Alteration of cortical excitability in patients with fibromyalgia

We assessed cortical excitability and intracortical modulation systematically, by transcranial magnetic stimulation (TMS) of the motor cortex, in patients with fibromyalgia. In total 46 female patients with fibromyalgia and 21 normal female subjects, matched for age, were included in this study. TMS was applied to the hand motor area of both hemispheres and motor evoked potentials (MEPs) were recorded for the first interosseous muscle of the contralateral hand. Single-pulse stimulation was used for measurements of the rest motor threshold (RMT) and suprathreshold MEP. Paired-pulse stimulation was used to assess short intracortical inhibition (SICI) and intracortical facilitation (ICF). Putative correlations were sought between changes in electrophysiological parameters and major clinical features of fibromyalgia, such as pain, fatigue, anxiety, depression and catastrophizing. The RMT on both sides was significantly increased in patients with fibromyalgia and suprathreshold MEP was significantly decreased bilaterally. However, these alterations, suggesting a global decrease in corticospinal excitability, were not correlated with clinical features. Patients with fibromyalgia also had lower ICF and SICI on both sides, than controls, these lower values being correlated with fatigue, catastrophizing and depression. These neurophysiological alterations were not linked to medication, as similar changes were observed in patients with or without psychotropic treatment. In conclusion, fibromyalgia is associated with deficits in intracortical modulation involving both GABAergic and glutamatergic mechanisms, possibly related to certain aspects of the pathophysiology of this chronic pain syndrome. Our data add to the growing body of evidence for objective and quantifiable changes in brain function in fibromyalgia.     

Feasibility Study of Transcutaneous Electrical Nerve Stimulation (TENS) for Cancer Bone Pain

This multicenter study assessed the feasibility of conducting a phase III trial of transcutaneous electrical nerve stimulation (TENS) in patients with cancer bone pain recruited from palliative care services. Eligible patients received active and placebo TENS for 1 hour at site of pain in a randomized crossover design; median interval between applications 3 days. Responses assessed at 30 and 60 minutes included numerical and verbal ratings of pain at rest and on movement, and pain relief. Recruitment, tolerability, adverse events, and effectiveness of blinding were also evaluated. Twenty-four patients were randomised and 19 completed both applications. The intervention was well tolerated. Five patients withdrew: 3 due to deteriorating performance status, and 2 due to increased pain (1 each following active and placebo TENS). Confidence interval estimation around the differences in outcomes between active and placebo TENS suggests that TENS has the potential to decrease pain on movement more than pain on rest. Nine patients did not consider that a placebo was used; the remaining 10 correctly identified placebo TENS. Feasibility studies are important in palliative care prior to undertaking clinical trials. Our findings suggest that further work is required on recruitment strategies and refining the control arm before evaluating TENS in cancer bone pain.PerspectiveCancer bone pain is common and severe, and partly mediated by hyperexcitability. Animal studies suggest that Transcutaneous Electrical Nerve Stimulation can reduce hyperalgesia. This study examined the feasibility of evaluating TENS in patients with cancer bone pain in order to optimize methods before a phase III trial.     

The effects of unilateral transcutaneous electrical nerve stimulation of the median nerve on bilateral somatosensory thresholds

Transcutaneous electrical nerve stimulation (TENS) is used to relieve acute and chronic pain. TENS electrodes are applied at the site of pain or in segments related to the pain, although there is limited research to support either approach. This study investigated the effects of unilateral TENS on mechanical and thermal thresholds at ipsilateral and contralateral sites in healthy human participants. Sensory perception thresholds were measured on the ipsilateral and contralateral thenar eminence of 16 volunteers for von Frey filaments, sharpness, warm, cold and heat pain. TENS was administered over the right median nerve for 10 min at 100 pulses per second (pps) and an intensity which elicited mild tingling in the hand. During TENS, ipsilateral threshold was greater than contralateral threshold for all sensory modalities, although differences were less marked for thermal stimuli. TENS effects had disappeared 30 min after TENS had been switched off although there was a tendency for thermal thresholds to remain elevated. We conclude that during stimulation, TENS elevates somatosensory thresholds within the distribution of the stimulated nerve. The rapid and short-lived ipsilateral effect is consistent with findings from animal studies and suggests a central segmental mechanism.     

