Julie G. Pilitsis, MD PhD MBA: No relevant disclosure to display
Introduction: Assessment of chronic pain is limited to patient reported outcomes. Evoked compound action potentials have been introduced as a means of monitoring physiological responses to spinal cord stimulation (SCS). Electroencephalography (EEG) has been suggested as a means of obtaining feedback that has the potential to not only monitor physiology but also provide insight into mechanism. Here we show proof of principle of assessing the effects of intraoperative motor evoked potentials using a high-resolution SCS paddle and EEG.
Methods: A HR-SCS paddle (Micro-leads Inc.) was acutely placed over T10 in a patient with failed back surgery syndrome and tested using vertical tripolar configurations at 60 Hz/300µs. EMG signals from 18 muscle groups were recorded simultaneously with 60-channel EEG signals at various stimulation amplitudes (0-10mA). EEG signals were filtered along with a common average referencing. EMG signals were pre-processed, and root mean square (RMS) values of stimulation-induced activities were computed and normalized with respect to the baseline (stim-OFF).
Results: Average theta (4-8 Hz) and beta (12-30 Hz) powers in prefrontal cortex (PFC) showed a significant difference (p < 0.05) between the hemispheres when SCS was applied from the most lateral contacts with respect to anatomic midline. Stimulation of the left and right lateral contacts over the dorsal column showed decreased and increased alpha (8-12 Hz) power in the left and right PFC respectively. Alpha power in the somatosensory and motor cortex at baseline and in response to stimulation from all SCS contacts correlates opposite for bilateral contacts with upper and lower rectus abdominis, gluteus maximus and quadriceps muscles.
Conclusion : We found significant differences in theta, alpha, and beta power between right and left PFC in response to contralateral stimulation of the most lateral SCS contacts. Our initial analysis demonstrated that EEGs might be responsive to the stimulation from different mediolateral targets over the dorsal column.
