Video polysomnographic analysis of elevated EMG activity and rapid eye movements before abnormal behaviors in REM sleep behavior disorder.

The pathogenesis of rapid eye movement (REM) sleep behavior disorder (RBD) is unclear. According to the cortical hypothesis, severe RBD episode (RBDE) occurs when spinal motoneurons are less inhibited and cortical and limbic systems are more active. We made this study to prove the hypothesis for the development of RBDE using video-polysomnography (VPSG). VPSG records of 35 patients with RBD were analyzed. According to severity, RBDEs were classified into three motor events (MEs): ME 1; small movements or jerks, ME 2; proximal movements including violent behavior, and ME 3; axial movements including bed falls. For each ME, we measured the number of MEs preceded or not preceded by both REM sleep without atonia (RWA) and REMs during the 10-s-period immediately before ME onset. In severe RBDE (ME 3), the number of MEs preceded by both RWA and REMs was significantly higher than that of MEs not preceded by both (0.8 vs. 0.2, P = 0.033). This was not the case for mild RBDE (ME 1) and moderate RBDE (ME 2). Our results suggest that both RWA and REMs are associated with the development of severe RBDE.

[Effects of ramelteon on a patient with circadian rhythm sleep disorder and mood disorder].

Ramelteon is a novel hypnotic characterized by its action as a melatonin receptor (MT1/MT2) agonist. It has been reported that ramelteon can alter the phase of the sleep period. We report a patient with circadian rhythm sleep disorder and mood disorder who improved with ramelteon. A 25-year-old man had a 5-year history of emotional instability, excessive daytime sleepiness, and difficulty awakening. He had been diagnosed with mood disorder and narcolepsy by a psychiatrist. Sertraline, milnacipran, valproate, and methylphenidate were ineffective, and so he presented to our hospital. Interview data and a sleep log demonstrated a delayed sleep phase. As other examinations such as actigraphy and video-polysomnography indicated no other diseases, the patient was diagnosed with circadian rhythm sleep disorder, delayed sleep phase type (ICSD-2). In addition, his mental symptoms were consistent with the criteria for cyclothymia (ICD-10). After the administration of ramelteon, the phase of his sleep period gradually advanced and his emotional instability improved. Because of the high rate of comorbidity between these two diseases, we should be aware of circadian rhythm sleep disorders that are masked by mood disorders.