orf72 expansion carriers with FTD (n = 39), ALS (n = 33), both (n = 35), or who are unaffected (n = 21). Multivariate linear regressions were performed to assess whether C9orf72 expansion size from peripheral DNA was associated with clinical phenotype, age of disease onset, disease duration and age at death. Mode values of C9orf72 expansion size were significantly shorter in FTD compared to ALS (p = 0.0001) but were not associated with age at onset in either FTD or ALS. A multivariate regression model correcting for patient's age at DNA collection and disease phenotype revealed that C9orf72 expansion size is significantly associated with shorter disease duration (p = 0.0107) for individuals with FTD, but not with ALS. Despite considerable somatic instability of the C9orf72 expansion, semi-automated expansion size measurements demonstrated an inverse relationship between C9orf72 expansion size and disease duration in patients with FTD. Our finding suggests that C9orf72 repeat size may be a molecular disease modifier in FTD linked to hexanucleotide repeat expansion.

Young-onset dementia epidemiology applied to neuropsychiatry practice

A substantial number of adults suffer young-onset dementia (YOD). The diversity of types and syndromes makes recognition and diagnosis difficult. An algorithmic approach to interpreting clinical data, informed by clinical epidemiology, integrates data pertaining to defining syndromes and their chronology and tempo, family history, and other neuropsychiatric features and neurologic signs, is used to reach a preliminary diagnosis and direct diagnostic tests and their interpretation. Screening for YOD in the psychiatric context is a rational process in which vigilance is combined with careful searches for red flags that signal a neurodegenerative etiology.

Occupational attainment influences survival in autopsy-confirmed frontotemporal degeneration

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Frontotemporal lobar degeneration: defining phenotypic diversity through personalized medicine

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

Cognitive correlates in amyotrophic lateral sclerosis: a population-based study in Italy

BACKGROUND

There is less data available regarding the characteristics of cognitive impairment in patients with amyotrophic lateral sclerosis (ALS) in a population-based series.

METHODOLOGY

Patients with ALS incident in Piemonte, Italy, between 2009 and 2011 underwent an extensive neuropsychological battery. Cognitive status was classified as follows: normal cognition, frontotemporal dementia (ALS-FTD), executive cognitive impairment (ALS-ECI), non-executive cognitive impairment (ALS-NECI), behavioural impairment (ALS-Bi), non-classifiable cognitive impairment. We also assessed 127 age-matched and gender-matched controls identified through patients' general practitioners.

RESULTS

Out of the 281 incident patients, 207 (71.9%) underwent the neuropsychological testing; of these, 19 were excluded from the analysis due previous conditions affecting cognition. Ninety-one (49.7%) patients were cognitively normal, 23 (12.6%) had ALS-FTD, 36 (19.7%) ALS-ECI, 10 (5.5%) ALS-NECI, 11 (6.0%) ALS-Bi and 11 (6.0%) non-classifiable cognitive impairment, 1 had comorbid Alzheimer's disease. Patients with ALS-FTD were older, had a lower education level, and had a shorter survival than any other cognitive group. Of the nine cases with C9ORF72 mutation, six had ALS-FTD, two ALS-ECI and one was cognitively normal; one of the five patients with SOD1 mutations and one of the five patients with TARBDP mutations had ALS-Bi.

CONCLUSIONS

About 50% of Italian patients with ALS had some degree of cognitive impairment, in keeping with a previous Irish study, despite the largely different genetic background of the two populations. The lower educational attainment in patients with ALS-FTD indicated a possible role of cognitive reserve in ALS-related cognitive impairment. ALS-ECI and ALS-NECI may represent discrete cognitive syndromes in the continuum of ALS and FTD.

Deficits in sentence expression in amyotrophic lateral sclerosis

Quantitative examinations of speech production in amyotrophic lateral sclerosis (ALS) are rare. To identify language features minimally confounded by a motor disorder, we investigated linguistic and motor sources of impaired sentence expression in ALS, and we related deficits to gray matter (GM) and white matter (WM) MRI abnormalities. We analyzed a semi-structured speech sample in 26 ALS patients and 19 healthy seniors for motor- and language-related deficits. Regression analyses related grammaticality to GM atrophy and reduced WM fractional anisotropy (FA). Results demonstrated that ALS patients were impaired relative to controls on quantity of speech, speech rate, speech articulation errors, and grammaticality. Speech rate and articulation errors were related to the patients' motor impairment, while grammatical difficulty was independent of motor difficulty. This was confirmed in subgroups without dysarthria and without executive deficits. Regressions related grammatical expression to GM atrophy in left inferior frontal and anterior temporal regions and to reduced FA in superior longitudinal and inferior frontal-occipital fasciculi. In conclusion, patients with ALS exhibit multifactorial deficits in sentence expression. They demonstrate a deficit in grammatical expression that is independent of their motor disorder. Impaired grammatical expression is related to disease in a network of brain regions associated with syntactic processing.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The epidemiology of frontotemporal dementia

