1234 The Transposition Technique of Internal Carotid Artery in Endonasal Endoscopic Surgery: Beyond the Lateral Boundary of Middle Line Approach

INTRODUCTION: There was no report regarding the transposition technique of ICA in endonasal endoscopic surgery (EES) METHODS: Six cadaveric heads (3 arterial and venous injected, 1 embalmed artery injected, 1 fresh artery injected) were prepared for dissection. The trabecular fiber (parasellar ligaments) in cavernous sinus(CS), small branches of ICA, dura, bony structures along ICA were meticulously dissected and photographed. The endoscopic dissections were performed using 0° (4-mm-diameter, 18-cm-long) rod lens endoscopes (Karl Storz). 36 cases (Jan 2014 to June 2022) underwent EES ICA transposition were reviewed. RESULTS: The trabecular fiber and small branches of ICA formed four sets of limiting structures around ICA: the medial, lateral, anterior, and posterior group. The medial group consisted of carotid clinoid ligaments (12/12), inferior hypophyseal artery (11/12), inferior parasellar ligament (6/12). The lateral groupcomprised inferolateral trunk (12/12), the sympathetic nerve plexus (12/12), the trabecular fibers between ICA and CN3 (6/12),CN4 (5/12), CN6 (12/12). The anterior group consisted of trabecular fibers between the proximal dural ring and the ICA (7/12). The posterior group was made of trabecual fibers (8/12) around the post genu and posterior wall of CS. Proximal and distal dura ring was the main dura structures impeding mobilizing ICA. The anterior clinoid and lingual process obstructed ICA lateral transposition. Grade 1 (inner CS limiting structures), Grade 2 (inner CS + dura ring open), Grade 3 (inner CS + dura ring + bony remove) transposition were used in 24 (66.7%), 9 (25%), 3 (8.3%) cases respectively. CSF leakage (2.7%), ICA injury (2.7%), new transient CN palsy (8.3%), permanent CN palsy (5.4%) were developed postoperatively. CONCLUSIONS: The EES ICA transposition technique is technically feasible and could be graded according to extent of freeing the limiting structures. It is a novel technique worth exploring in suitable cases to enlarge the working zone and surgical freedom in middle line approaches.