Successful treatment of a recurrent dissecting aneurysm with flow diverter placement following occipital artery-posterior inferior cerebellar artery bypass.

Branch involvement can serve as a predicting factor of incomplete occlusion after flow diverter (FD) treatment, including pipeline embolization device. This study reports a case of subarachnoid hemorrhage owing to bilateral vertebral artery dissection with parent artery occlusion to the left side and stent-assisted coiling to the right side. However, a marked enlargement of the dissected lesion was observed at the right dissecting aneurysm at 6 months. Considering that the posterior inferior cerebellar artery (PICA) originating from the aneurysm could prevent aneurysm occlusion after the FD, we first conducted open surgery to perform a bypass from the occipital artery to the PICA and occluded the PICA origin to eliminate blood flow from the dissection site. Subsequently, we placed a pipeline embolization device at the same location. Complete occlusion of the aneurysm was confirmed after 6 months. Thus far, only one case report of a recurrent middle cerebral artery aneurysm treated with an FD following bypass has been reported. This is the first report of a similar procedure applied to the posterior circulation and dissecting aneurysm. This report highlights the potential for successful outcomes when branches arising from an aneurysm are occluded via bypass prior to the placement of an FD.