Auricular transcutaneous electrical nerve stimulation (TENS) reduces phantom limb pain

The present paper evaluates the efficacy of low frequency, high intensity auricular transcutaneous electrical nerve stimulation (TENS) for the relief of phantom limb pain. Auricular TENS was compared with a no-stimulation placebo condition using a controlled crossover design in a group of amputees with (1) phantom limb pain (Group PLP), (2) nonpainful phantom limb sensations (Group PLS), and (3) no phantom limb at all (Group No PL). Small, but significant, reductions in the intensity of nonpainful phantom limb sensations were found for Group PLS during the TENS but not the placebo condition. In addition, 10 min after receiving auricular TENS, Group PLP demonstrated a modest, yet statistically significant decrease in pain as measured by the McGill Pain Questionnaire. Ratings of mood, sleepiness, and anxiety remained virtually unchanged across test occasions and sessions, indicating that the decrease in pain was not mediated by emotional factors. Further placebo-controlled trials of auricular TENS in patients with phantom limb pain are recommended in order to evaluate the importance of electrical stimulation parameters such as pulse width and rate, and to establish the duration of pain relief.     

Transcutaneous Electrical Nerve Stimulation for Phantom Pain and Stump Pain in Adult Amputees

Abstract Following amputation, 50% to 90% of individuals experience phantom and/or stump pain. Transcutaneous electrical nerve stimulation (TENS) may prove to be a useful adjunct analgesic intervention, although a recent systematic review was unable to judge effectiveness owing to lack of quality evidence. The aim of this pilot study was to gather data on the effect of TENS on phantom pain and stump pain at rest and on movement. Ten individuals with a transtibial amputation and persistent moderate‐to‐severe phantom and/or stump pain were recruited. Inclusion criteria was a baseline pain score of ≥3 using 0 to 10 numerical rating scale (NRS). TENS was applied for 60 minutes to generate a strong but comfortable TENS sensation at the site of stump pain or projected into the site of phantom pain. Outcomes at rest and on movement before and during TENS at 30 minutes and 60 minutes were changes in the intensities of pain, nonpainful phantom sensation, and prosthesis embodiment. Mean (SD) pain intensity scores were reduced by 1.8 (1.6) at rest (P < 0.05) and 3.9 (1.9) on movement (P < 0.05) after 60 minutes of TENS. For five participants, it was possible to project TENS sensation into the phantom limb by placing the electrodes over transected afferent nerves. Nonpainful phantom sensations and prosthesis embodiment remained unchanged. This study has demonstrated that TENS has potential for reducing phantom pain and stump pain at rest and on movement. Projecting TENS sensation into the phantom limb might facilitate perceptual embodiment of prosthetic limbs. The findings support the delivery of a feasibility trial.     

CONTRALATERAL EFFECTS OF DISINHIBITORY TENS ON QUADRICEPS FUNCTION IN PEOPLE WITH KNEE OSTEOARTHRITIS FOLLOWING UNILATERAL TREATMENT

Background:

Quadriceps activation failure is common in patients with tibiofemoral osteoarthritis (TFOA) and has been reported to occur bilaterally following acute and chronic knee injuries. Sensory transcutaneous electrical stimulation (TENS) applied to the knee has increased ipsilateral quadriceps activation, yet it remains unknown if repeated sensory TENS treatments affect activation in the contralateral quadriceps.

Objective:

To determine the effects of unilateral TENS treatment to the involved leg, in conjunction with 4-weeks of therapeutic exercise, on volitional quadriceps activation in the contralateral leg.

Methods:

Thirty-three patients with radiographically diagnosed TFOA were randomly assigned to the TENS, placebo, and the control groups. The involved leg was defined as the knee with highest degree of radiographically assessed TFOA. All participants completed a supervised 4-week lower extremity exercise program for the involved leg only. TENS and placebo TENS were worn throughout the rehabilitation sessions as well as during daily activities for those groups on the involved leg. Quadriceps central activation ratio (CAR), a measure of volitional muscular activation, was assessed in the uninvolved leg at baseline, 2-weeks and 4-weeks following the initiation of the intervention.

