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

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. SIGNIFICANCE: 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.

Intraoperative Neuromonitoring in Percutaneous Spinal Cord Stimulator Placement.

INTRODUCTION: Placement of spinal cord stimulation (SCS) paddles under general anesthesia using intraoperative neuromonitoring (IONM) has been shown to be associated with equivocal or superior clinical outcomes in comparative studies. The value of IONM in percutaneous permanent SCS placement has not been demonstrated. METHODS: Outcomes for patients under percutaneous SCS placement performed with IONM were prospectively collected. Descriptive outcomes included numerical rating scale (NRS), the Oswestry disability index (ODI), McGill pain questionnaire, pain catastrophizing scale score (PCS), and Beck Depression Inventory. We also assessed satisfaction, willingness to repeat surgery, complication rates, and opioid use at baseline and follow-up using chart data and the New York Internet System for Tracking Over-Prescribing data base. RESULTS: The mean follow-up for our 46 patients was 22.04 ± 15.03 months (range 6-52 months). There were 10 patients (21.3%) who underwent revisions or removals with a mean time to revision/explant of 11.4 ± 11.7 months. About 85% of patients were satisfied with surgery. A total of 24 of 46 patients were on opioids at baseline. Following surgery, 17 of 24 (70.83%) patients demonstrated decreased opioid use in Morphine Milligram Equivalents. Of the 17 patients that reduced opioid use, 14 (82.35%) ceased opioid use entirely. Improvement from baseline was noted in NRS, ODI, and PCS (p < .05). CONCLUSIONS: Permanent percutaneous implantation of a SCS system using IONM with general anesthesia demonstrates results within range to those in the literature. Patients demonstrated statistically significant improvement in outcomes and opioid use was reduced in 71% of patients who were using opioids at baseline. We recommend its use in patients with morbid obesity, sleep apnea, and considerable anxiety. Further research is warranted to define the possible future role for percutaneous SCS implantation under IONM.

Prospective Study of the Use of Intraoperative Neuromonitoring in Determining Post-Operative Energy Requirements and Physiologic Midline in Spinal Cord Stimulation.

BACKGROUND: Intraoperative neuromonitoring (IONM) through electromyography (EMG) studies has been shown to be a safe, effective way to determine the laterality of the spinal cord and guide electrode placement during spinal cord stimulation (SCS). However, the use of IONM to predict post-operative energy requirements and midline has not been examined and offers a new avenue to streamline programming and device selection. Further, the impact of cerebrospinal fluid (CSF) thickness on intraoperative and post-operative amplitudes is understood but has not been explicitly characterized. METHODS: A total of 24 patients undergoing SCS implantation for chronic pain had intraoperative EMG studies performed to determine physiologic midline. The intraoperative midline was compared to the midline determined on post-operative day 1 based on paresthesia patterns during programming. For patients who had thoracic leads placed, the amplitudes needed to induce abdominal and extremity lateralization during SCS placement were compared with the intensities needed to induce therapy at post-operative day 1. Additionally, we examined whether CSF thickness, body mass index, diabetes, drug use, and smoking correlated with intraoperative and post-operative amplitudes. RESULTS: Intraoperative EMG was able to predict post-operative paresthesia-based midline in 70.83% of patients. There was a statistically significant relationship between the intraoperative intensity needed to induce extremity lateralization with the post-operative intensity to induce therapy (p = 0.009) as well as the intraoperative intensity needed to stimulate abdominals with the post-operative intensity (p = 0.033). There was also a relationship seen between CSF thickness and the post-operative energy requirements in patients (p = 0.039). DISCUSSION: EMG accurately predicts post-operative energy requirements and midline in SCS patients. While 29.17% of patients did not have a match between their intraoperative and post-operative midlines, EMG testing was still valuable in guiding electrode placement and providing information to predict post-operative intensities. Additionally, CSF thickness correlated with amplitude settings on the first post-operative day.

A Prospective Study of the Intra- and Postoperative Efficacy of Intraoperative Neuromonitoring in Spinal Cord Stimulation.

BACKGROUND: Accurate lead placement is critical for spinal cord stimulation (SCS) efficacy. The traditional gold standard of awake placement is often technically difficult. While there is retrospective evidence supporting the use of intraoperative neurophysiological monitoring (IOM) as an alternative, a prospective assessment has not yet been performed. OBJECTIVE: To prospectively evaluate pain and functionality outcomes for IOM-guided SCS, validate two IOM modalities as a means to lateralize lead placement and assess whether IOM can be useful for postoperative programming. METHODS: A total of 73 patients were implanted with SCS using electromyography (EMG) and somatosensory-evoked potential collision studies (SSEP-CS) to verify lead placement. Patient pain and function were assessed through serial administration of several validated questionnaires. Stimulation parameters at 6 months were documented. RESULTS: Statistically significant (p < 0.05) improvements were observed in the McGill Pain Questionnaire, Oswestry Disability Index, Pain Catastrophizing Scale, and Visual Analog Scale. EMG and SSEP-CS appropriately lateralized leads in 65/73 (89.0%) and 40/58 (69.0%) cases, respectively. EMG predicted active contacts in use at follow-up with 82.7% sensitivity. CONCLUSIONS: We provide prospective evidence that IOM can be used to verify SCS placement. Additionally, EMG may help to streamline device programming and thereby improve outcomes by predicting the ideal stimulation contacts in many cases.