Different histopathology accounting for a decrease in myocardial MIBG uptake in PD and MSA

Distribution of proteinase K-resistant anti-α-synuclein immunoreactive axons in the cardiac plexus is unbiased to the left ventricular anterior wall

Lewy body disease (LBD) is characterized by the appearance of Lewy neurites and Lewy bodies, which are predominantly composed of α-synuclein. Notably, the cardiac plexus (CP) is one of the main targets of LBD research. Although previous studies have reported obvious differences in the frequency of Lewy body pathology (LBP) in the CP, none of them have confirmed whether LBP preferably appears in any part of the CP. Thus, we aimed to clarify the emergence and/or propagation of LBP in the CP. In this study, 263 consecutive autopsy cases of patients aged ≥50 years were included, with one region per case selected from three myocardial perfusion areas (MPAs) and subjected to proteinase K and then immunohistochemically stained with anti-α-synuclein antibodies to assess LBP. We stained all three MPAs in 17 cases with low-density LBP and observed the actual distribution of LBP. LBP were identified in the CP in 20.2% (53/263) of patients. Moreover, we found that LBP may appear in only one region of MPAs, mainly in the young-old group (35.3% (6/17) of patients). These findings suggest that it is possible to underestimate LBP in the CP, especially in the young-old group, by restricting the search to only one of the three MPAs.

Postganglionic Sudomotor Assessment in Early Stage of Multiple System Atrophy and Parkinson Disease: A Morpho-functional Study

BACKGROUND AND OBJECTIVES

Sudomotor impairment has been recognized as a key feature in differentiating Parkinson disease (PD) and multiple system atrophy-parkinsonian type (MSA-P), with the latter characterized by diffuse anhidrosis in prospective study, including patients in late stage of disease. We aimed to evaluate morphologic and functional postganglionic sudomotor involvement in patients with newly diagnosed MSA-P and PD to identify possible biomarkers that might be of help in differentiating the 2 conditions in the early stage.

METHODS

One hundred patients with parkinsonism within 2 years from onset of motor symptoms were included in the study. At the time of recruitment, questionnaires to assess nonmotor, autonomic, and small fiber symptoms were administered, and patients underwent postganglionic sudomotor function assessment by the dynamic sweat test and punch skin biopsy from the distal leg. Skin samples were processed for indirect immunofluorescence with a panel of antibodies, including noradrenergic and cholinergic markers. The density of intraepidermal, sudomotor, and pilomotor nerve fibers was measured on confocal images with dedicated software. A follow-up visit 12 months after recruitment was performed to confirm the diagnosis.

RESULTS

We recruited 57 patients with PD (M/F 36/21, age 63.5 ± 9.4 years) and 43 patients with MSA-P (M/F 27/16, age 62.3 ± 9.0 years). Clinical scales and questionnaires showed a more severe clinical picture in patients with MSA-P compared to those with PD. Sweating output and intraepidermal, pilomotor, and sudomotor nerve densities, compared to controls, were lower in both groups but with a greater impairment in patients with MSA-P. Pilomotor and sudomotor nerve density correlated with sweating function and with nonmotor clinical symptoms. A composite sudomotor parameter defined as the arithmetic product of sweat production multiplied by the density of sudomotor fibers efficiently separated the 2 populations; the receiver operating characteristics curve showed an area under the curve of 0.83.

DISCUSSION

Dynamic sweat test and the quantification of cutaneous autonomic nerves proved to be a sensitive morpho-functional approach to assess the postganglionic component of the sudomotor pathway, revealing a more severe involvement in MSA-P than in PD early in the disease course. This approach can be applied to differentiate the 2 conditions early.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that postganglionic sudomotor morpho-functional assessment accurately distinguish patients with PD from patients with MSA-P.

Autopsy Validation of the Diagnostic Accuracy of 123I-Metaiodobenzylguanidine Myocardial Scintigraphy for Lewy Body Disease

BACKGROUND AND OBJECTIVES

¹²³I-meta-iodobenzyl-guanidine (¹²³I-MIBG) myocardial scintigraphy is employed as a diagnostic imaging test to differentiate Lewy body diseases (LBDs), including Parkinson's disease and dementia with Lewy bodies, from other similar diseases. However, its diagnostic accuracy lacks validation compared with that of the gold standard. We aimed to validate the diagnostic accuracy of ¹²³I-MIBG myocardial scintigraphy for LBD against autopsy, the gold standard.

METHODS

This retrospective, cross-sectional study included consecutive autopsy patients from the Brain Bank for Aging Research who had undergone ¹²³I-MIBG myocardial scintigraphy. We compared the ¹²³I-MIBG myocardial scintigraphy findings with autopsy findings. Furthermore, the proportion of residual tyrosine hydroxylase (TH)-immunoreactive sympathetic fibers in the anterior wall of the left ventricle was investigated to assess the condition of the cardiac sympathetic nerves assumed to cause reduced ¹²³I-MIBG uptake in LBDs.

RESULTS

We analyzed the data of 56 patients (30 with pathologically confirmed LBDs and 26 without LBD pathology). Compared with the neuropathological diagnosis, the early heart-to-mediastinum (H/M) ratio had a sensitivity and specificity of 70.0% (95% confidence interval [CI]: 50.6-85.3%) and 96.2% (95% CI: 80.4-99.9%), respectively. The delayed H/M ratio had a sensitivity and specificity of 80.0% (95% CI: 61.4-92.3%) and 92.3% (95% CI: 74.9-99.1%), respectively. The washout rate had a sensitivity and specificity of 80.0% (95% CI: 61.4-92.3%) and 84.6% (95% CI: 65.1-95.6%), respectively. The proportion of residual TH-immunoreactive cardiac sympathetic fibers strongly correlated with the amount of cardiac ¹²³I-MIBG uptake when assessed with early and delayed H/M ratio values (correlation coefficient: 0.75 and 0.81, respectively; p < 0.001).

DISCUSSION

This clinicopathological validation study revealed that ¹²³I-MIBG myocardial scintigraphy could robustly differentiate LBDs from similar diseases. Abnormal ¹²³I-MIBG myocardial scintigraphy findings strongly support the presence of LBD and cardiac sympathetic denervation. However, LBD pathology should not necessarily be excluded by normal myocardial scintigraphy results, especially when other biomarkers suggest the presence of comorbid Alzheimer's disease pathology.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that ¹²³I-MIBG myocardial scintigraphy accurately identifies patients with LBD.

