Endoscopic Endonasal Trans-Agger Nasi Approach for Resection of Ossifying Fibroma Involving the Anterior Skull Base: Surgical Anatomy and Technical Note

Objective A variety of approaches for resection of the ossifying fibromas in sinonasal cavities have been described. However, for those involving the anterior skull base, endoscopic surgery remains challenging because of limitations in identification of tumor boundaries from the anterior skull base and proper control of the tumor-feeding vessel. This study aimed to describe a technique for resection of ossifying fibromas involving the anterior skull base through an endoscopic endonasal trans-agger nasi approach, based on anatomic studies and surgeries. Methods Two human cadaveric heads were prepared for study of the anatomic relationship between agger nasi and anterior skull base. Two clinical cases were used to illustrate the technique and feasibility of the approach. Results The agger nasi was located anterior and inferior to the frontal ostium and the anterior skull base. The frontal ostium and anterior skull base could be visualized and accessed under the 0-degree endoscope by removing the agger nasi. Application of the endoscopic endonasal trans-agger nasi approach in the two patients resulted in complete resection of the tumors with no surgical complications. Conclusions An endoscopic endonasal trans-agger nasi approach provides a direct access to the anterior skull base. It would be feasible, effective, and safe for selected cases of ossifying fibroma involving anterior skull base.