発見より8年目に増大した，内頸動脈後交通動脈分岐部の小膨隆像

Eight Year Documented Study of an Aneurysm Growth at the Origin of the Posterior Communicating Artery

　直径3mm以下の小さな脳動脈瘤は，増大しくも膜下出血を来たすことは非常に稀であるとされている8）．我々は，眼瞼下垂で発症した内頸動脈後交通動脈分岐部の小膨隆陰影を呈している症例を経験し，長期間にわたり観察したところ，発見より8年目に小指頭大の脳動脈瘤に増大した事実を確認した．本文は，追跡脳血管写と共に症例を報告し，あわせて小脳動脈瘤症例に対するfollow up studyの必要性を述べた．

We have experienced a case of a 64-year-old woman in whom a small bulging at the origin of the left posterior communicating artery, which had been demonstrated 8 years previously, developed into large aneurysm. Intracranial definitive surgery was performed successfully and prevented a fatal subarachnoid hemorrhage. Although documentation of formation of an aneurysm from a small bulging has been rare, it is certain that some of them become large and develop into saccular aneurysms.