Preoperative transcranial direct current stimulation: Exploration of a novel strategy to enhance neuroplasticity before surgery to control postoperative pain. A randomized sham-controlled study

Brain-Derived Neurotrophic Factor, Nociception, and Pain

This article examines the involvement of the brain-derived neurotrophic factor (BDNF) in the control of nociception and pain. BDNF, a neurotrophin known for its essential role in neuronal survival and plasticity, has garnered significant attention for its potential implications as a modulator of synaptic transmission. This comprehensive review aims to provide insights into the multifaceted interactions between BDNF and pain pathways, encompassing both physiological and pathological pain conditions. I delve into the molecular mechanisms underlying BDNF's involvement in pain processing and discuss potential therapeutic applications of BDNF and its mimetics in managing pain. Furthermore, I highlight recent advancements and challenges in translating BDNF-related research into clinical practice.

Transcranial Direct Current Stimulation for Anxiety During Laparoscopic Colorectal Cancer Surgery: A Randomized Clinical Trial

Importance

Perioperative anxiety is prevalent among patients undergoing surgical treatment of cancer and often influences their prognosis. Transcranial direct current stimulation (tDCS) has shown potential in the treatment of various anxiety-related disorders, but data on the impact of tDCS on perioperative anxiety are limited.

Objective

To evaluate the effect of tDCS in reducing perioperative anxiety among patients undergoing laparoscopic colorectal cancer (CRC) resection.

Design, Setting, And Participants

This randomized clinical trial was conducted from March to August 2023 at the Affiliated Hospital of Xuzhou Medical University. Patients aged 18 years or older undergoing elective laparoscopic radical resection for CRC were randomly assigned to either the active tDCS group or the sham tDCS group. Intention-to-treat data analysis was performed in September 2023.

Interventions

Patients were randomly assigned to receive 2 sessions of either active tDCS or sham tDCS over the left dorsolateral prefrontal cortex on the afternoon of the day before the operation and in the morning of the day of operation.

Main Outcomes and Measures

The main outcome was the incidence of perioperative anxiety from the day of the operation up to 3 days after the procedure, as measured using the Hospital Anxiety and Depression Scale-Anxiety (HADS-A) subscale (range: 0-21, with higher scores indicating more anxiety). Secondary outcomes included postoperative delirium (assessed by the Confusion Assessment Method or Confusion Assessment Method intensive care unit scale); pain (assessed by the 10-point Numeric Rating Scale [NRS], with scores ranging from 0 [no pain] to 10 [worst pain]); frailty (assessed by the Fatigue, Resistance, Ambulation, Illness and Loss of Weight [FRAIL] Index, with scores ranging from 0 [most robust] to 5 [most frail]; and sleep quality (assessed by the Pittsburgh Sleep Quality Index [PSQI], with scores ranging from 0 to 21 and higher scores indicating worse sleep quality) after the 2 sessions of the tDCS intervention.

Results

A total of 196 patients (mean [SD] age, 63.5 [11.0] years; 124 [63.3%] men) were recruited and randomly assigned to the active tDCS group (98 patients) or the sham tDCS group (98 patients). After the second tDCS intervention on the day of the operation, the incidence of perioperative anxiety was 38.8% in the active tDCS group and 70.4% in the sham tDCS group (relative risk, 0.55 [95% CI, 0.42-0.73]; P < .001). Patients in the active tDCS group vs the sham tDCS group were less likely to have postoperative delirium (8.2% vs 25.5%) and, at 3 days after the operation, had lower median (IQR) pain scores (NRS, 1.0 [1.0-1.0] vs 2.0 [2.0-2.0]), better median (IQR) sleep quality scores (PSQI, 10.5 [10.0-11.0] vs 12.0 [11.0-13.0]), and lower median (IQR) FRAIL Index (2.0 [1.0-2.0] vs 2.0 [2.0-3.0]).

Conclusions and Relevance

Findings of this randomized clinical trial indicate that administration of 2 preoperative sessions of tDCS was associated with a decreased incidence of perioperative anxiety in patients undergoing elective CRC resection. Active tDCS was also associated with better anxiety scores, pain levels, and sleep quality as well as reduced postoperative delirium and frailty. The findings suggest that tDCS may be a novel strategy for improving perioperative anxiety in patients undergoing CRC resection.

Trial Registration

Chinese Clinical Trial Register Identifier: ChiCTR2300068859.

Perioperative Anxiety and Depression in Older Adults: Epidemiology and Treatment

The intervals before and after major surgery is a high-risk period for older adults; in this setting, anxiety and depression are common and serious problems. We comprehensively reviewed current evidence on perioperative anxiety and depression in older adults, focusing on epidemiology, impact, correlates, medication risks, and treatment. Principles of perioperative mental healthcare are proposed based on the findings. Prevalence estimates of clinically significant anxiety and depression range from 5% to 45% for anxiety and 6% to 52% for depression, depending on surgical populations and measurement tools. Anxiety and depression may increase risk for surgical complications and reduce patient participation during rehabilitation. Medical comorbidities, pain, insomnia, cognitive impairment, and delirium are common co-occurring problems. Concomitant uses of central nervous system acting medications (benzodiazepines, anticholinergics, and opioids) amplify the risks of delirium and falls. Based on these findings, we propose that anxiety and depression care should be part of perioperative management in older adults; components include education, psychological support, opioid-sparing pain management, sleep management, deprescribing central nervous system active medications, and continuation and optimization of existing antidepressants. More research is needed to test and improve these care strategies.

