Recent radiological studies have demonstrated that formation of the sphenoid sinus is preceded by a phase of fatty transformation of the bone marrow, and then by a phase of fat involution prior to the appearance of an aerated cavity and that this process can sometimes be interrupted, resulting in the persistence of images of arrested pneumatisation. The objective of the study was to confirm the existence of arrested pneumatisation in the sphenoid bone, and to investigate the presence of similar images in the maxilla, frontal and ethmoid bones.

In this single-centre, retrospective study, 207 CT scans with no signs of mucosal opacity or sinus retention performed for assessment of septorhinoplasty or chronic nasal dysfunction were reviewed according to Welker's criteria to detect images of arrested pneumatisation.

Twenty-two patients presented 30 images suggestive of arrested pneumatisation of the maxilla (13/30), sphenoid (10/30) and frontal (7/30) bones. No images of arrested pneumatisation were observed in the ethmoid bone.

The results of this study question the classical mechanisms of formation of the paranasal sinuses. According to the hypothesis of postnatal bone cavitation resulting from bone marrow involution and centripetal gas production, paranasal sinuses would constitute distinct organs that develop independently of the ethmoidal olfactory organ, which is formed from the embryonic cartilaginous olfactory capsule.