Neuroimaging and clinical predictors of fatigue in Parkinson disease

Evaluation of the effect of bilateral subthalamic nucleus deep brain stimulation on fatigue in Parkinson's Disease as measured by the non-motor symptoms scale

BACKGROUND

Fatigue is a common and disabling non-motor symptom (NMS) in Parkinson's disease (PD) patients. However, the effect of subthalamic nucleus (STN) deep brain stimulation (DBS) on fatigue has not been widely studied.

OBJECTIVE

To determine the effect of STN DBS on fatigue in PD patients, measured by the Non-motor symptoms scale (NMSS).

METHODS

Cross-sectional analysis of 50 patients with PD who underwent STN DBS at King's College Hospital and Salford Royal Hospital with fatigue scores (measured by question number 4 from domain 2 (sleep/fatigue) of the NMSS as the primary outcome measure. Secondary outcome measures included the PD Sleep Scale (PDSS), Scales for Outcome in PD (SCOPA)-motor examination, activities of daily living, motor complications, Hoehn and Yahr (HY) stage and changes in Levodopa Equivalent Daily Dose (LEDD).

RESULTS

50 patients with a mean follow-up period of 1.98 ± 1.36 years were studied. Significant improvement in median fatigue scores (4.00 (0.75-9.00) to 1.00 (0.00-4.50); p = .001) was observed. In addition, improvements in question 5 (sleep maintenance and fragmentation; 8.00 (4.00-12.00) to 0.00 (0.00-4.00); p < .001) and in domain 2 total score (sleep/fatigue; 20.00 (8.75-27.25) to 6.00 (0.75-16.00); p < .001) were also significant, together with improvements in NMSS total score, SCOPA scores and HY stage (p ≤ .02). Moreover, LEDD but especially dopamine agonists LEDD was significantly reduced after DBS (310.00 (0.00-480.00) to 150.00 (0.00-300.00); p < .020).

CONCLUSIONS

Even though open label and not using a validated fatigue scale, this observational analysis suggest that fatigue improves significantly after STN DBS with persisting benefits at two years follow-up.

Outcome Measures for Disease-Modifying Trials in Parkinson's Disease: Consensus Paper by the EJS ACT-PD Multi-Arm Multi-Stage Trial Initiative

BACKGROUND

Multi-arm, multi-stage (MAMS) platform trials can accelerate the identification of disease-modifying treatments for Parkinson's disease (PD) but there is no current consensus on the optimal outcome measures (OM) for this approach.

OBJECTIVE

To provide an up-to-date inventory of OM for disease-modifying PD trials, and a framework for future selection of OM for such trials.

METHODS

As part of the Edmond J Safra Accelerating Clinical Trials in Parkinson Disease (EJS ACT-PD) initiative, an expert group with Patient and Public Involvement and Engagement (PPIE) representatives' input reviewed and evaluated available evidence on OM for potential use in trials to delay progression of PD. Each OM was ranked based on aspects such as validity, sensitivity to change, participant burden and practicality for a multi-site trial. Review of evidence and expert opinion led to the present inventory.

RESULTS

An extensive inventory of OM was created, divided into: general, motor and non-motor scales, diaries and fluctuation questionnaires, cognitive, disability and health-related quality of life, capability, quantitative motor, wearable and digital, combined, resource use, imaging and wet biomarkers, and milestone-based. A framework for evaluation of OM is presented to update the inventory in the future. PPIE input highlighted the need for OM which reflect their experience of disease progression and are applicable to diverse populations and disease stages.

CONCLUSION

We present a range of OM, classified according to a transparent framework, to aid selection of OM for disease-modifying PD trials, whilst allowing for inclusion or re-classification of relevant OM as new evidence emerges.

Resting-state fMRI study on drug-naïve early-stage patients with Parkinson's disease and with fatigue

INTRODUCTION

Fatigue is one of the most common and debilitating non-motor symptoms in patients with Parkinson's disease (PD), which could manifest during the early stage of the disease and persist through the disease course. However, the treatment options for fatigue remain limited for patients with PD.

METHODS

Using seed-based resting-state functional magnetic resonance imaging, we explored the fatigue-related functional deficiencies in the anterior caudate nucleus, anterior putamen, and posterior putamen in a cohort of early-stage drug-naïve patients with PD. Thirty-eight patients with PD, 19 with and 19 without fatigue, and 31 matched healthy controls were selected. The fatigue status was defined based on the score obtained from the fatigue severity scale (FSS).

