Referred pain as an indicator for neural plasticity

Musculoskeletal Disorders Related to Upper Limb Disability after One-Year Lung Cancer Resection

Lung resection represents the main curative treatment in lung cancer; however, this surgical process leads to several disorders in tissues and organs. Previous studies have reported cardiovascular, pulmonary, and muscular disturbances that affect the functional capacity of these patients in the short, mid, and long term. However, upper limb impairment has been scarcely explored in the long term, despite the relevance in the independence of the patients. The aim of this study was to characterize the upper limb impairment in survivors of lung cancer one year after pulmonary resection. In this observational trial, patients who underwent lung cancer surgery were compared to control, healthy subjects matched by age and gender. Upper limb musculoskeletal disorders (shoulder range of motion, pain pressure threshold, nerve-related symptoms) and functional capacity (upper limb exercise capacity) were evaluated one-year post-surgery. A total of 76 survivors of lung cancer and 74 healthy subjects were included in the study. Significant differences between groups were found for active shoulder mobility (p < 0.05), widespread hypersensitivity to mechanical pain (p < 0.001), mechanosensitivity of the neural tissue (p < 0.001), and upper limb exercise capacity (p < 0.001). Patients who undergo lung cancer surgery show upper limb musculoskeletal disorders and upper limb functional impairment after a one-year lung resection. This clinical condition could limit the functionality and quality of life of patients with lung cancer.

Myofascial Pain Syndrome: A Nociceptive Condition Comorbid with Neuropathic or Nociplastic Pain

Myofascial pain syndrome is featured by the presence of myofascial trigger points (TrPs). Whether TrPs are primary or secondary phenomena or if they relate to central or peripheral nervous system disorders is controversial. Referred pain, a cardinal sign of TrPs, is a central phenomenon driven by peripheral input. In 2021, the International Association for the Study of Pain (IASP) proposed a clinical criteria and grading system for classifying patients with pain on nociceptive, neuropathic, or nociplastic phenotypes. Myofascial TrP pain has been traditionally categorized as a nociceptive phenotype; however, increasing evidence supports that this condition could be present in patients with predominantly nociplastic pain, particularly when it is associated with an underlying medical condition. The clinical response of some therapeutic approaches for managing TrPs remains unclear. Accordingly, the ability to classify myofascial TrP pain into one of these phenotypes would likely be critical for producing more successful clinical treatment outcomes by a precision medicine approach. This consensus paper presents evidence supporting the possibility of subgrouping individuals with myofascial TrP pain into nociceptive, nociplastic, or mixed-type phenotype. It is concluded that myofascial pain caused by TrPs is primarily a nociceptive pain condition, is unlikely to be classified as neuropathic or nociplastic, but can be present in patients with predominantly neuropathic or nociplastic pain. In the latter cases, management of the predominant central pain problem should be a major treatment goal, but the peripheral drive from TrPs should not be ignored, since TrP treatment has been shown to reduce sensitization-associated symptomatology in nociplastic pain conditions, e.g., fibromyalgia.

Assessment of visceral pain with special reference to chronic pancreatitis

A thorough pain assessment is of utmost importance when managing pain in clinical practice as it is the foundation for defining pain in need of treatment, either interventional or pharmacological. Pain characteristics can also guide interventional strategies and help evaluate the effect of treatment. In research settings, standardized pain assessment is crucial to improve comparability across studies and facilitate meta-analysis. Due to the importance of thorough visceral pain assessment, this manuscript describes the key elements of pain evaluation focusing on chronic pancreatitis. Most studies in pain assessment have focused on somatic pain, and although chronic pain often shares characteristics between etiologies, some differences must be addressed when assessing visceral pain. Especially differences between somatic and visceral pain are apparent, where visceral pain is diffuse and difficult to localize, with referred pain aspects and often autonomic symptoms dominating the clinical picture. These aspects need to be incorporated into the pain assessment instrument. The manuscript will discuss the different ways of assessing pain, including unidimensional measurement scales, multidimensional questionnaires, and quantitative sensory testing. The advantages and challenges linked to the different methods will be evaluated.

Pain Characteristics in Patients with Inflammatory Bowel Disease: A Monocentric Cross-Sectional Study

BACKGROUND AND AIMS

The abdominal pain common in inflammatory bowel disease [IBD] patients is traditionally associated with inflammation but may persist during clinical remission. Central sensitization [CS] has not previously been explored in these patients. This study aimed to determine the epidemiology of pain in IBD patients and to specify pain characteristics with particular attention to CS.

METHODS

This cross-sectional study included 200 patients; 67% had Crohn's disease [CD]. Pain was assessed using the McGill questionnaire, using the Douleur Neuropathique 4 [DN4] questionnaire and by clinical examination. Its impacts on quality of life, depression and anxiety were also assessed.

RESULTS

Three-quarters of IBD patients complained of pain, including intermittent pain attacks, 62% reported abdominal pain and 17.5% had CS. The prevalence of pain [83.6% vs 59.1%; p < 0.001] and abdominal pain [68.7% vs 48.5%; p = 0.006] was higher in CD patients than in ulcerative colitis [UC] patients. Multivariate analysis confirmed that age [p = 0.02], sex [female] [p = 0.004] and CD [p = 0.005] were independent risk factors for pain. Pain intensity was greater in the case of CS (6 [5-3] vs 3 [1.5-5], p < 0.003) which significantly impaired quality of life [p < 0.003] compared with pain without CS.

CONCLUSIONS

The prevalence of pain was high in IBD patients [≈75%] and higher in CD patients. Significant impacts on quality of life were confirmed. More than 25% of patients with abdominal pain described CS as responsible for more severe pain and worsened quality of life.

TRIAL REGISTRATION REF

NCT04488146.

[Spinal manipulation therapy in low back pain : Why? When? Where? How?]

BACKGROUND

Manipulation and mobilisation for low back pain are presented in an evidence-based manner with regard to mechanisms of action, indications, efficacy, cost-effectiveness ratio, user criteria and adverse effects. Terms such as non-specific or specific are replaced by the introduction of "entities" related to possible different low back pain forms.

