Hypoalgesia to experimental visceral and somatic stimulation in painful chronic pancreatitis

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.

Perineural Invasion and Associated Pain Transmission in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the cancers with the highest incidence of perineural invasion (PNI), which often indicates a poor prognosis. Aggressive tumor cells invade nerves, causing neurogenic inflammation; the tumor microenvironment also induces nerves to undergo a series of structural and functional reprogramming. In turn, neurons and the surrounding glial cells promote the development of pancreatic cancer through autocrine and/or paracrine signaling. In addition, hyperalgesia in PDAC patients implies alterations of pain transmission in the peripheral and central nervous systems. Currently, the studies on this topic are relatively limited. This review will elaborate on the mechanisms of tumor-neural interactions and its possible relationship with pain from several aspects that have been focused on in recent years.

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

BACKGROUND

Abdominal pain is the most common symptom in chronic pancreatitis (CP) and has an extensive impact on patients' lives. Quantitative sensory testing (QST) provides information on sensitivity to pain and mechanisms that can help quantify pain and guide treatment. The aims of this study were (1) to explore sensitivity to pain in patients with CP using QST and (2) to associate patient and disease characteristics with QST results.

METHODS

Ninety-one patients with painful CP and 28 healthy control participants completed a QST paradigm using static tests (muscle pressure stimulation and electrical skin stimulations) to unravel segmental and widespread hyperalgesia as a consequence of visceral pain. A dynamic conditioned pain modulation (CPM) paradigm was used as a proxy of pain modulation from the brainstem to inhibit incoming nociceptive barrage, and questionnaires were used to gather information on pain experience and quality of life.

RESULTS

Patients had impaired CPM compared with controls (18.0±29.3% vs. 30.9±29.3%, P=0.04) and were hypersensitive to pressure stimulation, specifically in the pancreatic (Th10) dermatome (P<0.001). The capacity of CPM was associated with clinical pain intensity (P=0.01) and (in the univariate analysis only) the use of opioids was associated with hyperalgesia to pressure stimulation (P<0.05).

CONCLUSIONS

Sensitivity to pain in CP patients can be characterized by a simple bedside QST. Severe clinical pain in CP was associated with reduced CPM function and should be targeted in management.

Sensitized brain response to acute pain in patients using prescription opiates for chronic pain: A pilot study

BACKGROUND

Chronic opiate use leads to a sensitized behavioral response to acute pain, which in turn, leads to escalating doses of opiates. This study was designed to test the hypothesis that chronic opiate usage is also associated with a sensitized neurobiological response to acute pain in individuals that have used prescription opiates for 6 or more months.

METHODS

Fourteen patients with non-alcoholic chronic pancreatitis that have been taking prescription opiates for 6 or more months and 14 gender matched, non-opiate using controls were enrolled. Functional neuroimaging data was acquired while participants received blocks of thermal stimulation to their wrist (individually-tailored to their pain threshold).

RESULTS

Self-reported pain was significantly greater in opiate using patients (3.4 ± 3.4) than controls (0.2 ± 0.8: Brief Pain Inventory p < 0.005), however no significant difference between groups was observed in the individually-tailored pain thresholds. Opiate using patients evidenced a significantly greater response to pain than controls in two established nodes of the "Pain Matrix": somatosensory cortex (p_FWE≤0.001) and anterior cingulate cortex (p ≤ 0.01). This response was positively correlated with prescribed morphine equivalent dosages (average: 133.5 ± 94.8 mg/day).

CONCLUSION

The findings suggest that in chronic pancreatitis patients, a dose of opiates that normalizes their behavioral response to acute pain is associated with an amplified neural response to acute pain. Further longitudinal studies are needed to determine if this neural sensitization hastens a behavioral tolerance to opiates or the development of an opioid use disorder.

Somatosensory Test Responses and Physical and Psychological Functioning of Children and Adolescents with Chronic Non-neuropathic Pain: An Exploratory Study

OBJECTIVES

This study was designed to establish preliminary feasibility testing of a set of inherently benign somatosensory stimulus-response tests (to cutaneous and deep stimuli) for bedside or office evaluation of pain disorders in children and adolescents. Associations between, and the relative influence of, cutaneous somatosensory testing (SST) responses, deep SST responses, and psychological factors (depression, pain-related catastrophizing) on pain outcomes (worst pain intensity, pain-related disability) were considered.

