Corticoperipheral neuromuscular disconnection in obstructive sleep apnoea

The roles of central nervous mechanisms and cortical output in obstructive sleep apnea remain unclear. We addressed corticomuscular coupling between cortical sensorimotor areas and lower facial motor units as a mechanistic pathway and as a possible surrogate marker of cortico-peripheral motor control in obstructive sleep apnea. In this exploratory cross-sectional retrospective study we analysed EEG (C3- and C4-leads) and chin EMG from polysomnography recordings in 86 participants (22 females; age range: 26-81 years), 27 with mild (respiratory disturbance index = 5-15 events/hour), 21 with moderate (15-30 events/h) and 23 with severe obstructive sleep apnea (> 30 events/h) and 15 control subjects (<5 events/h). By computing C3-/C4-EEG- chin EMG coherence of signal dynamics in time and frequency domains we investigated corticomuscular coupling between cortical sensorimotor areas and lower facial motor units with increasing obstructive sleep apnea severity during the entire sleeping time, during different sleep stages and during obstructive respiratory events, including 5 seconds before (stable breathing) and after events (breathing resumption). Additionally, we studied a possible influence of body-mass-index and autonomic nervous system activation. We found that both average and respiratory event-specific corticomuscular coupling between cortical sensorimotor areas and lower facial motor units weakened significantly with increasing obstructive sleep apnea severity, was strongest during N3 and weakened in N1, N2 and rapid-eye-movement stages (in decreasing order). Coupling increases significantly during the obstructive respiratory events compared with coupling just before and following them. Results were independent of body-mass-index or autonomic nervous system activation. We conclude that obstructive respiratory events in obstructive sleep apnea are very strongly associated both quantitatively and temporally with the degree of disconnection within the cortical sensorimotor areas - lower facial motor units ...