Impact of demographics and comorbid conditions on plasma biomarkers concentrations and their diagnostic accuracy in a memory clinic cohort

Plasma biomarkers have emerged as promising tools for identifying amyloid beta (Aβ) pathology. Before implementation in routine clinical practice, confounding factors modifying their concentration beyond neurodegenerative diseases should be identified. We studied the association of a comprehensive list of demographics, comorbidities, medication and laboratory parameters with plasma p-tau181, glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) on a prospective memory clinic cohort and studied their impact on diagnostic accuracy for discriminating CSF/amyloid PET-defined Aβ status. Three hundred sixty patients (mean age 66.5 years, 55% females, 53% Aβ positive) were included. Sex, age and Aβ status-adjusted models showed that only estimated glomerular filtration rate (eGFR, standardized β -0.115 [-0.192 to -0.035], p = 0.005) was associated with p-tau181 levels, although with a much smaller effect than Aβ status (0.685 [0.607-0.763], p < 0.001). Age, sex, body mass index (BMI), Charlson comorbidity index (CCI) and eGFR significantly modified GFAP concentration. Age, blood volume (BV) and eGFR were associated with NfL levels. p-tau181 predicted Aβ status with 87% sensitivity and specificity with no relevant increase in diagnostic performance by adding any of the confounding factors. Using two cut-offs, plasma p-tau181 could have spared 62% of amyloid-PET/CSF testing. Excluding patients with chronic kidney disease did not change the proposed cut-offs nor the diagnostic performance. In conclusion, in a memory clinic cohort, age, sex, eGFR, BMI, BV and CCI slightly modified plasma p-tau181, GFAP and NfL concentrations but their impact on the diagnostic accuracy of plasma biomarkers for Aβ status discrimination was minimal.

Cortical thickness modeling and variability in Alzheimer's disease and frontotemporal dementia

BACKGROUND AND OBJECTIVE

Alzheimer's disease (AD) and frontotemporal dementia (FTD) show different patterns of cortical thickness (CTh) loss compared with healthy controls (HC), even though there is relevant heterogeneity between individuals suffering from each of these diseases. Thus, we developed CTh models to study individual variability in AD, FTD, and HC.

METHODS

We used the baseline CTh measures of 379 participants obtained from the structural MRI processed with FreeSurfer. A total of 169 AD patients (63 ± 9 years, 65 men), 88 FTD patients (64 ± 9 years, 43 men), and 122 HC (62 ± 10 years, 47 men) were studied. We fitted region-wise temporal models of CTh using Support Vector Regression. Then, we studied associations of individual deviations from the model with cerebrospinal fluid levels of neurofilament light chain (NfL) and 14-3-3 protein and Mini-Mental State Examination (MMSE). Furthermore, we used real longitudinal data from 144 participants to test model predictivity.

RESULTS

We defined CTh spatiotemporal models for each group with a reliable fit. Individual deviation correlated with MMSE for AD and with NfL for FTD. AD patients with higher deviations from the trend presented higher MMSE values. In FTD, lower NfL levels were associated with higher deviations from the CTh prediction. For AD and HC, we could predict longitudinal visits with the presented model trained with baseline data. For FTD, the longitudinal visits had more variability.

CONCLUSION

We highlight the value of CTh models for studying AD and FTD longitudinal changes and variability and their relationships with cognitive features and biomarkers.

Clinicopathological correlates in 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 FTLD in MND is difficult to estimate. In this work we describe a large clinicopathologic series of MND, 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, multi-centre 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% vs 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.

Multifocal Transcranial Direct Current Stimulation in Primary Progressive Aphasia Does Not Provide a Clinical Benefit Over Speech Therapy

BACKGROUND

Primary progressive aphasia (PPA) is a group of neurodegenerative disorders including Alzheimer's disease and frontotemporal dementia characterized by language deterioration. Transcranial direct current stimulation (tDCS) is a non-invasive intervention for brain dysfunction.

OBJECTIVE

To evaluate the tolerability and efficacy of tDCS combined with speech therapy in the three variants of PPA. We evaluate changes in fMRI activity in a subset of patients.

METHODS

Double-blinded, randomized, cross-over, and sham-controlled tDCS study. 15 patients with PPA were included. Each patient underwent two interventions: a) speech therapy + active tDCS and b) speech therapy + sham tDCS stimulation. A multifocal strategy with anodes placed in the left frontal and parietal regions was used to stimulate the entire language network. Efficacy was evaluated by comparing the results of two independent sets of neuropsychological assessments administered at baseline, immediately after the intervention, and at 1 month and 3 months after the intervention. In a subsample, fMRI scanning was performed before and after each intervention.

