Endoscopic Transorbital Extended Middle Fossa Approach: A Potential Addition to the Lateral Skull Base Surgical Armamentarium-Anatomic Feasibility Study.

Background And Objectives: Various approaches have been developed to treat diseases of the lateral skull base. The endoscopic transorbital approach has been recently used as stand-alone or as a complementary approach for selected pathologies of the anterior, middle, and posterior cranial base. However, its anatomy and applicability to structures of temporal bone (TB) at the lateral skull base have not been previously described. We propose the endoscopic transorbital approach as an alternative to access structures of the TB at the lateral skull base, a strategy introduced herein as the endoscopic transorbital extended middle cranial fossa approach (ETEMF). This study aims to evaluate its feasibility.

Methods: ETEMF was carried out in 7 cadaveric heads (14 sides). The tegmen, internal acoustic canal, and petrous apex were unroofed and structures exposed. Anatomy relevant to ETEMF was examined.

Results: Structures including the crista ovale, eustachian groove, tegmen, petrous internal carotid artery, cochlea, geniculate ganglion, the superior and lateral semicircular canals, internal acoustic canal, intracanalicular, labyrinthine, and tympanic portions of facial nerve were exposed. The crista ovale, foramen ovale, foramen spinosum, eustachian groove, greater superficial petrosal nerve, and arcuate eminence served as major landmarks during the dissection. Minimal retraction of the orbital globe and dura were required.

Conclusion: Exposure of the TB anatomy at the lateral skull base is feasible through ETEMF. This is the first study to propose this application. Major structures within the TB are accessible through this approach. Additional studies are necessary to define its role in the surgical armamentarium.