Free-run electromyogram for nerve root function monitoring during lumbar surgery

English Keywords:Free-run electromyogram  Intraoperative neurophysiology monitoring  Lumbar surgery  Nerve root

English Abstract:

  【Abstract】 Objectives: To study the use of free-run electromyogram(F-EMG) for nerve root monitoring during lumbar surgery. Methods: From October 2014 to October 2015, 246 patients(129 males, 117 females) who underwent lumbar surgery (L2-S1) and F-EMG for nerve root monitoring during operation were enrolled in this study. The mean age was 50.3±16.4 years(16-75 years). Intraoperative EMG activity, duration, the corresponding operation or event, treatment and outcome of EMG activity were recorded in all patients. The function of nerve roots were compared between preoperation and postoperation. True positive, false positive, true negative and false negative cases were collected from all patients. Sensitivity, specificity, positive predictive value and negative predictive value were calculated, and the value of F-EMG was analyzed. Results: The mean intraoperative monitoring time was 115.0±17.7min(80-140min). 49/246 cases were F-EMG positive alterations, among them, burst EMG activity, train EMG activity and spontaneous EMG activity were recorded in 19, 27 and 3 cases, respectively. Among them, 28/49 cases were excess pulled the nerve root, the EMG activity returned to normal when operator stopped the operation or release the nerve; 8/49 cases were recorded oppressed nerve root during cage or bone graft implantation, when operator removed and changed the angle, 6/8 cases returned to normal EMG activity, 2/8 cases were still spontaneous EMG activity; 9/49 cases were recorded stimulated nerve root during pedicle screw placement, when operator removed and changed the insertion angle, 8/9 cases returned to normal EMG activity, 1/9 case were still train EMG activity and showed muscle weakness of the right foot dorsiflexion postoperatively; 4/49 cases did not find stimulus or damage factors, abnormal EMG activity continued until the end of surgery, 1/4 case was found the right S1 nerve root function deficit and planter numb; 47/49 cases had no neurologic deficit postoperatively. 197/246 cases were F-EMG negative alterations, 1 case had the left foot drop. Among all the positive cases, 46 cases were the true positive, 2 cases had neurological deficit; 3 cases were the false positive, and the positive predictive value was 93.88%. Among all the negative cases, 196 cases were the true negative, 1 case was the false negative and had neurological deficit. The negative predictive value was 99.49%. The sensitivity and specificity of F-EMG were 97.87% and 98.49%, respectively. Conclusions: Free-run electromyogram for nerve root monitoring during lumbar surgery(L2-S1) can reflect the irritation and injury of nerve root. Free-run electromyogram decreases the incidence of the neurological deficit, which is a effective method.