METHODS

Sixty participants (6 to 18 y) were recruited from the pediatric chronic pain clinic. SST responses were assessed at the pain site (PS) and control sites to diverse stimuli (static/dynamic touch, punctate pressure, vibration, cool, deep pressure) using Colored Analogue Scales (CAS) with modified anchors. Validated measures of depression, pain-related catastrophizing, and pain-related functional interference were administered.

RESULTS

Responses at the PS were more frequently hypersensitive than hyposensitive for all SST measures except vibration. Deep pressure responses were the only statistically significant predictor of worst pain intensity. Depression and pain-related catastrophizing accounted for a statistically significant amount of variance of pain-related disability, over and above that which was accounted for by SST responses.

DISCUSSION

Preliminary feasibility of a set of somatosensory stimulus-response tests for bedside or office evaluation of pain disorders in children and adolescents was established. Deep pressure responses contributed unique information in predicting worst pain intensity but not functional interference. Although cutaneous SST responses at the PSs were frequently abnormal, cutaneous SST responses were not confirmed in this study to have clinical utility, but rather might be centrally mediated epiphenomena.

Pancreatic pain

PURPOSE OF REVIEW

Pain is the most common symptom of chronic pancreatitis, with a profound socioeconomic impact. Historical management paradigms failed, as they did not adequately address the fundamental underlying mechanisms. The present article describes the neurobiology of pain and sensitization in this condition, in an effort to explain prior failings and provide future directions for managing pain in chronic pancreatitis.

RECENT FINDINGS

A number of recent advances have been made in understanding the neurobiology of pain for this condition. This has been coupled with clinical advances in assessing sensitization to pain in these patients, which has been shown to predict response to medical and surgical therapy.

SUMMARY

Pain in chronic pancreatitis is complex. Addressing the mechanical and morphological findings in chronic pancreatitis without addressing the underlying neurobiological mechanisms is destined to fail. New advances in our understanding of the neurobiology of pain in chronic pancreatitis helps to explain prior failings and provides future direction for managing pain in patients afflicted by this disease.

Association between visceral, cardiac and sensorimotor polyneuropathies in diabetes mellitus

AIMS

Gastrointestinal complaints are common in diabetes mellitus. However, its association to peripheral sensorimotor and autonomic neuropathies is not well investigated. The aim was to assess skin, muscle, bone and visceral sensitivity in diabetes patients with sensorimotor neuropathy, and correlate these with gastrointestinal symptoms and degree of cardiac autonomic neuropathy.

METHODS

Twenty patients with sensorimotor neuropathy (65% type 2 diabetes, aged 58.3±12.0 years, diabetes duration 15.8±10.0 years) and 16 healthy controls were recruited. Cutaneous sensitivity to von Frey filaments, mechanical allodynia, muscle/bone/rectosigmoid sensitivities, and heart rate variability were examined. Gastrointestinal symptom scores (PAGI-SYM) and health-related quality of life (SF-36) were also recorded.

RESULTS

Patients displayed hypesthesia to von Frey filaments (p=0.028), but no difference to muscle and bone pain sensitivities. Also, patients were hyposensitive to multimodal rectal stimulations (all p<0.05), although they suffered more gastrointestinal complaints. Heart rate variability was reduced in the patient cohort. Rectal mechanical and cutaneous sensitivities correlated (p<0.001), and both were associated with heart rate variability as well as PAGI-SYM and SF-36 scores (p<0.01).

CONCLUSIONS

In diabetic sensorimotor neuropathy there is substantial evidence of concomitant cutaneous, cardiac and visceral autonomic neuropathies. The neuropathy may reduce quality of life and explain the higher prevalence of gastrointestinal complaints.

Anatomical and functional characterization of a duodeno-pancreatic neural reflex that can induce acute pancreatitis

