Cerebellar Transcranial Direct Current Stimulation (ctDCS) Ameliorates Phantom Limb Pain and Non-painful Phantom Limb Sensations

Phantom limb pain (PLP) is a disabling and intractable sensation arising in about 80% of patients after amputation. The aim of this study was to evaluate the possibility to modulate nociceptive processing and pain perception with cerebellar transcranial direct current stimulation (ctDCS) in patients suffering from painful and non-painful phantom limb sensations. Fourteen upper limb amputees underwent ctDCS (anodal or sham, 2.0 mA, 20 min per day, 5 days a week). Clinical scores and electrophysiological parameters were assessed before tDCS, at the end of the 5-day treatment, 2 and 4 weeks later. Laser-evoked potentials (LEPs) were obtained from the stump using a Nd:YAP laser by pulses with short duration (5 ms) and small diameter spots (5 mm). Changes in visual analogue scores (VAS) were evaluated (chronic pain, paroxysmal pain, stump pain, phantom movements, phantom sensations). Anodal polarization significantly dampened LEP amplitudes (N1, p = 0.021 and N2/P2, p = 0.0034), whereas sham intervention left them unchanged. Anodal ctDCS significantly reduced paroxysmal pain (p < 0.0001), non-painful phantom limb sensations (p < 0.0001) and phantom limb movements (p = 0.0003), whereas phantom limb and stump pain did not change compared to the sham condition. Anodal ctDCS significantly improves both paroxysmal pain and non-painful phantom limb sensations, which are likely induced by maladaptive changes in the sensorimotor network and posterior parietal cortex respectively.