Transcutaneous electrical nerve stimulation and transcutaneous spinal electroanalgesia: A preliminary efficacy and mechanisms-based investigation

Abstract 

Objectives

To determine the effects of transcutaneous electrical nerve stimulation (TENS) and transcutaneous spinal electroanalgesia (TSE) on mechanical pain threshold (MPT) and vibration threshold (VT).

Design

A prospective, single-blind, randomised, placebo-controlled trial.

Setting

Laboratory based.

Participants

Thirty-four healthy volunteers (12 men and 22 women; mean age±standard deviation 30±8 years). Exclusion criteria were conditions affecting upper limb sensation and contraindications to electrical stimulation.

Interventions

Participants were allocated at random to receive TENS (n=8), TSE (n=8), placebo (n=9) or control (n=9). Electrical stimulation was applied for 30minutes (from time 18minutes to 48minutes) via electrodes (5cm×5cm) placed centrally above and below the space between the C6 and C7 spinous processes, with 5cm between electrodes.

Main outcome measures

MPT (using an algometer) and VT (using a vibrameter) were recorded on seven occasions from the first dorsal interosseous muscle of the right hand – at baseline (0minutes) and then at 10-minute intervals until the end of the 60-minute testing period.

Results

There were no statistically significant group differences in MPT (all p>0.05). Significant group differences in VT were found at 20, 30 and 40minutes (all p<0.05). Post-hoc tests showed that the TENS group had significantly greater VT than both the placebo [median difference 0.30μm, 95% confidence interval (CI) −0.05 to 0.66] and control (0.51μm, 95% CI 0.05 to 0.97) groups at 20minutes, and significantly greater VT than the control group (0.69μm, 95% CI 0.20 to 1.17) at 30minutes (all p<0.008).

Conclusions

Electrical stimulation did not alter MPT. The increase in VT during TENS may be due to distraction or antidromic block of large-diameter nerve fibres. TSE failed to alter either outcome measure significantly.

Keywords: TENS, TSE, Mechanical pain threshold, Vibration threshold, Healthy