Predictive value of dopamine transporter SPECT imaging with [¹²³I]PE2I in patients with subtle parkinsonian symptoms

Long-Term Impact of Diffuse Traumatic Brain Injury on Neuroinflammation and Catecholaminergic Signaling: Potential Relevance for Parkinson's Disease Risk

Traumatic brain injury (TBI) is associated with an increased risk of developing Parkinson's disease (PD), though the exact mechanisms remain unclear. TBI triggers acute neuroinflammation and catecholamine dysfunction post-injury, both implicated in PD pathophysiology. The long-term impact on these pathways following TBI, however, remains uncertain. In this study, male Sprague-Dawley rats underwent sham surgery or Marmarou's impact acceleration model to induce varying TBI severities: single mild TBI (mTBI), repetitive mild TBI (rmTBI), or moderate-severe TBI (msTBI). At 12 months post-injury, astrocyte reactivity (GFAP) and microglial levels (IBA1) were assessed in the striatum (STR), substantia nigra (SN), and prefrontal cortex (PFC) using immunohistochemistry. Key enzymes and receptors involved in catecholaminergic transmission were measured via Western blot within the same regions. Minimal changes in these markers were observed, regardless of initial injury severity. Following mTBI, elevated protein levels of dopamine D1 receptors (DRD1) were noted in the PFC, while msTBI resulted in increased alpha-2A adrenoceptors (ADRA2A) in the STR and decreased dopamine beta-hydroxylase (DβH) in the SN. Neuroinflammatory changes were subtle, with a reduced number of GFAP+ cells in the SN following msTBI. However, considering the potential for neurodegenerative outcomes to manifest decades after injury, longer post-injury intervals may be necessary to observe PD-relevant alterations within these systems.

Serial Nigrostriatal Dopaminergic Imaging in Mild Cognitive Impairment With Lewy Bodies, Alzheimer Disease, and Age-Matched Controls

BACKGROUND AND OBJECTIVES

Progressive nigrostriatal pathway degeneration occurs in individuals with dementia with Lewy bodies (LB). Our objective was to investigate whether repeat 123[I]-N-(3-fluoropropyl)-2β-carboxymethoxy-3β-(4-iodophenyl) nortropane (FP-CIT) single photon emission computed tomography (SPECT) can identify progressive dopaminergic loss in mild cognitive impairment (MCI) with Lewy bodies (MCI-LB).

METHODS

Individuals with MCI-LB and MCI due to Alzheimer disease (MCI-AD) underwent comprehensive clinical assessment, 123[I]-FP-CIT SPECT at baseline and annual reviews, and baseline cardiac 123 iodine metaiodobenzylguanidine (I-MIBG). Mixed-effects models were used to investigate changes in 123[I]-FP-CIT specific binding ratio (SBR) in the striatum for each diagnostic group compared with controls. The time interval to the development of a quantitatively abnormal 123[I]-FP-CIT SPECT in the possible and probable MCI-LB groups was determined as the time it took for these groups to reach a striatal uptake 2 SDs below aged-matched controls. Test-retest variation was assessed using baseline and repeat scans in controls.

RESULTS

We recruited 20 individuals with MCI-AD, 11 with possible MCI-LB, 25 with probable MCI-LB, and 29 age-matched controls. The mean time between baseline and the final image was 1.6 years (SD = 0.9, range 1.0-4.3). The annual estimated change in SBR was 0.23 for controls (95% CI -0.07 to 0.53), -0.09 (-0.55 to 0.36) for MCI-AD, -0.50 (-1.03 to 0.04) for possible MCI-LB, and -0.48 (-0.89 to -0.06) for probable MCI-LB. The median annual percentage change in SBR in MCI-LB was -5.6% (95% CI -8.2% to -2.9%) and 2.1% (-3.5% to 8.0%) for MCI-AD. The extrapolated time for a normal scan to become abnormal was 6 years. Controls and MCI-AD showed no significant change in dopaminergic binding over time. The mean test-retest variation in controls was 12% (SD 5.5%), which cautions against overinterpretation of small changes on repeat scanning.

DISCUSSION

Progressive dopaminergic loss in the striatum is detectable using 123[I]-FP-CIT SPECT in MCI-LB at a group level. In clinical practice, individual change in striatal 123[I]-FP-CIT uptake seems to be of limited diagnostic value because of high test-retest variation.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that longitudinal declines in striatal uptake measured using 123[I]-FP-CIT SPECT are associated with MCI due to Lewy body disease but not MCI due to Alzheimer disease.