Neural cross talk between visceral organs may play a role in mediating inflammation and pain remote from the site of the insult. We hypothesized such a cross talk exists between the duodenum and pancreas, and further it induces pancreatitis in response to intraduodenal toxins. A dichotomous spinal innervation serving both the duodenum and pancreas was examined, and splanchnic nerve responses to mechanical stimulation of these organs were detected. This pathway was then excited on the duodenal side by exposure to ethanol followed by luminal mustard oil to activate transient receptor potential subfamily A, member 1 (TRPA1). Ninety minutes later, pancreatic inflammation was examined. Ablation of duodenal afferents by resiniferatoxin (RTX) or blocking TRPA1 by Chembridge (CHEM)-5861528 was used to further investigate the duodeno-pancreatic neural reflex via TRPA1. ~40% of dorsal root ganglia (DRG) from the spinal cord originated from both duodenum and pancreas via dichotomous peripheral branches; ~50% splanchnic nerve single units responded to mechanical stimulation of both organs. Ethanol sensitized TRPA1 currents in cultured DRG neurons. Pancreatic edema and myeloperoxidase activity significantly increased after intraduodenal ethanol followed by mustard oil (but not capsaicin) but significantly decreased after ablation of duodenal afferents by using RTX or blocking TRPA1 by CHEM-5861528. We found the existence of a neural cross talk between the duodenum and pancreas that can promote acute pancreatitis in response to intraduodenal chemicals. It also proves a previously unexamined mechanism by which alcohol can induce pancreatitis, which is novel both in terms of the site (duodenum), process (neurogenic), and receptor (TRPA1).

Improved quality of life following total pancreatectomy and auto-islet transplantation for chronic pancreatitis

BACKGROUND

Total pancreatectomy (TP) with auto-islet transplant (AIT) is an extreme treatment for chronic pancreatitis, and we reviewed our experience to assess the impact on quality of life (QOL).

METHODS

A prospective cohort study from 2007 through 2010 with pre- and postoperative assessments of the Depression Anxiety Stress Scale, Pain Disability Index, and visual analogue pain scale was performed.

RESULTS

Twenty patients underwent TP-AIT with a median follow-up of 12 months (6.75-24 months). All patients reported moderate (45 %) to severe (55 %) pain prior to surgery. TP-AIT resulted in significant decreases in abdominal pain (p < 0.001), 80 % reporting no or mild pain. Despite pain improvement, only 30 % discontinued narcotics. Improvements in all PDI QOL domains improved from 79 to 90 % (p = 0.002), with greatest improvements seen in those without prior pancreatic surgery, younger patients, and in those with higher levels of preoperative pain. Patients were less affected by depression and anxiety prior to surgery, but 60 and 70 % did show improvement in depression and anxiety, respectively (p = 0.033). Sixteen patients (80 %) required exogenous insulin at last follow-up (mean total dose of insulin 11.6 U/day).

CONCLUSIONS

TP-AIT significantly improves pain and QOL measures in appropriately selected patients with CP.

The absorption profile of pregabalin in chronic pancreatitis

It was recently shown that pregabalin decreased pain associated with chronic pancreatitis. It is well known that pancreatitis patients suffer from fat malabsorption with accompanying diarrhoea because of loss of exocrine pancreatic enzyme production. This may lead to changes in the mucosal surface in the small intestine and possibly affect the absorption of pregabalin. The pharmacokinetics of pregabalin has never been investigated in patients suffering from chronic pancreatitis. The aim of this study was to develop a population pharmacokinetic model of pregabalin administered to patients with chronic pancreatitis. The pregabalin population pharmacokinetic analysis was conducted on data from fifteen patients with chronic pancreatitis. Each patient received 75 mg of pregabalin (oral capsule). Pregabalin concentrations were measured using a validated liquid chromatographic method. Data analysis was performed using non-linear mixed effects modelling methodology as implemented by NONMEM. A one-compartment model with first-order absorption and elimination adequately described pregabalin pharmacokinetics. Time to maximum observed plasma concentration (T(max) ) was 1.53 (95% CI 1.09-2.05). The maximum plasma concentration (C(max) ) was 1.98 μg/ml (95% CI 1.69-2.34), and area under the plasma concentration-time profile (area under the curve) was 18.2 μg*hr/ml (95% CI 14.7-26.3). Pregabalin is well absorbed in patients with chronic pancreatitis, and the pharmacokinetic profile of pregabalin is not extensively affected by chronic pancreatitis.

Reduced cortical thickness of brain areas involved in pain processing in patients with chronic pancreatitis

BACKGROUND & AIMS

Patients with painful chronic pancreatitis (CP) might have abnormal brain function. We assessed cortical thickness in brain areas involved in visceral pain processing.

METHODS

We analyzed brain morphologies of 19 patients with painful CP and compared them with 15 healthy individuals (controls) by using a 3T magnetic resonance scanner. By using an automated method with surface-based cortical segmentation, we assessed cortical thickness of the primary (SI) and secondary (SII) somatosensory cortex; prefrontal cortex (PFC); frontal cortex (FC); anterior (ACC), mid (MCC), and posterior (PCC) cingulate cortex; and insula. The occipital middle sulcus was used as a control area. The pain score was determined on the basis of the average daily amount of pain during 1 week.

