Coronal ring involvement in patients treated for unilateral coronal craniosynostosis

The etiopathology of the clinical entity normally referred to as unilateral coronal synostosis is commonly used to connote unilateral fusion of the frontoparietal suture. However, other sutures in the coronal ring may exhibit synostosis concomitant with or independent from frontoparietal synostosis and give rise to similar clinical phenotypes. This study retrospectively analyzes high-resolution computed tomographic data sets to determine patency of sutures within the coronal ring. Computed tomographic scan digital data from 33 infants who subsequently underwent surgical correction of unilateral coronal synostosis were assessed for sutural patency using Analyze imaging software. The frontosphenoidal suture was subdivided into intraorbital frontosphenoidal and extraorbital frontosphenoidal portions, and the patency of the frontoethmoidal suture was also assessed. Patients were sorted into two groups on the basis of the status of their frontosphenoidal sutures: group 1 had patent frontosphenoidal but synostotic frontoparietal sutures (n = 21) and group 2 had both frontosphenoidal and frontoparietal synostoses. Observer reproducibility was tested. The vertical and horizontal dimensions of the bony orbit and the endocranial base deflection angle were measured with the observer blinded with regard to sutural status group. Frontoethmoidal synostosis was not noted in any patients in either group. Two patients had no frontoparietal suture synostosis with isolated intraorbital frontosphenoidal and extraorbital frontosphenoidal suture closures. Suture diagnosis reproducibility was 99 percent. In group 1, the ipsilateral-to-contralateral vertical orbit dimension ratio averaged 1.11, whereas in group 2 it averaged 1.04 (p < 0.05). The ratio of horizontal orbit measurements was not significantly different between groups. In both groups, the endocranial base was deflected ipsilateral to the synostotic frontoparietal suture, with an average angle of 12 degrees in group 1 and 17 degrees in group 2 (p < 0.005). The extent of synostosis along the coronal sutural ring contributes to the dysmorphology of the orbit and the endocranial base deflection in patients whose clinical phenotypic diagnosis is unilateral coronal synostosis.