Surgery Section - Spinal Cord Stimulation for Treatment of Pain

IMPORTANT REMINDER

This Medical Policy has been developed through consideration of medical necessity, generally accepted standards of medical practice, and review of medical literature and government approval status.

Benefit determinations should be based in all cases on the applicable contract language. To the extent there are any conflicts between these guidelines and the contract language, the contract language will control.

The purpose of medical policy is to provide a guide to coverage. Medical Policy is not intended to dictate to providers how to practice medicine. Providers are expected to exercise their medical judgment in providing the most appropriate care.

Description

Spinal cord stimulation delivers low voltage electrical stimulation to the dorsal columns of the spinal cord to block the sensation of pain. The neurophysiology of pain relief after spinal cord stimulation is uncertain, but may be related to either activation of an inhibitory system or blockage of facilitatory circuits. Spinal cord stimulation devices consist of several components:

1. The lead which delivers the electrical stimulation to the spinal cord
2. An extension wire which conducts the electrical stimulation from the power source to the lead
3. A power source which generates the electrical stimulation

The lead may incorporate from four to eight electrodes, with eight electrodes more commonly used for complex pain patterns, such as bilateral pain, or pain extending from the limbs to the trunk. There are two basic types of power source. In one type the power source (battery) can be surgically implanted. In another a radiofrequency receiver is implanted and the power source is worn externally with an antenna over the receiver. Totally implantable systems are most commonly used.

The patient's pain distribution pattern dictates at what level in the spinal cord the stimulation lead is placed. The pain pattern may influence the type of device used. For example, a lead with eight electrodes may be selected for those with complex pain patterns or bilateral pain. Implantation of the spinal cord stimulator is typically a two step process. Initially, the electrode is temporarily implanted in the epidural space, allowing a trial period of stimulation. Once treatment effectiveness is confirmed, defined as at least 50% reduction in pain, the electrodes and radio-receiver/transducer are permanently implanted. Successful spinal cord stimulation may require extensive programming of the neurostimulators in order to identify the optimal electrode combinations and stimulation channels. Computer controlled programs are often used to assist the physician in studying the numerous programming options when complex systems are used.

Spinal cord stimulation has been used in a variety of chronic refractory pain conditions, including pain associated with cancer, failed back syndromes, arachnoiditis, visceral pain, drug-refractory chronic cluster headaches and chronic reflex sympathetic dystrophy. There has also been interest in spinal cord stimulation as a treatment of chronic refractory angina pectoris and treatment of chronic limb ischemia, primarily in patients who are poor candidates for revascularization.  Spinal cord stimulation is generally not effective in treating nociceptive pain (resulting from irritation, not damage to the nerves) and central deafferentation pain (related to central nervous system damage from stroke or spinal cord injury).

Note: Deep brain stimulation as a treatment of movement disorders is addressed in a separate Regence medical policy, Surgery No. 84.

Policy/Criteria

Scientific Background

Chronic Back and Extremity Pain

The bulk of published literature regarding spinal cord stimulation (SCS) consists of case series. In a systematic literature synthesis of these studies, Turner and colleagues reported that in patients with chronic low back pain, an average of 59% of patients had 50% or greater pain relief with SCS. (2) Results of a randomized controlled clinical trial reported that a significantly greater proportion of patients initially randomized to repeat lumbosacral surgery opted to cross over to the spinal cord stimulation arm of the trial, compared to those initially in the spinal cord stimulation arm of the trial crossing over to lumbosacral surgery. (3) A prospective multicenter study of spinal cord stimulation in 219 patients with chronic back and extremity pain reported successful management of pain in 55% of patients. (4) A multicenter randomized trial (the PROCESS study) compared SCS (plus conventional medical management) with medical management alone in 100 patients with failed back surgery syndrome (FBSS). (15) Leg pain relief (>50%) at six months was observed in 24 (48%) SCS-treated patients and four (9%) controls, with an average leg pain visual analog scale (VAS) score of 40 in the SCS group and 67 in the conventional management control group. Between 6 and 12 months, five (10%) patients in the SCS group and 32 (73%) patients in the control group crossed over to the other condition. Of the 84 patients who were implanted with a stimulator over the 12 months of the study, 27 (32%) experienced device-related complications.

More recently, Kemler and colleagues reported on favorable outcomes of SCS among patients with chronic reflex sympathetic dystrophy (CRSD) who were randomized to the SCS arm compared to those treated with physical therapy alone. (5) The favorable outcomes were still present at two years’ follow-up. (10) Another study reported 5-year outcomes from a randomized trial of 54 patients with CRPS. (16) Twenty-four of the 36 patients assigned to SCS and physical therapy were implanted with a permanent stimulator after successful test stimulation; 18 patients were assigned to physical therapy alone. Five-year follow-up showed a 2.5 cm change in VAS pain score in the SCS group (n=20), and a 1.0 cm change for the control group (n=13). Pain relief at 5 years was not significantly different between the groups; 19 (95%) patients reported that for the same result they would undergo the treatment again. Ten (42%) patients underwent reoperation due to complications.

