The Effect of Transcranial Direct Current Stimulation on Inflammation in Older Adults With Knee Osteoarthritis: A Bayesian Residual Change Analysis

Non-invasive neurostimulation to improve sleep quality and depressive symptoms in patients with major depressive disorder: A meta-analysis of randomized controlled trials

BACKGROUND

Non-invasive neurostimulation, including bright light therapy (BLT), repetitive transcranial magnetic (rTMS) and transcranial direct current stimulation (tDCS), has been shown to alleviate depressive symptoms in major depressive disorder (MDD). However, the efficacy of these interventions in addressing sleep disturbances in MDD patients remains a subject of debate.

OBJECTIVE

We aimed to conduct a meta-analysis of available randomized controlled trials (RCTs) to assess the effectiveness of non-invasive neurostimulation in improving sleep disturbances and depressive symptoms in MDD patients.

METHODS

Systematic searches for relevant RCTs were conducted in the databases PubMed, Cochrane Library, Web of Science, EMBASE, Wanfang and China National Knowledge Infrastructure up to January 2024. Data on outcomes comparable across the studies were meta-analyzed using Review Manager 5.3 and Stata 14. The pooled results were reported as standardized mean differences (SMD) with their respective 95% confidence intervals (CI).

RESULTS

Our analysis encompassed 15 RCTs involving 1348 patients. Compared to sham or no stimulation, non-invasive neurostimulation significantly improved sleep quality (SMD -0.74, 95%CI -1.15 to -0.33, p = 0.0004) and sleep efficiency (SMD 0.35, 95%CI 0.10 to 0.60, p = 0.006). It also significantly reduced severity of depressive symptoms (SMD -0.62, 95%CI -0.90 to -0.35, p < 0.00001). Subgroup analysis further demonstrated that patients experiencing sleep improvements due to neurostimulation showed a marked decrease in depressive symptoms compared to the control group (SMD = -0.90, 95% CI [-1.26, -0.54], p < 0.0001).

CONCLUSION

Current evidence from RCTs suggests that neurostimulation can enhance sleep quality and efficiency in individuals with MDD, which in turn may be associated with mitigation of depressive symptoms.

PROSPERO REGISTRATION

CRD42023423844.

Neurovascular coupling impairment as a mechanism for cognitive deficits in COVID-19

Components that comprise our brain parenchymal and cerebrovascular structures provide a homeostatic environment for proper neuronal function to ensure normal cognition. Cerebral insults (e.g. ischaemia, microbleeds and infection) alter cellular structures and physiologic processes within the neurovascular unit and contribute to cognitive dysfunction. COVID-19 has posed significant complications during acute and convalescent stages in multiple organ systems, including the brain. Cognitive impairment is a prevalent complication in COVID-19 patients, irrespective of severity of acute SARS-CoV-2 infection. Moreover, overwhelming evidence from in vitro, preclinical and clinical studies has reported SARS-CoV-2-induced pathologies in components of the neurovascular unit that are associated with cognitive impairment. Neurovascular unit disruption alters the neurovascular coupling response, a critical mechanism that regulates cerebromicrovascular blood flow to meet the energetic demands of locally active neurons. Normal cognitive processing is achieved through the neurovascular coupling response and involves the coordinated action of brain parenchymal cells (i.e. neurons and glia) and cerebrovascular cell types (i.e. endothelia, smooth muscle cells and pericytes). However, current work on COVID-19-induced cognitive impairment has yet to investigate disruption of neurovascular coupling as a causal factor. Hence, in this review, we aim to describe SARS-CoV-2's effects on the neurovascular unit and how they can impact neurovascular coupling and contribute to cognitive decline in acute and convalescent stages of the disease. Additionally, we explore potential therapeutic interventions to mitigate COVID-19-induced cognitive impairment. Given the great impact of cognitive impairment associated with COVID-19 on both individuals and public health, the necessity for a coordinated effort from fundamental scientific research to clinical application becomes imperative. This integrated endeavour is crucial for mitigating the cognitive deficits induced by COVID-19 and its subsequent burden in this especially vulnerable population.

