Cardiac MIBG scintigraphy is a sensitive tool for detecting cardiac sympathetic denervation in Parkinson's disease

Interoception in Parkinson's disease: A narrative review and framework for translational research

Parkinson's disease (PD) is the second most common, and the fastest growing, neurodegenerative disease worldwide. Non-motor manifestations, particularly autonomic nervous system dysfunction, are common throughout the disease course, in some cases preceding motor symptom onset by years, and are often more disabling and harder to treat than motor symptoms and contribute significantly to disability. An understudied consequence of autonomic and visceral dysfunction in PD is interoception, the neural processing of internal organ system signals. Interoceptive processes form a foundational body-brain interface, mediating basic homeostatic reflexes and complex physiologic and behavioral adaptive responses to internal perturbations. Emerging evidence exists that interoception is impaired in some individuals with PD, potentially explaining why those who have objective evidence of autonomic dysfunction do not always report typical symptoms. Failure to recognize these impairments may lead to missed opportunities for early intervention, particularly in addressing 'silent' autonomic disturbances (e.g., orthostatic hypotension leading to sudden falls, dysphagia leading to aspiration pneumonia). In this narrative review, we synthesize current findings on the neuroanatomical networks underlying interoception, examine clinical manifestations of interoceptive dysfunction across multiple organ systems in PD, and identify key gaps in knowledge. We propose a translational research framework to enhance early detection, symptom management, and intervention strategies for PD. This framework integrates cognitive, mood, and autonomic dysfunctions with clinical factors (disease stage, duration, motor subtype, levodopa status) to understand interoceptive dysfunction within a translational model. This approach highlights novel opportunities for personalized care and improved therapeutic interventions in PD.

Cardiovascular dysautonomia and cognitive impairment in Parkinson's disease (Review)

Cognitive impairment is a prevalent non-motor symptom of Parkinson's disease (PD), which can result in significant disability and distress for patients and caregivers. There is a marked variation in the timing, characteristics and rate at which cognitive decline occurs in patients with PD. This decline can vary from normal cognition to mild cognitive impairment and dementia. Cognitive impairment is associated with several pathophysiological mechanisms, including the accumulation of β-amyloid and tau in the brain, oxidative stress and neuroinflammation. Cardiovascular autonomic dysfunctions are commonly observed in patients with PD. These dysfunctions play a role in the progression of cognitive impairment, the incidents of falls and even in mortality. The majority of symptoms of dysautonomia arise from changes in the peripheral autonomic nervous system, including both the sympathetic and parasympathetic nervous systems. Cardiovascular changes, including orthostatic hypotension, supine hypertension and abnormal nocturnal blood pressure (BP), can occur in both the early and advanced stages of PD. These changes tend to increase as the disease advances. The present review aimed to describe the cognitive changes in the setting of cardiovascular dysautonomia and to discuss strategies through which these changes can be modified and managed. It is a multifactorial process usually involving decreased blood flow to the brain, resulting in the development of cerebral ischemic lesions, an increased presence of abnormal white matter signals in the brain, and a potential influence on the process of neurodegeneration in PD. Another possible explanation is this association being independent observations of PD progression. Patients with clinical symptoms of dysautonomia should undergo 24-h ambulatory BP monitoring, as they are frequently subtle and underdiagnosed.

Effectiveness of Lee Silverman Voice Treatment (LSVT-LOUD) in Parkinsonian-Type Multiple System Atrophy (MSA-P): A Case Report

We describe a case of Parkinsonian-type multiple system atrophy (MSA-P) treated with Lee Silverman Voice Treatment (LSVT-LOUD; LSVT Global, Inc., Phoenix, AZ, USA). At age 73, the patient developed motor symptoms, including gait disturbances with a tendency to fall, as well as swallowing difficulties and impaired dexterity in his right hand, prompting a visit to our hospital. Brain magnetic resonance imaging (MRI) revealed atrophy in the cerebellum and brainstem, particularly in the pons, along with enlargement of the fourth ventricle; however, the "cross sign" on the pons was not clearly visible. Dopamine transporter single-photon emission computed tomography (DAT-SPECT) showed decreased nuclide accumulation in the striatum. Additionally, 123I-MIBG cardiac scintigraphy demonstrated preserved nuclide accumulation in the heart. L-dopa challenge tests were conducted, but no significant improvement in motor symptoms was observed. Based on these findings, he was diagnosed with MSA-P. Over the following years, his condition progressively worsened, with increasing orthostatic hypotension, dysphagia, and falls. Various treatments, including anti-Parkinson's medications and vasopressors, provided little relief. At age 75, due to severe dysphagia and hoarseness, he was admitted for LSVT-LOUD therapy. After LSVT-LOUD treatment, the patient improved voice volume, tongue pressures, alternating motion rates of "pa," "ta," and "ka," and the Frontal Assessment Battery (FAB) score. These results suggest that LSVT-LOUD may positively impact both speech and swallowing functions, as well as frontal lobe function. Larger studies are needed to validate these results.

Abnormal Cerebrovascular Activity, Perfusion, and Glymphatic Clearance in Lewy Body Diseases

Cerebrovascular activity is not only crucial to optimal cerebral perfusion, but also plays an important role in the glymphatic clearance of interstitial waste, including α-synuclein. This highlights a need to evaluate how cerebrovascular activity is altered in Lewy body diseases. This review begins by discussing how vascular risk factors and cardiovascular autonomic dysfunction may serve as upstream or direct influences on cerebrovascular activity. We then discuss how patients with Lewy body disease exhibit reduced and delayed cerebrovascular activity, hypoperfusion, and reductions in measures used to capture cerebrospinal fluid flow, suggestive of a reduced capacity for glymphatic clearance. Given the lack of an existing framework, we propose a model by which these processes may foster α-synuclein aggregation and neuroinflammation. Importantly, this review highlights several avenues for future research that may lead to treatments early in the disease course, prior to neurodegeneration. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Parkinson's disease patients with absence of normal dipping status were more vulnerable to cognitive impairment from the early stages

INTRODUCTION

The objective of this study was to determine the characteristics of cognitive function in Parkinson's disease (PD) patients with different dipping statuses.

METHODS

Consecutive PD patients were recruited for this study. All participants underwent 24-h ambulatory blood pressure monitor (ABPM). Corresponding scales were employed to evaluate both motor and non-motor symptoms. The subjects were categorized into reverse, reduced, normal, and extreme dipping groups based on dipping patterns. Additionally, they were divided into early and non-early stage groups according to the disease duration being more than 5 years.

RESULTS

The proportions of the four dipping groups in the early and non-early stage groups exhibited no significant differences. The Montreal Cognitive Assessment (MoCA) scores in the reverse group were significantly lower than those in the normal dipping group (16.2 ± 5.8 vs 21.1 ± 6.1,P = 0.003). The attention as well as delayed recall scores in the reverse dipping group were significant lower than those in the normal dipping group (P = 0.042; P < 0.001). The multivariate linear regression analysis revealed that absence of normal dipping was an independent risk factor (OR = -2.252; P = 0.027) for MoCA scores for PD patients.

CONCLUSIONS

PD patients with absence of normal dipping status were more vulnerable to cognitive impairment from the early stages of the disease. The 24-h ABPM is recommended for early detection of abnormal dipping status and identification of individuals at risk for cognitive decline.

Unveiling autonomic failure in synucleinopathies: Significance in diagnosis and treatment

Autonomic failure is frequently encountered in synucleinopathies such as multiple system atrophy (MSA), Parkinson's disease (PD), Lewy body disease, and pure autonomic failure (PAF). Cardiovascular autonomic failure affects quality of life and can be life threatening due to the risk of falls and the increased incidence of myocardial infarction, stroke, and heart failure. In PD and PAF, pathogenic involvement is mainly post-ganglionic, while in MSA, the involvement is mainly pre-ganglionic. Cardiovascular tests exploring the autonomic nervous system (ANS) are based on the analysis of continuous, non-invasive recordings of heart rate and digital blood pressure (BP). They assess facets of sympathetic and parasympathetic activities and provide indications on the integrity of the baroreflex arc. The tilt test is widely used in clinical practice. It can be combined with catecholamine level measurement and analysis of baroreflex activity and cardiac variability for a detailed analysis of cardiovascular damage. MIBG myocardial scintigraphy is the most sensitive test for early detection of autonomic dysfunction. It provides a useful measure of post-ganglionic sympathetic fiber integrity and function and is therefore an effective tool for distinguishing PD from other parkinsonian syndromes such as MSA. Autonomic cardiovascular investigations differentiate between certain parkinsonian syndromes that would otherwise be difficult to segregate, particularly in the early stages of the disease. Exploring autonomic failure by gathering information about residual sympathetic tone, low plasma norepinephrine levels, and supine hypertension can guide therapeutic management of orthostatic hypotension (OH).

