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Background: Reliable biomarkers for Parkinson's disease (PD) diagnosis are urgently needed. Alpha-synuclein (α-syn) and its proteoforms play a key role in PD pathology but in vivo measurements have raised conflicting results, and whether α-syn in blood could distinguish PD patients from healthy controls is still controversial., Methods: A systematic literature search yielded 35 eligible studies for meta-analysis reporting the concentration of total, oligomeric or phosphorylated α-syn in plasma and/or serum of PD patients and healthy controls. Standardized mean differences (SMD) were pooled using multivariate/multilevel linear mixed-effects models. Meta-regression analyses were conducted to investigate possible modifiers., Results: A meta-analysis of 32 articles involving 2683 PD patients and 1838 controls showed a significant overall effect of PD on total α-syn levels (SMD = 0.85, p = 0.004). Meta-regression showed that increased SMD of total α-syn in PD was significantly associated with lower age, shorter disease duration, mild motor impairment, and Immunomagnetic Reduction assay for protein quantification. In contrast, no significant differences were observed for oligomeric or phosphorylated α-syn between PD and controls but increased oligomeric α-syn was significantly associated with shorter disease duration. The heterogeneity among studies was high (>98%)., Conclusions: These findings suggest that increased total plasma/serum α-syn levels in PD primarily occur in early phases of the disease. The evidence obtained from a small number of studies measuring plasma/serum concentrations of oligomeric and phosphorylated species of α-syn shows no difference. The clinical applicability of measuring plasma or serum α-syn species for differentiating PD from healthy control warrants further studies with better clinical profiling of PD patients., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Introduction: Blood and cerebrospinal fluid represent emerging candidate fluids for biomarker identification in Parkinson's disease (PD)., Methods: We studied 8 individuals carrying the E46K-SNCA mutation (3 PD dementia (PDD), 1 tremor-dominant PD, 2 young rigid-akinetic PD and 2 asymptomatic) and 8 age- and sex-matched healthy controls. We quantified the levels of total alpha-synuclein (a-syn), neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), Tau and ubiquitin carboxy-terminal hydrolase L1 (UCHL1) with SiMoA (Quanterix) in cerebrospinal fluid (CSF) of mutation carriers and in serum of all participants. The correlation between the concentration of biofluid markers and clinical outcomes was evaluated., Results: Although based on a small number of cases, CSF a-syn was decreased in symptomatic E46K-SNCA carriers compared to the asymptomatic ones. Asymptomatic carriers exhibited similar serum biomarker levels as compared to matched controls, except for serum a-syn, which was higher in asymptomatic individuals. Carriers with PDD diagnosis displayed increased levels of serum NfL and GFAP compared to matched controls. These findings highly correlated with cognitive and motor status of E46K-SNCA carriers, but not with disease duration., Conclusions: Patients with familial forms of neurodegenerative disease exhibit variable penetrance of the phenotype and are exceptionally valuable for delineating biomarkers. Serum and CSF molecular biomarkers in E46K-SNCA mutation carriers show that a-syn might be suitable to track the conversion from asymptomatic to PD, whereas NfL and GFAP might serve to foresee the progression to PD dementia. These findings should be interpreted with caution and need to be replicated in other genetic synucleinopathy cohorts., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Introduction: Visual dysfunction and cognitive impairment are common in Parkinson's disease (PD) but the precise contribution of lower-level visual impairment to visual-input based cognitive performance has not been extensively characterized in PD., Methods: We included 49 PD patients and 22 healthy controls (HC). Lower-level visual function tests [high and low contrast visual acuity (HCVA and LCVA) and contrast sensitivity (CS)] and a neuropsychological battery (involving visual cognition) were performed. Pairwise correlations between lower-level visual functions and visual cognition were computed and stepwise linear regressions were fitted introducing age, Geriatric Depression Scale, and lower-level