EFFICACY

MM is effective for acute and chronic low back pain in terms of pain relief, recovery of function and relapse prevention. It is equally effective but less risky compared to other recommended therapies. MM can be used alone in acute cases and not only in the case of chronic low back pain where it is always and necessarily part of a multimodal therapy programme, especially in combination with activating measures. The users of MM should exclusively be physician specialists trained according to the criteria of the German Medical Association (Bundesärztekammer) with an additional competence in manual medicine or appropriately trained certified therapists. The application of MM follows all rules of Good Clinical Practice.

ADVERSE EFFECTS

Significant adverse effects of MM for low back pain are reported in the international literature with a frequency of 1 per 50,000 to 1 per 3.7 million applications, i.e. MM for low back pain is practically risk-free and safe if performed according to the rules of the European Training Requirements of the UEMS.

Background pain in persons with chronic leg ulcers: An exploratory study of symptom characteristics and management

This exploratory descriptive study aimed to describe characteristics and management of background pain related to chronic leg ulcers. A total of 121 participants were recruited from two wound care clinics using a consecutive sampling method. Data were obtained through screening interview, clinical examination, and questionnaires. The mean average background pain intensity was 4.5 (SD 2.56) (CI 95% 4.0-5.0). Pain interfered mostly with general activity (mean 4.3), sleep (mean 4.1), and walking ability (mean 4.0) (0-10 NRS). The most frequently reported descriptors of background pain were 'tender', 'stabbing', 'aching', and 'hot-burning'. Most of the participants stated that the pain was intermittent. Less than 60% had analgesics prescribed specifically for ulcer related pain, and the respondents reported that pain management provided a mean pain relief of 45.9% (SD 33.9, range 0-100). The findings indicate that ulcer related background pain is a significant problem that interferes with daily function, and that pain management in wound care is still inadequate.

Manual medicine, manual therapy

Manual medicine is the medical discipline that deals with diagnosis, treatment, and prevention of reversible functional disturbances in the locomotor system and other related organ systems. The current article illustrates neuroanatomical and neurophysiological fundamentals of the mechanisms of manual diagnostics and treatment. Based on the recent literature and consideration of different scientifically based clinical guidelines, the evidence-based effectiveness of manual therapeutic procedures is presented. Acute and chronic low back pain, cervicogenic headache, neck and shoulder pain, radicular arm pain, dysfunctional thoracic pain syndromes, diseases of the rotator cuff, carpal tunnel syndrome, and plantar fasciitis are included. Clinical case studies illustrate the clinical procedures. The term, the origin, and the clinical presence of “osteopathy” are addressed in detail, and the national and international societies of manual medicine (Deutsche Gesellschaft für Manuelle Medizin [DGMM], European Scientific Society of Manual Medicine [ESSOMM], Fédération Internationale de Medicine Manuelle [FIMM]) are portrayed lexically. Finally, contraindications to manual intervention are presented and an outlook on the requirements and possibilities of scientific pain analysis is given in accordance with the preamble of the Deutsche Gesellschaft für Orthopädie und Orthopädische Chirurgie (GSOOC) guidelines on specific low back pain.

Sensory Innervation of the Hip Joint and Referred Pain: A Systematic Review of the Literature

OBJECTIVES

The aim of this literature review was to establish consensus with respect to the anatomic features of the articular branches innervating the hip joint and the distribution of sensory receptors within its capsule.

METHODS

Five electronic databases were queried, with the search encompassing articles published between January 1945 and June 2019. Twenty-one original articles providing a detailed description of sensory receptors around the hip joint capsule (n=13) and its articular branches (n=8) were reviewed.

RESULTS

The superior portions of the anterior capsule and the labrum were found to be the area of densest nociceptive innervation. Similar to the distribution of nociceptors, mechanoreceptor density was found to be higher anteriorly than posteriorly. Hip joint capsular innervation was found to consistently involve the femoral and obturator nerves, which supply the anterior capsule, and the nerve to the quadratus femoris, which supplies the posterior capsule. The femoral, obturator, and superior gluteal nerves supply articular branches to the most nociceptor-rich region of the hip capsule.

CONCLUSIONS

The femoral and obturator nerves and the nerve to the quadratus femoris were found to consistently supply articular branches to both the anterior and posterior capsule of the hip joint. The anterior capsule, primarily supplied by the femoral and obturator nerves, and the superior labrum appear to be the primary pain generators of the hip joint, given their higher density of nociceptors and mechanoreceptors.

LEVEL OF EVIDENCE

Anatomy study, literature review.

[Manual medicine, manual treatment : Principles, mode of action, indications and evidence]

Manual medicine is the medical discipline that comprehensively deals with the diagnosis, treatment and prevention of reversible functional disorders of the musculoskeletal system and other related organ systems. The article illustrates the neuroanatomical and neurophysiological basic elements and mechanisms of manual medical diagnostics and treatment. Based on the most recent literature and in consideration of various scientific guidelines, the evidence-based effectiveness of manual medical procedures is presented. In detail: acute and chronic low back pain, cervicogenic headache, neck and shoulder pain, radicular arm pain, dysfunctional thoracic pain syndromes, diseases of the rotator cuff, carpal tunnel syndrome and plantar fasciitis. Clinical case examples illustrate the clinical approach. The terminology, origin and clinical presence of "osteopathy" are described in detail and the national and international associations and societies of manual medicine, the German Society for Manual Medicine (DGMM), the European Scientific Society of Manual Medicine (ESSOMM) and the Fédération Internationale de Medicine Manuelle (FIMM) are lexically presented. Finally, contraindications for manual interventions and an outlook on requirements and possibilities of the scientific analysis of pain are presented, as they are postulated in the preamble of the guidelines on specific low back pain of the German Society for Orthopedics and Orthopedic Surgery (DGOOC).

Immediate Effects of Dry Needling and Myofascial Release on Local and Widespread Pressure Pain Threshold in Individuals With Active Upper Trapezius Trigger Points: A Randomized Clinical Trial

OBJECTIVE

This study sought to compare the immediate effects of a single session of dry needling (DN), myofascial release (MR), and sham DN on pressure pain threshold (PPT) and neck pain intensity in individuals with chronic neck pain.

