前大脳動脈遠位部非分岐部に発生したnarrow neck囊状脳動脈瘤の1例

Saccular Aneurysm Arising in the Non-Branching Segment of the Distal Anterior Cerebral Artery with Stalk-like Narrow Neck: A Case Report

Ⅰ．は じ め に

　前大脳動脈遠位部（distal anterior cerebral artery：DACA）に発生する動脈瘤は比較的稀であるが，その多くは，通常の囊状動脈瘤と同様に血管分岐部にあって血行力学的機序により増大すると考えられている．一方，血管分岐部以外に発生する動脈瘤はこれとは異なる機序により発生・増大するという説があるが，その多くは解離性動脈瘤，もしくはいわゆる血豆状動脈瘤であり，非分岐部囊状動脈瘤の報告例は少ない．今回われわれは，DACA非分岐部囊状動脈瘤の1例を経験したので，病理組織学的考察とともに報告する．

　An aneurysm arising in the distal anterior cerebral artery (DACA) is relatively rare. Among them, those in the non-branching segment are seldom reported so far. The authors present the case of an 87-year-old woman who developed intracerebral hemorrhage and acute hydrocephalus due to rupture of an aneurysm arising in the non-branching site of DACA. External ventricular drainage followed by aneurysm clipping by bifrontal craniotomy was performed as treatment. Microscopic observations revealed that the aneurysm was saccular-shaped, located at the non-branching site of the A3 portion of the anterior cerebral artery, and had significant atherosclerosis neither on its parent artery nor neck. Histopathological examinations of the aneurysm wall denied traumatic aneurysm or mycotic aneurysm, and showed partial disruption of the internal elastic lamina, suggesting a difference from common aneurysms arising at arterial branchings. Profound knowledge of this type of aneurysms would be useful in dealing with them at surgery.