Differentiating Prodromal Dementia with Lewy Bodies from Prodromal Alzheimer's Disease: A Pragmatic Review for Clinicians

This pragmatic review synthesises the current understanding of prodromal dementia with Lewy bodies (pDLB) and prodromal Alzheimer's disease (pAD), including clinical presentations, neuropsychological profiles, neuropsychiatric symptoms, biomarkers, and indications for disease management. The core clinical features of dementia with Lewy bodies (DLB)-parkinsonism, complex visual hallucinations, cognitive fluctuations, and REM sleep behaviour disorder are common prodromal symptoms. Supportive clinical features of pDLB include severe neuroleptic sensitivity, as well as autonomic and neuropsychiatric symptoms. The neuropsychological profile in mild cognitive impairment attributable to Lewy body pathology (MCI-LB) tends to include impairment in visuospatial skills and executive functioning, distinguishing it from MCI due to AD, which typically presents with impairment in memory. pDLB may present with cognitive impairment, psychiatric symptoms, and/or recurrent episodes of delirium, indicating that it is not necessarily synonymous with MCI-LB. Imaging, fluid and other biomarkers may play a crucial role in differentiating pDLB from pAD. The current MCI-LB criteria recognise low dopamine transporter uptake using positron emission tomography or single photon emission computed tomography (SPECT), loss of REM atonia on polysomnography, and sympathetic cardiac denervation using meta-iodobenzylguanidine SPECT as indicative biomarkers with slowing of dominant frequency on EEG among others as supportive biomarkers. This review also highlights the emergence of fluid and skin-based biomarkers. There is little research evidence for the treatment of pDLB, but pharmacological and non-pharmacological treatments for DLB may be discussed with patients. Non-pharmacological interventions such as diet, exercise, and cognitive stimulation may provide benefit, while evaluation and management of contributing factors like medications and sleep disturbances are vital. There is a need to expand research across diverse patient populations to address existing disparities in clinical trial participation. In conclusion, an early and accurate diagnosis of pDLB or pAD presents an opportunity for tailored interventions, improved healthcare outcomes, and enhanced quality of life for patients and care partners.

The clinical phenotype of psychiatric-onset prodromal dementia with Lewy bodies: a scoping review

BACKGROUND

Recent consensus research criteria have identified a 'psychiatric onset' form of prodromal dementia with Lewy bodies (DLB) characterised by prominent late-onset psychiatric symptoms. Although recognised as important to raise the index of diagnostic suspicion, evidence regarding this cohort was deemed too limited to impose formal criteria. We reviewed the published literature on psychiatric-onset DLB to identify key clinical characteristics and evidence gaps to progress our understanding of this entity.

METHODS

Medline, PubMed and Embase were searched for relevant articles containing longitudinal follow-up of patients initially presenting with a psychiatric illness who subsequently developed DLB according to the diagnostic criteria available at the time.

RESULTS

Two cohort studies (18 and 21 patients) along with 12 case series (13 cases) were identified totalling 52 patients (63% female). Initial psychiatric presentation occurred at a mean of 63 years (range 53-88), with depression being the most frequently reported psychiatric presentation (88%). Psychotic presentations were less common on presentation (11%) but became more prevalent throughout the prodromal period before the diagnosis of DLB (83%). Relapses of the psychiatric disease were common occurring in 94% (32/34) of patients. Parkinsonism, cognitive fluctuations, visual hallucinations, and REM sleep behaviour disorder were uncommonly reported at initial presentation (3.8%).

CONCLUSIONS

Psychiatric-onset DLB is characterized by a female predominant relapsing-remitting psychiatric illness presenting with affective symptoms but later developing psychotic features prior to the onset of DLB. Additional prospective studies including other neurodegenerative cohorts with harmonised assessments are required to inform definitive diagnostic criteria for this condition.

Mitochondrial function-associated genes underlie cortical atrophy in prodromal synucleinopathies

Isolated rapid eye movement sleep behaviour disorder (iRBD) is a sleep disorder characterized by the loss of rapid eye movement sleep muscle atonia and the appearance of abnormal movements and vocalizations during rapid eye movement sleep. It is a strong marker of incipient synucleinopathy such as dementia with Lewy bodies and Parkinson's disease. Patients with iRBD already show brain changes that are reminiscent of manifest synucleinopathies including brain atrophy. However, the mechanisms underlying the development of this atrophy remain poorly understood. In this study, we performed cutting-edge imaging transcriptomics and comprehensive spatial mapping analyses in a multicentric cohort of 171 polysomnography-confirmed iRBD patients [67.7 ± 6.6 (49-87) years; 83% men] and 238 healthy controls [66.6 ± 7.9 (41-88) years; 77% men] with T1-weighted MRI to investigate the gene expression and connectivity patterns associated with changes in cortical thickness and surface area in iRBD. Partial least squares regression was performed to identify the gene expression patterns underlying cortical changes in iRBD. Gene set enrichment analysis and virtual histology were then done to assess the biological processes, cellular components, human disease gene terms, and cell types enriched in these gene expression patterns. We then used structural and functional neighbourhood analyses to assess whether the atrophy patterns in iRBD were constrained by the brain's structural and functional connectome. Moreover, we used comprehensive spatial mapping analyses to assess the specific neurotransmitter systems, functional networks, cytoarchitectonic classes, and cognitive brain systems associated with cortical changes in iRBD. All comparisons were tested against null models that preserved spatial autocorrelation between brain regions and compared to Alzheimer's disease to assess the specificity of findings to synucleinopathies. We found that genes involved in mitochondrial function and macroautophagy were the strongest contributors to the cortical thinning occurring in iRBD. Moreover, we demonstrated that cortical thinning was constrained by the brain's structural and functional connectome and that it mapped onto specific networks involved in motor and planning functions. In contrast with cortical thickness, changes in cortical surface area were related to distinct genes, namely genes involved in the inflammatory response, and to different spatial mapping patterns. The gene expression and connectivity patterns associated with iRBD were all distinct from those observed in Alzheimer's disease. In summary, this study demonstrates that the development of brain atrophy in synucleinopathies is constrained by specific genes and networks.

Dystonia and Parkinson's disease: Do they have a shared biology?

Parkinsonism and dystonia co-occur across many movement disorders and are most encountered in the setting of Parkinson's disease. Here we aim to explore the shared neurobiological underpinnings of dystonia and parkinsonism through the clinical lens of the conditions in which these movement disorders can be seen together. Foregrounding the discussion, we briefly review the circuits of the motor system and the neuroanatomical and neurophysiological aspects of motor control and highlight their relevance to the proposed pathophysiology of parkinsonism and dystonia. Insight into shared biology is then sought from dystonia occurring in PD and other forms of parkinsonism including those disorders in which both can be co-expressed simultaneously. We organize these within a biological schema along with important questions to be addressed in this space.

‘Where there's smoke’: longitudinal cognitive disintegration after postoperative delirium?

Postoperative delirium is an important complication of surgery and is associated with poor long-term cognitive outcomes, although the neural basis underlying this relationship is poorly understood. Neuroimaging studies and network-based approaches play an important role in our understanding of the mechanism by which delirium relates to longitudinal cognitive decline. A recent resting state functional MRI study is reviewed, which shows reduced global connectivity up to 3 months after delirium, supporting recent models of delirium and opening the door for applying this approach to understanding the complex inter-relationship between delirium and dementia.