Transcranial Direct Current Stimulation for Knee Osteoarthritis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

The effects of transcranial direct current stimulation (tDCS) in the treatment of knee osteoarthritis (KOA) is still unclear. The objective is to evaluate the efficacy and safety of tDCS in improving symptoms in patients with KOA.

METHODS

The following electronic databases were searched for eligible randomized controlled trials (RCTs): PubMed, Embase, Web of Science, and the Cochrane Library. The search was performed from the inception dates to April 30, 2023. Data extraction and quality assessment were performed by two independent reviewers. Standard mean differences (SMDs) with 95% confidence intervals (95% CIs) for pooled data were calculated. A random-effects model was used for the data analyses. The primary outcomes were pain and physical function. Secondary outcomes included stiffness, mobility performance, quality of life, pressure pain tolerance, and plasma levels of brain-derived neurotrophic factor (BDNF).

RESULTS

This meta-analysis included 13 RCTs. tDCS was significantly associated with pain decrease compared with sham tDCS (SMD = -0.62, 95% CI -0.87 to -0.37, P < 0.00001). When comparing tDCS plus other non-tDCS with sham tDCS plus other non-tDCS, there was no longer a significant association with pain decrease (SMD = -0.45, 95% CI -1.08 to 0.17, P = 0.16). The changes in physical function were not significantly different between the tDCS and sham tDCS groups (SMD = -0.09, 95% CI -0.56 to 0.38, P = 0.71). When comparing tDCS plus other non-tDCS with sham tDCS plus other non-tDCS, there was still no significant association with improvement in physical function (SMD = -0.66, 95% CI -1.63 to 0.30, P = 0.18). There was no significant difference with improvement in stiffness (SMD = -0.21, 95% CI -0.77 to 0.34, P = 0.45), mobility performance (SMD = 4.58, 95% CI -9.21 to 18.37, P = 0.51), quality of life (SMD = -7.01, 95% CI -22.61 to 8.59, P = 0.38), and pressure pain tolerance (SMD = 0.30, 95% CI -0.09 to 0.69, P = 0.13). There was a statistically significant reduction in plasma levels of BDNF (SMD = -13.57, 95% CI -24.23 to -2.92, P = 0.01).

CONCLUSION

In conclusion, tDCS could significantly alleviate pain, but it might have no efficacy in physical function, stiffness, mobility performance, quality of life, and pressure pain tolerance among patients with KOA.

Transcranial direct current stimulation (tDCS) in the treatment of neuropsychiatric symptoms of long COVID

The study aimed to assess the efficacy of transcranial direct current stimulation (tDCS) in the treatment of neuropsychiatric (NP) symptoms of the post-acute sequelae of SARS-CoV-2 infection (PASC), known as the long COVID. A double-blind, randomized, sham-controlled study compared the efficacy and safety of prefrontal cortex active tDCS to sham-tDCS in treating NP-PASC. Patients diagnosed with NP-PASC, with a Fatigue Impact Scale (FIS) score ≥ 40, were eligible for the study. Twenty tDCS sessions were administered within four weeks, with continuous, end-of-treatment, and follow-up measurements. The primary outcome was a change in the FIS at the end-of-treatment, analyzed in the intention-to-treat population. Data from 33 patients assigned to active (n = 16) or sham-tDCS (n = 17) were analyzed. After the treatment, a decrease in the FIS score was more pronounced in the sham than in the active group, yet the intergroup difference was insignificant (11.7 [95% CI -11.1 to 34.5], p = 0.6). Furthermore, no significant intergroup differences were observed regarding anxiety, depression, quality of life, and cognitive performance. The small cohort sample, differences in baseline FIS scores between groups (non-stratified randomization), or chosen stimulation parameters may have influenced our findings. However, it might also be possible that the expected mechanism of action of tDCS is insufficient to treat these conditions.

Comorbid treatment of traumatic brain injury and mental health disorders

BACKGROUND

The Emory Healthcare Veterans Program (EHVP) is a multidisciplinary intensive outpatient treatment program for post-9/11 veterans and service members with invisible wounds, including posttraumatic stress disorder (PTSD), traumatic brain injury (TBI), substance use disorders (SUD), and other anxiety- and depression-related disorders.