Cardiac Changes in Parkinson's Disease: Lessons from Clinical and Experimental Evidence

Dysautonomia is a common non-motor symptom in Parkinson's disease (PD). Most dysautonomic symptoms appear due to alterations in the peripheral nerves of the autonomic nervous system, including both the sympathetic and parasympathetic nervous systems. The degeneration of sympathetic nerve fibers and neurons leads to cardiovascular dysfunction, which is highly prevalent in PD patients. Cardiac alterations such as orthostatic hypotension, heart rate variability, modifications in cardiogram parameters and baroreflex dysfunction can appear in both the early and late stages of PD, worsening as the disease progresses. In PD patients it is generally found that parasympathetic activity is decreased, while sympathetic activity is increased. This situation gives rise to an imbalance of both tonicities which might, in turn, promote a higher risk of cardiac damage through tachycardia and vasoconstriction. Cardiovascular abnormalities can also appear as a side effect of PD treatment: L-DOPA can decrease blood pressure and aggravate orthostatic hypotension as a result of a negative inotropic effect on the heart. This unwanted side effect limits the therapeutic use of L-DOPA in geriatric patients with PD and can contribute to the number of hospital admissions. Therefore, it is essential to define the cardiac features related to PD for the monitorization of the heart condition in parkinsonian individuals. This information can allow the application of intervention strategies to improve the course of the disease and the proposition of new alternatives for its treatment to eliminate or reverse the motor and non-motor symptoms, especially in geriatric patients.

Sympathetic and sensory nerve fiber function in multiple system atrophy and idiopathic Parkinson's disease

OBJECTIVE

To explore small fiber somatosensory and sympathetic function in PD and MSA.

METHODS

We recruited 20 PD patients (7 women, median age 65.5 years; IQR 54.75-70.0), 10 MSA patients (4 women; median age 68 years; IQR 66.25-74.0), and 10 healthy subjects (HC; 4 women, median age 68; IQR 59.0-71.0 years). Autonomic testing included forehead cooling, intradermal microdialysis of norepinephrine (NE; 10^-5; 10^-6; 10^-7; and 10^-8), and orthostatic hypotension (OH); somatosensory testing included quantitative sensory testing (QST) according to the protocol of the German Research Network on Neuropathic Pain (DFNS).

RESULTS

OH occurred more frequently in PD (p = 0.018) and MSA (p = 0.002) compared to HC. Vasoconstriction responses were stronger in PD compared to MSA during forehead cooling (p = 0.044) and microdialysis of physiologically concentrated NE solutions (10^-7; 10-8; p = 0.017). PD and MSA had impaired cold (PD: p < 0.01; MSA: p < 0.05) and warm detection thresholds (PD and MSA, both p < 0.05). The mechanical detection threshold was higher in PD (p < 0.01). Conversely, mechanical pain thresholds were decreased in PD and MSA (both p < 0.001), indicating mechanical hyperalgesia.

CONCLUSION

In contrast to MSA, we found evidence of peripheral adrenoreceptor hypersensitivity in PD, probably caused by peripheral sympathetic denervation. Sensory testing revealed peripheral neuropathy and central pain sensitization in PD and MSA. Jointly, our data demonstrate autonomic and somatosensory dysfunction in PD and MSA.

Fatigability and Cardiorespiratory Impairments in Parkinson's Disease: Potential Non-Motor Barriers to Activity Performance

Parkinson's disease (PD) is the second most common neurodegenerative condition after Alzheimer's disease, affecting an estimated 160 per 100,000 people 65 years of age or older. Fatigue is a debilitating non-motor symptom frequently reported in PD, often manifesting prior to disease diagnosis, persisting over time, and negatively affecting quality of life. Fatigability, on the other hand, is distinct from fatigue and describes the magnitude or rate of change over time in the performance of activity (i.e., performance fatigability) and sensations regulating the integrity of the performer (i.e., perceived fatigability). While fatigability has been relatively understudied in PD as compared to fatigue, it has been hypothesized that the presence of elevated levels of fatigability in PD results from the interactions of homeostatic, psychological, and central factors. Evidence from exercise studies supports the premise that greater disturbances in metabolic homeostasis may underly elevated levels of fatigability in people with PD when engaging in physical activity. Cardiorespiratory impairments constraining oxygen delivery and utilization may contribute to the metabolic alterations and excessive fatigability experienced in individuals with PD. Cardiorespiratory fitness is often reduced in people with PD, likely due to the combined effects of biological aging and impairments specific to the disease. Decreases in oxygen delivery (e.g., reduced cardiac output and impaired blood pressure responses) and oxygen utilization (e.g., reduced skeletal muscle oxidative capacity) compromise skeletal muscle respiration, forcing increased reliance on anaerobic metabolism. Thus, the assessment of fatigability in people with PD may provide valuable information regarding the functional status of people with PD not obtained with measures of fatigue. Moreover, interventions that target cardiorespiratory fitness may improve fatigability, movement performance, and health outcomes in this patient population.

Skin Biopsy May Help to Distinguish Multiple System Atrophy-Parkinsonism from Parkinson's Disease With Orthostatic Hypotension

BACKGROUND

The differential diagnosis between multiple system atrophy parkinsonism type (MSA-P) and Parkinson's disease with orthostatic hypotension (PD+OH) is difficult because the 2 diseases have a similar clinical picture. The aim of this study is to distinguish MSA-P from PD+OH by immunostaining for abnormal phosphorylated α-synuclein at serine 129 (p-syn) in cutaneous nerves.

METHOD

We recruited 50 patients with parkinsonism and chronic orthostatic hypotension: 25 patients fulfilled the diagnostic criteria for MSA-P and 25 patients for PD+OH. The patients underwent a skin biopsy from the cervical area, thigh, and leg to analyze somatic and autonomic skin innervation and p-syn in skin nerves.

RESULTS

Intraneural p-syn positivity was found in 72% of patients with MSA-P, mainly in distal skin sites. More important, p-syn deposits in MSA-P differed from PD+OH because they were mainly found in somatic fibers of subepidermal plexi, whereas scant autonomic fiber involvement was found in only 3 patients. All patients with PD+OH displayed widely distributed p-syn deposits in the autonomic skin fibers of proximal and distal skin sites, whereas somatic fibers were affected only slightly in 4 patients with PD+OH. Skin innervation mirrored p-syn deposits because somatic innervation was mainly reduced in MSA-P. Sympathetic innervation was damaged in PD+OH but fairly preserved in MSA-P.

CONCLUSIONS

The p-syn in cutaneous nerves allows the differentiation of MSA-P from PD+OH; MSA-P mainly shows somatic fiber involvement with relatively preserved autonomic innervation; and by contrast, PD+OH displays prevalent abnormal p-syn deposits and denervation in autonomic postganglionic nerves. © 2020 International Parkinson and Movement Disorder Society.

