[Cortico-basal syndrome and cortico-basal degeneration: From the clinical diagnosis to the lesional substrate for an adapted care]. / Le syndrome cortico-basal et la dégénérescence cortico-basale : du diagnostic clinique au substrat lésionnel pour une prise en charge adaptée.

Cortico-basal degeneration is a relatively uncommon cause of degenerative parkinsonism in the elderly. From a clinical point of view, it manifests as a cortico-basal syndrome (CBS), featuring a highly asymmetrical akinetic-rigid syndrome, dystonia, myoclonus and cognitive-behavioral impairment with predominant apraxia. Other clinical phenotypes are possible, including variants with mainly language or behavioral impairment, or with axial, symmetrical parkinsonism resembling progressive supranuclear palsy (PSP). Current diagnostic criteria take into account the heterogeneity of clinical presentations. However, a diagnosis of certainty can only be reached by a pathological study, with the evidence of TAU-positive intraneuronal inclusions. Indeed SCB may be underpinned by other lesional substrates, ranging from frontotemporal degeneration to Alzheimer's disease. Symptom management must be early, multidisciplinary and adapted to the progression of the disorder. The identification of the pathological substrate is an essential prerequisite for pathophysiological therapeutic trials.

Atypical White Matter Hyperintensities Markedly Impact Plasma Neurofilament Light Chain Variability in GRN Patients.

GRN mutations, causing frontotemporal dementia, can be associated with atypical white matter hyperintensities (WMH). We hypothesized that the presence of WMH may impact neurofilament light chain (NfL) levels, markers of neuroaxonal damage. We analyzed plasma NfL in 20 GRN patients and studied their association to visually-scored WMH burden. The 12 patients displaying atypical WMH had significantly higher NfL levels (98.4±34.9 pg/mL) than those without WMH (47.2±29.4 pg/mL, p = 0.003), independently from age, disease duration and Fazekas-Schmidt grade. NfL correlated with WMH burden (rho = 0.55, p = 0.01). This study prompts considering WMH burden as a variability factor when evaluating NfL levels in GRN patients.

Evaluation of MRI-based machine learning approaches for computer-aided diagnosis of dementia in a clinical data warehouse.

A variety of algorithms have been proposed for computer-aided diagnosis of dementia from anatomical brain MRI. These approaches achieve high accuracy when applied to research data sets but their performance on real-life clinical routine data has not been evaluated yet. The aim of this work was to study the performance of such approaches on clinical routine data, based on a hospital data warehouse, and to compare the results to those obtained on a research data set. The clinical data set was extracted from the hospital data warehouse of the Greater Paris area, which includes 39 different hospitals. The research set was composed of data from the Alzheimer's Disease Neuroimaging Initiative data set. In the clinical set, the population of interest was identified by exploiting the diagnostic codes from the 10th revision of the International Classification of Diseases that are assigned to each patient. We studied how the imbalance of the training sets, in terms of contrast agent injection and image quality, may bias the results. We demonstrated that computer-aided diagnosis performance was strongly biased upwards (over 17 percent points of balanced accuracy) by the confounders of image quality and contrast agent injection, a phenomenon known as the Clever Hans effect or shortcut learning. When these biases were removed, the performance was very poor. In any case, the performance was considerably lower than on the research data set. Our study highlights that there are still considerable challenges for translating dementia computer-aided diagnosis systems to clinical routine.

C9ORF72 knockdown triggers FTD-like symptoms and cell pathology in mice.

The GGGGCC intronic repeat expansion within C9ORF72 is the most common genetic cause of ALS and FTD. This mutation results in toxic gain of function through accumulation of expanded RNA foci and aggregation of abnormally translated dipeptide repeat proteins, as well as loss of function due to impaired transcription of C9ORF72. A number of in vivo and in vitro models of gain and loss of function effects have suggested that both mechanisms synergize to cause the disease. However, the contribution of the loss of function mechanism remains poorly understood. We have generated C9ORF72 knockdown mice to mimic C9-FTD/ALS patients haploinsufficiency and investigate the role of this loss of function in the pathogenesis. We found that decreasing C9ORF72 leads to anomalies of the autophagy/lysosomal pathway, cytoplasmic accumulation of TDP-43 and decreased synaptic density in the cortex. Knockdown mice also developed FTD-like behavioral deficits and mild motor phenotypes at a later stage. These findings show that C9ORF72 partial loss of function contributes to the damaging events leading to C9-FTD/ALS.