visual functions in the model to calculate their predicted effect on visual cognition., Results: Compared to controls, patients presented a significant impairment in all cognitive domains (visual attention, visual processing speed and visual perception, visuospatial abilities, visuoconstructive abilities, and visual memory), and lower-level visual functions. HCVA and LCVA were significantly associated with visual cognition in PD. HCVA explained up to 49.3% and 34.2% of the variability in visual perception and visuospatial abilities, respectively, whereas LCVA was mainly associated with short- and long-term visual memory and visuospatial abilities., Conclusion: Lower-level visual dysfunction is highly associated with cognitive performance in PD, when cognitive tests are based on visual input. Our results support that lower-level visual functions should be considered when assessing cognitive status of PD patients and might be useful for predicting cognitive deterioration., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background and Objective: In 2004 we described the E46K mutation in alpha-synuclein gene (E46K-SNCA), a rare point mutation causing an aggressive Lewy body disease with early prominent non-motor features and small fiber denervation of myocardium. Considering the potential interest of the skin as a target for the development of biomarkers in Parkinson's Disease (PD), in this work we aimed to evaluate structural and functional integrity of small autonomic nerve fibers and phosphorylated alpha-synuclein (p-synuclein) deposition in the skin of E46K-SNCA carriers as compared to those observed in parkin gene mutation (PARK2) carriers and healthy controls., Patients and Methods: We studied 7 E46K-SNCA carriers (3 dementia with Lewy bodies, 2 pure autonomic failure, 1 PD and 1 asymptomatic), 2 PARK2 carriers and 2 healthy controls to quantify intraepidermal nerve fiber density and p-synuclein deposition with cervical skin punch biopsies (immunohistochemistry against anti PGP9.5/UCHL-1, TH and p-synuclein) and sudomotor function with electrochemical skin conductance (ESC) (SudoScan)., Results: All E46K-SNCA carriers had moderate to severe p-synuclein deposits and small fiber neurodegeneration in different epidermal and dermal structures including nerve fascicles and glands, especially in carriers with Pure Autonomic Failure, while p-synuclein aggregates where absent in healthy controls and in one of two PARK2 carriers. The severity of the latter skin abnormalities in E46K-SNCA were correlated with sudomotor dysfunction (lower ESC) in hands (p = 0.035)., Interpretation: These results together with our previous findings support the relevance of E46K-SNCA mutation as a suitable model to study small fiber neuropathy in Lewy body diseases., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Objective: To assess whether functional neural connectivity is disrupted between the regions of the default mode network (DMN) in Parkinson's disease (PD) and how this connectivity is related to cognition, brain gray matter structure and white matter integrity and diffusivity., Methods: Thirty-seven PD patients and 16 healthy controls were evaluated, using resting-state functional magnetic resonance imaging (MRI), T1-weighted MRI, diffusion-weighted imaging and a battery of cognitive tests. Functional connectivity between the regions of the DMN, specifically in the precuneus, anterior and posterior cingulate, medial prefrontal and temporal and inferior parietal cortices was assessed with seed-to-voxel connectivity; gray matter volume and white matter values were determined using voxel-based morphometry and tract-based spatial statistics., Results: Reduced functional connectivity was observed between the posterior cingulate and medial temporal lobe in PD. Lower cognitive performance, gray matter loss in posterior, medial temporal and parietal areas, and fractional anisotropy reduction in the white matter adjacent to DMN regions were also observed in PD patients compared with healthy controls. Lower DMN functional connectivity correlated with lower verbal and visual memory and visual abilities performance in PD. In addition, lower DMN functional connectivity correlated with lower gray matter volume in the posterior cingulate and precuneus, and with lower white matter fractional anisotropy of the inferior longitudinal and posterior cingulate fasciculi in PD., Conclusions: By combining different neuroimaging techniques and cognitive data, results