Nelly Huynh

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 ≤ 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 ≤ 0.06). The cross‐correlation plot revealed that SWA decreases following SB onset (P ≤ 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 ≤ 0.03). In moderate to severe SB subjects, a clear increase in sympathetic activity precedes SB onset.

Sleep bruxism: a comprehensive overview for the dental clinician interested in sleep medicine.

Sleep bruxism (SB) is a common sleep-related motor disorder characterized by tooth grinding and clenching. SB diagnosis is made on history of tooth grinding and confirmed by polysomnographic recording of electromyographic (EMG) episodes in the masseter and temporalis muscles. The typical EMG activity pattern in patients with SB is known as rhythmic masticatory muscle activity (RMMA). The authors observed that most RMMA episodes occur in association with sleep arousal and are preceded by physiologic activation of the central nervous and sympathetic cardiac systems. This article provides a comprehensive review of the cause, pathophysiology, assessment, and management of SB.

Prevalence and risk factors of sleep bruxism and wake‐time tooth clenching in a 7‐ to 17‐yr‐old population

Sleep-related bruxism (SB) and wake-time tooth clenching (TC) have been associated with temporomandibular disorders (TMDs), headache, and sleep and behavioral complaints. This study aimed to assess the prevalence and risk factors of these signs and symptoms in a 7- to 17-yr-old population (n = 604) seeking orthodontic treatment. Data were collected by questionnaire and by a clinical examination assessing craniofacial morphology and dental status. Sleep-related bruxism was reported by 15% of the population and TC was reported by 12.4%. The SB group (n = 58) was mainly composed of children (67.3% were ≤12 yr of age) and the TC group (n = 42) was mainly composed of adolescents (78.6% were ≥13 yr of age). The craniofacial morphology of over 60% of SB subjects was dental class II and 28.1% were a brachyfacial type. Compared with controls (n = 220), SB subjects were more at risk of experiencing jaw muscle fatigue [adjusted OR (AOR) = 10.5], headache (AOR = 4.3), and loud breathing during sleep (AOR = 3.1). Compared with controls, TC subjects reported more temporomandibular joint clicking (AOR = 5), jaw muscle fatigue (AOR = 13.5), and several sleep and behavioral complaints. Sleep- and wake-time parafunctions are frequently associated with signs and symptoms suggestive of TMDs, and with sleep and behavioral problems. Their clinical assessment during the planning of orthodontic treatment is recommended.

Associations between sleep-disordered breathing symptoms and facial and dental morphometry, assessed with screening examinations.

INTRODUCTION Chronic snoring is considered abnormal in a pediatric population. This disorder is often attributed to enlarged tonsils and adenoids, but multiple anatomic obstructions should also be considered. Facial and dental morphometry associations with various sleep-disordered breathing symptoms were investigated at an orthodontic clinic. METHODS Parents or guardians were asked to complete a 4-part questionnaire on behalf of their children (n = 604; <18 years of age), including medical and dental history, bruxism and temporomandibular disorder habits, sleep and daytime behavior, and sleep duration and quality. All subjects underwent a clinical screening assessment by the same orthodontist to identify standard dental, skeletal, functional, and esthetic factors. RESULTS In contrast to sleep-disordered breathing or sleep apnea in adults, which is predominantly associated with obesity, sleep-disordered breathing symptoms in this pediatric cohort were primarily associated with adenotonsillar hypertrophy, morphologic features related to a long and narrow face (dolichofacial, high mandibular plane angle, narrow palate, and severe crowding in the maxilla and the mandible), allergies, frequent colds, and habitual mouth breathing. CONCLUSIONS Because of the recognized impact of pediatric snoring on childrens health, the determination of these good predictors can help in preventing and managing sleep-disordered breathing. If a health professional notices signs and symptoms of sleep-disordered breathing, the young patient should be referred to a sleep medicine specialist in conjunction with an orthodontist if there are dentoskeletal abnormalities.

Comparison of hypopnea definitions in lean patients with known obstructive sleep apnea hypopnea syndrome (OSAHS).

