The Foramen magnum in isolated and syndromic brachycephaly

Abstract

Though the foramen magnum (FM) is often altered in complex craniosynostosis, no study analysed the FM dimensions in patients with brachycephaly specifically. We measured the FM area, sagittal and transverse diameters on preoperative CT scans in patients with bicoronal synostosis (n = 40) and age-matched control group (n = 18). Our study included 16 children with FGFR3 p.Pro250Arg mutation (mean age 6.1months), 10 with TWIST-1 mutation (mean age7.6months) and 14 patients with isolated bicoronal synostosis (mean age 6.1). We observed a significantly smaller FM area in FGFR3 group compared to control group and isolated brachycephaly group (p = 0.001 and p = 0.038, respectively). The mean FM area in FGFR3 group was 426.13mm(2) (p = 0.001), while in TWIST-1 group was 476.34mm(2) (p = 0.103), and in isolated brachycephaly group 489.43mm(2) (p = 0.129) compared to control group: 528.90mm(2). The posterior segment of the sagittal diameter of the FM and its width as well as the bi-interoccipital synchondrosis diameters were significantly smaller in FGFR3 group compared to control group. In TWIST-1 group, the only altered dimension was the FM anterior segment of the sagittal diameter (p = 0.008). We did not observe any significant alteration of FM in patients with isolated brachycephaly compared to control group. The FM area is significantly altered in FGFR3-related brachycephaly, whereas in patients with Saethre-Chotzen syndrome (TWIST-1 mutation) the mean FM area is similar to control group. This study confirms the importance of FGFRs on FM growth whereas TWIST-1 seems to have a minor role.