Gilles Lavigne

Sleep Bruxism: Validity of Clinical Research Diagnostic Criteria in a Controlled Polysomnographic Study

The clinical validity of diagnostic criteria for sleep orofacial motor activity-more specifically, bruxism-has never been tested. Polysomnographic recordings from 18 bruxers and 18 asymptomatic subjects, selected according to American Sleep Disorders Association criteria, were analyzed (1) to discriminate sleep bruxism from other orofacial motor activities and (2) to calculate sensitivity, specificity, and predictive values of research criteria. Clinical observations and reports revealed that all 18 bruxers reported frequent tooth-grinding during sleep. Tooth wear was noted in 16 out of 18 bruxers and jaw discomfort reported by six of them. These findings were present in none of the controls. The analysis of polysomnographic data showed that the asymptomatic subjects presented a mean of 1.7 ± 0.3 bruxism episodes per hour of sleep (sustained or repetitive bursting activity in jaw closer muscles), while bruxers had a significantly higher level of activity: 5.4 ± 0.6. Controls exhibited 4.6 ± 0.3 bruxism bursts per episode and 6.2 (from 0 to 23) bruxism bursts per hour of sleep, whereas bruxers showed, respectively, 7.0 ± 0.7 and 36.1 (5.8 to 108). Bruxism-like episodes with at least two grinding sounds were noted in 14 of the 18 bruxers and in one control. The two groups exhibited no difference in any of the sleep parameters. Based on the present findings, the following polysomnographic diagnostic cut-off criteria are suggested: (1) more than 4 bruxism episodes per hour, (2) more than 6 bruxism bursts per episode and/or 25 bruxism bursts per hour of sleep, and (3) at least 2 episodes with grinding sounds. When the polysomnographic bruxism-related variables were combined under logistic regression, the clinical diagnosis was correctly predicted in 81.3% of the controls and 83.3% of the bruxers. The validity of these clinical research criteria needs now to be challenged in a larger population, over time, and in subjects presenting various levels of severity of sleep bruxism.

Neurobiological Mechanisms Involved in Sleep Bruxism

Sleep bruxism (SB) is reported by 8% of the adult population and is mainly associated with rhythmic masticatory muscle activity (RMMA) characterized by repetitive jaw muscle contractions (3 bursts or more at a frequency of 1 Hz). The consequences of SB may include tooth destruction, jaw pain, headaches, or the limitation of mandibular movement, as well as tooth-grinding sounds that disrupt the sleep of bed partners. SB is probably an extreme manifestation of a masticatory muscle activity occurring during the sleep of most normal subjects, since RMMA is observed in 60% of normal sleepers in the absence of grinding sounds. The pathophysiology of SB is becoming clearer, and there is an abundance of evidence outlining the neurophysiology and neurochemistry of rhythmic jaw movements (RJM) in relation to chewing, swallowing, and breathing. The sleep literature provides much evidence describing the mechanisms involved in the reduction of muscle tone, from sleep onset to the atonia that characterizes rapid eye movement (REM) sleep. Several brainstem structures (e.g., reticular pontis oralis, pontis caudalis, parvocellularis) and neurochemicals (e.g., serotonin, dopamine, gamma aminobutyric acid [GABA], noradrenaline) are involved in both the genesis of RJM and the modulation of muscle tone during sleep. It remains unknown why a high percentage of normal subjects present RMMA during sleep and why this activity is three times more frequent and higher in amplitude in SB patients. It is also unclear why RMMA during sleep is characterized by co-activation of both jaw-opening and jaw-closing muscles instead of the alternating jaw-opening and jaw-closing muscle activity pattern typical of chewing. The final section of this review proposes that RMMA during sleep has a role in lubricating the upper alimentary tract and increasing airway patency. The review concludes with an outline of questions for future research.

SPECT imaging of striatal pre- and postsynaptic dopaminergic status in restless legs syndrome with periodic leg movements in sleep.

