SPECT measurement of iodine-123-beta-CIT binding to dopamine and serotonin transporters in Parkinson's disease: correlation with symptom severity

Spatial judgment in Parkinson's disease: Contributions of attentional and executive dysfunction

Spatial judgment is impaired in Parkinson's disease (PD), with previous research suggesting that disruptions in attention and executive function are likely contributors. If judgment of center places demands on frontal systems, performance on tests of attention/executive function may correlate with extent of bias in PD, and attentional disturbance may predict inconsistency in spatial judgment. The relation of spatial judgment to attention/executive function may differ for those with left-side versus right-side motor onset (LPD, RPD), reflecting effects of attentional lateralization. We assessed 42 RPD, 37 LPD, and 67 healthy control participants with a Landmark task (LM) in which a cursor moved horizontally from the right (right-LM) or left (left-LM). The task was to judge the center of the line. Participants also performed neuropsychological tests of attention and executive function. LM group differences were found on left-LM only, with both PD subgroups biased leftward of the control group (RPD p < .05; LPD p < .01; no RPD-LPD difference). For left-LM trials, extent of bias significantly correlated with performance on the cognitive tasks for PD but not for the control group. PD showed greater variability in perceived center than the control group; this variability correlated with performance on the cognitive tasks. The correlations between performance on the test of spatial judgment and the tests of attention/executive function suggest that frontal-based attentional dysfunction affects dynamic spatial judgment, both in extent of spatial bias and in consistency of response as indexed by intertrial variability. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The effect of Parkinson's disease subgroups on verbal and nonverbal fluency

BACKGROUND

Parkinson's disease (PD) leads to deficits in executive function, including verbal and nonverbal fluency, as a result of compromised frontostriatal circuits. It is unknown whether deficits in verbal and nonverbal fluency in PD are driven by certain subgroups of patients, or how strategy use may facilitate performance.

PARTICIPANTS

Sixty-five nondemented individuals with PD, including 36 with right-body onset (RPD; 20 with tremor as their initial symptom, 16 nontremor) and 29 with left-body onset (LPD; 14 with tremor as their initial symptom, 15 nontremor), and 52 normal control participants (NC) took part in the study.

MEASUREMENTS

Verbal fluency was assessed using the FAS and Animals tests. Nonverbal fluency was assessed using the Ruff Figural Fluency Test.

RESULTS

Both RPD and LPD were impaired in generating words and in using clustering and switching strategies on phonemic verbal fluency, whereas different patterns of impairment were found on nonverbal fluency depending on the interaction of side of onset and initial motor symptom (tremor vs. nontremor). Strategy use correlated with number of correct responses on verbal fluency in LPD, RPD, and NC. By contrast, on nonverbal fluency, strategy use correlated with correct responses for RPD and LPD, but not for NC.

CONCLUSION

Our findings demonstrate the importance of considering subgroups in PD and analyzing subcomponents of verbal and nonverbal fluency (correct responses, errors, and strategies), which may depend differently on the integrity of dorsolateral prefrontal cortex, inferior frontal cortex, and anterior cingulate cortex.

Parkinson's disease as a disconnection syndrome

Parkinson's disease (PD) is a major neurodegenerative disorder that is usually considered in terms of midbrain and basal ganglia dysfunction. Regarding PD instead as a disconnection syndrome may prove beneficial to understanding aspects of cognition, perception, and other neuropsychological domains in the disease. PD is usually of unilateral onset, providing evidence of intrahemispheric dissociations and an imbalance in the usual relative strengths of the right and left hemispheres. Hence, in order to appreciate the neuropsychology of PD, it is important to apply to this disease our understanding of hemispheric lateralization effects and within-hemisphere circuitry from brainstem to higher-order association cortex. The focus of this review is on the relevance of PD-related disconnections among subcortical and cortical structures to cognition, perception, emotion, and associated brainstem-based domains such as sleep and mood disturbance. Besides providing information on disease characteristics, regarding PD as a disconnection syndrome allows us to more completely understand normal brain-behavior relations in general.

