ACoA angle measured by computed tomographic angiography and its relevance in the pterional approach for ACoA aneurysms

Abstract

The purpose of this study was to analyze the spatial disposition of the anterior communicating artery (ACoA) complex and the orientation of the ACoA plane by computed tomographic angiography with threedimensional reconstruction (3D-CTA) and to evaluate the relevance of the orientation of the ACoA plane in the planification of the surgical approach to the ACoA complex aneurysms. The dominance of the right or left A1 segment of the anterior cerebral artery, the position of the A1-A2 junction in relation to the transverse plane and the angulation of plane of the ACoA traject were studied using 3D-CTA in 30 patients with subarachnoid hemorrhage. Twelve patients harbored an aneurysm on the ACoA complex and the most relevant anatomic characteristics of these lesions were recorded. In 56.7% of cases both A1 segments were similar in size, whereas in 33.3% of cases the left A1 segment was dominant and in the remaining 10% the right A1 segment was dominant. The position of the left A1-A2 junction was anterior to the transverse plane in 30% of cases with an angulation of the ACoA plane of 42 ± 6 degrees. All patients with this anatomical arrangement and left A1 dominance (seven cases) harbored an aneurysm of the ACoA complex located on the left A1-A2 junction. The right A1-A2 junction was anterior to the transverse plane in 13.3% of cases with an angulation of the ACoA plane of 37 ± 9 degrees. All patients in this situation and right A1 dominance (three cases) had an aneurysm on the ACoA complex. Finally, in 50% of cases the ACoA plane was on the transverse plane. In this group of cases only two patients harbored an aneurysm located on the ACoA segment. The dominance of an A1 segment of the anterior cerebral artery may develop anatomical changes in the ACoA complex due to the hemodynamic stress. The main result is the advance of the A1-A2 junction point in the dominant side and the angulation of the ACoA plane in relation to the transverse plane as well as the development of aneurismatic lesions. The angulation of the ACoA plane, in combination with the orientation of the aneurysm, must be included among the criteria for the selection of the route of the surgical approach. This information is given by the 3D-CTA. All of these data allows a pre-operative simulation of the surgical approach to the lesion for a safer clipping of the neck of the aneurysm. [Neurol Res 2002; 24: 291-295]