真の“PICA communicating artery”aneurysmの1例

True “PICA communicating artery” aneurysm:a case report

I．はじめに

　頭蓋内に発生する動脈瘤の中で後下小脳動脈poste—rior inferior cerebellar artery（PICA）末梢部に見られる動脈瘤は比較的稀な動脈瘤である^9,11,14）．一方，後下小脳動脈の走行には変異が多く，両側の後下小脳動脈を交通する側副血管の存在も認められている．1991年，Hlavin^4）らは両側PICAを交通する動脈に発生した動脈瘤を“PICA communicating artery”aneurysmとして報告した．今回，われわれは両側の後下小脳動脈を交通する側副血管に発生した動脈瘤の1症例を経験したので，Hlavinの症例との比較並びにその発生機序などについて若干の文献的考察を加えて報告する．

We present an unusual case of an aneurysm of the distal posterior inferior cerebellar artery (PICA). A 51-year-old female presented a subarachnoid hemorrhage with mild consciousness disturbance on August 6, 1992. Computed tomography (CT) on admission showed sub-arachnoid hemorrhage with thick hematoma in the cis-terna magna and intraventricular hematoma in the 4th, 3rd and both lateral ventricles. The angiogram on admission revealed no definite vascular anomalies. Re-peated angiograms on the 11th day after onset showed an aneurysm on anastomotic branch between the bilate-ral distal PICAs. The aneurysm was clipped success-fully through a suboccipital craniectomy 14 days after the onset. In the literature reviewed, only one such aneurysm, located at an anastomotic vessel of the bi-lateral PICAs, has been reported by Hlavin et al in 1991. They reported that the aneurysm was associated with a unilateral PICA that supplied both cerebellar hemispheres and arose from an anastomotic vessel in the contralateral circulation. They called the aneurysm as “a PICA communicating artery” aneurysm. We assume that this “PICA communicating artery” is a remnant of a primitive lateral vertebrobasilar anasto-mosis, which appears in the embryo at the 9mm stage. It is suggested that the pathogenesis may be not only the hemodynamic factor but also a congenital anomaly.