Loss of thalamic serotonin transporters in early drug-naïve Parkinson's disease patients is associated with tremor: an [(123)I]beta-CIT SPECT study

In vitro studies revealed serotonin transporter (5-HTT) decline in Parkinson’s disease (PD). Yet, few studies investigated thalamic 5-HTT in vivo and its effect on PD heterogeneity. We analyzed thalamic [¹²³I]β-CIT binding (mainly reflecting 5-HTT binding) in 32 drug-naïve PD patients and 13 controls with SPECT. Twenty-six patients were examined twice (17 months apart). Based on UPDRS scores, we identified subgroups of patients with moderate/severe tremor (PD_T) and without tremor (PD_WT) at the time of clinical diagnosis. Additionally, depressive symptoms were evaluated using the Beck Depression Inventory (BDI) at baseline. Mean thalamic specific to non-specific [¹²³I]β-CIT binding ratio was lower in patients when compared to controls, and further decreased during follow-up. At baseline, average thalamic ratio was significantly lower in the PD_T than in the PD_WT subgroup. No correlation was found between BDI scores and thalamic binding ratios. Our findings show decline of [¹²³I]β-CIT binding to thalamic 5-HTT in PD and its possible contribution to tremor onset.

SPECT neuroimaging in translational research of CNS disorders

High resolution SPECT imaging is an emerging field and there are only limited studies as yet available in this direction. Still there is continuous effort to achieve better spatial and temporal resolution in order to obtain detailed structural and functional information of different brain regions in small experimental animals. Recently, SPECT imaging system has been used to perform in vivo imaging using specific radioligands to further elucidate the role of dopaminergic, serotonergic, and cholinergic neurotransmission in relation to regional cerebral blood flow in various human CNS disorders and in gene-manipulated mouse models of neurodegeneration. Although in vivo and non-invasive translational research can be performed by high-resolution microPET imaging system, its limited spatial resolution restricts detailed anatomical and functional information of different brain regions involved in disease process. Recently developed NanoSPECT/CT imaging system has a better spatial resolution hence can be used to correlate and confirm microPET imaging data and determine the precise structural and functional anatomy of CNS disorders and their remission. Moreover SPECT imaging system reduces the cost and number of animals and provides detailed information of CNS disorders at the cellular, molecular and genetic level. Furthermore, SPECT system is economical, provides less radiation burden, and can be used to study bio-distribution of newly synthesized radioligands with increased target to non-target ratios, quality control, and clinical applications. It is envisaged that high-resolution SPECT imaging system will further improve in vivo non-invasive translational research on CNS disorders of unknown etiopathogenesis and their treatment in future.

Quantification of dopamine transporter binding using [18F]FP-beta-CIT and positron emission tomography

The purpose of this study was to compare different kinetic and semi-quantitative methods for analysing human [18F]FP-beta-CIT studies: plasma input models, simplified (SRTM) and full (FRTM) reference tissue models, standard uptake values (SUV) and SUV ratios (SUVr). Both simulations and clinical evaluations were performed to determine the effects of noise, scan duration and blood volume on Akaike model selection, and on precision and accuracy of estimated parameters. For typical noise levels (COV approximately 2.5%) and scan durations (<90 mins), simulations provided poor fits (Akaike criterion) in case of reversible plasma input models showing a relatively high number of outliers compared with the two-tissue irreversible model. Reference tissue models provided more reliable fits, which were nearly independent of noise and scan duration. For clinical data, two tissue irreversible and reversible plasma input models fitted striatum curves equally well (Akaike criterion). BP with plasma input models were less precise and contained more outliers than BP obtained with SRTM or FRTM. Among all methods tested, SRTM showed the highest contrast between patients and controls. When differentiating between patients and controls, SUVr performed almost equally well as SRTM, although contrast between striatum and background was lower. In conclusion, SRTM provided BP estimates with the highest precision and accuracy. Moreover, SRTM provided good contrast between patients and controls, and between striatum and background. SRTM is therefore the method of choice for quantitative [18F]FP-beta-CIT studies. SUVr might be an alternative for larger clinical trials.

Does combined imaging of the pre- and postsynaptic dopaminergic system increase the diagnostic accuracy in the differential diagnosis of parkinsonism?

PURPOSE

We hypothesized that combining pre- and postsynaptic quantitative information about the dopaminergic system would provide a higher diagnostic accuracy in the differential diagnosis of parkinsonism than specific striatal D(2) receptor binding alone. Therefore, the aim of the study was to introduce new semi-quantitative parameters and evaluate their ability to discriminate between Parkinson's disease (IPS) and non-idiopathic parkinsonian syndromes (non-IPS).

METHODS

In 100 patients (69 IPS, 31 non-IPS), postsynaptic [(123)I]IBZM and presynaptic [(123)I]FP-CIT SPECT scans were evaluated by observer-independent techniques. The diagnostic performances of striatal dopamine transporter (DAT) and D(2) receptor binding, their respective asymmetries, and a combination of pre- and postsynaptic asymmetry were evaluated with ROC analyses. A logistic regression model was generated combining factors to calculate the probability for each patient of belonging to either diagnostic group.

