Delayed bleeding of unruptured intracranial aneurysms after coil embolization: a retrospective case series.

Abstract Objective Delayed bleeding of unruptured intracranial aneurysms (UIAs) after coil embolization is a rare event. Methods We retrospectively analyzed patients with UIA after coil embolization at our institution and affiliated hospitals between January 2002 and December 2018, and assesed the features of the aneurysms with delayed bleeding afer coil embolization. Results In total, 307 patients with 335 UIAs were included. The average follow-up period was 7.1 ± 4.9 years, and the total follow-up period was 2365 aneurysm-years. There were 271 (80.9%) aneurysm located in the anterior circulation and 64 (19.1%) in the posterior circulation. Significant differences were observed between the two groups in terms of maximum size of the aneurysm (p Conclusion Cautious follow-up with digital subtraction angiography is important particularly within the first 5 years after the procedure. If there are changes in the anatomic outcomes, short-term reassessment or additional treatment should be actively considered, particularly in the posterior circulation.