When blood pressure refuses to budge: exploring the complexity of resistant hypertension

Resistant hypertension, defined as blood pressure that remains above goal despite using three or more antihypertensive medications, including a diuretic, affects a significant proportion of the hypertensive population and is associated with increased cardiovascular morbidity and mortality. Despite the availability of a wide range of pharmacological therapies, achieving optimal blood pressure control in patients with resistant hypertension remains a significant challenge. However, recent advances in the field have identified several promising treatment options, including spironolactone, mineralocorticoid receptor antagonists, and renal denervation. In addition, personalized management approaches based on genetic and other biomarkers may offer new opportunities to tailor therapy and improve outcomes. This review aims to provide an overview of the current state of knowledge regarding managing resistant hypertension, including the epidemiology, pathophysiology, and clinical implications of the condition, as well as the latest developments in therapeutic strategies and future prospects.

Multifocal tDCS Targeting the Motor Network Modulates Event-Related Cortical Responses During Prolonged Pain

Multifocal transcranial direct current stimulation (tDCS) targeting several brain regions is promising for inducing cortical plasticity. It remains unknown whether multifocal tDCS aimed at the resting-state motor network (network-tDCS) can revert N2-P2 cortical responses otherwise attenuated during prolonged experimental pain. Thirty-eight healthy subjects participated in 2 sessions separated by 24 hours (Day1, Day2) of active (n = 19) or sham (n = 19) network-tDCS. Experimental pain induced by topical capsaicin was maintained for 24 hours and assessed using a numerical rating scale. Electrical detection and pain thresholds, and N2-P2 evoked potentials (electroencephalography) to noxious electrical stimulation were recorded before capsaicin-induced pain (Day1-baseline), after capsaicin application (Day1-post-cap), and after 2 sessions of network-tDCS (Day2). Capsaicin induced moderate pain at Day1-post-cap, which further increased at Day2 in both groups (P = .01). Electrical detection/pain thresholds did not change over time. N2-P2 responses were reduced on Day1-post-cap compared to Day1-baseline (P = .019). At Day2 compared with Day1-post-cap, N2-P2 responses were significantly higher in the Active network-tDCS group (P<.05), while the sham group remained inhibited. These results suggest that tDCS targeting regions associated with the motor network may modulate the late evoked brain responses to noxious peripheral stimulation otherwise initially inhibited by capsaicin-induced pain. PERSPECTIVE: This study extends the evidence of N2-P2 reduction due to capsaicin-induced pain from 30 minutes to 24 hrs. Moreover, 2 sessions of tDCS targeting the motor network in the early stage of nociceptive pain may revert the inhibition of N2-P2 associated with capsaicin-induced pain.

Efficacy of transcranial direct current stimulation on postoperative delirium in elderly patients undergoing lower limb major arthroplasty: A randomized controlled trial

BACKGROUND

Postoperative delirium (POD) is a common and severe postoperative complication in elderly patients undergoing major surgery linked to increased morbidity and mortality. It is reported that transcranial direct current stimulation (tDCS) effectively enhances cognitive function and improves impaired consciousness.

OBJECTIVE

This study aimed to evaluate the efficacy of tDCS on POD in elderly patients undergoing lower limb major arthroplasty, including total hip arthroplasty (THA) or total knee arthroplasty (TKA).

METHODS

Patients aged ≥65 years scheduled for THA or TKA were randomly assigned to receive 2 mA tDCS for 20 min active-tDCS (n = 61) or sham-tDCS (n = 61). The primary outcome was the incidence of POD during the first 3 postoperative days.

RESULTS

All 122 patients (median age, 70 years; 80 women [65.6%]) completed the trial. The incident delirium risk was 4.9% (n = 3) vs. 19.7% (n = 12) in active-tDCS and sham-tDCS groups, respectively (relative risk, 0.250; 95% CI, 0.074 to 0.842; P = 0.013). Compared to the sham-tDCS group, the anxiety and depression scores of patients in the active-tDCS group were lower at 2 h and one day after surgery (P < 0.001 for each), and pain scores of patients in the active-tDCS group were lower during the first three days after surgery (P < 0.05).

CONCLUSION

One session of anodal tDCS over the left dorsolateral prefrontal cortex may decrease the incidence of POD in elderly patients undergoing lower limb major arthroplasty.

The effect of home-based transcranial direct current stimulation in cognitive performance in fibromyalgia: A randomized, double-blind sham-controlled trial

Background

Transcranial Direct Current Stimulation (tDCS) is a promising approach to improving fibromyalgia (FM) symptoms, including cognitive impairment. So, we evaluated the efficacy and safety of home-based tDCS in treating cognitive impairment. Besides, we explored if the severity of dysfunction of the Descendant Pain Modulation System (DPMS) predicts the tDCS effect and if its effect is linked to changes in neuroplasticity as measured by the brain-derived neurotrophic factor (BDNF).

Methods

This randomized, double-blind, parallel, sham-controlled clinical trial, single-center, included 36 women with FM, aged from 30 to 65 years old, assigned 2:1 to receive a-tDCS (n = 24) and s-tDCS (n = 12). The primary outcome was the Trail Making Test's assessment of executive attention, divided attention, working memory (WM), and cognitive flexibility (TMT-B-A). The secondary outcomes were the Controlled Oral Word Association Test (COWAT), the WM by Digits subtest from the Wechsler Adult Intelligence Scale (WAIS-III), and quality of life. Twenty-minute daily sessions of home-based tDCS for 4 weeks (total of 20 sessions), 2 mA anodal-left (F3) and cathodal-right (F4) prefrontal stimulation with 35 cm² carbon electrodes.

