Psychophysiological responses to visceral and somatic pain in functional chest pain identify clinically relevant pain clusters

Vagal Neuromodulation in Chronic Heart Failure With Reduced Ejection Fraction: A Systematic Review and Meta-Analysis

Objectives: The aim of this study was to evaluate the effects of invasive vagal nerve stimulation (VNS) in patients with chronic heart failure (HF) and reduced ejection fraction (HFrEF).

Background: Heart failure is characterized by autonomic nervous system imbalance and electrical events that can lead to sudden death. The effects of parasympathetic (vagal) stimulation in patients with HF are not well-established.

Methods: From May 1994 to July 2020, a systematic review was performed using PubMed, Embase, and Cochrane Library for clinical trials, comparing VNS with medical therapy for the management of chronic HFrEF (EF ≤ 40%). A meta-analysis of several outcomes and adverse effects was completed, and GRADE was used to assess the level of evidence.

Results: Four randomized controlled trials (RCT) and three prospective studies, totalizing 1,263 patients were identified; 756 treated with VNS and 507 with medical therapy. RCT data were included in the meta-analysis (fixed-effect distribution). Adverse effects related to VNS were observed in only 11% of patients. VNS was associated with significant improvement (GRADE = High) in the New York Heart Association (NYHA) functional class (OR, 2.72, 95% CI: 2.07–3.57, p < 0.0001), quality of life (MD −14.18, 95% CI: −18.09 to −10.28, p < 0.0001), a 6-min walk test (MD, 55.46, 95% CI: 39.11–71.81, p < 0.0001) and NT-proBNP levels (MD −144.25, 95% CI: −238.31 to −50.18, p = 0.003). There was no difference in mortality (OR, 1.24; 95% CI: 0.82–1.89, p = 0.43).

Conclusions: A high grade of evidence demonstrated that vagal nerve stimulation improves NYHA functional class, a 6-min walk test, quality of life, and NT-proBNP levels in patients with chronic HFrEF, with no differences in mortality.

Functional Chest Pain and Esophageal Hypersensitivity: A Clinical Approach

Functional chest pain, functional heartburn, and reflux hypersensitivity are 3 functional esophageal disorders defined by the Rome IV criteria. Specific criteria, combining symptoms and the results of objective testing, allow for an accurate diagnosis of these conditions. Management may include medications targeted at optimizing acid suppression or neuromodulation, as well as a host of complementary or alternative treatment options. Psychological and behavioral interventions, such as cognitive behavioral therapy and hypnotherapy, have displayed substantial benefits in the treatment of functional chest pain and functional heartburn. Acid suppression and focused neuromodulation are key evidence-based treatment options for reflux hypersensitivity.

Post-inflammatory Abdominal Pain in Patients with Inflammatory Bowel Disease During Remission: A Comprehensive Review

Patients with inflammatory bowel disease often experience ongoing pain even after achieving mucosal healing (i.e., post-inflammatory pain). Factors related to the brain-gut axis, such as peripheral and central sensitization, altered sympatho-vagal balance, hypothalamic-pituitary-adrenal axis activation, and psychosocial factors, play a significant role in the development of post-inflammatory pain. A comprehensive study investigating the interaction between multiple predisposing factors, including clinical psycho-physiological phenotypes, molecular mechanisms, and multi-omics data, is still needed to fully understand the complex mechanism of post-inflammatory pain. Furthermore, current treatment options are limited and new treatments consistent with the underlying pathophysiology are needed to improve clinical outcomes.

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).

Short-term transcutaneous non-invasive vagus nerve stimulation may reduce disease activity and pro-inflammatory cytokines in rheumatoid arthritis: results of a pilot study

Objective: Rheumatoid arthritis (RA) is a chronic, autoimmune, inflammatory disease. Studies suggest that pro-inflammatory cytokines may be attenuated by the vagus nerve through the cholinergic anti-inflammatory pathway. We aimed to evaluate the anti-inflammatory effects of short-term transcutaneous non-invasive vagus nerve stimulation (n-VNS) applied to the cervical vagus nerve in patients with RA. Method: We conducted a single-centre, open-label, preliminary proof-of-concept study of n-VNS in two cohorts of participants with RA: one with high disease activity (n = 16) and one with low disease activity (n = 20). Disease Activity Score based on 28-joint count-C-reactive protein (DAS28-CRP), cardiac vagal tone, and pro-inflammatory cytokines were measured at baseline and after 1 and 4 days of n-VNS. Results: In the high disease activity group, n-VNS resulted in reductions in DAS28-CRP (4.1 to 3.8, p = 0.02), CRP (8.2 to 6 mg/mL, p = 0.01), and interferon-γ (29.8 to 22.5 pg/mL, p = 0.02). In the low disease activity group, there was no effect on DAS28-CRP, and n-VNS was associated with a decrease in cardiac vagal tone (p = 0.03) and a reduction in interleukin-10 (0.8 to 0.6 pg/mL, p = 0.02). Participants with high disease activity had lower baseline cardiac vagal tone than those with low disease activity (3.6 ± 2 vs 4.9 ± 3 linear vagal scale, p = 0.03). Cardiac vagal tone was negatively associated with DAS28-CRP (r = -0.37, p = 0.03). Overall, n-VNS was well tolerated. Conclusion: This study provides preliminary support for an anti-inflammatory effect of n-VNS in patients with RA. These findings warrant further investigation in larger placebo-controlled trials.

