The Tough Fibrous Tissue of The Supracondylar Groove As A Useful Landmark Via The Endoscopic Endonasal Approach To The Lower Clivus

Abstract Background: The hypoglossal canal (HGC) is the most important structural landmark for the endoscopic endonasal approach to access the lower clivus (LC). We explored the feasibility of using the tough fibrous tissue covering the supracondylar groove (SCG) as a useful landmark to identify the location of the HGC. Methods: Four cadaveric specimens were dissected and analyzed. The craniovertebral junction (CVJ) region was accessed utilizing 4-mm endoscope with either 0° or 30° lenses. CVJ exposure and the surgical corridor areas were measured. The relationship between the tough fibrous tissue covering the SCG and the HGC was analyzed.Results: Tough fibrous connective tissue was tightly attached the SCG and ran superomedially to inferolaterally. The angle between the horizontal plane and the long axis of the SCG was 30°. Separating the tough tissue inferolaterally, we could locate the external orifice (EO) of the HGC to further accurately isolate the hypoglossal nerve. Conclusion: The tough fibrous connective tissue covered the SCG to the upper part of the HGC EO. The course of the tough fibrous connective tissue was superomedial to inferolateral. Using the tough fibrous connective tissue covering the SCG as a landmark, it was possible to accurately locate the HGC EO via the endoscopic endonasal approach to access the LC.