RESULTS

Patients with PD with fatigue exhibited a decreased connectivity in the cerebellar-striatal, cortico-striatal, and mesolimbic-striatal loops. No increased functional connectivity was observed. The abnormal connections of the dorsal striatum subdivisions overlapped to extensive brain regions, including the cerebellum, inferior frontal gyrus, inferior temporal gyrus, lingual gyrus, rolandic operculum, insular, and hippocampus.

CONCLUSIONS

Our findings revealed that the widespread functional deficiency in the striatal-cerebellar-cerebral cortical network may be critical to the pathology underlying fatigue in the early-stage PD. The key feature of fatigue-related connectivity was observed between the caudate nucleus and the cerebellum, which could serve as a potential biomarker or treatment target for fatigue in early-stage patients with PD in future studies.

Identifying trajectories of fatigue in patients with primary mitochondrial disease due to the m.3243A > G variant

Severe fatigue is a common complaint in patients with primary mitochondrial disease. However, less is known about the course of fatigue over time. This longitudinal observational cohort study of patients with the mitochondrial DNA 3243 A>G variant explored trajectories of fatigue over 2 years, and characteristics of patients within these fatigue trajectories. Fifty-three adult patients treated at the Radboud University Medical Center Nijmegen were included. The majority of the patients reported consistent, severe fatigue (41%), followed by patients with a mixed pattern of severe and mild fatigue (36%). Then, 23% of patients reported stable mild fatigue levels. Patients with a stable high fatigue trajectory were characterized by higher disease manifestations scores, more clinically relevant mental health symptoms, and lower psychosocial functioning and quality of life compared to patients reporting stable low fatigue levels. Fatigue at baseline and disease manifestation scores predicted fatigue severity at the 2-year assessment (57% explained variance). This study demonstrates that severe fatigue is a common and stable complaint in the majority of patients. Clinicians should be aware of severe fatigue in patients with moderate to severe disease manifestation scores on the Newcastle Mitochondrial Disease Scale, the high prevalence of clinically relevant mental health symptoms and overall impact on quality of life in these patients. Screening of fatigue and psychosocial variables will guide suitable individualized treatment to improve the quality of life.

Neuroimaging markers of chronic fatigue in older people: a narrative review

BACKGROUND

Chronic fatigue is a common symptom in older adults. Although some studies have attempted to identify the neuronal correlates of fatigue associated with chronic diseases, the scientific evidence is scarce regarding fatigue in older people not suffering from a specific disease.

AIMS

To gather available evidence of neuroimaging studies investigating the associations between fatigue and brain health in older adults out of the context of a specific disease, and to identify potential brain structures associated with this symptom.

METHODS

Studies considering exclusively patients with a specific disease and/or studies focusing on physiological mechanisms of acute fatigue induced by the realization of cognitive and physical tasks were excluded.

RESULTS

Very few studies on the associations of fatigue with neuroimaging markers are currently available. Fatigue was associated with reduced hippocampus volumes and with hippocampal amyloid deposition. Regarding the association between fatigue and the circuit of basal ganglia, putamen and thalamus were associated with physical fatigability, whereas amygdala and thalamus with mental fatigability. Very limited evidence about white matter integrity found that healthy individuals with high levels of fatigue had a greater total volume of leukoaraiosis.

CONCLUSION

This review suggests that hippocampus damage and potentially loss of function in basal ganglia networks could play a role on chronic fatigue during aging. Further studies are needed to assess the associations of fatigue with white matter alterations.

Frontal Transcranial Direct Current Stimulation as a Potential Treatment of Parkinson's Disease-Related Fatigue

In contrast to motor symptoms, non-motor symptoms in Parkinson’s disease (PD) are often poorly recognized and inadequately treated. Fatigue is one of the most common non-motor symptoms in PD and affects a broad range of everyday activities, causes disability, and substantially reduces the quality of life. It occurs at every stage of PD, and once present, it often persists and worsens over time. PD patients attending the 2013 World Parkinson Congress voted fatigue as the leading symptom in need of further research. However, despite its clinical significance, little progress has been made in understanding the causes of Parkinson’s disease-related fatigue (PDRF) and developing effective treatment options, which argues strongly for a greater effort. Transcranial direct current stimulation (tDCS) is a technique to non-invasively modulate cortical excitability by delivering low electrical currents to the cerebral cortex. In the past, it has been consistently evidenced that tDCS has the ability to induce neuromodulatory changes in the motor, sensory, and cognitive domains. Importantly, recent data present tDCS over the frontal cortex as an effective therapeutic option to treat fatigue in patients suffering from multiple sclerosis (MS). The current opinion paper reviews recent data on PDRF and the application of tDCS for the treatment of fatigue in neuropsychiatric disorders to further develop an idea of using frontal anodal tDCS as a potential therapeutic strategy to alleviate one of the most common and severe non-motor symptoms of PD.