An evidence-based review from the American Society of Pain Physicians found the evidence for SCS in failed back surgery syndrome and complex regional pain syndrome strong for short-term relief and moderate for long-term relief. (17) Reported complications with spinal cord stimulation ranged from infection, hematoma, nerve damage, lack of appropriate paraesthesia coverage, paralysis, nerve injury, and death. Evidence-based guidelines from the European Federation of Neurological Societies found level B (i.e., at least 1 prospective matched-group cohort study or randomized controlled trial in a representative population) evidence for the effectiveness of SCS in failed back surgery syndrome and CRPS I. (18) The task force indicated that implantable stimulators are typically used when all other treatments have failed, and that this context should be taken into account when making recommendations.

Chronic Refractory Angina

Several randomized studies were identified which focused on two populations of patients: 1. Patients who were not considered candidates for a revascularization procedure due to comorbidities or other factors, where SCS was compared to continued medical management; or 2. Patients who would be considered candidates for a revascularization procedure for the purpose of symptom relief only, where SCS was compared to coronary artery bypass grafting. The following results were reported:

1. Spinal Cord Stimulation as an Alternative to Medical Management

Hautvast and colleagues reported on a study that randomized 25 patients with chronic angina who were not considered candidates for surgery to receive either an active or sham SCS. (6) Patients were followed for six weeks. Primary outcomes included symptom relief (frequency of angina episodes, nitrate use, and self-assessment), ischemic episodes as noted on 24 hour monitoring, and improvement in cardiac function as noted on exercise stress test. All outcomes were significantly improved in the active treatment group compared to the control group. In another small trial, seventeen patients were randomized to receive SCS or continued medical management. (7) After the eight-week study period, the control group received a SCS and the entire group was followed for one year. Those receiving SCS reported a significant improvement in exercise capacity and quality of life.

2. Spinal Cord Stimulation as an Alternative to Coronary Artery Bypass Surgery

The Electrical Stimulation versus Coronary Bypass (ESBY) study randomized 104 patients with chronic refractory angina to SCS or coronary artery bypass grafting (CABG). (8) Patients were included in the study only if the CABG was considered solely as a technique for reducing angina pain. The primary outcomes, measured after six months, were symptom relief and myocardial ischemia (as measured by exercise tests). At six months, both treatments were associated with similar improvement in symptom relief. Among those undergoing CABG, there was greater improvement in various cardiac function measures, such as exercise capacity and less ST segment depression. The lack of improvement of cardiac function measures in the active treatment group contrasts with other trials of SCS. However, in this trial the device was turned off for the 24-hour period prior to exercise testing, suggesting that SCS does not have a permanent effect on cardiac function.

Limb Ischemia

Critical limb ischemia is described as pain at rest or the presence of ischemic limb lesions. If the patient is not a suitable candidate for limb revascularization (typically due to insufficient distal run-off), it is estimated that amputation will be required in 60-80% of these patients within a year. Spinal cord stimulation has been investigated in this small subset of patients as a technique to relieve pain and decrease the incidence of amputation. Klomp and colleagues conducted a study that randomized 120 patients with critical limb ischemia not suitable for vascular reconstruction to undergo either best medical care, or medical care in addition to SCS. (9) The primary endpoint was limb survival at two years. The difference in amputation rate at 12 months was no longer present at 24 months. The addition of SCS did not improve amputation-free survival nor was the risk of major amputation significantly reduced. Both groups also reported similar levels of pain reduction. In both groups, the rates of amputation were highest within the first three months of the study, reflecting the limitations with both treatment options.

A 2005 update of a systematic review from the Cochrane group on use of SCS in non-reconstructible critical leg ischemia included six European studies with a total of 444 patients, including the Klomp study summarized above. (11) None of the studies were blinded due to the nature of the treatment.  One of the studies was non-randomized and one included only patients with ischemic ulcers. Treatment groups received SCS along with the same standard nonsurgical treatment as the control groups. At 12, 18 and 24 months follow-up individual studies showed a trend toward a better limb salvage that did not reach statistical significance. However, when results were pooled, a significant decrease in amputations was found for the SCS group at 12 months follow-up with a number needed to treat (NNT) of nine. Outcomes for pain relief and ulcer healing were mixed. Quality of life was unchanged in both control and treatment groups. The overall risk of complications or additional SCS treatment was 17% with a number needed to harm (NNH) of six. Although the only statistically significant difference favoring the SCS group was in the pooled data for limb salvage at 12 months follow-up, the report concluded that there was “evidence that SCS is better than conservative treatment alone to achieve amputation risk reduction, pain relief and improvement of the clinical situation” in these patients. This seemingly incongruous conclusion may be explained by the authors’ conclusion that “The benefits of SCS against the possible harm of relatively mild complications and costs must be considered.”  A potential conflict of interest was noted for the principal investigator.

