nial aneurysms of the anterior circulation. Among them, 68 an- eurysms in 61 patients were clipped via the lateral supraorbital (LSO) approach were enrolled as the LSO group. Then, we en- rolled the same number of patients (n=61) with 69 aneurysms clipped via the pterional approach between July 2009 and May 2010 as the Pterional group. In both groups, all operations with two different approach methods were performed by a single sur- geon, at a single institute, over 2-year period. All distal ICA an- eurysms were clipped without removal of the anterior clinoid process. Patients with ruptured aneurysms or multiple aneu- rysms of more than 3 were excluded from this study. Aneu- rysms treated by wrapping with cotton were also excluded. All data in the present study were based on the medical records and radiologic findings of the patients. We analyzed the two groups and compared demographic, radiologic and clinical variables, including age, sex, duration of hospitalization, operation time, craniotomy size, aneurysm location, and postoperative compli- cations. The statistical significance of observed differences be- tween the variables was assessed by the Student’s t-test and the chi-square test. Operative technique The lateral supraorbital approach conducted in the present study was described in detail by Hernesniemi et al.3) The patient was placed in the supine position, with the head slightly elevat- ed above the cardiac level. The head is fixed with three pins in the Mayfield head frame and was rotated about 30 degrees to- wards the opposite side and tilted slightly depending on the precise location of the aneurysm. Hair shaving was minimal Lateral Supraorbital Approach | KC Cha, et al. but still allowing a large enough curvilinear frontotemporal skin incision. The skin incision was usually behind the hair line and did not descend in front of the ear to the level of the zygo- matic arch (Fig. 1A). The one layer skin-galea-muscle flap was dislocated after detachment from the bone by periosteal eleva- tor and diathermy, thus avoiding any injury of the branches of the facial nerve, and the flap was retracted anteriorly with spring hooks, until the superior orbital rim and the anterior zygomatic arch were exposed. The temporalis muscle was split only in its superior and anterior part (Fig. 1B). Only one burr hole was made posteriorly, just below the insertion line of the temporalis muscle. The bone flap was detached mainly by side-cutting cra- niotome, but the basal part was drilled off before lifting the flap (Fig. 1C). The bone flap size was about 3×4 cm (Fig. 1D). The dura mater was opened in a curvilinear incision pointing an- terolaterally and elevated with stitches (Fig. 1E). The micro- scope was brought in place. After minimally opening the Sylvi- an fissure, the dissection was made toward the aneurysm site. Only one spatula was used on the frontal lobe for brain disloca- tion. After aneurysm clipping, the bone flap was secured using one skull fixator and two plate and screw systems (Fig. 1F). RESULTS Thirteen of the 122 patients (6 from the LSO group and 7 from the Pterional group) had two aneurysms simultaneously at different locations, and they were treated via a single surgical approach. Therefore, they were counted as a single case. Two of the 122 patients (one from the LSO group and the other from A B C D E F Fig. 1. The skin incision is usually behind the hair line and did not even go down in front of the ear to the level of zygomatic arch (A). The one layer skin-galea-muscle flap is dislocated after detachment from the bone by periosteal elevator and diathermy, and the flap is retracted anteriorly with spring hooks (B). Only one burr hole is made posteriorly and the bone flap is detached mainly by side-cutting craniotome with the basal part drilled off before lifting the flap (C). The bone flap size is about 3×4 cm (D). The dura mater is opened in a curvilinear incision pointing anterolaterally and elevat- ed with stitches (E). After aneurysm clipping, the bone flap is secured using one skull fixator and two plate and screw systems (F). 335