Technical and Anatomical Determinants of Ischemic Complications in Unruptured Middle Cerebral Artery Aneurysm Surgery: The Role of Temporary Arterial Occlusion

Ischemic complications (IC) remain a major source of morbidity following microsurgical treatment of unruptured middle cerebral artery (MCA) aneurysms. The contribution of temporary arterial occlusion (TAO) to ischemic risk remains debated, particularly given potential confounding by anatomical and intraoperative factors. What are the primary determinants of clinically evident IC in unruptured MCA aneurysm surgery, and what is the role of TAO? We retrospectively analyzed consecutive patients undergoing clipping of unruptured MCA aneurysms between 2023 and 2025. Clinically evident IC was defined as a new postoperative neurological deficit with corresponding ischemic lesions on MRI in symptomatic patients only. Associations with IC were assessed using Firth’s penalized logistic regression. Forty-seven patients were included. TAO was used in 60% of cases and was associated with larger aneurysm size (8.3 ± 2.7 vs 6.8 ± 2.4 mm; p = 0.048). TAO, including repeated and prolonged applications, was not associated with IC (OR 0.67, 95% CI 0.06–6.97; p = 0.74). A short pre-aneurysmal M1 segment (OR 30.4; p = 0.034) and intraoperative rupture (OR 17.4; p = 0.031) were associated with IC. All IC occurred in patients with a short M1 segment and were related to perforator injury during dissection or clipping. Complete occlusion was achieved in all cases; morbidity was 4.3%. Clinically evident ischemic complications are primarily driven by anatomical constraints and clipping strategy rather than TAO. TAO should be considered a technical adjunct rather than a dominant determinant of ischemic risk. These findings warrant validation in larger prospective studies. • Clinically evident ischemic risk is driven primarily by anatomical constraints and clipping strategy, rather than temporary arterial occlusion • A short pre-aneurysmal M1 segment and intraoperative rupture are the principal determinants of ischemic complications in unruptured MCA aneurysm surgery • Temporary arterial occlusion — including repeated and prolonged applications — was not associated with postoperative ischemic events • TAO should be regarded primarily as a technical adjunct facilitating dissection and clip placement rather than as a dominant driver of ischemic risk