Transcutaneous vagus nerve stimulation prevents the development of, and reverses, established oesophageal pain hypersensitivity

Unveiling the Multifaceted Problems Associated with Dysrhythmia

Dysrhythmia is a term referring to the occurrence of spontaneous and repetitive changes in potentials with parameters deviating from those considered normal. The term refers to heart anomalies but has a broader meaning. Dysrhythmias may concern the heart, neurological system, digestive system, and sensory organs. Ion currents conducted through ion channels are a universal phenomenon. The occurrence of channel abnormalities will therefore result in disorders with clinical manifestations depending on the affected tissue, but phenomena from other tissues and organs may also manifest themselves. A similar problem concerns the implementation of pharmacotherapy, the mechanism of which is related to the impact on various ion currents. Treatment in this case may cause unfavorable effects on other tissues and organs. Drugs acting through the modulation of ion currents are characterized by relatively low tissue specificity. To assess a therapy's efficacy and safety, the risk of occurrences in other tissues with similar mechanisms of action must be considered. In the present review, the focus is shifted prominently onto a comparison of abnormal electrical activity within different tissues and organs. This review includes an overview of the types of dysrhythmias and the basic techniques of clinical examination of electrophysiological disorders. It also presents a concise overview of the available pharmacotherapy in particular diseases. In addition, the authors review the relevant ion channels and their research technique based on patch clumping.

Non-invasive neuromodulation: an emerging intervention for visceral pain in gastrointestinal disorders

Gastrointestinal (GI) disorders, which extend from the esophagus to the anus, are the most common diseases of the GI tract. Among these disorders, pain, encompassing both abdominal and visceral pain, is a predominant feature, affecting the patients' quality of life and imposing a substantial financial burden on society. Pain signals originating from the gut intricately shape brain dynamics. In response, the brain sends appropriate descending signals to respond to pain through neuronal inhibition. However, due to the heterogeneous nature of the disease and its limited pathophysiological understanding, treatment options are minimal and often controversial. Consequently, many patients with GI disorders use complementary and alternative therapies such as neuromodulation to treat visceral pain. Neuromodulation intervenes in the central, peripheral, or autonomic nervous system by alternating or modulating nerve activity using electrical, electromagnetic, chemical, or optogenetic methodologies. Here, we review a few emerging noninvasive neuromodulation approaches with promising potential for alleviating pain associated with functional dyspepsia, gastroparesis, irritable bowel syndrome, inflammatory bowel disease, and non-cardiac chest pain. Moreover, we address critical aspects, including the efficacy, safety, and feasibility of these noninvasive neuromodulation methods, elucidate their mechanisms of action, and outline future research directions. In conclusion, the emerging field of noninvasive neuromodulation appears as a viable alternative therapeutic avenue for effectively managing visceral pain in GI disorders.

Transcutaneous electrical stimulation for gastrointestinal motility disorders

BACKGROUND/PURPOSE

Gastrointestinal (GI) dysmotility is categorized by muscle or nerve dysfunctions in any portion of the GI tract, which leads to abnormalities in GI motor and sensory function. Symptoms may vary depending on the organ affected and can be debilitating. Treatment usually involves diet and lifestyle changes. Pharmacotherapy is limited in effectiveness with various side effects. Transcutaneous electrical stimulation (TES), a noninvasive, needleless technique that provides electrical stimulation using cutaneous non-needle electrodes, has become increasingly popular. It has been shown to be beneficial in treating GI motility disorders.

METHODS

This review paper navigates through the different TES techniques, including transcutaneous peripheral nerve (vagal/sacral/tibial nerves) electrical stimulation, transcutaneous electrical acustimulation (stimulation via acupuncture point), transcutaneous interferential current therapy, and transcutaneous electrical nerve stimulation.

KEY RESULTS

As we delve deeper, we explore the promising effects of TES on dysphagia, gastroesophageal reflux disease, functional dyspepsia, gastroparesis, postoperative ileus, constipation, and irritable bowel syndrome. The literature at hand speaks volumes about the therapeutic prowess of this noninvasive technique.

