Variation in Recent Onset Parkinson's Disease: Implications for Prodromal Detection

A postmortem study suggests a revision of the dual-hit hypothesis of Parkinson's disease

The dual-hit hypothesis of Parkinson's disease (PD) originally postulated that a neurotropic pathogen leads to formation of α-synuclein pathology in the olfactory bulb (OB) and dorsal motor nucleus of the vagus (DMV) and then invades the brain from these two entry points. Little work has been conducted to validate an important underlying premise for the dual-hit hypothesis, namely that the initial Lewy pathology does arise simultaneously in the OB and the enteric nervous system (ENS) plexuses and DMV at the earliest disease stage. We conducted a focused re-analysis of two postmortem datasets, which included large numbers of mild Lewy body disease (LBD) cases. We found that cases with α-synuclein pathology restricted to the peripheral autonomic nervous system and/or lower brainstem (early body-first LBD cases) very rarely had any OB pathology, suggesting that Lewy pathology commonly arises in the ENS without concomitant involvement of the OB. In contrast, cases with mild amygdala-predominant Lewy pathology (early brain-first LBD cases) nearly always showed OB pathology. This is compatible with the first pathology being triggered in the OB or amygdala followed by secondary spreading to connected structures, but without early involvement of the ENS or lower brainstem. These observations support that the pathologic process starts in either the olfactory bulb or the ENS, but rarely in the olfactory bulb and gut simultaneously. More studies on neuropathological datasets are warranted to reproduce these findings. The agreement between the revised single-hit hypothesis and the recently proposed brain-first vs. body-first model of LBD is discussed.

Impact of Gastrointestinal Symptoms on Health-Related Quality of Life in an Australian Parkinson’s Disease Cohort

Background. Gastrointestinal symptoms (GIS) in people with Parkinson’s disease (PwP) are often underreported and may remain untreated. Constipation is a common nonmotor symptom that can adversely affect health-related quality of life (QoL); however, the impact of other GIS has not been adequately investigated. Objectives. To investigate the relationship between QoL and constipation using the Bristol Stool Chart, bowel movement frequency, and a perceived constipation measure; and to explore the relationship between QoL and other GIS in an Australian PD cohort. Methods. The impact of constipation and other GIS on QoL, as measured using the PDQ-39 scale, was assessed in a cohort of 144 (89 males, 55 females) clinic-attending PwP. Constipation was assessed using the Bristol Stool Chart as well as a composite constipation measure, and the Gastrointestinal Symptom Rating Scale (GSRS) was used to rate other GIS. Covariate corrected linear regression models were utilised to determine significant associations between GIS and QoL scores. Results. Individual and combined constipation measures were significantly associated with poorer QoL ( $p=0.032$ and $p=0.002$ , respectively). Analysis of GSRS symptom domains showed that in addition to symptoms of gastrointestinal hypomotility, a number of other symptoms such as increased eructation and increased flatus were also associated with poorer QoL. Conclusions. The findings point to the importance of GIS as contributor to health-related QoL in PwP. A better understanding of the relationship between GIS and QoL will help facilitate the development of more effective screening and treatment programs to improve symptom management and QoL for PwP.

International consensus statement on allergy and rhinology: Olfaction

BACKGROUND

The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O).

METHODS

Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus.

RESULTS

The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies.

CONCLUSION

This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

Induced Cognitive Impairments Reversed by Grafts of Neural Precursors: A Longitudinal Study in a Macaque Model of Parkinson's Disease

Parkinson's disease (PD) evolves over an extended and variable period in humans; years prior to the onset of classical motor symptoms, sleep and biological rhythm disorders develop, significantly impacting the quality-of-life of patients. Circadian-rhythm disorders are accompanied by mild cognitive deficits that progressively worsen with disease progression and can constitute a severe burden for patients at later stages. The gold-standard 6-methyl-1-methyl-4-phenyl-1,2,3,6-tetrahydropyridin (MPTP) macaque model of PD recapitulates the progression of motor and nonmotor symptoms over contracted periods of time. Here, this multidisciplinary/multiparametric study follows, in five animals, the steady progression of motor and nonmotor symptoms and describes their reversal following grafts of neural precursors in diverse functional domains of the basal ganglia. Results show unprecedented recovery from cognitive symptoms in addition to a strong clinical motor recuperation. Both motor and cognitive recovery and partial circadian rhythm recovery correlate with the degree of graft integration, and in a subset of animals, with in vivo levels of striatal dopaminergic innervation and function. The present study provides empirical evidence that integration of neural precursors following transplantation efficiently restores function at multiple levels in parkinsonian nonhuman primates and, given interindividuality of disease progression and recovery, underlines the importance of longitudinal multidisciplinary assessments in view of clinical translation.