METHODS

This was a randomized trial with a blinded outcome assessor. Forty-four individuals with chronic neck pain and unilateral myofascial trigger points in the upper trapezius muscle (UTM) were randomized to receive DN (n = 15), MR (n = 14), or sham DN (n = 15). The PPT over the UTM (ipsilateral and contralateral sides) and the proximal head of the radius (ipsilateral and contralateral to the treated side) and neck pain were assessed immediately and 10 minutes after the intervention.

RESULTS

There was no significant Group × Time interaction for PPT in the UTM on the treated side (F = 0.63, P = .641) or the contralateral side (F = 1.77, P = .144). However, there was a main effect of time on both the treated side (F = 4.917, P = .001) and the contralateral side (F = 4.70, P = .015), with DN and MR increasing PPT at the UTM. No significant Group × Time × Side interaction was found for PPT at the proximal head of the radius (F = 1.23, P = .276). Within-group analysis revealed a significant increase in PPT on the ipsilateral and contralateral sides in both DN and MR. Neck pain decreased after DN (P < .001), MR (P < .001), and sham DN (P = .008).

CONCLUSION

A single application of DN or MR generated local and distant hypalgesic responses superior to placebo. Future trials are needed to examine whether these findings occur in long-term follow-ups.

Gastrointestinal pain

Gastrointestinal (GI) pain - a form of visceral pain - is common in some disorders, such as irritable bowel syndrome, Crohn's disease and pancreatitis. However, identifying the cause of GI pain frequently represents a diagnostic challenge as the clinical presentation is often blurred by concomitant autonomic and somatic symptoms. In addition, GI pain can be nociceptive, neuropathic and associated with cancer, but in many cases multiple aetiologies coexist in an individual patient. Mechanisms of GI pain are complex and include both peripheral and central sensitization and the involvement of the autonomic nervous system, which has a role in generating the symptoms that frequently accompany pain. Treatment of GI pain depends on the precise type of pain and the primary disorder in the patient but can include, for example, pharmacological therapy, cognitive behavioural therapies, invasive surgical procedures, endoscopic procedures and lifestyle alterations. Owing to the major differences between organ involvement, disease mechanisms and individual factors, treatment always needs to be personalized and some data suggest that phenotyping and subsequent individual management of GI pain might be options in the future.

A clinically feasible method for the assessment and characterization of pain in patients with chronic pancreatitis

BACKGROUND AND AIMS

Pain is the primary symptom of chronic pancreatitis (CP), but methods for sensory testing and pain characterization have not previously been validated for clinical use. We present a clinically feasible method for the assessment and characterization of pain mechanisms in patients with CP based on quantitative sensory testing (QST).

METHODS

This was a cross-sectional, multicenter study of 122 control subjects without pancreatic disease and another 60 patients with painful CP. All subjects underwent standardized QST assessments including a cold pressor test, a conditioned pain modulation paradigm, repetitive pin-prick stimuli (temporal summation) and pressure stimulation of the upper abdominal (pancreatic) and control dermatomes. The effects of age and gender on QST assessment parameters were investigated and normative reference values based on quartile regression were derived and implemented in algorithms to categorize patients according to their patterns of central pain processing (normal vs. segmental sensitization vs. widespread sensitization).

RESULTS

Absolute pressure thresholds were subject to clinically relevant gender effects (all p < 0.001), while the remainder of QST parameters were unaffected by age and gender. The algorithm with the best discriminatory capacity showed good separation between patients and controls (p < 0.001); 50% of patients had normal central pain processing, 23% had evidence of segmental sensitization and 27% had evidence of widespread sensitization.

CONCLUSION

We show normative reference values for a clinically feasible method for assessment and characterization of pain mechanisms in patients with CP. Application of this method streamlines the evaluation of pancreatic pain and may be used to inform treatment. CLINICALTRIALS.

GOV ID

NCT03434392.

Is Virtual Reality Effective in Orthopedic Rehabilitation? A Systematic Review and Meta-Analysis

BACKGROUND

Virtual reality (VR) is an interactive technology that allows customized treatment and may help in delivering effective person-centered rehabilitation.

PURPOSE

The purpose of this review was to systematically review and critically appraise the controlled clinical trials that investigated VR effectiveness in orthopedic rehabilitation.

DATA SOURCES

Pubmed, CINAHL, Embase, PEDro, REHABDATA, and Sage publications were searched up to September 2018. In addition, manual searching and snowballing using Scopus and Web of Science were done.

STUDY SELECTION

Two reviewers screened studies for eligibility first by title and abstract and then full text.

DATA EXTRACTION

Articles were categorized into general or region-specific (upper limbs, lower limbs, and spine) orthopedic disorders. Study quality was assessed using the Evaluation Guidelines for Rating the Quality of an Intervention Study scoring. Meta-analysis quantified VR effectiveness, compared with no treatment, in back pain.

DATA SYNTHESIS

Nineteen studies were included in the quality assessment. The majority of the studies were of moderate quality. Fourteen studies showed that VR did not differ compared with exercises. Compared with the no-treatment control, 5 studies favored VR and 3 other studies showed no differences. For low back pain, the meta-analysis revealed no significant difference between VR and no-treatment control (n = 116; standardized mean difference = -0.21; 95% confidence interval = -0.58 to 0.15).

LIMITATIONS

Limitations included heterogeneity in interventions and the outcome measures of reviewed studies. Only articles in English were included.

CONCLUSION

The evidence of VR effectiveness is promising in chronic neck pain and shoulder impingement syndrome. VR and exercises have similar effects in rheumatoid arthritis, knee arthritis, ankle instability, and post-anterior cruciate reconstruction. For fibromyalgia and back pain, as well as after knee arthroplasty, the evidence of VR effectiveness compared with exercise is absent or inconclusive.

Cervical hyperaesthesia in dogs: an epidemiological retrospective study of 185 cases

OBJECTIVES

To describe the prevalence, clinical findings and predictors of disease in dogs with cervical hyperaesthesia.