OBJECTIVE

This article reviews the EHVP.

METHODS

The different treatment tracks that provide integrated and comprehensive treatment are highlighted along with a review of the standard, adjunctive, and auxiliary services that complement individualized treatment plans.

RESULTS

This review particularly emphasizes the adjunctive neurorehabilitation service offered to veterans and service members with a TBI history and the EVHP data that indicate large reductions in PTSD and depression symptoms across treatment tracks that are maintained across 12 months follow up. Finally, there is a discussion of possible suboptimal treatment response and the pilot programs related to different treatment augmentation strategies being deploying to ensure optimal treatment response for all.

CONCLUSION

Published data indicate that the two-week intensive outpatient program is an effective treatment program for a variety of complex presentations of PTSD, TBI, SUD, and other anxiety- and depression-related disorders in veterans and active duty service members.

Efficacy of transcranial direct current stimulation in patients with knee osteoarthritis: A systematic review

OBJECTIVE

Transcranial direct current stimulation (tDCS) has demonstrated its efficacy in alleviating pain among individuals with musculoskeletal disorders. This review focuses on the application of tDCS as a therapeutic intervention for managing knee osteoarthritis (OA), a prevalent musculoskeletal condition. The primary objective is to assess the effectiveness of tDCS(add-on tDCS and /or stand-alone tDCS), whether as an add-on to existing treatments or as a standalone therapy, in reducing pain and enhancing functional capacity in patients with knee OA.

METHODS

A comprehensive search was conducted across multiple databases, including PubMed, Science Direct, OVID, MEDLINE, CINAHL, EMBASE, ProQuest, and Google Scholar, and Web of Science. The search terms employed were "Transcranial direct current stimulation" or "tDCS" in combination with "Osteoarthritis" or "OA" and "knee." After eliminating duplicates and studies that did not meet the inclusion criteria, a total of 14 relevant articles were identified for review.

RESULTS

Among the included studies, twelve reported statistically significant improvements in pain levels when comparing the active tDCS group to the sham tDCS group. Only two studies reported no significant difference in pain intensity between the active tDCS and sham tDCS groups. Findings regarding functional abilities were diverse, with some studies demonstrating a significant enhancement in functional outcomes in the active tDCS group, while others observed no statistically significant differences.

CONCLUSION

The results of this review suggest that tDCS holds promise as a pain management intervention for individuals with knee OA. Notably, anodal tDCS applied over the primary motor cortex (M1) appears to be particularly effective in alleviating pain in patients with knee OA. However, the impact of tDCS on functional performance appears to be limited.

Investigation into the Effectiveness of Combining Transcranial Direct Current Stimulation and Transcutaneous Electrical Nerve Stimulation as Treatment Options for Poststroke Shoulder Pain by Utilizing Functional Near-Infrared Spectroscopy

Objective

The aim of this study is to explore the therapeutic effects of transcranial direct current stimulation (tDCS) and transcutaneous electrical nerve stimulation (TENS) on post stroke shoulder pain (PSSP).

Methods

We enrolled 13 individuals in this study who underwent three different treatments in a random sequence: active tDCS+active TENS, active tDCS+sham TENS, and sham tDCS+active TENS. Each treatment was administered once, with a 3-day washout period between interventions. A blinded rater assessed the visual analog scale (VAS) scores, fNIRS readings, and sensory and pain tolerance thresholds of the participants before and after the stimulation.

Results

All three treatment methods can significantly alleviate PSSP (p<0.05). Compared with using tDCS alone, tDCS+TENS can significantly improve pain, with a statistically significant difference (p<0.05). In the 2KHz PTT task, the three treatment methods showed significant differences (p<0.05) in the mean oxygenated hemoglobin (HbO) levels in the false premotor cortex (PMC)/auxiliary motor area (SMA) before and after intervention.

Conclusion

The combination of tDCS+TENS can increase the pain-relieving impact on PSSP when compared to using tDCS alone. TENS may contribute an additional effect on the inhibitory systems influenced by tDCS that help reduce pain.

