Maxillomandibular advancement surgery (MMA) has been described as the most effective surgical treatment for OSAHS, with success rates above 90%. Most studies on MMA aim to confirm the efficiency of this treatment modality, but few describe the anatomical changes produced by the surgery in the pharynx, with the exact mechanism by which MMA enlarges the pharynx being still unknown.

Objective: To quantify the anatomical changes of the pharynx that occurs in patients with OSAHS after MMA using magnetic resonance during wakefulness and during induced sleep.

Materials and methods: Twenty patients (15 males and five females) with a polysonographic diagnosis of OSAHS participated in the study. All patients were submitted to image acquisition by magnetic resonance performed during wakefulness and during Propofol-induced sleep performed preoperatively and six months after MMA.

Results: During induced sleep and wakefulness, MMA resulted in a significant mean increase ( p < 0.001) of approximately 33% in the pharyngeal area. The minimum pharyngeal area during induced sleep after MMA was 2.3 times greater than the minimum area measure preoperatively.

Conclusion: MMA promoted a significant increase of the pharynx in three-dimensional (MR) measurements, and during induced sleep it generated the maintenance of an airway opening, resulting in a lower possibility of collapse, contributing to a reduction of obstructive events.

Conflict of interest: None declared.