Enrico Premi

Tau forms in CSF as a reliable biomarker for progressive supranuclear palsy

Objective: In CSF, extended (55 kDa) and truncated (33 kDa) tau forms have been previously recognized, and the tau 33 kDa/55 kDa ratio has been found significantly reduced in progressive supranuclear palsy (PSP) vs in other neurodegenerative disorders. The aim of this study was to evaluate the diagnostic value of the CSF tau form ratio as a biomarker of PSP and to correlate the structural anatomic changes as measured by means of voxel-based morphometry (VBM) to CSF tau form ratio decrease. Methods: A total of 166 subjects were included in the study (21 PSP, 20 corticobasal degeneration syndrome, 44 frontotemporal dementia, 29 Alzheimer disease, 10 Parkinson disease, 15 dementia with Lewy bodies, and 27 individuals without any neurodegenerative disorder). Each patient underwent a standardized clinical and neuropsychological evaluation. In CSF, a semiquantitative immunoprecipitation was developed to evaluate CSF tau 33 kDa/55 kDa ratio. MRI assessment and VBM analysis was carried out. Results: Tau form ratio was significantly reduced in patients with PSP (0.504 ± 0.284) when compared to age-matched controls (0.989 ± 0.343), and to patients with other neurodegenerative conditions (range = 0.899–1.215). The area under the curve (AUC) of the receiver operating characteristic analysis in PSP vs other subgroups ranged from 0.863 to 0.937 (PSP vs others, AUC = 0.897, p < 0.0001). VBM study showed that CSF tau form ratio decrease correlated significantly with brainstem atrophy. Conclusions: Truncated tau production, which selectively affects brainstem neuron susceptibility, can be considered a specific and reliable marker for PSP. Tau form ratio was the lowest in progressive supranuclear palsy with no overlap with any other neurodegenerative illness. GLOSSARY: AD = Alzheimer disease; AUC = area under the curve; BADL = Basic Activity of Daily Living; CBDS = corticobasal degeneration; CON = controls; DLB = dementia with Lewy bodies; DSM-IV = Diagnostic and Statistical Manual of Mental Disorders, 4th edition; FTD = frontotemporal dementia; IADL = Instrumental Activities of Daily Living; MMSE = Mini-Mental State Examination; MSA = multiple system atrophy; PD = Parkinson disease; PSP = progressive supranuclear palsy; ROC = receiver operating characteristic; UPDRS = Unified Parkinson’s Disease Rating Scale; VBM = voxel-based morphometry.

Granulin mutation drives brain damage and reorganization from preclinical to symptomatic FTLD

Granulin (GRN) mutations have been identified as a major cause of frontotemporal lobar degeneration (FTLD) by haploinsufficiency mechanism, although their effects on brain tissue dysfunction and damage still remain to be clarified. In this study, we investigated the pattern of neuroimaging abnormalities in FTLD patients, carriers and noncarriers of GRN Thr272fs mutation, and in presymptomatic carriers. We assessed regional gray matter (GM) atrophy, and resting (RS)-functional magnetic resonance imaging (fMRI). The functional connectivity maps of the salience (SN) and the default mode (DMN) networks were considered. Frontotemporal gray matter atrophy was found in all FTLD patients (more remarkably in those GRN Thr272fs carriers), but not in presymptomatic carriers. Functional connectivity within the SN was reduced in all FTLD patients (again more remarkably in those mutation carriers), while it was enhanced in the DMN. Conversely, presymptomatic carriers showed increased connectivity in the SN, with no changes in the DMN. Our findings suggest that compensatory mechanisms of brain plasticity are present in GRN-related FTLD, but with different patterns at a preclinical and symptomatic disease stage.

Brain Magnetic Resonance Imaging Structural Changes in a Pedigree of Asymptomatic Progranulin Mutation Carriers

Mutations in the progranulin (PGRN) gene have been recently demonstrated as a cause of frontotemporal lobar degeneration (FTLD) with ubiquitin-immunoreactive neuronal inclusion (FTD-U). Neuropathologic, clinical, and neuroimaging features associated with PGRN mutations have been carefully described. No studies on asymptomatic subjects carrying pathogenetic PGRN mutations are available yet. These would be crucial for establishing the timing of brain changes and bringing new insight into disease pathogenesis and disease course. The aim of this study was to evaluate structural brain morphology using diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) in asymptomatic carriers of PGRN delCACT mutation belonging to a four-generation FTLD pedigree (mean age, 37.0 +/- 12.0). The evaluation of the family proband presenting with progressive nonfluent aphasia at 53 years of age, revealed left frontotemporal hypoperfusion and atrophy. VBM analysis of gray and white matter reductions revealed no differences between asymptomatic carriers (n = 7) and controls (n = 15), and between no-carriers (n = 10) and controls (p < 0.001). DTI analysis revealed a reduction in fractional anisotropy in healthy PGRN mutation carriers in the left uncinate fasciculus, connecting the orbito-frontal regions to the temporal pole, and in the left inferior occipitofrontal fasciculus, connecting the parieto-occipital cortex to the dorsolateral frontal cortex (p < 0.001). No significant difference in fractional anisotropy between no-carriers and controls was found. Our data indicate loss of white matter integrity as an early preclinical feature in familial FTD that might antedate the onset of specific neurologic features. Alteration of fiber tracts within the perisylvian language network might represent the early hallmark of subsequent aphasia onset. The study of other pedigrees of asymptomatic PGRN mutation carriers is warranted.

