A preliminary study of transcranial direct current stimulation for the treatment of refractory chronic pelvic pain

Effectiveness of transcranial direct current stimulation preceding cognitive behavioural management for chronic low back pain: sham controlled double blinded randomised controlled trial

OBJECTIVE

To evaluate the effectiveness of transcranial direct current stimulation alone and in combination with cognitive behavioural management in patients with non-specific chronic low back pain.

DESIGN

Double blind parallel group randomised controlled trial with six months' follow-up conducted May 2011-March 2013. Participants, physiotherapists, assessors, and analyses were blinded to group allocation.

SETTING

Interdisciplinary chronic pain centre.

PARTICIPANTS

135 participants with non-specific chronic low back pain >12 weeks were recruited from 225 patients assessed for eligibility.

INTERVENTION

Participants were randomised to receive anodal (20 minutes to motor cortex at 2 mA) or sham transcranial direct current stimulation (identical electrode position, stimulator switched off after 30 seconds) for five consecutive days immediately before cognitive behavioural management (four week multidisciplinary programme of 80 hours).

MAIN OUTCOMES MEASURES

Two primary outcome measures of pain intensity (0-100 visual analogue scale) and disability (Oswestry disability index) were evaluated at two primary endpoints after stimulation and after cognitive behavioural management.

RESULTS

Analyses of covariance with baseline values (pain or disability) as covariates showed that transcranial direct current stimulation was ineffective for the reduction of pain (difference between groups on visual analogue scale 1 mm (99% confidence interval -8.69 mm to 6.3 mm; P=0.68)) and disability (difference between groups 1 point (-1.73 to 1.98; P=0.86)) and did not influence the outcome of cognitive behavioural management (difference between group 3 mm (-10.32 mm to 6.73 mm); P=0.58; difference between groups on Oswestry disability index 0 point (-2.45 to 2.62); P=0.92). The stimulation was well tolerated with minimal transitory side effects.

CONCLUSIONS

This results of this trial on the effectiveness of transcranial direct current stimulation for the reduction of pain and disability do not support its clinical use for managing non-specific chronic low back pain.Trial registration Current controlled trials ISRCTN89874874.

Regulatory Considerations for the Clinical and Research Use of Transcranial Direct Current Stimulation (tDCS): review and recommendations from an expert panel

The field of transcranial electrical stimulation (tES) has experienced significant growth in the past 15 years. One of the tES techniques leading this increased interest is transcranial direct current stimulation (tDCS). Significant research efforts have been devoted to determining the clinical potential of tDCS in humans. Despite the promising results obtained with tDCS in basic and clinical neuroscience, further progress has been impeded by a lack of clarity on international regulatory pathways. We therefore convened a group of research and clinician experts on tDCS to review the research and clinical use of tDCS. In this report, we review the regulatory status of tDCS, and we summarize the results according to research, off-label and compassionate use of tDCS in the following countries: Australia, Brazil, France, Germany, India, Iran, Italy, Portugal, South Korea, Taiwan and United States. Research use, off label treatment and compassionate use of tDCS are employed in most of the countries reviewed in this study. It is critical that a global or local effort is organized to pursue definite evidence to either approve and regulate or restrict the use of tDCS in clinical practice on the basis of adequate randomized controlled treatment trials.

Investigation of central nervous system dysfunction in chronic pelvic pain using magnetic resonance spectroscopy and noninvasive brain stimulation

BACKGROUND

Recent studies demonstrate that chronic pelvic pain is associated with altered afferent sensory input resulting in maladaptive changes in the neural circuitry of pain. To better understand the central changes associated with chronic pelvic pain, we investigated the contributions of critical pain-related neural circuits using single-voxel proton magnetic resonance spectroscopy (MRS) and transcranial direct current stimulation (tDCS).

