Gastric emptying time and its correlation with cardiac MIBG in body-first and brain-first subtype Parkinson’s disease

Introduction Recently, “body-first” and “brain-first” subtype in Parkinson's disease (PD) was proposed based on the propagation of α-synuclein. In isolated RBD considered as a premotor stage of body-first PD, α-synuclein was supposed to originate in the enteric nervous system and spreads via autonomic nervous system. Therefore, we hypothesized that body-first PD is more likely to have a delayed gastric emptying time and reduced cardiac sympathetic denervation. In this study, we aimed to assess gastric motility and its correlation with cardiac sympathetic denervation, dopamine transporter uptake in PD with the body-first PD in comparison with brain-first PD. Methods We investigated gastric scintigraphy, dual-phase 18F-FP-CIT PET, and cardiac MIBG scintigraphy in patients with PD. Based on the presence of RBD and delayed H/M ratio in MIBG scintigraphy, we classified patients into the body-first PD and brain-first PD groups. Gastric emptying time (GET) was assessed by dynamic gastric scintigraphy, and half-emptying time ( T 1/2 ) was measured. Results A total of 18 PD patients (mean age 68.8) were classified into body-first PD group ( n = 10) and brain-first PD group ( n = 8). Delayed GET was more prevalent in body-first PD group compared to brain-first PD ( T 1/2 > 110 min, 90.0 vs 37.5%, p = 0.043). Striatal dopamine depletion was similar between groups and no significant correlation with T 1/2 . Washout rate of cardiac MIBG showed a tendency of correlation with T 1/2 ( r = 0.454, p = 0.077). Conclusion This study showed that body-first PD may be associated with a higher prevalence of delayed gastric emptying time compared to the brain-first PD, suggesting higher burden of gastrointestinal dysmotility in brain-first PD.