RESULTS

D(2) receptor binding provided a sensitivity of 87.1% and a specificity of 72.5% with an area under the curve (AUC) of 0.866. The AUCs of other single parameters were lower than that of D(2) binding. A gain of diagnostic power (p = 0.026) was reached with a model combining pre- and postsynaptic asymmetries and D(2) binding (sensitivity 90.3%, specificity 73.9%, AUC 0.893).

CONCLUSION

The combination of quantitative parameters of presynaptic DAT and postsynaptic D(2) receptor binding demonstrates superior diagnostic power in the differentiation of patients with IPS and non-IPS than the established approach based on D(2) binding alone. Striatal D(2) receptor binding and the combination of DAT and IBZM binding asymmetries are the factors contributing most in separating these diagnostic groups.

Discrimination between parkinsonian syndrome and essential tremor using artificial neural network classification of quantified DaTSCAN data

BACKGROUND

In the semi-quantitative assessment of DaTSCAN images, it has been suggested that the ratio of tracer accumulation in the putamen to that in the caudate nucleus may be helpful and could allow parkinsonian syndromes progression to be assessed. Separation of ratio values has been reported when early Parkinson's disease is compared with essential tremor. The separation is lost, however, when the Parkinson's disease is not early stage.

OBJECTIVES

To evaluate whether a two-stage analysis can differentiate between parkinsonian syndromes, of various stages, and essential tremor, and whether such a two-stage analysis can be undertaken in a single step using artificial neural networks (ANNs).

METHODS

Data from 18 patients were analysed. Quantification was undertaken by manually drawing irregular regions of interest (ROIs): over each caudate nucleus and putamen and over an occipital cortex area near the posterior edge of the brain. A two-stage analysis was undertaken and was repeated, in a single step, using an ANN.

RESULTS

The first stage, of the two-stage analysis, identified 12 patients with non-early parkinsonian syndromes. The remaining six patients were then successfully classified into early parkinsonian syndromes and essential tremor. The ANN analysis successfully discriminated parkinsonian syndromes from essential tremor, in all patients, in a single step.

CONCLUSIONS

The two-stage process provides a method for classifying early disease without being compromised by the noise from non-early disease. The results of the single stage ANN analysis were very definite and it may be considered to have potential in the quantification of DaTSCAN images for clinical use.

Serotonergic mechanisms in Parkinson’s disease: opposing results from preclinical and clinical data

Parkinson's disease (PD) is a neuropsychiatric disease affecting approximately 1-2% of the general population. The classical triad of symptoms, tremor, rigidity, and bradykinesia is mainly caused by degeneration of dopaminergic neurons from the substantia nigra. However, other neurotransmitter systems also show signs of degeneration, among which the serotonergic system. The exact role of serotonin in PD remains unclear. We present here a review about functional serotonergic interventions and serotonergic imaging studies in PD, and will go into the importance of combining preclinical and clinical research data in order to gain more insight into the role of serotonin in PD. More specifically, the present review is aimed at bridging the gap between data from animal models of PD and data from human research.

Correlation of dopamine transporter imaging with parkinsonian motor handicap: How close is it?

During the past decade, dopamine transporter (DAT) imaging with single photon emission computerized tomography (SPECT) or positron emission tomography (PET) has evolved as an objective in vivo marker of nigrostriatal neuron loss in Parkinson's disease (PD). We investigate the relationship between striatal DAT binding, measured with [(123)I]beta-CIT SPECT, and parkinsonian motor handicap in a sample of 59 PD patients with minimal to severe disability, and review published cross-sectional studies on the correlation between DAT imaging and motor symptoms in PD. Earlier studies as well as the present results show a good correlation between overall striatal DAT binding and global measures of disease severity such as the Hoehn and Yahr scale, the total score on the Unified Parkinson's Disease Rating Scale (UPDRS), and UPDRS activities of daily living, with a progressive decline of DAT binding with increasing disability. A number of studies found a significant inverse correlation of striatal DAT binding with UPDRS motor score. Bradykinesia, posture, gait, and other midline symptoms, such as speech and facial expression, compared with rigidity, seem to be more closely related to striatal DAT binding. By contrast, neither the severity of parkinsonian rest nor of action tremor is related to the degree of dopaminergic denervation as measured by DAT imaging. Motor symptoms in the clinically less affected body side show a closer correlation with striatal DAT binding than do symptoms occurring in the dominantly affected body side. The correlation of putamen and caudate DAT binding with parkinsonian motor handicap seems to be similar. Although there have been limited comparative studies applying [(18)F]fluorodopa PET and DAT imaging in the same group of PD patients, available data suggest that putamen [(18)F]fluorodopa uptake, when compared with striatal DAT binding, may be more closely related to parkinsonian motor handicap.

