脳室内出血で発症した後下小脳動脈末梢部新生動脈瘤の1例

A case of de novo aneurysm of the distal posterior inferior cerebellar artery with intraventricular hemorrhage

I．はじめに

　後下小脳動脈末梢に生じる動脈瘤はきわめて稀で，全頭蓋内動脈瘤の0.99％と言われている^4），今回，著者らは脳室内出血で発症し，新生動脈瘤の可能性が示唆された後下小脳動脈末梢部動脈瘤を経験したので，文献的考察を加えて報告する．

A case is presented of a de novo aneurysm of the distal posterior inferior cerebellar artery with in-traventricular hemorrhage.

A 67-year-old woman was admitted to our hospital with sudden onset of severe headache and loss of con-sciousness. Computed tomography (CT) scans showed subarachnoid hemorrhage. Angiography demonstrated three aneurysms: an aneurysm of the right vertebral-posterior inferior cerebellar artery, an aneurysm of the bifurcation of the basilar artery, and an aneurysm of the left middle cerebral artery. Considering the distribu-tion of the hemorrhage on CT scans, we concluded that the cause of the hemorrhage was rupture of the verte-bral-posterior inferior cerebellar aneurysm. The verte-bral-posterior inferior cerebellar aneurysm and the mid-dle cerebral aneurysm were successfully clipped, post-operative angiograms showing the complete clippings. At that time, however, there were no abnormal findings in the left posterior inferior cerebellar artery. Six years later, she was readmitted to our hospital because of sudden onset of headache, nausea, and vertigo. CT scans showed an intraventricular hemorrhage, especial-ly in the fourth ventricle, although subarachnoid hemorrhage was not clearly found. Angiography re-vealed an aneurysm of the left distal posterior inferior cerebellar artery. She underwent clipping of the aneu-rysm verified by postoperative angiograms. However she had bacterial meningitis and died from pneumonia and disseminated intravascular coagulopathy.De novo aneurysms of the anterior circulation have often been reported. Carotid ligation, smoking, the use of oral contraceptives, congenital anomalies and hyper-tension are major risk factors in the formation of aneurysms. A de novo aneurysm of the distal posterior inferior cerebellar artery is, however, extremely rare. In this case, the right posterior inferior cerebellar artery disappeared when the de novo aneurysm was found. So it is supposed that hemodynamic changes caused by the clipping of the right vertebral-posterior inferior cerebellar aneurysm and the left middle cerebral aneurysm had contributed to the formation of the de novo aneurysm of the left distal posterior inferior cere-bellar artery.

In the present study, we review the literature on the aneurysm at the distal posterior inferior cerebellar artery and on the de novo aneurysm of the vertebro-basilar artery, and discuss the radiological findings and features.