showed that functional connectivity alteration between the regions of the DMN is associated with lower cognitive performance and gray and white matter abnormalities in PD., (Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background and Objectives: The objective of this study was to assess the presence of autonomic nervous system dysfunction in PARK2 mutation carriers., Patients and Methods: We performed a cross-sectional analysis of 8 PARK2 carriers (age: 60.1 ± 12.8 years) and 13 individuals with idiopathic PD (iPD) (age: 59.2 ± 8.9 years). Autonomic dysfunction was measured using the SCOPA-AUT questionnaire, non-invasive autonomic tests and responses of noradrenaline and vasopressin levels to postural changes. Myocardial sympathetic denervation was assessed with metaiodobenzylguanidine (MIBG) scintigraphy. This damage was further investigated in postmortem epicardial tissue of one PARK2 carrier and three control cases (two PD patients and one subject without PD)., Results: The prevalence of autonomic symptoms and orthostatic hypotension (OH) was lower in PARK2 mutation carriers than in iPD patients (SCOPA OUT: 3.4 ± 4.8 vs. 14.7 ± 7.2, p < 0.001; OH: present in three iPD patients but none of the PARK2 mutation carriers). Second, sympathetic myocardial denervation was less severe in PARK2 mutation carriers compared to controls, both in MIBG scintigraphy (late H/M uptake ratio: 1.52 ± 0.35 vs. 1.32 ± 0.25 p < 0.05) and in postmortem tissue study. Interestingly, axonal alpha-synuclein deposits were absent in epicardial tissue of the PARK2 mutation carrier while they were present in the two PD patients., Interpretation: Our study supports the view that autonomic nervous system dysfunction and myocardial sympathetic denervation are less pronounced in PARK2 mutation carriers than in individuals with iPD, suggesting that the involvement of small peripheral sympathetic nerve fibers is a minor pathological hallmark in PARK2 carriers., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objective: To compare the cognitive and psychiatric status of patients with Parkinson's disease related to the G2019S and the R1441G mutations of the LRRK2 gene (LRRK2-PD) and idiopathic Parkinson's disease (iPD) patients., Methods: We examined cognition and psychiatric symptoms in 27 patients with LRRK2-PD (12 G2019S and 15 R1441G) and 27 iPD patients., Results: The groups were similar in age, education, disease duration, levodopa equivalent daily dose, and Unified Parkinson's Disease Rating Scale (UPDRS) II-IV; however, the LRRK2-PD showed less impairment on UPDRS-I (2.0 ± 1.7 vs. 4.2 ± 2.8, p = 0.003). The LRRK2-PD presented less frequent subjective cognitive complaints (18.5% vs. 63.0%, p = 0.002), and mild cognitive impairment or dementia (25.9% vs. 59.2%, p = 0.027). They also showed less impairment on scales for general cognition (Mattis dementia rating scale 131.2 ± 10.9 vs. 119 ± 24.0, p = 0.022), episodic verbal memory (Rey's auditory verbal learning test, immediate recall 39.2 ± 9.5 vs. 27.6 ± 12.8 p < 0.001, delayed recall 7.2 ± 3.7 vs. 4.7 ± 4.0 p = 0.022), and the Neuropsychiatric Inventory (9.7 ± 9.2 vs. 20.5 ± 14.3, p = 0.004, significant differences for apathy and hallucinations). The LRRK2-PD subjects were less frequently treated with antipsychotic medication (0% vs. 25.9%, p = 0.010). There were no significant differences between G2019S and R1441G mutation carriers., Conclusions: Mutations of the LRRK2 gene might cause PD associated with less cognitive and neuropsychiatric impairment as compared to iPD., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Introduction: The aim of this study was to compare autonomic function in PD symptomatic carriers of the LRRK2 mutations and idiopathic Parkinson's disease (iPD) patients., Material and Methods: We studied 25 PD patients: 12 with the LRRK2 mutation (6 G2019S and 6 R1441G), and 13 with iPD. All patients underwent blood pressure and heart rate monitoring during head up tilt, Valsalva maneuver and deep breathing, along with recording of sympathetic skin response (SSR) and cardiac MIBG scintigraphy., Results: Three of the patients with iPD and one of the LRRK2 carriers had orthostatic hypotension. Arterial pressure "overshoot" during phase IV of Valsalva maneuver was less pronounced in patients with iPD. During passive tilt, LRRK2 carries had higher increase of blood pressure than iPD patients MIBG late myocardial/mediastinal uptake ratios were higher in LRRK2 mutation carriers (1.51 ± 0.28 