CONCLUSION & INFERENCES

The time is ripe to evaluate further the full therapeutic potential of TES, a noninvasive, nonpharmaceutical, nonsurgical, and home-based self-administrative technique in managing GI motility disorders.

Role of Vagus Nerve Stimulation in the Treatment of Chronic Pain

Vagus nerve stimulation (VNS) can modulate vagal activity and neuro-immune communication. Human and animal studies have provided growing evidence that VNS can produce analgesic effects in addition to alleviating refractory epilepsy and depression. The vagus nerve (VN) projects to many brain regions related to pain processing, which can be affected by VNS. In addition to neural regulation, the anti-inflammatory property of VNS may also contribute to its pain-inhibitory effects. To date, both invasive and noninvasive VNS devices have been developed, with noninvasive devices including transcutaneous stimulation of auricular VN or carotid VN that are undergoing many clinical trials for chronic pain treatment. This review aimed to provide an update on both preclinical and clinical studies of VNS in the management for chronic pain, including fibromyalgia, abdominal pain, and headaches. We further discuss potential underlying mechanisms for VNS to inhibit chronic pain.

[Clinical efficacy of auricular vagus nerve stimulation in the treatment of chronic and acute pain : A systematic review]

BACKGROUND

Current guidelines recommend a personalized, multimodal, and interdisciplinary approach for the treatment of chronic pain. Already in the acute treatment of postoperative pain, it can be useful to minimize risk factors for chronification. Auricular vagus nerve stimulation (aVNS) could be an effective non-drug therapy for the treatment of chronic and acute pain.

AIM OF THE WORK

The aim of this systematic review is to evaluate the clinical efficacy of aVNS in chronic and acute pain as well as its effect on medication intake.

MATERIALS AND METHODS

A systematic literature search was carried out on the application of auricular electrical stimulation in chronic and acute pain. Studies were classified according to their level of evidence and evaluated via the Jadad scale as well as their scientific validity, and then analyzed in terms of indication, method, stimulation parameters, duration of treatment, efficacy, and safety.

RESULTS

Twenty studies on chronic pain indications, ten studies on acute postoperative pain, as well as seven studies on experimental acute pain were identified and analyzed. The search revealed a total of n = 1105 aVNS-treated patients. The best evidence on the efficacy of aVNS is available for the indications chronic low back pain, chronic cervical syndrome, chronic abdominal pain, and chronic migraine as well as acute postoperative pain in oocyte aspiration, laparoscopic nephrectomy, and open colorectal surgery. Additionally a significant reduction in analgesic or opiate intake was evident in most studies. In three randomized controlled trials in chronic pain patients, a sustainable pain reduction over a period of up to 12 months was shown. Overall, aVNS was very well tolerated.

CONCLUSION

This review indicates that aVNS can be a complementary and effective non-drug treatment for patients with chronic and acute postoperative pain. Future studies in these indications should focus on standardizing and optimizing treatment parameters, inclusion of quality-of-life outcome parameters, and longer follow-up periods to better understand the sustainable therapeutic effect of aVNS.

Brain effect of transcutaneous vagal nerve stimulation: A meta-analysis of neuroimaging evidence

BACKGROUND

Dysfunction in the autonomic nervous system is common throughout many functional gastrointestinal diseases (FGIDs) that have been historically difficult to treat. In recent years, transcutaneous vagal nerve stimulation (tVNS) has shown promise for improving FGID symptoms. However, the brain effects of tVNS remain unclear, which we investigated by neuroimaging meta-analysis.

METHODS

A total of 157 studies were identified, 4 of which were appropriate for inclusion, encompassing 60 healthy human participants. Using activation likelihood analysis estimation, we statistically quantified functional brain activity changes across three domains: (1) tVNS vs. null stimulation, (2) tVNS vs. sham stimulation, and (3) sham stimulation vs. null stimulation.