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.     

An investigation of the development of analgesic tolerance to TENS in humans

Transcutaneous electrical nerve stimulation (TENS) is a noninvasive modality used to control pain. Animal models show that repeated TENS application produces analgesic tolerance and cross-tolerance at spinal opioid receptors. The aim of the present investigation was to examine whether repeated application of TENS produces analgesic tolerance in humans. One hundred healthy subjects were randomly assigned to 1 of 4 groups: control, placebo, low-frequency (4 Hz) or high-frequency (100 Hz) TENS. TENS was applied daily for 5 days to the nondominant upper limb; pressure-pain threshold (PPT) measurements were recorded before and after TENS. Temporal summation to mechanical stimulation was recorded on days 1 and 5, before and after TENS. Diffuse noxious inhibitory control (DNIC) was tested on day 5 using the cold pressor test and PPT measurements. There was an initial increase in PPTs in both low- and high-frequency TENS groups when compared with placebo or control groups. However, by day 5 this TENS-induced increase in PPT did not occur, and there was no difference between active TENS and placebo or control groups. High-frequency TENS decreased temporal summation on day 1 when compared with day 5. DNIC increased the PPT similarly in all groups. These data suggest that repeated daily application of TENS results in a decrease in its hypoalgesic effect by the fifth day and that the tolerance-like effect to repeated TENS results from tolerance at centrally located opioid receptors. The lack of change in DNIC response suggests that TENS and DNIC utilize separate pathways to produce analgesia.     

Pain relief by applying transcutaneous electrical nerve stimulation (TENS) during unsedated colonoscopy: A randomized double‐blind placebo‐controlled trial

Transcutaneous electrical nerve stimulation (TENS) is a noninvasive alternative to traditional pain treatments. TENS has been studied in the past as a pain reduction modality in colonoscopy with limited success. Reviews and meta‐analysis have shown that the inconclusive results of TENS may be due to the lack of randomized controlled trials and the difficulty in defining precise output parameters. The objective of this double‐blind randomized placebo‐controlled trial was to investigate the pain‐relieving effect of a new application of TENS in unsedated screening colonoscopy. Ninety patients undergoing unsedated screening colonoscopy were randomly allocated to one of three groups: a control group (n=30), a group to receive active TENS (n=30), or a group to receive placebo TENS (n=30). A visual analogue scale (VAS) and a five‐point Likert scale were used to assess pain 5min into the procedure and at the end of the procedure. The patient's bloating sensation during colonoscopy and the effect on the duration of the procedure were also evaluated. Throughout the procedure, the active TENS group experienced a VAS pain score reduction ≥50% compared to the placebo TENS group (P<0.001) and the control group (P<0.001). On the five‐point Likert scale, there was also a significant reduction in pain score in the active TENS group compared to the placebo TENS and control groups (P=0.009). No significant differences were found between the study groups as to the bloating sensation and the duration of the procedure. We conclude that TENS can be used as a pain relief therapy in unsedated screening colonoscopy.     

Effects of electric stimulation on C and A delta fiber-mediated thermal perception thresholds

OBJECTIVE: To determine if interferential current (IFC) or transcutaneous electric nerve stimulation (TENS) alters C and A delta fiber-mediated thermal perception thresholds. DESIGN: Single-blind, randomized controlled trial. SETTING: Laboratory. PARTICIPANTS: One hundred forty healthy women volunteers (mean age +/- standard deviation, 20.6+/-2.7 y). INTERVENTIONS: Subjects were randomly and exclusively assigned to 1 of 7 groups (n=20 in each): 0, 5, and 100 Hz of IFC; 5 and 100 Hz of TENS; placebo and control stimulation. Stimulation was applied through 2 electrodes placed over the median nerve. Warm sensation, cold sensation, hot pain, and cold pain perception thresholds were measured from the thenar eminence by using a quantitative sensory testing device and a method of limits algorithm. MAIN OUTCOME MEASURES: Warm sensation, cold sensation, hot pain, and cold pain thresholds (degrees C) before, during, and after stimulation. RESULTS: There was a statistically significant effect of time for all 4 thermal perception thresholds (separate 2-way analyses of variance with repeated measures, all P<.001). There were no statistically significant differences between experimental groups, nor any interaction effects (all P>.05). CONCLUSIONS: Neither IFC nor TENS altered C and A delta fiber-mediated thermal perception thresholds. The results suggest that any analgesic mechanisms with these modalities are likely to be complex.     