Abstract Restless legs syndrome (RLS) is a common sleep-related disorder principally characterised by leg paresthesia associated with an irresistible urge to move. A majority of RLS patients experience periodic leg movements during sleep (PLMS) and wakefulness. Pharmacological evidence suggests that RLS-PLMS may be caused by a central nervous system dopaminergic (DA) dysfunction. The aim of the present study was to evaluate the striatal pre- and postsynaptic DA status in patients suffering from both RLS and PLMS, by means of [123I]b-CIT and [123I]IBZM SPECT respectively. Ten drug-naïve patients and ten age-matched controls participated in this study. All participants were recorded for at least one night of polysomnography before the SPECT studies. No difference was seen in DA transporter ([123I]b-CIT) binding between RLS-PLMS patients (MD=4.89) and controls (MD=4.81; p=0.81). The study of the striatal D2-receptor binding ([123I]IBZM) revealed a significantly lower binding in patients (MD= 1.72) compared with controls (MD=1.85; p=0.006). These results support the hypothesis that a central DA dysfunction is involved in the physiopathology of RLS-PLMS. Several mechanisms may be responsible for the decrease of the D2-receptor binding. However, since [123I]b-CIT binding is normal, a decreased number of D2-receptors or a decreased affinity of D2-receptors for [123I]IBZM is more likely than an increased level of synaptic DA with attendant down-regulation of D2-receptors.

Nocturnal blood pressure changes in patients with restless legs syndrome

Objectives: To assess heart rate (HR) and blood pressure (BP) changes associated with periodic leg movements during sleep (PLMS) with or without EEG signs of arousal in subjects with primary restless legs syndrome (RLS). Methods: Ten patients with RLS (4 women, aged 47.3 ± 13.5 years) underwent one night of polysomnography along with noninvasive beat-to-beat BP monitoring. Ten PLMS with microarousals (PLMS-MA) and 10 PLMS without microarousals (PLMS-noMA) were analyzed in each subject. Systolic and diastolic BP (SBP, DBP) were measured within a 25-beat temporal window comprising 10 beats before and 15 beats after onset of each movement. PLMS-related BP changes were assessed by repeated measures one-way analysis of variance. BP changes associated with PLMS-MA and PLMS-noMA were compared by paired t-tests. Pearson correlation coefficients were used to assess the relationship between cardiovascular changes and clinical and polysomnographic variables. Results: BP increased significantly in association with all PLMS (on average, SBP 22 mm Hg, DBP 11 mm Hg). BP changes associated with PLMS-MA were greater vs those associated with PLMS-noMA (p < 0.05). SBP and DBP changes increased with age and the duration of illness. Conclusions: Periodic leg movements–related repetitive nocturnal blood pressure fluctuations could contribute to the risk of cardiovascular diseases in patients with restless legs syndrome, especially in the elderly.

The efficacy of oral splints in the treatment of myofascial pain of the jaw muscles: a controlled clinical trial

&NA; Oral splints are widely used in the treatment of myofascial pain of masticatory muscles, even though their mechanism of action is unknown. The present study evaluated the therapeutic efficacy of splints using a parallel, randomized, controlled and blind design. Following a sample size estimation, 63 subjects were recruited and assigned to 3 groups: (1) passive control: full occlusal splint worn only 30 min at each appointment: (2) active control: palatal splint worn 24 h/day: and (3) treatment: full occlusal splint worn 24 h/day. On each of 7 visits over 10 weeks, subjects rated on 100 mm visual analogue scales their pain intensity and unpleasantness at rest and after experimental mastication. The effect of pain on the quality of life was also rated on category scales. All pain ratings decreased significantly with time, and quality of life improved for all 3 groups. However, there were no significant differences between groups in any of the variables. These data suggest that the gradual reduction in the intensity and unpleasantness of myofascial pain, as well as the improvement of quality of life during the trial, was non‐specific and not related to the type of treatment.

Periodic leg movements in REM sleep behavior disorder and related autonomic and EEG activation

