Orbital Foraminal Morphometrics in Non-Syndromic Unilateral Coronal Craniosynostosis

Abstract

Purpose : Non-syndromic unilateral coronal synostosis (UCS) is a rare congenital disorder that results from premature fusion of either coronal suture. The result is growth restriction across the suture, between the ipsilateral frontal and parietal bones, leading to bony dysmorphogenesis affecting the calvarium, orbit, and skull base. Prior studies have reported associations between UCS and visual abnormalities, however, to our knowledge, there have been no previous studies characterizing the morphology of orbital and periorbital osseous structures outside of the orbit. As such, there has not been any focus on objective correlation of anatomical measurements to the presence or absence or severity of visual defects.

Methods : The present study utilizes a novel geometric morphometric analysis to compare dimensions of orbital foramina on synostotic versus nonsynostotic sides in patients with UCS. Computed tomography (CT) head scans of pediatric UCS patients were converted into 3D mesh models. Anatomical borders of left and right orbital structures were plotted by a single trained team member. Dimensions between synostotic and nonsynostotic sides were measured and compared. Medical records were examined to determine prevalence of visual abnormalities in this patient cohort.

Results : Visual abnormalities were reported in 22 of the 27 UCS patients (77.8%). Astigmatism (66.7%), anisometropic amblyopia (44.4%), and motor nerve palsies (33.3%) represented the three most prevalent ophthalmologic abnormalities. Orbits on synostotic sides were 11.3% narrower (p<0.001) with 21.2% less volume (p=0.028) than orbits on nonsynostotic sides. However, average widths, circumferences, and areas were similar between synostotic and nonsynostotic sides upon comparison of supraorbital foramina, infraorbital foramina, optic foramina, and foramina ovalia.

Conclusions : Therefore, previously proposed compression or distortion of vital neurovascular structures within bony orbital foramina does not seem to be a likely etiology of visual abnormalities in UCS patients. Future studies will examine the role of ocular and/or neuro-ophthalmologic pathology in this disease process.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Morphometric comparisons of orbits and orbital foramina, synostotic vs. nonsynostotic sides

 

Prevalence of Eye Condition in Study Cohort vs. General Population