METHODS

We measured concentrations of neural metabolites in 4 regions of interest (thalamus, anterior cingulate cortex, primary motor, and occipital cortex [control]) at baseline and after 10 days of active or sham tDCS in patients with chronic pelvic pain. We then compared our results to those observed in healthy controls, matched by age and gender.

RESULTS

We observed a significant increase in pain thresholds after active tDCS compared with sham conditions. There was a correlation between metabolite concentrations at baseline and quantitative sensory assessments. Chronic pelvic pain patients had significantly lower levels of NAA/Cr in the primary motor cortex compared with healthy patients.

CONCLUSIONS

tDCS increases pain thresholds in patients with chronic pelvic pain. Biochemical changes in pain-related neural circuits are associated with pain levels as measured by objective pain testing. These findings support the further investigation of targeted cortical neuromodulatory interventions for chronic pelvic pain.

Non-invasive brain stimulation techniques for chronic pain

BACKGROUND

This is an updated version of the original Cochrane review published in 2010, Issue 9. Non-invasive brain stimulation techniques aim to induce an electrical stimulation of the brain in an attempt to reduce chronic pain by directly altering brain activity. They include repetitive transcranial magnetic stimulation (rTMS), cranial electrotherapy stimulation (CES), transcranial direct current stimulation (tDCS) and reduced impedance non-invasive cortical electrostimulation (RINCE).

OBJECTIVES

To evaluate the efficacy of non-invasive brain stimulation techniques in chronic pain.

SEARCH METHODS

We searched CENTRAL (2013, Issue 6), MEDLINE, EMBASE, CINAHL, PsycINFO, LILACS and clinical trials registers. The original search for the review was run in November 2009 and searched all databases from their inception. To identify studies for inclusion in this update we searched from 2009 to July 2013.

SELECTION CRITERIA

Randomised and quasi-randomised studies of rTMS, CES, tDCS or RINCE if they employed a sham stimulation control group, recruited patients over the age of 18 with pain of three months duration or more and measured pain as a primary outcome.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted and verified data. Where possible we entered data into meta-analyses. We excluded studies judged as being at high risk of bias from the analysis. We used the GRADE system to summarise the quality of evidence for core comparisons.

MAIN RESULTS

We included an additional 23 trials (involving 773 participants randomised) in this update, making a total of 56 trials in the review (involving 1710 participants randomised). This update included a total of 30 rTMS studies, 11 CES, 14 tDCS and one study of RINCE(the original review included 19 rTMS, eight CES and six tDCS studies). We judged only three studies as being at low risk of bias across all criteria.Meta-analysis of studies of rTMS (involving 528 participants) demonstrated significant heterogeneity. Pre-specified subgroup analyses suggest that low-frequency stimulation is ineffective (low-quality evidence) and that rTMS applied to the dorsolateral prefrontal cortex is ineffective (very low-quality evidence). We found a short-term effect on pain of active high-frequency stimulation of the motor cortex in single-dose studies (low-quality evidence, standardised mean difference (SMD) 0.39 (95% confidence interval (CI) -0.27 to -0.51 P < 0.01)). This equates to a 12% (95% CI 8% to 15%) reduction in pain, which does not exceed the pre-established criteria for a minimal clinically important difference (≥ 15%). Evidence for multiple-dose studies was heterogenous but did not demonstrate a significant effect (very low-quality evidence).For CES (six studies, 270 participants) no statistically significant difference was found between active stimulation and sham (low-quality evidence).Analysis of tDCS studies (11 studies, 193 people) demonstrated significant heterogeneity and did not find a significant difference between active and sham stimulation (very low-quality evidence). Pre-specified subgroup analysis of tDCS applied to the motor cortex (n = 183) did not demonstrate a statistically significant effect and this lack of effect was consistent for subgroups of single or multiple-dose studies.One small study (n = 91) at unclear risk of bias suggested a positive effect of RINCE over sham stimulation on pain (very low-quality evidence).Non-invasive brain stimulation appears to be frequently associated with minor and transient side effects, though there were two reported incidences of seizure related to active rTMS in the included studies.

