Expanded Exposure and Detailed Anatomic Analysis of the Superior Orbital Fissure and the Associated Neurovascular Structures

Introduction: The superior orbital fissure (SOF) lies between the greater and lesser wings of the sphenoid bone and can be accessed through either an endonasal or transorbital approach. The purposes of this study were to maximize the exposure of SOF and its transmitting neurovascular tract using an endonasal combining a trans-orbital approach.

Methods: Six cadaveric specimens (12 sides) were dissected using an endonasal and trans-orbital approaches. Via an endonasal approach, cranial nerves III through VI were visualized in the lateral wall of the cavernous sinus and traced forward to the inferomedial SOF. Through the trans-orbital approach, the superolateral SOF and the transmitting structures were explored.

Results: Through an endonasal approach, the inferomedial one-third of the SOF including the proximal segment of the oculomotor, ophthalmic and abducens nerves could be accessed; the terminal branches of the oculomotor nerve and nasociliary nerve within intraconal space could also be accessed. Through a transorbital approach, the superolateral two-thirds of the SOF could be explored, including the superior ophthalmic vein, lacrimal nerve and abducens nerve located at the lateral aspect; the nasociliary nerve and divisions of oculomotor nerve centrally; and the frontal and trochlear nerves located at the dorsal aspect of levator palpebrae superioris.

Conclusion: A combined endonasal and trans-orbital approaches provide expanded exposure of the SOF and its transmitting neurovascular structures. The endonasal approach was better for exposure of the inferomedial one-third of the SOF. The trans-orbital approach provided good exposure of the superolateral two-thirds of the SOF. The detailed anatomical knowledge presented here will be helpful for managing lesions in this challenging region.