Multiportal, Combined Transorbital and Endoscopic Endonasal Approach to Middle Cranial Fossa: Surgical Anatomy and Technique

Background: The cavernous sinus (CS) and Meckel’s cave (MC) are both deep-seated within the inter-dural space of the middle cranial fossa (MCF), making surgical access to them difficult. The inferolateral transorbital approach offers unhindered access to these compartments but via a tight operative corridor. The endoscopic endonasal route also provides access to this region but with blind corners.

Objectives: To describe a multiportal route to the anterior portion of the MCF, by combining the endoscopic endonasal approach with the inferolateral transorbital approach.

Methods: The multiportal approach (inferior transorbital and endoscopic endonasal transmaxillary, trans-inferior orbital fissure approach) was simulated in sixteen cadaveric specimens. Meeting at the inferior orbital fissure (IOF), the two routes allowed concurrent bimanual inter-dural dissection to expose the MC and CS, and as well as the posterior fossa. The key landmarks accessed, boundaries of surgical exposure and the fraction of bone window on the lateral orbital wall contributed by each approach, as well as the working angle between the two corridors, were assessed and recorded using a neuronavigation system.

Results: A pentagonal region bound by foramen rotundum, trigeminal nerve porus, middle meningeal artery, medial edge of arcuate eminence, lateral side of orbital apex, and tentorial edge, was exposed using both corridors. From the nostril, the length of the corridor to the Trigeminal Nerve (TN) was 9.01 ± 0.52cm, while it was found to be 7.20 ± 0.49cm from the orbital rim. The working angle between the two trajectories was 35.27 ± 2.56 degrees. 68.5% of the bone drilled on the lateral orbital wall was contributed by the endoscopic endonasal approach.

Conclusions: The described combined approach provides multiportal interdural access to the MCF. It provides expanded exposure of the CS and posterior fossa and allows more surgical freedom than either approach used alone. The two corridors can be used simultaneously to efficiently access the CS and MC. The angle between trajectories allowed comfortable and efficient dissection within the MCF.