Motor cortical excitability and pre-supplementary motor area neurochemistry in healthy adults with substantia nigra hyperechogenicity

Substantia nigra (SN) hyperechogenicity, viewed with transcranial ultrasound, is a risk marker for Parkinson's disease. We hypothesized that SN hyperechogenicity in healthy adults aged 50-70 years is associated with reduced short-interval intracortical inhibition in primary motor cortex, and that the reduced intracortical inhibition is associated with neurochemical markers of activity in the pre-supplementary motor area (pre-SMA). Short-interval intracortical inhibition and intracortical facilitation in primary motor cortex was assessed with paired-pulse transcranial magnetic stimulation in 23 healthy adults with normal (n = 14; 61 ± 7 yrs) or abnormally enlarged (hyperechogenic; n = 9; 60 ± 6 yrs) area of SN echogenicity. Thirteen of these participants (7 SN- and 6 SN+) also underwent brain magnetic resonance spectroscopy to investigate pre-SMA neurochemistry. There was no relationship between area of SN echogenicity and short-interval intracortical inhibition in the ipsilateral primary motor cortex. There was a significant positive relationship, however, between area of echogenicity in the right SN and the magnitude of intracortical facilitation in the right (ipsilateral) primary motor cortex (p = .005; multivariate regression), evidenced by the amplitude of the conditioned motor evoked potential (MEP) at the 10-12 ms interstimulus interval. This relationship was not present on the left side. Pre-SMA glutamate did not predict primary motor cortex inhibition or facilitation. The results suggest that SN hyperechogenicity in healthy older adults may be associated with changes in excitability of motor cortical circuitry. The results advance understanding of brain changes in healthy older adults at risk of Parkinson's disease.

Current Insights into the Risks of Using Melatonin as a Treatment for Sleep Disorders in Older Adults

Exogenous melatonin is commonly used for sleep disorders in older adults, and its use is increasing over time. It appears to have modest efficacy in treating insomnia and circadian rhythm sleep-wake disorders. Melatonin is commonly perceived to be a safe alternative to other hypnotics and is available without prescription in some jurisdictions. New evidence suggests that endogenous melatonin has pleomorphic effects on multiple organ systems, many of which are poorly understood. This narrative review summarizes the current evidence regarding the safety of melatonin in older adults (defined by age over 65 years). Melatonin appears to have a favorable safety profile in this population, however there is a dearth of evidence regarding the safety of prolonged use. There are several factors which increase the risk of adverse effects of melatonin in older adults, and these should be taken into consideration when prescribing to this population.

0633 The relationship between sleep and Parkinson's disease progression: A Mendelian Randomization study

Introduction

Sleep disturbances and disorders are common in Parkinson’s disease and significantly impact quality of life. Often, such sleep disturbances are considered sequelae of neurodegeneration affecting sleep-wake circuitry. However, there is emerging evidence that sleep disturbance may itself play a causal role in neurodegenerative processes via altered clearance of pathological proteins. Whether sleep disturbance affects the pathological progression of Parkinson’s disease is unknown. Recently, a several genetic variants have been discovered for sleep-related parameters through genome-wide association studies (GWAS) providing a unique opportunity to examine the evidence for causal relationships through the use of the Mendelian randomization.

Methods

To elucidate the causality between sleep disorders and progression of Parkinson’s disease, we performed two sample Mendelian randomization analysis using genetic variants identified from publicly available GWAS data for sleep variables including insomnia, sleep duration, chronotype, napping and daytime sleepiness as exposure variables. Outcome measures were derived from a large collective GWAS of PD progression (N=4093 cases) including the Unified Parkinson’s disease rating scale (UPDRS total and UPDRS- III), motor fluctuations, Age of onset of PD (PD-AOO), Mini-mental state examination (MMSE) and Montreal Cognitive Assessment (MOCA). The robustness of results was examined using conventional Mendelian randomization sensitivity analyses.

Results

Genetic liability to increased sleep duration was associated with a lower rate of progression of motor symptoms in PD using UPDRS-III score. Meanwhile insomnia was associated with increased rate of motor progression of PD. Predisposition to daytime sleep was associated with lower rates of progression of cognitive decline in PD measured using MMSE. No robust relationships were determined between markers of progression and chronotype or daytime napping. Statistical measures showed significant pleiotropy for the relationships identified.

Conclusion

Sleep-related variables may have a deterministic role in the clinical progression in Parkinson’s disease and may represent a modifiable target for altering the trajectory of neurodegeneration.

Support (If Any)

 

An adaptive measure of visuospatial impairment in Dementia with Lewy Bodies

Background

Dementia with Lewy bodies (DLB) is a common cause of dementia with poor prognosis and high hospitalization rates. DLB is frequently misdiagnosed, with clinical features that overlap significantly with other diseases including Parkinson's disease (PD). Clinical instruments that discriminate and track the progression of cognitive impairment in DLB are needed.

Objectives

The current study was designed to assess the utility of a mental rotation (MR) task for assessing visuospatial impairments in early DLB.

Methods

Accuracy of 22 DLB patients, 22 PD patients and 22 age‐matched healthy controls in the MR task were compared at comparing shapes with 0°, 45° and 90° rotations.

Results

Healthy controls and PD patients performed at similar levels while the DLB group were significantly impaired. Further, impairment in the visuospatial and executive function measures correlated with MR poor outcomes.

Conclusion

These findings support the MR task as an objective measure of visuospatial impairment with the ability to adjust difficulty to suit impairments in a DLB population. This would be a useful tool within clinical trials.

Brain atrophy in prodromal synucleinopathy is shaped by structural connectivity and gene expression

Isolated REM sleep behaviour disorder (iRBD) is a synucleinopathy characterized by abnormal behaviours and vocalizations during REM sleep. Most iRBD patients develop dementia with Lewy bodies, Parkinson's disease, or multiple system atrophy over time. Patients with iRBD exhibit brain atrophy patterns that are reminiscent of those observed in overt synucleinopathies. However, the mechanisms linking brain atrophy to the underlying alpha-synuclein pathophysiology are poorly understood. Our objective was to investigate how the prion-like and regional vulnerability hypotheses of alpha-synuclein might explain brain atrophy in iRBD. Using a multicentric cohort of 182 polysomnography-confirmed iRBD patients who underwent T1-weighted MRI, we performed vertex-based cortical surface and deformation-based morphometry analyses to quantify brain atrophy in patients (67.8 years, 84% men) and 261 healthy controls (66.2 years, 75%) and investigated the morphological correlates of motor and cognitive functioning in iRBD. Next, we applied the agent-based Susceptible-Infected-Removed model (i.e., a computational model that simulates in silico the spread of pathologic alpha-synuclein based on structural connectivity and gene expression) and tested if it recreated atrophy in iRBD by statistically comparing simulated regional brain atrophy to the atrophy observed in patients. The impact of SNCA and GBA gene expression and brain connectivity was then evaluated by comparing the model fit to the one obtained in null models where either gene expression or connectivity was randomized. The results showed that iRBD patients present with cortical thinning and tissue deformation, which correlated with motor and cognitive functioning. Next, we found that the computational model recreated cortical thinning (r = 0.51, p = 0.0007) and tissue deformation (r = 0.52, p = 0.0005) in patients, and that the connectome's architecture along with SNCA and GBA gene expression contributed to shaping atrophy in iRBD. We further demonstrated that the full agent-based model performed better than network measures or gene expression alone in recreating the atrophy pattern in iRBD. In summary, atrophy in iRBD is extensive, correlates with motor and cognitive function, and can be recreated using the dynamics of agent-based modelling, structural connectivity, and gene expression. These findings support the concepts that both prion-like spread and regional susceptibility account for the atrophy observed in prodromal synucleinopathies. Therefore, the agent-based Susceptible-Infected-Removed model may be a useful tool for testing hypotheses underlying neurodegenerative diseases and new therapies aimed at slowing or stopping the spread of alpha-synuclein pathology.

Narrow doorways alter brain connectivity and step patterns in isolated REM sleep behaviour disorder

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iRBD had slower and more variable stepping compared to controls in this VR task.

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iRBD showed exaggerated responses when passing narrow compared to wide doorways iRBD had altered task-related brain connectivity which was correlated to motor deficits.

Background

Motor impairments in those with isolated REM sleep behaviour disorder (iRBD) significantly increases the likelihood of developing Lewy body disease (e.g. Parkinson’s disease and Dementia with Lewy Bodies).

Objective

This study sought to explore the prodromal process of neurodegeneration by examining the neural signature underlying motor deficits in iRBD patients.

