Dobutamine stress test unmasks cardiac sympathetic denervation in Parkinson's disease

Functional and 123I-MIBG scintigraphy assessment of cardiac adrenergic dysfunction in diabetes

OBJECTIVES

To assess the agreement between clinical cardiovascular adrenergic function and cardiac adrenergic innervation in type 2 diabetes patients (T2D).

METHODS

Thirty-three patients with T2D were investigated bimodally through (1) a standardized clinical cardiovascular adrenergic assessment, evaluating adequacy of blood pressure responses to the Valsalva maneuver and (2) 123I-meta-iodobenzylguanidine (MIBG) scintigraphy assessing myocardial adrenergic innervation measured as early and delayed heart heart/mediastinum (H/M) ratio, and washout rate (WR).

RESULTS

T2D patients had significantly lower early and delayed H/M-ratios, and lower WR, compared to laboratory specific reference values. Thirteen patients had an abnormal adrenergic composite autonomic severity score (CASS > 0). Patients with abnormal CASS scores had significantly higher early H/M ratios (1.76 [1.66-1.88] vs. 1.57 [1.49-1.63], p < 0.001), higher delayed H/M ratios (1.64 [1.51:1.73] vs. 1.51 [1.40:1.61] (p = 0.02)), and lower WR (-0.13(0.10) vs -0.05(0.07), p = 0.01). Lower Total Recovery and shorter Pressure Recovery Time responses from the Valsalva maneuver was significantly correlated to lower H/M early (r = 0.55, p = 0.001 and r = 0.5, p = 0.003, respectively) and lower WR for Total Recovery (r = -0.44, p = 0.01).

CONCLUSION

The present study found impairment of sympathetic innervation in T2D patients based on parameters derived from MIBG cardiac scintigraphy (low early H/M, delayed H/M, and WR). These results confirm prior studies. We found a mechanistically inverted relationship with favourable adrenergic cardiovascular responses being significantly associated unfavourable MIBG indices for H/M early and delayed. This paradoxical relationship needs to be further explored but could indicate adrenergic hypersensitivity in cardiac sympathetic denervated T2D patients.

EKGDR: An End-to-End Knowledge Graph-Based Method for Computational Drug Repurposing

The lengthy and expensive process of developing new drugs from scratch, coupled with a high failure rate, has prompted the emergence of drug repurposing/repositioning as a more efficient and cost-effective approach. This approach involves identifying new therapeutic applications for existing approved drugs, leveraging the extensive drug-related data already gathered. However, the diversity and heterogeneity of data, along with the limited availability of known drug-disease interactions, pose significant challenges to computational drug design. To address these challenges, this study introduces EKGDR, an end-to-end knowledge graph-based approach for computational drug repurposing. EKGDR utilizes the power of a drug knowledge graph, a comprehensive repository of drug-related information that encompasses known drug interactions and various categorization information, as well as structural molecular descriptors of drugs. EKGDR employs graph neural networks, a cutting-edge graph representation learning technique, to embed the drug knowledge graph (nodes and relations) in an end-to-end manner. By doing so, EKGDR can effectively learn the underlying causes (intents) behind drug-disease interactions and recursively aggregate and combine relational messages between nodes along different multihop neighborhood paths (relational paths). This process generates representations of disease and drug nodes, enabling EKGDR to predict the interaction probability for each drug-disease pair in an end-to-end manner. The obtained results demonstrate that EKGDR outperforms previous models in all three evaluation metrics: area under the receiver operating characteristic curve (AUROC = 0.9475), area under the precision-recall curve (AUPRC = 0.9490), and recall at the top-200 recommendations (Recall@200 = 0.8315). To further validate EKGDR's effectiveness, we evaluated the top-20 candidate drugs suggested for each of Alzheimer's and Parkinson's diseases.

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.