Fatigue in hypokinetic, hyperkinetic, and functional movement disorders

The emerging science of fatigue has soundly endorsed the need for its unified definition, shared terminology and increased recognition in neurological illnesses. Nevertheless, the real impact of fatigue remains under-recognized. Fatigue describes a sense of tiredness, lack of energy or need for increased effort often perceived as overwhelming, pervasive, and disabling. It is a common feature of chronic medical conditions and neurological diseases, including Parkinson's disease (PD) and other hypokinetic, hyperkinetic, and functional movement disorders (FMD). While there is solid evidence for the burden of fatigue in PD, knowledge of fatigue in other movement disorders (MDS) is still limited. Lack of consensus definition, rigorous measures and the high prevalence of potential confounders such as apathy, depression and sleepiness are the main obstacles in studying fatigue in MDS. This review of the prevalence, impact, and clinical correlates of fatigue in common MDS summarizes current hypotheses for the pathophysiological mechanisms underlying fatigue and gives a brief overview of treatment options. Fatigue is a prevalent, disabling, primary non-motor symptom (NMS) in MDS, including atypical and secondary parkinsonisms, dystonia, essential tremor (ET) and a hallmark feature of FMD. We report the hypothesis that fatigue is a perceptual disorder of the sensorimotor system. Given the relevance of this burdensome symptom, fatigue deserves greater clinical and research attention to better understand its manifestation and pathophysiology and to improve diagnosis and treatment.

Triggers and alleviating factors for fatigue in Parkinson's disease

BACKGROUND

Fatigue is common in Parkinson's Disease, but few effective treatments are available for it. Exploring triggers and alleviating factors, including effects of exercise, could inform development of management strategies for Parkinson's Disease fatigue.

OBJECTIVES

To examine triggers and alleviating factors for fatigue reported by individuals with Parkinson's Disease, including perceived effect of exercise.

METHODS

A sample of individuals with self-reported Parkinson's Disease participating in the study Fox Insight were administered an online survey. The survey included the Parkinson's Fatigue Scale, the Physical Activity Scale for the Elderly, and multiple-choice questions about triggers and alleviating factors for fatigue.

RESULTS

Among the sample of 1,029 individuals with Parkinson's disease, mean (standard deviation (SD)) age was 67.4 (9.3) years, 44.0% were female. Parkinson's Fatigue Scale score ranged from 16-80, mean (SD) 48.8 (16.2). Poor sleep (62.1%) and physical exertion (45.1%) were frequently reported triggers for fatigue. Coping strategies including sitting quietly (58.1%), laying down with or without napping, and exercise (20%). Physical Activity Scale for the Elderly scores were higher in those who reported that exercise alleviated their fatigue (49.7%) compared to those who reported it worsened their fatigue (18.9%) (mean (SD) score 158.5 (88.8) vs 119.8 (66.6) respectively; p<0.001).

CONCLUSIONS

Several behavioral and environmental triggers and alleviating strategies for fatigue are reported by individuals with Parkinson's disease. Many feel that exercise alleviates fatigue, though the relationship between exercise and fatigue in Parkinson's Disease appears complex. This exploratory study may inform future development of treatments or coping strategies for Parkinson's disease fatigue.

The Neurobiology of Pathological Fatigue: New Models, New Questions

The last decade has seen the emergence of new theoretical frameworks to explain pathological fatigue, a much neglected, yet highly significant symptom across a wide range of diseases. While the new models of fatigue provide new hypotheses to test, they also raise a number of questions. The primary purpose of this essay is to examine the predictions of three recently proposed models of fatigue, the overlap and differences between them, and the evidence from diseases that may lend support to the models of fatigue. I also present expansions for the sensory attenuation model of fatigue. Further questions examined here are the following: What are the neural substrates of fatigue? How can sensory attenuation, which underpins agency also explain fatigue? Are fatigue and agency related?

Progression of fatigue in Parkinson's disease - a 9-year follow-up

BACKGROUND AND PURPOSE

Although highly disabling, the pathogenesis and evolution of fatigue in Parkinson's disease (PD) is largely unknown, and no sufficiently documented treatment currently exists. The aim of the present study was to investigate the evolution of fatigue during the first 9 years after diagnosis.

METHODS

This study is part of the Norwegian ParkWest collaboration, a prospective population-based longitudinal cohort study. The present study comprised 191 newly diagnosed patients and 170 control participants. Fatigue was assessed by the Fatigue Severity Scale, with examinations at baseline and then every other year up to 9 years of follow-up. Linear mixed models were applied to investigate possible variables associated with fatigue.

