Outflow Occlusion with Occipital Artery–Posterior Inferior Cerebellar Artery Bypass for Growing Vertebral Artery Fusiform Aneurysm with Ischemic Onset: A Case Report

Surgical treatments should be considered for vertebral artery fusiform aneurysms, which become symptomatic due to cerebral ischemia or mass effect. Ischemic complication is one of the major problems after surgical or endovascular trapping, which is associated with unfavorable outcomes. The authors present a case with growing vertebral artery (VA) fusiform aneurysm with ischemic onset successfully treated with outflow occlusion with occipital artery–posterior inferior cerebellar artery (OA-PICA) bypass. A 50-year-old woman presented with left PICA territory infarction. Left vertebral angiography (VAG) showed occlusion of the left VA at the proximal V4 segment. Right VAG revealed that the distal part of the left V4 segment with fusiform aneurysmal dilatation was reconstituted through vertebrobasilar junction, and the left PICA was the outlet of the blood flow from the fusiform aneurysm. Although the patient was treated conservatively, enlargement of the left VA fusiform aneurysm was observed 8 months after the initial presentation. Considering the potential risks for future stroke or bleeding, we performed clip occlusion of the origin of the left PICA, which could achieve outflow occlusion of the fusiform aneurysm with preservation of the perforators arising around the aneurysm. We created OA-PICA anastomosis for revascularization of the distal PICA. The postoperative course was uneventful, and the postoperative right VAG revealed occlusion of the fusiform aneurysm. Outflow occlusion instead of trapping is an effective surgical option for VA fusiform aneurysm to achieve obliterate the aneurysm with preservation of the perforator at the blind end.