Patient and Disease Characteristics Associate With Sensory Testing Results in Chronic Pancreatitis

Somatosensory profiling to differentiate distinct painful diseases of the pancreas-a quantitative sensory testing case-control study

ABSTRACT

Mechanisms of pancreatic pain are insufficiently understood, and quantitative sensory testing (QST) may help to identify the underlying mechanisms. Accordingly, this study assessed comprehensive somatosensory profiles encompassing nociceptive and nonnociceptive parameters in 70 patients with distinct pancreatic diseases, namely acute (n = 23), chronic (n = 20), or autoimmune pancreatitis (n = 10) and pancreatic cancer (n = 17) and compared it with 30 healthy control subjects by standardized QST (protocol of the German research network on neuropathic pain). Patients with pancreatic diseases presented significant somatosensory deficits in all thermal and tactile detection and pain thresholds in the pancreatic viscerotome (Th10), when compared with a remote control area (dermatome C5) or reference data of matched healthy controls (P < 0.05-P < 0.0001). Unaltered vibration detection emphasizes the strictly regional character of losses. Loss of sensitivity paralleled the occurrence of paradoxical heat sensation (Th10 vs C5; P < 0.05), an indicator of thermal integration deficit. Punctate hyperalgesia or pain to light touch, the hallmark signs of spinal central sensitization were mostly absent and pain summation remained unchanged (P > 0.05). Stratification of patients revealed that somatosensory deficits were significantly more pronounced in acute compared with chronic pancreatitis (eg, cold and warm detection thresholds: -2.19 ± 1.42 vs -1.10 ± 1.23 and -1.30 ± 1.68 vs -0.11 ± 1.80 z-values; P < 0.05 each). Notably, blunt pressure hyperalgesia, the only somatosensory parameter exhibiting significant gain compared with the patients' remote C5 segment, was a frequent finding only in acute, but not in chronic pancreatitis. The somatosensory phenotype of patients with distinct pancreatic disorders was characterized by a wide array of sensory losses being most severe in acute pancreatitis.

16. Pain in chronic pancreatitis

INTRODUCTION

Chronic pancreatitis is defined as a disease of the pancreas in which recurrent inflammatory episodes result in replacement of the pancreatic parenchyma by fibrous connective tissue in individuals with genetic, environmental, and other risk factors. Pain is one of the most important symptoms of chronic pancreatitis and, in many cases, has chronic visceral nociceptive, nociplastic, and even neuropathic components, with evidence of both central and peripheral sensitization, neuroplasticity, and neurogenic inflammation.

METHODS

The literature on the diagnosis and treatment of pain in chronic pancreatitis was reviewed and summarized.

RESULTS

Treatment of abdominal pain in chronic pancreatitis is guided by pancreatic morphology on imaging, although the correlation between pain symptoms and pathoanatomical changes is not always straightforward. Patients with pancreatic duct obstruction are initially offered endoscopic or surgical therapies, while non-obstructive disease is mostly managed medically. Lifestyle changes and psychological support are of particular importance for all chronic pancreatitis patients. Analgesic options range from non-opioid medications to opioids and adjuvant agents. Interventional pain management may consist of radiofrequency treatment of the splanchnic nerves and spinal cord stimulation. To date, there are no randomized trials supporting their efficacy in the treatment of chronic pancreatitis pain, and the recommendation to consider these treatment options is justified by evidence from observational studies. Possible opioid-sparing effects of interventional pain treatments are important to consider because opioid use and dependency are common in chronic pancreatitis patients and associated with worse outcomes. Celiac plexus block is not generally recommended for chronic pancreatitis due to the limited quality of evidence, overall short duration of effect, and invasiveness of the procedure. Central sensitization can impact the effectiveness of invasive treatments.

CONCLUSIONS

Managing pain in chronic pancreatitis is a complex task that requires a multidimensional and individualized approach. Due to the lack of randomized trials, treatment decisions are often guided by expert opinion. Integrating pharmacological and non-pharmacological interventions and collaborating with a multidisciplinary team are key components of effective chronic pancreatitis pain management.