RESULTS

The interventions were well tolerated. Participants in both arms showed clinical improvement, but no differences were found between active and sham tDCS interventions in any of the evaluations. There were trends toward better outcomes in the active tDCS group for semantic association and reading skills. fMRI identified an activity increase in the right frontal medial cortex and the bilateral paracingulate gyrus after the active tDCS intervention.

CONCLUSION

We did not find differences between active and sham tDCS stimulation in clinical scores of language function in PPA patients.

Creating the Pick's disease International Consortium: Association study of MAPT H2 haplotype with risk of Pick's disease

Background

Pick's disease (PiD) is a rare and predominantly sporadic form of frontotemporal dementia that is classified as a primary tauopathy. PiD is pathologically defined by argyrophilic inclusion Pick bodies and ballooned neurons in the frontal and temporal brain lobes. PiD is characterised by the presence of Pick bodies which are formed from aggregated, hyperphosphorylated, 3-repeat tau proteins, encoded by the MAPT gene. The MAPT H2 haplotype has consistently been associated with a decreased disease risk of the 4-repeat tauopathies of progressive supranuclear palsy and corticobasal degeneration, however its role in susceptibility to PiD is unclear. The primary aim of this study was to evaluate the association between MAPT H2 and risk of PiD.

Methods

We established the Pick's disease International Consortium (PIC) and collected 338 (60.7% male) pathologically confirmed PiD brains from 39 sites worldwide. 1,312 neurologically healthy clinical controls were recruited from Mayo Clinic Jacksonville, FL (N=881) or Rochester, MN (N=431). For the primary analysis, subjects were directly genotyped for MAPT H1-H2 haplotype-defining variant rs8070723. In secondary analysis, we genotyped and constructed the six-variant MAPT H1 subhaplotypes (rs1467967, rs242557, rs3785883, rs2471738, rs8070723, and rs7521).

Findings

Our primary analysis found that the MAPT H2 haplotype was associated with increased risk of PiD (OR: 1.35, 95% CI: 1.12-1.64 P=0.002). In secondary analysis involving H1 subhaplotypes, a protective association with PiD was observed for the H1f haplotype (0.0% vs. 1.2%, P=0.049), with a similar trend noted for H1b (OR: 0.76, 95% CI: 0.58-1.00, P=0.051). The 4-repeat tauopathy risk haplotype MAPT H1c was not associated with PiD susceptibility (OR: 0.93, 95% CI: 0.70-1.25, P=0.65).

Interpretation

The PIC represents the first opportunity to perform relatively large-scale studies to enhance our understanding of the pathobiology of PiD. This study demonstrates that in contrast to its protective role in 4R tauopathies, the MAPT H2 haplotype is associated with an increased risk of PiD. This finding is critical in directing isoform-related therapeutics for tauopathies.

Classifying Alzheimer's disease and frontotemporal dementia using machine learning with cross-sectional and longitudinal magnetic resonance imaging data

Alzheimer's disease (AD) and frontotemporal dementia (FTD) are common causes of dementia with partly overlapping, symptoms and brain signatures. There is a need to establish an accurate diagnosis and to obtain markers for disease tracking. We combined unsupervised and supervised machine learning to discriminate between AD and FTD using brain magnetic resonance imaging (MRI). We included baseline 3T-T1 MRI data from 339 subjects: 99 healthy controls (CTR), 153 AD and 87 FTD patients; and 2-year follow-up data from 114 subjects. We obtained subcortical gray matter volumes and cortical thickness measures using FreeSurfer. We used dimensionality reduction to obtain a single feature that was later used in a support vector machine for classification. Discrimination patterns were obtained with the contribution of each region to the single feature. Our algorithm differentiated CTR versus AD and CTR versus FTD at the cross-sectional level with 83.3% and 82.1% of accuracy. These increased up to 90.0% and 88.0% with longitudinal data. When we studied the classification between AD versus FTD we obtained an accuracy of 63.3% at the cross-sectional level and 75.0% for longitudinal data. The AD versus FTD versus CTR classification has reached an accuracy of 60.7%, and 71.3% for cross-sectional and longitudinal data respectively. Disease discrimination brain maps are in concordance with previous results obtained with classical approaches. By using a single feature, we were capable to classify CTR, AD, and FTD with good accuracy, considering the inherent overlap between diseases. Importantly, the algorithm can be used with cross-sectional and longitudinal data.

Loss of brainstem white matter predicts onset and motor neuron symptoms in C9orf72 expansion carriers: a GENFI study

BACKGROUND AND OBJECTIVES

The C9orf72 expansion is the most common genetic cause of frontotemporal dementia (FTD) and/or motor neuron disease (MND). Corticospinal degeneration has been described in post-mortem neuropathological studies in these patients, especially in those with MND. We used MRI to analyze white matter (WM) volumes in presymptomatic and symptomatic C9orf72 expansion carriers and investigated whether its measure may be helpful in predicting the onset of symptoms.

