Sham Transcutaneous Electrical Nerve Stimulation Research Articles

Assessment: Efficacy of transcutaneous electric nerve stimulation in the treatment of pain in neurologic disorders (an evidence-based review)

To determine if transcutaneous electric nerve stimulation (TENS) is efficacious in the treatment of pain in neurologic disorders. We performed a systematic literature search of Medline and the Cochrane Library from inception to April 2009. There are conflicting reports of TENS compared to sham TENS in the treatment of chronic low back pain, with 2 Class II studies showing benefit, but 2 Class I studies and another Class II study not showing benefit. Because the Class I studies are stronger evidence, TENS is established as ineffective for the treatment of chronic low back pain (2 Class I studies). TENS is probably effective in treating painful diabetic neuropathy (2 Class II studies). Transcutaneous electric nerve stimulation (TENS) is not recommended for the treatment of chronic low back pain (Level A). TENS should be considered in the treatment of painful diabetic neuropathy (Level B). Further research into the mechanism of action of TENS is needed, as well as more rigorous studies for determination of efficacy.

A New Transient Sham TENS Device Allows for Investigator Blinding While Delivering a True Placebo Treatment

This study compared a new transient sham transcutaneous electrical nerve stimulation (TENS) that delivers current for 45 seconds to an inactive sham and active TENS to determine the degree of blinding and influence on pain reduction. Pressure-pain thresholds (PPT), heat-pain thresholds (HPT), and pain intensities to tonic heat and pressure were measured in 69 healthy adults before and after randomization. Allocation investigators and subjects were asked to identify the treatment administered. The transient sham blinded investigators 100% of the time and 40% of subjects compared to the inactive sham that blinded investigators 0% of the time and 21% of subjects. Investigators and subjects were blinded only 7% and 13% of the time, respectively, with active TENS. Neither placebo treatment resulted in significant changes in PPT, HPT, or pain intensities. Subjects using higher active TENS amplitudes (> or =17 mAs) had significantly higher PPTs and lower pain intensities to tonic pressure than subjects using lower amplitudes (<17 mAs). HPTs and pain intensities to tonic heat were not significantly changed. The transient TENS completely blinds investigators to treatment and does not reduce pain, thereby providing a true placebo treatment. This article presents the benefits of a new transient sham TENS device for use in prospective, randomized, clinical trials. This device facilitates blinding of subjects and investigators to eliminate expectation bias and determine the true efficacy of TENS for use in clinical populations.

Effect of Transcutaneous Electrical Nerve Stimulation on Primary Dysmenorrhea

Objectives. Dysmenorrhea is a disturbing problem among women of childbearing age. The purpose of this study is to investigate the effect of high-frequency transcutaneous electrical nerve stimulation (TENS) on primary dysmenorrhea and to compare the placebo effect by sham TENS in a randomized controlled study. Materials and Methods. Twenty-two women participated in the two-month experiment by using TENS or sham TENS in a random order for their dysmenorrhea. Outcome measures included self-reported pain intensity, symptom and function questionnaire related to dysmenorrhea, quality of life, satisfaction after TENS application, and other pain management agents adapted by the participants. Two-way repeated measures analysis of variance (two-way ANOVA) was conducted to compare pain intensity between pre-post values and groups (TENS vs. placebo). One-way repeated measures analysis of variance (one-way ANOVA) was conducted to compare scores from questionnaire of symptoms and quality of life at baseline, and after placebo or TENS stimulation. Results. Pain intensity in TENS is significantly decreased than in the placebo group (p= 0.018). The decrease of pain intensity after TENS and placebo TENS were both significant, with p < 0.00005 and p < 0.00005 respectively. Furthermore, TENS significantly changed the degree of autonomic symptoms (p= 0.048); but not after placebo TENS. Conclusion. This result supports that women in our country who suffer from primary dysmenorrhea could benefit by using TENS, which is consistent with the previous studies. In addition to pain-relieving effects, relief of the autonomic symptoms associated with dysmenorrhea also indicated that the mechanism of TENS might be different from the placebo effect of the sham TENS stimulation. These findings indicate the immediate effects of TENS in women with primary dysmenorrheal.

