Differentiation of Parkinson's disease and multiple system atrophy in early disease stages by means of I-123-MIBG-SPECT

Levodopa challenge test and (123) I-metaiodobenzylguanidine scintigraphy for diagnosing Parkinson's disease

OBJECTIVES

To explore the possibility of a generally applicable tool for the immediate diagnosis of Parkinson's disease (PD) in its early stage, we compared the sensitivity and specificity of an acute levodopa challenge test with that of (123) I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy.

MATERIALS AND METHODS

A consecutive series of 45 patients with extrapyramidal symptoms were recruited to the acute levodopa challenge and evaluated for improvement by use of the Unified Parkinson's Disease Rating Scale motor scores. Of these patients, 32 of them were also examined by MIBG scintigraphy. The patients were followed up for at least 24 months, and 22 patients were diagnosed as having clinically definite PD.

RESULTS

The sensitivity and specificity of the acute levodopa challenge test to predict clinical diagnosis of PD were 81.8% and 81.8%, respectively, which were better than those obtained by MIBG scintigraphy (62.5% and 62.5%). In both early- and middle-stages of PD, the test gave better sensitivity than MIBG scintigraphy.

CONCLUSIONS

Considering that the well-established and frequently referred clinical diagnostic criteria require longitudinal observation for at least 24 months, the acute levodopa challenge test can be used as an immediate diagnostic tool for PD with sensitivity and specificity comparable to those of MIBG.

Evaluation of Parkinson disease and Alzheimer disease with the use of neuromelanin MR imaging and (123)I-metaiodobenzylguanidine scintigraphy

BACKGROUND AND PURPOSE

Progressive changes in the substantia nigra pars compacta and locus ceruleus of patients with Parkinson disease and Alzheimer disease visualized by neuromelanin MRI and cardiac postganglionic sympathetic nerve function on (123)I-metaiodobenzylguanidine scintigraphy have not been fully evaluated. We compared the diagnostic value of these modalities among patients with early Parkinson disease, late Parkinson disease, and Alzheimer disease.

MATERIALS AND METHODS

We compared contrast ratios of signal intensity in medial and lateral regions of the substantia nigra pars compacta and locus ceruleus with those of the tegmentum of the midbrain and the pons, respectively, by use of neuromelanin MRI in patients with early Parkinson disease (n = 13), late Parkinson disease (n = 31), Alzheimer disease (n = 6), and age-matched healthy control subjects (n = 20). We calculated heart-to-mediastinum ratios on (123)I-metaiodobenzylguanidine scintigrams after setting regions of interest on the left cardiac ventricle and upper mediastinum.

RESULTS

The signal intensity of the lateral substantia nigra pars compacta on neuromelanin MRI was significantly reduced in early and late Parkinson disease, and that of the medial substantia nigra pars compacta was gradually and stage-dependently reduced in Parkinson disease. The signal intensity of the locus ceruleus was obviously reduced in late Parkinson disease. Signal reduction was not significant in the substantia nigra pars compacta and locus ceruleus of patients with Alzheimer disease. The heart-to-mediastinum ratio on (123)I-metaiodobenzylguanidine scintigrams was stage-dependently reduced in Parkinson disease and normal in Alzheimer disease. The signal intensity ratios in substantia nigra pars compacta and locus ceruleus on neuromelanin MRI positively correlated with the heart-to-mediastinum ratio on (123)I-metaiodobenzylguanidine scintigrams.

CONCLUSIONS

Both neuromelanin MRI and (123)I-metaiodobenzylguanidine scintigraphy can help to evaluate disease progression in Parkinson disease and are useful for differentiating Parkinson disease from Alzheimer disease.

Diagnostic accuracy of apparent diffusion coefficient and 123I-metaiodobenzylguanidine for differentiation of multiple system atrophy and Parkinson's disease

Background

It is often hard to differentiate Parkinson’s disease (PD) and parkinsonian variant of multiple system atrophy (MSA-P), especially in the early stages. Cardiac sympathetic denervation and putaminal rarefaction are specific findings for PD and MSA-P, respectively.

Purpose

We investigated diagnostic accuracy of putaminal apparent diffusion coefficient (ADC) test for MSA-P and ¹²³I-metaiodobenzylguanidine (MIBG) scintigram for PD, especially in early-stage patients.

