Appearance and Disappearance of Intracranial Aneurysm Wall Enhancement during Follow-Up: A Multicenter Cohort Study

BACKGROUND AND PURPOSE: Aneurysm wall enhancement on MRI after administration of gadolinium is associated with aneurysm growth or rupture. Aneurysm wall enhancement has mostly been studied at baseline. The change in the presence or absence of aneurysm wall enhancement with time is largely unknown but can provide a better understanding of the pathophysiological processes occurring within the aneurysm wall. Therefore, we aimed to determine the proportion of aneurysm wall enhancement appearance or disappearance.

MATERIALS AND METHODS: In this multicenter cohort study, we analyzed individual patient data from 11 international cohorts. Patients 18 years of age or older with at least 1 untreated saccular unruptured intracranial aneurysm were included if they had 2 consecutive MRIs with aneurysm wall imaging. A Wilson score interval was used to calculate confidence intervals for the proportion of aneurysms with aneurysm wall enhancement changes, defined as appearance or disappearance between the 2 MRIs.

RESULTS: We included 305 patients with 387 unruptured intracranial aneurysms. Aneurysm wall enhancement was present at baseline in 142 (37%) aneurysms in 122 patients. Aneurysm wall enhancement appeared or disappeared in 20/387 aneurysms (5.2% [95% CI, 3.4–7.8]) after a median follow-up of 12 months (interquartile range, 5–13). Of the 245 aneurysms without enhancement at baseline, 13 (5.3% [95% CI, 3.1–8.9]) had the appearance of wall enhancement at the second MR aneurysm wall imaging. Of the 142 aneurysms with aneurysm wall enhancement at baseline, 7 aneurysms (4.9% [95% CI, 2.4–9.8]) had the disappearance of aneurysm wall enhancement.

CONCLUSIONS: Most unruptured intracranial aneurysms have persistent presence or absence of aneurysm wall enhancement during a median 1-year follow-up period. This finding suggests that underlying pathophysiological processes in the aneurysm wall are long-lasting.