Impact of rapid eye movement sleep behavior disorder and autonomic disorders on Parkinson's disease: a review

Parkinson's disease (PD) has heterogeneous clinical manifestations and prognoses. It is accompanied by a group of motor and non-motor symptoms ranging from independence to total disability, limiting work and personal care activities. Currently, disease subtype markers for informing prognosis remain elusive. However, some studies have reported an association between rapid eye movement (REM) sleep behavior disorder (RBD) and faster motor and non-motor symptom progression, including autonomic dysfunction and cognitive decline. Moreover, since autonomic dysfunction has been described in idiopathic forms of RBD, and they share some central regulatory pathways, it remains unclear whether they have a primary association or if they are more severe in patients with PD and RBD, and thus are a disease subtype marker. This article aimed at critically reviewing the literature on the controversies about the prevalence of RBD in PD, the higher incidence of PD non-motor symptoms associated with RBD, the evidence of faster motor worsening in parkinsonian patients with this parasomnia, and the main pathophysiological hypotheses that support these findings.

Effects of depression and exercise on health-related quality of life in patients with Parkinson's disease

OBJECTIVES

There is limited literature describing the effect exercise may have on depression and an individual's health-related quality of life (HRQoL) in Parkinson's Disease (PD). We aim to quantify this effect.

METHODS

A cross-sectional questionnaire was administered to 60 PD subjects. The Parkinson's Disease Questionnaire-39 (PDQ-39) summary index and the Geriatric Depression Scale-30 were used to quantify HRQoL and depression, respectively. Data were obtained on exercise habits. ANOVA and multivariate linear regression analysis were used to calculate mean differences in HRQoL.

RESULTS

Depression was consistently related to HRQoL (p < 0.05). Of those who exercised as an adult before PD diagnosis, 49.02% (n = 25) reported depression as compared to 88.89% (n = 8) of those who did not report adult exercise (p = 0.03). Those who exercised frequently as an adult prior to PD diagnosis had a better PDQ-39 Cognitive Index (p = 0.03). Those who were not depressed and were currently exercising had a significantly higher HRQoL than those who were depressed and did not exercise (p < 0.01).

DISCUSSION

Exercising and depression may interact to affect HRQoL. Thus, coordination of mental health evaluation and exercise regimens in persons with PD may improve HRQoL.

Brain-First versus Gut-First Parkinson's Disease: A Hypothesis

Parkinson’s disease (PD) is a highly heterogeneous disorder, which probably consists of multiple subtypes. Aggregation of misfolded alpha-synuclein and propagation of these proteinacious aggregates through interconnected neural networks is believed to be a crucial pathogenetic factor. It has been hypothesized that the initial pathological alpha-synuclein aggregates originate in the enteric or peripheral nervous system (PNS) and invade the central nervous system (CNS) via retrograde vagal transport. However, evidence from neuropathological studies suggests that not all PD patients can be reconciled with this hypothesis. Importantly, a small fraction of patients do not show pathology in the dorsal motor nucleus of the vagus. Here, it is hypothesized that PD can be divided into a PNS-first and a CNS-first subtype. The former is tightly associated with REM sleep behavior disorder (RBD) during the prodromal phase and is characterized by marked autonomic damage before involvement of the dopaminergic system. In contrast, the CNS-first phenotype is most often RBD-negative during the prodromal phase and characterized by nigrostriatal dopaminergic dysfunction prior to involvement of the autonomic PNS. The existence of these subtypes is supported by in vivo imaging studies of RBD-positive and RBD-negative patient groups and by histological evidence— reviewed herein. The present proposal provides a fresh hypothesis-generating framework for future studies into the etiopathogenesis of PD and seems capable of explaining a number of discrepant findings in the neuropathological literature.

