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

A case is presented of a de novo aneurysm of the distal posterior inferior cerebellar artery with intraventricular hemorrhage. A 67-year-old woman was admitted to our hospital with sudden onset of severe headache and loss of consciousness. 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 distribution of the hemorrhage on CT scans, we concluded that the cause of the hemorrhage was rupture of the vertebral-posterior inferior cerebellar aneurysm. The vertebral-posterior inferior cerebellar aneurysm and the middle cerebral aneurysm were successfully clipped, postoperative 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, especially in the fourth ventricle, although subarachnoid hemorrhage was not clearly found. Angiography revealed an aneurysm of the left distal posterior inferior cerebellar artery. She underwent clipping of the aneurysm 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 hypertension 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 cerebellar 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 vertebrobasilar artery, and discuss the radiological findings and features.