Background Delayed complications associated with the implantation of flow diverter (FD) stents have not been completely understood and well characterized. There is sparse data on the frequency, severity and clinical consequences of in-stent stenosis following flow diversion treatment of intracranial aneurysms.
Methods A retrospective review of our institution’s neuroendovascular database was performed to identify all patients who underwent FD treatment of intracranial aneurysms. Clinical information was retrospectively collected. The procedural angiograms were compared to routine follow-up angiograms obtained at different timepoints. In-stent stenosis was defined as a growth process beyond the limits of the metallic mesh. Angiographically, this was observed as a “gap” between the vessel lumen filled with contrast and the actual stent wall. Stenosis was graded as mild (<25%), moderate (25–50%), or severe (>50%), depending on the degree of parent vessel narrowing.
Results Seventy-eight patients with 86 aneurysms were treated with FDs from June 2011 to March 2015. Angiographic follow-up data was available in 49 (62.8%) of patients. This included 38 (76%) females, with mean age of 54.7 years (range 19–82). Six (12%) were treated for subarachnoid hemorrhage, and the remainder for symptomatic unruptured aneurysms. Thirty-nine (85%) patients had aneurysms in the anterior circulation, and 7 (14%) in the posterior circulation. Average measurement of the largest aneurysm diameter was 12.6 mm (range 2–37 mm). A mean of 1.5 (range 1–5) flow diverters were used, with 19 (39%) requiring > 1 stent. The Pipeline embolization device was used in 44 (90%), and Surpass was used in the rest. Concomitant coil embolization was performed in 7 (14%) patients while 2 required balloon angioplasty for optimal deployment. Median follow-up was 10.4 months (range 1–28). In-stent stenosis on follow-up was detected in 8 (16%) patients, at a median of 6 months post procedure. In-stent stenosis was seen in flow diverters placed in 5 ophthalmic, 1 cavernous, 1 ICA aneurysm involving cavernous/supraclinoid segments and 1 basilar aneurysm. Stenosis was mild in 4 (50%), moderate in 3 (38%) and severe in 1(12%). Stenosis was in the mid segment in 7 stents, and at the distal end in one patient. None of the in-stent stenoses caused flow limitation, symptoms, or required treatment.
Conclusions Our preliminary results show a 16% rate of in-stent stenosis after FD treatment, which developed within a few months after placement, and did not cause flow restriction. All of our patients with narrowing remained asymptomatic. Further research on in-stent stenosis is needed to better understand contributing mechanisms and clinical relevance, with guidelines for follow-up and long-term management.
Disclosures S. John: None. M. Bain: None. F. Hui: None. M. Hussain: None. G. Toth: None.