Rhythmic Masticatory Muscle Activity Episodes Research Articles

A case-control study on the effect of rhythmic masticatory muscle activity (RMMA) clusters on sleep fragmentation and severity of orofacial muscle pain in sleep bruxism.

Rhythmic masticatory muscle activity (RMMA) is a periodic muscle activity that characterises sleep bruxism (SB) events. These can occur as a single event, in pairs, or in clusters. Since RMMA episodes often occur in clusters and the relevance of this occurrence is unknown, we conducted a study to investigate the effect of RMMA clusters on sleep fragmentation and the severity of orofacial muscle pain. This study involved a secondary analysis using data from 184 adult subjects with orofacial muscle pain who underwent definitive polysomnography (PSG) for sleep bruxism diagnosis. Self-reported orofacial muscle pain (OFMP) was assessed using the numeric rating scale, and additional evaluation of side-to-side equivalence (symmetry) was described using a binary system. Among the 184 participants, 60.8% (n = 112) did not exhibit clusters and among the 72 participants with clusters, 36.1% (n = 26) and 63.9% (n = 46) were in the high and low RMMA frequency groups, respectively. The high SB group had significantly three times more phasic RMMA events than the noncluster group. A total of 89.67% (n = 165) of subjects reported orofacial muscle pain. While there was no difference in the severity of OFMP among groups, a significant decrease in symmetry between the severity of temporal muscle pain on the left and right sides was noted in the cluster group compared with the noncluster group. Clustering of RMMA events is associated with sleep fragmentation. The asymmetry of temporal muscle pain is related to the presence of RMMA clusters in sleep bruxism.

Sleep architecture as a candidate for phenotyping sleep bruxism: A narrative physiological review.

Sleep bruxism (SB), an oral behaviour in otherwise healthy individuals, is characterised by frequent rhythmic masticatory muscle activity (RMMA) during sleep. RMMA/SB episodes occur over various sleep stages (N1-N3 and rapid eye movement (REM)), sleep cycles (non-REM to REM), and frequently with microarousals. It currently remains unclear whether these characteristics of sleep architecture are phenotype candidates for the genesis of RMMA/SB. This narrative review investigated the relationship between sleep architecture and the occurrence of RMMA as a SB phenotype candidate. PubMed research was performed using keywords related to RMMA/SB and sleep architecture. In non-SB and SB healthy individuals, RMMA episodes were most frequent in the light non-REM sleep stages N1 and N2, particularly during the ascending phase of sleep cycles. The onset of RMMA/SB episodes in healthy individuals was preceded by a physiological arousal sequence of autonomic cardiovascular to cortical activation. It was not possible to extract a consistent sleep architecture pattern in the presence of sleep comorbidities. The lack of standardisation and variability between subject complexified the search for specific sleep architecture phenotype(s). In otherwise healthy individuals, the genesis of RMMA/SB episodes is largely affected by oscillations in the sleep stage and cycle as well as the occurrence of microarousal. Furthermore, a specific sleep architecture pattern cannot be confirmed in the presence of sleep comorbidity. Further studies are needed to delineate sleep architecture phenotype candidate(s) that contribute to the more accurate diagnosis of SB and treatment approaches using standardised and innovative methodologies.

Coherence of jaw and neck muscle activity during sleep bruxism.

BackgroundStudies have shown co‐contraction of jaw and neck muscles in healthy subjects during (sub) maximum voluntary jaw clenching, indicating functional inter‐relation between these muscles during awake bruxism. So far, coherence of jaw and neck muscles has not been evaluated during either awake or sleep bruxism.ObjectiveThe objective of this study was to evaluate the coherence between jaw and neck muscle activity during sleep bruxism.MethodsIn a cross‐sectional observational design, the electromyographic activity of jaw (masseter, temporalis) and neck (sternocleidomastoid, trapezius) muscles in individuals with “definite” sleep bruxism was measured using ambulatory polysomnography (PSG). Coherence for masseter‐temporalis, masseter‐sternocleidomastoid and masseter‐trapezius was measured during phasic and mixed rhythmic masticatory muscle activity episodes using coherence‐analysing software. Outcome measures were as follows: presence or absence of significant coherence per episode (in percentages), frequency of peak coherence (FPC) per episode and sleep stage.Results A total of 632 episodes within 16 PSGs of eight individuals were analysed. Significant coherence was found between the jaw and neck muscles in 84.9% of the episodes. FPCs of masseter‐temporalis were significantly positively correlated with those of masseter‐sternocleidomastoid or masseter‐trapezius (P < .001). Sleep stages did not significantly influence coherence of these muscular couples.ConclusionDuring sleep bruxism, jaw and neck muscle activation is significantly coherent. Coherence occurs independently of sleep stage. These results support the hypothesis of bruxism being a centrally regulated phenomenon.