KEY RESULTS

tVNS significantly increased activity in the insula, anterior cingulate, inferior and superior frontal gyri, caudate and putamen, and reduced activity in the hippocampi, occipital fusiform gyri, temporal pole, and middle temporal gyri, when compared to null stimulation (all corrected p < 0.005). tVNS increased activity in the anterior cingulate gyrus, left thalamus, caudate, and paracingulate gyrus and reduced activity in right thalamus, posterior cingulate cortex, and temporal fusiform cortex, when compared to sham stimulation (all corrected p < 0.005). Sham stimulation significantly increased activity in the insula and reduced activity in the posterior cingulate and paracingulate gyrus (all corrected p < 0.001), when contrasted to null stimulation.

CONCLUSIONS

Brain effects of tVNS localize to regions associated with both physiological autonomic regulation and regions whose activity is modulated across numerous FGIDs, which may provide a neural basis for efficacy of this treatment. Functional activity differences between sham and null stimulation illustrate the importance of robust control procedures for future trials.

Transcutaneous vagal nerve stimulation protects against stress-induced intestinal barrier dysfunction in healthy adults

BACKGROUND

Intestinal barrier dysfunction is the likely initiating event in multiple human diseases. Currently, there are limited therapeutic strategies to address its dysfunction. Animal studies suggest that vagal nerve stimulation may improve intestinal barrier function, but this has not been evaluated in humans. This study aimed to determine the effect of vagal nerve stimulation on intestinal permeability in adults administered a bolus dose of intravenous corticotropin releasing hormone (CRH) which has been shown to increase small intestinal permeability in healthy human subjects.

METHODS

In a cross-over study, 16 volunteers (median age 34 years, 11 female) were randomized to receive auricular transcutaneous vagal nerve or sham stimulation (10 minutes each side) after intravenous administration of 100 µg of CRH. Intestinal barrier function was measured before and 2 h after each intervention with dual-sugar urine testing (lactulose:mannitol ratio) and intestinal fatty-acid binding protein (I-FABP).

KEY RESULTS

Exposure to CRH increased I-FABP concentrations by a median of 49 (IQR 4-71)% (p = 0.009). Lactulose:mannitol ratios were 0.029 (0.025-0.050) following vagal stimulation compared with 0.062 (0.032-0.170) following sham stimulation (p = 0.0092), representing a fall of 53 (22-71)%. I-FABP concentrations did not change (p = 0.90).

CONCLUSIONS

Brief non-invasive vagal nerve stimulation consistently reduces paracellular permeability of the small intestine after CRH administration, but does not entirely mitigate I-FABP release from the epithelium. Studies of vagal nerve stimulation in disease states are warranted.

Effect of Transauricular Vagus Nerve Stimulation on Rebound Pain After Ropivacaine Single Injection Femoral Nerve Block for Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

Purpose

The aim of this study was to investigate whether transauricular vagus nerve stimulation (taVNS) could reduce the incidence of rebound pain in patients undergoing anterior cruciate ligament reconstruction (ACLR) under general anesthesia combined with preoperative femoral nerve block.

Methods

In total, 78 patients were enrolled in this prospective, randomized, double-blind, and sham-controlled study. Patients were randomly assigned to 2 groups (n=39): Group taVNS received taVNS (1h /1time, 6times) within the first 12 h after surgery; Group SS received sham stimulation (SS) in the same manner. Pain scores at 0, 4, 8, 12, 24, 48 h after surgery were assessed with Numeric Pain Rating Scale (NRS). The incidence, duration and onset of rebound pain were recorded. In addition, additional analgesic requirements and side effects in the first 48 h postoperatively, as well as sleep disturbance on the night of surgery, were examined.