Results

GLM showed a main effect for treatment in the TMT-B-A [Wald χ2 = 6.176; Df = 1; P = 0.03]. The a-tDCS improved cognitive performance. The effect size estimated by Cohen's d at treatment end in the TMT-B-A scores was large [-1.48, confidence interval (CI) 95% = -2.07 to-0.90]. Likewise, the a-tDCS effects compared to s-tDCS improved performance in the WM, verbal and phonemic fluency, and quality-of-life scale. The impact of a-tDCS on the cognitive tests was positively correlated with the reduction in serum BDNF from baseline to treatment end. Besides, the decrease in the serum BDNF was positively associated with improving the quality of life due to FM symptoms.

Conclusion

These findings revealed that daily treatment with a home-based tDCS device over l-DLPFC compared to sham stimulation over 4 weeks improved the cognitive impairment in FM. The a-tDCS at home was well-tolerated, underlining its potential as an alternative treatment for cognitive dysfunction. Besides, the a-tDCS effect is related to the severity of DPMS dysfunction and changes in neuroplasticity state.

Clinical trial registration

[www.ClinicalTrials.gov], identifier [NCT03843203].

Effects of transcranial direct current stimulation in pain and opioid consumption after spine surgery

BACKGROUND

Transcranial direct current stimulation (tDCS) has shown promising results in alleviating different types of pain. The present study compares the efficacy of 3 sessions of anodal tDCS applied over primary motor area (M1) or the left dorsolateral prefrontal cortex (DLPFC) or sham on reducing pain and the total opioid consumption in post-operative spine surgery patients.

MATERIALS

Sixty-seven out of 75 eligible patients for post-operative spine surgery were randomly allocated into one of the three experimental groups. Group A received anodal tDCS applied over M1 cortex, group B over left DLPF cortex (2mA, 20 min) and group C received sham tDCS, all for 3 consecutive postoperative days. Patients were evaluated using a visual analogue scale (VAS) and adynamic visual analogue scale (DVAS) at baseline, and on each of the treatment days. The total morphine consumption over the 3 post-operative days was assessed.

RESULTS

Two-way repeated measures ANOVA showed no statistically significant difference in resting VAS between the 3 groups. However, there was significant pain improvement (P< 0.001) in DVAS in both active groups (group A and B) compared to the sham group (group C) in the post-operative period, with no significant difference between the active groups. Morphine consumption was significantly reduced in both active groups compared with the sham group, but there was no difference in consumption between the active groups.

CONCLUSION

There was a significant post-operative reduction in morphine consumption and DVAS scores after three sessions of active tDCS.

SIGNIFICANCE

tDCS is a promising tool for alleviating pain in the field of postoperative spine surgery.

Evaluation of the immediate effects of a single transcranial direct current stimulation session on astrocyte activation, inflammatory response, and pain threshold in naïve rats

Transcranial direct current stimulation (tDCS) has demonstrated clinical benefits such as analgesia, anti-inflammatory, and neuroprotective effects. However, the mechanisms of action of a single tDCS session are poorly characterized. The present study aimed to evaluate the effects of a single tDCS session on pain sensitivity, inflammatory parameters, and astrocyte activity in naive rats. In the first experiment, sixty-day-old male Wistar rats (n=95) were tested for mechanical pain threshold (von Frey test). Afterward, animals were submitted to a single bimodal tDCS (0.5mA, 20minutes) or sham-tDCS session. According to the group, animals were re-tested at different time intervals (30, 60, 120minutes, or 24hours) after the intervention, euthanized, and the cerebral cortex collected for biochemical analysis. A second experiment (n=16) was performed using a similar protocol to test the hypotheses that S100B levels in the cerebrospinal fluid (CSF) are altered by tDCS. Elisa assay quantified the levels of tumor necrosis factor-alfa (TNF-α), interleukin-10 (IL10), S100 calcium-binding protein B (S100B), and Glial fibrillary acidic protein (GFAP). Data were analyzed using ANOVA and independent t-test (P<0.05). Results showed that tDCS decreased pain sensitivity (30 and 60min), cerebral TNF-α and S100B levels (30min). CSF S100B levels increased 30minutes after intervention. There were no differences in IL10 and GFAP levels. TCDS showed analgesic, anti-inflammatory, and neuroprotective effects in naive animals. Therefore, this non-invasive and inexpensive therapy may potentially be a preemptive alternative to reduce pain, inflammation, and neurodegeneration in situations where patients will undergo medical procedures (e.g., surgery).

Impact of bifrontal home-based transcranial direct current stimulation in pain catastrophizing and disability due to pain in fibromyalgia: a randomized, double-blind sham-controlled study

This randomized, double-blind trial tested the hypothesis that twenty sessions of home-based anodal(a)-transcranial direct current stimulation (tDCS) (2mA for 20 min) bifrontal, with anodal on the left dorsolateral prefrontal cortex (l-DLPFC) would be better than sham-(s)-tDCS to reduce scores on Pain Catastrophizing Scale (PCS) and disability-related to pain (DRP) assessed by the Profile of Chronic Pain: Screen (PCP:S) (primary outcomes). Secondary outcomes were depressive symptoms, sleep quality, heat pain threshold (HPT), heat pain tolerance (HPTo), and serum brain-derived-neurotrophic-factor (BDNF). Forty-eight women with fibromyalgia, 30-65 years-old were randomized into 2:1 groups [a-tDCS (n=32) or s-tDCS (n=16)]. Post hoc analysis revealed that a-tDCS reduced the PCS total scores by 51.38% compared to 26.96% in s-tDCS, and a-tDCS reduced PCP:S total scores by 31.43% compared to 19.15% in s-tDCS. The a-tDCS improved depressive symptoms, sleep quality and increased the HPTo. The delta-value in the serum BDNF (mean post treatment end minus pre-treatment) was conversely correlated with the a-tDCS effect in pain catastrophizing. In contrast, the a-tDCS impact on reducing the DRP at the treatment end was positively associated with a reduction in the serum BDNF and improvement of depressive symptoms, sleep quality and pain catastrophizing symptoms. PERSPECTIVE: Home-based bifrontal tDCS with a-tDCS on the l-DLPFC are associated with a moderate effect size (ES) in the following outcomes: (i) Decreased rumination and magnification of pain catastrophizing. (ii) Improved the disability for daily activities due to fibromyalgia symptoms. Overall, these findings support the feasibility of self-applied home-based tDCS on DLPFC to improve fibromyalgia symptoms.