RESULTS

It was found that there was a statistically significant increase in the proportion of PD patients with fatigue during the first 9 years after diagnosis. A large proportion of patients had a significant increase or decrease in fatigue score between consecutive visits. In addition, the relative risk of persistent fatigue and ever having fatigue was higher than for controls. There were statistically significant longitudinal associations between higher levels of fatigue and female gender, comorbidity at baseline, depressive symptoms, dependency in activities of daily living and better cognitive functioning. Lower levels of fatigue were associated with the use of dopamine agonists.

CONCLUSION

Fatigue is a common, severely limiting symptom in PD. This study demonstrates associations with other factors that could yield a better understanding of the symptom and thus possible treatment strategies, although further investigations are necessary to establish causal relationships.

Effects of Vestibular Rehabilitation on Fatigue and Activities of Daily Living in People with Parkinson's Disease: A Pilot Randomized Controlled Trial Study

One of the most disabling nonmotor symptoms in persons with Parkinson's disease is fatigue, which can decrease the quality of life by restricting the function and activities of daily living (ADL). Nonetheless, sufficient evidence for treating fatigue, including drug or nondrug treatment, is not available. In this study, we evaluated the probable effects of vestibular rehabilitation on fatigue and ADL in patients with Parkinson's disease. Methods. This was a single-blind clinical trial study in which patients with Parkinson's disease voluntarily participated based on the inclusion and exclusion criteria. The patients were randomly assigned to the case and control groups. The case group received 24 sessions of vestibular rehabilitation protocol, and conventional rehabilitation was performed in the control group (i.e., 3 sessions each week, each lasted about 60 minutes). Both groups were also given fatigue management advice. Fatigue was measured by the Parkinson Fatigue Scale (PFS) and the Modified Fatigue Impact Scale (MFIS). ADL was measured by the Functional Independence Measure (FIM). All changes were measured from the baseline at the completion of the intervention. Results. Both fatigue (P ≤ 0.001) and ADL (P ≤ 0.001) improved significantly more in the vestibular intervention group than in the control one. Conclusion. Vestibular rehabilitation may improve fatigue and ADL and therefore can be used as an effective intervention for patients with Parkinson's disease, which was also found to be well tolerated.

Predictors of fatigue severity in early, de novo Parkinson disease patients: A 1-year longitudinal study

INTRODUCTION

Fatigue is one of the most common and disabling nonmotor symptom in Parkinson's disease (PD). The aim of the present study was to investigate the 1-year course of fatigue in a consecutive sample of de novo drug-naïve patients with PD, and at systematically searching for baseline motor and nonmotor predictors associated with fatigue severity over time.

METHODS

Fifty-five consecutive de novo PD patients (age: 64.71 ± 7.74 years) underwent a comprehensive examination, including Parkinson Fatigue Scale, Epworth Sleepiness Scale, Parkinson's Disease Sleep Scale, Beck Depression Inventory, Parkinson's Anxiety Scale, Apathy Evaluation Scale, and an extensive neuropsychological evaluation. Bivariate and multiple regression analyses were performed to identify baseline predictors independently related to fatigue severity at 1-year follow-up.

RESULTS

Prevalence rate of fatigue (defined by PFS cut-off) increased from 22% at baseline to 38% at 1-year follow-up. A similar increase in prevalence was observed for excessive daytime sleepiness, and apathy. Among patients with fatigue at baseline, 91% had fatigue at follow-up too (i.e., persistent fatigue). Multivariate regression analysis identified fatigue (p < 0.01), daytime sleepiness (p < 0.01), and emotional apathy (p < 0.01) as the main baseline variables significantly predicting fatigue severity at 1-year follow-up.

CONCLUSION

In early PD, fatigue increases and persists over time, and its severity is related to higher baseline levels of fatigue, excessive daytime sleepiness, and emotional apathy. These results warrant to monitor fatigue since the early stage of disease, and suggest that treating excessive daytime sleepiness and emotional apathy might prevent its worsening.

