title: Three-dimensional assessment of anatomical balance and oral appliance treatment outcome in obstructive sleep apnoea.
abstract: OBJECTIVE
  Mandibular advancement splints (MAS) are an effective treatment for obstructive sleep apnoea (OSA). However, MAS are not equally efficacious across all patients and the reasons are not well understood. Craniofacial and upper airway structure individually influence MAS response. We aimed to assess anatomical balance, defined as the ratio of upper airway soft tissue (ST) volume to maxillomandibular enclosure volume, between MAS treatment responders and non-responders.
  
  
  METHODS
  OSA patients (apnoea-hypopnea index (AHI) >10 h(-1)) were recruited for MAS treatment. Magnetic resonance imaging of the upper airway was performed during wakefulness without and with MAS in situ. Images were processed for volumetric analysis of upper airway soft tissues (tongue, soft palate, paraphayrngeal fat pads and lateral pharyngeal walls) and three-dimensional cephalometry to acquire intra-mandibular space area (IMA) and total maxillomandibular (Mm) volume. Anatomical balance ratios were compared between MAS treatment responders (AHI <10 h(-1) + 50 % reduction) and non-responders.
  
  
  RESULTS
  Image analysis was completed in 69 patients (68 % male, age 50.5 ± 10.1 years, BMI 29.6 ± 5.0 kgm(2), AHI 27.0 ± 14.7 h(-1)) including 36 responders. Soft tissue volumes did not differ between MAS responders and non-responders. Non-responders had increased ST/IMA compared to responders (4.9 ± 0.6 vs. 4.6 ± 0.6, p = 0.031). In multivariate logistic regression with AHI and BMI, ST/IMA was the only predictive variable (p = 0.036, ROC AUC 0.7). However, changes in ST/Mm did not directly relate to treatment response.
  
  
  CONCLUSIONS
  Anatomical imbalance assessed by intra-mandibular space area was associated with poor MAS treatment response. However, changes in anatomical balance with mandibular advancement did not reflect treatment outcome as static imaging may not adequately capture improvements in upper airway function.
authors.affiliation: Centre for Sleep Health and Research, Department of Respiratory Medicine, Royal North Shore Hospital, and Sydney Medical School, University of Sydney, Acute Services Building 8A Reserve Road, St Leonards, NSW, 2065, Sydney, Australia. Kate.sutherland@sydney.edu.au.|Woolcock Institute of Medical Research, University of Sydney, Sydney, Australia. Kate.sutherland@sydney.edu.au.
authors.forename: Kate
authors.initials: K
authors.lastname: Sutherland
authors.affiliation: Centre for Sleep Health and Research, Department of Respiratory Medicine, Royal North Shore Hospital, and Sydney Medical School, University of Sydney, Acute Services Building 8A Reserve Road, St Leonards, NSW, 2065, Sydney, Australia.
authors.forename: Andrew S L
authors.initials: AS
authors.lastname: Chan
authors.affiliation: Centre for Sleep Health and Research, Department of Respiratory Medicine, Royal North Shore Hospital, and Sydney Medical School, University of Sydney, Acute Services Building 8A Reserve Road, St Leonards, NSW, 2065, Sydney, Australia.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Cistulli
mesh_terms: D000328:Adult; D002508:Cephalometry / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D019186:Mandibular Advancement / Q000295:instrumentation*; D008875:Middle Aged; D010160:Palate, Soft / Q000033:anatomy & histology; D010614:Pharynx / Q000033:anatomy & histology; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis / Q000628:therapy*; D014059:Tongue / Q000033:anatomy & histology; D016896:Treatment Outcome
keywords: Anatomical balance; Magnetic resonance imaging; Mandibular advancement; Obstructive sleep apnoea; Oral appliances; Upper airway
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