Comparison of the association of sac growth and coil compaction with recurrence in coil embolized cerebral aneurysms.

BACKGROUND AND PURPOSE: In recurrent cerebral aneurysms treated by coil embolization, coil compaction is regarded as the presumptive mechanism. We test the hypothesis that aneurysm growth is the primary recurrence mechanism. We also test the hypothesis that the coil mass will translate a measurable extent when recurrence occurs. METHODS: An objective, quantitative image analysis protocol was developed to determine the volumes of aneurysms and coil masses during initial and follow-up visits from 3D rotational angiograms. The population consisted of 15 recurrence and 12 non-recurrence control aneurysms initially completely coiled at a single center. An investigator sensitivity study was performed to assess the objectivity of the methods. Paired Wilcoxon tests (p<0.05, one-tailed) were performed to assess for aneurysm and coil growth. The translation of the coil mass center at follow-up was computed. A Mann Whitney U-Test (p<0.05, one-tailed) was used to compare translation of coil mass centers between recurrence and control subjects. RESULTS: Image analysis protocol was found to be insensitive to the investigator. Aneurysm growth was evident in the recurrence cohort (p=0.003) but not the control (p=0.136). There was no evidence of coil compaction in either the recurrence or control cohorts (recurrence: p=0.339; control: p=0.429). The translation of the coil mass centers was found to be significantly larger in the recurrence cohort than the control cohort (p=0.047). CONCLUSION: Aneurysm sac growth, not coil compaction, was the primary mechanism of recurrence following successful coil embolization. The coil mass likely translates to a measurable extent when recurrence occurs and has the potential to serve as a non-angiographic recurrence marker.

Cerebral aneurysm sac growth as the etiology of recurrence after successful coil embolization.

BACKGROUND AND PURPOSE: Coil compaction is thought to be the main mechanism for recurrence in cerebral aneurysms with previously successful coil embolization. We hypothesize that sac growth may be equally or more important. The objective was to study the relative roles of coil compaction and sac growth as explanations for aneurysm recurrence requiring retreatment in a study population using quantitative 3D image processing methods. METHODS: From July 2009 to December 2010, 175 aneurysms were coiled at the University of Iowa hospitals and clinics. Eight aneurysms had major recurrence requiring retreatment (4.4-12.1 months between procedures; mean: 7.2 months). The 3D structures of the vessel and coil mass were reconstructed using rotational angiography data scanned before and after both initial coil embolization and retreatment. Changes in the sac and coil mass over time were visualized using model registration techniques and quantified using volume calculations. RESULTS: All 8 of the coiled aneurysms with major recurrence had significant aneurysm sac growth (15% to 102% increase in volume), independent of change in coil volume. Five aneurysms with major recurrence had sufficient data for assessment of coil compaction. The coil mass volume decreased in 1 aneurysm (12% compaction by volume), did not change significantly in 1 aneurysm (increased by 1%), and significantly increased in 3 aneurysms (8%, 21%, and 25%) between the first treatment and before the second treatment. CONCLUSIONS: In this study population, aneurysm sac growth, not coil compaction, was the primary mechanism associated with recurrence after initial coil embolization.