P 127. Evaluation of outcomes from Transcranial Direct Current Stimulation (tDCS) for the treatment of chronic pain

Abstract

Transcranial direct current stimulation (tDCS) has been proposed as an alternative non-invasive technique with potential to alleviate pain in patients with various pain syndromes. To evaluate the clinical outcomes of five-day tDCS treatment in patients with chronic pain of various etiologies. This is a retrospective review of medical records of 100 patients who had chronic pain of different etiologies and were treated with tDCS between November 2008 and September 2010. The patients were divided in the following categories based on the etiology of their pain: neuropathic, central, nociceptive/somatic, nociceptive/visceral and headaches. Patients provided self-ratings of pain using the 11-point Numerical Rating Scale (NRS) before and after each tDCS treatment, and ratings of pain characteristics before and after the five-day treatment course. The chart review was approved by the Institutional Review Board (IRB) at BIMC. Transcranial direct current stimulation was delivered using a Phoresor II 850 PM unit in five 20-min sessions on 5 consecutive days, at 2 mA, applying either anodal (a-tDCS) over the motor cortex or cathodal (c-tDCS) stimulation over the somatosensory cortex, using two saline-soaked sponge electrodes of size 25 cm 2 . One hundred patients received 172 five-day treatment courses. The patient distribution per category was the following: 59 neuropathic, 28 nociceptive/somatic, 6 headache, 6 central pain and 1 nociceptive/visceral pain. Eighty patients received a-tDCS only, 14 patients had c-tDCS only, 6 patients received both. Of those receiving a-tDCS, 57 got 1 treatment cycle and 23 got between 2 and 5 cycles; 2 of 20 c-tDCS patients received multiple cycles (2 and 7 respectively). Pain intensity (mean, SD) before and after a-tDCS was 6.2 ± 2.4 and 3.9 ± 2.9 ( n = 86); before c-tDCS 6.8 ± 2.2, after 4.2 ± 3.7 ( n = 20). Pain reduction ⩾ 30% was observed in: (i) Forty-four patients (76%) in the neuropathic pain group [with the highest number of responders among patients with facial pain, post-herpetic neuralgia and complex regional pain syndrome]; (ii) 20 patients (77%) in the nociceptive/somatic category ( n = 26); 83% in the headache group ( n = 6); 20% in the central-pain group ( n = 5). Secondary benefits besides pain relief were: decreased intake of pain medication, mood and sleep improvement, improved mobility and function, itch relief. Durability of analgesic effects was up to 12 weeks and showed high inter-individual variability. Neither a-tDCS nor c-tDCS resulted in any serious adverse events (AEs). The most frequently reported non-serious AEs were: (i) transient tingling/burning/itching under the electrode during the stimulation (reported in 27 (4.2%) of a-tDCS visits and 14 (7.9%) of c-tDCS visit); (ii) transient headache after the stimulation:16 (2.5%) of a-tDCS, 2 (1.1%) of c-tDCS; iii) Fatigue: reported in 7 (1.1%) of a-tDCS, 0 of c-tDCS. The findings support the evidence of analgesic efficacy of tDCS in a diversity of chronic pain types.