Methods

The referral standard diagnosis of PD and MSA-P were the diagnostic criteria of the United Kingdom Parkinson’s Disease Society Brain Bank Criteria and the second consensus criteria, respectively. Based on the referral standard criteria, diagnostic accuracy [area under the receiver-operator characteristic curve (AUC), sensitivity and specificity] of the ADC and MIBG tests was estimated retrospectively. Diagnostic accuracy of these tests performed within 3 years of symptom onset was also investigated.

Results

ADC and MIBG tests were performed on 138 patients (20 MSA and 118 PD). AUC was 0.95 and 0.83 for the ADC and MIBG tests, respectively. Sensitivity and specificity were 85.0% and 89.0% for MSA-P diagnosis by ADC test and 67.0% and 80.0% for PD diagnosis by MIBG test. When these tests were restricted to patients with disease duration ≤3 years, the sensitivity and specificity were 75.0% and 91.4% for the ADC test (MSA-P diagnosis) and 47.7% and 92.3% for the MIBG test (PD diagnosis).

Conclusions

Both tests were useful in differentiating between PD and MSA-P, even in the early stages. In early-stage patients, elevated putaminal ADC was a diagnostic marker for MSA-P. Despite high specificity of the MIBG test, careful neurological history and examinations were required for PD diagnosis because of possible false-negative results.

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.

Biology of Parkinson's disease: pathogenesis and pathophysiology of a multisystem neurodegenerative disorder

Parkinson's disease (PD) is the second most common movement disorder. The characteristic motor impairments - bradykinesia, rigidity, and resting tremor - result from degenerative loss of midbrain dopamine (DA) neurons in the substantia nigra, and are responsive to symptomatic treatment with dopaminergic medications and functional neurosurgery. PD is also the second most common neurodegenerative disorder. Viewed from this perspective, PD is a disorder of multiple functional systems, not simply the motor system, and of multiple neurotransmitter systems, not merely that of DA. The characteristic pathology - intraneuronal Lewy body inclusions and reduced numbers of surviving neurons - is similar in each of the targeted neuron groups, suggesting a common neurodegenerative process. Pathological and experimental studies indicate that oxidative stress, proteolytic stress, and inflammation figure prominently in the pathogenesis of PD. Yet, whether any of these mechanisms plays a causal role in human PD is unknown, because to date we have no proven neuroprotective therapies that slow or reverse disease progression in patients with PD. We are beginning to understand the pathophysiology of motor dysfunction in PD, but its etiopathogenesis as a neurodegenerative disorder remains poorly understood.

Sick sinus syndrome and orthostatic hypotension in Parkinson's disease

We present a case of Parkinson's disease patient whose initial symptoms were sick sinus syndrome and orthostatic hypotension. Our case illustrates difficulties in distinguishing syncope of primary cardiac or neurological origin and highlights the importance of a diagnostic workup including neurological examination.

Assessment of global cardiac I-123 MIBG uptake and washout using volumetric quantification of SPECT acquisitions

BACKGROUND

Assessment of cardiac innervation using single-photon emission computer tomography (SPECT) is less established than planar imaging, but may be more suitable for quantification. Therefore, a volumetric quantification of I-123 MIBG SPECT acquisitions was performed. Reproducibility, the effects of extra cardiac I-123 MIBG uptake and the relation with conventional planar indices were evaluated.

METHODS

54 patients referred for planar and SPECT I-123 MIBG acquisitions were included. Ellipsoidal or box-shaped volumes of interest were placed on the left ventricle, cardiac lumen, mediastinum, lung and liver. SPECT segmentation was performed twice in all patients. Indices were determined based on the heart-to-mediastinum (HM), myocardial wall-to-mediastinum and myocardial wall-to-lumen regions. HM ratios and washout rates were also determined based on anterior planar images.

RESULTS

Cardiac count densities were highly reproducible (CV 1.5-5.4, ICC 0.96-0.99) and inter-rater variability was low (CV 1.8-6.8, ICC 0.94-0.99). Mediastinal uptake was an important explanatory variable of uptake in the entire heart (early R(2) = 0.36; delayed R(2) =0.43) and myocardial wall (early R(2) = 0.28; delayed R(2) = 0.37). Lung washout was an explanatory variable of organ washout of the heart (heart R(2) = 0.38; myocardial wall R(2) = 0.33). In general, SPECT indices showed moderate-to-good correlations with the planar uptake (PCC 0.497-0.851).

