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 Other 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 Scattered reports regarding the treatment of intractable pain due to other causes distribution of EU and USA use of SCS for angina and peripheral vascular disease. skewed distribution favoring use in the EU since it isn't indicated here. The is one by Mannheimer (circa 2000) that mentions that 2000 patients have SCS in EU for those indications.

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 Linderroth:In vivo microdialysis study in the rat in 1994. Foreman:In 1976 primate spinothalamic tract neurons . action potentials ascending in the dorsal columns activating cells in the brainstem, which in turn might drive descending inhibition.

Mechanism Of Action Barolat 1993: Mapping of sensory responses Barolat 1998: Anatomical and electrical properties of the intraspinal structures and clinical correlations A basic tenet of SCS is to create an overlapping of paresthesia and pain region. Lateral placement at T11-12 will cover the anterior thigh, while placement at T11-L1 can cover the posterior thigh. Low back pain is very difficult to cover because mid- thoracic stimulation can affect the chest and abdominal wall. The experience of the author had best localization with midline placement at T8-9. Laterally placed thoracic electrodes are more likely to stimulate the thoracic nerve roots and result in painful stimulation.

Mechanism of Action-Electrodes Large fibers are activated near the cathode. Bipolar/tripolar etc… makes smaller electrical fields/different fields- closer spacing is likely more effective when it comes to fiber activation. The advent of the tripole electrodes and the ability to steer current has made it more plausible to aim for low back paresthesia. Further, flanking the cathode by lateral anodes also appears to increase the discomfort threshold theoretically-less activation of thoracic roots sharan 2007

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 Holsheimer:Based on their modelling work, developed a transverse tripole electrode which had a central cathode and two lateral anodes. The anodes were to increase the discomfort threshold over the roots by a shielding effect compared to the paresthesia threshold under the cathode in the center.

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 Also known as Failed Back Surgery Syndrome(FBSS). Post-laminectomy syndrome is vaguely defined. SCS is accepted in the treatment of leg pain. Studies do not routinely differentiate between axial back and leg pain. Although there is some recent data on back pain, it is still inconclusive. Most implanting physicians share the experience that SCS is far more effective for radicular pain than for axial low back pain.

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 North-1991 longitudinal study post-surgical lumbar arachnoid or epidural fibrosis without surgically remediable lesions, superior for back and leg pain (37). Successful outcome (at least 50% pain relief and patient satisfaction with the result) North 1995. Patients were allowed to crossover after six months. Ten of fifteen patients crossed over from back surgery to SCS, while only two of twelve patients crossed over from SCS to back surgery.

SCS had a positive, symptomatic, long-term effect in cases of: 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 Studies grouped on the basis of pain indication-retrospective review SCS was a safe and effective treatment for a variety of chronic neuropathic conditions.

Results CONCLUSIONS: Despite the positive findings, there is an urgent need for randomized, controlled, long-term studies on the efficacy of SCS involving larger patient sample sizes.

CLINICAL RESULTS: CLBP North et al Neurosurgery 2005;56:98-107 FBSS patients (%) More than 50% pain relief Increase in opiate analgesia SCS Reoperation 20 40 60 80 100 p = 0.0149 p = 0.0005 RCT North RB, Kidd DH, Farrokhi F, et al. Spinal cord stimulation versus repeated lumbosacral spine surgery for chronic pain: a randomized, controlled trial. Neurosurgery 56:98-107, 2005

SCS in CLBP Clinical efficacy: Cost effectiveness: 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 North et al. Spinal cord stimulation versus repeated lumbosacral spine surgery for chronic pain: a randomized, controlled trial. Neurosurgery 2005; 56: 98—107 Kumar et al. Treatment of chronic pain with spinal cord stimulation versus alternative therapies: costeffectiveness analysis. Neurosurgery 2002; 51: 106-16

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. This paper presents the protocol of the EVIDENCE study, a multicenter multinational randomized controlled trial through 36-month follow-up in patients with failed back surgery syndrome. We are collecting data on subject global impression of change, patient satisfaction with treatment, employment status, pain/paresthesia overlap, SCS programming, and adverse events. the EVIDENCE study will provide up-to-date evidence on the treatment of failed back surgery syndrome.

Complex Regional Pain Syndrome Swelling in one part of the body.-Burning pain/Edema/Skin discloration. The pain may start after an injury, where the nerves have been damaged-minor trauma or surgery (i.e., arthroscopy of the knee or shoulder, carpal tunnel surgery, removal of neuroma) Type 1 may not have any known cause. It used to be called Reflex Sympathetic Dystrophy (RSD), Sudecks Atrophy or Algodystrophy. Type 2 always follows an injury and used to be called causalgia. CRPS is quite rare and half of all people that develop it recover within a few months.

CRPS-Early Work Barolat et at-1989 Kumar et al- 1997 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 Barolat et al: No patients were made pain free but all ten reported a definitive difference when the stimulation was stopped. Kumar et al. Eight patients reported near complete resolution of their symptoms and four also maintained good 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 kemlar’s papers are NEJM articles no functional improvement was observed in either group. VAS:continuum scale of pain, highly subjective, these scales are of most value when looking at change within individuals, not for across a group of individuals at one time point In 2006. do not specify how reprogramming or modern devices might impact on the long term effects of SCS therapy.

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. A total of 35 eligible patients chose to participate. Patients with CRPS and FBSS have a high degree of satisfaction, indexed as willingness to undergo the same procedure again for the same outcome at a mean follow-up of approximately four years. The percentage of satisfaction with the SCS system is disproportionally greater than the percentage of patients reporting 50% pain relief, particularly among patients with FBSS. This suggests that the visual analog scale may not be the optimal measure to evaluate long-term outcomes in this patient population.

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 Initial improvement greatest in first 6 months but diminished over 5 years. May be limitation of earlier electrodes and lack of use of different stimulation parameters.

A retrospective review of 167 new internalization operations 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 Many studies looking at min invasive implantation under Awake surgery. Especially Beems. Patients between 2002-2007 implanted by one physicians at a single center Literature supports Awake Sx Efficacy predicted upon parastesia coverage in painful region. Awake Sz to optimize this distribution

No difference in repositioning or infection rate 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 A device failure was defined as any re-operation secondary to a traumatic break in the SCS system, a device malfunction requiring re-exploration, or a device removal secondary to lack of efficacy

Important Points: Conclusion: 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 re-operations, making it a viable alternative The electrode can be placed to the same location as the trial electrode. Any benefits of awake implantation should carefully be considered in the future. (Similar revision/Failure rates to Turner 2004. North 2005 showed Laminect>perc)

SCS-Conclusions SCS Technology is improving Reliable and safe modality 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 Very few other invasive modalities can claim this success rate with a few years of follow-up Long term follow up still needs to be studied.