Morphologic Differences in Sagittal Synostosis with Age before Surgery

Abstract

agittal synostosis presenting with scaphocephaly is the most common form of craniosynostosis. 1 Various phenotypes have been described, including frontal bossing, occipital protuberance, bitemporal protrusion, and coronal constriction, 2 in addition to variations in treatment with regard to timing 3,4 and technique. 5-8 However, a commonality is to achieve an increase in parietal width and a decrease the cephalic index, as a measure of cranial length to width. 9 There are several considerations that go into the timing of surgical treatment of sagittal synostosis, including the technique used, 5-7 implications on neurocognitive function, 4,10 and the potential to prevent a progressive deformity. 11,12 It is important for us to understand which morphometrics are consistent or worsen with time before surgery, and which have the potential to improve. In this way, we can tailor our surgical interventions to the areas at highest risk of progressive deformity.

Morphometric Outcomes of Non-Syndromic Sagittal Synostosis following Open Middle and Posterior Cranial Vault Expansion

“…37 Patients presenting to our center at younger ages presented with more severe scaphocephaly and increased relative posterior vault volume suggesting occipital protuberance; children presenting at older ages presented with more severe middle vault constriction. 3 When assessing for predictors of long-term morphometric outcomes in SS, we found that preoperative severity was the best predictor across all measurements. Performing open middle and posterior cranial vault expansion at older ages was associated with longer skulls and higher posterior cranial vault volumes.…”

“…31 In addition to cephalic index differences, SS results in frontal bossing, midline occipital protuberance, and biparietal narrowing. 3 The anthropometric study by Fearon et al 25 also noted that there was a reduction in frontal bossing as measured by the minimal frontal breadth, without any direct surgical manipulation of the anterior cranium. This is consistent with our previous study suggesting the forehead dysmorphology of SS improves without an anterior cranial surgery, reporting normalization of the horizontal bossing ratio, vertical bossing ratio, and the frontal bossing angle 2 years after middle and posterior vault cranial expansion.…”

“…31 In addition to cephalic index differences, SS results in frontal bossing, midline occipital protuberance, and biparietal narrowing. 3…”

“…We placed standard craniofacial landmarks and study points on the CT scans using 3D Slicer. 13 Using our previously described custom software 3,14,15 developed with open-source image analysis libraries (ITK/VTK), 16,17 we calculated standardized measures of shape: traditional, 18 normative, 19 and altered 20 cephalic indices; frontal bossing angle 6 ; vertical-longitudinal index 21 ; forehead takeoff angle 22 ; and occipital incline angle. 22 All images were aligned to a coordinate system where sella-nasion defined the anteroposterior axis and the axial plane was defined by right porion, left porion, and sella.…”

“…) We calculated total intracranial volume and also measured anterior, middle, and posterior cranial volumes using the landmarks of the sella, pterion, and asterion as previously described. 3,23 All vector contours and volumes were systematically audited to ensure validity.…”