Frontotemporal dementia, a heterogeneous neurodegenerative disorder, is a common cause of young onset dementia (i.e. dementia developing in midlife or earlier). The estimated point prevalence is 15-22/100,000, and incidence 2.7-4.1/100,000. Some 25% are late-life onset cases. Population studies show nearly equal distribution by gender, which contrasts with myriad clinical and neuropathology reports. FTD is frequently familial and hereditary; five genetic loci for causal mutations have been identified, all showing 100% penetrance. Non-genetic risk factors are yet to be identified. FTD shows poor life expectancy but with survival comparable to that of Alzheimer's disease. Recent progress includes the formulation of up-to-date diagnostic criteria for the behavioural and language variants, and the development of new and urgently needed instruments for monitoring and staging the illness. There is still need for descriptive population studies to fill gaps in our knowledge about minority groups and developing regions. More pressing, however, is the need for reliable physiological markers for disease. There is a present imperative to develop a translational science to form the conduit for transferring neurobiological discoveries and insights from bench to bedside.

Behavior matters--cognitive predictors of survival in amyotrophic lateral sclerosis

BACKGROUND

It is difficult to longitudinally characterize cognitive impairment in amyotrophic lateral sclerosis (ALS) due to motor deficits, and existing instruments aren't comparable with assessments in other dementias.

METHODS

The ALS Brief Cognitive Assessment (ALS-BCA) was validated in 70 subjects (37 with ALS) who also underwent detailed neuropsychological analysis. Cognitive predictors for poor survival were then analyzed in a longitudinal cohort of 171 ALS patients.

RESULTS

The ALS-BCA was highly sensitive (90%) and specific (85%) for ALS-dementia (ALS-D). ALS-D patients had shorter overall survival, primarily due to the poor survival among ALS-D patients with disinhibited or apathetic behaviors after adjusting for demographic variables, ALS site of onset, medications, and supportive measures. ALS-D without behavioral changes was not a predictor of poor survival.

CONCLUSION

ALS-D can present with or without prominent behavioral changes. Cognitive screening in ALS patients should focus on behavioral changes for prognosis, while non-behavioral cognitive impairments may impact quality of life without impacting survival.

Corticospinal tract degeneration associated with TDP-43 type C pathology and semantic dementia

Four subtypes of frontotemporal lobar degeneration with TDP-43 immunoreactive inclusions have been described (types A-D). Of these four subtypes, motor neuron disease is more commonly associated with type B pathology, but has also been reported with type A pathology. We have noted, however, the unusual occurrence of cases of type C pathology having corticospinal tract degeneration. We aimed to assess the severity of corticospinal tract degeneration in a large cohort of cases with type C (n = 31). Pathological analysis included semi-quantitation of myelin loss of fibres of the corticospinal tract and associated macrophage burden, as well as axonal loss, at the level of the medullary pyramids. We also assessed for motor cortex degeneration and fibre loss of the medial lemniscus/olivocerebellar tract. All cases were subdivided into three groups based on the degree of corticospinal tract degeneration: (i) no corticospinal tract degeneration; (ii) equivocal corticospinal tract degeneration; and (iii) moderate to very severe corticospinal tract degeneration. Clinical, genetic, pathological and imaging comparisons were performed across groups. Eight cases had no corticospinal tract degeneration, and 14 cases had equivocal to mild corticospinal tract degeneration. Nine cases, however, had moderate to very severe corticospinal tract degeneration with myelin and axonal loss. In these nine cases, there was degeneration of the motor cortex without lower motor neuron degeneration or involvement of other brainstem tracts. These cases most commonly presented as semantic dementia, and they had longer disease duration (mean: 15.3 years) compared with the other two groups (10.8 and 9.9 years; P = 0.03). After adjusting for disease duration, severity of corticospinal tract degeneration remained significantly different across groups. Only one case, without corticospinal tract degeneration, was found to have a hexanucleotide repeat expansion in the C9ORF72 gene. All three groups were associated with anterior temporal lobe atrophy on MRI; however, the cases with moderate to severe corticospinal tract degeneration showed right-sided temporal lobe asymmetry and greater involvement of the right temporal lobe and superior motor cortices than the other groups. In contrast, the cases with no or equivocal corticospinal tract degeneration were more likely to show left-sided temporal lobe asymmetry. For comparison, the corticospinal tract was assessed in 86 type A and B cases, and only two cases showed evidence of corticospinal tract degeneration without lower motor neuron degeneration. These findings confirm that there exists a unique association between frontotemporal lobar degeneration with type C pathology and corticospinal tract degeneration, with this entity showing a predilection to involve the right temporal lobe.