CONCLUSION

By applying a volumetric segmentation method we were able to segment the heart in all patients. SPECT I-123 MIBG quantification was found to be highly reproducible and had a moderate to good correlation with the planar indices.

Pattern of cardiac sympathetic denervation in idiopathic Parkinson disease studied with 11C hydroxyephedrine PET

PURPOSE

To determine whether cardiac sympathetic denervation in idiopathic Parkinson disease (IPD) affects the left ventricle in a distinct regional pattern versus a more global pattern with use of carbon 11 (11C) meta-hydroxyephedrine (HED) positron emission tomography (PET).

MATERIALS AND METHODS

This prospective study was approved by the institutional review board and was compliant with HIPAA. Informed consent was obtained from all subjects. Cardiac PET was performed with 11C HED in 27 patients with IPD (20 men and seven women aged 50-74 years; mean age, 62 years±6 [standard deviation]). 11C HED retention indexes (RIs), which reflect nerve density and integrity, were determined. RIs for 33 healthy control subjects (15 men and 18 women aged 20-78 years; mean age, 47 years±17) were used as a control database. Patients with IPD were compared with control subjects by using z score analysis. Global and segmental measurements of sympathetic denervation were expressed as percentage extent, z score severity, and severity-extent product (SEP). Group comparisons were performed with the Student t test.

RESULTS

The mean 11C HED RI was 0.086 mL of blood per minute per milliliter tissue±0.015 for control subjects and 0.043 mL of blood per minute per milliliter tissue±0.016 for patients with IPD (P<0001). When compared with normative data from the control database, profound cardiac denervation (global extent>50%) was seen in most patients (19 of 27 patients, 70%). Four patients had normal 11C HED studies and four had mild denervation (global extent<25%). The mean global denervation extent was 62%±38, the mean severity z score was -2.7±1.2, and the mean SEP was -202±131 (range, -358 to 0). Segmental analysis revealed relative sparing of anterior and proximal septal segments (mean extent, 48%-51%; mean severity z score, -2.47 to -2.0; mean SEP, -167 to -139), with lateral and proximal inferior segments more severely affected (mean extent, 68%-73%; mean severity z score, -2.8 to -2.62; mean SEP, -271 to -230). Patients with normal findings or preserved denervation did not significantly differ in mean age (t=1.09) or disease duration (t=0.44) compared to patients with severe sympathetic denervation.

CONCLUSION

Cardiac sympathetic denervation in IPD is extensive, with a segmental pattern that involves the proximal lateral left ventricular wall most severely, with relative sparing of the anterior and proximal septal walls.

Optimizing levodopa therapy to treat wearing-off symptoms in Parkinson's disease: focus on levodopa/carbidopa/entacapone

Levodopa has been the mainstay of Parkinson's disease (PD) therapy for over 40 years, with its efficacy surpassing that of other antiparkinsonian medications. As such, most PD patients eventually require levodopa-based therapy during the course of the disease. However, despite its proven efficacy, long-term levodopa therapy is associated with motor complications, with wearing-off being the most prevalent. Wearing-off occurs, in part, as a result of the short half-life of levodopa, which leads to fluctuations in plasma levodopa levels. A pharmacokinetic profile characterized by a higher trough value of levodopa can be achieved by combining levodopa/carbidopa with entacapone, which inhibits the peripheral breakdown of levodopa, resulting in higher plasma levodopa levels. Here, we review the limitations of conventional levodopa and the clinical data for levodopa/carbidopa/entacapone in treating patients with wearing-off.

