Suture Fusion, Cephalic Index, and Head Shape in Non-syndromic Sagittal Craniosynostosis

Abstract

INTRODUCTION: Sagittal craniosynostosis may present with complete or partial fusion of the sagittal suture.1 Previous studies describe high heterogeneity of phenotypic presentation for non-syndromic sagittal craniosynostosis in absence of particularly compelling evidence explaining such heterogeneity.1 One postulation for variation in head shape at presentation is degree and location of suture fusion; however, relationships between extent of sagittal suture fusion and head shape are currently poorly described.1 The aim of this study was to characterize the degree of sagittal suture fusion in a cohort of patients with non-syndromic sagittal craniosynostosis and determine associations with CI and head shape, including frontal bossing and occipital bulleting. METHODS: Patients with non-syndromic sagittal craniosynostosis at a tertiary care center with available CT imaging between 2014 and 2021 were retrospectively included in this study. Three-dimensional CT head images were imported into Materialise Mimics and parietal bones were manually isolated. The ‘measure’ tool was used to measure the distance of fused suture. The percentage of total sagittal suture fusion was quantified by dividing the distance of fused suture by the total length of the sagittal suture. Similar calculations were performed for anterior and posterior halves, and anterior, middle, and posterior thirds. Degree of sagittal suture fusion was compared to head shape characteristics, including cephalic index (CI), frontal bossing, and occipital bulleting, with Mann-Whitney U tests, Spearman’s correlations, and univariate and multivariate linear and logistic regression models. RESULTS: Ninety patients (69 male) were included in this retrospective study. The sagittal suture was on average 85.6 ± 20.1% fused, and 45 (50.0%) patients demonstrated complete fusion of the sagittal suture. CI was associated with increased degree of fusion for the anterior one-half (ρ = 0.26, p = 0.033) and anterior one-third (ρ = 0.30, p = 0.012) of the sagittal suture. Complete fusion of the anterior one-third of the sagittal suture predicted higher CI (β = 13.86, SE = 6.99, z = -0.25, p = 0.047). Logistic regression models revealed percentage of middle one-third sagittal suture fusion predicted the presence of frontal bossing (β = 2.42, SE = 0.96, z = 2.53, p = 0.012). Total degree of sagittal suture fusion was not predictive of CI or head shape in any analysis (all p > 0.05). CONCLUSION: Percentage of total sagittal suture fusion was not associated with CI or head shape in patients with non-syndromic sagittal craniosynostosis in this cohort. Decreased fusion of the anterior one-third of the sagittal suture was paradoxically associated with higher CI and more severe scaphocephalic head shape. These findings raise additional questions regarding suture fusion and head-shape morphology, and further research is needed to substantiate these results in patients with non-syndromic sagittal craniosynostosis. These findings may have implications for understanding suture fusion patterns in other variations of craniosynostosis. REFERENCE: 1. Di Rocco, F., Gleizal, A., Szathmari, A., Beuriat, P. A., Paulus, C., & Mottolese, C. (2019). Sagittal suture craniosynostosis or craniosynostoses? The heterogeneity of the most common premature fusion of the cranial sutures. Neurochirurgie, 65(5), 232-238.