New Rechargeable Spinal Cord Stimulator Systems Offer Advantages in CRPS Treatment
By Joshua P. Prager, MD, MS
Director, Center for the Rehabilitation of Pain Syndromes (CRPS)
Departments of Internal Medicine and Anesthesiology
David Geffen School of Medicine at UCLA

In April, 2004, the Food and Drug Administration (FDA) approved the first rechargeable spinal cord stimulator (SCS) system. This system, called Precision™, produced by Advanced Bionics, is the first in a new generation of SCS systems that offers a significant improvement in stimulation to people with CRPS. In early 2005, Advanced Neuromodulation Systems rechargeable system, the Eon™, was approved and shortly thereafter Medtronic, the largest producer of neurostimulator systems, received FDA approval for its Restore™ System.

This article will briefly review the use of SCS for treatment of CRPS and then describe the potential of the new systems in improving care and outcomes.

SCS as Part of the CRPS Treatment Algorithm

In 1995, the International Association for the Study of Pain (IASP) brought together a group of international experts to address treatment of CRPS. This was one of four meetings the IASP has held in the last two decades regarding various aspects of CRPS. Stanton-Hicks published results of the 1995 meeting as a treatment algorithm, which indicates that the mainstay of CRPS/RSD treatment is physical therapy, and that nerve blocks or SCS as adjuvant treatment are important for patients who are not adequately progressing with physical therapy alone. The important point of this article is that SCS can significantly enhance CRPS treatment by facilitating physical therapy as part of the entire rehabilitation process.

Stanton-Hicks suggested that the beneficial effect of SCS relates not only to pain relief, but it also to inhibits or modulates the sympathetic outflow to the region where the tingling produced by the stimulation is experienced.

SCS and CRPS

There have been numerous studies of SCS for the treatment of CRPS. These studies have been both retrospective and prospective randomized. In 1982, Broseta reported the use of SCS for CRPS-2 patients with 72 percent having experienced excellent results. Barolat reported a 73 percent success rate of pain in 18 patients with CRPS-1. Kumar discussed 12 patients treated with SCS for CRPS. Robaina compared SCS with TENS in 35 patients with late-stage CRPS-1; 66 percent of patients reported good results with SCS, experiencing rapid relief of pain and reduction in swelling. Bennett examined not only the effect of SCS on CRPS, but also looked at the effect of different lead arrays. He found that patient satisfaction was markedly improved with dual octapolar leads as opposed to traditional quadripolar leads.

There have been four prospective studies published of spinal cord stimulation in CRPS. The first, Calvillo in 1998, examined 31 patients with CRPS affecting the upper extremity with a significant reduction in pain scores compared to baseline. Oakley and Weiner observed statistically significant reduction in pain and an 80 percent success rate with SCS for CRPS. The largest prospective study in CRPS was that of Kemler , in the New England Journal of Medicine in 2000; 54 patients with CRPS-1 of one extremity were randomized to SCS plus physical therapy or physical therapy alone. A significantly greater number of patients with SCS plus physical therapy had a much improved global perceived effect than the physical therapy group alone. Most recently, Kemler published a two-year followup of the randomized trial. The mean pain score in the 24 implanted SCS patients was significantly reduced compared to those receiving physical therapy alone; 63 of the SCS patients reported improvement in their global perceived effect.

Thus, there is significant literature demonstrating the success with SCS in treating CRPS. This brief discussion above was not meant to thoroughly review or evaluate this literature, but merely to call attention to its presence and provide a reference list where one can review this information in greater detail.

Rechargeability and its Implication toward the Treatment of CRPS with SCS

The advent of rechargeability, being able to recharge the SCS battery, creates new opportunities. Previously, when a battery failed, the entire pulse generator needed to be replaced, which required expensive surgery and was uncomfortable for the patient. Rechargeability may significantly reduce the need to replace internal pulse generators.

Many CRPS patients with SCS systems have needed to use a lot of power to achieve the pain relief necessary to function. In order to reduce the need to replace the internal pulse generator, patients have often rationed the amount of stimulation by either reducing the power or turning the unit off some of the time. Thus, both patient and physician have attempted to manage the battery while compromising treatment. Rechargeability offers the opportunity to manage the patient instead of managing the battery.

Bennett notes that large arrays produce greater satisfaction than traditional quadripolar leads. Rechargeability offers the opportunity to use many contacts simultaneously, which uses a significantly greater amount of energy. Previously, this increased power consumption would have been prohibitive in some patients. Rechargeability allows the use of a greater number of electrodes at a given time to provide better coverage with stimulation.

