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

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 50% reduction in AHI), 9 were partial responders (>50% reduction in AHI but AHI>10events/h), and 29 non-responders (change in AHI 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.