Cardiac 123I-Metaiodobenzylguanidine (MIBG) Scintigraphy in Parkinson's Disease: A Comprehensive Review

Cardiac sympathetic denervation, as documented on 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy, is relatively sensitive and specific for distinguishing Parkinson's disease (PD) from other neurodegenerative causes of parkinsonism. The present study aims to comprehensively review the literature regarding the use of cardiac MIBG in PD. MIBG is an analog to norepinephrine. They share the same uptake, storage, and release mechanisms. An abnormal result in the cardiac MIBG uptake in individuals with parkinsonism can be an additional criterion for diagnosing PD. However, a normal result of cardiac MIBG in individuals with suspicious parkinsonian syndrome does not exclude the diagnosis of PD. The findings of cardiac MIBG studies contributed to elucidating the pathophysiology of PD. We investigated the sensitivity and specificity of cardiac MIBG scintigraphy in PD. A total of 54 studies with 3114 individuals diagnosed with PD were included. The data were described as means with a Hoehn and Yahr stage of 2.5 and early and delayed registration H/M ratios of 1.70 and 1.51, respectively. The mean cutoff for the early and delayed phases were 1.89 and 1.86. The sensitivity for the early and delayed phases was 0.81 and 0.83, respectively. The specificity for the early and delayed phases were 0.86 and 0.80, respectively.

Autonomic failure: Clinicopathologic, physiologic, and genetic aspects

Over the past century, generations of neuroscientists, pathologists, and clinicians have elucidated the underlying causes of autonomic failure found in neurodegenerative, inherited, and antibody-mediated autoimmune disorders, each with pathognomonic clinicopathologic features. Autonomic failure affects central autonomic nervous system components in the α-synucleinopathy, multiple system atrophy, characterized clinically by levodopa-unresponsive parkinsonism or cerebellar ataxia, and pathologically by argyrophilic glial cytoplasmic inclusions (GCIs). Two other central neurodegenerative disorders, pure autonomic failure characterized clinically by deficits in norepinephrine synthesis and release from peripheral sympathetic nerve terminals; and Parkinson's disease, with early and widespread autonomic deficits independent of the loss of striatal dopamine terminals, both express Lewy pathology. The rare congenital disorder, hereditary sensory, and autonomic neuropathy type III (or Riley-Day, familial dysautonomia) causes life-threatening autonomic failure due to a genetic mutation that results in loss of functioning baroreceptors, effectively separating afferent mechanosensing neurons from the brain. Autoimmune autonomic ganglionopathy caused by autoantibodies targeting ganglionic α3-acetylcholine receptors instead presents with subacute isolated autonomic failure affecting sympathetic, parasympathetic, and enteric nervous system function in various combinations. This chapter is an overview of these major autonomic disorders with an emphasis on their historical background, neuropathological features, etiopathogenesis, diagnosis, and treatment.

Power spectral analysis of heart rate variability is useful as a screening tool for detecting sympathetic and parasympathetic nervous dysfunctions in Parkinson’s disease

Background

Parkinson’s disease (PD) is a progressive neurodegenerative disorder that causes motor symptoms and autonomic dysfunction. However, autonomic function tests commonly performed in PD can only evaluate either the sympathetic or parasympathetic nervous system. Therefore, the purpose of this pilot study is to investigate whether power spectral analysis of heart rate variability could detect both sympathetic and parasympathetic nervous dysfunctions in patients with PD.

Methods

Seventeen patients with PD and 11 healthy control subjects underwent electrocardiogram recording for the spectral analysis of heart rate variability to obtain values of low-frequency (LF) (0.04–0.15 Hz) and high-frequency (HF) (0.15–0.4 Hz) powers. Moreover, we examined the coefficient of variation of R–R intervals (CVRR) as a parameter of parasympathetic function in all participants and performed ¹²³I-metaiodobenzylguanidine scintigraphy to measure the heart-to-mediastinum ratio as a parameter of cardiac sympathetic innervation in patients with PD.

Results

The median age of control subjects and PD patients was 63 and 66 years old, respectively. The median Hoehn and Yahr scale of PD patients was stage 2. The values of resting LF and HF powers widely varied. The median values of resting LF powers of control subjects and PD patients and those of HF powers were 169 and 70 ms², 279 and 65 ms², respectively, the difference was statistically insignificant. Approximately 41% of patients with PD had values below the first quartile of resting LF powers (< 58 ms²) or HF powers (< 50 ms²); however, no control subject had such low values. Positive correlations were found between resting LF powers and heart-to-mediastinum ratios of ¹²³I-metaiodobenzylguanidine uptake (r = 0.6) and between resting HF powers and CVRRs (r = 0.7). The resting LF power was also associated with CVRRs and constipation. Furthermore, a positive correlation was observed between resting LF powers and resting HF powers in patients with PD (r = 0.8).

Conclusions

The power spectral analysis of heart rate variability may be useful as a screening tool for detecting autonomic dysfunctions by detecting low resting LF and HF powers in patients with PD. Sympathetic and parasympathetic nerves may be concurrently damaged in patients with PD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02872-2.

Assessment of myocardial sympathetic innervation with 18F-FDOPA-PET/CT in patients with autonomic dysfunction: feasibility study in IPD patients

BACKGROUND

Dysfunction and denervation of myocardial nor-adrenergic sympathetic neurons has been documented in IPD patients with dysautonomia. The aim of this study was to evaluate the feasibility of single tracer imaging of myocardial sympathetic and cerebral striatal involvement in these patients.

METHODS

Twenty-two controls (mean-age 59.09 ± 12.39 years, 15 men) with no clinical autonomic-dysfunction and normal striatal-uptake in 18F-FDOPA-PET/CT; and 28 patients (mean-age 58.18 ± 8.25 years, 18 men) with autonomic-dysfunction (in Autonomic Function Tests) and striatal dopaminergic-dysfunction were enrolled. Both cardiac-PET/CT (40 minutes post IV-injection of 185-259MBq 18F-FDOPA) and Brain-PET/CT (60 minutes post-IV) were acquired in same session. ROIs were drawn over the entire left ventricular myocardium, individual walls and mediastinum for quantification. Patients and controls were followed-up for 26.93 ± 5.43 months and 37.91 ± 8.63 months, respectively.

RESULTS

Striatal and myocardial-parameters were significantly lower in patients compared to controls; with Myocardium/mediastinal ratio (MwMR) yielding the area-under-the-curve of .941 (P < .001). MwMR correlated negatively with the drop in systolic blood pressure (SBP) during AFTs {Pearson-coefficient (-).565, P = .002}. Mean MwMR in patients with abnormal-AFTs was significantly lower than patients with borderline-AFTs (1.39 ± .12 vs 1.55 ± .10; P = .002). 9/20 patients with abnormal-AFTs showed functional worsening during follow-up, compared to 2/8 with borderline-AFTs.

CONCLUSION

Single tracer, single session imaging of striatal and cardiac sympathetic dysfunction in patients with advanced IPD is feasible with use of 18F-FDOPA. Significantly reduced 18F-FDOPA uptake is seen in the myocardium of the IPD patients with sympathetic dysfunction.

To the Gut Microbiome and Beyond: The Brain-First or Body-First Hypothesis in Parkinson's Disease

There is continued debate regarding Parkinson’s disease etiology and whether it originates in the brain or begins in the gut. Recently, evidence has been provided for both, with Parkinson’s disease onset presenting as either a “body-first” or “brain-first” progression. Most research indicates those with Parkinson’s disease have an altered gut microbiome compared to controls. However, some studies do not report gut microbiome differences, potentially due to the brain or body-first progression type. Based on the etiology of each proposed progression, individuals with the body-first progression may exhibit altered gut microbiomes, i.e., where short-chain fatty acid producing bacteria are reduced, while the brain-first progression may not. Future microbiome research should consider this hypothesis and investigate whether gut microbiome differences exist between each type of progression. This may further elucidate the impact of the gut microbiome in Parkinson’s disease and show how it may not be homogenous across individuals with Parkinson’s disease.

