Anatomic variation in the pterygopalatine angle of the maxillary sinus and the maxillary bulla.

Bulges of the most posterior ethmoid air cells into the maxillary sinus were termed maxillary bullæ by Onodi. With few exceptions, they have since been ignored by anatomists through time. Likewise, Sieur cells-the spheno-ethmoido-maxillary air cells-are uncommonly found in anatomical texts. We therefore aimed to perform a retrospective cone beam computed tomography study on 50 patients to document the possibilities of anatomic variation in the situs of the orbital process of palatine bone-a variation related anatomically with the pterygopalatine fossa (PPF) and the respective angle of the maxillary sinus. Commonly occurring pneumatizations in this situs were the Sieur cell (58 %/64 % right/left side), and the maxillary recess of the sphenoidal sinus (20 %/22 % right/left side). Alone or in combination, these determined, but not exclusively, the maxillary bullæ. Uncommon pneumatizations in the anterior wall of the PPF were also found, such as a sphenoidal recess of the maxillary sinus, and lateral (maxillary, or pterygopalatine) recesses of the middle and superior, respectively, nasal meatuses. In two different cases, non-Haller, and non-Sieur posterior ethmoid air cells were found extruded posterior to the maxillary sinus. Significant statistical association indicated bilateral symmetry of Sieur's cell and of the maxillary recess of the sphenoidal sinus. It is important to identify such variant pneumatizations on a case-by-case basis in different surgical procedures and endoscopic corridors.

The pterygopalatine recess of the superior nasal meatus.

The pneumatizations surrounding the pterygopalatine fossa (PPF) and closely related to the sphenopalatine foramen are anatomically variable. During the assessment of a cone beam computed tomography of a 64-year-old male patient, we found bilaterally a previously unreported anatomic variant. This was represented by a lateral or pterygopalatine recess (PPR) of the superior nasal meatus which extended in the anterior wall of the PPF and protruded within the maxillary sinus to determine a maxillary bulla. The PPR was antero-superior to the sphenopalatine foramen. Additionally were found a right nasal septal deviation, seemingly compensated by a left middle concha bullosa and a left prominent ethmoidal bulla. The superior turbinates were also pneumatized. Such anatomic variants related to the pterygopalatine angle of the maxillary sinus should be explored prior to surgical or endoscopic procedures which target the maxillary sinus, the pterygopalatine fossa, or the skull base.

Regenerative potential of human schneiderian membrane: progenitor cells and epithelial-mesenchymal transition.

An innate osteogenic potential of the Schneiderian membrane (SM) is progressively assessed in studies ranging from non-human species to human subjects. It has relevance for endosteal placement and osseointegration. Nestin-expressing osteogenic progenitor cells are allegedly involved in bone formation and remodelling. Nestin phenotype was not assessed previously in human SM. We therefore aimed to fill that particular gap in the literature. Bioptic samples of human adult SM were obtained during surgery from eight adult patients, operated for non-malignant pathologies. Immunohistochemistry on paraffin-embedded tissue samples used primary antibodies against nestin, CD45, CD146, cytokeratin 7 (CK7), and alpha-smooth muscle actin (α-SMA). Nestin expression was consistently found in endothelial cells, and was scarcely encountered in pericytes, putative stromal stem/progenitor cells, as well as in glandular epithelial cells. Moreover, woven bone formation in the periosteal layer of the SM can also be regarded as evidence of the osteogenic potential of this membrane. Nestin and CD45 expression in cells of the primary bone supports the osteogenic potential of SM nestin-expressing cells and a possible involvement of hematopoietic stem cells in maxillary sinus floor remodeling. CD146, a known inducer of epithelial-mesenchymal transition (EMT), was expressed in epithelia, as was CK7. Isolated stromal cells were found expressing CD146, CK7 and α-SMA, suggesting that regenerative processes happening in the SM may also involve processes of EMT which generate stem/progenitor cells. This study provides additional evidence for the regenerative potential of the Schneiderian membrane and identifies potential roles for cells of its stem niche in osteogenesis.