Spinal cord stimulation (SCS) has been demonstrated to serve as a successful second-line treatment modality for painful diabetic peripheral neuropathy (PDPN), as documented in two randomized clinical trials (RCTs) (1,2). Besides the fact that these two RCTs demonstrate a pain-relieving effect for a period of 6 months after the start of SCS treatment, only small observational studies suggest a long-term sustained effect in PDPN (3–5). In this article, we present the 24-month follow-up data of our recently published RCT in Diabetes Care (1).
Thirty-six patients were enrolled in this study, and after randomization, 22 patients with PDPN in the lower limbs (15 male, mean age 57.1 years [SD 12.4], years of PDPN 6.0 [SD 5.1]) were assigned to the SCS group. A 2-week trial stimulation was performed to evaluate sufficient pain relief. After 6 months, 93% of patients in the control group crossed over to receive SCS. Treatment success of SCS was predefined in the protocol as ≥50% relief of pain intensity on a numeric rating scale (NRS) for 4 days during the daytime or nighttime or “(very) much improved” for pain and sleep on the patient global impression of change (PGIC) scale at 24 months. Additional outcome parameters were assessed as previously described (1). The linear rate of change in postbaseline measurements was examined based on a random intercept regression model. A treatment success comparison between 6 and 24 months was performed using the McNemar test. Differences between baseline and follow-up data were analyzed by means of paired sample t tests.
Out of 22 patients, 17 patients (12 male, mean age 54.9 years [SD 11.5], years of PDPN 6.2 [SD 5.4]) underwent positive trial stimulation and were implanted with a permanent SCS device as described elsewhere (1). Mean pain scores during day and night decreased by 3.3 points at daytime (P < 0.001) and 3.2 points at nighttime (P < 0.001) at 24-month follow-up (Fig. 1). In total, eight (47%) and six (35%) patients reported a 50% pain reduction during day and night at 24 months, respectively. Clinically significant improvements on the PGIC for pain and sleep were reported by nine (53%) patients at 24-month follow-up. Treatment success of SCS was observed in 11 out of 17 patients (65%) (Table 1). No significant difference was observed in treatment success rate at 24-month follow-up (65%) compared with treatment success rate at 6-month follow-up (76%).
During the follow-up period, a new pulse generator was implanted in two patients, and four patients had a revision of the stimulation lead. One patient withdrew due to an infection and removal of the SCS system after 6 weeks. At 24-month follow-up, one patient did not respond to the questionnaires, resulting in available data of 15 patients.
In conclusion, the data of this prospective two-center RCT demonstrate a sustained effect of SCS on pain relief in PDPN after 24 months.
Article Information
Acknowledgments. The authors would like to acknowledge the patients who participated in the study. Furthermore, the authors would like to thank the members of the multidisciplinary steering committee for designing and guiding the protocol.
Duality of Interest. This work was supported by a grant from Medtronic for the employment of one researcher (R.S.) for 3 years. No other potential conflicts of interest relevant to this article were reported.
Medtronic was not involved in the analysis and interpretation of the data.
Author Contributions. M.v.B. contributed to the analysis and interpretation of the data and wrote the manuscript. R.S. contributed to the study design and analysis and interpretation of the data. N.C.S., C.G.F., E.A.J., C.D.D., and R.T.v.D. contributed to the study design. A.G.H.K. contributed to the study design and analysis of the data. M.v.K. contributed to the study design and interpretation of the data and reviewed the manuscript. M.v.K. is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Clinical trial reg. no. NCT01162993, clinicaltrials.gov.
