125. Addressing Facial Asymmetry and Craniofacial Microsomia For Gender-affirming Reconstruction

PURPOSE: A secondary benefit of modern craniofacial technology is the resulting library of high-quality anatomical data. Performing a thorough clinical exam and constructing 3D surgical plans for transgender and gender diverse (TGD) adults undergoing facial gender-affirming surgery (FGAS) has created a unique opportunity to describe variations in facial asymmetry, particularly craniofacial microsomia (CFM), that have not been well described in adults. While CFM is characterized by same-sided hypoplasia of the skeleton and soft tissues, there is no universal precise definition and estimates of its incidence vary widely from one in 3,500 to 40,000 births. Therefore, this study analyzes facial asymmetry and CFM among individuals undergoing FGAS and discusses appropriate surgical strategies. METHODS: Adults registered male at birth who completed FGAS or surgical planning for an upcoming FGAS from 2020 to 2024 without a prior facial surgery were retrospectively reviewed. CFM was diagnosed in patients with same-sided hypoplasia in multiple features including skeletal structures (mandible, maxilla, zygoma), malar soft tissue, nerves (mandibular or buccal nerve branches), and the external ear. The OMENS classification was used to characterize orbital asymmetry, mandibular hypoplasia, ear anomaly, nerve impairment, and soft tissue deficiency on a scale of 0 (normal) to 3 (most severe). Descriptive statistics, Fisher’s exact tests, and Mann-Whitney U tests were performed. RESULTS: Among 175 patients with a median age of 28.0 (interquartile range, IQR: 24.0-34.0) years, 10 were diagnosed with unilateral CFM (5.7%) and demonstrated greater asymmetry compared to their non-CFM counterparts (total OMENS score of 5.0 (IQR: 4.0-6.0) vs. 0.0 (IQR: 0.0-1.0), respectively, p<0.001). All patients with CFM had mandibular hypoplasia, demonstrating an average ramus height asymmetry of 6.0±2.9 mm, as well as a chin cant and deviation (90.0%) or chin deviation alone (10.0%). Discrepancies in orbital position were noted in three patients, while four displayed mild ear hypoplasia. The entire CFM cohort exhibited malar soft tissue hypoplasia and a deviated septum. House Brackmann grade II was also observed in all patients with CFM particularly in the buccal (70.0%) and mandibular branches (40.0%). Overall, asymmetry in at least one facial feature was commonly observed throughout the entire cohort regardless of a CFM diagnosis (83.4%). In addition, varying surgical maneuvers were performed. Patients with CFM who underwent an osseous genioplasty required more uneven vertical lengthening to correct for chin cants, whereas patients without CFM underwent equivalent vertical repositioning (3.5 (IQR: 0.0-4.2) mm vs. 0.0 (IQR: 0.0) mm, respectively, p<0.001). No statistically significant differences in other procedures were identified; however, patients with CFM tended to require slightly more uneven mandibular contouring and malar fat grafting than the unaffected cohort. CONCLUSIONS: Based on our analysis of TGD adults, the true prevalence of CFM may be substantially higher than previously estimated. The primary difference in surgical maneuvers for individuals with CFM seeking FGAS is the osseous genioplasty to address mandibular asymmetry.