Influence of the perianeurysmal environment on rupture of cerebral aneurysms. Preliminary observation.

We evaluate the perianeurysmal environment and study parameters potentially influencing rupture of cerebral aneurysms. 101 consecutive aneurysm cases were retrospectively evaluated using radiological observation including imaging documents such as MR, CT and DSA studies. Aneurysm contact with perianeurysmal environment was classified and correlated with aneurysm shape, size, location and likely rupture point. Topographic relation of the aneurysm to the cisternal compartment was studied. Presence of contact with the surrounding structures was evaluated for bone, dura, brain, cranial nerves, arteries, and veins. The aneurysm shape and likely rupture point was found to be significantly influenced by the aneurysm environment. Depending on aneurysm type, location and size, the growth pattern also exhibited signs of interaction with the environment. Overall, there was no significant difference in the largest average diameter of the dome of ruptured (7.8 mm) and unruptured (6.7 mm) aneurysms. When compared to unruptured aneurysms (6/42), the presence of a bleb was more frequent in ruptured aneurysm (41/59). The perianeurysmal environment was found to have a significant influence on aneurysmal rupture pattern, whenever direct contact between the aneurysm and the anatomical structures in the perianeurysmal environment was visualized. This influence was independent of aneurysm size. Aneurysm size seems to be a poor indicator for the risk of rupture when compared to shape of the aneurysm and the degree of direct contact with the perianeurysmal environment.