Quality of life instruments in acute and chronic pancreatitis: a consensus-based standards for the selection of health measurement instruments (COSMIN) approach

BACKGROUND

Pancreatitis is a common surgical emergency, associated with pain and poor quality of life for patients. However, assessment of patient-reported outcome measures in these patients is unclear. This study aimed to identify and evaluate the methodological quality of the health-related quality of life instruments used for patients with acute or chronic pancreatitis.

METHODS

Prospective studies that evaluated health-related quality of life in acute or chronic pancreatitis were identified from systematic review of MEDLINE, EMBASE, and Web of Science until 28th June 2023 (PROSPERO: CRD42021274743). Instrument characteristics were extracted, and methodological quality assessed using COSMIN (COnsensus-based Standards for the selection of health status Measurement Instruments) guidelines and GRADE approach. Narrative synthesis was conducted, with recommendations for use based on COSMIN criteria, evaluated according to World Health Organisation (WHO) quality of life domains.

RESULTS

From 3850 records screened, 41 quality of life instruments were identified across 138 studies included. The majority (69.8%, n = 26) were designed to assess general health-related quality of life, whereas the remainder were abdominal-specific (n = 5) or pancreas-specific (n = 10). Only ten instruments (24.3%) demonstrated sufficient content validity, incorporating items in ≥5 WHO quality of life domains. However, only nine instruments (21.9%) incorporated public and patient involvement. Only the Gastrointestinal Quality of Life Index and PAN-PROMISE met the criteria to be recommended for use based on COSMIN methodological assessment.

CONCLUSION

There is significant heterogeneity in instruments used to assess quality of life after pancreatitis, with almost all instruments considered insufficient. Robust, validated, and relevant instruments are needed to better understand and determine appropriate interventions to improve quality of life for these patients.

Recent advances in the understanding and management of chronic pancreatitis pain

Abdominal pain is the most common symptom of chronic pancreatitis (CP) and is often debilitating for patients and very difficult to treat. To date, there exists no cure for the disease. Treatment strategies focus on symptom management and on mitigation of disease progression by reducing toxin exposure and avoiding recurrent inflammatory events. Traditional treatment protocols start with medical management followed by consideration of procedural or surgical intervention on selected patients with severe and persistent pain. The incorporation of adjuvant therapies to treat comorbidities including psychiatric disorders, exocrine pancreatic insufficiency, mineral bone disease, frailty, and malnutrition, are in its early stages. Recent clinical studies and animal models have been designed to improve investigation into the pathophysiology of CP pain, as well as to improve pain management. Despite the array of tools available, many therapeutic options for the management of CP pain provide incomplete relief. There still remains much to discover about the neural regulation of pancreas-related pain. In this review, we will discuss research from the last 5 years that has provided new insights into novel methods of pain phenotyping and the pathophysiology of CP pain. These discoveries have led to improvements in patient selection for optimization of outcomes for both medical and procedural management, and identification of potential future therapies.

Spinal Excitability in Patients with Painful Chronic Pancreatitis

Purpose

Abdominal pain is common in patients with chronic pancreatitis (CP), but management is challenging - possibly due to altered pain processing within the central nervous system rendering conventional treatments ineffective. We hypothesized that many patients with painful CP have generalized hyperalgesia correlating with central neuronal hyperexcitability.

Patients and Methods

Seventeen CP patients with pain and 20 matched healthy controls underwent experimental pain testing, including repeated pain stimuli (temporal summation), pressure algometry performed in dermatomes with same spinal innervation as the pancreatic gland (pancreatic areas) and remote dermatomes (control areas), a cold pressor test and a conditioned pain modulation paradigm. To probe central neuronal excitability, the nociceptive withdrawal reflex was elicited by electrical stimulation of the plantar skin, and electromyography was obtained from the ipsilateral anterior tibial muscle together with somatosensory evoked brain potentials.

Results

Compared to healthy controls, patients with painful CP had generalized hyperalgesia as evidenced by 45% lower pressure pain detection thresholds (P<0.05) and decreased cold pressor endurance time (120 vs 180 seconds, P<0.001). In patients, reflex thresholds were lower (14 vs 23 mA, P=0.02), and electromyographic responses were increased (16.4 vs 9.7, P=0.04) during the withdrawal reflex, reflecting predominantly spinal hyperexcitability. Evoked brain potentials did not differ between groups. A positive correlation was found between reflex thresholds and cold pressor endurance time (ρ=0.71, P=0.004).