[Decreased myocardial uptake of meta-iodobenzylguanidine in an autopsy-confirmed case of corticobasal degeneration with Lewy bodies restricted to the sympathetic ganglia]

We report on an autopsy case of corticobasal degeneration (CBD) with Lewy bodies in only the sympathetic ganglia. A 79-year-old man showed walking disturbance as an initial symptom, and developed dementia and bradykinesia within the next 2 years. Neurological examination revealed parkinsonism-like akinesia and rigidity in the trunk and neck without resting tremor. Brain magnetic resonance imaging showed frontal lobe atrophy predominantly on the right side. Cardiac uptake of meta-iodobenzylguanidine (MIBG) was reduced (H/M ratio: 1.14). A diagnosis of dementia with Lewy bodies (DLB) was made, but L-dopa treatment was not effective. Seven years later he died of pneumonia. On pathological examination, the frontal cortex and white matter were degenerated, predominantly on the right side. Gallyas-Braak silver staining and AT-8 immunostaining revealed neurofibrillary tangles, pretangles, argyrophilic threads, and astrocytic plaques in the cerebral cortex and basal ganglia, confirming the diagnosis of CBD. Lewy bodies, which were not seen in the central nervous system, were seen only in the sympathetic ganglia, and a severe loss of nerve fibers was apparent in the sympathetic nerve endings in the heart. MIBG is currently used to differentiate DLB from other parkinsonisms, such as CBD, multiple system atrophy, and progressive supranuclear palsy, because reduced cardiac uptake of MIBG represents a pathological change in the sympathetic nerve endings in the heart. However, the distribution of Lewy bodies cannot be determined from this finding. Thus, MIBG should not be used alone to confirm a diagnosis of DLB; other neurodegenerative diseases with incidental Lewy body disease, as in the present case, must be also considered.

Diagnostic markers for Parkinson's disease

PURPOSE OF REVIEW

This review enumerates recent developments in the early diagnosis of Parkinson's disease, with an emphasis on detection of preclinical Parkinson's disease.

RECENT FINDINGS

Several clinical, laboratory, and imaging tests are now being investigated as potential early markers of Parkinson's disease. These include various nonmotor features that predate the motor manifestations of Parkinson's disease, including sleep abnormalities, neurobehavioral symptoms, and olfactory dysfunction. Tests of the autonomic nervous system, such as cardiac functional imaging, allow for a measure of cardiac sympathetic denervation. Cerebrospinal fluid and serum tests, including α-synuclein and DJ-1, are being developed and refined. Various imaging modalities have contributed to the diagnostic armamentarium in Parkinson's disease, including transcranial Doppler ultrasonography, radiolabeled tracer imaging, and magnetic resonance imaging. Early Parkinson's disease detection will pave the way for major advances in disease modifying therapies.

SUMMARY

Various diagnostic modalities hold promise for the early and preclinical diagnosis of Parkinson's disease. It is likely that the future diagnosis of Parkinson's disease will rely on a combination of clinical, laboratory, imaging, and genetic data.

[Clinical and imaging diagnostics of Parkinson's disease and multiple system atrophy]

The diagnosis of Parkinson's disease (PD) and multiple system atrophy (MSA) is primarily made by clinical symptoms, but might still remain challenging even for experienced neurologists. Neuroradiologic imaging may be a useful tool in the diagnostic work-up, particularly for excluding other diseases, such as normal pressure hydrocephalus, multi-infarct dementia and cerebellar lesions. Nuclear medicine methods can additionally support the diagnosis and differential diagnosis of PD and MSA.

Biomarkers for Parkinson's disease

Biomarkers for detecting the early stages of Parkinson's disease (PD) could accelerate development of new treatments. Such biomarkers could be used to identify individuals at risk for developing PD, to improve early diagnosis, to track disease progression with precision, and to test the efficacy of new treatments. Although some progress has been made, there are many challenges associated with developing biomarkers for detecting PD in its earliest stages.

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.

Mechanisms of orthostatic hypotension and supine hypertension in Parkinson disease

Non-motor aspects of Parkinson disease (PD) are now recognized to be important both clinically and scientifically. Among these facets are abnormalities in blood pressure regulation. As much as 40% of PD patients have orthostatic hypotension (OH), which is usually associated with supine hypertension (SH). Symptoms of OH range from light-headedness to falls with serious trauma. SH, while typically asymptomatic, poses a significant increased risk for cardiovascular morbidity and mortality. Neuroimaging, neurochemical, and neuropharmacological studies indicate cardiac and extra-cardiac sympathetic noradrenergic denervation and baroreflex failure in virtually all PD patients with OH, and cardiac sympathetic denervation has been confirmed histopathologically. Mechanisms of SH in PD+OH remain poorly understood. The diurnal blood pressure profile shows increased variability that is correlated with decreased baroreflex gain and with increased morbidity and mortality. Treatment should be individually tailored according to the timing of OH or SH, using primarily short-acting sympathomimetic medications in the daytime for OH and short-acting antihypertensive in the nighttime for SH. Future research is needed to understand better and attenuate blood pressure fluctuations through manipulations that improve baroreflex function.

