Are coil compaction and aneurysmal growth two distinct etiologies leading to recurrence following endovascular treatment of intracranial aneurysm?

BACKGROUND: Recurrence following endovascular treatment of intracranial aneurysm is attributed to either coil compaction or aneurysm growth but these processes have not been studied as distinct processes. METHODS: The pixel size of the coil mass and aneurysm sac, and the adjacent parent artery were measured and expressed as a ratio to the pixel size of the parent vessel diameter on immediate post-procedure and follow-up angiograms. Increase of aneurysm area or decrease in coil mass of 30% or greater on follow-up angiogram was used to define "significant" aneurysm growth and coil compaction, respectively. RESULTS: Eleven patients had coil compaction, 14 patients had significant aneurysm growth and 4 patients had small aneurysm regrowth. Retreatment was performed in the 14 patients with "significant" aneurysm regrowth and 8 of the 11 patients with coil compaction at mean follow of 11 months (range 5-20 months) following the initial procedure. There were no events of new aneurysmal rupture in either 11 patients with coil compaction or 14 patients with significant aneurysm regrowth over a mean follow-up period of 22 months (range of 9-42 months). CONCLUSION: This is one of the first studies to differentiate coil compaction and aneurysm growth as distinct etiologies for aneurysm recurrence.