REM sleep behavior disorder, as assessed by questionnaire, in G2019S LRRK2 mutation PD and carriers

A Remote Longitudinal Observational Study of Individuals at Genetic Risk for Parkinson Disease

Background and Objectives

To recruit and characterize a national cohort of individuals who have a genetic variant (LRRK2 G2019S) that increases risk of Parkinson disease (PD), assess participant satisfaction with a decentralized, remote research model, and evaluate interest in future clinical trials.

Methods

In partnership with 23andMe, Inc., a personal genetics company, LRRK2 G2019S carriers with and without PD were recruited to participate in an ongoing 36-month decentralized, remote natural history study. We examined concordance between self-reported and clinician-determined PD diagnosis. We applied the Movement Disorder Society Prodromal Parkinson's Disease Criteria and asked investigators to identify concern for parkinsonism to distinguish participants with probable prodromal PD. We compared baseline characteristics of LRRK2 G2019S carriers with PD, with prodromal PD, and without PD.

Results

Over 15 months, we enrolled 277 LRRK2 G2019S carriers from 34 states. At baseline, 60 had self-reported PD (mean [SD] age 67.8 years [8.4], 98% White, 52% female, 80% Ashkenazi Jewish, and 67% with a family history of PD), and 217 did not (mean [SD] age 53.7 years [15.1], 95% White, 59% female, 73% Ashkenazi Jewish, and 57% with a family history of PD). Agreement between self-reported and clinician-determined PD status was excellent (κ = 0.94, 95% confidence interval 0.89–0.99). Twenty-four participants had prodromal PD; 9 met criteria for probable prodromal PD and investigators identified concern for parkinsonism in 20 cases. Compared with those without prodromal PD, participants with prodromal PD were older (63.9 years [9.0] vs 51.9 years [15.1], p < 0.001), had higher modified Movement Disorders Society-Unified Parkinson's Disease Rating Scale motor scores (5.7 [4.3] vs 0.8 [2.1], p < 0.001), and had higher Scale for Outcomes in PD for Autonomic Symptoms scores (11.5 [6.2] vs 6.9 [5.7], p = 0.002). Two-thirds of participants enrolled were new to research, 97% were satisfied with the overall study, and 94% of those without PD would participate in future preventive clinical trials.

Discussion

An entirely remote national cohort of LRRK2 G2019S carriers was recruited from a single site. This study will prospectively characterize a large LRRK2 G2019S cohort, refine a new model of clinical research, and engage new research participants willing to participate in future therapeutic trials.

Molecular mechanisms defining penetrance of LRRK2-associated Parkinson’s disease

Mutations in Leucine-rich repeat kinase 2 (LRRK2) are the most frequent cause of dominantly inherited Parkinson’s disease (PD). LRRK2 mutations, among which p.G2019S is the most frequent, are inherited with reduced penetrance. Interestingly, the disease risk associated with LRRK2 G2019S can vary dramatically depending on the ethnic background of the carrier. While this would suggest a genetic component in the definition of LRRK2-PD penetrance, only few variants have been shown to modify the age at onset of patients harbouring LRRK2 mutations, and the exact cellular pathways controlling the transition from a healthy to a diseased state currently remain elusive. In light of this knowledge gap, recent studies also explored environmental and lifestyle factors as potential modifiers of LRRK2-PD. In this article, we (i) describe the clinical characteristics of LRRK2 mutation carriers, (ii) review known genes linked to LRRK2-PD onset and (iii) summarize the cellular functions of LRRK2 with particular emphasis on potential penetrance-related molecular mechanisms. This section covers LRRK2’s involvement in Rab GTPase and immune signalling as well as in the regulation of mitochondrial homeostasis and dynamics. Additionally, we explored the literature with regard to (iv) lifestyle and (v) environmental factors that may influence the penetrance of LRRK2 mutations, with a view towards further exposomics studies. Finally, based on this comprehensive overview, we propose potential future in vivo, in vitro and in silico studies that could provide a better understanding of the processes triggering PD in individuals with LRRK2 mutations.

