Surgical Anatomy of the Superior Orbital Fissure and Implications in Open and Endoscopic Skull Base Surgery

Introduction: Tumors involving the cavernous sinus, anterior clinoid process, sphenoid wing, or orbital apex may extend towards the superior orbital fissure (SOF) and be the cause of multiple cranial neuropathies. Depending on the nature of the lesion, surgery may be indicated for diagnostic, bone decompression or tumor resection purposes. Several approaches may be elected to access this area such as transcranial, transorbital, or endonasal endoscopic approaches.

Methods: Cadaveric transcranial and endonasal endoscopic dissections at Skull Base Lab, Mayo Clinic, Florida, were performed in specimens injected with intravascular colored silicone for anatomical analysis and illustrations of technical nuances. Three surgical cases were included for demonstration of application of surgical techniques and anatomy in endoscopic endonasal and transcranial microsurgery.

Results: A total of 12 approaches were performed, 6 endoscopic endonasal (3 heads) and 6 transcranial.

Transcranial approaches involved a pretemporal approach with extradural clinoidectomy to access to the cavernous sinus, unroofing of the optic nerve, and decompression of SOF.

The endoscopic endonasal approaches were developed through a sphenoidectomy providing access to the sellar and parasellar region. Both ICAs were unroofed drilling lateral to medial with en-block resection of the middle clinoid process (MCP). Identification of anatomical landmarks, namely, optic canal and lateral optic carotid recess (optic struts) allows for endoscopic bony decompression of both optic nerve and SOF lateral to parasellar ICA.

A description of this technique is depicted with the identification of anatomical landmarks.

Two transcranial microsurgery cases are included to illustrate the role of pretemporal approaches in the management of meningiomas extending to the SOF. One case of endoscopic endonasal surgery is included to demonstrate its role in the management of selected cavernous sinus meningiomas with diplopia and progressive visual decline.

Conclusion: Lesions involving the SOF may require surgery for diagnosis, decompression, or oncological purposes. The election for a specific approach is associated to the type of tumor and location of the lesion, its relations to adjacent areas (e.g., cavernous sinus), as well to the surgeon’s experience. Understanding the complex anatomy of this region is paramount for the success of the procedure.

When compressive neuropathy is settled, EEA is a safe, effective, and minimally invasive technique that may help the neurosurgeon in its purpose of decompressing neural structures, achieving diagnosis, and allowing for posterior observation or alternative therapies.

Timing, selection of cases, and a good understanding of skull base anatomy are mandatory for management of tumors involving the superior orbital fissure ([Figs. 1]–[4]).

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Publication History

Article published online:
05 February 2024