Subcortical and deep cortical atrophy in Frontotemporal Lobar Degeneration

Though neuroimaging, pathology and pathophysiology suggest a subcortical and deep cortical involvement in Frontotemporal Lobar Degeneration (FTLD), no studies have comprehensively assessed the associated gray matter (GM) volume changes. We measured caudate, putamen, thalamus, and amygdala GM volume using probabilistic a-priori regions of interest (ROIs) in 53 early FTLD patients (38 behavioral variant FTD [bvFTD], 9 Semantic Dementia [SD], 6 Progressive Non-Fluent Aphasia [PNFA]), and 25 age-matched healthy controls (HC). ANOVA showed significant (P<0.001) main effect of diagnosis, and significant interactions for diagnosis and region, and diagnosis and hemisphere. Post-hoc comparisons with HC showed bilateral GM atrophy in the caudate, putamen and thalamus, in bvFTD; a left-confined GM reduction in the amygdala in SD; and bilateral GM atrophy in the caudate and thalamus, and left-sided GM reduction in the putamen and amygdala in PNFA. Correlation analyses suggested an association between GM volumes and language, psychomotor speed and behavioral disturbances. This study showed a widespread involvement of subcortical and deep cortical GM in early FTLD with patterns specific for clinical entity.

The FTLD-modified Clinical Dementia Rating scale is a reliable tool for defining disease severity in Frontotemporal Lobar Degeneration: evidence from a brain SPECT study

Background:  Frontotemporal Lobar Degeneration (FTLD) is a heterogeneous disorder characterized by impairment in executive functions, behavioural disturbance and language deficit. Reliable scales of global impairment are under evaluation. A consortium of Mayo Clinic and University of California FTLD Centers has recently developed the FTLD‐modified Clinical Dementia Rating (CDR) scale to assess FTLD severity.

Founder effect and estimation of the age of the Progranulin Thr272fs mutation in 14 Italian pedigrees with frontotemporal lobar degeneration

Progranulin (PGRN) mutations have been recognized to be monogenic causes of frontotemporal lobar degeneration (FTLD). PGRN Thr272fs mutation in the Italian population has been previously identified. In the present study, we evaluated the occurrence of a founder effect studying 8 polymorphic microsatellite markers flanking the PGRN gene in 14 apparently unrelated families. We identified a common haplotype associated with PGRN Thr272fs carriers, assuming common ancestry. The inferred age analysis (range between 260 [95% credible set: 227-374] and 295 [95% credible set: 205-397] generations) places the introduction of the mutation back to the Neolithic era when the Celts, the population of that period, settled in Northern Italy. PGRN Thr272fs mutation appears to be as either behavioral frontotemporal dementia (80%) or primary progressive aphasia (20%), it was equally distributed between male and female, and the mean age at onset was 59.6 ± 5.9 (range 53-68). In 14 families, autosomal dominant pattern of inheritance was present in 64.2% of cases. No clinical predictors of disease onset were demonstrated. The identification of a large cohort of frontotemporal lobar degeneration (FTLD) patients with homogeneous genetic background well may be used in the search of disease modulators to elucidate genotype-phenotype correlations of progranulopathies.

Revisiting Brain Reserve Hypothesis in Frontotemporal Dementia: Evidence from a Brain Perfusion Study

Background: Literature data on Alzheimer’s disease suggest that years of schooling and occupational level are associated with a reserve mechanism. No data on patients with behavioral variant frontotemporal dementia (bvFTD) are available yet. Objective: To evaluate the impact of education, occupation, and midlife leisure activities on brain reserve in bvFTD. Methods: Fifty-four bvFTD patients entered the study and underwent neuropsychological and behavioral assessment, including the FTD-modified Clinical Dementia Rating for FTD (FTD-modified CDR), and SPECT imaging. We tested for the linear correlation of educational and occupational level, and midlife leisure activities with regional cerebral blood flow (rCBF), controlling for demographic variables (age and gender) and for cognitive performance (FTD-modified CDR) (statistical parametric mapping). Results: A significant relationship between higher educational and occupational attainments and lower rCBF in medial frontal cortex and dorsolateral frontal cortex, bilaterally, was found (p < 0.005). When midlife leisure activities were considered, no correlation was found. The correlation between a reserve index, accounting for both educational and occupational level, and rCBF showed the same pattern of hypoperfusion. Conclusions: This study suggests that education and occupation act as proxies for reserve capacity in bvFTD. These lifestyle attainments may counteract the onset of this genetic-based disease in at-risk individuals.

