Background Contrast-induced encephalopathy (CIE) following endovascular interventions is a rare but serious complication. This study aimed to investigate the risk factors of contrast leakage (CL) and CIE in patients who underwent coil embolization of unruptured intracranial aneurysms (UIAs).

Methods Patients with UIAs who underwent coil embolization at a single tertiary institute between January 2019 and January 2022 were enrolled retrospectively. CL was defined as cortical or subcortical contrast enhancement with effacement of the cortical sulci. CIE was defined as the new onset of neurological deficits associated with CL. Following the procedure, all patients underwent CT scans, and MRI scans were performed on those with symptoms. Patient and procedural risk factors were investigated.

Results In total, 459 patients were analyzed. The median procedure time and contrast dose were 69 min and 96 mL, respectively. CL was evident in 35 patients. In the multivariate analysis, hypertension, large aneurysm, longer procedure time, and greater contrast dose were associated with CL. CIE was diagnosed in 19 patients, and the risk factors included large aneurysm, longer procedure time, and greater contrast dose. The procedure time was predictive of both CL (P<0.001) and CIE (P=0.01). The optimal cut-off value for procedure time was 81.5 min. All CIE patients recovered completely within 8–96 hours.

Conclusions A large aneurysm and prolonged procedure time may increase the patient’s risk of CL and CIE due to increased contrast exposure. Patients who underwent a procedure that exceeded 1.5 hours necessitate post-procedure evaluation and monitoring.