J Korean Neurosurg Soc 51 | June 2012 the Pterional group) had mirror aneurysms at both MCA bi- furcations, and they were clipped consecutively under a single general anesthesia. They were counted as two different cases be- cause they had craniotomies on both sides. One of 61patients of the LSO group had re-operation after surgical treatment for the anterior communicating artery (ACA) aneurysm, because a re- sidual sac was detected at the postoperative radiologic evalua- tion. All aneurysms, except this one, were clipped successfully. Seventy-one patients were female. The mean age was 55.3 years. Clinical data were presented in Table 1. Operation time was estimated from the moment of skin incision to that of skin closure. Craniotomy size was calculated by the equation, {(long axis diameter+short axis diameter)/2/2}2×3.14, and the axis di- ameters were obtained from postoperative computed tomogra- phy (CT) images. The two groups showed similar distributions of aneurysm location and the anterior communicating artery and MCA bifurcation were the major aneurysm locations found in both groups (60.3% in the LSO group and, 73.9% in the Pterion group). The number of patients with gyrus rectus partially removed in each group was 11 out of 16 in the LSO group and 14 out of 20 in the Pterional group. In the LSO group, the mean operation time of the patients with gyrus rectus removed was 116.2 minutes, which was shorter than (129.0 minutes) in the patients with gy- Table 1. Clinical data of patients Variables LSO group (No. of patients) Pterional group (No. of patients) Sex (F/M) 33/28 37/24 Age (mean years) 54.6 55.7 Duration of hosp. (mean days) 7.9 9.0 Operation time (mean minutes) 117.1 164.3 Craniotomy size (mean mm2) 1275.4 2858.9 Location Acom 16 (*11) 20 (*14) MCA bif. 25 31 Pcom 8 7 AChA 8 4 ICA bif. 3 2 Oph. Seg. 1 0 M1 4 3 A1 3 2 *The number of patients whose gyrus rectus were partially removed. LSO : lateral supraorbital, hosp. : hospital- ization, Acom : anterior communicating artery, bif. : bifurcation, Pcom : posterior communicating artery, Oph. Seg. : ophthalmic segment of internal carotid artery, M1 : the first segment of MCA, A1 : the first segment of ACA Table 2. Postoperative complications Complication Epidural hematoma Intracerebral hematoma Subdural hematoma Infarction LSO : lateral supraorbital LSO group (No. of patients) 2 1 1 0 rus rectus preserved. In contrast, in the Pterional group, the mean operation time of the patients with gyrus rectus removed (194.5 minutes) was longer than in patients with gyrus rectus preserved. Several complications were noted postoperatively (Table 2), with low incidence of postoperative complications in both groups and no significant difference between the groups. DISCUSSION Not only the improvement of operating microscopes and re- fined instrumentation but also the development of diagnostic imaging tools focusing on certain intracranial lesions currently allows minimal invasive surgery for the treatment of intracranial aneurysms, instead of the conventional pterional approach, which requires relatively extensive skin, bone, and brain expo- sure6). Most keyhole approaches, such as the frontolateral, fron- tolaterobasal, supraorbital and transorbital keyholes, can provide access to various pathologies in the suprasellar and parasellar re- gions; however, they have limited working angle, which makes it difficult for the surgeon to manipulate and observe the lesions4,8). The lateral supraorbital approach was introduced by Hernesn- iemi and is a modified version of the classic pterional approach. When compared with the pterional approach, the lateral supra- orbital approach provides more anteri- or trajectory, and consequently offers p value lesser exposure of the origin of the pos- terior communicating artery and the an- 0.576 terior choroidal artery. Because the ori- gin of posterior communicating artery 0.125 arises from the posteromedial surface <0.001 of internal carotid artery and the ante- <0.001 rior choroidal artery makes a medial curve initially, the pterional approach with more lateral trajectory has advan- tage in surgical clipping of these distal interal carotid artery aneurysms. In this study, these aneurysms were successful- ly clipped via lateral supraorbital ap- proach with no additional difficulties, comparing with clipping via pterional approach. When the origins of these ar- teries were not identified, the patency of these arteries after clipping was con- firmed by both intraoperative Doppler sonography and indocyanine green flu- Pterional group orescence angiography, and motor func- (No. of patients) tion of the patient was checked using 2 motor evoked potential (MEP) monitor- 0 ing device during operation. When spe- 0 cific surgical approach is selected, the 1 decision-making process must be con- sidered various factors such as surgeon’s 336