Mandibular advancement splint response is associated with the pterygomandibular raphe.

Mandibular advancement increases the lateral dimensions of the nasopharyngeal airway via a direct connection from the airway to the ramus of the mandible. The anatomical structure in this region is the pterygomandibular raphe, but a tendinous component is not always present. Whether tendon presence influences treatment outcome is unknown. STUDY OBJECTIVES To investigate whether presence of tendinous pterygomandibular raphe could predict treatment outcome, and how it affects lateral wall mechanical properties. METHODS 105 subjects with obstructive sleep apnoea completed detailed anatomical MRI with and without mandibular advancement. The study design was case control. Variables were compared between participants with and without the tendon present. RESULTS Amount of maximum mandibular advancement decreased when pterygomandibular tendon was present (4.0 ± 1.2mm present versus 4.6 ± 1.4mm absent, p= 0.04). Pterygomandibular raphe tendon absent subjects had a lower post treatment apnea hypopnea index (16 ± 12 events/hour tendon present versus 9 ± 9 events/hour absent, p= 0.007) and were more likely to have complete response (63% versus 36%, p= 0.02). However, tendon absent subjects were more likely to not complete the study (χ 2 (3) =10.578, p= 0.014). Tendon absent subjects had a greater increase in midline antero-posterior airway diameter (1.6 ± 1.7 mm versus 0.6 ± 2.3 mm, p= 0.04). CONCLUSION When pterygomandibular raphe tendon is absent, treatment response and amount of maximum advancement improves, possibly at the expense of reduced splint tolerability. Tendon presence may help predict a group less likely to respond to mandibular advancement splint therapy.