Plasma lysosphingolipids in GRN-related diseases: Monitoring lysosomal dysfunction to track disease progression.

GRN mutations are among the main genetic causes of frontotemporal dementia (FTD). Considering the progranulin involvement in lysosomal homeostasis, we aimed to evaluate if plasma lysosphingolipids (lysoSPL) are increased in GRN mutation carriers, and whether they might represent relevant fluid-based biomarkers in GRN-related diseases. We analyzed four lysoSPL levels in plasmas of 131 GRN carriers and 142 non-carriers, including healthy controls and patients with frontotemporal dementias (FTD) carrying a C9orf72 expansion or without any mutation. GRN carriers consisted of 102 heterozygous FTD patients (FTD-GRN), three homozygous patients with neuronal ceroid lipofuscinosis-11 (CLN-11) and 26 presymptomatic carriers (PS-GRN), the latter with longitudinal assessments. Glucosylsphingosin d18:1 (LGL1), lysosphingomyelins d18:1 and isoform 509 (LSM18:1, LSM509) and lysoglobotriaosylceramide (LGB3) were measured by electrospray ionization-tandem mass spectrometry coupled to ultraperformance liquid chromatography. Levels of LGL1, LSM18:1 and LSM509 were increased in GRN carriers compared to non-carriers (p < 0.0001). No lysoSPL increases were detected in FTD patients without GRN mutations. LGL1 and LSM18:1 progressively increased with age at sampling, and LGL1 with disease duration, in FTD-GRN. Among PS-GRN carriers, LSM18:1 and LGL1 significantly increased over 3.4-year follow-up. LGL1 levels were associated with increasing neurofilaments in presymptomatic carriers. This study evidences an age-dependent increase of ß-glucocerebrosidase and acid sphingomyelinase substrates in GRN patients, with progressive changes as early as the presymptomatic phase. Among FTD patients, plasma lysoSPL appear to be uniquely elevated in GRN carriers, and thus might serve as suitable non-invasive disease-tracking biomarkers of progression, specific to the pathophysiological process. Finally, this study might add lysoSPL to the portfolio of fluid-based biomarkers, and pave the way to disease-modifying approaches based on lysosomal function rescue in GRN diseases.

Behavioural disinhibition in frontotemporal dementia investigated within an ecological framework.

Disinhibition is a core symptom in behavioural variant frontotemporal dementia (bvFTD) particularly affecting the daily lives of both patients and caregivers. Yet, characterisation of inhibition disorders is still unclear and management options of these disorders are limited. Questionnaires currently used to investigate behavioural disinhibition do not differentiate between several subtypes of disinhibition, encompass observation biases and lack of ecological validity. In the present work, we explored disinhibition in an original semi-ecological situation, by distinguishing three categories of disinhibition: compulsivity, impulsivity and social disinhibition. First, we measured prevalence and frequency of these disorders in 23 bvFTD patients and 24 healthy controls (HC) in order to identify the phenotypical heterogeneity of disinhibition. Then, we examined the relationships between these metrics, the neuropsychological scores and the behavioural states to propose a more comprehensive view of these neuropsychiatric manifestations. Finally, we studied the context of occurrence of these disorders by investigating environmental factors potentially promoting or reducing them. As expected, we found that patients were more compulsive, impulsive and socially disinhibited than HC. We found that 48% of patients presented compulsivity (e.g., repetitive actions), 48% impulsivity (e.g., oral production) and 100% of the patients group showed social disinhibition (e.g., disregards for rules or investigator). Compulsivity was negatively related with emotions recognition. BvFTD patients were less active if not encouraged in an activity, and their social disinhibition decreased as activity increased. Finally, impulsivity and social disinhibition decreased when patients were asked to focus on a task. Summarising, this study underlines the importance to differentiate subtypes of disinhibition as well as the setting in which they are exhibited, and points to stimulating area for non-pharmacological management.

