Effect of dry-electrode-based transcranial direct current stimulation on chronic low back pain and low back muscle activities: A double-blind sham-controlled study

Uncorking the limitation-improving dual tasking using transcranial electrical stimulation and task training in the elderly: a systematic review

Introduction

With aging, dual task (DT) ability declines and is more cognitively demanding than single tasks. Rapidly declining DT performance is regarded as a predictor of neurodegenerative disease. Task training and non-invasive transcranial electrical stimulation (tES) are methods applied to optimize the DT ability of the elderly.

Methods

A systematic search was carried out in the PUBMED, TDCS (transcranial direct current stimulation) databases, as well as Web of Science, and a qualitative analysis was conducted in 56 included studies. Aiming to summarize the results of studies that implemented tES, task training, or the combination for improving DT ability and related performance changes in healthy elderly and geriatric patients. For different approaches, the training procedures, parameters, as well as outcomes were discussed.

Results

Task training, particularly cognitive-motor DT training, has more notable effects on improving DT performance in the elderly when compared to the neuromodulation method.

Discussion

Anodal transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (L-DLPFC), or its combination with task training could be promising tools. However, additional evidence is required from aged healthy people and patients, as well as further exploration of electrode montage.

Non-invasive brain neuromodulation techniques for chronic low back pain

Structural and functional changes of the brain occur in many chronic pain conditions, including chronic low back pain (CLBP), and these brain abnormalities can be reversed by effective treatment. Research on the clinical applications of non-invasive brain neuromodulation (NIBS) techniques for chronic pain is increasing. Unfortunately, little is known about the effectiveness of NIBS on CLBP, which limits its application in clinical pain management. Therefore, we summarized the effectiveness and limitations of NIBS techniques on CLBP management and described the effects and mechanisms of NIBS approaches on CLBP in this review. Overall, NIBS may be effective for the treatment of CLBP. And the analgesic mechanisms of NIBS for CLBP may involve the regulation of pain signal pathway, synaptic plasticity, neuroprotective effect, neuroinflammation modulation, and variations in cerebral blood flow and metabolism. Current NIBS studies for CLBP have limitations, such as small sample size, relative low quality of evidence, and lack of mechanistic studies. Further studies on the effect of NIBS are needed, especially randomized controlled trials with high quality and large sample size.

Analysis of Muscular Electrical Activity and Blood Perfusion of Upper Extremity in Patients with Hemiplegic Shoulder Pain: A Pilot Study

Background

Hemiplegic shoulder pain (HSP) is a common symptom for post-stroke patients, which has a severely adverse impact on their rehabilitation outcomes. However, the cause of HSP has not been clearly identified due to its complicated multifactorial etiologies. As possible causes of HSP, the abnormality of both muscular electrical activity and blood perfusion remains lack of investigations.

Objective

This study aimed to analyze the alteration of muscular electrical activity and blood perfusion of upper extremity in patients with HSP by using surface electromyography (sEMG) and laser speckle contrast imaging (LSCI) measurement techniques, which may provide some insight into the etiology of HSP.

Methods

In this observational and cross-sectional study, three groups of participants were recruited. They were hemiplegic patients with shoulder pain (HSP group), hemiplegic patients without shoulder pain (HNSP group), and healthy participants (Healthy group). The sEMG data and blood perfusion data were collected from all the subjects and used to compute three different physiological measures, the root-mean-square (RMS) and median-frequency (MDF) parameters of sEMG recordings, and the perfusion unit (PU) parameter of blood perfusion imaging.

Results

The RMS parameter of sEMG showed significant difference (p < 0.05) in the affected side between HSP, HNSP, and Healthy groups. The MDF parameter of sEMG and PU parameter of blood perfusion showed no significant difference in both sides among the three groups (p > 0.05). The RMS parameter of sEMG showed a statistically significant correlation with the pain intensity (r = -0.691, p =0.012).

Conclusion

This study indicated that the muscular electrical activity of upper extremity had a correlation with the presence of HSP, and the blood perfusion seemed to be no such correlation. The findings of the study suggested an alternative way to explore the mechanism and treatment of HSP.

Correlation between change in pain, disability, and surface electromyography topographic parameters after interferential current treatment in patients with chronic low back pain

[Purpose] Surface electromyography (SEMG) topography is used to objectively assess patients with low back pain (LBP). This study aimed to investigate the correlation between SEMG topographic variables, pain, and disability in patients with chronic LBP (CLBP) after interferential current (IFC) treatment, and to evaluate IFC treatment efficacy using SEMG topography. [Participants and Methods] Twenty nine patients with CLBP were recruited for a 6-week IFC treatment. Pain and disability scores, and the root-mean-square difference (RMSD) of SEMG topographic variables (relative areas [RAs] at flexion and extension) were compared before and after the intervention by repeated measures ANOVA; the correlation between variables was also explored and p-value was set at 0.001. [Results] Significant positive correlations between changes in pain score and the RMSD of RA at flexion (r(29)=0.593), and between changes in pain and disability scores (r(29)=0.426) were observed. All participants showed statistically significant improvements in the RMSD of RA at flexion, pain score, and disability score after IFC treatment. [Conclusion] SEMG topographic variables are closely associated with changes in pain score in patients with CLBP after IFC treatment. The RMSD of RA at flexion can be used as an objective marker in IFC treatment efficacy evaluation.