Cardiac sympathetic innervation in Parkinson's disease versus multiple system atrophy

PURPOSE

The aims of this study were to evaluate the diagnostic accuracy of the dual imaging method combining cardiac iodine-123-metaiodobenzylguanidine single-photon emission computed tomography combined with low-dose chest computed tomography compared to routine cardiac scintigraphy, and assess regional differences in tracer distribution and the relationships between imaging and autonomic function in Parkinson's disease and multiple system atrophy.

METHODS

A prospective study including 19 Parkinson's disease and 12 multiple system atrophy patients was performed. Patients underwent clinical evaluation, iodine-123-metaiodobenzylguanidine single-photon emission computed tomography combined with chest computed tomography, planar scintigraphy, and cardiovascular autonomic function tests.

RESULTS

Co-registration of single-photon emission computed tomography and chest computed tomography resulted in three groups with distinct patterns of tracer uptake: homogeneous, non-homogeneously reduced and absent. There was a significant difference in group allocation among patients with multiple system atrophy and Parkinson's disease (p = 0.001). Most multiple system atrophy patients showed homogeneous uptake, and the majority of Parkinson's disease patients showed absent cardiac tracer uptake. We identified a pattern of heterogeneous cardiac tracer uptake in both diseases with reductions in the apex and the lateral myocardial wall. Sympathetic dysfunction reflected by a missing blood pressure overshoot during Valsalva manoeuvre correlated with cardiac tracer distribution in Parkinson's disease patients (p < 0.001).

CONCLUSIONS

The diagnostic accuracy of the dual imaging method and routine cardiac scintigraphy were similar. Anatomical tracer allocation provided by the dual imaging method of cardiac iodine-123-metaiodobenzylguanidine single-photon emission computed tomography and chest computed tomography identified a heterogeneous subgroup of Parkinson's disease and multiple system atrophy patients with reduced cardiac tracer uptake in the apex and the lateral wall. Sympathetic dysfunction correlated with cardiac imaging in Parkinson's disease patients.

Locus Coeruleus Shows a Spatial Pattern of Structural Disintegration in Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) causes a loss of neuromelanin-positive, noradrenergic neurons in the locus coeruleus (LC), which has been implicated in nonmotor dysfunction.

OBJECTIVES

We used "neuromelanin sensitive" magnetic resonance imaging (MRI) to localize structural disintegration in the LC and its association with nonmotor dysfunction in PD.

METHODS

A total of 42 patients with PD and 24 age-matched healthy volunteers underwent magnetization transfer weighted (MTw) MRI of the LC. The contrast-to-noise ratio of the MTw signal (CNR_MTw ) was used as an index of structural LC integrity. We performed slicewise and voxelwise analyses to map spatial patterns of structural disintegration, complemented by principal component analysis (PCA). We also tested for correlations between regional CNR_MTw and severity of nonmotor symptoms.

RESULTS

Mean CNR_MTw of the right LC was reduced in patients relative to controls. Voxelwise and slicewise analyses showed that the attenuation of CNR_MTw was confined to the right mid-caudal LC and linked regional CNR_MTw to nonmotor symptoms. CNR_MTw attenuation in the left mid-caudal LC was associated with the orthostatic drop in systolic blood pressure, whereas CNR_MTw attenuation in the caudal most portion of right LC correlated with apathy ratings. PCA identified a bilateral component that was more weakly expressed in patients. This component was characterized by a gradient in CNR_MTw along the rostro-caudal and dorso-ventral axes of the nucleus. The individual expression score of this component reflected the overall severity of nonmotor symptoms.

CONCLUSION

A spatially heterogeneous disintegration of LC in PD may determine the individual expression of specific nonmotor symptoms such as orthostatic dysregulation or apathy. © 2022 International Parkinson and Movement Disorder Society.

Autonomic nervous system activity in primary Raynaud's phenomenon: Heart rate variability, plasma catecholamines and [123 I]MIBG heart scintigraphy

Background and Aim

Primary Raynaud's phenomenon (pRP) is characterized by an exaggerated response to cold, resulting in the whitening typically of the fingers and toes. The patients are generally perceived as healthy individuals with a benign condition. However, the condition has been associated with increased cardiovascular mortality and changes in autonomic nervous system activity. This study aimed to investigate whether pRP is associated with pervasive changes in autonomic nervous activity. The hypothesis was that patients with pRP have increased sympathetic nervous activity.

Methods

The autonomic nervous activity of 22 patients with pRP was investigated by means of heart rate variability (HRV) and the plasma catecholamine response to head‐up tilt and compared with 22 age‐ and gender‐matched controls. In addition, the patients were examined with a [¹²³I]metaiodobenzylguanidine heart scintigraphy and compared with an external control group.

Results

The plasma norepinephrine response to head‐up tilt was significantly lower in the patient group than in the control group. Similarly, the heart scintigraphy revealed a lower heart‐to‐mediastinum ratio in the patient group than in the control group. HRV analysis did not reveal significant differences between the groups.

Conclusion

The findings of the study showed that the autonomic nervous activity of patients with pRP was altered compared with the activity of healthy individuals. This was observed both during rest and after positional stress, but the findings did not uniformly concur with our initial hypothesis.

Myelin Basic Protein and Cardiac Sympathetic Neurodegeneration in Nonhuman Primates

Minimal myelination is proposed to be a contributing factor to the preferential nigral neuronal loss in Parkinson's disease (PD). Similar to nigral dopaminergic neurons, sympathetic neurons innervating the heart have long, thin axons which are unmyelinated or minimally myelinated. Interestingly, cardiac sympathetic loss in PD is heterogeneous across the heart, yet the spatial relationship between myelination and neurodegeneration is unknown. Here, we report the mapping of myelin basic protein (MBP) expression across the left ventricle of normal rhesus macaques (n = 5) and animals intoxicated with systemic 6-OHDA (50 mg/kg iv) to model parkinsonian cardiac neurodegeneration (n = 10). A subset of 6-OHDA-treated rhesus received daily dosing of pioglitazone (5 mg/kg po; n = 5), a PPARγ agonist with neuroprotective properties. In normal animals, MBP-immunoreactivity (-ir) was identified surrounding approximately 14% of axonal fibers within nerve bundles of the left ventricle, with more myelinated nerve fibers at the base level of the left ventricle than the apex (p < 0.014). Greater MBP-ir at the base was related to a greater number of nerve bundles at that level relative to the apex (p < 0.05), as the percent of myelinated nerve fibers in bundles was not significantly different between levels of the heart. Cardiac sympathetic loss following 6-OHDA was associated with decreased MBP-ir in cardiac nerve bundles, with the percent decrease of MBP-ir greater in the apex (84.5%) than the base (52.0%). Interestingly, cardiac regions and levels with more MBP-ir in normal animals showed attenuated sympathetic loss relative to areas with less MBP-ir in 6-OHDA + placebo (r = -0.7, p < 0.014), but not in 6-OHDA + pioglitazone (r = -0.1) subjects. Our results demonstrate that myelination is present around a minority of left ventricle nerve bundle fibers, is heterogeneously distributed in the heart of rhesus macaques, and has a complex relationship with cardiac sympathetic neurodegeneration and neuroprotection.

Uniformity of cardiac 123I-MIBG uptake on SPECT images in older adults with normal cognition and patients with dementia

INTRODUCTION

Some studies report that assessing regional 123I-cardiac MIBG uptake can aid in the diagnosis of Lewy body disease, but others report heterogeneity in healthy controls. We aimed to evaluate regional cardiac MIBG uptake patterns in healthy older adults and patients with dementia.

METHODS

31 older adults with normal cognition, 15 Alzheimer's disease (AD), and 17 Dementia with Lewy bodies (DLB) patients were recruited. 5 individuals had previous myocardial infarction. Participants with sufficient cardiac uptake for regional SPECT analysis (29/31 controls, 15/15 AD, 5/17 DLB) had relative uptake pattern recorded. Controls were assessed for risk of future cardiovascular events using QRISK2, a validated online tool.