A preliminary study on potential association between psychopathological status and rhythmic masticatory muscle activity of young patients with sleep bruxism in Tianjin China

ObjectivesThe aim of this cross-sectional study was to assess the psychological status of patients with bruxism and to explore the potential relationship between psychological status and rhythmic masticatory muscle activity (RMMA), since the basic manifestation of sleep bruxism is RMMA. MethodsTwenty-five patients (nine males, 16 females, and mean age 27.84 ± 5.60) who self-reported having SB and 25 normal subjects were randomly recruited. Fifty subjects filled out the Symptom Checklist-90 (SCL-90) to assess their psychopathological status. SB was diagnosed by polysomnography (PSG), and RMMA was recorded based on the results of PSG. ResultsIn this study we detected 15.89 ± 4.23 RMMA episodes per hour in normal subjects, whereas 41.23 ± 16.78 RMMA episodes per hour were recorded in patients with SB, which was nearly three times of the former group with statistical significance (P = 0.001). Paired t-test revealed significant differences between SB patients and normal subjects in any of the SCL-90 subscales (P = 0.001). Regarding total psychopathological scores, 10 of the 25 SB patients endorsed scores higher than 160, and the positive rate was 40%. In addition, obsessive-compulsive behavior, interpersonal sensitivity, depression, anxiety, paranoid ideation and psychoticism were all statistically associated with RMMA (P < 0.05). ConclusionWithin the limitations of the study, we found that patients with sleep bruxism tend to have poor psychological status, and obsessive-compulsive behavior, interpersonal sensitivity, depression, anxiety, paranoid ideation and psychoticism are related to onset of SB.

Effect of clonazepam and clonidine on primary sleep bruxism: a double-blind, crossover, placebo-controlled trial.

The aim of this study was to assess the acute effects of clonazepam and clonidine on rhythmic masticatory muscle activity in young adults with primary sleep bruxism, as well as accompanying effects on sleep architecture and cardiac activity. This study used a double-blind, crossover, placebo-controlled design. Polysomnography was performed on 19 subjects [nine men and 10 women; mean age (±SE): 25.4±2.7years] for 5nights. The first 2nights were used for the habituation and diagnosis of sleep bruxism. The other 3nights were randomly assigned for clonazepam (1.0mg), clonidine (0.15mg) or placebo (all administered 30min before bedtime). Sleep, oromotor activity and cardiac activity variables were assessed and compared among the three drug conditions. Clonidine significantly reduced the median percentage of time spent in the rapid eye movement sleep stage compared with placebo and clonazepam. The number of rhythmic masticatory muscle activity episodes was reduced with clonidine by >30% compared with placebo and clonazepam. The reduction of rhythmic masticatory muscle activity index by clonidine was associated with an increase of mean RR intervals (slower heart rate) during quiet sleep periods and during a 70-s period before the onset of rhythmic masticatory muscle activity episodes. However, no changes in cardiac activity variables were observed for clonazepam. In young adults with primary sleep bruxism, clonidine was significantly more effective in suppressing sleep bruxism than clonazepam. The acute effects of clonidine on rhythmic masticatory muscle activity episodes may be mediated by suppression of autonomic nervous system activity and non-rapid eye movement-rapid eye movement sleep processes.

