Background. The presence of intraneuronal aggregates of phosphorylated alpha-synuclein (pAS), the histological hallmark of Parkinson disease (PD), has been already demonstrated to be present in the autonomic nerve fibres that innervate the submandibular gland in approximately 75% of living PD patients. The presence of pAS in the peripheral autonomic nervous system in carriers of LRRK2 mutations has not been studied so far. The objective of the current study is to evaluate the presence of abnormal pAS aggregates in the submandibular gland tissue of LRRK2 p.G2019S mutations carriers. Methods. This is a prospective observational study conducted between 2014 and 2015 at Hospital Clínic de Barcelona, Spain. A random sample of nine asymptomatic LRRK2 (a LRRK2) and 11 LRRK2 associated PD ( LRRK2 -PD) patients were recruited among a cohort of LRRK2 -PD patients and their relatives already identified at our centre. All the participants underwent transcutaneous needle core biopsy of the submandibular gland under ultrasound guidance. The presence of pAS was assessed in all the participants by immunohistochemistry using anti-Serine 129-phosphorylated AS antibody. Results. Submandibular biopsy material containing glandular parenchyma was obtained in 4 (44.44%) a LRRK2 and in 6 (54.55%) LRRK2 -PD patients. Aggregates of pAS were detected in the glandular parenchyma in one of the four (25%) a LRRK2 subjects and in none (0%) of the LRRK2 -PD patients. Conclusions. Our study shows that pAS aggregates obtained by needle core biopsy of the submandibular gland are infrequent in LRRK2 mutation carriers but may be detected in asymptomatic mutation carriers. The low rate of pAS positive biopsies suggests either a different physiopathology between LRRK2 -related and idiopathic PD or that a one-time unilateral submandibular gland biopsy is not the optimal procedure for the study of synuclein aggregation in LRRK2 mutation carriers.

Abstract Background Optical coherence tomography (OCT) of the retina is a fast and easily accessible tool for the quantification of retinal structural measurements. Multiple studies show that patients with Alzheimer’s disease (AD) exhibit thinning in several retinal layers compared to age-matched controls. Subjective cognitive decline (SCD) has been proposed as a risk factor for progression to AD. There is little data about retinal changes in preclinical AD and their correlation with amyloid-β (Aβ) uptake. Aims We investigated the association of retinal thickness quantified by OCT with Aβ accumulation and conversion to mild cognitive impairment (MCI) over 24 months in individuals with SCD. Methods One hundred twenty-nine individuals with SCD enrolled in Fundació ACE Healthy Brain Initiative underwent comprehensive neuropsychological testing, OCT scan of the retina and florbetaben (FBB) positron emission tomography (PET) at baseline (v0) and after 24 months (v2). We assessed the association of sixteen retinal thickness measurements at baseline with FBB-PET status (+/−) and global standardize uptake value ratio (SUVR) as a continuous measure at v0 and v2 and their predictive value on clinical status change (conversion to mild cognitive impairment (MCI)) at v2. Results Mean age of the sample was 64.72 ± 7.27 years; 62.8% were females. Fifteen participants were classified as FBB-PET+ at baseline and 22 at v2. Every 1 μm of increased thickness in the inner nasal macular region conferred 8% and 6% higher probability of presenting a FBB-PET+ status at v0 (OR = 1.08, 95% CI = 1.02–1.14, p = 0.007) and v2 (OR = 1.06, 95% CI = 1.02–1.11, p = 0.004), respectively. Inner nasal macular thickness also positively correlated with global SUVR (at v0: β = 0.23, p = 0.004; at v2: β = 0.26, p = 0.001). No retinal measurements were associated to conversion to MCI over 24 months. Conclusions Subtle retinal thickness changes in the macular region are already present in SCD and correlate with Aβ uptake.

