Delayed Progression to Major Recanalization in Coiled Aneurysms with Minor Recanalization at 36-Month Follow-up: Incidence and Related Risk Factors

Purpose: The aim was to monitor aneurysms that show imaging evidence of minor recanalization 36 months after coil embolization and to determine the rate and related risk factors of major recanalization during more prolonged observation. Methods: A total of 54 patients with 55 aneurysms showing minor recanalization at 36-month follow-up imaging between 2011 and 2013 were retrospectively reviewed. Medical records and radiological data accumulating in the course of extended monitoring (mean 83.9 ± 21.5 months) were assessed. Incidence and average annual risk of progression to major recanalization were then calculated. Univariate and multivariate regression analyses were applied to determine possible risk factors for progression to major recanalization. Results: In the 55 aneurysms studied 26 showed sustained minor recanalization since month 6 of follow-up, whereas minor recanalization of 29 completely occluded coiled lesions appeared in follow-up images after 6–24 months. Only 8 coiled aneurysms (14.5%) with minor recanalization at 36 months progressed to major recanalization during 219.3 aneurysm-years of observation (3.6% per aneurysm-year), 2 surfacing within 72 months and 6 developing thereafter. Additional embolization was performed in six of these patients. By multivariate analysis, no clinical or anatomic factors were statistically linked to such progression, but younger age showed marginal significance (hazard ratio, HR = 1.076; p = 0.099). Conclusion: Most coiled aneurysms (85.5%) showing minor recanalization at 36 months postembolization proved to be stable in extended observation. Given the low probability but seriousness of delayed major recanalization, careful monitoring is still warranted in this setting but at less frequent intervals (every 2–3 years) beyond 36 months.