Evaluation of a Proton Pump Inhibitor for Sleep Bruxism

Bruxism is a repetitive jaw-muscle activity characterized by clenching or grinding of the teeth and/or bracing or thrusting of the mandible. Recent advances have clarified the relationship between gastroesophageal reflux and sleep bruxism (SB). However, the influence of pharmacological elimination of gastric acid secretion on SB has not been confirmed. The authors aimed to assess the efficacy of a proton pump inhibitor (PPI) on SB and to examine the gastrointestinal (GI) symptoms and endoscopic findings of the upper GI tract in SB patients. The authors performed a randomized double-blind placebo-controlled crossover study at Kagoshima University Hospital. Twelve patients with polysomnography (PSG)–diagnosed SB underwent an assessment of GI symptoms using the frequency scale for the symptoms of gastroesophageal reflux disease (FSSG) and esophagogastroduodenoscopy. At baseline (i.e., before interventions), the mean frequencies of electromyography (EMG) bursts and rhythmic masticatory muscle activity (RMMA) episodes were 65.4 ± 49.0 bursts/h and 7.0 ± 4.8 episodes/h, respectively, and at least 1 RMMA episode with grinding noise was confirmed in all participants. The mean FSSG score was 8.4 ± 5.6, and 41.7% of patients were diagnosed with gastroesophageal reflux disease. Mild reflux esophagitis was confirmed in 6 patients. PSG, including EMG of the left masseter muscle and audio-video recording, was performed on days 4 and 5 of administration of 10 mg of the PPI (rabeprazole) or placebo. PPI administration yielded a significant reduction in the frequency of EMG bursts, RMMA episodes, and grinding noise. No significant differences were observed regarding the swallowing events and sleep variables. Since the clinical application of PPI for SB treatment should remain on hold at present, the results of this trial highlight the potential application of pharmacological gastroesophageal reflux disease treatment for SB patients. Larger scale studies are warranted to corroborate these findings. (UMIN Clinical Trials Registry: UMIN000004577).

CRITICAL APPRAISAL. Sleep Bruxism and Sleep-Disordered Breathing.

Sleep bruxism (SB) is a repetitive jaw muscle activity with clenching or grinding of the teeth during sleep. SB is characterized by what is known as rhythmic masticatory muscle activity (RMMA). RMMA is the laboratory polysomnographic finding that differentiates SB from other oromandibular movements seen during sleep. Most often RMMA episodes are associated with sleep arousal. Some patients will report similar complaints related to both SB and sleep disordered breathing (SDB). There are some reports that would suggest that SB is a result of SDB. It has has been postulated that SB is a compensatory mechanism to re establish muscle tone of the upper airway. While these disorders do in fact often present concomitantly, the relationship between the two is yet to be fully elucidated. This Critical Appraisal reviews 3 recent publications with the intent to better define what relationships may exists between SDB and SB. While the current evidence appears to support the notion that these are often concomitant disorders, it also makes clear that evidence to support the hypothesis that SDB is causative for SB is currently lacking.

Could transient hypoxia be associated with rhythmic masticatory muscle activity in sleep bruxism in the absence of sleep‐disordered breathing? A preliminary report

Sleep bruxism (SB) is a repetitive jaw-muscle activity characterised by clenching or grinding of the teeth during sleep. Sleep bruxism activity is characterised by rhythmic masticatory muscle activity (RMMA). Many but not all RMMA episodes are associated with sleep arousal. The aim of this study was to evaluate whether transient oxygen saturation level change can be temporally associated with genesis of RMMA/SB. Sleep laboratory or home recordings data from 22 SB (tooth grinding history in the absence of reported sleep-disordered breathing) and healthy subjects were analysed. A total of 143 RMMA/SB episodes were classified in four categories: (i) no arousal+no body movement; (ii) arousal+no body movement; (iii) no arousal+body movement; (iv) arousal+body movement. Blood oxygen levels (SaO2 ) were assessed from finger oximetry signal at the baseline (before RMMA), and during RMMA. Significant variation in SaO2 over time (P=0·001) was found after RMMA onset (+7 to +9s). No difference between categories (P=0·91) and no interaction between categories and SaO2 variation over time (P=0·10) were observed. SaO2 of six of 22 subjects (27%) remained equal or slight increase after the RMMA/SB onset (+8s) compared to baseline; 10 subjects (45%) slightly decreased (drop 0·01-1%) and the remaining (27%) decreased between 1% and 2%. These preliminary findings suggest that a subgroup of SB subjects had (i) a minor transient hypoxia potentially associated with the onset of RMMA episodes, and this (ii) independently of concomitant sleep arousal or body movements.

Validity of self-reported sleep bruxism among myofascial temporomandibular disorder patients and controls.