Genetic variations in GBA1 and LRRK2 genes: Biochemical and clinical consequences in Parkinson disease

Variants in the GBA1 and LRRK2 genes are the most common genetic risk factors associated with Parkinson disease (PD). Both genes are associated with lysosomal and autophagic pathways, with the GBA1 gene encoding for the lysosomal enzyme, glucocerebrosidase (GCase) and the LRRK2 gene encoding for the leucine-rich repeat kinase 2 enzyme. GBA1-associated PD is characterized by earlier age at onset and more severe non-motor symptoms compared to sporadic PD. Mutations in the GBA1 gene can be stratified into severe, mild and risk variants depending on the clinical presentation of disease. Both a loss- and gain- of function hypothesis has been proposed for GBA1 variants and the functional consequences associated with each variant is often linked to mutation severity. On the other hand, LRRK2-associated PD is similar to sporadic PD, but with a more benign disease course. Mutations in the LRRK2 gene occur in several structural domains and affect phosphorylation of GTPases. Biochemical studies suggest a possible convergence of GBA1 and LRRK2 pathways, with double mutant carriers showing a milder phenotype compared to GBA1-associated PD. This review compares GBA1 and LRRK2-associated PD, and highlights possible genotype-phenotype associations for GBA1 and LRRK2 separately, based on biochemical consequences of single variants.

Genetic heterogeneity on sleep disorders in Parkinson's disease: a systematic review and meta-analysis

A growing amount of evidence has indicated contributions of variants in causative genes of Parkinson’s disease (PD) to the development of sleep disturbance in PD and prodromal PD stages. In this article, we aimed to investigate the role of genetics in sleep disorders in PD patients and asymptomatic carriers at prodromal stage of PD. A systematic review and meta-analysis of observational studies was conducted based on the MEDLINE, EMBASE and PsychINFO databases. A pooled effect size was calculated by odds ratio (OR) and standard mean difference (SMD). Forty studies were selected for quantitative analysis, including 17 studies on glucocerebrosidase (GBA), 25 studies on Leucine-rich repeat kinase 2 (LRRK2) and 7 on parkin (PRKN) genes, and 3 studies on alpha-synuclein gene (SNCA) were used for qualitative analysis. Patients with PD carrying GBA variants had a significantly higher risk for rapid-eye-movement behavior disorders (RBD) (OR, 1.82) and higher RBD Screening Questionnaire scores (SMD, 0.33). Asymptomatic carriers of GBA variants had higher severity of RBD during follow-up. Patients with PD carrying the LRRK2 G2019S variant had lower risk and severity of RBD compared with those without LRRK2 G2019S. Variants of GBA, LRRK2 and PRKN did not increase or decrease the risk and severity of excessive daytime sleepiness and restless legs syndrome in PD. Our findings suggest that the genetic heterogeneity plays a role in the development of sleep disorders, mainly RBD, in PD and the prodromal stage of PD.

Monogenetic Forms of Parkinson’s Disease – Bridging the Gap Between Genetics and Biomarkers

The therapy of neurodegenerative diseases such as Parkinson’s disease (PD) is still limited to the treatment of symptoms and primarily aimed at compensating for dopaminergic hypofunction. Numerous disease-modifying therapies currently in the pipeline attempt to modify the underlying pathomechanisms. In recent decades, the results of molecular genetics and biomarker research have raised hopes of earlier diagnosis and new neuroprotective therapeutic approaches. As the disease-causing processes in monogenetic forms of PD are better understood than in sporadic PD, these disease subsets are likely to benefit first from disease-modifying therapies. Recent studies have suggested that disease-relevant changes found in genetically linked forms of PD (i.e., PARK-LRRK2, PARK-GBA) can also be reproduced in patients in whom no genetic cause can be found, i.e., those with sporadic PD. It can, therefore, be assumed that as soon as the first causal therapy for genetic forms of PD is approved, more patients with PD will undergo genetic testing and counseling. Regarding future neuroprotective trials in neurodegenerative diseases and objective parameters such as biomarkers with high sensitivity and specificity for the diagnosis and course of the disease are needed. These biomarkers will also serve to monitor treatment success in clinical trials. Promising examples in PD, such as alpha-synuclein species, lysosomal enzymes, markers of amyloid and tau pathology, and neurofilament light chain, are under investigation in blood and CSF. This paper provides an overview of the opportunities and current limitations of monogenetic diagnostic and biomarker research in PD and aims to build a bridge between current knowledge and association with PD genetics and biomarkers.

