A lack of specific motor patterns between rhythmic/non-rhythmic masticatory muscle activity and bodily movements in sleep bruxism

Abstract

Purpose: The aims of the present study were to investigate the temporal relationships between jaw and bodily movements and clarify motor processes in the genesis of rhythmic masticatory muscle activity (RMMA) in sleep bruxism (SB). Methods: Video-polysomnography recordings were obtained from ten subjects with SB (mean age: 23.4 ± 1.6 years) and ten matched normal controls (CTL) (mean age: 24.4 ± 3.2 years). RMMA and nonspecific masseter activity (NSMA) were scored in association with bodily movements in the leg, arm, head, and trunk using electromyography and video recordings. The relationship between oromotor episodes and bodily movements was assessed in terms of sleep stage distributions and temporal relationships. Cardiac changes preceding oromotor episodes in stage N2 were assessed. Results: Approximately 80% of RMMA and NSMA were associated with movements in one or more body sites. RMMA and NSMA were more frequently associated with movements of the leg (70-75%) and arm (40-55%) than movements of the head (17-22%) and trunk (5-25%). The relationship between oromotor episodes and bodily movements did not significantly differ among sleep stages. Oromotor episodes and bodily movements did not show a consistent temporal pattern in the SB and CTL groups. Regardless of the temporal relationship between oromotor episodes and bodily movements, the mean heart rate significantly increased by 5 beats before the onset of oromotor episodes. Conclusions: No specific temporal motor patterns were found between RMMA and bodily movements. RMMA and NSMA represent a repertoire of arousalrelated autonomic motor responses during sleep.

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

“… 11,15,30 In recent studies, to avoid the influence of a sleep stage shift accompanying oromotor events, 15,30 the sleep stage preceding RMMA was identified as the sleep stage of epochs in which RMMA occurred. In young adult subjects, the frequency of RMMA was the highest in stage N1 followed by N2, while it was the lowest in N3 and R 15,30,55,56 . A recent study on middle‐aged SB subjects showed that the frequency of RMMA episodes was the highest in N1 but was also high in N2 and R 11 .…”

“…11,15,30 In recent studies, to avoid the influence of a sleep stage shift accompanying oromotor events, 15,30 the sleep stage preceding RMMA was identified as the sleep stage of epochs in which RMMA occurred. In young adult subjects, the frequency of RMMA was the highest in stage N1 followed by N2, while it was the lowest in N3 and R. 15,30,55,56 A recent study on middle-aged SB subjects showed that the frequency of RMMA episodes was the highest in N1 but was also high in N2 and R. 11 In comparisons with control participants, SB individuals presented with a larger amount of REM sleep, which correlated with a linear increase in the frequency of RMMA/SB episodes. This unique finding indicates a relationship with emotional memory processing.…”

“…However, microarousals may not be the specific trigger(s) for the genesis of RMMA. Microarousals may precede not only RMMA, but also other oromotor activities and leg movements 56,62 . Furthermore, RMMA/SB episodes were not induced when microarousals and CAP were experimentally induced in normal subjects without SB, indicating the need for other factors 33,36 .…”

Reciprocal first night effect on rhythmic and non‐rhythmic oromotor episodes in moderate to severe primary sleep bruxism: A retrospective physiological study

“…The physiological mechanisms underlying the generation of motor activity sleep has been suggested to differ between RMMA and NSMA. RMMA and NSMA were found to occur in association with arousal responses 20,21,44 . However, additional rhythmic inputs to trigeminal motoneurons may be needed to generate the rhythmic activation of masticatory muscles, such as RMMA, during sleep 45 .…”

“…RMMA and NSMA were found to occur in association with arousal responses. 20,21,44 However, additional rhythmic inputs to trigeminal motoneurons may be needed to generate the rhythmic activation of masticatory muscles, such as RMMA, during sleep. 45 Therefore, RMMA and NSMA are two different arousal-related motor repertoires in the trigeminal motor system during sleep.…”