'Atypical' Parkinson's disease - sporadic

Parkinson's disease still is a clinical diagnosis. Also, the MDS Clinical Diagnostic Criteria for Parkinson's disease published in 2015 are based on clinical characteristics and were designed codifying the diagnostic process of an expert. The purpose was to support less experienced neurologists to achieve the diagnostic procedure up to the level of an expert. The criteria include both negative and positive properties. However, some features exclude patients with typical Parkinson's disease mainly during their early or late stages. These includes symptoms such as the absence of the combination of typical motor symptoms, the insufficient response to dopaminergic treatment, autonomic dysfunction, dystonia, postural instability or cognitive impairment. This chapter discusses those "atypical" symptom constellations that complicate the differential diagnosis of PD versus atypical parkinsonism and illustrates additional considerations that might be helpful to achieve a correct diagnosis.

Sleep and risk of parkinsonism and Parkinson's disease: a population-based study

Sleep disturbances may signal presence of prodromal parkinsonism, including Parkinson's disease. Whether general sleep quality or duration in otherwise healthy subjects is related to the risk of parkinsonism remains unclear. We hypothesized that both worse self-reported sleep quality and duration, as well as a longitudinal deterioration in these measures, are associated with the risk of parkinsonism, including Parkinson's disease. In the prospective population-based Rotterdam Study, we assessed sleep quality and duration with the Pittsburgh Sleep Quality Index in 7726 subjects (mean age 65 years, 57% female) between 2002 and 2008, and again in 5450 subjects between 2009 and 2014. Participants were followed until 2015 for a diagnosis of parkinsonism and Parkinson's disease. Outcomes were assessed using multiple modalities: interviews, physical examination, and continuous monitoring of pharmacy records and medical records of general practitioners. We used Cox regression to associate sleep, and changes in sleep over time, with incident parkinsonism and Parkinson's disease, adjusting for age, sex, education and smoking status. Over 64 855 person-years in 13 years of follow-up (mean: 8.4 years), 75 participants developed parkinsonism, of whom 47 developed Parkinson's disease. We showed that within the first 2 years of follow-up, worse sleep quality {hazard ratio (HR) 2.38 per standard deviation increase [95% confidence interval (CI 0.91-6.23)]} and shorter sleep duration [HR 0.61 per standard deviation increase (95% CI 0.31-1.21)] related to a higher risk of parkinsonism. Associations of worse sleep quality [HR 3.86 (95% CI 1.19-12.47)] and shorter sleep duration [HR 0.48 (95% CI 0.23-0.99)] with Parkinson's disease were more pronounced, and statistically significant, compared to parkinsonism. This increased risk disappeared with longer follow-up duration. Worsening of sleep quality [HR 1.76 per standard deviation increase (95% CI 1.12-2.78)], as well as shortening of sleep duration [HR 1.72 per standard deviation decrease (95% CI 1.08-2.72)], were related to Parkinson's disease risk in the subsequent 6 years. Therefore, we argue that in the general population, deterioration of sleep quality and duration are markers of the prodromal phase of parkinsonism, including Parkinson's disease.

Prevalence and duration of non-motor symptoms in prodromal Parkinson's disease

Background and purpose

The prevalence and duration of non‐motor symptoms (NMS) in prodromal Parkinson's disease (PD) has not been extensively studied. The aim of this study was to determine the prevalence and duration of prodromal NMS (pNMS) in a cohort of patients with recently diagnosed PD.

Methods

We evaluated the prevalence and duration of pNMS in patients with early PD (n = 154). NMS were screened for using the Non‐Motor Symptom Questionnaire (NMSQuest). We subtracted the duration of the presence of each individual NMS reported from the duration of the earliest motor symptom. NMS whose duration preceded the duration of motor symptoms were considered a pNMS. Individual pNMS were then grouped into relevant pNMS clusters based on the NMSQuest domains. Motor subtypes were defined as tremor dominant, postural instability gait difficulty (PIGD) and indeterminate type according to the Movement Disorder Society Unified Parkinson's Disease Rating Scale revision.

Results

Prodromal NMS were experienced by 90.3% of patients with PD and the median number experienced was 4 (interquartile range, 2–7). A gender difference existed in the pNMS experienced, with males reporting more sexual dysfunction, forgetfulness and dream re‐enactment, whereas females reported more unexplained weight change and anxiety. There was a significant association between any prodromal gastrointestinal symptoms [odds ratio (OR), 2.30; 95% confidence interval (CI), 1.08–4.89, P = 0.03] and urinary symptoms (OR, 2.54; 95% CI, 1.19–5.35, P = 0.016) and the PIGD phenotype. Further analysis revealed that total pNMS were not significantly associated with the PIGD phenotype (OR, 1.10; 95% CI, 0.99–1.21, P = 0.068).

