In approximately 85% of cases, craniosynostosis affects a single suture, with the anatomical classification predicated on the involved suture [5]. The most prevalent form, accounting for 45–50% of all nonsyndromic craniosynostosis cases, is sagittal synostosis. Recent epidemiological studies indicate that approximately 25% of patients present with metopic synostosis, constituting the second most common form [3]. Coronal synostosis (unilateral or bilateral) comprises 17% of cases, while lambdoid synostosis is estimated to account for 1–5% of all nonsyndromic craniosynostosis [6].
About 15% of cases involve syndromic synostoses, often implicating multiple sutures, including at least bilateral coronal sutures [3]. Fusion of the sagittal and bilateral coronal sutures results in membranous bone expansion between the sutures, resembling a cloverleaf in Kleeblattschädel syndrome or a high, forward-tilted head in the form of acrocephaly seen in Apert syndrome. Craniosynostosis involving bilateral coronal and lambdoid sutures leads to forehead recession, resulting in a posteriorly inclined head and pointed skull shape associated with compensatory hypergrowth of the bregmatic fontanel, termed oxycephaly in Crouzon syndrome [7–9].
Apart from these syndromic craniosynostoses, a small subset of patients presents with a multisutural synostosis pattern where the underlying syndrome is not readily discernible. Czerwinski et al. conducted a retrospective analysis of 858 patients who underwent craniosynostosis treatment over an 18-year period and identified only 37 (4%) cases of nonsyndromic multisutural craniosynostosis [4]. In this study, metopic and sagittal suture synostosis (10 of 37), followed by bilateral lambdoid and sagittal suture synostosis (7 of 37), were most commonly observed [4]. Another study found sagittal and lambdoid synostosis to be the most prevalent forms of nonsyndromic craniosynostosis (6 in 20 cases of nonsyndromic multisutural craniosynostosis) [6].
Given that the metopic suture is a continuum of the sagittal suture and both run longitudinally at the center of the head, their fusion results in a prominent or broad forehead with frontal bossing, characteristic of scaphocephaly [10]. Bilateral lambdoid and sagittal synostosis, known as Mercedes-Benz pattern craniosynostosis, manifests as anterior turricephaly combined with mild brachycephaly [1, 11]. Flattening of the occipital bone with a sublambdoidal depression and a small posterior fossa compensated by frontal bone protrusion are typical features.
In the subgroup of multisutural, nonsyndromic, complex craniosynostoses, simultaneous involvement of the sagittal, metopic, and bilateral coronal sutures is exceedingly rare. Czerwinski et al. described only 3 cases (0.35% of craniosynostosis patients), while Boulet et al. identified just one case (0.42% of infants with craniosynostosis) [4, 6]. In our case, a distinctive head shape resulted from closure of the sagittal, metopic, and bilateral coronal sutures: flattening of the forehead and anterior skull, contrasting the typical Mercedes-Benz pattern craniosynostosis [1, 12]. Due to restricted anterior growth, a combination of scaphocephaly and trigonocephaly associated with brachycephaly was observed. The term "Scapho-trigo-brachicephaly" is proposed to designate this relatively rare form of multiple suture craniosynostosis.