New therapeutic approaches to Parkinson's disease targeting GBA, LRRK2 and Parkin

Parkinson's disease (PD) is defined as a complex disorder with multifactorial pathogenesis, yet a more accurate definition could be that PD is not a single entity, but rather a mixture of different diseases with similar phenotypes. Attempts to classify subtypes of PD have been made based on clinical phenotypes or biomarkers. However, the most practical approach, at least for a portion of the patients, could be to classify patients based on genes involved in PD. GBA and LRRK2 mutations are the most common genetic causes or risk factors of PD, and PRKN is the most common cause of autosomal recessive form of PD. Patients carrying variants in GBA, LRRK2 or PRKN differ in some of their clinical characteristics, pathology and biochemical parameters. Thus, these three PD-associated genes are of special interest for drug development. Existing therapeutic approaches in PD are strictly symptomatic, as numerous clinical trials aimed at modifying PD progression or providing neuroprotection have failed over the last few decades. The lack of precision medicine approach in most of these trials could be one of the reasons why they were not successful. In the current review we discuss novel therapeutic approaches targeting GBA, LRRK2 and PRKN and discuss different aspects related to these genes and clinical trials.

Dementia with Lewy bodies in first-generation immigrants in a European memory clinic

We wanted to explore possible differences in disease presentation, frequency, and age of onset of dementia with Lewy bodies (DLB) between first-generation immigrants (FGI) and patients born in Belgium (PBIB). We conducted a retrospective study on all patients of our Memory Clinic between June 1, 2010 and January 31, 2020. A synucleinopathy was diagnosed in 150 of 2702 patients (5.5%): 91 received a diagnosis of DLB (3.4%). FGI were two times more likely to receive a diagnosis of DLB, due to a higher prevalence in North-Africans and Latin-Americans. Visual hallucinations were less frequent in North-Africans than in other immigrants. FGI were younger than PBIB and reported more often parasomnia. Our data suggest a higher risk for DLB in certain immigrant groups. Especially for North-African patients, a genetic factor can be suspected, namely mutations in Leucine-rich repeat kinase 2 (LRRK2). Memory clinics with a high rate of FGI may provide interesting data and insights into the prevalence of DLB, genetic and environmental differences.

REM sleep behavior in Parkinson disease: Frequent, particularly with higher age

This retrospective single-center polysomnography-based study was designed to assess the frequency of REM sleep behavior disorder (RBD) in consecutive patients with Parkinsonism, including Parkinson disease, dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration. We observed RBD in 77% of 540 Parkinson patients, with rising frequency at higher age and regardless of sex, in >89% of 89 patients with dementia with Lewy bodies or multiple system atrophy, and in <15% of 42 patients with progressive supranuclear palsy or corticobasal degeneration. Thus, the prevalence of RBD in sporadic Parkinson disease might be higher than previously assumed, particularly in elderly patients.

Profiling Non-motor Symptoms in Monogenic Parkinson's Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease in the elder population, pathologically characterized by the progressive loss of dopaminergic neurons in the substantia nigra. While the precise mechanisms underlying the pathogenesis of PD remain unknown, various genetic factors have been proved to be associated with PD. To date, at least 23 loci and 19 disease-causing genes for PD have been identified. Although monogenic (often familial) cases account for less than 5% of all PD patients, exploring the phenotypes of monogenic PD can help us understand the disease pathogenesis and progression. Primary motor symptoms are important for PD diagnosis but only detectable at a relatively late stage. Despite typical motor symptoms, various non-motor symptoms (NMS) including sensory complaints, mental disorders, autonomic dysfunction, and sleep disturbances also have negative impacts on the quality of life in PD patients and pose major challenges for disease management. NMS is common in all stages of the PD course. NMS can occur long before the onset of PD motor symptoms or can present in the middle or late stage of the disease accompanied by motor symptoms. Therefore, the profiling and characterization of NMS in monogenic PD may help the diagnosis and differential diagnosis of PD, which thereby can execute early intervention to delay the disease progression. In this review, we summarize the characteristics, clinical phenotypes, especially the NMS of monogenic PD patients carrying mutations of SNCA, LRRK2, VPS35, Parkin, PINK1, DJ-1, and GBA. The clinical implications of this linkage between NMS and PD-related genes are also discussed.

