Abstract
The pathophysiology of rapid eye movement sleep behavior disorder (RBD) associated with narcolepsy type 1 (NT1) is still poorly understood, potentially distinct from idiopathic RBD (iRBD), but may share affected common pathways. We investigated whether MIBG cardiac uptake differs between iRBD and NT1 comorbid with RBD. Thirty-four patients with NT1-RBD and 15 patients with iRBD underwent MIBG cardiac scintigraphy. MIBG uptake was measured by calculating the early and delayed heart to mediastinum (H/M) ratios. A delayed H/M ratio lower than 1.46 was considered abnormal based on a population of 78 subjects without neurological or cardiac diseases. Patients with iRBD were older, had an older RBD onset age and higher REM sleep phasic and tonic muscular activities than NT1-RBD. Lower delayed and early H/M ratios were associated with iRBD, but not with NT1-RBD, in crude and adjusted associations. The delayed H/M ratio differed between iRBD and controls, after adjustment, but not between patients with NT1-RBD and controls. In conclusion, the MIBG cardiac uptake difference between NT1-RBD and iRBD supports the hypothesis of different processes involved in RBD pathogenesis, providing for the first time a cardiac biomarker to differentiate those disorders.
Highlights
The presence of rapid eye movement sleep behavior disorder (RBD) is frequently associated with autonomic dysfunction in both idiopathic and secondary form associated with Parkinson’s disease (PD)
Clinical RBD episodes were documented by vPSG recording in all patients with idiopathic RBD (iRBD), but only in 57.1% of patients with Narcolepsy type 1 (NT1)-RBD
Among NT1 patients, eleven had obstructive sleep apnea syndrome (OSAS), but only four patients were treated by continuous positive airway pressure (C-PAP) at time of scintigraphy, as this investigation was performed the day after PSG in most of NT1 patients
Summary
The presence of RBD is frequently associated with autonomic dysfunction in both idiopathic and secondary form associated with Parkinson’s disease (PD). Narcolepsy type 1 (NT1) is a rare disease caused by the selective and irreversible loss of hypocretin neurons[7] It is characterized by excessive daytime sleepiness (EDS), cataplexy, clinical manifestations related to REM sleep dysregulation (RBD, sleep paralysis and hypnagogic hallucinations) and frequent autonomic dysfunction[7,8]. Few studies reported the development of PD in patients with NT113–16, but the role of RBD in this association is unknown, and no study has assessed the frequency of synucleinopathies among patients with NT1 It is not known whether RBD is a predictor for neurodegeneration in NT1. Despite clear differences in phenotype between patients with iRBD and NT1 comorbid with RBD, we aimed in this study to investigate whether the 123I-MIBG cardiac uptake profiles can differentiate patients with RBD whether idiopathic or symptomatic in the context of NT1
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