Transcutaneous electrical nerve stimulation improves oppilative symptoms and increases colonic transit in patients with slow transit constipation

To evaluate the therapeutic value of transcutaneous electrical nerve stimulation (TENS) at acupoints in slow transit constipation (STC). Thirty-nine patients with (STC) who met the Rome III diagnostic criteria, were randomly assigned to 2 groups: TENS treatment group including 2 males and 18 females, aged (46 +/- 14), undergoing TENS at the acupoints ST36 (Zusanli) and PC6 (Neiguan) twice a day, 30 min after breakfast and 30 min before going to bed, for 2 weeks, and control group, including 2 males and 17 females, undergoing sham TENS treatment at 2 sham acupoints. Questionnaire survey was conducted to investigate the dyschezia scores. Self-rating depression scale (SDS) and self-rating anxiety scale (SAS) were used to assess the depression and anxiety status. X-ray examination with barium strips, radio-opaque marker, was used to detect the colonic transit status. (1) The dyschezia symptom total score after treatment in the TENS treatment group was (9.05 +/- 0.58), significantly lower than that before treatment (18.30 +/- 0.45, P < 0.01), and the oppilative symptom total score after the sham treatment of the control group was (18.00 +/- 0.46), not significantly different from that before the treatment (18.03 +/- 0.45, P > 0.05). (2) The number of vestigial barium strips of the TENS treatment group was (7.2 +/- 1.2), significantly lower than that before treatment (15.1 +/- 1.1, P < 0.01), and the change was especially obvious in the colon sector (3.3 +/- 0.8 vs 11.0 +/- 1.0, P < 0.01). However, there was no significant difference in the number of barium strips in the control group before and after the sham treatment. (3) The score of SDS and SAS of the TENS treatment group after the treatment were 34.7 +/- 0.9 and (43.7 +/- 1.5 respectively, both significantly lower than those before the treatment (37.3 +/- 0.9 and 48.1 +/- 1.8 respectively, both P < 0.05), however, there were not significant differences in the SDS and SAS scores before and after the sham treatment in the control group. TENS at the acupoints Zusanli and Neiguan is capable of improving the oppilative symptoms and ameliorating anxiety and depression state, promoting colonic transit in STC patients.

Blockade of NMDA Receptors Prevents Analgesic Tolerance to Repeated Transcutaneous Electrical Nerve Stimulation (TENS) in Rats

Repeated daily application of transcutaneous electrical nerve stimulation (TENS) results in tolerance, at spinal opioid receptors, to the antihyperalgesia produced by TENS. Since N-methyl-D-aspartate (NMDA) receptor antagonists prevent analgesic tolerance to opioid agonists, we hypothesized that blockade of NMDA receptors will prevent tolerance to TENS. In rats with knee joint inflammation, TENS was applied for 20 minutes daily at high-frequency (100 Hz), low-frequency (4 Hz), or sham TENS. Rats were treated with the NMDA antagonist MK-801 (0.01 mg/kg to 0.1 mg/kg) or vehicle daily before TENS. Paw withdrawal thresholds were tested before and after inflammation and before and after TENS treatment for 4 days. On day 1, TENS reversed the decreased mechanical withdrawal threshold induced by joint inflammation. On day 4, TENS had no effect on the decreased withdrawal threshold in the group treated with vehicle, demonstrating development of tolerance. However, in the group treated with 0.1 mg/kg MK-801, TENS significantly reversed the mechanical withdrawal thresholds on day 4, demonstrating that tolerance did not develop. Vehicle-treated animals developed cross-tolerance at spinal opioid receptors. Treatment with MK-801 reversed this cross-tolerance at spinal opioid receptors. In summary, blockade of NMDA receptors prevents analgesic tolerance to daily TENS by preventing tolerance at spinal opioid receptors. Observed tolerance to the clinical treatment of TENS could be prevented by administration of pharmaceutical agents with NMDA receptors activity such as ketamine or dextromethorphan.

