When a White Horse is a Horse: Embracing the (Obvious?) Overlap Between Acupuncture and Neuromodulation

Recent advances in acupuncture for pain relief

Introduction

Acupuncture therapy has achieved global expansion and shown promise for health promotion and treatment of acute/chronic pain.

Objectives

To present an update on the existing evidence base for research and clinical practice supporting acupuncture analgesia.

Methods

This Clinical Update elaborates on the 2023 International Association for the Study of Pain Global Year for Integrative Pain Care "Factsheet Acupuncture for Pain Relief" and reviews best evidence and practice.

Results

Acupuncture is supported by a large research evidence base and growing utilization. Mechanisms of acupuncture analgesia include local physiological response at the needling site, suppression of nociceptive signaling at spinal and supraspinal levels, and peripheral/central release of endogenous opioids and other biochemical mediators. Acupuncture also produces pain relief by modulating specific brain networks, integral for sensory, affective, and cognitive processing, as demonstrated by neuroimaging research. Importantly, acupuncture does not just manage pain symptoms but may target the sources that drive pain, such as inflammation, partially by modulating autonomic pathways. Contextual factors are important for acupuncture analgesia, which is a complex multifaceted intervention. In clinical practice, historical records and many providers believe that acupuncture efficacy depends on specific acupoints used, the technique of needle placement and stimulation, and the person who delivers the procedure. Clinical research has supported the safety and effectiveness of acupuncture for various pain disorders, including acupuncture as a complementary/integrative therapy with other pain interventions.

Conclusion

Although the quality of supportive evidence is heterogeneous, acupuncture's potential cost-effectiveness and low risk profile under standardized techniques suggest consideration as a neuromodulatory and practical nonpharmacological pain therapy.

Exploratory Study of Biomechanical Properties and Pain Sensitivity at Back-Shu Points

OBJECTIVES

Hypersensitive acupoints in specific body areas are associated with corresponding internal or visceral disorders. Back-shu points are clinically significant for the diagnosis of visceral organ disease, according to the biomechanical characteristics of the acupoints. In this study, we assessed the biomechanical characteristics and pain sensitivities of five back-shu points linked to five visceral organs in healthy participants.

METHODS

The study included 48 volunteer participants. A myotonometry was used to assess muscle tone and muscle stiffness at five back-shu points associated with visceral organs. Pressure was monitored using a microcontroller and a force sensor. Pain sensitivity was assessed in response to deep pressure pain produced by a constant force.

RESULTS

Substantial differences in muscle tone and stiffness were observed at the five back-shu points; muscle tone was highest at BL15, whereas muscle tone and muscle stiffness were lowest at BL23. Moreover, pain sensitivity was significantly different among the acupoints; pain sensitivity was highest at BL23. There was a significant negative correlation between muscle tone and pain sensitivity.

CONCLUSIONS

We found significant differences in muscle tone, muscle stiffness, and pain sensitivity among five back-shu points associated with visceral organs, which may be attributable to anatomical variations at each point. Our findings suggest that differences at back-shu points should be considered to ensure the accurate diagnosis of visceral disease.

Using the right design controls for acupuncture trials: Methodological rigor and validity in research

Acupuncture treatment can be defined as a medical procedure with an acupuncture needle at acupoints. Establishing suitable control settings is essential, based on the target elements of the acupuncture therapy. In order to properly design a clinical trial or an experiment, a control group must be established. Here, we overview the significance of the control group and its limitations in acupuncture research. Clinical trials have employed a variety of study designs and controls for acupuncture treatment in order to compare the effects of actual treatments with control groups that include no treatment or treatment as usual, sham acupuncture at true acupoints, real acupuncture at non-acupoints, and sham acupuncture at non-acupoints. In order to determine the point-specificity of acupuncture, real acupuncture at non-acupoints should be taken into consideration, whereas sham acupuncture at the same true acupoints should be used to determine the needling-specific effect of acupuncture. It is crucial to choose the optimum control for acupuncture treatments depending on the study's main goal and to interpret the results in accordance with the research design.

Potential role of acupuncture in the treatment of Parkinson's disease: A narrative review

Background

The prevalence of Parkinson's disease (PD) has grown rapidly compared to that of other neurological disorders. Acupuncture has been used to address the complex symptoms of PD. Recently, similarities in the mechanisms of action between acupuncture and neuromodulation have received considerable attention. This review aims to summarize the evidence regarding these similarities to suggest potential role of acupuncture in the treatment of PD.

Methods

The literature from two electronic databases, PubMed and Google Scholar, was searched using the search terms 'Acupuncture', 'Parkinson's disease', 'Vagus nerve stimulation', and 'Brain functional connectivity'. We then explored the evidence for the effectiveness of acupuncture in PD and evaluated the evidence for similarities in the mechanisms of action between acupuncture and neuromodulation.