Clinical Registration Number

Registration website: https://www.chictr.org.cn. Registration date: 2022-02-25. Registration number: ChiCTR2200056970.

Management of Chronic Pain and PTSD in Veterans With tDCS+Prolonged Exposure: A Pilot Study

INTRODUCTION

Chronic pain and posttraumatic stress disorder (PTSD) are prevalent comorbid conditions, particularly in Veterans; however, there are few integrated treatments for chronic pain and PTSD. Instead, interventions are typically implemented separately and may involve addictive opioids. Although there are highly effective, non-pharmacological treatments for PTSD, they are plagued by high dropout, which may be exacerbated by comorbid pain, as these PTSD treatments typically require increased activity. Importantly, a noninvasive pain treatment, tDCS (transcranial direct current stimulation) shows indications of effectiveness and may be integrated with psychological treatments, even when delivered via telehealth. This study examines the feasibility and initial efficacy of integrating home telehealth tDCS with prolonged exposure (PE), an evidence-based PTSD treatment.

MATERIALS AND METHODS

Thirty-nine Veterans were contacted, 31 consented to evaluation, 21 were enrolled, and 16 completed treatment and provided pre- and post-treatment data at one of two Veterans Affairs Medical Centers. Transcranial direct current stimulation sessions corresponded with PE exposure assignments, as there is theoretical reason to believe that tDCS may potentiate extinction learning featured in PE.

RESULTS

Patients evinced significant improvement in both pain interference and PTSD symptoms and a trend toward improvement in depression symptoms. However, a significant change in pain intensity was not observed, likely because of the small sample size.

DISCUSSION

The findings provide initial support for the feasibility of an entirely home-based, integrated treatment for comorbid PTSD and pain.

Transcranial Direct Current Stimulation in Nicotine Use: Nursing Implications for Patient Outcomes

ABSTRACT

Tobacco use is a leading cause of cancer, cardiovascular and respiratory disease, and preventable death in the United States. The brains of individuals with nicotine dependence are characterized by damaged mesolimbic pathways in the medial portion of the limbic and frontal lobes, creating positive reinforcing mechanisms. Transcranial direct current stimulation (tDCS) targets this neuroadaptation to improve smokers' nicotine-related outcomes, such as craving and smoking behavior, by depolarizing or hyperpolarizing the neurons of the brain. Recent literature reported promising outcomes in smokers after tDCS treatment interventions. tDCS has great potential for clinical nursing research for tobacco control given its multiple methodological advantages and few disadvantages. Nurse researchers can consider individualized and home-based tDCS interventions for community-based tobacco control research and may need to consider objective outcome measures (e.g., cotinine in urine) and addiction-related cognitive variables (e.g., self-regulation). Users of electronic nicotine delivery systems also need to be considered as participants in tDCS interventions. Additional considerations for nursing research are discussed.

IL-10/β-Endorphin-Mediated Neuroimmune Modulation on Microglia during Antinociception

Microglia are glial cells centrally related to pathophysiology and neuroimmunological regulation of pain through microglia-neuron crosstalk mechanisms. In contrast, anti-inflammatory mechanisms guided by immunological effectors such as IL-10 trigger the secretion of analgesic substances, culminating in the differential expression of genes encoding endogenous opioid peptides, especially β-endorphin. Thus, when β-endorphin binds to the µ-opioid receptor, it generates neuronal hyperpolarization, inhibiting nociceptive stimuli. This review aimed to summarize the recent advances in understanding the mechanism by which IL-10/β-endorphin can reduce pain. For this, databases were searched for articles from their inception up until November 2022. Two independent reviewers extracted the data and assessed the methodological quality of the included studies, and seventeen studies were considered eligible for this review. Several studies have demonstrated the impact of IL-10/β-endorphin in reducing pain, where IL-10 can stimulate GLP-1R, GRP40, and α7nAChR receptors, as well as intracellular signaling pathways, such as STAT3, resulting in increased β-endorphin expression and secretion. In addition, molecules such as gabapentinoids, thalidomide, cynandione A, morroniside, lemairamin, and cinobufagin, as well as non-pharmacological treatments such as electroacupuncture, reduce pain through IL-10 mediated mechanisms, reflecting a microglia-dependent β-endorphin differential increase. This process represents a cornerstone in pain neuroimmunology knowledge, and the results obtained by different studies about the theme are presented in this review.