Psychological Distress in a Sample of Adult Italian Patients Affected by Vocal Nodules and Muscle-Tension Dysphonia: Preliminary Results.

OBJECTIVES: To evaluate the correlation between voice disorders and psychological distress, in terms of anxiety, stress, and depression, in a sample of adult Italian patients and to compare our results with those obtained in a group of adult healthy controls matched by age, sex, geographic distribution, and occupation. METHODS: This prospective-controlled study included 100 adults with Vocal nodules (VN) and Muscle Tension Dysphonia (MTD1), aged between 18 and 65 years, as Experimental Group (EG) and 100 age-matched subjects without any voice disorders as a Control Group (CG). All patients in the EG underwent a phoniatric evaluation, including the administration of the Voice Handicap Index (VHI) and laryngeal examination. Both patients of EG and CG underwent a Psychological evaluation by means of standardized tests; Beck's Depression Inventory, State Anxiety Inventory (STAI 1-State Anxiety), Trait Anxiety Inventory (STAI 2- Trait Anxiety), and Perceived Stress Scale (PSS-10) were completed by patients. Fisher's exact test and chi-squared test were used to compare all categorical variables, whereas numerical variables were compared either with the nonparametric Mann-Whitney-Wilcoxon or with Kruskal Wallis test. General linear models were used to study continuous variables between patients and controls and between different groups within the sample. RESULTS: In the study group, the Physical domain (P score) of the VHI was more affected than the Emotional (E score) and Functional ones (F score) both in patients with MTD1 and VN; patients with VN presented a significant difference in P score, E score and VHI total score than patients with isolated MTD 1 (P < 0.005). Psychological assessment showed a significant difference (P < 0.005) between VN and MTD 1 regarding PSS-10 and STAI-1 scores. Low Beck's Depression Inventory scores were present in our sample without significant differences between patients with VN and those with MTD 1. Scores related to psychological distress in the EG were far superior to those obtained by the healthy CG, with markedly significant values especially for PSS-10 (P < 0.0001) and STAI 2 (P < 0.01). Finally, younger patients (18-35 years) with VN showed a highest risk of psychosocial distress. CONCLUSION: the present study identified a high prevalence of psychological distress among patients with vocal disorders without any prior specific psychiatric diagnosis, especially in terms of anxiety and perceived stress. For this reason both these symptoms should be taken into consideration in the diagnostic, therapeutic, and follow-up process of patients with MTD1 and VN.

Brain Metabolic Profile in Presymptomatic GRN Carriers Throughout a 5-Year Follow-up.

BACKGROUND AND OBJECTIVES: GRN variants are a frequent cause of familial frontotemporal dementia (FTD). Monitoring disease progression in asymptomatic carriers of genetic variants is a major challenge in delivering preventative therapies before clinical onset. This study aimed to assess the usefulness of fluorodeoxyglucose (FDG)-PET in identifying metabolic changes in presymptomatic GRN carriers (PS-GRN+) and to trace their longitudinal progression. METHODS: Participants were longitudinally evaluated over 5 years in a prospective cohort study focused on GRN disease (Predict-PGRN). They underwent cognitive/behavioral assessment, plasma neurofilament measurement, brain MRI, and FDG-PET. Voxel-wise comparisons of structural and metabolic imaging data between 2 groups were performed for each time point. Longitudinal PET changes were evaluated with voxel-wise comparisons and the metabolic percent annual changes method. The association of regional brain metabolism with plasma neurofilament and cognitive changes was analyzed. RESULTS: Among the 80 individuals enrolled in the study, 58 (27 PS-GRN+ and 31 noncarriers) were included in the analyses. Cross-sectional comparisons between PS-GRN+ and controls found a significant hypometabolism in the left superior temporal sulcus (STS) region (encompassing the middle and superior temporal gyri), approximately 15 years before the expected disease onset, without significant cortical atrophy. The longitudinal metabolic decline over the following 5 years peaked around the right STS in carriers (p < 0.001), without significantly greater volume loss compared with that in controls. Their estimated annualized metabolic decrease (-1.37%) was higher than that in controls (-0.21%, p = 0.004). Lower glucose uptake was associated with higher neurofilament increase (p = 0.003) and lower frontal cognitive scores (p = 0.014) in PS-GRN+. DISCUSSION: This study detected brain metabolic changes in the STS region, preceding structural and cognitive alterations, thus contributing to the characterization of the pathochronology of preclinical GRN disease. Owing to the STS involvement in the perception of facially communicated cues, it is likely that its dysfunction contributes to social cognition deficits characterizing FTD. Overall, our study highlights brain metabolic changes as an early disease-tracking biomarker and proposes annualized percent decrease as a metric to monitor therapeutic response in forthcoming trials.

