The Endocranial Bifrontal Angle: A Longitudinal Evaluation in Two Patients With Metopic Synostosis

Metopic craniosynostosis is the early fusion of the skull bones in the frontal region of the metopic suture, which leads to trigonocephaly and neurological sequelae. Severe metopic craniosynostosis is defined by an endocranial bifrontal angle less than 124°, and this serves as a threshold for neurological deficit and significant skull deformity, typically warranting surgical treatment.

Two patients presented for evaluation for metopic craniosynostosis. Low-dose computed tomography imaging was performed in both patients due to concern for underlying metopic craniosynostosis.

In both patients, imaging demonstrated an initial endocranial bifrontal angle greater than 124°. However, in subsequent evaluation, the children developed severe trigonocephaly, and an angle less than 124°.

The authors present 2 patients with metopic craniosynostosis, which became severe over time. The authors hypothesize that this may be due to an initial smaller head circumference, which later experienced rapid growth, leading to narrower endocranial bifrontal angle. Therefore, younger children with suspected metopic craniosynostosis, with initially smaller head circumference (but not meeting the threshold of 124°) should be followed longitudinally, as the head circumference may demonstrate greater narrowing subsequently into a more severe form of trigonocephaly and possibly surgery.