Predicting outcome of TENS in chronic pain: A prospective, randomized, placebo controlled trial

Transcutaneous electrical nerve stimulation (TENS) is an easy to use non-invasive analgesic intervention applied for diverse pain states. However, effects in man are still inconclusive, especially for chronic pain. Therefore, to explore the factors predicting result of TENS treatment in chronic pain we conducted a prospective, randomized, placebo-controlled trial ( n = 163), comparing high frequency TENS ( n = 81) with sham TENS ( n = 82). Patients’ satisfaction (willingness to continue treatment; yes or no) and pain intensity (VAS) were used as outcome measures. The origin of pain and cognitive coping strategies were evaluated as possible predictors for result of TENS treatment. Results: Fifty-eight percent of the patients in the TENS group and 42.7% of the sham-TENS group were satisfied with treatment result (chi square = 3.8, p = 0.05). No differences were found for pain intensity. Patients diagnosed with osteoarthritis and related disorders (especially of the vertebral column) or peripheral neuropathic pain were less satisfied with high frequency TENS (OR = 0.12 (95% CI 0.04–0.43) and 0.06 (95% CI 0.006–0.67), respectively). Injury of bone and soft tissue (especially postsurgical pain disorder) provided the best results. Treatment modality or interactions with treatment modality did not predict intensity of pain as a result of treatment. We conclude, that predicting the effect of high frequency TENS in chronic pain depends on the choice of outcome measure. Predicting patients’ satisfaction with treatment result is related to the origin of pain. Predicting pain intensity reflects mechanisms of pain behavior and perceived control of pain, independent of treatment modality. Pain catastrophizing did not predict TENS treatment outcome.

TENS Relieves Acute Posttraumatic Hip Pain During Emergency Transport

In Central Europe, ambulances for patients suffering from pain caused by nonlife-threatening trauma, such as hip fractures are staffed by medical personnel (medics) without physicians. Thus, there is an urgent need for nonpharmacological interventions that can be applied during the transport by basic life-support (BLS) medical personnel. In all, 101 patients were screened for participation in this randomized placebo-controlled double-blind study, and randomly assigned to two groups (verum and sham transcutaneous electrical nerve stimulation [TENS]). First, medic A recorded all baseline parameters and measurements, then medic B performed TENS in absence of medic A. At the end of transportation, medic A performed data collection. Each patient was asked to grade his/her pain and anxiety level on visual analog scales (VAS, 0 to 100 mm). From 101 screened patients fulfilling the entry criteria, 29 declined consent and 9 had to be excluded from the analysis because of their final diagnosis. Therefore, the data from 30 patients (group 1, verum TENS) as well as from 33 patients (group 2 [control], sham TENS) were analyzed. No significant differences in potentially influencing factors were found before treatment. Pain scores upon arrival at the hospital differed significantly between group 1 and group 2 (p < 0.01). In group 1, pain reduction was observed between departure from the site of emergency and arrival at the hospital (VAS: 89 +/- 9 to 59 +/- 6 mm), whereas pain scores remained nearly unchanged in group 2 (VAS: 86 +/- 12 to 79 +/- 11 mm). Our findings show that TENS is a valuable and fast-acting pain treatment under the difficult circumstances of "out-of-hospital rescue". Because of its lack of side effects, it could also be a valuable tool in the hospital.

Pain Relief by Transcutaneous Electric Nerve Stimulation With Bidirectional Modulated Sine Waves in Patients With Chronic Back Pain: A Randomized, Double-Blind, Sham-Controlled Study

Objectives. Newly developed bidirectional modulated sine waves (BMW) might provide some derived benefit to patients with low back pain. Pain relief by transcutaneous electric nerve stimulation (TENS) with BMWs was tested. Materials and Methods. Analgesic effects of BMWs and conventional bidirectional pulsed waves on chronic back pain in 28 patients were compared, and effects of repeated TENS using BMWs on chronic back pain were investigated in 21 patients by means of a randomized double-blind, sham-controlled, parallel-group method. Pain intensity was assessed using numerical rating scale (NRS). Results. There was significant immediate reduction in NRS in patients receiving BMWs, and 60min after treatment compared to sham TENS. Weekly repeated treatments using massage and TENS with BMWs for 5weeks resulted in a decrease of NRS, but there were no significant differences between the TENS plus massage and sham TENS plus massage groups. Conclusions. This study shows that TENS with BMWs significantly inhibits chronic back pain, and treatment effects are attained within a day. The results also suggest that there were no statistically significant long-term effects of TENS with BMW in the repeated treatment.