RESULTS

In controls uptake was reduced in the inferior wall (85%), apex (23%), septum (15%), and lateral wall (8%). AD and DLB showed similar patterns to controls. Lung or liver interference was present in 61% of cases. Myocardial infarction cases showed regional reductions in uptake, but normal/borderline planar uptake. In controls, there was no relationship between cardiovascular risk score and uptake pattern.

CONCLUSIONS

Significant variability of regional cardiac 123I-MIBG uptake is common in cases with normal planar cardiac uptake. Heterogeneity of regional uptake appears non-specific and unlikely to aid in the diagnosis of Lewy body disease.

X-Linked Dystonia-Parkinsonism ("Lubag") May Present with Peripheral Synucleinopathy

BACKGROUND

X-linked dystonia parkinsonism (XDP) or "Lubag" is a genetic dystonia syndrome observed among Filipinos that can present with levodopa-responsive parkinsonism and abnormal dopamine transporter (DAT) imaging.

OBJECTIVE

The aim of this study is to describe the results of skin biopsies for phosphorylated α-synuclein (P-SYN) in XDP.

METHOD

This study used the retrospective chart review.

RESULTS

We report 6 patients who carried the XDP gene mutation with DAT imaging and skin biopsies to detect P-SYN. Five had segmental or multifocal dystonia and parkinsonism: 4 were levodopa-responsive and 1 non-levodopa-responsive. One patient was asymptomatic but had mild bradykinesia. Cutaneous P-SYN and abnormal DAT scans were noted in the 4 levodopa-responsive patients and 1 asymptomatic patient.

CONCLUSION

We report for the first time the presence of cutaneous P-SYN in XDP. Our findings suggest that XDP may be a hitherto-undescribed synucleinopathy or that some XDP patients may have concurrent Parkinson's disease.

Diagnostic Value of the Early Heart-to-Mediastinum Count Ratio in Cardiac 123I-mIBG Imaging for Parkinson's Disease

BACKGROUND

Early diagnosis of Parkinson's disease (PD) is of primary importance. The delayed (3-4 h after injection) Iodine-123-Metaiodobenzylguanidine (123I-mIBG) scintigraphy has been proven to be effective in early differential diagnosis for Lewy body disease. But early imaging (15-30 min after injection) has only been marginally studied for its possible diagnostic role. In this prospective study, a threshold for the early Heart-to-Mediastinum (H/M) count ratio has been investigated, obtaining a diagnostic accuracy analogous to conventional, delayed imaging.

METHODS

One hundred and eight patients with suspected Parkinson's disease (PD) were acquired after 15 and 240 minutes from the injection of 150-185 MBq of 123I-mIBG. The early and late H/M (He/Me and Hl/Ml) were evaluated by drawing Region-of-Interests on the heart and the upper half of the mediastinum. Optimal threshold (Youden index) and overall predictive performance were determined by receiver operating characteristic curve, classifying tentatively patients having an Hl/Ml lower than 1.6 as suffering from PD.

RESULTS

He/Me was not significantly different from Hl/Ml (p-value=0.835). The Area-under-curve was 0.935 (95%CI: 0.845-1.000). The He/Me optimal threshold was 1.66, with sensitivity, specificity, and diagnostic accuracy of 95.5%, 85.7 and 90.7% respectively.

CONCLUSION

The He/Me Ratio is almost as accurate as the widely used delayed 123I-mIBG imaging, reducing the burden of delayed imaging but preserving the diagnostic accuracy of the method. Moreover the differential diagnosis in Parkinson's disease can be made in just 25 minutes against the 4 hours currently needed, lowering costs of the healthcare system and improving patients compliance.

Positron emission tomographic imaging in drug discovery

Positron emission tomography (PET) is an extensively used nuclear functional imaging technique, especially for central nervous system (CNS) and oncological disorders. Currently, drug development is a lengthy and costly pursuit. Imaging with PET radiotracers could be an effective way to hasten drug discovery and advancement, because it facilitates the monitoring of key facets, such as receptor occupancy quantification, drug biodistribution, pharmacokinetic (PK) analyses, validation of target engagement, treatment monitoring, and measurement of neurotransmitter concentrations. These parameters demand careful analyses for the robust appraisal of newly formulated drugs during preclinical and clinical trials. In this review, we discuss the usage of PET imaging in radiopharmaceutical development; drug development approaches with PET imaging; and PET developments in oncological and cardiac drug discovery.

123I-Metaiodobenzylguanidine Myocardial Scintigraphy in Discriminating Degenerative Parkinsonisms

Background

¹²³I-Metaiodobenzylguanidine (¹²³I-MIBG) myocardial scintigraphy is a useful technique to differentiate Parkinson's disease (PD) from atypical parkinsonisms, since it is generally abnormal in PD and normal in the latter. Reduction of myocardial MIBG uptake is a supportive feature in the latest PD diagnostic criteria.

Objectives

To explore the clinical contribution of myocardial scintigraphy in discriminating different forms of parkinsonisms, especially when atypical features are present.

Methods

Forty-one patients with parkinsonism underwent a ¹²³I-MIBG myocardial scintigraphy in our Movement Disorders Center. Disease evolution was reviewed by applying the latest disease criteria for PD, multiple system atrophy (MSA), progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS), as appropriate. Three diagnostic times were defined: T1 (before scintigraphy execution), T2 (immediately after the exam) and T3 (two years later). Early and delayed heart/mediastinum (H/M) ratios and washout rate (WR) were analyzed.

Results

Myocardial scintigraphy showed impaired MIBG uptake in 12 out of 15 patients with a definite PD diagnosis, while normal uptake was found in 20 of 26 patients with no-PD. Early and delayed H/M ratios were significantly lower in PD compared to overall no-PD patients and MSA patients. ¹²³I-MIBG myocardial scintigraphy was abnormal in all PD patients with dysautonomia. After ¹²³I-MIBG myocardial scintigraphy (T2), in 9 patients (22%) an improvement of diagnostic accuracy was reached.

Conclusions

Diagnostic accuracy of myocardial scintigraphy in distinguishing PD from atypical parkinsonism was suboptimal. Nevertheless, this study confirmed the relevance of ¹²³I-MIBG myocardial scintigraphy for the discrimination of PD from atypical parkinsonism, especially when dysautonomic symptoms are present.

Management of Hypertension and Blood Pressure Dysregulation in Patients with Parkinson's Disease-a Systematic Review

PURPOSE OF REVIEW

The aim of this review article was to summarize the cardiovascular and blood pressure profile regarding Parkinson disease patients and to provide an update on the recent advancements in the field of the diagnosis and management of blood pressure abnormalities in these patients. Our goal was to guide physicians to avoid pitfalls in current practice while treating patients with Parkinson disease and blood pressure abnormalities. For this purpose, we searched bibliographic databases (PubMed, Google Scholar) for all publications published on blood pressure effects in Parkinson disease until May 2020. Furthermore, we highlight some thoughts and potential perspectives for the next possible steps in the field.

RECENT FINDINGS

Blood pressure dysregulation in patients with Parkinson's disease has several implications in clinical practice and presents an ongoing concern. Compared with chronic essential hypertension, the syndrome of combined neurogenic orthostatic hypotension and supine hypertension in Parkinson's disease has received little attention. If left untreated, hypertension may lead to cardiovascular disease whereas hypotension may lead to fall-related complications, with tremendous impact on the quality of life of affected individuals. The effect of blood Epressure control and the risk of death from cardiovascular disease in Parkinson disease are largely unexplored. Blood pressure abnormalities in Parkinson disease present bidirectional relationship and the rationale for treating and controlling hypertension in persons with Parkinson disease and concurrent neurogenic orthostatic hypotension and/or supine hypertension is compelling. Further research is warranted in order to clarify the mechanisms, clinical implications, and potential reversibility of compromised cardiovascular function, in persons with Parkinson disease.

