破裂脳底動脈-上小脳動脈瘤のコイル塞栓術後に数年で新生した対側遠位部上小脳動脈瘤の1例

De Novo Distal Superior Cerebellar Artery Aneurysm after Embolization of a Ruptured Aneurysm at the Bifurcation of the Contralateral Basilar and Superior Cerebellar Arteries

Ⅰ．緒　　言

　破裂脳動脈瘤に対する術後，新たに他部位に発生する脳動脈瘤（新生動脈瘤：de novo aneurysm）は比較的稀な病態ではあるが，動脈瘤性くも膜下出血の再発の一因として重要である^4,9,10)．今回われわれは，破裂脳底動脈-上小脳動脈瘤（BA-SCA動脈瘤）コイル塞栓術後に新生した対側遠位部上小脳動脈瘤（distal SCA動脈瘤）を経験した．後頭蓋窩破裂脳動脈瘤の治療後に後頭蓋窩にde novo aneurysmをみることは極めて稀である．脳動脈瘤治療後のde novo aneurysm形成のメカニズム，くも膜下出血術後患者の最適な画像フォローアップについて考察を加える．

　The formation of de novo aneurysms in the posterior fossa after successful treatment of a previous aneurysm in the same fossa is rare. Here we describe a case of a de novo generated aneurysm at the distal superior cerebellar artery（SCA）7 years after the successful obliteration of an aneurysm at the contralateral basilar artery（BA)-SCA bifurcation. The treatment of the original posterior fossa aneurysm may lead to hemodynamic changes that may contribute to the formation of a de novo aneurysm at another vulnerable point in the posterior fossa circulation. We conclude that a close surveillance is required after the initial treatment of posterior fossa aneurysms in order to detect the possible formation of de novo aneurysms.