De Novo Aneurysm Formation After Internal Carotid Artery Sacrifice: Impact of Aneurysmal Versus Non-Aneurysmal Etiology

Background Endovascular trapping of the internal carotid artery (ICA) remains a definitive treatment for both aneurysmal and non-aneurysmal conditions when vessel-preserving strategies are not feasible. However, increasing attention has been directed toward the risk of de novo aneurysm formation following ICA sacrifice, presumably due to hemodynamic alterations within the Circle of Willis. This study aimed to evaluate the incidence and potential risk factors for de novo aneurysm development after ICA trapping, particularly focusing on differences based on the underlying pathology, aneurysmal versus non-aneurysmal. Methods A retrospective, single-center study was conducted on patients who underwent unilateral endovascular ICA trapping between 2003 and 2023, with a minimum of one year of angiographic follow-up. Patients were categorized into the aneurysm-trapping (AT) or non-aneurysm-trapping (NT) group according to the underlying indication for ICA sacrifice. Clinical, angiographic, and procedural data were reviewed to evaluate the development of de novo aneurysms or the progression of pre-existing lesions. Results Among the 47 included patients (37 and 10 in the AT and NT groups, respectively), de novo aneurysm formation or significant growth of pre-existing aneurysms was observed exclusively in the AT group (10/37, 27.0%), with no such events in the NT group (0/10), although the difference did not reach statistical significance (p = 0.064). Most newly developed aneurysms (60%) arose at the anterior communicating artery (ACoA), predominantly in patients with well-developed ACoA collateral flow. Most lesions appeared within two years after ICA trapping. Additional treatment was required in two patients due to progressive enlargement of pre-existing aneurysms. Conclusion De novo aneurysm formation following ICA trapping appears to occur exclusively in patients with an underlying aneurysmal etiology, particularly at sites of hemodynamic stress such as the ACoA. Close imaging surveillance is recommended during the first two years post-trapping, especially in patients with robust collateral circulation or pre-existing aneurysms.