Brain Circuits Involved in the Development of Chronic Musculoskeletal Pain: Evidence From Non-invasive Brain Stimulation

It has been well-documented that the brain changes in states of chronic pain. Less is known about changes in the brain that predict the transition from acute to chronic pain. Evidence from neuroimaging studies suggests a shift from brain regions involved in nociceptive processing to corticostriatal brain regions that are instrumental in the processing of reward and emotional learning in the transition to the chronic state. In addition, dysfunction in descending pain modulatory circuits encompassing the periaqueductal gray and the rostral anterior cingulate cortex may also be a key risk factor for pain chronicity. Although longitudinal imaging studies have revealed potential predictors of pain chronicity, their causal role has not yet been determined. Here we review evidence from studies that involve non-invasive brain stimulation to elucidate to what extent they may help to elucidate the brain circuits involved in pain chronicity. Especially, we focus on studies using non-invasive brain stimulation techniques [e.g., transcranial magnetic stimulation (TMS), particularly its repetitive form (rTMS), transcranial alternating current stimulation (tACS), and transcranial direct current stimulation (tDCS)] in the context of musculoskeletal pain chronicity. We focus on the role of the motor cortex because of its known contribution to sensory components of pain via thalamic inhibition, and the role of the dorsolateral prefrontal cortex because of its role on cognitive and affective processing of pain. We will also discuss findings from studies using experimentally induced prolonged pain and studies implicating the DLPFC, which may shed light on the earliest transition phase to chronicity. We propose that combined brain stimulation and imaging studies might further advance mechanistic models of the chronicity process and involved brain circuits. Implications and challenges for translating the research on mechanistic models of the development of chronic pain to clinical practice will also be addressed.

Mapping Responses of Lumbar Paravertebral Muscles to Single-Pulse Cortical TMS Using High-Density Surface Electromyography

Motor evoked potential (MEP), which was elicited by transcranial magnetic stimulation (TMS), has been widely used to detect corticospinal projection from TMS cortical site to trunk muscles. It can help to find the stimulation hotspot in the scalp. However, it fails to precisely describe coordinated activities of trunk muscle groups with only single-channel myoelectric signal. In this study, we aimed to use high-density surface electromyography (sEMG) to explore the effect of cortical TMS on lumbar paravertebral muscles in healthy subjects. The cortical site at 1 cm anterior and 4 cm lateral to vertex was chosen to simulate using a single-pulse TMS with different intensities and forward-bending angles. A high-density electrode array (45 channels) was placed on the surface of lumbar paravertebral muscles to record sEMG signals during a TMS experiment. MEP signals elicited by TMS were extracted from 45-channel recordings and one topographic map of the MEP amplitudes with six spatial features was constructed at each sampling point. The results showed TMS could successfully evoke an oval area with high intensity in the MEP topographic map, while this area mainly located in ipsilateral side of the TMS site. Intensity features related to the high intensity area rose significantly with TMS intensity and forward-bending angle increasing, but location features showed no change. The optimal stimulation parameters were 80% of maximum stimulator output (MSO) for TMS intensity and 30/60 degree for forward-bending angle. This study provided a potentially effective mapping tool to explore the hotspot for transcranial stimulation on trunk muscles.

Invasive and Non-Invasive Electrical Neuromodulation in Trigeminal Nerve Neuralgia: A Systematic Review and Meta-Analysis

BACKGROUND

Trigeminal neuralgia is a chronic disease characterized by intense facial pain that is caused by trigeminal nerve affectation. It usually affects adults from 50 years of age, and is more frequent in women. Additionally, it presents serious psychological effects that often lead to depression, which is why it is considered highly disabling. The therapeutic approach is based on the modification of nerve activity through electrical, surgical or chemical stimulation in specific regions of the nervous system.

OBJECTIVE

To perform a meta-analysis of the scientific literature related to invasive and non-invasive electrical neuromodulation of trigeminal neuralgia, in order to assess their effects over pain and adverse effects.

METHODS

A literature search was conducted in 4 databases, followed by a manual search of articles on invasive or non-invasive electrical neuromodulation to control the pain of trigeminal neuralgia, including the last 15 years.

RESULTS

Regarding non-invasive methods, clinical trials did not present enough results in order to perform a meta-analysis. Regarding invasive methods, clinical trials meta-analysis showed no statistical differences between different treatment methods. In all cases, improvements in patients' pain were reported, although results regarding adverse effects were variable.

CONCLUSION

In the treatment of trigeminal neuralgia, the continuous radiofrequency provides better short and medium-term results, but pulsed radiofrequency shows less adverse effects after treatment, and has better results in the long-term.

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.