Cardiac 18F-Dopamine PET Distinguishes PD with Orthostatic Hypotension from Parkinsonian MSA

BACKGROUND

Parkinson's disease with orthostatic hypotension (PD + OH) can be difficult to distinguish clinically from the parkinsonian form of multiple system atrophy (MSA-P). Previous studies examined cardiac sympathetic neuroimaging to differentiate PD from MSA but without focusing specifically on PD + OH versus MSA-P, which often is the relevant differential diagnostic issue.

OBJECTIVE

To investigate the utility of cardiac sympathetic neuroimaging by 18F-dopamine positron emission tomographic (PET) scanning for separating PD + OH from MSA-P.

METHODS

Cardiac 18F-dopamine PET data were analyzed from 50 PD + OH and 68 MSA-P patients evaluated at the NIH Clinical Center from 1990 to 2020. Noradrenergic deficiency was defined by interventricular septal 18F-dopamine-derived radioactivity <6000 nCi-kg/cc-mCi in the 5' frame with mid-point 8' after initiation of 3' tracer injection.

RESULTS

18F-Dopamine PET separated the PD + OH from the MSA-P group with a sensitivity of 92% and specificity of 96%.

CONCLUSION

Cardiac 18F-dopamine PET scanning efficiently distinguishes PD + OH from MSA-P.

Altered heart rate variability during sleep in mild cognitive impairment

STUDY OBJECTIVES

Cardiovascular autonomic dysfunction, as measured by short-term diurnal heart rate variability (HRV), has been reported in older adults with mild cognitive impairment (MCI). However, it is unclear whether this impairment also exists during sleep in this group. We, therefore, compared overnight HRV during sleep in older adults with MCI and those with subjective cognitive impairment (SCI).

METHODS

Older adults (n = 210) underwent overnight polysomnography. Eligible participants were characterized as multi-domain MCI or SCI. The multi-domain MCI group was comprised of amnestic and non-amnestic subtypes. Power spectral analysis of HRV was conducted on the overnight electrocardiogram during non-rapid eye movement (NREM), rapid eye movement (REM), N1, N2, N3 sleep stages, and wake periods. High-frequency HRV (HF-HRV) was employed as the primary measure to estimate parasympathetic function.

RESULTS

The MCI group showed reduced HF-HRV during NREM sleep (p = 0.018), but not during wake or REM sleep (p > 0.05) compared to the SCI group. Participants with aMCI compared to SCI had the most pronounced reduction in HF-HRV across all NREM sleep stages-N1, N2, and N3, but not during wake or REM sleep. The naMCI sub-group did not show any significant differences in HF-HRV during any sleep stage compared to SCI.

CONCLUSIONS

Our study showed that amnestic MCI participants had greater reductions in HF-HRV during NREM sleep, relative to those with SCI, suggesting potential vulnerability to sleep-related parasympathetic dysfunction. HF-HRV, especially during NREM sleep, may be an early biomarker for dementia detection.

Two Cases of Decreased 123I-Metaiodobenzylguanidine Lung Uptake in Metaiodobenzylguanidine Scintigraphy While Taking Selective Serotonin Reuptake Inhibitor/Serotonin Noradrenaline Reuptake Inhibitor

ABSTRACT

123I-metaiodobenzylguanidine scintigraphy is used to differentiate Lewy body disease from other neurodegenerative disorders. We identified 2 cases with remarkably changed pulmonary uptake between 2 metaiodobenzylguanidine scintigraphies; pulmonary uptake was reduced when patients were taking selective serotonin reuptake inhibitor/serotonin noradrenaline reuptake inhibitor and preserved during the medication-naive or withdrawal state, suggesting that pulmonary uptake involves not only the noradrenaline transporter, but also the serotonin transporter. Pulmonary accumulation may affect the heart-to-mediastinum ratio as the region of interest on the planner image is usually placed on the heart and includes part of the lung. Therefore, we should pay attention to the medication state of patients with decreased pulmonary uptake.

Baroreflex dysfunction in Parkinson's disease: integration of central and peripheral mechanisms

The incidence of Parkinson's disease (PD) is increasing worldwide. Although the PD hallmark is the motor impairments, nonmotor dysfunctions are now becoming more recognized. Recently, studies have suggested that baroreflex dysfunction is one of the underlying mechanisms of cardiovascular dysregulation observed in patients with PD. However, the large body of literature on baroreflex function in PD is unclear. The baroreflex system plays a major role in the autonomic, and ultimately blood pressure and heart rate, adjustments that accompany acute cardiovascular stressors on a daily basis. Therefore, impaired baroreflex function (i.e., decreased sensitivity or gain) can lead to altered neural cardiovascular responses. Since PD affects parasympathetic and sympathetic branches of the autonomic nervous system and both are orchestrated by the baroreflex system, understanding of this crucial mechanism in PD is necessary. In the present review, we summarize the potential altered central and peripheral mechanisms affecting the feedback-controlled loops that comprise the reflex arc in patients with PD. Major factors including arterial stiffness, reduced number of C1 and activation of non-C1 neurons, presence of central α-synuclein aggregation, cardiac sympathetic denervation, attenuated muscle sympathetic nerve activity, and lower norepinephrine release could compromise baroreflex function in PD. Results from patients with PD and from animal models of PD provide the reader with a clearer picture of baroreflex function in this clinical condition. By doing so, our intent is to stimulate future studies to evaluate several unanswered questions in this research area.

Increased atrial fibrillation risk in Parkinson's disease: A nationwide population-based study

OBJECTIVE

Parkinson's disease (PD) is the second most common neurodegenerative disorder associated with various morbidities. Although the relationship between cardiovascular disease and PD has been studied, a paucity of information on PD and atrial fibrillation (AF) association exists. Thus, we aimed to investigate whether patients with PD have an increased risk of AF.

METHODS

This study included 57,585 patients with newly diagnosed PD (≥40-year-old, mean age 69.7 years, men 40.2%) and without a history of AF from the Korean National Health Insurance Service (NHIS) database between 2010 and 2015. Furthermore, an equal number of age- and sex-matched subjects without PD were selected for comparison. The primary outcome was new-onset AF.

RESULTS

During the mean follow-up period of 3.4 ± 1.8 years, AF was newly diagnosed in 3,665 patients. A significantly higher incidence rate of AF was noted among patients with PD than among patients without PD (10.75 and 7.86 per 1000 person-year, respectively). Multivariate Cox-regression analysis revealed that PD was an independent risk factor for AF (hazard ratio [HR]: 1.27, 95% confidence interval [CI]: 1.18-1.36). Furthermore, subgroup analyses revealed that AF risk was higher in the younger age subgroups, and compared with the non-PD group, the youngest PD group (age: 40-49 years) had a threefold increased risk of AF (HR: 3.06, 95% CI: 1.20-7.77).

INTERPRETATION

Patients with PD, especially the younger age subgroups, have an increased risk of AF. Active surveillance and management of AF should be considered to prevent further complications.

Effects of Cardiac Sympathetic Neurodegeneration and PPARγ Activation on Rhesus Macaque Whole Blood miRNA and mRNA Expression Profiles

Degeneration of sympathetic innervation of the heart occurs in numerous diseases, including diabetes, idiopathic REM sleep disorder, and Parkinson's disease (PD). In PD, cardiac sympathetic denervation occurs in 80-90% of patients and can begin before the onset of motor symptoms. Today, there are no disease-modifying therapies for cardiac sympathetic neurodegeneration, and biomarkers are limited to radioimaging techniques. Analysis of expression levels of coding mRNA and noncoding RNAs, such as microRNAs (miRNAs), can uncover pathways involved in disease, leading to the discovery of biomarkers, pathological mechanisms, and potential drug targets. Whole blood in particular is a clinically relevant source of biomarkers, as blood sampling is inexpensive and simple to perform. Our research group has previously developed a nonhuman primate model of cardiac sympathetic denervation by intravenous administration of the catecholaminergic neurotoxin 6-hydroxydopamine (6-OHDA). In this rhesus macaque (Macaca mulatta) model, imaging with positron emission tomography showed that oral administration of the peroxisome proliferator-activated receptor gamma (PPARγ) agonist pioglitazone (n = 5; 5 mg/kg daily) significantly decreased cardiac inflammation and oxidative stress compared to placebo (n = 5). Here, we report our analysis of miRNA and mRNA expression levels over time in the whole blood of these monkeys. Differential expression of three miRNAs was induced by 6-OHDA (mml-miR-16-2-3p, mml-miR-133d-3p, and mml-miR-1262-5p) and two miRNAs by pioglitazone (mml-miR-204-5p and mml-miR-146b-5p) at 12 weeks posttoxin, while expression of mRNAs involved in inflammatory cytokines and receptors was not significantly affected. Overall, this study contributes to the characterization of rhesus coding and noncoding RNA profiles in normal and disease-like conditions, which may facilitate the identification and clinical translation of biomarkers of cardiac neurodegeneration and neuroprotection.