Results

Data suggests that acupuncture treatment is effective for PD symptoms by modulating inflammation and brain functional connectivity (BFC). These acupuncture effects have been shown to be similar to neuromodulation in controlling inflammation and BFC. Based on the shared mechanisms of action, potential acupuncture mechanisms that may ameliorate a wide range of PD symptoms include but are not limited to (1) vagal activation of the anti-inflammatory pathway and (2) BFC enhancement.

Conclusion

The development of acupuncture strategies based on shared mechanisms with neuromodulation will provide new treatment options for patients with PD as personalized neuromodulating therapies. Further studies are needed to gather scientific evidence for optimizing parameters in PD patients.

Intramuscular Electrical Stimulation to Trigger Points: Insights into Mechanisms and Clinical Applications—A Scoping Review

Intramuscular electrical stimulation (IMES) is a modality used by clinicians to treat myofascial pain. Recent studies have shown positive results for the use of IMES on pain outcomes, yet studies investigating the potential mechanisms of IMES directly to trigger points (TrPs) are lacking. We performed a scoping review of the literature to summarize the current evidence from human and animal studies on the mechanisms of IMES to the TrP location, and to identify gaps in the existing literature. Electronic literature searches were conducted across five databases from inception to 15 August 2022, including PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Allied and Complementary Medicine Database (AMED), Scopus and Cochrane Register of Controlled Trials. Four studies met our full criteria for inclusion in this review. Three studies assessed the effects of IMES to TrPs on human subjects with MPS, and only one study used an animal model with experimentally generated TrPs. Based on the results of the included studies, IMES within a TrP region was reported to normalize muscle blood flow, decrease endplate noise of the TrP and elicit antinociceptive effects, at least partially, through engaging supraspinal descending pain inhibitory systems. At present, no clinical implications can be determined on the use of IMES to TrPs due to the limited amount and quality of the available evidence. Further studies investigating the clinical effectiveness and also underlying mechanisms of IMES to TrPs are clearly needed.

Memory-directed acupuncture as a neuromodulatory treatment for PTSD: Theory, clinical model and case studies

Posttraumatic stress disorder (PTSD) poses an ongoing challenge to society, to health systems, and to the trauma victims themselves. Today PTSD is often considered an incurable chronic problem that lacks effective treatment. While PTSD is closely related to memory, it also affects many physiological systems. PTSD is usually treated with medications and psychotherapy with moderate success, leaving a substantial proportion of patients with enduring distress and disability. Therefore, a search for better treatment options is vital. In this paper, we propose a model in which a conversation-based technique is integrated with bodily manipulation through acupuncture. This approach first emerged in clinical experience showing intriguing results from treating PTSD patients using acupuncture as a main strategy. Its theoretical foundations derive from the clinic and rely on contemporary neuroscience's understanding of memory consolidation and reconsolidation processes. Research shows that acupuncture can have potentially positive effects at three levels: (a) achieving a balance between sympathetic and parasympathetic neural activity; (b) reducing activation in the limbic system, hence inducing a calming effect; (c) reshaping the functional connectivity map within important and relevant cortical regions that encompass the default-mode network. We suggest that coupling traumatic memory retrieval leading to reconsolidation, combined with acupuncture, offers considerable potential for positive clinical improvement in patients with PTSD. This may explain the positive results of the described case studies and can pave the path for future advances in research and treatment in this field.

Activation of Subcutaneous Mast Cells in Acupuncture Points Triggers Analgesia

This review summarizes experimental evidence indicating that subcutaneous mast cells are involved in the trigger mechanism of analgesia induced by acupuncture, a traditional oriental therapy, which has gradually become accepted worldwide. The results are essentially based on work from our laboratories. Skin mast cells are present at a high density in acupuncture points where fine needles are inserted and manipulated during acupuncture intervention. Mast cells are sensitive to mechanical stimulation because they express multiple types of mechanosensitive channels, including TRPV1, TRPV2, TRPV4, receptors and chloride channels. Acupuncture manipulation generates force and torque that indirectly activate the mast cells via the collagen network. Subsequently, various mediators, for example, histamine, serotonin, adenosine triphosphate and adenosine, are released from activated mast cells to the interstitial space; they or their downstream products activate the corresponding receptors situated at local nerve terminals of sensory neurons in peripheral ganglia. The analgesic effects are thought to be generated via the reduced electrical activities of the primary sensory neurons. Alternatively, these neurons project such signals to pain-relevant regions in spinal cord and/or higher centers of the brain.