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 (≥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.PerspectiveThis 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.     

Site-specific Effects of Transcranial Direct Current Stimulation on Sleep and Pain in Fibromyalgia: A Randomized, Sham-controlled Study

Objective: To investigate whether active anodal transcranial direct current stimulation (tDCS) (of dorsolateral prefrontal cortex [DLPFC] and primary motor cortex [M1]) as compared to sham treatment is associated with changes in sleep structure in fibromyalgia. Methods: Thirty‐two patients were randomized to receive sham stimulation or active tDCS with the anode centered over M1 or DLPFC (2 mA, 20 minutes for five consecutive days). A blinded evaluator rated the clinical symptoms of fibromyalgia. All‐night polysomnography was performed before and after five consecutive sessions of tDCS. Results: Anodal tDCS had an effect on sleep and pain that was specific to the site of stimulation: such as that M1 and DLPFC treatments induced opposite effects on sleep and pain, whereas sham stimulation induced no significant sleep or pain changes. Specifically, whereas M1 treatment increased sleep efficiency (by 11.8%, P = 0.004) and decreased arousals (by 35.0%, P = 0.001), DLPFC stimulation was associated with a decrease in sleep efficiency (by 7.5%, P = 0.02), an increase in rapid eye movement (REM) and sleep latency (by 47.7%, P = 0.0002, and 133.4%, P = 0.02, respectively). In addition, a decrease in REM latency and increase in sleep efficiency were associated with an improvement in fibromyalgia symptoms (as indexed by the Fibromyalgia Impact Questionnaire). Finally, patients with higher body mass index had the worse sleep outcome as indexed by sleep efficiency changes after M1 stimulation. Interpretation: Our findings suggest that one possible mechanism to explain the therapeutic effects of tDCS in fibromyalgia is via sleep modulation that is specific to modulation of primary M1 activity. ?     

Conventional versus acupuncture-like transcutaneous electrical nerve stimulation on cold-induced pain in healthy human participants: effects during stimulation

Objectives: To compare the hypoalgesic effects of conventional transcutaneous electrical nerve stimulation (TENS) (high frequency, low intensity) and acupuncture‐like TENS (AL‐TENS, low frequency, high intensity) on cold‐induced pain. Design: Randomized controlled parallel group study comparing the effects of strong non‐painful AL‐TENS, conventional TENS and placebo (no current) TENS on cold‐pressor pain threshold (CPT) and pain intensity. Two baseline (pre‐intervention) measures and three during intervention measures of CPT and cold pain intensity (four point category scale) were recorded. Setting: Physiology laboratory in Leeds Metropolitan University. Participants: One hundred and twenty‐one healthy participants. Interventions: Each participant received one of three TENS interventions over their flexor digitorum profundus: (i) high pulse rate TENS with a strong non‐painful paraesthesia (conventional), (ii) low‐rate burst mode TENS that caused strong non‐painful phasic muscle twitching (acupuncture like) or (iii) no current (placebo) TENS. Main outcome measure: Difference between conventional TENS and AL‐TENS in cold pain threshold relative to pre‐TENS baseline after 25 min of stimulation. Results: No differences were detected for CPT or cold pain intensity during conventional TENS compared with AL‐TENS. When compared with placebo TENS, the confidence intervals for the ratio of intervention CPT to baseline CPT, for both AL‐TENS (0·966, 1·424) and conventional TENS (0·948, 1·401), were close to the positive side of one, although neither reached statistical significance. Conclusions: Unlike some previous studies, the present study detected no differences in hypoalgesia between AL‐TENS, conventional TENS and placebo (no current) TENS during stimulation.     

