Morphology of Ruptured and Unruptured Intracranial Aneurysms

In addition to size and location, morphology of intracranial aneurysm has been proposed to predict rupture. This study was undertaken to compare morphological features between ruptured and unruptured aneurysms and identify those associated with higher rupture risk.

Between 2010 and 2014, 301 patients with SAH and 204 with unruptuted aneurysms were admitted to our hospital. Two investigators reviewed 3-dimensional angiograms of all aneurysms. Risk factors for rupture were identified. Morphology was classified into single sac aneurysms with smooth margin, single sac with irregular margin, aneurysms with daughter sac and multilobulated aneurysms. The value of morphology in predicting rupture was tested using logistic regression.

420 aneurysms met the inclusion criteria. Multilobulated aneurysm was the most frequent finding among ruptured aneurysms followed by single sac with irregular margin, aneurysm with daughter sac and single sac with smooth margin, 44.9%, 25.9%, 18% and 11.2%, respectively. Among unruptured aneurysms, single sac with smooth margin was the most frequent finding, followed by single sac with irregular margin, multilobulated aneurysm and aneurysm with daughter sac, 38.1%, 29.8%, 20.9% and 11.2%, respectively.

Morphology was an independent predictor of rupture, (ROC-AUC 0.693, p<0.001). Risk of rupture increased by factor of 3 (5-95% CI 1.6-5.3) from single sac with regular margin to irregular margin, by factor of 5.5 (5-95% CI 2.8-11.0) to daughter sac and by factor of 7.2 (5-95% CI 4.1-13.1) to multilobulated aneurysm.

Morphology might have an independent predictive value of aneurysm rupture. Risk of rupture might increase according to extent of morphological change. Prospective studies will be necessary to evaluate the influence of aneurysm morphology on natural history.