Endoscopic endo- and extra-orbital corridors for spheno-orbital region: anatomic study with illustrative case

Background and objective: Management of selected spheno-orbital meningiomas via the endoscopic transorbital route has been reported. Surgical maneuverability in a narrow corridor as that offered by the orbit may be challenging. We investigate the additional use of an extra-orbital (EXO) path to be used in combination with the endo-orbital (EO) corridor. Material and methods: Three human cadaveric heads (six orbits) were dissected at the Laboratory of Surgical Neuroanatomy at the University of Barcelona. The superior eyelid endoscopic transorbital approach was adopted, introducing surgical instruments via both corridors. Surgical freedom analysis was run to determine directionality of each corridor and to calculate the surgical maneuverability related to three anatomic targets: superior orbital fissure (SOF), foramen rotundum (FR), and foramen ovale (FO). We also reported of a 37-year-old woman with a spheno-orbital meningioma with hyperostosis of the lateral wall of the right orbit, treated with such combined endo-orbital and extra-orbital endoscopic approach. Results: Combining both endo-orbital and extra-orbital corridors permitted a greater surgical freedom for all the targets compared with the surgical freedom of each corridor alone (EO + EXO to SOF: 3603.8 mm2 ± 2452.5 mm2; EO + EXO to FR: 1533.0 mm2 ± 892.2 mm2; EO + EXO to FO: 1193.9 mm2 ± 782.6 mm2). Analyzing the extra-orbital pathway, our results showed that the greatest surgical freedom was gained in the most medial portion of the considered area, namely the SOF (1180.5 mm2 ± 648.3 mm2). Regarding the surgical case, using both pathways, we gained enough maneuverability to nearly achieve total resection with no postoperative complications. Conclusion: An extra-orbital corridor may be useful to increase the instruments’ maneuverability, during a pure endoscopic superior eyelid approach, and to reach the most medial portion of the surgical field from a lateral-to-medial trajectory. Further studies are needed to better define the proper indications for such strategy.