Table 1.

Characteristics of studies included in the systematic review

Study	Year	Study design	n	Follow-up	Allocation concealment	Blinding	Primary outcome	Findings
Galan et al. (SENZA-PPN Study) [16]	2020	Prospective cohort study Subgroup analysis	9	12 months	Yes	No	Pain intensity using a Visual Analogue Scale	Mean VAS scores decreased from 8.0 ± 1.2 cm at baseline to 2.0 ± 1.2 cm after 6 months and 2.1 ± 2.3 cm after 12 months of 10-kHz SCS. At the 6-month follow-up, seven of eight (87.5%) subjects were responders, defined by pain relief of 50% or more
van Beek et al. [17]	2018	Prospective cohort study	48	5 years	No	No	Pain intensity using a Visual Analogue Scale	After 1-year follow-up, NRS pain scores decreased from 6.7 to 3.8 (day) and 39 (night) (p < 0.001). 80% of patients with a permanent implant still used their device after 5 years
Denisova [18]	2016	Prospective cohort study Subgroup analysis	4	6–18 months	No	No	Pain intensity using a Visual Analogue Scale	A VAS decrease of about 5 points was achieved in patients with diabetic neuropathy
Duarte et al. [19]**	2016	Multicenter randomized controlled trial	60	6 months	Unknown	No	Quality-adjusted life years (QALY)	Quality-adjusted life years, adjusted for baseline EQ-50 score, demonstrated a statistically significant difference in between SCS and conventional medical practice, respectively (0.258 vs. 0.178, p < 0.001)
Pluijms et al. [20]	2015	Prospective cohort study	15	12 months	No	No	Pain intensity evaluated using an NRS-based pain diary	SCS therapy was considered successful in 67% of patients at 12 months, as defined by > 50% decrease in pain intensity or a rating of pain being “much improved” or “completely resolved” on the Patients' Global Impression of Change (PGIC) survey. Responders were found to have increased dorsal forearm latency during contact heat evoked potential testing. The primary focus in this study was comparing responders vs. non-responders to SCS treatment based on sensory characteristics and small nerve fiber function
de Vos et al. [21]	2014	Multicenter randomized controlled trial	60	6 months	Unknown	No	Percentage of patients with more that 50% pain reduction at 6 months of treatment	A statistically significant number of patients in the SCS group achieved > 50% pain reduction at 6 months of treatment versus the control group (60 vs. 5%, p < 0.001). The average VAS score for pain intensity was significantly reduced at 6 months from baseline in the SCS group compared the control group: 73 to 31 in the SCS group (p < 0.001) vs. 67 to 67 in the control group (p = 0.97). The SF-MPQ and EuroWoL 5D questionnaires also showed reduced pain and improved health and quality of life after 6 months of treatment in the SCS group, and no significant change in the control group
Slangen [22]	2014	Multicenter randomized controlled trial	36	6 months	Yes	No	Pain intensity using a Visual Analogue Scale	Treatment success was observed in 59% of the SCS and in 7% of the best medical treatment group (p < 0.01). Pain and sleep were “very much improved” in 36% in the SCS group with no change in the best medical treatment group (p < 0.01 and p < 0.05)
De Vos [23]	2014	Prospective cohort study Subgroup Analysis	12	2 weeks	No	No	Pain intensity using a Visual Analogue Scale	Burst stimulation resulted in a pain reduction of 44% in patients with PDN (p < 0.001). Average initial pain score was 70 prior to implantation, reduced to 28 with tonic stimulation, and reduced to 16 with 2 weeks of burst stimulation; 67% of patients had pain reduction with burst stimulation compared to tonic stimulation
Slangen et al. [24]*	2013	Prospective cohort study	15	36 months	No	No	Pain intensity evaluated using an NRS-based pain diary	73, 55, and 64% of patients demonstrated > 50% pain relief at 12, 24, and 36 months, respectively. PGIC for pain revealed improvement in pain in 73, 27, and 36% of patients at 12, 24, and 36 months, respectively. An improvement in QoL was seen in 64% of patients at 12 months, 55% at 24 months, and 64% at 36 months
Pluijms et al. [25]	2012	Prospective cohort study	15	12 months	No	No	Pain intensity evaluated using an NRS-based pain diary	A clinically relevant (> 50%) reduction in pain was achieved in 8 patients at 2 weeks and 7 patients at 12 months. Improvements in EuroQoL utility score and quality of sleep were also demonstrated at 2 weeks and 12 months
de Vos [26]	2009	Prospective cohort study	11	30 months	No	No	Pain intensity using a Visual Analogue Scale	Average VAS was 77 at baseline and 34 at 6 months after implantation of SCS. Average VAS decreased to 23 at 12 months after implantation, and remained 23 at 30 months. Of the 9 patients implanted with an SCS, 5 experienced > 50% relief of neuropathic pain at 1 month. At 3 and 6 months, > 50% pain relief was experienced by 6 patients
Daousi [27]	2005	Prospective cohort study	8	3–7 years	No	No	Pain intensity using a Visual Analogue Scale	There were 6 patients remaining in the cohort at 3 years, and all demonstrated > 50% improvement in pain relief while using the spinal cord stimulator. At 7-year follow-up, all of the four remaining patients reported sustained benefit Improvement of McGill Pain Questionnaire scores were noted at 3- and 7-year follow-up, with results being statistically significant at 3 years (total score of 53 with stimulator off vs. 9.5 with stimulator on, p < 0.03)
Tesfaye [28]	1996	Prospective cohort study	10	14 months	No	No	Pain intensity using a Visual Analogue Scale	Eight of ten patients had a clinically significant reduction in VAS (p < 0.02). Seven of 10 patients had continued clinically significant reduction in pain at 3, 6 and 14 months (p = 0.016, 0.03, 0.06, respectively)
Kumar et al. [29]	1996	Prospective cohort study Subgroup Analysis	4	12 months	No	No	Pain intensity using a Visual Analogue Scale	4 patients demonstrated improvement in pain relief over the first 6 months, while 3 of the 4 patients reported continued pain relief after a year

*This is a 36-month follow-up of the Plujims et al. 2012 study

**This is presenting a re-analysis of data obtained from the DeVos 2014 study, in order to compare the quality-adjusted life years