Relationship between cephalometric characteristics and obstructive sites in obstructive sleep apnea syndrome

Patients with obstructive sleep apnea syndrome (OSAS) have characteristic dentofacial features, but the sites of obstruction differ greatly. The purpose of this study was to investigate the dentofacial characteristics of patients with OSAS with respect to the obstructive sites. The subjects consisted of 30 Japanese men with OSAS divided into 3 groups of 10 patients each. One group had obstruction at the retropalatal and retroglossal region (Rp + Rg group), a second group had obstruction at the retropalatal region (Rp group), and a third group had obstruction due to tonsillar hypertrophy (tonsillar hypertrophy group). To identify the Rp + Rg and Rp groups, dynamic magnetic resonance imaging (MRI) was used. To identify the tonsillar hypertrophy group, Mackenzie's classification, axial MRI, and the weight of the tonsils were used. A control group was composed of 10 Japanese men showing no symptoms suggestive of OSAS. Lateral cephalometric radiographs were obtained for all of the subjects, and analysis of variance was performed for the 46 cephalometric parameters. Among the many dentofacial characteristics of OSAS patients, the tendencies for retrognathia, micrognathia, and skeletal Class II were strongest in the Rp + Rg group and somewhat strong in the Rp group. The presence of a long soft palate was dominant in the Rp group, whereas the tendency for a long face was dominant in the tonsillar hypertrophy group. All of the groups shared the characteristic of having an inferior position of the hyoid bone. Based on the results of the current study, we conclude that many features of OSAS are specifically related to each obstructive type of OSAS.