Transcranial Electrical Stimulation (TCES) treatment involves applying electrodes to an individual’s scalp to allow electrical current to be applied and presumably stimulate the underlying cerebrum (Tan et al. 2006).
Despite the fact that TCES is a relatively new treatment for post-SCI pain, 4 RCTs (Capel et al. 2003; Fregni et al. 2006; Soler et al. 2010; Tan et al. 2006) have been published; all of the studies suggest that it may be useful in reducing SCI-related chronic pain. Each of these investigations employed a sham stimulation control condition, using modified equipment. Although patients in all 3 studies reported some pain relief following treatment, there was no comment on how long the treatments should continue or how often they should be used.
Soler et al. (2010) divided participants into four groups: the tDCS group, visual illusion group, combined tDCS and visual illusion group and the control group. The tDCS group received direct current simulation over C3 or C4 at a constant 2mA intensity for 20 minutes along with a control visual illusion which involved watching a video of faces or landscapes. The actual visual illusion group was provided with a sham tDCS treatment, after 5 minutes they were shown a video of someone walking in front of a vertical mirror so patients perceive themselves walking for 15 minutes. The combined tDCS and visual illusion group received active treatment for both, while the last group, the control group, received inactive treatment for both tDCS and visual illusion group. Each participant received a total of 10 sessions of therapy, 20 minutes each for 2 weeks. The study found significant improvement in NRS pain perception, pain reduction, ability to work, perform daily tasks, enjoyment, and interference of pain in sleep (p<0.05) in the combined tDCS and visual illusion group compared to the other groups. The study showed clinical significance where 30% improvement in pain intensity was seen in 30% of participants in the combined group.
Tan et al. (2006) conducted a double-blind RCT with 38 SCI participants with either chronic musculoskeletal or neuropathic pain receiving either active transcranial electrical stimulation (TCES) or inactive TCES (sham control) over 21 days. The electrical stimulation was set at a subthreshold level ensuring that patients were blind to their treatment group. The study found that SCI patients receiving transcranial electrotherapy stimulation (n=18) experienced a significant reduction in post-SCI neuropathic and musculoskeletal average daily rating of pain intensity (p=0.03); however, there was no significant reduction in pain as noted on the Brief Pain Inventory (BPI).
Capel et al. (2003) reported that TCES resulted in lower pain scores on the McGill Pain Questionnaire for those in the treatment group (n=15), while those in the control group (n=15) reported no change. No statistical differences were noted across different pain types, although the authors did comment that subjects had greater relief of visceral pain following each active 4-day treatment phase of the study. TCES was associated with a reduction in the use of analgesics and antidepressants.
Fregni et al. (2006) found similar results after examining the effects of transcranial direct current stimulation (tDCS) on central neuropathic pain. The treatment group (n=11), those receiving active tDCS for 5 consecutive days, experienced a significant reduction in pain relief over time (p<0.0001) compared to those receiving sham treatments (n=6).
One prospective controlled study (Yoon et al. 2014) found that 10 days of active transcranial direct current stimulation significantly improved pain intensity compared to sham treatment. One cohort study (Kumru et al. 2012) found that combined transcranial direct current stimulation and visual imagery may improve pain intensity among individuals with neuropathic pain post SCI.
There is strong evidence (level 1a – from four randomized controlled trials; Capel et al. 2003; Fregni et al. 2006; Soler et al. 2010; Tan et al. 2006) for the benefits of transcranial electrical stimulation in reducing neuropathic and neuropathic and musculoskeletal post-SCI pain.
Transcranial electrical stimulation is effective in reducing post SCI neuropathic pain.