Differentiation of idiopathic and non-idiopathic parkinsonian syndromes with [18F]-desmethoxyfallypride

Objectives The utility of the selective dopamine D2/3-receptor ligand [18F]-desmethoxyfallypride (DMFP) for the differential diagnosis of patients with idiopathic parkinsonian syndrome (IPS) and non-idiopathic parkinsonian syndrome (non-IPS)was evaluated.

Methods 81 patients with parkinsonism (mean age 68 ± 11 years) were included in this study. A 30-minute [18F]DMFP PET recording was acquired starting one hour after i.v. injection of the tracer. The specific binding (SB) in divisions of the striatum was calculated relative to occipital cortex using and observer-independent semi-automatic VOI-based technique. The optimal SB threshold was defined by means of receiver operating characteristic (ROC) analysis which was also used for the evaluation of the diagnostic performance of SB, ratios between striatal sub-regions, and absolute asymmetries in SB.

Results Significant differences (P<0.001) were found in striatal SB between IPS and non-IPS, most notably in the posterior putamen, where the diagnostic power for discrimination of IPS and non-IPS was the highest (sensitivity 87%, specificity 96%, accuracy 91%). A further gain of diagnostic power (sensitivity 92%, specificity 96%, accuracy 94%) was obtained through discriminant analysis combining three parameters: SB of the posterior putamen, the posterior to anterior putamen ratio, and the posterior putamen to caudate ratio.

Conclusions [18F]DMFP PET is useful for the differential diagnosis of IPS and non-IPS in patients with parkinsonism. The findings are consistent with relative sparing of D2/3-receptors in the dopamine-denervated putamen of IPS patients, in contrast to a more substantial loss of striatal dopamine receptors in non-IPS patients