[123I] meta-iodobenzylguanidine myocardial scintigraphy differentiates corticobasal degeneration from Parkinson's disease

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.

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.

Optimizing Parkinson's disease diagnosis: the role of a dual nuclear imaging algorithm

The diagnosis of Parkinson's disease (PD) currently relies almost exclusively on the clinical judgment of an experienced neurologist, ideally a specialist in movement disorders. However, such clinical diagnosis is often incorrect in a large percentage of patients, particularly in the early stages of the disease. A commercially available, objective and quantitative marker of nigrostriatal neurodegeneration was recently provided by 123-iodine ¹²³I-ioflupane SPECT imaging, which is however unable to differentiate PD from a variety of other parkinsonian syndromes associated with striatal dopamine deficiency. There is evidence to support an algorithm utilizing a dual neuroimaging strategy combining ¹²³I-ioflupane SPECT and the noradrenergic receptor ligand ¹²³I-metaiodobenzylguanidine (MIBG), which assesses the post-ganglion peripheral autonomic nervous system. Evolving concepts regarding the synucleinopathy affecting the central and peripheral autonomic nervous systems as part of a multisystem disease are reviewed to sustain such strategy. Data are presented to show how MIBG deficits are a common feature of multisystem Lewy body disease and can be used as a unique feature to distinguish PD from atypical parkinsonisms. We propose that the combination of cardiac (MIBG) and cerebral ¹²³I-ioflupane SPECT could satisfy one of the most significant unmet needs of current PD diagnosis and management, namely the early and accurate diagnosis of patients with typical Lewy body PD. Exemplary case scenarios will be described, highlighting how dual neuroimaging strategy can maximize diagnostic accuracy for patient care, clinical trials, pre-symptomatic PD screening, and special cases provided by specific genetic mutations associated with PD.

New development of diagnosis and treatment for Parkinson's disease

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

(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.

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.

(123)I-Metaiodobenzylguanidine Myocardial Scintigraphy in Lewy Body-Related Disorders: A Literature Review

Lewy body-related disorders are characterized by the presence of Lewy bodies and Lewy neurites, which have abnormal aggregations of α-synuclein in the nigral and extranigral areas, including in the heart. ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy is a well-known tool to evaluate cardiac sympathetic denervation in the Lewy body-related disorders. MIBG scintigraphy showed low uptake of MIBG in the Lewy body-related disorders, including Parkinson’s disease, dementia with Lewy bodies, pure autonomic failure and rapid eye movement sleep behavior disorder. This review summarizes previous results on the diagnostic applications of MIBG scintigraphy in Lewy body-related disorders.

MIBG scintigraphy in differential diagnosis of Parkinsonism: a meta-analysis

OBJECTIVE

Differential diagnosis between Parkinson's disease (PD) and other Parkinsonism using clinical criteria or imaging methods is often difficult. The purpose of this study is to systematically review and meta-analyze published data about the diagnostic performance of myocardial innervation imaging using (123)I-metaiodobenzylguanidine (MIBG) scintigraphy in differential diagnosis between PD and other Parkinsonism.

METHODS

A comprehensive computer literature search of studies published through March 2011 regarding MIBG scintigraphy in patients with PD and other Parkinsonism was performed in PubMed/MEDLINE and Embase databases. Only studies in which MIBG scintigraphy was performed for differential diagnosis between PD and other Parkinsonism were selected. Pooled sensitivity, pooled specificity and area under the ROC curve were calculated to measure the accuracy of MIBG scintigraphy in differential diagnosis between PD and other Parkinsonism.

RESULTS

Nineteen studies comprising 1,972 patients (1,076 patients with PD, 117 patients with other Lewy body diseases and 779 patients with other diseases) were included in this meta-analysis. The pooled sensitivity of MIBG scintigraphy in detecting PD was 88% (95% CI 86-90%); the pooled specificity of MIBG scintigraphy in discriminating between PD and other Parkinsonism was 85% (95% CI 81-88%). The area under the ROC curve was 0.93.

CONCLUSIONS

In patients with clinically suspected PD, myocardial innervation imaging demonstrated high sensitivity and specificity. MIBG scintigraphy is an accurate test in this setting. Nevertheless, possible causes of false-negative and false-positive results should be kept in mind when interpreting the scintigraphic results.