MATERIALS AND METHODS

Medical records of dogs referred for neurological investigation of cervical hyperaesthesia between 2009 and 2013 were retrospectively reviewed. Dogs were assigned to one of the following groups according to the final diagnosis: Non-Neurologic, Brain, Cervical Spine, Multifocal, and Chiari-like Malformation/Syringomyelia. Demographic data, clinical and neurological signs and laboratory findings were compared between groups using univariate analysis; predictors of disease location were assessed by multivariate analysis.

RESULTS

Final diagnostic allocations of the 185 records included in the study were as follows: 2.7% Non-Neurologic, 2.2% Brain, 63.2% Cervical Spine, 22.2% Multifocal and 9.7% Chiari Malformation/Syringomyelia. Intervertebral disc extrusion and steroid-responsive meningitis arteritis were the most common diseases. Compared to Multifocal dogs, those allocated a Cervical Spine diagnosis were older, heavier, more frequently ataxic and lame on a thoracic limb; furthermore, they were less frequently depressed or hyperthermic at presentation. Leucocytosis, neutrophilia and monocytosis were more frequent in dogs allocated a Multifocal diagnosis. Dogs with cervical hyperaesthesia older than 36 months and non-hyperthermic at presentation were more likely to have a lesion of the cervical region rather than a multi-focal disease.

CLINICAL SIGNIFICANCE

Although non-specific, these results may be useful to guide clinicians in management of dogs presenting with cervical hyperaesthesia. Animal age and body temperature may support the suspicion of either focal or multi-focal cervical spinal disease.

Enhanced Plasticity of Human Evoked Potentials by Visual Noise During the Intervention of Steady-State Stimulation Based Brain-Computer Interface

Neuroplasticity, also known as brain plasticity, is an inclusive term that covers the permanent changes in the brain during the course of an individual's life, and neuroplasticity can be broadly defined as the changes in function or structure of the brain in response to the external and/or internal influences. Long-term potentiation (LTP), a well-characterized form of functional synaptic plasticity, could be influenced by rapid-frequency stimulation (or "tetanus") within in vivo human sensory pathways. Also, stochastic resonance (SR) has brought new insight into the field of visual processing for the study of neuroplasticity. In the present study, a brain-computer interface (BCI) intervention based on rapid and repetitive motion-reversal visual stimulation (i.e., a "tetanizing" stimulation) associated with spatiotemporal visual noise was implemented. The goal was to explore the possibility that the induction of LTP-like plasticity in the visual cortex may be enhanced by the SR formalism via changes in the amplitude of visual evoked potentials (VEPs) measured non-invasively from the scalp of healthy subjects. Changes in the absolute amplitude of P1 and N1 components of the transient VEPs during the initial presentation of the steady-state stimulation were used to evaluate the LTP-like plasticity between the non-noise and noise-tagged BCI interventions. We have shown that after adding a moderate visual noise to the rapid-frequency visual stimulation, the degree of the N1 negativity was potentiated following an ~40-min noise-tagged visual tetani. This finding demonstrated that the SR mechanism could enhance the plasticity-like changes in the human visual cortex.

From acute to chronic pain after thoracic surgery: the significance of different components of the acute pain response

Purpose

Acute postoperative pain is a strong predictor for postthoracotomy pain syndrome (PTPS), but the mechanism is unknown. Even though thoracic pain is usually considered the dominating acute pain after thoracic surgery, up to 45% of patients consider shoulder pain to be dominating pain and often this shoulder pain is referred visceral pain. This study aims to examine which components of the acute pain response after thoracic surgery were associated with PTPS and if any signs of a generalized central hypersensitivity could be identified in patients with PTPS.

Patients and methods

In a prospective cohort study, 60 consecutive patients for lobectomy were included and examined preoperatively and 12 months postoperatively for pain and signs of hypersensitivity using a comprehensive protocol for quantitative sensory testing. Thoracic pain, shoulder pain, referred pain, and overall pain were assessed five times daily during the first four postoperative days.

Results

Sixteen patients (31% of the 52 patients who completed the study) developed PTPS. Thoracic pain was the only pain component that was associated with PTPS and was a stronger predictor for PTPS than overall pain. There were no signs of hypersensitivity before or after the operation in patients with PTPS, but patients with PTPS more often suffered from preoperative pain.

Conclusion

Thoracic pain was the only component of the acute pain response that predicted PTPS and was a stronger predictor than overall pain.

Potential of Endocannabinoids to Control Bladder Pain

Bladder-related pain is one of the most common forms of visceral pain, and visceral pain is among the most common complaints for which patients seek physician consultation. Despite extensive studies of visceral innervation and treatment of visceral pain, opioids remain a mainstay for management of bladder pain. Side effects associated with opioid therapy can profoundly diminish quality of life, and improved options for treatment of bladder pain remain a high priority. Endocannabinoids, primarily anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are endogenously-produced fatty acid ethanolamides with that induce analgesia. Animal experiments have demonstrated that inhibition of enzymes that degrade AEA or 2-AG have the potential to prevent development of visceral and somatic pain. Although experimental results in animal models have been promising, clinical application of this approach has proven difficult. In addition to fatty acid amide hydrolase (FAAH; degrades AEA) and monacylglycerol lipase (MAGL; degrades 2-AG), cyclooxygenase (COX) acts to metabolize endocannabinoids. Another potential limitation of this strategy is that AEA activates pro-nociceptive transient receptor potential vanilloid 1 (TRPV1) channels. Dual inhibitors of FAAH and TRPV1 or FAAH and COX have been synthesized and are currently undergoing preclinical testing for efficacy in providing analgesia. Local inhibition of FAAH or MAGL within the bladder may be viable options to reduce pain associated with cystitis with fewer systemic side effects, but this has not been explored. Further investigation is required before manipulation of the endocannabinoid system can be proven as an efficacious alternative for management of bladder pain.

What Is the Future of Impedance Planimetry in Gastroenterology?