METHODS

We studied 102 presymptomatic C9orf72 mutation carriers, 52 symptomatic carriers: 42 suffering from FTD and 11 from MND, and 75 non-carriers from the Genetic Frontotemporal dementia Initiative (GENFI). All subjects underwent T1-MRI acquisition. We used FreeSurfer to estimate the volume proportion of WM in the brainstem regions (midbrain, pons, and medulla oblongata). We calculated group differences with ANOVA tests and performed linear and non-linear regressions to assess group-by-age interactions.

RESULTS

A reduced WM ratio was found in all brainstem subregions in symptomatic carriers compared to both noncarriers and pre-symptomatic carriers. Within symptomatic carriers, MND patients presented a lower ratio in pons and medulla oblongata compared with FTD patients. No differences were found between presymptomatic carriers and non-carriers. Clinical severity was negatively associated with the WM ratio. C9orf72 carriers presented greater age-related WM loss than non-carriers, with MND patients showing significantly more atrophy in pons and medulla oblongata.

DISCUSSION

We find consistent brainstem WM loss in C9orf72 symptomatic carriers with differences related to the clinical phenotype supporting the use of brainstem measures as neuroimaging biomarkers for disease tracking.

Diagnostic Performance and Clinical Applicability of Blood-Based Biomarkers in a Prospective Memory Clinic Cohort

BACKGROUND AND OBJECTIVES

Blood-based biomarkers have emerged as minimally invasive options for evaluating cognitive impairment. Most studies to date have assessed them in research cohorts, limiting their generalization to everyday clinical practice. We evaluated their diagnostic performance and clinical applicability in a prospective, real-world, memory clinic cohort.

METHODS

All patients referred with suspected cognitive impairment between July 2019 and June 2021 were prospectively invited to participate. Five plasma biomarkers (tau phosphorylated at threonine 181 [p-tau181], glial fibrillary acidic protein [GFAP], neurofilament light chain [NfL], total tau [t-tau], and ubiquitin C-terminal hydrolase L1 [UCH-L1]) were determined with single-molecule array. Performance was assessed in comparison to clinical diagnosis (blinded to plasma results) and amyloid status (CSF/PET). A group of cognitively unimpaired (CU) controls was also included.

RESULTS

Three hundred forty-nine participants (mean age 68, SD 8.3 years) and 36 CU controls (mean age 61.7, SD 8.2 years) were included. In the subcohort with available Alzheimer disease (AD) biomarkers (n = 268), plasma p-tau181 and GFAP had a high diagnostic accuracy to differentiate AD from non-neurodegenerative causes (area under the receiver operating characteristic curve 0.94 and 0.92, respectively), with p-tau181 systematically outperforming GFAP. Plasma p-tau181 levels predicted amyloid status (85% sensitivity and specificity) with accurate individual prediction in approximately 60% of the patients. Plasma NfL differentiated frontotemporal dementia (FTD) syndromes from CU (0.90) and non-neurodegenerative causes (0.93), whereas the discriminative capacity with AD and between all neurodegenerative and non-neurodegenerative causes was less accurate. A combination of p-tau181 and NfL identified FTD with 82% sensitivity and 85% specificity and had a negative predictive value for neurodegenerative diagnosis of 86%, ruling out half of the non-neurodegenerative diagnoses. In the subcohort without AD biomarkers, similar results were obtained. T-tau and UCH-L1 did not offer added diagnostic value.

DISCUSSION

Plasma p-tau181 predicted amyloid status with high accuracy and could have potentially avoided CSF/amyloid PET testing in approximately 60% of subjects in a memory clinic setting. NfL was useful for identifying FTD from non-neurodegenerative causes but behaved worse than p-tau181 in all other comparisons. Combining p-tau181 and NfL improved diagnostic performance for FTD and non-neurodegenerative diagnoses. However, the 14% false-negative results suggest that further improvement is needed before implementation outside memory clinics.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that plasma p-tau181 correlates with the presence or absence of AD and a combination of plasma p-tau181 and NfL correlates moderately well with a diagnosis of FTD.

Barcelona scale for buccophonatory apraxia: Quantitative assessment tool

INTRODUCTION

Currently there is no tool to quantify buccophonatory apraxia to stratify, compare and monitor patients longitudinally in an objective manner. Our aim in this study is to create a quantitative scale for buccophonatory apraxia and evaluate it in patients with the non-fluent/grammatical variant of primary progressive aphasia (nfvPPA) and other neurodegenerative diseases that occur with speech and/or language problems.