MicroRNA signatures in genetic frontotemporal dementia and amyotrophic lateral sclerosis.

OBJECTIVE: MicroRNAs are promising biomarkers of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), but discrepant results between studies have so far hampered their use in clinical trials. We aim to assess all previously identified circulating microRNA signatures as potential biomarkers of genetic FTD and/or ALS, using homogeneous, independent validation cohorts of C9orf72 and GRN mutation carriers. METHODS: 104 individuals carrying a C9orf72 or a GRN mutation, along with 31 controls, were recruited through the French research network on FTD/ALS. All subjects underwent blood sampling, from which circulating microRNAs were extracted. We measured differences in the expression levels of 65 microRNAs, selected from 15 published studies about FTD or ALS, between 31 controls, 17 C9orf72 presymptomatic subjects, and 29 C9orf72 patients. We also assessed differences in the expression levels of 30 microRNAs, selected from five studies about FTD, between 31 controls, 30 GRN presymptomatic subjects, and 28 GRN patients. RESULTS: More than half (35/65) of the selected microRNAs were differentially expressed in the C9orf72 cohort, while only a small proportion (5/30) of microRNAs were differentially expressed in the GRN cohort. In multivariate analyses, only individuals in the C9orf72 cohort could be adequately classified (ROC AUC up to 0.98 for controls versus presymptomatic subjects, 0.94 for controls versus patients, and 0.77 for presymptomatic subjects versus patients) with some of the signatures. INTERPRETATION: Our results suggest that previously identified microRNAs using sporadic or mixed cohorts of FTD and ALS patients could potentially serve as biomarkers of C9orf72-associated disease, but not GRN-associated disease.

Disease Progression Score Estimation From Multimodal Imaging and MicroRNA Data Using Supervised Variational Autoencoders.

Frontotemporal dementia and amyotrophic lateral sclerosis are rare neurodegenerative diseases with no effective treatment. The development of biomarkers allowing an accurate assessment of disease progression is crucial for evaluating new therapies. Concretely, neuroimaging and transcriptomic (microRNA) data have been shown useful in tracking their progression. However, no single biomarker can accurately measure progression in these complex diseases. Additionally, large samples are not available for such rare disorders. It is thus essential to develop methods that can model disease progression by combining multiple biomarkers from small samples. In this paper, we propose a new framework for computing a disease progression score (DPS) from cross-sectional multimodal data. Specifically, we introduce a supervised multimodal variational autoencoder that can infer a meaningful latent space, where latent representations are placed along a disease trajectory. A score is computed by orthogonal projections onto this path. We evaluate our framework with multiple synthetic datasets and with a real dataset containing 14 patients, 40 presymptomatic genetic mutation carriers and 37 controls from the PREV-DEMALS study. There is no ground truth for the DPS in real-world scenarios, therefore we use the area under the ROC curve (AUC) as a proxy metric. Results with the synthetic datasets support this choice, since the higher the AUC, the more accurate the predicted simulated DPS. Experiments with the real dataset demonstrate better performance in comparison with state-of-the-art approaches. The proposed framework thus leverages cross-sectional multimodal datasets with small sample sizes to objectively measure disease progression, with potential application in clinical trials.