Sleep bruxism (SB), primarily involving rhythmic grinding of the teeth during sleep, has been advanced as a causal or maintenance factor for a variety of oro-facial problems, including temporomandibular disorders (TMD). As laboratory polysomnographic (PSG) assessment is extremely expensive and time-consuming, most research testing this belief has relied on patient self-report of SB. The current case-control study examined the accuracy of those self-reports relative to laboratory-based PSG assessment of SB in a large sample of women suffering from chronic myofascial TMD (n= 124) and a demographically matched control group without TMD (n=46). A clinical research coordinator administered a structured questionnaire to assess self-reported SB. Participants then spent two consecutive nights in a sleep laboratory. Audiovisual and electromyographic data from the second night were scored to assess whether participants met criteria for the presence of 2 or more (2+) rhythmic masticatory muscle activity episodes accompanied by grinding sounds, moderate SB, or severe SB, using previously validated research scoring standards. Contingency tables were constructed to assess positive and negative predictive values, sensitivity and specificity, and 95% confidence intervals surrounding the point estimates. Results showed that self-report significantly predicted 2+ grinding sounds during sleep for TMD cases. However, self-reported SB failed to significantly predict the presence or absence of either moderate or severe SB as assessed by PSG, for both cases and controls. These data show that self-report of tooth grinding awareness is highly unlikely to be a valid indicator of true SB. Studies relying on self-report to assess SB must be viewed with extreme caution.

The effect of rapid palatal expansion on sleep bruxism in children.

Sleep bruxism (SB) is a movement described as an involuntary mastication movement during sleep, also defined as rhythmic masticatory muscle activity (RMMA). It is observed in 2-40% of the pediatric population. A link was suggested between respiratory events and RMMA. Rapid palatal expansion (RPE) is an effective orthopedic treatment for correcting maxillary transverse deficiency and sleep-disordered breathing (SDB) in children. The aim was to evaluate the possible reduction of SB after rapid palatal expansion (RPE) therapy. A total of 32 patients (8-14years old; 22 girls and 10 boys) received an orthodontic treatment for transverse maxillary deficiency (5mm or more) at the orthodontics department of the Université de Montréal. They underwent an ambulatory polysomnography (PSG) before, after expansion with the expander, and at the end of the study without the expander. They were classified into three subgroups based on sleep electromyography (EMG) data. Total sleep time and stage NREM 3 presented significant differences between the types of appliances. Moreover, there was a time effect observed for total sleep time, sleep cycles, stage NREM 2, and stage REM, while only a trend suggested for stage NREM 3. Significant differences were observed between subgroups for both RMMA episodes and burst indexes, similarly, for the oxygen desaturation index (ODI). A total of 50% of the patients were classified as responders when RMMA episodes index decreased by more than 25% when comparing treatment efficacy at baseline night. Most bruxers (65%) reduced their RMMA episode index after expansion, but sleep and respiratory variables remained unchanged.

Effects of Botulinum Toxin on Jaw Motor Events during Sleep in Sleep Bruxism Patients: A Polysomnographic Evaluation

To investigate the effects of botulinum toxin type A (BoNT-A) injection on jaw motor episodes during sleep in patients with or without orofacial pain who did not respond to oral splint treatment. Twenty subjects with a clinical diagnosis of SB completed this study. Ten subjects received bilateral BoNT-A injections (25 U per muscle) into the masseter muscles only (group A), and the other 10 received the injections into both the masseter and temporalis muscles (group B). Video-polysomnographic (vPSG) recordings were made before and at 4 weeks after injection. Rhythmic masticatory muscle activity (RMMA) and orofacial activity (OFA) were scored and analyzed for several parameters (e.g., frequency of episodes, bursts per episode, episode duration). The peak amplitude of electromyographic (EMG) activity in the two muscles was also measured. BoNT-A injection did not reduce the frequency, number of bursts, or duration for RMMA episodes in the two groups. The injection decreased the peak amplitude of EMG burst of RMMA episodes in the injected muscles (p < 0.001, repeated measure ANOVA) in both groups. At 4 weeks after injection, 9 subjects self-reported reduction of tooth grinding and 18 subjects self-reported reduction of morning jaw stiffness. A single BoNT-A injection is an effective strategy for controlling SB for at least a month. It reduces the intensity rather than the generation of the contraction in jaw-closing muscles. Future investigations on the efficacy and safety in larger samples over a longer follow-up period are needed before establishing management strategies for SB with BoNT-A. Shim YJ; Lee MK; Kato T; Park HU; Heo K; Kim ST. Effects of botulinum toxin on jaw motor events during sleep in sleep bruxism patients: a polysomnographic evaluation.