Noninvasive motor cortex stimulation effects on quantitative sensory testing in healthy and chronic pain subjects: a systematic review and meta-analysis

ABSTRACT

One of the potential mechanisms of motor cortex stimulation by noninvasive brain stimulation (NIBS) effects on pain is through the restoration of the defective endogenous inhibitory pain pathways. However, there are still limited data on quantitative sensory testing (QST), including conditioned pain modulation (CPM), supporting this mechanism. This systematic review and meta-analysis aimed to evaluate the effects of noninvasive motor cortex stimulation on pain perception as indexed by changes in QST outcomes. Database searches were conducted until July 2019 to include randomized controlled trials that performed sham-controlled NIBS on the motor cortex in either the healthy and/or pain population and assessed the QST and CPM. Quality of studies was assessed through the Cochrane tool. We calculated the Hedge's effect sizes of QST and CPM outcomes and their 95% confidence intervals (95% CIs) and performed random-effects meta-analyses. Thirty-eight studies were included (1178 participants). We found significant increases of pain threshold in healthy subjects (ES = 0.16, 95% CI = 0.02-0.31, I2 = 22.2%) and pain populations (ES = 0.48, 95% CI = 0.15-0.80, I2 = 68.8%), and homogeneous higher CPM effect (pain ratings reduction) in healthy subjects (ES = -0.39, 95% CI = -0.64 to -0.14, I2 = 17%) and pain populations (ES = -0.35, 95% CI = -0.60 to -0.11, I2 = 0%) in the active NIBS group compared with sham. These results support the idea of top-down modulation of endogenous pain pathways by motor cortex stimulation as one of the main mechanisms of pain reduction assessed by QST, which could be a useful predictive and prognostic biomarker for chronic pain personalized treatment with NIBS.

Evidence-Based Guidelines and Secondary Meta-Analysis for the Use of Transcranial Direct Current Stimulation in Neurological and Psychiatric Disorders

BACKGROUND

Transcranial direct current stimulation has shown promising clinical results, leading to increased demand for an evidence-based review on its clinical effects.

OBJECTIVE

We convened a team of transcranial direct current stimulation experts to conduct a systematic review of clinical trials with more than 1 session of stimulation testing: pain, Parkinson's disease motor function and cognition, stroke motor function and language, epilepsy, major depressive disorder, obsessive compulsive disorder, Tourette syndrome, schizophrenia, and drug addiction.

METHODS

Experts were asked to conduct this systematic review according to the search methodology from PRISMA guidelines. Recommendations on efficacy were categorized into Levels A (definitely effective), B (probably effective), C (possibly effective), or no recommendation. We assessed risk of bias for all included studies to confirm whether results were driven by potentially biased studies.

RESULTS

Although most of the clinical trials have been designed as proof-of-concept trials, some of the indications analyzed in this review can be considered as definitely effective (Level A), such as depression, and probably effective (Level B), such as neuropathic pain, fibromyalgia, migraine, post-operative patient-controlled analgesia and pain, Parkinson's disease (motor and cognition), stroke (motor), epilepsy, schizophrenia, and alcohol addiction. Assessment of bias showed that most of the studies had low risk of biases, and sensitivity analysis for bias did not change these results. Effect sizes vary from 0.01 to 0.70 and were significant in about 8 conditions, with the largest effect size being in postoperative acute pain and smaller in stroke motor recovery (nonsignificant when combined with robotic therapy).

CONCLUSION

All recommendations listed here are based on current published PubMed-indexed data. Despite high levels of evidence in some conditions, it must be underscored that effect sizes and duration of effects are often limited; thus, real clinical impact needs to be further determined with different study designs.

Efficacy of Physical Therapy on Nociceptive Pain Processing Alterations in Patients with Chronic Musculoskeletal Pain: A Systematic Review and Meta-analysis

INTRODUCTION

Chronic musculoskeletal pain is a major health, social, and economic problem. Most of the subjects who suffer from chronic musculoskeletal pain present processes of central sensitization. Temporal summation and conditioned pain modulation are the two most commonly used clinical measures of this. The objective of this review is to evaluate the effects of physical therapy on temporal summation (TS) and conditioned pain modulation (CPM) in patients with chronic musculoskeletal pain.

METHODS

This is a systematic review and meta-analysis. We searched the MEDLINE, EMBASE, CINAHL, EBSCO, PubMed, PEDro, Cochrane Collaboration Trials Register, Cochrane Database of Systematic Reviews, and SCOPUS databases. Different mesh terms and key words were combined for the search strategy, with the aim of encompassing all studies that have used any type of physical therapy treatment in patients with chronic musculoskeletal pain and have measured both TS and CPM.