An ecological approach to identify distinct neural correlates of disinhibition in frontotemporal dementia.

Disinhibition is a core symptom of many neurodegenerative diseases, particularly frontotemporal dementia, and is a major cause of stress for caregivers. While a distinction between behavioural and cognitive disinhibition is common, an operational definition of behavioural disinhibition is still missing. Furthermore, conventional assessment of behavioural disinhibition, based on questionnaires completed by the caregivers, often lacks ecological validity. Therefore, their neuroanatomical correlates are non-univocal. In the present work, we used an original behavioural approach in a semi-ecological situation to assess two specific dimensions of behavioural disinhibition: compulsivity and social disinhibition. First, we investigated disinhibition profile in patients compared to controls. Then, to validate our approach, compulsivity and social disinhibition scores were correlated with classic cognitive tests measuring disinhibition (Hayling Test) and social cognition (mini-Social cognition & Emotional Assessment). Finally, we disentangled the anatomical networks underlying these two subtypes of behavioural disinhibition, taking in account the grey (voxel-based morphometry) and white matter (diffusion tensor imaging tractography). We included 17 behavioural variant frontotemporal dementia patients and 18 healthy controls. We identified patients as more compulsive and socially disinhibited than controls. We found that behavioural metrics in the semi-ecological task were related to cognitive performance: compulsivity correlated with the Hayling test and both compulsivity and social disinhibition were associated with the emotion recognition test. Based on voxel-based morphometry and tractography, compulsivity correlated with atrophy in the bilateral orbitofrontal cortex, the right temporal region and subcortical structures, as well as with alterations of the bilateral cingulum and uncinate fasciculus, the right inferior longitudinal fasciculus and the right arcuate fasciculus. Thus, the network of regions related to compulsivity matched the "semantic appraisal" network. Social disinhibition was associated with bilateral frontal atrophy and impairments in the forceps minor, the bilateral cingulum and the left uncinate fasciculus, regions corresponding to the frontal component of the "salience" network. Summarizing, this study validates our semi-ecological approach, through the identification of two subtypes of behavioural disinhibition, and highlights different neural networks underlying compulsivity and social disinhibition. Taken together, these findings are promising for clinical practice by providing a better characterisation of inhibition disorders, promoting their detection and consequently a more adapted management of patients.

Systematic Review on the Role of Lobar Cerebral Microbleeds in Cognition.

BACKGROUND: Cerebral microbleeds (CMBs) are small round/oval lesions seen in MRI-specific sequences. They are divided in deep and lobar according to their location. Lobar CMBs (L-CMBs) are commonly associated with amyloid angiopathy. Although CMBs have been considered clinically silent for a long time, a growing body of evidence has shown that they could play a crucial role in cognitive functioning. OBJECTIVE: The aim of this systematic review was to estimate the role of L-CMBs in cognitive performance. METHODS: We selected, from the Cochrane Library, Embase, PubMed, and ScienceDirect databases, clinical studies, published from January 2000 to January 2020 and focused on the association between L-CMBs and cognitive functions. The inclusion criteria were: 1) participants grouped according to presence or absence of CMBs, 2) extensive neuropsychological examination, 3) CMBs differentiation according to topographical distribution, and 4) MRI-based CMB definition (< 10 mm and low signal in T2*/SWI). The impact of L-CMBs was separately assessed for executive functions, visuospatial skills, language, and memory. RESULTS: Among 963 potentially eligible studies, six fulfilled the inclusion criteria. Four studies reported a greater reduction in executive performances in participants with L-CMB and two studies showed a statistically significant association between visuospatial dysfunction and L-CMBs. No association was found between hippocampal memory or language abilities and L-CMBs. CONCLUSION: Lobar CMBs are associated with a reduction of processing speed and visuospatial performances, thus suggesting the contribution of vascular amyloid deposition to this cognitive profile. This occurrence enables us to suspect an underlying Alzheimer's disease pathology even in absence of typical hippocampal memory impairment.

