Influence of mandibular advancement on tongue dilatory movement during wakefulness and how this is related to oral appliance therapy outcome for obstructive sleep apnea

Abstract

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<5 or AHI≤10events/hr with >50% reduction in AHI), 9 were partial responders (>50% reduction in AHI but AHI>10events/h), and 29 non-responders (change in AHI <50% and AHI ≥10events/rh). Sixty two percent (45/72) of participants had minimal inspiratory tongue movement (<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 >1mm) were non-responders, and 71% (5/7) of those who changed to beneficial (anterior movement >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.

Regional associations between inspiratory tongue dilatory movement and genioglossus activity during wakefulness in people with obstructive sleep apnoea

“…MRI and EMG experiments were performed an average of 2.5 ± 2.5 [0.0-12.1] weeks apart. Inspiratory tongue movement and patterns have been described previously in controls and OSA participants (Juge, Knapman et al, 2020).…”

“…Still, during wakefulness, it has been reported that both phasic inspiratory and tonic components of genioglossus EMG may be higher in people with OSA than in healthy control participants (Fogel et al, 2001), possibly to counteract the increased negative pressure in the upper airway during inspiration in people with OSA. Inspiratory airway dilatation during wakefulness is larger in those with narrower airways (Cheng et al, 2014) and with OSA (Juge, Knapman et al, 2020).…”

“…Participants were imaged using an Achieva 3TX MRI (Philips Healthcare, Best, The Netherlands) and a neurovascular coil during nasal breathing in wakefulness while lying supine. The detailed imaging and analysis protocols have been described previously (Juge, Knapman et al, 2020). In brief, we collected axial anatomical images with a turbo spin echo sequence to measure the nasopharyngeal upper airway cross-sectional area (behind the soft palate), where it is narrowest (Fig.…”

“…Previous definitions (Juge, Knapman et al, 2020) of four inspiratory dilatory patterns were used to classify regional tongue movement: (1) Minimal (anterior movement of all four neuromuscular compartments >1 mm); (2) En bloc (anterior movement of all four neuromuscular compartments <1 mm); (3) Oropharyngeal (anterior movement of the horizontal posterior compartment was <1 mm and the oblique posterior compartments >1 mm); and (4) Bidirectional (the two posterior compartments moved in opposite directions).…”

“…Airway patency is preserved during wakefulness in people with OSA via active stiffening and dilatory movement of the tongue, with the magnitude and spatial extent of this motion being greater in people with more severe OSA (Juge, Knapman et al, 2020). However, how much the tongue can move to dilate the airway is influenced by both neural drive and local mechanics .…”