術前診断が困難であった末梢性中大脳動脈瘤の1例

A Case of Aneurysm of the Peripheral Middle Cerebral Artery Undetectable on Preoperative Angiogram

I．はじめに

　脳動脈瘤の発生部位はウィルス動脈輪周囲の主幹動脈分岐部が圧倒的に多く，末梢部での発生は少ない．末梢部脳動脈瘤では前大脳動脈領域のものは比較的多く認められるが，中大脳動脈末梢部領域のものは，全動脈瘤中の約2％と少なく稀である^12,14）．

　今回筆者らは，くも膜下出血を伴った右脳内出血症例を経験したが，入院後に施行した脳血管撮影では右内頸動脈海綿静脈洞部に動脈瘤が認められたものの，中大脳動脈領域には明らかな血管奇形を指摘できなかった．緊急開頭手術中に中大脳動脈末梢部の動脈瘤を確認できた症例であるが，手術上の注意点を含め検討したので報告する．

The authors describe a rare case of an aneurysm of the peripheral middle cerebral artery. A 63-year-oldfemale with a past history of hypertension suddenly fell into a comatose state, and was brought to our hos-pital. On admission, CT scan showed intracerebral hematoma located in the right putamen with diffusesubarachnoid hemorrhage. To exclude vascular lesions, an angiography was performed just after admis-sion. The right carotid angiogram showed an aneurysm at the cavernous portion of the internal carotidartery (ICA), but failed to show any aneurysms in the rest of the intracranial circulation. Just after theangiography, emergent operation was performed for the main purpose of evacuation of the hematoma, andwith only the secondary purpose of searching for undetectable aneurysms. The patient underwent a rightfrontotemporal craniotomy. After partial evacuation of the hematoma through the corticotomy of the rightfrontal operculum, the Sylvian fissure was opened widely. No aneurysm was observed either in the maintrunk of the right ICA or the middle cerebral artery (MCA). During the final stage of evacuation of thehematoma through the corticotomy, arterial bleeding occurred. While evacuating the blood, we detected asaccular aneurysm arising from MCA branch (M2-M3 junction) andwe clipped the aneurysm. We dis-cuss peripheral MCA aneurysms with a review of the literature.