Primary progressive aphasias associated with C9orf72 expansions: Another side of the story.

C9orf72 repeat expansions are rarely associated with primary progressive aphasias (PPA). In-depth characterization of the linguistic deficits, and the underlying patterns of grey-matter atrophy in PPA associated with the C9orf72 expansions (PPA-C9orf72) are currently lacking. In this study, we comprehensively analyzed a unique series of 16 patients affected by PPA-C9orf72. Eleven patients were issued from two independent French and Finnish cohorts, and five were identified by means of literature review. Voxel-based morphometry (VBM) studies were performed on three of them. This study depicts the spectrum of C9orf72-related aphasic phenotypes, and illustrates their linguistic presentation. The non-fluent/agrammatic variant was the most frequent phenotype in our series (9/16 patients, 56%), with apraxia of speech being the main defining feature. Left frontal lobe atrophy was present in these subjects, peaking in inferior frontal gyrus. Three patients (19%) showed the semantic variant, with progression of atrophy in temporo-polar regions, later involving orbitofrontal cortex. Anterior temporal lobe dysfunction was also particularly relevant in two patients (12.5%) with mixed forms of PPA. Lastly, two patients (12.5%) had unclassifiable PPA with predominating word-finding difficulties. No PPA-C9orf72 patients in our series fulfilled the criteria of the logopenic variant. Importantly, this study underlines the role of C9orf72 mutation in the disruption of the most anterior parts of the language network, including prefrontal and temporo-polar areas. It provides guidelines for C9orf72 testing in PPA patients, with important clinical impact as gene-specific therapies are upcoming.

Implication of folate deficiency in CYP2U1 loss of function.

Hereditary spastic paraplegias are heterogeneous neurodegenerative disorders. Understanding of their pathogenic mechanisms remains sparse, and therapeutic options are lacking. We characterized a mouse model lacking the Cyp2u1 gene, loss of which is known to be involved in a complex form of these diseases in humans. We showed that this model partially recapitulated the clinical and biochemical phenotypes of patients. Using electron microscopy, lipidomic, and proteomic studies, we identified vitamin B2 as a substrate of the CYP2U1 enzyme, as well as coenzyme Q, neopterin, and IFN-α levels as putative biomarkers in mice and fluids obtained from the largest series of CYP2U1-mutated patients reported so far. We also confirmed brain calcifications as a potential biomarker in patients. Our results suggest that CYP2U1 deficiency disrupts mitochondrial function and impacts proper neurodevelopment, which could be prevented by folate supplementation in our mouse model, followed by a neurodegenerative process altering multiple neuronal and extraneuronal tissues.

Plasma NfL levels and longitudinal change rates in C9orf72 and GRN-associated diseases: from tailored references to clinical applications.

OBJECTIVE: Neurofilament light chain (NfL) is a promising biomarker in genetic frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). We evaluated plasma neurofilament light chain (pNfL) levels in controls, and their longitudinal trajectories in C9orf72 and GRN cohorts from presymptomatic to clinical stages. METHODS: We analysed pNfL using Single Molecule Array (SiMoA) in 668 samples (352 baseline and 316 follow-up) of C9orf72 and GRN patients, presymptomatic carriers (PS) and controls aged between 21 and 83. They were longitudinally evaluated over a period of >2 years, during which four PS became prodromal/symptomatic. Associations between pNfL and clinical-genetic variables, and longitudinal NfL changes, were investigated using generalised and linear mixed-effects models. Optimal cut-offs were determined using the Youden Index. RESULTS: pNfL levels increased with age in controls, from ~5 to~18 pg/mL (p<0.0001), progressing over time (mean annualised rate of change (ARC): +3.9%/year, p<0.0001). Patients displayed higher levels and greater longitudinal progression (ARC: +26.7%, p<0.0001), with gene-specific trajectories. GRN patients had higher levels than C9orf72 (86.21 vs 39.49 pg/mL, p=0.014), and greater progression rates (ARC:+29.3% vs +24.7%; p=0.016). In C9orf72 patients, levels were associated with the phenotype (ALS: 71.76 pg/mL, FTD: 37.16, psychiatric: 15.3; p=0.003) and remarkably lower in slowly progressive patients (24.11, ARC: +2.5%; p=0.05). Mean ARC was +3.2% in PS and +7.3% in prodromal carriers. We proposed gene-specific cut-offs differentiating patients from controls by decades. CONCLUSIONS: This study highlights the importance of gene-specific and age-specific references for clinical and therapeutic trials in genetic FTD/ALS. It supports the usefulness of repeating pNfL measurements and considering ARC as a prognostic marker of disease progression. TRIAL REGISTRATION NUMBERS: NCT02590276 and NCT04014673.

