Follow-up study of cardiac 123I-MIBG scintigraphy in idiopathic REM sleep behavior disorder

Background: Cardiac I-123-metaiodobenzylguanidine (123 I-MIBG) uptake in patients with idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) is markedly reduced, as in Parkinson's disease (PD). Methods: We performed I-123-MIBG scintigrams on patients with iRBD and PD. After the initial I-123-MIBG scintigram, we retested subjects after a mean of 2.8 years. Results: The delayed heart-to-mediastinum (H/M) ratio of cardiac I-123-MIBG uptake was not significantly reduced between the first and second study in either group (P = 0.050, P = 0.091, respectively). Follow-up imaging revealed a mean decline of 4.21 +/- 9.06% or 6.40 +/- 19.02% in the delayed H/M ratio in those with iRBD or PD, respectively. Conclusions: The I-123-MIBG uptake findings might indicate progression early in the course of iRBD or PD, but the progression is heterogeneous and independent of development of motor symptoms.