Investigation of the Intraoperative Cortical Responses to Spinal Motor Mapping in a Patient with Chronic Pain.

Abstract

Intraoperative neurophysiological monitoring (IONM) in spinal cord stimulation (SCS) surgery for chronic pain is shown to provide effective guidance during device placement. Electromyography (EMG) is utilized to determine the laterality of the paddle. In some SCS cases due to patient physiology, laterality cannot be obtained via EMG. Electroencephalography (EEG) is already used in IONM to monitor cortical responses. Here, we show proof-of-concept of assessing the responses of epidurally evoked EMGs simultaneously with EEGs to determine laterality during IONM-using a high-resolution (HR) SCS paddle. An 8 column HR-SCS paddle was acutely placed at T9-10 interspace in patient with Failed Back Surgery Syndrome. EMG signals from 18 muscle groups were recorded simultaneously with 60-channel EEG signals at various stimulation amplitudes (0-10mA). Particular attention was paid to regions associated with pain including the somatosensory cortex (S1), prefrontal cortex (PFC) and motor cortex (M1).When left and right lateral contacts were stimulated at low amplitudes (1-2mA), significant changes were seen in theta, alpha and beta powers in the contralateral PFC but not M1 or S1. There was a significant correlation between M1 and contralateral contacts in alpha power. At higher currents (7-8mA), right-sided contacts resulted in alpha power change.We found significant differences in alpha, theta, and beta powers in PFC for contralateral stimulation of the lateral SCS contacts at low amplitudes and alpha power at higher amplitudes. The changes in PFC suggest the potential of EEG for understanding a cortical mechanism of action of SCS and provide insight into pathophysiology of chronic pain.