Minimally Invasive Approaches for Optic Nerve Decompression: Comparison between EEA and Endoscopic-Assisted Transorbital Transconjunctival Approach

Background Treatment of optic nerve lesions, traumatic or nontraumatic, is widely variable and depend on the site and type of the lesion. Optic nerve decompression may be the primary goal or part of the management. Selection of the appropriate minimally invasive approach is crucial. Recently, transorbital approaches have gained popularity. An analytical comparison of the transconjunctival endoscopic-assisted transorbital (pre- or post-caruncular) approach with the endoscopic endonasal approach (EEA) as minimally invasive procedures directed toward the medial side of the optic nerve has not been addressed previously.

Objective The aim of this anatomical study is to measure the depth of the surgical corridor, angle of attack, surgical freedom, area of exposure to show differences between the two approaches.

Methods Five colored latex-injected cadaveric heads (10 sides), were dissected with the aid of a 0° rod-lens endoscope. On the right side, the transorbital approach was performed first and the endonasal approach followed. The opposite order was performed on the left. A point in the middle of the intra-canalicular portion of the optic nerve was used to measure the angle of attack in both approaches. Three points were utilized to calculate surgical freedom, one at the tuberculum sellae mid-line, the second at the lateral opticocarotid recess (LOCR) and the third at a point superior to the LOCR on the roof of the optic nerve at the optic ring making a triangle with its base at the orbital side and the apex toward the midline resembling the appearance of the optic nerve protuberance. The shortest distances to the optic nerve, from the nostril and the conjunctival incision, were also measured.

Results The transorbital approach requires a shorter corridor, and provides a more direct approach to the optic nerve. Overall, the endonasal route afforded more surgical maneuverability, although the transorbital approach allows more maneuverability toward the superomedial optic canal and the endonasal approach toward the inferomedial part.

Conclusion We believe that each surgery should be tailored based on the lesion of the optic nerve and whether the circumstances require more surgical maneuverability or a direct short procedure. Regardless, these two approaches can be used in a complementary fashion.