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Objective The main objective of this study was to study rapid eye movement (REM) sleep behavior disorder (RBD) and other sleep disorders in dementia with Lewy bodies (DLB). Methods Consecutive patients with DLB and mild dementia severity were recruited irrespective of sleep complaints. Patients underwent clinical interview, assessment of sleep scales, and video-polysomnography (V-PSG). RBD was diagnosed with V-PSG based on electromyographic and audiovisual analysis. Results Thirty-five patients (65.7% men; mean age 77.7 ± 6.1 years) were evaluated. Poor sleep quality (54.3%), hypersomnia (37.1%), snoring (60%), and abnormal nocturnal behaviors (77.1%) were reported. Sleep–wake architecture abnormalities occurred in 75% patients and consisted of occipital slowing on awake electroencephalography (EEG; 34.4%), the absence of sleep spindles and K complexes (12.9%), slow frequency sleep spindles (12.9%), delta activity in REM sleep (19.2%), and REM sleep without atonia (44%). Three patients showed hallucinatory-like behaviors and 10 patients showed abnormal behaviors during arousals mimicking RBD. RBD was diagnosed in 50% of those patients in whom sufficient REM sleep was attained. Of these, 72.7% were not aware of displaying dream-enacting behaviors and in 63.7% RBD preceded the onset of cognitive impairment. For RBD diagnosis, the sensitivity of Mayo Sleep Questionnaire was 50%, specificity was 66.7%, positive predictive value was 83.3%, and negative predictive value was 28%. False-positive RBD cases according to clinical history had hallucinatory-like behaviors, severe obstructive sleep apnea, and prominent periodic limb movements in sleep. Occipital EEG frequency while awake and rate of electromyographic activity in REM sleep were negatively correlated, suggesting a common subcortical origin. Conclusion In DLB, RBD and sleep–wake disorders are common, heterogeneous, and complex, challenging their identification without performing V-PSG.

Study Objectives To compare two electromyographic (EMG) montages, isolated mentalis muscle versus mentalis in combination with upper limb muscles in the baseline diagnostic video-polysomnography (V-PSG) of patients with idiopathic REM sleep behaviors disorder (IRBD) who eventually were diagnosed with a clinically defined neurodegenerative syndrome. Methods Forty-nine patients were included. At baseline, diagnosis of RBD was based on a typical history of dream enactment behaviors plus V-PSG showing REM sleep with qualitative increased EMG activity and/or abnormal behaviors. Quantification of EMG activity (tonic, phasic and "any") in the mentalis and upper limb muscles (biceps brachii-BB, n = 36 or flexor digitorum superficialis-FDS, n = 13) was performed manually and compared with published cut-offs. Results Nine (18.4%) patients had either tonic or phasic EMG below the cut-offs for the isolated mentalis and four of them (11.1 %) also had values below the cut-off for the mentalis combined with BB. All 13 patients recorded with the FDS were above the mentalis combined with FDS cut-off. For the diagnosis of IRBD, sensitivity of isolated mentalis was 81.6% and of the combination of mentalis plus upper limb muscles was 91.8% (p = .03). Audiovisual analysis showed abnormal REM sleep behaviors in all nine patients with values below the cut-offs. Conclusion Quantification of EMG activity in the upper limbs combined with the mentalis increases the ability to diagnose IRBD when compared with the isolated measurement of the mentalis. Detection of typical abnormal behaviors during REM sleep with audiovisual analysis is essential for the diagnosis of IRBD in patients with EMG values below the published cut-offs.