Results:

There were no differences between groups for quadriceps CAR (P=0.3).

Discussion:

Although significant differences were not found, strong to moderate within group effect sizes were calculated for the TENS group at 2 (d = .87) and 4 weeks (d = .54), suggesting that significant differences may be found in a larger population.

Conclusions:

Contralateral quadriceps CAR was not affected following a 4-week unilateral disinhibitory intervention in this sample.     

Brain somatic representation of phantom and intact limb: a fMRI study case report.

Reports on phantom limb patients concerning neuronal reorganization using non-invasive methods have focused mainly on the cortical regions and suggest the presence of pain as the cause of this reorganization. The phantom limb, however, includes other somatic and motor sensations other than pain. Here we describe the results of non-painful stimulation in cortical and subcortical lateralization and reorganization and also examine the involvement of subcortical structures in phantom limb telescoping perception. We describe an enlarged contralateral cortical representation of the stump, a cortical and thalamic bilateral representation of the remaining leg, and a neuronal correlate of a telescoping perception of the phantom limb. The missing leg produces an enlarged cortical representation due to abnormal information and the remaining leg has a bilateral SII representation, which could be related to new, compensatory functions. The telescoping perception of a phantom limb by the stimulation of misallocation points was correlated with lenticular nuclei, thalamic and cingulate gyrus activation.We therefore propose that the reorganization concept of a phantom limb, applied mainly to the cortex, must extend to the thalamic and the somatosensory and motor systems (pathways and relay nuclei).     

Effect of burst-mode transcutaneous electrical nerve stimulation on peripheral vascular resistance

BACKGROUND AND PURPOSE: Based on changes in skin temperature alone, some authors have proposed that postganglionic sympathetic vasoconstrictor fibers can be stimulated transcutaneously. Our goal was to determine the effects of low-frequency (2 bursts per second), burst-mode transcutaneous electrical nerve stimulation (TENS) on calf vascular resistance, a more direct marker of sympathetic vasoconstrictor outflow than skin temperature, in subjects with no known pathology. SUBJECTS: Fourteen women and 6 men (mean age=31 years, SD=13, range=18-58) participated in this study. METHODS: Calf blood flow, arterial pressure, and skin temperature were measured while TENS was applied over the common peroneal and tibial nerves. RESULTS: Blood flow immediately following stimulation was not affected by TENS applied just under or just above the threshold for muscle contraction. Transcutaneous electrical nerve stimulation applied at 25% above the motor threshold caused a transient increase in calf blood flow. Regardless of stimulation intensity, TENS had no effect on arterial pressure; therefore, calf vascular resistance decreased only during the trial that was 25% above the motor threshold. Regardless of stimulation intensity, TENS failed to alter dorsal or plantar skin temperature. DISCUSSION AND CONCLUSION: These results demonstrate that the effects of TENS on circulation depend on stimulation intensity. When the intensity was sufficient to cause a moderate muscle contraction, a transient, local increase in blood flow occurred. Cooling of the dorsal and plantar skin occurred in both the stimulated and control legs, most likely because skin temperature acclimatized to ambient room temperature, rather than because of any effect of TENS on circulation. The data, therefore, call into question the idea that postganglionic sympathetic efferent fibers are stimulated when TENS is applied at clinically relevant intensities to people without symptoms of cardiovascular or neuromuscular pathology.     

经皮电神经刺激治疗中电极位置对改善截肢后幻肢痛的不同影响

目的观察经皮电神经刺激(TENS)不同电极放置治疗截肢后幻肢痛的疗效。方法截肢后幻肢痛患者60例,分为治疗组和对照组各30例,治疗组电极置于对侧肢体相当于幻肢痛的部位,对照组电极置于残端部位。结果治疗2个疗程后,治疗组总有效率为93.3%,总显效率为76.7%,优于对照组(P<0.05)。结论经皮电神经刺激治疗电极放置部位对疗效有影响。     

An investigation into the effect of electrode placement of transcutaneous electrical nerve stimulation (TENS) on experimentally induced ischemic pain in healthy human participants

