Introduction: Despite level 1a evidence demonstrating the clinical benefit of mechanical thrombectomy in selected large vessel ischemic stroke patients, a gender disparity exists. Women not only have less favorable clinical outcomes after all stroke types, but the causes of this disparity remain elusive. Gender differences in cerebral vascular anatomy have been previously published. We hypothesize that differences in circle of Willis diameters may contribute to the gender disparity seen in clinical outcomes after mechanical thrombectomy for acute ischemic stroke.
Methods: Clinical and radiographic data from a consecutive series undergoing mechanical thrombectomy for anterior circulation large vessel ischemic strokes were reviewed. Measurements of the proximal middle cerebral artery (M1) segment and supraclinoid internal carotid artery (ICA) diameters were obtained in a standardized fashion from the thrombectomy procedure angiogram. All M1 measurements were recorded at 3 mm of the vessel origin while ICA measurements were taken 3 mm proximal to the ICA terminus. Covariates included age, occlusion location, vascular risk factors, admission NIHSS score and final TICI grade. Modified Rankin score (mRS) at 90 days was the dependent variable. Variable significance between male and female cohorts was determined using student T-Tests. Multivariate regression analysis was also performed.
Results: Ninety-four patients (41 female) between 6/2013 and 6/2016 fit the inclusion criteria. ICA terminus measurements for men and women were 3.07 mm (SD=0.46) and 2.88 mm (SD=0.47), respectively. M1 origin measurements for men and women were 2.46 mm (SD=0.31) and 2.21 mm (SD=0.37), respectively. Male ICA terminus and M1 origin measurements were larger than female (p = 0.05 and p < 0.001, respectively). 61% of men vs. 25% of women had 90-day mRS ≤ 2. Multivariate analysis indicated that only age was significantly associated with 90-day mRS ≤ 2.
Conclusions: Our single center series suggests that differences in intracranial vessel diameter may contribute to the gender disparity in outcomes after mechanical thrombectomy. Smaller circle of Willis arterial diameters may compromise collateral blood flow and increase the difficulty in achieving sufficient reperfusion.