Combined motor- and somatosensory-evoked potential monitoring for spine and spinal cord surgery: correlation of clinical and neurophysiological data in 85 consecutive procedures

Study design: Prospective study. Objectives: The primary objective of neurophysiological monitoring during surgery is to prevent permanent neurological sequelae. To avoid neurological injury, we applied somatosensory-evoked potentials (SEPs) and/or motor-evoked potentials (MEPs). We evaluated whether the combination of SEP and MEP for spinal surgery may be beneficial. Setting: Asian Medical Center, University of Ulsan College of Medicine, Seoul, Korea. Methods: Combined SEP/MEP monitoring was attempted in 100 consecutive procedures for spinal operations. Trains of transcranial electrical stimulation over the motor cortex were used to elicit MEPs from the muscles of the upper/lower limbs. The tibial and median nerves were stimulated to record SEP. Results: Combined SEP/MEP recording was successfully achieved in 85 of 100 operations. In 61 of 85 operations (71%), SEP and MEP were stable, and all patients remained neurologically intact after surgery. Significant MEP changes were recorded in 20 operations, either combined with (n=4) or without (n=16) SEP changes. In 7 of these 20 operations, MEP recovered to some extent after surgical intervention, and these patients showed no neurological changes. In the remaining 13 operations, MEP did not recover and the patients had a transient (n=4) or a permanent (n=3) motor deficit. Significant SEP changes with stable MEP were observed in four operations, all of which were not related to postoperative motor deficit. Conclusion: Combined SEP/MEP monitoring provided higher sensitivity and higher positive/negative predictive value than single-modality monitoring techniques. Detection of MEP changes and adjustment of surgical strategy may prevent irreversible pyramidal tract damage. Spinal Cord (2009) 47, 616-622; doi: 10.1038/sc.2009.11; published online 17 February 2009