Progression in the LRRK2-Asssociated Parkinson Disease Population

Importance

Few prospective longitudinal studies have evaluated the progression of Parkinson disease (PD) in patients with the leucine-rich repeat kinase 2 (LRRK2 [OMIM 609007]) mutation. Knowledge about such progression will aid clinical trials.

Objective

To determine whether the longitudinal course of PD in patients with the LRRK2 mutation differs from the longitudinal course of PD in patients without the mutation.

Design, Setting, and Participants

A prospective comprehensive assessment of a large cohort of patients from 3 sites with LRRK2 PD or with nonmutation PD was conducted from July 21, 2009, to September 30, 2016. All patients of Ashkenazi Jewish ancestry with PD were approached at each site; approximately 80% agreed to an initial visit. A total of 545 patients of Ashkenazi Jewish descent with PD who had 1 to 4 study visits were evaluated. A total of 144 patients (26.4%) had the LRRK2 G2019S mutation. Patients with GBA (OMIM 606463) mutations were excluded from the analysis.

Main Outcomes and Measures

Linear mixed-effects models for longitudinal motor scores were used to examine the association of LRRK2 mutation status with the rate of change in Unified Parkinson's Disease Rating Scale III scores using disease duration as the time scale, adjusting for sex, site, age, disease duration, cognitive score, and levodopa-equivalent dose at baseline. Mixed-effects models were used to assess change in cognition, as measured by Montreal Cognitive Assessment scores.

Results

Among the 545 participants, 233 were women, 312 were men, and the mean (SD) age was 68.2 (9.1) years for participants with the LRRK2 mutation and 67.8 (10.7) years for those without it. Seventy-two of 144 participants with the LRRK2 mutation and 161 of 401 participants with no mutation were women. The estimate (SE) of the rate of change in the Unified Parkinson's Disease Rating Scale III motor score per year among those with the LRRK2 mutation (0.689 [0.192] points per year) was less than among those without the mutation (1.056 [0.187] points per year; difference, -0.367 [0.149] points per year; P = .02). The estimate (SE) of the difference in the rate of change of the Montreal Cognitive Assessment score between those with the LRRK2 mutation (-0.096 [0.090] points per year) and those without the mutation (-0.192 [0.102] points per year) did not reach statistical significance (difference, 0.097 [0.055] points per year; P = .08).

Conclusions and Relevance

Prospective longitudinal follow-up of patients with PD with or without the LRRK2 G2019S mutation supports data from a cross-sectional study and demonstrates a slower decline in motor Unified Parkinson's Disease Rating Scale scores among those with LRRK2 G2019S-associated PD.

Hierarchical Data-Driven Analysis of Clinical Symptoms Among Patients With Parkinson's Disease

Mutations in the LRRK2 and GBA genes are the most common inherited causes of Parkinson's disease (PD). Studies exploring phenotypic differences based on genetic status used hypothesis-driven data-gathering and statistical-analyses focusing on specific symptoms, which may influence the validity of the results. We aimed to explore phenotypic expression in idiopathic PD (iPD) patients, G2019S-LRRK2-PD, and GBA-PD using a data-driven approach, allowing screening of large numbers of features while controlling selection bias. Data was collected from 1525 Ashkenazi Jews diagnosed with PD from the Tel-Aviv Medical center; 161 G2019S-LRRK2-PD, 222 GBA-PD, and 1142 iPD (no G2019S-LRRK2 or any of the 7 AJ GBA mutations tested). Data included 771 measures: demographics, cognitive, physical and neurological functions, performance-based measures, and non-motor symptoms. The association of the genotypes with each of the measures was tested while accounting for age at motor symptoms onset, gender, and disease duration; p-values were reported and corrected in a hierarchical approach for an average over the selected measures false discovery rate control, resulting in 32 measures. GBA-PD presented with more severe symptoms expression while LRRK2-PD had more benign symptoms compared to iPD. GBA-PD presented greater cognitive and autonomic involvement, more frequent hyposmia and REM sleep behavior symptoms while these were less frequent among LRRK2-PD compared to iPD. Using a data-driven analytical approach strengthens earlier studies and extends them to portray a possible unique disease phenotype based on genotype among AJ PD. Such findings could help direct a more personalized therapeutic approach.