Esophageal physiology-an overview of esophageal disorders from a pathophysiological point of view

The esophagus serves the principal purpose of transporting food from the pharynx into the stomach. A complex interplay between nerves and muscle fibers ensures that swallowing takes place as a finely coordinated event. Esophageal function can be tested by a variety of methods, endoscopy, manometry, and reflux monitoring being some of the most important. Regarding pathophysiology, motor disorders, such as achalasia, often cause dysphagia and/or chest pain. Functional esophageal disorders are a heterogeneous group with hypersensitivity as a dominant pathophysiological factor. Gastroesophageal reflux disease often causes symptoms, such as heartburn and regurgitation, and a spectrum of disease, ranging from minimal mucosal damage visible only in the microscope to esophageal ulcers and strictures in the most severe cases. Eosinophilic esophagitis is an immune-mediated condition that can result in significant dysphagia and associated luminal narrowing. In the following, we will provide an overview of the most common esophageal disorders from a combined pathophysiological and clinical view.

The anatomical basis for transcutaneous auricular vagus nerve stimulation

The array of end organ innervations of the vagus nerve, coupled with increased basic science evidence, has led to vagus nerve stimulation (VNS) being explored as a management option in a number of clinical disorders, such as heart failure, migraine and inflammatory bowel disease. Both invasive (surgically implanted) and non-invasive (transcutaneous) techniques of VNS exist. Transcutaneous VNS (tVNS) delivery systems rely on the cutaneous distribution of vagal afferents, either at the external ear (auricular branch of the vagus nerve) or at the neck (cervical branch of the vagus nerve), thus obviating the need for surgical implantation of a VNS delivery device and facilitating further investigations across a wide range of uses. The concept of electrically stimulating the auricular branch of the vagus nerve (ABVN), which provides somatosensory innervation to several aspects of the external ear, is relatively more recent compared with cervical VNS; thus, there is a relative paucity of literature surrounding its operation and functionality. Despite the increasing body of research exploring the therapeutic uses of auricular transcutaneous VNS (tVNS), a comprehensive review of the cutaneous, intracranial and central distribution of ABVN fibres has not been conducted to date. A review of the literature exploring the neuroanatomical basis of this neuromodulatory therapy is therefore timely. Our review article explores the neuroanatomy of the ABVN with reference to (1) clinical surveys examining Arnold's reflex, (2) cadaveric studies, (3) fMRI studies, (4) electrophysiological studies, (5) acupuncture studies, (6) retrograde tracing studies and (7) studies measuring changes in autonomic (cardiovascular) parameters in response to auricular tVNS. We also provide an overview of the fibre composition of the ABVN and the effects of auricular tVNS on the central nervous system. Cadaveric studies, of which a limited number exist in the literature, would be the 'gold-standard' approach to studying the cutaneous map of the ABVN; thus, there is a need for more such studies to be conducted. Functional magnetic resonance imaging (fMRI) represents a useful surrogate modality for discerning the auricular sites most likely innervated by the ABVN and the most promising locations for auricular tVNS. However, given the heterogeneity in the results of such investigations and the various limitations of using fMRI, the current literature lacks a clear consensus on the auricular sites that are most densely innervated by the ABVN and whether the brain regions secondarily activated by electrical auricular tVNS depend on specific parameters. At present, it is reasonable to surmise that the concha and inner tragus are suitable locations for vagal modulation. Given the therapeutic potential of auricular tVNS, there remains a need for the cutaneous map of the ABVN to be further refined and the effects of various stimulation parameters and stimulation sites to be determined.

There might be a distinctive clinical phenotype of constipation with non-cardiac chest pain which responds to combination laxatives: A retrospective, longitudinal symptom analysis

Proton pump inhibitor (PPI)-refractory non-cardiac chest pain (NCCP) is often resolved when constipation was relieved. This study aimed to investigate the clinical features of patients with both NCCP and constipated functional bowel disorders (FBD).Among 692 consecutive patients diagnosed with functional constipation or irritable bowel syndrome with constipation and underwent anorectal manometry (ARM) in our hospital, PPI-refractory NCCP was present in 37. The clinical course of various torso symptoms including NCCP and ARM findings were retrospectively evaluated.The mean age was lower in the NCCP than in the non-NCCP group (57.4 vs 61.3 years, respectively, P = .042). Back pain (16.2% vs 2.0%, P < .001) and sharp abdominal pain (13.5% vs 0.9%, P < .001) were more common in the NCCP group. Increased resting pressure (16.2% vs 6.9%, P = .036) and squeezing pressure (62.2% vs 50.7%, P = .049) of the anal sphincter, increased urgency volume (40.5% vs 23.2%, P = .004), and maximal volume (25.7% vs 15.0%, P = .032) for rectal sensation were more frequently observed in the NCCP group. After taking laxatives for 1 to 3 months, 81.1% of patients with NCCP reported improvement.Subjects with NCCP showed decreased rectal sensation more frequently at anorectal manometry. Majority of patients with NCCP reported improvement of symptom upon relief of constipation. Constipation might be a therapeutic target in patients with NCCP related to constipated functional bowel disorders.

