1. Evidence Based Medicine for SCS
Steven M. Falowski MD
St. Lukes Health Network
Bethlehem, PA

2. Advantages of SCS Therapy
Safe
Testable
Non-destructive
Mostly reversible
Long-term cost is low
Less Risky

3. Disadvantages of SCS Therapy
Limited to specific indications and diseases
Equipment failure
Follow-up lifelong?
Short-term cost is high
Inability to get MRI

4. 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.

5. Mechanism of Action Foreman et al. 1976 Primate Studies
Linderoth et al 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 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.

6. 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.

7. 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

8. 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.

9. 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.

10. 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 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.

11. 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.

12. 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.

13. 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 =
p =
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

14. 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:

15. Quality of life with neurostimulation in CLBP6%
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: [dual leads were required for these patients]

16. 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 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.

17. 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.

18. 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.

19. 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 do not specify how reprogramming or modern devices might impact on the long term effects of SCS therapy.

20. 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 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.

21. 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.

22. 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 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 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

23. 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

24. 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 North 2005 showed Laminect>perc)

25. 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.