Factors associated with in-stent stenosis after cerebral aneurysm embolization using a Pipeline embolization device

Flow-diverting (FD) stents, with or without coiling, are a mainstay in endovascular treatment of intracranial aneurysms (IAs). One observed complication from flow diverter stent (FDS) insertion has been in-stent stenosis. Though previously studied in the short-term period, the long-term history of this complication has yet to be described.We performed a retrospective cohort study of consecutive IAs treated with Pipeline Embolization Device (PED), with or without coiling, at our centre between September 2014 and December 2018 that had at least one digital subtraction angiogram (DSA) during follow-up. In-stent stenosis was measured from DSA images, and associated patient and procedural characteristics were analysed.94 patients treated with PED for IA were identified. On initial DSA during follow-up, 52 patients (55.3%) had in-stent stenosis within the PED. Of these 52 patients, 17 had a second DSA during follow-up. In this 2nd DSA, improvement and/or stable in-stent stenosis was seen 16 patients (94.1%). One patient in this group had worsening in-stent stenosis had a vertebrobasilar junction FD stent. Of the patients without in-stent stenosis on initial DSA, 15 had a second DSA during follow-up. Only one of these patients (6.7%) had new appearance of in-stent stenosis (measuring 5%). Multivariate analysis found statin use to be predictive of in-stent stenosis (p = 0.020, Odds ratio = 0.279 and 95% confidence interval = 0.095-0.821).In-stent stenosis after FDS placement was seen in 53.2% of cases, which had between 1-50% of stenosis. 82.4% had resolution/improvement of their stenosis. Statin use was protective of in-stent stenosis.