Differences in Waveform Characteristics Have No Effect on the Anti-Hyperalgesia Produced by Transcutaneous Electrical Nerve Stimulation (TENS) in Rats With Joint Inflammation

Transcutaneous electrical nerve stimulation (TENS) is a nonpharmacological method for pain management. Commercial TENS units differ in their waveform characteristics. However, effects of different waveforms on analgesia produced by TENS are unknown. Therefore, we compared effects of high-frequency TENS with different waveforms--asymmetric biphasic square and symmetric biphasic square--on inflammatory hyperalgesia. Paw withdrawal latency to heat (PWL) was assessed prior to inflaming the knee joint with 3% carrageenan/kaolin in rats. Four hours after induction of inflammation, PWL significantly decreased in all groups, indicating development of hyperalgesia. High-frequency TENS was then applied to the inflamed knee joint for 20 minutes while the rat was lightly anesthetized with halothane. TENS treatment with either the asymmetric or symmetric waveform significantly increased the PWL when compared with sham TENS. Thus, differences in waveform characteristics do not affect the anti-hyperalgesia produced by TENS. This study shows that different waveforms of TENS do not affect analgesic efficacy. This suggests that clinicians can select different waveforms to provide comfort during treatment but that reduction in pain is not a factor for waveform selection.

Transcutaneous Electrical Nerve Stimulation at Both High and Low Frequencies Reduces Primary Hyperalgesia in Rats With Joint Inflammation in a Time-Dependent Manner

Clinical studies of transcutaneous electrical nerve stimulation (TENS) have used a variety of outcome measures to assess its effectiveness, with conflicting results. It is possible that TENS is effective on some measures of pain and not on others. The purpose of this study was to test the hypothesis that TENS reduces primary hyperalgesia of the knee induced by joint inflammation. Male Sprague-Dawley rats were used in this study. Inflammation of the knee joint was induced by intra-articular injection of a mixture of 3% kaolin and 3% carrageenan. Primary hyperalgesia was measured as the compression withdrawal threshold of the knee joint before and after the induction of inflammation (4 hours, 24 hours, and 2 weeks) and after sham TENS treatment, treatment with high-frequency TENS (100 Hz), or treatment with low-frequency TENS (4 Hz). The compression withdrawal threshold was significantly reduced at 4 hours, 24 hours, and 2 weeks after the induction of inflammation. Either high-frequency TENS or low-frequency TENS completely reversed the compression withdrawal threshold when applied at 24 hours or 2 weeks after the induction of inflammation but not when applied at 4 hours after the induction of inflammation. These data suggest that TENS inhibits primary hyperalgesia associated with inflammation in a time-dependent manner after inflammation has already developed during both acute and chronic stages.

Outcome of transcutaneous electrical nerve stimulation in chronic pain: short-term results of a double-blind, randomised, placebo-controlled trial

The aim of this study was to test the efficacy of shortterm transcutaneous electrical nerve stimulation (TENS) treatment in chronic pain with respect to pain intensity and patients’ satisfaction with treatment results. We therefore performed a randomised controlled trial comparing TENS and sham TENS. Patients, researchers and therapists were blinded for treatment allocation. One hundred and sixty-three patients with chronic pain referred to the Pain Centre entered the study. Conventional TENS and sham TENS were applied in the segments of pain, for a period of ten days. Outcome measures were pain intensity (visual analogue scale) and patients’ satisfaction with treatment result (yes or no). The proportions of patients satisfied with treatment result differed significantly for TENS compared to sham TENS (58 and 42.7% respectively, x2=3.8, p=0.05). However, no differences in pain intensity were found for patients treated with TENS or sham TENS. Only for patients satisfied with treatment results pain intensity gradually decrease equally both for TENS and sham TENS with repeated treatment application.

Transcutaneous Electrical Nerve Stimulation as Prehospital Emergency Interventional Care: Treating Acute Pelvic Pain in Young Women

Objectives. In Europe, patients with acute pelvic pain are transported to the hospital in an ambulance without an emergency physician. We hypothesized that transcutaneous electrical nerve stimulation (TENS) would be an effective noninvasive procedure for pain treatment. Methods. We conducted a prospective, randomized, blinded study where 100 women were randomly assigned into a real- or a sham-TENS group. TENS began before the transport to the ambulance and was left in place until the arrival at the hospital. Each patient rated her pain on paper using a visual analog scale. Results. Compared to sham TENS, patients with active TENS felt that their pain was reduced by half after treatment (p<0.01), anxiety scores significantly decreased (p<0.01), heart rate and arteriolar vasoconstriction decreased significantly (p<0.01), and nausea (p<0.01) was lessened. Overall satisfaction with the received care was significantly higher (p<0.01). Conclusion. TENS is a safe, rapid, and effective analgesic treatment for acute pelvic pain.

