Frontal Bone

Calvarial bones arise from two embryonic tissues, namely, the neural crest and the mesoderm. In this study we have addressed the important question of whether disparate embryonic tissue origins impart variable osteogenic potential and regenerative capacity to calvarial bones, as well as what the underlying molecular mechanism(s). Thus, by performing in vitro and in vivo studies, we have investigated whether differences exist between neural crest-derived frontal and paraxial mesodermal-derived parietal bone. Of interest, our data indicate that calvarial bone osteoblasts of neural crest origin have superior potential for osteogenic differentiation. Furthermore, neural crest-derived frontal bone displays a superior capacity to undergo osseous healing compared with calvarial bone of paraxial mesoderm origin. Our study identified both in vitro and in vivo enhanced endogenous canonical Wnt signaling in frontal bone compared with parietal bone. In addition, we demonstrate that constitutive activation of canonical Wnt signaling in paraxial mesodermal-derived parietal osteoblasts mimics the osteogenic potential of frontal osteoblasts, whereas knockdown of canonical Wnt signaling dramatically impairs the greater osteogenic potential of neural crest-derived frontal osteoblasts. Moreover, fibroblast growth factor 2 (FGF-2) treatment induces phosphorylation of GSK-3beta and increases the nuclear levels of beta-catenin in osteoblasts, suggesting that enhanced activation of Wnt signaling might be mediated by FGF. Taken together, our data provide compelling evidence that indeed embryonic tissue origin makes a difference and that active canonical Wnt signaling plays a major role in contributing to the superior intrinsic osteogenic potential and tissue regeneration observed in neural crest-derived frontal bone.

Premature closure of the metopic suture results in a growth restriction of the frontal bones, which leads to a skull malformation known as trigonocephaly. Over the course of recent decades, its incidence has been rising, currently making it the second most common type of craniosynostosis. Treatment consists of a cranioplasty, usually preformed before the age of 1 year. Metopic synostosis is linked with an increased level of neurodevelopmental delays. Theories on the etiology of these delays range from a reduced volume of the anterior cranial fossa to intrinsic malformations of the brain. This paper aims to provide an overview of this entity by giving an update on the epidemiology, etiology, evolution of treatment, follow-up, and neurodevelopment of metopic synostosis.

Using morphological, histological, and TEM analyses of the cranium, we provide a detailed description of bone and suture growth in zebrafish. Based on expression patterns and localization, we identified osteoblasts at different degrees of maturation. Our data confirm that, unlike in humans, zebrafish cranial sutures maintain lifelong patency to sustain skull growth. The cranial vault develops in a coordinated manner resulting in a structure that protects the brain. The zebrafish cranial roof parallels that of higher vertebrates and contains five major bones: one pair of frontal bones, one pair of parietal bones, and the supraoccipital bone. Parietal and frontal bones are formed by intramembranous ossification within a layer of mesenchyme positioned between the dermal mesenchyme and meninges surrounding the brain. The supraoccipital bone has an endochondral origin. Cranial bones are separated by connective tissue with a distinctive architecture of osteogenic cells and collagen fibrils. Here we show RNA in situ hybridization for col1a1a, col2a1a, col10a1, bglap/osteocalcin, fgfr1a, fgfr1b, fgfr2, fgfr3, foxq1, twist2, twist3, runx2a, runx2b, sp7/osterix, and spp1/ osteopontin, indicating that the expression of genes involved in suture development in mammals is preserved in zebrafish. We also present methods for examining the cranium and its sutures, which permit the study of the mechanisms involved in suture patency as well as their pathological obliteration. The model we develop has implications for the study of human disorders, including craniosynostosis, which affects 1 in 2,500 live births.

Background and Objectives: Frontal bone osteomas are benign tumors characterized by the abnormal proliferation of bone. Though typically asymptomatic, these masses often produce visible forehead deformity and may cause localized discomfort. Endoscopic resection has emerged as an optimal technique for appropriately selected frontal osteomas because it enables complete excision while minimizing visible scarring and risk of neurovascular injury. This case series reviews the senior author's patient outcomes and complications using a scalp-based, endoscopic-assisted surgical approach for frontal bone osteoma excision. Materials and Methods: A review was conducted of all patients (n = 22) who underwent endoscopic-assisted frontal bone osteoma excision performed by a single surgeon between February 2019 and December 2025. All procedures involved endoscopic visualization through remote scalp incisions, osteoma excision, and frontal bone contouring. Patient demographics, presenting symptoms, CT imaging findings, operative details, histopathology results, and postoperative outcomes were recorded. Results: Twenty-two patients underwent endoscopic-assisted excision of frontal bone osteomas performed by the senior author (NT). The primary concern prompting surgical intervention was aesthetic deformity, with localized pain reported in some cases. For all patients, CT imaging was obtained preoperatively to evaluate lesion size and anatomical relationships to nearby facial structures. Histopathology confirmed cortical bone consistent with osteoma in all cases. Postoperative swelling and ecchymosis were common in the first week but resolved spontaneously. No contour irregularities, fluid collections, residual bone, or sensory deficits were observed. Some alopecia was noted in the first three patients, prompting the senior author to modify the technique. All patients healed with small, flat, well-concealed scars adjacent to the hairline. Conclusions: This single-surgeon experience demonstrates that endoscopic-assisted excision of frontal bone osteomas is a safe and effective technique that permits complete excision with excellent aesthetic outcomes and minimal morbidity. The operative framework presented in this study, including surgical planning, technique steps, and postoperative management, supports endoscopic resection as an ideal alternative to traditional direct approaches for frontal bone osteomas.