Advancements in the use of manometry and impedance testing for esophageal functional disorders

The utilization of high-resolution manometry (HRM) has enhanced our understanding and assessment of esophageal motor disorders. Moreover, the combination of impedance technology with HRM (HRIM) has further improved our knowledge of esophageal physiology and the clinical evaluation of dysmotility, thanks to the addition of accurate measurement of bolus transit. Areas covered. This paper provides an overview of current knowledge in the use of HRIM for the study of esophageal functional disorders by reporting mainly the results of many publications and several systematic reviews in this field. Expert opinion. HRIM has represented a relevant improvement in the assessment of esophageal motility and has required the development of new metrics, such as the esophageal impedance integral ratio, the bolus flow time, the nadir impedance pressure and the impedance bolus height, which increase the evaluation of esophageal bolus transit. An extension of impedance is represented by functional lumen imaging probe (FLIP), which determines the biophysical properties and the distensibility of the esophagus and permits to detect contractility patterns not seen on HRM alone. We eagerly wait for a new and fruitful iteration of the Chicago Classification, now in version 3.0, which can cover the ongoing clinical experience of HRIM.

The gut-brain axis in health neuroscience: implications for functional gastrointestinal disorders and appetite regulation

Over the past few years, scientific interest in the gut-brain axis (i.e., the bidirectional communication system between the gastrointestinal tract and the brain) has exploded, mostly due to the identification of the gut microbiota as a novel key player in this communication. However, important progress has also been made in other aspects of gut-brain axis research, which has been relatively underemphasized in the review literature. Therefore, in this review, we provide a comprehensive, although not exhaustive, overview of recent research on the functional neuroanatomy of the gut-brain axis and its relevance toward the multidisciplinary field of health neuroscience, excluding studies on the role of the gut microbiota. More specifically, we first focus on irritable bowel syndrome, after which we outline recent findings on the role of the gut-brain axis in appetite and feeding regulation, primarily focusing on the impact of subliminal nutrient-related gut-brain signals. We conclude by providing future perspectives to facilitate translation of the findings from gut-brain axis neuroscientific research to clinical applications in these domains.

Can a Brief Relaxation Exercise Modulate Placebo or Nocebo Effects in a Visceral Pain Model?

Translational research aiming to elucidate mediators and moderators of placebo and nocebo effects is highly relevant. This experimental study tested effects of a brief progressive muscle relaxation (PMR) exercise, designed to alter psychobiological stress parameters, on the magnitude of placebo and nocebo effects in a standardized psychosocial treatment context. In 120 healthy volunteers (60 men, 60 women), pain expectation, pain intensity, and pain unpleasantness in response to individually-calibrated rectal distensions were measured with visual analog scales during a baseline. Participants were then randomized to exercise PMR (relaxation group: N = 60) or a simple task (control group: N = 60), prior to receiving positive (placebo), negative (nocebo) or neutral suggestions regarding an intravenous administration that was in reality saline in all groups. Identical distensions were repeated (test). State anxiety, salivary cortisol, heart rate, and blood pressure were assessed repeatedly. Data were analyzed using analysis of covariance, planned Bonferroni-corrected group comparisons, as well as exploratory correlational and mediation analyses. Treatment suggestions induced group-specific changes in pain expectation, with significantly reduced expectation in placebo and increased expectation in nocebo groups. PMR had no discernable effect on pain expectation, state anxiety or cortisol, but led to significantly lower heart rate and systolic blood pressure. Relaxation significantly interacted with positive treatment suggestions, which only induced placebo analgesia in relaxed participants. No effects of negative suggestions were found in planned group comparisons, irrespective of relaxation. Exploratory correlation and mediation analyses revealed that pain expectation was a mediator to explain the association between treatment suggestions and pain-related outcomes. Clearly, visceral pain modulation is complex and involves many cognitive, emotional, and possibly neurobiological factors that remain to be fully understood. Our findings suggest that a brief relaxation exercise may facilitate the induction of placebo analgesia by positive when compared to neutral treatment suggestions. They underscore the contribution of relaxation and stress as psychobiological states within the psychosocial treatment context-factors which clearly deserve more attention in translational studies aiming to maximize positive expectancy effects in clinical settings.

