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

Abstract

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.