Evaluation of the α-synuclein PET radiotracer (d3)-[11C]MODAG-001 in pigs

BACKGROUND

A positron emission tomography (PET) radiotracer to neuroimage α-synuclein aggregates would be a crucial addition for early diagnosis and treatment development in disorders such as Parkinson's disease, where elevated aggregate levels are a histopathological hallmark. The radiotracer (d₃)-[¹¹C]MODAG-001 has recently shown promise for visualization of α-synuclein pre-formed fibrils (α-PFF) in rodents. We here test the radiotracer in a pig model where proteins are intracerebrally injected immediately before scanning. Four pigs were injected in one hemisphere with 150 μg α-PFF, and in the other hemisphere, either 75 μg α-PFF or human brain homogenate from either dementia with Lewy bodies (DLB) or Alzheimer's disease (AD) was injected. All pigs underwent one or two (d₃)-[¹¹C]MODAG-001 PET scans, quantified with the non-invasive Logan graphical analysis using the occipital cortex as a reference region.

RESULTS

The α-PFF and AD homogenate injected brain regions had high uptake of (d₃)-[¹¹C]MODAG-001 compared to the occipital cortex or cerebellum. BP_ND values in 150 μg α-PFF injected regions was 0.78, and in the AD homogenate injected regions was 0.73. By contrast, the DLB homogenate injected region did not differ in uptake and clearance compared to the reference regions. The time-activity curves and BP_ND values in the 150 μg and 75 μg injected regions of α-PFFs show a dose-dependent effect, and the PET signal could be blocked by pretreatment with unlabeled MODAG-001.

CONCLUSION

We find that both α-PFF and AD brain homogenates give rise to increased binding of (d₃)-[¹¹C]MODAG-001 when injected into the pig brain. Despite its limited specificity for cerebral α-synuclein pathology, (d₃)-[¹¹C]MODAG-001 shows promise as a lead tracer for future radiotracer development.

Biophysical Modeling of Dopaminergic Denervation Landscapes in the Striatum Reveals New Therapeutic Strategy

Parkinson’s disease (PD) results from a loss of dopaminergic neurons. What triggers the break-down of neuronal signaling, and how this might be compensated, is not understood. The age of onset, progression and symptoms vary between patients, and our understanding of the clinical variability remains incomplete. In this study, we investigate this, by characterizing the dopaminergic landscape in healthy and denervated striatum, using biophysical modeling. Based on currently proposed mechanisms, we model three distinct denervation patterns, and show how this affect the dopaminergic network. Depending on the denervation pattern, we show how local and global differences arise in the activity of striatal neurons. Finally, we use the mathematical formalism to suggest a cellular strategy for maintaining normal dopamine (DA) signaling following neuronal denervation. This strategy is characterized by dual enhancement of both the release and uptake capacity of DA in the remaining neurons. Overall, our results derive a new conceptual framework for the impaired dopaminergic signaling related to PD and offers testable predictions for future research directions.

Nuclear Imaging in the Diagnosis of Clinically Uncertain Parkinsonian Syndromes

BACKGROUND

Parkinsonian syndromes are classified by etiology mainly on clinical grounds, that is, on the basis of the clinical manifestations and with the aid of conventional ancillary studies. In most cases, the clinical diagnosis is clear. In up to 30% of cases, however, the etiological classification remains uncertain after completion of the basic clinical diagnostic evaluation, and additional investigation with nuclear imaging may be indicated. In particular, cerebral single-photon emission computed tomography (SPECT) with dopamine transporter (DAT) ligands may be helpful. DAT-SPECT can be used to demonstrate or rule out nigrostriatal degeneration and thereby differentiate neurodegenerative parkinsonian syndromes from symptomatic parkinsonian syndromes and other differential diagnoses. Positron emission tomography (PET) with the glucose analogue [18F]fluorodeoxyglucose (FDG) can be used to identify disease-specific patterns of neuronal dysfunction/degeneration in order to differentiate the various neurodegenerative parkinsonian syndromes from one another.

METHODS

In this review, we summarize the current state of the evidence on DAT-SPECT and FDG-PET for the indications mentioned above on the basis of a selective review of the literature.

