Analysis of multiple factors affecting surgical outcomes of proximal middle cerebral artery aneurysms

Objective: We analyzed multiple factors including anatomical characteristics that influence the surgical outcomes of proximal middle cerebral artery (M1) aneurysms. Methods: Between January 1999 and February 2007, 189 patients had middle cerebral artery aneurysms and 60 had M1 aneurysms. Eleven patients were excluded from this study. The aneurysms were classified into two groups (superior- and inferior-wall type). Retrospectively, we evaluated characteristics of these patients and investigated factors affecting surgical outcomes. Results: Of the 49 patients, 28 had ruptured aneurysms and 43 had aneurysms sized less than 10 mm in diameter. There were no giant aneurysms, the incidence of multiple aneurysms was high (22 patients, 45%), and intracerebral hematomas (ICH) were recognized in 13 patients (27%). The superior-wall group included 29 patients (59.2%) and the inferior-wall group had 20 (40.8%). Overall mortality and morbidity rates were 6.1% and 24.5%, respectively. Thirty-four patients (69%) showed good outcomes (GOS 4-5). Eleven and five patients showed unfavorable outcomes from the superior- and inferior-wall group, respectively. Of the four operation-related morbidity patients, three were from the superior-wall and one from the inferior-wall group. There were no statistically significant differences with respect to clinical outcome between the superior- and inferior-wall groups. Patients with poor Hunt-Hess (H-H) grades on admission showed worse outcomes than those with good H-H grades (p = 0.002) and those patients without ICH revealed better outcomes than those with ICH (p = 0.004). Conclusions: In patients with M1 aneurysms, clinical status on admission and the presence of ICH were significant factors for surgical outcome. Surgical morbidity seems to be related to the direction of the aneurysm. It is critical to save the lenticulostriate arteries and their branches in patients with superior-wall type aneurysms. Thorough preoperative angiographic evaluation, careful brain retraction, and meticulous inspection for hidden small branches are crucial to successful outcomes.