A diagnostic strategy for Lewy body disease using DAT-SPECT, MIBG and Combined index

PURPOSE

The functional imaging methods widely used for the diagnosis of Lewy body disease (LBD) are ¹²³I-N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropan (FP-CIT) with dopamine transporter single photon emission computed tomography (DAT-SPECT) and ¹²³I-iodobenzylguanidine (MIBG) myocardial scintigraphy. The aim of this study was to determine whether DAT-SPECT or ¹²³I-MIBG myocardial scintigraphy should be examined first and to evaluate whether the combined use of DAT-SPECT and MIBG myocardial scintigraphy is superior to using either modality alone for diagnosing suspected LBD.

METHODS

In this retrospective study, a total of 117 patients suspected of having LBD underwent DAT-SPECT imaging followed by MIBG myocardial scintigraphy. The delayed heart-to-mediastinum (H/M) ratio of MIBG scintigraphy, and the specific binding ratio (SBR) of DAT-SPECT imaging, and Combined index (defined as SBR mean × H/M in the delayed phase) were used as semi-quantitative measures. The diagnostic ability was evaluated using these indexes.

RESULTS

The sensitivity, specificity, and accuracy of diagnosing Lewy body disease were 59.6%, 71.4%, and 67.5% by SBR mean of DAT-SPECT, 85.1%, 91.4%, and 88.9% by delayed H/M ratio of MIBG myocardial scintigraphy, 76.6%, 74.3%, and 75.2% by Combined index, respectively.

CONCLUSION

In the diagnosis of LBD, DAT-SPECT, MIBG myocardial scintigraphy, and Combined index may be reliable indices. In particular, MIBG myocardial scintigraphy was the specific modality for LBD diagnosis. Understanding the effectiveness and limits of DAT-SPECT and MIBG myocardial scintigraphy and using both properly will lead to a more accurate diagnosis and better treatment.

Association of innervation-adjusted alpha-synuclein in arrector pili muscles with cardiac noradrenergic deficiency in autonomic synucleinopathies

BACKGROUND

Autonomic synucleinopathies feature deposition of the protein alpha-synuclein (AS) in neurons [e.g., Lewy body neurogenic orthostatic hypotension (nOH)] or glial cells (multiple system atrophy, MSA). AS in skin biopsies might provide biomarkers of these diseases; however, this approach would be complicated or invalidated if there were substantial loss of AS-containing nerves. We report AS content in arrector pili muscles in skin biopsies after adjustment for local innervation in patients with Lewy body nOH or MSA. Cardiac sympathetic neuroimaging by myocardial ¹⁸F-dopamine positron emission tomography (PET) was done to examine pathophysiological correlates of innervation-adjusted AS.

METHODS

Thirty-one patients (19 Lewy body nOH, 12 MSA) underwent thoracic ¹⁸F-dopamine PET and skin biopsies. AS signal intensity analyzed by immunofluorescence microscopy was adjusted for innervation by the ratio of AS to protein gene product (PGP) 9.5, a pan-axonal marker (Harvard lab site), or the ratio of AS to tyrosine hydroxylase (TH), an indicator of catecholaminergic neurons (NIH lab site).

RESULTS

The Lewy body nOH group had higher ratios of AS/PGP 9.5 or log AS/TH than did the MSA group (0.89 ± 0.05 vs. 0.66 ± 0.04, -0.13 ± 0.05 vs. -1.60 ± 0.33; p < 0.00001 each). All 19 Lewy body patients had AS/PGP 9.5 > 0.8 or log AS/TH > 1.2 and had myocardial ¹⁸F-dopamine-derived radioactivity < 6000 nCi-kg/cc-mCi, the lower limit of normal. Two MSA patients (17%) had increased AS/PGP or log AS/TH, and two (17%) had low ¹⁸F-dopamine-derived radioactivity.

CONCLUSIONS

Lewy body forms of nOH are associated with increased innervation-adjusted AS in arrector pili muscles and neuroimaging evidence of myocardial noradrenergic deficiency.

Spectrum of abnormalities of sympathetic tyrosine hydroxylase and alpha-synuclein in chronic autonomic failure

OBJECTIVE

Lewy body forms of primary chronic autonomic failure (CAF) such as incidental Lewy body disease (ILBD), Parkinson's disease (PD), and pure autonomic failure evolving into dementia with Lewy bodies (PAF+DLB) feature cardiac sympathetic denervation, whereas multiple system atrophy (MSA) in most cases does not. What links Lewy bodies with cardiac sympathetic denervation in CAF? In familial PD, abnormalities of the alpha-synuclein (AS) gene cause CAF and cardiac sympathetic denervation; and in sporadic PD, brainstem Lewy bodies contain AS co-localized with tyrosine hydroxylase (TH), a marker of catecholaminergic neurons. Cytotoxicity from AS deposition within sympathetic neurons might explain noradrenergic denervation in Lewy body forms of CAF. We used immunofluorescence microscopy (IM) to explore this possibility in sympathetic ganglia obtained at autopsy from CAF patients.

METHODS

Immunoreactive AS and TH were imaged in sympathetic ganglion tissue from 6 control subjects (2 with ILBD), 5 PD patients (1 with concurrent PSP), and 3 patients with CAF (2 PAF + DLB, 1 MSA).

RESULTS

MSA involved normal ganglionic TH and no AS deposition. In ILBD TH was variably decreased, and TH and AS were co-localized in Lewy bodies. In PD TH was substantially decreased, and TH and AS were co-localized in Lewy bodies. In PAF + DLB TH was virtually absent, but AS was present in Lewy bodies. The PD + PSP patient had AS co-localized with tau but not TH.

CONCLUSIONS

Sympathetic denervation and intraneuronal AS deposition are correlated across CAF syndromes, consistent with a pathogenic contribution of synucleinopathy to cardiac noradrenergic deficiency in Lewy body diseases.

Does sympathetic dysfunction occur before denervation in pure autonomic failure?

