Intraoperative factors influencing transcranial motor-evoked potential measurements using higher frequency multi-train stimulation in adolescent scoliosis surgery: A prospective observational study

Measurement of transcranial motor-evoked potentials (TcMEPs) in scoliosis surgery has been reported to be a sensitive and specific method for detecting postoperative new neurological defects. However, the influence of intraoperative factors makes the interpretation of TcMEPs difficult. This study aimed to investigate the influence of intraoperative factors on TcMEP amplitude using higher frequency multi-train stimulation (hfMTS) in adolescent scoliosis surgery, and the complications of hfMTS. We included 50 patients and 706 TcMEP measurements in the analysis. The median number of train stimuli was 13 [IQR: 11, 14], and the median TcMEP amplitude was 3.25 [IQR: 2.50, 4.18] mV. Based on a mixed-effect model with random intercept for TcMEP amplitude, we estimated the mean difference and its 95% confidence interval and the predicted mean difference and its confidence interval by the interquartile range of each factor. The predicted mean differences in TcMEP amplitude were clinically limited compared to the actual TcMEP amplitude, suggesting that each factor had a limited effect on TcMEP amplitude. No intraoperative bite injuries or seizures were observed. The use of hfMTS in adolescent scoliosis surgery may provide sufficient TcMEP amplitude without the influence of intraoperative factors or complications.