Effects of left anodal transcranial direct current stimulation on hypothalamic-pituitary-adrenal axis activity in depression: a randomized controlled pilot trial

The main objective of this study was to evaluate the effect of left anodal transcranial direct current stimulation (tDCS) on hypothalamic-pituitary-adrenal axis (HPAA) activity in individuals with depression. We conducted a 3-week, randomized, triple-blind pilot trial with 47 participants (dropout rate: 14.89%) randomly assigned to either the tDCS or control group (sham stimulation). Salivary cortisol was used as an HPAA activity marker since cortisol is the effector hormone of the HPAA. The primary outcome was the effect of tDCS on the diurnal cortisol pattern (DCP and area under the curve with respect to ground -AUCg-). Secondary outcomes included tDCS effects on cortisol awakening response (CAR) and cortisol decline (CD), as well as the variation of cortisol concentrations between the initiation of tDCS and 2 weeks later. Intention-to-treat and per-protocol analyses were conducted. Our primary outcome showed an absent effect of tDCS on DCP and AUCg. Additionally, tDCS had an absent effect on CAR, CD, and cortisol concentration variation before-after stimulation. Our pilot study suggests that anodal tDCS showed an absent effect on HPAA activity in individuals with depression. More studies are needed to confirm these findings.

Feasibility, Acceptability, and Efficacy of Home-Based Transcranial Direct Current Stimulation on Pain in Older Adults with Alzheimer's Disease and Related Dementias: A Randomized Sham-Controlled Pilot Clinical Trial

Although transcranial direct current stimulation (tDCS) is emerging as a convenient pain relief modality for several chronic pain conditions, its feasibility, acceptability, and preliminary efficacy on pain in patients with Alzheimer's disease and related dementias (ADRD) have not been investigated. The purpose of this pilot study was to assess the feasibility, acceptability, and preliminary efficacy of 5, 20-min home-based tDCS sessions on chronic pain in older adults with ADRD. We randomly assigned 40 participants to active (n = 20) or sham (n = 20) tDCS. Clinical pain intensity was assessed using a numeric rating scale (NRS) with patients and a proxy measure (MOBID-2) with caregivers. We observed significant reductions of pain intensity for patients in the active tDCS group as reflected by both pain measures (NRS: Cohen's d = 0.69, p-value = 0.02); MOBID-2: Cohen's d = 1.12, p-value = 0.001). Moreover, we found home-based tDCS was feasible and acceptable intervention approach for pain in ADRD. These findings suggest the need for large-scale randomized controlled studies with larger samples and extended versions of tDCS to relieve chronic pain on the long-term for individuals with ADRD.

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.

Non-invasive brain stimulation for osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease, the prevalence of OA is increasing, and the elderly are the most common in patients with OA. OA has a severe impact on the daily life of patients, this increases the demand for treatment of OA. In recent years, the application of non-invasive brain stimulation (NIBS) has attracted extensive attention. It has been confirmed that NIBS plays an important role in regulating cortical excitability and oscillatory rhythm in specific brain regions. In this review, we summarized the therapeutic effects and mechanisms of different NIBS techniques in OA, clarified the potential of NIBS as a treatment choice for OA, and provided prospects for further research in the future.

Changes in Brain-derived Neurotrophic Factor From Active and Sham Transcranial Direct Current Stimulation in Older Adults With Knee Osteoarthritis

OBJECTIVES

Previous work has shown effects of transcranial direct current stimulation (tDCS) on clinical pain measures, qualitative sensory testing measures, and peripheral inflammation. The present report extends this research to investigate the effect of tDCS on brain-derived neurotrophic factor (BDNF) levels.