The feasibility of statistical parametric mapping for the analysis of positron emission tomography studies using 11C-2-beta-carbomethoxy-3-beta-(4-fluorophenyl)-tropane in patients with movement disorders

Movement disorders, including Parkinson's disease and parkinsonian syndromes, e.g. progressive supranuclear palsy, multiple system atrophy, and Lewy body dementia, may be difficult to differentiate among each other at an early stage, since they may share similar clinical features and response to dopaminergic drugs. As new tracers for imaging the dopamine transporters become available, the use of positron emission tomography (PET) for the differential diagnosis of movement disorders is gaining clinical relevance. Visual interpretation is generally used for PET image analysis. However, the use of some form of less subjective analysis is desirable in order to detect subtle changes that may be difficult to identify by visual interpretation and to achieve an operator independent analysis. To this end this study was aimed at assessing the feasibility of using statistical parametric mapping (SPM) for the clinical evaluation of single PET scans performed with 2-beta-carbomethoxy-3-beta-(4-fluorophenyl)-tropane ( C-beta-CIT-FE). Eleven healthy volunteers and five patients with movement disorders (Parkinson's disease, essential tremor, PSP and Lewy body dementia) were included in this study. Each subject underwent a PET study after i.v. injection of C-beta-CIT-FE. The PET images of C-beta-CIT-FE distribution acquired between 60 and 90 min were spatially fitted into the Talairach and Tournoux space. A template of normal C-beta-CIT-FE distribution was derived from studies in the 11 normal control subjects. Different patterns of reduction of the uptake of the tracer were detected in the basal ganglia of the five patients, in relation to each pathological condition. The patterns of distribution were all consistent with the severity and type of disease. The results of this study demonstrate the feasibility of differentiating among different states of dopaminergic impairment, due to Parkinson's disease and parkinsonian syndromes, by using PET scans with C-beta-CIT-FE and by using the SPM procedure for analysis of the data.

Parametric mapping of [18F]FPCIT binding in early stage Parkinson's disease: a PET study

We have shown that fluorinated N-3-fluoropropyl-2-beta-carboxymethoxy-3-beta-(4-iodophenyl) nortropane ([(18)F]FPCIT) and PET offer a valuable means of quantifying regional abnormality in dopamine transporter (DAT) imaging associated with Parkinson's disease (PD). The objective of this study was to delineate the topographic distribution of DAT binding in early stage idiopathic PD using statistical parametric analysis of [(18)F]FPCIT PET data. We performed dynamic PET studies in 15 hemi-parkinsonian (Hoehn & Yahr I) patients and 10 age-matched normal volunteers over 100 min and calculated images of [(18)F]FPCIT binding ratios on a pixel-by-pixel basis. Statistical parametric mapping (SPM) was then used to localize binding reductions in PD and to compute the absolute change relative to normal. [(18)F]FPCIT binding decreased significantly in the contralateral posterior putamen of the PD group (P < 0.001, corrected). A significant reduction was also seen in the ipsilateral putamen, which was smaller in extent but localized more posteriorly. A quantitative comparison of DAT binding in the two clusters showed that the onset of motor symptoms in PD was associated with an approximate 70% loss relative to the normal mean in the contralateral posterior putamen. These results suggest that SPM analysis of [(18)F]FPCIT PET data can be used to quantify and map abnormalities in DAT activity within the human striatum. This method provides a useful tool to track the onset and progression of PD at its earliest stages.

Differentiation of dementia with Lewy bodies from Alzheimer's disease using a dopaminergic presynaptic ligand

BACKGROUND

Dementia with Lewy bodies (DLB) is one of the main differential diagnoses of Alzheimer's disease (AD). Key pathological features of patients with DLB are not only the presence of cerebral cortical neuronal loss, with Lewy bodies in surviving neurones, but also loss of nigrostriatal dopaminergic neurones, similar to that of Parkinson's disease (PD). In DLB there is 40-70% loss of striatal dopamine.

OBJECTIVE

To determine if detection of this dopaminergic degeneration can help to distinguish DLB from AD during life.