Preliminary report: parasympathetic tone links to functional brain networks during the anticipation and experience of visceral pain

The mechanisms that underpin the anti-nociceptive effect of the parasympathetic nervous system (PNS) on visceral pain remain incompletely understood. We sought to describe the effect of resting parasympathetic tone on functional brain networks during the anticipation and experience of oesophageal pain. 21 healthy participants had their resting cardiac vagal tone (CVT), a validated measure of the PNS, quantified, and underwent functional magnetic resonance imaging during the anticipation and experience of painful oesophageal distention. The relationship between resting CVT and functional brain networks was examined using 11 hypothesis-driven nodes and network-based statistics. A network comprising all nodes was apparent in individuals with high resting CVT, compared to those with low CVT, during oesophageal pain (family wise error rate (FWER)-corrected p < 0.048). Functional connections included the thalamus-amygdala, thalamus-hypothalamus, hypothalamus-nucleus accumbens, amygdala-pallidum, pallidum-nucleus accumbens and insula-pallidum. A smaller network was seen during pain anticipation, comprising the amygdala, pallidum and anterior insula (FWER-corrected p < 0.049). These findings suggest that PNS tone is associated with functional brain networks during the anticipation and experience of visceral pain. Given the role of these subcortical regions in the descending inhibitory modulation of pain, these networks may represent a potential neurobiological explanation for the anti-nociceptive effect of the PNS.

Heart rate variability characteristics of patients with irritable bowel syndrome and associations with symptoms

BACKGROUND

Disturbed brain-gut interactions are assumed to be of importance for symptom generation in patients with irritable bowel syndrome (IBS). The autonomic nervous system (ANS) is part of the bidirectional brain-gut communication, but previous studies in IBS show diverging results. We aimed to identify subgroups of IBS patients with distinct ANS characteristics differentiating them from healthy controls (HC), and to study associations between ANS status and symptoms.

METHODS

Heart rate variability (HRV) was measured in IBS patients and HC (Holter monitoring: supine and standing positions with controlled respiration and ambulatory 24-hour period). Frequency (5 minutes, supine, standing) and time domains (24 hours, day, night) were analyzed. Validated questionnaires were used to measure gastrointestinal and psychological symptoms in patients. Patients and HC were compared on a univariate and multivariate level (principal component analysis [PCA] and orthogonal partial least squares discriminatory analysis (OPLS-DA)).

KEY RESULTS

We analyzed 158 IBS patients (Rome III) and 39 HC. Patients differed significantly from HC in HRV parameters during daytime and in standing position. In the PCA, a majority of patients overlapped with HC, but the weighted means differed (P < .01). A subset of patients (n = 30; 19%) with an aberrant global HRV profile was identified through PCA and OPLS-DA; these patients reported more severe symptoms of frequent (P < .05) and loose stools (P = .03), as well as urgency (P = .01).

CONCLUSIONS AND INFERENCES

Altered ANS function was demonstrated in patients with IBS, and this might be of particular relevance for symptoms in a subset of the patients.

Visceral hypersensitivity is associated with GI symptom severity in functional GI disorders: consistent findings from five different patient cohorts

OBJECTIVE

Our aim was to evaluate the association between visceral hypersensitivity and GI symptom severity in large cohorts of patients with functional GI disorder (FGID) and to adjust for psychological factors and general tendency to report symptoms.

DESIGN

We included five cohorts of patients with FGIDs (IBS or functional dyspepsia; n=1144), who had undergone visceral sensitivity testing using balloon distensions (gastric fundus, descending colon or rectum) and completed questionnaires to assess GI symptom severity, non-GI somatic symptoms, anxiety and depression. Subjects were divided into sensitivity tertiles based on pain/discomfort thresholds. GI symptom severity was compared between sensitivity tertiles in each cohort and corrected for somatisation, and anxiety and depression.

RESULTS

In all five cohorts, GI symptom severity increased gradually with increasing visceral sensitivity, with significant differences in GI symptom severity between the sensitivity tertiles (p<0.0001), with small to medium effect sizes (partial η²: 0.047-0.11). The differences between sensitivity tertiles remained significant in all cohorts after correction for anxiety and depression, and also after correction for non-GI somatic symptom reporting in all of the cohorts (p<0.05).

CONCLUSIONS

A gradual increase in GI symptom severity with increasing GI sensitivity was demonstrated in IBS and functional dyspepsia, which was consistent across several large patient groups from different countries, different methods to assess sensitivity and assessments in different parts of the GI tract. This association was independent of tendency to report symptoms or anxiety/depression comorbidity. These findings confirm that visceral hypersensitivity is a contributor to GI symptom generation in FGIDs.

