Surgical Approaches to the Orbital Apex: Comparison of Endoscopic Endonasal and Transcranial Approaches using a Novel 3D Endoscope

Extended endoscopic endonasal approaches are increasingly applied to treat a variety of orbital pathologies. We performed a cadaveric study, comparing the endonasal approach with a transcranial approach to the orbital apex, using a two-dimensional (2D) and novel three-dimensional (3D) endoscope.Dissection was performed on two fresh cadaver heads using a novel 3D endoscope for the endonasal approach to the orbit and orbital apex. On the same heads, a fronto-orbito-zygomatic (FOZ) approach was performed to expose the orbital apex region. Anatomical boundaries and limitations of each exposure were noted. 2D and 3D images of the approaches and anatomical dissections were captured and recorded.The endonasal endoscopic approach achieved direct exposure to the inferior and medial aspects of the orbit. The FOZ approach, on the other hand, provided excellent access to the superior and lateral aspects of the orbit. Appreciation of the spatial relationships of the intracranial skull base anatomy was significantly improved using the 3D endoscope compared with the 2D endoscope.The endoscopic endonasal approach achieves direct exposure to the inferomedial aspect of the orbit and orbital apex, which is not exposed using the transcranial approach, hence the two approaches are complementary. 3D endoscopes augment the spatial orientation of extracranial and intracranial anatomical structures. This may improve patient's safety and hasten the learning curve for endoscopic approaches to the midline skull base.