Imagerie multimodale dans la maladie de Parkinson: PET FDOPA, IRM quantitative sensible au fer et à la neuromélanine

peer reviewedParkinson’s disease is a neurodegenerative synucleinopathy characterized by the degeneration of neuromelanin-containing dopaminergic neurons and deposition of iron in the substantia nigra (SN). How regional neuromelanin (NM) loss and iron accumulation within specific areas of SN relates to nigro-striatal dysfunction needs to be clarified. We measured dopaminergic function in pre- and post-commissural putamen by [18F]DOPA PET in twenty-three Parkinson’s disease (PD) patients and 23 healthy control (HC) participants in whom NM content and iron load was assessed in medial and lateral SN, respectively by neuromelanin-sensitive and quantitative R2* MRI. Data analysis consisted of voxelwise regressions testing the group effect and its interaction with NM or iron signals. In PD patients, R2* was selectively increased in left lateral SN as compared to healthy participants, suggesting a local accumulation of iron in Parkinson’s disease. By contrast, NM signal differed between PD and HC, without specific regional specificity within SN. Dopaminergic function in posterior putamen decreased as R2* increased in lateral SN, indicating that dopaminergic function impairment progresses with iron accumulation in the SN. Dopaminergic function was also positively correlated with NM signal in lateral SN, indicating that dopaminergic function impairment progresses with depigmentation in the SN. A complex relationship was detected between R2* in the lateral SN and NM signal in the medial substantia nigra. In conclusion, multimodal imaging reveals regionally-specific relationships between iron accumulation and depigmentation within the SN of Parkinson’s disease and provides in vivo insights in its neuropathology.Parkinson's disease multimodal imagin