Conclusions

Prodromal NMS are common and a gender difference in pNMS experienced in prodromal PD may exist. The PIGD phenotype had a higher prevalence of prodromal gastrointestinal and urinary tract symptoms.

Regulatory-accepted drug development tools are needed to accelerate innovative CNS disease treatments

Central Nervous System (CNS) diseases represent one of the most challenging therapeutic areas for successful drug approvals. Developing quantitative biomarkers as Drug Development Tools (DDTs) can catalyze the path to innovative treatments, and improve the chances of drug approvals. Drug development and healthcare management requires sensitive, reliable, validated, and regulatory accepted biomarkers and endpoints. This review highlights the regulatory paths and considerations for developing DDTs required to advance biomarker and endpoint use in clinical development (e.g., consensus CDISC [Clinical Data Interchange Standards Consortium] data standards, precompetitive sharing of anonymized patient-level data, and continual alignment with regulators). Summarized is the current landscape of biomarkers in a range of CNS diseases including Alzheimer disease, Parkinson Disease, Amyotrophic Lateral Sclerosis, Autism Spectrum Disorders, Depression, Huntington's disease, Multiple Sclerosis and Traumatic Brain Injury. Advancing DDTs for these devastating diseases that are both validated and qualified will require an integrated, cross-consortium approach to accelerate the delivery of innovative CNS therapeutics.

Sleep-wake disturbances in the premotor and early stage of Parkinson's disease

PURPOSE OF REVIEW

Review of recent literature pertaining to frequency, associations, mechanisms, and overall significance of sleep--wake disturbances (SWD) in the premotor and early phase of Parkinson's disease.

RECENT FINDINGS

SWD are frequent in Parkinson's disease and their prevalence increases with disease progression. Recent studies confirm previous findings that SWD can appear as initial manifestation of Parkinson's disease even decades before motor signs appear and highlight their clinical associations in these early stages. More intriguingly, new evidence underpins their role as risk factors, predictors, or even as driving force for the neurodegenerative process. As our understanding of sleep--wake neurobiology increases, new hypotheses emerge concerning the pathophysiology of SWD in early Parkinson's disease stages involving dopaminergic and nondopaminergic mechanisms.

SUMMARY

SWD are predictors for the development of parkinsonian syndromes including Parkinson's disease. This may offer the opportunity of developing new preventive strategies and interventions at an early stage of this neurodegenerative disease.

Transplantation in the nonhuman primate MPTP model of Parkinson's disease: update and perspectives

In order to calibrate stem cell exploitation for cellular therapy in neurodegenerative diseases, fundamental and preclinical research in NHP (nonhuman primate) models is crucial. Indeed, it is consensually recognized that it is not possible to directly extrapolate results obtained in rodent models to human patients. A large diversity of neurological pathologies should benefit from cellular therapy based on neural differentiation of stem cells. In the context of this special issue of Primate Biology on NHP stem cells, we describe past and recent advances on cell replacement in the NHP model of Parkinson's disease (PD). From the different grafting procedures to the various cell types transplanted, we review here diverse approaches for cell-replacement therapy and their related therapeutic potential on behavior and function in the NHP model of PD.

Autonomic Dysfunction in Early Parkinson's Disease: Results from the United Kingdom Tracking Parkinson's Study

BACKGROUND

Autonomic dysfunction is common in the later stages of Parkinson's disease (PD), but less is known about its presence and severity in early disease.

OBJECTIVE

To analyze features of autonomic dysfunction in recent onset PD cases, and their relationship to motor severity, medication use, other nonmotor symptoms (NMS), and quality-of-life scores.

METHODS

Detailed patient-reported symptoms of autonomic dysfunction were assessed in a multicenter cohort study in PD cases that had been diagnosed within the preceding 3.5 years.

