Validity of single-channel masseteric electromyography by using an ultraminiature wearable electromyographic device for diagnosis of sleep bruxism

Abstract Purpose The purpose of this study was to clarify the validity of assessment of sleep bruxism (SB) by using single-channel electromyogram (EMG) and a cut-off value with optimum sensitivity and specificity. Methods The subjects were twenty volunteers with clinical diagnosis of SB. Assessment by masseteric EMG data only by using a wearable EMG was compared with reference standard assessment by masseteric EMG data using polysomnography with audio-visual recording (PSG-AV). From EMG activities recorded by single-channel EMG, bursts of more than two times the baseline amplitude with a duration of 0.25 s or more were selected by a burst unit (EMG-burst-all). Furthermore, from EMG-burst-all, bursts that were more than 5–20% of the maximum voluntary contraction value (EMG-burst-5%, EMG-burst-10%, EMG-burst-20%) were selected. By an episode unit, phasic, tonic, and mixed episodes were selected by single-channel EMG (EMG-episodes). Among the EMG-episodes, further, reference standard episodes of SB (PSG-episodes) were selected by PSG-AV assessment. Results Sixteen subjects were diagnosed as bruxers based on PSG-AV (PSG-episodes/h >2). By a burst unit and an episode unit, there were significant correlations between assessment variables of SB by single-channel EMG and PSG-AV except for EMG-burst-20%/h. When the cut-off value in EMG-episodes/h was 5.5/h for sleep bruxers, both sensitivity and specificity were 100%. As for variables by a burst unit, EMG-burst-all/h and EMG-burst-5% had higher values of sensitivity and specificity. Conclusions The results suggested that single-channel EMG is valid for diagnosis of SB if a cut-off value that is appropriate for single-channel EMG is used.