Partial intracranial volumes in metopic synostosis – pre- and postoperative comparisons with healthy controls

Surgical intervention for metopic synostosis has been much debated but aims to correct trigonocephaly and hypotelorism while ensuring enough space for undisturbed brain growth. The aim of this study was to evaluate changes in partial intracranial volumes and the interfrontal angle following fronto-orbital advancement. Twenty-six non-syndromic metopic synostosis patients treated with fronto-orbital advancement at Uppsala University Hospital between 2012 and 2022 who had undergone computed tomography preoperatively and at age three were included, as well as 40 age- and sex-matched controls who had undergone computed tomography for post-traumatic evaluation. Demographic information, imaging, pre-, peri-, and postoperative data were collected. The frontal-, middle-, and posterior intracranial volume and their relative distribution were calculated in the softwares Craniosyn and ITK-SNAP 3.8.0. Preoperatively, patients had smaller interfrontal angles (p < 0.001), total intracranial volumes (p = 0.03), and frontal volumes (p = 0.02), compared with controls. At age three, the total intracranial volume (p = 0.96) and frontal volume (p = 0.51) did not differ significantly between patients and controls, whereas the interfrontal angle remained smaller in the synostosis group (p < 0.001). The relative intracranial volume distribution between frontal-, middle-, and posterior volumes did not match the distribution in healthy controls pre- or postoperatively, where the middle volume ratio was notably greater, and both the frontal- and posterior volume ratios were smaller in patients. Fronto-orbital advancement and subsequent growth improve the total- and partial intracranial volume in metopic synostosis to match the volumes of healthy controls at age three but does not restore the relative intracranial volume distribution.