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 ¹²³I-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 ¹²³I-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 ¹²³I-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 ¹²³I-MIBG uptake results.