Pharyngeal enlargement via tongue advancement differs with mandibular advancement therapy response and improves treatment prediction

INTRODUCTION: Mandibular advancement splint (MAS) treatment outcome prediction for obstructive sleep apnoea (OSA) is currently unreliable. Lower baseline AHI has been associated with better MAS response but is a poor predictor on its own. Imaging markers may enhance prediction. We investigate how the upper airway enlarges via posterior tongue advancement, using tagged MRI during mandibular advancement, as a potential predictor of MAS treatment response. METHODS: 101 untreated OSA participants (AHI 10–102 events/hr) underwent an MRI scan wearing a MAS. Mid-sagittal tagged MRI images were collected to quantify tongue movement during passive jaw advancement. Upper airway cross-sectional areas were measured with the mandible in a neutral position and advanced to 70% of the maximum protrusion. Treatment outcome was determined after a minimum of 9 weeks of therapy. RESULTS: 71 participants completed the study: 33 were responders (AHI<5 or AHI≤10 events/hr with >50% AHI reduction), 11 were partial responders (>50% AHI reduction but AHI>10 events/hr), and 27 non-responders (AHI reduction<50% and AHI≥10 events/hr). Responders had the greatest naso- and oropharyngeal tongue advancement (0.40±0.08 and 0.47±0.13mm, respectively) and oropharynx enlargement (6.41±2.12%) per millimetre of mandibular advancement. The inclusion of these imaging markers along with baseline AHI in a multivariate model classified more patients in the right MAS response group (69.2%) than a model based only on baseline AHI (50.0%) when the mandible was advanced by at least 4 mm. CONCLUSIONS: Tongue advancement and upper airway enlargement with mandibular advancement in conjunction with baseline AHI improves MAS treatment response categorisation to a satisfactory level.