There are some reports that increased frequency improves stimulation in patients with CRPS. Although this not been well documented, it is important to note that higher frequency produces higher energy consumption. Higher frequency potentially compromises battery life. Thus, rechargeability provides an opportunity to fully utilize the potential of any system without needing to worry about battery failure.

Conventional SCS four-and eight-contact leads were placed relatively far apart. Oakley and Prager in their discussion of SCS, indicate that when SCS leads are placed closer together the result is deeper penetration of the spinal cord, which provides a stronger effect. New lead configurations have been and will be designed specifically for rechargeable systems because the more-effective configurations will use more energy. Thus, once again, rechargeability provides a platform to allow for a more effective form of stimulation that conventional primary cell internal pulse generator source would not support.

Cost-Effectiveness of SCS

Taylor et.al recently reviewed the cost effectiveness of SCS for treating chronic pain. They conclude that in the medium to long term, SCS is economically favorable compared to other therapies for people with CRPS. Taylor indicates that pay back ranged from 15 months to five years after the SCS was implanted. The pay back period was sensitive to the efficiency level of the battery/electrode life and the amount of patient usage. However, this review was performed before rechargeable batteries. Considering the advantages of rechargeability, it is possible that pay back will be shortened and that the costs of SCS plus physical therapy will be lower than the cost of physical therapy alone. SCS initial costs are offset by a reduction in healthcare expenditures after the implant.

The Future with Rechargeability

The release of rechargeable systems has prompted the development of many new lead configurations that will enhance the effectiveness of SCS for the CRPS patient. New leads and extensions are currently in development. In particular, one product that will be available in the near future will allow four limbs to be treated simultaneously from a single-pulse generator. For patients with advanced four-limb CRPS, this eliminates the need for multiple systems; four limbs can be treated with a rechargeable single-pulse generator that, despite high energy consumption, will not require frequent replacement.

Summary

Spinal cord stimulation has a demonstrated efficacy in treating patients with CRPS when it is used in conjunction with a comprehensive rehabilitation program. Rechargeability enhances the ability to perform stimulation without requiring as frequent internal pulse generator battery replacements. SCS is cost effective in CRPS and future developments will enhance its effectiveness.

References

1. Stanton Hicks, M. et.al. An updated interdisciplinary clinical pathway for CRPS: Report of an expert panel. Pain Practice 2002; 2(1):1-16.
2. Stanton-Hicks M., Spinal cord stimulation for the management of complex regional pain syndromes. Neuromodulation 1999; 2(3):193-201.
3. Broseta J, et.al. Chronic epidural dorsal column stimulation in the treatment of causalgia pain. Appl Neurophys 1982;45: 190-194.
4. Barolat G. Schwartzman R., et.al., Epidural spinal cord stimulation management of reflex sympathetic dystrophy. Stereotact Funct Neurosurg 1999; 53:29-39.
5. Kumar K., et.al., Spinal cord stimulation is effective in the management of reflex sympathetic dystrophy. Neurosurgery 1997; 40:503-508.
6. Robaina F. J., et.al., Transcutaneous electrical nerve stimulation and spinal cord stimulation for pain relief in reflex sympathetic dystrophy. Stereotact Funct Neurosurg 1989; 52(1): 53-62.
7. Bennett D. S., et.al., Spinal cord stimulation for complex regional pain syndrome (RSD): A retrospective multicenter experience from 1995-1998 of 100 patients. Neuromodulation 1999;2:202-210.
8. Calvillo O, et.al., Neuroaugmentation in treatment of complex regional pain syndrome of the upper extremity. Acta Orthop Belg 1998; 64: 57-62.
9. Oakley, J. and Weiner, R. L., Spinal cord stimulation for complex regional pain syndrome: A prospective study of 19 patients at two centers. Neuromodulation 1999; 2:47-50.
10. Kemler, M.A., et.al., Spinal cord stimulation in patients with chronic reflex dystrophy. N Engl J Med 2000; 43:618-24.
11. Kemler, M.A., The effect of spinal cord stimulation in patients with chronic reflex sympathetic dystrophy: Two years followup of the randomized control trial. Ann Neurol 2004; 55:13-18.
12. Bennett, D.S., ibid.
13. Oakley, J., Prager, J., Mechanism of spinal cord stimulation. Spine. 27 (22):2574-2583.
14. Taylor, R. S., The cost effectiveness of spinal cord stimulation: A systematic review of the literature. J Pain Symptom Manage 2004; 27 (4): 370-8.

Updated February 27, 2006