Introduction In neurosurgical operation intraoperative monitoring is now a essential tool for treatment. Expecialy in craniotomy as in clipping and tumor resection. However in the endovascular treatment it is not so often the case. In our institute we used Transcranial motor evoked potential monitoring (TC-MEP) in endovascular treatment from 2014. We will show the effectiveness from our experience.

Methods We studied 15 patients (n = 16) with Anterior choroidal artery (Anch.A) aneurysms who underwent coiling between September 2014 and February 2016. All patients were fully anesthetized by total intravenous Anastasia (TIVA) and TC-MEP were checked after delivering every each coil. The stimulation strength was set at 120 mA. Electromyograms of the bilateral tibias anterior and abductor policies brevis muscle were obtained.

Results TC-MEP of all patients was recorded successfly. No deficits and no decrease in the voltage was seen in the end of the treatment but in 3 cases we experienced significant decrease during the treatment. In 2 cases of these, the decrease was seen just after we inserted the micro catheter into the aneurysm neck. In the other 1 case the decrease was seen when the coil loop prolapsed and covered the Ach.A inflow. Each cases recovered after repositioning. Interestingly the angiographical appearance of the Ach.A didn’t change in any case.

Conclusion We were able to treat the Ach.A aneurysms with endovascular surgery using TC-MEP safely and no deficits were seen. There was no change in the angiographic appearance of the Ach.A but TC-MEP voltage decreased in 3 cases. It suspects that TC-MEP could predict the ischemic changes and contribute to the treatment in the endovascular surgery.

Disclosures S. Hataoka: None.