To determine whether lower performance on executive function tests in subjective cognitive decline (SCD) individuals are associated with higher levels of brain amyloid beta (Aβ) deposition and regional volumetric reduction in areas of interest for Alzheimer’s disease (AD). 195 individuals with SCD from the FACEHBI study were assessed with a neuropsychological battery that included the following nine executive function tests: Trail Making Test A and B (TMTA, TMTB), the Rule Shift Cards subtest of BADS, the Automatic Inhibition subtest of the Syndrom Kurz Test (AI-SKT), Digit Span Backwards and Similarities from WAIS-III, and the letter, semantic, and verb fluency tests. All subjects underwent an 18F-Florbetaben positron emission tomography (FBB-PET) scan to measure global standard uptake value ratio (SUVR), and a magnetic resonance imaging (MRI). A multiple regression analysis, adjusted for age, was carried out to explore the association between global SUVR and performance on executive tests. Then, on those tests significantly associated with amyloid burden, a voxel-based morphometry (VBM) analysis was carried out to explore their correlates with grey matter volume. Multiple regression analysis revealed a statistically significant association between Aβ deposition and performance on one of the executive tests (the AI-SKT). Moreover, VBM analysis showed worse AI-SKT scores were related to lower volume in bilateral hippocampus and left inferior frontal regions. In conclusion, in SCD individuals, worse automatic inhibition ability has been found related to higher cerebral Aβ deposition and lower volume in the hippocampus and frontal regions. Thus, our results may contribute to the early detection of AD in individuals with SCD.

Individuals with autosomal dominant Alzheimer's disease (ADAD) present amyloid deposits before symptoms onset. We aimed to investigate efficacy and safety of 18F-florbetaben (FBB) for assessing amyloid deposition in ADAD. We acquired FBB positron emission tomography and magnetic resonance imaging of 25 individuals from PSEN1 families (NCT02362880). We studied individual uptake patterns, group differences, and correlation with estimated years to symptoms onset, as well as adverse events. We found that asymptomatic carriers (N = 14) showed increased FBB uptake across the cerebral cortex and in the caudate. FBB accumulation appeared more than 15 years before onset in the precuneus and bankssts, among other regions, overlapping regions showing increased cortical thickness in the same subjects. FBB uptake correlated with estimated years to symptoms onset in several areas, especially the rostral anterior cingulate. Symptomatic carriers (N = 7) had an elevated FBB uptake plateau. No adverse events were reported. Overall, we found progressive FBB uptake in ADAD starting 2 decades before symptoms. The rostral anterior cingulate is a candidate area to track Aβ deposition in addition to the precuneus.

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 F-18-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.

The Centiloid scale has been developed to standardize measurements of amyloid PET imaging. Reference cut-off values of this continuous measurement enable the consistent operationalization of decision-making for multicentre research studies and clinical trials. In this study, we aimed at deriving reference Centiloid thresholds that maximize the agreement against core Alzheimer’s disease (AD) cerebrospinal fluid (CSF) biomarkers in two large independent cohorts. A total of 516 participants of the ALFA+ Study (N = 205) and ADNI (N = 311) underwent amyloid PET imaging ([18F]flutemetamol and [18F]florbetapir, respectively) and core AD CSF biomarker determination using Elecsys® tests. Tracer uptake was quantified in Centiloid units (CL). Optimal Centiloid cut-offs were sought that maximize the agreement between PET and dichotomous determinations based on CSF levels of Aβ42, tTau, pTau, and their ratios, using pre-established reference cut-off values. To this end, a receiver operating characteristic analysis (ROC) was conducted, and Centiloid cut-offs were calculated as those that maximized the Youden’s J Index or the overall percentage agreement recorded. All Centiloid cut-offs fell within the range of 25–35, except for CSF Aβ42 that rendered an optimal cut-off value of 12 CL. As expected, the agreement of tau/Aβ42 ratios was higher than that of CSF Aβ42. Centiloid cut-off robustness was confirmed even when established in an independent cohort and against variations of CSF cut-offs. A cut-off of 12 CL matches previously reported values derived against postmortem measures of AD neuropathology. Together with these previous findings, our results flag two relevant inflection points that would serve as boundary of different stages of amyloid pathology: one around 12 CL that marks the transition from the absence of pathology to subtle pathology and another one around 30 CL indicating the presence of established pathology. The derivation of robust and generalizable cut-offs for core AD biomarkers requires cohorts with adequate representation of intermediate levels. ALFA+ Study, NCT02485730 ALFA PET Sub-study, NCT02685969

