Clinically uncertain parkinsonism shows nigral depigmentation in the presence and absence of dopaminergic deficit: a multimodal imaging study

Brain dopamine transporter (DAT) imaging with 123I-FP-CIT SPECT has been used for detecting striatal deficits in clinically uncertain parkinsonism (CUP). Neuromelanin(NM)-MRI assesses nigral depigmentation with high accuracy in confirmed PD; but its diagnostic value in CUP is unclear. Here, we compare nigral NM in CUP with (DAT+) or without (DAT-) striatal dopaminergic deficits, to established PD and healthy controls. CUP with DAT+ had more nigral NM deficits (vs. controls and DAT-CUP) but were less pronounced than in established PD. Interestingly, DAT- cases showed ventrolateral nigral deficits. Our results suggest that nigral depigmentation possibly starts before striatal dopaminergic decline.