RESULTS

DAT-SPECT has been adequately validated as an in vivo marker for nigrostriatal degeneration. Studies using the clinical diagnosis of a movement disorders specialist over the course of the disease as a reference have shown that DAT- SPECT is 78-100% sensitive (median, 93%) and 70-100% specific (median, 89%) for the differentiation of neurodegenerative parkinsonian syndromes from symptomatic parkinsonism and other differential diagnoses in clinically unclear cases. DAT- SPECT scanning led to a change of diagnosis in 27-56% of patients (median, 43%) and to a change of treatment in 33-72% (median, 43%). FDG-PET enables the differentiation of atypical neurodegenerative parkinsonian syndromes from the idiopathic parkinsonian syndrome (i.e., Parkinson's disease proper) with high sensitivity and specificity (both approximately 90%), when the clinical diagnosis by a movement disorders specialist over the course of the disease is used as a reference.

CONCLUSION

DAT-SPECT has been well documented to be highly diagnostically accurate and to have a relevant influence on the diagnosis and treatment of patients with clinically uncertain parkinsonian or tremor syndrome. It has not yet been shown to improve patient-relevant endpoints such as mortality, morbidity, and health-related quality of life; proof of this will probably have to await the introduction of neuroprotective treatments. The current evidence for the high differential diagnostic accuracy of FDG-PET in neurodegenerative parkinsonian syndromes needs to be reinforced by prospective studies with neuropathological verification of the diagnosis.

The Story of the Dopamine Transporter PET Tracer LBT-999: From Conception to Clinical Use

The membrane dopamine transporter (DAT) is involved in a number of brain disorders and its exploration by positron emission tomography (PET) imaging is highly relevant for the early and differential diagnosis, follow-up and treatment assessment of these diseases. A number of carbon-11 and fluor-18 labeled tracers are to date available for this aim, the majority of them being derived from the chemical structure of cocaine. The development of such a tracer, from its conception to its use, is a long process, the expected result being to obtain the best radiopharmaceutical adapted for clinical protocols. In this context, the cocaine derivative (E)-N-(4-fluorobut-2-enyl)2β-carbomethoxy-3β-(4′-tolyl)nortropane, or LBT-999, has passed all the required stages of the development that makes it now a highly relevant imaging tool, particularly in the context of Parkinson's disease. This review describes the different steps of the development of LBT-999 which initially came from its non-fluorinated derivative (E)-N-(3-iodoprop-2-enyl)-2-carbomethoxy-3-(4-methylphenyl) nortropane, or PE2I, because of its high promising properties. [¹⁸F]LBT-999 has been extensively characterized in rodent and non-human primate models, in which it demonstrated its capability to explore in vivo the DAT localized at the dopaminergic nerve endings as well as at the mesencephalic cell bodies, in physiological conditions. In lesion-induced rat models of Parkinson's disease, [¹⁸F]LBT-999 was able to precisely quantify in vivo the dopaminergic neuron loss, and to assess the beneficial effects of therapeutic approaches such as pharmacological treatment and cell transplantation. Finally recent clinical data demonstrated the efficiency of [¹⁸F]LBT-999 in the diagnosis of Parkinson's disease.

Advances in SPECT Methodology

The emerging role of molecular imaging has made possible to evaluate and quantify biochemical changes of molecular targets in specific neurochemical systems involved in movement disorders, providing neurochemical information of clinical changes before the pathological features occurred. In detail, radionuclides imaging techniques are frequently used for the in vivo study of neurotransmitter and receptor function, alterations in cerebral blood flow and metabolic activity, abnormal protein deposition, and inflammation, with a central role in molecular imaging for preclinical and clinical studies. The present chapter represents an overview of main use of single-photon emission computed tomography (SPECT) in movement disorders, with a focal attention on specific radiotracers used, recent advances in SPECT technology and reconstruction algorithm and added specific value of semiquantitative methods for images analysis. Finally, a brief paragraph is dedicated to description of SPECT/CT devices and advantages of using hybrid technology.

Altered cardiovascular function is related to reduced BDNF in Parkinson's disease

