Boggio 2009

Methods	Cross‐over RCT; 3 conditions
Participants	Country of study: Brazil Setting: laboratory Condition: neuropathic pain (mixed central, peripheral and facial) Prior management details: refractory to drug management n = 8 Age: 40‐82 years; mean 63.3 (SD 5.6) Duration of symptoms: 1‐20 years; mean 8.3 (SD 5.6) Gender distribution: 2 M, 6 F
Interventions	Stimulation type: tDCS Stimulation parameters: intensity 2 mA, 35 cm2 electrodes, duration 30 min Condition 1: active tDCS/active TENS Condition 2: active tDCS/sham TENS Condition 3: sham tDCS/sham TENS Stimulation location: M1 contralateral to painful side Number of treatments: 1 for each condition Control type: sham tDCS (switched off after 30 s stimulation)
Outcomes	Primary: VAS 0‐10 anchors "no pain" to "worst possible pain" When taken: pre and post each stimulation Secondary: none
Notes	Sources of support: not declared COI: not declared
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "All the patients received the 3 treatments.... in a randomised order (we used a computer generated randomisation list with the order of entrance)."
Adequate blinding of participants?	Unclear risk	Comment: there is evidence that participant blinding of tDCS may be inadequate at 2 mA intensity (see Assessment of risk of bias in included studies)
Adequate blinding of assessors?	Unclear risk	Quote: "All evaluations were carried out by a blinded rater" Comment: there is evidence that assessor blinding of tDCS may be inadequate at 2 mA intensity (see Assessment of risk of bias in included studies)
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Comment: 2 participants lost to follow‐up. It is unclear how these data were accounted for as there were no missing data apparent in the results tables. However, this may have an impact given the small sample size
Selective reporting (reporting bias)	Low risk	Comment: primary outcome data presented clearly and in full
Free from carry‐over effects?	Low risk	Comment: a 48‐h washout period was observed between stimulation conditions and possible carry‐over effects were checked and ruled out in the analysis Quote: "To analyze whether there was a carryover effect, we initially performed and showed that the baselines for the 3 conditions were not significantly different (P = 0.51). We also included the variable order in our model and this model also showed that order is not a significant term (P = 0.7)."
Study Size	High risk	Comment: < 50 participants per treatment arm
Study duration	High risk	Comment: < 2 weeks' follow‐up
Other bias	Low risk	Comment: no significant other bias detected