Dual Endoscopic Endonasal Transphenoidal and Precaruncular Transorbital Approaches for Clipping of the Cavernous Carotid Artery-Enhanced Degrees of Freedom: A Cadaveric Cerebral Perfusion Simulation

Objective: To demonstrate that combined dual port, the endoscopic endonasal approach (EEA) and the transorbital approach (TOA), in addition to the use of a single shaft aneurysm clip applier and clip designed for multi-angled application/removal leads to improved degrees of freedom, ergonomics, visualization and clip application and removal.

Background: Simulated neurosurgical and otolaryngology training experiences are critical for developing endoscopic skull base technical skills and proficiency. In an effort to minimize intra-operative complications secondary to inexperience and unfamiliarity with the anatomy and instrumentation, cadaveric simulation is the best medium. The centers with the most significant experience with endonasal endoscopic clipping of anterior and posterior circulation aneurysms cite degrees of freedom, angles of visualization, angles of clip application and safe clip removal as areas of limitation. Similar limitations are experienced when EA techniques are utilized to address tumors within the cavernous sinus, lateral to the cavernous carotid (e.g trigeminal schwannomas) and petrous apex. The growing literature on clipping of ICA aneurysms, addressing eccentric parasellar pathology and lesions lateral to the cavernous carotid artery reflect the importance of gaining endoscopic proximal vascular control of the cavernous carotid artery.

Methods: Cadaveric specimens were all prepared at OHSU in accordance with the body donation program and VirtuOHSU laboratories. The cadavers were utilized to illustrate the carotid artery anatomy were prepared with an embalming and microfil injection technique. Other cadavers were prepared fresh and preserved in formalin. Each cadaver was utilized innumerable times to demonstrate the reproducibility of this technique for simulation training and cost effectiveness. EA and TOA were performed in each cadaver. The degrees of freedom, angles of visualization, ergonomics, multi-angled aneurysm clip and applier were evaluated.

Results: The contralateral pre-caruncular transorbital port was found to be an improvement to the purely EA approach in the following ways: 1) improved visualization of the endonasal clip application of the cavernous carotid artery; 2) it improved the functional endonasal working area; 3) it allowed for better appreciation of the distal clip tines; 4) there was better visualization of the laterally positioned cranial nerves 3, 4, and 6 within the lateral wall of the cavernous sinus: 5) it improved the ergonomics between surgeons and 6) it facilitated a 4 handed technique The nares ipsilateral to its cavernous carotid artery was a more favorable approach for clipping vs the contralateral approach; both were feasible. The single shaft applier, inside out design and multi-angled aneurysm clip design allowed for smooth application/removal of the clip especially when the clip angle changed after application. The transorbital approach improved the ability to use binaries for then endonasal instruments.

Conclusion: This is a reproducible and cost effective anatomic and simulation model that can be utilized by neurosurgery and otolaryngology residents as well as skull base fellows and skull base teams in preparation for these challenging cases.