INTRODUCTION: It is claimed that transcutaneous electrical nerve stimulation (TENS) operates via a segmental mechanism by reducing ongoing transmission and sensitization of nociceptive dorsal horn neurons. Hence, TENS electrodes are usually placed at the site of pain. OBJECTIVE: This study compared TENS administered at the site of experimentally induced ischemic pain (ipsilateral forearm) with TENS administered at a location not related to pain (contralateral lower leg). METHODS: Ten healthy, pain free volunteers took part in a cross-over study during which ischemic pain was induced in the nondominant arm using a modified version of submaximal effort tourniquet technique. Pain intensity was taken at 1-minute interval/s for 5 minutes while receiving TENS either at the ipsilateral arm or contralateral leg. RESULTS: There were no statistically significant differences in pain intensity or McGill Pain Questionnaire ratings between TENS given at the arm compared with the leg. DISCUSSION: Taken at face value, the findings suggest that TENS effects were nonspecific and that electrode location does not affect outcome. However, this study should be seen as a call for further research rather than a definitive conclusion.     

‘Sympathetic Slump’: The Effects of a Novel Manual Therapy Technique on Peripheral Sympathetic Nervous System Function

Abstract

The present study examined the physiological effects of the ‘sympathetic slump’ on measures of peripheral sympathetic nervous system (SNS) function in normal volunteers. ‘Sympathetic slump’ has been proposed (1) as a technique to load the sympathetic trunk (ST). It is suggested that mechanical stimulation of the ST will result in alterations in peripheral SNS function and/or target tissue sensitivity. This technique forms part of an overall examination and treatment protocol for patients with features of sympathetically maintained pain (2 = 13). The present study evaluated the effect of ‘sympathetic slump’ on two measures (skin conductance and skin temperature) of peripheral SNS function.

Twenty-two normal, asymptomatic subjects with no previous experience of manual therapy participated in the study. A randomised, repeated measures, double-blind, placebo controlled protocol was used to evaluate the effects of ‘sympathetic slump’, placebo and control conditions on skin conductance and skin temperature in the upper limbs.

‘Sympathetic slump’ produced a significantly greater increase in skin conductance than either placebo or control. A greater increase in skin conductance was observed in the right upper limb compared to the left upper limb, in keeping with the fact that the technique used in this study was intended to bias the right ST. Significant changes in skin temperature occurred for both ‘sympathetic slump’ and placebo compared to control, however there was no significant difference between ‘sympathetic slump’ and placebo. ‘Sympathetic slump’ did however appear to exert a greater differential effect between sides (R < L) than did the placebo technique.

The results of this study demonstrate that the ‘sympathetic slump’ technique influences peripheral SNS function. The technique has the capacity to differentially increase sympathetic activity in the ipsilateral upper limb.     

TENS and FES for sensory impairment and gait dysfunction following removal of spinal cord ependymoma — a case report

Background . Sensory deficits are commonly reported following the resection of spinal cord tumours. The use of transcutaneous electrical nerve stimulation (TENS) as augmented sensory input is described in the research literature but rarely in the clinical literature. Functional electrical stimulation (FES) is used for people with motor impairments rather than sensory impairments. Method and results . This case report describes the use of TENS and FES for a patient with severe sensory loss and mild weakness in the right leg following the removal of an intramedullary spinal cord tumour. The patient was able to walk more quickly and more confidently when using TENS and FES in combination. She consistently reported greater benefits from TENS alone compared to FES alone and continued to use TENS delivered via a sock electrode at six months after surgery. Conclusion . The use of TENS as a sensory stimulus was an invaluable component of this patient's treatment, allowing her to engage in a more challenging balance and gait programme at an earlier stage in her rehabilitation. Combining FES with TENS was also useful and allowed treatment to address motor and sensory impairments concurrently during functional activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparison of TENS treatments in hemiplegic shoulder pain

The aim of this paper is to evaluate the effectiveness of high-intensity versus low-intensity transcutaneous electrical nerve stimulation (TENS) and versus placebo for treatment of hemiplegic shoulder pain. Three groups of 20 patients each (A, B, C) were studied. In group A high-intensity TENS was delivered at 3 times the sensory threshold with frequency of 100 Hz; in group B low-intensity TENS was delivered at the sensory threshold with frequency of 100 Hz. Group C received placebo stimulation. The treatment protocol consisted of 12 sessions (4 weeks). Before treatment, at the end of it and one month after, passive range of motion (PROM) for flexion, extension, abduction and external rotation were evaluated. Statistically significant improvements of PROMs were recorded for group A, but not for groups B or C.     

