Extrastriatal SPECT-DAT uptake correlates with clinical and biological features of de novo Parkinson's disease

Dopaminergic damage pattern predicts phenoconversion time in isolated rapid eye movement sleep behavior disorder

PURPOSE

The exact phenoconversion time from isolated rapid eye movement (REM) sleep behavior disorder (iRBD) to synucleinopathies remains unpredictable. This study investigated whole-brain dopaminergic damage pattern (DDP) with disease progression and predicted phenoconversion time in individual patients.

METHODS

Age-matched 33 iRBD patients and 20 healthy controls with 11C-CFT-PET scans were enrolled. The patients were followed up 2-10 (6.7 ± 2.0) years. The phenoconversion year was defined as the base year, and every 2 years before conversion was defined as a stage. Support vector machine with leave-one-out cross-validation strategy was used to perform prediction.

RESULTS

Dopaminergic degeneration of iRBD was found to occur about 6 years before conversion and then abnormal brain regions gradually expanded. Using DDP, area under curve (AUC) was 0.879 (90% sensitivity and 88.3% specificity) for predicting conversion in 0-2 years, 0.807 (72.7% sensitivity and 83.3% specificity) in 2-4 years, 0.940 (100% sensitivity and 84.6% specificity) in 4-6 years, and 0.879 (100% sensitivity and 80.7% specificity) over 6 years. In individual patients, predicted stages correlated with whole-brain dopaminergic levels (r =  - 0.740, p < 0.001).

CONCLUSION

Our findings suggest that DDP could accurately predict phenoconversion time of individual iRBD patients, which may help to screen patients for early intervention.

Brain metabolic changes in patients with disseminated malignant melanoma under immunotherapy

Although there is evidence that chemotherapy can have side effects on metabolism and brain function, there are few studies on the occurrence of these side effects with immunotherapy. The present study was conducted to assess whether brain metabolic changes occur in patients with malignant melanoma under immunotherapy. Thirty-nine patients after surgical intervention and with a diagnosis of malignant melanoma were retrospectively included and were divided into two groups: one group under the first-line therapy with anti-programmed cell death-1 ± anti-cytotoxic T lymphocyte antigen-4 monoclonal antibodies and the other group without any treatment after surgery, which served as a control. Basal and follow-up whole body and brain 2-[ 18 F]fluoro-2-deoxy-D-glucose ( 18 F]FDG) PET/computed tomography (CT) studies were performed. Changes in brain glucose metabolism after treatment initiation of the immunotherapy group were compared with the findings in the control group. In addition, longitudinal regression analysis to investigate whether the time under immunotherapy influenced the changes of brain metabolism was performed. None of the patients presented cognitive impairment or other neurological alterations between basal and follow-up brain [ 18 F]FDG PET/CT examinations. The statistical analysis revealed a significant relative SUV (SUVr)-loss in the left frontal region in patients of the immunotherapy group compared with the control group, with radjusted = -0.62 and P = 0.008. Severity of SUVr-loss was correlated with duration of treatment. Patients with disseminated malignant melanoma receiving immunotherapy may present a decrease of brain metabolism in the left frontal region, which is related with time-under-treatment, without any clinical evidence of neurological disorder.

Molecular Imaging in Parkinsonian Disorders—What’s New and Hot?

Highlights

Abstract

Neurodegenerative parkinsonian disorders are characterized by a great diversity of clinical symptoms and underlying neuropathology, yet differential diagnosis during lifetime remains probabilistic. Molecular imaging is a powerful method to detect pathological changes in vivo on a cellular and molecular level with high specificity. Thereby, molecular imaging enables to investigate functional changes and pathological hallmarks in neurodegenerative disorders, thus allowing to better differentiate between different forms of degenerative parkinsonism, improve the accuracy of the clinical diagnosis and disentangle the pathophysiology of disease-related symptoms. The past decade led to significant progress in the field of molecular imaging, including the development of multiple new and promising radioactive tracers for single photon emission computed tomography (SPECT) and positron emission tomography (PET) as well as novel analytical methods. Here, we review the most recent advances in molecular imaging for the diagnosis, prognosis, and mechanistic understanding of parkinsonian disorders. First, advances in imaging of neurotransmission abnormalities, metabolism, synaptic density, inflammation, and pathological protein aggregation are reviewed, highlighting our renewed understanding regarding the multiplicity of neurodegenerative processes involved in parkinsonian disorders. Consequently, we review the role of molecular imaging in the context of disease-modifying interventions to follow neurodegeneration, ensure stratification, and target engagement in clinical trials.

Apathy Reflects Extra-Striatal Dopaminergic Degeneration in de novo Parkinson's Disease

BACKGROUND

Apathy represents a core neuropsychiatric symptom in Parkinson's disease (PD). As there is currently no established effective treatment for apathy in PD, further investigating the biological origin of this symptom is needed to design novel therapeutic strategies. Among the multiple neurotransmitter alterations that have been associated with apathy, the involvement of extra-striatal dopaminergic degeneration remains to be fully explored.

OBJECTIVE

To investigate whether apathy in PD reflects increased dopaminergic degeneration extending beyond striatal regions.