Phasic jaw motor episodes in healthy subjects with or without clinical signs and symptoms of sleep bruxism: a pilot study

To investigate the association between each clinical diagnosis criterion for sleep bruxism (SB) and the frequency of jaw motor events during sleep. Video-polysomnography was performed on 17 healthy adult subjects (mean age, 26.7 ± 2.8 years), with at least one of the following clinical signs and symptoms of SB: (1) a report of frequent tooth grinding, (2) tooth attrition with dentine exposure through at least three occlusal surfaces, (3) morning masticatory muscle symptoms, and (4) masseter muscle hypertrophy. Episodes of rhythmic masticatory muscle activity (RMMA) and isolated tonic activity were scored visually. These variables were compared with regards to the presence or absence of each clinical sign and symptom. In 17 subjects, 4.0 ± 2.5/h (0.1-10.2) RMMA and 1.0 ± 0.8/h (0-2.4) isolated tonic episodes were observed (total episodes: 5.0 ± 2.4/h (1.2-11.6)). Subjects with self-reported grinding sounds (n=7) exhibited significantly higher numbers of RMMA episodes (5.7 ± 2.3/h) than those without (n=10; 2.8 ± 1.8/h) (p=0.011). Similarly, subjects with tooth attrition (n=6) showed significantly higher number of RMMA episodes (5.6 ± 3.1/h) than those without (n=11; 3.2 ± 1.6/h) (p=0.049). The occurrence of RMMA did not differ between the presence and absence of morning masticatory muscle symptoms or muscle hypertrophy. Clinical signs and symptoms frequently used for diagnosing SB can represent different clinical and physiological aspects of jaw motor activity during sleep.

Comparison between the rhythmic jaw contractions occurring during sleep and while chewing

The masticatory central pattern generator (CPG) may be implicated in the pathophysiology of sleep bruxism (SB). The aim of this study was to compare rhythmic masticatory muscle activity (RMMA) occurring during sleep related to SB with that of natural voluntary chewing in a sample of sleep bruxers. It was hypothesized that the pace of RMMA during sleep is correlated with the chewing pace. Electromyographic (EMG) surface activity was recorded unilaterally from the masseter muscle of 13 participants diagnosed with SB (mean age±standard deviation=26.1±9.0years) by means of portable recorders. For each participant, recordings were carried out in the natural environment setting, always including the dinner time and the entire sleeping period. The time-frequency features of RMMA episodes were extracted automatically offline using a previously validated algorithm. Comparisons between chewing and SB activity indicated that chewing RMMA episodes almost doubled sleep RMMA in duration and power. The mean frequency of SB episodes was 1.0±0.3Hz, whereas the mean frequency of chewing episodes was 1.5±0.4Hz. The pace of SB and that of chewing were not correlated significantly (R=-0.13; P=0.96). We conclude that sleep RMMA is not related to that of chewing. Despite both activities being accompanied by rhythmic jaw contractions, the pace-generating mechanism of SB may be independent from that of chewing.

Influence of Experimental Esophageal Acidification on Sleep Bruxism

The aim of this cross-over, randomized, single-blinded trial was to examine whether intra-esophageal acidification induces sleep bruxism (SB). Polysomnography with electromyogram (EMG) of masseter muscle, audio-video recording, and esophageal pH monitoring were performed in a sleep laboratory. Twelve healthy adult males without SB participated. Intra-esophageal infusions of 5-mL acidic solution (0.1 N HCl) or saline were administered. The frequencies of EMG bursts, rhythmic masticatory muscle activity (RMMA) episodes, grinding noise, and the RMMA/microarousal ratio were significantly higher in the 20-minute period after acidic infusion than after saline infusion. RMMA episodes including SB were induced by esophageal acidification. This trial is registered with the UMIN Clinical Trials Registry, UMIN000002923. Abbreviations: ASDA, American Sleep Disorders Association; EMG, electromyogram; GER, gastroesophageal reflux; LES, lower esophageal sphincter; NREM, non-rapid eye movement; REM, rapid eye movement; RMMA, rhythmic masticatory muscle activity; SB, sleep bruxism; SD, standard deviation; UES, upper esophageal sphincter.

