Cardiac 123I-MIBG uptake is reduced more markedly in patients with REM sleep behavior disorder than in those with early stage Parkinson's disease.

We investigated cardiac uptake of (123)I-metaiodobenzylguanidine (MIBG) in patients with REM sleep behavior disorder (RBD) and compared the findings with those of idiopathic Parkinson's disease (IPD). Thirteen RBD, 222 IPD and 50 controls underwent cardiac (123)I-MIBG scintigraphy. Resulting heart-to-mediastinum (H/M) ratios were significantly lower in patients with RBD and IPD as compared to the control ratios. H/M ratios were lower for delayed than for early images in patients with RBD and IPD; whereas, the controls had higher ratios for delayed images. H/M ratios were significantly lower for patients with RBD than for those with IPD at Hoehn and Yahr stages 1 and 2. Disease duration did not differ between the two groups. Our study revealed that cardiac (123)I-MIBG uptake was more markedly reduced in patients with RBD than in those with early stage IPD. RBD may not necessarily be a prodromal condition of IPD with respect to cardiac (123)I-MIBG uptake results.