Intraoperative motor-evoked potential monitoring during coil embolization for anterior choroidal artery aneurysms

Purpose: Intraoperative motor-evoked potential (MEP) monitoring is widely used in the neck clipping of cerebral aneurysms. Little is known regarding the usefulness of intraoperative MEP monitoring in endovascular aneurysm surgery. The purpose of this study was to validate the feasibility of intraoperative MEP monitoring during the coil embolization of anterior choroidal artery (AChA) aneurysms. Methods: Clinical and angiographic data of consecutive patients who underwent coil embolization for unruptured AChA aneurysms with or without intraoperative MEP monitoring between January 2014 and December 2018 at our institute were abstracted and analyzed retrospectively. Results: Twenty-three unruptured AChA aneurysms were treated. Eleven patients received MEP monitoring, and three of them experienced intraoperative reduction or disappearance of the MEP wave. Even during MEP changes, AChA filling showed no change in any of the three cases. Although one case with MEP monitoring encountered the disappearance of AChA filling, there was no change in MEP. This might be due to retrograde filling of the AChA from the anastomosis with the lateral posterior choroidal artery. AChA blood flow detected by angiography did not always reflect MEP status. When comparing the presence or absence of MEP monitoring, the volume embolization ratio of coiled aneurysms was significantly better in the MEP group. Conclusion: Intraoperative MEP monitoring during endovascular coiling for AChA aneurysms may be feasible. AChA blood flow detected by angiography does not always reflect MEP status.