Key points Coordination of the neuromuscular compartments of the tongue is critical to maintain airway patency. Currently, little is known about the extent to which regional tongue dilatory motion is coordinated in heathy people and if this coordination is altered in people with obstructive sleep apnoea (OSA). We show that regional tongue muscle coordination in people with and without OSA during wakefulness is associated with effective airway dilatation during inspiration, using dynamic tagged magnetic resonance imaging. The maximal movement of four compartments of the tongue were correlated and occurred concurrently towards the end of inspiration. If tongue movement was observed, people with more severe OSA had larger movement and moved more compartments (up to four) to maintain airway patency, while people without OSA moved only one compartment. These results suggest that airway patency is preserved during wakefulness in people with OSA via active dilatory movement of the genioglossus. Abstract Maintaining airway patency when supine requires neural drive to the genioglossus horizontal and oblique neuromuscular compartments (superior fan‐like and inferior horizontal genioglossus, regions that are innervated by different branches of the hypoglossal nerve) to be coordinated during breathing, but it is unknown if this coordination is altered in obstructive sleep apnoea (OSA). This study aimed to assess coordination of airway dilatory motion across four mid‐sagittal tongue compartments during inspiration (i.e. anterior and posterior of the horizontal and oblique compartments), and compare it in controls and OSA patients. Fifty‐four participants (12 women, aged 20–73 years) underwent dynamic ‘tagged’ magnetic resonance imaging during wakefulness. Ten participants had no OSA [apnoea hypopnoea index (AHI) < 5 events h–1], 14 had mild OSA (5 < AHI ≤ 15 events h–1), 12 had moderate OSA (15 < AHI ≤ 30 events h–1) and 18 had severe OSA (AHI > 30 events h–1). A higher AHI was associated with a greater anterior movement of the anterior and posterior horizontal compartments (Spearman, r = −0.32, P = 0.02 for both), but not in the oblique compartments. If movement was observed, higher OSA severity was associated with an anterior movement of a greater number of compartments. Controls only moved the posterior horizontal compartment while the anterior horizontal compartment also moved in OSA participants. Oblique compartments moved only in people with severe OSA. The maximal anterior inspiratory movement of the four compartments was highly correlated (Spearman, P < 0.001) and occurred concurrently. The posterior horizontal compartment had the greatest anterior motion. These results suggest that airway patency is preserved during wakefulness in people with OSA via active dilatory movement of the genioglossus.

Study Objectives To investigate the effect of upper airway fat composition on tongue inspiratory movement and obstructive sleep apnea (OSA). Methods Participants without or with untreated OSA underwent a 3T magnetic resonance imaging (MRI) scan. Anatomical measurements were obtained from T2-weighted images. Mid-sagittal inspiratory tongue movements were imaged using tagged MRI during wakefulness. Tissue volumes and percentages of fat were quantified using an mDIXON scan. Results 40 predominantly overweight participants with OSA were compared to 10 predominantly normal weight controls. After adjusting for age, BMI and gender, the percentage of fat in the tongue was not different between groups (ANCOVA, P=0.45), but apnoeic patients had a greater tongue volume (ANCOVA, P=0.025). After adjusting for age, BMI and gender, higher OSA severity was associated with larger whole tongue volume (r=0.51, P&lt;0.001), and greater dilatory motion of the anterior horizontal tongue compartment (r=-0.33, P=0.023), but not with upper airway fat percentage. Higher tongue fat percentage was associated with higher BMI and older age (Spearman r=0.43, P=0.002, and r=0.44, P=0.001, respectively), but not with inspiratory tongue movements. Greater inspiratory tongue movement was associated with larger tongue volume (e.g. horizontal posterior compartment, r=-0.44, P=0.002) and smaller nasopharyngeal airway (e.g. oblique compartment, r=0.29, P=0.040). Conclusions Larger tongue volume and a smaller nasopharynx are associated with increased inspiratory tongue dilation during wakefulness in people with and without OSA. This compensatory response was not influenced by higher tongue fat content. Whether this is also true in more obese patient populations requires further investigation.

Study Objectives To characterise how mandibular advancement splint (MAS) alters inspiratory tongue movement in people with obstructive sleep apnoea (OSA) during wakefulness and whether this is associated with MAS treatment outcome. Methods 87 untreated OSA participants (20 women, apnoea hypopnoea index (AHI) 7-102events/hr, aged 19-76years) underwent a 3T MRI with a MAS in situ. Mid-sagittal tagged images quantified inspiratory tongue movement with the mandible in a neutral position and advanced to 70% of the maximum. Movement was quantified with harmonic phase methods. Treatment outcome was determined after at least 9 weeks of therapy. Results 72 participants completed the study: 34 were responders (AHI&lt;5 or AHI≤10events/hr with &gt;50% reduction in AHI), 9 were partial responders (&gt;50% reduction in AHI but AHI&gt;10events/h), and 29 non-responders (change in AHI &lt;50% and AHI ≥10events/rh). Sixty two percent (45/72) of participants had minimal inspiratory tongue movement (&lt;1mm) in the neutral position, and this increased to 72% (52/72) after advancing the mandible. Mandibular advancement altered inspiratory tongue movement pattern for 40% (29/72) of participants. When tongue dilatory patterns altered with advancement, 80% (4/5) of those who changed to a counterproductive movement pattern (posterior movement &gt;1mm) were non-responders, and 71% (5/7) of those who changed to beneficial (anterior movement &gt;1mm) were partial or complete responders. Conclusions The mandibular advancement action on upper airway dilator muscles differs between individuals. When mandibular advancement alters inspiratory tongue movement, therapeutic response to MAS therapy was more common among those who convert to a beneficial movement pattern.