Gadolinium Enhancement of the Aneurysm Wall in Unruptured Intracranial Aneurysms Is Associated with an Increased Risk of Aneurysm Instability: A Follow-Up Study

Abstract

Background and purpose: Previous studies have suggested that gadolinium enhancement of the wall of unruptured intracranial aneurysms on MR imaging may reflect aneurysm wall instability. However, all previous studies were cross-sectional. In this longitudinal study, we investigated whether aneurysm wall enhancement is associated with an increased risk of aneurysm instability.

Materials and methods: We included all patients 18 years of age or older with ≥1 unruptured aneurysm from the University Medical Center Utrecht, the Netherlands, who were included in 2 previous studies with either 3T or 7T aneurysm wall MR imaging and for whom it was decided not to treat the aneurysm but to monitor it with follow-up imaging. We investigated the risk of growth or rupture during follow-up of aneurysms with and without gadolinium enhancement of the aneurysm wall at baseline and calculated the risk difference between the 2 groups with corresponding 95% confidence intervals.

Results: We included 57 patients with 65 unruptured intracranial aneurysms. After a median follow-up of 27 months (interquartile range, 20-31 months), growth (n = 2) or rupture (n = 2) was observed in 4 of 19 aneurysms (21%; 95% CI, 6%-54%) with wall enhancement and in zero of 46 aneurysms (0%; 95% CI, 0%-8%) without enhancement (risk difference, 21%; 95% CI, 3%-39%).

Conclusions: Gadolinium enhancement of the aneurysm wall on MR imaging is associated with an increased risk of aneurysm instability. The absence of wall enhancement makes it unlikely that the aneurysm will grow or rupture in the short term. Larger studies are needed to investigate whether aneurysm wall enhancement is an independent predictor of aneurysm instability.

Fig 1.

Aneurysm wall imaging of a patient with aneurysm growth at follow-up. A 63-year-old woman with a right middle cerebral artery aneurysm. A, Aneurysm wall imaging without gadolinium. B, Aneurysm wall imaging after administration of gadolinium shows focal posterior enhancement (arrow). C, TOF-MRA at baseline shows a 9-mm aneurysm. D, TOF-MRA after 12 months of follow-up shows a 12-mm aneurysm.

Fig 2.

Aneurysm wall imaging of a patient with aneurysm rupture at follow-up. A 47-year-old woman with a right middle cerebral artery aneurysm. A, Aneurysm wall imaging without gadolinium. B, Aneurysm wall imaging after administration of gadolinium shows focal posterior enhancement (arrow). C, At baseline, the aneurysm is 4 mm. D, After 31 months, the aneurysm ruptured, with CTA showing aneurysm growth (7 mm). E, Head CT shows SAH.