Anatomic study and clinical significance of extended endonasal anterior skull base surgery.

Objective: This study is to investigate the anatomical relationship of endonasal approach for anterior skull base surgery, and to determine the boundaries between anterior basicranial craniotomy and the security of operative techniques. Materials and Methods: A total of 10 adult dry skulls and 13 adult cadaveric heads processed by formalin were examined under operating microscope. The micro-anatomic structures of the turbinate, sphenoid sinus, ethmoid sinus, anterior ethmoidal artery, posterior ethmoidal artery and anterior skull base were observed. Artificial anatomy was performed and the deep-seated regions of the surgical approach were observed under operating microscope and endoscope. Results: Examined from the intracranial and intranasal aspects, it was found that the middle turbinate, uncinate process, ethmoid bulla, lamina papyracea, anterior ethmoid canal, posterior ethmoid canal, prominence of the optic canal and opticocarotid recess were all important anatomic landmarks for surgery. The horizontal distances between medial orbital wall on both sides at the level of crista galli, anterior ethmoid canal, and posterior ethmoid canal were (22.31 +/- 3.08) mm, (23 +/- 2.93) mm, and (26.25 +/- 2.88) mm, respectively. The distance between the double optic canal cranial opening was (14.67 +/- 3.82) mm. Conclusions: During the endonasal approach for anterior skull base surgery, full advantage of the surgical corridor made by the middle turbinate resection should be taken. To control intraoperative bleeding, it is critical to identify anterior and posterior ethmoidal artery. Identification and protection of medial orbital wall and the optic nerve, and controlling the ranges of anterior basicranial craniotomy are of great importance for surgical safety.