APOE genotype has been shown to be strongly correlated with brain amyloid load in cognitively normal individuals, either in vivo or in pathological studies. However, the influence of APOE genotype in the topographic patterns of amyloid deposition has been less studied in vivo. The aim of this work is to explore the amyloid PET burden deposition, and how the APOE status contributes to this distribution in individuals with subjective cognitive decline (SCD). 195 participants with SCD, from the FACEHBI cohort (description in Table 1), underwent 18F-Florbetaben (FBB)-PET and 1.5T MR scanning. Standardized Uptake Value Ratio (SUVR) from FBB-PET was estimated using FreeSurfer and FSL, Cerebellum as RR. A linear model was used to asses SUVR associations with age, gender, years of education, WAIS vocabulary and APOE status. MRI data was normalized according Dartel, in SPM12. Flow fields were applied to the aligned PET images, finally a smooth of 8mm was applied. A regression analysis, accounting for age and sex, was driven to explore amyloidosis changes (FWE-p<0.05; k=100). Additionally, the analysis involving the interaction between SUVR and APOE status was also conducted (unc.-p<0.001; k=100). 16 out of the 195 individuals with SCD (8.2%) had a FBB-PET global mean SUVR that exceeded the threshold for positivity (1.45). SUVR was highly associated with the APOE status (p<0.0001) and age (p<0.0004; e2e2+e2e3:p<0.0003; e3e3+e2e4:p<0.009; e3e4+e4e4: p<0.03).Regarding neuroimaging, SUVR strongly correlated with bilateral frontal, insula, parietal and precuneus (Fig 1, Table 2). Different selection of these regions was found linked to the APOE status (Fig 2, Table 3). Carriers of risk allele exhibited larger patterns of distribution, involving frontal and precuneus, while carriers of protective allele were only affected in right occipital and left insula. Distribution of amyloid deposits in the FACEHBI cohort (FWE - p<0.05; k= 100). Overlap of the distribution of amyloid deposits in association with APOE (unc. p<0.001; k=l 00). As expected the mean SUVR values were strongly influenced by age and APOE status in the FACEHBI cohort. Strong amyloid distribution dependence on the APOE: e4-carriers exhibited larger pattern of amyloid deposition than e2- and e3-carriers; e2-carriers presented significantly reduced pattern. Results from the follow-up that is ongoing will be essential to capture the distinctive dynamic patterns of deposition associated with different APOE genotypes.

Peripheral biomarkers that identify individuals at risk of developing Alzheimer’s disease (AD) or predicting high amyloid beta (Aβ) brain burden would be highly valuable. To facilitate clinical trials of disease-modifying therapies, plasma concentrations of Aβ species are good candidates for peripheral AD biomarkers, but studies to date have generated conflicting results.

The aim of this work was to obtain a set of parameters to be applied in [123I]FP-CIT SPECT reconstruction in order to minimize the error between standardized and true values of the specific uptake ratio (SUR) in dopaminergic neurotransmission SPECT studies. To this end, Monte Carlo simulation was used to generate a database of 1380 projection data-sets from 23 subjects, including normal cases and a variety of pathologies. Studies were reconstructed using filtered back projection (FBP) with attenuation correction and ordered subset expectation maximization (OSEM) with correction for different degradations (attenuation, scatter and PSF). Reconstruction parameters to be optimized were the cut-off frequency of a 2D Butterworth pre-filter in FBP, and the number of iterations and the full width at Half maximum of a 3D Gaussian post-filter in OSEM. Reconstructed images were quantified using regions of interest (ROIs) derived from Magnetic Resonance scans and from the Automated Anatomical Labeling map. Results were standardized by applying a simple linear regression line obtained from the entire patient dataset. Our findings show that we can obtain a set of optimal parameters for each reconstruction strategy. The accuracy of the standardized SUR increases when the reconstruction method includes more corrections. The use of generic ROIs instead of subject-specific ROIs adds significant inaccuracies. Thus, after reconstruction with OSEM and correction for all degradations, subject-specific ROIs led to errors between standardized and true SUR values in the range [−0.5, +0.5] in 87% and 92% of the cases for caudate and putamen, respectively. These percentages dropped to 75% and 88% when the generic ROIs were used.