Conclusion

We demonstrated somatic hyperalgesia in patients with painful CP associated with spinal hyperexcitability. This highlights that management should be directed at central mechanisms using, eg, gabapentinoids or serotonin-noradrenaline reuptake inhibitors.

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 patterns in chronic pancreatitis and chronic primary pain

BACKGROUND

Abdominal pain is the most distressing symptom of chronic pancreatitis (CP), and current treatments show limited benefit. Pain phenotypes may be more useful than diagnostic categories when planning treatments, and the presence or absence of constant pain in CP may be a useful prognostic indicator.

AIMS

This cross-sectional study examined dimensions of pain in CP, compared pain in CP with chronic primary pain (CPP), and assessed whether constant pain in CP is associated with poorer outcomes.

METHODS

Patients with CP (N = 91) and CPP (N = 127) completed the Comprehensive Pancreatitis Assessment Tool. Differences in clinical characteristics and pain dimensions were assessed between a) CP and CPP and b) CP patients with constant versus intermittent pain. Latent class regression analysis was performed (N = 192) to group participants based on pain dimensions and clinical characteristics.

RESULTS

Compared to CPP, CP patients had higher quality of life (p < 0.001), lower pain severity (p < 0.001), and were more likely to use strong opioids (p < 0.001). Within CP, constant pain was associated with a stronger response to pain triggers (p < 0.05), greater pain spread (p < 0.01), greater pain severity, more features of central sensitization, greater pain catastrophising, and lower quality of life compared to intermittent pain (all p values ≤ 0.001). Latent class regression analysis identified three groups, that mapped onto the following patient groups 1) combined CPP and CP-constant, 2) majority CPP, and 3) majority CP-intermittent.

CONCLUSIONS

Within CP, constant pain may represent a pain phenotype that corresponds with poorer outcomes. CP patients with constant pain show similarities to some patients with CPP, potentially indicating shared mechanisms.

Somatosensory assessments in patients with inflammatory bowel disease: a cross-sectional study examining pain processing pathways and the role of multiple patient factors

BACKGROUND

Pain affects the majority of patients with inflammatory bowel disease (IBD), where pain experiences may be influenced by multiple patient factors and changes within central pain processing pathways, termed central sensitization. The current study aimed to investigate pain processing pathways in patients with IBD through somatosensory testing and associations with multiple patient factors.

METHODS

A cross-sectional study of adults with IBD. Assessments included: somatosensory tests [i.e. pressure pain thresholds (PPT), temporal summation (TS), conditioned pain modulation (CPM)], and patient factors (i.e. demographics, comorbidity, sleep quality, psychological, pain severity and interference, and IBD features). Multiple regression analyses explored associations between somatosensory tests and multiple patient factors.

RESULTS

Decreased CPM in participants (N = 51) was associated with worse abdominal pain severity and use of biologic therapies (R2 = 0.30, F(5,44) = 5.18, P = 0.001). Increased TS was associated with biologic use (R2 = 0.11, F(1,49) = 6.13, P = 0.017). Decreased PPT at the low back (R2 = 0.29, F(2,48) = 11.21, P < 0.001) and Tibialis anterior (R2 = 0.41, F(2,48) = 18.26, P < 0.001) were associated with female sex and the absence of a stoma.

CONCLUSION

Study results demonstrated associations between multiple patient factors and somatosensory tests in patients with IBD. The absence of a stoma and female sex was associated with greater sensitivity to pressure in two remote body regions, suggestive of widespread hyperalgesia. Worse abdominal pain severity and biologic use were associated with decreased pain inhibition, and biologic use was also associated with increased pain facilitation. These findings suggest the presence of altered pain processing and mechanisms of central sensitization in patients with IBD.

Pancreatic QST Differentiates Chronic Pancreatitis Patients into Distinct Pain Phenotypes Independent of Psychiatric Comorbidities

BACKGROUND & AIMS

Quantitative sensory testing (QST) has been previously used to study pain in chronic pancreatitis (CP) but included methods that are not suitable for clinical purposes. The aims of this study were to determine if pancreatic QST (P-QST) can differentiate patients into distinct pain phenotypes and to determine the association of these with their clinical pain and psychiatric comorbidities.

