Extended endonasal approach to the anterior skull base: endoscopic anatomic study

Abstract

Objective To discuss the feasibility of using the extended endoscopic endonasal approach for exposing the anterior skull base,exploring surgical indications and preventing complications.Methods Endoscopic dissections were performed with the adjunct of neuronavigation using a rigid endoscope (Karl Storz) that was 4 mm in diameter,18 cm in length,and equipped with 0,30,and 45lenses.An extended endoscopic endonasal approach to the anterior skull base was made through two nostrils in all cases to measure the distance between the main anatomical landmarks and areas of exposure.Results A maximum lateral extension was obtained between the two medial orbital walls,separately at the base of crista galli (mean distance 34.1 ± 4.2 mm),and in the middle of the cribriform plate (mean distance 24.7 ± 3.1 mm).The distance between the bilateral anterior ethmoidal arteries was (26.8± 3.4) mm,and the distance between the bilateral posterior ethmoidal arteries was (24.3 ± 4.1) mm.In addition,the mean distance between the anterior and posterior ethmoidal arteries,at the level of lamina papyracea,was (17.9 ±2.7) mm.The area of the anterior skull base was (430.6 ±53.4) mm2 under the endoscopic view through this approach.Once the dura was opened,the recognizable structures were the olfactory nerves,the gyri recti of the frontal lobes,and the anterior interhemispheric fissure.Conclusion The extended endoscopic endonasal approach,guided by neuronavigation,could provide wider operative fields.Furthermore,it can be considered a minimally invasive technique to approach the anterior skull base.Adequate endoscopic skills,ample endoscopic anatomy,and reliable reconstruction techniques were required for the clinical application of this method. Key words: Endoscopy ; Endonasal approach; Anterior skull base