Altered central nervous system processing of noxious stimuli contributes to decreased nociceptive responding in individuals at risk for hypertension

Previous evidence indicates that individuals with hypertension and those at increased risk for the disorder exhibit decreased pain perception. To test the hypothesis that attenuation of nociceptive processing in individuals at genetic risk for hypertension is related to differential central modulation of nociceptive transmission, the present study examined descending modulation, alpha-motoneuron excitability, and temporal summation of nociceptive input in young adults with and without a parental history of hypertension. Nociceptive flexion (NFR) and non-nociceptive Hoffman reflexes were assessed at rest and during performance of a mental arithmetic task. Temporal summation was assessed by examining NFR threshold in response to a series of five electrical pulses delivered at 2 Hz. Compared to participants without a parental history of hypertension, offspring of individuals with hypertension exhibited significantly higher NFR thresholds, suggesting that risk for hypertension may be associated with enhanced activation of central pain inhibition pathways.     

Hypoalgesic Effect of the Transcutaneous Electrical Nerve Stimulation Following Inguinal Herniorrhaphy: A Randomized,Controlled Trial

We investigated the effect of transcutaneous electrical nerve stimulation (TENS) for inguinal herniorrhaphy postoperative pain control in a prospective, randomized, double-blinded, placebo-controlled study. Forty patients undergoing unilateral inguinal herniorrhaphy with an epidural anesthetic technique were randomly allocated to receive either active TENS or placebo TENS. Postoperative pain was evaluated using a standard 10-point numeric rating scale (NRS). Analgesic requirements were also recorded. TENS (100 Hz, strong but comfortable sensory intensity) was applied for 30 minutes through 4 electrodes placed around the incision twice, 2 and 4 hours after surgery. Pain was assessed before and after each application of TENS and 8 and 24 hours after surgery. In the group treated with active TENS, pain intensity was significantly lower 2 hours (P = .028), 4 hours (P = .022), 8 hours (P = .006), and 24 hours (P = .001) after the surgery when compared with the group that received placebo TENS. Active TENS also decreased analgesic requirements in the postoperative period when compared with placebo TENS (P = .001). TENS is thus beneficial for postoperative pain relief after inguinal herniorrhaphy; it has no observable side effects, and the pain-reducing effect continued for at least 24 hours. Consequently, the routine use of TENS after inguinal herniorrhaphy is recommended.PerspectiveThis study presents the hypoalgesic effect of high-frequency TENS for postoperative pain after inguinal herniorrhaphy. This may reinforce findings from basic science showing an opioid-like effect provided by TENS, given that high-frequency TENS has been shown to activate δ-opioid receptors.     

Reactivity to superficial and deep stimuli in patients with chronic musculoskeletal pain

In this study, we evaluated pain sensitivity in patients with fibromyalgia or other types of chronic, diffuse musculoskeletal pain to establish whether fibromyalgia represents the end of a continuum of dysfunction in the nociceptive system. One hundred and forty five patients and 22 healthy subjects (HS) completed an epidemiological questionnaire to provide information about fatigue, stiffness, sleep, the intensity of pain (VAS 0–100) and its extent both at onset and at present. Algometry was performed at all American College of Rheumatology (ACR) tender points and at ten control points. Patients were divided into five main groups: fibromyalgia (FS) patients, secondary-concomitant fibromyalgia (SCFS) patients, patients with widespread pain (WP) but not reaching the ACR criterion of 11 tender points, patients with diffuse multiregional pain (MP) not reaching the ACR criteria (widespread pain, tender point counts), and patients with multiregional pain associated with at least 11 tender points (MPTE). von Frey monofilaments were used to assess superficial punctate pressure pain thresholds. Heat and cold pain thresholds were determined with a thermal stimulator. Ischemic pain was assessed by the cold pressure test and the submaximal effort tourniquet test. The scores for stiffness and present pain intensity gradually increased concomitantly with the increase in tender point count and pain extent. The pressure pain thresholds for positive tender and positive control points were significantly lower in the SCFS, FS and MPTE groups than in HS, MP and WP groups, the latter three groups displaying similar values. In all groups, there were no differences in pain thresholds between positive tender and positive control points. The heat pain threshold and the pain threshold in the cold pressure test were lower in the FS and SCFS groups than in HS. The cold pressure tolerance was lower in patients with widespread pain than in HS. In the von Frey test, all patient groups except MP had similar values, which were significantly lower than in HS. Finally, all patient groups displayed lower tourniquet tolerance than HS. In each psychophysical test, patients with widespread pain and patients with multiregional pain showed similar thresholds; however, the thresholds in the MP or MPTE groups differed from those in the FS and SCFS groups. In the FS group, pain thresholds and pain tolerance did not differ according to the presence of ongoing pain at the stimulated site and were not correlated to ongoing pain. The results indicate that dysfunction in the nociceptive system is already present in patients with multiregional pain with a low tender point count; it becomes more and more severe as the positive tender point count and pain extent increase and it is maximal in fibromyalgia patients.     