Primary Progressive Aphasia Associated With GRN Mutations: New Insights Into the Nonamyloid Logopenic Variant.

OBJECTIVE: To determine relative frequencies and linguistic profiles of primary progressive aphasia (PPA) variants associated with GRN (progranulin) mutations and to study their neuroanatomic correlates. METHODS: Patients with PPA carrying GRN mutations (PPA-GRN) were selected among a national prospective research cohort of 1,696 patients with frontotemporal dementia, including 235 patients with PPA. All patients with amyloid-positive CSF biomarkers were excluded. In this cross-sectional study, speech/language and cognitive profiles were characterized with standardized evaluations, and gray matter (GM) atrophy patterns using voxel-based morphometry. Comparisons were performed with controls and patients with sporadic PPA. RESULTS: Among the 235 patients with PPA, 45 (19%) carried GRN mutations, and we studied 32 of these. We showed that logopenic PPA (lvPPA) was the most frequent linguistic variant (n = 13, 41%), followed by nonfluent/agrammatic (nfvPPA; n = 9, 28%) and mixed forms (n = 8, 25%). Semantic variant was rather rare (n = 2, 6%). Patients with lvPPA, qualified as nonamyloid lvPPA, presented canonical logopenic deficit. Seven of 13 had a pure form; 6 showed subtle additional linguistic deficits not fitting criteria for mixed PPA and hence were labeled as logopenic-spectrum variant. GM atrophy involved primarily left posterior temporal gyrus, mirroring neuroanatomic changes of amyloid-positive-lvPPA. Patients with nfvPPA presented agrammatism (89%) rather than apraxia of speech (11%). CONCLUSIONS: This study shows that the most frequent PPA variant associated with GRN mutations is nonamyloid lvPPA, preceding nfvPPA and mixed forms, and illustrates that the language network may be affected at different levels. GRN testing is indicated for patients with PPA, whether familial or sporadic. This finding is important for upcoming GRN gene-specific therapies.

Clinical Update on C9orf72: Frontotemporal Dementia, Amyotrophic Lateral Sclerosis, and Beyond.

The identification of C9orf72 gene has led to important scientific progresses and has considerably changed our clinical practice. However, a decade after C9orf72 discovery, some important clinical questions remain unsolved. The reliable cutoff for the pathogenic repeat number and the implication of intermediate alleles in frontotemporal dementia, amyotrophic lateral sclerosis, or in other diseases are still uncertain. The occurrence of an anticipation phenomenon - at the clinical and molecular levels - in C9orf72 kindreds is still debated as well, and the factors driving age at onset and phenotype variability are largely unknown. All these questions have a significant impact not only in clinical practice for diagnosis and genetic counseling but also in a research context for the initiation of therapeutic trials. In this chapter, we will address all those issues and summarize the recent updates about clinical aspects of C9orf72 disease, focusing on both the common and the less typical phenotypes.

Singular cases of Alzheimer's disease disclose new and old genetic "acquaintances".