123I-MIBG cardiac uptake and smell identification in parkinsonian patients with LRRK2 mutations

Reduced uptake of (123)I- metaiodobenzylguanidine (MIBG) on cardiac gammagraphy and impaired odor identification are markers of neurodegenerative diseases with Lewy bodies (LB) as a pathological hallmark, such as idiopathic Parkinson's disease (IPD). LRRK2 patients present with a clinical syndrome indistinguishable from IPD, but LB have not been found in some cases. Patients with such mutations could behave differently than patients with IPD with respect to MIBG cardiac uptake and olfaction. We studied 14 LRRK2 patients, 14 IPD patients matched by age, gender, disease duration and severity, and 13 age and gender matched control subjects. Olfaction was analyzed through the University of Pennsylvania Smell Identification Test (UPSIT). MIBG cardiac uptake was evaluated through the H/M ratio. The late H/M was 1.44 ± 0.31 for LRRK2 patients, 1.19 ± 0.15 for PD patients, and 1.67 ± 0.16 for control subjects. LRRK2 patients presented lower but not statistically significant MIBG cardiac uptake than controls (p = 0.08) and significant higher uptake than PD patients (p = 0.04). UPSIT mean scores were 21.5 ± 7.3 for LRRK2 patients, 18.7 ± 6.2 for IPD patients and 29.7 ± 5.7 for control subjects. UPSIT score was lower in both LRRK2 and PD than in controls. In LRRK2 patients a positive correlation was found between myocardial MIBG uptake and UPSIT scores, (R = 0.801, p < 0.001). In LRRK2 patients, MIBG cardiac uptake was less impaired than in PD; a positive correlation between MIBG cardiac uptake and UPSIT scores was observed. As MIBG cardiac reduced uptake and impaired odor identification are markers of LB pathology, this findings may represent neuropathological heterogeneity among LRRK2 patients.

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.

Diagnostic and Pathophysiological Impact of Myocardial MIBG Scintigraphy in Parkinson's Disease

Myocardial MIBG scintigraphy is established in the diagnosis and differential diagnosis of Parkinson's disease (PD). Numerous studies address the pathophysiological impact of myocardial MIBG scintigraphy: the myocardial MIBG uptake correlates with the clinical phenotype of PD; the background of this phenomenon is unclear. Furthermore MIBG scintigraphy enables to study the extracranial Lewy body type-degeneration. In combination with cerebral dopamine transporter imaging, MIBG scintigraphy allows to correlate cerebral and extracranial Lewy body type-degeneration in PD.

Multipoint analysis of reduced (125)I-meta-iodobenzylguanidine uptake and norepinephrine turnover in the hearts of mice with 1-methyl-4-phenyl-1,2,3,6-tetrahydroxypyridine-induced parkinsonism

INTRODUCTION

(125)I-Meta-iodobenzylguanidine (MIBG) cardiac uptake is reduced in mice with 1-methyl-4-phenyl-1,2,3,6-tetrahydroxypyridine (MPTP)-induced parkinsonism, although the cause of disturbance of norepinephrine (NE) turnover is unclear.

METHODS

C57BL6 mice (15 weeks old) were divided into six groups (n=14 each) according to the timing of MPTP injection (40 mg/kg) before (125)I-MIBG: Group A, control (no MPTP injection); Group B, 1 day; Group C, 4 days; Group D, 7 days; Group E, 21 days; Group F, 7, 14 and 21 days. (125)I-MIBG (0.185 MBq) was injected and the cardiac percentage injected dose per gram of tissue (%ID/g), dopamine (DA) and NE concentrations were measured. The cardiac maximal binding potential (B(max)) of NE transporter (NET) was also calculated in 20 mice per group.

RESULTS

The %ID/g of B, C, D, E and F mice were significantly lower than in A; those of C, D and E were significantly higher than in B; and that of F was significantly lower than in E. The DA concentrations were similar among all groups. The NE concentrations of B, C and F mice were significantly lower than in A, while those of C, D, E and F were significantly higher than in B, and that of F was significantly lower than in E. The B(max) of NET in B was significantly lower than in A.

CONCLUSIONS

Thus, MPTP causes rapid reductions in cardiac (125)I-MIBG uptake and B(max) of NET, followed by partial recovery of (125)I-MIBG uptake. Changes in cardiac (125)I-MIBG uptake and NE turnover were closely related in postganglionic cardiac sympathetic nerve terminals in mice with MPTP-induced parkinsonism.

[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.

[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.

