Translucent Appearance of Middle Cerebral Artery Bifurcation Aneurysms Is Risk Factor for Intraoperative Aneurysm Rupture During Clipping.

INTRODUCTION:The rupture rate of unruptured intracranial aneurysms is influenced by certain angioarchitectural and hemodynamic characteristics. Recently the translucent appearance of aneurysms was described as a possible risk factor for aneurysm rupture. In this study, we investigate the intraoperative rupture risk of surgically clipped unruptured translucent aneurysms (TAs). METHOD:Clinical and radiologic data of microsurgically treated unruptured middle cerebral artery (MCA) bifurcation aneurysms between 2013 and 2015 were collected and analyzed. Aneurysms were divided into TA as defined as >90% reddish pigmentation appearance of the aneurysm wall or non-TA (NTA) according to the observation under microscope by a single neurosurgeon. Parameters were analyzed using univariate and multivariate statistical analyses. RESULT:A total of 41 unruptured MCA bifurcation aneurysms were included in the analysis, and 68.2% (28/41) were defined as TA. The univariate analysis showed that aneurysm characteristics (Dmax, Wmax, height, and lower size ratio [SR]) that were small in nature were associated with TAs. TAs were associated with intraoperative rupture (28.6% vs. 0%, P = 0.04). Multivariate logistic regression analysis found that the lower SR is the independent risk factor for TAs. CONCLUSION:The results demonstrate that a lower SR correlates with TA in the MCA bifurcation and the thinner wall of the TA causes intraoperative rupture more likely. These results provide important information on the fragility of TAs and might influence the treatment decisions in unruptured MCA bifurcation aneurysms with lower SRs.