Important role and future perspective of embolization for intra‒cranial tumors

Purpose：Embolization for intracranial tumors currently plays a supporting role to open surgery. The reasons for embo-lization include：1）tumor necrosis resulting in a safer operation and more aggressive surgery, 2）reduction in intraoperative bleeding and avoidance of blood transfusion, and 3）decrease in operative time. Functional vascular anatomy and endovascular technique are the most important issues for safe embolization. Herein we report our standard techniques for tumor emboliza-tion and compare our results with those of the Japanese Registry of NeuroEndovascular Therapy（JR‒NET）. Methods：Our standard procedure is as follows：1）embolization is performed several days before open surgery, 2）in cases with strong peritumoral edema, steroid administration or embolization may be performed immediately before surgery, 3）patients undergo the procedure under local anesthesia, 4）insertion of the microcatheter is as close as possible to the tumor, 5）particulate emboli are the first line material, 6）embolization is occasionally performed with N‒butyl cyanoacrylate （NBCA）glue, and 7）if possible, additional proximal feeder occlusion with coils is performed. Results：During the past 12 years, 169 intra‒cranial tumor embolization procedures were performed in our department. Meningioma was the main target of embolization（154 of 169 patients, 91.1%）. Seven procedure‒related complications were observed, with one permanent complication（0.6%）of hearing loss after anterior inferior cerebellar artery embolization for hemangioblastoma with NBCA. Transient complications included three middle meningeal arterio‒venous fistulas, two cranial nerve paresis, and a pseudoaneurysm of the femoral artery（puncture site）. We conducted the JR‒NET 2（2007‒2009）and JR‒NET 3（2010‒2014）in Japan. Complications of tumor embolization occurred in 57 of 1,544 JR‒NET 3 patients（3.69%）, although the complication rate for JR‒NET 2 was only 1.48%（15 of 1,012 patients）. Tumors other than meningioma were a significant risk factor for the occurrence of JR‒NET 2 complications. Further, embolization of vessels other than the external carotid artery（ECA）and use of liquid embolic material were significantly associated with the development of JR‒NET 3 complications. We suggest that more aggressive embolization targeted to vessels other than the ECA and increased applica-tion of liquid embolic materials might worsen the risk of complications. Conclusions：Although embolization was safe for extra‒axial tumors such as meningiomas fed by the ECA, embolization of vessels other than the ECA as occurs in hemangioblastomas was a significant risk factor for complications. Use of liquid embolic material increased the risk for complications. Endovascular neurosurgeons should fully discuss the indications and strategies for preoperative embolization with tumor neurosurgeons to perform safe and effective procedures.