Clinical Heterogeneity Among LRRK2 Variants in Parkinson's Disease: A Meta-Analysis

Background: Parkinson's disease (PD) is one of the most common neurodegenerative diseases. Variants in the LRRK2 gene have been shown to be associated with PD. However, the clinical characteristics of LRRK2-related PD are heterogeneous. In our study, we performed a comprehensive pooled analysis of the association between specific LRRK2 variants and clinical features of PD.

Methods: Articles from the Medline, Embase, and Cochrane databases were included in the meta-analysis. Strict inclusion criteria were applied, and detailed information was extracted from the final original articles included. Revman 5.3 software was used for publication biases and pooled and sensitivity analyses.

Results: In all, 66 studies having the clinical manifestations of PD patients with G2019S, G2385R, R1628P, and R1441G were included for the final analysis. The prominent clinical features of LRRK2-G2019S-related PD patients were female sex, higher rates of early-onset PD (EOPD), and family history (OR: 0.77 [male], 1.37, 2.62; p < 0.00001, 0.02, < 0.00001). PD patients with G2019S were more likely to have high scores of Schwab & England (MD: 1.49; p < 0.00001), low GDS scores, high UPSIT scores (MD: 0.43, 4.70; p = 0.01, < 0.00001), and good response to L-dopa (OR: 2.33; p < 0.0001). Further, G2019S carriers had higher LEDD (MD: 115.20; p < 0.00001) and were more likely to develop motor complications, such as dyskinesia and motor fluctuations (OR: 2.18, 2.02; p < 0.00001, 0.04) than non-carriers. G2385R carriers were more likely to have family history (OR: 2.10; p = 0.007) than non-G2385R carriers and lower H-Y and higher MMSE scores (MD: −0.13, 1.02; p = 0.02, 0.0007). G2385R carriers had higher LEDD and tended to develop motor complications, such as motor fluctuations (MD: 53.22, OR: 3.17; p = 0.01, < 0.00001) than non-carriers. Other clinical presentations did not feature G2019S or G2385R. We observed no distinct clinical features for R1628P or R1441G. Our subgroup analyses in different ethnic group for specific variant also presented with relevant clinical characteristics of PD patients.

Conclusions: Clinical heterogeneity was observed among LRRK2-associated PD in different variants in total and in different ethnic groups, especially for G2019S and G2385R.

Genetic analysis of LRRK2 in Parkinson's disease in Han Chinese population

Mutations in Leucine-rich repeat kinase 2 (LRRK2) are recognized as the most frequent genetic factors contributing to Parkinson's disease (PD). The aim of our study was to explore LRRK2 variants in PD patients within the mainland Han Chinese population. The whole coding regions of LRRK2 from 296 PD patients were sequenced by targeted regions sequencing and exome sequencing. Eighteen rare variants were identified in 27 PD patients, and 13 of them (M100T, L153W, A459S, S722N, R792K, C925Y, R981K, S1007T, V1447M, R1677S, N2308D, N2313S, and S2350I) were firstly reported in PD. We also tried to explore the genotype-phenotype associations of LRRK2 variants in our data and found that PD with common and rare LRRK2 variants was more likely to have motor fluctuation and nonmotor symptoms. The identification of novel variants in LRRK2 suggests that this gene plays an important role in the pathogenesis and phenotype of PD in Han Chinese population, and our data also rang the alarm bell-more attention should be paid to the whole coding regions of LRRK2.

Application of the Movement Disorder Society prodromal criteria in healthy G2019S-LRRK2 carriers

BACKGROUND

In 2015, the International Parkinson and Movement Disorder Society Task Force recommended research criteria for the estimation of prodromal PD.

