Introduction: The Pipeline Embolization Device (PED) is increasingly used for both on- and off-label purposes for treatment of intracranial aneurysms. The device gradually slows flow of blood into the aneurysm, but the high metal coverage of PED promotes endothelialization of the device. Occasionally, this leads to in-stent stenosis that is clinically well-tolerated. We present a multi-institutional Pipeline series that includes 4 cases of gradual, asymptomatic tourniquet occlusion within the PED and parent vessel.

Methods: Institutional databases at each participating center were searched for patients treated with the Pipeline Embolization Device (ev3, Irvine, CA). We selected patients that had at least 50% stenosis or occlusion, and reviewed all relevant clinical and radiographic data.

Results: A total of 326 cases performed by 5 neurointerventionalists across 4 institutions were reviewed. Among these, there were 4 cases of complete occlusion and 2 cases of 50% stenosis, for an occlusion rate of 1.2%. All patients were clinically asymptomatic.

Conclusions: A gradual, tourniquet-like occlusion can occur following placement of PED, leading to vessel occlusion. This has been clinically well-tolerated by patients in our series due to the formation of pial collaterals as the stenosis progresses, likely due to ischemic preconditioning. Small parent vessel, preexisting stenosis, fusiform pathology, overlapping devices, and suboptimal antiplatelet therapy seem to be predisposing factors. Further experience and follow-up with these patients will allow us to characterize risk factors and optimize post-procedural therapy for these patients.

Patient Care: By identifying the common complications and this newly described phenomenon associated with Pipeline, we may glean a better understanding of this phenomenon and tailor patient care appropriately. This initial description should prompt further investsigation.

Learning Objectives: 1) Be able to identify the common applications for Pipeline 2) Be able to describe the common complications with Pipeline 3) Be able to distinguish between acute thrombosis and tourniquet occlusion

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