AUTHORS' CONCLUSIONS

Single doses of high-frequency rTMS of the motor cortex may have small short-term effects on chronic pain. It is likely that multiple sources of bias may exaggerate this observed effect. The effects do not meet the predetermined threshold of minimal clinical significance and multiple-dose studies do not consistently demonstrate effectiveness. The available evidence suggests that low-frequency rTMS, rTMS applied to the pre-frontal cortex, CES and tDCS are not effective in the treatment of chronic pain. While the broad conclusions for rTMS and CES have not changed substantially, the addition of this new evidence and the application of the GRADE system has modified some of our interpretation and the conclusion regarding the effectiveness of tDCS has changed. We recommend that previous readers should re-read this update. There is a need for larger, rigorously designed studies, particularly of longer courses of stimulation. It is likely that future evidence may substantially impact upon the presented results.

Non-surgical interventions for the management of chronic pelvic pain

BACKGROUND

Chronic pelvic pain is a common and debilitating condition; its aetiology is multifactorial, involving social, psychological and biological factors. The management of chronic pelvic pain is challenging, as despite interventions involving surgery, many women remain in pain without a firm gynaecological diagnosis.

OBJECTIVES

To assess the effectiveness and safety of non-surgical interventions for women with chronic pelvic pain.

SEARCH METHODS

We searched the Menstrual Disorders and Subfertility Group Specialised Register. We also searched (from inception to 5 February 2014) AMED, CENTRAL, MEDLINE, EMBASE, PsycINFO, CINAHL and LILACS. We handsearched sources such as citation lists, trial registers and conference proceedings.

SELECTION CRITERIA

Randomised controlled trials (RCTs) on non-surgical management of chronic pelvic pain were eligible for inclusion. We included studies of women with a diagnosis of pelvic congestion syndrome or adhesions but excluded those with pain known to be caused by endometriosis, primary dysmenorrhoea (period pain), active chronic pelvic inflammatory disease or irritable bowel syndrome. We considered studies of any non-surgical intervention, including lifestyle, physical, medical and psychological treatments.

DATA COLLECTION AND ANALYSIS

Study selection, quality assessment and data extraction were performed independently by two review authors. Meta-analysis was performed using the Peto odds ratio (Peto OR) for dichotomous outcomes and the mean difference (MD) for continuous outcomes, with 95% confidence intervals (CIs). The primary outcome measure was pain relief, and secondary outcome measures were psychological outcomes, quality of life, requirement for analgesia and adverse effects. The quality of the evidence was assessed by using GRADE methods.