Pure autonomic failure (PAF) is a rare sporadic disorder characterized by autonomic failure in the absence of a movement disorder or dementia and is associated with very low plasma norepinephrine (NE) levels-suggesting widespread sympathetic denervation, however due to its rarity the pathology remains poorly elucidated. We sought to correlate clinical and neurochemical findings with sympathetic nerve protein abundances, accessed by way of a forearm vein biopsy, in patients with PAF and in healthy controls and patients with multiple systems atrophy (MSA) in whom sympathetic nerves are considered intact. The abundance of sympathetic nerve proteins, extracted from forearm vein biopsy specimens, in 11 patients with PAF, 8 patients with MSA and 9 age-matched healthy control participants was performed following a clinical evaluation and detailed evaluation of sympathetic nervous system function, which included head-up tilt (HUT) testing with measurement of plasma catecholamines and muscle sympathetic nerve activity (MSNA) in addition to haemodynamic assessment to confirm the clinical phenotype. PAF participants were found to have normal abundance of the NE transporter (NET) protein, together with very low levels of tyrosine hydroxylase (TH) (P<0.0001) and reduced vesicular monoamine transporter 2 (VMAT2) (P<0.05) protein expression compared with control and MSA participants. These findings were associated with a significantly higher ratio of plasma 3,4-dihydroxyphenylglycol (DHPG):NE in PAF participants when compared with controls (P<0.05). The finding of normal NET abundance in PAF suggests intact sympathetic nerves but with reduced NE synthesis. The finding of elevated plasma ratio of DHPG:NE and reduced VMAT2 in PAF indicates a shift towards intraneuronal NE metabolism over sequestration in sympathetic nerves and suggests that sympathetic dysfunction may occur ahead of denervation.

123I-metaiodobenzylguanidine myocardial scintigraphy with early images alone is useful for the differential diagnosis of dementia with Lewy bodies

123I-metaiodobenzylguanidine cardiac scintigraphy (MIBG) is a useful imaging technique for the diagnosis of dementia with Lewy bodies (DLB). However, MIBG has a serious disadvantage in that it demands a long examination time. The objective of this study was to evaluate statistically the usefulness of the heart/mediastinum ratio (H/M) from the early phase of MIBG for the differential diagnosis of DLB. In total, 113 patients were examined, including 32 non-DLB (19 with Alzheimer's dementia) and 79 DLB patients. The mean early-H/M ratio was 2.83 in the non-DLB group and 1.95 in the DLB group. The mean delayed-H/M ratio was 3.0 in the non-DLB group and 1.76 in the DLB group. With a cutoff point of 2.27 on early images, the sensitivity, specificity, and diagnostic accuracy were 65%, 94%, and 73%, respectively, and the area under the curve was 0.82, indicating moderate accuracy. This analysis indicates that images from the early phase of MIBG alone are sufficient for the differential diagnosis of Alzheimer's disease and DLB.

Diagnosis of dementia with Lewy bodies: can 123I-IMP and 123I-MIBG scintigraphy yield new core features?

OBJECTIVE

Since the clinical symptoms of different types of dementia frequently overlap, especially in the earlier stages at onset, it is difficult to distinguish dementia with Lewy bodies (DLB) from other neurodegenerative dementias based on their clinical manifestations alone. Nuclear medicine imaging has been reported as a high-value index for the objective evaluation and diagnosis of DLB. The aim of this study was to evaluate whether nuclear medicine imaging findings may yield core features to be added to the diagnosis of DLB.

METHODS

We enrolled 332 patients with suspected DLB. All were evaluated by both ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG) myocardial scintigraphy and ¹²³I-labelled N-isopropyl-p-iodoamphetamine (¹²³I-IMP). brain perfusion single-photon emission CT. The final clinical diagnosis indicated probable DLB in 92 patients (40 males, 52 females; mean age ± standard deviation, 77.4 ± 6.4 years; range, 56-89 years); 240 patients (98 males, 142 females; mean age, 75.5 ± 9.0 years; range, 70-87 years) were recorded as being without DLB. The accepted core features used for clinical evaluations were fluctuating cognition, visual hallucinations and Parkinsonism. The nuclear medicine evaluation indices were the severity score of cerebral blood flow on ¹²³I-IMP scintigraphs of the posterior cingulate and praecuneus and a reduction in the blood flow in the occipital lobe. For ¹²³I-MIBG evaluation, we recorded the early and delayed heart-to-mediastinum (H/M) ratios and the washout rate.

RESULTS

Univariate and multivariate analyses of fluctuating cognition, visual hallucinations, Parkinsonism and early H/M ratio in patients with probable and without DLB revealed significant differences. Parameters based on ¹²³I-IMP studies did not show any significant differences by multivariate analysis. The area under the curve for the early H/M ratio was 0.918; for fluctuating cognition, visual hallucinations and Parkinsonism, it was 0.693, 0.760 and 0.611, respectively, by receiver-operating characteristic analysis. The early H/M ratio of <2.0 on ¹²³I-MIBG scintigraphs was of the highest diagnostic accuracy. The sensitivity, specificity and accuracy for the diagnosis of probable DLB were 82.4%, 96.3% and 92.5%, respectively.

CONCLUSION

The early H/M ratio obtained by ¹²³I-MIBG myocardial scintigraphy can serve as a reliable diagnostic index for the core clinical features of DLB. It can be used for the early diagnosis and treatment of DLB. Advances in knowledge: ¹²³I-MIBG myocardial scintigraphy performed at the initial clinical examination can facilitate the early identification or exclusion of DLB and the early H/M ratio may be a diagnostic biomarker for DLB.

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.

123I-MIBG myocardial scintigraphy for the evaluation of Lewy body disease: are delayed images essential? Is visual assessment useful?

OBJECTIVE:

We performed ¹²³I-meta-iodobenzylguanidine (¹²³I-MIBG) myocardial scintigraphy for the diagnosis of Lewy body disease (LBD) and assessed whether the early heart-to-mediastinum (H/M) ratio was diagnostic and whether visual image analysis was useful.

METHODS:

Our study included 453 patients with clinically suspected LBD who had undergone ¹²³I-MIBG myocardial scintigraphy. We evaluated semi-quantitative values (early and delayed H/M ratio, washout rate) and performed visual image analysis. The sensitivity, specificity, accuracy, positive-predictive value (PPV) and negative-predictive value (NPV) of both analyses were calculated.

RESULTS:

The early H/M ratio exhibited the best diagnostic ability. Its overall sensitivity, specificity, accuracy, PPV and NPV were 72.2%, 93.1%, 84.3%, 88.5% and 82.2%, respectively (cut-off value 2.2 or less). However, there was no significant difference from the delayed H/M ratio or the results of visual assessment.

CONCLUSION:

¹²³I-MIBG myocardial scintigraphy accurately differentiates between patients with and without LBD and a correct diagnosis can be established based on the early H/M ratio. We also document that visual evaluation of scintigrams is useful. Therefore, patients may benefit from the single performance of the procedure because a correct diagnosis can be obtained early in the disease process and their prognosis and appropriate treatment can be determined.

ADVANCES IN KNOWLEDGE:

¹²³I-MIBG myocardial scintigraphy on the early H/M ratio makes it possible to differentiate between patients with LBD and patients without LBD.

Chronological changes of 123I-MIBG myocardial scintigraphy and clinical features of Parkinson's disease

OBJECTIVES

The aim of this study was to investigate chronological changes of (123)I-meta-iodobenzylguanidine (MIBG) myocardial scintigraphy and its relation to clinical features in patients with Parkinson's disease (PD), and to characterise patients with PD with normal or mildly low MIBG uptakes at their early stages.