Myocardial nerve fibers are preserved in MPTP-treated mice, despite cardiac sympathetic dysfunction

Recently, we reported a profound depletion of cardiac sympathetic nerve fibers in Parkinson's disease (PD). This cardiac sympathetic denervation is a characteristic hallmark of PD. Cardiac sympathetic dysfunction was also observed in 1-methyl-4-phenyl-1,2,3,6-tetrahydroxypyridine (MPTP)-treated mice, a model of PD. Although binding assay showed a decreased density of norepinephrine transporter (NET) in the hearts of the mice, their histopathological alterations have not been demonstrated. In this study, we investigated hearts of MPTP-treated mice with immunohistochemical method and Western blot analyses. MPTP-treated mice showed significant decreases in the contents of cardiac noradrenaline and dopamine, suggesting the sympathetic dysfunction. Synaptophysin-, tyrosine hydroxylase- or NET-immunoreactive nerve fibers were abundant in the hearts of control mice and MPTP-treated mice, without apparent differences between the two groups. Western blot analyses also showed no difference in the amounts of these proteins. Myocardial nerve fibers were well preserved in MPTP-treated mice, despite apparent cardiac sympathetic dysfunction.

The role of 123I-metaiodobenzylguanidine myocardial scintigraphy in the diagnosis of Lewy body disease in patients with dementia in a memory clinic

Reduction in cardiac (123)I-metaiodobenzylguanidine (MIBG) uptake is a characteristic feature of Parkinson's disease (PD) and dementia with Lewy bodies (DLB), and is useful in distinguishing them from other neurodegenerative disorders. The aim of this study was to investigate the role of this method of scintigraphy in the differential diagnosis of dementia in our Memory Clinic. We performed MIBG scintigraphy in patients with dementia referred to the Memory Clinic and compared the heart-to-mediastinum (H/M) ratio of MIBG uptake. Thirty out of 32 patients with DLB and all 9 PD with dementia patients had reduced H/M ratios, whereas 37 out of 40 patients with Alzheimer's disease had normal H/M ratios. Most patients with vascular dementia, frontotemporal dementia, and other dementias had normal H/M ratios. The overall sensitivity to positively identify patients with Lewy body disease (including DLB and PD with dementia) was 95%, and the specificity to distinguish them from patients with other types of dementias was 87%. MIBG scintigraphy showed a high sensitivity for the detection of Lewy body disease, and also a high specificity for discrimination from other types of dementia. The scintigraphy may provide a valuable and adjunctive method in the diagnosis of Lewy body disease and a differential diagnostic tool for patients with dementias.

Degeneration of cardiac sympathetic nerve begins in the early disease process of Parkinson's disease

Decreased cardiac uptake of meta-iodobenzylguanidine (MIBG) on [(123)I] MIBG myocardial scintigraphy has been reported in the early stages of Parkinson's disease (PD), which suggests involvement of the cardiac sympathetic nerve in the early disease process of PD. For confirmation, we immunohistochemically examined cardiac tissue, sympathetic ganglia and medulla oblongata of 20 patients with incidental Lewy body disease (ILBD), which is thought to be a presymptomatic stage of PD, and 10 control subjects, using antibodies against tyrosine hydroxylase (TH) and neurofilament (NF). Immunoreactive nerve fibers of fascicles in the epicardium were well preserved in 10 of the 20 patients with ILBD and in the control subjects. In contrast, TH-immunoreactive nerve fibers had nearly disappeared in six subjects and were moderately decreased in four of the 20 patients with ILBD. Neuronal cell loss in the dorsal vagal nucleus and the sympathetic ganglia was not detectable in any of the ILBD patients examined. These findings suggest that degeneration of the cardiac sympathetic nerve begins in the early disease process of PD and that it occurs before neuronal cell loss in the dorsal vagal nucleus.

Reduced 125I-meta-iodobenzylguanidine uptake and norepinephrine transporter density in the hearts of mice with MPTP-induced parkinsonism

Uptake of (123)I-meta-iodobenzylguanidine ((123)I-MIBG) is markedly reduced in the hearts of patients with Parkinson's disease. Although the mechanism of this reduction is unclear, (12)(5)I-MIBG uptake is similarly reduced in the hearts of mice with 1-methyl-4-phenyl-1,2,3,6-tetrahydroxypyridine (MPTP)-induced parkinsonism. Three groups of ten 15-week-old C57BL6 mice received intraperitoneal injections of (1) saline (control), (2) 10 mg/kg MPTP or (3) 40 mg/kg MPTP. After 0.185 MBq of (125)I-MIBG was injected, the percent injected dose of (125)I-MIBG per gram of tissue (%ID/g) was determined and cardiac concentrations of norepinephrine were measured. Cardiac concentrations of norepinephrine transporter (NET) were measured in three groups of twenty 15-week-old C57BL6 mice receiving these same treatments. The %ID/g in mice receiving 10 or 40 mg/kg MPTP (5.7 +/- 1.1 and 4.4 +/- 1.2%/g) was significantly lower than that in control mice (11.3 +/- 2.2%/g; P < .00001 and P < .0000001, respectively). The norepinephrine concentration in mice receiving 10 or 40 mg/kg MPTP (7.86 +/- 0.67 x 10(5) and 7.50 +/- 0.89 x 10(5) pg/wet g) was significantly lower than that in control mice (9.21 +/- 0.97 x 10(5) pg/wet g; P < .01 and P < .001, respectively). The NET density in mice receiving 10 or 40 mg/kg MPTP (81 +/- 12, 61 +/- 7 fmol/mg protein) was significantly lower than that in control mice (126 +/- 7 fmol/mg protein; P < .000001 and P < .0000001, respectively). The %ID/g of (125)I-MIBG and NET density decreased as the dose of MPTP increased. This study clearly shows that reduced cardiac (12)(5)I-MIBG uptake in mice with MPTP-induced parkinsonism is closely related to the reduced NET density in postganglionic cardiac sympathetic nerve terminals.