Neural and dopaminergic correlates of fatigue in Parkinson's disease

Fatigue is one of the most common non-motor symptoms in Parkinson's disease (PD). Despite its clinical importance, there are few studies on the cause or mechanism of fatigue. Our aim was to find brain areas related to fatigue and to explore the association between striatal dopaminergic dysfunction and fatigue. We consecutively screened forty-seven patients with de novo PD from 2012 to 2017 and enrolled 32 patients. The gray matter volumes, white matter tracts, and striatal dopaminergic activity between PD without fatigue and with fatigue were compared. The correlation between fatigue and striatal dopaminergic activity was also analyzed. Our data did not show any significant difference in gray matter volume between PD without fatigue and with fatigue (familywise error [FWE] corrected p > 0.05) but revealed significantly higher mean fractional anisotropy (FA) values for all analyzed white matter tracts in PD with fatigue (false discovery rate [FDR] corrected p < 0.05), except left cingulum-hippocampus (CH), right superior longitudinal fasciculus, and right longitudinal fasciculus temporal part (FDR corrected p > 0.06); lower mean diffusivity (MD) values for all analyzed white matter tracts in PD with fatigue (FDR corrected p < 0.05), except in the left CH and uncinate fasciculus (FDR corrected p > 0.05). The mean radial diffusivity (RD) values, except for the left CH (FDR corrected p = 0.0576), were also significantly lower (FDR corrected p < 0.05). There was no difference in dopaminergic deficits between PD without fatigue and PD with fatigue (p > 0.50). The alteration of the white matter tract may reflect the degree of fatigue in PD. This is not true of the gray matter and striatal dopaminergic activity. These results show the possibility that white matter changes can be used as a biomarker for fatigue.

Brazilian version of the Multidimensional Fatigue Inventory for Parkinson’s disease

Abstract Introduction: The multidimensional fatigue inventory (MFI) has not been applied in Brazilian Parkinson`s disease (PD) population due to the lack of validation. Objective: The aim of this study was to cross-culturally adapt, to validate, and investigate the psychometric properties of Brazilian version of the MFI in PD. Method: Idiopathic PD individuals (N = 90) were recruited. The MFI was translated into Brazilian Portuguese using established forward-backward translation procedures, and the psychometric properties were evaluated. All individuals were assessed by socio-clinical questionnaire, Mini-Mental State Examination (MMSE), Unified Parkinson’s Disease Rating Scale (MDS-UPDRS Part I-IV), Hoehn-Yahr disability scale (HY), hospital anxiety and depression scale (HADS), fatigue severity scale (FSS), Parkinson Fatigue Scale (PFS-16) and MFI-PD/ BR with retest of the MFI-PD/BR after seven days. Results: The adaptation phase kept the same items of original MFI-PD. No data missing, floor nor ceiling effects were found. The overall Cronbach's alpha coefficient for the 20 items was 0.81, ranging from 0.73 to 0.81 for each of the five subscales. Bland and Altman analysis showed no systematic differences between assessments. The intraclass correlation coefficient test-retest was higher or equal 0.70 (p < 0.01) for the MFI-PD/BR score, which was moderately correlated with the HADS, MDS-UPDRS score (motor examination, motor and non-motor experiences of daily living and motor complications), FSS and PFS-16. It was revealed the MFI-PD/ BR > 55 points as cut-off point to indicate fatigued subjects with accuracy of 0.84 (p < 0.001). Conclusion: The MFI-PD/BR can be considered a valid and reproducible instrument for assessing PD-related fatigue.

Association between fatigue and motor progression in Parkinson's disease in southern Chinese

Study objectives

The aim was to investigate whether fatigue could predict the development of motor symptoms of Parkinson’s disease (PD) in a southern Chinese population.

Methods

In total, 246 PD patients were recruited. All patients were evaluated by Fatigue Severity Scale (FSS), Hamilton Anxiety Rating Scale, Hamilton Depression Rating Scale, and Unified PD Rating Scale provided by Movement Disorders Society (MDS-UPDRS). MDS-UPDRS was re-evaluated after 2 years.

Results

FSS scores were associated with total score and subparts of MDS-UPDRS (total: p 0.039, p 0.030, adjusted; part III: p 0.022, p 0.016, adjusted).

Conclusions

The symptom of subjective fatigue could predict the progression of PD.

Translational Informatics for Parkinson's Disease: from Big Biomedical Data to Small Actionable Alterations

Parkinson's disease (PD) is a common neurological disease in elderly people, and its morbidity and mortality are increasing with the advent of global ageing. The traditional paradigm of moving from small data to big data in biomedical research is shifting toward big data-based identification of small actionable alterations. To highlight the use of big data for precision PD medicine, we review PD big data and informatics for the translation of basic PD research to clinical applications. We emphasize some key findings in clinically actionable changes, such as susceptibility genetic variations for PD risk population screening, biomarkers for the diagnosis and stratification of PD patients, risk factors for PD, and lifestyles for the prevention of PD. The challenges associated with the collection, storage, and modelling of diverse big data for PD precision medicine and healthcare are also summarized. Future perspectives on systems modelling and intelligent medicine for PD monitoring, diagnosis, treatment, and healthcare are discussed in the end.

