Transcutaneous electrical nerve stimulation (TENS) for chronic neck pain

Background: Chronic neck pain is a highly prevalent condition, affecting 10% to 24% of the general population. Transcutaneous electrical nerve stimulation (TENS) is the noninvasive, transcutaneous use of electrical stimulation to produce analgesia. It is a simple, low-cost and safe intervention used in clinical practice as an adjunct treatment for painful musculoskeletal conditions that have a considerable impact on daily activities, such as chronic neck pain. This review is a split from a Cochrane Review on electrotherapy for neck pain, published in 2013, and focuses specifically on TENS for chronic neck pain.

Objectives: To evaluate the effectiveness of transcutaneous electrical nerve stimulation (TENS) (alone or in association with other interventions) compared with sham and other clinical interventions for the treatment of chronic neck pain.

Search methods: We searched Cochrane Back and Neck Trials Register, CENTRAL, MEDLINE, Embase, five other databases and two trials registers to 9 November 2018. We also screened the reference lists of relevant studies to identify additional trials. There were no language, source, or publication date restrictions.

Selection criteria: We included randomised controlled trials (RCTs) involving adults (≥ 18 years of age) with chronic neck pain (lasting > 12 weeks) that compared TENS alone or in combination with other treatments versus active or inactive treatments. The primary outcomes were pain, disability and adverse events.

Data collection and analysis: Two independent review authors selected the trials, extracted data and assessed the risk of bias of included studies. A third review author was consulted in case of disagreements. We used the Cochrane 'Risk of bias' tool (adapted by Cochrane Back and Neck), to assess the risk of bias of individual trials and GRADE to assess the certainty of evidence. We used risk ratios (RRs) to measure treatment effects for dichotomous outcomes, and mean differences (MDs) for continuous outcomes, with their respective 95% confidence intervals (CIs).

Main results: We included seven RCTs with a total of 651 participants, mean age 31.7 to 55.5 years, conducted in three different countries (Turkey, Jordan and China). The length of follow-up ranged from one week to six months. Most RCTs used continuous TENS, with a frequency of 60 Hz to 100 Hz, pulse width of 40 μs to 250 μs and tolerable intensity, described as a tingling sensation without contraction, in daily sessions lasting 20 to 60 minutes. Due to heterogeneity in interventions and outcomes, we did not pool individual study data into meta-analyses. Overall, we judged most studies as being at low risk for selection bias and high risk for performance and detection bias. Based on the GRADE approach, there was very low-certainty evidence from two trials about the effects of conventional TENS when compared to sham TENS at short-term (up to 3 months after treatment) follow-up, on pain (assessed by the Visual Analogue Scale (VAS)) (MD -0.10, 95% CI -0.97 to 0.77) and the percentage of participants presenting improvement of pain (RR 1.57, 95% CI 0.84 to 2.92). None of the included studies reported on disability or adverse events.

Authors' conclusions: This review found very low-certainty evidence of a difference between TENS compared to sham TENS on reducing neck pain; therefore, we are unsure about the effect estimate. At present, there is insufficient evidence regarding the use of TENS in patients with chronic neck pain. Additional well-designed, -conducted and -reported RCTs are needed to reach robust conclusions.