Anatomic Study About Endoscopic Endonasal Approach To The Midline Skull Base

Objective:The aim of study was to understand the endoscopic anatomical landmarks and the extent of exposure to the midline skull base by endoscopic endonasal approach, and to discuss the feasibility of exposing the midline skull base, the indication of the approach and prevention of complications.Methods:Forty fresh adult cadaver heads whose arterial and ventracal system was injected with latex and keeped in75%alchol for5days. Endoscopic endonasial dissections were performed using a rigid endoscope ((AESCULAP, Germany) with4mm indiameter,18cm in length, and equipped with0°,30°and45°lenses. An extended endoscopic endonasal approach to the midline skull base was made through two nostrils in all cases to measure the distance between main anatomical landmarks and area of exposure.Results:During the step in nasal, the detailed endoscopic anatomy consisted of the inferiorturbinate, the middle turbinate, superior turbinate, nasal septum, choana, speno-ethmoidrecess and the sphenoidal ostium. During the step involve the clivus, the endoscopic anatomy landmark was composed of the sellae floor, tuberculum sellae, sphenoidal planum, anterior ethmoidal cell, posterior ethmoidal cell, clivus recess, optic-carotid recess, optic protuberance, carotid protuberance. The mean maximum distance between the two medial orbital walls was34.7±3.5mm, The the anterior and posterior ethmoidal arteries was17.1±2.8mm, The distance between bilateral optic-carotid recess was15.3±2.2mm, the width of sallae was19.8±3.9mm, between anterior and posterior margin was9.1±1.5mm, the distance from sellae to the anterior margin of foramen magnum was39.6±4.3mm, from sallae to clivus recess was16.2±3.7mm, the distance between the two crotid arterys in the clivus was16.8±3.5mm.Conclusions:The endoscopic endonasal approach could export the anterior, medial and posterior skull base, and provide wide and clear operative field, it is a minimally invasive technique to approach the midline skull base. Adequate endoscopic skill and ample endoscopic anatomy were required for clinical application of this approach.