前脈絡叢動脈と後交通動脈の起始に関する検討

Angiographic Analysis of Variations and Anomalous Origin of the Anterior Choroidal Artery and Posterior Communicating Artery

Ⅰ．はじめに

　前脈絡叢動脈（anterior choroidal artery：AchoA）はすべての脳神経外科医，脳血管内治療医にとって，非常に重要な血管であることに疑いの余地はない．AchoAと後交通動脈（posterior communicating artery：PcomA）の内頚動脈からの分岐や起始については解剖学，発生学的にすでに多く報告されている^{1,8,9,11,14,15)}．AchoAが内頚動脈─PcomA分岐部から起始するものや，PcomAと共通幹をもつもの，中大脳動脈（middle cerebral artery：MCA）から起始するものなどが報告されている．またAchoAとPcomA起始部が逆転している報告は過去3例あり^3,6,7)，AchoAの欠損の報告はほとんどない．今回，AchoA，PcomA分岐部近傍の脳動脈瘤に対して，読影に難渋した2症例を経験したので発生学的，文献的考察を加え検討する．

　Object: The anterior choroidal artery (AchoA) is a very important artery for neurosurgeons and neuroendovascular surgeons. In fact the AchoA not only supplies the ventricles but also has important branches to the diencephalon,mesencephalon and cerebrum and also supplies motor and visual pathways. Review of the cerebrovascular embryology explains this variability in the anatomy of the developing AchoA and posterior communicating artery (PcomA)- posterior cerebral artery (PCA) distributions.

　Case 1: A 47-year-old woman, with an unruptured left internal carotid artery (ICA) aneurysm. For the cerebral arterial aneurysm approximately 7mm in size, we performed coil embolization with an assist balloon under general anaesthesia.

　Case 2: A 63-year-old woman, with an unruptured right ICA aneurysm. Endeavouring to preserve the branch vessels, we undertook a craniotomy neck clipping operation.

　Discussion and Conclusion: It is thought that,usually,AchoA has its origin at the supraclinoid ICA distal to the PcomA. Our analysis of these two cases may be helpful for a better understanding of the vascular relations and anatomy of the AchoA and PcomA-PCA distributions. We emphasize the importance of recognizing such anomalies in planning surgical and interventional treatment.