Methods

A virtual reality (VR) gait paradigm (which has previously been shown to elicit adaptive changes in gait performance whilst navigating doorways in Parkinson’s Disease - PD) was paired with fMRI to investigate whether iRBD patients demonstrated worsened motor performance and altered connectivity across frontoparietal, motor and basal ganglia networks compared to healthy controls. Forty participants (23 iRBD and 17 healthy controls) completed the virtual reality gait task whilst in the MRI scanner, and an additional cohort of 19 Early PD patients completed the behavioural virtual reality gait task.

Results

As predicted, iRBD patients demonstrated slower and more variable stepping compared to healthy control participants and demonstrated an exaggerated response when navigating narrow compared to wide doorways, a phenomenon characteristically seen in PD. The iRBD patients also demonstrated less BOLD signal change in the left posterior putamen and right mesencephalic locomotor region, as well as reduced functional connectivity between the frontoparietal network and the motor network, when navigating narrow versus wide doorways compared to healthy control participants.

Conclusions

Taken together, this study demonstrates that iRBD patients have altered task-related brain connectivity, which may represent the neural underpinnings of early motor impairments that are evident in iRBD.

Dynamic network impairments underlie cognitive fluctuations in Lewy body dementia

Cognitive fluctuations are a characteristic and distressing disturbance of attention and consciousness seen in patients with Dementia with Lewy bodies and Parkinson's disease dementia. It has been proposed that fluctuations result from disruption of key neuromodulatory systems supporting states of attention and wakefulness which are normally characterised by temporally variable and highly integrated functional network architectures. In this study, patients with DLB (n = 25) and age-matched controls (n = 49) were assessed using dynamic resting state fMRI. A dynamic network signature of reduced temporal variability and integration was identified in DLB patients compared to controls. Reduced temporal variability correlated significantly with fluctuation-related measures using a sustained attention task. A less integrated (more segregated) functional network architecture was seen in DLB patients compared to the control group, with regions of reduced integration observed across dorsal and ventral attention, sensorimotor, visual, cingulo-opercular and cingulo-parietal networks. Reduced network integration correlated positively with subjective and objective measures of fluctuations. Regions of reduced integration and unstable regional assignments significantly matched areas of expression of specific classes of noradrenergic and cholinergic receptors across the cerebral cortex. Correlating topological measures with maps of neurotransmitter/neuromodulator receptor gene expression, we found that regions of reduced integration and unstable modular assignments correlated significantly with the pattern of expression of subclasses of noradrenergic and cholinergic receptors across the cerebral cortex. Altogether, these findings demonstrate that cognitive fluctuations are associated with an imaging signature of dynamic network impairment linked to specific neurotransmitters/neuromodulators within the ascending arousal system, highlighting novel potential diagnostic and therapeutic approaches for this troubling symptom.

The ascending arousal system promotes optimal performance through mesoscale network integration in a visuospatial attentional task

Previous research has shown that the autonomic nervous system provides essential constraints over ongoing cognitive function. However, there is currently a relative lack of direct empirical evidence for how this interaction manifests in the brain at the macroscale level. Here, we examine the role of ascending arousal and attentional load on large-scale network dynamics by combining pupillometry, functional MRI, and graph theoretical analysis to analyze data from a visual motion-tracking task with a parametric load manipulation. We found that attentional load effects were observable in measures of pupil diameter and in a set of brain regions that parametrically modulated their BOLD activity and mesoscale network-level integration. In addition, the regional patterns of network reconfiguration were correlated with the spatial distribution of the α2a adrenergic receptor. Our results further solidify the relationship between ascending noradrenergic activity, large-scale network integration, and cognitive task performance.

Progression of Clinical Features in Lewy Body Dementia Can Be Detected Over 6 Months

OBJECTIVE

This study aimed to quantify the trajectory and magnitude of change of the key clinical features and corresponding symptom domains of dementia with Lewy bodies (DLB) and Parkinson disease dementia (PDD), including global cognition, parkinsonism, recurrent visual hallucinations, cognitive fluctuations, and sleep disturbance.

METHODS

One hundred sixteen patients with Lewy body dementia (DLB = 72, PDD = 44) underwent assessment at baseline and 3 and 6 months as part of a prospective multicenter randomized controlled trial. Linear mixed models were constructed for core outcome measures using the Mini-Mental State Examination (MMSE), motor section of the Unified Parkinson's Disease Rating Scale (UPDRS-III), Dementia Cognitive Fluctuations Scale (DCFS), and Neuropsychiatric Inventory (NPI).

RESULTS

Within the time frame of our study (6 months), we were able to identify a significant cognitive decline of 1.3 points on the MMSE (p = 0.002) and significant worsening of motor parkinsonism with an increase in UPDRS-III score of 3.2 points (p = 0.018). Fluctuation severity also increased using the DCFS with a 6-month change in score of 1.3 points (p = 0.001). Uniquely, a signal for increased severity of sleep symptoms of 1.2 points (NPI-sleep) was also detectable (p = 0.04). Significant changes in neuropsychiatric symptoms were not detected. There was no difference in rates of change of scores between DLB and PDD.

DISCUSSION

Clinically significant rates of change in core clinical features can be detected and quantified in Lewy body dementia over a relatively short period (6 months) using common clinical instruments and thus may be useful as clinical endpoints for therapeutic trials of disease-modifying and symptomatic agents.

Clinical Teacher Training for health professionals: From blended to online and (maybe) back again?

BACKGROUND

The Clinical Teacher Training (CTT) programme was originally developed as an interprofessional, blended learning programme, to support health professionals working across health services within Australia, although it has also been delivered internationally. With the disruption of COVID-19, we rapidly moved to 'online only' delivery. We sought to modify the programme, ensuring that the constructivist paradigms important for our learner experience through the original blended format were maintained in the online platform.

APPROACH

Consisting of 10 modules on a range of topics, the new CTT online only programme was facilitated online across 6 weeks with asynchronous and synchronous assessable activities, and provision of peer and facilitator feedback. The learning outcomes for each module were similar to the 'blended learning' format. The new programme was delivered three times throughout 2020 and completed by a total of 208 health professionals from across 10 metropolitan and rural health districts.

EVALUATION

The focus of our evaluation was on the programme's final 2020 iteration, for which we had ethics approval. Participants (n = 59) were from diverse health professions, across five metropolitan and rural health districts. We prioritised the learner experience in constructing our evaluation strategy. Quantitative and qualitative data were collected by post-course questionnaire and analysed using descriptive statistics and thematic analysis. Twenty participants (34%) responded to the post-course questionnaire. Participants valued the structure, topics, clear outcomes, timeframe, online resources, small group activities, feedback and the flexibility and accessibility afforded by online only delivery. However, participants identified a need for additional 'real-time' engagement in activities. Faculty were surprised by the time required to adequately facilitate online learning, and similarly, valued the real-time interactions.

IMPLICATIONS

The online only CTT programme provided an excellent, scalable framework to ensure continued provision of a relevant and accessible training resource for clinicians working in metropolitan and regional/rural health services. Learner-reported achievement of programme learning outcomes was not negatively impacted by online only delivery. Balancing these resource advantages with learner preferences and our desire to build active teaching networks, we will continue to host the majority of the programme online, while offering short face-to-face sessions within local contexts.

Scaffolding medical student knowledge and skills: team-based learning (TBL) and case-based learning (CBL)

BACKGROUND

Two established small-group learning paradigms in medical education include Case-based learning (CBL) and Team-based learning (TBL). Characteristics common to both pedagogies include the use of an authentic clinical case, active small-group learning, activation of existing knowledge and application of newly acquired knowledge. However, there are also variances between the two teaching methods, and a paucity of studies that consider how these approaches fit with curriculum design principles. In this paper we explore student and facilitator perceptions of the two teaching methods within a medical curriculum, using Experience based learning (ExBL) as a conceptual lens.