Severe blood pressure elevation following ephedrine administration during carotid endarterectomy under general anesthesia: A CARE-compliant case report

RATIONALE

During carotid endarterectomy (CEA) surgery, blood pressure management is particularly important to prevent cerebrovascular and cardiac complications. Ephedrine is a commonly used vasopressor, however, we report the case of a patient with unusually severe blood pressure elevation following intravenous ephedrine administration during CEA.

PATIENT CONCERNS

A 72-year-old man diagnosed with right proximal internal carotid artery stenosis underwent CEA under general anesthesia. After declamping the common carotid artery, blood pressure rapidly increased by 125 mm Hg (from 90 to 215 mm Hg) after ephedrine (4 mg) was administered, but the heart rate was stable.

DIAGNOSES

There was an ordinal increase in blood pressure after the same small dose of ephedrine was administered at the early stage of the surgery. And the surgical approach was difficult because he had a high location of carotid bifurcation and a prominent mandibular angle. Because of the anatomical proximity of the cervical sympathetic trunk to the carotid bifurcation and the particularly complicated surgical process in the present case, we postulate the reason for this adverse reaction as transient sympathetic denervation supersensitivity.

INTERVENTIONS

Perdipine (0.5 mg) was administered repeatedly to reduce blood pressure.

OUTCOMES

After surgery, he was diagnosed with right hypoglossal nerve palsy, and no other abnormal signs were found.

CONCLUSION

This case highlights the need for caution in the use of ephedrine, which is commonly used in CEA surgery, wherein blood pressure management is particularly important. Although it is a rare and unpredictable case, α-agonists are considered safer in situations where sympathetic supersensitivity is possible.

Stress cardiomyopathy (Takotsubo syndrome) in patients who received adrenergic agonist drugs: A pharmacovigilance study using the Japanese Adverse Drug Event Report (JADER) database

INTRODUCTION

Stress cardiomyopathy, or Takotsubo syndrome (TTS), is an acute and reversible syndrome developing in strong association with psychological or physiological stressors. While a surge in the circulating catecholamine level is suspected as one of its pathophysiologies, the contribution of treatment with sympathomimetic drugs to the development of TTS remains uncertain.

METHODS

We conducted a disproportionality analysis using the Japanese Adverse Drug Event Report (JADER) database containing more than 500,000 patient cases recorded between April 2004 and March 2019, to detect TTS ('stress cardiomyopathy') as adverse event signals associated with adrenergic agonist drugs usage by calculating reporting odds ratio (ROR).

RESULTS

Among 306 TTS cases reported to JADER, we identified 58 TTS cases with exposure to adrenergic agonist drugs, predominantly of women (52/58, 89.7%) and those in the median age-decades of the 70s. After adjusting for age in decades and sex, most of the intravenous catecholamines showed significantly higher reporting (lower 95% ROR > 1) for TTS, including adrenaline, noradrenaline, dobutamine, dopamine, phenylephrine, and ephedrine. In addition, peroral midodrine, transdermal tulobuterol, inhaled salbutamol, and inhaled procaterol also showed significantly higher ROR for TTS. We also identified a small number of TTS cases with Parkinson's disease taking midodrine or droxidopa, but not receiving other adrenergic agonists.

CONCLUSION

The current pharmacovigilance study showed significantly higher RORs for TTS following the use of some of the adrenergic drugs, being mostly consistent with the TTS-related adrenergic drugs reported in earlier literature. A potential association of taking midodrine or droxidopa with the development of TTS was also suggested.

Adrenergic supersensitivity and impaired neural control of cardiac electrophysiology following regional cardiac sympathetic nerve loss