METHODS

A multicenter cross-sectional study was conducted where patients completed validated questionnaires assessing quality of life (QoL), depression and anxiety scores as well as clinical pain symptoms followed by P-QST which included a cold pressor test, repetitive pinprick stimuli and pressure stimulation of the upper abdominal (T10) and control dermatomes. P-QST categorized patients into pain phenotypes based on a previously established nomogram. QoL, clinical pain and psychiatric assessment scores were compared across these groups.

RESULTS

A total of 179 patients were enrolled with a mean age of 54.1±13.6 years among whom 59% were males and 42% had an alcoholic etiology. P-QST showed no hyperalgesia in 91 (51%), segmental hyperalgesia in 50 (28%) and widespread hyperalgesia in 38 (21%) patients. Patients with widespread hyperalgesia had significantly higher pain intensity scores (P = .03) and rates of constant pain (P = .002) as well as decreased QoL (P < .001) and physical functioning (P =.03) in comparison with the other two pain phenotypes. In contrast, psychiatric comorbidities were similar across all groups.

CONCLUSIONS

P-QST may serve as a novel unbiased pain assessment tool in CP as it categorizes patients into distinct pain phenotypes independent of their psychiatric comorbidities.

Prevalence of primary painless chronic pancreatitis: A systematic review and meta-analysis

BACKGROUND/OBJECTIVES

While pain is the predominant symptom of chronic pancreatitis (CP), a subset of patients may experience a painless course. This systematic review aimed to determine the prevalence of primary painless CP.

METHODS

MEDLINE (PubMed), EMBASE and Web of Science Core Collection databases were searched for published studies through September 15, 2020 that included at least 10 consecutive patients with CP and which reported the number with painless CP. The presence of a history of recurrent acute pancreatitis (RAP), exocrine pancreatic insufficiency (EPI), diabetes mellitus (DM) and pancreatic adenocarcinoma (PA) in the painless CP patients was also recorded. A random effects model was used to determine pooled prevalence estimates with 95% confidence intervals (95% CI).

RESULTS

Among the 5057 studies identified and screened, 42 full-text articles were included in the final analysis. There were a total of 14,277 patients with CP among whom 1569 had painless CP. The pooled prevalence of painless CP was 12% (95% CI 10-15%). Among a subset of studies that reported on calcifications (n = 11), DM (n = 12), EPI (n = 8) and history of RAP (n = 14), the pooled prevalence estimates were 96% (95% CI 73-100%), 51% (95% CI 32-70%), and 47% (95% CI 15-81%), respectively. Alcohol, idiopathic/genetic and other etiologies were attributed to be the cause of painless CP in 32.4%, 56.9% and 8.9% patients, respectively.

CONCLUSION

Approximately one in ten patients with CP have primary painless disease with the majority being attributable to an idiopathic/genetic etiology. Further research is needed to determine the optimal management of these patients.

Rationale for and Development of the Pancreatic Quantitative Sensory Testing Consortium to Study Pain in Chronic Pancreatitis

OBJECTIVES

Abdominal pain is the primary symptom of chronic pancreatitis (CP), but pain is difficult to assess, and objective methods for pain assessment are lacking. The characterization of the sensory component of pain as a surrogate for nociception can be achieved by sensory testing using standardized stimuli. Herein, we describe the rationale for and development of an international consortium to better understand and characterize CP pain.

METHODS

A collaboration was initially formed between the University of Aalborg, Johns Hopkins University, and the University of Pittsburgh. This group refined the protocol for pancreatic quantitative sensory testing (P-QST) and then expanded the collaboration with plans for incorporating P-QST into prospective studies.

RESULTS

The collaboration has successfully developed a P-QST nomogram. Chronic pancreatitis patients identified with P-QST as having widespread hyperalgesia had higher pain intensity scores, higher prevalence of constant pain, and decreased quality of life. Psychiatric comorbidities were independent of pain phenotypes. Multiple studies are underway to validate these findings and evaluate their utility in clinical trials.

CONCLUSIONS

Development of the P-QST Consortium will facilitate collaborative efforts to use P-QST as a means for evaluation and characterization of pain in CP patients, and optimize methods to guide individualized pain management approaches.