BACKGROUND: Alzheimer's disease (AD) is the most common age-related dementia. Besides its typical presentation with amnestic syndrome at onset, atypical AD cases are being increasingly recognized, often in presenile age. OBJECTIVES: To provide an extensive clinical and genetic characterization of six AD patients carrying one or more singular features, including age of onset, atypical phenotype and disease progression rate. By reviewing the pertinent literature and accessing publicly available databases, we aimed to assess the frequency and the significance of the identified genetic variants. METHODS: Biomarkers of amyloid-ß deposition and neurodegeneration were used to establish the in vivo diagnosis of probable AD, in addition to neurological and neuropsychological evaluation, extensive laboratory assays and neuroradiological data. Considering the presenile onset of the majority of the cases, we hypothesized genetically determined AD and performed extensive genetic analyses by both Sanger sequencing and next generation sequencing (NGS). RESULTS: We disclosed two known missense variants, one in PSEN1 and the other in PSEN2, and a novel silent variant in PSEN2. Most notably, we identified several additional variants in other dementia-related genes by NGS. Some of them have never been reported in any control or disease databases, representing variants unique to our cases. CONCLUSIONS: This work underlines the difficulties in reaching a confident in vivo diagnosis in cases of atypical dementia. Moreover, a wider genetic analysis by NGS approach may prove to be useful in specific cases, especially when the study of the so-far known AD causative genes produces negative or conflicting results.

Hyperkinetic manifestations in superficial siderosis: evidence for pathogenic network disruption.

Superficial siderosis (SS) of central nervous system is a rare condition characterized by hemosiderin deposition diffusely involving supratentorial and infratentorial compartments. SS usually manifests with ataxia and sensorineural hearing loss. Basal ganglia are almost always spared by the degenerative process, and movement disorders are only rarely reported. We describe the case of an aged woman with apparently idiopathic SS presenting with cerebellar ataxia, hearing loss, and orofacial dyskinesias. Together with some previously reported patients affected by SS and presenting with dystonic manifestations, our case reinforces the current hypothesis supporting a wide network disruption, rather than a direct basal ganglia damage, as the likely underlying cause of some dystonic syndromes.

Plasma microRNA signature in presymptomatic and symptomatic subjects with C9orf72-associated frontotemporal dementia and amyotrophic lateral sclerosis.

OBJECTIVE: To identify potential biomarkers of preclinical and clinical progression in chromosome 9 open reading frame 72 gene (C9orf72)-associated disease by assessing the expression levels of plasma microRNAs (miRNAs) in C9orf72 patients and presymptomatic carriers. METHODS: The PREV-DEMALS study is a prospective study including 22 C9orf72 patients, 45 presymptomatic C9orf72 mutation carriers and 43 controls. We assessed the expression levels of 2576 miRNAs, among which 589 were above noise level, in plasma samples of all participants using RNA sequencing. The expression levels of the differentially expressed miRNAs between patients, presymptomatic carriers and controls were further used to build logistic regression classifiers. RESULTS: Four miRNAs were differentially expressed between patients and controls: miR-34a-5p and miR-345-5p were overexpressed, while miR-200c-3p and miR-10a-3p were underexpressed in patients. MiR-34a-5p was also overexpressed in presymptomatic carriers compared with healthy controls, suggesting that miR-34a-5p expression is deregulated in cases with C9orf72 mutation. Moreover, miR-345-5p was also overexpressed in patients compared with presymptomatic carriers, which supports the correlation of miR-345-5p expression with the progression of C9orf72-associated disease. Together, miR-200c-3p and miR-10a-3p underexpression might be associated with full-blown disease. Four presymptomatic subjects in transitional/prodromal stage, close to the disease conversion, exhibited a stronger similarity with the expression levels of patients. CONCLUSIONS: We identified a signature of four miRNAs differentially expressed in plasma between clinical conditions that have potential to represent progression biomarkers for C9orf72-associated frontotemporal dementia and amyotrophic lateral sclerosis. This study suggests that dysregulation of miRNAs is dynamically altered throughout neurodegenerative diseases progression, and can be detectable even long before clinical onset. TRIAL REGISTRATION NUMBER: NCT02590276.