168. Establishing Craniometric Data For Evaluating Micrognathia In Neonates With Pierre Robin Sequence: A Case-control Study

PURPOSE: The diagnosis of micrognathia is largely unstandardized and may rely on subjective assessments of the craniofacial surgeon. Moreover, there is a paucity of data presenting the mandibular craniometrics of healthy neonates and neonates with Pierre Robin Sequence (PRS). The purpose of this study was to compare the craniometric data of neonates with Pierre Robin Sequence with age-matched controls to better understand the mandibular anatomic differences in PRS and, in extension, the anatomical context of micrognathia and airway obstruction in these patients. METHODS: Computed Tomography (CT) scan data of the head for 25 patients with PRS (mean age 15 days) and 25 age-matched controls (mean age 14 days) were identified and included for analysis. Three dimensional reconstructions were generated and standardized craniometric measurements were performed. Statistical analysis was then performed, identifying statistically significant anatomic differences between the two cohorts. RESULTS: While establishing a craniometric dataset for control mandibles and those with PRS, significant craniometric differences were found. The degree of asymmetry in PRS body length was significantly higher than in control mandibles (p=0.006). For all other asymmetry indices, PRS mandibles were not significantly different than controls. PRS measurements significantly larger than control measurements included intercondylar distance (p = 0.044), intergonial distance (p=0.008), pogonion-interdental distance (p=0.015), ramus height (p=0.001), and ramus height to body length ratio (p<0.001). PRS measurements significantly smaller than control measurements included intercondylar angle (p<0.001), body length (p<0.001), pogonion lateral condyle distance (p<0.001), and 3D overjet distance (p=0.001). CONCLUSION: These findings indicate that micrognathia is constituted by a wide and antero-posteriorly short mandible for its height. Moreover, asymmetry is common in condyles and rami of control mandibles. Except body length, the mandibles of neonates with PRS are not differently asymmetrical than controls. The results may explain how mandibular structural differences reduce oral cavity space and promote glossoptosis and subsequently airway obstruction in PRS.