Myocardial infarction (MI) can result in sympathetic nerve loss in the infarct region. However, the contribution of hypo-innervation to electrophysiological remodeling, independent from MI-induced ischemia and fibrosis, has not been comprehensively investigated. We present a novel mouse model of regional cardiac sympathetic hypo-innervation utilizing a targeted-toxin (dopamine beta-hydroxylase antibody conjugated to saporin, DBH-Sap), and measure resulting electrophysiological and Ca²⁺ handling dynamics. Five days post-surgery, sympathetic nerve density was reduced in the anterior left ventricular epicardium of DBH-Sap hearts compared to control. In Langendorff-perfused hearts, there were no differences in mean action potential duration (APD₈₀) between groups; however, isoproterenol (ISO) significantly shortened APD₈₀ in DBH-Sap but not control hearts, resulting in a significant increase in APD₈₀ dispersion in the DBH-Sap group. ISO also produced spontaneous diastolic Ca²⁺ elevation in DBH-Sap but not control hearts. In innervated hearts, sympathetic nerve stimulation (SNS) increased heart rate to a lesser degree in DBH-Sap hearts compared to control. Additionally, SNS produced APD₈₀ prolongation in the apex of control but not DBH-Sap hearts. These results suggest that hypo-innervated hearts have regional super-sensitivity to circulating adrenergic stimulation (ISO), while having blunted responses to SNS, providing important insight into the mechanisms of arrhythmogenesis following sympathetic nerve loss.

Development of early diagnosis of Parkinson's disease: Illusion or reality?

The fight against neurodegenerative diseases, Alzheimer disease and Parkinson's disease (PD), is a challenge of the 21st century. The low efficacy of treating patients is due to the late diagnosis and start of therapy, after the degeneration of most specific neurons and depletion of neuroplasticity. It is believed that the development of early diagnosis (ED) and preventive treatment will delay the onset of specific symptoms. This review evaluates methodologies for developing ED of PD. Since PD is a systemic disease, and the degeneration of certain neurons precedes that of nigrostriatal dopaminergic neurons that control motor function, the current methodology is based on searching biomarkers, such as premotor symptoms and changes in body fluids (BF) in patients. However, all attempts to develop ED were unsuccessful. Therefore, it is proposed to enhance the current methodology by (i) selecting among biomarkers found in BF in patients at the clinical stage those that are characteristics of animal models of the preclinical stage, (ii) searching biomarkers in BF in subjects at the prodromal stage, selected by detecting premotor symptoms and failure of the nigrostriatal dopaminergic system. Moreover, a new methodology was proposed for the development of ED of PD using a provocative test, which is successfully used in internal medicine.

Ephedrine-Induced Increases in Blood Pressure and Heart Rate Due to Suspected Cardiac Sympathetic Denervation Supersensitivity in a Patient with Parkinson's Disease Under Spinal Anesthesia

BACKGROUND Denervation supersensitivity to sympathomimetic drugs has been noted in patients with Parkinson's disease (PD) whose cardiac sympathetic nerves are denervated. This phenomenon is not as well recognized as other complications of PD patients, but anesthesiologists should be aware of it because sympathomimetic drugs can sometimes be dangerous to these patients. CASE REPORT A 60-year-old woman was scheduled for total hip joint replacement under combined spinal-epidural anesthesia and sedation. She had been diagnosed as PD (stage 4 on the Hoehn and Yahr scale) with a history of orthostatic hypotension. Her ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy revealed marked reduction of ¹²³I-MIBG accumulation in the heart. In the operating room, we placed an epidural catheter through the Th12-L1 space, and spinal anesthesia (2.6 mL of 0.5% normobaric bupivacaine) was administered. During the surgery, we infused propofol at 100 mg·hr⁻¹ for sedation. When 4 mg of ephedrine was administered intravenously because of marked decrease in patient's blood pressure, we observed unexpectedly large increases in the systolic blood pressure, from 78 mmHg to 168 mmHg, and the heart rate increased from 52 to 84 beats per minute (bpm). This phenomenon recurred each time 4 mg of ephedrine was administered. CONCLUSIONS We report a case in which ephedrine induced unexpectedly large increases in blood pressure and heart rate in a patient who suffered from PD with severe cardiac sympathetic nerve denervation. We speculate that this phenomenon was caused by denervation supersensitivity of the patient's heart.

Unusually large ephedrine-induced blood pressure increases due to cardiac sympathetic denervation supersensitivity in a patient with Parkinson's disease

BACKGROUND

Parkinson's disease (PD) patients often suffer from cardiac sympathetic denervation, a hallmark of which is orthostatic hypotension. Denervation supersensitivity to sympathomimetic drugs is also seen in such patients, and this phenomenon is important and can be sometimes dangerous.

