The Analysis Of Predictive And Prognostic Values Of Intraoperative Motor Evoked Potentials During The Surgery For Thoracic Spinal Stenosis

Objectives:To analysis the necessity,efficiency and prognostic value of motor evoked potentials(MEP)during the surgery for thoracic spinal stenosis(TSS);To explore the influencing factors of intraoperative MEP improvement.Methods:From January 2013 to June 2017,MEP monitoring was performed simultaneously during 60 thoracic decompression surgeries,which mainly include posterior laminectomy and transforaminal thoracic interbody fusion(TTIF).MEP was used to monitor the function of the spinal cord,and we recorded the preoperative and postoperative function of spinal cord and intraoperative electrophysiological data.All patients are divided into three groups:the patients with intraoperative improved MEP,without obvious MEP change and positive MEP change.To determine the prognostic value of intraoperative MEP changes in thoracic decompression by comparing postoperative neurologic recovery between different groups.The influencing factors of intraoperative MEP improvement were analyzed through univariate analysis and multivariate logistics regression analysis.Results:The baseline of MEP monitoring was obtained successfully in 49 decompression surgeries,and the success rate of MEP recording was 81.7%.There were five cases with true positive results and four patients showed transient neurological deficits after methylprednisolone shock treatment.There were two false positive results and no false negative result;the sensitivity and specificity of MEP monitoring was 100%and 95.5%,respectively;the positive predictive value and negative predictive value was also 71.4%and 100%,respectively.There were three patients occurring delayed spinal cord injury after decompression caused by ischemia reperfusion injury of spinal cord,which gradually recovered with a large dose of methylprednisolone,dehydration and neurotrophic drugs.The improvement rates of early postoperative motor,sensory and neurologic outcomes in MEP improvement group were significantly better than that another group(84.6%vs.33.3%,P=0.005;70.6%vs.52.2%,P=0.046;84.2%vs.52.2%,P=0.028).While after at least 6-month follow-up,there was no statistical significance in long-term neurologic recoveries among groups(P>0.05).Univariate analysis showed that there were significant difference in the preoperative symptom duration and degree of spinal cord occupation on axon MRI between groups with MEP improvement and without obvious change(P<0.05),and multivariate logistics regression analysis revealed that preoperative symptom duration(≤12 months)significantly correlated with intraoperative MEP improvement(P<0.05).Conclusions:Thoracic decompression surgery is a kind of difficulty and high-risk procedure,but MEP are used to monitor neurological function and can provide objective safety evaluation index for the surgery,but it is still necessary to pay close attention to the presence of delayed spinal cord injury.The improvement of intraoperative MEP can predict good early clinical outcome after thoracic decompression but not long-term neurologic recovery;When the preoperative symptom duration was less than 12 months,it was easier to appear MEP improvement after thoracic decompression.