Transcutaneous Electrical Nerve Stimulation Reduces Acute Low Back Pain during Emergency Transport

Patients with acute low back pain may require emergency transport because of pain and immobilization. Transcutaneous electrical nerve stimulation (TENS) is a nonpharmaceutical therapy for patients with low back pain. To evaluate the efficacy of paramedic-administered TENS in patients with acute low back pain during emergency transport. This was a prospective, randomized study involving 74 patients transported to hospital. The patients were randomly assigned to two groups: group 1 (n = 36) was treated with true TENS, while group 2 (n = 36) was treated with sham TENS. The authors recorded pain and anxiety as the main outcome variables using a visual analog scale (VAS). The authors recorded a significant (p < 0.01) pain reduction (mean +/- standard deviation) during transport in group 1 (79.2 +/- 6.5 mm VAS to 48.9 +/- 8.2 mm VAS), whereas pain scores remained unchanged in group 2 (75.9 +/- 16.4 mm VAS and 77.1 +/- 11.2 mm VAS). Similarly, the scores for anxiety were significantly reduced (p < 0.01) in group 1 (81.7 +/- 7.9 mm VAS to 69.2 +/- 12.1 mm VAS) after treatment. No significant change was noted (84.5 +/- 5.8 mm VAS and 83.5 +/- 8.9 mm VAS, respectively) in group 2. TENS was found to be effective and rapid in reducing pain during emergency transport of patients with acute low back pain and should be considered due to its ease of use and lack of side effects in the study population.

The effects of transcutaneous electrical nerve stimulation on experimental pain and sympathetic nervous system response.

Transcutaneous electrical nerve stimulation (TENS) is a technique widely used in clinical practice to control pain, although its clinical efficacy remains controversial. Though many mechanisms have been proposed for its analgesic effects, there is a conspicuous lack of experimentally controlled research investigating whether TENS analgesia is related to its effects on the sympathetic nervous system (SNS). Using an established psychophysiological paradigm, the present study investigated the effects of high-frequency/low-intensity TENS, low-frequency/high-intensity TENS, and sham TENS on the perception of experimental pain and SNS function in healthy volunteers. Measures of heart rate, digital pulse volume, and skin conductance were recorded during a 20-minute TENS stimulation period and in anticipation of a series of painful electric shocks prior to and following TENS stimulation. Healthy volunteers rated the intensity of the shocks using a 0-10-point verbal pain rating scale. The three TENS conditions failed to differentially effect SNS responses during either the 20-minute TENS treatment period or the shock anticipation periods, and TENS did not affect ratings of pain intensity to the shock stimuli. While these results may not generalize to acute or chronic pain patients, within the limitations of the present experimental paradigm, no support was found for TENS affecting either SNS function or acute experimental pain perception.

Evaluation of TENS During Screening Flexible Sigmoidoscopy

The expectation of pain is a statistically significant factor negatively affecting patient compliance with current screening flexible sigmoidoscopy recommendations. Numerous pain reduction modalities have been studied with limited success. Transcutaneous electrical nerve stimulation (TENS) has been used to treat pain of various origins. The purpose of this pilot study was to determine the efficacy of TENS in reducing discomfort experienced during screening flexible sigmoidoscopy.A double-blind study was conducted in which 90 subjects were randomized to receive TENS, sham TENS, or control (standard care). The same pulse frequency and intensity were used for all subjects in the TENS group. Subjects completed preprocedural and postprocedural questionnaires, and the endoscopist completed a postprocedural questionnaire. A slight, but statistically insignificant (p =.526) reduction in the mean pain score reported by the TENS group was noted when compared with the sham TENS and control groups (2.00, 2.27, and 2.23 respectively). In light of the fact that only one pulse frequency and intensity of the TENS intervention were used in this study, further study with this safe and cost-effective modality is warranted.

Transcutaneous electrical nerve stimulation for postoperative pain relief after total knee arthroplasty

Transcutaneous electrical nerve stimulation (TENS) has been used to treat chronic pain syndromes and has been reported to be of some utility in the treatment of postsurgical pain. A randomized, blinded, placebo-controlled trial was designed to evaluate the utility of TENS after total knee arthroplasty. Patients were randomly enrolled into patient-controlled anesthesia (PCA) alone, PCA plus TENS, or PCA plus sham TENS. The cumulative dose of morphine by PCA for each group was used as the end-point of the study. There was no significant reduction in the requirement for patient-controlled analgesia with or without TENS. We conclude that there is no utility for TENS in the postoperative management of pain after knee arthroplasty.