Brain-derived neurotrophic factor (BDNF) has been linked to cardiovascular health and function, however, the exact role is yet to be understood. The current study examined the relationship of circulatory BDNF with vascular function in Parkinson's disease (PD). ELISA was used to determine plasma BDNF in PD patients and healthy control (CT). Additionally, forearm resting blood flow (RBf), vascular resistance (RVr), venous capacitance (RVc), and venous outflow (RVo) as well as post occlusion blood flow (OcBf), vascular resistance (OcVr), venous capacitance (OcVc), and venous outflow (OcVo) were obtained using strain-gauge plethysmography. Simple linear regression showed that being PD patient can predict (p < 0.05) 12.9% of BDNF, 16.8% of RVc, 15.0% of OcVc, and 13.6% of OcVo. Subsequent stepwise regression included BDNF, RVc, OcVc, and OcVo, showed that being PD patient predicted (p < 0.05) 58.0% of BDNF, 47.7% of OcVo, and 15.1% of OcVc. Another simple linear regression demonstrated that BDNF predicted (p < 0.05) 18.5% of OcBf, 22.0% of OcVr, and 24.1% of OcVc in PD. In a subsequent stepwise linear regression, BDNF explained 26% ofOcVr (p = 0.008) and 42% of OcVc (p = 0.002) in PD. The study showed that BDNF is reduced and related to altered vascular function in PD. The results suggest that BDNF might contribute to preserving and maybe improving vascular function in PD.

Mouse models of neurodegenerative disease: preclinical imaging and neurovascular component

Neurodegenerative diseases represent great challenges for basic science and clinical medicine because of their prevalence, pathologies, lack of mechanism-based treatments, and impacts on individuals. Translational research might contribute to the study of neurodegenerative diseases. The mouse has become a key model for studying disease mechanisms that might recapitulate in part some aspects of the corresponding human diseases. Neurodegenerative disorders are very complicated and multifactorial. This has to be taken in account when testing drugs. Most of the drugs screening in mice are very difficult to be interpretated and often useless. Mouse models could be condiderated a 'pathway models', rather than as models for the whole complicated construct that makes a human disease. Non-invasive in vivo imaging in mice has gained increasing interest in preclinical research in the last years thanks to the availability of high-resolution single-photon emission computed tomography (SPECT), positron emission tomography (PET), high field Magnetic resonance, Optical Imaging scanners and of highly specific contrast agents. Behavioral test are useful tool to characterize different animal models of neurodegenerative pathology. Furthermore, many authors have observed vascular pathological features associated to the different neurodegenerative disorders. Aim of this review is to focus on the different existing animal models of neurodegenerative disorders, describe behavioral tests and preclinical imaging techniques used for diagnose and describe the vascular pathological features associated to these diseases.

Comparison of diagnostic utility of semi-quantitative analysis for DAT-SPECT for distinguishing DLB from AD

PURPOSE

It is widely known that there is low striatal ¹²³I-FP-CIT dopamine transporter single photon emission computed tomography (DAT-SPECT) uptake in patients with dementia with Lewy bodies (DLB). However, a consistent quantitative evaluation method for DAT-SPECT has not yet been established. There are two semi-quantitative software packages for DAT-SPECT available in Japan, namely, DaTView and DaTQUANT. The aim of this study was to identify which of these is superior for distinguishing DLB from AD. Moreover, we aimed to identify which region of the striatum is more suitable for distinguishing DLB from AD.

METHODS

Patients with Alzheimer's disease (AD) (n=95) and patients with DLB (n=133) who underwent DAT-SPECT were enrolled. DaTView and DaTQUANT were used as semi-quantitative analysis tools for DAT-SPECT.

RESULTS

There were significant correlations in DAT uptake between DaTView and entire regions by DaTQUANT. There was no significant difference in diagnostic accuracy between DaTView and DaTQUANT except in the posterior putamen by DaTQUANT.

CONCLUSIONS

For distinguishing DLB from AD, both of DaTView and DaTQUANT software are useful. Moreover, assessing the DAT uptake in entire striatum by DaTView might be sufficient for distinguishing DLB from AD.

Utility of the combination of DAT SPECT and MIBG myocardial scintigraphy in differentiating dementia with Lewy bodies from Alzheimer's disease

Purpose

¹²³I-2β-Carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (¹²³I-FP-CIT) dopamine transporter single photon emission computed tomography (DAT SPECT) and ¹²³I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy can be used to assist in the diagnosis of patients with dementia with Lewy bodies (DLB). We compared the diagnostic value of these two methods in differentiating DLB from Alzheimer’s disease (AD). Furthermore, we evaluated whether a combination of DAT SPECT and MIBG myocardial scintigraphy would provide a more useful means of differentiating between DLB and AD.

Methods

Patients with AD (n = 57) and patients with DLB (n = 76) who underwent both DAT SPECT and MIBG myocardial scintigraphy were enrolled. The sensitivity, specificity, and accuracy of both methods as well as their combination for differentiating DLB from AD were calculated. Moreover, we examined whether symptoms of the patients with DLB were associated with the patterns of the abnormalities displayed on DAT SPECT and MIBG myocardial scintigraphy.