METHODS

The participants were 70 patients with PD who underwent (123)I-MIBG myocardial scintigraphy twice or more. A cluster analysis was performed using parameters calculated from heart to mediastinum (H/M) ratio and washout ratio (WR).

RESULTS

At baseline, the mean early H/M ratio (H/M(E)), delayed H/M ratio (H/M(D)) and WR were 1.83, 1.69 and 41.7%, respectively. After a mean interval of 3.0 years, follow-up studies showed significantly declined H/M(E) (1.69, p<0.001), declined H/M(D) (1.47, p<0.001) and enhanced WR (43.8%, p=0.007). Our longitudinal observations revealed that there existed heterogeneous changes in MIBG uptakes among patients. The cluster analysis classified the patients into two subgroups: 42 patients with markedly low MIBG uptakes at baseline (group A) and 28 patients with normal or mildly low MIBG uptakes at baseline (group B). Group B showed a significantly higher ratio of females, younger age at onset, lower Hoehn and Yahr stage and less demented, compared with group A.

CONCLUSIONS

Follow-up studies of MIBG divided the patients with PD into two major subgroups. A subgroup of patients with PD with normal or mildly low MIBG uptakes at the early stages of illness was characterised by female-dominant, young onset, slow progression in motor dysfunctions and preserved cognitive function.

TRIAL REGISTRATION NUMBER

1033.

Deficient vesicular storage: A common theme in catecholaminergic neurodegeneration

Several neurodegenerative diseases involve loss of catecholamine neurons--Parkinson's disease (PD) is a prototypical example. Catecholamine neurons are rare in the nervous system, and why they are lost has been mysterious. Accumulating evidence supports the concept of "autotoxicity"--inherent cytotoxicity caused by catecholamine metabolites. Since vesicular sequestration limits the buildup of toxic products of enzymatic and spontaneous oxidation of catecholamines, a vesicular storage defect could play a pathogenic role in the death of catecholaminergic neurons in a variety of neurodegenerative diseases. In putamen, deficient vesicular storage is revealed in vivo by accelerated loss of (18)F-DOPA-derived radioactivity and post-mortem by decreased tissue dopamine (DA):DOPA ratios; in myocardium in vivo by accelerated loss of (18)F-dopamine-derived radioactivity and post-mortem by increased 3,4-dihydroxyphenylglycol:norepinephrine (DHPG:NE) ratios; and in sympathetic noradrenergic nerves overall in vivo by increased plasma F-dihydroxyphenylacetic acid (F-DOPAC):DHPG ratios. We retrospectively analyzed data from 20 conditions with decreased or intact catecholaminergic innervation, involving different etiologies, pathogenetic mechanisms, and lesion locations. All conditions involving parkinsonism had accelerated loss of putamen (18)F-DOPA-derived radioactivity; in those with post-mortem data there were also decreased putamen DA:DOPA ratios. All conditions involving cardiac sympathetic denervation had accelerated loss of myocardial (18)F-dopamine-derived radioactivity; in those with post-mortem data there were increased myocardial DHPG:NE ratios. All conditions involving localized loss of catecholaminergic innervation had evidence of decreased vesicular storage specifically in the denervated regions. Thus, across neurodegenerative diseases, loss of catecholaminergic neurons seems to be associated with decreased vesicular storage in the residual neurons.

Dysautonomia in Parkinson disease

Dysautonomias are conditions in which altered function of one or more components of the autonomic nervous system (ANS) adversely affects health. This review updates knowledge about dysautonomia in Parkinson disease (PD). Most PD patients have symptoms or signs of dysautonomia; occasionally, the abnormalities dominate the clinical picture. Components of the ANS include the sympathetic noradrenergic system (SNS), the parasympathetic nervous system (PNS), the sympathetic cholinergic system (SCS), the sympathetic adrenomedullary system (SAS), and the enteric nervous system (ENS). Dysfunction of each component system produces characteristic manifestations. In PD, it is cardiovascular dysautonomia that is best understood scientifically, mainly because of the variety of clinical laboratory tools available to assess functions of catecholamine systems. Most of this review focuses on this aspect of autonomic involvement in PD. PD features cardiac sympathetic denervation, which can precede the movement disorder. Loss of cardiac SNS innervation occurs independently of the loss of striatal dopaminergic innervation underlying the motor signs of PD and is associated with other nonmotor manifestations, including anosmia, REM behavior disorder, orthostatic hypotension (OH), and dementia. Autonomic dysfunction in PD is important not only in clinical management and in providing potential biomarkers but also for understanding disease mechanisms (e.g., autotoxicity exerted by catecholamine metabolites). Since Lewy bodies and Lewy neurites containing alpha-synuclein constitute neuropathologic hallmarks of the disease, and catecholamine depletion in the striatum and heart are characteristic neurochemical features, a key goal of future research is to understand better the link between alpha-synucleinopathy and loss of catecholamine neurons in PD.

Is the denervation or hyperinnervation of the cardiac sympathetic nerve in the subepicardium related to unexpected cardiac death?

BACKGROUND

Past studies have reported that abnormal innervation of cardiac sympathetic nerve can cause sudden cardiac death through the arrythmogenesis; however, the severe cardiac sympathetic degeneration does not necessarily cause clinical problems. This study aimed to examine whether denervation or hyperinnervation of cardiac sympathetic nerves in the subepicardium is associated with unexpected cardiac death (UCD).

METHODS

Cardiac tissues of 278 forensic autopsy cases within 48 h after death were analyzed by double-staining immunohistochemistry for tyrosine hydroxylase and neurofilament. The density of nerve fascicles and the degeneration rate in the subepicardium of the left ventricular anterior wall were compared between the UCD group and the non-UCD group.

RESULTS

The density of nerve fascicles was lower in the SCD group (median: 51.9/cm(2)) than in the non-SCD group (median: 58.9/cm(2)); however, the difference was not significant (P = .08). The degeneration rate was higher in the SCD group (median: 0.19) than in the non-SCD group (median: 0.17), but again, the difference was not significant (P = .43). The multiple logistic regression model did not show a significant association between the incidence of UCD and the density of nerve fascicles or the degeneration rate.

CONCLUSIONS

It cannot be concluded that the denervation or hyperinnervation of cardiac sympathetic nerves in the subepicardium is related to UCD. Abnormal innervation of cardiac sympathetic nerves in the subepicardium may not have a substantial effect on UCD, compared to other arrhythmogenic factors.

