破裂内頚動脈-重複中大脳動脈分岐部動脈瘤に対してコイル塞栓術を施行した1例

A Ruptured Aneurysm at the Origin of a Duplicated Middle Cerebral Artery, Treated by Coil Embolization:A Case Report

Ⅰ．はじめに

　重複中大脳動脈や副中大脳動脈は，脳卒中の診療に際して時にみられる破格であり，剖検上，それぞれ0.7〜2.9%，0.3〜2.7%と報告されている¹⁾．前者は前脈絡叢動脈分岐部より遠位の内頚動脈より分岐して側頭葉の先端を栄養し，後者は前大脳動脈水平部より分岐して前頭葉下面を栄養する．いずれも穿通枝を有していることが多い¹⁰⁾．内頚動脈と重複中大脳動脈の分岐部に動脈瘤が生じることがあり，これまでは主に開頭クリッピング術が行われてきた．今回われわれは，くも膜下出血にて発症した破裂内頚動脈-重複中大脳動脈分岐部動脈瘤の症例に対してコイル塞栓術を施行したので，症例を提示し，動脈瘤の特徴や治療法について文献的考察を加える．

　Duplication of the middle cerebral artery（MCA）is an anatomical variant of the MCA, originating from the distal portion of the internal carotid artery（ICA）and supplying blood flow to the tip of the temporal lobe. Cerebral aneurysms rarely develop at the bifurcation of the ICA and the duplicated MCA, but when they do develop, they may result in subarachnoid hemorrhage. We treated a 41-year-old man, who was urgently brought to our hospital because of severe headache. A computed tomography（CT）scan showed subarachnoid hemorrhage due to the rupture of an aneurysm at the origin of the duplicated MCA. The aneurysm was small and projected laterally, and coil embolization was performed employing a balloon catheter. The neck of the aneurysm was not embolized to preserve the origin of the duplicated MCA. The patient had an uneventful postoperative course, and he returned to his usual daily activities. Coil embolization is rapidly developing for treatment of cerebral aneurysms and may be the first-line treatment for duplicated MCA aneurysms. Owing to the relatively small size of such aneurysms, the risk of intraprocedural rupture should be considered, and a carefully performed balloon-assisted procedure is recommended.