MAIN RESULTS

Twenty-one RCTs were identified that involved non-surgical management of chronic pelvic pain: 13 trials were included in the review, and eight were excluded. The studies included a total of 750 women-406 women in the intervention groups and 344 in the control groups. Included studies had high attrition rates, and investigators often did not blind adequately or did not clearly describe randomisation procedures. Medical treatment versus placebo Progestogen (medroxyprogesterone acetate (MPA)) was more effective than placebo at the end of treatment in terms of the number of women achieving a greater than 50% reduction in visual analogue scale (VAS) pain score immediately after treatment (Peto OR 3.00, 95% CI 1.70 to 5.31, two studies, n = 204, I(2) = 22%, moderate-quality evidence). Evidence of benefit was maintained up to nine months after treatment (Peto OR 2.09, 95% CI 1.18 to 3.71, two studies, n = 204, I(2) = 0%, moderate-quality evidence). Women treated with progestogen reported more adverse effects (e.g. weight gain, bloatedness) than those given placebo (high-quality evidence). The estimated effect of lofexidine on pain outcomes when compared with placebo was compatible with benefit and harm (Peto OR 0.42, 95% CI 0.11 to 1.61, one study, 39 women, low-quality evidence). Women in the lofexidine group reported more adverse effects (including drowsiness and dry mouth) than women given placebo (moderate-quality evidence). Head-to-head comparisons of medical treatments Head-to-head comparisons showed that women taking goserelin had greater improvement in pelvic pain score (MD 3, 95% CI 2.08 to 3.92, one study, n = 47, moderate-quality evidence) at one year than those taking progestogen. Women taking gabapentin had a lower VAS pain score than those taking amytriptyline (MD -1.50, 95% CI -2.06 to -0.94, n = 40, low-quality evidence). Study authors reported that no statistically significant difference was observed in the rate of adverse effects among women taking gabapentin compared with women given amytriptyline. The study comparing goserelin versus progestogen did not report on adverse effects. Psychological treatment Women who underwent reassurance ultrasound scans and received counselling were more likely to report improved pain than those treated with a standard 'wait and see' policy (Peto OR 6.77, 95% CI 2.83 to 16.19, n = 90, low-quality evidence). Significantly more women who had writing therapy as a disclosure reported improvement in pain than those in the non-disclosure group (Peto OR 4.47, 95% CI 1.41 to 14.13, n = 48, very low-quality evidence). No difference between groups in pain outcomes was noted when other psychological therapies were compared with standard care or placebo (quality of evidence ranged from very low to low). Studies did not report on adverse effects. Complementary therapy Distension of painful pelvic structures was more effective for pain when compared with counselling (MD 35.8, 95% CI 23.08 to 48.52 on a zero to 100 scale, one study, n = 48, moderate-quality evidence). No difference in pain levels was observed when magnetic therapy was compared with use of a control magnet (very low-quality evidence). Studies did not report on adverse effects.The results of studies examining psychological and complementary therapies could not be combined to yield meaningful results.

AUTHORS' CONCLUSIONS

Evidence of moderate quality supports progestogen as an option for chronic pelvic pain, with efficacy reported during treatment. In practice, this option may be most acceptable among women unconcerned about progestogenic adverse effects (e.g. weight gain, bloatedness-the most common adverse effects). Although some evidence suggests possible benefit of goserelin when compared with progestogen, gabapentin as compared with amytriptyline, ultrasound versus 'wait and see' and writing therapy versus non-disclosure, the quality of evidence is generally low, and evidence is drawn from single studies.Given the prevalence and healthcare costs associated with chronic pelvic pain in women, RCTs of other medical, lifestyle and psychological interventions are urgently required.

Therapeutic time window of noninvasive brain stimulation for pain treatment: inhibition of maladaptive plasticity with early intervention

Neuromodulatory effects of noninvasive brain stimulation (NIBS) have been extensively studied in chronic disorders such as major depression, chronic pain and stroke. However, few studies have explored the use of these techniques in acute conditions. A possible use of NIBS in acute disorders is to prevent or reverse ongoing maladaptive plastic alterations, seemingly responsible for treatment refractoriness and detrimental behavioral changes. In this review, the authors discuss the potential role of NIBS in blocking maladaptive plasticity using the transition of acute to chronic pain in conditions such as postsurgical pain, central poststroke pain, pain after spinal cord injury and pain after traumatic brain injury as a model. The authors also present suggestions for clinical trial design using NIBS in the acute stage of illnesses.

Effects of non-pharmacological pain treatments on brain states

OBJECTIVE

To (1) evaluate the effects of a single session of four non-pharmacological pain interventions, relative to a sham tDCS procedure, on pain and electroencephalogram- (EEG-) assessed brain oscillations, and (2) determine the extent to which procedure-related changes in pain intensity are associated with changes in brain oscillations.

METHODS

30 individuals with spinal cord injury and chronic pain were given an EEG and administered measures of pain before and after five procedures (hypnosis, meditation, transcranial direct current stimulation [tDCS], neurofeedback, and a control sham tDCS procedure).

RESULTS

Each procedure was associated with a different pattern of changes in brain activity, and all active procedures were significantly different from the control procedure in at least three bandwidths. Very weak and mostly non-significant associations were found between changes in EEG-assessed brain activity and pain.

