Care of Late-Stage Parkinsonism: Resource Utilization of the Disease in Five European Countries.

BACKGROUND: Parkinson's disease (PD) is a neurodegenerative disease that leads to progressive disability. Cost studies have mainly explored the early stages of the disease, whereas late-stage patients are underrepresented. OBJECTIVE: The aim is to evaluate the resource utilization and costs of PD management in people with late-stage disease. METHODS: The Care of Late-Stage Parkinsonism (CLaSP) study collected economic data from patients with late-stage PD and their caregivers in five European countries (France, Germany, the Netherlands, UK, Sweden) in a range of different settings. Patients were eligible to be included if they were in Hoehn and Yahr stage >3 in the on state or Schwab and England stage at 50% or less. In total, 592 patients met the inclusion criteria and provided information on their resource utilization. Costs were calculated from a societal perspective for a 3-month period. A least absolute shrinkage and selection operator approach was utilized to identify the most influential independent variables for explaining and predicting costs. RESULTS: During the 3-month period, the costs were €20,573 (France), €19,959 (Germany), €18,319 (the Netherlands), €25,649 (Sweden), and €12,156 (UK). The main contributors across sites were formal care, hospitalization, and informal care. Gender, age, duration of the disease, Unified Parkinson's Disease Rating Scale 2, the EQ-5D-3L, and the Schwab and England Scale were identified as predictors of costs. CONCLUSION: Costs in this cohort of individuals with late-stage PD were substantially higher compared to previously published data on individuals living in earlier stages of the disease. Resource utilization in the individual sites differed in part considerably among these three parameters mentioned. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Mobile digital gait analysis captures effects of botulinum toxin in hereditary spastic paraplegia.

BACKGROUND AND PURPOSE: Hereditary spastic paraplegias (HSPs) comprise a group of inherited neurodegenerative disorders characterized by progressive spasticity and weakness. Botulinum toxin has been approved for lower limb spasticity following stroke and cerebral palsy, but its effects in HSPs remain underexplored. We aimed to characterize the effects of botulinum toxin on clinical, gait, and patient-reported outcomes in HSP patients and explore the potential of mobile digital gait analysis to monitor treatment effects and predict treatment response. METHODS: We conducted a prospective, observational, multicenter study involving ambulatory HSP patients treated with botulinum toxin tailored to individual goals. Comparing data at baseline, after 1 month, and after 3 months, treatment response was assessed using clinical parameters, goal attainment scaling, and mobile digital gait analysis. Machine learning algorithms were used for predicting individual goal attainment based on baseline parameters. RESULTS: A total of 56 patients were enrolled. Despite the heterogeneity of treatment goals and targeted muscles, botulinum toxin led to a significant improvement in specific clinical parameters and an improvement in specific gait characteristics, peaking at the 1-month and declining by the 3-month follow-up. Significant correlations were identified between gait parameters and clinical scores. With a mean balanced accuracy of 66%, machine learning algorithms identified important denominators to predict treatment response. CONCLUSIONS: Our study provides evidence supporting the beneficial effects of botulinum toxin in HSP when applied according to individual treatment goals. The use of mobile digital gait analysis and machine learning represents a novel approach for monitoring treatment effects and predicting treatment response.

Fast and reliable detection of repeat expansions in spinocerebellar ataxia using exomes.

Usually, molecular diagnosis of spinocerebellar ataxia is based on a step-by-step approach with targeted sizing of four repeat expansions accounting for most dominant cases, then targeted sequencing of other genes. Nowadays, genome sequencing allows detection of most pathogenic variants in a single step. The ExpansionHunter tool can detect expansions in short-read genome sequencing data. Recent studies have shown that ExpansionHunter can also be used to identify repeat expansions in exome sequencing data. We tested ExpansionHunter on spinocerebellar ataxia exomes in a research context as a second-line analysis, after exclusion of main CAG repeat expansions in half of the probands. First, we confirmed the detection of expansions in seven known expansion carriers and then, after targeted analysis of ATXN1, 2, 3 and 7, CACNA1A, TBP, ATN1, NOP56, AR and HTT in 498 exomes, we found 22 additional pathogenic expansions. Comparison with capillary migration sizing in 247 individuals and confirmation of all expanded alleles detected by ExpansionHunter demonstrated that for these loci, sensitivity and specificity reached 100%. ExpansionHunter detected but underestimated the repeat size for larger expansions, and the normal alleles distribution at each locus should be taken into account to detect expansions. Exome combined with ExpansionHunter is reliable to detect repeat expansions in selected loci as first-line analysis in spinocerebellar ataxia.