Long-term maintenance of the analgesic effects of transcranial magnetic stimulation in fibromyalgia

We assessed for the first time the long-term maintenance of repetitive transcranial magnetic stimulation (rTMS)-induced analgesia in patients with chronic widespread pain due to fibromyalgia. Forty consecutive patients were randomly assigned, in a double-blind fashion, to 2 groups: one receiving active rTMS (n = 20) and the other, sham stimulation (n = 20), applied to the left primary motor cortex. The stimulation protocol consisted of 14 sessions: an “induction phase” of 5 daily sessions followed by a “maintenance phase” of 3 sessions a week apart, 3 sessions a fortnight apart, and 3 sessions a month apart. The primary outcome was average pain intensity over the last 24 hours, measured before each stimulation from day 1 to week 21 and at week 25 (1 month after the last stimulation). Other outcomes measured included quality of life, mood and anxiety, and several parameters of motor cortical excitability. Thirty patients completed the study (14 in the sham stimulation group and 16 in the active stimulation group). Active rTMS significantly reduced pain intensity from day 5 to week 25. These analgesic effects were associated with a long-term improvement in items related to quality of life (including fatigue, morning tiredness, general activity, walking, and sleep) and were directly correlated with changes in intracortical inhibition. In conclusion, these results suggest that TMS may be a valuable and safe new therapeutic option in patients with fibromyalgia.     

Effects of treatment of peripheral pain generators in fibromyalgia patients

Fibromyalgia syndrome (FS) frequently co‐occurs with regional pain disorders. This study evaluated how these disorders contribute to FS, by assessing effects of local active vs placebo treatment of muscle/joint pain sources on FS symptoms. Female patients with (1) FS+myofascial pain syndromes from trigger points (n=68), or (2) FS+joint pain (n=56) underwent evaluation of myofascial/joint symptoms [number/intensity of pain episodes, pressure pain thresholds at trigger/joint site, paracetamol consumption] and FS symptoms [pain intensity, pressure pain thresholds at tender points, pressure and electrical pain thresholds in skin, subcutis and muscle in a non‐painful site]. Patients of both protocols were randomly assigned to two groups [34 each for (1); 28 each for (2)] to receive active or placebo local TrP or joint treatment [injection/hydroelectrophoresis] on days 1 and 4. Evaluations were repeated on days 4 and 8. After therapy, in active – but not placebo‐treated groups: number and intensity of myofascial/joint episodes and paracetamol consumption decreased and pressure thresholds at trigger/joint increased (p<0.001); FS pain intensity decreased and all thresholds increased progressively in tender points and the non‐painful site (p<0.0001). At day 8, all placebo‐treated patients requested active local therapy (days 8 and 11) vs only three patients under active treatment. At a 3‐week follow‐up, FS pain was still lower than basis in patients not undergoing further therapy and had decreased in those undergoing active therapy from day 8 (p<0.0001). Localized muscle/joint pains impact significantly on FS, probably through increased central sensitization by the peripheral input; their systematic identification and treatment are recommended in fibromyalgia.     

