The Long-term Outcome of Usual and Unusual Indications for Spinal Cord Stimulation: A Prospective Study

Background: Evidence of the efficacy of spinal cord stimulation (SCS) has been well demonstrated as a method of pain control for patients who exhibit failed back surgery syndrome (FBSS), complex regional pain syndrome (CRPS), and inoperable peripheral vascular diseases (PVD) ("usual indications"). However, a long-term study comparing the usual indications for which SCS is employed with those of other intractable painful conditions is still lacking. Objectives: To assess the long-term effectiveness of SCS treatment for both usual and unusual indications. Study Design: Observational study and original research. Setting: This work was conducted at the Faculty of Medicine Siriraj Hospital, Mahidol University, Thailand. Methods: We recruited patients undergoing SCS treatment for chronic refractory pain caused by various conditions and followed up on those patients for up to 36 months. The patients were divided into usual indications for SCS, including FBSS, CRPS, and PVD; and unusual indications for SCS, including chronic refractory neuropathic pain of various etiologies. Pain intensity, pain- related interference, and health-related quality of life (HRQOL) were collected at the baseline, 6 months, and one, 2, and 3 years after SCS implantation, and the values seen at each time point were compared to the baseline values. Results: Forty-six patients were recruited, 30 of whom underwent successful SCS implantation (24 usual and 6 unusual indications). The overall pain intensity was significantly lower than it was at the baseline, decreasing from 6 to 3, 5, 4, 4 out of 10 at 6, 12, 24 and 36 months after implantation, respectively (P < 0.01). Pain-related interference and HRQOL tended to improve over time after implantation. Patients with usual indications had a significantly higher rate of trial-per-implant ratio than those with unusual indications, with an odd ratio of 5.14 (95% CI 1.36-19.50). Furthermore, patients with usual indications tended to see greater improvement and more constancy in pain intensity, pain-related interference, and HRQOL than those with unusual indications. Limitations: This analysis was a single-center prospective study with a nonrandomized design and a relatively small sample size. Conclusions: Overall, SCS is an effective long-term treatment for chronic refractory pain. However, patients with usual indications for SCS have a higher success rate in SCS trials and a trend toward better outcomes after SCS implantation than do patients with unusual indications.