Clinical heterogeneity of alpha-synuclein gene duplication in Parkinson's disease

OBJECTIVE

Recently, genomic multiplications of alpha-synuclein gene (SNCA) have been reported to cause hereditary early-onset parkinsonism. The objective of this study was to assess the frequency of SNCA multiplications among autosomal dominant hereditary Parkinson's disease (ADPD).

METHODS

We screened 113 ADPD probands and 200 sporadic PD cases by quantitative polymerase chain reaction and confirmed SNCA multiplications by fluorescence in situ hybridization (FISH) and comparative genomic hybridization array.

RESULTS

Two families (two patients from Family A and one from Family B) with SNCA duplication were identified among ADPD patients. Even though they had the same SNCA duplication, one patient had dementia. Because there was exactly the same difference between the regions originated from each patient, the finding suggests that the phenotype of SNCA multiplication may be also influenced by the range of duplication region. We also detected asymptomatic carriers in the families of both patients. Interestingly, the penetrance ratio was 33.3% (2/6) in one kindred, indicating that the ratio was very much lower than expected.

INTERPRETATION

These two newly identified Japanese patients with SNCA duplication and the five previously identified American and European families with SNCA triplication or duplication mutations indicate that the incidence of SNCA multiplication may be more frequent than previously estimated.

Clinical Implications of Cardiac-MIBG SPECT in the Differentiation of Parkinsonian Syndromes

Background and Purpose

¹²³I cardiac meta-iodobenzylguanidine (MIBG), an analogue of norepinephrine, has been used to estimate myocardial sympathetic nerve function. We investigate whether cardiac-MIBG SPECT is clinically applicable in the differentiation of Parkinson's disease (PD) from parkinsonian syndromes.

Methods

Cardiac-MIBG scintigraphy was performed in 27 controls, in 40 patients with PD and in 52 patients with other parkinsonian syndromes comprising 23 with multiple system atrophy (MSA), 26 with drug-induced parkinsonism (DIP), and 3 with corticobasal degeneration (CBD). The heart to mediastinum (H/M) uptake ratio was calculated for each subjects. Patients who either had medical conditions that confused the MIBG SPECT results or who took medications that interfere with MIBG accumulation were excluded from the study.

Results

Both early and delayed H/M ratios were in patients with PD significantly lower than in controls (early, 1.34±0.15 vs 1.79±0.19; delayed, 1.29±0.15 vs 2.06±0.29, p<0.001). In patients with PD, both early and delayed H/M ratios were significantly lower than those in patients with MSA (early, 1.68±0.23; delayed, 1.80±0.34, p<0.001), DIP (early, 1.83±0.24; delayed, 2.07±0.4, p<0.001), or CBD (early, 1.85±0.01; delayed, 1.99±0.19, p<0.001). Two patients with DIP, who were within the range of patients with PD, showed clinically similar courses of PD.

Conclusions

This study demonstrates that cardiac-MIBG is a clinically powerful tools to differentiate PD from other parkinsonian syndromes.