METHODS

The integrity of the nigrostriatal metabolism in 27 patients with DLB, 17 with AD, 19 drug naive patients with PD, and 16 controls was assessed using a dopaminergic presynaptic ligand, (123)I-labelled 2beta-carbomethoxy-3beta-(4-iodophenyl)-N-(3-fluoropropyl)nortropane (FP-CIT), and single photon emission tomography (SPET). A SPET scan was carried out with a single slice, brain dedicated tomograph (SME 810) 3.5 hours after intravenous injection of 185 MBq FP-CIT. With occipital cortex used as a radioactivity uptake reference, ratios for the caudate nucleus and the anterior and posterior putamen of both hemispheres were calculated. All scans were also rated by a simple visual method.

RESULTS

Both DLB and PD patients had significantly lower uptake of radioactivity than patients with AD (p<0.001) and controls (p<0.001) in the caudate nucleus and the anterior and posterior putamen.

CONCLUSION

FP-CIT SPET provides a means of distinguishing DLB from AD during life.

[123I]beta-CIT SPECT demonstrates decreased brain dopamine and serotonin transporter levels in untreated parkinsonian patients

Striatal dopamine transporters (DATs) and serotonin transporters (SERTs) were evaluated in untreated patients with Parkinson's disease (PD) and controls using single-photon emission computed tomography (SPECT) with 2beta-carboxymethoxy-3beta-(4-iodophenyl)tropane ([123I]beta-CIT). The striatal DAT specific to non-displaceable uptake ratios of 29, and the SERT uptake measurements of 27, PD patients were compared with those of 21 and 16 controls, respectively. The results were correlated with Unified Parkinson's Disease Rating Scale (UPDRS) scores, the Hoehn & Yahr stage, age, duration of the disease, and the major PD signs. The specific DAT binding in the caudate, the putamen and the caudate/putamen ratio were measured. In all of the PD patients the striatal uptake values were bilaterally reduced, being 36.9% (P < 0.001) lower than those of the controls. In the hemiparkinsonian patients the reduction was greater on the side contralateral to the initial symptoms (33.3% vs. 27.8%) and the uptake ratios indicated a more pronounced deficit in the putamen (39.1%) than in the caudate (27.9%). The DAT uptake correlated with the UPDRS total score and activities of daily living (ADL) and motor subscores, the Hoehn & Yahr stage, and rigidity score. PD patients had significantly higher caudate to putamen ratios than the controls. In the PD patients the SERT values were lower in the thalamic and frontal regions. The SERT uptake ratio of the frontal area correlated with the UPDRS subscore I. [123I]beta-CIT SPECT provides a useful method for confirming the clinical diagnosis of PD with correlation to disease severity. Additionally, this technique allows the simultaneous measurement of SERT uptake and shows that PD patients, interestingly, seem to have decreased SERT availability in the thalamic and frontal areas.

The utility of neuroSPECT imaging in the investigation of dementia and parkinsonism

Functional neuroimaging is playing an increasing role in psychiatry and has moved from academic isolation into clinical practice. This review examines the basis for the use of Single Photon Emission Computed Tomography, the most widely available functional modality, in the two important areas of dementia and parkinsonism. Its contribution to the diagnosis and management of patients is discussed and its likely impact in clinical trials indicated. As functional imaging moves closer to those most able to utilise its power its impact in these and other areas of psychiatry and neurology will increase further.

Relationship between striatal [123I]beta-CIT binding and four major clinical signs in Parkinson's disease

We investigated the correlation between clinical severity and striatal [123I]-CIT binding in 12 patients with Parkinson's Disease (PD: 6 men and 6 women, age: 65 +/- 7 years, Hoehn & Yahr stage: 1 to 3). The clinical severity of PD patients was measured with the Unified Parkinson's Disease Rating Scale (UPDRS) after withdrawal of antiparkinsonian medication at least 12 hours before assessment. [123I]beta-CIT binding in the caudate and putamen was measured at 3 hours [V''3 (day 1)], and at 24 hours [V''3 (day 2)) after tracer injection with small square ROIs. The specific striatal uptake index (day 2) was calculated with large square ROIs that encompassed the whole striatum. The best correlation (r = -0.82, p < 0.0012) was between putamenal V''3 (day 2) and the motor UPDRS scores. When the motor UPDRS scores were divided into four subscales, bradykinesia was the only sign that correlated significantly with putamenal V''3 (day 2) (r = -0.81, p < 0.002). [123I]beta-CIT SPECT is a useful marker of disease severity in PD with potential utility in the serial monitoring of disease progression.