Effects of Transcutaneous Electrical Nerve Stimulation (TENS) Electrode Placement on Spontaneous and Noxiously Evoked Dorsal Horn Cell Activity in the Cat.

The objectives of this study were to examine the effects of ipsilateral vs. contralateral as well as simultaneous placement of transcutaneous electrical nerve stimulation (TENS) electrodes in somatic receptive fields on spontaneous and noxiously evoked dorsal horn cell activity in anesthetized cats. Recordings were made from cells in the left gray matter of lumbosacral segments. In this study ipsilateral means left and contralateral means right. Results showed that mean cell activity decreased significantly (p < 0.001) when electrodes were placed in somatic receptive fields of either the contralateral (right) or ipsilateral (left) lower extremity. When comparing contralateral vs. ipsilateral effects, the most significant reduction (p < 0.004) in mean cell activity occurred with ipsilateral (left) placement of the electrodes. For bilateral application (simultaneous ipsilateral and contralateral) of TENS electrodes, 66% of the cells demonstrated a significant additive effect in reducing spontaneous and noxiously evoked cell activity. Clinically, the results might suggest that analgesia can result from bilateral placement of electrodes or by placement of electrodes in the contralateral dermatome (somatic field) when certain clinical conditions may prevent the placement of electrodes on the same side (ipsilateral) as the perceived pain.