Morphology of subcortical brain nuclei is associated with autonomic function in healthy humans

The autonomic nervous system (ANS) is a brain body interface which serves to maintain homeostasis by influencing a plethora of physiological processes, including metabolism, cardiorespiratory regulation and nociception. Accumulating evidence suggests that ANS function is disturbed in numerous prevalent clinical disorders, including irritable bowel syndrome and fibromyalgia. While the brain is a central hub for regulating autonomic function, the association between resting autonomic activity and subcortical morphology has not been comprehensively studied and thus was our aim. In 27 healthy subjects [14 male and 13 female; mean age 30 years (range 22-53 years)], we quantified resting ANS function using validated indices of cardiac sympathetic index (CSI) and parasympathetic cardiac vagal tone (CVT). High resolution structural magnetic resonance imaging scans were acquired, and differences in subcortical nuclei shape, that is, 'deformation', contingent on resting ANS activity were investigated. CSI positively correlated with outward deformation of the brainstem, right nucleus accumbens, right amygdala and bilateral pallidum (all thresholded to corrected P < 0.05). In contrast, parasympathetic CVT negatively correlated with inward deformation of the right amygdala and pallidum (all thresholded to corrected P < 0.05). Left and right putamen volume positively correlated with CVT (r = 0.62, P = 0.0047 and r = 0.59, P = 0.008, respectively), as did the brainstem (r = 0.46, P = 0.049). These data provide novel evidence that resting autonomic state is associated with differences in the shape and volume of subcortical nuclei. Thus, subcortical morphological brain differences in various disorders may partly be attributable to perturbation in autonomic function. Further work is warranted to investigate these findings in clinical populations. Hum Brain Mapp 39:381-392, 2018. © 2017 Wiley Periodicals, Inc.

The Potential Role of Sensory Testing, Skin Biopsy, and Functional Brain Imaging as Biomarkers in Chronic Pain Clinical Trials: IMMPACT Considerations

Valid and reliable biomarkers can play an important role in clinical trials as indicators of biological or pathogenic processes or as a signal of treatment response. Currently, there are no biomarkers for pain qualified by the U.S. Food and Drug Administration or the European Medicines Agency for use in clinical trials. This article summarizes an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials meeting in which 3 potential biomarkers were discussed for use in the development of analgesic treatments: 1) sensory testing, 2) skin punch biopsy, and 3) brain imaging. The empirical evidence supporting the use of these tests is described within the context of the 4 categories of biomarkers: 1) diagnostic, 2) prognostic, 3) predictive, and 4) pharmacodynamic. Although sensory testing, skin punch biopsy, and brain imaging are promising tools for pain in clinical trials, additional evidence is needed to further support and standardize these tests for use as biomarkers in pain clinical trials.

PERSPECTIVE

The applicability of sensory testing, skin biopsy, and brain imaging as diagnostic, prognostic, predictive, and pharmacodynamic biomarkers for use in analgesic treatment trials is considered. Evidence in support of their use and outlining problems is presented, as well as a call for further standardization and demonstrations of validity and reliability.

Acute physiological and electrical accentuation of vagal tone has no effect on pain or gastrointestinal motility in chronic pancreatitis

Background

The effective management of pain in chronic pancreatitis (CP) remains a therapeutic challenge. Analgesic drugs, such as opioids, and the underlying pathology can impair gut function. The autonomic nervous system influences hormone secretion and gut motility. In healthy volunteers, electrical (using noninvasive transcutaneous vagal nerve stimulation [t-VNS]) and physiological (using deep slow breathing [DSB]) modulation of parasympathetic tone results in pain attenuation and enhanced gut motility. Thus, the aims were to investigate whether t-VNS and DSB could enhance the parasympathetic tone, decrease pain sensitivity and improve gut motility in CP.

Patients and methods

A total of 20 patients (12 males, mean age=61 years, range: 50–78 years) with CP were randomized to short-term (60 minutes) t-VNS and DSB, or their placebo equivalent, in a crossover design. Cardiometrically derived parameters of autonomic tone, quantitative sensory testing of bone and muscle pain pressure, conditioned pain modulation (CPM) and assessments of gastroduodenal motility with ultrasound were performed.

Results

In comparison to sham, t-VNS and DSB increased cardiac vagal tone (CVT) (P<0.001). However, no changes in pain pressure thresholds for bone (P=0.95) or muscle (P=0.45) were seen. There was diminished CPM (P=0.04), and no changes in gastroduodenal motility were observed (P=0.3).

Conclusion

This explorative study demonstrated that t-VNS and DSB increased CVT in patients with CP. However, this short-lasting increase did not affect pain sensitivity to musculoskeletal pain or gastroduodenal motility. The chronic pain in CP patients is complex, and future trials optimizing neuromodulation for pain relief and improved motility are needed.

Transcutaneous cervical vagal nerve stimulation modulates cardiac vagal tone and tumor necrosis factor-alpha

The vagus nerve is a central component of cholinergic anti-inflammatory pathways. We sought to evaluate the effect of bilateral transcutaneous cervical vagal nerve stimulation (t-VNS) on validated parameters of autonomic tone and cytokines in 20 healthy subjects. 24 hours after t-VNS, there was an increase in cardiac vagal tone and a reduction in tumor necrosis factor-α in comparison to baseline. No change was seen in blood pressure, cardiac sympathetic index or other cytokines. These preliminary data suggest that t-VNS exerts an autonomic and a subtle antitumor necrosis factor-α effect, which warrants further evaluation in larger controlled studies.

