Impact of preaneurysmal M1 length in unruptured middle cerebral artery aneurysm: mid-term outcome and single-center experience

Objective: This study was design to investigate the surgical and functional outcome based on the preaneurysmal M1 length for unruptured MCA aneurysm. Methods: Among 250 consecutive patients with unruptured aneurysms operated in our institution between 2015 and 2017, 72 were MCA aneurysms. Risk factors for IR (i.e., intraoperative rupture) were investigated including age, sex, preaneurysmal M1 length, maximal MCA aneurysm diameter, neck size, aneurysm shape, sphenoid ridge proximation sign. Outcome was measured at discharge, 1 yr and last follow-up. Outcome was compared according to the preaneurysmal M1 length. Results: Among 68 patients included, five patients (7.3%) suffered IR. Mean maximal diameter of MCA aneurysm (7.9 mm +/- 3.4 vs. 4.5 +/- 1.8; p = 0.01) was significantly associated with IR risk. Mean M1 length seemed to be shorter in the IR group although not statistically significant (16.2 mm +/- 5.1 vs. 11.5 mm +/- 4.8; p = 0.053). Midterm outcome was favorable for all patients at last follow-up but was worsen in case of short preaneurysmal M1 segment (10.7 mm +/- 4.8 vs. 16.4 mm +/- 5.3, p = 0.02). Complete aneurysm occlusion was achieved for sixtynine patients (95.5%) with 6.9% of early postoperative complications. Conclusions: The microsurgical treatment of unruptured MCA aneurysm was associated with favorable mid-term outcome in all patients and high rates of complete occlusion. Aneurysm size was significantly associated with the intraoperative rupture risk for unruptured MCA aneurysm and patients with a short preaneurysmal M1 segment seemed to have a greater risk of intraoperative rupture although not statistically significant. Short preaneurysmal M1 patients had worsen mid-term outcome.