S1 Brain Connectivity in Carpal Tunnel Syndrome Underlies Median Nerve and Functional Improvement Following Electro-Acupuncture

Carpal Tunnel Syndrome (CTS) is a median nerve entrapment neuropathy that alters primary somatosensory cortex (S1) organization. While electro-acupuncture (EA), a form of peripheral neuromodulation, has been shown to improve clinical and neurophysiological CTS outcomes, the role of EA-evoked brain response during therapy (within and beyond S1) for improved outcomes is unknown. We investigated S1-associated whole brain fMRI connectivity during both a resting and sustained EA stimulation state in age-matched healthy controls (N = 28) and CTS patients (N = 64), at baseline and after 8 weeks of acupuncture therapy (local, distal, or sham EA). Compared to healthy controls, CTS patients at baseline showed decreased resting state functional connectivity between S1 and thalamic pulvinar nucleus. Increases in S1/pulvinar connectivity strength following verum EA therapy (combined local and distal) were correlated with improvements in median nerve velocity (r = 0.38, p = 0.035). During sustained local EA, compared to healthy controls, CTS patients demonstrated increased functional connectivity between S1 and anterior hippocampus (aHipp). Following 8 weeks of local EA therapy, S1/aHipp connectivity significantly decreased and greater decrease was associated with improvement in patients' functional status (r = 0.64, p = 0.01) and increased median nerve velocity (r = -0.62, p = 0.013). Thus, connectivity between S1 and other brain areas is also disrupted in CTS patients and may be improved following EA therapy. Furthermore, stimulus-evoked fMRI connectivity adds therapy-specific, mechanistic insight to more common resting state connectivity approaches. Specifically, local EA modulates S1 connectivity to sensory and affective processing regions, linked to patient function and median nerve health.

International Consensus Based Review and Recommendations for Minimum Reporting Standards in Research on Transcutaneous Vagus Nerve Stimulation (Version 2020)

Given its non-invasive nature, there is increasing interest in the use of transcutaneous vagus nerve stimulation (tVNS) across basic, translational and clinical research. Contemporaneously, tVNS can be achieved by stimulating either the auricular branch or the cervical bundle of the vagus nerve, referred to as transcutaneous auricular vagus nerve stimulation(VNS) and transcutaneous cervical VNS, respectively. In order to advance the field in a systematic manner, studies using these technologies need to adequately report sufficient methodological detail to enable comparison of results between studies, replication of studies, as well as enhancing study participant safety. We systematically reviewed the existing tVNS literature to evaluate current reporting practices. Based on this review, and consensus among participating authors, we propose a set of minimal reporting items to guide future tVNS studies. The suggested items address specific technical aspects of the device and stimulation parameters. We also cover general recommendations including inclusion and exclusion criteria for participants, outcome parameters and the detailed reporting of side effects. Furthermore, we review strategies used to identify the optimal stimulation parameters for a given research setting and summarize ongoing developments in animal research with potential implications for the application of tVNS in humans. Finally, we discuss the potential of tVNS in future research as well as the associated challenges across several disciplines in research and clinical practice.

Exploring traditional acupuncture point selection patterns for pain control: data mining of randomised controlled clinical trials

BACKGROUND

The underlying principles of traditional acupuncture point selection for pain control are complex. Analysis of acupuncture treatments from clinical studies may provide us with a potential rule when selecting traditional acupuncture points (hereafter abbreviated as "points") in treatment protocols for pain control. The aim of this study was to investigate which points were most commonly used to treat pain in randomised controlled clinical trials (RCTs).

METHODS

We searched acupuncture treatment regimens in RCTs included in the Cochrane Database of Systematic Reviews for pain management. We analysed information on point selection (more than 10 RCTs included) from seven eligible systematic reviews on pain control. The frequency of the points used was calculated and visualised using a human body template.

RESULTS

The points most commonly used across diseases were SP6, ST36, LI4 and LR3. However, the most frequently used points varied across individual conditions. For example, the most frequently used points to treat migraine were GB20, LR3, GV20, Taiyang, LI4 and TE5, while the most frequently used points to manage dysmenorrhoea were SP6, CV4, SP8, LR3 and BL32. Both regional and distal points were used for pain management with acupuncture.

CONCLUSIONS

Our findings suggest that local and segmental/extra-segmental neuromodulation appear to be the most common phenomena for pain control in acupuncture research. Analysis of information on point selection using a data-driven approach may unveil the hidden patterns of traditional acupuncture point utilisation in clinical practice.

Statistical inference of acupoint specificity: forward and reverse inference

Background

The acupoint specificity has been considered important issue in acupuncture research. In clinical aspects, it is essential to identify which acupoints are associated specifically with a particular disease. The present study aimed to identify the specificity of acupoint selection (forward inference) and the specificity of acupoint indication (reverse inference) from the online virtual diagnosis experiment.

Methods

Eighty Korean Medicine doctors conducted the virtual medical diagnoses provided for 10 different case reports. For forward inference, the acupoints prescribed for each disease were quantified and the data were normalised among 30 frequently used acupoints using Z-scores. For reverse inference, diseases for each acupoint were quantified and the data were normalized among 10 disease using Z-scores.

Results

Using forward inference we demonstrated the specificity of acupoint selection in each disease. Using reverse inference we identified the specificity of acupoint indication in each acupoint. In general, a certain acupoint can be selected specifically for a particular disease, and it has a specific indication for the disease. However, the specificity of acupoint indication and the specificity of acupoint selection are not always identical.

Conclusions

The selection of an acupoint for a particular disease does not imply that the acupoint has specific indications for that disease. Inferring the specificity of acupoint indication from clinical observations should be considered.