Objective: To assess the frequency of periodic leg movements (PLM) in idiopathic REM sleep behavior disorder (RBD) and to analyze their polysomnographic characteristics and associated autonomic and cortical activation. Background: PLM during sleep (PLMS) and wakefulness (PLMW) are typical features of restless legs syndrome (RLS), but are also frequently observed in patients with RBD. Methods: Forty patients with idiopathic RBD underwent one night of polysomnographic recording to assess PLMS frequency. PLM features, PLMS-related cardiac activation during stage 2 sleep, and EEG changes were analyzed in 15 of these patients with RBD. Results were compared with similar data obtained in 15 sex- and age-matched patients with primary RLS. Results: Twenty-eight (70%) of 40 patients with RBD showed a PLMS index greater than 10. No between-group differences were found in sleep architecture or indexes of PLMW and PLMS during non-REM sleep, but a trend for a higher PLMS index during REM sleep was found in patients with RBD. PLM mean duration and interval in the two conditions were similar. A transient tachycardia followed by a bradycardia was observed in close association with every PLMS in both groups, but the amplitude of the cardiac activation was significantly reduced in patients with RBD. In addition, significantly fewer PLMS were associated with microarousal in this condition. Conclusions: Periodic leg movements are very common in idiopathic RBD, occurring in all stages of sleep, especially during REM sleep. In idiopathic RBD, the reduction of cardiac and EEG activation associated with PLMS suggests the presence of an impaired autonomic and cortical reactivity to internal stimuli.

Quality of sleep and its daily relationship to pain intensity in hospitalized adult burn patients.

&NA; Sleep disturbances are frequently reported in victims following burn injuries. This prospective study was designed to assess sleep quality and to examine its daily relationship to pain intensity within the first week of hospitalization. Twenty‐eight non‐ventilated patients were interviewed during 5 consecutive mornings (number of observations=140) to collect information about perceived quality of sleep (visual analogue scale, number of hours, number of awakenings, presence of nightmares). Pain intensity was assessed at rest (nighttime, morning, during the day) and following therapeutic procedures using a 0–10 numeric scale. Seventy‐five percent of patients reported sleep disturbances at some point during the study although, in most patients, sleep quality was not consistently poor. Pooled cross‐section regression analyses showed significant temporal relationships between quality of sleep and pain intensity such that a night of poor sleep was followed by a significantly more painful day. Pain during the day was not found to be a significant predictor of poor sleep on the following night. These results support previous findings that perceived quality of sleep following burn injury is poor. Moreover, they show a daily relationship between quality of sleep and acute burn pain in which poor sleep is linked to higher pain intensity during the day.

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.

Jaw Pain Prevalence Among French-speaking Canadians in Quebec and Related Symptoms of Temporomandibular Disorders

The purpose of this study was to assess the prevalence and pattern of self-reported TMD jaw pain in a randomized stratified sample from the general population living in the Province of Quebec, Canada. Through a telephone survey, standardized questions were asked to 897 French-speaking respondents, aged 18 years old and over, regarding frequency, severity, daily pattern of jaw pain, presence of difficulty in opening, joint clicking, and sleeping problems. All prevalence estimates were adjusted to the sociodemographic distribution of the non-institutionalized population. The results indicate that TMD jaw pain is self-reported by 30% of the general population; however, the prevalence of cases reporting frequent episodes (quite often or very often) is estimated at 7%, with more than two-thirds (69%) of the respondents in this subgroup experiencing moderate to severe pain. The prevalence rates of frequent difficulty in opening and joint clicking were estimated at 9% and 4%, respectively. Approximately one in four subjects with frequent episodes of jaw pain also reported frequent joint clicking or difficulty in opening, and a strong association (Gamma coefficient > 0.6) was found among all three TMD symptoms. Our data suggest that the prevalence of clinically significant TMDrelated jaw pain (frequent jaw pain of moderate to severe intensity) is approximately 5% in the general population of the Province of Quebec. In the nine months preceding the survey, about 2% of the total population sought treatment for a TMD symptom.

Rhythmic Masticatory Muscle Activity during Sleep in Humans

Rhythmic Masticatory Muscle Activity (RMMA) is frequently observed during sleep in normal subjects and sleep bruxers. We hypothesized that some normal subjects exhibit RMMA at a lower frequency than sleep bruxers. Polysomnographic data from 82 normal subjects were compared with data from 33 sleep bruxers. RMMA episodes were defined as three or more consecutive bursts of masseter EMG activity, with or without tooth-grinding. Such episodes were observed in nearly 60% of normal subjects. A lower frequency of episodes was noted in normal subjects than in bruxers. Sleep organization was similar between groups. Bruxers had twice as many masseter muscle bursts per episode and episodes of higher amplitude compared with controls with RMMA. The high prevalence of RMMA observed in normal subjects suggests that this activity is related to certain sleep-related physiological functions, including autonomic activation.