A Anatomical Study Of Endoscopic Endonasal Approach For The Lesions Of Midline Skull Base Area

Objective For the purpose of guiding clinical practice, to study the anatomical features of endoscopic endonasal approach for the lesions of midline skull base area.Methods Ten human cadaver heads were dissected to perform the endoscopic endonasal approach for the lesions of midline skull base area. To study the areas can be explored, route and each area's anatomical features through this approach. Summarize the instructive anatomic landmarks can be used in surgical operations.Results Take the route through two nostrils and nasal septum mucosa, can significantly improve the convenience and expand the view in the operation. The anatomy of sellar region can be fully revealed through endoscopic endonasal approach. The anterior and posterior ethmoid sinus, superior and middle turbinate should be selectively removed as needed. Use the line between the bilateral opto-carotid recess (OCR) to locate. Open the skull base bone in the tuberculum sellae and sphenoid platform. Forward to expose midline anterior skull base area include both sides of the medial orbital wall and the frontal sinus. In the suprasellar area, the suprasellar cistern, cistern of the lamina terminalis, chiasmatic cistern, and the important structures within them can be exposed. We can enter the third ventricle through lamina terminalis. Use OCR and prominence of internal carotid artery to locate position, we can expose the medial and inferior wall of cavernous sinus. Vessels and nerves within cavernous sinus can be exposed by opening the medial and inferior wall. By removing the bone of clivus, mesencephalon, pons, medulla oblongata and the important blood vessels, nerves on their surface can be exposed. By performing surgical operation on cadaver heads, summarized the operative route and instructive anatomic landmarks of each region above. The length of the long axis of Sphenoid sinus ostia is 5.0±0.82mm(4～6mm), the length between inner edge of the bilateral sphenoid sinus ostia is 4.7±0.67mm(4～6mm).The length between nasal columella and Sphenoid sinus ostia, sellar floor, tuberculum sellae, inner edge of OCR, clivus , posterior ethmoid artery, anterior ethmoid artery is as follows: 52.6～78.3(63.4±7.6)mm, 63.8～90.1(75.7±8.2)mm, 71.4～92.5(80.5±6.4)mm, 73.5～93.6(82.6±6.3)mm, 76.4～96.8(84.8±6.8)mm , 64.5～87.5(74.4±7.1)mm, 60.3～77.5(67.8±5.6)mm. The length between inner edge of the bilateral OCR is 15.0～26.0(22.7±3.7)mm. The most distance between both sides of the medial orbital wall is 25.4～51.5(36.4±8.2)mm.Conclusion Endoscopic endonasal approach can be used for the lesions of whole midline skull base area. This approach significantly expand the view and explore more area in the operation, and of advantages such as directly to the lesions, avoid to drag brain tissue and vessels. Through comparing each anatomic landmark and the adjacent relationship of each structure, avoid to lose orientation.