Factors Contributing to Spinal Cord Stimulation Outcomes for Chronic Pain

History and Future of Spinal Cord Stimulation

Spinal cord stimulation (SCS) is a surgical treatment for chronic neuropathic pain refractory to medical management. An SCS system comprised one or more leads implanted in the epidural space, typically connected to an implantable pulse generator. This review discusses the history, indications, surgical technique, technological advances, and future directions of SCS.

sPinal coRd stimulatiOn coMpared with lumbar InStrumEntation for low back pain after previous lumbar decompression (PROMISE): a prospective multicentre RCT

INTRODUCTION

Persistent spine pain syndrome type 2 (PSPS2) represents a significant burden to the individual and society. Treatment options include revision surgery, stabilisation surgery of the spine, neuromodulation, analgesics and cognitive behavioural therapy. Nevertheless, structured treatment algorithms are missing as high-level evidence on the various treatments is sparse. The aim of this study is to compare higher frequency neuromodulation with instrumentation surgery in patients suffering from PSPS2.

METHODS AND ANALYSIS

The sPinal coRd stimulatiOn coMpared with lumbar InStrumEntation for low back pain after previous lumbar decompression (PROMISE) trial is a prospective randomised rater blinded multicentre study. Patients suffering from PSPS2 with a functional burden of Oswestry Disability Index (ODI) >20 points are randomised to treatment via spinal cord stimulation or spinal instrumentation. Primary outcome is back-related functional outcome according to the ODI 12 months after treatment. Secondary outcomes include pain perception (visual analogue scale), Short Form-36, EuroQOL5D, the amount of analgesics, the length of periprocedural hospitalisation and adverse events. Follow-up visits are planned at 3 and 12 months after treatment. Patients with previous lumbar instrumentation, symptomatic spinal stenosis, radiographical apparent spinal instability or severe psychiatric or systemic comorbidities are excluded from the study. In order to detect a significant difference of ≥10 points (ODI) with a power of 80%, n=72 patients need to be included. The recruitment period will be 24 months with a subsequent 12 months follow-up. The beginning of enrolment is planned for October 2022.

ETHICS AND DISSEMINATION

The PROMISE trial is the first randomised rater blinded multicentre study comparing the functional effectiveness of spinal instrumentation versus neuromodulation in patients with PSPS2 in order to achieve high-level evidence for these commonly used treatment options in this severely disabling condition. Patient recruitment will be performed at regular outpatient clinic visits. No further (print, social media) publicity is planned. The study is approved by the local ethics committee (LMU Munich, Germany) and will be conducted according to the Declaration of Helsinki.

TRIAL REGISTRATION NUMBER

NCT05466110.

Role of patient selection and trial stimulation for spinal cord stimulation therapy for chronic non-cancer pain: a comprehensive narrative review

Background/importance

Patient selection for spinal cord stimulation (SCS) therapy is crucial and is traditionally performed with clinical selection followed by a screening trial. The factors influencing patient selection and the importance of trialing have not been systematically evaluated.

Objective

We report a narrative review conducted to synthesize evidence regarding patient selection and the role of SCS trials.

Evidence review

Medline, EMBASE and Cochrane databases were searched for reports (any design) of SCS in adult patients, from their inception until March 30, 2022. Study selection and data extraction were carried out using DistillerSR. Data were organized into tables and narrative summaries, categorized by study design. Importance of patient variables and trialing was considered by looking at their influence on the long-term therapy success.

Findings

Among 7321 citations, 201 reports consisting of 60 systematic reviews, 36 randomized controlled trials (RCTs), 41 observational studies (OSs), 51 registry-based reports, and 13 case reports on complications during trialing were included. Based on RCTs and OSs, the median trial success rate was 72% and 82%, and therapy success was 65% and 61% at 12 months, respectively. Although several psychological and non-psychological determinants have been investigated, studies do not report a consistent approach to patient selection. Among psychological factors, untreated depression was associated with poor long-term outcomes, but the effect of others was inconsistent. Most RCTs except for chronic angina involved trialing and only one RCT compared patient selection with or without trial. The median (range) trial duration was 10 (0–30) and 7 (0–56) days among RCTs and OSs, respectively.

Conclusions

Due to lack of a consistent approach to identify responders for SCS therapy, trialing complements patient selection to exclude patients who do not find the therapy helpful and/or intolerant of the SCS system. However, more rigorous and large studies are necessary to better evaluate its role.

Efficacy of Spinal Cord Stimulation for Failed Back Surgery Syndrome in Elderly Patients: A Retrospective Study

Objectives

Failed back surgery syndrome (FBSS) refers to a condition where symptoms such as low back pain, leg pain, and numbness persist or recur after lumbar surgery; it has been reported to occur in 10%-40% of patients who have undergone lumbar surgery. Spinal cord stimulation (SCS) has been reported useful for low back and leg pain due to FBSS. In this study, we studied the efficacy and safety of SCS for FBSS in older adults.

Methods

Among FBSS patients who underwent an SCS trial between November 2017 and December 2020, those with at least 50% pain reduction during the trial phase who requested spinal cord stimulator implantation underwent implantation of a stimulator under local anesthesia. The patients were divided into two groups: patients aged <75 years (<75-year-old group) and patients aged ≥75 years (≥75-year-old group). The male/female ratio, symptom duration, operative duration, visual analog scale (VAS) scores before and after one year of surgery, responder rate (RR), complications one year after surgery, and stimulator removal rate were analyzed.

Results

There were 27 cases in the <75-year-old group and 46 in the ≥75-year-old group, with no significant differences in male/female ratio, duration of pain, or operative time between the two groups. VAS scores for low back pain, leg pain, and overall pain one year after surgery were improved significantly from respective preoperative scores in both groups (P < 0.001). There were no significant differences in low back pain VAS, leg pain VAS, overall pain VAS, RR, complications one year after surgery, or stimulator removal rate between the two groups.

Conclusion

SCS reduced pain effectively in both <75-year-old and ≥75-year-old groups with no differences in complications. Therefore, spinal cord stimulator implantation was considered a viable option for FBSS treatment in older adults because it can be performed under local anesthesia and is associated with a low incidence of complications.