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Evidence Based Medicine for SCS Steven M. Falowski MD St. Lukes Health Network Bethlehem, PA Advantages of SCS Therapy Safe Testable Non-destructive Mostly reversible Long-term cost is low Less Risky Disadvantages of SCS Therapy Limited to specific indications and diseases Equipment failure Follow-up lifelong? Short-term cost is high Inability to get MRI Indications Most Common – – – – Post-laminectomy syndrome Complex regional pain syndrome (CRPS) Ischemic limb pain Angina Other – – – – – visceral/abdominal pain cervical neuritis pain spinal cord injury pain post-herpetic neuralgia neurogenic thoracic outlet syndrome Mechanism of Action Foreman et al. 1976 Primate Studies Linderoth et al. 1992 Rat Studies At the chemical level, animal studies suggest that the SCS triggers the release of serotonin, substance P, and GABA within the dorsal horn ?Descending Inhibition Mechanism Of Action Barolat 1993: Mapping of sensory responses Barolat 1998: Anatomical and electrical properties of the intraspinal structures and clinical correlations Mechanism of Action-Electrodes Transverse tripolar stimulation (4 pts) Central cathode and two lateral anodes Anodes increase the discomfort threshold over the roots compared to the paresthesia threshold (thus increasing the therapeutic range) Lateral/medial steering advantage by setting different voltages of the flanking anodes Closer spacing = More effective fiber activation Post- Laminectomy Syndrome Etiology: – Pain in Center Lower Lumbar Area – Pain in Buttocks – Radicular Pain Also included: – – – – – Arachnoiditis Epidural Fibrosis Radiculitis Microinstability Recurrents Disc Herniations – Infections Post- Laminectomy Syndrome North et al-1991: SCS is superior to repeat surgery – 50 patients – Average 3 surgeries for FBSS prior to SCS – 53% of patients had pain relief at 2.2 years – Patient Satisfaction North et al-1995: Better outcomes with SCS – Prospective RCT – Repeat back surgery vs SCS – Allowed Crossover – 51 studies – Total of 3,700 patients – SCS had a positive, symptomatic, long-term effect in cases of: refractory angina pain, severe ischemic limb pain secondary to peripheral vascular disease, peripheral neuropathic pain, and chronic low-back pain Results CLINICAL RESULTS: CLBP North et al Neurosurgery 2005;56:98107 FBSS patients (%) 100 RCT p = 0.0005 80 SCS Reoperation p = 0.0149 60 40 20 0 More than 50% pain relief Increase in opiate analgesia SCS in CLBP Clinical efficacy: – RCT: 47% SCS patients had 50% pain relief and expressed satisfaction with treatment, compared with only 12% reoperation patients 87% of SCS patients had stable or reduced opioid use; 42% reoperation patients required an increase Cost effectiveness: – Considerable cost savings after 2.5 years Quality of life with neurostimulation in CLBP 6% 34% 60% Worsening Improved No change 78% of patients would recommend SCS to someone with a similar problem, 75% of patients would have the procedure performed again if they had known their outcome before implantation 1. Ohnmeiss DD, Rashbaum RF. The Spine Journal 2001;1:258-363 [dual leads were required for these patients] Spinal cord stimulation versus re-operation in patients with failed back surgery syndrome: an international multicenter randomized controlled trial (EVIDENCE study). North RB, Kumar K, Wallace MS, Henderson JM, Shipley J, Hernandez J, Mekel-Bobrov N, Jaax KN. Neuromodulation. 2011 Jul-Aug Assess the effectiveness and cost-effectiveness of spinal cord stimulation (SCS) with rechargeable pulse generator versus re-operation Study subjects have neuropathic radicular leg pain exceeding or equaling any low back pain and meet specified entry criteria. Co-primary endpoints are proportion of subjects reporting ≥ 50% leg pain relief without crossover after SCS screening trial or re-operation. Secondary endpoints include cost-effectiveness; relief of leg, back, and overall pain; change in disability and quality of life; and rate of crossover. Complex Regional Pain Syndrome CRPS-Early Work Barolat et at-1989 – Pain reduction in 10 of 13 patients – Short follow up Kumar et al- 1997 – 41 month follow up of 12 patients – All patients with pain relief CRPS Kemlar -1999: 78% pain relief – 23 patients Kemlar- 2000: SCS vs Physical Therapy – 54 Patients randomized – 67% pain relief at 6 months – Improved VAS scores Kemlar- 2006: Diminished effectiveness over 5 year follow up Long-term outcomes of spinal cord stimulation with paddle leads in the treatment of complex regional pain syndrome and failed back surgery syndrome. Sears NC, Machado AG, Nagel SJ, Deogaonkar M, Stanton-Hicks M, Rezai AR, Henderson JM. Neuromodulation. 2011 Jul-Aug More than 50% of the patients with CRPS reported greater than 50% pain relief at a mean follow-up of 4.4 years. Approximately 30% of the FBSS patients reported a 50% or greater improvement at a mean follow-up of 3.8 years. However, 77.8% of patients with CRPS and 70.6% of patients with FBSS indicated that they would undergo SCS surgery again for the same outcome. CRPS-Limitations Difficult to cover affected area with stimulation Long- term efficacy is yet to be determined Improvement in pain scores, but not necessarily improvement in functional impairment Awake vs. Asleep Placement of Spinal Cord Stimulators: A Cohort Analysis of Complications Associated With Placement Steven M. Falowski, MD, Amanda Celii, MD, Anthony K. Sestokas, PhD, Daniel M. Schwartz, PhD, Craig Matsumoto, MPAS, Ashwini Sharan, MD Neuromodulation. 2011 Mar-Apr;14(2):130-4; discussion 134-5 A retrospective review of 167 new internalization operations Electrode implantation performed either under monitored (local anesthetic and intravenous sedation) or under general anesthesia Awake versus non-Awake Surgery for Placement of Spinal Cord Stimulators Device failure for patients implanted using neurophysiologically-guided placement under general anesthesia was one-half that for patients implanted awake (14.94% vs 29.7%). No difference in repositioning or infection rate Awake versus non-Awake Surgery for Placement of Spinal Cord Stimulators Important Points: – Radiographical position and motor stimulation responses to assure proper electrode positioning under general anesthesia – Performed after a percutaneous trial Conclusion: – Non-awake surgery is associated with fewer failure rates and therefore fewer reoperations, making it a viable alternative SCS-Conclusions SCS Technology is improving – Equipment and stimulation parameters Reliable and safe modality Goal of neurostimulation is to reduce pain rather than to eliminate pain – 50% improvement in pain relief – Reduce use of pain medications Increasing amount of uses – Importance of selection criteria