Evaluation of Sex-Related Differences in Cerebrovascular Bypass Patency: Review of 357 Direct Cerebral Bypasses

BACKGROUND: Demographics and comorbid conditions play a role in vascular health, yet their specific impact on cerebrovascular bypass patency remains unclear. METHODS: An institutional database of 357 patients with intracranial bypass procedures between August 2001 and May 2022 was retrospectively reviewed. Patients with bypass for all causes (eg, aneurysm, atherosclerotic disease, moyamoya disease) were included. Medical history, surgical technique, and flow-related measurements (intraoperatively and on quantitative magnetic resonance angiography at follow-up) were compared across biological sex and in relation to bypass patency. Bonferroni correction was applied to the initial analysis ( P ≤0.00167). The remaining analyses were considered exploratory. Propensity score–matched analysis matched cardiovascular risk factors and compared women and men in bypass patency. RESULTS: Of 357 patients, 141 were men (39.5%) and 216 were women (60.5%) with average age of 49.0±16.7 years and an average follow-up of 1.97 years. Bypass patency at last follow-up was 84.4% (n=114) for men versus 69.2% (n=148) for women ( P =0.001). Differences were seen in underlying diagnoses, with more aneurysm and moyamoya cases represented in female sex ( P <0.001); irrespective of diagnosis, lower patency rates were seen in women when considering bypass for aneurysm ( P =0.032), moyamoya disease ( P =0.035), and for atherosclerotic disease ( P =0.159). Medical comorbidities were seen at higher rates in men, with comorbidity score of 2.7 versus 2.1 ( P <0.001). Cut flow was higher in men 59.2 versus 51.1 ( P =0.028), with no differences in intraoperative bypass flow, cut flow index, or follow-up quantitative magnetic resonance angiography. After removing cases using interposition grafts, similar differences were redemonstrated. Propensity score–matched analysis found women have a 2.71 higher chance of bypass occlusion after adjusting for cut flow index ( P =0.017 [95% CI, 1.19–6.18]). CONCLUSIONS: Biological sex appears to play a role in bypass patency, across diagnoses. Women were less likely to have patent bypasses at the last follow-up, despite having fewer medical comorbidities than men and despite having similar intraoperative and perioperative flows.