CONCLUSIONS

Different non-pharmacological pain treatments have distinctive effects on brain oscillation patterns. However, changes in EEG-assessed brain oscillations are not significantly associated with changes in pain, and therefore such changes do not appear useful for explaining the benefits of these treatments.

SIGNIFICANCE

The results provide new findings regarding the unique effects of four non-pharmacological treatments on pain and brain activity.

Putative physiological mechanisms underlying tDCS analgesic effects

Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique that induces changes in excitability, and activation of brain neurons and neuronal circuits. It has been observed that beyond regional effects under the electrodes, tDCS also alters activity of remote interconnected cortical and subcortical areas. This makes the tDCS stimulation technique potentially promising for modulation of pain syndromes. Indeed, utilizing specific montages, tDCS resulted in analgesic effects in experimental settings, as well as in post-operative acute pain and chronic pain syndromes. The promising evidence of tDCS-induced analgesic effects raises the challenging and complex question of potential physiologic mechanisms that underlie/mediate the accomplished pain relief. Here we present hypotheses on how the specific montages and targets for stimulation may affect the pain processing network.

Therapeutic effects of non-invasive brain stimulation with direct currents (tDCS) in neuropsychiatric diseases

Neuroplasticity, which is the dynamic structural and functional reorganization of central nervous system connectivity due to environmental and internal demands, is recognized as a major physiological basis for adaption of cognition, and behavior, and thus of utmost importance for normal brain function. Pathological alterations of plasticity are increasingly explored as pathophysiological foundation of diverse neurological and psychiatric diseases. Non-invasive brain stimulation techniques (NIBS), such as repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS), are able to induce and modulate neuroplasticity in humans. Therefore, they have potential to alter pathological plasticity on the one hand, and foster physiological plasticity on the other, in neuropsychiatric diseases to reduce symptoms, and enhance rehabilitation. tDCS is an emerging NIBS tool, which induces glutamatergic plasticity via application of relatively weak currents through the scalp in humans. In the last years its efficacy to treat neuropsychiatric diseases has been explored increasingly. In this review, we will give an overview of pathological alterations of plasticity in neuropsychiatric diseases, gather clinical studies involving tDCS to ameliorate symptoms, and discuss future directions of application, with an emphasis on optimizing stimulation effects.

Is transcranial alternating current stimulation effective in modulating brain oscillations?

Transcranial alternating current stimulation (tACS) is a promising tool for modulating brain oscillations, as well as a possible therapeutic intervention. However, the lack of conclusive evidence on whether tACS is able to effectively affect cortical activity continues to limit its application. The present study aims to address this issue by exploiting the well-known inhibitory alpha rhythm in the posterior parietal cortex during visual perception and attention orientation. Four groups of healthy volunteers were tested with a Gabor patch detection and discrimination task. All participants were tested at the baseline and selective frequencies of tACS, including Sham, 6 Hz, 10 Hz, and 25 Hz. Stimulation at 6 Hz and 10 Hz over the occipito-parietal area impaired performance in the detection task compared to the baseline. The lack of a retinotopically organised effect and marginal frequency-specificity modulation in the detection task force us to be cautious about the effectiveness of tACS in modulating brain oscillations. Therefore, the present study does not provide significant evidence for tACS reliably inducing direct modulations of brain oscillations that can influence performance in a visual task.

