Extended Transsphenoidal Approach: Microscopic Anatomic Study With An Endoscope-assisted Technique And Imaging Anatomic Study

Objective (1) The goal of this study was to provide pertinent anatomic data and details for the clinical application of the extended transsphenoidal approach; to probe the anat- omic characteristic and method under microscope or under endoscope. (2) To investig- ate the feasibility of neuronavigation in study of the skull base anatomy so as to discuss the application of neuronavigation on microanatomy measurement.Methods (1) In the anatomic study, ten formalin-fixed, silicone-injected, adult cadaver- ic heads were used. A direct endonasal extended transsphenoidal approach was perform- ed with a microscopic and endoscopic technique. The direct microscopic and endoscopic views were taken photograph step by step. (2) Neuronavigation was used to measure some important anatomical parameters.Results (1) The olfactory cisterns, the chiasmatic cisterns, the terminal lamina cisterns, the internal carotid cisterns, and their internal strucutre, the cavernous sinus segment of internal carotid artery and the branches, the iterpeduncular cisterns, the prepontine cisterns, the premedullary cisterns, and their internal strucutre,could be exposed clearly by extended transsphenoidal approach. Compared with microsurgical transsphenoidal route, endoscopic transsphenoidal procedure provided a wider exposure in sellar and surrounding region. And surgical landmarks such as the recessus sphenoethmoidalis, the ostia of sphenoidal sinus, the prominence of internal carotid artery and the prominence of optic canal, the carotid artery optic recesses, the pharyngeal tubercle, and the anterior rim of great occipital foramen were established. (2) Some important anatomical parameters were measured on navigation system: Average distances from the anterior nasal spina to the ostia of sphenoidal sinus, sellar base, entrances of internal carotid artery and optic canal to cranial cavity, pharyngeal tubercle, and anterior rim of great occipital foramen were (57.61±5.18)mm, (72.83±6.75)mm, (67.27±6.27)mm, (68.89±6.51)mm, (78.27±5.74)mm, (91.08±5.20)mm; distance between bilateral foramen lacerum, distance between bilateral jugular tubercles, distance between bilateral jugular foramens, distance between bilateral internal carotid canal external aperture and distance between bilateral fissura petrooccipitalis at the level of the internal acoustic pores were (21.12±4.78)mm, (21.37±2.16)mm, (38.26±3.45)mm,(50.14±5.54)mm, (24.27±4.31)mm.Conclusion (1) An adequate exposure of the central skull base can be achieved via a simple, direct extended transsphenoidal approach with either a microscopic or endoscopic technique. The anatomic characteristics under endoscope were different from those under microscope. The application of the extended transsphenoidal approach under endoscope could provide more extensive vision and satisfied exposure to reach the area of the central skull base. (2) With the assistance of neuronavigation system, it could be advantageous in saving time and rendering more efficient in the study on microanatomy of skull base.