0680 Alteration Of Two Imaging Biomarkers Along With The Progression Of Idiopathic RBD: MIBG Myocardial Scintigraphy And DAT-SPECT Study. (27th April 2018) - Ishii, T
Abstract: Introduction: Idiopathic rapid-eye-movement sleep behavior disorder (iRBD) is now recognized as the prodromal stage of synucleinopathies such as Parkinson's disease and dementia with Lewy bodies. Cardiac iodine-123 metaiodobenzylguanidine ( 123 I-MIBG) and 123I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane ( 123 I-FP-CIT) DAT-SPECT are useful imaging biomarkers for iRBD, which can detect progressive degeneration of cardiac sympathetic nerves and nigrostriatal dopaminergic dysfunction, respectively. However, individual variability in progression of the disorder and how findings of imaging biomarkers change over time are still not fully understood. We aimed to investigate relation between iRBD duration and alterations in two imaging biomarkers. Methods: We identified sixteen patients (12 men and 4 women: mean age 78.0 ± 4.2 years) diagnosed as iRBD and have undergone cardiac 123 I-MIBG scintigraphy and 123 I-FP-CIT DAT-SPECT at some point during the clinical follow-up. The heart-to-mediastinum uptake ratio (H/M ratio) of 123 I-MIBG was calculated by dividing the count density of the left ventricular ROI by that of the mediastinal ROI. Every DAT-SPECT image was normalized to a template obtained from the 30 controls. The specific striatal-to-occipital cortex uptake ratio of 123 I-FP-CIT was calculated. The association between iRBD duration and uptake of 123 I-MIBG or 123 I-FP-CIT was assessed by the regression analysis. Results: The early and late H/M ratios of 123 I-MIBG uptake were 1.43 + 0.22 and 1.16 + 0.28 (institutional normal value: 2.0 - 2.8 and 2.0 - 3.0), respectively. Both of the early and late H/M ratios showed no significant correlation with the duration of iRBD. The specific striatal-to-occipital cortex uptake ratio of 123 I-FP-CIT showed significant negative correlation with the iRBD duration (P < 0.05). Conclusion: Our results suggest that uptake of 123 I-FP-CIT decreases in proportion to the iRBD duration and may corroborate the Braak's hypothesis of PD progression. Meanwhile, the result and literature review show that uptake of 123 I-MIBG in iRBD patients tend to be already markedly low at the stage which the decrease of DAT-SPECT uptake is still not apparent. This suggests that clinically defined iRBD is a unique subtype of 'Lewy body disease', which has specific type of propagation in its pathology. Support (If Any):