Examining Braak's hypothesis by imaging Parkinson's disease

In this review, in vivo patterns of structural, metabolic, and neurotransmitter binding changes revealed by imaging in both symptomatic Parkinson's disease (PD) and at-risk subjects are compared with those predicted at different Braak stages. It is concluded that the dysfunction revealed by imaging in PD is only partially in line with the sequential ascending topography of Lewy body pathology reported by Braak, suggesting that neurons in different brain regions are likely to be selectively vulnerable to the presence of intracellular synuclein aggregates.

Parasympathetic but not sympathetic cardiac dysfunction at early stages of Parkinson's disease

BACKGROUND

Autonomic cardiovascular dysfunction is common in Parkinson's disease (PD). Imaging studies suggest loss of cardiac sympathetic nerves even in the absence of clinical signs of autonomic dysfunction. Aim of the study was to investigate the functional significance of autonomic cardiovascular denervation at early stages of PD.

METHODS

Seven PD patients (Hoehn and Yahr class 1 or 1.5) without clinical signs of autonomic dysfunction and seven age-matched healthy control subjects were studied. To evaluate the pre- and post-synaptic components of sympathetic innervation, dose-response curves of isoproterenol (no neuronal uptake) and epinephrine (neuronal uptake) on heart rate, contractility, cardiac output and systemic vascular resistance were determined echocardiographically. Additionally, measurements of baroreflex sensitivity and 24-h heart rate variability were done.

RESULTS

The chronotropic and inotropic responses during stimulation with isoproterenol and epinephrine were similar in PD patients and control subjects. Assessment of baroreflex sensitivity yielded no difference. Of the parameters of 24-h heart rate variability, only measures of high-frequency heart rate variation that more purely reflect parasympathetic activity were significantly depressed in PD patients as compared with control subjects.

CONCLUSIONS

The results of our study using direct determination of catecholamine-mediated chronotropic and contractile responses provide evidence against a functionally relevant sympathetic dysfunction. Possibly, sympathetic denervation is incomplete and the remaining fibers are sufficient for the maintenance of autonomic control. In contrast, the depression of several parameters of heart rate variability supports a significant change of parasympathetic activity at an early stage of PD with subclinical autonomic failure.

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

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

Vulnerability of peripheral catecholaminergic neurons to MPTP is not regulated by alpha-synuclein

Although generally considered a prototypical movement disorder, Parkinson's disease is commonly associated with a broad-spectrum of non-motor symptoms, including autonomic dysfunctions caused by significant alterations in catecholaminergic neurons of the peripheral sympathetic nervous system. Here we present evidence that alpha-synuclein is highly expressed by sympathetic ganglion neurons throughout embryonic and postnatal life and that it is found in tyrosine hydroxylase-positive sympathetic fibers innervating the heart of adult mice. However, mice deficient in alpha-synuclein do not exhibit any apparent alterations in sympathetic development. Sympathetic neurons isolated from mouse embryos and early postnatal mice are sensitive to the parkinsonian drug MPTP/MPP(+) and intoxication requires entry of the neurotoxin through the noradrenaline transporter. Furthermore, recovery of noradrenaline from cardiac sympathetic fibers is reduced in adult mice treated with MPTP systemically. However, MPP(+)-induced sympathetic neuron loss in vitro or MPTP-induced cardiac noradrenaline depletion in vivo is not modified in mice lacking alpha-synuclein. This is in clear contrast with the observation that dopaminergic neurons of the central nervous system are significantly less vulnerable to MPTP/MPP(+) in the absence of alpha-synuclein, suggesting different actions of this molecule in central and peripheral catecholaminergic neurons.

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.

