Reduced Gastric Contraction in Rapid‐Eye‐Movement Sleep Behavior Disorder and De Novo Parkinson's Disease.

Background: Reduced gastric motility in Parkinson's disease (PD) has been reported, but hardly any study exists in subjects with isolated rapid‐eye‐movement (REM) sleep behavior disorder (iRBD), a specific prodrome of α‐synucleinopathies. Objectives: We compared the gastric motility of 17 iRBD subjects with that of 18 PD subjects (15 drug naive, 3 early treated in defined off) and 15 healthy controls (HC) with real‐time magnetic resonance imaging (rtMRI). Methods: After overnight fasting, participants consumed a standardized breakfast and underwent a 3‐T rtMRI of the stomach. Amplitude and velocity of the peristaltic waves were analyzed under blinded conditions. Gastric motility index (GMI) was calculated. The procedure was repeated in 12 of 17 iRBD subjects ~2.5 years later. Nine of these 12 iRBD subjects were hyposmic. Results: In iRBD and PD subjects the amplitude of the peristaltic waves was significantly reduced compared with HCs (iRBD vs. HC: 8.7 ± 3.7 vs. 11.9 ± 4.1 mm, P = 0.0097; PD vs. HC: 6.8 ± 2.2 vs. 11.9 ± 4.1 mm, P = 0.0001). The amplitude in iRBD and PD subjects was decreased to the same extent. The GMI was reduced in only PD subjects (PD vs. HC: P = 0.0027; PD vs. iRBD: P = 0.0203). After ~2.5 years the amplitude in iRBD subjects did not significantly decrease further. Conclusion: The amplitude of the peristaltic waves was markedly reduced in iRBD, a prodrome of α‐synucleinopathies. This reduction was similar to the extent observed already in manifest early PD. This finding implies that the α‐synuclein pathology affects the innervation of the stomach already in the prodromal stage. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. [ABSTRACT FROM AUTHOR]