METHODS

A total of 34/255 (13%) Year 2 medical students completed four CBLs during the 2019 Renal and Urology teaching block, concurrent to their usual curriculum activities, which included weekly TBLs. Questionnaires were distributed to all students (n = 34) and CBL facilitators (n = 13). In addition, all students were invited to attend focus groups. Data were analysed using descriptive statistics and thematic analysis.

RESULTS

In total, 23/34 (71%) of students and 11/13 (85%) of facilitators completed the questionnaires. Twelve students (35%) participated in focus groups. Findings indicate their experience in CBL to be positive, with many favourable aspects that built on and complemented their TBL experience that provided an emphasis on the basic sciences. The learning environment was enriched by the CBL framework that allowed application of knowledge to solve clinical problems within the small groups with consistent facilitator guidance and feedback, their capacity to focus discussion, and associated efficiencies in learning.

CONCLUSION

While the TBL model was integral in developing students' knowledge and understanding of basic science concepts, the CBL model was integral in developing students' clinical reasoning skills. The strengths of CBL relative to TBL included the development of authentic clinical reasoning skills and guided facilitation of small group discussion. Our findings suggest that delivery of a medical curriculum may be enhanced through increased vertical integration, applying TBL in earlier phases of the medical program where the focus is on basic science principles, with CBL becoming more relevant as students move towards clinical immersion.

Limbic hypoconnectivity in idiopathic REM sleep behaviour disorder with impulse control disorders

INTRODUCTION

Current neuroimaging research has revealed several brain alterations in idiopathic REM sleep behaviour disorder (iRBD) that mirror and precede those reported in PD. However, none have specifically addressed the presence of changes across the reward system, and their role in the emergence of impulse control disorders (ICDs). We aimed to compare the volumetric and functional connectivity characteristics of the reward system in relation to the psychobehavioral profile of patients with iRBD versus healthy controls and PD patients.

METHODS

Twenty patients with polysomnography confirmed iRBD along with 17 PD patients and 14 healthy controls (HC) underwent structural and functional resting-state brain MRI analysis. Participants completed the questionnaire for impulsive-compulsive disorders in PD (QUIP), the short UPPS-P impulsive behaviour scale, as well as neuropsychological testing of cognitive function.

RESULTS

A higher percentage of iRBD patients reported hypersexuality, compared to HC and PD (p = 0.008). Whole-brain and striatal voxel-based morphometry analyses showed no significant clusters of reduced grey matter volume between groups. However, iRBD compared to HC demonstrated functional hypoconnectivity between the limbic striatum and temporo-occipital regions. Furthermore, the presence of ICDs correlated with hypoconnectivity between the limbic striatum and clusters located in cuneus, lingual and fusiform gyrus.

CONCLUSION

Altered functional connectivity between the limbic striatum and posterior cortical regions was associated with increased hypersexuality in iRBD. It is possible that this change may ultimately predispose individuals to the emergence of ICDs when they receive dopaminergic medications, after transitioning to PD.

Current Concepts and Controversies in the Management of REM Sleep Behavior Disorder

Rapid eye movement (REM) sleep behavior disorder (RBD) is characterized by dream enactment and the loss of muscle atonia during REM sleep, known as REM sleep without atonia (RSWA). RBD can result in significant injuries, prompting patients to seek medical attention. However, in others, it may present only as non-violent behaviors noted as an incidental finding during polysomnography (PSG). RBD typically occurs in the context of synuclein-based neurodegenerative disorders but can also be seen accompanying brain lesions and be exacerbated by medications, particularly antidepressants. There is also an increasing appreciation regarding isolated or idiopathic RBD (iRBD). Symptomatic treatment of RBD is a priority to prevent injurious complications, with usual choices being melatonin or clonazepam. The discovery that iRBD represents a prodromal stage of incurable synucleinopathies has galvanized the research community into delineating the pathophysiology of RBD and defining biomarkers of neurodegeneration that will facilitate future disease-modifying trials in iRBD. Despite many advances, there has been no progress in available symptomatic or neuroprotective therapies for RBD, with recent negative trials highlighting several challenges that need to be addressed to prepare for definitive therapeutic trials for patients with this disorder. These challenges relate to i) the diagnostic and screening strategies applied to RBD, ii) the limited evidence base for symptomatic therapies, (iii) the existence of possible subtypes of RBD, (iv) the relevance of triggering medications, (v) the absence of objective markers of severity, (vi) the optimal design of disease-modifying trials, and vii) the implications around disclosing the risk of future neurodegeneration in otherwise healthy individuals. Here, we review the current concepts in the therapeutics of RBD as it relates to the above challenges and identify pertinent research questions to be addressed by future work.

Evaluating a novel behavioral paradigm for visual hallucinations in Dementia with Lewy bodies

The aim of this study was to evaluate the utility of the Bistable Percept Paradigm (BPP), a computerised behavioural task that has previously been utilised for the assessment of visual hallucinations in Parkinson's Disease, in a Dementia with Lewy bodies (DLB) cohort. Dementia with Lewy bodies patients demonstrated poorer performance than healthy controls (HC) on the BPP with significantly more misperceptions and a greater failure to detect bistable percepts correctly compared to HC. Further, the number of misperceptions was also correlated with the severity of hallucinations. The findings from this study demonstrate that the BPP is a viable tool to measure misperceptions in DLB patients.

Treating hallucinations in Parkinson's disease

Introduction: Hallucinations in Parkinson's disease are common, can complicate medication management and significantly impact upon the quality of life of patients and their carers.Areas covered: This review aims to examine current evidence for the management of hallucinations in Parkinson's disease.Expert opinion: Treatment of hallucinations in Parkinson's disease should be both individualized and multifaceted. Screening, education, medication review and the avoidance of common triggers are important. For well-formed visual hallucinations, acetylcholinesterase inhibitors are recommended first-line. Refractory or severe symptoms may require the cautious use of atypical antipsychotics. Antidepressants may be beneficial in the appropriate setting. Unfortunately, current therapies for hallucinations offer only limited benefits and future research efforts are desperately required to improve the management of these challenging symptoms.

A Prodromal Brain-Clinical Pattern of Cognition in Synucleinopathies

OBJECTIVE

Isolated (or idiopathic) rapid eye movement sleep behavior disorder (iRBD) is associated with dementia with Lewy bodies (DLB) and Parkinson's disease (PD). Biomarkers are lacking to predict conversion to a dementia or a motor-first phenotype. Here, we aimed at identifying a brain-clinical signature that predicts dementia in iRBD.

METHODS

A brain-clinical signature was identified in 48 patients with polysomnography-confirmed iRBD using partial least squares between brain deformation and 27 clinical variables. The resulting variable was applied to 78 patients with iRBD followed longitudinally to predict conversion to a synucleinopathy, specifically DLB. The deformation scores from patients with iRBD were compared with 207 patients with PD, DLB, or prodromal DLB to assess if scores were higher in DLB compared to PD.

RESULTS

One latent variable explained 31% of the brain-clinical covariance in iRBD, combining cortical and subcortical deformation and subarachnoid/ventricular expansion to cognitive and motor variables. The deformation score of this signature predicted conversion to a synucleinopathy in iRBD (p = 0.036, odds ratio [OR] = 2.249; 95% confidence interval [CI] = 1.053-4.803), specifically to DLB (OR = 4.754; 95% CI = 1.283-17.618, p = 0.020) and not PD (p = 0.286). Patients with iRBD who developed dementia had scores similar to clinical and prodromal patients with DLB but higher scores compared with patients with PD. The deformation score also predicted cognitive performance over 1, 2, and 4 years in patients with PD.

INTERPRETATION

We identified a brain-clinical signature that predicts conversion in iRBD to more severe/dementing forms of synucleinopathy. This pattern may serve as a new biomarker to optimize patient care, target risk reduction strategies, and administer neuroprotective trials. ANN NEUROL 2021;89:341-357.