Effects of acupuncture and placebo TENS in addition to exercise in treatment of rotator cuff tendinitis

OBJECTIVE: To compare the effect of acupuncture with placebo transcutaneous electrical nerve stimulation (TENS) when added to the exercise treatment of rotator cuff tendinitis with respect to pain, shoulder movements and function. DESIGN: Prospective alternate allocation controlled trial. SETTING: Outpatient department. PATIENTS: Thirty-three patients (12 women and 21 men) were included in the study. All had clinically diagnosed rotator cuff tendinitis. INTERVENTION: Both groups underwent a standardized training programme. Each patient received in addition either 10 treatments with acupuncture or placebo TENS, 1-2 times per week. MAIN OUTCOME MEASURES: The parameters investigated were intensity of pain (measured with visual analogue scale), active, passive as well as functional movements in the shoulder (hand in neck (HIN) and pour out of a pot (POP)). Patients were tested before treatment, after treatment and at a six-month follow-up. Medicine intake, ability to lie on the affected side and sleep disturbances were evaluated. A subjective assessment was made after the treatment and at follow-up. RESULTS: Sixteen patients had acupuncture, 17 placebo TENS. Eight patients endured pain at rest in the placebo TENS group, and 10 in the acupuncture group. After treatment both groups improved, the improvement persisted at the six-month follow-up. Both groups increased range of movement. Except for the functional test HIN in the acupuncture group, there were no differences between the groups regarding other parameters investigated directly after treatment or at six-month follow-up. CONCLUSION: There is no difference between the effect of additional acupuncture treatment and placebo TENS in the treatment of rotator cuff tendinitis.     

Effectiveness of transcutaneous electrical nerve stimulation on postoperative pain with movement.

This study tested the effectiveness of episodic transcutaneous electrical nerve stimulation (TENS) as a supplement to pharmacologic analgesia on pain with movement and at rest after abdominal surgery and evaluated whether its use during walking and vital capacity maneuvers enhances performance of these activities. TENS, with a modulated frequency, intensity as high as the subject could tolerate, and electrodes placed on either side and parallel to the incision, was compared to placebo TENS and pharmacologic analgesia alone (control) by using a crossover design. Self-report of pain intensity, walking function, and vital capacity were assessed on 33 subjects. TENS resulted in significantly less pain than the control during both walking (P <.5) and vital capacity activities (P <.1) and significantly less pain than placebo TENS during vital capacity (P <.01). TENS also produced significantly better gait speeds than the control (P <.05) and greater gait distances (P <.01) than the control and placebo TENS. Vital capacity and pain intensity at rest were not significantly different among the 3 treatments. These results suggest TENS reduces pain intensity during walking and deep breathing and increases walking function postoperatively when used as a supplement to pharmacologic analgesia. The lack of effect on pain at rest supports the hypothesis that TENS works through reducing hyperalgesia.     

Intact cognitive inhibition in patients with fibromyalgia but evidence of declined processing speed

Patients with fibromyalgia frequently report cognitive complaints. In this study we examined performance on 2 cognitive inhibition tests, the Stroop Color-Word Test (SCWT) and the Multi-Source Interference Test (MSIT), in 35 female patients with fibromyalgia and 35 age-matched healthy female controls. Experimental pressure pain thresholds (PPT) were determined, and fibromyalgia patients rated their current pain on a visual analog scale and completed the pain and fatigue subscales of the Fibromyalgia Impact Questionnaire. Further, all subjects completed questionnaires assessing symptoms of pain catastrophizing, depression, and anxiety. Significant group differences were found for SCWT and MSIT performance in both the neutral (N) and interference (I) conditions with slower reaction times in patients versus controls. However, no significant group differences were found for the difference (I-N) or proportion (I/N) scores, or on the number of errors made. For patients, pain experienced during PPT correlated significantly to several indices of cognition. Psychosocial variables were not related to cognitive test performance. Fibromyalgia patients performed worse on both tests but to a similar extent for the neutral condition and the interference condition, indicating that there is no specific problem in cognitive inhibition. Evidence of decreased mental processing and/or psychomotor speed was found in patients with fibromyalgia. PERSPECTIVE: Fibromyalgia patients performed worse on interference tests, but no specific problem in cognitive inhibition was found. Decreased reaction time performance may instead point to an underlying problem of psychomotor or mental processing speed in fibromyalgia. Future studies should examine potential deficits in psychomotor function in fibromyalgia patients in more detail.