Microsurgical clipping of unruptured middle cerebral artery bifurcation aneurysms: incidence of and risk factors for procedure-related complications

Objective: To report our experiences in microsurgical clipping of unruptured middle cerebral artery (MCA) bifurcation aneurysms and to evaluate the incidence of and risk factors for procedure-related complications.

Methods: The study comprised 416 patients treated between March 2003 and February 2014. All patients met the following criteria: 1) microsurgical clipping of an unruptured MCA bifurcation aneurysm was performed, and 2) clinical and radiographic follow-up data were available including preoperative digital subtraction angiography. The incidence of and risk factors for procedure-related complications were retrospectively evaluated.

Results: Procedure-related complications occurred in 15 (3.6%) patients, including asymptomatic complications in 10 (2.4%) patients and symptomatic complications in 5 (1.2%) patients. Multivariate logistic regression analysis showed that posteroinferior projection of the aneurysm (odds ratio = 2.814, 95% confidence interval = 0.995-6.471, P = 0.042), distance between the internal carotid artery bifurcation and the MCA bifurcation (Dt) in a linear line (odds ratio = 1.813, 95% confidence interval = 0.808-6.173, P = 0.043), and horizontal angle between the vertical line to the base of the skull and Dt (odds ratio = 2.046, 95% confidence interval = 1.048-10.822, P = 0.048) were independent risk factors for procedure-related complications.

Conclusions: When performing clipping of unruptured MCA bifurcation aneurysms, the procedure-related complication rate was 3.6%. Patients with MCA bifurcation aneurysms with posteroinferior projection, shorter Dt, and larger horizontal angle may be at a higher risk of procedure-related complications when performing microsurgical clipping.