Evaluating the Sustained Attention Response Task to Quantify Cognitive Fluctuations in Dementia With Lewy Bodies

Cognitive fluctuations (CFs) are a core diagnostic feature of dementia with Lewy bodies (DLB). Detection of CF is still mostly based on subjective reports from the patient or informant; more quantitative measures are likely to improve the accuracy for the diagnosis of DLB. The purpose of the current study is to test whether performance on the Sustained Attention Response Task (SART) could distinguish those patients with DLB with and without CF. Twenty-four patients with DLB were tested on the SART and performance was related to scores on the Clinical Assessment of Fluctuations (CAFs) and One Day Fluctuation Assessment Scale (ODFAS). The number of "misses" made was a significant predictor of their fluctuation severity, attentional performance, disorganized thinking, and language production ratings on the ODFAS. However, measures on the SART did not correlate with measures on the CAF scale. In conclusion, these findings suggest that SART is a feasible measure of sustained attention in this population and has clinical and diagnostic relevance to the measurement of CF, particularly those aspects measured by the ODFAS.

1127 Utility of Quantitative EEG During Sleep as a Potential Biomarker of Lewy Body Disease Progression

Introduction

Sleep disturbances are common among patients with Lewy body disorders. Idiopathic REM sleep behavior disorder (iRBD) has been identified as a prodromal Lewy body condition with a significantly increased risk of conversion to either Parkinson’s disease (PD) or Dementia with Lewy Bodies (DLB). Pathological involvement of thalamic and brainstem structures involved in sleep regulation has been reported in these disorders, especially in later stages. We hypothesized that progression along the Lewy body disease spectrum may be associated with unique changes in spindle density and EEG power spectra during sleep reflecting involvement of these deep brain structures.

Methods

A cross-sectional design was used. 9 polysomnography confirmed iRBD, 18 early PD, 23 DLB and 13 controls underwent overnight polysomnography, neurological and neuropsychological assessment. Power spectrum analysis during NREM and REM sleep was undertaken using a previously validated quantitative EEG algorithm and compared between groups. Following artefact and outlier removal, results were analysed using the Cz derivation. Groups were statistically compared with a non-parametric Jonckheree-Terpstra test for ordered alternatives, controlling for age and sex.

Results

We found a significant and ordered reduction in power in the spindle frequency band (12-15 Hz) in NREM sleep across the Lewy body disease spectrum compared to controls (Controls > iRBD > early PD > DLB; TJT = 521.00, z = -2.902. p<0.001). In REM sleep we found a shift in power to slower frequencies with increased power in the theta (4.5-8 Hz) band in order of disease severity (DLB > early PD > iRBD > Controls; TJT = 950.00, z = 2.253. p=0.024). No differences were found across the other frequency bands in NREM or REM sleep.

Conclusion

There is a significant and progressive reduction in spindle density and corresponding slowing in REM sleep frequencies during sleep with clinical Lewy body staging. Thus, such measures have the potential to be useful biomarkers of progression towards Lewy body dementia from prodromal stages.

Support

This work was supported by a NHMRC Dementia Team Grant (#1095127), the NHMRC Postgraduate Scholarship and the University of Sydney Research Excellence Initiative 2020 grant.

Prevalence and predictors of mood disturbances in idiopathic REM sleep behaviour disorder

Depression and anxiety are commonly associated with synucleinopathies. Mood disturbances have also been reported in patients with idiopathic REM sleep behaviour disorder (iRBD) and are difficult to treat due to exacerbation of sleep symptoms with standard antidepressants. Despite this, detailed prevalence studies of mood symptomatology and contributors to mood disturbances in iRBD are limited. Mood, sleep, autonomic, cognitive and motor symptoms were assessed in 49 well-characterized patients with iRBD using a variety of clinical scales. Spearman correlations, factor analysis and multiple linear regression were used to uncover associations between mood and non-motor and motor symptoms. The prevalence of significant depression was 17.0% and that of anxiety was 14.6% in the iRBD cohort. Age and disease duration were not correlated with these affective symptoms in iRBD patients. We found depression was significantly predicted by the presence and severity of motor, sleep and cognitive symptoms. Anxiety was predicted by the severity of nocturnal and daytime sleep-related symptoms, cognitive symptoms and autonomic symptoms, with a differential effect depending on the questionnaire used. Depression and anxiety are common in iRBD patients and can be significantly explained by specific sets of non-motor and motor symptoms. These associations provide insight into the underlying pathophysiology and emphasize the importance of a holistic approach to mood disturbance in this population, which may circumvent the reliance on pharmacotherapy that can exacerbate dream enactment behaviour.

Interprofessional Team-based Learning: Building Social Capital

Often the first-time health professionals work together is as new graduates, with a paucity of shared learning among the various health disciplines within university curricula. This is largely due to the complexities of delivering interprofessional education (IPE) and the preference of individuals to work within their established silos. With its ability to nurture collaboration among students, there is a developing trend to use team-based learning (TBL) as a teaching method to engage health care students in IPE. Using the conceptual lens of social capital theory, the purpose of this article is to provide readers with an overview and evidence for the use of TBL within the interprofessional health care education setting, highlighting the benefits and challenges.

Assessing the role of nocturnal core body temperature dysregulation as a biomarker of neurodegeneration

The vast majority of patients with idiopathic rapid eye movement sleep behaviour disorder will develop a neurodegenerative α-synuclein-related condition, such as Parkinson's disease or dementia with Lewy bodies. The pathology underlying dream enactment overlaps anatomically with the brainstem regions that regulate circadian core body temperature. Previously, nocturnal core body temperature regulation has been shown to be impaired in Parkinson's disease. However, no study to date has investigated nocturnal core body temperature changes in patients with idiopathic rapid eye movement sleep behaviour disorder, which may prove to be an early objective biomarker for α-synucleinopathies. Ten healthy controls, 15 patients with idiopathic rapid eye movement sleep behaviour disorder, 31 patients with Parkinson's disease and six patients with dementia with Lewy bodies underwent clinical assessment and nocturnal polysomnography with core body temperature monitoring. A validated cosinor method was utilised for core body temperature analysis. No differences in mesor, nadir or time of nadir were observed between groups. However, when compared with healthy controls, the amplitude of the nocturnal core body temperature (mesor minus nadir) was significantly reduced in patients with idiopathic rapid eye movement sleep behaviour disorder, Parkinson's disease with concurrent rapid eye movement sleep behaviour disorder and dementia with Lewy bodies (p < 0.001, p = 0.043 and p = 0.017, respectively). Importantly, this relationship was not seen in those patients with Parkinson's disease without rapid eye movement sleep behaviour disorder. In addition, there was a significant negative correlation between amplitude of the core body temperature and self-reported rapid eye movement sleep behaviour disorder symptoms. Changes in thermoregulatory circadian rhythm may be specifically associated with the pathology underlying rapid eye movement sleep behaviour disorder rather than simply that of α-synucleinopathy. These findings implicate thermoregulatory dysfunction as a potential early biomarker for development of rapid eye movement sleep behaviour disorder-associated neurodegeneration, and suggest that subpopulations with differing pathological underpinnings might exist in Parkinson's disease.

A longitudinal faculty development program: supporting a culture of teaching

BACKGROUND

Recent trends in faculty development demonstrate a shift from short term to long-term programs; formal to informal learning in the workplace; individual to group settings; and from individual support to institutional support. The purpose of this study was to develop and evaluate a one-year Clinical Teaching Fellowship (CTF) program designed to equip early career medical practitioners and basic scientists with necessary skills to facilitate Team-based learning (TBL).

METHODS

The CTF program provided formal training, a choice of informal professional development activities, and practical co-teaching opportunities in TBL. Of the 40 registrants, 31 (78%) completed the program. Data were collected via questionnaire and focus group. Data were analysed using descriptive statistics and framework analysis.

RESULTS

Participants considered the CTF program as relevant to their needs and useful to their career. Learning was enriched through the combination of training, practical teaching experience alongside senior clinical teachers, the multi-disciplinary context of training and co-teaching in TBLs; and the sense of community. Competing clinical responsibilities made it difficult to attend training and TBL teaching.