METHODS

The scale was designed based on useful elements in the assessment of buccophonatory apraxia and the total was quantified in seconds. The scale was administered to 64 participants with diagnoses of: nfvPPA, semantic variant of primary progressive aphasia (svPPA), logopenic variant of primary progressive aphasia (lvPPA), Huntington's disease, Parkinson's disease, as well as a group of healthy controls.

RESULTS

Patients showed a significantly higher score compared to controls. The nfvPPA group had the highest mean score on the scale (429 seconds ± 278). The scale was useful to differentiate vnfPPA from svPPA and Parkinson's disease (area under curve [AUC] of 0.956 and 0.989, respectively), but less to differentiate it from Huntington's disease (AUC = 0.67) and lvPPA. There was a statistically significant relationship between total score and disease severity in nfvPPA (P < .029).

CONCLUSIONS

The Barcelona scale for buccophonatory apraxia could be useful to quantitatively evaluate buccophonatory apraxia in different neurodegenerative diseases, and compare patients, especially in nfvPPA.

Sex differences in early-onset Alzheimer's disease

INTRODUCTION

Sex is believed to drive heterogeneity in Alzheimer's disease (AD), although evidence in early-onset AD (<65 years, EOAD) is scarce.

METHODS

We included 62 EOAD patients and 44 healthy controls (HC) with cerebrospinal fluid (CSF) AD's core biomarkers and neurofilament light chain levels, neuropsychological assessment, and 3T-MRI. We measured cortical thickness (CTh) and hippocampal subfield volumes (HpS) using Freesurfer. Adjusted linear models were used to analyze sex-differences and the relationship between atrophy and cognition.

RESULTS

Compared to same-sex HC, female-EOAD showed greater cognitive impairment and broader atrophy burden than male-EOAD. In a direct female-EOAD and male-EOAD comparison, there were slight differences in temporal CTh, with no differences in cognition or HpS. CSF tau levels were higher in female-EOAD than in male-EOAD. Greater atrophy was associated with worse cognition in female-EOAD.

CONCLUSIONS

At diagnosis, there are sex-differences in the pattern of cognitive impairment, atrophy burden and CSF tau in EOAD, suggesting there is an influence of sex on pathology spreading and susceptibility to the disease in EOAD.

Evolution of Clinical-Pathological Correlations in Early-Onset Alzheimer's Disease Over a 25-Year Period in an Academic Brain Bank

BACKGROUND

Early onset Alzheimer's disease (EOAD) represents a diagnostic challenge and is associated with a high diagnostic delay and misdiagnosis.

OBJECTIVE

To describe clinical and pathological data from a pathologically confirmed EOAD cohort and evaluate evolving trends in clinical-pathological correlation accuracy.

METHODS

Retrospective review of clinical and neuropathological data of pathologically confirmed EOAD patients (age at onset [AAO] < 60). Comparison between two periods: 1994- 2009 and 2010- 2018.

RESULTS

Eighty brain donors were included. Mean AAO, age at death, and diagnostic delay was 55, 66, and 3 years, respectively. Twenty-nine percent had a nonamnestic presentation. Sixteen percent were given a non-AD initial clinical diagnosis (initial misdiagnosis) and 14% received a final misdiagnosis. Nonamnestic presentation patients received more misdiagnoses than amnestic presentation ones (39% versus 7% and 39% versus 3.5%, on initial and final misdiagnosis, respectively). When comparing both time periods, a trend towards a higher diagnostic accuracy in the 2010- 2018 period was observed, mainly on initial misdiagnosis in nonamnestic presentation patients (53% versus 13%, p = 0.069). Diagnostic delay was similar between both periods. Cerebral amyloid angiopathy (96%) and Lewy body co-pathology (55%) were very frequent, while limbic-predominant age-related TDP-43 encephalopathy pathologic changes were only present in 12.5%.

CONCLUSION

In the last decade, there has been a trend towards improved diagnostic accuracy in EOAD, which might be explained by improved diagnostic criteria, increasing experience on EOAD and the beginning of the use of biomarkers, although diagnostic delay remains similar. Concomitant neuropathology was very frequent despite the relatively young age of brain donors.

Cortical microstructure in primary progressive aphasia: a multicenter study

BACKGROUND

Cortical mean diffusivity is a novel imaging metric sensitive to early changes in neurodegenerative syndromes. Higher cortical mean diffusivity values reflect microstructural disorganization and have been proposed as a sensitive biomarker that might antedate macroscopic cortical changes. We aimed to test the hypothesis that cortical mean diffusivity is more sensitive than cortical thickness to detect cortical changes in primary progressive aphasia (PPA).

METHODS

In this multicenter, case-control study, we recruited 120 patients with PPA (52 non-fluent, 31 semantic, and 32 logopenic variants; and 5 GRN-related PPA) as well as 89 controls from three centers. The 3-Tesla MRI protocol included structural and diffusion-weighted sequences. Disease severity was assessed with the Clinical Dementia Rating scale. Cortical thickness and cortical mean diffusivity were computed using a surface-based approach.

