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Background Endovascular embolization is an established treatment for brain arteriovenous malformations (bAVMs), supported by advances in embolic agents and catheter technology. However, long-term outcomes after angiographically confirmed complete obliteration, especially delayed recanalization, remain underreported.Objective Our study’s aim is to describe delayed recanalization of bAVMs following complete obliteration via endovascular embolization and to identify potential radiographic indicators and risk factors.Methods A retrospective review was conducted on individuals treated at a single center from 2006 to 2024. Inclusion criteria were bAVMs with complete obliteration confirmed on post-procedural and 6–12 month follow-up digital subtraction angiography (DSA), followed by recanalization evidence on long-term imaging. Four individuals met the criteria and were analyzed with a focus on nidus-cast and vessel-cast correspondence.Results All four individuals developed delayed recanalization 8–11 years post-embolization, despite complete occlusion on initial and short-term imaging. In three individuals, embolic cast mismatch with draining veins or feeding arteries was identified. In one individual, residual hematoma may have masked an occult nidus compartment, creating a pseudo-match on initial DSA. All individuals were successfully retreated by transvenous embolization (TVE).Conclusion Delayed recanalization of bAVMs after angiographically complete endovascular obliteration is rare but significant. Vein- or artery-cast mismatch and residual hematoma may increase recurrence risk. Long-term imaging surveillance is advised, particularly when vessel-cast correspondence is imperfect. These findings underscore the need for tailored follow-up protocols with patients with embolic cast mismatch to reduce recurrence risk.