Monitoring of Motor and Somatosensory Evoked Potentials During Spine Surgery: Intraoperative Changes and Postoperative Outcomes

OBJECTIVE To evaluate whether the combination of muscle motor evoked potentials (mMEPs) and somatosensory evoked potentials (SEPs) measured during spinal surgery can predict immediate and permanent postoperative motor deficits. METHODS mMEP and SEP was monitored in patients undergoing spinal surgery between November 2012 and July 2014. mMEPs were elicited by a train of transcranial electrical stimulation over the motor cortex and recorded from the upper/lower limbs. SEPs were recorded by stimulating the tibial and median nerves. RESULTS Combined mMEP/SEP recording was successfully achieved in 190 operations. In 117 of these, mMEPs and SEPs were stable and 73 showed significant changes. In 20 cases, motor deficits in the first 48 postoperative hours were observed and 6 patients manifested permanent neurological deficits. The two potentials were monitored in a number of spinal surgeries. For surgery on spinal deformities, the sensitivity and specificity of combined mMEP/SEP monitoring were 100% and 92.4%, respectively. In the case of spinal cord tumor surgeries, sensitivity was only 50% but SEP changes were observed preceding permanent motor deficits in some cases. CONCLUSION Intraoperative monitoring is a useful tool in spinal surgery. For spinal deformity surgery, combined mMEP/SEP monitoring showed high sensitivity and specificity; in spinal tumor surgery, only SEP changes predicted permanent motor deficits. Therefore, mMEP, SEP, and joint monitoring may all be appropriate and beneficial for the intraoperative monitoring of spinal surgery.