SINE-WAVE AURICULAR TENS PRODUCES FREQUENCY-DEPENDENT HYPESTHESIA IN THE TRIGEMINAL NERVE

Objective: To evaluate the effects of different frequencies of auricular (ear-to-ear) sine-wave transcutaneous electrical nerve stimulation (TENS), administered at subliminal intensity, on trigeminal nerve sensitivity. Design: In a double-blind protocol, healthy volunteer subjects were administered one of three different frequencies of active TENS (5, 100, or 2,000 Hz) or placebo TENS (no current was passed) for 30 min. Setting: Department of Psychology, City University of New York. Subjects: 72 healthy undergraduate volunteers with no preexisting pain problems (16 men and 56 women), from the Department of Psychology, City University of New York. Outcome measure: Pretreatment to posttreatment changes were measured in sensation threshold for a 250-Hz electrical stimulus applied transcutaneously to an area 1 cm anterior to the tragus of the ear (mandibular division of the trigeminal nerve). Conclusions: Analysis of variance indicated no group differences in baseline trigeminal sensation threshold, but there were significant group differences in pretreatment to posttreatment changes in sensation threshold (p < 0.001). A postiori analysis showed significant increases in trigeminal sensation threshold after active TENS as compared to placebo TENS (p < 0.05), with 5- and 100-Hz TENS producing significantly greater hypesthesia than 2,000-Hz TENS (p < 0.05). Conclusions: Sine-wave auricular TENS produces frequency-dependent trigeminal hypesthesia that is not a placebo effect.