The Role of Esophageal Hypersensitivity in Functional Esophageal Disorders

The Rome IV diagnostic criteria delineates 5 functional esophageal disorders which include functional chest pain, functional heartburn, reflux hypersensitivity, globus, and functional dysphagia. These are a heterogenous group of disorders which, despite having characteristic symptom profiles attributable to esophageal pathology, fail to demonstrate any structural, motility or inflammatory abnormalities on standard clinical testing. These disorders are associated with a marked reduction in patient quality of life, not least considerable healthcare resources. Furthermore, the pathophysiology of these disorders is incompletely understood. In this narrative review we provide the reader with an introductory primer to the structure and function of esophageal perception, including nociception that forms the basis of the putative mechanisms that may give rise to symptoms in functional esophageal disorders. We also discuss the provocative techniques and outcome measures by which esophageal hypersensitivity can be established.

Pharmacological and other treatment modalities for esophageal pain

Treatment of esophageal pain remains a major challenge for the clinician. Although many patients have heartburn and may respond to proton pump inhibitors, there in an unmet need for other treatment modalities in patients where there are no obvious pathological findings. Although analgesics are the mainstay in esophageal pain treatment, many patients are nonresponders to these drugs. The current concise review focuses on other systems affecting pain processing, where better understanding may serve as a framework for therapy. These are the parasympathetic nervous system, exercise, and personality profiles. Finally, treatment with analgesics for functional chest pain remains a challenge, and an overview of treatment with antidepressive drugs is provided.

Practice guidelines on the use of esophageal manometry - A GISMAD-SIGE-AIGO medical position statement

Patients with esophageal symptoms potentially associated to esophageal motor disorders such as dysphagia, chest pain, heartburn and regurgitation, represent one of the most frequent reasons for referral to gastroenterological evaluation. The utility of esophageal manometry in clinical practice is: (1) to accurately define esophageal motor function, (2) to identify abnormal motor function, and (3) to establish a treatment plan based on motor abnormalities. With this in mind, in the last decade, investigations and technical advances, with the introduction of high-resolution esophageal manometry, have enhanced our understanding and management of esophageal motility disorders. The following recommendations were developed to assist physicians in the appropriate use of esophageal manometry in modern patient care. They were discussed and approved after a comprehensive review of the medical literature pertaining to manometric techniques and their recent application. This position statement created under the auspices of the Gruppo Italiano di Studio per la Motilità dell'Apparato Digerente (GISMAD), Società Italiana di Gastroenterologia ed Endoscopia Digestiva (SIGE) and Associazione Italiana Gastroenterologi ed Endoscopisti Digestivi Ospedalieri (AIGO) is intended to help clinicians in applying manometric studies in the most fruitful manner within the context of their patients with esophageal symptoms.

Understanding the sensory irregularities of esophageal disease

Symptoms relating to esophageal sensory abnormalities can be encountered in the clinical environment. Such sensory abnormalities may be present in demonstrable disease, such as erosive esophagitis, and in the ostensibly normal esophagus, such as non-erosive reflux disease or functional chest pain. In this review, the authors discuss esophageal sensation and the esophageal pain system. In addition, the authors provide a primer concerning the techniques that are available for investigating the autonomic nervous system, neuroimaging and neurophysiology of esophageal sensory function. Such technological advances, whilst not readily available in the clinic may facilitate the stratification and individualization of therapy in disorders of esophageal sensation in the future.

Age, Gender and Women's Health and the Patient

Patients with functional gastrointestinal disorders (FGIDs) often experience distress, reduced quality of life, a perceived lack of validation, and an unsatisfactory experience with health care providers. A health care provider can provide the patient with a framework in which to understand and legitimize their symptoms, remove self-doubt or blame, and identify factors that contribute to symptoms that the patient can influence or control. This framework is implemented with the consideration of important factors that impact FGIDs, such as gender, age, society, and the patient's perspective. Although the majority of FGIDs, including globus, rumination syndrome, IBS, bloating, constipation, functional abdominal pain, sphincter of Oddi dyskinesia, pelvic floor dysfunction, and extra-intestinal manifestations, are more prevalent in women than men, functional chest pain, dyspepsia, vomiting, and anorectal pain do not appear to vary by gender. Studies suggest sex differences in somatic but not visceral pain perception, motility, and central processing of visceral pain; although further research is required in autonomic nervous system dysfunction, genetics and immunologic/microbiome. Gender differences in response to psychological treatments, antidepressants, fiber, probiotics, and anticholinergics have not been adequately studied. However, a greater clinical response to 5-HT3 antagonists but not 5-HT4 agonists has been reported in women compared with men.

Neurophysiology of the esophagus

The following, from the 12th OESO World Conference: Cancers of the Esophagus, includes commentaries on the methods and characteristics of esophageal afferents in humans; the pitfalls in characterization of mechanosensitive afferents; the sensitization of esophageal afferents in human studies; the brain source modeling in the understanding of the esophagus-brain axis; the use of evoked brain potentials in the esophagus; and measuring descending inhibition in animal and human studies.