OBJECTIVES

We aimed to evaluate, for the first time, the criteria in first-degree relatives of Ashkenazi Jewish G2019S-LRRK2 PD patients, who are considered a population at risk for developing PD, and assess the sensitivity and specificity of the criteria in identifying phenoconverters.

METHODS

Participants were evaluated longitudinally over a period of 5 years (average follow-up: 49.2 ± 12.3 months). Likelihood ratios and probability estimations were calculated based on the International Parkinson and Movement Disorder Society Research Criteria for Prodromal Parkinson's Disease markers and examined for each assessment point.

RESULTS

One hundred twenty healthy carriers (49.53 ± 13.4 years; 54% female) and 111 healthy noncarriers (48.43 ± 15.79 years; 49% female) participated in this study. Probability scores were significantly higher in healthy carriers than healthy noncarriers (P < 0.0001). Of the 20 participants (8.6%) who met criteria for probable prodromal PD at baseline, 17 were healthy carriers. Participants who reached the threshold were older (P < 0.0001), had higher UPDRS-III (P < 0.001), lower cognitive function (P = 0.001), and more nonmotor symptoms (P < 0.0001), compared to those who did not. Ten participants were diagnosed with incident PD within 5 years from baseline resulting in a specificity of 91.82% (95% confidence interval: 86.69-96.94), sensitivity of 80% (95% confidence interval: 55.21-100), positive predictive value of 47.06% (95% confidence interval: 23.33-70.79), and negative predictive value of 98.06% (95% confidence interval: 95.39-100). All 10 phenoconvertors were G2019S-LRRK2 carriers.

CONCLUSIONS

The results showed the utility of using the criteria and high sensitivity and specificity in identifying prodromal PD in this high-risk unique cohort. These results may be valuable for future disease modification clinical trials. © 2018 International Parkinson and Movement Disorder Society.

Sleep disorders and Parkinson disease; lessons from genetics

Parkinson disease is a common, age-related neurodegenerative disorder, projected to afflict millions of individuals in the near future. Understanding its etiology and identifying clinical, genetic or biological markers for Parkinson disease onset and progression is therefore of major importance. Various sleep-related disorders are the most common group of non-motor symptoms in advanced Parkinson disease, but they can also occur during its prodromal phase. However, with the exception of REM sleep behavior disorder, it is unclear whether they are part of the early pathological process of Parkinson disease, or if they develop as Parkinson disease advances because of treatments and neurodegeneration progression. The advancements in genetic studies in the past two decades have generated a wealth of information, and recent genetic studies offer new insight on the association of sleep-related disorders with Parkinson disease. More specifically, comparing genetic data between Parkinson disease and sleep-related disorders can clarify their association, which may assist in determining whether they can serve as clinical markers for Parkinson disease risk or progression. In this review, we discuss the current knowledge on the genetics of sleep-related disorders in Parkinson disease context, and the potential implications on research, diagnosis, counseling and treatment.

Clinical Significance of REM Sleep Behavior Disorders and Other Non-motor Symptoms of Parkinsonism

Rapid eye movement sleep behavior disorder (RBD) is one of the most common non-motor symptoms of parkinsonism, and it may serve as a prodromal marker of neurodegenerative disease. The mechanism underlying RBD is unclear. Several prospective studies have reported that specific non-motor symptoms predict a conversion risk of developing a neurodegenerative disease, including olfactory dysfunction, abnormal color vision, autonomic dysfunction, excessive daytime sleepiness, depression, and cognitive impairment. Parkinson's disease (PD) with RBD exhibits clinical heterogeneity with respect to motor and non-motor symptoms compared with PD without RBD. In this review, we describe the main clinical and pathogenic features of RBD, focusing on its association with other non-motor symptoms of parkinsonism.

The prodromal phase of leucine-rich repeat kinase 2-associated Parkinson disease: Clinical and imaging Studies

BACKGROUND

Asymptomatic, nonmanifesting carriers of leucine-rich repeat kinase 2 mutations are at increased risk of developing PD. Clinical and neuroimaging features may be associated with gene carriage and/or may demarcate individuals at greater risk for phenoconversion to PD.