Diminished tyrosine hydroxylase immunoreactivity in the cardiac conduction system and myocardium in Parkinson's disease: an anatomical study

Clinical and autopsy studies have consistently reported cardiac sympathetic dysfunction in the left ventricular wall in patients with Parkinson's disease (PD). Whether the nerve fibers of the cardiac conduction system or the atrial walls are equally affected in this disease process has not yet been well documented. Therefore, the aim of this study was to investigate sympathetic nerves in the cardiac conduction system as well as in the walls of all four heart chambers in patients with PD, in incidental Lewy body disease (iLBD), and in controls. Heart tissue from five PD patients, two iLBD cases, and seven controls were investigated immunohistochemically using antibodies directed against tyrosine hydroxylase (TH) and alpha-synuclein (syn-1). A marked diminution of TH immunoreactivity (IR) within nerve fibers was observed in four PD patients and in both individuals with iLBD. In contrast, all control subjects displayed dense TH-IR nerve structures. The depletion in TH-IR involved not only the ventricles, but also the conduction system and the atrium showing a global change within cardiac TH-IR nerve fibers in the course of PD. In conclusion, the alterations in cardiac sympathetic nerves of patients with PD or in individuals with iLBD are homogeneous and global within the heart. The clinical implications related to this complete cardiac sympathetic dysfunction, including clinical correlates, diagnostic implications, and treatment, however, remain to be determined in a larger autopsy-controlled cohort of prospectively followed individuals.

Diagnostic accuracy of cardiac metaiodobenzylguanidine scintigraphy in Parkinson disease

BACKGROUND AND PURPOSE

To estimate the diagnostic accuracy of cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigram for detection of Parkinson disease.

METHODS

A cross-sectional study with index test of MIBG scintigram and reference standard of U.K. Parkinson's Disease Brain Bank Criteria was performed in 403 patients. Ratio of cardiac-to-mediastinum MIBG accumulation was determined at 20 min (early H/M) and 4 h (late H/M). Area under the receiver-operator characteristic (ROC) curve, sensitivity and specificity in detecting Parkinson disease were analyzed. Accuracy was analyzed in a subgroup of patients with disease duration of 3 years or less.

RESULTS

Area under the ROC curve was 0.89 using either early or late H/M as a diagnostic marker (95% CI 0.85-0.92 for early H/M and 0.86-0.93 for late H/M). Sensitivity and specificity were 81.3% (76.1-85.8%) and 85.0% (77.7-90.6%) for early H/M and 84.3% (79.3-88.4%) and 89.5% (83.01-94.1%) for late H/M. In the subgroup with duration of 3 years or less, the ROC curve area, sensitivity, and specificity were 0.86 (0.79-0.92), 76.0% (64.8-85.1%), and 83.9% (71.7-92.4%) for early H/M and 0.85 (0.78-0.92), 73.3% (61.9-82.9%), and 87.5% (75.9-94.8%) for late H/M.

CONCLUSION

Although diagnostic accuracy of cardiac MIBG scintigram is high, it is limited because of insufficient sensitivity in patients with short duration.

Systemic postganglionic adrenergic studies do not distinguish Parkinson's disease from multiple system atrophy

BACKGROUND

Multiple system atrophy (MSA) affects the preganglionic adrenergic neuron and Parkinson's disease (PD) involves the postganglionic counterpart. Widespread postganglionic denervation should result in denervation supersensitivity and a failure of the axon to release norepinephrine (NE). We examined if pharmacological dissection of the adrenergic neuron can distinguish between MSA and PD.

METHOD

We measured blood pressure, heart rate, and plasma NE responses to direct (phenylephrine) and indirect (tyramine) acting adrenergic agonists in 15 patients with probable MSA, 16 patients with idiopathic PD, and 16 age- and gender-matched controls.

RESULTS

Baroreflex sensitivity was impaired in MSA and intact in PD. Pressor responses to phenylephrine (direct acting) were higher in MSA (p<0.01) and PD patients (p=0.04) than in controls. Blood pressure responses to tyramine (indirect acting) were increased in MSA only (p<0.01). Tyramine increased plasma catecholamine levels in all groups with no significant differences between groups.

