Orbito-facial dysmorphology in patients with different degrees of trigonocephaly severity: quantitative morpho-volumetric analysis in infants with non-syndromic metopic craniosynostosis

Purpose: Craniofacial dysmorphology varies significantly along a wide spectrum of severity in metopic cranial synostosis (MCS). This study aimed to quantify craniofacial changes, in MCS, to investigate their relationships with the severity of trigonocephaly. Methods: By combining the metopic ridge and interfrontal angles, we identified three groups of trigonocephaly severity (mild group n.14, moderate group n.19, severe group n.18). We perform a quantitative analysis using high-resolution CT images evaluating (1) cranial fossae dimensions; (2) vault indices and ratios: interparietal/ intercoronal (IPD/ICD), interparietal/intertemporal (IPD/ITD), cephalic index, vertico-longitudinal index; (3) orbito-facial distances (midfacial depth, maxillary height, upper facial index, orbital distances, globe protrusions), maxilla and orbital volumes; (4) supratentorial (ICV) and infratentorial (PCFV) cranial volumes and supratentorial (WBV) and infratentorial (PCFBV) brain volumes. Results: In all groups, middle skull base lengths and upper midface index were increased. In moderate and severe groups: anterior hemifossa lengths were reduced, IPD/ICD and vertico-longitudinal index were changed; midfacial depth, anterior, mild, and lateral interorbital distances were reduced; globe protrusions were increased. The comparison between moderate and severe groups showed an increase of both globe protrusions and IPD/ICD. Among all groups, ICV and WBV were reduced in the severe group. Conclusion: This morpho-volumetric study provides new insights in understanding the craniofacial changes occurring in infants at different severity of trigonocephaly. The increase of globe protrusions and the reduction of supratentorial volumes found in the severe group reflect the severity of trigonocephaly; these findings might have a clinical and surgical relevance.