1. Spinal Cord Stimulation
Jennifer Yanow, MD
The New Jersey Pain Management Institute
first thing we need to understand is how scs works, then i will talk about how to pick a good candidate, the trial process, and some of the data regarding outcomes and cost effectiveness.

2. Hands on part- st jude

3. So you hit your finger with a hammer
So you hit your finger with a hammer. Instinctively, you grab it and rub it. In simple terms, What you are doing is distracting your brain from the pain. So if we look at this picture a little more scientifically, what happens when you hit your finger

4. Very simply, the pathway is-
Very simply, the pathway is- . When you rub your finger, you are distracting your brain from the pain, and you are activating these nerves in the spinal cord that can interrupt the pain signal. In medical terms, this is called the gate theory

5. Gate Theory
In the dorsal horn (where pain signals relay), there is a ‘gate’ that opens and closes to allow pain signals up to the brain.
C and A delta fibers are small pain fibers. When their signals get to the brain, you feel pain
A beta fibers are larger fibers that carry non painful signals (vibration, light touch, etc)
When A beta fibers are stimulated, they ‘close the gate’, and signals from the smaller pain fibers cannot get up to the brain
In medical terms, you are demonstrating something called the ‘gate theory’. Proposed 50 years ago, way to explain why we are able to trick our brains into not feeling as much pain. So for us to feel pain, a pain signal has to get to the brain.

6. SCS: Mechanisms of Action
One of the main ways we believe SCS works is by utilizing this gate theory. SCS stimulates these A-beta fibers in the dorsal horn, so instead of patients feeling pain they feel a tingling/vibration sensation instead.
SCS was first used in 1967, a few years after the Gate Theory was published. This can not fully explain how scs works. Scs if effective for chronic pain, but don’t stop new, acute pain- if you cut your leg you will still feel it, so the gate is not completely closed

7. SCS: Mechanisms of Action
Releases certain neurotransmitters that cause vasodilation- helpful for angina, PVD and CRPS
Increases levels of GABA… in patients with allodynia (CRPS), GABA levels are decreased in the CSF
Blocks sympathetic outflow. For some CRPS patients, abnormal activity of the SNS is responsible for a lot of their symptoms, and SCS can help significantly with temperature and skin color changes as well as with pain.
it also causes the release of NT cause vasodilation, and is very effective in patients with PVD. This mechanism of action is also part of the reason that SCS helps CRPS patients, a lot of whom have decreased blood flow to the affected limb

9. “Supraspinal Mechanisms”
Can’t explain all of the ways SCS works by the mechanisms we just discussed. We know it affects the brain, and this is especially imp for the crps patients.

10. Diagnoses
In our patient population, we use SCS for FBSS (low back or neck), CRPS, chronic pain s/p crush injury, and phantom limb pain.
However, this doesn’t mean that any patient who carries one of these diagnoses is a good candidate…
So what diagnoses is sCS appropriate for? There are actually quite a lot, but only some are relevant to WC. Some, like PVD and angina, DPN, chronic abdominal pain, are not typically diagnoses we deal with.

11. What Makes a Good SCS Candidate?
Of course it would be great if we had a foolproof way to determine who would do well.

12. Neuropathic vs Nociceptive Pain
Patients with neuropathic pain respond better to SCS. Peripheral neuropathy has published success rates of nearly 75%, whereas FBSS (which is both neuropathic + nociceptive) has published success rates closer to 60%.
Nociceptive pain is more responsive to anti- inflammatories and opioid medication, whereas neuropathic pain typically is not.
First factor is the type of pain the patient has.
Neuropathic pain is basically nerve damage- remember these nerves that transmit pain synapse in the dorsal horn, where SCS is able to ‘close the gate’. Nocicpetive pain is caused by damage to body tissues- burn yourself, paper cut, etc
Those of you who were here last year may remember that I spoke about cRPS last year, and we discussed that these patients do not respond well to opioids, and require very high doses