Pain

Invasive stimulation of the motor (precentral) cortex using surgically implanted epidural electrodes is indicated for the treatment of neuropathic pain that is refractory to medical treatment. Controlled trials have demonstrated the efficacy of epidural motor cortex stimulation (MCS), but MCS outcome remains variable and validated criteria for selecting good candidates for implantation are lacking. Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive approach that could be used as a preoperative tool to predict MCS outcome and also could serve as a therapeutic procedure in itself to treat pain disorders. This requires repeated rTMS sessions and a maintenance protocol. Other studies have also demonstrated the efficacy of transcranial direct current stimulation (tDCS) in relieving chronic pain syndromes. The most studied target is the precentral cortex, but other targets, such as the prefrontal and parietal cortices, could be of interest. The analgesic effects of cortical stimulation relate to the activation of various circuits modulating neural activities in remote structures, such as the thalamus, limbic cortex, insula, or descending inhibitory controls. In addition to the treatment of refractory neuropathic pain by epidural MCS, new developments of this type of strategy are ongoing, for other types of pain syndrome and stimulation techniques.

No effect of a single session of transcranial direct current stimulation on experimentally induced pain in patients with chronic low back pain--an exploratory study

Transcranial direct current stimulation (tDCS) has been shown to modulate cortical excitability. A small number of studies suggested that tDCS modulates the response to experimental pain paradigms. No trials have been conducted to evaluate the response of patients already suffering from pain, to an additional experimental pain before and after tDCS. The present study investigated the effect of a single session of anodal, cathodal and sham stimulation (15 mins/1 mA) over the primary motor cortex on the perceived intensity of repeated noxious thermal and electrical stimuli and on elements of quantitative sensory testing (thermal pain and perception thresholds) applied to the right hand in 15 patients with chronic low back pain. The study was conducted in a double-blind sham-controlled and cross-over design. No significant alterations of pain ratings were found. Modalities of quantitative sensory testing remained equally unchanged. It is therefore hypothesized that a single 15 mins session of tDCS at 1 mA may not be sufficient to alter the perception of experimental pain and in patients with chronic pain. Further studies applying repetitive tDCS to patients with chronic pain are required to fully answer the question whether experimental pain perception may be influenced by tDCS over the motor cortex.

Effectiveness of anodal transcranial direct current stimulation in patients with chronic low back pain: design, method and protocol for a randomised controlled trial

Background

Electrical stimulation of central nervous system areas with surgically implanted stimulators has been shown to result in pain relief. To avoid the risks and side effects of surgery, transcranial direct current stimulation is an option to electrically stimulate the motor cortex through the skull. Previous research has shown that transcranial direct current stimulation relieves pain in patients with fibromyalgia, chronic neuropathic pain and chronic pelvic pain. Evidence indicates that the method is pain free, safe and inexpensive.

Methods/Design

A randomised controlled trial has been designed to evaluate the effect of transcranial direct current stimulation over the motor cortex for pain reduction in patients with chronic low back pain. It will also investigate whether transcranial direct current stimulation as a prior treatment enhances the symptom reduction achieved by a cognitive-behavioural group intervention. Participants will be randomised to receive a series of 5 days of transcranial direct current stimulation (2 mA, 20 mins) or 20 mins of sham stimulation; followed by a cognitive-behavioural group programme. The primary outcome parameters will measure pain (Visual Analog Scale) and disability (Oswestry Disability Index). Secondary outcome parameters will include the Fear Avoidance Beliefs Questionnaire, the Funktionsfragebogen Hannover (perceived function), Hospital Anxiety Depression Scale, bothersomeness and Health Related Quality of Life (SF 36), as well as Patient-Perceived Satisfactory Improvement. Assessments will take place immediately prior to the first application of transcranial direct current stimulation or sham, after 5 consecutive days of stimulation, immediately after the cognitive-behavioural group programme and at 4 weeks, 12 weeks and 24 weeks follow-up.

Discussion

This trial will help to determine, whether transcranial direct current stimulation is an effective treatment for patients with chronic low back pain and whether it can further enhance the effects of a cognitive behavioural pain management programme. Trial registration: Current Controlled Trials ISRCTN89874874.