Results

The incidence and duration of rebound pain were lower in the taVNS group than in the SS group (P=0.025 and P=0.015, respectively). Pain scores at 8 h and 12 h postoperatively were significantly lower in the taVNS group compared with the SS group (P<0.05). The number of times to press the patient-controlled analgesia (PCA) pump and the number of patients requiring additional analgesic were significantly lower in the taVNS group than in the SS group until 12 h after surgery (P=0.021 and P=0.004, respectively). The number of patients with sleep disturbance in the taVNS group was lower than that in the SS group (P=0.030).

Conclusion

The taVNS exerts beneficial effect on rebound pain after femoral nerve block in patients undergoing ACLR, which reduces the incidence and duration of rebound pain, the need for postoperative additional analgesic, and the number of complications.

Review article: current and future treatment approaches for pain in IBS

BACKGROUND

Abdominal pain is a core symptom of IBS and a primary driver of care seeking. Visceral hypersensitivity is a key pathophysiological mechanism and therapeutic target for pain in IBS, with components of peripheral and central sensitisation and psychological factors.

AIM

To review current and future treatment approaches specifically for the pain component of IBS.

METHODS

Pubmed search terms included combinations of irritable bowel, pain, visceral hypersensitivity, novel, new, emerging, future and advances.

RESULTS

Established non-pharmacological treatments for IBS pain include the low FODMAP diet, probiotics and psychological interventions, especially hypnotherapy. Tricyclics remain the best evidenced pharmacological approach with GCC agonists, tenapanor, lubiprostone, eluxadoline and 5HT3 antagonists second line according to patient characteristics and availability. Less well-evidenced current options include anti-spasmodics, peppermint oil, SSRIs, SNRIs, alpha 2 delta ligands, melatonin and histamine antagonists. Patients are vulnerable to iatrogenesis and harmful approaches to be avoided include opioids and unwarranted surgical interventions. For severe pain, the concept of augmentation with combined gut-brain neuromodulators and psychotherapy in a multi-disciplinary setting is considered. A plethora of molecular targets and ligands are emerging from pre-clinical studies, together with early clinical evidence for a range of pharmacological, dietary, neurostimulation and novel psychological treatment delivery methods which are reviewed. The history of such emerging approaches, however, merits both caution and optimism in equal measure.

CONCLUSIONS

Despite good in-roads and emerging options, the management of abdominal pain remains one of the biggest challenges and research priorities for patients with IBS.

Ameliorating effects and mechanisms of transcutaneous auricular vagal nerve stimulation on abdominal pain and constipation

BackgroundAbdominal pain and constipation are 2 main symptoms in patients with constipation-predominant irritable bowel syndrome (IBS-C). This study aimed to investigate the effects and possible mechanisms of transcutaneous auricular vagal nerve stimulation (taVNS) in patients with IBS-C.MethodsForty-two patients with IBS-C were randomized into a 4-week sham-taVNS or taVNS treatment. The primary outcomes were complete spontaneous bowel movements per week (CSBMs/week) and visual analog scale (VAS) for abdominal pain. High-resolution anorectal manometry (HRAM) was performed to evaluate anorectal motor and sensory function. Cytokines and brain gut peptides were analyzed in blood samples. ECG was recorded for the assessment of autonomic function.ResultsCompared with sham-taVNS, (a) taVNS increased CSBMs/week (P = 0.001) and decreased VAS pain score (P = 0.001); (b) improved quality of life (P = 0.020) and decreased IBS symptom score (P = 0.001); (c) improved rectoanal inhibitory reflex (P = 0.014) and improved rectal sensation (P < 0.04); (d) decreased a number of proinflammatory cytokines and serotonin in circulation; and (e) enhanced vagal activity (P = 0.040). The vagal activity was weakly correlated with the CSBMs/week (r = 0.391; P = 0.010) and the VAS pain score (r = -0.347; P = 0.025).ConclusionsNoninvasive taVNS improves both constipation and abdominal pain in patients with IBS-C. The improvement in IBS-C symptoms might be attributed to the integrative effects of taVNS on intestinal functions mediated via the autoimmune mechanisms.Trial registrationwww.chictr.org.cn, no. ChiCTR2000029644.FundingNational Natural Science Foundation of China (grant no. 81970538 for FL).