Referred pain from amputation stump trigger points into the phantom limb

OBJECTIVES: The aim of the study was to examine whether/how myofascial stump trigger points (TPs) after lower leg amputations are able to produce stump pain (SP), phantom pain (PP), and sensations (PS) in the phantom limb. METHODS: Palpation of the 5 most striking stump TPs of 30 leg amputees (12 transfemoral, 18 transtibial) was documented in a standardized manner. Patients were asked to localize SP, PP, and PS. RESULTS: Of 150 TPs, 14 produced involuntary stump movements and 10 stump fasciculations. Dorsal PP after ventral TP palpation occurred as well as PP in the toes from TPs near the hip. Of 30 patients, 20 reported PS and 8 PP; 60 of 150 TPs produced PS and 17 PP. Phantom phenomena were localized in 62.8% in the toes (1st toe 19.8%, toes 2-5 about 10% each), 17.9% midfoot, and the rest were more proximal. TPs were localized more in the lateral/dorsal stump than medial/ventral. About 70% of the TPs were found between 3 and 7 cm from the stump end, those with toe projections more distal than those with tibial projections. CONCLUSIONS: Myofascial TPs in amputation stumps are common and able to produce sensations and pain in the phantom limb. Most reported experiences were localized in the toes, as phantom pain usually is. There seems to be a "stump representation" and it seems possible that "referred TP pain" and "phantom pain" may develop from similar origin.     

Comparative analgesic effects of H-wave therapy and transcutaneous electrical nerve stimulation on pain threshold in humans.

OBJECTIVE: To assess the comparative analgesic efficacy of H-wave therapy (HWT) and transcutaneous electrical nerve stimulation (TENS) using a mechanical model of pain threshold measurement. STUDY DESIGN: Forty-eight healthy human volunteers (24 women, 24 men) were recruited and randomly assigned into one of six experimental groups; control, HWT (placebo, 2Hz, or 60Hz), or TENS (placebo or 110Hz). For each subject, mechanical pain threshold (MPT) measurements were recorded at three standardized recording points marked on the dorsal web space of the dominant hand. Two MPT measurements were recorded at each point at the following time intervals: before treatment was initiated (baseline), after each of three consecutive 10-minute periods of stimulation (HWT or TENS), and at four intervals within 30 minutes after stimulation. In the control and placebo groups MPT measurements were recorded at similar time intervals. RESULTS: Difference scores, calculated from patients' baseline values, were analyzed by ANOVA for each of the three recording points. Although results showed a significant increase in MPT levels in all three stimulation groups when compared with their relative placebo (indicating a hypoalgesic effect), no differences were observed between the different modalities or HWT frequencies. Significant hypoalgesia continued for 5 minutes after stimulation. CONCLUSION: The findings showed that HWT and TENS provided localized hypoalgesia during stimulation and for up to 5 minutes after it. No frequency- or modality-specific effects were observed between the groups.     

Sympathetic nerve activity to amputated lower leg in humans. Evidence of altered skin vasoconstrictor discharge