The gastrointestinal (GI) tract is efficient in transporting ingested material to the site of delivery in healthy subjects. A fine balance exists between peristaltic forces, the mixing and delivery of the contents, and sensory signaling. This fine balance is easily disturbed by diseases. It is mandatory to understand the pathophysiology to enhance our understanding of GI disorders. The inaccessibility and complex nervous innervation, geometry and mechanical function of the GI tract make mechanosensory evaluation difficult. Impedance planimetry is a distension technology that assesses luminal geometry, mechanical properties including muscle dynamics, and processing of nociceptive signals from the GI tract. Since standardized models do not exist for GI muscle function in vivo, models, concepts, and terminology must be borrowed from other medical fields such as cardiac mechanophysiology. The review highlights the impedance planimetric technology, muscle dynamics assessment, and 3 applied technologies of impedance planimetry. These technologies are the multimodal probes that assesses sensory function, the functional luminal imaging probe that dynamically measures the geometry of the lumen it distends, and Fecobionics that is a simulated feces providing high-resolution measurements during defecation. The advanced muscle analysis and 3 applied technologies can enhance the quality of future interdisciplinary research for gaining more knowledge about mechanical function, sensory-motor disorders, and symptoms. This is a step in the direction of individualized treatment for GI disorders based on diagnostic subtyping. There seems to be no better alternatives to impedance planimetry, but only the functional luminal imaging probe is currently commercially available. Wider use depends on commercialization of the multimodal probe and Fecobionics.

Assessment and manifestation of central sensitisation across different chronic pain conditions

Different neuroplastic processes can occur along the nociceptive pathways and may be important in the transition from acute to chronic pain and for diagnosis and development of optimal management strategies. The neuroplastic processes may result in gain (sensitisation) or loss (desensitisation) of function in relation to the incoming nociceptive signals. Such processes play important roles in chronic pain, and although the clinical manifestations differ across condition processes, they share some common mechanistic features. The fundamental understanding and quantitative assessment of particularly some of the central sensitisation mechanisms can be translated from preclinical studies into the clinic. The clinical perspectives are implementation of such novel information into diagnostics, mechanistic phenotyping, prevention, personalised treatment, and drug development. The aims of this paper are to introduce and discuss (1) some common fundamental central pain mechanisms, (2) how they may translate into the clinical signs and symptoms across different chronic pain conditions, (3) how to evaluate gain and loss of function using quantitative pain assessment tools, and (4) the implications for optimising prevention and management of pain. The chronic pain conditions selected for the paper are neuropathic pain in general, musculoskeletal pain (chronic low back pain and osteoarthritic pain in particular), and visceral pain (irritable bowel syndrome in particular). The translational mechanisms addressed are local and widespread sensitisation, central summation, and descending pain modulation.

Significance

Central sensitisation is an important manifestation involved in many different chronic pain conditions. Central sensitisation can be different to assess and evaluate as the manifestations vary from pain condition to pain condition. Understanding central sensitisation may promote better profiling and diagnosis of pain patients and development of new regimes for mechanism based therapy. Some of the mechanisms underlying central sensitisation can be translated from animals to humans providing new options in development of therapies and profiling drugs under development.

Opioid-Induced Constipation and Bowel Dysfunction: A Clinical Guideline

OBJECTIVE

To formulate timely evidence-based guidelines for the management of opioid-induced bowel dysfunction.

SETTING

Constipation is a major untoward effect of opioids. Increasing prescription of opioids has correlated to increased incidence of opioid-induced constipation. However, the inhibitory effects of opioids are not confined to the colon, but also affect higher segments of the gastrointestinal tract, leading to the coining of the term "opioid-induced bowel dysfunction."

METHODS

A literature search was conducted using Medline, EMBASE, and EMBASE Classic, and the Cochrane Central Register of Controlled Trials. Predefined search terms and inclusion/exclusion criteria were used to identify and categorize relevant papers. A series of statements were formulated and justified by a comment, then labeled with the degree of agreement and their level of evidence as judged by the Strength of Recommendation Taxonomy (SORT) system.

RESULTS

From a list of 10,832 potentially relevant studies, 33 citations were identified for review. Screening the reference lists of the pertinent papers identified additional publications. Current definitions, prevalence, and mechanism of opioid-induced bowel dysfunction were reviewed, and a treatment algorithm and statements regarding patient management were developed to provide guidance on clinical best practice in the management of patients with opioid-induced constipation and opioid-induced bowel dysfunction.

CONCLUSIONS

In recent years, more insight has been gained in the pathophysiology of this "entity"; new treatment approaches have been developed, but guidelines on clinical best practice are still lacking. Current knowledge is insufficient regarding management of the opioid side effects on the upper gastrointestinal tract, but recommendations can be derived from what we know at present.

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.

Migraine With Isolated Facial Pain: A Diagnostic Challenge

We present a series of seven migraine patients with typical features of a migraine attack without aura, but atypical pain localization in the face in one or both of the lower two distributions of the trigeminal nerve (V2 and V3). All of them responded well to triptans. Three patients responded to preventive treatment for migraine with β-blockers ( n = 2) or valproic acid ( n = 1). These cases underline the heterogenic clinical presentation of migraine, which is sometimes difficult to diagnose even for headache specialists, and broaden the pathophysiological understanding of trigeminal nociceptive processing in migraine in the light of neuronal plasticity.

Management of chronic visceral pain

Despite marked differences in underlying pathophysiology, the current management of visceral pain largely follows the guidelines derived from the somatic pain literature. The effective management of patients with chronic visceral pain should be multifaceted, including both pharmacological and psychological interventions, thereby providing a mechanism-orientated approach to treatment. Patients can frequently become disenfranchised, and subsequently disengaged, with healthcare providers leading to repeated consultations. Thus, a key aspect of management is to break this cycle by validating patients' symptoms, adopting an empathic approach and taking time to educate patients. To optimize treatment and outcomes in chronic visceral pain we need to move away from approaches exclusively based on dealing with peripheral nociceptive input toward more holistic strategies, taking into account alterations in central pain processing.