The molecular basis of the frontotemporal lobar degeneration-amyotrophic lateral sclerosis spectrum

There is increasing evidence that frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS) represent a continuum of neurodegenerative diseases. FTLD is complicated by ALS in a significant proportion of patients, and neuropsychological studies have demonstrated frontotemporal dysfunction in up to 50% of ALS patients. More recently, advances in neuropathology and molecular genetics have started to disclose the biological basis for the observed clinical concurrence. TDP-43 and FUS have been discovered as key pathological proteins in both FTLD and ALS. The most recent discovery of a pathological hexanucleotide repeat expansion in the gene C9orf72 as a frequent cause of both FTLD and ALS has eventually confirmed the association of these two at first sight distinct neurodegenerative diseases. Mutations in the TARDBP, FUS, and VCP genes had previously been associated with different phenotypes of the FTLD-ALS spectrum, although in these cases one end of the spectrum predominates. Whilst on the one hand providing evidence for overlap, these discoveries have also highlighted that FTLD and ALS are etiologically diverse. In this review, we review the recent advances that support the existence of an FTLD-ALS spectrum, with particular emphasis on the molecular genetic aspect.

Frontal lobe abnormalities on MRS correlate with poor letter fluency in ALS

OBJECTIVE

To examine whether frontal lobe abnormalities on magnetic resonance spectroscopy (MRS) in amyotrophic lateral sclerosis (ALS) correlate with poor letter fluency (LF).

METHODS

Twenty-five patients with ALS (20 with definite, probable, or possible ALS and 5 with progressive muscular atrophy) performed an LF task, involving F word generation in 1 minute, and underwent MRS. Comparisons were made between patients with ALS with impaired LF and unimpaired LF based on an empirically derived cutoff score. A Spearman correlation was performed between the patient's N-acetyl acetate/creatinine-phosphocreatinine ratio (NAA/Cr) and the number of F words generated.

RESULTS

LF was impaired in 50% of patients with ALS. Patients with impaired LF had reduced NAA/Cr in the DLPFC compared with those with unimpaired LF (p = 0.007). There was a significant correlation between LF and NAA/Cr in the DLPFC (r = 0.51, p = 0.0009). The ALS Functional Rating Scale score, clinical region of motor onset, and disease category had no effect on LF or NAA/Cr in the DLPFC.

CONCLUSIONS

A reduced NAA/Cr in the DLPFC of patients with ALS is a marker of neuronal dysfunction and correlates with impaired performance on a clinical measure of executive function.

Deficits in concept formation in amyotrophic lateral sclerosis

OBJECTIVE

Amyotrophic Lateral Sclerosis (ALS) is associated with impaired executive control. The aim of the current research was to test the hypothesis that concept formation deficits associated with an extramotor neurocognitive network involving executive and semantic resources can be found in some ALS patients.

METHOD

Forty-one patients with clinically definite ALS were assessed with Delis Kaplan Executive Function System Sorting Test (D-KEFS), a measure of concept formation requiring patients to manipulate verbal and visual semantic information and neuropsychological tests measuring naming, semantic memory, and executive control. Using D-KEFS scale scores, a k-mean cluster analysis specifying a 3-group solution was able to classify ALS patients into groups presenting with mildly impaired, average, and above average sorting test performance. High-resolution T1 structural MRI was used to examine cortical thickness in a subset of 16 ALS patients.

RESULTS

Stepwise regression analyses related free and recognition sorting test performance to measures of action naming, single word semantic knowledge, and mental search/working memory. MRI studies found widespread cortical thinning involving bilateral frontal, temporal, and parietal regions. Regression analyses related recognition sorting performance to reduced MRI cortical thickness involving the left prefrontal and left parietal cortex.

CONCLUSIONS

An extramotor cognitive network is associated with impaired concept formation in ALS.