Introduction: Open- and closed-cell stents represent two principal options for stent-assisted coiling of internal carotid artery (ICA) aneurysms. This study seeks to compare clinical outcomes and procedural thromboembolic risk in treating sidewall ICA aneurysms with stent-assisted coiling (SAC) using these stent designs.

Methods: 122 consecutive patients (mean age, 56.8 years) receiving open-cell (n = 53) or closed-cell stents (n = 69) for SAC of sidewall ICA aneurysms underwent routine post-procedural magnetic resonance diffusion weighted imaging (MR-DWI) within 48 hours. Patient demographics, aneurysm location and size and, intra-procedural clotting function, presence and number of MR-DWI lesions (MR-DWI+), and peri-procedural complications were analyzed.

Results: Within the <5 mm aneurysm subset, no open-cell (0/31) patients demonstrated MR-DWI lesions, compared to 12/36 or 33.3% of patients in the closed-cell group, (P <0.01). Within the > 5 mm aneurysm subset, 8/22 or 36.4% of patients in the open-cell group demonstrated post-procedural MR-DWI lesions, compared to 13/33 or 39.4% of patients in the closed-cell group, (P=0.82). The rate of MR-DWI+ among patients with new neurologic deficits (7/10) was significantly higher than among those without deficits (26/108), (P<0.01). Among open-cell patients’ post procedural deficits 1 out of 2 (50%) completely resolved by discharge compared to 3 out of 8 (37.5%) for closed-cell patients.

Conclusions: The previously described lower rate of procedural thromboembolic lesions associated with open-cell stent design owing to superior vessel apposition is aneurysm size-dependent and is voided in larger aneurysms. Although the exact mechanism needs further research, it could be the result of complex hemodynamics and inflow-outflow interactions across stent struts in larger aneurysms. Our findings may help guide stent choice based on lesion size and provide procedural thromboembolic estimates when considering SAC versus flow-diverter therapy in sidewall carotid aneurysms.

Patient Care: Our findings may help guide stent choice based on lesion size and provide procedural thromboembolic estimates when considering SAC versus flow-diverter therapy in sidewall carotid aneurysms.

Learning Objectives: By the conclusion of this session, participants should be able to: 1. Be aware of the compared post-procedure MR-DWI findings for open cell and closed cell stent-assisted coiling (SAC) of sidewall ICA aneurysms as a means of evaluating the thromboembolic risk associated with each stent. 2. Be aware of the demonstrated interaction between thromboembolic risk and maximal aneurysm diameter across stent types, open cell and closed cell. 3. Understand the evaluated and compared clinical outcomes associated with stent-assisted coiling of ICA sidewall aneurysms for both open cell and closed cell stents.