OBJECTIVES

To investigate clinical and dopamine transporter single-photon emission computed tomography imaging characteristics of leucine-rich repeat kinase 2 asymptomatic carriers.

METHODS

A total of 342 carriers' and 259 noncarriers' relatives of G2019S leucine-rich repeat kinase 2/PD patients and 39 carriers' and 31 noncarriers' relatives of R1441G leucine-rich repeat kinase 2/PD patients were evaluated. Motor and nonmotor symptoms were assessed using specific scales and questionnaires. Neuroimaging quantitative data were obtained in 81 carriers and compared with 41 noncarriers.

RESULTS

G2019S carriers scored higher in motor scores and had lower radioligand uptake compared to noncarriers, but no differences in nonmotor symptoms scores were observed. R1441G carriers scored higher in motor scores, had lower radioligand uptake, and had higher scores in depression, dysautonomia, and Rapid Eye Movements Sleep Behavior Disorder Screening Questionnaire scores, but had better cognition scores than noncarriers. Among G2019S carriers, a group with "mild motor signs" was identified, and was significantly older, with worse olfaction and lower radioligand uptake.

CONCLUSIONS

G2019S and R1441G carriers differ from their noncarriers' relatives in higher motor scores and slightly lower radioligand uptake. Nonmotor symptoms were mild, and different nonmotor profiles were observed in G2019S carriers compared to R1441G carriers. A group of G2019S carriers with known prodromal features was identified. Longitudinal studies are required to determine whether such individuals are at short-term risk of developing overt parkinsonism. © 2017 International Parkinson and Movement Disorder Society.

Genetics of Parkinson's Disease: Genotype-Phenotype Correlations

Since the first discovery of a specific genetic defect in the SNCA gene, encoding for α-synuclein, as a causative factor for Parkinson's disease 20 years ago, a multitude of other genes have been linked to this disease in rare cases with Mendelian inheritance. Furthermore, the genetic contribution to the much more common sporadic disease has been demonstrated through case control association studies and, more recently, genome-wide association studies. Interestingly, some of the genes with Mendelian inheritance, such as SNCA, are also relevant to the sporadic disease, suggesting common pathogenetic mechanisms. In this review, we place an emphasis on Mendelian forms, and in particular genetic defects which present predominantly with Parkinsonism. We provide details into the particular phenotypes associated with each genetic defect, with a particular emphasis on nonmotor symptoms. For genetic defects for whom a sufficient number of patients has been assessed, there are evident genotype-phenotype correlations. However, it should be noted that patients with the same causative mutation may present with distinctly divergent phenotypes. This phenotypic variability may be due to genetic, epigenetic or environmental factors. From a clinical and genetic point of view, it will be especially interesting in the future to identify genetic factors that modify disease penetrance, the age of onset or other specific phenotypic features.

The underlying mechanism of prodromal PD: insights from the parasympathetic nervous system and the olfactory system

Neurodegeneration of Parkinson's disease (PD) starts in an insidious manner, 30-50% of dopaminergic neurons have been lost in the substantia nigra before clinical diagnosis. Prodromal stage of the disease, during which the disease pathology has started but is insufficient to result in clinical manifestations, offers a valuable window for disease-modifying therapies. The most focused underlying mechanisms linking the pathological pattern and clinical characteristics of prodromal PD are the prion hypothesis of alpha-synuclein and the selective vulnerability of neurons. In this review, we consider the two potential portals, the vagus nerve and the olfactory bulb, through which abnormal alpha-synuclein can access the brain. We review the clinical, pathological and neuroimaging evidence of the parasympathetic nervous system and the olfactory system in the neurodegenerative process and using the two systems as models to discuss the internal homogeneity and heterogeneity of the prodromal stage of PD, including both the clustering and subtyping of symptoms and signs. Finally, we offer some suggestions on future directions for imaging studies in prodromal Parkinson's disease.