Catecholamines and Neurodegeneration in Parkinson's Disease-From Diagnostic Marker to Aggregations of α-Synuclein

Parkinson's disease is the second most prevalent disease of the brain. It is characterized by midbrain dopaminergic neuronal degeneration accompanied by Lewy bodies, intra-cytoplasmic neuronal inclusions that consist mainly of alpha-synuclein. The cardinal motor features are muscular rigidity, bradykinesia, and resting tremor and, in advanced cases, postural instability. Symptoms are relieved by dopamine replacement therapy, but progress slowly. Clinical diagnosis is made according to medical history, neurological examinations and the response to anti-Parkinsonian drugs. There are no laboratory tests for diagnosis of the disease; however, for development of disease-modifying treatment, early diagnosis by objective laboratory test is required. Recently, postsynaptic sympathetic norepinephrine nerve terminals were found to be degenerated as well as mesencephalic dopaminergic neurons. Cardiac norepinephrine denervation can be seen by meta-iodine-benzyl guanidine scintigraphy, and may be a reliable diagnostic marker. Degeneration of norepinephrinergic and dopaminergic neurons suggests that catecholamines may play a central role in the neurodegeneration in Parkinson's disease. Recently several studies showed that alpha-synuclein aggregates in cells exposed to dopamine. Here, we review findings relating to an early diagnostic marker for detecting degeneration of the peripheral sympathetic nerves, and propose the hypothesis that catecholamines cause alpha-synuclein to aggregate and play an important role in disease pathogenesis.

Sympathetic neuroimaging

Sympathetic neuroimaging provides an important supplement to physiological, neurochemical, and neuropharmacological approaches in the evaluation of patients with clinical autonomic disorders. Almost all sympathetic neuroimaging to date has involved visualization of noradrenergic innervation in the left ventricular myocardium. Single-photon emission computed tomography (SPECT) scanning after injection of the sympathomimetic amine (123)I-metaiodobenzylguanidine ((123)I-MIBG) constitutes by far the most commonly used means worldwide to assess cardiac sympathetic innervation. Based on heart:mediastinum ratios of (123)I-MIBG-derived radioactivity, decreased uptake, increased washout, or both have been reported in many disorders and relate to diagnosis and prognosis. Cardiac sympathetic neuroimaging and postmortem neuropathological findings have linked α-synucleinopathy with noradrenergic denervation in Lewy body diseases. Especially because of the utility of cardiac sympathetic neuroimaging in distinguishing Parkinson disease from multiple system atrophy in patients with clinical evidence of central neurodegeneration and orthostatic hypotension, sympathetic neuroimaging seems a valuable addition to physiological, neuropharmacological, and neurochemical approaches in the diagnostic evaluation of selected patients with autonomic and neurodegenerative disorders.

Cerebrospinal fluid biomarkers of central catecholamine deficiency in Parkinson's disease and other synucleinopathies

Central catecholamine deficiency characterizes α-synucleinopathies such as Parkinson's disease. We hypothesized that cerebrospinal fluid levels of neuronal metabolites of catecholamines provide neurochemical biomarkers of these disorders. To test this hypothesis we measured cerebrospinal fluid levels of catechols including dopamine, norepinephrine and their main respective neuronal metabolites dihydroxyphenylacetic acid and dihydroxyphenylglycol in Parkinson's disease and two other synucleinopathies, multiple system atrophy and pure autonomic failure. Cerebrospinal fluid catechols were assayed in 146 subjects-108 synucleinopathy patients (34 Parkinson's disease, 54 multiple system atrophy, 20 pure autonomic failure) and 38 controls. In 14 patients cerebrospinal fluid was obtained before or within 2 years after the onset of parkinsonism. The Parkinson's disease, multiple system atrophy and pure autonomic failure groups all had lower cerebrospinal fluid dihydroxyphenylacetic acid [0.86 ± 0.09 (SEM), 1.00 ± 0.09, 1.32 ± 0.12 nmol/l] than controls (2.15 ± 0.18 nmol/l; P < 0.0001; P < 0.0001; P = 0.0002). Dihydroxyphenylglycol was also lower in the three synucleinopathies (8.82 ± 0.44, 7.75 ± 0.42, 5.82 ± 0.65 nmol/l) than controls (11.0 ± 0.62 nmol/l; P = 0.009, P < 0.0001, P < 0.0001). Dihydroxyphenylacetic acid was lower and dihydroxyphenylglycol higher in Parkinson's disease than in pure autonomic failure. Dihydroxyphenylacetic acid was 100% sensitive at 89% specificity in separating patients with recent onset of parkinsonism from controls but was of no value in differentiating Parkinson's disease from multiple system atrophy. Synucleinopathies feature cerebrospinal fluid neurochemical evidence for central dopamine and norepinephrine deficiency. Parkinson's disease and pure autonomic failure involve differential dopaminergic versus noradrenergic lesions. Cerebrospinal fluid dihydroxyphenylacetic acid seems to provide a sensitive means to identify even early Parkinson's disease.

Cardiac ¹²³I-MIBG scintigraphy as an outcome-predicting tool for subthalamic nucleus stimulation in Parkinson's disease

BACKGROUND

¹²³I-meta-iodobenzylguanidine (MIBG) myocardial scintigraphy is a useful tool for differentiating idiopathic Parkinson's disease (PD) from other parkinsonian syndromes, but its prognostic value in PD has not been established. The objective of this study was to clarify the correlation between cardiac MIBG uptake parameters and the outcome in PD patients subjected to the subthalamic nucleus stimulation.

METHOD

We enrolled 31 consecutive PD patients and calculated the heart-to-mediastinum ratio (H/M) and washout rate (WR) based on the activity measured at 15 min (early phase) and 3 h (delayed phase) after the intravenous injection of MIBG (111 MBq). Cardinal motor symptoms and activity of daily living (ADL) were assessed on the Unified Parkinson's Disease Rating Scale (UPDRS) and Schwab and England (S-E) ADL scale, before and 3 months after surgery.

FINDINGS

Neither early nor delayed H/M correlated with any of the preoperative subscores on the UPDRS or S-E, nor with postoperative outcome. On the other hand, increased WR was a positive predictor for postoperative improvement rate on S-E in medication-off state (p = 0.00003). Also, WR showed a more faint but significant correlation with preoperative levodopa responsiveness on S-E (p = 0.008).

CONCLUSION

Our findings suggest that ¹²³I-MIBG scintigraphy in combination with levodopa-responsiveness evaluation may represent a useful tool for prediction of outcomes in patients subjected to STN stimulation.