Study objectivesIn the interest of improving inter-rater reliability and standardization between sleep laboratories, hypopnea definitions were recently changed to place less emphasis on arousal scoring and more emphasis on oxygen desaturations. We sought to determine whether these changes would affect detection and treatment of OSAHS in lean patients—a group known to desaturate less-than-obese patients.MethodsThirty-five lean subjects (15 male, 20 women, five post-menopausal) diagnosed OSAHS and a documented benefit from treatment had diagnostic polysomnograms (PSG) originally scored using the American Academy of Sleep Medicine (AASM) rule from 1999 (referred to as “Rule C”). These patients had appropriate clinical care based on those results. PSG records were then re-scored in a randomized and blinded fashion utilizing hypopnea Rule A and B of the 2007 AASM guidelines.ResultsBaseline mean (SD) apnea hypopnea indices (AHI) for rules A, B, and C were 6.4 (3.1), 20.6 (8.2), and 26.9 (7.3), respectively (p < 0.0001). Mean (SD) BMI was 24.4 (1.0). By design, all subjects were treatment responders. Eighty-six percent with CPAP, 83% with oral appliance, and 100% with surgical intervention reported resolution of their initial daytime or sleep complaint. Post-treatment AHIs for rules A, B, and C were 0.8 (0.9), 1.8 (1.2) and 2.3 (1.6; p < 0.001). In all three scoring conditions, the AHI was reduced significantly with treatment (p < 0.001). A repeated measures ANOVA of the difference between scoring methods indicated statistically significant differences between all three strategies at both pre- and post-treatment (p < 0.001). Sleepiness on the Epworth sleepiness scale decreased from a mean of 10.9 (2.3) to 5.7 (1.3) with treatment (p < 0.001). This change in subjective rating of sleepiness was more strongly correlated with rules B and C (r = 0.6) and more modestly correlated with Rule A scoring (r = 0.4).ConclusionResponse to treatment was more tightly correlated with arousal based scoring rules B and C in this group of lean subjects. The1999 hypopnea rule was used at baseline to detect this cohort of patients with OSAHS that ultimately benefitted from treatment. Rule B detected OSAHS and correlated well with response to treatment, but many more were categorized as mild (5 < AHI < 15) at baseline. Since 40% of the subjects had an AHI less than 5 with Rule A, lack of sensitivity should be considered before applying Rule A to the scoring of sleep studies in lean patients.

Sleep bruxism, snoring, and headaches in adolescents: short-term effects of a mandibular advancement appliance.

OBJECTIVES Sleep bruxism (SB) frequently is associated with other sleep disorders and pain concerns. Our study assesses the efficacy of a mandibular advancement appliance (MAA) for SB management in adolescents reporting snoring and headache (HA). METHODS Sixteen adolescents (mean age, 14.9±0.5) reporting SB, HA (>1d/wk), or snoring underwent four ambulatory polysomnographies for baseline (BSL) and while wearing MAA during sleep. MAA was worn in three positions (free splints [FS], neutral position [NP], and advanced to 50% of maximum protrusion [A50]) for 1 week each in random order (FS-NP-A50 or NP-A50-FS; titration order, NP-A50). Reports of HA were assessed with pain questionnaires. RESULTS Overall, sleep variables did not differ across the four nights. SB index decreased up to 60% with MAA in A50 (P=.004; analysis of variance). Snoring was measured as the percentage of sleep time spent snoring. The subgroup of snorers (n=8) showed significant improvement with MAA (-93%; P=.002). Initial HA intensity was reported at 42.7±5/100 mm, showing a decreasing trend with MAA (-21% to -51%; P=.07). CONCLUSION Short-term use of an MAA appears to reduce SB, snoring, and reports of HA. However, interactions between SB, breathing during sleep, and HA as well as the long-term effectiveness and safety of MAA in adolescents need further investigation.

An fMRI study of cerebrovascular reactivity and perfusion in obstructive sleep apnea patients before and after CPAP treatment.

OBJECTIVE Cerebrovascular reactivity is impaired in patients suffering from obstructive sleep apnea syndrome (OSAS) as demonstrated by transcranial Doppler studies. We use magnetic resonance imaging techniques to investigate the anatomical distribution of cerebrovascular reactivity changes in patients with OSAS, as well as their evolution after therapeutic and sham continuous positive airway pressure (CPAP) treatment. METHODS Twenty-three men with moderate or severe obstructive sleep apnea were compared to a healthy control group (n=7) using a breath-holding functional magnetic resonance imaging task and the flow-sensitive alternating inversion recovery (FAIR) imaging before and after 2 months of therapeutic (active) or sub-therapeutic (sham) CPAP treatment. RESULTS Significantly higher cerebrovascular reactivity was found in healthy controls as compared to patients in bilateral cortical and subcortical brain regions. Cerebrovascular reactivity increased with therapeutic CPAP in the thalamus and decreased with sham CPAP in medial frontal regions in OSAS patients. Duration of nocturnal hypoxemia and body mass index negatively correlated with cerebrovascular reactivity, particularly in the medial temporal lobe structures, suggesting a possible pathophysiological mechanism for hippocampal injury. There was no difference in perfusion between patients and control group, and no effect of CPAP or sham-CPAP treatment on perfusion in patients. CONCLUSIONS Observed cerebrovascular reactivity changes were neither homogeneous throughout the brain nor followed vascular territories, but rather corresponded to underlying neuronal networks, establishing a relationship between cerebrovascular reactivity and surrounding neuronal activity.

