Surgical techniques: Endoscopic transseptal approach (Video 1)
After lateralization of bilateral turbinates, the first incision was made anterior to the nasal septal body to avoid bleeding. The mucosal flap was elevated from the subperichondrial and continuing subperiosteal planes, followed by dissection superiorly to the perpendicular plate of the ethmoid bone, posteriorly to the sphenoid rostrum, laterally to the sphenoid sinus ostium, and inferiorly to the nasal floor. Another incision on the other side was made posterior to the nasal septal body to avoid perforation, followed by the same dissection. Partial removal of the perpendicular plate was performed, and we applied a Cottle nasal speculum between the septal flaps to establish a surgical corridor and to prevent unexpected injury to the septal mucosa and olfactory neuroepithelium (Fig. 1A and 1B). Then we performed sphenoidotomy by removing the rostrum. After creating a sufficient space for four-hand surgery, neurosurgeons removed the tumor until the arachnoid membrane descended (Fig. 1C and 1D). Finally, we repositioned the septal flaps and restore bilateral middle turbinates to the neutral position to prevent sinusitis. Bilateral incision wounds were left unsutured to facilitate drainage of exudate.