EMG, MEP, and SSEP in the Intraoperative Neurophysiologic Monitoring of Lumbar Surgeries

Objective: To assess EMG, SSEP, and MEP changes in monitoring for neural damage during lumbar surgeries. Background: Intraoperative Neurophysiologic Monitoring (IONM) is used to assess for and reverse damage during surgeries that place the nervous system at risk. Lumbar surgeries are done to address progressive spinal lesions or instability of the spinal column. Deficits occur when neural structures are damaged, for example, when local perfusion changes cause cord ischemia, or pedicle screws breach the spinal canal, or spinal correction mechanically strains the cord or roots. Postoperative weakness or numbness can result. Design/Methods: A retrospective review of 100 lumbar surgical cases from August 2017 to July 2018 was performed via electronic medical records review of IONM reports, and pre- and post-operative exams. All included free running electromyography (EMG), 98 included transcranial motor evoked potentials (MEPs), and 32 included somatosensory evoked potentials (SSEPs). Results: IONM changes occurred in 7 cases: 6 involving EMG changes, 4 involving MEP changes, and 1 involving an SSEP change. Four had changes in multiple modalities. Two patients experienced new postoperative deficits, one of which experienced both EMG and MEP changes. The other involved no IONM changes, but rather, worsening of preoperative deficits in the setting of an expanding spinal epidural abscess causing cord compression. Some “false positives” may have resulted in postoperative deficits if not for interventions taken as a result of the IONM changes. For example, the only SSEP change occurred with an MEP change, both in the right arm, due to an unintended change in arm positioning, and resolved by repositioning the arm. Conclusions: EMG and MEP can be useful in monitoring for neural damage in lumbar surgeries. The only SSEP change occurred alongside an MEP change. Some “false positives” may be due to interventions done as a result of IONM changes to prevent postoperative deficits. Disclosure: Dr. Nguyen has nothing to disclose. Dr. Atikilt has nothing to disclose. Dr. Cho has nothing to disclose. Dr. Lee has nothing to disclose. Dr. Le has nothing to disclose. Dr. Lopez has nothing to disclose.