Cardiac sympathetic denervation precedes neuronal loss in the sympathetic ganglia in Lewy body disease

Decreased cardiac uptake of meta-iodobenzylguanidine (MIBG) on [123I]MIBG myocardial scintigraphy has been reported in Parkinson's disease (PD) and dementia with Lewy bodies (DLB). We hypothesized that cardiac sympathetic denervation might account for the pathomechanism. To elucidate the extent, frequency and pattern of cardiac sympathetic nerve involvement in Lewy body disease and related neurodegenerative disorders, we immunohistochemically examined heart tissues from patients with PD (n=11), DLB (n=7), DLB with Alzheimer's disease (DLB/AD; n=4), multiple system atrophy (MSA; n=8), progressive supranuclear palsy (PSP; n=5), pure AD (n=10) and control subjects (n=5) together with sympathetic ganglia from patients with PD (n=5) and control subjects (n=4), using an antibody against tyrosine hydroxylase (TH). TH-immunoreactive nerve fibers in the hearts had almost entirely disappeared in nearly all the patients with PD, DLB and DLB/AD, whereas they were well preserved in all the patients with PSP and pure AD as well as in all except for one patient with MSA. In PD, neurons in the sympathetic ganglia were preserved in all except for one patient. Decreased cardiac uptake of MIBG in Lewy body disease reflects actual cardiac sympathetic denervation, which precedes the neuronal loss in the sympathetic ganglia.

Significance of 123I-MIBG scintigraphy as a pathophysiological indicator in the assessment of Parkinson's disease and related disorders: it can be a specific marker for Lewy body disease

Recently, reliable and clear evidence for the usefulness of 123I-MIBG scintigraphy in the diagnosis of Parkinson's disease (PD) has been accumulated and it has become increasingly popular as one of the most accurate means of diagnosing the disease. PD, one of the most common neurodegenerative disorders, is characterized by resting tremor, rigidity, bradykinesia or akinesia, and postural instability. The disease is characterized pathologically by distinctive neuronal inclusions called Lewy bodies in many surviving cells of dopaminergic neurons of the substantia nigra pars compacta and other specific brain regions. Furthermore Lewy body type degeneration in the cardiac plexus has been observed in PD. In PD, cardiac MIBG uptake is reduced markedly even in the early disease stages; therefore, MIBG imaging can be used as an indicator of the presence of PD rather than disease severity. Other parkinsonian syndromes such as multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration demonstrate normal cardiac MIBG uptake or only mild reduction of MIBG uptake, indicating that MIBG imaging is a powerful method to differentiate PD from other parkinsonian syndromes. Dementia with Lewy bodies (DLB) also shows severe reduction of MIBG uptake, whereas Alzheimer's disease (AD) demonstrates normal MIBG uptake, permitting differentiation of DLB from AD using MIBG scintigraphy. In pure autonomic failure, which shares similar pathological findings with PD and is thought to be associated with diffuse loss of sympathetic terminal innervation, cardiac MIBG uptake also decreases markedly. Considering all the data together, marked reduction of cardiac MIBG uptake seems to be a specific marker of Lewy body disease and thus extremely useful in the differentiation from other diseases with similar symptoms without Lewy bodies.

Preserved cardiac sympathetic nerve accounts for normal cardiac uptake of MIBG in PARK2

We performed [123I] MIBG myocardial scintigraphy in two of three patients with PARK2 from unrelated families and examined the heart tissues from the three patients immunohistochemically using an antibody against tyrosine hydroxylase (TH) to see whether cardiac sympathetic nerve is involved. Cardiac uptake of MIBG was normal except for a slight decrease in the late phase in one of the patients. Postmortem examination revealed that TH-immunoreactive nerve fibers in the epicardium were well preserved in all three patients. The present study confirmed that cardiac sympathetic nerve is well preserved in PARK2 with a homozygous exon deletion, which accounts for normal cardiac uptake of MIBG. Moreover, normal cardiac uptake of MIBG might be of potential diagnostic value to indicate the absence of Lewy body pathology, even in patients with levodopa-responsive Parkinsonism, as in PARK2.

Profound cardiac sympathetic denervation occurs in Parkinson disease

In the last few years, cardiac sympathetic dysfunction in Parkinson disease (PD) has been postulated on the basis of decreased cardiac uptake of sympathoneural imaging tracers. However, the pathological substrate for the dysfunction remains to be established. We examined the left ventricular anterior wall from postmortem specimens with immunohistochemical staining for tyrosine hydroxylase (TH), neurofilament (NF) and S-100 protein in PD patients and control subjects, and quantified the immunoreactive areas. As TH-immunoreactive axons nearly disappeared and NF-immunoreactive axons drastically decreased in number, the morphological degeneration of the cardiac sympathetic nerves in PD was confirmed. Quantitative analysis showed that sympathetic nerves were preferentially involved. Triple immunofluorolabeling for NF, TH, and myelin basic protein showed clearly the profound involvement of sympathetic axons in PD. The extent of involvement of the cardiac sympathetic nerves seems likely to be equivalent to that in the central nervous system, including the nigrostriatal dopaminergic system. PD affects the cardiac sympathetic nervous system profoundly as well as nigrostriatal dopaminergic system.