Pipeline embolization device thrombosis induced peri-construct collateral channels.

More than half a decade of experience and follow-up has now been accumulated with regard to flow diversion as a treatment for intracranial aneurysms; however, many uncertainties, such as the nature of aneurysmal remnants and the meaning of non-regressed, non-perfused aneurysmal masses, are still unknown. Here we discuss a 22-year-old man who presented with a grade 1 subarachnoid hemorrhage secondary to a dissecting right anterior cerebral artery aneurysm who was subsequently treated with a Pipeline Embolization Device construct. After ceasing dual antiplatelet therapy himself, he was found on MRI to have an area of increased aneurysmal remnant reperfusion. This was found to connect to multiple channels which reconstituted flow within the distal construct on angiography. The central area of construct thrombosis could not be visualized on MRI. The finding suggests that non-opacified aneurysmal remnants that have not regressed are biologically active and raises concerns regarding using MRI for long term follow-up.