Factors influencing surgical outcome of the basilar bifurcation aneurysms

To contribute to a better understanding of the clipping operation of the basilar bifurcation aneurysm, factors influencing the surgical outcome were analyzed in 80 patients. The age range of the patients was 34-74 years, with a mean age of 58.4 years, and there were 61 females and 19 males. Fifty-eight patients had been admitted because of subarachnoid hemorrhage and a basilar bifurcation aneurysm ruptured in 49 patients. The size of the aneurysms ranged between 2 and 19 mm with a mean of 7.9 +/- 3.9 mm. The height of the aneurysm neck was between -10 and 17 mm measured above a biclinoid line with a mean of 4.8 +/- 5.2 mm. Pterional approach was utilized in 72 patients and subtemporal in eight. Optic unroofing or removal of anterior clinoid process were performed in five patients, zygomatic osteotomy in 10, posterior clinoid removal in seven, and anterior petrosectomy in one. A bridging vein of the temporal lobe was divided in 16 patients. A short and/or hypoplastic posterior communicating artery was divided in 11 patients. Temporary occlusion of the basilar trunk was performed in 39 patients. Surgical outcome (Glasgow Outcome Scale) at 3 months after the operation was good recovery in 42 (53%), moderately disabled in 23 (29%), severely disabled in five (6%), vegetative survival in two (3%), and dead in eight (10%). The aneurysm size proved to be a single preoperative factor which significantly correlated with the surgical outcome (Spearman's rank correlation test, p < 0.0001). Division of the posterior communicating artery significantly contributed to the surgical outcome as an intraoperative factor (Mann-Whitney's U test, p = 0.01). The larger the aneurysm size was, the more often the posterior communicating artery was sectioned. Extreme care should be taken to obliterate a large aneurysm with a clip graft especially when division of the posterior communicating artery is required.