On reflection, this isn't the study you've requested, but goes to a fundamental point that is all too often ignored . . .

Spinal cord stimulation for chronic reflex sympathetic dystrophy--five-year follow-up, Kemler MA, de Vet HC, Barendse GA, van den Wildenberg FA, van Kleef M, N Engl J Med. 2006 Jun 1;354(22):2394-6, 96.

Academic Medical Center, Vrije Universiteit Medical Center, Amsterdam, and Maastricht University Hospital, Maastricht, the Netherlands

The long-term follow-up analysis demonstrates that the pain-alleviating effect of spinal cord stimulation in chronic reflex sympathetic dystrophy diminishes with time, as compared with that in a control group, and is no longer statistically significant after three years. [Emphasis added.]

But, see, 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;14(4):312-8; discussion 318. doi: 10.1111/j.1525-1403.2011.00372.x. Epub 2011 Jul 7.

Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, USA.

Abstract

INTRODUCTION: Spinal cord stimulation (SCS) is frequently used to treat chronic, intractable back, and leg pain. Implantation can be accomplished with percutaneous leads or paddle leads. Although there is an extensive literature on SCS, the long-term efficacy, particularly with paddle leads, remains poorly defined. Outcome measure choice is important when defining therapeutic efficacy for chronic pain. Numerical rating scales such as the NRS-11 remain the most common outcome measure in the literature, although they may not accurately correlate with quality of life improvements and overall satisfaction.

METHODS: We reviewed the medical records of patients with failed back surgery syndrome (FBSS) or complex regional pain syndrome (CRPS) implanted with SCS systems using paddle leads between 1997 and 2008 at the Cleveland Clinic with a minimum six-month follow-up. Patients were contacted to fill out a questionnaire evaluating outcomes with the NRS-11 as well as overall satisfaction.

RESULTS:A total of 35 eligible patients chose to participate. 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.

CONCLUSION: 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. [Emphasis added.]

© 2011 International Neuromodulation Society.

PMID: 21992424 [PubMed - indexed for MEDLINE]

Unfortunately, the abstract to the article by Sears NC et al, doesn’t provide a link through which I could purchase it, so I have no way to comment on its methodology, etc. The latter is a particular concern where an "n of 35 eligible patients" is a remarkably small number, in light of the number of SCS implantation procedures on CRPS patients done by the two institutions - including The Cleveland Clinic - over the relevant 11-year time period, certainly numbering well into the hundreds.

Finally, it should be born in mind, that, while Kemler et al reported on a bona fide longitudinal study - which found its way into the NEJM - the report out of Cleveland is based solely on those patients who chose to respond to a survey questionnaire, which may explain while it was published in Neuromodulation, the journal of the International Neuromodulation Society, which describes the “Scope of Neuromodulation Advances” as follows:

Neuromodulation employs advanced medical device technologies to enhance or suppress activity of the nervous system for the treatment of disease. These technologies include implantable as well as non-implantable devices that deliver electrical, chemical or other agents to reversibly modify brain and nerve cell activity.

In other words, it’s a trade journal.


Mike


PS And my apologies f I missed an earlier request for the citation.