RESULTS

Eighteen studies remained for qualitative analysis and 16 for quantitative analysis. Statistically significant differences with a 95% confidence interval (CI) were obtained for TS (-0.21, 95% CI = -0.39 to -0.03, Z = 2.50, P = 0.02, N = 721) and CPM (0.34, 95% CI = 0.12 to 0.56, Z = 2.99, P = 0.003, N = 680) in favor of physical therapy as compared with control. Manual therapy produces a slight improvement in TS, and physical therapy modalities in general improve CPM. No significant differences between the subgroups of the meta-analysis were found. The methodological quality of the studies was high.

CONCLUSIONS

Physical therapy produces a slight improvement in central sensitization (CS)-related variables, with TS decreased and CPM increased when compared with a control group in patients with CMP. Only significant differences in TS were identified in the manual therapy subgroup.

The Hypnotic Analgesia Suggestion Mitigated the Effect of the Transcranial Direct Current Stimulation on the Descending Pain Modulatory System: A Proof of Concept Study

Objective

We evaluated whether active(a)-tDCS combined with hypnotic analgesia suggestion (HS) would be more effective than a single active(a)-tDCS, and/or sham-(s)-tDCS and s-tDCS/HS on the following outcomes: function of descending pain modulatory system (DPMS) during the conditioned pain modulation test (CPM-test) (primary outcome), heat pain threshold (HPT), heat pain tolerance (HPTo) and cold pressor test (CPT) (secondary outcomes). We also examined whether their effects are related to neuroplasticity state evaluated by serum brain-derived-neurotropic factor (BDNF).

Materials and Methods

Forty-eight females received one session of one of the four interventions (a-tDCS/HS, s-tDCS/HS, a-tDCS, and s-tDCS) in an incomplete randomized crossover sequence. The a-tDCS or s-tDCS was applied over the left dorsolateral prefrontal cortex (DLPFC) for 30 minutes at 2mA.

Results

A generalized linear model revealed a significant main effect for the intervention group (P <0.032). The delta-(Δ) pain score on the Numerical Pain Scale (NPS0-10) during CPM-test in the a-tDCS/HS group was -0.25 (0.43). The (Δ) pain score on NPS (0-10) during CPM-test in the other three groups was a-tDCS=-0.54 (0.41), HS -0.01 (0.41) and s-tDCS/HS=-0.19 (0.43). A-tDCS/HS intervention increased the CPT substantially compared to all other interventions. Also, higher baseline levels of BDNF were associated with a larger change in CPT and HPTo.

Conclusion

These findings indicate that the HS combined with a-tDCS mitigated the effect of the a-tDCS on the DPMS. The a-tDCS up-regulates the inhibition on DPMS, and the HS improved pain tolerance. And, together they enhanced the reaction time substantially upon the CPT.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT03744897.

Methods and strategies of tDCS for the treatment of pain: current status and future directions

INTRODUCTION

Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation technique that has been widely studied for the treatment of chronic pain. It is considered a promising and safe alternative pain therapy. Different targets have been tested, each having their own particular mechanisms for modulating pain perception.

AREAS COVERED

We discuss the current state of the art of tDCS to manage pain and future strategies to optimize tDCS' effects. Current strategies include primary motor cortex tDCS, prefrontal tDCS and tDCS combined with behavioral interventions while future strategies, on the other hand, include high-intensity tDCS, transcutaneous spinal direct current stimulation, cerebellar tDCS, home-based tDCS, and tDCS with extended number of sessions.

EXPERT COMMENTARY

It has been shown that the stimulation of the prefrontal and primary motor cortex is efficient for pain reduction while a few other new strategies, such as high-intensity tDCS and network-based tDCS, are believed to induce strong neuroplastic effects, although the underlying neural mechanisms still need to be fully uncovered. Hence, conventional tDCS approaches demonstrated promising effects to manage pain and new strategies are under development to enhance tDCS effects and make this approach more easily available by using, for instance, home-based devices.

Neuroplasticity and Epilepsy Surgery in Brain Eloquent Areas: Case Report

Introduction: Neuronal plasticity includes changes in any component of the central nervous system in response to intrinsic or extrinsic stimuli. Brain functions that depend on the epileptogenic cortex pose a challenge in epilepsy surgery because many patients are excluded from pre-surgical evaluation for fear of the possible sequelae. Some of these patients may be rescued by enhancing neuronal plasticity with brain neuromodulation techniques.

Case Report: We describe a 6-year-old child with refractory focal motor seizures symptomatic to a neuroepithelial dysembryoblastic tumor in the left temporo-parietal region. He underwent limited resection of the lesion in order to avoid sequelae in his language function. A functional study at age of 17 years revealed an overlap of Wernicke's area with the tumor and areas of incipient language reorganization in the contralateral hemisphere. An invasive neuromodulation procedure was designed to enhance neuroplasticity. After craniotomy, he underwent language training and simultaneous electrical inhibition of language using an electrode grid placed over the lesion. The intensity of the language inhibitory stimulus was increased every day to force the use of accessory language areas in the right hemisphere by neuroplasticity.

Results: The language of the patient improved for six consecutive days until he was able to speak and understand while undergoing maximum electrical inhibition. The tumor was resected using a cortical mapping guide.

Discussion: Application of direct cortical stimulation techniques and language pre-habilitation before epilepsy surgery can be useful to rescue patients excluded from resective surgery, especially young patients with long-term lesions.

