Efficacy of transcutaneous electrical nerve stimulation (TENS) for chronic low-back pain in a multiple sclerosis population - A randomized, placebo-controlled clinical trial

Objective: This study was designed to investigate the hypoalgesic effects of self-applied transcutaneous electrical nerve stimulation (TENS) on chronic low-back pain (LBP) in a multiple sclerosis (MS) population. Methods: Ninety participants with probable or definite MS (aged 21 to 78 y) presenting with chronic LBP were recruited and randomized into 3 groups (n = 30 per group): (1) low-frequency TENS group (4 Hz, 200 mu s); (2) high-frequency TENS group (110 Hz, 200 mu s); and (3) placebo TENS. Participants self-applied TENS for 45 minutes, a minimum of twice daily, for 6 weeks. Outcome measures were recorded at weeks 1, 6, 10, and 32. Primary outcome measures included: Visual Analog Scale for average LBP and the McGill Pain Questionnaire. Secondary outcome measures included: Visual Analog Scale for worst and weekly LBP, back and leg spasm; Roland Morris Disability Questionnaire; Barthel Index; Rivermead Mobility Index; Multiple Sclerosis Quality of Life-54 Instrument, and a daily logbook. Data were analyzed blind using parametric and nonparametric tests, as appropriate. Results: Results indicated a statistically significant interactive effect between groups for average LBP (P = 0.008); 1-way analysis of covariance did not show any significant effects at any time point once a Bonferonni correction was applied (P > 0.05). However, clinically important differences were observed in some of the outcome measures in both active treatment groups during the treatment and follow-up periods. Discussion: Although not statistically significant, the observed effects may have implications for the clinical prescription and the use of TENS within this population.