[Improvement of the treatment of patients with spastic movement disorder after stroke]. / Verbesserung der Versorgung von Patientinnen und Patienten mit spastischer Bewegungsstörung nach Schlaganfall.

BACKGROUND: Spastic movement disorder (SMD) develops in up to 43% of cases as a sequela of stroke. In the event of a functionally relevant or daily life impairing SMD or to avoid an impending complication, the medicinal treatment of a focal, multifocal and segmental increase in muscle tone with botulinum neurotoxin A (BoNT-A) is recommended; however, treatment data reveal a lack of guideline-conform treatment with BoNT­A in Germany. OBJECTIVE: The aim of the reported expert meeting was to discuss solutions to the incorrect treatment and undertreatment of patients with SMD and to formulate consensus recommendations to improve the care situation. METHODS: At a consensus meeting held in April 2022, eight experts from the fields of neurology, physical medicine and rehabilitation discussed the causes for the incorrect treatment and undertreatment and formulated consensus solution approaches. RESULTS: Possible reasons for the current incorrect treatment and undertreatment in SMD management in Germany include insufficient awareness of SMD among physicians, a lack of treatment capacities, a lack of information transfer in discharge management as well as staff shortages in the specialized inpatient and outpatient SMD treatment centers. The committee therefore recommended a patient pathway in which affected patients with SMD are provided with correctly implemented BoNT­A treatment in combination with physical measures. CONCLUSION: The recommended treatment pathway for use in stroke patients is intended to close gaps in care and thus ensure guideline-conform treatment of post-stroke SMD.

Brainstem Infarction in Immunodeficiency Identified as Adenosine Deaminase 2 Deficiency: Case Report.

PURPOSE: We present the case of a 24-year-old male with CNS granulomatosis due to an immunodeficiency syndrome which was identified as deficiency of adenosine deaminase 2 (DADA2) as a cause of brainstem infarction. METHODS: Case report and detailed description of the clinical course of diagnosis and treatment. CASE: The patient's medical history consisted of an unknown immunodeficiency syndrome. Based on former findings, common variable immunodeficiency (CVID) was diagnosed. The patient suffered from three consecutive brainstem strokes of unknown etiology within 3 years. An MRI scan detected gadolinium-enhancing, granulomatous-suspect lesions in the interpeduncular cistern, temporal lobe, and tegmentum. Laboratory analysis was compatible with CVID, with leukopenia and immunoglobulin deficiency. Because granulomatous CNS inflammation was suspected, the patient received methylprednisolone immunosuppressive therapy, which led to partially regressive MRI lesions. However, in contrast to imaging, the patient showed a progressive cerebellar syndrome, indicating plasma exchange therapy and immunoglobulin treatment, which led to rapid symptom amelioration. After a relapse and a further stroke, expanded analysis confirmed DADA2 (and not CVID) as the inflammatory cause for recurrent stroke. After starting the therapy with immunoglobulins and adalimumab, no further strokes occurred. CONCLUSION: We present the case of a young adult with diagnosis of DADA2 as a cause for recurrent strokes due to vasculitis. This stroke etiology is rare but should be considered as a cause of recurrent stroke of unknown origin in young patients to avoid a disabling disease course by disease-specific treatment options.

Intermediate repeat expansions of TBP and STUB1: Genetic modifier or pure digenic inheritance in spinocerebellar ataxias?

