Cerebral Aneurysm Sac Growth as the Etiology of Recurrence After Successful Coil Embolization

Cerebral aneurysm recurrence is characterized by the recanalization of an aneurysm lumen after treatment with embolization coils, necessitating additional interventional measures. Recurrence rates of ≤ 34% have been reported (with major recurrence rates of ≤ 21% cited).¹ The etiology of cerebral aneurysm recurrence remains unclear; however, compaction of embolization coils within a treated aneurysm lumen has been referenced in the literature as the primary mechanism of recurrence.^2–4 Nevertheless, it should be noted that the evidence presented has been observational in nature and thus qualitative.^2–4 While coil compaction is a conceivable mechanism of cerebral aneurysm recanalization (allowing for increased luminal volume), it is hypothesized by the authors that growth of the sac itself is the primary recurrence mechanism. Previous studies concerning aneurysm sac growth have been limited to qualitative observations of 2D angiographic data.^5–6 In these studies the ability to accurately measure aneurysm sac and coil mass size was vital; however, changes in scan magnification and patient orientation between initial and follow-up angiographic scans makes the reliable discernment of aneurysm sac and coil mass size over time difficult, and therefore limits the ability to rigorously assess the temporal evolution of both the coil mass and the aneurysm sac. The objective of this study was to utilize 3D image processing methods to quantify both aneurysm sac growth and coil mass volume in order to assess the association of each mechanism with recurrence. A study population of patients presenting with recurrent cerebral aneurysms post treatment with embolization coils at The University of Iowa Hospitals and Clinics (UIHC) were examined.