CASE PRESENTATION

A 65-year-old male underwent gastrojejunostomy. The patient had severe PD and did not exhibit metaiodobenzylguanidine (MIBG) accumulation in his heart, which was indicative of cardiac sympathetic nerve denervation. When 8 mg of ephedrine was administered intravenously, an unexpectedly large increase in blood pressure was observed. The phenomenon recurred when 4 mg of ephedrine was administered again, and nicardipine was required to suppress the patient's blood pressure.

CONCLUSIONS

Denervation supersensitivity is not as well recognized as other complications seen in PD patients, but anesthesiologists should be aware of it because sympathomimetic drugs can have excessively strong effects in patients with the condition.

Role of peripheral vascular resistance as an indicator of cardiovascular abnormalities in patients with Parkinson's disease

The aim of this study was to evaluate cardiovascular autonomic modulation in response to an orthostatic stress in healthy subjects and Parkinson's disease (PD). The study included 47 controls and 56 PD patients divided into groups (vasoconstrictor PD, vasodilator PD, control) according to vasodilation/vasoconstriction response during 70° head up tilt test. Using impedance cardiography (ICG) and electrocardiography (ECG) we measured stroke volume, cardiac output, left ventricular work index, left ventricular ejection time, acceleration index, index of contractility, Heather index, thoracic fluid content, total peripheral resistance, total arterial compliance. We also analyzed heart rate variability (HRV), using spectral analysis and continuous blood pressure (contBP). At rest, the vasodilator PD group showed significantly higher values of total peripheral resistance and lower values of stroke volume and cardiac output, compared to the vasoconstrictor PD and the control groups. A post-tilt drop in ∆ (change rest - tilt) systolic blood pressure, ∆mean blood pressure, ∆total peripheral resistance and ∆Heather index, and a significantly lower increase in ∆diastolic blood pressure was observed in subjects from the vasodilator PD group compared to the vasoconstrictor PD and the control groups. No statistically significant differences were observed for HRV parameters between the vasoconstrictor and vasodilator PD groups, P > .05. Longer duration and higher disease stage of PD correlated with a reduction in post-tilt systolic blood pressure changes in vasodilator group. Positive inotropy of the cardiac muscle represents a significant factor preventing orthostatic hypotension in PD subjects with a concurrent drop in peripheral vascular resistance during orthostatic stress.

Cardiac parasympathetic dysfunction in the early phase of Parkinson's disease

Cardiac parasympathetic function is strongly affected by aging. Although sympathetic dysfunction has been well documented in Parkinson's disease (PD), cardiac parasympathetic dysfunction has not been well studied. The objective of this study was to clarify the development of cardiac parasympathetic dysfunction in the early phase of PD and to explore the age-corrected correlation between cardiac parasympathetic dysfunction and cardiac sympathetic dysfunction. We reviewed 25 healthy controls and 56 patients with idiopathic PD of Hoehn and Yahr stages I-III. We evaluated cardiac parasympathetic function using the Valsalva ratio, the baroreflex sensitivity (BRS) and the coefficient of variation of RR intervals in the resting state (resting-CVRR) and during deep breathing (DB-CVRR). In addition, we measured cardiac ¹²³I-metaiodobenzylguanidine (MIBG) uptake to investigate the relationship between cardiac sympathetic and parasympathetic dysfunction in PD. Compared with healthy controls, patients with PD showed significantly decreased cardiac parasympathetic parameters (resting-CVRR 2.8 ± 1.3 vs. 1.7 ± 0.6%, p < 0.001; DB-CVRR 5.8 ± 2.3 vs. 3.8 ± 1.7%, p < 0.001; Valsalva ratio 1.52 ± 0.26 vs. 1.34 ± 0.17, p < 0.01; BRS 10.6 ± 9.5 vs. 5.0 ± 5.4 ms/mmHg, p < 0.01). In particular, resting-CVRR and DB-CVRR were significantly decreased in the early phase of PD. In age-corrected analyses, none of the parasympathetic indices correlated with the delayed cardiac ¹²³I-MIBG uptake. These observations indicate that cardiac parasympathetic dysfunction occurs in the early phase of PD, but not necessarily in parallel with cardiac sympathetic dysfunction.