PURPOSE: CAG/CAA repeat expansions in TBP>49 are responsible for spinocerebellar ataxia (SCA) type 17 (SCA17). We previously detected cosegregation of STUB1 variants causing SCA48 with intermediate alleles of TBP in 2 families. This cosegregation questions the existence of SCA48 as a monogenic disease. METHODS: We systematically sequenced TBP repeats in 34 probands of dominant ataxia families with STUB1 variants. In addition, we searched for pathogenic STUB1 variants in probands with expanded alleles of TBP>49 (n = 2) or intermediate alleles of TBP≥40 (n = 47). RESULTS: STUB1 variants were found in half of the TBP40-49 cohort. Mirroring this finding, TBP40-49 alleles were detected in 40% of STUB1 probands. The longer the TBP repeat length, the more likely the occurrence of cognitive impairment (P = .0129) and the faster the disease progression until death (P = .0003). Importantly, 13 STUB1 probands presenting with the full SCA48 clinical phenotype had normal TBP37-39 alleles, excluding digenic inheritance as the sole mode. CONCLUSION: We show that intermediate TBP40-49 alleles act as disease modifiers of SCA48 rather than a STUB1/TBP digenic model. This distinction from what has been proposed before has crucial consequences for genetic counseling in SCA48.

De Novo and Dominantly Inherited SPTAN1 Mutations Cause Spastic Paraplegia and Cerebellar Ataxia.

BACKGROUND: Pathogenic variants in SPTAN1 have been linked to a remarkably broad phenotypical spectrum. Clinical presentations include epileptic syndromes, intellectual disability, and hereditary motor neuropathy. OBJECTIVES: We investigated the role of SPTAN1 variants in rare neurological disorders such as ataxia and spastic paraplegia. METHODS: We screened 10,000 NGS datasets across two international consortia and one local database, indicative of the level of international collaboration currently required to identify genes causative for rare disease. We performed in silico modeling of the identified SPTAN1 variants. RESULTS: We describe 22 patients from 14 families with five novel SPTAN1 variants. Of six patients with cerebellar ataxia, four carry a de novo SPTAN1 variant and two show a sporadic inheritance. In this group, one variant (p.Lys2083del) is recurrent in four patients. Two patients have novel de novo missense mutations (p.Arg1098Cys, p.Arg1624Cys) associated with cerebellar ataxia, in one patient accompanied by intellectual disability and epilepsy. We furthermore report a recurrent missense mutation (p.Arg19Trp) in 15 patients with spastic paraplegia from seven families with a dominant inheritance pattern in four and a de novo origin in one case. One further patient carrying a de novo missense mutation (p.Gln2205Pro) has a complex spastic ataxic phenotype. Through protein modeling we show that mutated amino acids are located at crucial interlinking positions, interconnecting the three-helix bundle of a spectrin repeat. CONCLUSIONS: We show that SPTAN1 is a relevant candidate gene for ataxia and spastic paraplegia. We suggest that for the mutations identified in this study, disruption of the interlinking of spectrin helices could be a key feature of the pathomechanism. © 2022 International Parkinson and Movement Disorder Society.

Blood-based biomarker in Parkinson's disease: potential for future applications in clinical research and practice.

The clinical presentation of Parkinson's disease (PD) is both complex and heterogeneous, and its precise classification often requires an intensive work-up. The differential diagnosis, assessment of disease progression, evaluation of therapeutic responses, or identification of PD subtypes frequently remains uncertain from a clinical point of view. Various tissue- and fluid-based biomarkers are currently being investigated to improve the description of PD. From a clinician's perspective, signatures from blood that are relatively easy to obtain would have great potential for use in clinical practice if they fulfill the necessary requirements as PD biomarker. In this review article, we summarize the knowledge on blood-based PD biomarkers and present both a researcher's and a clinician's perspective on recent developments and potential future applications.

ADHD-associated PARK2 copy number variants: A pilot study on gene expression and effects of supplementary deprivation in patient-derived cell lines.

