Background and purpose The risk factors for intraprocedural rupture (IPR) of unruptured intracranial aneurysms (UIAs) and the outcomes of IPR itself are unclear. This study was performed to identify the independent risk factors for and outcomes of IPR.

Materials and methods We retrospectively evaluated the medical records and radiologic data of 1375 patients (1406 UIAs) who underwent coil embolization from January 2001 to October 2016.

Results IPR occurred in 20 aneurysms of 20 patients (1.4%). Univariate analyses showed that the rate of IPR was significantly higher in the treatment of aneurysms with a small dome size, aneurysms in the anterior communicating artery (AcomA) (6.6%), and patients with a medical history of dyslipidemia. Multivariate analyses showed that a small dome size and aneurysms in the AcomA were independently associated with IPR (p=0.0096 and p=0.0001, respectively). IPR induced by a microcatheter was associated with a higher risk of severe subarachnoid hemorrhage than other causes of IPR (57% vs 0%, respectively). Thromboembolic complications occurred in seven (35%) patients with IPR. Six (30%) patients required external ventricular drainage placement after developing symptoms of acute hydrocephalus. The overall morbidity and mortality rates from IPR were 0.22% and 0.15%, respectively.

Conclusions Aneurysms in the AcomA and with a small dome size are likely to be risk factors for IPR. IPR induced by microcatheters can result in poor outcomes. The rate of IPR-associated thromboembolic complications is high, and IPR itself is associated with acute hydrocephalus. If managed appropriately, however, most patients with IPR can survive without neurological deterioration.