Differences in EEG patterns between tonic and high frequency spinal cord stimulation in chronic pain patients.

• Intraoperative EEG changes in chronic pain patients under spinal cord stimulation are investigated. • Spectral and topographical differences between high frequency and tonic stimulation are observed. • High frequency stimulation-induced spatio-spectral features are associated to pain relief. To investigate the differences in neural patterns between spinal cord stimulation (SCS) waveforms (60-Hz tonic vs 10-KHz high frequency stimulation, HFS) and their correlation to stimulation-induced pain relief. We recorded 10-channel electroencephalogram (EEG) in response to stimulation ON and OFF in 9 chronic pain patients (4 women, 5 men) during SCS surgery and examined the intraoperative spatio-spectral EEG features. We discovered stronger relative alpha power in the somatosensory region and higher trend in alpha/theta peak power ratio in frontal cortex with HFS. We also observed a shift in peak frequency from theta to alpha rhythms in HFS as compared to baseline and tonic stimulation, where slower theta activity was maintained. Further, a positive correlation was found between changes in Oswestry disability index (ODI) scores (from preoperative to postoperative) and HFS-induced alpha/theta peak power ratio in frontal and somatosensory regions. Altogether, our findings suggest that dynamic spectral interactions in theta-alpha band and their spatial distributions might be the first intraoperative neural signatures of pain relief induced by HFS in chronic pain. Examining electrophysiological changes intraoperatively has a potential to elucidate response to SCS therapy prior to device selection, reducing the healthcare expenditures associated with failed implants. [ABSTRACT FROM AUTHOR]