Does small aneurysm size predict intraoperative rupture during coiling in ruptured and unruptured aneurysms?

Background: Aneurysm size is a possible risk factor for intraoperative rupture (IOR) during coiling procedures. We aim to determine if aneurysm size 4 mm or smaller predicts IOR.

Methods: Between January 1997 and August 2010, 689 aneurysms in 595 patients were treated by coiling at a single institution. In all, 41 were excluded from statistical analysis due to missing data leaving 648 aneurysms in 562 patients. Demographic, clinical, and procedural outcomes were collected. We compared the rate of IOR in small aneurysms (≤4 mm) with larger aneurysms (>4 mm). We also compared the rate of IOR in ruptured versus unruptured aneurysms in the above categories.

Results: The overall rate of IOR was 4.9%. Aneurysms 4 mm or smaller were more than twice as likely to rupture on table compared to larger aneurysms (8.7% versus 3.9%; P=.022). Of note, ruptured aneurysms were more prone to IOR compared to unruptured aneurysms (7.0% versus 2.2%; P=.005). Aneurysm size 4 mm or smaller was a risk factor in small, ruptured aneurysms only (P=.019). In addition, unruptured aneurysms that were complicated by IOR were associated with higher rates of 30-day mortality (P<.001).

Conclusions: Aneurysm size 4 mm or smaller is a risk factor for IOR in ruptured but not unruptured aneurysms. This additional risk factor should be considered when planning the management of small, ruptured aneurysms.