vs 1.32 ± 0.25; p < 0.05)., Discussion: Carriers of the LRRK2 mutation had less autonomic impairment than those with iPD as shown by higher cardiac MIBG uptake and a tendency to less impairment of autonomic non-invasive tests. It is important to carry out larger studies comparing the clinical, functional and pathological characteristics of these patients., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Objective: The aim of this study was to analyze autonomic function and cardiac sympathetic innervation in symptomatic and asymptomatic carriers of the E46K alpha-synuclein gene (SNCA) mutation., Patients and Methods: Autonomic function tests were performed in six patients, four of whom were symptomatic carriers (ages: 46, 59, 52 and 28-years) and two who were asymptomatic carriers (ages: 52 and 29 years). Autopsy studies were performed on an additional two symptomatic carriers not eligible for autonomic testing. Patients completed the SCOPA autonomic questionnaire, and underwent the head-up tilt test accompanied by measurements of plasma norepinephrine. Valsalva maneuver and deep breathing tests, along with recording of sympathetic skin response (SSR) and cardiac MIBG scintigraphy were carried out. Myocardial tissue sections removed from the two autopsied cases were subjected to routine histological staining and immunohistochemical processing with monoclonal antibodies against tyrosine hydroxylase and alpha-synuclein., Results: Both the four symptomatic and the older asymptomatic carriers reported abnormalities in the SCOPA questionnaire and had markedly diminished cardiac MIBG uptake. Plasma norepinephrine in the supine and tilted positions was normal in all subjects. Only one patient had significant orthostatic hypotension. There was a complete absence of tyrosine hydroxylase immunostaining in the myocardium of the two autopsied cases., Interpretation: We have found imaging and histological evidence of cardiac sympathetic denervation in symptomatic and asymptomatic carriers of the E46K alpha-synuclein gene mutation. The sympathetic denervation appears to be organ-specific, with selective affectation of the heart given that plasma norepinephrine levels and blood pressure were normal., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Introduction: Our objective was to assess the usefulness of the Scales for Outcomes in Parkinson's disease - Autonomic (SCOPA-AUT) in the differential diagnosis of Parkinsonisms and clarify its relation with 123-I-MIBG cardiac scintigraphy., Methods: A total of 112 patients with Parkinson's disease (PD), 12 with multiple system atrophy parkinsonian variant (MSA-P) and 20 with progressive supranuclear palsy (PSP) participated in the study. The following variables were collected: age, sex, age at onset, length of illness, type and dose of anti-Parkinson medication, and score on the Unified Parkinson's Disease Rating Scale. The Unified Multiple System Atrophy Rating Scale was administered to patients with MSA and the Progressive Supranuclear Palsy Rating Scale to those with PSP. Finally, the SCOPA-AUT was administered to all the patients. Cardiac 123I-MIBG SPECT scans were performed on a subset of patients (25 with PD and 5 with MSA-P)., Results: Statistically significant differences were observed (p < 0.01) in the SCOPA-AUT scores between patients with PD (14.75+/-8.09) and those with MSA (21.07+/-5.56), the latter having higher scores on the bowel function (20.07+/-13.40 vs 34.92+/-14.91) and urinary domains (30.21+/-21.55 vs 49.26+/-21.40) (p < 0.01). No correlation was found between the SCOPA-AUT score and anti-Parkinson's medication and heart:mediastinum (H/M) MIBG uptake ratio in the cardiac SPECT (at 4 h)., Discussion: Severity of dysautonomia as measured by the SCOPA-AUT was not correlated with clinical severity, time since onset or the H/M ratio. In the patients with PD, the only variable associated with the H/M ratio was age at onset of the disease., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Herein we describe a comparative clinical and genetic study of Lrrk2-associated parkinsonism in Northern Spain. In our sample from the Basque region, Lrrk2 R1441G and G2019S account for 15 out of 50 kindreds (30%) with familial Parkinson's disease. We observe common founder haplotypes for both R1441G and G2019S carriers. Our findings highlight the importance of Lrrk2 parkinsonism in this population and may have important consequences for its extended Diaspora in North, Central and South Americas.