Orthodontics treatments for managing obstructive sleep apnea syndrome in children: A systematic review and meta-analysis

A small maxilla and/or mandible may predispose children to sleep-disordered breathing, which is a continuum of severity from snoring to obstructive sleep apnea. Preliminary studies have suggested that orthodontic treatments, such as orthopedic mandibular advancement or rapid maxillary expansion, may be effective treatments. The aim is to investigate the efficacy of orthopedic mandibular advancement and/or rapid maxillary expansion in the treatment of pediatric obstructive sleep apnea. Pubmed, Medline, Embase, and Internet were searched for eligible studies published until April 2014. Articles with adequate data were selected for the meta-analysis; other articles were reported in the qualitative assessment. Data extraction was conducted by two independent authors. A total of 58 studies were identified. Only eight studies were included in the review; of these, six were included in the meta-analysis. The research yielded only a small number of studies. Consequently, any conclusions from the pooled diagnostic parameters and their interpretation should be treated carefully. Although the included studies were limited, these orthodontic treatments may be effective in managing pediatric snoring and obstructive sleep apnea. Other related health outcomes, such as neurocognitive and cardiovascular functions have not yet been systematically addressed. More studies are needed with larger sample size, specific inclusion and exclusion criteria and standardized data reporting to help establish guidelines for the orthodontic treatment of pediatric obstructive sleep apnea.

Is there a first night effect on sleep bruxism? A sleep laboratory study.

STUDY OBJECTIVES Sleep bruxism (SB) is reported to vary in frequency over time. The aim of this study was to assess the first night effect on SB. METHODS A retrospective polysomnographic (PSG) analysis was performed of data from a sample of SB patients (12 females, 4 males; age range: 17-39 years) recorded in a sleep laboratory over 2 consecutive nights. Sleep parameters and jaw muscle activity variables (i.e., rhythmic masticatory muscle activity [RMMA]) for SB were quantified and compared between the 2 nights. Subjects were classified into groups according to severity of RMMA frequency, such as low frequency (2-4 episodes/h and/or < 25 bursts/h) and moderate-high frequency (≥ 4 episodes/h and ≥ 25 bursts/h). RESULTS Overall, no first night effects were found for most sleep variables. However, total sleep time, sleep efficiency, and stage transitions showed significant time and group interactions (repeated measures ANOVAs, p ≤ 0.05). The RMMA episode index did not differ between the 2 nights, whereas the second night showed significantly higher burst index, bruxism time index, and mean burst duration (repeated measure ANOVAs, p ≤ 0.05). Five patients of 8 in the low frequency group were classified into the moderate-high frequency group on the second night, whereas only one patient in the moderate-high frequency group moved to the low frequency group. CONCLUSIONS The results showed no overall first night effect on severity of RMMA frequency in young and healthy patients with SB. In clinical practice, one-night sleep recording may be sufficient for moderate-high frequency SB patients. However, low RMMA frequency in the first night could be confirmed by a second night based on the patients medical and dental history.

The Effects of CPAP Treatment on Task Positive and Default Mode Networks in Obstructive Sleep Apnea Patients: An fMRI Study

Introduction Functional magnetic resonance imaging studies enable the investigation of neural correlates underlying behavioral performance. We investigate the effect of active and sham Continuous Positive Airway Pressure (CPAP) treatment on working memory function of patients with Obstructive Sleep Apnea Syndrome (OSAS) considering Task Positive and Default Mode networks (TPN and DMN). Methods An experiment with 4 levels of visuospatial n-back task was used to investigate the pattern of cortical activation in 17 men with moderate or severe OSAS before and after 2 months of therapeutic (active) or sub-therapeutic (sham) CPAP treatment. Results Patients with untreated OSAS had significantly less deactivation in the temporal regions of the DMN as compared to healthy controls, but activation within TPN regions was comparatively relatively preserved. After 2 months of treatment, active and sham CPAP groups exhibited opposite trends of cerebral activation and deactivation. After treatment, the active CPAP group demonstrated an increase of cerebral activation in the TPN at all task levels and of task-related cerebral deactivation in the anterior midline and medial temporal regions of the DMN at the 3-back level, associated with a significant improvement of behavioral performance, whereas the sham CPAP group exhibited less deactivation in the temporal regions of Default Mode Network and less Task Positive Network activation associated to longer response times at the 3-back. Conclusion OSAS has a significant negative impact primarily on task-related DMN deactivation, particularly in the medial temporal regions, possibly due to nocturnal hypoxemia, as well as TPN activation, particularly in the right ventral fronto-parietal network. After 2 months of active nasal CPAP treatment a positive response was noted in both TPN and DMN but without compete recovery of existing behavioral and neuronal deficits. Initiation of CPAP treatment early in the course of the disease may prevent or slow down the occurrence of irreversible impairment.