Transcutaneous Auricular Vagus Nerve Stimulation Combined With Slow Breathing: Speculations on Potential Applications and Technical Considerations

OBJECTIVES

Transcutaneous auricular vagus nerve stimulation (taVNS) is a relatively novel noninvasive neurostimulation method that is believed to mimic the effects of invasive cervical VNS. It has recently been suggested that the effectiveness of taVNS can be enhanced by combining it with controlled slow breathing. Slow breathing modulates the activity of the vagus nerve and is used in behavioral medicine to decrease psychophysiological arousal. Based on studies that examine the effects of taVNS and slow breathing separately, this article speculates on some of the conditions in which this combination treatment may prove effective. Furthermore, based on findings from studies on the optimization of taVNS and slow breathing, this article provides guidance on how to combine taVNS with slow breathing.

MATERIALS AND METHODS

A nonsystematic review.

RESULTS

Both taVNS and slow breathing are considered promising add-on therapeutic approaches for anxiety and depressive disorders, chronic pain, cardiovascular diseases, and insomnia. Therefore, taVNS combined with slow breathing may produce additive or even synergistic beneficial effects in these conditions. Studies on respiratory-gated taVNS during spontaneous breathing suggest that taVNS should be delivered during expiration. Therefore, this article proposes to use taVNS as a breathing pacer to indicate when and for how long to exhale during slow breathing exercises.

CONCLUSIONS

Combining taVNS with slow breathing seems to be a promising hybrid neurostimulation and behavioral intervention.

Bioelectronics in the brain-gut axis: focus on inflammatory bowel disease (IBD)

Accumulating evidence shows that intestinal homeostasis is mediated by cross-talk between the nervous system, enteric neurons and immune cells, together forming specialized neuroimmune units at distinct anatomical locations within the gut. In this review, we will particularly discuss how the intrinsic and extrinsic neuronal circuitry regulates macrophage function and phenotype in the gut during homeostasis and aberrant inflammation, such as observed in inflammatory bowel disease (IBD). Furthermore, we will provide an overview of basic and translational IBD research using these neuronal circuits as a novel therapeutic tool. Finally, we will highlight the different challenges ahead to make bioelectronic neuromodulation a standard treatment for intestinal immune-mediated diseases.

Vagal Nerve Stimulation-Modulation of the Anti-Inflammatory Response and Clinical Outcome in Psoriatic Arthritis or Ankylosing Spondylitis

Objectives

The vagal nerve exerts an essential pathway in controlling the cholinergic anti-inflammatory reflex. Thus, the study is aimed at investigating the acute effect of a noninvasive transcutaneous vagus nerve stimulation on clinical disease activity and systemic levels of inflammation in patients with psoriatic arthritis or ankylosing spondylitis.

Methods

Twenty patients with psoriatic arthritis (PsA) and 20 patients with ankylosing spondylitis (AS) were included and stimulated bilaterally with a handheld vagal nerve stimulator for 120 seconds 3 times a day for 5 consecutive days. All patients were in remission. Cardiac vagal tone, clinical scores, CRP, and cytokine levels were assessed.

Results

In PsA and AS, decreased heart rate was observed, confirming compliance. Furthermore, in PsA, a clear reduction of clinical disease activity associated with a 20% reduction in CRP was shown. In AS, a reduction in interferon-γ, interleukin- (IL-) 8, and 10 was shown. No side effects were described.

Conclusion

This open-label study provides support for an anti-inflammatory effect of transcutaneous vagus nerve stimulation in patients with psoriatic arthritis and ankylosing spondylitis. The modulated immune response and reduced disease activity and CRP-levels raise the fascinating possibility of using neuromodulation as an add-on to existing pharmacological treatments.