Relation between Metopic Suture Persistence and Frontal Sinus Development

Abstract

The frontal bone develops as two halves, which further unite in a single bone by the closure of the mid-sagittal metopic suture, typically by the end of the first postnatal year. The frontal sinus begins to expand into the orbital and vertical plates of the frontal bone postnatally and reaches the level of the nasion by the fourth year of age. At this time, the metopic suture is usually entirely closed. However, in the cases of failed closure of the metopic suture, its relationship to the frontal sinus development is still obscure. Here, we review the relevant literature and discuss the frontal bone development and maturation, from the viewpoint of the frontal sinus pneumatization in relation to the metopic craniosynostosis and failed closure of the metopic suture. The peculiar to the metopic skulls frontal bone configuration is rather an expression of the underlying neural mass demands than a consequence of the metopic suture persistence. Furthermore, the persistent metopic suture is frequently associated with a frontal sinus underdevelopment. It seems that the metopic suture does not inhibit the frontal sinus pneumatization itself, but rather both traits are an expression or an aftereffect of a certain condition during the early development.

Metopic skull with occipitalisation of the atlas

“…In this case, the cranium is of medium size without any obvious deformations in its shape and size. Metopism is frequently associated with underdevelopment of the frontal sinus [17,19,20,23,24]. However, in the reported case all paranasal sinuses are well-developed.…”

“…Metopic crania have distinctive cranial morphology [26,27,29] with frequently manifested supernumerary calvarial bones, remnants from embryonic sutures [9,21,26,35] and underdeveloped frontal sinus [23,24]. They demonstrate a general delay in calvarial sutures closure [28] and a wide array of midline closure defects [37].…”

Variation, sexual dimorphism, and enlargement of the frontal sinus with age in adult South Africans

“…Finally, there is some evidence that a complete persistent metopic suture affects the presence and/or size of a frontal sinus (Guerram et al, 2014;Nikolova et al, 2016Nikolova et al, , 2018 Despite the claim by Bilgin et al (2013) that no reasonable explanation has been provided for this association, it is perhaps a reasonable expectation insofar as a complete suture extending from nasion to bregma will result in a wide separation of the left and right pneumatic spaces. On the other hand, while the suture itself should theoretically not affect the superior expansion of either sinus, there may be an indirect relationship between a persistent metopic suture and sinus size if the mechanisms that result in persistent metopism also affect the development of the frontal sinuses (Nikolova et al, 2019). Regardless, and in light of the evidence published to date, we excluded two (2) individuals (both female) who exhibited persistent full metopism from the sample.…”

Anatomic variations in the frontal and occipital bones: a comparative study of neurocranial morphology

“…The unusual obliteration of the squamous suture has been found to be related to slight bilateral differences in the middle and posterior part of the neurocranium (Nikolova et al, 2021a). It has also been found that the condition of a bipartite frontal bone in adult individuals, known as metopism, is related to specific characteristics including frontal sinus underdevelopment (Nikolova et al, 2018a(Nikolova et al, , 2018b, significant delay of sagittal suture closure (Nikolova et al, 2022a), supernumerary bones (Hanihara and Ishida, 2001a;Nikolova et al, 2016Nikolova et al, , 2020, and modification of cranial morphology (Nikolova et al, 2021b(Nikolova et al, , 2022b. Metopism has been reported to occur in different population groups with varying frequencies from 0% to exceeding 15% (Berry and Berry, 1967;Hauser and De Stefano, 1989;Hanihara and Ishida, 2001a;Zdilla et al, 2018) The squamous part of the occipital bone is composed of interparietal and supraoccipital parts.…”