13. Duration of Symptoms
Inverse relationship b/n the chronicity of the pain and the outcomes of SCS
For FBSS, patients who received their SCS within 2 years of symptoms onset had a success rate of 85%. Those with pain >15 years only had a 9% success rate.1
CRPS- considered before central sensitization has set in/ as soon as other treatments have failed.2
1.Kumar et al Impact of Wait Times on Spinal Cord Stimulation Therapy Outcomes. Pain Practice 2013
2.Kumar et al Neurosurgery 69;

14. Psychological Factors
Psych “clearance” extrapolated from IT pumps
Looks at patient’s ability to understand procedure and operate controls, have realistic expectations regarding outcome, coping skills, levels of anxiety, degree of somatization (“everything hurts”).
** Risk factors for poorer outcome-litigation, chemical dependency, spousal reinforcement of pain behaviors, negative outcome expectancy, and lack of English proficiency.
Stephens KA, Ward A. Patient Selection for Spinal Cord Stimulator: Mental Health Perspective. Curr Pain Headache Rep 2014;18:398.
Standard, but actually no controlled trials have been done to support this practice
Clearance is only a partial use of this evaluation. Aside from psychological roadblocks to understnading the procedure and using the equipment, what we should use this eval for is to help determine appropriate candidacy
Psychiatrists have identified risk factors for poorer SCS outcomes. Patients who are better able to self manage their symptoms have a better outcome, presumably because they arent looking to get 100% better

15. Common sense factors- Is patient willing to undergo additional surgery if they have a good trial, or in the case of CRPS- any surgery?

16. SCS Trial
So you identify a patient that you think would be a good candidate. This is a picture of a percutaneous trial lead. PAIN VS SURGERY Notice in this picture that the lead is at T9.
T7-8 for back, 9 covers more of the legs. Why?

18. Trial Lead Placement
Go over a little anatomy. Spinal cord ends at L1. below that, it’s just a bunch of nerve roots floating around, which you can’t reliably stimulate. Stimulate at the level of the cord where the nerves are coming out before they travel down and out the foramen. Tell patients thoracic surgery!!

19. SCS Trial… Realistic Expectations
Managing expectations

20. SCS Trial The trial process is not ideal
Positionality: the leads are in the epidural space and float around a bit. With change in position, there is a change in coverage.
Type of sensation?
Patients must be able to understand that the purpose of the trial is 'does this help with your pain/function'  
Trial duration – infection risk? No shower?!
Generally speaking, the trial success rate is 70%, however in the WC population this number is lower.
3-5 days. It is very important that patients understand the pitfalls of the trial.

21. Trial Follow Up
1) Pain relief- what percentage? Did the stimulator cover the whole painful area?  Reprogramming…
2) Function- hard because of the positionality, but look for sitting/standing tolerance, walking. Not going to be able to assess things like bending/lifting during the trial.  
3) Medication usage: did they need less medication? Short trial period, plus procedural pain, may be hard to assess  
Look for at least 50%, however if function is much improved I don’t worry as much about the number. So subjective. Patient comes in after an epidural walking and wearing 4 inch heels and say they got 10% better….

22. SCS Implant 2 ways to implant- surgical and percutaneous
One of the variables in how patients respond during a trial is the amount of space- (CSF)- between the electrode and the cord.
Paddle lead eliminates this, and gives a greater area of coverage. Also, because the lead is fixed, there is less chance of breakage.
(16)
surgical, in which a paddle lead is placed through a laminectomy defect and sewn into place, and percutaenous in which trial leads are used.

24. Outcomes: FBSS- Pain
Only 2 Randomized Controlled Trials, both industry sponsored!
North et al 2005: 45 FBSS pts- compared SCS to re- operation; at 3 year follow up SCS had a more favorable outcome than re-op, nearly obviated the need for re-op, and sig less meds. **67% of the re-op patients then crossed over to SCS
Kumar et al 2007: 100 FBSS patients randomized to CMM vs SCS with 2 year f/u. 48% of SCS vs 9% of CMM had 50% improvement in pain. Also with better function and QOL
Overall for FBSS, 50-60% of patients get >=50% better
Turner JA et al. Spinal Cord Stimulation for Patients with Failed Back Surgery Syndrome or Complex Regional Pain Syndrome: A Systematic Review of Effectiveness and Complications. Pain 2004;108:
FBSS occurs in approx 30% of patients= in our pop prob higher. Wc patients not allowed in study 2, in study 1 they were allowed
North study- 9/19 pts with scs and 3/26 surgery had more than 50% pain relief.