Effect of Transcranial Direct Current Stimulation Combined With Patient-Controlled Intravenous Morphine Analgesia on Analgesic Use and Post-Thoracotomy Pain. A Prospective, Randomized, Double-Blind, Sham-Controlled, Proof-of-Concept Clinical Trial

Background

Transcranial direct current stimulation (tDCS) is used for various chronic pain conditions, but experience with tDCS for acute postoperative pain is limited. This study investigated the effect of tDCS vs. sham stimulation on postoperative morphine consumption and pain intensity after thoracotomy.

Methods

This is a single-center, prospective, randomized, double-blind, sham-controlled trial in lung cancer patients undergoing thoracotomy under general anesthesia. All patients received patient-controlled (PCA) intravenous morphine and intercostal nerve blocks at the end of surgery. The intervention group (a-tDCS, n = 31) received anodal tDCS over the left primary motor cortex (C3-Fp2) for 20 min at 1.2 mA, on five consecutive days; the control group (n = 31) received sham stimulation. Morphine consumption, number of analgesia demands, and pain intensity at rest, with movement and with cough were recorded at the following intervals: immediately before (T1), immediately after intervention (T2), then every hour for 4 h (Т3-Т6), then every 6 h (Т7-Т31) for 5 days. We recorded outcomes on postoperative days 1 and 5 and conducted a phone interview inquiring about chronic pain 1 year later (NCT03005548).

Results

A total of 62 patients enrolled, but tDCS was prematurely stopped in six patients. Fifty-five patients (27 a-tDCS, 28 sham) had three or more tDCS applications and were included in the analysis. Cumulative morphine dose in the first 120 h after surgery was significantly lower in the tDCS [77.00 (54.00-123.00) mg] compared to sham group [112.00 (79.97-173.35) mg, p = 0.043, Cohen's d = 0.42]. On postoperative day 5, maximum visual analog scale (VAS) pain score with cough was significantly lower in the tDCS group [29.00 (20.00-39.00) vs. 44.50 (30.00-61.75) mm, p = 0.018], and pain interference with cough was 80% lower [10.00 (0.00-30.00) vs. 50.00 (0.00-70.00), p = 0.013]. One year after surgery, there was no significant difference between groups with regard to chronic pain and analgesic use.

Conclusion

In lung cancer patients undergoing thoracotomy, three to five tDCS sessions significantly reduced cumulative postoperative morphine use, maximum VAS pain scores with cough, and pain interference with cough on postoperative day 5, but there was no obvious long-term benefit from tDCS.

Patient-Controlled Intravenous Morphine Analgesia Combined with Transcranial Direct Current Stimulation for Post-Thoracotomy Pain: A Cost-Effectiveness Study and A Feasibility For Its Future Implementation

This prospective randomized study aims to evaluate the feasibility and cost-effectiveness of combining transcranial direct current stimulation (tDCS) with patient controlled intravenous morphine analgesia (PCA-IV) as part of multimodal analgesia after thoracotomy. Patients assigned to the active treatment group (a-tDCS, n = 27) received tDCS over the left primary motor cortex for five days, whereas patients assigned to the control group (sham-tDCS, n = 28) received sham tDCS stimulations. All patients received postoperative PCA-IV morphine. For cost-effectiveness analysis we used data about total amount of PCA-IV morphine and maximum visual analog pain scale with cough (VASP-C_max). Direct costs of hospitalization were assumed as equal for both groups. Cost-effectiveness analysis was performed with the incremental cost-effectiveness ratio (ICER), expressed as the incremental cost (RSD or US$) per incremental gain in mm of VASP-C_max reduction. Calculated ICER was 510.87 RSD per VASP-C_max 1 mm reduction. Conversion on USA market (USA data 1.325 US$ for 1 mg of morphine) revealed ICER of 189.08 US$ or 18960.39 RSD/1 VASP-C_max 1 mm reduction. Cost-effectiveness expressed through ICER showed significant reduction of PCA-IV morphine costs in the tDCS group. Further investigation of tDCS benefits with regards to reduction of postoperative pain treatment costs should also include the long-term benefits of reduced morphine use.

Transcranial Direct Current Stimulation to Improve the Dysfunction of Descending Pain Modulatory System Related to Opioids in Chronic Non-cancer Pain: An Integrative Review of Neurobiology and Meta-Analysis

Background: Opioid long-term therapy can produce tolerance, opioid-induced hyperalgesia (OIH), and it induces dysfunction in pain descending pain inhibitory system (DPIS). Objectives: This integrative review with meta-analysis aimed: (i) To discuss the potential mechanisms involved in analgesic tolerance and opioid-induced hyperalgesia (OIH). (ii) To examine how the opioid can affect the function of DPIS. (ii) To show evidence about the tDCS as an approach to treat acute and chronic pain. (iii) To discuss the effect of tDCS on DPIS and how it can counter-regulate the OIH. (iv) To draw perspectives for the future about the tDCS effects as an approach to improve the dysfunction in the DPIS in chronic non-cancer pain. Methods: Relevant published randomized clinical trials (RCT) comparing active (irrespective of the stimulation protocol) to sham tDCS for treating chronic non-cancer pain were identified, and risk of bias was assessed. We searched trials in PubMed, EMBASE and Cochrane trials databases. tDCS protocols accepted were application in areas of the primary motor cortex (M1), dorsolateral prefrontal cortex (DLPFC), or occipital area. Results: Fifty-nine studies were fully reviewed, and 24 with moderate to the high-quality methodology were included. tDCS improved chronic pain with a moderate effect size [pooled standardized mean difference; -0.66; 95% confidence interval (CI) -0.91 to -0.41]. On average, active protocols led to 27.26% less pain at the end of treatment compared to sham [95% CI; 15.89-32.90%]. Protocol varied in terms of anodal or cathodal stimulation, areas of stimulation (M1 and DLPFC the most common), number of sessions (from 5 to 20) and current intensity (from 1 to 2 mA). The time of application was 20 min in 92% of protocols. Conclusion: In comparison with sham stimulation, tDCS demonstrated a superior effect in reducing chronic pain conditions. They give perspectives that the top-down neuromodulator effects of tDCS are a promising approach to improve management in refractory chronic not-cancer related pain and to enhance dysfunctional neuronal circuitries involved in the DPIS and other pain dimensions and improve pain control with a therapeutic opioid-free. However, further studies are needed to determine individualized protocols according to a biopsychosocial perspective.

