Re-growth of a posterior inferior cerebellar artery aneurysm after resection of the associated posterior fossa arteriovenous malformation

Arteriovenous malformation (AVM)-related aneurysms have been described in the literature. Their behavior varies based on their location in relation to and the activity of the shunting through the index AVM. The intuitive expectation supported by numerous reports is that these aneurysms should regress if the AVM is excluded from the circulation. We describe a case of 46-year-old man who presented with a posterior fossa AVM with an aneurysm on the posterior inferior cerebellar artery feeding the AVM. The nidus of the AVM was successfully excluded by glue embolization, with initial regression of the PICA aneurysm on serial imaging. Five years after the endovascular treatment, the aneurysm showed significant re-growth necessitating endovascular coiling. This case presents the re-growth of an AVM-related aneurysm and emphasizes the importance of long-term follow-up of such aneurysms even if the AVM is completely excluded.