Preoperative Simulation of Intraoperative Findings in Surgical Clipping of Posterior Communicating Artery Aneurysms Using T2-Weighted 3D Images

Background: Tentorium resection and detachment from the oculomotor nerve are sometimes required for surgical clipping of unruptured posterior communicating artery (PCoA) aneurysms. Using T2-weighted 3D images, we aimed to identify the preoperative radiological features required to determine the necessity of these additional procedures. Methods: We reviewed 30 patients with unruptured PCoA aneurysms who underwent surgical clipping and preoperative simulation using T2-weighted 3D images for measurement of the distance between the tentorium and aneurysm. Aneurysms were classified into superior type (superior to the tentorium) and inferior type (inferior to the tentorium). Results: Seven patients (23%) underwent tentorium resection; all had the inferior type (superior vs. inferior, 0% vs. 33%, p = 0.071). In the 21 patients with the inferior type, the distance from the tentorium to the aneurysmal neck was 2.2 +/- 1.1 mm and 0.0 +/- 0.5 mm without and with tentorium resection (p < 0.01), respectively. An optimal cutoff value of <= +0.84 mm was identified for tentorium resection (area under the curve (AUC) = 0.96). Furthermore, 17 patients (57%) showed tight aneurysm attachment to the oculomotor nerve; all had the inferior type (0% vs. 81%, p < 0.01). The distance from the aneurysm tip to the tentorium was 1.1 +/- 1.2 mm and-1.7 +/- 1.4 mm without and with attachment (p < 0.01). The optimal cutoff value was <= +0.45 mm (AUC = 0.92). Conclusions: Measurement of the distance between the tentorium and aneurysmal neck or tip with T2- weighted 3D images is effective for preoperative simulation for surgical clipping of PCoA aneurysms.