A Brief Nonmotor Screen Combined with Transcranial Ultrasound may Improve Diagnostic Accuracy of Parkinson's Disease

Background

The addition of a simple nonmotor symptom (NMS) screen and transcranial sonography (TCS) to standard clinical assessment may improve the diagnostic accuracy of Parkinson's disease (PD).

Methods

Sixty-nine subjects (23 established PD group, 23 healthy controls, and 23 possible PD) were enrolled. All completed 3 "yes-no" NMS questions (score, 0-3) and had a transcranial ultrasound assessing nigral hyperechogenicity (score, 0-1). A combined PD risk score of 0 to 4 was obtained for each subject. A PD risk score of ≥2 was used as the diagnostic cutoff for PD.

Results

In the established PD group, there was an average of 2 NMSs per person or a group total of 46 of 69 possible NMSs, but only 4 of 69 NMSs in the healthy control group. Of the technically satisfactory TCS, 16 of 20 (80%) of the established PD group and 2 of 16 (12.5%) of the healthy control group were TCS positive. Using ≥2 NMSs alone as the cutoff identified 17 of 23 (74%) of the established PD and 100% of the healthy controls. The PD risk score of ≥2 identified 21 of 23 (91%) of the established PD as PD and 22 of 23 (96%) of the healthy control group as non-PD. In the possible PD group, the PD risk score identified 9 of 18 (50%) of those with a final clinical diagnosis of PD and 4 of 5 (80%) of non-PD.

Conclusions

The combination of a brief NMS screen and TCS discriminated well between normal healthy controls and established PD. A positive TCS and one NMS, or a negative TCS with two NMSs, indicated a likely diagnosis of PD.

A Personalized Approach to Parkinson's Disease Patients Based on Founder Mutation Analysis

While the phenotype of Parkinson disease (PD) is heterogeneous, treatment approaches are mostly uniform. Personalized medicine aims to treat diseases with targeted therapies based on cumulative variables, including genotype. We believe that sufficient evidence has accumulated to warrant the initiation of personalized medicine in PD based on subjects genotype and provide examples for our reasoning from observations of GBA and LRRK2 mutations carriers. While PD patients who carry the G2019S mutation in the LRRK2 gene seem to develop relatively mild disease with more frequent postural instability gait disturbance phenotype, carriers of mutations in the GBA gene tend to have an early onset, rapidly deteriorating disease, with more pronounced cognitive and autonomic impairments. These characteristics have significant implications for treatment and outcome and should be addressed from an early stage in the attempt to improve the patient's quality of life.

Motor and nonmotor heterogeneity of LRRK2-related and idiopathic Parkinson's disease

BACKGROUND

Parkinson's disease (PD) associated with LRRK2 mutations has been described as similar to idiopathic PD with minor clinical differences. No study has compared the clinical features of LRRK2-associated PD due to different mutations. The objective of this study was to compare LRRK2-associated PD due to G2019S and G2385R mutations and to compare each to idiopathic PD.

METHODS

Sites within the international LRRK2 Cohort Consortium undertook family-based, community-based, or clinic-based studies to gather clinical data on manifesting carriers and patients with idiopathic PD.

RESULTS

Five hundred sixteen PD patients with the G2019S mutation, 199 with the G2385R mutation, and 790 patients with idiopathic PD were included in the data set. Adjusted for age, sex, disease duration, and levodopa-equivalent daily dose, mean MDS-UPDRS part II or III scores and the frequency of motor fluctuations were higher in the G2385R mutation carriers than in either the G2019S mutation carriers or idiopathic PD patients. G2019S mutation carriers had significantly lower UPDRS part III scores than idiopathic PD patients. Both G2019S and G2385R mutation carriers had a higher proportion of the postural instability gait disorder phenotype compared with idiopathic PD patients. LRRK2 G2019S PD patients had better UPSIT scores and lower Geriatric Depression Scale scores than idiopathic PD patients in adjusted analyses.

CONCLUSIONS

G2385R and G2019S PD appear to have motor differences that may be explained by contrasting local treatment or measurement practices or differences in the biology of the disease. Longitudinal studies should evaluate whether progression is faster in G2385R mutation carriers compared with G2019S PD or idiopathic PD. © 2016 International Parkinson and Movement Disorder Society.