Effect of Unmodulated 5-kHz Alternating Currents Versus Transcutaneous Electrical Nerve Stimulation on Mechanical and Thermal Pain, Tactile Threshold, and Peripheral Nerve Conduction: A Double-Blind, Placebo-Controlled Crossover Trial

Abstract

ObjectiveTo investigate the effect of unmodulated 5-kHz alternating current on mechanical pain threshold (MPT), heat pain threshold (HPT), tactile threshold (TT), and peripheral nerve conduction (PNC) compared with transcutaneous electrical nerve stimulation (TENS) and sham stimulation. SettingNational referral center. DesignRandomized, double-blind, placebo-controlled crossover trial. ParticipantsHealthy volunteers (N=38). No dropouts or adverse events were reported. InterventionTENS, unmodulated 5-kHz currents, and sham stimulation were applied on the radial nerve for 20 minutes with a 24-hour washout period between them and concealed intervention allocation. Main Outcome MeasuresFour measures were taken: before, during, and 2 after the interventions. Algometry was used to assess MPT, a Peltier thermode for HPT using the method of limits, Von Frey filaments for TT, and radial nerve compound action potential. ResultsNo differences were observed on MPT, HPT, and PNC when 5-kHz current and TENS were compared. However, TT increased 56.2mN (95% confidence interval [CI], 28.8–83.6) in the TENS group compared with the 5-kHz current group during intervention. Compared with sham stimulation during intervention, MPT increased 4.7N (95% CI, 0.3–9.2) using 5-kHz current and 10.4N (95% CI, 3.5–17.3) with TENS. TT increased 17.2mN (95% CI, 4.7–29.7) with 5-kHz current and 73.4mN (95% CI, 47.5–99.2) with TENS. However, HPT increased 1.0°C (95% CI, 0.2–2.0) only with TENS. For the PNC, no differences were found among the 3 groups. ConclusionsUnmodulated 5-kHz current produced an increase in somatosensory thresholds that was greater than placebo but not when compared with TENS; however, participants perceived 5-kHz currents to be more comfortable and showed more habituation to them.