CONCLUSION

There is denervation supersensitivity in PD patients that is, however, insufficient to shift the dose-response curve to the left. The excessive pressor responses to both tyramine and phenylephrine in MSA are due to baroreflex failure. We conclude that this diagnostic approach lacks sufficient sensitivity to differentiate PD and MSA.

Intracellular and extracellular targets of molecular imaging in the myocardium

Utilization of molecular imaging has significantly advanced the field of cardiovascular medicine. In addition to the targets currently in use, novel targets are being developed, including those involved in the processes of myocardial metabolism, myocardial injury, cardiac neurotransmission, and interstitial dysregulation. Further development of these imaging targets may lead to improved characterization of disease processes and guide provision of individualized therapies.

Multiple system atrophy

BACKGROUND

It has been almost 4 decades since the descriptions of the 3 parts of multiple system atrophy (MSA) have taken place, characterized clinically by dysautonomia, parkinsonism, and cerebellar dysfunction. The discovery of a distinctive pathologic maker has finally provided the conceptual synthesis of these 3 entities into the universal designation of MSA as a distinct disease process with a complex combination of clinical presentations. Although advances have been made in terms of awareness and knowledge concerning the clinical features and pathophysiology of MSA, it remains challenging for neurologists who treat these patients to differentiate MSA from its mimics as well as providing them with effective treatment.

REVIEW SUMMARY

The aim of this review is to provide an overview of the advances in the knowledge of the disease, to highlight typical features useful for the recognition of its entity, and to enlist different treatment options.

CONCLUSION

Despite the fact that there is still no treatment modality that can alter the disease progression, a number of useful symptomatic treatment measures are available and should be offered to patients to ameliorate the nonmotor features of MSA and even the motor features that may at least transiently respond to treatment.

Oculomotor function in multiple system atrophy: clinical and laboratory features in 30 patients

We reviewed the clinical and laboratory oculomotor features in 30 patients with probable multiple system atrophy (MSA), 22 with MSA-P and 8 with MSA-C. Six patients were also examined post mortem, MSA being confirmed in four and excluded in two (Parkinson's disease and progressive supranuclear palsy). Clinical examination showed the following abnormalities; excessive square wave jerks--21 of 30 patients; mild vertical supranuclear gaze palsy--8 of 30; gaze-evoked nystagmus--12 of 30 patients, three of whom had no extraocular evidence of cerebellar dysfunction; positioning downbeat nystagmus--10 of 25; mild or moderate saccadic hypometria--22 of 30; impaired ("broken up") smooth pursuit--28 of 30; reduced VOR suppression--16 of 24. Electro-oculography and caloric testing did not add significant extra information. In patients presenting with an akinetic-rigid syndrome it can be difficult to differentiate idiopathic Parkinson's disease from MSA-P and other causes of atypical parkinsonism. Our findings suggest that the presence of excessive square wave jerks, mild-moderate hypometria of saccades, impaired VOR suppression, spontaneous nystagmus or positioning downbeat nystagmus may be oculomotor "red flags" or clues to the presence of MSA. Further, the presence of clinically slow saccades, or moderate-to-severe gaze restriction, suggests a diagnosis other than MSA.

Diffusion weighted imaging best discriminates PD from MSA-P: A comparison with tilt table testing and heart MIBG scintigraphy

Both diffusion weighted magnetic resonance imaging (DWI) of the basal ganglia and meta-iodobenzylguanidin (MIBG) scintigraphy of the heart have been reported useful in the differential diagnosis of patients with Parkinson's disease (PD) vs. the parkinson variant of multiple system atrophy (MSA-P). Their diagnostic value, however, has never been directly compared in patients with parkinsonism and autonomic dysfunction. We have studied 9 patients with PD and 9 patients with MSA-P matched for age and disease severity. Regional trace of the diffusion tensor values were determined in the putamina. Cardiac MIBG uptake was quantified by comparing regions of interest over heart and mediastinum Heart/Mediastinum (H/M) ratio. Furthermore, all patients underwent tilt testing. PD patients showed significantly lower H/M ratios than normal controls; however, there was considerable overlap between the two patient groups. We did not detect any significant differences of blood pressure response to passive tilt between the two patient groups. Sensitivity of MIBG scintigraphy versus DWI for the differentiation of MSA-P from PD was 55.6% vs. 100%, specificity 88.8% vs. 100%, and area under the curve 0.802 vs. 1.000. Our data suggest that DWI is superior to both tilt table testing and MIBG scintigraphy in the differential diagnosis of PD versus MSA-P.