Recent studies show an association of Parkin RBR E3 ubiquitin protein ligase (PARK2) copy number variations (CNVs) with attention deficit hyperactivity disorder (ADHD). The aim of our pilot study to investigate gene expression associated with PARK2 CNVs in human-derived cellular models. We investigated gene expression in fibroblasts, hiPSC and dopaminergic neurons (DNs) of ADHD PARK2 deletion and duplication carriers by qRT PCR compared with healthy and ADHD cell lines without PARK2 CNVs. The selected 10 genes of interest were associated with oxidative stress response (TP53, NQO1, and NFE2L2), ubiquitin pathway (UBE3A, UBB, UBC, and ATXN3) and with a function in mitochondrial quality control (PINK1, MFN2, and ATG5). Additionally, an exploratory RNA bulk sequencing analysis in DNs was conducted. Nutrient deprivation as a supplementary deprivation stress paradigm was used to enhance potential genotype effects. At baseline, in fibroblasts, hiPSC, and DNs, there was no significant difference in gene expression after correction for multiple testing. After nutrient deprivation in fibroblasts NAD(P)H-quinone-dehydrogenase 1 (NQO1) expression was significantly increased in PARK2 CNV carriers. In a multivariate analysis, ubiquitin C (UBC) was significantly upregulated in fibroblasts of PARK2 CNV carriers. RNA sequencing analysis of DNs showed the strongest significant differential regulation in Neurontin (NNAT) at baseline and after nutrient deprivation. Our preliminary results suggest differential gene expression in pathways associated with oxidative stress, ubiquitine-proteasome, immunity, inflammation, cell growth, and differentiation, excitation/inhibition modulation, and energy metabolism in PARK2 CNV carriers compared to wildtype healthy controls and ADHD patients.

[Deep brain stimulation in neurological and psychiatric diseases]. / Tiefe Hirnstimulation bei neurologischen und psychiatrischen Erkrankungen.

Invasive deep brain stimulation (DBS) has become an established treatment procedure for a number of neurological diseases, especially movement disorders. The number of patients treated with DBS is continuously increasing, the technical development of DBS systems is progressing and new indications are currently being tested in studies. This review gives an overview of the current indications and an outlook on future developments of DBS in movement disorders and psychiatric diseases.

[New Therapeutic Options for the Individualised Titration of Levodopa]. / Neue Therapieoption zur individualisierten Titration von Levodopa.

Levodopa is the most effective medication in the treatment of Parkinson's disease. In the course of the disease the storage facility of dopaminergic neurones deteriorates, so that the duration of the half-life period likewise converges. This results in fluctuations in performance, and also in dyskinesias as a further consequence of the narrowing therapeutic window. Therapeutically, this in turn leads to further fractioning of the levodopa dosage and a reduction of single-dose levels. There is, however, only limited scope for doing this with the conventional levodopa formulations. For this reason, the introduction of water-soluble microtablets à 5 / 1.25 mg levodopa / carbidopa can be regarded as a beneficial extension permitting for fine titration of the dopaminergic stimulation. Here we present this new therapeutic principle, the available data and concepts for clinical use.

Clinical, neuropathological, and genetic characterization of STUB1 variants in cerebellar ataxias: a frequent cause of predominant cognitive impairment.

PURPOSE: Pathogenic variants in STUB1 were initially described in autosomal recessive spinocerebellar ataxia type 16 and dominant cerebellar ataxia with cerebellar cognitive dysfunction (SCA48). METHODS: We analyzed a large series of 440 index cerebellar ataxia cases, mostly with dominant inheritance. RESULTS: STUB1 variants were detected in 50 patients. Age at onset and severity were remarkably variable. Cognitive impairment, predominantly frontal syndrome, was observed in 54% of STUB1 variant carriers, including five families with Huntington or frontotemporal dementia disease-like phenotypes associated with ataxia, while no STUB1 variant was found in 115 patients with frontotemporal dementia. We report neuropathological findings of a STUB1 heterozygous patient, showing massive loss of Purkinje cells in the vermis and major loss in the cerebellar hemispheres without atrophy of the pons, hippocampus, or cerebral cortex. This screening of STUB1 variants revealed new features: (1) the majority of patients were women (70%) and (2) "second hits" in AFG3L2, PRKCG, and TBP were detected in three families suggesting synergic effects. CONCLUSION: Our results reveal an unexpectedly frequent (7%) implication of STUB1 among dominantly inherited cerebellar ataxias, and suggest that the penetrance of STUB1 variants could be modulated by other factors, including sex and variants in other ataxia-related genes.

