Cephalometric Analysis of Pierre Robin Sequence

Objective: This study cephalometrically characterizes the facies of patients diagnosed with Pierre Robin Sequence (PRS) and compares the cephalometric measurements of PRS patients to: 1) standards of normal patients 2) standards of Angle Class II Div. 1 malocclusion 3) a population of isolated cleft palate (ICP) patients. Methods: Data was gathered from 11 PRS patients, 7 female, 4 male, ages 4-16. The comparison group consisted of 11 ICP patients, 7 female, 4 male, ages 4-15. The data for normal patients and for Class II Div. 1 patients were gathered from previously published standards. Direct comparison of means and standard deviations and z-score analysis were used to analyze the data. Results: Several features of the PRS patients varied from each of the three comparison groups. In reference to normal and to Class II Div. 1, the PRS had a larger mandibular plane angle, a flatter (smaller) palatal plane angle, a greater interjaw angle, a steeper ramal inclination, a normal gonial angle due to the steeper ramal inclination, a longer posterior cranial base, a shorter, more posteriorly positioned maxilla, a shorter mandibular ramus, a shorter mandibular body, a smaller SNA angle, and a smaller SNPg angle. The PRS patients were more similar to the ICP patients in each of the aforementioned features, in particular, the mandibular plane angle, the interjaw angle, the SNA angle, and the SNPg angle. Conclusion: There is significant difference between the PRS patients versus normal standards and versus Class II Div. 1 standards. The PRS patients are significantly similar to ICP patients, reflecting a gradual continuum of severity, with ICP being less severe and PRS being more severe. New findings include that PRS patients as compared to normal standards and to Class II Div. 1 have 1) a steeper ramal inclination and 2) a more posteriorly positioned maxilla.