Biomarkers for Dementia, Fatigue, and Depression in Parkinson's Disease

Parkinson's disease is a common multisystem neurodegenerative disorder characterized by typical motor and non-motor symptoms. There is an urgent need for biomarkers for assessment of disease severity, complications and prognosis. In addition, biomarkers reporting the underlying pathophysiology assist in understanding the disease and developing neuroprotective therapies. Ultimately, biomarkers could be used to develop a more efficient personalized approach for clinical trials and treatment strategies. With the goal to improve quality of life in Parkinson's disease it is essential to understand and objectively monitor non-motor symptoms. This narrative review provides an overview of recent developments of biomarkers (biofluid samples and imaging) for three common neuropsychological syndromes in Parkinson's disease: dementia, fatigue, and depression.

Does fatigue in Parkinson's disease correlate with autonomic nervous system dysfunction?

BACKGROUND

Despite its negative impact on quality of life, fatigue in Parkinson's disease (PD) remains an under-recognized issue and the underlying pathology is undetermined.

OBJECTIVE

To contribute at understanding the pathogenesis of fatigue in a naturalistic cohort of cognitively intact PD patients.

METHODS

In a Caucasian population of PD patients (n = 27), we evaluated to what extent fatigue (quantified as PFS-16 score) is associated with PD duration and with autonomic dysfunction, studied by both MIBG scintigraphy and autonomic nervous system testing. The latter included the head-up tilt test, Valsalva maneuver, deep breathing, and handgrip tests.

RESULTS

PFS-16 score correlated with disease duration (R = 0.57, p = 0.002). Fatigue showed a clear correlation with deep breathing test (R = - 0.53, p = 0.004) but not with the MIBG H/M ratios.

CONCLUSIONS

Our data are consistent with a multifactorial pathogenesis of fatigue and with effects of dopamine depletion in PD-related fatigue; on the other hand, our findings do not support a role for sympathetic denervation in PD-related fatigue.

Molecular Imaging of the Cholinergic System in Parkinson's Disease

One of the first identified neurotransmitters in the brain, acetylcholine, is an important modulator that drives changes in neuronal and glial activity. For more than two decades, the main focus of molecular imaging of the cholinergic system in Parkinson's disease (PD) has been on cognitive changes. Imaging studies have confirmed that degeneration of the cholinergic system is a major determinant of dementia in PD. Within the last decade, the focus is expanding to studying cholinergic correlates of mobility impairments, dyskinesias, olfaction, sleep, visual hallucinations and risk taking behavior in this disorder. These studies increasingly recognize that the regional topography of cholinergic brain areas associates with specific functions. In parallel with this trend, more recent molecular cholinergic imaging approaches are investigating cholinergic modulatory functions and contributions to large-scale brain network functions. A novel area of research is imaging cholinergic innervation functions of peripheral autonomic organs that may have the potential of future prodromal diagnosis of PD. Finally, emerging evidence of hypercholinergic activity in prodromal and symptomatic leucine-rich repeat kinase 2 PD may reflect neuronal cholinergic compensation versus a response to neuro-inflammation. Molecular imaging of the cholinergic system has led to many new insights in the etiology of dopamine non-responsive symptoms of PD (more "malignant" hypocholinergic disease phenotype) and is poised to guide and evaluate future cholinergic drug development in this disorder.

Locus Coeruleus atrophy doesn't relate to fatigue in Parkinson's disease

Fatigue is a frequent complaint among healthy population and one of the earliest and most debilitating symptoms in Parkinson's disease (PD). Earlier studies have examined the role of dopamine and serotonin in pathogenesis of fatigue, but the plausible role of noradrenalin (NA) remains underexplored. We investigated the relationship between fatigue in Parkinsonian patients and the extent of degeneration of Locus Coeruleus (LC), the main source of NA in the brain. We quantified LC and Substantia Nigra (SN) atrophy using neuromelanin-sensitive imaging, analyzed with a novel, fully automated algorithm. We also assessed patients' fatigue, depression, sleep disturbance and vigilance. We found that LC degeneration correlated with the levels of depression and vigilance but not with fatigue, while fatigue correlated weakly with atrophy of SN. These results indicate that LC degeneration in Parkinson's disease is unlikely to cause fatigue, but may be involved in mood and vigilance alterations.

Brain metabolic correlates of fatigue in Parkinson's disease: a PET study

PURPOSE

The neural bases of fatigue in Parkinson's disease (PD) remain uncertain. We aimed to assess the brain metabolic correlates of fatigue in patients with PD.

PATIENTS AND METHODS

Twenty-seven PD patients without clinically relevant depression (17-item Hamilton Depression Rating Scale (HAMD) score ≥ 14), apathy (Apathy Scale (AS) score ≥ 14) and excessive daytime somnolence (Epworth Sleepiness Scale (ESS) score ≥ 10) were evaluated with Fatigue Severity Scale (FSS). Each patient had an F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) scan. Motor symptoms were measured with the Unified Parkinson's Disease Rating Scale motor part. Levodopa equivalent daily dose for each patient was also calculated. The PET images were analyzed using statistical parametric mapping software. We introduced the age, educational level, HAMD scores, AS scores and ESS scores as covariates.