A Significant Increase in Breathing Amplitude Precedes Sleep Bruxism

Sleep bruxism (SB) is a stereotyped movement disorder that is characterized by rhythmic masticatory muscle activity (RMMA) and tooth grinding. Evidence has suggested that SB is associated with sleep arousals and that most RMMA episodes are preceded by physiologic changes occurring in sequence, namely, a rise in autonomic sympathetic-cardiac activity followed by a rise in the frequency of EEG and suprahyoid muscle activity. In the present study, we hypothesize that an increase in respiration also characterizes the onset of SB within the arousal sequence. Polygraphic sleep recordings of 20 SB subjects without any sleep-related breathing disorders were analyzed for changes in respiration (ie, root mean square, area under the curve, peak, peak-to-peak, and length) extracted from a nasal cannula signal. Variables were analyzed and compared using analysis of variance and correlation tests. Measurements of respiration showed significant changes over time. Four seconds before RMMA muscle activity, the amplitude of respiration is already increased (8 to 23%); the rise is higher at the onset of the suprahyoid activity (60 to 82% 1 s before RMMA); the rise is maximal during RMMA (108 to 206%) followed by a rapid return to levels preceding RMMA. A positive and significant correlation was found between the frequencies of RMMA episodes and the amplitude of breath (R(2) = 0.26; p = 0.02). The amplitude of respiratory changes was 11 times higher when arousal was associated with RMMA in comparison to arousal alone. To our knowledge, this is the first report showing that RMMA-SB muscle activity is associated with a rise in respiration within arousal.

Genesis of sleep bruxism: Motor and autonomic-cardiac interactions

This is a short review paper presenting hypothesis to explain the mechanism that may be involved in the genesis of sleep bruxism (SB). In humans, SB is a repetitive sleep movement disorder mainly characterized by rhythmic masticatory muscle activity (RMMA) at a frequency of 1 Hz and by occasional tooth grinding. Until recently, the mechanism by which RMMA and SB episodes are triggered has been poorly understood. It is reported that during light sleep, most SB episodes are observed in relation to brief cardiac and brain reactivations (3–15 s) termed “micro-arousals”. We showed that RMMA are secondary to a sequence of events in relation to sleep micro-arousals: the heart (increase in autonomic sympathetic activity) and brain are activated in the minutes and seconds, respectively, before the onset of activity in suprahyoid muscles and finally by RMMA in jaw closing masseter or temporalis muscles. In non-human primate study, we have shown that the excitability of cortico-bulbar pathways is depressed during sleep; no rhythmic jaw movements (RJM) are observed following intracortical microstimulation (ICMS) of cortical masticatory area (CMA) during sleep compared to the quiet awake state. The above results suggest that the onset of RMMA and SB episodes during sleep are under the influences of brief and transient activity of the brainstem arousal—reticular ascending system contributing to the increase of activity in autonomic-cardiac and motor modulatory networks.

Sleep bruxism is associated to micro‐arousals and an increase in cardiac sympathetic activity

Sleep bruxism (SB) subjects show a higher incidence of rhythmic masticatory muscle activity (RMMA) than control subjects. RMMA is associated with sleep micro-arousals. This study aims to: (i) assess RMMA/SB episodes in relation to sleep cycles; (ii) establish if RMMA/SB and micro-arousals occur in relation to the slow wave activity (SWA) dynamics; (iii) analyze the association between RMMA/SB and autonomic cardiac activity across sleep cycles. Two nights of polygraphic recordings were made in three study groups (20 subjects each): moderate to high SB, low SB and control. RMMA episodes were considered to occur in clusters when several groups of RMMA or non-specific oromotor episodes were separated by less than 100 s. Correlations between sleep, RMMA/SB index and heart rate variability variables were assessed for the first four sleep cycles of each study group. Statistical analyses were done with SYSTAT and SPSS. It was observed that 75.8% of all RMMA/SB episodes occurred in clusters. Micro-arousal and SB indexes were highest during sleep cycles 2 and 3 (P < 0.001). Within each cycle, micro-arousal and RMMA/SB indexes showed an increase before each REM sleep (P <or= 0.02). The cross-correlation plot for micro-arousal index showed positive association from 4 min preceding SB onset in the moderate to high SB subjects (P <or= 0.06). The cross-correlation plot revealed that SWA decreases following SB onset (P <or= 0.05). Further cross-correlation analysis revealed that a shift in sympatho-vagal balance towards increased sympathetic activity started 8 min preceding SB onset (P <or= 0.03). In moderate to severe SB subjects, a clear increase in sympathetic activity precedes SB onset.