(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.

Cardiocirculatory manifestations in Parkinson's disease patients without orthostatic hypotension

The objective of this study was to characterize cardiac sympathetic denervation in Parkinson's disease (PD) patients without neurogenic orthostatic hypotension (NOH), both in terms of hemodynamics and in its relation with vascular denervation. We studied 20 PD patients without NOH. We analyzed the heart rate and blood pressure variability during various physical maneuvers. The following parameters were calculated: expiratory-inspiratory ratio, stroke volume, cardiac output, cardiac index, left ventricular ejection time, left ventricular work index, thoracic fluid content, total peripheral resistance and baroreflex sensitivity (BRS). We also measured direct and spectral derivatives of cardiac (cardiovagal) parasympathetic function. Myocardial I-123 metaiodobenzylguanidine (MIBG) scintigraphy was performed and early and late heart/mediastinum uptake ratios were analyzed. We observed that the late heart/mediastinum uptake ratio was 1.33±0.21. This parameter was correlated with years since diagnosis (correlation coefficient:-0.485; P=0.05), Unified Parkinson's Disease Rating Scale (UPDRS) III score (cc:-0.564; P=0.02) and pressure recovery time in the Valsalva maneuver (cc: 0.61; P<0.001). At rest, it was correlated with BRS (cc:0.75; P=0.003) and low-frequency diastolic blood pressure (LFDBP; cc: 0.58;P=0.017). We found no correlations with any of the cardiography impedance variables. In linear regression models, the variable that best correlated with MIBG results was LFDBP. Our results support that in absence of NOH the degree of denervation of the heart does not produce any effect on its inotropic function. Moreover, BRS and LFDBP can be used as an indirect measure of cardiac sympathetic denervation at rest.

Hyposmia and cardiovascular dysautonomia correlatively appear in early-stage Parkinson's disease

OBJECTIVE

Olfactory dysfunction is considered to precede motor symptoms and early markers of Parkinson's disease (PD), while the relative time at which cardiovascular dysautonomia appears in PD is not well understood. To assess the appearance of cardiovascular dysautonomia in PD, we evaluated its relation to olfactory dysfunction in early-stage PD patients.

METHODS

Twenty-three non-demented PD patients within 2 years from the onset of motor symptoms were enrolled. We evaluated olfactory dysfunction by the Odor Stick Identification Test for Japanese (OSIT-J) and analyzed its relationship to the results of other cardiovascular autonomic tests and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphy.

RESULTS

There was a correlation between olfactory scores and increased blood pressure in both the norepinephrine (r = 0.75, p < 0.0001, n = 21) and dobutamine (r = 0.57, p = 0.0087, n = 20) infusion tests and cardiac MIBG uptake (r = 0.42, p = 0.049, n = 23). The fall in orthostatic blood pressure during the head-up tilt test was not correlated with the olfactory scores, but the Valsalva maneuver revealed that OSIT-J scores correlated with the pressure recovery time from phase III to the return of blood pressure to baseline (r = 0.54, p = 0.037, n = 15) and with the magnitude of blood pressure overshoot during phase IV (r = 0.67, p = 0.0016, n = 20).

CONCLUSION

Our results demonstrate that extensive components of the cardiovascular sympathetic system as well as the olfactory system are correlatively impaired in the early stage of PD, suggesting that degeneration of broad aspects of the cardiovascular sympathetic system occurs concurrently with olfactory system degeneration during the premotor phase of PD.