RESULTS

The comparison between each PPA variant and controls revealed cortical mean diffusivity increases and cortical thinning in overlapping regions, reflecting the canonical loci of neurodegeneration of each variant. Importantly, cortical mean diffusivity increases also expanded to other PPA-related areas and correlated with disease severity in all PPA groups. Cortical mean diffusivity was also increased in patients with very mild PPA when only minimal cortical thinning was observed and showed a good correlation with measures of disease severity.

CONCLUSIONS

Cortical mean diffusivity shows promise as a sensitive biomarker for the study of the neurodegeneration-related microstructural changes in PPA.

Errorless Learning Therapy in Semantic Variant of Primary Progressive Aphasia

BACKGROUND

The semantic variant of primary progressive aphasia (svPPA) is characterized by a progressive loss of semantic knowledge impairing the ability to name and to recognize the meaning of words.

OBJECTIVE

We aimed to evaluate the immediate and short-term effect of errorless learning speech therapy on the naming and recognition of commonly used words in patients with svPPA.

METHODS

Eight participants diagnosed with svPPA received 16 sessions of intensive errorless learning speech therapy. Naming and word comprehension tasks were evaluated at baseline, immediately postintervention, and at follow-up after 1, 3, and 6 months. These evaluations were performed using two item sets (a trained list and an untrained list).

RESULTS

In the naming tasks, patients showed a significant improvement in trained items immediately after the intervention, but that improvement decayed progressively when therapy ended. No improvements were found either in trained comprehension or in untrained tasks.

CONCLUSION

Errorless learning therapy could improve naming ability in patients with svPPA. This effect may be due to the relative preservation of episodic memory, but the benefit is not maintained over time, presumably because there is no consolidation.

Longitudinal brain atrophy and CSF biomarkers in early-onset Alzheimer's disease

There is evidence of longitudinal atrophy in posterior brain areas in early-onset Alzheimer's disease (EOAD; aged < 65 years), but no studies have been conducted in an EOAD cohort with fluid biomarkers characterization. We used 3T-MRI and Freesurfer 6.0 to investigate cortical and subcortical gray matter loss at two years in 12 EOAD patients (A + T + N + ) compared to 19 controls (A-T-N-) from the Hospital Clínic Barcelona cohort. We explored group differences in atrophy patterns and we correlated atrophy and baseline CSF-biomarkers levels in EOAD. We replicated the correlation analyses in 14 EOAD (A + T + N + ) and 55 late-onset AD (LOAD; aged ≥ 75 years; A + T + N + ) participants from the Alzheimer's disease Neuroimaging Initiative. We found that EOAD longitudinal atrophy spread with a posterior-to-anterior gradient and beyond hippocampus/amygdala. In EOAD, higher initial CSF NfL levels correlated with higher ventricular volumes at baseline. On the other hand, higher initial CSF Aβ42 levels (within pathological range) predicted higher rates of cortical loss in EOAD. In EOAD and LOAD subjects, higher CSF t-tau values at baseline predicted higher rates of subcortical atrophy. CSF p-tau did not show any significant correlation. In conclusion, posterior cortices, hippocampus and amygdala capture EOAD atrophy from early stages. CSF Aβ42 might predict cortical thinning and t-tau/NfL subcortical atrophy.

Diagnostic Utility of Measuring Cerebral Atrophy in the Behavioral Variant of Frontotemporal Dementia and Association With Clinical Deterioration

IMPORTANCE

The presence of atrophy on magnetic resonance imaging can support the diagnosis of the behavioral variant of frontotemporal dementia (bvFTD), but reproducible measurements are lacking.

OBJECTIVE

To assess the diagnostic and prognostic utility of 6 visual atrophy scales (VAS) and the Magnetic Resonance Parkinsonism Index (MRPI).

DESIGN, SETTING, AND PARTICIPANTS

In this diagnostic/prognostic study, data from 235 patients with bvFTD and 225 age- and magnetic resonance imaging-matched control individuals from 3 centers were collected from December 1, 1998, to September 30, 2019. One hundred twenty-one participants with bvFTD had high confidence of frontotemporal lobar degeneration (FTLD) (bvFTD-HC), and 19 had low confidence of FTLD (bvFTD-LC). Blinded clinicians applied 6 previously validated VAS, and the MRPI was calculated with a fully automated approach. Cortical thickness and subcortical volumes were also measured for comparison. Data were analyzed from February 1 to June 30, 2020.