Miscellaneous

The use of SCS for other conditions such as visceral pain has been reported, though no randomized controlled trials have been published.  A pilot study on occipital nerve stimulation for drug-resistant chronic cluster headache reported reduced preventive drug treatment in seven of the eight patients. (13) The British Pain Society recommended that its use in this and other emerging indications be carefully audited. (14)

An updated search of the MEDLINE database through December 15, 2008 did not return any clinical studies that alter the above conclusions.

References

1. BlueCross and BlueShield Association Medical Policy Reference Manual, Policy No. 7.01.25
2. Turner JA, Loesser JD, Bell KG. Spinal cord stimulation for chronic low back pain: a systematic literature synthesis. Neurosurgery 1995;37:1088-96
3. Burchiel KJ, Anderson VC, Brown FD. Prospective multicenter study of spinal cord stimulation for relief of chronic back and extremity pain. Spine 1996;21:2786-94
4. North RB, Kidd DH, Lee MS, Piantodosi S. A prospective, randomized study of spinal cord stimulation versus reoperation for failed back syndrome: Initial results. Stereotactic Funct Neurosurg 1994;62:267-72
5. Kemler MA, Barendse GA, van Kleef M, de Vet HC, et al. Spinal cord stimulation in patients with reflex sympathetic dystrophy. NEJM 2000;343:618-24
6. Hautvast RWM, DeJongste MJL, Staal MJ et al. Spinal cord stimulation in chronic intractable angina pectoris: a randomized, controlled efficacy study. Am Heart J 1998;136:114-20
7. DeJongste MJL, Hautvast RWM, Hillege JL, Lie KI. Efficacy of spinal cord stimulation as adjuvant therapy for intractable angina pectoris. A prospective, randomized clinical study. J Am Coll Cardiol 1994;23:1592-97
8. Mannheimer C, Eliasson T, Augustinsson LE, Blomstrand C et al. Electrical stimulation versus coronary artery bypass surgery in severe angina pectoris: The ESBY study. Circulation 1998;97:1157-1163
9. Klomp HM, Spincemaille GHJJ, Steyerberg EW et al. Spinal cord stimulation in critical limb ischemia: A randomized trial. Lancet 1999;353:1040-44
10. Kemler MA, de Vet HC, Barendse GA, et al. The effect of spinal cord stimulation in patients with reflex sympathetic dystrophy: two years’ follow-up of the randomized controlled trial. Ann Neurol 2004;55(1):13-8
11. Ubbink DT, Vermeulen H. Spinal cord stimulation for non-reconstructable chronic critical leg ischaemia. Cochrane Database Syst Rev 2005;3:CD004001
12. Klomp HM, Steyerberg EW, van Urk H et al. ESES Study Group. Spinal cord stimulation is not cost-effective for non-surgical management of critical limb ischaemia. Eur J Vasc Endovasc Surg. 2006;31(5):500-8
13. Magis D, Allena M, Bolla M, et al. Occipital nerve stimulation for drug-resistant chronic cluster headache: a prospective pilot study. Lancet Neurol. 2007;6(4):289-91
14. The British Pain Society. Spinal cord stimulation for the management of chronic pain: Recommendations for best clinical practice.  www.britishpainsociety.org/SCS_2005.pdf  (Verified 12/15/08)
15. Kumar K, Taylor RS, Jacques L et al. Spinal cord stimulation versus conventional medical management for neuropathic pain: a multicentre randomised controlled trial in patients with failed back surgery syndrome. Pain 2007;132(1-2):179-88
16. Kemler MA, de Vet HC, Barendse GA et al. Effect of spinal cord stimulation for chronic complex regional pain syndrome type I: five-year final follow-up of patients in a randomized controlled trial. J Neurosurg 2008;108(2):292-8
17. Boswell MV, Trescot AM, Datta S et al; American Society of Interventional Pain Physicians. Interventional techniques: evidence-based practice guidelines in the management of chronic spinal pain. Pain Physician 2007;10(1):7-111
18. Cruccu G, Aziz TZ, Garcia-Larrea L et al. EFNS guidelines on neurostimulation therapy for neuropathic pain. Eur J Neurol 2007;14(9):952-70

Cross References

Percutaneous Electrical Nerve Stimulation (PENS) and Percutaneous Neuromodulation Therapy (PNT), Regence Medical Policy Manual, Surgery, Policy No. 44

Deep Brain Stimulation for Movement Disorders and Miscellaneous Conditions, Regence Medical Policy Manual, Surgery, Policy No. 84

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