MATERIALS AND METHODS

This secondary analysis examined a sample of 40 older adults (50 to 70 y old) with symptomatic knee osteoarthritis randomly assigned in a 1:1 fashion to active (n=20) or sham (n=20) tDCS for 20 minutes on 5 consecutive days. BDNF was measured before the first session and after the final treatment session. Generalized linear modeling evaluated BDNF plasma levels as a function of tDCS group, adjusted for baseline. Bayesian statistical inference was used to quantify the probability that effects of the treatment exist.

RESULTS

Generalized linear modeling indicated a 90.4% posterior probability that the sham condition had 49.9% higher BDNF at the end of treatment, controlling for baseline. Follow-up analyses within the active TDCS group supported an association between change in BDNF and change in clinical pain, and exploratory analyses found an effect of tDCS on irisin.

DISCUSSION

Results indicated that tDCS could be a potential nonpharmacological treatment to decrease BDNF levels, which may in turn decrease pain. This study adds to a growing literature suggesting that tDCS affects cortical excitability, and consequentially, the neural circuits implicated in pain modulation. In addition to a direct connection to analgesia, BDNF changes may reflect tDCS-induced changes in different cortical areas and/or neural circuits.

The effect of transcranial direct stimulation as an add-on treatment to conventional physical therapy on pain intensity and functional ability in individuals with knee osteoarthritis: A randomized controlled trial

OBJECTIVE

To investigate the effect of adding transcranial direct current stimulation (tDCS) to conventional physiotherapy treatment (PT) on pain and performance of individuals with knee osteoarthritis (KOA).

METHODS

Eighty people suffering from chronic KOA participated in this study. They were randomly divided into four treatment groups, including PT combined with tDCS over the primary motor cortex (M1), PT combined with tDCS over the primary sensory cortex (S1), PT combined with tDCS over the dorsolateral prefrontal cortex (DLPFC), and PT combined with sham tDCS. A visual analog scale (VAS) for pain intensity, the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire for knee-related disability, and several performance tests (stepping 15 s, chair stand test in 30 s, and walking 4 × 10 m) were used for assessment following 10 sessions of tDCS (T1), and one month after the last session of tDCS (T2).

RESULTS

Differential effects on pain intensity, knee-related disability, and performance were found between groups. Compared to sham tDCS: (i) tDCS over M1 improved VAS pain score, KOOS disability score, and performance tests at T1 and T2; (ii) tDCS over S1 improved VAS pain score at T1 and T2 and KOOS disability score and performance tests at T2; (iii) tDCS over the DLPFC improved VAS pain score at T1 and performance tests at T1 and T2.

CONCLUSION

tDCS could be a beneficial add-on treatment to conventional PT for pain relief, disability reduction and functional improvement in patients with KOA.

Beta-Endorphin as a Biomarker in the Treatment of Chronic Pain with Non-Invasive Brain Stimulation: A Systematic Scoping Review

A scoping review to synthesize evidence and assess articles describing the use of beta-endorphins as a pain biomarker in chronic pain patients treated with non-invasive brain stimulation techniques was systematically performed with respect to the study quality, the technique employed and the results. Independent reviewers determined if the article met the study criteria at each stage for it to be included. Content analysis was applied and summarized. The results are described in a narrative form grouped by pain condition, type of intervention, stimulation protocol, outcome measures and main results. A total of 67 of 73 references were excluded, and 6 identified studies met the inclusion criteria. The study design, sample size, stimulation type, session protocol and the main findings of each study were extracted. The studies in this scoping review ranged from unsatisfactory to good based on the adopted criteria, with no study achieving an excellent rating. There is limited evidence on the dosage of beta-endorphin in chronic pain conditions during treatment with NIBS. Based on this literature, evidence suggests that BE may not only be useful for acute and persistent pain, but also for a variety of chronic pain states in which opioids are not effective.

Motor cortex transcranial direct current stimulation effects on knee osteoarthritis pain in elderly subjects with dysfunctional descending pain inhibitory system: A randomized controlled trial

BACKGROUND

Although evidence has indicated a positive effect of transcranial direct current stimulation (tDCS) on reducing pain, few studies have focused on the elderly population with knee osteoarthritis (KOA).

