In-Pipeline stenosis [Neurosurgery Wiki]

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The main concern with the use of the [[pipeline embolization device]] (PED) in treating cerebral aneurysms is the risk of hemorrhagic and [[thromboembolism]], including several cases of branch artery occlusion and delayed occlusion of the stented parent vessel shortly after antiplatelet medications were discontinued, highlighting the potential need for long-term antiplatelet therapy, and disastrous bleeding complications in unruptured aneurysm. 

In addition, these microcell stents are difficult to use in distal aneurysms located over the ICA bifurcation and basilar tip because of the stiffness of the device, and perforating vessel occlusion is more likely to occur due to the characteristics of the stent. Before the era of flow-diverting microcell stents, large cell intracranial stents like the [[Neuroform]] stent (Boston Scientific/Target Therapeutic, Fremont, CA, USA) and [[Enterprise stent]] without coiling were used to provide flow-diverting effects for complex intracranial aneurysms. 

Aneurysm treatment with the Pipeline Embolization Device is associated with the lowest complication rates when used to treat small ICA aneurysms. Procedure-related morbidity and mortality are higher in the treatment of posterior circulation and giant aneurysms
((Kallmes DF, Hanel R, Lopes D, Boccardi E, Bonafé A, Cekirge S, Fiorella D,
Jabbour P, Levy E, McDougall C, Siddiqui A, Szikora I, Woo H, Albuquerque F,
Bozorgchami H, Dashti SR, Almandoz JD, Kelly ME, Turner R 4th, Woodward BK,
Brinjikji W, Lanzino G, Lylyk P. International Retrospective Study of the
Pipeline Embolization Device: A Multicenter Aneurysm Treatment Study. AJNR Am J
Neuroradiol. 2014 Oct 29. [Epub ahead of print] PubMed PMID: 25355814.
)).

===In-Pipeline stenosis===
In-Pipeline stenosis (IPS) is a common, early, and mostly benign complication. Patients with [[internal carotid artery aneurysm]]s are more likely to develop IPS. [[Aspirin]] plays a key role in preventing IPS
((Chalouhi N, Polifka A, Daou B, Kung D, Barros G, Tjoumakaris S, Gonzalez LF,
Starke RM, Hasan D, Judy B, Rosenwasser RH, Jabbour P. In-Pipeline Stenosis:
Incidence, Predictors, and Clinical Outcomes. Neurosurgery. 2015 Dec;77(6):875-9.
doi: 10.1227/NEU.0000000000000908. PubMed PMID: 26200770.
)).
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Aneurysm [[clip]]s placed on canine parent arteries bearing a Pipeline flow diverter were unable to reliably stop blood flow. Application of aneurysm clips can cause mild damage to the device and neointima, which might translate into thromboembolic risks. If possible, vascular control should be sought beyond the terminal ends of the implanted device
((Darsaut TE, Salazkin I, Gentric JC, Magro E, Gevry G, Bojanowski MW, Raymond
J. Temporary surgical clipping of flow-diverted arteries in an experimental
aneurysm model. J Neurosurg. 2016 Jan 8:1-6. [Epub ahead of print] PubMed PMID:
26745475.
)).

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Acute embolism following use of the PED for treatment of intracranial aneurysms is more common than hypothesized. The only identifiable risk factor for embolism appears to be greater aneurysm size, perhaps indicating significant disturbed flow across the aneurysm neck with ingress and egress through the PED struts. The strength of antiplatelet therapy, as measured by residual platelet aggregation, did not appear to be associated with cases of procedural embolism. Further work is needed to determine the implications of these findings and whether anticoagulation regimens can be altered to lower the rate of complications following PED deployment
((Heller RS, Dandamudi V, Lanfranchi M, Malek AM. Effect of antiplatelet therapy
on thromboembolism after flow diversion with the pipeline embolization device. J 
Neurosurg. 2013 Dec;119(6):1603-10. doi: 10.3171/2013.7.JNS122178. Epub 2013 Aug 
23. PubMed PMID: 23971953.
)).
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Significant heterogeneity in [[dual antiplatelet therapy]] regimens following [[Pipeline Embolization Device]] (PED) placement and associated costs, exists at major academic [[neurovascular center]]s. The most commonly used first line dual antiplatelet regimen consists of [[aspirin]] and [[clopidogrel]]. Two major alternate protocols involving [[ticagrelor]] and [[prasugrel]], are administered to clopidogrel hypo-responders. The optimal dual antiplatelet regimen for patients with cerebrovascular conditions has not been established, given limited prospective data within the neurointerventional literature
((Gupta R, Moore JM, Griessenauer CJ, Adeeb N, Patel AS, Youn R, Poliskey K,
Thomas AJ, Ogilvy CS. Assessment of Dual Antiplatelet Regimen for Pipeline
Embolization Device Placement: A Survey of Major Academic Neurovascular Centers
in the United States. World Neurosurg. 2016 Sep 15. pii: S1878-8750(16)30839-7.
doi: 10.1016/j.wneu.2016.09.013. [Epub ahead of print] PubMed PMID: 27641263.
)).