Volumetric analysis of the pharynx in patients with obstructive sleep apnea (OSA) treated with maxillomandibular advancement (MMA).

Introduction: Maxillomandibular advancement (MMA) has been reported to be the most effective surgical treatment of obstructive sleep apnea (OSA). Most reports about MMA aim to confirm the efficiency of this treatment modality, but few describe the anatomical changes produced in the pharynx by the surgery. Thus, the objective of the present investigation was to quantify the anatomical changes of the pharynx that occur in patients with OSA after MMA surgery using magnetic resonance (MR).

Methods: Twenty patients with a polysomnographic diagnosis of OSA participated in the study. All patients were submitted to image acquisition by MR performed during wakefulness. Polysomnography and MR were performed preoperatively and 6 months after MMA. Volume analysis (in cubic millimeters) was performed as the sum of the areas multiplied by their thickness, with no intervals between sections. The pharyngeal air space of the region between the hard palate and the base of the epiglottis was divided into a retropalatal (RP) region and a retrolingual (RL) region.

Results: Postoperative MR showed a mean volumetric increase of 26.72 % in the RP region and of 27.2 % in the RL region.

Discussion: MMA increases the air space of the pharynx by expanding the facial skeletal structure to which the soft tissues of the pharynx and tongue are fixed, with a consequent reduction of collapsibility in the presence of negative pressure during inspiration. This reduced possibility of pharyngeal collapse may contribute to the reduction of obstructive events.