Structural and functional imaging study in dementia with Lewy bodies and Parkinson's disease dementia

INTRODUCTION Dementia with Lewy Bodies (DLB) and Parkinsons disease with Dementia (PDD) are neurodegenerative disorders with complex clinical picture (parkinsonism, cognitive decline and neuropsychiatric disturbances). The conundrum of whether DLB and PDD represent the same or different entities is still under debate. Advanced neuroimaging techniques may represent a point of view to assess brain correlates in DLB and PDD. The study aimed at evaluating whether DLB and PDD may be labelled under the same disease entity or be considered distinctive pathologies. We compared DLB and PDD patients by assessing structural and functional brain imaging and including PD patients. METHODS Patients with diagnosis of PD, PDD, DLB and a group of healthy controls for neuroimaging comparisons were recruited and changes in structural and resting-state functional MR (Regional Homogeneity, ReHo) were studied. RESULTS No significant atrophy in VBM analysis was evident in PD. Conversely, PDD showed a significant bilateral frontal atrophy, whereas DLB was characterized by a predominant parietal, occipital atrophy; a similar involvement of subcortical regions in PDD and DLB was observed. ReHo demonstrated reduced local coherence of frontal regions in PD and in PDD, whereas DLB patients presented a reduced local connectivity in posterior regions. CONCLUSION Different brain areas are specifically involved in PDD and DLB. In the former group, greater atrophy of frontal regions with concomitant functional connectivity impairment was evident; conversely, structural and functional damage in the posterior regions characterized DLB. Despite an overlapping clinical spectrum, DLB and PDD have different networks involved and different underlying pathogenic pathways.

Multimodal fMRI Resting-State Functional Connectivity in Granulin Mutations: The Case of Fronto-Parietal Dementia

Background Monogenic dementias represent a great opportunity to trace disease progression from preclinical to symptomatic stages. Frontotemporal Dementia related to Granulin (GRN) mutations presents a specific framework of brain damage, involving fronto-temporal regions and long inter-hemispheric white matter bundles. Multimodal resting-state functional MRI (rs-fMRI) is a promising tool to carefully describe disease signature from the earliest disease phase. Objective To define local connectivity alterations in GRN related pathology moving from the presymptomatic (asymptomatic GRN mutation carriers) to the clinical phase of the disease (GRN- related Frontotemporal Dementia). Methods Thirty-one GRN Thr272fs mutation carriers (14 patients with Frontotemporal Dementia and 17 asymptomatic carriers) and 38 healthy controls were recruited. Local connectivity measures (Regional Homogeneity (ReHo), Fractional Amplitude of Low Frequency Fluctuation (fALFF) and Degree Centrality (DC)) were computed, considering age and gender as nuisance variables as well as the influence of voxel-level gray matter atrophy. Results Asymptomatic GRN carriers had selective reduced ReHo in the left parietal region and increased ReHo in frontal regions compared to healthy controls. Considering Frontotemporal Dementia patients, all measures (ReHo, fALFF and DC) were reduced in inferior parietal, frontal lobes and posterior cingulate cortex. Considering GRN mutation carriers, an inverse correlation with age in the posterior cingulate cortex, inferior parietal lobule and orbitofrontal cortex was found. Conclusions GRN pathology is characterized by functional brain network alterations even decades before the clinical onset; they involve the parietal region primarily and then spread to the anterior regions of the brain, supporting the concept of molecular nexopathies.

Extrapyramidal symptoms in Frontotemporal Dementia : Prevalence and clinical correlations

In the present study we aimed at evaluating the prevalence and the associated clinical, neuropsychological and behavioral features of extrapyramidal symptoms in Frontotemporal Dementia (FTD) patients. Seventy-five patients fulfilling clinical criteria of FTD were consecutively enrolled. Each patient underwent clinical and extrapyramidal sign examination, and neuropsychological and behavioral disturbance evaluation. Each patient was submitted to both brain MRI and SPECT, documenting frontotemporal atrophy/hypoperfusion pattern. Parkinsonian symptoms in FTD were associated with a specific endophenotype characterized by higher incidence of psychotic symptoms, memory deficits and psychomotor speed ability abnormalities. Careful description of the spectrum of presentation of FTD may be of help for further understanding the underpinnings of the disease.