Computed tomography quantitative analysis of cranial vault dysmorphology and severity of facial complex changes in posterior synostotic plagiocephaly patients

Background: Posterior synostotic plagiocephaly (PSP) impacts craniofacial skeleton. Study quantifies facial changes in children with PSP to investigate the impact of age and PSP severity at diagnosis on the facial dysmorphology. Material and methods: High-resolution preoperative CT images of 22 infants with PSP were analyzed. They were divided according to the early or late age at time of diagnosis. Each group was further subdivided according to the severity of PSP evaluated by the cranial vault asymmetry index (CVAI): mild-moderate PSP (CVAI between 3 and 12%) and severe PSP (CVAI > 12%). Analysis of the facial complex was performed. Each group was compared with age-matched healthy subjects. Results: All children exhibited unilateral lambdoid suture synostosis. The “early” diagnosis group consisted of 7 children with mild-moderate PSP while the “late” diagnosis group of 15 children in which 6 children had mild-moderate and 9 children severe PSP. All children showed altered position of glenoid fossae and mandibular asymmetry characterized by reduced mandibular diagonal distance length on the affected side while the subgroup of children with severe PSP detected in “late” diagnosis group had also altered mandibular inclination and reduced midfacial depth on both sides. Conclusions: PSP causes cranial base dysmorphology which drives changes in facial complex growth; the severity of facial changes mainly depends on the severity of cranial vault dysmorphology detected by CVAI. Mandible reshapes early under the stress of altered biomechanical forces of the skull base while changes in the maxilla are secondary to the asymmetric growth of the mandible and occur only in severe cases.