Delayed Internal Carotid Artery Pseudoaneurysm Following Endoscopic Endonasal Approach for Anterior Clinoid Process...

Anterior clinoid process (ACP) mucoceles are extremely rare lesions that may pose significant surgical challenges due to their proximity to the internal carotid artery (ICA). We report a case of a 54-year-old male with an ACP mucocele who presented with rapidly progressive visual loss in the left eye. Endoscopic endonasal approach (EEA) was performed, during which inadvertent ICA injury occurred following bone removal, resulting in massive bleeding that required immediate gauze packing and termination of the procedure. Despite unremarkable early postoperative imaging, a pseudoaneurysm detected one week later at cavernous ICA and rapidly enlarged with findings of a carotid-cavernous fistula. Urgent endovascular treatment with a flow-diverting stent and adjunctive coil embolization was performed and the gauze packing was removed one week after endovascular treatment. Follow-up MRA and DSA at 1 year confirmed successful vessel remodeling and sustained exclusion of the pseudoaneurysm. This case highlights the risk of ICA injury during EEA for ACP lesions, the importance of careful postoperative imaging surveillance for delayed pseudoaneurysm formation, and the effectiveness of a combined endovascular reconstructive strategy in managing unstable pseudoaneurysms.