METHODS

In the de novo PD cohort of the Parkinson's Progression Markers Initiative (PPMI), we performed whole-brain I123-Ioflupane Single Photon Emission Computed Tomography (DAT-SPECT) analyses to characterize cross-sectional and longitudinal differences in DAT uptake associated with the presence of apathy. We also assessed the relationship between apathy and cognition in this sample, as apathy has been suggested to herald cognitive decline.

RESULTS

Apathetic PD patients (N = 70) had similar sociodemographic, clinical, and biomarker profiles compared to the non-apathetic group (N = 333) at baseline. However, apathy was associated with an increased risk of developing cognitive impairment after a four-year follow-up period (p = 0.006). Compared to non-apathetic patients, apathetic patients showed a widespread reduction of extra-striatal DAT uptake at baseline as well as an increased longitudinal loss of DAT uptake (corrected p < 0.05).

CONCLUSIONS

Isolated apathy in PD is associated with extra-striatal dopaminergic degeneration. As this abnormal dopamine depletion was in turn related to cognitive performance, this might explain, at least partially, the increased risk of apathetic PD patients to develop cognitive impairment or dementia.

A common polymorphism in the dopamine transporter gene predicts working memory performance and in vivo dopamine integrity in aging

Dopamine (DA) integrity is suggested as a potential cause of individual differences in working memory (WM) performance among older adults. Still, the principal dopaminergic mechanisms giving rise to WM differences remain unspecified. Here, 61 single-nucleotide polymorphisms, located in or adjacent to various dopamine-related genes, were assessed for their links to WM performance in a sample of 1313 adults aged 61-80 years from the Berlin Aging Study II. Least Absolute Shrinkage and Selection Operator (LASSO) regression was conducted to estimate associations between polymorphisms and WM. Rs40184 in the DA transporter gene, SLC6A3, showed allelic group differences in WM, with T-carriers performing better than C homozygotes (p<0.01). This finding was replicated in an independent sample from the Cognition, Brain, and Aging study (COBRA; baseline: n = 181, ages: 64-68 years; 5-year follow up: n = 129). In COBRA, in vivo DA integrity was measured with ¹¹C-raclopride and positron emission tomography. Notably, WM as well as in vivo DA integrity was higher for rs40184 T-carriers at baseline (p<0.05 for WM and caudate and hippocampal D2-receptor availability) and at the 5-year follow-up (p<0.05 for WM and hippocampal D2 availability). Our findings indicate that individual differences in DA transporter function contribute to differences in WM performance in old age, presumably by regulating DA availability.

Dopamine Transporter Imaging, Current Status of a Potential Biomarker: A Comprehensive Review

A major goal of current clinical research in Parkinson's disease (PD) is the validation and standardization of biomarkers enabling early diagnosis, predicting outcomes, understanding PD pathophysiology, and demonstrating target engagement in clinical trials. Molecular imaging with specific dopamine-related tracers offers a practical indirect imaging biomarker of PD, serving as a powerful tool to assess the status of presynaptic nigrostriatal terminals. In this review we provide an update on the dopamine transporter (DAT) imaging in PD and translate recent findings to potentially valuable clinical practice applications. The role of DAT imaging as diagnostic, preclinical and predictive biomarker is discussed, especially in view of recent evidence questioning the incontrovertible correlation between striatal DAT binding and nigral cell or axon counts.

Clinical and Dopamine Transporter Imaging Trajectories in a Cohort of Parkinson's Disease Patients with GBA Mutations

BACKGROUND

Glucosylceramidase (GBA) mutations are considered the most common genetic risk factors for developing Parkinson's disease (PD).

OBJECTIVES

We aimed to assess, at different time points, the integrity of brain striatal and extra-striatal dopamine pathways and clinical phenotype of a group of PD subjects bearing heterozygous GBA mutations (GBA-PD), compared with a group of idiopathic PD patients (iPD) stratified by age at disease onset. A longitudinal approach was adopted to evaluate the progression over time for clinical and ¹²³ I-FP-CIT SPECT imaging features.

METHODS

We considered 46 GBA-PD patients and 339 iPD patients, subdivided into two groups according to age at PD onset (n = 58 < 50 years and n = 281 > 50 years). We measured differences in the occurrence/severity/progression of motor and non-motor features, ¹²³ I-FP-CIT standard uptake value ratios (SUVr) in striatal and extra-striatal regions, and global cognitive deterioration over time in a subset of 168 cases with available follow-up.

RESULTS

At baseline, the GBA-PD cohort showed more severe motor and cognitive deficits than the early-iPD cohort. The ¹²³ I-FP-CIT SUVr reduction in the striatal and the extra-striatal regions was more marked in the GBA-PD than the early- and late-iPD cohorts. Both GBA-PD and late-iPD patients had a significant annual deterioration in their global cognitive performance, while the early-iPD group showed global cognitive stability over time. At follow-up, the iPD cohorts became similar to the GBA-PD group in ¹²³ I-FP-CIT SUVr reduction.

CONCLUSION

These new findings support the hypothesis of a biological role of GBA mutations in accelerating the early neurodegenerative processes in PD, leading to the malignant clinical phenotype. © 2021 International Parkinson and Movement Disorder Society.