Analgesic effects of vibration and transcutaneous electrical nerve stimulation applied separately and simultaneously to patients with chronic pain.

The analgesic effects of transcutaneous electrical nerve stimulation (TENS) and vibratory stimulation (VS), used both separately and simultaneously, were compared in 24 patients suffering from chronic pain. We tested the hypothesis that these combined procedures might improve the pain reducing effects obtained with a single type of stimulation, since they make it possible to recruit a larger number of large diameter afferents and/or to increase the discharge frequencies. Four 35-minute treatment sessions (VS, TENS, VS + TENS, Sham stimulation) were run with each patient. The vibrations (100 Hz) and TENS (100 Hz) were applied to the surface of the painful region. The sham stimulation treatment consisted of positioning the TENS electrodes without actually delivering any current. The short form of the McGill pain questionnaire was used to assess the subjects' pain levels. The assessments took place immediately after any treatment (0h.), and again 4 hours and 24 hours later. The results showed that dual stimulation not only alleviated pain in more cases than either VS or TENS alone, but also had stronger and more long-lasting analgesic effects. On the other hand, all three types of stimulation used produced stronger analgesic effects than those obtained with the sham stimulation.