Optimised transcranial direct current stimulation (tDCS) for fibromyalgia-targeting the endogenous pain control system: a randomised, double-blind, factorial clinical trial protocol

INTRODUCTION

Fibromyalgia (FM) is a common debilitating condition with limited therapeutic options. Medications have low efficacy and are often associated with adverse effects. Given that FM is associated with a defective endogenous pain control system and central sensitisation, combining interventions such as transcranial direct current stimulation (tDCS) and aerobic exercise (AE) to modulate pain-processing circuits may enhance pain control.

METHODS AND ANALYSIS

A prospective, randomised (1:1:1:1), placebo-controlled, double-blind, factorial clinical trial will test the hypothesis that optimised tDCS (16 anodal tDCS sessions combined with AE) can restore of the pain endogenous control system. Participants with FM (n=148) will undergo a conditioning exercise period and be randomly allocated to one of four groups: (1) active tDCS and AE, (2) sham tDCS and AE, (3) active tDCS and non-aerobic exercise (nAE) or (4) sham tDCS and nAE. Pain inhibitory activity will be assessed using conditioned pain modulation (CPM) and temporal slow pain summation (TSPS)-primary outcomes. Secondary outcomes will include the following assessments: Transcranial magnetic stimulation and electroencephalography as cortical markers of pain inhibitory control and thalamocortical circuits; secondary clinical outcomes on pain, FM, quality of life, sleep and depression. Finally, the relationship between the two main mechanistic targets in this study-CPM and TSPS-and changes in secondary clinical outcomes will be tested. The change in the primary efficacy endpoint, CPM and TSPS, from baseline to week 4 of stimulation will be tested with a mixed linear model and adjusted for important demographic variables.

ETHICS AND DISSEMINATION

This study obeys the Declaration of Helsinki and was approved by the Institutional Review Board (IRB) of Partners Healthcare under the protocol number 2017P002524. Informed consent will be obtained from participants. Study findings will be reported in conferences and peer-reviewed journal publications.

TRIAL REGISTRATION NUMBER

NCT03371225.

Large Treatment Effect With Extended Home-Based Transcranial Direct Current Stimulation Over Dorsolateral Prefrontal Cortex in Fibromyalgia: A Proof of Concept Sham-Randomized Clinical Study

This randomized, double-blind controlled trial tested the hypothesis that 60 sessions of home-based anodal (a)-transcranial direct current stimulation (tDCS) over dorsolateral prefrontal cortex (DLPFC) would be better than home-based sham-tDCS to improve the widespread pain and the disability-related to pain. The anodal-tDCS (2 mA for 30 minutes) over the left DLPFC was self-administered with a specially developed device following in-person training. Twenty women, 18 to 65 years old were randomized into 2 groups [active-(a)-tDCS (n = 10) or sham-(s)-tDCS (n = 10)]. Post hoc analysis revealed that after the first 20 sessions of a-tDCS, the cumulative pain scores reduced by 45.65% [7.25 (1.43) vs 3.94 (1.14), active vs sham tDCS, respectively]. After 60 sessions, during the 12-week assessment, pain scores reduced by 62.06% in the actively group [visual analogue scale reduction, 7.25 (1.43) to 2.75 (.85)] compared to 24.92% in the s-tDCS group, [mean (SD) 7.10 (1.81) vs 5.33 (.90)], respectively. It reduced the risk for analgesic use in 55%. Higher serum levels of the brain-derived neurotrophic factor predicted higher decreases on the pain scores across of treatment. PERSPECTIVE: These findings bring 3 important insights: 1) show that an extended period of treatment (60 sessions, to date the largest number of tDCS sessions tested) for fibromyalgia induces large pain decreases (a large effect size of 1.59) and 2) support the feasibility of home-based tDCS as a method of intervention; 3) provide additional data on DLPFC target for the treatment of fibromyalgia. Finally, our findings also highlight that brain-derived neurotrophic factor to index neuroplasticity may be a valuable predictor of the tDCS effect on pain scores decreases across the treatment.

Intramuscular electrical stimulus potentiates motor cortex modulation effects on pain and descending inhibitory systems in knee osteoarthritis: a randomized, factorial, sham-controlled study

Background

Neuroplastic changes in nociceptive pathways contribute to severity of symptoms in knee osteoarthritis (KOA). A new look at neuroplastic changes management includes modulation of the primary motor cortex by transcranial direct current stimulation (tDCS).

Objectives

We investigated whether tDCS combined with intramuscular electrical stimulation (EIMS) would be more efficacious than a sham (s) intervention (s-tDCS/s-EIMS) or a single active(a)-tDCS/s-EIMS intervention and/or s-tDCS/a-EIMS in the following domains: pain measures (visual analog scale [VAS] score and descending pain modulatory system [DPMS], and outcomes, and analgesic use, disability, and pain pressure threshold (PPT) for secondary outcomes.