OBJECTIVE

To evaluate whether tDCS reduces KOA pain in elderly individuals with a dysfunctional descending pain inhibitory system (DPIS).

METHODS

In a double-blind trial, individuals ≥ 60 years with KOA pain and a dysfunctional DPIS, we randomly assigned patients to receive 15 daily sessions of 2 mA tDCS over the primary motor cortex (anode) and contralateral supraorbital area (cathode) (M1-SO) for 20 min or sham tDCS. Change in pain perception indexed by the Brief Pain Inventory (BPI) at the end of intervention was the primary outcome. Secondary outcomes included: disability, quantitative sensory testing, pain pressure threshold and conditioned pain modulation (CPM). Subjects were followed-up for 2 months.

RESULTS

Of the 104 enrolled subjects, with mean (SD) age of 73.9 (8.01) years and 88 (84.6%) female, 102 finished the trial. In the intention-to-treat analysis, the active tDCS group had a significantly greater reduction in BPI compared to the sham group (difference, 1.59; 95% CI, 0.95 to 2.23; P < 0.001; Cohen's d, 0.58); and, also a significantly greater improvement in CPM-pressure in the knee (P = 0.01) and CPM-pain in the hand (P = 0.01). These effects were not sustained at follow-up. The intervention was well tolerated, with no severe adverse effects.

CONCLUSION

M1-SO tDCS is associated with a moderate effect size in reducing pain in elderly patients with KOA after 15 daily sessions of stimulation. This intervention has also shown to modulate the DPIS.

Risk factors of pain, physical function, and health-related quality of life in elderly people with knee osteoarthritis: A cross-sectional study

Data on the precise mechanisms of the complex interactions of factors related to clinical impact of knee osteoarthritis (KOA) in the elderly population remain limited. To find predictors that explain pain intensity, physical function, and quality of life in elderly KOA subjects, we performed a cross-sectional analysis of the baseline data from a randomized trial. The trial included 104 subjects (aged ≥60) with KOA pain and dysfunctional endogenous pain-inhibitory system activity assessed by conditioned pain modulation (CPM). Three multiple linear regression models were performed to understand the independent predictors of Brief Pain Inventory (BPI), WOMAC function subscale (WOMACFunc), and SF-12 physical subscale (SF12-PCS). Model 1 showed that BPI pain score was predicted by low CPM response, high von-Frey light touch threshold, worse radiological severity as indexed by Kellgren-Lawrence grade (KL), high von-Frey punctate pain intensity and high levels of anxiety (adjusted R2 = 27.1%, F (6,95) = 7.27, P < 0.0001). In model 2, von-Frey light touch threshold, KL, depressive symptoms indexed by Beck Depression Inventory (BDI), level of sleepiness and pain pressure threshold were risk factors for SF12-PCS (adjusted R2 = 31.9%, F (5,96) = 10.5, P < 0.0001). Finally, model 3 showed that WOMACFunc was predicted by BDI, KL and BPI (adjusted R2 = 41%, F (3,98) = 24.42, P < 0.0001). Our data provides an interesting framework to understand the predictors of KOA pain in the elderly and highlights how its related outcomes are affected by disease-specific factors, somatosensory dysfunction and emotional factors.

Transcranial direct current stimulation for knee osteoarthritis: a single-blind randomized sham-controlled trial

OBJECTIVE

To evaluate the effects of transcranial direct current stimulation on pain and other symptoms of knee osteoarthritis.

METHODS

We performed a single-blind randomized sham-controlled trial with two parallel arms in an outpatient clinic of physical medicine and rehabilitation at a teaching hospital. We randomized 54 patients, 30-70 years of age, with knee osteoarthritis into two groups. They had morning stiffness ≤ 30 min, knee pain ≥ 3 months, joint crepitus, and Kellgren-Lawrence grade 1 or 2 on radiographs. For the active stimulation we administered 2 mA current, 20 min for each session and for the sham group 30 s stimulation and 20 min no current. Using the 10/20 International EEG system, the anode was fixed over the contralateral primary motor cortex (C3 or C4), and the cathode was placed on the ipsilateral supraorbital region (Fp1 or Fp2), with respect to the included knee. The program was repeated once daily over 5 consecutive days. Both groups received acetaminophen. We assessed the patients before and after the interventions, and three months post-intervention. The primary outcome was knee pain on the visual analog scale, and the secondary outcome was the Knee injury and Osteoarthritis Outcome Score.

