Evaluation of various evoked potential techniques for spinal cord monitoring during scoliosis surgery

Abstract

Study Design. This prospective study compared the outcomes of different evoked potential (EP) techniques for intraoperative spinal cord monitoring. Objectives. To evaluate the reliability of different EP techniques administered during scoliosis surgery. Summary of Background Data. A number of different methods of intraoperative spinal cord monitoring are available. Because each has its own advantages and limitations, multimodal spinal cord monitoring has been proposed to improve monitoring reliability. Materials and Methods. Cortical somatosensory-evoked potential (CSEP), cortical motor-evoked potential (CMEP), spinal somatosensory-evoked potential (SSEP), and spinal cord-evoked potential (SCEP) were applied simultaneously to 30 patients undergoing surgical correction for spinal deformity. The presence of the EP waveforms and their reproducibilities over separate tests were compared. In addition, the monitoring outcomes were evaluated with the clinical results. Results. Of the 30 patients, CSEP waveforms were successfully recorded in 28 cases (93%), SCEP in 25 cases (83%), CMEP in 24 cases (80%), and SSEP in 21 cases (70%). Latencies of each EP technique showed no significant variability. However, amplitudes showed significant differences between different techniques. SCEP and CMEP showed clearer waveforms of greater amplitude that could be detected faster than CSEP and SSEP waveforms. SCEP and SSEP waveforms were more easily influenced by the surgical procedure. Conclusion. CSEP and CMEP are recommended for routine monitoring, so that both ascending and descending tracts are monitored. If adequate signals for either of these proposed monitoring methods cannot be easily obtained, SSEP can substitute for CSEP, whereas SCEP can substitute for CMEP.