MAIN OUTCOMES AND MEASURES

The main outcomes of this study were bvFTD-HC or a neuropathological diagnosis of 4-repeat (4R) tauopathy and the clinical deterioration rate (assessed by longitudinal measurements of Clinical Dementia Rating Sum of Boxes). Measures of cerebral atrophy included VAS scores, the bvFTD atrophy score (sum of VAS scores in orbitofrontal, anterior cingulate, anterior temporal, medial temporal lobe, and frontal insula regions), the MRPI, and other computerized quantifications of cortical and subcortical volumes. The areas under the receiver operating characteristic curve (AUROC) were calculated for the differentiation of participants with bvFTD-HC and bvFTD-LC and controls. Linear mixed models were used to evaluate the ability of atrophy measures to estimate longitudinal clinical deterioration.

RESULTS

Of the 460 included participants, 296 (64.3%) were men, and the mean (SD) age was 62.6 (11.4) years. The accuracy of the bvFTD atrophy score for the differentiation of bvFTD-HC from controls (AUROC, 0.930; 95% CI, 0.903-0.957) and bvFTD-HC from bvFTD-LC (AUROC, 0.880; 95% CI, 0.787-0.972) was comparable to computerized measures (AUROC, 0.973 [95% CI, 0.954-0.993] and 0.898 [95% CI, 0.834-0.962], respectively). The MRPI was increased in patients with bvFTD and underlying 4R tauopathies compared with other FTLD subtypes (14.1 [2.0] vs 11.2 [2.6] points; P < .001). Higher bvFTD atrophy scores were associated with faster clinical deterioration in bvFTD (1.86-point change in Clinical Dementia Rating Sum of Boxes score per bvFTD atrophy score increase per year; 95% CI, 0.99-2.73; P < .001).

CONCLUSIONS AND RELEVANCE

Based on these study findings, in bvFTD, VAS increased the diagnostic certainty of underlying FTLD, and the MRPI showed potential for the detection of participants with underlying 4R tauopathies. These widely available measures of atrophy can also be useful to estimate longitudinal clinical deterioration.

Disease-related cortical thinning in presymptomatic granulin mutation carriers

•

No differences in cortical thickness were found between presymptomatic GRN mutation carriers and non-carriers at the group-wise comparison.

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Presymptomatic GRN mutations carriers present distinct age-related CTh loss in frontal areas.

•

We do not fount influence of the TMEM106B genotype in the age-related CTh of GRN carriers.

Mutations in the granulin gene (GRN) cause familial frontotemporal dementia. Understanding the structural brain changes in presymptomatic GRN carriers would enforce the use of neuroimaging biomarkers for early diagnosis and monitoring. We studied 100 presymptomatic GRN mutation carriers and 94 noncarriers from the Genetic Frontotemporal dementia initiative (GENFI), with MRI structural images. We analyzed 3T MRI structural images using the FreeSurfer pipeline to calculate the whole brain cortical thickness (CTh) for each subject. We also perform a vertex-wise general linear model to assess differences between groups in the relationship between CTh and diverse covariables as gender, age, the estimated years to onset and education. We also explored differences according to TMEM106B genotype, a possible disease modifier. Whole brain CTh did not differ between carriers and noncarriers. Both groups showed age-related cortical thinning. The group-by-age interaction analysis showed that this age-related cortical thinning was significantly greater in GRN carriers in the left superior frontal cortex. TMEM106B did not significantly influence the age-related cortical thinning. Our results validate and expand previous findings suggesting an increased CTh loss associated with age and estimated proximity to symptoms onset in GRN carriers, even before the disease onset.

Synaptic, axonal damage and inflammatory cerebrospinal fluid biomarkers in neurodegenerative dementias

INTRODUCTION

Synaptic damage, axonal neurodegeneration, and neuroinflammation are common features in Alzheimer's disease (AD), frontotemporal dementia (FTD), and Creutzfeldt-Jakob disease (CJD).

METHODS

Unicentric cohort of 353 participants included healthy control (HC) subjects, AD continuum stages, genetic AD and FTD, and FTD and CJD. We measured cerebrospinal fluid neurofilament light (NF-L), neurogranin (Ng), 14-3-3, and YKL-40 proteins.

RESULTS

Biomarkers showed differences in HC subjects versus AD, FTD, and CJD. Disease groups differed between them except AD versus FTD for YKL-40. Only NF-L differed between all stages within the AD continuum. AD and FTD symptomatic mutation carriers presented differences with respect to HC subjects. Applying the AT(N) system, 96% subjects were positive for neurodegeneration if 14-3-3 was used, 94% if NF-L was used, 62% if Ng was used, and 53% if YKL-40 was used.

DISCUSSION

Biomarkers of synapse and neurodegeneration differentiate HC subjects from neurodegenerative dementias and between AD, FTD, and CJD. NF-L and 14-3-3 performed similar to total tau when AT(N) system was applied.