Transection of a peripheral nerve in the cat is known to cause a regional change in sympathetic impulse pattern. Our aim was to determine whether microneurography can be used to study sympathetic activity in the transected nerve of human amputees, and whether any such activity shows an abnormal pattern similar to that observed in the cat. Seven successful sympathetic recording sessions were performed in the peroneal nerve of four subjects with posttraumatic transtibial leg amputation; one of them was studied on four occasions. Muscle nerve sympathetic activity (MSA) was detected in all four subjects. Skin nerve sympathetic activity (SSA) was found in one patient only, but on three occasions. It was more difficult to obtain high quality sympathetic recordings than for intact nerves, particularly in patients amputated many years before our studies. MSA showed a qualitatively normal pattern at rest and during various manoeuvres. In three recordings from skin nerve fascicles without innervation zone, SSA displayed normal characteristics at room temperature and qualitatively normal responses to arousal stimuli and various manoeuvres. During body cooling there was an abnormal shift in SSA pattern with a reduction in burst duration instead of the increase occurring normally. Cardiac rhythmicity of SSA was more pronounced during body cooling than during body heating. This is also a reversal of the normal pattern. The abnormal SSA pattern during body cooling suggests increased baroreflex regulation of cutaneous vasoconstrictor neurones, similar to the change after nerve transection in the cat. This is the first time that human nerve recordings support the hypothesis of a regional alteration in sympathetic impulse pattern following a nerve lesion. The implications of this phenomenon for pain conditions remains to be explored; our patients did not suffer from phantom or stump pain.     

The Long‐Term Outcome of Transcutaneous Electrical Nerve Stimulation in the Treatment for Patients with Chronic Pain: A Randomized,Placebo‐Controlled Trial

Background: Transcutaneous electrical nerve stimulation (TENS) is an easy to use analgesic intervention. However, long‐term randomized placebo‐controlled studies with treatment periods of more than 3 months have not been executed to date. The aim of our study is to explore the long‐term (1 year) time course of the treatment effects of TENS compared to placebo (sham TENS). Method: We performed a randomized placebo‐controlled trial in patients with chronic pain (165), referred to a multidisciplinary pain center of a university hospital. Main outcome measures are the proportion of patients satisfied with treatment result and willing to continue treatment, pain intensity, pain disability, and perceived health status. Results: Survival analysis of time courses of proportions of satisfied patients revealed no significant differences (P = 0.79; log‐rank test) for TENS treatment compared to sham TENS. After 1 year, 30% (24/81) of the patients of the TENS group and 23% (19/82) of the sham TENS group were satisfied with treatment result. These patients experienced a mean overall improvement of 62.7% (n = 43). This effect was not significantly different between both groups. For satisfied patients, there were no differences in pain intensity or disability and perceived health status between the TENS and sham TENS group. Conclusions: Transcutaneous electrical nerve stimulation and sham TENS show similar effects in patients with chronic pain over a period of 1 year. We found support for a long sustained placebo effect.     

Effect of transcutaneous electrical nerve stimulation at auricular points on experimental cutaneous pain threshold

The purposes of this study were 1) to examine the effect of high intensity, low frequency transcutaneous electrical nerve stimulation at auricular acupuncture points on experimental pain threshold measured at the wrist and 2) to determine the changes in effect over time. Forty-four healthy adult men and women were assigned randomly to one of three treatment groups. Group 1 (n = 15) received TENS to appropriate auricular points for wrist pain, Group 2 (n = 14) received TENS to inappropriate (placebo) auricular points, and Group 3 (n = 15) received no TENS. We measured experimental pain threshold at the wrist after an electrical stimulus during one pretreatment and three posttreatment time periods. Group 1 was the only group that had a statistically significant increase (p less than .05) in pain threshold after testing. This increase remained significant for all posttreatment measurements for Group 1. These results suggest that high intensity, low frequency TENS applied to appropriate auricular acupuncture points can increase pain threshold.     

The effect of transcutaneous electrical nerve stimulation (TENS) on catecholamine metabolism during pacing-induced angina pectoris and the influence of naloxone

