中大脳動脈遠位部に未破裂でみつかった動脈硬化性脳動脈瘤の1例

Unruptured Arteriosclerotic Aneurysm in the Distal Middle Cerebral Artery:A Case Report

Ⅰ．はじめに

　中大脳動脈遠位部の脳動脈瘤の報告は稀である^4,6,12)．遠位部の脳動脈瘤の原因としては感染が多いといわれており^1,10,13)，解離も稀ながら報告がある^{5,7,8,11,14,15)}．ほとんどが破裂による脳内出血やくも膜下出血でみつかったケースでの報告であるが，本症例は未破裂例であり，病理組織では動脈瘤壁の大部分で非常に強い動脈硬化の所見を呈していた稀なケースであった．病理学的知見ならびに文献的考察を加え報告する．

　We report a rare case of an unruptured cerebral aneurysm in the left distal middle cerebral artery（MCA). A 76-year-old woman was referred to our department for unruptured cerebral aneurysms detected incidentally by magnetic resonance angiography. A left carotid angiogram revealed a saccular aneurysm arising in an arterial trunk unrelated to the branching zone of the distal MCA. The patient underwent an operation for trapping and excision of the saccular aneurysm in the distal MCA followed by end-to-end anastomosis. Histological analysis revealed an aneurysmally-dilated artery exhibiting thickened fibrous intima with foci of calcification and fragmented internal elastic lamina. Neither dissection nor infection were observed. The histological findings suggested that the aneurysm in this case was associated with arteriosclerotic change. Considering the medical history of the patient, we conclude that aging and hypertension are factors of the development of the cerebral aneurysm in our case, although the aneurysm is located in the distal MCA in which it is considered to low hemodynamic stress. We report this extremely rare case with a literature review.