Transcutaneous electrical nerve stimulation reduces pain, fatigue and hyperalgesia while restoring central inhibition in primary fibromyalgia

Abstract

Because transcutaneous electrical nerve stimulation (TENS) works by reducing central excitability and activating central inhibition pathways, we tested the hypothesis that TENS would reduce pain and fatigue and improve function and hyperalgesia in people with fibromyalgia who have enhanced central excitability and reduced inhibition. The current study used a double-blinded randomized, placebo-controlled cross-over design to test the effects of a single treatment of TENS with people with fibromyalgia. Three treatments were assessed in random order: active TENS, placebo TENS and no TENS. The following measures were assessed before and after each TENS treatment: pain and fatigue at rest and in movement; pressure pain thresholds, 6-m walk test, range of motion; 5-time sit-to-stand test, and single-leg stance. Conditioned pain modulation was completed at the end of testing. There was a significant decrease in pain and fatigue with movement for active TENS compared to placebo and no TENS. Pressure pain thresholds increased at the site of TENS (spine) and outside the site of TENS (leg) when compared to placebo TENS or no TENS. During active TENS, conditioned pain modulation was significantly stronger compared to placebo TENS and no TENS. No changes in functional tasks were observed with TENS. Thus, the current study suggests TENS has short-term efficacy in relieving symptoms of fibromyalgia while the stimulator is active. Future clinical trials should examine the effects of repeated daily delivery of TENS, similar to the way in which TENS is used clinically on pain, fatigue, function, and quality of life in individuals with fibromyalgia.

Keywords: Analgesia; Chronic widespread pain; Electrical stimulation; Fatigue; Fibromyalgia; Hyperalgesia; Pain; Transcutaneous electrical nerve stimulation (TENS).

Figure 1

Consort diagram for the study

Figure 2

Session order with randomization of TENS treatment

Figure 3

Picture of electrode used in the study (Stimcare Premium Electrode, Empi Inc, St. Paul, MN)

Figure 4

Graphs represent the percent improvement in pain (A) and fatigue (B) at rest and during movement (6MWT) during active TENS, placebo TENS, or no TENS. Significant differences were seen between active TENS and placebo TENS and no TENS for pain with movement and fatigue with movement. * p<0.05, significantly different from active and no TENS.

Figure 5

A. Graphs represent percent improvement in pressure pain thresholds (PPTs) in the lumbar region, cervical region, and leg after active TENS, placebo TENS, or no TENS. Significant increases in PPTs were observed in all areas for active TENS (*p<0.05). B. Changes in PPTs during conditioned pain modulation (CPM) during active TENS, placebo TENS or no TENS when compared to the TENS condition alone. A significantly greater change in PPTs occurred in the treatment group that received active TENS when compared to placebo TENS or no TENS treatment group (* p<0.05).