Results

The sensitivity and specificity of differentiating DLB from AD were 72.4 and 94.4 % by the heart to mediastinum ratio of MIBG uptake, 88.2 and 88.9 % by the specific binding ratio on DAT SPECT, and 96.1 and 90.7 % by their combination, respectively. The combined use of DAT SPECT and MIBG myocardial scintigraphy enabled more accurate differentiation between DLB and AD compared with either DAT SPECT or MIBG myocardial scintigraphy alone. There was a significantly higher frequency of parkinsonism in the abnormal DAT SPECT group than the normal DAT SPECT group. On the other hand, there was a higher frequency of the appearance of rapid eye movement (REM) sleep behavior disorder in the abnormal MIBG uptake group than the normal MIBG uptake group.

Conclusion

These results suggested that using a combination of these scintigraphic methods is a useful and practical approach to differentiate DLB from AD.

The diagnostic accuracy of dopamine transporter SPECT imaging to detect nigrostriatal cell loss in patients with Parkinson's disease or clinically uncertain parkinsonism: a systematic review

In specialized movement disorder centers, Parkinson's disease (PD) is wrongly diagnosed in 6 to 25% of cases. To improve the accuracy of the clinical diagnosis, it is necessary to have a reliable and practical reference standard. Dopamine transporter single-photon emission computed tomography (DAT SPECT) imaging might have the potential (high diagnostic accuracy and practical to use) to act as reference standard in detecting nigrostriatal cell loss in patients with (early stage) parkinsonism. We performed a systematic review to evaluate if DAT SPECT imaging can be used as such. Relevant studies were searched in the MEDLINE and EMBASE databases. Studies were selected when they met the following criteria: (1) all patients were adults with a clinical diagnosis of PD or clinically uncertain parkinsonism and (2) the study reported original data. In addition, studies needed to fulfill one of the two following criteria: (1) patients underwent at least one DAT SPECT and had a neuropathological confirmed diagnosis and (2) patients underwent at least two DAT SPECT scans, performed at least 2 years apart. The search identified 1,649 articles. Eight studies fulfilled our selection criteria and were included in this review. There was only one study including patients with diagnostic uncertainty. Sensitivity and specificity of DAT SPECT imaging to detect nigrostriatal cell loss were 98%. The other studies included patients with a diagnosis of PD in whom there was no uncertainty. In these studies, sensitivity was 100%. Our systematic review indicates that DAT SPECT imaging seems to be accurate to detect nigrostriatal cell loss in patients with parkinsonism.

Increased DAT binding in the early stage of the dopaminergic lesion: a longitudinal [11C]PE2I binding study in the MPTP-monkey

The delayed appearance of motor symptoms in PD poses a crucial challenge for early detection of the disease. We measured the binding potential of the selective dopamine active transporter (DAT) radiotracer [(11)C]PE2I in MPTP-treated macaque monkeys, thus establishing a detailed profile of the nigrostriatal DA status following MPTP intoxication and its relation to induced motor and non-motor symptoms. Clinical score and cognitive performance were followed throughout the study. We measured longitudinally in vivo the non-displaceable binding potential to DAT in premotor, motor-recovered (i.e. both non-symptomatic) and symptomatic MPTP-treated monkeys. Results show an unexpected and pronounced dissociation between clinical scores and [(11)C]PE2I-BP(ND) during the premotor phase i.e. DAT binding in the striatum of premotor animals was increased around 20%. Importantly, this broad increase of DAT binding in the caudate, ventral striatum and anterior putamen was accompanied by i) deteriorated cognitive performance, showing a likely causal role of the observed hyperdopaminergic state (Cools, 2011; Cools and D'Esposito, 2011) and ii) an asymmetric decrease of DAT binding at a focal point of the posterior putamen, suggesting that increased DAT is one of the earliest, intrinsic compensatory mechanisms. Following spontaneous recovery from motor deficits, DAT binding was greatly reduced as recently shown in-vivo with other radiotracers (Blesa et al., 2010, 2012). Finally, high clinical scores were correlated to considerably low levels of DAT only after the induction of a stable parkinsonian state. We additionally show that the only striatal region which was significantly correlated to the degree of motor impairments is the ventral striatum. Further research on this period should allow better understanding of DA compensation at premature stages of PD and potentially identify new diagnosis and therapeutic index.