Neuroscience and heart-brain medicine: the year in review

Important recent publications in the area of neuroscience and heart-brain medicine center largely around three topics: (1) mechanisms of cardiac sympathetic denervation in Parkinson disease, (2) cytoplasmic monoamine metabolites as autotoxins, and (3) the validity of power spectral analysis of heart rate variability to indicate cardiac sympathetic tone. Findings by Orimo et al support a centripetal, retrograde pathogenetic process involving alpha-synuclein deposition and degeneration of cardiac noradrenergic neurons in Parkinson disease. Several studies suggest that processes increasing cytoplasmic monoamines lead to neuronal loss from auto-oxidation or enzymatic oxidation. Lack of correlation between commonly used indices from power spectral analysis of heart rate variability and cardiac norepinephrine spillover casts doubt on the validity of power spectral analysis to indicate cardiac sympathetic tone.

[Influence of subthalamic deep brain stimulation on dysautonomia observed in Parkinson's disease]

Dysfunctions of the autonomic nervous system (DA) are common in Parkinson's disease (PD). DA appear in the premotor phase of PD and may antedate cardinal motor symptoms by years or decades. DA significantly impair quality of life in the majority of PD patients. DA are related to accumulation of Lewy bodies in the central and peripheral nervous system. Progression of neurodegeneration and chronic dopaminergic therapy may increase DA as well. It is accepted that bilateral deep brain stimulation of the subthalamic nucleus (STN DBS) improves motor symptoms in PD. The effect of STN DBS on DA, such as cardio-vascular symptoms and urinary, gastrointestinal and sexual dysfunction in PD, is not clear. STN DBS ameliorates some DA, but others might deteriorate at the same time.

Combined use of DAT-SPECT and cardiac MIBG scintigraphy in mixed tremors

The cooccurrence of rest and postural tremor (mixed tremor) as the predominant clinical manifestation in patients who do not fulfill diagnostic established criteria for essential tremor (ET) or Parkinson's disease (PD) poses a clinical diagnostic challenge. Twenty-two patients with mixed tremor and additional mild extrapyramidal features, such as bradykinesia and rigidity, 20 patients with probable PD, 10 patients with probable ET, and 18 controls were investigated through the combined use of dopamine transporter (123)I-FP-CIT-single-photon emission tomography (DAT-SPECT) and cardiac (123)metaiodobenzylguanidine (MIGB) scintigraphy. Six of the 22 mixed-tremor patients had normal DAT-SPECT, a condition usually found in patients with ET, whereas 16 patients showed damage to the nigrostriatal system. Cardiac MIBG allowed further differentiation between these 16 patients because eight of them had decreased tracer uptakes (heart/mediastinum [H/M] ratio in delayed image, H/M ratio delayed: 1.16 +/- 0.11, P < 0.001 vs controls), indicating a PD, whereas the remaining eight had normal cardiac tracer uptakes, a finding suggestive of a parkinsonian syndrome (H/M ratio delayed: 1.90 +/- 0.13). Both DAT-SPECT and cardiac MIBG scintigraphies were abnormal in the 20 patients with probable PD, whereas these were normal in both the patients with probable ET as well as in the controls. Our study suggests that the combined use of both DAT-SPECT and MIBG scintigraphy in mixed tremors with additional extrapyramidal features can help distinguish patients with ET from those with PD and parkinsonism.

Detection of Lewy body disease in patients with late-onset depression, anxiety and psychotic disorder with myocardial meta-iodobenzylguanidine scintigraphy

PURPOSE

Lewy body disease (LBD) is comprised of a spectrum of diseases that includes Parkinson's disease (PD), PD dementia (PDD) and dementia with LBD (DLBD), an array of dementia, and motor symptoms. Low uptake of myocardial meta-iodobenzylguanidine (MIBG) validates diagnosis of LBD. Psychiatric symptoms sometimes precede atypical Parkinsonian syndromes in LBD. Of 34 patients with low MIBG uptake, late-onset depressive, anxiety, or psychotic symptoms were analyzed in term of clinical profiles.

METHOD

Thirty-four patients were classed into three groups according to three main symptoms, 11 patients with visual hallucination (VH), 13 with depression-anxiety (DA), and 10 with psychosis with cognitive disturbance (PCD). Cutoff values of heart-to-mediastinum (HM) ratio of MIBG were set at 1.78 in early phase or 1.68 in late phase.

RESULTS

Group VH patients showed a trend toward higher age at onset and occipital lobe hypoperfusion. Group DA patients lacked central and core features of DLBD and five of them showed frontal lobe hypoperfusion. Group PCD patients had the highest frequencies of suggestive symptoms and UPDRS scores and showed temporal lobe hypoperfusion. HM ratio was not associated with clinical profiles of three groups. Cognitive function was more severely disturbed in atypical Parkinsonian syndrome cases at an initial visit.

CONCLUSION

Group VH was considered to DLBD, and Group PCD was regarded as PDD or DLBD with early psychotic presentation. Group DA has a possibility of early depression or anxiety disorder of LBD although it lacked DLBD criteria. Atypical Parkinsonian syndromes are associated with cognitive disturbance irrespective of psychiatric profiles.

Generalized and neurotransmitter-selective noradrenergic denervation in Parkinson's disease with orthostatic hypotension

Patients with Parkinson's disease (PD) often have manifestations of autonomic failure. About 40% have neurogenic orthostatic hypotension (NOH), and among PD+NOH patients virtually all have evidence of cardiac sympathetic denervation; however, whether PD+NOH entails extra-cardiac noradrenergic denervation has been less clear. Microdialysate concentrations of the main neuronal metabolite of norepinephrine (NE) and dihydroxyphenylglycol (DHPG) were measured in skeletal muscle, and plasma concentrations of NE and DHPG were measured in response to i.v. tyramine, yohimbine, and isoproterenol, in patients with PD+NOH, patients with pure autonomic failure (PAF), which is characterized by generalized catecholaminergic denervation, and control subjects. Microdialysate DHPG concentrations were similarly low in PD+NOH and PAF compared to control subjects (163 +/- 25, 153 +/- 27, and 304 +/- 27 pg/mL, P < 0.01 each vs. control). The two groups also had similarly small plasma DHPG responses to tyramine (71 +/- 58 and 82 +/- 105 vs. 313 +/- 94 pg/mL; P < 0.01 each vs. control) and NE responses to yohimbine (223 +/- 37 and 61 +/- 15 vs. 672 +/- 130 pg/mL, P < 0.01 each vs. control), and virtually absent NE responses to isoproterenol (20 +/- 34 and 14 +/- 15 vs. 336 +/- 78 pg/mL, P < 0.01 each vs. control). Patients with PD+NOH had normal bradycardia responses to edrophonium and normal epinephrine responses to glucagon. The results support the concept of generalized noradrenergic denervation in PD+NOH, with similar severity to that seen in PAF. In contrast, the parasympathetic cholinergic and adrenomedullary hormonal components of the autonomic nervous system seem intact in PD+NOH.