Diagnosing multiple system atrophy at the prodromal stage

Identifying individuals at the earliest disease stage becomes crucial as we aim to develop disease-modifying treatments for neurodegenerative disorders. Prodromal diagnostic criteria were recently developed for Parkinson's disease (PD) and are forthcoming for dementia with Lewy bodies (DLB). The latest 2008 version of diagnostic criteria for multiple system atrophy (MSA) have improved diagnostic accuracy in early disease stages compared to previous criteria, but we do not yet have formal criteria for prodromal MSA. Building on similar approaches as for PD and DLB, we can identify features on history-taking, clinical examination, and ancillary clinical testing that can predict the likelihood of an individual developing MSA, while also distinguishing it from PD and DLB. The main clinical hallmarks of MSA are REM sleep behavior disorder (RBD) and autonomic dysfunction (particularly orthostatic hypotension and urogenital symptoms), and may be the primary means by which patients with potential prodromal MSA are identified. Preserved olfaction, absence of significant cognitive deficits, urinary retention, and respiratory symptoms such as stridor and respiratory insufficiency can be clinical features that help distinguish MSA from PD and DLB. Finally, ancillary test results including neuroimaging as well as serological and cerebrospinal fluid (CSF) biomarkers may lend further weight to quantifying the likelihood of phenoconversion into MSA. For prodromal criteria, the primary challenges are MSA's lower prevalence, shorter lead time to diagnosis, and strong overlap with other synucleinopathies. Future prodromal criteria may need to first embed the diagnosis into a general umbrella of prodromal alpha-synucleinopathies, followed by identification of features that suggest prodromal MSA as the specific cause.

Post mortem evaluation of inflammation, oxidative stress, and PPARγ activation in a nonhuman primate model of cardiac sympathetic neurodegeneration

Cardiac dysautonomia is a common nonmotor symptom of Parkinson’s disease (PD) associated with loss of sympathetic innervation to the heart and decreased plasma catecholamines. Disease-modifying strategies for PD cardiac neurodegeneration are not available, and biomarkers of target engagement are lacking. Systemic administration of the catecholaminergic neurotoxin 6-hydroxydopamine (6-OHDA) recapitulates PD cardiac dysautonomia pathology. We recently used positron emission tomography (PET) to visualize and quantify cardiac sympathetic innervation, oxidative stress, and inflammation in adult male rhesus macaques (Macaca mulatta; n = 10) challenged with 6-OHDA (50mg/kg; i.v.). Twenty-four hours post-intoxication, the animals were blindly and randomly assigned to receive daily doses of the peroxisome proliferator-activated receptor gamma (PPARγ) agonist pioglitazone (n = 5; 5mg/kg p.o.) or placebo (n = 5). Quantification of PET radioligand uptake showed increased oxidative stress and inflammation one week after 6-OHDA which resolved to baseline levels by twelve weeks, at which time pioglitazone-treated animals showed regionally preserved sympathetic innervation. Here we report post mortem characterization of heart and adrenal tissue in these animals compared to age and sex matched normal controls (n = 5). In the heart, 6-OHDA-treated animals showed a significant loss of sympathetic nerve fibers density (tyrosine hydroxylase (TH)-positive fibers). The anatomical distribution of markers of sympathetic innervation (TH) and inflammation (HLA-DR) significantly correlated with respective in vivo PET findings across left ventricle levels and regions. No changes were found in alpha-synuclein immunoreactivity. Additionally, CD36 protein expression was increased at the cardiomyocyte intercalated discs following PPARγ-activation compared to placebo and control groups. Systemic 6-OHDA decreased adrenal medulla expression of catecholamine producing enzymes (TH and aromatic L-amino acid decarboxylase) and circulating levels of norepinephrine, which were attenuated by PPARγ-activation. Overall, these results validate in vivo PET findings of cardiac sympathetic innervation, oxidative stress, and inflammation and illustrate cardiomyocyte CD36 upregulation as a marker of PPARγ target engagement.

Non-Motor Symptoms of the Postural Instability and Gait Difficulty Subtype in De Novo Parkinson's Disease Patients: A Cross-Sectional Study in a Single Center

BACKGROUND AND PURPOSE

Little is known about non-motor symptoms (NMSs) associated with the postural instability and gait difficulty (PIGD) phenotype, especially in de novo Parkinson's disease (PD) patients. The aims of this study were to compare NMSs between the tremor dominant (TD) and PIGD phenotypes in de novo PD patients and to determine factors that are associated with the PIGD subtype.

PATIENTS AND METHODS

In a cross-sectional study conducted at our single center, 226 de novo PD patients with a median disease duration of 2 years were recruited. Data, including comprehensive demographics, motor subtypes and NMSs were obtained. Motor subtypes were classified as PIGD and non-PIGD (TD and indeterminate) by Jankovic's method. NMSs were evaluated by the non-motor symptoms questionnaire (NMSQuest).

RESULTS

We identified 73 (32.3%), 34 (15.0%) and 119 (52.7%) patients with TD, intermediate and PIGD subtypes, respectively. Patients with the PIGD subtype had poorer ADL, motor, depression, anxiety, sleep, and non-motor scores compared with those with the TD subtype. In the NMSQuest, the prevalence of cardiovascular, sleep, mood/cognitive and miscellaneous domains was increased in patients with the PIGD subtype compared with patients with the TD subtype. Multivariable forward stepwise logistic regression revealed that the Hamilton Depression Scale (HAMD) [odds ratio (OR), 1.059; 95% confidence interval (CI), 1.016-1.104, p = 0.007] and pain (OR, 3.175; 95% CI, 1.695-5.947, p < 0.001) exhibit significant discriminative power in differentiating PIGD and non-PIGD groups.

CONCLUSION

The PIGD group had more severe cardiovascular symptoms, sleep impairments, mood disturbances and pain. We demonstrated for the first time that pain was associated with the PIGD phenotype. Prompt detection and early treatment of NMSs related to the PIGD phenotype may improve patient outcomes.

Autonomic dysfunction in Parkinson disease and animal models

Parkinson disease has traditionally been classified as a movement disorder, despite patients' accounts of diverse symptoms stemming from impairments in numerous body systems. Today, Parkinson disease is increasingly recognized by clinicians and scientists as a complex neurodegenerative disorder featuring both motor and nonmotor manifestations concomitant with pathology throughout all major branches of the nervous system. Dysfunction of the autonomic nervous system, or dysautonomia, is a common feature of Parkinson disease. It produces signs and symptoms that severely affect patients' quality of life, such as blood pressure dysregulation, hyperhidrosis, and constipation. Treatment options for dysautonomia are limited to symptom alleviation because the cause of these symptoms and Parkinson disease overall are still unknown. Animal models provide a platform to interrogate mechanisms of Parkinson disease-related autonomic nervous system dysfunction and test novel treatment strategies. Several animal models of Parkinson disease are available, each with different effects on the autonomic nervous system. This review critically analyses key dysautonomia signs and symptoms and associated pathology in Parkinson disease patients and relevant findings in animal models. We focus on the cardiovascular system, adrenal medulla, skin/thermoregulation, bladder, pupils, and gastrointestinal tract, to assess the contribution of animal models to the understanding of Parkinson disease autonomic dysfunction.