25. Outcomes: FBSS- Function/Med Intake
No RCT has looked specifically at function
3 case series did show improvements in function
Functional outcome is also a function of timing- Study looked at long term outcomes of SCS; noted that function was most improved in patients who were implanted <1 year after onset of symptoms1
North study- SCS group used significantly less opioids than the re-operation group- 45%2
1. Kumar K et al. Spinal Cord Stimulation is Effective in Management of Complex Regional Pain Syndrome 1: Fact or Fiction. Neurosurgery 2011;69(3):
2. North RB et al. Spinal Cord Stimulation versus Repeated Lumbosacral Spine Surgery for Chronic Pain: A Randomized Controlled Trial. Neurosurgery 2005;56:

26. What About WC?
Study compared ONLY WC patients with FBSS who had a SCS, were treated in a pain clinic, or had no specialized treatment.
Trial success rate was 53%.
Overall, this study showed no benefit to SCS, either in terms of long term pain relief, function, or return to work status.
Turner JA et al. Spinal Cord Stimulation for Failed Back Surgery Syndrome: Outcomes in a Workers’ Compensation Setting. Pain 2010;148:14-25/ 
(1) Inclusion criteria: open claim with back/leg pain more than 6 for more than 6 months, no history of dm or cancer, speak english or spanish. Patient selection!!

27. Outcomes: FBSS-RTW
Several studies have looked at FBSS patients’ return to work after SCS: in one, 8/23 resumed work2, in a second 4/32 resumed3, in a third 15% of the 60 patients who received a SCS returned, vs 0/44 who did not get implanted4.
In the outcome paper specifically looking at SCS for FBSS in WC, fewer than 10% of patients in any group were working at 12 months
Dario A et al. Treatment of failed back surgery syndrome. Neuromodulation 2001;4:
Ohnmeiss DD et al. Prospective outcome evaluation of spinal cord stimulation in patients with intractable leg pain. Spine 1996;21:
Kumar K et al. Treatment of chronic pain iwht spinal cord stimulation versus alternative therapies: cost-effectiveness analysis. Neurosurgery 2002;51:

28. Outcomes: CRPS One Randomized Controlled Trial!
24/36 patients got SCS + PT, 18 only PT
SCS group had reduced pain (-3.6/10 compared to +0.2), overall 39% of the SCS group were ‘much improved’, and all 24 had improved HR QOL at 6 months
No improvement in functional status in either group
At 1 year follow up, results the same. At 5 year follow up, results became less impressive, but 20 of the SCS patients still had improved global perceived effect and pain relief.
**95% of the patients who had SCS would opt for it again
Kemler et al. Spinal Cord Stimulation in Patients With Chronic Reflex Sympathetic Dystrophy. NEJM 2000;353:
In this study, 2/3 got implanted, which is about average. 1/3 of crps patients do not have a good trial.
(9) Did not exclude patients involved in litigation. 50% had at least 50% decrease in pain
(11)

29. Outcomes: CRPS
Prospective study followed 84 consecutive patients with CRPS who underwent SCS implantation1
SCS was determined to be an effective long term treatment (12 years) for 63% of patients
Average decrease in pain 25-30% from baseline, but 59% rated their pain as much or very much improved.
No data on function or medication intake
Meta-analysis performed in 2006 showed 67% of CRPS patients got at least 50% better following SCS, with sig improved QOL and functional mobility2
Geurts JW et al. Spinal Cord Stimulation for CRPS 1; A Propsepctive Cohort Study with Long-Term Follow up. Neuromodulation 2013;16(6):523-9.
Journal of Pain and Symptoms Management 2006;31(4):S13-19.
(20)
(journal of pain and symptom management 2006;31(4):S13-S19)  

