Ghost twisting of the dual-layer flow-diverting stent.

The twisting phenomenon of the flow diverter stents rarely occurs, but it recently became relatively well-recognized. There have been few reports on single-layer flow diverters only. The Flow Redirection Endoluminal Device (FRED) (MicroVention, Tustin, California) has a unique design characterized by a braided dual-layer self-expanding stent. There have been no reports on the twisting phenomenon of FRED. This study reports two cases of acute in-stent blood flow disturbances after the deployment of FRED in a patient with intracranial aneurysms associated with "ghost twisting." In this phenomenon, the inner layer does not expand with the coning deformation, even though the outer layer is fully open. This was confirmed through high-resolution cone-beam computed tomography, but not conventional angiography. The two cases were successfully treated using balloon angioplasty and showed favorable outcomes. The structural issue of "ghost twisting" was a possible underlying factor for the ischemic complications associated with FRED deployment.