RESULTS

Compared with controls, patients with CP had reduced overall cortical thickness (P = .0012), without effects of modification for diabetes, alcoholic etiologies, or opioid treatment (all P values >.05). In patients with CP, the cortical thickness was decreased in SII (P = .002, compared with controls), PFC (P = .046), FC (P = .0003), MCC (P = .001), and insula (P = .002). There were no differences in cortical thickness between CP patients and controls in the control area (P = .20), SI (P = .06), ACC (P = .95), or PCC (P = .42). Cortical thickness in the affected areas correlated with pain score (r = 0.47, P = .003).

CONCLUSIONS

In patients with CP, brain areas involved in pain processing have reduced cortical thickness. As a result of long-term, ongoing pain input to the neuromatrix, cortical thickness might serve as a measure for overall pain system dysfunction, as observed in other diseases characterized by chronic pain.

Unraveling the mystery of pain in chronic pancreatitis

Chronic pancreatitis is typically a painful condition and it can be associated with a severe burden of disease. The pathogenesis of pain in this disorder is poorly understood and its treatment has been largely empirical, often consisting of surgical or other invasive methods, with an outcome that is variable and frequently unsatisfactory. Human and experimental studies have indicated a critical role for neuronal mechanisms that result in peripheral and central sensitization. The pancreatic nociceptor seems to be significantly affected in this condition, with increased excitability associated with downregulation of potassium currents. Some of the specific molecules implicated in this process include the vanilloid receptor, TRPV1, nerve growth factor, the protease activated receptor 2 and a variety of others that are discussed in this Review. Studies have also indicated novel therapeutic targets for this condition.

Pain-associated adaptive cortical reorganisation in chronic pancreatitis

BACKGROUND/AIMS

In various chronic pain conditions cortical reorganisation seems to play a role in the symptomatology. The aims of this study were to investigate cortical reorganisation in patients with pain caused by chronic pancreatitis (CP) and to correlate putative cortical reorganisation to clinical pain scores.

METHODS

24 patients suffering from CP and 14 healthy volunteers were included. Patients' daily experience of pain was recorded in a pain diary. The sigmoid was stimulated electrically with simultaneous recording of evoked brain potentials (EPs). The brain source localisations reflecting direct neuronal activity were fitted by a five-dipole model projected to magnetic resonance imaging of the individual brains.

RESULTS

Patients showed prolonged latencies of the EPs confined to the frontal region of the brain (p < 0.01). The corresponding brain sources were located in the bilateral insula, cingulate gyrus and bilateral secondary somatosensory area. The insular dipoles were localised more posterior in the patients than in healthy subjects (p < 0.01). The shift in insular dipole localisation was negatively correlated with the patients' clinical pain scores (p < 0.05).

CONCLUSIONS

The findings indicate that sustained pain in CP leads to functional reorganisation of the insular cortex. We suggest its physiological correlate to be an adaptive response to chronic pain. and IAP.

Pain mechanisms in chronic pancreatitis: of a master and his fire

BACKGROUND

Unraveling the mechanisms of pain in chronic pancreatitis (CP) remains a true challenge. The rapid development of pancreatic surgery in the twentieth century, usage of advanced molecular biological techniques, and emergence of clinician-scientists have enabled the elucidation of several mechanisms that lead to the chronic, complicated neuropathic pain syndrome in CP. However, the proper analysis of pain in CP should include three main arms of mechanisms: "peripheral nociception," "peripheral/pancreatic neuropathy and neuroplasticity," and "central neuropathy and neuroplasticity."

DISCUSSION

According to our current knowledge, pain in CP involves sustained sensitization of pancreatic peripheral nociceptors by neurotransmitters and neurotrophic factors following neural damage. This peripheral pancreatic neuropathy leads to intrapancreatic neuroplastic alterations that involve a profound switch in the autonomic innervation of the human pancreas via "neural remodeling." Furthermore, this neuropathy entails a hyperexcitability of spinal sensory second-order neurons, which are subject to modulation from the brainstem via descending facilitation. Finally, viscerosensory cortical areas react to this central sensitization via spatial reorganization and thus a central neuroplasticity. The present review summarizes the current findings in these arms of mechanisms and introduces a novel concept to consistently describe pain in CP as a "predominantly neuropathic," "mixed-type" pain.