RESULTS

High FSS scores were associated with brain hypermetabolism in areas including the right middle temporal gyrus (Brodmann area (BA) 37) and left middle occipital gyrus (BA 19). Increased FSS scores correlated with hypometabolism in regions such as the right precuneus (BA 23), left inferior frontal gyrus (BA 45) and left superior frontal gyrus (orbital part, BA 11).

CONCLUSION

This study demonstrates that brain areas including frontal, temporal and parietal regions indicative of emotion, motivation and cognitive functions are involved in fatigue in PD patients.

Alterations in regional homogeneity of resting-state brain activity in fatigue of Parkinson's disease

Fatigue is a common complaint in patients with Parkinson's disease (PD). However, the neural bases of fatigue in PD remain uncertain. In this cross-sectional study, our aim was to study the change of the local brain function in PD patients with fatigue. Among 49 patients with PD, 17 of them had fatigue and the remaining 32 patients without fatigue, and 25 age- and gender-matched healthy controls were enrolled. All subjects were evaluated with Fatigue Severity Scale (FSS) and had a resting-state functional magnetic resonance imaging (rs-fMRI) scan. The fMRI images were analyzed using regional homogeneity (ReHo) to study the change of the local brain function. ReHo analysis controlling for gray matter volume, age, gender, and education showed decreased ReHo in the left anterior cingulate cortex (ACC) and the right superior frontal gyrus (dorsolateral part), and increased ReHo in the left postcentral gyrus and the right inferior frontal gyrus (orbital and triangular part), compared PD-F with PD-NF; In PD patients, the regional activity in the left ACC and the right superior frontal gyrus (dorsolateral part) was negatively correlated with the FSS scores, while that in the left postcentral gyrus, the right inferior frontal gyrus (orbital and triangular part) was positively correlated with the FSS scores. This study demonstrates that brain areas including frontal, postcentral and ACC regions indicative of sensory, motor, and cognitive systems are involved in fatigue in PD patients.

Nonmotor Effects of Conventional and Transdermal Dopaminergic Therapies in Parkinson's Disease

Nonmotor symptoms (NMS) are an integral component of Parkinson's disease (PD). Because the burden and range of NMS are key determinants of quality of life for patients and caregivers, their management is a crucial issue in clinical practice. Although a range of NMS have a dopaminergic pathophysiological basis, this fact is underrecognized, and thus, they are often regarded as dopamine unresponsive symptoms. However, substantial evidence indicates that many NMS respond to oral and transdermal dopaminergic therapies. In contrast, certain NMS are exacerbated or even precipitated by dopaminergic drugs and these unwanted effects may be seriously dangerous. Therefore, a dopaminergic strategy for NMS should be based on a consideration of the benefits vs the risks in individual patients with PD.

Imaging the Nonmotor Symptoms in Parkinson's Disease

Parkinson's disease is acknowledged to be a multisystem syndrome, manifesting as a result of multineuropeptide dysfunction, including dopaminergic, cholinergic, serotonergic, and noradrenergic deficits. This multisystem disorder ultimately leads to the presentation of a range of nonmotor symptoms, now appreciated to be an integral part of the disease-specific spectrum of symptoms, often preceding the diagnosis of motor Parkinson's disease. In this chapter, we review the dopaminergic and nondopaminergic basis of these symptoms by exploring the neuroimaging evidence based on several techniques including positron emission tomography, single-photon emission computed tomography molecular imaging, magnetic resonance imaging, functional magnetic resonance imaging, and diffusion tensor imaging. We discuss the role of these neuroimaging techniques in elucidating the underlying pathophysiology of NMS in Parkinson's disease.

Association between autonomic dysfunction and fatigue in Parkinson disease

OBJECTIVE

Fatigue is a disabling non-motor symptom in Parkinson disease (PD). We investigated the relationship between autonomic dysfunction and fatigue in PD while accounting for possible confounding factors.

METHODS

29 subjects with PD (8F/21M; mean age 61.6±5.9; mean disease duration 4.8±3.0years), underwent clinical assessment and completed several non-motor symptom questionnaires, including a modified version of the Mayo Clinic Composite Autonomic Symptom Score (COMPASS) scale and the Fatigue Severity Scale (FSS).

