Vessel Wall Imaging of Evolving Unruptured Intracranial Aneurysms

Background and Purpose- Unruptured intracranial aneurysms (UIAs) have various scenarios of growth and rupture. Magnetic resonance vessel wall imaging can detect aneurysmal wall thickening with inflammation and neovascularization. This study was performed to explore the vessel wall imaging findings of UIAs with consecutive follow-up. Methods- A total of 60 aneurysms with serial angiography over 2 years (mean period, 49 months, range, 24-192 months) were evaluated by vessel wall imaging. UIAs were morphologically categorized into 3 patterns: stable, whole sac expansion, or daughter sac formation. Aneurysm wall enhancement (AWE) was evaluated after administration of gadolinium. Results- Thirty-three of the 60 UIAs (55%) demonstrated no morphological changes, whereas 16 UIAS (27%) showed whole sac expansion and 11 UIAs (18%) demonstrated daughter sac formation. AWE was significantly less frequent in stable UIAs compared with UIAs showing morphological changes (P<0.01). Aneurysms with daughter sac formation showed a significantly higher frequency of AWE than those demonstrating whole sac expansion. In the majority of UIAs with daughter sac formation, AWE was detected in the main aneurysm and not in the developing component. Conclusions- UIAs demonstrate various modes of growth. The pattern of AWE might be useful for identifying unfavorable morphological changes of UIAs.