APP-derived peptides reflect neurodegeneration in frontotemporal dementia

Objective

We aimed to investigate the relationship between cerebrospinal fluid levels (CSF) of amyloid precursor protein (APP)‐derived peptides related to the amyloidogenic pathway, cortical thickness, neuropsychological performance, and cortical gene expression profiles in frontotemporal lobar degeneration (FTLD)‐related syndromes, Alzheimer’s disease (AD), and healthy controls.

Methods

We included 214 participants with CSF available recruited at two centers: 93 with FTLD‐related syndromes, 57 patients with AD, and 64 healthy controls. CSF levels of amyloid β (Aβ)1‐42, Aβ1‐40, Aβ1‐38, and soluble β fragment of APP (sAPPβ) were centrally analyzed. We compared CSF levels of APP‐derived peptides between groups and, we studied the correlation between CSF biomarkers, cortical thickness, and domain‐specific cognitive composites in each group. Then, we explored the relationship between cortical thickness, CSF levels of APP‐derived peptides, and regional gene expression profile using a brain‐wide regional gene expression data in combination with gene set enrichment analysis.

Results

The CSF levels of Aβ1‐40, Aβ1‐38, and sAPPβ were lower in the FTLD‐related syndromes group than in the AD and healthy controls group. CSF levels of all APP‐derived peptides showed a positive correlation with cortical thickness and the executive cognitive composite in the FTLD‐related syndromes group but not in the healthy control or AD groups. In the cortical regions where we observed a significant association between cortical thickness and CSF levels of APP‐derived peptides, we found a reduced expression of genes related to synaptic function.

Interpretation

APP‐derived peptides in CSF may reflect FTLD‐related neurodegeneration. This observation has important implications as Aβ1‐42 levels are considered an indirect biomarker of cerebral amyloidosis.

Novel P397S MAPT variant associated with late onset and slow progressive frontotemporal dementia

Mutations in the MAPT gene cause frontotemporal dementia with tau deposits. We report the novel p.P397S MAPT variant in eight subjects from five apparently nonrelated families suffering from frontotemporal dementia with autosomal dominant pattern of inheritance. In silico analysis reported conflicting evidence of pathogenicity. The segregation analysis support that this variant is likely pathogenic. The mean age at onset (61.4 years) and mean disease duration (13.9 years) of these subjects and their affected relatives were significantly higher compared with our series of p.P301L MAPT mutation carriers. These findings suggest that p.P397S variant could be a new MAPT mutation associated with a less aggressive phenotype than other MAPT mutations.

Cortical microstructure in the behavioural variant of frontotemporal dementia: looking beyond atrophy

Cortical mean diffusivity has been proposed as a novel biomarker for the study of the cortical microstructure in Alzheimer's disease. In this multicentre study, we aimed to assess the cortical microstructural changes in the behavioural variant of frontotemporal dementia (bvFTD); and to correlate cortical mean diffusivity with clinical measures of disease severity and CSF biomarkers (neurofilament light and the soluble fraction beta of the amyloid precursor protein). We included 148 participants with a 3 T MRI and appropriate structural and diffusion weighted imaging sequences: 70 patients with bvFTD and 78 age-matched cognitively healthy controls. The modified frontotemporal lobar degeneration clinical dementia rating was obtained as a measure of disease severity. A subset of patients also underwent a lumbar puncture for CSF biomarker analysis. Two independent raters blind to the clinical data determined the presence of significant frontotemporal atrophy to dichotomize the participants into possible or probable bvFTD. Cortical thickness and cortical mean diffusivity were computed using a surface-based approach. We compared cortical thickness and cortical mean diffusivity between bvFTD (both using the whole sample and probable and possible bvFTD subgroups) and controls. Then we computed the Cohen's d effect size for both cortical thickness and cortical mean diffusivity. We also performed correlation analyses with the modified frontotemporal lobar degeneration clinical dementia rating score and CSF neuronal biomarkers. The cortical mean diffusivity maps, in the whole cohort and in the probable bvFTD subgroup, showed widespread areas with increased cortical mean diffusivity that partially overlapped with cortical thickness, but further expanded to other bvFTD-related regions. In the possible bvFTD subgroup, we found increased cortical mean diffusivity in frontotemporal regions, but only minimal loss of cortical thickness. The effect sizes of cortical mean diffusivity were notably higher than the effect sizes of cortical thickness in the areas that are typically involved in bvFTD. In the whole bvFTD group, both cortical mean diffusivity and cortical thickness correlated with measures of disease severity and CSF biomarkers. However, the areas of correlation with cortical mean diffusivity were more extensive. In the possible bvFTD subgroup, only cortical mean diffusivity correlated with the modified frontotemporal lobar degeneration clinical dementia rating. Our data suggest that cortical mean diffusivity could be a sensitive biomarker for the study of the neurodegeneration-related microstructural changes in bvFTD. Further longitudinal studies should determine the diagnostic and prognostic utility of this novel neuroimaging biomarker.