CONCLUSIONS

The CTF program provided a longitudinal faculty development framework promoting preparation, practice and development of teaching skills. Securing institutional support to invest in the growth and development of early career teachers is essential to sustained innovation and excellence in teaching.

Cognitive fluctuations in Lewy body dementia: towards a pathophysiological framework

Fluctuating cognition is a complex and disabling symptom that is seen most frequently in the context of Lewy body dementias encompassing dementia with Lewy bodies and Parkinson’s disease dementia. In fact, since their description over three decades ago, cognitive fluctuations have remained a core diagnostic feature of dementia with Lewy bodies, the second most common dementia in the elderly. In the absence of reliable biomarkers for Lewy body pathology, the inclusion of such patients in therapeutic trials depends on the accurate identification of such core clinical features. Yet despite their diagnostic relevance, cognitive fluctuations remain poorly understood, in part due to the lack of a cohesive clinical and scientific explanation of the phenomenon itself. Motivated by this challenge, the present review examines the history, clinical phenomenology and assessment of cognitive fluctuations in the Lewy body dementias. Based on these data, the key neuropsychological, neurophysiological and neuroimaging correlates of cognitive fluctuations are described and integrated into a novel testable heuristic framework from which new insights may be gained.

Impaired Color Discrimination-A Specific Marker of Hallucinations in Lewy Body Disorders

There is emerging evidence indicating that color discrimination impairments can predict the development of Lewy body dementia in patients with rapid eye movement sleep behavior disorder, Parkinson disease, and in patients with mild cognitive impairment. Despite this clear relationship, color vision deficits are not seen uniformly in patients with dementia with Lewy bodies (DLB), suggesting a more nuanced association with the underlying neuropathology. Visual hallucinations represent a discriminating feature of DLB, and recent evidence implicates visual pathway dysfunction as a significant contributor to this phenomenon. In this study, we examined the relationship between color vision impairment and visual hallucinations, along with other clinical and neuropsychological features in 24 well-characterized patients with DLB alongside 25 healthy controls. Color discrimination impairment was seen in 16 (67%) of 24 DLB participants with a higher error score relative to controls (P = .001). We demonstrate for the first time a strong association between color discrimination errors on the Farnsworth-Munsell 100 hue test and both the presence and severity of hallucinatory symptoms in DLB based on clinician-derived (P = .008) and questionnaire-derived (P = .03) measures. Correlation with clinical and neuropsychological variables revealed that color discrimination is significantly related to visuospatial difficulties measured by the clock-drawing task (P = .02) but not to global measures of cognition, motor severity, age, or disease duration in our cohort. Factor analysis confirmed a unique relationship between color discrimination, visual hallucinations, and visuospatial function. Our results suggest that color discrimination does not simply relate to dementia but rather indexes higher order perceptual deficits that may predict visual hallucinations in Lewy body disorders and share a common pathophysiological substrate.

095 Predicting parkinson’s and dementia with lewy bodies (pre-D) research study – a sydney-based longitudinal biobanking program

Introduction

Idiopathic REM sleep behaviour(iRBD) disorder represents the most specific prodromal marker of an impending synucleinopathy with over 90% developing either Parkinson’s disease(PD), Dementia with Lewy Bodies(DLB) or Multiple System Atrophy(MSA) after 15 years. This finding has stimulated efforts to actively register and track progression of such patients. Here we present experience of a biobanking program established with the aim of identifying prodromal synucleinopathies to facilitate recruitment to neuroprotective trials as they become available.

Methods

Patients with iRBD were prospectively and sequentially recruited. Cross-sectional comparator groups consisting of healthy controls, idiopathic PD (within 5 years of diagnosis) and DLB were also recruited. Patients underwent a standardized assessment protocol including clinical phenotyping, neuropsychometric testing, multimodal MRI, polysomnography, quantitative electroencephalography, chronobiology (melatonin and clock gene expression profiling) and gait testing. Subjects were invited for annual and biennial review.

Results

102 patients have been recruited into the study since July 2016 including 35 patients with iRBD, 26 DLB, 19 early PD and 16 controls. 15 patients have returned for follow-up with 3 converting to a synucleinopathy(2 DLB, 1 PD). 75% of participants were able to complete all elements of assessment protocol. Preliminary evaluation of iRBD participants reveals early changes in clock gene expression(BMAL1) and subtle changes in patterns of gait compared to older controls.

Conclusions

Our preliminary findings demonstrate utility and feasibility of a prodromal biobanking program within the Australian context aimed at identifying prodromal synucleinopathies. Similar models can be applied to other centers to improve access and create an extended national collaborative network.

001 Altered interval timing as a novel marker of cognitive fluctuations in lewy body dementia

Introduction

Cognitive fluctuations are a core clinical feature of Dementia with Lewy Bodies(DLB), characterized by marked spontaneous variations in cognitive abilities and alertness. There is a paucity of objective measurements of fluctuations in the clinical setting. Altered time awareness represents a potential clinical marker of fluctuations and/or their severity. In this study we aimed to investigate qualities of interval timing in patients with DLB.

Methods

25 patients with probable DLB and 14 older controls underwent testing using a simple time perception paradigm testing probing different aspects of interval timing including time estimation(retrospective estimation of interval length),time production(prospective determination of an interval) and time pacing(explicit timing of an interval).Intervals of 10 to 90s were randomized between trials.Self/carer-reporting of fluctuations were measured using the clinician assessment of fluctuation(CAF) and one-day fluctuation(OFS) scales.

Results

We found significant differences in interval timing between controls and DLB for time estimation and time production. Overall, DLB patients estimated less time which was significant at 90 seconds(proportion of interval=0.92 vs 0.69; p=0.03). DLB produced less time(proportion of 90s interval 0.58 vs 1.0; p<0.001). Errors in time estimation at 90 seconds correlated with fluctuation presence according to the CAF(r­=0.47;p=0.009) whilst errors in time pacing at 90s correlated strongest with fluctuation severity according to the OFS(r=0.65,p<0.001). ROC analysis identified time production(90s) as a good test to distinguish DLB from controls (AUC=0.8;95%CI:0.75–0.98).

Conclusion

We demonstrate objective evidence for altered temporal processing in DLB and suggest abnormal interval timing as a novel and clinically useful bedside marker of cognitive fluctuations.

060 Impaired color discrimination is associated with hallucinations in dementia with lewy bodies

Introduction

Emerging evidence indicates that color discrimination impairments can predict the development of dementia across a range of prodromal Lewy body conditions. However, color vision deficits are not seen uniformly in patients with Dementia with Lewy Bodies (DLB), suggesting a more nuanced association. Visual hallucinations(VH) represent a discriminating feature of DLB, and recent evidence implicates visual pathway dysfunction as a significant contributor to this phenomenon. We therefore hypothesized that color impairment will more closely associate with VH in DLB rather than general cognition.

Methods

In this study, we examined the relationship between color vision impairment and VH, along with other clinical and neuropsychological features in 24 patients with DLB alongside 25 age-matched controls. Color discrimination was assessed using the Farnsworth-Munsell-100 Hue (FM-100) test.

Results

Color discrimination impairment was seen in 16/24 DLB participants (67%) with a higher error score relative to controls(p=0.001). We demonstrate for the first time a strong association between color discrimination errors and both the presence and severity of VH in DLB based on clinician-derived(p=0.008) and questionnaire-derived(p=0.03) measures. Correlation with clinical and neuropsychological variables revealed that color discrimination is significantly related to visuospatial impairment(p=0.02) but not to global measures of cognition, motor severity, age or disease duration. Factor analysis confirmed a unique relationship between color discrimination, visual hallucinations and visuospatial function.

Conclusion

Our results suggest that color impairments may be a specific biomarker of visual hallucinations and associated visuoperceptual deficits in evolving Lewy body disorders rather than dementia per se and thus providing insight into a shared pathophysiological substrate.

