Electromyographic/Somatosensory-Evoked Potential Monitoring During Thoracolumbar Spinal Cord Stimulation

Abstract

Intraoperative neurophysiological monitoring has become a routine procedure in complex spine surgery. Somatosensory-evoked potential (SSEP) recording has been advocated to monitor the functional integrity of the nervous system during surgical manipulation. When stimulated, sensory afferents give rise to signals carried via the dorsal columns (DCs) within the spinal cord to the medial lemniscus and spinocerebellar tracts, ending in the primary somatosensory cortex. SSEP monitoring does not involve the motor pathways, which in some clinical situations can lead to false-negative results and postoperative neurological deficits undetected intraoperatively. Dermatomal SSEP testing allows for assessment of individual nerve roots during surgery and has been shown to be more sensitive. However, the sensitivity and specificity of this method varies and is inferior to electromyographic (EMG) monitoring. EMG has become the standard of practice in complex spine surgery, providing surgeons with accurate feedback about individual nerve root activity during surgical manipulation of neural structures and the presence of malpositioned screws.