A Case of Vertebral Artery Fusiform Aneurysm Treated by Flow Alteration: Successful Prediction of Therapeutic Effects Using Computational Fluid Dynamics

The treatment of intracranial complicated aneurysms remains challenging. In patients with complicated aneurysms that are neither clippable nor coilable, flow alteration treatment (FAT) with a combined procedure of proximal/distal occlusion or trapping of an aneurysm with bypass surgery has been reported. However, it is difficult to predict whatever FAT can achieve aneurysmal obliteration without ischemic complications. A 69-year-old female was incidentally diagnosed with a left vertebral artery (VA) fusiform aneurysm distal to the left posterior inferior cerebellar artery (PICA). Because one-year follow-up three-dimensional computed tomography angiography showed that the aneurysm grew significantly, surgical management was considered the therapy of choice. For determining treatment strategies, we assumed left VA occlusion at the proximal to the left PICA as a FAT model and performed computational fluid dynamics (CFD) analyses. The FAT model had much lower wall shear stress and shear rate at the aneurysm dome than presumed thresholds necessary to thrombus formation, while those at the PICA were obviously higher than the thresholds, and streamlines into the left PICA from the distal VA were preserved. These findings theoretically meant that surgical occlusion of the left VA proximal to the left PICA and aneurysm would induce intra-aneurysmal thrombus formation with preservation of the left PICA flow. The treatment was performed successfully and achieved the predicted results. CFD simulations may be useful to predict effects of FAT for complicated aneurysms.