Comparison of severity of obstructive sleep apnea and degree of accumulation of cardiac 123I-MIBG radioactivity as a diagnostic marker for idiopathic REM sleep behavior disorder

ObjectiveWe investigated cardiac 123I-metaiodobenzylguanidine (MIBG) scintigraphic assessment as a supportive diagnostic indicator for idiopathic REM sleep behavior disorder (RBD) complicated by moderate to severe obstructive sleep apnea (OSA).Methods123I-MIBG was intravenously injected in 23 idiopathic RBD patients with AHI < 5/h, 9 idiopathic RBD patients with 5 ⩽ AHI < 15/h, 15 idiopathic RBD patients complicated with moderate to severe OSA with AHI ⩾ 15/h, and 16 moderate to severe obstructive sleep apnea syndrome (OSAS) patients without RBD by polysomnography.ResultsCardiac MIBG uptake based on H/M was significantly decreased in RBD patients with or without OSA compared with patients with moderate to severe OSAS without RBD. ROC analysis revealed that a delayed H/M cut-off value of 1.97 was useful for differentiating idiopathic RBD complicated by moderate to severe OSA from moderate to severe OSAS without RBD.Conclusions123I-MIBG cardiac scintigraphy has the potential to distinguish true RBD from pseudo-RBD associated with OSA. These results are noteworthy because treatment options and follow-up protocols are determined based on evaluation of moderate to severe OSA complicated with RBD, such as overlapping primary sleep disorders.