Preliminary report: modulation of parasympathetic nervous system tone influences oesophageal pain hypersensitivity

OBJECTIVES

Autonomic nervous system dysfunction has been implicated in visceral hypersensitivity. However, the specific contribution of the parasympathetic nervous system (PNS) is unclear. We aimed to determine whether physiological and pharmacological manipulation of parasympathetic tone influences the development of hypersensitivity in a validated model of acid-induced oesophageal pain.

DESIGN

Prior to, and following, a 30-min distal oesophageal infusion of 0.15 M hydrochloric acid, pain thresholds to electrical stimulation were determined in the proximal non-acid exposed oesophagus in healthy subjects. Validated sympathetic (skin conductance response) and parasympathetic (cardiac vagal tone) parameters were measured at baseline and continuously thereafter. In study 1, 55 subjects were randomised in a pragmatic blinded crossover design to receive deep breathing or un-paced breathing during acid infusion. In study 2, 32 subjects were randomised in a blinded, crossover design to receive intravenous atropine or placebo (saline) with deep breathing during acid infusion.

RESULTS

Study 1: Deep breathing increased cardiac vagal tone (2.1±2.3 vs -0.3±2.3, p=0.0006) with concomitant withdrawal of skin conductance response (-0.6±4.9 vs 3±4.8, p=0.03) in comparison with un-paced breathing. Deep breathing prevented the development of acid-induced oesophageal hypersensitivity in comparison with sham breathing (p=0.0001). Study 2: Atropine, in comparison with placebo, blocked the attenuating effect of deep breathing on the development of acid-induced oesophageal hypersensitivity (p=0.046).

CONCLUSIONS

The development of oesophageal hyperalgesia is prevented by physiologically increasing parasympathetic tone. This effect is pharmacologically blocked with atropine, providing evidence that the PNS influences the development of oesophageal pain hypersensitivity.

Functional brain imaging in gastroenterology: to new beginnings

With more than 100 studies published over the past two decades, functional brain imaging research in gastroenterology has become an established field; one that has enabled improved insight into the supraspinal responses evoked by gastrointestinal stimulation both in health and disease. However, there remains considerable inter-study variation in the published results, largely owing to methodological differences in stimulation and recording techniques, heterogeneous patient selection, lack of control for psychological factors and so on. These issues with reproducibility, although not unique to studies of the gastrointestinal tract, can lead to unjustified inferences. To obtain consistent and more clinically relevant results, there is a need to optimize and standardize brain imaging studies across different centres. In addition, the use of complementary and more novel brain imaging modalities and analyses, which are now being used in other fields of research, might help unravel the factors at play in functional gastrointestinal disorders. This Review highlights the areas in which functional brain imaging has been useful and what it has revealed, the areas that are in need of improvement, and finally suggestions for future directions.

Mechanisms and management of functional abdominal pain

Functional abdominal pain syndrome is characterised by frequent or continuous abdominal pain associated with a degree of loss of daily activity. It has a reported population prevalence of between 0.5% and 1.7%, with a female preponderance. The pathophysiology of functional abdominal pain is incompletely understood although it has been postulated that peripheral sensitisation of visceral afferents, central sensitisation of the spinal dorsal horn and aberrancies within descending modulatory systems may have an important role. The management of patients with functional abdominal pain requires a tailored multidisciplinary approach in a supportive and empathetic environment in order to develop an effective therapeutic relationship. Patient education directed towards an explanation of the pathophysiology of functional abdominal pain is in our opinion a prerequisite step and provides the rationale for the introduction of interventions. Interventions can usefully be categorised into general measures, pharmacotherapy, psychological interventions and 'step-up' treatments. Pharmacotherapeutic/step-up options include tricyclic antidepressants, serotonin noradrenergic reuptake inhibitors and the gabapentinoids. Psychological treatments include cognitive behavioural therapy and hypnotherapy. However, the objective evidence base for these interventions is largely derived from other chronic pain syndrome, and further research is warranted in adult patients with functional abdominal pain.

Heterogeneity of mucosal mast cell infiltration in subgroups of patients with esophageal chest pain

BACKGROUND

Although there is growing evidence that an increase in mucosal mast cells (MMCs) in the small and large intestine is associated with visceral hypersensitivity, few studies have evaluated MMCs in humans with esophageal symptoms. The aim of this study was to investigate esophageal MMC distribution in patients with non-cardiac chest pain (NCCP) and to examine the association between the number of gut MMCs and other functional gastrointestinal disorders.

METHODS

Forty-two consecutive NCCP patients and 10 healthy controls completed a questionnaire for bowel symptoms, chest pain intensity score, and psychologic depression. Esophageal, duodenal, and rectal MMCs were identified immunohistochemically and quantified by image analysis.

KEY RESULTS

Numbers of MMCs were significantly higher in NCCP patients vs healthy controls (11.8 ± 5.6 vs 7.6 ± 3.7 MMCs/high-power field, p = 0.026). In comparison of subgroups classified by 24-h impedance-pH monitoring, esophageal MMC counts were highest in the hypersensitive esophagus group (p < 0.01) and were also significantly increased in the functional chest pain group (p < 0.05). A positive correlation between esophageal and duodenal MMC counts was observed in patients with functional dyspepsia (FD; Spearman ρ = 0.604, p = 0.037). In particular, patients with clinical overlap with irritable bowel syndrome showed a strong positive correlation between esophageal and rectal MMC numbers (Spearman ρ = 0.857, p = 0.010).

