Transcranial motor-evoked potentials combined with response recording through compound muscle action potential as the sole modality of spinal cord monitoring in spinal deformity surgery

Study Design. This study is a prospective review of all spinal cord monitoring procedures in our unit from 1999 to 2004 in patients undergoing spinal deformity correction surgery. Objective. To report the sensitivity and specificity of transcranial motor-evoked potentials (MEP) and compound muscle action potential (CMAP) monitoring as the sole modality in spinal deformity correction surgery. Summary of Background Data. Combined spinal cord monitoring with somatosensory-evoked potentials and MEP has been widely used. The use of CMAP as the only modality has not been widely used and its efficacy has not been fully elucidated. Methods. The intraoperative monitoring outcomes were compared with patient's postoperative clinical outcomes. The sensitivity and specificity were calculated and determined for our monitoring protocol. Results. Transcranial MEPs were measured in 144 patients in 172 procedures. In 2 patients (3 procedures), we were unable to record any CMAPs. There were 15 intraoperative monitoring changes. There were no new postoperative neurological deficits. Conclusion. The monitoring criteria are sufficiently strict to achieve a sensitivity of 1.0 and a specificity of 0.97. Monitoring of CMAPs alone has been adequate to avoid clinical neurological deficits.