Combined transcranial direct current stimulation and breathing-controlled electrical stimulation for management of neuropathic pain after spinal cord injury.

OBJECTIVE: To determine whether transcranial direct current stimulation augments the analgesic effect of breathing-controlled electrical stimulation in patients with spinal cord injury who have chronic neuropathic pain.

DESIGN: Sham-controlled, single-blinded, single-centre, cross-over study of 12 participants with incomplete spinal cord injury. The treatment protocol included a 20-min transcranial direct current stimulation (sham or active), followed by a 20-min breathing-controlled electrical stimulation to the median nerve on the dominant side. The treatment session with sham or control transcranial direct current stimulation was given on different days in a randomized order. Visual analogue scale was used to assess neuropathic pain at baseline, 10 min after transcranial direct current stimulation, and 10 min after breathing-controlled electrical stimulation.

RESULTS: Participants were blinded to the status of transcranial direct current stimulation. Out of the 12 participants, 10 completed sessions of both sham and active transcranial direct current stimulation, while the other 2 completed only active transcranial direct current stimulation and breathing-controlled electrical stimulation treatment. Out of the 12 participants, 7 showed analgesic effects after active transcranial direct current stimulation, while sham transcranial direct current stimulation produced some analgesic effects in 4 out of 10 participants. At the group level, there was no difference between active and sham transcranial direct current stimulation treatment. All except one participant responded positively to breathing-controlled electrical stimulation in all sessions. Visual analogue scale score for pain decreased significantly after breathing-controlled electrical stimulation combined with either active transcranial direct current stimulation or sham transcranial direct current stimulation treatment.

CONCLUSION: The immediate analgesic effect of breathing-controlled electrical stimulation was confirmed. However, this effect was not augmented after one session of transcranial direct current stimulation treatment.