Cephalometric Assessment of Craniofacial Morphology in Patients With Treacher Collins Syndrome

Background and Purpose: Treacher Collins syndrome is an autosomal dominant craniofacial disorder affecting derivatives of the first and second branchial arches. Given the conflicting reports in the literature regarding the extent of anterior-posterior and vertical (superior-inferior) dysplasia of the cranial base, maxilla, and mandible, this study was designed to provide a comprehensive lateral cephalometric assessment of the craniofacial morphology of unoperated patients with Treacher Collins syndrome. Methods: The records of 45 patients with Treacher Collins syndrome registered at the Institute of Reconstructive Plastic Surgery of the NYU Langone Medical Center from the period of 1975 to 2008 were reviewed. Inclusion criteria included (1) patients between with the ages of 5 and 17 years, (2) no history of prior surgical intervention to correct skeletal deformity, and (3) diagnostic quality lateral cephalograms. Twenty patients satisfied the inclusion criteria with 12 male and 8 female patients in the sample and a mean age at the time of the lateral cephalogram of 8.8 years (range 5.2 to 16.7 years). Thirty angular and linear variables were measured to assess anterior-posterior and vertical (superior-inferior) position of the cranial base, maxilla, and mandible. Each patient's measurements were compared to age-matched and sex-matched control samples derived from the Moyers growth studies. The mean and standard deviation for each variable was then determined. Results: Lateral cephalometric analysis showed decreased anterior, posterior, and total cranial base lengths and a reduced cranial base angle. The anteroposterior dimension or length of the maxilla is deficient and the maxilla is positioned posteriorly with respect to the cranial base. Both anterior and posterior facial heights (superior-inferior dimension) are decreased. Lower face height is increased, whereas total face is decreased. The maxillary and functional occlusal planes are tipped upwards posteriorly. The mandibular morphology is characteristically small in both body length and total mandibular length, and the maximum ramus width is also deficient. The mandibular plane angle and gonial angle are increased. The mandible is retropositioned. Conclusions: A lateral cephalometric analysis is described that provides a skeletal basis for the hallmark clinical findings associated with Treacher Collins syndrome. This is of importance because an understanding of the underlying skeletal dysmorphology may shed light on the etiology and growth pattern, and impacts the overall treatment planning for skeletal correction.