A critical evaluation of Quintner et al: missing the point

The objective of this article is to critically analyze a recent publication by Quinter, Bove and Cohen, published in Rheumatology, about myofascial pain syndrome and trigger points (Quintner et al., 2014). The authors concluded that the leading trigger point hypothesis is flawed in reasoning and in science. They claimed to have refuted the trigger point hypothesis. The current paper demonstrates that the Quintner et al. paper is a biased review of the literature replete with unsupported opinions and accusations. In summary, Quintner et al. have not presented any convincing evidence to believe that the Integrated TrP Hypothesis should be laid to rest.

Systematic mechanism-orientated approach to chronic pancreatitis pain

Pain in chronic pancreatitis (CP) shows similarities with other visceral pain syndromes (i.e., inflammatory bowel disease and esophagitis), which should thus be managed in a similar fashion. Typical causes of CP pain include increased intrapancreatic pressure, pancreatic inflammation and pancreatic/extrapancreatic complications. Unfortunately, CP pain continues to be a major clinical challenge. It is recognized that ongoing pain may induce altered central pain processing, e.g., central sensitization or pro-nociceptive pain modulation. When this is present conventional pain treatment targeting the nociceptive focus, e.g., opioid analgesia or surgical/endoscopic intervention, often fails even if technically successful. If central nervous system pain processing is altered, specific treatment targeting these changes should be instituted (e.g., gabapentinoids, ketamine or tricyclic antidepressants). Suitable tools are now available to make altered central processing visible, including quantitative sensory testing, electroencephalograpy and (functional) magnetic resonance imaging. These techniques are potentially clinically useful diagnostic tools to analyze central pain processing and thus define optimum management approaches for pain in CP and other visceral pain syndromes. The present review proposes a systematic mechanism-orientated approach to pain management in CP based on a holistic view of the mechanisms involved. Future research should address the circumstances under which central nervous system pain processing changes in CP, and how this is influenced by ongoing nociceptive input and therapies. Thus we hope to predict which patients are at risk for developing chronic pain or not responding to therapy, leading to improved treatment of chronic pain in CP and other visceral pain disorders.

Myofascial trigger points: peripheral or central phenomenon?

Trigger points (TrP) are hyperirritable spots in a taut band of a skeletal muscle, which usually have referred pain. There is controversy over whether TrP are a peripheral or central nervous system phenomenon. Referred pain, the most characteristic sign of TrP, is a central phenomenon initiated and activated by peripheral sensitization, whereby the peripheral nociceptive input from the muscle can sensitize dorsal horn neurons that were previously silent. TrP are a peripheral source of nociception, and act as ongoing nociceptive stimuli contributing to pain propagation and widespread pain. Several studies support the hypothesis that TrP can induce central sensitization, and appropriate TrP treatment reduces central sensitization. In contrast, preliminary evidence suggests that central sensitization can also promote TrP activity, although further studies are needed. Proper TrP management may prevent and reverse the development of pain propagation in chronic pain conditions, because inactivation of TrP attenuates central sensitization.

Functional reorganization of brain networks in patients with painful chronic pancreatitis

BACKGROUND

The underlying pain mechanisms of chronic pancreatitis (CP) are incompletely understood, but recent research points to involvement of pathological central nervous system processing involving pain-relevant brain areas. We investigated the organization and connectivity of brain networks involved in nociceptive processing in patients with painful CP.

METHODS

Contact heat-evoked potentials (CHEPs) were recorded in 15 patients with CP and in 15 healthy volunteers. The upper abdominal area (sharing spinal innervation with the pancreatic gland) was used as a proxy of 'pancreatic stimulation', while stimulation of a heterologous region remote to the pancreas (right forearm) was used as a control. Subjective pain scores were assessed by visual analogue scale. The brain source organization and connectivity of CHEPs components were analysed.

RESULTS

After pancreatic area stimulation, brain source analysis revealed abnormalities in the cingulate/operculo-insular network. A posterior shift of the operculo-insular source (p = 0.004) and an anterior shift of the cingulate source (p < 0.001) were seen in CP patients, along with a decreased strength of the cingulate source (p = 0.01). The operculo-insular shift was positively correlated with the severity of patient clinical pain score (r = 0.61; p = 0.03). No differences in CHEPs characteristics or source localizations were seen following stimulation of the right forearm.

CONCLUSIONS

CP patients showed abnormal cerebral processing after stimulation of the upper abdominal area. These changes correlated to the severity of pain the patient was experiencing. Since the upper abdominal area shares spinal innervation with the pancreatic gland, these findings likely reflect maladaptive neuroplastic changes, which are characteristic of CP.

Bilateral myofascial trigger points and pressure pain thresholds in the shoulder muscles in patients with unilateral shoulder impingement syndrome: a blinded, controlled study

OBJECTIVES

To identify the presence of myofascial trigger points (TrPs) and pressure pain threshold (PPT) levels in the shoulder muscles of both involved and uninvolved sides in patients with unilateral shoulder impingement syndrome (SIS).

METHODS

Twenty-seven patients with SIS and 20 matched control patients participated in this study. TrPs of 10 shoulder muscles and 8 PPTs, including tibialis anterior PPT, were assessed.

RESULTS

SIS group showed a greater number of TrPs (t=-2.697; P=0.010) than the control group. The muscles of the uninvolved side of the SIS group also presented some active TrPs. PPTs showed small differences between involved and uninvolved sides of patients with SIS and higher differences between both sides of the SIS group and dominant side of controls although with significant difference only in the supraspinatus PPT (F=3.239; P=0.045). The muscle PPTs of the patients presenting TrPs in each muscle of the involved side were lower than the PPTs of the patients without TrPs in the same muscle for both involved and uninvolved sides with few significant differences.

DISCUSSION

The high number of TrPs in the involved side of patients with SIS suggests the presence of peripheral sensitization. The results reject the presence of central alterations. Finally, the patients with unilateral SIS may present bilateral deficits related to myofascial pain.