We present a modified version of the SISCOM procedure that uses interictal PET instead of interictal SPECT for seizure onset zone localization. We called this new nuclear imaging processing technique PISCOM (PET interictal subtracted ictal SPECT coregistered with MRI).

Autosomal dominant Alzheimer's disease individuals show elevated 11C-Pittsburgh compound B (PiB) and 18-florbetapir uptake about 15 years before the estimated age of symptoms onset (EYO). It has not yet been established whether different amyloid tracers bind to identical sites on amyloid-β (Aβ) fibrils, offering the same ability to detect the regional Aβ burden. Regional disparities in fibrillar Aβ accumulation have also important implications for clinical trials. We aim to investigate the pattern of 18F- florbetaben (FBB) uptake in PSEN1 mutations carriers. We studied 25 individuals from PSEN1 mutation families. Participants received a dose of 300 MBq of FBB and were scanned at a Siemens Biograph molecular-CT. 3D T1 MRI dataset was also acquired. MRI and PET images were processed with Freesurfer 6.0. We obtained the standardized uptake value ratio (SUVR) for each region within an atlas of cortical and subcortical regions, using the pons as the reference region. Group comparisons were performed using Kruskal-Wallis test. Spearman's test assessed the correlation of SUVR values with EYO. Fourteen participants were asymptomatic mutation carriers (AMC) and 7 symptomatic (SMC). In AMC, FBB uptake was significantly increased in almost all the cortical areas studied and in the caudate. SUVR showed the strongest correlation with EYO in the rostral anterior cingulate and pallidum, while the precuneus showed moderate correlation (rho=0.75, 0.74 and 0.59 respectively). In SMC, we observed increased FBB uptake in all the cortical and subcortical areas, but not significant correlations with EYO. Across all MC, SUVR significantly correlated with EYO in all the regions studied, especially in the amygdala, rostral anterior cingulate and isthmus of cingulate (rho = 0.84, 0.83 and 0.81 respectively). Regions with increased FBB uptake compared to controls (p<0.05) across the different stages in MC according to EYO are shown in the Figure. FBB uptake suggest progressive deposition of fibrillar Aβ in PSEN1 mutation carriers in cortical and subcortical areas, starting in temporal, precuneus and medial orbital frontal more than 15 years from predicted symptoms onset. The rostral anterior cingulate might be useful to track fibrillar Aβ deposition both in AMC and across MC . Regional 18F-FBB uptake at different stages (I-III). Regions with significant differences compared to controls (K-W p<0.05) and cortical representation of the magnitude of the differences (i.e., differences in the median SUVR).

Tau and amyloid-β (Aβ) aggregates have been suggested to play a role in the development of dementia in Parkinson's disease (PD). Positron emission tomography (PET) with [18F]FDDNP and the determination of cerebrospinal fluid (CSF) levels of these proteins constitute a means to visualize in vivo Aβ and tau brain accumulation. Information about longitudinal changes of these CSF and PET biomarkers in PD with regard to progression to dementia is lacking. We assessed the cross-sectional and longitudinal associations of CSF and PET biomarkers of tau and Aβ with PD-related cognitive dysfunction in 6 healthy-controls (HC), 16 patients with PD without dementia (PDND), and 8 PD with dementia (PDD). All subjects underwent comprehensive neuropsychological testing, [18F]FDDNP PET, and CSF Aβ-tau determination. After 18 months, the PDND group was re-assessed clinically and by neuropsychological, PET, and CSF determinations. Cross-sectionally, PDD had higher [18F]FDDNP binding in lateral temporal regions and lower levels of CSF Aβ levels compared to PDND, with a congruent correlation between the [18F]FDDNP binding and CSF Aβ levels. Longitudinally, higher baseline lateral temporal [18F]FDDNP binding was associated to longitudinal worsening in cognitive performances and progression to dementia among subjects classified as PDND at baseline, who additionally disclosed at follow-up an increase in lateral-temporal FDDNP binding, as well as a reduction in CSF Aβ and an increase in CSF tau levels. These results confirm the relevance of these CSF and PET biomarkers to PDD, being specifically the first to show [18F]FDDNP PET as a dementia risk biomarker in PD, along with longitudinal CSF and PET changes over time.