30. Outcomes: CRPS/RTW
Several studies have looked at CRPS patients’ return to work after SCS: in one study, 41% of 24 patients returned,1 in another 5/25 returned2, and one study had a 70% RTW rate3
Calvillo O et al. Neuroagumentation in the treatment of CRPS of the upper extremity. Acta Orthop Belg 1998;64:57-63.
Kumar K et al. Spinal cord stimulation is effective in management of complex regional pain syndrome I: fact or fiction. Neurosurgery 2011;69:
Harke H et al. Spinal cord stimulation in sympathetically maintained complex regional pain syndrome type I with severe disability. Eur J Pain 2005;9:
In this last study, the patients had a sig response to a sympathetic block, and scs as we mentioned earlier acts as a continuous sympathetic blockade

31. What about Depression?
Severe depression is seen as a contra-indication to SCS.
However, unlike physical functioning, the level of depression has been shown to markedly improve following SCS implantation.1-31
Pre-implantation depression scores have not been shown to affect long term outcomes.
Pain Physician 2013;16(3):

32. How to Improve Outcomes?
Smart patient selection
Psychological factors/eval
TIMING- Much better response at <2 years for FBSS
For CRPS, before dystrophic changes are present. Best results seen within a year of symptom onset.1
For CRPS, SCS should be considered as soon as alternative therapies have failed; even within the first 3 months.2
1. Kumar et al. Neurosurgery 2011;69;  
2. Poree et al. Neuromodulation 2013;16(2):125-41

33. Do the Results Wane Over Time?
Results vary. Some studies show that the effect decreases 25-50% over 2 years, others only see a slight decrease in efficacy over time. This may be due to progression of disease, or electrode dislocation/ breakage.
In 2011 an outcome analysis of patients with paddle electrodes was published- in patients with CRPS, more than 50% of patients still had greater than 50% pain relief at 4.4 years, and 77.8% of them would choose to get implanted again.  
(1) Some concern that no matter what we do to try to improve outcome, the results don’t stick.

34. Cost Effectiveness: FBSS
(17). 2.5 years
Neuromodulation 2014

35. And What About for WC?
(2). And this is why patient selection is so important= in this study they took allcomers receiving WC who had back pain radiating into both legs rated more than 6/10 for more than 6 months who did not have diabetes or cancer.

36. Cost Effectiveness: CRPS
Compared to conventional medical management, SCS has an approximately 85% likelihood of being more cost effective for CRPS.
Kumar et al. Current Challenges in Spinal Cord Stimulation. Neuromodulation 2014;17:22-35.

37. Complications
1) Hardware complication- most common. Less with paddle leads, and also less of an issue with new technology. With new leads/programming, revision rates for this complication dropped to 4% from 15%
2) Pain at surgical site
3) Thoracic radiculopathy- 2% ? Pre-op MRI
4) Infection
5) Serious neurologic sequelae (ie hematoma)- very rare 17

38. On the Horizon
‘High frequency and “burst” stimulation- patients feel NO paresthesias, works better for axial pain and RSD. Approved in Europe, should be here by the end of the year
MRI compatibility: Medtronic has the indication for full body MRI (perc leads only, low intensity magnet only). St. Jude has head and extremity, Boston has perc/paddle but only head  
Position adaptive technology- “adaptive stim”- typically, laying = more stim b/c the amount of CSF around the cord changes. New technology adjusts intensity with position changes.
DRG stimulation: Electrode is placed directly next to a spinal nerve, so patient feels stimulation in a single dermatome. Great for patients with foot pain
Schultz DM et al. Pain Physician 1020;15(1):1-12

39. Invisible Trial System
Much better trial- pt controls their stimulator through an ipad, connected to their trial system by bluetooth. No wires, and much greater control. This has the burst technology in its software

40. Thank You!