Difference in configuration of ruptured and unruptured intracranial aneurysms determined by biplanar digital subtraction angiography.

There is an ongoing discussion about the risk of bleeding from unruptured intracranial aneurysms. Management guidelines were developed recently and some of the recommendations for decision making are based on the anatomical configuration of the aneurysm. The common assumption is that the presence of multiple lobes or a daughter sac indicates a higher risk of rupture. We have investigated the anatomical configuration of ruptured and unruptured intracranial aneurysms using biplanar digital subtraction angiography (DSA). The objective was to determine, whether there was a difference between ruptured and unruptured aneurysms regarding lobulation, the presence of a daughter sac or the shape as measured by the height/neck ratio. Biplanar DSA images of 124 patients were retrospectively analyzed. A total of 53 unruptured and 94 ruptured aneurysms were found (=147 aneurysms in total). Aneurysms of less than 10 mm diameter accounted for 82% of all aneurysms. Overall, 10% of unruptured aneurysm showed a multilobular appearance on DSA compared with 20% of ruptured aneurysms (Fisher's exact test, p=0.10). In the 5-9 mm aneurysm group, multiple lobes were found significantly more frequent in ruptured aneurysms (26% vs. 4%, Fisher's exact test, p<0.05). A height/neck ratio of less than 1.5 was not found in unruptured aneurysms (0/26) but in 21% (12/57) of ruptured aneurysms (p<0.05). Our data provide scientific support for using morphological features for the decision making process in the management of unruptured intracranial aneurysms. An irregular multilobar appearance was significantly more common in aneurysms of 5-9 mm size that ruptured.