Anatomical study of unilateral endoscopic endonasal transsphenoidal approach for sellar operation

Objective To study the identification of the endoscopic anatomical landmarks in the unilateral endoscopic endonasal transsphenoidal approach, and discuss the verification of the anterior wall of the sphenoid sinus and expansion of the bone exposure of the sellar region according to different growth patterns of the sellar tumors. Methods Ten formalin-fixed adult cadaveric heads and 5 fresh cadaveric heads were perfused with red silicone through the internal carotid artery, and blue glass cement was perfused through the internal jugular vein. The endoscope was introduced through the unilateral nasal cavity, and the contralateral nasal cavity was fully exposed by removing the superficial nasofacial structures for observation and measurement. Results The distance from the pharyngopalatine arch to the inferior edge of the sphenoidal ostium was 15.13±1.99 mm, and that from the inferior edge of the posterior middle turbinate to the center of the sellar floor was 10.20±0.15 mm. The content of the sphenoid sinus was 8.73±2.90 mL after removal of the compartment of the sphenoid sinus, with the sellar floor thickness of 3.68±1.96 mm. The angles between the nasal septum and the anterior wall of the sphenoid sinus varied significantly on different planes （P〈0.05）. Conclusion When difficult to locate the sphenoidal ostium, the opening site can be determined by observing the peculiar oval protuberance on the anterior wall of the sphenoid sinus, the relationship between the anterior wall of the sphenoid sinus and the middle turbinate, and the average distance from the superior limit of the pharyngopalatine arch to the sphenoidal ostium. The vomer on the midline position can be used as the landmark of the midline of the sellar floor. When the tumor has an extrasellar portion, as in the planum sphenoidale, the modified enlarged approach can be the choice. Key words: Neuroendoscope;  Single-nostril transsphenoidal approach;  Endoscopic anatomy