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

Cardiac uptake of meta-iodobenzylguanidine (MIBG) is specifically reduced in Lewy body disease (LBD). To see pathological basis of the reduced cardiac uptake of MIBG in LBD, we immunohistichemically examined cardiac tissues from patients with LBD, related movement disorders and Alzheimer's disease (AD). In LBD, cardiac sympathetic denervation occurs, which accounts for the reduced cardiac uptake of MIBG. Patients with LBD have Lewy bodies (LBs) in the nervous system, whereas patients with the other neurodegenerative parkinsonism, parkin-associated Parkinson's disease (PD) and AD and have no LBs. Therefore, cardiac sympathetic denervation is closely related to the presence of LBs in a wide range of neurodegenerative processes. We further investigate how a-synuclein aggregates are involved in degeneration of the cardiac sympathetic nerve in PD. Accumulation of alpha-synuclein aggregates in the distal axons of the cardiac sympathetic nervous system precedes that of neuronal somata or neurites in the paravertebral sympathetic ganglia and that it heralds centripetal degeneration of the cardiac sympathetic nerve in PD. This chronological and dynamic relationship between alpha-synuclein aggregates and degeneration of the cardiac sympathetic nervous system may represent the pathological mechanism underlying a common degenerative process in PD.

Myocardial (123)I-MIBG scintigraphy for differentiation of Lewy bodies disease from FTD

Clinical distinction between Lewy bodies disease (LBD) and frontotemporal dementia (FTD) is sometimes difficult. Nigrostriatal dopaminergic degeneration occurs in both LBD and FTD, limiting helpfulness of DAT imaging to differentiate these forms of dementia. Several studies have emphasized the usefulness of myocardial scintigraphy with (123)Metaiodobenzylguanidine ((123)I-MIGB) in assessing the sympathetic nerve terminals in LBD demonstrating that cardiac (123)I-MIGB uptake is decreased in patients with this disease. We investigated the role of cardiac (123)I-MIBG scintigraphy in differentiating patients with LBD from those with FTD. Clinical diagnosis of LBD and FTD was determined according to established consensus criteria. Nine patients with LBD (1 possible and 8 probable), 6 patients with FTD, and 16 control subjects were involved in the study. The heart to mediastinum ratio (H/M) of (123)I-MIBG uptake was markedly reduced in all patients with LBD (H/M early: 1.25±0.12; delayed: 1.14±0.13) whereas it was normal in patients with FTD (H/M early: 1.86±0.20; delayed: 1.80±0.23) and in controls (H/M early: 1.91±0.17; delayed: 1.99±0.19), suggesting that cardiac (123)I-MIBG scintigraphy can help distinguish patients with LBD from those with FTD.

Biomarkers to detect central dopamine deficiency and distinguish Parkinson disease from multiple system atrophy

OBJECTIVE

Biomarkers are increasingly important to diagnose and test treatments of neurodegenerative diseases such as Parkinson disease (PD). This study compared neuroimaging, neurochemical, and olfactory potential biomarkers to detect central dopamine (DA) deficiency and distinguish PD from multiple system atrophy (MSA).

METHODS

In 77 PD, 57 MSA, and 87 control subjects, radioactivity concentrations in the putamen (PUT), caudate (CAU), occipital cortex (OCC), and substantia nigra (SN) were measured 2h after 6-[18F]fluorodopa injection, septal myocardial radioactivity measured 8min after 6-[18F]fluorodopamine injection, CSF and plasma catechols assayed, or olfaction tested (University of Pennsylvania Smell Identification Test (UPSIT)). Receiver operating characteristic curves were constructed, showing test sensitivities at given specificities.

RESULTS

PUT:OCC, CAU:OCC, and SN:OCC ratios of 6-[18F]fluorodopa-derived radioactivity were similarly low in PD and MSA (p<0.0001, p<0.0001, p=0.003 compared to controls), as were CSF dihydroxyphenylacetic acid (DOPAC) and DOPA concentrations (p<0.0001, each). PUT:SN and PUT:CAU ratios were lower in PD than in MSA (p=0.004; p=0.005). CSF DOPAC correlated positively with PUT:OCC ratios (r=0.61, p<0.0001). Myocardial 6-[18F]fluorodopamine-derived radioactivity distinguished PD from MSA (83% sensitivity at 80% specificity, 100% sensitivity among patients with neurogenic orthostatic hypotension). Only PD patients were anosmic; only MSA patients had normal olfaction (61% sensitivity at 80% specificity).

CONCLUSIONS

PD and MSA feature low PUT:OCC ratios of 6-[18F]fluorodopa-derived radioactivity and low CSF DOPAC and DOPA concentrations, cross-validating the neuroimaging and neurochemical approaches but not distinguishing the diseases. PUT:SN and PUT:CAU ratios of 6-[18F]fluorodopa-derived radioactivity, cardiac 6-[18F]fluorodopamine-derived radioactivity, and olfactory testing separate PD from MSA.

[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.

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

OBJECTIVE

Cardiac uptake of [(123)I]metaiodobenzyl guanidine (MIBG) is reduced in patients with Parkinson's disease (PD). However, the cardiac sympathetic abnormality associated with this reduction is unclear. To unmask this abnormality in PD patients we examined the functional consequences of cardiac beta-receptor activation.

METHODS

Cardiovascular responses to stepwise administration of the beta1-receptor agonist, dobutamine (DOB), were assessed in 25 PD patients and 12 age-matched controls. Changes in blood pressure were compared to determine the optimal dose at which to detect denervation supersensitivity, and cardiac contractility was measured by DOB echocardiography, based on peak aortic flow velocity. The relations of these cardiovascular responses to the ratio of MIBG uptake into the heart vs. that into the mediastinum (H/M ratio) were analyzed.

RESULTS

At 4 microg/kg/min DOB, systolic blood pressure increased more in PD patients than in controls (PD, 17.5+/-12.3 mm Hg; control, 7.2+/-6.2 mm Hg, p<0.01), suggesting the presence of denervation supersensitivity. At this DOB dose cardiac contractility also increased more in PD than in controls (PD, 39.0+/-15.7%; control, 23.5+/-5.2%, p<0.005) and this hyperdynamic response was significantly correlated with reduced H/M ratios (early: r=-0.63, p<0.01, delayed: r=-0.66, p<0.01).

CONCLUSION

Low-dose DOB unmasks cardiac sympathetic denervation in PD patients, and decreased MIBG uptake indicates the presence of denervation supersensitivity within the heart, resulting in hyperdynamic cardiac contractility in response to a beta 1-stress condition.