The analgesic effect of transcutaneous electrical nerve stimulation (TNS) in patients with rheumatoid arthritis. A comparative study of different pulse patterns.

Transcutaneous electrical nerve stimulation (TNS) was used on 20 patients with severe wrist pain due to rheumatoid arthritis. Three different stimulation frequencies were used: high 70 Hz stimulation (70 TNS), low frequency 3 Hz stimulation (3 TNS) and brief trains of stimuli with an internal frequency of 70 Hz and with a repetition rate of 3 Hz (3-70 TNS). The analgesic effect was evaluated on the patient's own estimate of pain relief and by means of a loading test in which the length of time the patient could hold a weight before and after TNS was used. The loading test and the patients' own estimate of pain relief corresponded well. After 70 TNS, 18 patients could double their loading time. The corresponding figure for 3-70 TNS was 16 patients and for 3 TNS 5 patients. The average duration of pain relief after cessation of stimulation was 18 h for 70 TNS and 15 h for 3-70 TNS, while those who responded to 3 TNS experienced pain relief for only 4 h on average.