Two invasive studies (invasive study I and invasive study II) showed positive effects of transcutaneous electrical nerve stimulation (TENS) in pacing-induced angina pectoris in terms of increased tolerance to pacing, improved lactate metabolism and less anginal pain. Invasive study I demonstrated a decrease in left ventricular afterload by TENS treatment as reflected by a fall in systolic blood pressure, and this fact was thought to be explained by reduced sympathetic activity since arterial levels of epinephrine and norepinephrine dropped during TENS in TENS responders. In invasive study II, the influence of naloxone on the effects of TENS in pacing-induced angina pectoris was studied in 11 patients with severe coronary artery disease. The patients were catheterized and treated with TENS on 2 occasions; one with a single intravenous (i.v.) dose of saline as placebo and one with a single i.v. dose of 50 mg naloxone, double-blind, in random order. Treatment with TENS increased tolerance to pacing (P less than 0.01 with placebo and P less than 0.01 with naloxone, respectively) and improved lactate metabolism (P less than 0.05 with placebo and P less than 0.01 with naloxone, respectively). The positive effects of TENS were thus reproducible and not reversed by single i.v. doses of naloxone. The results of this study indicate that the effects of TENS on the heart are not mediated by beta-endorphin but do not exclude activation of more short-acting opioids like delta or kappa receptor agonists (met-enkephalin and/or dynorphin) since naloxone has a low affinity for these receptors. It is also possible that non-opioid mechanisms are of importance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sympathetic skin response (SSR)]

The sympathetic skin response (SSR) is a slow wave resulting from activation of the sudomotor sympathetic efferent fibers. Records are usually made with surface electrodes on hand or foot after the electrical stimulation. Either the amplitude or the latency of the response varies greatly on consecutive stimulations and there is also a remarkable tendency to habituation. Therefore SSR is considered abnormal if no significant responses are detected. SSR is well correlated with other autonomic function tests and its abnormality is documented in a variety of neurologic disorders such as diabetic neuropathy, cerebrovascular disease and Parkinson's disease. In good methodological conditions, SSR is a simple, reliable indicator of sympathetic sudomotor outflow in central and peripheral nervous system disorders.     

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

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.     

Auslösung von Phantomschmerzen und -sensationen durch muskuläre Stumpftriggerpunkte nach Beinamputationen

Objectives

The aim of the study was to examine whether/how myofascial stump trigger points (TPs) after lower leg amputations are able to produce stump pain (SP), phantom pain (PP), and sensations (PS) in the phantom limb.

Methods

Palpation of the 5 most striking stump TPs of 30 leg amputees (12 transfemoral, 18 transtibial) was documented in a standardized manner. Patients were asked to localize SP, PP, and PS.

Results

Of 150 TPs, 14 produced involuntary stump movements and 10 stump fasciculations. Dorsal PP after ventral TP palpation occurred as well as PP in the toes from TPs near the hip. Of 30 patients, 20 reported PS and 8 PP; 60 of 150 TPs produced PS and 17 PP. Phantom phenomena were localized in 62.8% in the toes (1st toe 19.8%, toes 2–5 about 10% each), 17.9% midfoot, and the rest were more proximal. TPs were localized more in the lateral/dorsal stump than medial/ventral. About 70% of the TPs were found between 3 and 7 cm from the stump end, those with toe projections more distal than those with tibial projections.

Conclusions

Myofascial TPs in amputation stumps are common and able to produce sensations and pain in the phantom limb. Most reported experiences were localized in the toes, as phantom pain usually is. There seems to be a “stump representation” and it seems possible that “referred TP pain” and “phantom pain” may develop from similar origin.     

Treatment of Headache by Transcutaneous Electrical Stimulation

SYNOPSIS
Transcutaneous electrical stimulation (TENS) has been used extensively for many types of pain but only rarely for headache. The object of this study was to judge the efficacy of TENS against placebo. Contrary to popular use, TENS (and placebo) were applied in a rigid manner, probably prejudicial to maximum effectiveness.
62 patients with migraine or muscle contraction headache, or both, were studied using TENS equipment of low amperage and high frequency. One of three modalities was chosen at random for each patient: TENS just above the patient's ability to perceive the stimuli (perceived stimuli), TENS just below the perception threshold (subliminal stimuli), and electrodes applied without electrical stimulation (placebo). Degree of improvement was judged by the patient using a scale of pain from 1 to 10. Following treatment with TENS perceived by the patient, 55% of patients noted improvement as compared to 18% after application of placebo; a significant difference (p < .025 chi-square test). Subliminal TENS was not statistically better than placebo.