Registration

The trial is registered in Clinicaltrials.gov: NCT01747070.

Methods

Sixty women with KOA, aged 50–75 years old, randomly received five sessions of one of the four interventions (a-tDCS/a-EIMS, s-tDCS/s-EIMS, a-tDCS/s-EIMS, and s-tDCS/a-EIMS). tDCS was applied over the primary motor cortex (M1), for 30 minutes at 2 mA and the EIMS paraspinal of L1–S2.

Results

A generalized estimating equation model revealed the main effect of the a-tDCS/a-EIMS in the VAS pain scores at end treatment compared with the other three groups (P<0.0001). There existed a significant effect of time and a significant interaction between group and time (P<0.01 for both). The delta-(Δ) pain score on VAS in the a-tDCS/a-EIMS group was −3.59, 95% CI: −4.10 to −2.63. The (Δ) pain scores on VAS in the other three groups were: a-tDCS/s-EIMS=−2.13, 95% CI: −2.48 to −1.64; s-tDCS/a-EIMS=−2.25, 95% CI: −2.59 to −1.68; s-tDCS/s-EIMS MR =–1.77, 95% CI: −2.08 to −1.38. The a-tDCS/a-EIMS led to better effect in DPMS, PPT, analgesic use, and disability related to pain.

Conclusion

This study provides additional evidence regarding additive clinical effects to improve pain measures and descending pain inhibitory controls when the neuromodulation of the primary motor cortex with tDCS is combined with a bottom-up modulation with EIMS in KOA. Also, it improved the ability to walk due to reduced pain and reduced analgesic use.

Developing an optimized strategy with transcranial direct current stimulation to enhance the endogenous pain control system in fibromyalgia

INTRODUCTION

Fibromyalgia affects more than 5 million people in the United States and has a detrimental impact on individuals' quality of life. Current pharmacological treatments provide limited benefits to relieve the pain of fibromyalgia, along with a risk of adverse effects; a scenario that explains the increasing interest for multimodal approaches. A tailored strategy to focus on this dysfunctional endogenous pain inhibitory system is transcranial direct current stimulation (tDCS) of the primary motor cortex. By combining tDCS with aerobic exercise, the effects can be optimized. Areas covered: The relevant literature was reviewed and discussed the methodological issues for designing a mechanistic clinical trial to test this combined intervention. Also, we reviewed the neural control of different pathways that integrate the endogenous pain inhibitory system, as well as the effects of tDCS and aerobic exercise both alone and combined. In addition, potential neurophysiological assessments are addressed: conditioned pain modulation, temporal slow pain summation, transcranial magnetic stimulation, and electroencephalography in the context of fibromyalgia. Expert commentary: By understanding the neural mechanisms underlying pain processing and potential optimized interventions in fibromyalgia with higher accuracy, the field has an evident potential of advancement in the direction of new neuromarkers and tailored therapies.

Effects of Transcranial Direct Current Stimulation Block Remifentanil-Induced Hyperalgesia: A Randomized, Double-Blind Clinical Trial

Background: Remifentanil-induced hyperalgesia (r-IH) involves an imbalance in the inhibitory and excitatory systems. As the transcranial Direct Current Stimulation (tDCS) modulates the thalamocortical synapses in a top-down manner, we hypothesized that the active (a)-t-DCS would be more effective than sham(s)-tDCS to prevent r-IH. We used an experimental paradigm to induce temporal summation of pain utilizing a repetitive cold test (rCOLDT) assessed by the Numerical Pain Score (NPS 0-10) and we evaluated the function of the descending pain modulatory system (DPMS) by the change on the NPS (0–10) during the conditioned pain modulation (CPM)-task (primary outcomes). We tested whether a-tDCS would be more effective than s-tDCS to improve pain perception assessed by the heat pain threshold (HPT) and the reaction time during the ice-water pain test (IPT) (secondary outcomes).

Methods: This double-blinded, factorial randomized trial included 48 healthy males, ages ranging 19–40 years. They were randomized into four equal groups: a-tDCS/saline, s-tDCS/saline, a-tDCS/remifentanil and s-tDCS/remifentanil. tDCS was applied over the primary motor cortex, during 20 min at 2 mA, which was introduced 10 min after starting remifentanil infusion at 0.06 μg⋅kg^-1⋅min^-1 or saline.

Results: An ANCOVA mixed model revealed that during the rCOLDT, there was a significant main effect on the NPS scores (F = 3.81; P = 0.01). The s-tDCS/remifentanil group presented larger pain scores during rCOLDT, [mean (SD) 5.49 (1.04)] and a-tDCS/remifentanil group had relative lower pain scores [4.15 (1.62)]; showing its blocking effect on r-IH. a-tDCS/saline and s-tDCS/saline groups showed lowest pain scores during rCOLDT, [3.11 (1.2)] and [3.15 (1.62)], respectively. The effect of sedation induced by remifentanil during the rCOLDT was not significant (F = 0.76; P = 0.38). Remifentanil groups showed positive scores in the NPS (0–10) during the CPM-task, that is, it produced a disengagement of the DPMS. Also, s-tDCS/Remifentanil compared to a-tDCS showed lower HPT and larger reaction-time during the IPT.

Conclusion: These findings suggest that effects of a-tDCS prevent the summation response induced by r-IH during rCOLDT and the a-tDCS blocked the disengagement of DPMS. Thereby, tDCS could be considered as a new approach to contra-regulate paradoxical mechanisms involved in the r-IH. Clinical trials identification: NCT02432677. URL:https://clinicaltrials.gov/.