Functional neuroimaging and clinical features of de novo, drug naive PD patients with probable RBD

Introduction: The association between Parkinson Disease (PD) and REM sleep behavior disorder (RBD)
has been related to a specific, malignant clinical phenotype. Definite RBD diagnosis requires videopolysomnography
that is often unfeasible. A malignant clinical PD-RBD phenotype could be expected
also in PD patients with probable RBD. Aim of this cross-sectional study was to evaluate whether a more
severe neuropsychological and functional neuroimaging phenotype can be identified in PD patients with
probable RBD.
Methods: Thirty-eight de novo, drug naïve PD patients underwent a first-line clinical assessment and a
second-line multimodal assessment, including neuropsychological evaluation, 123I-FP-CIT-SPECT and 18FFDG-
PET, which were compared between PD patients with (PD þ RBDþ) and without (PD þ RBD-)
probable RBD.
Results: On first-line assessment, PD þ RBD þ patients had significantly more constipation (p ¼ 0.02) and
showed worse olfaction (p ¼ 0.01) compared with PD þ RBD-while the two groups were similar as for
age, presence of orthostatic hypotension, UPDRS-III and MMSE scores. On second-line assessment,
PD þ RBD þ patients showed a worse neuropsychological test profile, more severe nigro-striatal
dopaminergic impairment, mainly at caudate level in the less affected hemisphere (p ¼ 0.004) and
impaired brain glucose metabolism, with relative hypometabolism in posterior cortical regions and
relative hypermetabolism mainly in anterior regions of the more affected hemisphere (p ¼ 0.015).
Conclusions: PD patients with probable RBD are likely to have a more severe neuropsychological and
functional brain-imaging phenotype already at the time of diagnosis.