RESULTS

There was a statistically significant reduction in the intensity of pain within sham and active groups (both p < 0.001), but no significant difference between the groups (p = 0.226). Analyses of the Knee injury and Osteoarthritis Outcome Scores showed no clinically important changes.

CONCLUSIONS

Transcranial direct current stimulation does not reduce knee pain, does not abate other symptoms, and does not restore knee function in patients with knee osteoarthritis. The pain reduction in our study could be attributed to either placebo or the acetaminophen effect.

Changes in Experimental Pain Sensitivity from Using Home-Based Remotely Supervised Transcranial Direct Current Stimulation in Older Adults with Knee Osteoarthritis

OBJECTIVE

The present study examined the effects of home-based remotely supervised transcranial direct current stimulation on quantitative sensory testing measurements in older adults with knee osteoarthritis. Participants were hypothesized to experience improved pain measurements over time.

DESIGN

Open-label, single-arm trial.

SETTING

Southeast Texas between March and November 2018 at a nursing school and participant homes.

SUBJECTS

Older adults (aged 50-85 years) with self-reported unilateral or bilateral knee osteoarthritis pain who met eligibility criteria set by the American College of Rheumatology.

METHODS

The intervention was applied with a constant current intensity for 20 minutes every weekday for two weeks (10 total sessions). Quantitative measures of pain were collected three times over 10 days (days 1, 5, and 10) and included heat threshold and tolerance, pressure pain threshold, punctate mechanical pain, pain, and conditioned pain modulation. Analyses used nonparametric tests to evaluate differences between day 1 and day 10. Generalized linear mixed models were then used to evaluate change across all three time points for each measure. Bayesian inference was used to provide the posterior probability of longitudinal effects.

RESULTS

Nonparametric tests found improvements in seven measures, and longitudinal models supported improvements in 10 measures, with some nonlinear effects.

CONCLUSIONS

The home-based, remotely supervised intervention improved quantitative measurements of pain in older adults with knee osteoarthritis. This study contributes to the growing body of literature supporting home-based noninvasive stimulation interventions.

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.

Longitudinal effect of transcranial direct current stimulation on knee osteoarthritis patients measured by functional infrared spectroscopy: a pilot study

Significance: Knee osteoarthritis (OA) is a common joint disease causing chronic pain and functional alterations (stiffness and swelling) in the elderly population. OA is currently treated pharmacologically with analgesics, although neuromodulation via transcranial direct current stimulation (tDCS) has recently generated a growing interest as a safe side-effect free treatment alternative or a complement to medications for chronic pain conditions. Although a number of studies have shown that tDCS has a beneficial effect on behavioral measures of pain, the mechanistic action of neuromodulation on pain sensitivity and coping at the central nervous system is not well understood. Aim: We aimed at observing longitudinal changes of cortical hemodynamics in older adults with knee OA associated with a two-week-long tDCS self-treatment protocol. Approach: Hemodynamics was measured bilaterally in the motor and somatosensory cortices with functional near-infrared spectroscopy (fNIRS) in response to thermal pain induced ipsilaterally to the knee primarily affected by OA. Results: We found that both oxyhemoglobin- and deoxyhemoglobin-related functional activations significantly increased during the course of the tDCS treatment, supporting the notion that tDCS yields an increased cortical excitability. Concurrently, clinical measures of pain decreased with tDCS treatment, hinting at a potential spatial dissociation between cortically mediated pain perception and suppression and the prevalence of neuromodulatory effects over cortical pain processing. Conclusions: fNIRS is a valid method for objectively tracking pain in an ambulatory setting and it could potentially be used to inform strategies for optimized tDCS treatment and to develop innovative tDCS protocols.