Genotype-phenotype correlation in a novel ABHD12 mutation underlying PHARC syndrome.

PHARC syndrome is a rare neurodegenerative disorder caused by mutations in the ABHD12 gene. It is a genetically heterogeneous and clinically variable disease, which is characterized by demyelinating polyneuropathy, hearing loss, cerebellar ataxia, retinitis pigmentosa, and early-onset cataract and can easily be misdiagnosed as other neurologic disorders with a similar clinical picture, such as Charcot-Marie-Tooth disease and Refsum disease. We describe the genotype-phenotype correlation of two siblings with a novel genotype underlying PHARC syndrome. The genotype was identified using next-generation sequencing. We examined both patients by means of thorough history taking and clinical examination, nerve conduction studies (NCS), brain imaging, and optical coherence tomography to establish a genotype-phenotype correlation. We identified a novel homozygous point mutation (c.784C > T, p.Arg262*) in the ABHD12 gene. This mutation was detected in both siblings, who had bilateral hearing loss and cataracts, signs of cerebellar ataxia, and neuropathy with a primarily demyelinating pattern in NCS. In one case, retinitis pigmentosa was also evident. As PHARC syndrome is a rare autosomal recessive disorder, our findings highlight the importance of an interdisciplinary diagnostic workup with clinical and molecular genetic testing to avoid a misdiagnosis as Charcot-Marie-Tooth disease or Refsum disease.

[Genetic testing for Parkinson's disease: indication and practical implementation]. / Genetische Untersuchungen beim Parkinson-Syndrom: Indikation und praktische Durchführung.

More than 20 years have passed since the first description of a monogenic cause of Parkinson's disease. Despite the tremendous advances of genetic testing these techniques are rarely used in Parkinson's disease. However, genetic tests in patients with Parkinson's syndrome will play an important role in the future. This is not only to ensure the diagnosis of Parkinson's patients with a young onset and / or a positive family history, but also in the context of personalised medicine with new therapeutic options. In the following we would like to give an overview of the basics of genetic testing, the legal requirements, the procedure for genetic testing and an outlook into the future for hereditary Parkinson's diseases.

Examining the Reserve Hypothesis in Parkinson's Disease: A Longitudinal Study.

BACKGROUND: Whether reserve plays a role in Parkinson's disease (PD) patients has received less attention than in dementia and has been mainly examined in relation with cognitive function. OBJECTIVE: To investigate whether reserve plays a role in the severity and progression of motor, cognitive, and nonmotor PD symptoms by examining whether education level (proxy of reserve) is associated with baseline performance and rate of progression. METHODS: We used data from a longitudinal cohort of PD patients (≤5-year disease duration at baseline) annually followed up to 5 years (n = 393; 41% women; mean age = 62.3 years, standard deviation = 10.0; mean disease duration = 2.6 years, standard deviation = 1.5). We examined the relationship of education with time to reach Hoehn and Yahr stage ≥3 using Cox regression and with baseline severity and progression of motor (Movement Disorder Society-Unified Parkinson's Disease Rating Scale parts II and III, gait speed), cognitive (Mini-Mental State Examination), and nonmotor (depression, anxiety, nonmotor symptoms scale, quality of life) symptoms using mixed models. RESULTS: Education level was not associated with age at onset or diagnosis. Compared with the low-education group, the incidence of Hoehn and Yahr ≥3.0 was 0.42 times lower (95% confidence interval, 0.22-0.82, P = 0.012) in the high-education group. Higher education was associated with better baseline motor function (P < 0.001), but not with the rate of motor decline (P > 0.15). Similar results were observed for cognition. Education was not associated with nonmotor symptoms. CONCLUSIONS: Higher education is associated with better baseline motor/cognitive function in PD, but not with rate of decline, and with a lower risk of reaching Hoehn and Yahr ≥3 during the follow-up. Our observations are consistent with a passive reserve hypothesis for motor/cognitive symptoms. © 2019 International Parkinson and Movement Disorder Society.

