Pipeline embolization device induced collateral channels in elective flow diversion treatment

The pipeline embolization device (PED) is a well recognized treatment for intracranial aneurysms. However, uncertainty remains regarding its effects on flow alteration, which is particularly highlighted by persistently perfused aneurysmal remnants and nonregressing, non-perfused aneurysmal masses. Here we present a 68-year-old woman with an incidental giant fusiform right paraophthalmic aneurysm electively treated with a PED. After lowering her antiplatelet therapy to promote aneurysm thrombosis, she was found to have a progressively enlarging perfused aneurysmal remnant. Angiography revealed PED occlusion, but curiously the development of a peri-construct collateral channel which feeds the aneurysmal remnant, and gives rise to distal branches and contributes to middle cerebral artery flow. The large 'thrombosed' aneurysmal mass showed tiny internal vessels on cone beam CT angiography as well as florid enhancement on MRI, further confirming that apparently thrombosed remnants are biologically active and may be remodeled depending on flow demand.