Assessment of pain associated with chronic pancreatitis: An international consensus guideline

Pain is the most common symptom in chronic pancreatitis (CP) with a major impact on quality of life. Few validated questionnaires to assess pain in CP exist, and the lack of consensus negatively impacts clinical management, research and meta-analysis. This guideline aims to review generic pain questionnaires for their usability in CP, to outline how pain assessment can be modified by confounding factors and pain types, to assess the value of additional measures such as quality of life, mental health and quantitative sensory testing, and finally to review pain assessment questionnaires used specifically in CP. A systematic review was done to answer 27 questions that followed the PICO (Population; Intervention; Comparator; Outcome) template. Quality of evidence of the statements was judged by Grades of Recommendation, Assessment, Development and Evaluation (GRADE) criteria. The manuscript was sent for review to 36 experts from various disciplines and continents in a multi-stage Delphi process, and finally reviewed by patient representatives. Main findings were that generic pain instruments are valid in most settings, but aspects of pain are specific for CP (including in children), and instruments have to account for the wide phenotypic variability and development of sensitization of the central nervous system. Side effects to treatment and placebo effects shall also be considered. Some multidimensional questionnaires are validated for CP and are recommended together with assessment of quality of life and psychiatric co-morbidities. This guideline will result in more homogeneous and comprehensive pain assessment to potentially improve management of painful CP.

Painful chronic pancreatitis - new approaches for evaluation and management

PURPOSE OF REVIEW

Management of abdominal pain in patients with chronic pancreatitis is often suboptimal. We review recent data on the epidemiology and new approaches for managing pain in chronic pancreatitis.

RECENT FINDINGS

Chronic pancreatitis duration does not appear to affect the pain experience. Pain pattern in chronic pancreatitis patients frequently changes and is not related to traditional patient and disease-related factors. Psychologic comorbidities, i.e. anxiety and depression, are frequent in patients with chronic pancreatitis, and are associated with more severe pain and pain interference. Adjunctive treatments, such as cognitive behavioral therapy, may positively influence pain management in chronic pancreatitis. Total pancreatectomy with islet autotransplantation (TPIAT) is an increasingly adopted treatment option in painful chronic pancreatitis. Ongoing multicenter studies will help define optimal candidates, predictors of successful pain remission and diabetes outcomes after TPIAT. Pancreatic quantitative sensory testing, a promising technique to interrogate nociception and sensory response, holds promise to identify patients with central sensitization. Initial studies show feasibility to stratify patients into defined pain profiles, and future studies will explore if these can help in prognostication of pain therapy.

SUMMARY

Several lines of investigations currently under evaluation are likely to have a positive impact on the management of pain in chronic pancreatitis.

Pancreatic Pain-Knowledge Gaps and Research Opportunities in Children and Adults: Summary of a National Institute of Diabetes and Digestive and Kidney Diseases Workshop

ABSTRACT

A workshop was sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases to focus on research gaps and opportunities in pancreatic pain. The event was held on July 21, 2021, and structured into 4 sessions: (1) pathophysiology; (2) biomarkers, mediators, and pharmacology of pain; (3) pain assessment; and (4) pain treatment challenges and opportunities. The current state of knowledge was reviewed; many knowledge gaps and research needs were identified that require further investigation. Common themes included the need to better understand the underlying mechanisms of pain in pancreatic diseases, the relationship of visceral neural pathways and central pain centers, the role of behavioral factors and disorders on the perception of pain, and differences in pain perception and processes in children when compared with adults. In addition, the role of genetic risk factors for pain and the mechanisms and role of placebos in pain treatment were discussed. Methods of pain assessment including quantitative sensory testing were examined, as well as the process of central sensitization of pain. Finally, newer approaches to pain management including cognitive behavioral therapy, nerve stimulation, experimental (nonopioid) drugs, and cannabinoid compounds were covered.

