Polysomnogram showing sleep-related bruxism episode

Polysomnogram showing an episode of bruxism (red asterisk) characterized by tonic chin contractions lasting more than two seconds, in association with rhythmic artifact in the electroencephalography (EEG) recording. The episode was associated with typical audible teeth grinding sounds.
Standard polysomnogram montage includes (from top to bottom): left and right outer canthus (LOC/ROC) electrooculography electrodes; chin electromyography (EMG); F4 (right frontal), C4 (right central), and O2 (right occipital) references to M1 (left mastoid) EEG electrodes; standard electrocardiogram (EKG) lead; left and right lower leg EMG electrodes; snore microphone; airflow; pressure transducer airflow (PTAF); chest and abdominal wall motion sensors; and pulse oximetry by finger probe (SaO2).