The Research Of Cerebral Ischemia And The Tolerance In Evoked Potential Monitoring Of Intracranial Aneurysm Surgery

Objective To evaluate the relationship between evoked potential signal changes and cerebral ischemia and the tolerance in the intracranial aneurysm surgery. Methods 47 patients with somatosensory evoked potential (SEP) and / or motor evoked potentials (MEP) monitoring in intracranial aneurysm surgery, recording the appearing time ,duration and recovery time of temporary occlusion of artery, wrong clipping of perforating vessels or cerebral vasospasm when the evoked potentials change, and using the appearance of new postoperative motor function impairment (decreased myodynamia) and / or postoperative CT examination corresponding to the emergence of fresh infarct area to determine whether the result of new cerebral ischemic injury, and analysing the correlation between the evoked potentials changes and new cerebral ischemic injury .Results 35 cases with SEP and MEP monitoring, 10 cases with single SEP monitoring, two cases with single MEP monitoring, a total of 10 cases with fresh infarct and / or new motor function impairment after sugery, 3 patients died. 7 cases suffer from ischemic changes within 24 hours (6 cases with ischemic changes in CT, 3 cases with impaired motor function), 3 cases suffer from ischemic changes after 24 hours( of which CT ischemic changes occurred in 2 cases with ischemic changes in CT, 1 case with motor function impairment). The intraoperative SEP changed in 13 cases(5 cases suffered from ischemic changes), and among them 4 cases suffered from postoperative ischemia which the Ischemic Tolerance Ratio was more than 80%,8 cases did not suffer from postoperative ischemia which the Ischemic Tolerance Ratio was less than 50%, another one case which suffered from postoperative ischemia was caused by the clipping of perforating vessel. The intraoperative MEP changed in 8 cases, of which 4 cases suffering from postoperative ischemia (including 3 cases which the intraoperative SEP was normal). Conclusion Intraoperative significant changes in evoked potentials was related to postoperative ischemia, particularly the Ischemic Tolerance Ratio was a objective indicator to predict postoperative ischemia, but in monitoring the ischemia of perforating vessel, MEP monitoring was better than SEP, so combining SEP with MEP in the process of intracranial aneurysm surgery was very important.