Efficacy and limitations of current methods of intraoperative spinal cord monitoring

Abstract

The purpose of this study was to evaluate the efficacy and reliability of intraoperative spinal monitoring using spinal cord-evoked and compound muscle action potentials. We reviewed 716 cases of spinal monitoring performed over 15 years. The series contained 672 patients with spinal functions that could be monitored intraoperatively; 44 (6.1%) were impossible to record. Based on the 21 impossibleto- record patients, it is evident that missing a serious case such as a Frankel B type spinal cord injury indicates the limitations of the current monitoring methods for stimulating and recording. The monitoring outcomes were true-negative in 652 patients, true-positive in 12, false-negative in four, and falsepositive in four. In two of the patients with false-negative results, postoperative myelomere motor paralysis was observed temporarily even though it was possible to record the muscle-evoked potential after electrical stimulation to the brain [Br(E)-MsEP] at the end of the operation. In cases in which the spinal parenchyma or spinal nerve root might be selectively damaged, Br(E)-MsEPs may not diagnose the disorder accurately. By employing multimodal monitoring, it should be possible to eliminate patients with false-negative results and to detect spinal disorders during the early stages, as well as to examine whether the abnormality that had been recorded by a single method is false-positive.