Actual state of the diurnal masseteric electromyogram: Differences between awareness and non-awareness of awake bruxism.

PURPOSE: This study aimed to elucidate the relationship between diurnal masseter muscle activity and awareness of diurnal awake bruxism (d-AB) by conducting a comparative analysis of electromyographic (EMG) data from individuals with and without awareness of diurnal awake bruxism (d-AB), utilizing EMG data gathered from multiple subjects. METHODS: Unilateral masseter electromyography (EMG) recordings were performed during the daytime using an ultraminiature wearable EMG device. A total of 119 participants (59 with awareness of diurnal tooth clenching [d-TC] and 60 without awareness of d-TC) were included. Waveforms longer than 0.25 s with the two amplitude conditions, exceeding twice the baseline and >5% of maximum voluntary clenching, were extracted. In addition, the number of bursts and episodes (groups of bursts), burst duration, and burst peak amplitude were calculated for each participant. RESULTS: There were no significant differences in the EMG parameters between the groups with and without awareness of d-TC. Additionally, the frequency distribution of the number of EMG waveforms exhibited wide ranges and substantial overlap between the two groups. CONCLUSIONS: The variability in the number of bursts and episodes, burst peak amplitude, and burst duration among subjects suggests the need for an objective classification of d-AB severity based on EMG values. The absence of significant differences and large overlap in frequency distributions between the groups with and without awareness of d-TC indicate difficulty in predicting muscle activity solely based on awareness of d-AB.

Comparison of the occurrence of sleep bruxism under accustomed conditions at home and under polysomnography conditions in a sleep laboratory.

PURPOSE: We aimed to clarify the relationship between the number of sleep bruxism (SB) bursts at home and in a laboratory equipped with polysomnography with audio-video recording (PSG-AV). We applied an identical single-channel wearable electromyography (EMG) device for both types of SB burst scorings. METHODS: The subjects were 20 healthy student volunteers (12 men and 8 women; mean age, 21.9 years) who were clinically diagnosed with bruxism based on the criteria set forth by the International Classification of Sleep Disorders (ICSD-2). We used a wearable EMG device attached to the masseteric area (the FLA-500-SD [FLA]), for scoring SB bursts at home and in the laboratory. PSG-AV was set within the laboratory environment as well. The mean interval for both sleep studies was 28.8 days. EMG bursts with amplitudes greater than twice the baseline amplitude and with durations of longer than 0.25 s were selected. EMG bursts with amplitudes ≥5% MVC (maximum voluntary contraction), ≥10% MVC, and ≥20% MVC were selected as well. A cluster of bursts was defined as an episode. RESULTS: In all the conditions for selecting EMG bursts specified above, the number of SB bursts and episodes recorded under laboratory conditions was statistically significantly smaller than that recorded at home. There were no statistically significant differences between the data obtained on the first and second recording days. CONCLUSION: The results of this study suggest that the unfamiliar environment of a sleep laboratory equipped with PSG-AV affects the emergence of SB as compared with home conditions.

Quantitative analyses of jaw-opening muscle activity during the active phase of jaw-closing muscles in sleep bruxism.

Rhythmic masticatory muscle activity (RMMA), which is defined as three or more consecutive phasic bursts, accounts for a large part of sleep bruxism (SB). RMMA is thought to be characterized by co-contraction, a jaw muscle activity in which jaw-opening muscles contract during the active phase of jaw-closing muscles, which is different from that during mastication. However, there has been limited information about co-contraction. The aim of the present study was to clarify the amplitudes and patterns of jaw-opening muscle activity during the active phase of jaw-closing muscles in RMMA. Data from 14 healthy volunteers with bruxism, which was diagnosed by using polysomnographic recording with audio-video, were analysed. RMMA with electromyographic amplitudes of more than two times the baseline amplitude was selected. From the selected RMMA, burst groups consisting of five or more consecutive phasic bursts, including tonic bursts, were selected for analyses. Electromyographic activities during gum chewing were also recorded before sleeping. The minimum, maximum and average value of the amplitudes of jaw-opening muscle activity during the active phase of jaw-closing muscles were calculated. Jaw-opening muscle activity during the active phase of jaw-closing muscles in RMMA was closer to the baseline than that in gum chewing. The minimum, maximum and average values of amplitudes of jaw-opening muscle activity during the phase were significantly smaller than those of gum chewing. Contrary to our hypothesis prior to the study, the obtained results suggested that the pattern of electromyogram activity of jaw-opening and jaw-closing muscles in RMMA was not necessarily co-contraction.

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.

Risk of coronary artery lesions in young infants with Kawasaki disease: need for a new diagnostic method.

AIM: To examine clinical characteristics of Kawasaki disease (KD) in infants younger than 3 months of age and to develop a method for detecting KD in febrile infants. METHOD: In a case-control study, we retrospectively collected clinical and laboratory data from 24 KD infants younger than 3 months of age out of 410 KD patients. We then compared younger infants with both older patients and febrile infants with respiratory syncytial virus (RSV) infection and urinary tract infections (UTI). RESULTS: The frequency of incomplete KD was higher in the younger group than in the control group (79% vs. 36%, P < 0.0001). Furthermore, before treatment, the incidence of coronary artery lesions (CAL) was significantly higher in the younger group (29% vs. 3.9%, P = 0.0001), resulting in a higher incidence of coronary artery sequelae (21% vs. 3.4%, P = 0.0023). Our results revealed that the serum N-terminal prohormone of brain natriuretic peptide (NT-proBNP) level of KD patients was higher than that of RSV and UTI patients (3110 ± 2076 vs. 698 ± 436, P = 0.0001; and 971 ± 589 pg/mL, P = 0.0002, respectively). Thus, NT-proBNP might be suitable as a diagnostic marker of KD in young infants (P = 0.0005, criterion values: 1555 pg/mL [sensitivity: 80%, specificity: 85%]). CONCLUSION: Kawasaki disease infants younger than 3 months of age appear to be at higher risk for incomplete KD and early-onset CAL prior to the appearance of coronary artery sequelae. We suggest performing an echocardiogram and evaluating NT-proBNP in young infants with fever that has lasted longer than 2 days, regardless of the presence or absence of manifestations associated with KD.

Electromyographic activity of the jaw-closing muscles during jaw opening in patients with masseter muscle contracture.

Contracture of the jaw-closing muscles is one of the causes of limitation of jaw opening. This study examined whether there is any difference between the EMG activities of jaw-closing muscles during jaw opening in healthy people and in patients with masseter muscle contracture (MMC), who do not have a history of trauma or infection. The patient group consisted of eleven females, 18 to 62 years old with no history of trauma or infections, with limited mouth opening due to MMC. The control group included eleven healthy females, 23 to 50 years old. The EMG activity was recorded bilaterally in the central portion of masseter muscles (Mm), the anterior portion of temporal muscles (Tm), and the anterior belly of digastric muscles (Dm). Nine out of the patient group showed obvious EMG activity in Mm during jaw opening which was different from typical EMG patterns during jaw opening of up to 40 mm in the control group. Among the nine patients, eight showed antagonistic contraction in Tm as well as Mm. The mean integral value of Mm and Tm during jaw opening in the patient group was significantly higher than in the control group (P<0.01). These results suggest that EMG activity during jaw opening in MMC patients with no history of trauma or infections is different from that in healthy people.