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

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 0.25s 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.