093 How to diagnose lewy body dementia? Prevalence and underlying relationship between clinical and neuropsychological features of DLB

Introduction

Despite its importance for management, prognostication and selection of patients for clinical trials, the diagnosis of Dementia with Lewy Bodies (DLB) remains challenging. Complicating this is a recent change in the diagnostic criteria which has arguably shifted the expected phenotype of DLB patients. In this study we aimed to characterize and examine the relationship between cognitive and clinical diagnostic variables in DLB patients to uncover latent symptom clusters that may streamline future diagnostic approaches in the clinic.

Methods

The clinical and neuropsychological profile of 27 prospectively recruited participants diagnosed with probable DLB and 25 age-matched controls was characterized according to the most recent consensus criteria.Symptoms were scored using a novel combination of established clinical and research instruments.

Results

We demonstrate comparable sensitivity of formal neuropsychological testing and bedside screening tools (MOCA/MMSE) for identifying domain-specific differences between controls and patients(p<0.001). Optimal sensitivity thresholds for diagnosis of Parkinsonism (88.9%) were explored yielding a prevalence range of 50%-90% within our cohort.Factor analysis using all core and supportive features of the diagnostic criteria identified 6 independent factors accounting for 81% of the total variance. Unique relationships identified included between hallucinations and fluctuations and excessive daytime somnolence; between REM sleep behavior disorder and orthostatic hypotension; and Parkinsonism and urinary disturbance. ‘Prodromal’ symptoms including autonomic and early neuropsychiatric features are represented in the remaining factors.

Conclusion

Parsimonious delineation of clinical variables using identified symptom clusters can aid DLB diagnosis.Clusters are also used to highlight latent pathological relationships. Appropriate instruments and thresholds for detecting dementia and core and suggestive features are presented.

The functional network signature of heterogeneity in freezing of gait

Freezing of gait is a complex, heterogeneous, and highly variable phenomenon whose pathophysiology and neural signature remains enigmatic. Evidence suggests that freezing is associated with impairments across cognitive, motor and affective domains; however, most research to date has focused on investigating one axis of freezing of gait in isolation. This has led to inconsistent findings and a range of different pathophysiological models of freezing of gait, due in large part to the tendency for studies to investigate freezing of gait as a homogeneous entity. To investigate the neural mechanisms of this heterogeneity, we used an established virtual reality paradigm to elicit freezing behaviour in 41 Parkinson's disease patients with freezing of gait and examined individual differences in the component processes (i.e. cognitive, motor and affective function) that underlie freezing of gait in conjunction with task-based functional MRI. First, we combined three unique components of the freezing phenotype: impaired set-shifting ability, step time variability, and self-reported anxiety and depression in a principal components analysis to estimate the severity of freezing behaviour with a multivariate approach. By combining these measures, we were then able to interrogate the pattern of task-based functional connectivity associated with freezing (compared to normal foot tapping) in a sub-cohort of 20 participants who experienced sufficient amounts of freezing during task functional MRI. Specifically, we used the first principal component from our behavioural analysis to classify patterns of functional connectivity into those that were associated with: (i) increased severity; (ii) increased compensation; or (iii) those that were independent of freezing severity. Coupling between the cognitive and limbic networks was associated with 'worse freezing severity', whereas anti-coupling between the putamen and the cognitive and limbic networks was related to 'increased compensation'. Additionally, anti-coupling between cognitive cortical regions and the caudate nucleus were 'independent of freezing severity' and thus may represent common neural underpinnings of freezing that are unaffected by heterogenous factors. Finally, we related these connectivity patterns to each of the individual components (cognitive, motor, affective) in turn, thus exposing latent heterogeneity in the freezing phenotype, while also identifying critical functional network signatures that may represent potential targets for novel therapeutic intervention. In conclusion, our findings provide confirmatory evidence for systems-level impairments in the pathophysiology of freezing of gait and further advance our understanding of the whole-brain deficits that mediate symptom expression in Parkinson's disease.

Subtle gait and balance impairments occur in idiopathic rapid eye movement sleep behavior disorder

BACKGROUND

Although motor abnormalities have been flagged as potentially the most sensitive and specific clinical features for predicting the future progression to Parkinson's disease, little work has been done to characterize gait and balance impairments in idiopathic rapid eye movement sleep behavior disorder (iRBD).

OBJECTIVE

The objective of this study was to quantitatively determine any static balance as well as gait impairments across the 5 independent domains of gait in polysomnography-confirmed iRBD patients using normal, fast-paced, and dual-task walking conditions.

METHODS

A total of 38 participants (24 iRBD, 14 healthy controls) completed the following 5 different walking trials across a pressure sensor carpet: (1) normal pace, (2) fast pace, (3) while counting backward from 100 by 1s, (4) while naming as many animals as possible, (5) while subtracting 7s from 100.

RESULTS

Although no gait differences were found between the groups during normal walking, there were significant differences between groups under the fast-paced and dual-task gait conditions. Specifically, in response to the dual tasking, healthy controls widened their step width without changing step width variability, whereas iRBD patients did not widen their step width but, rather, significantly increased their step width variability. Similarly, changes between the groups were observed during fast-paced walking wherein the iRBD patients demonstrated greater step length asymmetry when compared with controls.

CONCLUSIONS

This study demonstrates that iRBD patients have subtle gait impairments, which likely reflect early progressive degeneration in brainstem regions that regulate both REM sleep and gait coordination. Such gait assessments may be useful as a diagnostic preclinical screening tool for future fulminant gait abnormalities for trials of disease-preventive agents. © 2019 International Parkinson and Movement Disorder Society.

Dopamine depletion alters macroscopic network dynamics in Parkinson's disease

Parkinson's disease is primarily characterized by diminished dopaminergic function; however, the impact of these impairments on large-scale brain dynamics remains unclear. It has been difficult to disentangle the direct effects of Parkinson's disease from compensatory changes that reconfigure the functional signature of the whole brain network. To examine the causal role of dopamine depletion in network-level topology, we investigated time-varying network structure in 37 individuals with idiopathic Parkinson's disease, both ON and OFF dopamine replacement therapy, along with 50 age-matched, healthy control subjects using resting state functional MRI. By tracking dynamic network-level topology, we found that the Parkinson's disease OFF state was associated with greater network-level integration than in the ON state. The extent of integration in the OFF state inversely correlated with motor symptom severity, suggesting that a shift toward a more integrated network topology may be a compensatory mechanism associated with preserved motor function in the dopamine depleted OFF state. Furthermore, we were able to demonstrate that measures of both cognitive and brain reserve (i.e. premorbid intelligence and whole brain grey matter volume) had a positive relationship with the relative increase in network integration observed in the dopaminergic OFF state. This suggests that each of these factors plays an important role in promoting network integration in the dopaminergic OFF state. Our findings provide a mechanistic basis for understanding the Parkinson's disease OFF state and provide a further conceptual link with network-level reconfiguration. Together, our results highlight the mechanisms responsible for pathological and compensatory change in Parkinson's disease.

Identifying the neural correlates of doorway freezing in Parkinson's disease

Freezing of gait (FOG) in Parkinson's disease (PD) is frequently triggered upon passing through narrow spaces such as doorways. However, despite being common the neural mechanisms underlying this phenomenon are poorly understood. In our study, 19 patients who routinely experience FOG performed a previously validated virtual reality (VR) gait paradigm where they used foot-pedals to navigate a series of doorways. Patients underwent testing randomised between both their "ON" and "OFF" medication states. Task performance in conjunction with blood oxygenation level dependent (BOLD) signal changes between "ON" and "OFF" states were compared within each patient. Specifically, as they passed through a doorway in the VR environment patients demonstrated significantly longer "footstep" latencies in the OFF state compared to the ON state. As seen clinically in FOG this locomotive delay was primarily triggered by narrow doorways rather than wide doorways. Functional magnetic resonance imaging revealed that footstep prolongation on passing through doorways was associated with selective hypoactivation in the presupplementary motor area (pSMA) bilaterally. Task-based functional connectivity analyses revealed that increased latency in response to doorways was inversely correlated with the degree of functional connectivity between the pSMA and the subthalamic nucleus (STN) across both hemispheres. Furthermore, increased frequency of prolonged footstep latency was associated with increased connectivity between the bilateral STN. These findings suggest that the effect of environmental cues on triggering FOG reflects a degree of impaired processing within the pSMA and disrupted signalling between the pSMA and STN, thus implicating the "hyperdirect" pathway in the generation of this phenomenon.

