Objective: In this study we investigate striatal binding patterns in patients with Idiopathic Parkinson’s disease (IPD), compared to those with Parkinson Plus syndromes (PPS) versus controls. The objective was to confirm the diagnostic utility of F-DOPA PET as a first step towards establishing national reference ranges for discriminating indices.

Background: F-DOPA PET is an alternative method to Dopamine transporter (DaT) imaging to assess presynaptic dopaminergic neuronal integrity. F-DOPA uptake has been shown to be normal in Essential Tremor (ET) and dopa responsive dystonia (DRD). In IPD, there is asymmetric reduction of F-DOPA uptake in the striatum, maximal and contralateral to the most severely and earliest affected hemibody. In PPS there is pre and post synaptic dopaminergic dysfunction and impaired F-DOPA uptake often with a more symmetric pattern.

Method: F-DOPA PET scans of 36 patients were analysed. 18 had IPD (10 H&Y1 and 8 H&Y2+). The control group included 8 subjects with ET and 2 with DRD. The PPS group included 5 patients with possible or probable Multisystem Atrophy, 3 with probable Progressive Supranuclear Palsy and 1 with probable Dementia with Lewy bodies. For each F-DOPA PET-CT the ratio of striatal structures to the occipital normalisation region generated; striatal-occipital (SOR), caudate-occipital (COR), putamen-occipital (POR), anterior putamen-occipital (APOR) and posterior putamen-occipital (PPOR) ratios. Asymmetry indices (AI) were generated for each ratio using the formula [(side A – side B)/(side A + side B)] x 2.

Results: All the ratios discriminated the IPD and PPS groups from controls with 100% accuracy (AUC 1, p <0.001). COR discriminated PPS from IPD, correctly classifying 82% patients. AI outperformed ratio analysis in discriminating IPD from PPS. Striatal and whole putamen AI cut-points distinguished IPD from controls, and from PPS, correctly classifying ≥85% patients (AUC > 0.9, p≤ 0.01). PPOR AI correctly classified 95% H&Y1 and 88% H&Y2 IPD patients from PPS.  Putamen AI also discriminated H&Y1 from H&Y2 IPD.

Conclusion: Our findings add to evolving evidence for F-DOPA PET in discrimination between IPD, PPS and controls based on ratio and asymmetry analyses.  Dopaminergic patterns on F-DOPA PET-CT have potential to increase diagnostic confidence and positively impact on clinical care.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/6-18ffluoro-l-34-dihydroxyphenylalanine-f-dopa-pet-striatal-binding-patterns-in-patients-with-parkinsons-disease-and-parkinson-plus-syndromes/