Pelvic floor therapies in chronic pelvic pain syndrome

Chronic pelvic pain syndrome is a poorly understood clinical entity associated with urinary symptoms, pelvic floor dysfunction, and multisystem disorders. Treatment of pelvic floor dysfunction is difficult and often frustrating for the patient as well as for the involved physician. The purpose of this review is to update clinicians on the latest research for the treatment of pelvic floor dysfunction in relation to chronic pelvic pain syndrome.

Modulating cortico-striatal and thalamo-cortical functional connectivity with transcranial direct current stimulation

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that has been shown to alter cortical excitability and activity via application of weak direct currents. Beyond intracortical effects, functional imaging as well as behavioral studies are suggesting additional tDCS-driven alterations of subcortical areas, however, direct evidence for such effects is scarce. We aimed to investigate the impact of tDCS on cortico-subcortical functional networks by seed functional connectivity analysis of different striatal and thalamic regions to prove tDCS-induced alterations of the cortico-striato-thalamic circuit. fMRI resting state data sets were acquired immediately before and after 10 min of bipolar tDCS during rest, with the anode/cathode placed over the left primary motor cortex (M1) and the cathode/anode over the contralateral frontopolar cortex. To control for possible placebo effects, an additional sham stimulation session was carried out. Functional coupling between the left thalamus and the ipsilateral primary motor cortex (M1) significantly increased following anodal stimulation over M1. Additionally, functional connectivity between the left caudate nucleus and parietal association cortices was significantly strengthened. In contrast, cathodal tDCS over M1 decreased functional coupling between left M1 and contralateral putamen. In summary, in this study, we show for the first time that tDCS modulates functional connectivity of cortico-striatal and thalamo-cortical circuits. Here we highlight that anodal tDCS over M1 is capable of modulating elements of the cortico-striato-thalamo-cortical functional motor circuit.

Daily transcranial direct current stimulation (tDCS) leads to greater increases in cortical excitability than second daily transcranial direct current stimulation

BACKGROUND

Evidence from recent clinical trials suggests that transcranial direct current stimulation (tDCS) may have potential in treating neuropsychiatric disorders. However, the optimal frequency at which tDCS sessions should be administered is unknown.

OBJECTIVE/HYPOTHESIS

This study investigated the effects of daily or second daily tDCS sessions on motor cortical excitability, over a 5-day period.

METHODS

Twelve healthy volunteers received daily or second daily sessions of tDCS to the left primary motor cortex over the study period, in a randomized, intraindividual crossover design. Motor cortical excitability was assessed before and after tDCS at each session through responses to transcranial magnetic stimulation.

RESULTS

Over a fixed 5-day period, tDCS induced greater increases in MEP amplitude when given daily rather than second daily. Analyses showed that this difference reflected greater cumulative effects between sessions rather than a greater response to each individual tDCS session.

CONCLUSIONS

These results demonstrate that in the motor cortex of healthy volunteers, tDCS alters cortical excitability more effectively when given daily rather than second daily over a 5-day period.

Application of Patient-Reported Outcomes Measurement Information System to chronic pelvic pain

STUDY OBJECTIVES

To apply the Patient-Reported Outcomes Measurement Information System (PROMIS) recently developed by the National Institutes of Health in patients with chronic pelvic pain. Secondary objectives included evaluation of individual pain categories and of the effect of the occurrence of myofascial abdominal wall and pelvic floor muscle pain.

DESIGN

Retrospective study (Canadian Task Force classification III).

SETTING

Chronic pelvic pain multidisciplinary referral center.

PATIENTS

A total of 149 consecutive patients with chronic pelvic pain provided evaluable results.

INTERVENTIONS

As part of a comprehensive evaluation, patients were assigned diagnoses based on standard criteria, and completed the 96-item short-form PROMIS.

MEASUREMENTS AND MAIN RESULTS

Pain-related and global PROMIS scores were significantly worse than in the reference population (p <.05). The presence of myofascial pain was also associated with worse PROMIS scores.

CONCLUSION

Chronic pelvic pain is associated with impaired quality of life regardless of the diagnosis, including myofascial pain.

