鏡面像を呈した前大脳動脈遠位部の極小破裂脳動脈瘤の1症例

A Mirror Image of a Tiny Distal Anterior Cerebral Artery Aneurysm that Ruptured

Ⅰ．はじめに

　鏡面像を呈する脳動脈瘤にはしばしば遭遇するが，その多くは中大脳動脈であり，前大脳動脈遠位部（distal anterior cerebral artery：DACA）での発生は極めて稀である⁶⁾．近年の未破裂脳動脈瘤の観察研究によると，サイズが5mm以下の脳動脈瘤の破裂率は一般的には低いとされるが^8,10)，実際の臨床では5mm未満，さらには3mm以下の極小瘤の破裂症例もときに経験する．

　今回われわれは，鏡面像を呈したDACAの極小破裂脳動脈瘤の1症例を経験したので，文献的考察を加えて報告する．

　Distal anterior cerebral artery（DACA）aneurysms have a low incidence. Particularly, DACA mirror aneurysms are extremely rare, although DACA multiple aneurysms are not rare. Generally, it is said that tiny aneurysms have a low risk of rupture. However, we sometimes encounter cases of ruptured tiny aneurysm. We describe a rare case of a mirror image of DACA ruptured tiny aneurysm.

　A tiny aneurysm can rupture if the aneurysmal wall is fragile. Detection of the aneurysm may often be difficult with a single modality, even if the modality is digital subtraction angiography. Moreover, the distribution of subarachnoid hemorrhage may not be typical.

　It might be important to capture a slight change of aneurysm in follow-up imaging to detect a ruptured aneurysm over multiple iterations of imaging.