Effects of TENS frequency, intensity and stimulation site parameter manipulation on pressure pain thresholds in healthy human subjects

This study evaluated the effects of varying frequency, intensity and stimulation site, of transcutaneous electrical nerve stimulation (TENS) in an experimental model of pain. In a double-blind design 240 volunteers were randomised to one of six experimental TENS groups, a sham TENS or control ( n=30 per group; gender balanced). Two TENS frequencies (110 or 4 Hz) and two intensities (strong but comfortable or highest tolerable) at a fixed pulse duration (200 μs) were applied at three sites relative to the measurement site (segmentally, extrasegmentally or a combination of these), for 30 min. Pressure pain thresholds (PPT) were measured using a pressure algometer, in the first dorsal interosseous muscle, every 10 min, during stimulation and for a further 30 min. The high frequency, high intensity segmental, and combined stimulation groups, showed rapid onset and significant hypoalgesic effects. This effect was sustained for 20 min post-stimulation in the high frequency segmental group. All other TENS intervention groups showed hypoalgesic responses similar to the sham TENS group, and none of these groups reached a clinically significant hypoalgesic level. Conclusions: The role of TENS frequency, intensity and site are pivotal to achieving optimal hypoalgesic effects, during and after stimulation. Clinical applications of these parameter combinations require further investigations.

Sensory stimulation (TENS): effects of parameter manipulation on mechanical pain thresholds in healthy human subjects

Transcutaneous electrical nerve stimulation (TENS) is a popular form of electrostimulation. Despite an extensive research base, there remains no consensus regarding the parameter selection required to achieve maximal hypoalgesic effects. The aim of this double blind, sham-controlled study was to investigate the relative hypoalgesic effects of different TENS parameters (frequency, intensity and stimulation site) upon experimentally induced mechanical pain. Two hundred and forty participants were recruited in order to provide statistical analysis with 80% power at α=0.05. Subjects were randomised to one of the six TENS groups, a control, and a sham TENS group ( n=30, 15 males, 15 females, per group). TENS groups differed in their combinations of stimulation; frequency (4 or 110 Hz), intensity (‘to tolerance’ or ‘strong but comfortable’) and stimulation site (segmental – over the distribution of the radial nerve or, extrasegmental – over acupuncture point ‘gall bladder 34’, or a combination of both segmental and extrasegmental). Pulse duration was fixed at 200 μs. Stimulation was delivered for 30 min and subjects were then monitored for a further 30 min. Mechanical pain threshold (MPT) was measured using a pressure algometer and taken from the first dorsal interosseous muscle of the dominant hand, ipsilateral to the stimulation site. MPT measures were taken, at baseline, and at 10-min intervals for 60 min. Difference scores were analysed using repeated measures and one-way ANOVA and relevant post hoc tests. Low frequency, high intensity, extrasegmental stimulation produced a rapid onset hypoalgesic effect, which increased during the stimulation period ( P<0.0005 control and sham) and was sustained for 30 min post-stimulation ( P<0.0005 control, P=0.024 sham). Whilst high frequency, ‘strong but comfortable’ intensity, segmental stimulation produced comparable hypoalgesic levels during stimulation, this effect was not sustained post-stimulation. Stimulation at a combination of the two sites did not produce any greater hypoalgesic effects. These results may have implications for the clinical use of sensory stimulation.

Efficacy of the transcutaneous electrical nerve stimulation for the treatment of chronic low back pain: a meta-analysis.