Management of delirium in Parkinson's disease.

Delirium is an acute and fluctuating disturbance of attention and awareness. Pre-existing cognitive disturbances or dementia are the most significant risk factors for developing delirium and precipitating factors such as drug treatment, infections, trauma, or surgery may trigger delirium. Patients with Parkinson's disease (PD) are at an increased risk for delirium which may be underdiagnosed due to phenomenological overlap between delirium and chronic neuropsychiatric features of PD or side effects of dopaminergic medication. Prognosis of delirium is detrimental in many cases including permanent cognitive decline, motor impairment, and increased mortality. Management of delirium comprises of pharmacological and non-pharmacological measures. Pharmacotherapy is aimed at treating medical precipitating factors such as infections, pain, and sleep deprivation. Adjustments of anti-parkinsonian medication are recommended to prevent or treat delirium, but no hard evidence in this respect is available from controlled studies. Administration of neuroleptics and other psychoactive drugs in the treatment of delirium is controversially discussed and should be reserved for patients with severe agitation or distressing psychosis. Non-pharmacological interventions to prevent or palliate delirium are based on withdrawing precipitating or distressing factors, and to provide sensory, emotional and environmental support. Appropriate instruments to detect and assess delirium in PD are needed, and efforts are warranted to improve understanding and treatment of this severe and common disorder.

[Genetics of movement disorders-rare but important]. / Genetik von Bewegungsstörungen ­ selten aber wichtig.

Rare genetic movement disorders are a heterogeneous group of diseases. The causes of many of these rare movement disorders could be resolved due to the progress in molecular genetic diagnostics. This led to a better pathophysiological characterization of rare movement disorders and also to the fact that many phenotypical overlaps could be found between different diseases. The classification of genetic results requires a close cooperation between neurologists and geneticists. Therefore, modern diagnostic procedures cannot replace the clinical classification of genetic movement disorders and the exact patient history. This article provides the reader with an overview of the most important groups of genetic movement disorders. Genetic Parkinson syndromes, dystonia, essential tremor, genetic chorea, cerebellar ataxia and hereditary spastic paraplegia are dealt with in detail. For a better understanding individual genetic terms are explained and differences in molecular genetic diagnostics are presented.

Comprehensive analysis of the mutation spectrum in 301 German ALS families.

OBJECTIVES: Recent advances in amyotrophic lateral sclerosis (ALS) genetics have revealed that mutations in any of more than 25 genes can cause ALS, mostly as an autosomal-dominant Mendelian trait. Detailed knowledge about the genetic architecture of ALS in a specific population will be important for genetic counselling but also for genotype-specific therapeutic interventions. METHODS: Here we combined fragment length analysis, repeat-primed PCR, Southern blotting, Sanger sequencing and whole exome sequencing to obtain a comprehensive profile of genetic variants in ALS disease genes in 301 German pedigrees with familial ALS. We report C9orf72 mutations as well as variants in consensus splice sites and non-synonymous variants in protein-coding regions of ALS genes. We furthermore estimate their pathogenicity by taking into account type and frequency of the respective variant as well as segregation within the families. RESULTS: 49% of our German ALS families carried a likely pathogenic variant in at least one of the earlier identified ALS genes. In 45% of the ALS families, likely pathogenic variants were detected in C9orf72, SOD1, FUS, TARDBP or TBK1, whereas the relative contribution of the other ALS genes in this familial ALS cohort was 4%. We identified several previously unreported rare variants and demonstrated the absence of likely pathogenic variants in some of the recently described ALS disease genes. CONCLUSIONS: We here present a comprehensive genetic characterisation of German familial ALS. The present findings are of importance for genetic counselling in clinical practice, for molecular research and for the design of diagnostic gene panels or genotype-specific therapeutic interventions in Europe.