CONCLUSIONS & INFERENCES

Among NCCP patients, increased MMC infiltration occurs in subgroups with hypersensitive esophagus and functional chest pain. In subpopulations with overlap with FD or irritable bowel syndrome, esophageal MMC counts demonstrated significant positive correlations with duodenal or rectal MMC counts.

Mechanisms of visceral pain in health and functional gastrointestinal disorders

Background and aims Chronic visceral pain is common both in patients with identifiable organic disease and also in those without any structural, biochemical or immunological abnormality such as in the functional gastrointestinal disorders (FGIDs). We aim to provide a contemporaneous summary of pathways involved in visceral nociception and how a variety of mechanisms may influence an individual's experience of visceral pain. Methods In this narrative review, we have brought together evidence through a detailed search of Medline in addition to using our experience and exposure to recent research developments from ourselves and other research groups. Results FGIDs are a heterogeneous group of disorders whose aetiology largely remains an enigma. The germane hypothesis for the genesis and maintenance of chronic visceral pain in FGIDs is the concept of visceral hypersensitivity. A number of peripheral and central mechanisms have been proposed to account for this epiphenomenon. In the periphery, inflammatory mediators activate and sensitize nociceptive afferent nerves by reducing their transduction thresholds and by inducing the expression and recruitment of hitherto silent nociceptors culminating in an increase in pain sensitivity at the site of injury known as primary hyperalgesia. Centrally, secondary hyperalgesia, defined as an increase in pain sensitivity in anatomically distinct sites, occurs at the level of the spinal dorsal horn. Moreover, the stress responsive physiological systems, genetic and psychological factors may modulate the experience of visceral pain. We also address some novel aetiological concepts in FGIDs, namely the gastrointestinal microbiota, connective tissue abnormalities and the gastrointestinal neuromuscular disorders. Firstly, the gastrointestinal microbiota is a diverse and dynamic ecosystem, that safeguards the host from external pathogens, aids in the metabolism of polysaccharides and lipids, modulates intestinal motility, in addition to modulating visceral perception. Secondly, connective tissue disorders, which traditionally have been considered to be confined largely to the musculoskeletal system, have an increasing evidence base demonstrating the presence of visceral manifestations. Since the sensorimotor apparatus of the GI tract is embedded within connective tissue it should not be surprising that such disorder may result in visceral pain and abnormal gut motility. Thirdly, gastrointestinal neuromuscular diseases refer to a heterogeneous group of disorders in which symptoms arise from impaired GI motor activity often manifesting as abnormal transit with or without radiological evidence of transient or persistent dilation of the viscera. Although a number of these are readily recognizable, such as achalasia or Hirschsprung's disease, the cause in a number of patients is not. An international working group has recently addressed this "gap", providing a comprehensive morphologically based diagnostic criteria. Conclusions/implications Although marked advances have been made in understanding the mechanisms that contribute to the development and maintenance of visceral pain, many interventions have failed to produce tangible improvement in patient outcomes. In the last part of this review we highlight an emerging approach that has allowed the definition and delineation of temporally stable visceral pain clusters, which may improve participant homogeneity in future studies, potentially facilitate stratification of treatment in FGID and lead to improvements in diagnostic criteria and outcomes.

Do patients with functional chest pain have neuroplastic reorganization of the pain matrix? A diffusion tensor imaging study

Background and aims

In functional chest pain (FCP) of presumed esophageal origin central nervous system hyperexcitability is generally believed to play an important role in pain pathogenesis. However, this theory has recently been challenged. Using magnetic resonance diffusion tensor imaging, the aim was to characterize any microstructural reorganization of the pain neuromatrix in FCP patients.

Methods

13 FCP patients and 20 matched healthy controls were studied in a 3T MR scanner. Inclusion criteria were relevant chest pain, normal coronary angiogram and normal upper gastrointestinal evaluation. Apparent diffusion coefficient (ADC) (i.e. mean diffusivity of water) and fractional anisotropy (FA) (i.e. directionality of water diffusion as a measure of fiber organization) values were assessed in the secondary sensory cortex, cingulate cortex, insula, prefrontal cortex, and amygdala.

Results

Overall, including all regions, no difference in ADC and FA values was found between the patients and controls (P = 0.79 and P = 0.23, respectively). Post-hoc tests revealed no difference in ADC and FA values of the individual regions. However, a trend of patients having increased ADC in the mid insula grey matter and increased FA in the mid insula white matter was observed (both P = 0.065).

Conclusions

This explorative study suggests that microstructural reorganization of the central pain neuromatrix may not be present in well-characterized FCP patients.

Implications

This finding, together with recent neurophysiologal evidence, challenges the theory of visceral hypersensitivity due to changes in the central nervous system in FCP patients.