Roles of cardiac sympathetic neuroimaging in autonomic medicine

Sympathetic neuroimaging is based on the injection of compounds that either radiolabel sites of the cell membrane norepinephrine transporter (NET) or that are taken up into sympathetic nerves via the NET and radiolabel intra-neuronal catecholamine storage sites. Detection of the radioactivity is by planar or tomographic radionuclide imaging. The heart stands out among body organs in terms of the intensity of radiolabeling of sympathetic nerves, and virtually all of sympathetic neuroimaging focuses on the left ventricular myocardium. The most common cardiac sympathetic neuroimaging method worldwide is ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG) scanning. ¹²³I-MIBG scanning is used routinely in Europe and East Asia in the diagnostic evaluation of neurogenic orthostatic hypotension (nOH), to distinguish Lewy body diseases (e.g., Parkinson disease with orthostatic hypotension (OH), pure autonomic failure) from non-Lewy body diseases (e.g., multiple system atrophy) and to distinguish dementia with Lewy bodies from Alzheimer's disease. In the USA, ¹²³I-MIBG scanning has been approved by the Food and Drug Administration for the evaluation of pheochromocytoma and some forms of heart failure-but not for the above-mentioned differential diagnoses. Positron emission tomographic methods based on imaging agents such as ¹⁸F-dopamine are categorized as research tools, despite more than a quarter century of clinical experience with these modalities. Considering that ¹²³I-MIBG scanning is available at most academic medical centers in the USA, cardiac sympathetic neuroimaging by this methodology merits consideration as an autonomic test, especially in patients with nOH.

In vivo imaging of inflammation and oxidative stress in a nonhuman primate model of cardiac sympathetic neurodegeneration

Loss of cardiac postganglionic sympathetic innervation is a characteristic pathology of Parkinson’s disease (PD). It progresses over time independently of motor symptoms and is not responsive to typical anti-parkinsonian therapies. Cardiac sympathetic neurodegeneration can be mimicked in animals using systemic dosing of the neurotoxin 6-hydroxydopamine (6-OHDA). As in PD, 6-OHDA-induced neuronal loss is associated with increased inflammation and oxidative stress. To assess the feasibility of detecting changes over time in cardiac catecholaminergic innervation, inflammation, and oxidative stress, myocardial positron emission tomography with the radioligands [¹¹C]meta-hydroxyephedrine (MHED), [¹¹C]PBR28 (PBR28), and [⁶¹Cu]diacetyl-bis(N(4))-methylthiosemicarbazone (ATSM) was performed in 6-OHDA-intoxicated adult, male rhesus macaques (n = 10; 50 mg/kg i.v.). The peroxisome proliferator-activated receptor gamma (PPARγ) agonist pioglitazone, which is known to have anti-inflammatory and anti-oxidative stress properties, was administered to five animals (5 mg/kg, PO); the other five were placebo-treated. One week after 6-OHDA, cardiac MHED uptake was significantly reduced in both groups (placebo, 86% decrease; pioglitazone, 82%); PBR28 and ATSM uptake increased in both groups but were attenuated in pioglitazone-treated animals (PBR28 Treatment × Level ANOVA p < 0.002; ATSM Mann–Whitney p = 0.032). At 12 weeks, partial recovery of MHED uptake was significantly greater in the pioglitazone-treated group, dependent on left ventricle circumferential region and axial level (Treatment × Region × Level ANOVA p = 0.034); 12-week MHED uptake significantly correlated with tyrosine hydroxylase immunoreactivity across cardiac anatomy (p < 0.000002). PBR28 and ATSM uptake returned to baseline levels by 12 weeks. These radioligands thus hold potential as in vivo biomarkers of mechanisms of cardiac neurodegeneration and neuroprotection.

Three cardiac nerve loss biomarkers enable the visualization of cardiac neurodegeneration and response to neuroprotective treatment. The loss of sympathetic cardiac innervation in patients with PD causes symptoms such as postural hypotension, arrhythmia, and fatigue that do not respond to anti-parkinsonian medications. Marina Emborg and colleagues at University of Wisconsin–Madison, USA, used positron emission tomography with three radioligands to image changes in cardiac innervation, oxidative stress and inflammation in monkeys during neurotoxin-induced PD-like cardiac neurodegeneration. They were able to visualize the recruitment of inflammatory cells and increased production of reactive oxygen species during neurodegeneration as well as observe improvements in response to pioglitazone, a drug that has previously been shown to have neuroprotective effects in animal models of PD. These radioligands could be useful imaging biomarkers of cardiac nerve loss progression in patients with PD or cardiovascular disease.

Peripheral and central autonomic nervous system: does the sympathetic or parasympathetic nervous system bear the brunt of the pathology during the course of sporadic PD?

It is a well-established fact that the sympathetic, parasympathetic and enteric nervous systems are affected at early stages in Parkinson's disease (PD). However, it is not yet clarified whether the earliest pathological events preferentially occur in any of these three divisions of the autonomic nervous system (ANS). Significant involvement of the peripheral autonomic nervous system of the heart and gastrointestinal tract has been documented in PD. Accumulating evidence suggests that the PD pathology spreads centripetally from the peripheral to central nervous system through autonomic nerve fibers, implicating the ANS as a major culprit in PD pathogenesis and a potential target for therapy. This study begins with a brief overview of the structures of the central and peripheral autonomic nervous system and then outlines the major clinicopathological manifestations of cardiovascular and gastrointestinal disturbances in PD.

Role of Neuroimaging as a Biomarker for Neurodegenerative Diseases

It has recently been recognized that neurodegenerative diseases are caused by common cellular and molecular mechanisms including protein aggregation and inclusion body formation. Each type of neurodegenerative disease is characterized by the specific protein that aggregates. In these days, the pathway involved in protein aggregation has been elucidated. These are leading to approaches toward disease-modifying therapies. Neurodegenerative diseases are fundamentally diagnosed pathologically. Therefore, autopsy is essential for a definitive diagnosis of a neurodegenerative disease. However, recently, the development of various molecular brain imaging techniques have enabled pathological changes in the brain to be inferred even without autopsy. Some molecular imaging techniques are described as biomarker in diagnostic criteria of neurodegenerative disease. Magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), positron emission tomography (PET), and amyloid imaging are described in the diagnostic guidelines for Alzheimer’s disease in the National Institute on Aging-Alzheimer’s Association. MRI, dopamine transporter (DAT) imaging, and ¹²³I-metaiodobenzyl-guanidine (MIBG) myocardial scintigraphy listed in the guidelines for consensus clinical diagnostic criteria for dementia with Lewy bodies are described as potential biomarkers. The Movement Disorder Society Progressive Supranuclear Palsy Study Group defined MRI, SPECT/PET, DAT imaging, and tau imaging as biomarkers. Other diagnostic criteria for neurodegenerative disease described neuroimaging findings as only characteristic finding, not as biomarker. In this review, we describe the role of neuroimaging as a potential biomarker for neurodegenerative diseases.

Clinical and radiological diversity in genetically confirmed primary familial brain calcification

Primary familial brain calcification (PFBC) is a rare neuropsychiatric disorder with characteristic symmetrical brain calcifications. Patients with PFBC may have a variety of symptoms, although they also may be clinically asymptomatic. Parkinsonism is one of the most common movement disorders; however, the underlying mechanism remains unclear. This condition is typically transmitted in an autosomal dominant fashion. To date, mutations in SLC20A2, PDGFRB, PDGFB, and XPR1 have been reported to cause PFBC. The aim of the study was to identify the genetic cause of brain calcification in probands from three PFBC families and in 8 sporadic patients and to perform clinical and radiological assessments focusing on parkinsonism in mutation carriers. Three familial PFBC probands and their relatives and eight sporadic patients affected with brain calcifications were enrolled in this study. Whole-exome sequencing identified three novel mutations: c.269G > T, p.(Gly90Val) and c.516+1G > A in SLC20A2 in familial cases, and c.602-1G > T in PDGFB in a sporadic patient. The c.516+1G > A mutation resulted in exon 4 skipping in SLC20A2 (p.Val144Glyfs*85). Dopamine transporter single photon emission computed tomography using ¹²³I-ioflupane and ¹²³I-metaiodobenzylguanidine cardiac scintigraphy revealed pre-synaptic dopaminergic deficit and cardiac sympathetic nerve dysfunction in two SLC20A2-related PFBC patients with parkinsonism.

