Longstanding neuropathic pain after spinal cord injury is refractory to transcranial direct current stimulation: A randomized controlled trial

Abstract

Neuropathic pain remains one of the most difficult consequences of spinal cord injury (SCI) to manage. It is a major cause of suffering and adds to the physical, emotional, and societal impact of the injury. Despite the use of the best available treatments, two thirds of people experiencing neuropathic pain after SCI do not achieve satisfactory pain relief. This study was undertaken in response to a recent clinical trial reporting short-term, clinically significant reductions in neuropathic SCI pain with primary motor cortex transcranial direct current stimulation (tDCS). In this investigation, we aimed to build on this previous clinical trial by extending the assessment period to determine the short-, medium-, and long-term efficacy of tDCS for the treatment of neuropathic pain after SCI. We found that, contrary to previous reports, after 5 tDCS treatment periods, mean pain intensity and unpleasantness rating were not significantly different from initial assessment. That is, in this trial tDCS did not provide any pain relief in subjects with neuropathic SCI pain (n=10). A similar lack of effect was also seen after sham treatment. Because the injury duration in this study was significantly greater than that of previous investigations, it is possible that tDCS is an effective analgesic only in individuals with relatively recent injuries and pain. Future investigations comparing a range of injury durations are required if we are to determine whether this is indeed the case.

Delayed pain decrease following M1 tDCS in spinal cord injury: A randomized controlled clinical trial

“…Contrasting with these findings, other tDCS trials indicate there were no significant differences in pain reduction following active and sham stimulation [25]. In addition, nothing is known about the effects of tDCS on quality of life in people with sublesional neuropathic pain due to SCI.…”

“…One of them investigated the effect of 5 sessions of tDCS on pain level in a small sample of patients with SCI (n = 10); no difference between active and sham tDCS was observed [25]. The authors explained that lack of effects is likely due to refractoriness of pain and duration of disease since most of the patients enrolled had injury durations of 10 or more years.…”

“…The authors explained that lack of effects is likely due to refractoriness of pain and duration of disease since most of the patients enrolled had injury durations of 10 or more years. In addition, the limited number of [19][20][21][22][23][24][25][26] sessions and small sample size, may not have been sufficient to observe significant effects at follow-up. The second study, on low back pain, even though the sample size was large (n = 135), did not show significant differences between sham and active tDCS [58].…”

The CanPain SCI Clinical Practice Guidelines for Rehabilitation Management of Neuropathic Pain after Spinal Cord: Recommendations for treatment

“…33 A fourth study did not find a significant difference between tDCS and sham control. 34 A prospective-controlled trial that found a significant reduction in pain intensity, compared with sham control, was upgraded because of small confidence intervals and the inclusion of an intention-to-treat analysis. 35 A meta-analysis of the five studies found a positive effect for transcranial direct current stimulation on pain intensity.…”

Effectiveness of transcranial direct current stimulation for the management of neuropathic pain after spinal cord injury: a meta-analysis

“…These included two double-blinded randomized controlled trials (RCTs), 12,19 two doubleblinded crossover RCTs, 20,21 and one prospective controlled trial. 22 The methodological quality was excellent for the four RCTs, 12,[19][20][21] whereas the prospective controlled trial 22 was fair in quality (Table 1). …”