Clinical diagnostic criteria for dementia associated with Parkinson's disease

Dementia has been increasingly more recognized to be a common feature in patients with Parkinson's disease (PD), especially in old age. Specific criteria for the clinical diagnosis of dementia associated with PD (PD-D), however, have been lacking. A Task Force, organized by the Movement Disorder Study, was charged with the development of clinical diagnostic criteria for PD-D. The Task Force members were assigned to sub-committees and performed a systematic review of the literature, based on pre-defined selection criteria, in order to identify the epidemiological, clinical, auxillary, and pathological features of PD-D. Clinical diagnostic criteria were then developed based on these findings and group consensus. The incidence of dementia in PD is increased up to six times, point-prevelance is close to 30%, older age and akinetic-rigid form are associated with higher risk. PD-D is characterized by impairment in attention, memory, executive and visuo-spatial functions, behavioral symptoms such as affective changes, hallucinations, and apathy are frequent. There are no specific ancillary investigations for the diagnosis; the main pathological correlate is Lewy body-type degeneration in cerebral cortex and limbic structures. Based on the characteristic features associated with this condition, clinical diagnostic criteria for probable and possible PD-D are proposed.

[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.

Imaging Non-Dopaminergic Function in Parkinson’s Disease

In Parkinson's disease (PD), there is degeneration of the cholinergic, noradrenergic, and serotonergic systems in addition to dopaminergic projections. Function of these non-dopaminergic systems can be imaged with positron emission tomography (PET) and single photon emission computed tomography (SPECT) and correlated with motor and nonmotor symptomatology. In addition, neuronal loss in PD is associated with microglial activation. The role of microglia in driving the disease process remains uncertain. This review presents and discusses current findings in these areas.

Cardiac sympathetic denervation preceding motor signs in Parkinson disease

There is substantial interest in identifying biomarkers to detect early Parkinson disease (PD). Cardiac noradrenergic denervation and attenuated baroreflex-cardiovagal function occur in de novo PD, but whether these abnormalities can precede PD has been unknown. Here we report the case of a patient who had profoundly decreased left ventricular myocardial 6-[(18)F]fluorodopamine-derived radioactivity and low baroreflex-cardiovagal gain, 4 years before the onset of symptoms and signs of PD. The results lead us to hypothesize that cardiac noradrenergic denervation and decreased baroreflex-cardiovagal function may occur early in the pathogenesis of PD.

Assessment of cortico-spinal tract impairment in multiple system atrophy using transcranial magnetic stimulation

OBJECTIVE

Among Parkinsonian syndromes, pyramidal signs suggesting cortico-spinal impairment are a hallmark of multiple system atrophy (MSA). Although it is crucial to diagnose correctly this disease to choose the appropriate treatment, the available diagnostic criteria lack sensitivity. Cortical excitability patterns assessed by transcranial magnetic stimulation (TMS) do not differentiate Parkinsonian disorders. TMS using triple stimulation technique (TST) accurately detects cortico-spinal impairment. We hypothesized that this technique could detect such impairment in MSA patients.

METHODS

The TST was applied along with single and paired-pulse TMS to 31 patients fulfilling the diagnostic criteria for MSA-P (n=10), MSA-C (n=4), progressive supranuclear palsy (PSP; n=6) and Idiopathic Parkinson's disease (IPD; n=11) and 11 control subjects.

RESULTS

Single and paired-pulse TMS patterns did not differ between any patient group. The TST pattern was abnormal in five MSA-P, one MSA-C and one PSP patients but not in IPD patients or controls. The mean TST ratio for MSA-P (86.6%) was significantly different from IPD (99.1%; p<0.05) whereas ratios for MSA-C (92.1%) and PSP (93.3%) were not different from IPD or controls (99.5%).

CONCLUSIONS

These results suggest that TST is effective to assess cortico-spinal impairment in MSA.

SIGNIFICANCE

TST might be useful for the diagnosis of atypical Parkinsonism.