References: 1. Hetts SW, Turk A, English JD, Dowd CF, Mocco J, et al. (2014) Stent-assisted coiling versus coiling alone in unruptured intracranial aneurysms in the matrix and platinum science trial: safety, efficacy, and mid-term outcomes. AJNR Am J Neuroradiol 35: 698–705. 2. Lopes D, Sani S (2005) Histological postmortem study of an internal carotid artery aneurysm treated with the Neuroform stent. Neurosurgery 56: E416 3. Seibert B, et al. Intracranial aneurysms: review of current treatment options and outcomes. Front Neurol. 2011;2:45 4. Krischek O, Miloslavski E, Fischer S, Shrivastava S, Henkes H. A comparison of functional and physical properties of self-expanding intracranial stents [Neuro- form3, Wingspan, Solitaire, Leo1, Enterprise]. Minim Invasive Neurosurg. 2011; 54(1):21-28. 5. De Bock S, Iannaccone F, De Santis G, et al. Our capricious vessels: the influence of stent design and vessel geometry on the mechanics of intracranial aneurysm stent deployment. J Biomech. 2012;45(8):1353-1359. ? 6. Izar, B., Rai, A., Raghuram, K., Rotruck, J., & Carpenter, J. (2011). Comparison of devices used for stent-assisted coiling of intracranial aneurysms. PLoS ONE, 6(9). 7. Kadkhodayan, Y., Rhodes, N., Blackburn, S., Derdeyn, C. P., Cross, D. T., & Moran, C. J. (2013). Comparison of enterprise with neuroform stent-assisted coiling of intracranial aneurysms. American Journal of Roentgenology, 200(4), 872-878. 8. Lubicz B., Francois O., Levivier M., Brotchi J., Baleriaux D. (2008). Preliminary experience with the enterprise stent for endovascular treatment of complex intracranial aneurysms: potential advantages and limiting characteristics. Neurosurgery 62, 1063–1069 9. Heller RS, Dandamudi V, Calnan D, Malek AM Neuroform Intracranial Stenting for Aneurysms Using Simple and Multi-stent Technique Is Associated With Low Risk of Magnetic Resonance Diffusion-Weighted Imaging Lesions. J Neurosurg. 2013; 73(4):582-591 10. Heller RS, Miele WR, Do-Dai DD, Malek AM. Crescent sign on magnetic resonance angiography revealing incomplete stent apposition: correlation with diffusion-weighted changes in stent-mediated coil embolization of aneurysms. J Neurosurg. 2011;115(3):624-632. 11. Hong Y, Wang YJ, Deng Z, et al. Stent-assisted coiling versus coiling in treatment of intracranial aneurysm: a systematic review and meta-analysis. PLoS One. 2014;9:e82311 12. Lee YJ, Kim DJ, Suh SH, Lee SK, Kim J, et al. Stent-assisted coil embolization of intracranial wide-necked aneurysms. Neuroradiology. 2005;47:680–689. 13. Fargen KM, Hoh BL, Welch BG, Pride GL, Lanzino G, Boulos AS, et al. Long-term results of enterprise stent-assisted coiling of cerebral aneurysms. Neurosurgery. 2012 Aug;71(2):239–244 14. Geyik S, Yavuz K, Yurttutan N, Saatci I, Cekirge HS. Stent-assisted coiling in endovascular treatment of 500 consecutive cerebral aneurysms with long-term follow-up. AJNR Am J Neuroradiol. 2013 Nov;34(11):2157–2162. 15. Kang DH, Kim BM, Kim DJ, et al. MR-DWI-positive lesions and symptomatic ischemic complications after coiling of unruptured intracranial aneurysms. Stroke. 2012; 44(3): 789-791. 16. Heller RS, Malek AM. Parent vessel size and curvature strongly influence risk of incomplete stent apposition in enterprise intracranial aneurysm stent coiling. AJNR Am J Neuroradiol. 2011 Oct;32(9):1714–1720. 17. Heller R, Calnan DR, Lanfranchi M, Madan N, Malek AM. Incomplete stent apposition in Enterprise stent-mediated coiling of aneurysms: persistence over time and risk of delayed ischemic events. J Neurosurg. 2013; 118(5):1014-1022 18. Durst, C. R., Khan, P., Gaughen, J., Patrie, J., Starke, R. M., Conant, P., Liu, K. C., et al. (2014). Direct comparison of Neuroform and Enterprise stents in the treatment of wide-necked intracranial aneurysms. Clinical Radiology, 69(12), e471-e476. W.B. Saunders Ltd. 19. King B, Vaziri S, Singla A, Fargen K, Mocco J. Clinical and angiographic outcomes after stent-assisted coiling of cerebral aneurysms with Enterprise and Neuroform stents: a comparative analysis of the literature. J NeuroIntervent Surg. 2015; 7:905-909 20. Chalouhi N, Jabbour P, Singhal S, Drueding R, Starke RM, Dalyai RT, et al. Stent-assisted coiling of intracranial aneurysms: Predictors of complications, recanalization, and outcome in 508 cases. Stroke. 2013 May;44(5):1348–1353. 21. Piotin M, Blanc R, Spelle L, Mounayer C, Piantino R, et al. Stent-assisted coiling of intracranial aneurysms: clinical and angiographic results in 216 consecutive aneurysms. Stroke. 2010;41:110–115