Delayed recanalization of brain arteriovenous malformation after complete obliteration by endovascular embolization.

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.