[Placement of electrodes in transcutaneous stimulation for chronic pain]

Forty-six patients with chronic pain were treated with transcutaneous nerve stimulation (TNS). If there were any signs of sensory loss in the pain area, the electrodes were placed on the healthy side of the body. The effect of TNS was assessed quantitatively. After 9 months of repeated TNS, on average, the total pain score had improved by 39%. The subjective intensity of the pain, the frequency of pain and the need for analgesics had diminished by 46-47%. In those conditions in which total improvement was better than the mean (phantom limb pain, 65%; zoster neuralgia, 56%; thalamic pain, 45%), the healthy side of the body had been stimulated. In those in which the painful area had been stimulated (cancer pain, 32%; low back pain, 32%; brachialgia, 15%), the beneficial effect did not reach the mean for the whole series. This suggests that TNS of the healthy side of the body may give better long-term improvement than stimulation of the painful area. A theory of chronic pain and the mechanism of TNS is presented.