RESULTS

The mean modified COMPASS was 21.6±14.2 (range 1.7-44.2) and the mean FSS score was 3.3±1.6 (range 1.0-6.7). There was a significant bivariate relationship between the modified COMPASS and FSS scores (R=0.69, P<0.0001). Stepwise regression analysis was used to assess the specificity of the association between the modified COMPASS and FSS scores while accounting for possible confounder effects from other variables that were significantly associated with autonomic dysfunction. Results showed that the modified COMPASS (R²=0.52, F=28.4, P<0.0001) was highly associated with fatigue, followed by ESS (R²=0.13, F=8.4, P=0.008) but no other co-variates. Post-hoc analysis exploring the association between the different modified COMPASS autonomic sub-domain scores and FSS scores found significant regressor effects for the orthostatic intolerance (R²=0.45, F=21.2, P<0.0001) and secretomotor sub-domains (R²=0.09, F=4.8, P=0.04) but not for other autonomic sub-domains.

CONCLUSIONS

Autonomic dysfunction, in particular orthostatic intolerance, is highly associated with fatigue in PD.

Presynaptic dopaminergic terminal imaging and non-motor symptoms assessment of Parkinson's disease: evidence for dopaminergic basis?

Parkinson's disease (PD) is now considered to be a multisystemic disorder consequent on multineuropeptide dysfunction including dopaminergic, serotonergic, cholinergic, and noradrenergic systems. This multipeptide dysfunction leads to expression of a range of non-motor symptoms now known to be integral to the concept of PD and preceding the diagnosis of motor PD. Some non-motor symptoms in PD may have a dopaminergic basis and in this review, we investigate the evidence for this based on imaging techniques using dopamine-based radioligands. To discuss non-motor symptoms we follow the classification as outlined by the validated PD non-motor symptoms scale.

Abnormal Resting-State Neural Activity and Connectivity of Fatigue in Parkinson's Disease

AIMS

Fatigue is a common burdensome problem in patients with Parkinson's disease (PD), but its pathophysiological mechanisms are poorly understood. This study aimed at investigating the neural substrates of fatigue in patients with PD.

METHODS

A total of 17 PD patients with fatigue, 32 PD patients without fatigue, and 25 matched healthy controls were recruited. The 9-item fatigue severity scale (FSS) was used for fatigue screening and severity rating. Resting-state functional magnetic resonance imaging (RS-fMRI) data were obtained from all subjects. Amplitude of low-frequency fluctuations (ALFF) was used to measure regional brain activity, and functional connectivity (FC) was applied to investigate functional connectivity at a network level.

RESULTS

PD-related fatigue was associated with ALFF changes in right middle frontal gyrus within the attention network and in left insula as well as right midcingulate cortex within the salience network. FC analysis revealed that above three regions showing ALFF differences had altered functional connectivity mainly in the temporal, parietal, and motor cortices.

CONCLUSION

Our findings do reveal that abnormal regional brain activity within attention and salience network and altered FC of above abnormal regions are involved in neural mechanism of fatigue in patients with PD.

Fatigue in Parkinson's disease

Fatigue is one of the most common nonmotor symptoms in Parkinson's disease and may affect a wide range of everyday activities, cause disability and reduce quality of life. It occurs at every stage of PD, and once present will often persist and may worsen over time. Lack of a consensus of definition and classification, and a range of different self-reporting scales has so far made the study of fatigue challenging. We review a unifying taxonomy for defining fatigue in clinical and research contexts as well as case definition criteria for PD-related fatigue. The potential causes of fatigue in PD are discussed as are recommendations for treatment.

Serotonergic dysfunctions and abnormal iron metabolism: Relevant to mental fatigue of Parkinson disease

Fatigue is a very common non-motor symptom in Parkinson disease (PD) patients. It included physical fatigue and mental fatigue. The potential mechanisms of mental fatigue involving serotonergic dysfunction and abnormal iron metabolism are still unknown. Therefore, we evaluated the fatigue symptoms, classified PD patients into fatigue group and non-fatigue group, and detected the levels of serotonin, iron and related proteins in CSF and serum. In CSF, 5-HT level is significantly decreased and the levels of iron and transferrin are dramatically increased in fatigue group. In fatigue group, mental fatigue score is negatively correlated with 5-HT level in CSF, and positively correlated with the scores of depression and excessive daytime sleepiness, and disease duration, also, mental fatigue is positively correlated with the levels of iron and transferrin in CSF. Transferrin level is negatively correlated with 5-HT level in CSF. In serum, the levels of 5-HT and transferrin are markedly decreased in fatigue group; mental fatigue score exhibits a negative correlation with 5-HT level. Thus serotonin dysfunction in both central and peripheral systems may be correlated with mental fatigue through abnormal iron metabolism. Depression, excessive daytime sleepiness and disease duration were the risk factors for mental fatigue of PD.