Isolated frontosphenoidal synostosis: a rare cause of synostotic frontal plagiocephaly

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Unilateral fusion of the frontoparietal suture is the most common cause of synostotic frontal plagiocephaly. Localized fusion of the frontosphenoidal suture is rare but can lead to a similar, but subtly distinct, phenotype.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>A retrospective chart review of the authors' craniofacial database was performed. Patients with isolated frontosphenoidal synostosis on CT imaging were included. Demographic data, as well as the clinical and radiographic findings, were recorded.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Three patients were identified. All patients were female and none had an identifiable syndrome. Head circumference was normal in each patient. The mean age at presentation was 4.8 months (range 2.0–9.8 months); 2 fusions were on the right side. Frontal flattening and recession of the supraorbital rim on the fused side were consistent physical findings. No patient had appreciable facial angulation or orbital dystopia, and 2 patients had anterior displacement of the ipsilateral ear. All 3 patients were initially misdiagnosed with unilateral coronal synostosis, and CT imaging at a mean age of 5.4 months (range 2.1–10.8 months) was required to secure the correct diagnosis. Computed tomography findings included patency of the frontoparietal suture, minor to no anterior cranial base angulation, and vertical flattening of the orbit without sphenoid wing elevation on the fused side. One patient underwent CT scanning at 2.1 months of age, which demonstrated a narrow, but patent, frontosphenoidal suture. The patient's condition was assumed to be a deformational process, and she underwent 6 months of unsuccessful helmet therapy. A repeat CT scan obtained at 10.7 months of age demonstrated the synostosis. All 3 patients underwent fronto-orbital correction at mean age of 12.1 months (range 7.8–16.1 months). The mean duration of postoperative follow-up was 11.7 months (range 1.9–23.9 months).</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Isolated frontosphenoidal synostosis should be considered in the differential diagnosis of atypical frontal plagiocephaly.</jats:p></jats:sec>

Isolated Unilateral Frontosphenoidal Craniosynostosis

“…1 To our knowledge, fewer than 25 patients of isolated frontosphenoidal craniosynostosis have been reported in the literature. 1,2,5,6,[12][13][14] As previously mentioned, the clinical diagnosis of this entity is challenging given the similarity in physical findings between isolated frontosphenoidal craniosynostosis, deformational plagiocephaly, and UCS. As such, misdiagnoses of this condition may also contribute to its low incidence.…”

“…2 Similarly, deformational plagiocephaly exhibits ipsilateral frontal flattening and contralateral frontal bossing, but may alternatively yield malar flattening, inferior and posterior displacement of the ipsilateral ear, and a narrowed ipsilateral palpebral fissure and eyebrow. 2,3,9 In addition to these aforementioned physical findings, secondary effects may occur on the orbital and midfacial growth, such as the harlequin phenomenon (associated with relative, or compensatory, 10 verticalization of the greater wing of the sphenoid), 11,12 which is pathognomonic of UCS. 6 These secondary effects play an important role in differentiating between the different etiologies of plagiocephaly and are important to consider during the diagnostic workup.…”

“…Nevertheless, there are clear phenotypic differences that can help make the diagnosis. 2 The phenotypic changes associated with isolated fusion of the frontosphenoidal suture have been variably described in the literature over the past 20 years since the first reported case and are now well-established. 2,12 Clinically, the facial appearance of frontosphenoidal synostosis is similar to that of UCS, except the ipsilateral maxilla is symmetric or slightly retruded and deviation of the nasal root, when present, is more frequently contralateral.…”

“…2 The phenotypic changes associated with isolated fusion of the frontosphenoidal suture have been variably described in the literature over the past 20 years since the first reported case and are now well-established. 2,12 Clinically, the facial appearance of frontosphenoidal synostosis is similar to that of UCS, except the ipsilateral maxilla is symmetric or slightly retruded and deviation of the nasal root, when present, is more frequently contralateral. 4,6,9,13 The chin point and sagittal suture are midline in frontosphenoidal synostosis, and the ipsilateral ear is symmetric or slightly posterior.…”

“…UCS is the most common cause of synostotic frontal plagiocephaly with an estimated incidence of 1:10,000 live births. 2,3 The distinct phenotypic differences present in frontosphenoidal synostosis may be overlooked and attributed to UCS or perinatal deformational forces, including those in utero and at the time of delivery. As such, many infants may be unsuccessfully treated with helmets.…”