Low back pain affects a large proportion of the population. Transcutaneous electrical nerve stimulation (TENS) was introduced more than 30 years ago as an alternative therapy to pharmacologic treatments for chronic pain. However, despite its widespread use, the efficacy of TENS is still controversial. The aim of this meta-analysis was to determine the efficacy of TENS in the treatment of chronic low back pain. The authors searched MEDLINE, EMBASE, PEDro, and the Cochrane Controlled Trials Register up to June 1, 2000. Only randomized controlled clinical trials of TENS for the treatment of patients with a clinical diagnosis of chronic low back pain were included. Abstracts were excluded unless further data could be obtained from the authors. Two reviewers independently selected trials and extracted data using predetermined forms. Heterogeneity was tested with Cochrane's Q test. A fixed effects model was used throughout for continuous variables, except where heterogeneity existed, in which case, a random effects model was used. Results are presented as weighted mean differences with 95% confidence intervals, where the difference between the treated and control groups was weighted by the inverse of the variance. Standardized mean differences were calculated by dividing the difference between the treated and control by the baseline variance. Standardized mean differences were used when different scales were integrated to measure the same concept. Dichotomous outcomes were analyzed with odds ratios. Five trials were included, with 170 subjects randomized to the placebo group receiving sham TENS and 251 subjects receiving active TENS (153 for conventional mode, 98 for acupuncture-like TENS). The schedule of treatments varied greatly between studies ranging from one treatment/day for 2 consecutive days, to three treatments/day for 4 weeks. There were no statistically significant differences between the active TENS group compared with the placebo TENS group for any outcome measures. Subgroup analysis performed on TENS application and methodologic quality did not demonstrate a significant statistical difference (P > 0.05). Remaining preplanned subgroup analysis was not conducted because of the small number of included trials and the variety of outcome measures reported. The results of the meta-analysis present no evidence to support the use or nonuse of TENS alone in the treatment of chronic low back pain. Considering the small number of studies responding to the criteria to be included in this meta-analysis, it is clear that more appropriately designed studies are needed before a final conclusion. Clinicians and researchers should consistently report the characteristics of the TENS device and the application techniques used. New trials on TENS should make use of standardized outcome measures. This meta-analysis lacked data on how TENS efficacy is affected by four important factors: type of applications, site of application, treatment duration of TENS, and optimal frequencies and intensities.

Transcutaneous electrical nerve stimulation (TENS) for chronic pain.

Transcutaneous electrical nerve stimulation (TENS) is used in a variety of different clinical settings to treat a range of different acute and chronic pain conditions and has become popular with both patients and health professionals. To evaluate the effectiveness of TENS in chronic pain. The Cochrane Library, Embase, Medline, CINAHL and The Oxford Pain Database were searched. Reference lists from retrieved reports and reviews were examined. Date of the most recent search: March 1999. RCTs were eligible if they included the following treatment comparisons: active TENS versus sham TENS controls active TENS versus no treatment controls active TENS versus active TENS controls (for instance High Frequency TENS vs Low Frequency TENS) Studies of patients suffering chronic pain for three months or more which included subjective outcome measures for pain intensity, or pain relief were eligible for evaluation in this review. No restrictions were made to language or sample size. Data from abstracts, letters, or unpublished studies, and studies of TENS in angina, headache and migraine, and dysmenorrhoea were not included. Data were extracted and summarised on the following items: patients and details of pain condition, study treatments, study duration, design, methods, subjective pain outcome measures, methodological quality, results for pain outcome measures and adverse effects, and the conclusions made by the authors of the original studies. Extracted data and methodological quality of each report was confirmed by at least three of the reviewers. Of 107 reports identified from the searches, 88 were excluded as they did not fulfil the pre-defined entry criteria. Nineteen RCTs (from 18 reports) were evaluated. The included trials varied in terms of design, analgesic outcomes, chronic pain conditions, TENS treatments and overall methodological quality. Studies included single and multiple dose treatment comparisons of TENS. The studies were small. The reporting of the methods used and results for the analgesic outcomes were generally poor. TENS treatments and controls were often poorly defined. Few studies evaluated the long-term analgesic effectiveness of TENS and single dose evaluations of TENS are unhelpful in making clinical decisions of the long-term effectiveness of TENS in the management of chronic pain. Meta-analysis was not possible. Overall in 10 of 15 inactive control studies there was a positive analgesic outcome in favour of the active TENS treatments. For the multiple dose treatment comparison studies only three of seven were considered to be in favour of the active TENS treatments. For the active controlled studies, seven studies made direct comparisons between HFTENS and LFTENS. Five of seven studies could find no difference in terms of analgesic efficacy between HFTENS and LFTENS at any time point. The results of this review are inconclusive; the published trials do not provide information on the stimulation parameters which are most likely to provide optimum pain relief, nor do they answer questions about long-term effectiveness. Large multi-centre randomised controlled trials of TENS in chronic pain are urgently needed.