Three-dimensional Analysis of Phenotypic Variation in Mercedes Benz Craniosynostosis

Background: Mercedes Benz craniosynostosis is a rare tri-sutural closure pattern of the bilateral lambdoid and sagittal sutures. Variation due to the predominant deformational driving force leads to short and long phenotypes. This study aims to evaluate the volumetric and craniometrics differences between phenotypes and compare them to controls. Methods: Three-dimensional pre-operative CT scans of 15 patients with Mercedes Benz craniosynostosis were retrospectively reviewed along with age and gender-matched controls. The intracranial volume of the anterior, middle, and posterior fossa was calculated. Craniometric measurements included cranial index, frontal bossing angle, occipital bossing angle, and occipital bone angle. Results: The short phenotype was present in 60% of patients, and the long phenotype in 40%. The short phenotype volume was significantly greater in the anterior and middle fossa (P =.003; P =.002) and significantly less in the posterior fossa (P <.001). The volumes were not significantly different in the long phenotype. The cranial index was significantly greater in the short phenotype when compared to both the long phenotype and controls (P <.001; P =.006). Occipital bossing angle was significantly greater in the short phenotype than in controls(P =.029). The short phenotype had a significantly decreased occipital bone angle compared to the long phenotype and controls (P <.001; P =.001). Conclusion: The short phenotype has increased anterior and middle fossa and decreased posterior fossa volume. Long phenotype had no significant differences in volume distribution. The short phenotype has increased cranial index, increased occipital bossing angle, and decreased occipital bone angle. Craniometric measures were not significantly different in the long phenotype.