LRRK2-mediated Rab10 phosphorylation in immune cells from Parkinson's disease patients

BACKGROUND

Leucine-rich repeat kinase 2 is a potential therapeutic target for the treatment of Parkinson's disease, and clinical trials of leucine-rich repeat kinase 2 inhibitors are in development. The objective of this study was to evaluate phosphorylation of a new leucine-rich repeat kinase 2 substrate, Rab10, for potential use as a target engagement biomarker and/or patient enrichment biomarker for leucine-rich repeat kinase 2 inhibitor clinical trials.

METHODS

Peripheral blood mononuclear cells and neutrophils were isolated from Parkinson's disease patients and matched controls, and treated ex vivo with a leucine-rich repeat kinase 2 inhibitor. Immunoblotting was used to measure levels of leucine-rich repeat kinase 2 and Rab10 and their phosphorylation. Plasma inflammatory cytokines were measured by multiplex enzyme-linked immunosorbent assay.

RESULTS

Mononuclear cells and neutrophils of both controls and Parkinson's disease patients responded the same to leucine-rich repeat kinase 2 inhibitor treatment. Leucine-rich repeat kinase 2 levels in mononuclear cells were the same in controls and Parkinson's disease patients, whereas leucine-rich repeat kinase 2 was significantly increased in Parkinson's disease neutrophils. Rab10 T73 phosphorylation levels were similar in controls and Parkinson's disease patients and did not correlate with leucine-rich repeat kinase 2 levels. Immune-cell levels of leucine-rich repeat kinase 2 and Rab10 T73 phosphorylation were associated with plasma inflammatory cytokine levels.

CONCLUSIONS

Rab10 T73 phosphorylation appears to be a valid target engagement biomarker for potential use in leucine-rich repeat kinase 2 inhibitor clinical trials. However, a lack of association between leucine-rich repeat kinase 2 and Rab10 phosphorylation complicates the potential use of Rab10 phosphorylation as a patient enrichment biomarker. Although replication is required, increased leucine-rich repeat kinase 2 levels in neutrophils from Parkinson's disease patients may have the potential for patient stratification. leucine-rich repeat kinase 2 activity in peripheral immune cells may contribute to an inflammatory phenotype. © 2018 International Parkinson and Movement Disorder Society.

025 The neural correlates of doorway freezing in parkinson’s disease

Introduction

Freezing of gait (FOG) in Parkinson’s disease (PD) is a disabling symptom of advanced PD and is frequently triggered upon passing through narrow spaces such as doorways.1 Despite being common, the mechanisms underlying this phenomenon are poorly understood. We have previously shown that increased footstep latency in a virtual reality (VR) environment is a surrogate measure of FOG.2 In this study we aimed to model doorway freezing utilising the VR paradigm in conjunction with functional magnetic resonance imaging (fMRI) to determine the neural correlates of this phenomenon.

Methods

In our study, nineteen patients who routinely experience FOG performed a previously validated VR gait paradigm3 where they used foot-pedals to navigate a series of doorways. Patients underwent testing randomised between both their ‘ON’ and ‘OFF’ medication states. Task performance in conjunction with blood oxygenation level dependent signal changes were compared within each patient.

Results

We were able to reproduce the finding that patients in the OFF state demonstrated significantly longer ‘footstep’ latencies as they passed through a doorway in the VR environment compared to the ON state. As seen clinically with FOG this locomotive delay was primarily triggered by narrow doorways rather than wide doorways. fMRI analysis revealed that doorway-provoked footstep delay was associated with selective hypoactivation in the pre-supplementary motor area (pSMA) bilaterally. Task-based functional connectivity analyses showed that this delay was inversely correlated with the degree of functional connectivity between the pSMA and the subthalamic nucleus (STN) across both hemispheres. Furthermore, increased frequency of prolonged footstep latency was associated with increased connectivity between the bilateral STN.

Conclusion

These findings suggest that the effect of environmental cues on triggering FOG reflects a degree of impaired processing within the pSMA and disrupted signalling between the pSMA and STN, thus implicating the ‘hyperdirect’ pathway in the generation of this phenomenon.

References

. Giladi N, Treves TA, Simon ES, Shabtai H, Orlov Y, Kandinov B, Paleacu D, Korczyn AD. Freezing of gait in patients with advanced Parkinson’s disease. J Neural Transm (Vienna)2001;108:53–61.

. Matar E, Shine JM, Naismith SL, Lewis SJ.Virtual realitywalking and dopamine: opening new doorways to understanding freezing of gait in Parkinson’s disease. J Neurol Sci 2014;344:182–5.

. Shine JM, Matar E, Bolitho SJ, Dilda V, Morris TR, Naismith SL, Moore ST, Lewis SJ. Modelling freezing of gait in Parkinson’s disease with a virtual reality paradigm. Gait Posture2013;38:104–8.

110 Atrophy of the mediodorsal thalamus is associated with visual hallucinations in lewy body diseases

Introduction

Although limbic system dysfunction has been thought to underlie visual hallucinations in patients with Lewy body disorders, neuropathology within thalamic structures subserving limbic functions have not been examined. In this study, we assessed the degree of neuronal degeneration in thalamic regions involved in perceptual integration in patients with Parkinson’s disease (PD), Parkinson’s disease dementia (PDD) and dementia with Lewy bodies (DLB).

Methods

Post-mortem samples were acquired from twenty-four individuals with Lewy body disease (5 PD, 9 PDD, 10 DLB) and 10 age-matched controls. The anterior principal (AP) and mediodorsal (MD) thalamic nuclei were delineated and analysed using stereological and quantitative neuropathological techniques.

Results

Volume loss within the MD nucleus was observed in patients with DLB (31%) and PDD (18%) but not PD compared to controls (ANOVA, p<0.05). The atrophy was significantly greater in those patients with hallucinations than those without (p<0.05). Somal atrophy was seen in all patient groups and did not correlate with volume loss or visual hallucinations. Interestingly, there was no neuronal loss in this region compared to controls in the Lewy body disease groups. Analysis of the AP nucleus revealed similar patterns of volume loss but with somal atrophy only in patients with PDD and DLB. Both these measures did not correlate significantly with visual hallucinations, but was significantly different in patients with dementia compared to PD only and controls (p<0.05).

Conclusion

These results suggest that afferent denervation of the mediodorsal thalamus may contribute to visual hallucinations. This appears to support models that implicate upstream components of the limbic circuitry in the generation of this phenomenon.

REM sleep behaviour disorder: not just a bad dream

Rapid eye movement (REM) sleep behaviour disorder (RBD) is a parasomnia characterised by the loss of the normal atonia during the REM stage of sleep, resulting in overt motor behaviours that usually represent the enactment of dreams. Patients will seek medical attention due to sleep-related injuries or unpleasant dream content. Idiopathic RBD which occurs independently of any other disease occurs in up to 2% of the older population. Meanwhile, secondary RBD is very common in association with certain neurodegenerative conditions. RBD can also occur in the context of antidepressant use, obstructive sleep apnoea and narcolepsy. RBD can be diagnosed with a simple screening question followed by confirmation with polysomnography to exclude potential mimics. Treatment for RBD is effective and involves treatment of underlying causes, modification of the sleep environment, and pharmacotherapy with either clonazepam or melatonin. An important finding in the past decade is the recognition that almost all patients with idiopathic RBD will ultimately go on to develop Parkinson disease or dementia with Lewy bodies. This suggests that idiopathic RBD represents a prodromal phase of these conditions. Physicians should be aware of the risk of phenoconversion. They should educate idiopathic RBD patients to recognise the symptoms of these conditions and refer as appropriate for further testing and enrolment into research trials focused on neuroprotective measures.