Robust observer-based tracking control of hodgkin-huxley neuron systems under environmental disturbances

A nervous system consists of a large number of highly interconnected nerve cells. Nerve cells communicate by generation and transmission of short electrical pulses (action potential). In addition, membrane voltage is the only measurable state in nervous systems. A robust observer-based model reference tracking control is proposed for Hodgkin-Huxley (HH) neuron systems to generate a desired reference response in spite of environmental noises, uncertain initial values, and diffusion currents from other interconnected nerve cells. In order to simplify the robust tracking control design of nonlinear stochastic HH neuron systems, a fuzzy interpolation method is employed to interpolate several linear stochastic systems to approximate a nonlinear stochastic HH neuron system so that the nonlinear robust tracking control problem can be solved by the linear matrix inequality (LMI) technique with the help of Robust Control Toolbox in Matlab. The proposed robust observer-based tracking control scheme can provide new methods for desired action potential generation, suppression of oscillations, and blockage of action potential transmission under environmental noise and diffusion currents. These new methods are useful for patients with different neuron system dysfunctions. Finally, three simulation examples of tracking control of nervous systems are given to illustrate the design procedure and confirm the tracking performance of the proposed method.

Non-invasive brain stimulation techniques for chronic pain

BACKGROUND

Non-invasive brain stimulation techniques aim to induce an electrical stimulation of the brain in an attempt to reduce chronic pain by directly altering brain activity. They include repetitive transcranial magnetic stimulation (rTMS), cranial electrotherapy stimulation (CES) and transcranial direct current stimulation (tDCS).

OBJECTIVES

To evaluate the efficacy of non-invasive brain stimulation techniques in chronic pain.

SEARCH STRATEGY

We searched CENTRAL, MEDLINE, EMBASE, CINAHL, PsycINFO, LILACS, the Cochrane PaPaS Group Trials Register and clinical trials registers.

SELECTION CRITERIA

Randomised and quasi-randomised studies of rTMS, CES or tDCS if they employed a sham stimulation control group, recruited patients over the age of 18 with pain of three months duration or more and measured pain as a primary outcome.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted and verified data. Where possible we entered data into meta-analyses. We excluded studies judged as being at high risk of bias from the analysis.

MAIN RESULTS

We included 33 trials in the review (involving 937 people)(19 rTMS, eight CES and six tDCS). Only one study was judged as being at low risk of bias.Studies of rTMS (involving 368 participants ) demonstrated significant heterogeneity. Pre-specified subgroup analyses suggest that low-frequency stimulation is ineffective. A short-term effect on pain of active high-frequency stimulation of the motor cortex in single-dose studies was suggested (standardised mean difference (SMD) -0.40, 95% confidence interval (CI) -0.26 to -0.54, P < 0.00001). This equates to a 15% (95% CI 10% to 20%) reduction in pain which does not clearly exceed the pre-established criteria for a minimally clinically important difference (> 15%).For CES (four studies, 133 participants) no statistically significant difference was found between active stimulation and sham. Analysis of tDCS studies (five studies, 83 people) demonstrated significant heterogeneity and did not find a significant difference between active and sham stimulation. Pre-specified subgroup analysis of tDCS applied to the motor cortex suggested superiority of active stimulation over sham (SMD -0.59, 95% CI -1.10 to -0.08).Non-invasive brain stimulation appears to be associated with minor and transient side effects.

AUTHORS' CONCLUSIONS

Single doses of high-frequency rTMS of the motor cortex may have small short-term effects on chronic pain. The effects do not clearly exceed the predetermined threshold of minimal clinical significance. Low-frequency rTMS is not effective in the treatment of chronic pain. There is insufficient evidence from which to draw firm conclusions regarding the efficacy of CES or tDCS. The available evidence suggests that tDCS applied to the motor cortex may have short-term effects on chronic pain and that CES may be ineffective. There is a need for further, rigorously designed studies of all types of stimulation.