Association Between Sleep Bruxism, Swallowing-Related Laryngeal Movement, and Sleep Positions

To describe the relationships of sleep bruxism to swallowing and sleep positions. Controlled descriptive study. Polysomnography and audio-video recordings were done in a hospital sleep laboratory. Nine patients with sleep bruxism and 7 normal subjects were matched for age and sex. n/a. During sleep, patients with sleep bruxism showed a higher frequency of rhythmic masticatory muscle activity episodes (6.8 +/- 1.0 [SEM]/h) than did normals (0.5 +/- 0.1/h, p < 0.01). Swallowing-related laryngeal movements occurred more frequently in sleep of patients with sleep bruxism (6.8 +/- 0.8/h) than in normals (3.7 +/- 0.3/h, p < 0.01). In both groups, during sleep, close to 60% of rhythmic masticatory muscle activity episodes were associated with swallowing. In sleep bruxism patients, 68% of swallowing events occurred during rhythmic masticatory muscle activity episodes, while only 10% of swallowing events were associated with rhythmic masticatory muscle activity in normal subjects. Sleep bruxism patients and normals spent 95.5% and 87.3% of sleeping time in the supine and lateral decubitus positions, respectively. In both groups, up to 96% of rhythmic masticatory muscle activity and swallowing were observed in the supine and lateral decubitus position. In sleep bruxism patients, although sleeping time did not differ between the 2 sleeping body positions, 74% of rhythmic masticatory muscle activity and swallowing events were scored in the supine position compared to 23% in the lateral decubitus position. During sleep, rhythmic masticatory muscle activity is often associated with swallowing. In sleep bruxism patients, most of these oromotor events are observed in the supine position. The physiologic link between rhythmic masticatory muscle activity and swallowing and the clinical relevance of sleep position in sleep bruxism management need to be investigated.

Lower number of K-complexes and K-alphas in sleep bruxism: a controlled quantitative study

Objectives: Although patients with sleep bruxism (SB) show a higher incidence of rhythmic masticatory muscle activity (RMMA) during sleep than matched normal controls, they are good sleepers. Sleep macrostructure (e.g. total sleep time, sleep latency, number of awakenings or sleep stage shifts and sleep stage duration) is similar between groups. Differences in sleep microstructure between SB patients and normals have been investigated only in few studies. The aim of the present study was to quantify number of microarousals, K-complexes, K-alphas, EEG spindles, and the density of slow wave activity, in both groups, in order to better understand the pathophysiology of SB.Methods: Ten normal sleepers were matched for age and gender with 10 patients who exhibited frequent tooth-grinding during sleep. Using quantitative polysomnographic measures, we compared the above-mentioned sleep variables in both groups. Data are presented as indices for total sleep and for consecutive non-rapid eye movement (non-REM) episodes over non-REM to rapid eye movement (REM) cycles and per hour of sleep.Results: SB patients showed 6 times more RMMA episodes per hour of sleep than normals (P<0.001), with a higher frequency in the second and third non-REM to REM cycles. SB patients presented 42.7% fewer K-complexes per hour of stage 2 sleep, but only normals showed a decline from the first to fourth non-REM episode. Only 24% of SB-RMMA episodes were associated with K-complexes in 60s. The number of K-alphas was 61% lower in SB patients, no change across non-REM episodes was noted. While no difference in electroencephalographic (EEG) spindles or slow wave activity (SWA) was observed between groups, EEG spindles increased and SWA decreased linearly over consecutive non-REM to REM cycles.Conclusions: According to our observations, good sleep in SB patients is characterized by a low incidence of K-complexes or K-alphas and by the absence of any difference in other sleep microstructure variables or SWA.

Sleep bruxism: an oromotor activity secondary to micro-arousal.

Spontaneous rhythmic masticatory muscle activity (RMMA) during sleep occurs in relation to transient activation in the cerebral and autonomic nervous systems of normal subjects and in patients with sleep bruxism (SB). In this study, we made a quantitative assessment of the sequential changes in cortical electroencephalographic (EEG) and autonomic-cardiac activities associated with micro-arousals preceding RMMA episodes. We matched 10 SB patients with 10 normal subjects. The onset of RMMA episodes was defined in terms of the onset of activation in the suprahyoid muscles. In SB patients, an increase in cortical EEG activity was observed 4 seconds before the onset of suprahyoid activity in 79% of episodes. A significant acceleration in heart rate was initiated one cardiac cycle before RMMA onset. A clear sequence of cortical to autonomic-cardiac activation precedes jaw motor activity in SB patients. This suggests that SB is a powerful oromotor manifestation secondary to micro-arousal.