New development of diagnosis and treatment for Parkinson's disease

New methods for the diagnosis and new treatments for Parkinson's disease (PD) were explained. As imaging tools, neuromelanin imaging using brain MRI, meta-iodobenzylguanidine (MIBG) cardiac scintigraphy, dopamine transporter scintigraphy, and transcranial sonography were introduced. Olfactory dysfunction and REM sleep behavior disorders (RBD), which are important non-motor symptoms, and the new Clinical Criteria for PD launched by Movement Disorder Society (MDS) were also described. Investigative new medications and new anti-PD medications, which recently became available in Japan, were introduced. I explained the rationale of early treatment, strategy of initial treatment, the significance of continuous dopaminergic stimulation, strategy of treatment for advanced PD, and deep brain stimulation as a surgical treatment together with promising new treatments including gene therapy and cell transplantation.

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.

Heart rate variability in leucine-rich repeat kinase 2-associated Parkinson's disease

BACKGROUND

Heart rate variability is reduced in idiopathic PD, indicating cardiac autonomic dysfunction likely resulting from peripheral autonomic synucleinopathy. Little is known about heart rate variability in leucine-rich repeat kinase 2-associated PD.

OBJECTIVES

This study investigated heart rate variability in LRRK2-associated PD.

METHODS

Resting electrocardiograms were obtained from 20 individuals with LRRK2-associated PD, 37 nonmanifesting carriers, 48 related noncarriers, 26 idiopathic PD patients, and 32 controls. Linear regression modelling compared time and frequency domain values, adjusting for age, sex, heart rate, and disease duration.

RESULTS

Low-frequency power and the ratio of low-high frequency power were reduced in idiopathic PD versus controls (P < .008, P < .029 respectively). In contrast, individuals with LRRK2-associated PD were not statistically different from controls in any parameter measured. Furthermore, all parameters trended toward being higher in LRRK2-associated PD when compared with idiopathic PD.

CONCLUSIONS

Heart rate variability may remain intact in LRRK2-associated PD, adding to a growing literature supporting clinical-pathologic differences between LRRK2-associated and idiopathic PD. © 2017 International Parkinson and Movement Disorder Society.

Cardiovascular dysfunction in untreated Parkinson's disease: A multi-modality assessment

BACKGROUND

The clinical presentation of Parkinson's disease (PD) includes a wide spectrum of non-motor features, including cardiovascular autonomic failure.

OBJECTIVE

To evaluate cardiovascular autonomic status and cardiac functional capacity in drug-naïve PD patients.

METHODS

18 newly-diagnosed PD patients underwent laboratory cardiovascular autonomic function tests using power spectral analysis of the R-R interval, blood pressure (BP) short-term variability and non-invasive baroreflex sensitivity (BRS). A two-dimensional (2D) transthoracic echocardiogram, spirometry and cardiopulmonary exercise test (CPET) were also performed. Thirteen patients underwent myocardial scintigraphy with [¹²³I] metaiodobenzylguanidine (MIBG).

RESULTS

At rest, total power spectral analysis of heart rate variability was lower in PD patients than in controls. BRS decreased during sympathetic activation in both patients and controls. While echocardiography and spirometry were normal, a mild degree of exercise intolerance was observed at the CPET in PD patients (mean V'O_2max: 83% of predicted; mean W_max: 80% of predicted). The heart-to-mediastinum (H/M) ratio of MIBG uptake was pathologically impaired in 9 patients, one of whom displayed a definite cardiovascular dysautonomic pattern.

CONCLUSIONS

Our results confirm that subclinical to overt cardiovascular autonomic failure may occur from the early stages of PD. The less efficient adaptive response to physical stimuli during the CPET and postural changes observed in untreated PD patients possibly reflect cardiac sympathetic denervation, although the involvement of PD-related motor impairment in physical deconditioning cannot be excluded.

Studying the pathophysiologic connection between cardiovascular and nervous systems using stem cells

The cardiovascular and nervous systems are deeply connected during development, health, and disease. Both systems affect and regulate the development of each other during embryogenesis and the early postnatal period. Specialized neural crest cells contribute to cardiac structures, and a number of growth factors released from the cardiac tissue (e.g., glial cell line-derived neurotrophic factor, neurturin, nerve growth factor, Neurotrophin-3) ensure proper maturation of the incoming parasympathetic and sympathetic neurons. Physiologically, the cardiovascular and nervous systems operate in harmony to adapt to various physical and emotional conditions to maintain homeostasis through sympathetic and parasympathetic nervous systems. Moreover, neurocardiac regulation involves a neuroaxis consisting of cortex, amygdala, and other subcortical structures, which have the ability to modify lower-level neurons in the hierarchy. Given the interconnectivity of cardiac and neural systems, when one undergoes pathological changes, the other is affected to a certain extent. In addition, there are specific neurocardiac diseases that affect both systems simultaneously, such as Huntington disease, Lewy body diseases, Friedreich ataxia, congenital heart diseases, Danon disease, and Timothy syndrome. Over the last decade, in vitro modeling of neurocardiac diseases using induced pluripotent stem cells (iPSCs) has provided an invaluable opportunity to elevate our knowledge about the brain-heart connection, since previously primary cardiomyocytes and neurons had been extremely difficult to maintain long-term in vitro. Ultimately, the ability of iPSC technology to model abnormal functional phenotypes of human neurocardiac disorders, combined with the ease of therapeutic screening using this approach, will transform patient care through personalized medicine in the future. © 2016 Wiley Periodicals, Inc.

(123)I-meta-iodobenzylguanidine (MIBG) cardiac scintigraphy in α-synucleinopathies

Cardiac meta-iodobenzylguanidine (MIBG) uptake on (123)I-MIBG cardiac scintigraphy is reduced in patients with Lewy body disease such as Parkinson's disease (PD), dementia with Lewy bodies (DLB), and pure autonomic failure, and has been reported to be useful for differentiating PD from other parkinsonian syndromes, as well as DLB from Alzheimer disease (AD). Postmortem studies have shown that the number of tyrosine hydroxylase (TH)-immunoreactive nerve fibers of the heart was decreased in pathologically-confirmed Lewy body disease, supporting the findings of reduced cardiac MIBG uptake in Lewy body diseases. Now, reduced cardiac MIBG uptake can be a potential biomarker for the presence of Lewy bodies in the nervous system. (123)I-MIBG cardiac scintigraphy can allow us to determine the presence of Lewy bodies.

Dysautonomia in prodromal α-synucleinopathy: peripheral versus central autonomic degeneration

BACKGROUND AND PURPOSE

There is an urgent need for early predictive markers for the course of disease in prodromal α-synucleinopathies such as idiopathic rapid eye movement (REM) sleep behaviour disorder. Autonomic cardiac/vascular dysfunction is a prominent feature in advanced α-synucleinopathies, but its diagnostic value as an early neurodegenerative marker remains unclear. The latter may be complicated since synuclein-mediated neurodegeneration may involve central and peripheral components of the autonomic nervous system.

METHODS

The diagnostic value of autonomic symptoms and central and peripheral autonomic markers of blood pressure and heart rate regulation were prospectively evaluated in 20 subjects with idiopathic REM sleep behaviour disorder and 20 age-matched healthy controls.

RESULTS

Although subjects with REM sleep behaviour disorder showed no clinical autonomic symptoms, blood pressure (P ≤ 0.035) and heart rate response (P ≤ 0.065) were slightly diminished during orthostatic challenge. Autonomic dysregulation was distinctively reflected in lower resting heart rate (all components, P ≤ 0.05) and blood pressure variability (low frequency component, P ≤ 0.024) indicating peripheral cardiac/vascular denervation. In contrast, baroreflex sensitivity and central cardiac autonomic outflow (sympathovagal balance) were well preserved indicating intact central autonomic regulation. Heart rate variability [very low frequency component, receiver operating characteristic (ROC) area under the curve (AUC) 0.80, P ≤ 0.001] and blood pressure variability (low frequency component ROC AUC 0.73, P ≤ 0.01) but not baroreflex sensitivity and sympathovagal balance showed an excellent diagnostic accuracy in identifying subjects with REM sleep behaviour disorder and healthy controls.

CONCLUSIONS

Cardiac/vascular dysfunction in prodromal α-synucleinopathy arises from peripheral rather than from central autonomic degeneration. Autonomic indices encoded in heart rate and blood pressure variability are precise functional markers of early synuclein-mediated neurodegeneration.