The predictive value of quantitative sensory testing: a systematic review on chronic postoperative pain and the analgesic effect of pharmacological therapies in patients with chronic pain

Studies have suggested that quantitative sensory testing (QST) might hold a predictive value for the development of chronic postoperative pain and the response to pharmacological interventions. This review systematically summarizes the current evidence on the predictive value of QST for chronic postoperative pain and the effect of pharmacological interventions. The main outcome measures were posttreatment pain intensity, pain relief, presence of moderate-to-severe postoperative pain, responders of 30% and 50% pain relief, or validated questionnaires on pain and disability. A systematic search of MEDLINE and EMBASE yielded 25 studies on surgical interventions and 11 on pharmacological interventions. Seventeen surgical and 11 pharmacological studies reported an association between preoperative or pretreatment QST and chronic postoperative pain or analgesic effect. The most commonly assessed QST modalities were pressure stimuli (17 studies), temporal summation of pain (TSP, 14 studies), and conditioned pain modulation (CPM, 16 studies). Of those, the dynamic QST parameters TSP (50%) and CPM (44%) were most frequently associated with chronic postoperative pain and analgesic effects. A large heterogeneity in methods for assessing TSP (n = 4) and CPM (n = 7) was found. Overall, most studies demonstrated low-to-moderate levels of risk of bias in study design, attrition, prognostic factors, outcome, and statistical analyses. This systematic review demonstrates that TSP and CPM show the most consistent predictive values for chronic postoperative pain and analgesic effect, but the heterogeneous methodologies reduce the generalizability and hence call for methodological guidelines.

Pain Management in Chronic Pancreatitis: Summary of Clinical Practice, Current Challenges and Potential Contribution of the M-ANNHEIM Classification

Abdominal pain, diarrhea with weight loss, and endocrine insufficiency represent the dominant symptoms of chronic pancreatitis (CP). High intensity of pain and constant pain have been shown to reduce quality of life in CP and may result in disability and increased health resource utilization. Various basic challenges and unanswered questions still exist regarding the treatment of pain in CP. Recently, limited evidence has been gained that early surgery for painful disease might be associated with better treatment results. Thus, timing of pancreatic surgery in painful disease represents a major issue that needs to be clarified in future studies. In this context, surveillance of patients is necessary in clinical practice. It appears that a generally accepted classification of the disease represents a major requirement for inter-institutional comparison of data with future progress in clinical research. Among recently proposed classification systems, the M-ANNHEIM classification system of CP with its recently presented M-ANNHEIM Surgery Score might be a useful tool to picture the course of the disease and to monitor treatment results. Future research is required to clarify the possible role of this system in the management of pain in CP. In the present article, we provide an overview of current status, challenges, and unanswered questions in the treatment of pain in CP, and we demonstrate the potential benefits of the M-ANNHEIM classification system in the management of painful CP.

Tapentadol treatment results in long-term pain relief in patients with chronic low back pain and associates with reduced segmental sensitization

The endogenous pain system may be used as a biomarker in the pharmacological treatment of patients with CLBP, enabling an individualized, mechanism-based treatment approach.

Introduction:

Chronic low back pain (CLBP) is one of the most common chronic pain conditions in pain practice.

Objectives:

In the current study, we describe phenotypes of patients with CLBP based on the status of their endogenous pain modulatory system.

Methods:

Conditioned pain modulation (a measure of central pain inhibition), temporal summation (TS, a measure of pain facilitation), and offset analgesia (a measure of temporal filtering of nociception) were evaluated in 53 patients with CLBP at painful and nonpainful sites. Next, in a double-blind, randomized, placebo-controlled trial, 40 patients with defective conditioned pain modulation responses received treatment with tapentadol prolonged-release or placebo for 3 months.

Results:

The majority of patients (87%) demonstrated loss of central pain inhibition combined with segmentally increased TS and reduced offset analgesia at the lower back region. During treatment, tapentadol reduced pain intensity more than placebo (tapentadol −19.5 ± 2.1 mm versus placebo −7.1 ± 1.8 mm, P = 0.025). Furthermore, tapentadol significantly decreased pain facilitation by reduction of TS responses at the lower back (tapentadol −0.94 ± 1.9 versus placebo 0.01 ± 1.5, P = 0.020), which correlated with pain reduction (P < 0.001).

Conclusion:

Patients with CLBP demonstrated different phenotypes of endogenous pain modulation. In patients with reduced conditioned pain modulation, tapentadol produced long-term pain relief that coincided with reduction of signs of pain facilitation. These data indicate that the endogenous pain system may be used as a biomarker in the pharmacological treatment of CLBP, enabling an individualized, mechanism-based treatment approach.

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.