RESULTS

There were 1746 patients (1132 males, 65.2%), mean age 67.6 years (SD 9.3), mean disease duration 1.3 years (SD 0.9), mean Movement Disorder Society Unified Parkinson's Disease Rating Scale motor score 22.5 (SD 12.1). Orthostatic symptoms were reported by 39.6%, male erectile dysfunction by 56.1%, and female anorgasmia by 57.4%. Sialorrhea was an issue in 51.4% of patients, constipation in 43.6%, and dysphagia in 20.1%. Autonomic features increased with higher modified Hoehn and Yahr stages (P < 0.001). The severity of autonomic dysfunction was associated with the postural instability gait difficulty motor phenotype [β-coefficient 1.7, 95% confidence interval (CI) 0.7, 2.6, P < 0.001], depression (β-coefficient 4.1, CI 3.0, 5.2, P < 0.001), and excess daytime sleepiness (β-coefficient 3.1, CI 1.9, 4.2, P < 0.001). Dopamine agonists were the only drug class associated with greater autonomic dysfunction (P = 0.019). The severity of autonomic dysfunction strongly correlated with the presence of other NMS (ρ = 0.717, P < 0.001), and with poorer quality-of-life scores (ρ = 0.483, P < 0.001).

CONCLUSIONS

Autonomic dysfunction is common in early PD. Autonomic dysfunction correlates with the presence of other NMS, and with worse quality of life.

Assessment of Olfactory Function in MAPT-Associated Neurodegenerative Disease Reveals Odor-Identification Irreproducibility as a Non-Disease-Specific, General Characteristic of Olfactory Dysfunction

Olfactory dysfunction is associated with normal aging, multiple neurodegenerative disorders, including Parkinson's disease, Lewy body disease and Alzheimer's disease, and other diseases such as diabetes, sleep apnea and the autoimmune disease myasthenia gravis. The wide spectrum of neurodegenerative disorders associated with olfactory dysfunction suggests different, potentially overlapping, underlying pathophysiologies. Studying olfactory dysfunction in presymptomatic carriers of mutations known to cause familial parkinsonism provides unique opportunities to understand the role of genetic factors, delineate the salient characteristics of the onset of olfactory dysfunction, and understand when it starts relative to motor and cognitive symptoms. We evaluated olfactory dysfunction in 28 carriers of two MAPT mutations (p.N279K, p.P301L), which cause frontotemporal dementia with parkinsonism, using the University of Pennsylvania Smell Identification Test. Olfactory dysfunction in carriers does not appear to be allele specific, but is strongly age-dependent and precedes symptomatic onset. Severe olfactory dysfunction, however, is not a fully penetrant trait at the time of symptom onset. Principal component analysis revealed that olfactory dysfunction is not odor-class specific, even though individual odor responses cluster kindred members according to genetic and disease status. Strikingly, carriers with incipient olfactory dysfunction show poor inter-test consistency among the sets of odors identified incorrectly in successive replicate tests, even before severe olfactory dysfunction appears. Furthermore, when 78 individuals without neurodegenerative disease and 14 individuals with sporadic Parkinson's disease were evaluated twice at a one-year interval using the Brief Smell Identification Test, the majority also showed inconsistency in the sets of odors they identified incorrectly, independent of age and cognitive status. While these findings may reflect the limitations of these tests used and the sample sizes, olfactory dysfunction appears to be associated with the inability to identify odors reliably and consistently, not with the loss of an ability to identify specific odors. Irreproducibility in odor identification appears to be a non-disease-specific, general feature of olfactory dysfunction that is accelerated or accentuated in neurodegenerative disease. It may reflect a fundamental organizational principle of the olfactory system, which is more "error-prone" than other sensory systems.

Motor features in Parkinson's disease with normal olfactory function

BACKGROUND

Normosmic Parkinson's disease (PD) might be a unique clinical phenotype with a more benign course when compared with hyposmic PD.

OBJECTIVE

The objective of this study was to evaluate motor features and the acute levodopa response according to olfactory function.

METHODS

A total of 169 de novo PD patients that underwent olfactory testing and acute levodopa challenge for clinical prediction of sustained long-term dopaminergic response were evaluated.

RESULTS

The overall frequency of normosmia was 33%. Normosmic PD patients scored nonsignificantly different to hyposmic/anosmic patients on motor scale and on degree of improvement with levodopa. Motor scores at follow-up were comparable among groups.

CONCLUSIONS

Normal olfactory function is common in early PD and was not associated with a different motor phenotype when compared with PD patients with olfactory dysfunction. © 2016 International Parkinson and Movement Disorder Society.