Impaired baroreflex function in mice overexpressing alpha-synuclein

Cardiovascular autonomic dysfunction, such as orthostatic hypotension consequent to baroreflex failure and cardiac sympathetic denervation, is frequently observed in the synucleinopathy Parkinson’s disease (PD). In the present study, the baroreceptor reflex was assessed in mice overexpressing human wildtype alpha-synuclein (Thy1-aSyn), a genetic mouse model of synucleinopathy. The beat-to-beat change in heart rate (HR), computed from R–R interval, in relation to blood pressure was measured in anesthetized and conscious mice equipped with arterial blood pressure telemetry transducers during transient bouts of hypertension and hypotension. Compared to wildtype, tachycardia following nitroprusside-induced hypotension was significantly reduced in Thy1-aSyn mice. Thy1-aSyn mice also showed an abnormal cardiovascular response (i.e., diminished tachycardia) to muscarinic blockade with atropine. We conclude that Thy1-aSyn mice have impaired basal and dynamic range of sympathetic and parasympathetic-mediated changes in HR and will be a useful model for long-term study of cardiovascular autonomic dysfunction associated with PD.

[Cardiac reserve in Parkinson's disease and exercise therapy]

The clinical feature of Parkinson's disease (PD) is not based on the identification of the extrapyramidal symptom such as bradykinesia, restinbg tremor, rigidity, but also other non-motor symptom (REM sleep disorder, autonomic dysfunction, hyposmia etc). According to the cardio-sympathetic dysfunction, it is well known abnormal MIBG and orthostatic hypotension finding was seen in early disease stage. Furthermore denervation supersensitivity using β1 stimulant correlates the severity of MIBG image, so that this abnormal cardiac function induces inadequate cardiac capacity for exercise. Inadequate cardiac capacity makes easy fatigability, which correlates the abnormal MIBG image and cardio-sympathetic damage. So it is difficult to prescribe a specific exercise program to meet individual PD patients needs. Music therapy and trunk exercise (for example Tai-Chi exercise) are better suited for PD patients.

Urinary 8-hydroxydeoxyguanosine correlate with hallucinations rather than motor symptoms in Parkinson's disease

BACKGROUND

Oxidative stress is causally associated with the pathogenesis of Parkinson's disease (PD). Oxygen generates a large amount of reactive oxygen species (ROS). ROS including hydroxyl radicals and H(2)O(2) react with guanine residues in DNA and produce 8-hydroxydeoxyguanosine (8-OHdG). 8-OHdG serves as a biomarker for oxidative stress in various diseases.

METHOD

We investigated urinary 8-OHdG levels in 61 PD patients and 28 normal subjects to evaluate the correlation with various clinical features. We quantified disease severity using the Unified Parkinson's Disease Rating Scale for motor symptoms (UPDRS part 3), the Mini-Mental State Examination (MMSE) for mental function, and the Tottori University Hallucination Rating Scale (TUHARS) for quantifying hallucinations.

RESULTS

There were significant correlations between 8-OHdG and all the examined parameters, but the partial correlation coefficients excluding contributions of all the other parameters showed that only TUHARS and UPDRS part 3 are significantly related to 8-OHdG. In particular, TUHARS correlates best with urinary 8-OHdG levels.

CONCLUSION

The significant correlation between urinary 8-OHdG levels and hallucinations but not with dementia suggests that hallucinations are likely to have unique but unidentified mechanisms that lead to excessive production of 8-OHdG.

123I-metaiodobenzylguanidine scintigraphy in Parkinson's disease and related disorders