Hereditary spastic paraplegia: Clinicogenetic lessons from 608 patients.

OBJECTIVE: Hereditary spastic paraplegias (HSPs) are genetically driven disorders with the hallmark of progressive spastic gait disturbance. To investigate the phenotypic spectrum, prognostic factors, and genotype-specific differences, we analyzed baseline data from a continuous, prospective cohort. METHODS: We recruited 608 HSP cases from 519 families of mostly German origin. Clinical severity was assessed by the Spastic Paraplegia Rating Scale. Complicating symptoms were recorded by a standardized inventory. RESULTS: Family history indicated dominant (43%), recessive (10%), and simplex (47%) disease. We observed a significant male predominance, particularly in simplex cases without a genetic diagnosis. Disease severity increased with disease duration. Earlier disease onset was associated with less severe disease. Specific complicating features including cognitive impairment, extrapyramidal or peripheral motor involvement, and ataxia were associated with worse disease severity. Disease severity also depended on the genotype. HSP cases maintained the ability to walk independently for a median disease duration of 22 years. Early onset cases were able to maintain free walking significantly longer and were at less risk to become wheelchair dependent. INTERPRETATION: This cross-sectional cohort study provides the first large-scale data on disease manifestation, progression, and modifying factors, with relevance for counseling of HSP families and planning of future cross-sectional and natural history studies. Later age of onset, specific complicating features, and the SPG11 genotype are strongly associated with more severe disease. Future interventional studies will require stratification for modifiers of disease progression identified in this study. Prospective longitudinal studies will verify progression rates calculated in this baseline analysis.

Dermal phospho-alpha-synuclein deposits confirm REM sleep behaviour disorder as prodromal Parkinson's disease.

Phosphorylated alpha-synuclein (p-alpha-syn) deposits, one of the neuropathological hallmarks of Parkinson's disease (PD), have recently been detected in dermal nerve fibres in PD patients with good specificity and sensitivity. Here, we studied whether p-alpha-syn may serve as a biomarker in patients with a high risk of developing PD, such as those with REM sleep behaviour disorder (RBD). We compared the presence and distribution of p-alpha-syn deposits in dermal nerve fibres in 18 patients with RBD, 25 patients with early PD and 20 normal controls. Skin biopsy was taken at C7, Th10, and the upper and lower leg. Presynaptic dopamine transporter imaging using FP-CIT-SPECT was performed in all patients with RBD and in 11 patients with PD. All RBD patients underwent olfactory function testing. The likelihood ratio (LR) for prodromal PD was calculated for each patient based on published research criteria. Skin serial sections were assessed by double-immunofluorescence labelling with antibodies to pSer129-alpha-syn under blinded conditions. P-alpha-syn was visualized in 10/18 patients with RBD (sensitivity of 55.6%) and in 20/25 early PD patients (sensitivity of 80%) but in none of the controls (specificity of 100%). The percentage of dermal structures innervated by p-alpha-syn-positive fibres was negatively correlated with dopamine transporter binding in the FP-CIT-SPECT (ρ = -0.377, p = 0.048), with olfactory function (ρ = -0.668, p = 0.002), and positively correlated with the total LR for RBD to present prodromal PD (ρ = 0.531, p = 0.023). Dermal p-alpha-syn can be considered a peripheral histopathological marker of synucleinopathy and can be detected in a subgroup of RBD patients presumably representing prodromal PD. Dermal p-alpha-syn is detectable in RBD patients without PD motor symptoms, thereby stratifying a patient group that is of great interest for clinical trials testing disease-modifying drugs.