Reliability of static and dynamic quantitative sensory testing in patients with painful chronic pancreatitis

BACKGROUND AND OBJECTIVES

Quantitative sensory testing (QST) has proven to be an important instrument to characterize mechanisms underlying somatic and neuropathic pain disorders. However, its reliability has not previously been established in patients with visceral pain. We investigated the test-retest reliability of static and dynamic QST in patients with visceral pain due to chronic pancreatitis.

METHODS

Sixty-two patients (38 men, 53 [11] y) with painful chronic pancreatitis were included. Static QST comprised sensory thresholds for pressure and electrical stimulation performed in the ventral and dorsal T10 dermatomes (sharing spinal innervation with the pancreas, ie, pancreatic viscerotomes) and in 4 heterologous regions (control areas). Dynamic QST comprised conditioned pain modulation. Measurements were obtained from 2 subsequent test sessions separated by 1 week.

RESULTS

The reliability of static QST was generally high, with the best test-retest performance seen for pressure pain thresholds (intraclass correlation coefficients [ICC], 0.74) and electrical sensation thresholds (ICC, 0.66). In contrast, the reliability of dynamic QST was poor (ICC, 0.01). For static QST measures, the reliability was higher for pain thresholds compared with suprapain thresholds (P < 0.01). No differences between assessments in the pancreatic viscerotomes compared with heterologous regions were seen (P = 0.6).

CONCLUSIONS

Sensory thresholds in the pancreatic viscerotomes and control areas were reproducible over time. In contrast, dynamic QST measurements reflecting active central modulation of pain processing state (ie, conditioned pain modulation) were not stable over time and showed considerable variability. These factors should be taken into consideration in case QST is used to follow disease mechanisms, drug effects, or effects of pain intervention.

Quantitative sensory testing predicts pregabalin efficacy in painful chronic pancreatitis

BACKGROUND

A major problem in pain medicine is the lack of knowledge about which treatment suits a specific patient. We tested the ability of quantitative sensory testing to predict the analgesic effect of pregabalin and placebo in patients with chronic pancreatitis.

METHODS

Sixty-four patients with painful chronic pancreatitis received pregabalin (150-300 mg BID) or matching placebo for three consecutive weeks. Analgesic effect was documented in a pain diary based on a visual analogue scale. Responders were defined as patients with a reduction in clinical pain score of 30% or more after three weeks of study treatment compared to baseline recordings. Prior to study medication, pain thresholds to electric skin and pressure stimulation were measured in dermatomes T10 (pancreatic area) and C5 (control area). To eliminate inter-subject differences in absolute pain thresholds an index of sensitivity between stimulation areas was determined (ratio of pain detection thresholds in pancreatic versus control area, ePDT ratio). Pain modulation was recorded by a conditioned pain modulation paradigm. A support vector machine was used to screen sensory parameters for their predictive power of pregabalin efficacy.

RESULTS

The pregabalin responders group was hypersensitive to electric tetanic stimulation of the pancreatic area (ePDT ratio 1.2 (0.9-1.3)) compared to non-responders group (ePDT ratio: 1.6 (1.5-2.0)) (P = 0.001). The electrical pain detection ratio was predictive for pregabalin effect with a classification accuracy of 83.9% (P = 0.007). The corresponding sensitivity was 87.5% and specificity was 80.0%. No other parameters were predictive of pregabalin or placebo efficacy.

CONCLUSIONS

The present study provides first evidence that quantitative sensory testing predicts the analgesic effect of pregabalin in patients with painful chronic pancreatitis. The method can be used to tailor pain medication based on patient's individual sensory profile and thus comprises a significant step towards personalized pain medicine.

Quantitative sensory testing predicts pregabalin efficacy in painful chronic pancreatitis

BACKGROUND

A major problem in pain medicine is the lack of knowledge about which treatment suits a specific patient. We tested the ability of quantitative sensory testing to predict the analgesic effect of pregabalin and placebo in patients with chronic pancreatitis.

METHODS

Sixty-four patients with painful chronic pancreatitis received pregabalin (150-300 mg BID) or matching placebo for three consecutive weeks. Analgesic effect was documented in a pain diary based on a visual analogue scale. Responders were defined as patients with a reduction in clinical pain score of 30% or more after three weeks of study treatment compared to baseline recordings. Prior to study medication, pain thresholds to electric skin and pressure stimulation were measured in dermatomes T10 (pancreatic area) and C5 (control area). To eliminate inter-subject differences in absolute pain thresholds an index of sensitivity between stimulation areas was determined (ratio of pain detection thresholds in pancreatic versus control area, ePDT ratio). Pain modulation was recorded by a conditioned pain modulation paradigm. A support vector machine was used to screen sensory parameters for their predictive power of pregabalin efficacy.

RESULTS

The pregabalin responders group was hypersensitive to electric tetanic stimulation of the pancreatic area (ePDT ratio 1.2 (0.9-1.3)) compared to non-responders group (ePDT ratio: 1.6 (1.5-2.0)) (P = 0.001). The electrical pain detection ratio was predictive for pregabalin effect with a classification accuracy of 83.9% (P = 0.007). The corresponding sensitivity was 87.5% and specificity was 80.0%. No other parameters were predictive of pregabalin or placebo efficacy.

CONCLUSIONS

The present study provides first evidence that quantitative sensory testing predicts the analgesic effect of pregabalin in patients with painful chronic pancreatitis. The method can be used to tailor pain medication based on patient's individual sensory profile and thus comprises a significant step towards personalized pain medicine.

