Introduction: In coiled cerebral aneurysms coil compaction is regarded as the presumptive recurrence mechanism, but aneurysm growth is rarely thought of as its etiology. The objective was to assess the mechanism of recurrence by quantifying coil compaction and aneurysm growth. We hypothesize aneurysm growth is the primary recurrence mechanism.
Methods: The study population consisted of 15 recurrence and 12 non-recurrence control aneurysms initially completely coiled at The University of Iowa Hospitals and Clinics. Aneurysm and coil models, and corresponding volumes, were generated from 3D rotational angiograms using a highly objective image processing protocol. Aneurysm growth (VSG) and coil growth (VCG) were then computed. Paired Student’s t-Tests (p<0.05, two-tailed) were done to assess for aneurysm and coil growth in the population. The objectivity of the methods was assessed by comparing one user’s estimations of aneurysm and coil volumes against a blinded second user’s estimations in a subset of the study population.
Results: Aneurysm growth was present in the recurrence cohort with statistical significance. In the control cohort aneurysm growth did not exist with statistical significance. Coil volume was not found to be decreased (i.e. no coil compaction) in either the recurrence or control cohorts. Figure 1 summarizes these results. The coefficients of determination for the user sensitivity plots were 0.998 and 0.999 for the aneurysm and coil volumes respectively.
Conclusions: The image processing protocol used to estimate aneurysm and coil volumes is not sensitive to the user. In this small study population aneurysm growth was the predominant mechanism associated with recurrence. There is no evidence to support the association of coil compaction with recurrence. The limited size of the study population and the single-center data suggest caution in drawing definitive conclusions.
Patient Care: Rigorously assessing whether and to what extent aneurysm growth and coil compaction are associated with recurrence can provide insight into this complication and direct future patient management strategies, whether that be by redesigning coils to mitigate compaction or, conversely, preemptively avoiding the embolization procedure for patients with indications of a growing aneurysm.
Learning Objectives: By the conclusion of this session, participants should be able to:
1. Recognize the importance of understanding the etiology of recurrence in coiled cerebral aneurysms.
2. Understand the methods used in this study to independently quantify aneurysm and coil growth.
3. Understand the study limitations.