Therapeutic strategies for residual or recurrent intracranial aneurysms after microsurgical clipping

Objectives: Therapeutic strategies for residual or recurrent aneurysm (RRA) after microsurgical clipping have not been well established. The purpose of this study was to report our retreatment experiences with previously clipped aneurysms and to demonstrate retreatment strategies for these RRAs. Patients and Methods: From 1996–2016, we treated 68 RRAs after previous clipping. Among them, 34 patients underwent microsurgical retreatment, and the other 34 underwent endovascular retreatment. Radiographic images and clinical data were reviewed retrospectively to determine the treatment efficacy, clinical outcomes, and important factors for selecting the proper treatment modality. Results: The most common aneurysm location was the middle cerebral artery (50%) in the microsurgery group and the internal carotid artery (47.1%) in the endovascular surgery group (p = 0.001). In the microsurgery group, 16 (47.1%) patients had additional clipping without removal of previous clips, 17 (50.0%) had clipping with removal of previous clips, and 1 (2.9%) had bypass surgery with trapping. In the endovascular surgery group, 28 (82.4%) patients had simple coiling, 5 (14.7%) had stent-assisted coiling, and 1 (2.9%) had a flow diverter. Procedure-related complications during retreatment occurred in 4 (5.9%) patients. Complete obliteration was achieved in 51 (75.0%) patients (microsurgery group, 82.4% and endovascular surgery group, 67.6%; p = 0.002). Conclusions: In properly selected cases, treatment of RRAs could be safely performed either by microsurgery or endovascular surgery and result in a good clinical outcome with acceptable morbidity. The decision to choose the treatment modality for RRAs after clipping is not easy but should be considered to lower the risk of retreatment.