Table 1.

Results from our review of the literature for studies that investigated the efficacy of tDCS for SCI-related NP

Study	Design	Baseline characteristics	Intervention	Outcomes
Fregni et al. Pain 2006 [15]	Randomized double-blind placebo-controlled phase II parallel-group trial.	Patients: 17 Age: 35.7 ± 13.3 M/F: 14/3	Active tDCS with 2 mA of current for 20 minutes for 5 consecutive days	Significant (≥ 50%) pain reduction was observed in 63% of patients. Significant cumulative analgesic effect with the peak of pain reduction reached after the last stimulation session. Decreased pain compared to baseline among active tDCS patients for two weeks after the last stimulation session. Strong negative correlation between duration of pain and pain relief.
	Country: Brazil
Soler et al. Brain 2010 [16]	Randomized double-blind sham-controlled study.	Patients: 39 Age: 45.0 ± 15.5 M/F: 30/9	tDCS of the motor cortex combined with a walking visual illusion task or with control illusion and sham stimulation with visual illusion or with control illusion	Combined tDCS and visual illusion reduced the intensity of sustained NP significantly more than tDCS or visual illusion alone at 3 months.
	Country: Spain
Wrigley et al. Pain 2013 [17]	Prospective randomized crossover study.	Patients: 10 Age: 56.1 ± 14.9 M/F: 8/2	2 mA active tDCS or sham tDCS for 20 minutes for 5 consecutive days	tDCS positioned over M1 was not found to be significantly related with relief of pain at any time point.
	Country: Australia
Yoon et al. Neurorehabilitation and Neural Repair 2014 [19]	Prospective non-randomized sham-controlled study.	Patients: 16 Age: 44.1 ± 8.6 M/F: 12/4	2 mA active tDCS or sham tDCS for 20 minutes twice daily for 10 days	Significant reduction in pain scores. Increased metabolism in the subgenual anterior cingulate cortex, insula, medulla (emotional and cognitive part), and decreased metabolism in the left dorsolateral prefrontal cortex after active tDCS treatment.
	Country: Korea
Ngernyam et al. Clinical Neurophysiology 2015 [18]	Randomized double-blind placebo-controlled (sham tDCS) cross-over 1:1 trial.	Patients: 20 Age: 44.5 ± 9.16 M/F: 15/5	2 mA active tDCS or sham tDCS for 20 minutes for 1 treatment session only	Significant difference in pain intensity between active tDCS and sham tDCS was found immediately post-treatment and at 24 hours after treatment, but no difference was found between treatments at or after 48 hours.
	Country: Thailand
Thibaut et al.Neuroscience Letters 2017 [20]	Two-phase randomized double-blind sham-controlled study.	1. Phase I Patients: 33 Age: 51.2 ± 12.5 M/F: 24/9 2. Phase II Patients: 9 Age: 49.0 ± 14.38 M/F: 7/2	2 mA active tDCS or sham tDCS for 20 minutes for 5 consecutive days (Phase I) and 10 consecutive days (Phase II)	5 sessions of tDCS can reduce the level of pain in patients with SCI. The overall level of pain was significantly lower for tDCS group compared to sham in Phase II. Effects were not noticed directly after the end of the stimulation sessions but at 1-week follow-up.
	Country: USA