Autonomic dysfunction is common in Lewy body disorders (Parkinson's disease, Dementia with Lewy Bodies, Pure Autonomic Failure, and REM sleep disorder). The loss of post-ganglionic myocardial sympathetic nerve fibers is a prominent feature of autonomic dysfunction in such disorders. (123)I-metaiodobenzylguanidine (MIBG) scintigraphy that visualizes catecholaminergic terminals in vivo is a biomarker used to detect cardiac sympathetic degeneration. Abnormal MIBG uptake has been consistently reported in Lewy body disorders. Some studies agree in the notion that increasing bradykinesia is related with an incremental cardiac sympathetic denervation, whereas tremor is not closely linked to cardiac denervation. "Atypical" parkinsonian syndromes, including Multiple System Atrophy, Progressive Supranuclear Palsy, and others, show modest reductions of cardial MIBG uptake. MIBG scintigraphy is moderately sensitive and specific in differentiating Parkinson's disease from such syndromes. Conversely, its sensitivity and specificity might be better in cognitively impaired patients, helping differential diagnosis between Dementia with Lewy Bodies, and Alzheimer disease. Confounding factors (comorbidities, comedications) should be carefully controlled before analyzing MIBG scintigraphy.

[Clinical and pathological study on early diagnosis of Parkinson's disease and dementia with Lewy bodies]

[123I] Meta-iodobenzylguanidine (MIBG) myocardial scintigraphy has been used to evaluate postganglionic cardiac sympathetic innervation in heart diseases and some neurological disorders. To see clinical usefulness of MIBG myocardial scintigraphy to differentiate Parkinson's disease (PD) and dementia with Lewy bodies (DLB) from related movement disorders and Alzheimer disease (AD), we performed MIBG myocardial scintigraphy in patients with these disorders. Cardiac uptake of MIBG is specifically reduced in PD and DLB, and this imaging approach is a sensitive diagnostic tool that possibly differentiates PD and DLB from related movement disorders and AD. To see pathological basis of the reduced cardiac uptake of MIBG in Lewy body disease, we immunohistochemically examined cardiac tissues from patients with PD, DLB, related movement disorders and AD using antibodies against tyrosine hydroxylase (TH) and phosphorylated neurofilament (NF). Not only TH- but also NF-immunoreactive (ir) axons in the epicardial nerve fascicles were markedly decreased in Lewy body disease, namely cardiac sympathetic denervation, which accounts for the reduced cardiac uptake of MIBG in Lewy body disease. Patients with PD and DLB have Lewy bodies (LBs) in the nervous system, whereas patients with multiple system atrophy (MSA), progressive supranuclear palsy, corticobasal degeneration, parkin-associated PD and AD have no LBs in the nervous system. Even in patients with MSA, cardiac sympathetic denervation was associated with the presence of LBs. Therefore, cardiac sympathetic denervation is closely related to the presence of LBs in a wide range of neurodegenerative processes. Taken together, we conclude that the reduced cardiac uptake of MIBG is a potential biomarker for the presence of LBs. Because alpha-synuclein is one of the key molecules in the pathogenesis of PD, we further investigate how alpha-synuclein aggregates are involved in degeneration of the cardiac sympathetic nerve in PD. We immunohistochemically examined cardiac tissues from patients with incidental Lewy body disease (ILBD) and PD using antibodies against TH and phosphorylated alpha-synuclein. We found that (1) alpha-synuclein aggregates in the epicardial nerve fascicles, namely the distal axons of the cardiac sympathetic nerve, were much more abundant in ILBD with preserved TH-ir axons than in ILBD with decreased TH-ir axons and PD; (2) alpha-synuclein aggregates in the epicardial nerve fascicles were closely related to the disappearance of TH-ir axons; (3) in ILBD with preserved TH-ir axons, alpha-synuclein aggregates were consistently more abundant in the epicardial nerve fascicles than in the paravertebral sympathetic ganglia (pSG); and (4) this distal-dominant accumulation of alpha-synuclein aggregates was reversed in ILBD with decreased TH-ir axons and PD, which both showed decreased or depleted TH-ir axons but more abundant alpha-synuclein aggregates in the pSG. These findings indicate that accumulation of alpha-synuclein aggregates in the distal axons of the cardiac sympathetic nervous system precedes that of neuronal somata or neurites in the pSG and that heralds centripetal degeneration of the cardiac sympathetic nerve in PD. This chronological and dynamic relationship between alpha-synuclein aggregates and distal-dominant degeneration of the cardiac sympathetic nervous system may represent the pathological mechanism underlying a common degenerative process in PD.