Clinical applicability of diagnostic biomarkers in early-onset cognitive impairment

BACKGROUND AND PURPOSE

Several diagnostic biomarkers are currently available for clinical use in early-onset cognitive impairment. The decision on which biomarker is used in each patient depends on several factors such as its predictive value or tolerability.

METHODS

There were a total of 40 subjects with early-onset cognitive complaints (<65 years of age): 26 with Alzheimer's disease (AD), five with frontotemporal dementia and nine with diagnostic suspicion of non-neurodegenerative disorder. Clinical and neuropsychological evaluation, lumbar puncture for cerebrospinal fluid (CSF) AD core biochemical marker determination, medial temporal atrophy evaluation on magnetic resonance imaging, amyloid-positron emission tomography (PET) and ¹⁸ F-fluorodeoxyglucose-PET were performed. Neurologists provided pre- and post-biomarker diagnosis, together with diagnostic confidence and clinical/therapeutic management. Patients scored the tolerability of each procedure.

RESULTS

Cerebrospinal fluid biomarkers and amyloid-PET increased diagnostic confidence in AD (77.4%-86.2% after CSF, 92.4% after amyloid-PET, P < 0.01) and non-neurodegenerative conditions (53.6%-75% after CSF, 95% after amyloid-PET, P < 0.05). Biomarker results led to diagnostic (32.5%) and treatment (32.5%) changes. All tests were well tolerated.

CONCLUSIONS

Biomarker procedures are well tolerated and have an important diagnostic/therapeutic impact on early-onset cognitive impairment.

Distinct Clinical Features and Outcomes in Motor Neuron Disease Associated with Behavioural Variant Frontotemporal Dementia

AIM

To determine the motor phenotype and outcome in a clinically ascertained group of patients with motor neuron disease (MND) and frontotemporal dementia (FTD).

METHODS

This is an observational retrospective clinical study of patients fulfilling the clinical criteria for MND-FTD. A contemporary series of patients with amyotrophic lateral sclerosis (ALS) without dementia were included for comparison. Demographic, clinical, genetic, and neuropathological data were collected. A descriptive and comparative data analysis was performed.

RESULTS

We identified 22 patients with MND-FTD. Selective distal upper limb muscle weakness and atrophy with non-significant lower limb weakness during follow-up was the most frequent motor pattern, present in 18 patients - in 15 of them associated with severe dysphagia. Aspiration pneumonia was the most common cause of death (12/19; 63%) despite gastrostomy. One-third of the patients did not develop upper motor neuron dysfunction. When compared to classic ALS without dementia (n = 162), these features were significantly different. A neuro-pathological examination was performed on 7 patients, and it confirmed the presence of MND with TDP43 protein aggregates in all patients.

CONCLUSIONS

The MND-FTD patients frequently displayed a distinctive motor pattern characterized by weakness and atrophy in distal upper limb muscles and dysphagia, with no or little spreading to other regions. These features may help to define specific subgroups of patients, which is important with regard to clinical management, outcome, and research.

Frontotemporal Dementia Caused by the P301L Mutation in the MAPT Gene: Clinicopathological Features of 13 Cases from the Same Geographical Origin in Barcelona, Spain

BACKGROUND/AIMS

We identified and studied 13 patients carrying the P301L mutation in the MAPT gene from the same area (Baix Llobregat County) in Barcelona, Spain.

METHODS

The demographic and clinical features were reviewed retrospectively. Detailed neuropathological characterization was obtained in 9 subjects. To investigate the origin of the P301L mutation in these families, 20 single nucleotide polymorphisms (SNPs) in the MAPT gene were analyzed.

RESULTS

The mean age at disease onset was 51 years and the mean disease duration was 7 years. The most common initial symptoms were behavioral changes (54%), followed by language disturbances (31%) and memory loss (15%). 46% developed parkinsonism. Neuropathology showed an extensive neuronal and glial 4-repeat (4R) tauopathy with "mini-Pick"-like bodies in the dentate gyrus as the characteristic underlying pathology in all cases. In 1 subject, additional 4R globular glial inclusions were observed. All the mutation carriers showed the same haplotype for the SNPs analyzed, suggesting a common ancestor.

CONCLUSION

These findings suggest a relative homogeneous clinicopathological phenotype in P301L MAPT mutation carriers in our series. This phenotype might help in the differential diagnosis from other tauopathies and be a morphological hint for genetic testing. The haplotype analysis results suggest a founder effect of the P301L mutation in this area.