Anatomic and clinical study of the orbitopterional approach to anterior communicating artery aneurysms

OBJECTIVE: To evaluate the orbitopterional approach to anterior communicating artery (AComA) aneurysms, on the basis of the quantification of this surgical exposure, compared with the pterional approach, in a cadaveric study and a retrospective review of data for 40 patients who underwent clipping of AComA aneurysms via the orbitopterional approach. METHODS: In an anatomic study, four cadaveric heads underwent pterional craniotomies on the left side and orbitopterional craniotomies on the right side. A fifth head was initially subjected to bilateral pterional craniotomies and then underwent bilateral orbital osteotomies, for direct comparison of these approaches. Using frameless stereotaxy, we quantified the angles of exposure and surgical field depths provided by the pterional and orbitopterional craniotomies. In a clinical study, 40 patients who underwent clipping of AComA aneurysms via orbitopterional approaches were evaluated for basal brain injury, the need for resection of the gyrus rectus, dissection of the sylvian fissure, and approach-related complications. The incidence of postoperative hydrocephalus among patients with subarachnoid hemorrhage who underwent lamina terminalis fenestration was also reviewed. RESULTS: The angles of observation were increased 46% in the axial plane (orbitopterional, 72.92 ± 6.57 degrees; pterional, 49.75 ± 2.27 degrees; P < 0.01) and 137.5% in the projection plane (orbitopterional, 8 ± 2.19 degrees; pterional, 19 ± 1.78 degrees; P < 0.01). The surgical window depth was decreased 13% with the orbitopterional approach (P < 0.05). Clinically, there was no incidence of frontobasal hypodensities on postoperative computed tomographic scans. Three patients (7.5%) required resection of the gyrus rectus. No patient required sylvian fissure dissection for aneurysm exposure. Two of 29 patients (6.9%) who survived subarachnoid hemorrhage required ventriculoperitoneal shunts despite lamina terminalis fenestration. No approach-related complications were recognized. CONCLUSION: The orbitopterional approach improved the observation of the AComA complex and seemed to decrease the risk of intraoperative brain damage.