Progression of facial asymmetry in hemifacial microsomia

Hemifacial microsomia is a common craniofacial anomaly, variably affecting structures derived from the first and second pharyngeal arches. Correction of the skeletal deformity in children has been advocated to improve growth potential and reduce secondary deformity. However, contrary reports have su ggested that facial asymmetry in hemifacial microsomia does not increase wi th growth; therefore, skeletal correction can be postponed, even until adol escence. The purpose of this study was to test the hypothesis that facial a symmetry in hemifacial microsomia is progressive. This is a retrospective evaluation of 67 patients with untreated hemifacial microsomia. The patients were categorized as: group I (mandible type I, II a), n = 38, and group II (mandible type IIb, III), n = 29. Pretreatment pos terior-anterior cephalometric radiographs were used to analyze asymmetry by measuring the angle between the true horizontal and the following planes: piriform rim, maxillary occlusal plane, and intergonial angle. Angular meas urements were averaged for patients in the deciduous (<6 years), mixed (gre ater than or equal to 6<13 years), and permanent dentition (greater than or equal to 13 years). In group I, angle piriform rim, maxillary occlusal pla ne, and intergonial angle increased from 7.0, 4.3, and 4.4 to 8.4, 6.6, and 6.1 degrees, respectively [mean age, 4.1 (deciduous) to 8.6 (mixed) to 21. 0 (permanent) years]. In group TI, angle piriform rim, maxillary occlusal p lane, and intergonial angle increased from 9.5, 6.2, and 5.3 to 11.7, 7.6, and 8.0 degrees, respectively [mean age, 3.4 (deciduous) to 8.0 (mixed) yea rs]. These data demonstrate that hemifacial microsomia is progressive and unders cores the importance of early surgical correction of mandibular asymmetry i n this disorder.