The role of SPECT imaging of the dopaminergic system in translational research on Parkinson's disease

Imaging of the dopaminergic system with single photon emission computed tomography (SPECT), and particularly of the dopamine transporter (DAT) located in the striatum, is a well accepted tool in clinical practice to confirm or exclude loss of nigrostriatal dopamine (DA) neurons in patients suspected to suffer from Parkinson's disease (PD). SPECT techniques were developed successfully to image neurotransmitter systems, including the presynaptic DAT and postsynaptic dopamine D2/3 receptors, in rat and mouse models of PD. Here we review the results of preclinical SPECT studies of the dopaminergic system in rat and mouse models of PD. Initially, SPECT studies in animal models of PD were performed to validate that micro-SPECT is able to accurately assess parts of the dopaminergic system in small animals in-vivo. However, more recently, micro-SPECT DAT is increasingly used as a research tool to support the interpretation of human DAT SPECT studies in PD, including clinical trials examining the effects of potential neuroprotective drugs. Translational research with SPECT is an interesting development which may further increase our understanding of the pathophysiology and treatment of PD.

The role of preclinical SPECT in oncological and neurological research in combination with either CT or MRI

Preclinical imaging with SPECT combined with CT or MRI is used more and more frequently and has proven to be very useful in translational research. In this article, an overview of current preclinical research applications and trends of SPECT combined with CT or MRI, mainly in tumour imaging and neuroscience imaging, is given and the advantages and disadvantages of the different approaches are described. Today SPECT and CT systems are often integrated into a single device (commonly called a SPECT/CT system), whereas at present combined SPECT and MRI is almost always carried out with separate systems and fiducial markers to combine the separately acquired images. While preclinical SPECT/CT is most widely applied in oncology research, SPECT combined with MRI (SPECT/MRI when integrated in one system) offers the potential for both neuroscience applications and oncological applications. Today CT and MRI are still mainly used to localize radiotracer binding and to improve SPECT quantification, although both CT and MRI have additional potential. Future technology developments may include fast sequential or simultaneous acquisition of (dynamic) multimodality data, spectroscopy, fMRI along with high-resolution anatomic MRI, advanced CT procedures, and combinations of more than two modalities such as combinations of SPECT, PET, MRI and CT all together. This will all strongly depend on new technologies. With further advances in biology and chemistry for imaging molecular targets and (patho)physiological processes in vivo, the introduction of new imaging procedures and promising new radiopharmaceuticals in clinical practice may be accelerated.

Striatal dopamine transporter binding does not correlate with clinical severity in dementia with Lewy bodies

Patients who have dementia with Lewy bodies (DLB) show both clinical and histopathologic overlap with Alzheimer disease patients and Parkinson disease patients. In this study, we correlated the core features of DLB (dementia, parkinsonism, hallucinations, and fluctuations) with striatal dopamine transporter (DAT) availability as assessed with SPECT and (123)I-N-(3-iodoprop-2E-enyl)-2-β-carbomethoxy-3β-(4-methylphenyl) nortropane ((123)I-PE2I) in patients with newly diagnosed DLB.

METHODS

Two hundred eighty-eight patients were consecutively included in the study as they were referred for diagnostic SPECT scanning of DAT with (123)I-PE2I. Of those patients, 51 had, on the basis of clinical guideline criteria, a probable-DLB diagnosis at follow-up 16 ± 11.6 mo later. Before or on the day of the SPECT scan, DLB patients had a routine neurologic examination including Hoehn and Yahr grading and were cognitively evaluated with the Mini Mental State Examination.

RESULTS

There was no correlation between Mini Mental State Examination, Hoehn and Yahr score, fluctuations or hallucinations, and striatal DAT availability as measured with (123)I-PE2I and SPECT.

CONCLUSION

In patients with newly diagnosed DLB, symptoms are not associated with a reduction in striatal DAT despite its firm involvement in DLB pathology.

SPECT molecular imaging in Parkinson's disease

Parkinson's disease (PD) is a common disorder, and the diagnosis of Parkinson's disease is clinical and relies on the presence of characteristic motor symptoms. The accuracy of the clinical diagnosis of PD is still limited. Functional neuroimaging using SPECT technique is helpful in patients with first signs of parkinsonism. The changes detected may reflect the disease process itself and/or compensatory responses to the disease, or they may arise in association with disease- and/or treatment-related complications. This paper addresses the value of SPECT in early differential diagnosis of PD and its potential as a sensitive tool to assess the pathophysiology and progression, as well as the therapeutic efficacy of PD.