Microscopic and endoscopic anatomical study of the extended transsphenoidal approach

Background Traditional transsphenoidal approach has less treatment effect in invasive pituitary adenoma. To remove tumors growing outside the sella become one of the challenges in neurosurgery. This study aims to study anatomical characteristics of the extended transsphenoidal approach for clinical operation. Methods A mimetic surgery was performed on 10 adult cadaver heads through extended transsphenoidal approach by endoscopy. The study data of related anatomic structures were measured. Results The distance from sphenoidal ostium to anterior nasal spine is (59.68 ± 4.28) mm (52.62-63.16 mm), to posterior nasal aperture is (12.88 ± 1.46) mm (10.47-15.61 mm). The incidence of optic nerve and internal carotid artery protuberance in the lateral wall of sphenoidal sinus is 11/20 and 17/20, respectively. The medial wall of the cavernous sinus is comprised of one dural layer. The incidence of anterior intercavernous sinus, posterior intercavernous sinus, inferior intercavernous sinus and basilar sinus is 17/20, 12/20, 11/20 and 20/20, respectively. The distance between the bilateral hidden segment of internal carotid artery is (15.30 ± 1.25) mm (12.42-21.76 mm), between the bilateral inferior horizontal segment midpoint is (14.03 ± 1.19) mm (10.42-18.43 mm), between the bilateral anterior vertical segment is (18.87 ± 1.44) mm (16.75-24.88 mm), and between the bilateral inner edge of tuberculum sellae is (12.73 ± 0.94) mm (9.97-16.18 mm). In 7 cases (7/20), the intracavernous carotid is in direct contact with the sellar part of the medial wall; in all cases (20/20), the venous plexus extends into the space between the intracavernous carotid and the sphenoidal part of the medial wall. The incidence of the intracavernous carotid coursing along the inferior one third of the pituitary gland is 9/20, along the inferior two thirds of the pituitary gland is 7/20, along the all the thirds of the pituitary gland is 3/20, while below the level of the sellar floor is only 1/20. In 4/20 of the cases, the pituitary gland projects outward. Conclusion The extended transsphenoidal approach can clearly expose the structures in cavernous sinus, and it is suitable for the treatment of pituitary adenoma invading the cavernous sinus from sella.