Neurophysiological and clinical effects of TSDCS in patient with chronic pain

Background and aims Chronic pain (CP) is complex clinical condition, often devastating for patients and unmanageable with pharmacological treatments. Several findings indicate that transcutaneous spinal direct current stimulation (tsDCS) might represent a complementary therapy in managing CP. In this randomized, double-blind, sham-controlled crossover study, we assess tsDCS effects in CP patients. Methods Sixteen patients (aged 65.06 ± 16.16 years, 8 women) with CP of different aetiology underwent sham and anodal tsDCS (anode over the tenth thoracic vertebra, cathode over the somatosensory cortical area - 2.5 mA, 20 min, five days for one week). As outcomes, we considered the Visual Analogue Scale (VAS), the Neuropathic Pain Symptom Inventory (NPSI), and the components of the lower limb flexion reflex (LLFR), i.e., RIII threshold, RII latency and area, RIII latency and area, FR total area. Assessments were conducted before (T0) and at the end of the treatment (T1), and after one week (T2) and one month (T3). Results Compared to sham, anodal tsDCS reduced RIII area at T2 by more than 50% (p = 0.0043) and T3 by about 50% (p = 0.0012); similarly, FR total area was reduced at T3 by about 50% (p = 0.03). Clinically, anodal tsDCS dampened VAS score at T3 by about 50% (p = 0.015), and NPSI score at T1 (p = 0.0012) and T3 (p = 0.0015) by about 30%, compared to sham. Changes in VAS and NPSI scores linearly correlated with the reduction in LLFR areas (p = 0.0004). Conclusions Our findings suggest that anodal tsDCS could modulate central nociceptive signal transmission and pain perception in CP conditions.