Rapid Eye Movement Sleep Behavior Disorder: Abnormal Cardiac Image and Progressive Abnormal Metabolic Brain Pattern

Background: Isolated rapid eye movement sleep behavior disorder (iRBD) is prodromal for alpha-synucleinopathies. Objective: The aim of this study was to determine whether pathological cardiac [I-123]meta-iodobenzylguanidine scintigraphy ([I-123]MIBG) is associated with progression of [F-18]fluorodeoxyglucose-positron emission tomography-based Parkinson's disease (PD)-related brain pattern (PDRP) expression in iRBD. Methods: Seventeen subjects with iRBD underwent [F-18]fluorodeoxyglucose-positron emission tomography brain imaging twice similar to 3.6 years apart. In addition, [I-123]MIBG and [I-123]N-omega-fluoropropyl-2 beta-carbomethoxy-3 beta-(4-iodophenyl)nortropane single-photon emission computed tomography ([I-123]FP-CIT-SPECT) at baseline were performed. Olfactory, cognitive, and motor functions were tested annually. Results: Twelve of 17 subjects had pathological [I-123]MIBG. At baseline, 6 of 12 of these expressed the PDRP (suprathreshold PDRP z score). At follow-up, 12 of 17 subjects had suprathreshold PDRP z scores, associated with pathological [I-123]MIBG in 92% and with pathological [I-123]FP-CIT-SPECT in 75%. Subjects with pathological [I-123]MIBG had higher PDRP z score change per year (P = 0.027). Three subjects phenoconverted to PD; all had pathological [I-123]MIBG and [I-123]FP-CIT-SPECT, suprathreshold baseline PDRP z scores, and hyposmia. Conclusions: Pathological [I-123]MIBG was associated with progressive and suprathreshold PDRP z scores at follow-up. Abnormal [I-123]MIBG likely identifies iRBD as prodromal PD earlier than pathological [I-123]FP-CIT-SPECT. (C) 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society