Human experimental pain models for assessing the therapeutic efficacy of analgesic drugs

Pain models in animals have shown low predictivity for analgesic efficacy in humans, and clinical studies are often very confounded, blurring the evaluation. Human experimental pain models may therefore help to evaluate mechanisms and effect of analgesics and bridge findings from basic studies to the clinic. The present review outlines the concept and limitations of human experimental pain models and addresses analgesic efficacy in healthy volunteers and patients. Experimental models to evoke pain and hyperalgesia are available for most tissues. In healthy volunteers, the effect of acetaminophen is difficult to detect unless neurophysiological methods are used, whereas the effect of nonsteroidal anti-inflammatory drugs could be detected in most models. Anticonvulsants and antidepressants are sensitive in several models, particularly in models inducing hyperalgesia. For opioids, tonic pain with high intensity is attenuated more than short-lasting pain and nonpainful sensations. Fewer studies were performed in patients. In general, the sensitivity to analgesics is better in patients than in healthy volunteers, but the lower number of studies may bias the results. Experimental models have variable reliability, and validity shall be interpreted with caution. Models including deep, tonic pain and hyperalgesia are better to predict the effects of analgesics. Assessment with neurophysiologic methods and imaging is valuable as a supplement to psychophysical methods and can increase sensitivity. The models need to be designed with careful consideration of pharmacological mechanisms and pharmacokinetics of analgesics. Knowledge obtained from this review can help design experimental pain studies for new compounds entering phase I and II clinical trials.

Coronary microvascular function and cortical pain processing in patients with silent positive exercise testing and normal coronary arteries

ST-segment depression during exercise stress testing in asymptomatic subjects showing normal coronary arteries is considered a "false-positive" result. Coronary microvascular dysfunction, however, might be a possible cause of ST-segment depression in these cases. We assessed the coronary blood flow response to adenosine and to cold pressor test in the left anterior descending artery, using transthoracic Doppler echocardiography in 14 asymptomatic subjects with exercise-induced ST-segment depression and normal coronary arteries (group 1), 14 patients with microvascular angina (group 2), and 14 healthy subjects (group 3). Flow-mediated dilation was assessed in the brachial artery. Central pain processing was assessed using cortical laser evoked potentials during chest and right hand stimulation with 3 sequences of painful stimuli. The coronary blood flow response to adenosine was 1.8 ± 0.4, 1.9 ± 0.5, and 3.1 ± 0.9 in groups 1, 2, and 3, respectively (p <0.001). The corresponding coronary blood flow responses to the cold pressor test were 1.74 ± 0.4, 1.53 ± 0.3, and 2.3 ± 0.6 (p <0.001). The flow-mediated dilation was 5.5 ± 2.3%, 4.6 ± 2.4%, and 9.8 ± 1.2% in the 3 groups, respectively (p <0.001). The laser evoked potential N2/P2 wave amplitude decreased throughout the 3 sequences of stimulation in groups 1 and 3 but not in group 2 (chest, -19 ± 22%, +11 ± 42% and -36 ± 12%, p <0.001; right hand, -22 ± 25%, +12 ± 43% and -30 ± 20%, p = 0.009; in groups 1, 2, and 3). In conclusion, exercise stress test-induced ST-segment depression in asymptomatic subjects with normal coronary arteries cannot be considered as a simple false-positive result, because it can be related to coronary microvascular dysfunction. The different symptomatic state compared to patients with microvascular angina can, at least in part, be explained by differences in cortical processing of neural pain stimuli.

Spatial pain propagation over time following painful glutamate activation of latent myofascial trigger points in humans

The aim of this present study was to test the hypothesis that tonic nociceptive stimulation of latent myofascial trigger points (MTPs) may induce a spatially enlarged area of pressure pain hyperalgesia. Painful glutamate (.2 mL, 1M) stimulation of latent MTPs and non-MTPs in the forearm was achieved by an electromyography-guided procedure. Pain intensity (as rated on the visual analog scale [VAS]) and referred pain area following glutamate injections were recorded. Pressure pain threshold (PPT) was measured over 12 points in the forearm muscles and at the mid-point of tibialis anterior muscle before and at .5 hour, 1 hour, and 24 hours after glutamate injections. The results showed that maximal pain intensity, the area under the VAS curve, and referred pain area were significantly higher and larger following glutamate injection into latent MTPs than non-MTPs (all, P < .05). A significantly lower PPT level was detected over time after glutamate injection into latent MTPs at .5 hour (at 4 points), 1 hour (at 7 points), and 24 hours (at 6 points) in the forearm muscles. However, a significantly lower PPT was observed only at 24 hours after glutamate injection into non-MTPs in the forearm muscles (at 4 points, P < .05) when compared to the pre-injection PPT. PPT at the mid-point of the tibialis anterior was significantly decreased at 1 hour only as compared to the pre-injection PPT in both groups (< .05). The results of the present study indicate that nociceptive stimulation of latent MTPs is associated with an early onset of locally enlarged area of mechanical hyperalgesia.

PERSPECTIVE

This study shows that MTPs are associated with an early occurrence of a locally enlarged area of pressure hyperalgesia associated with spreading central sensitization. Inactivation of MTPs may prevent spatial pain propagation.

Cerebral excitability is abnormal in patients with painful chronic pancreatitis

BACKGROUND

We investigated whether patients with painful chronic pancreatitis (CP) present abnormalities in the cerebral response to experimental pain stimuli.

METHODS

Contact heat-evoked potentials (CHEPS) were recorded in 15 patients with CP and in 15 healthy volunteers during repetitive stimulation of the upper abdominal region (pancreatic 'viscerotome') and the right forearm (heterologous area). Three sequences of painful stimuli were applied at each site. Subjective pain scores were assessed by a visual analogue scale. Habituation was calculated as the relative change in CHEPS amplitudes between the first and the third stimulation sequence.

RESULTS

As expected pain scores decreased in healthy volunteers during successive stimulations at both sites (i.e., habituation), while in the CP group, they remained unchanged. The cerebral response consisted of an early-latency, low-amplitude response (N1, contralateral temporal region) followed by a late, high-amplitude, negative-positive complex (N2/P2, vertex). During successive stimulation of the pancreatic area, N2/P2 amplitude increased 25% in CP patients, while they decreased 20% in healthy volunteers (p = 0.006). After stimulation of the forearm, N2/P2 amplitudes increased 3% in CP patients compared to a decrease of 20% in healthy volunteers (p = 0.06).

CONCLUSIONS

Taken together, CP patients had an abnormal cerebral response to repetitive thermal stimuli. This was most prominent after stimulation of the upper abdominal area. As this area share spinal innervation with the pancreatic gland, these findings likely mirror distinctive abnormalities in cerebral pain processing.