Descending inhibitory pain modulation is impaired in patients with chronic pancreatitis

BACKGROUND & AIMS

Pain is a prominent symptom in chronic pancreatitis (CP), but the underlying mechanisms are incompletely understood. We investigated the role of descending pain modulation from supraspinal structures as well as central nervous system sensitization in patients with pain from CP.

METHODS

Twenty-five patients with CP and 15 healthy volunteers were included. Descending pain modulation was investigated by diffuse noxious inhibitory control (a descending inhibitory response after conditioning stimulation). Central pain processing was investigated as the perceptual responses to multimodal (electrical, thermal, and mechanical) stimulations of the rectosigmoid and evoked brain potentials after electrical stimulation of the rectosigmoid.

RESULTS

Compared with healthy volunteers, the efficacy of diffuse noxious inhibitory control was reduced in patients with CP (13% +/- 21% vs 39% +/- 22%, respectively; F = 3.8; P = .01); central sensitization was indicated by remote hyperalgesia in the rectosigmoid to electrical stimulation (21 +/- 15 mA vs 27 +/- 15 mA; F = 6.2; P = .02) and heat stimulation (51 degrees C +/- 5 degrees C vs 53 degrees C +/- 4 degrees C; F = 5.9; P = .02). Compared with controls, patients with CP had increased latency of the early P1 peak to rectosigmoid stimulation (85 +/- 21 ms vs 108 +/- 28 ms, respectively; P = .02), possibly reflecting reorganization of central pain pathways.

CONCLUSIONS

Patients with CP have impairments in inhibitory pain modulation and evidence of central sensitization. Treatment of their pain therefore should focus not only on the pancreas, but also on descending pain modulation from supraspinal structures and central nervous system sensitization.

Visceral organ cross-sensitization - an integrated perspective

Viscero-somatic referral and sensitization has been well documented clinically and widely investigated, whereas viscero-visceral referral and sensitization (termed cross-organ sensitization) has only recently received attention as important to visceral disease states. Because second order neurons in the CNS have been extensively shown to receive convergent input from different visceral organs, it has been assumed that cross-organ sensitization arises by the same convergence-projection mechanism as advanced for viscero-somatic referral and sensitization. However, increasing evidence also suggests participation of peripheral mechanisms to explain referral and sensitization. We briefly summarize behavioral, morphological and physiological support of and focus on potential mechanisms underlying cross-organ sensitization.

Sensory testing of the human gastrointestinal tract

The objective of this appraisal is to shed light on the various approaches to screen sensory information in the human gut. Understanding and characterization of sensory symptoms in gastrointestinal disorders is poor. Experimental methods allowing the investigator to control stimulus intensity and modality, as well as using validated methods for assessing sensory response have contributed to the understanding of pain mechanisms. Mechanical stimulation based on impedance planimetry allows direct recordings of luminal cross-sectional areas, and combined with ultrasound and magnetic resonance imaging, the contribution of different gut layers can be estimated. Electrical stimulation depolarizes free nerve endings non-selectively. Consequently, the stimulation paradigm (single, train, tetanic) influences the involved sensory nerves. Visual controlled electrical stimulation combines the probes with an endoscopic approach, which allows the investigator to inspect and obtain small biopsies from the stimulation site. Thermal stimulation (cold or warm) activates selectively mucosal receptors, and chemical substances such as acid and capsaicin (either alone or in combination) are used to evoke pain and sensitization. The possibility of multimodal (e.g. mechanical, electrical, thermal and chemical) stimulation in different gut segments has developed visceral pain research. The major advantage is involvement of distinctive receptors, various sensory nerves and different pain pathways mimicking clinical pain that favors investigation of central pain mechanisms involved in allodynia, hyperalgesia and referred pain. As impairment of descending control mechanisms partly underlies the pathogenesis in chronic pain, a cold pressor test that indirectly stimulates such control mechanisms can be added. Hence, the methods undoubtedly represent a major step forward in the future characterization and treatment of patients with various diseases of the gut, which provides knowledge to clinicians about the underlying symptoms and treatment of these patients.

Is the pain in chronic pancreatitis of neuropathic origin? Support from EEG studies during experimental pain

AIM: To prove the hypothesis that patients with chronic pancreatitis would show increased theta activity during painful visceral stimulation.

METHODS: Eight patients and 12 healthy controls underwent an experiment where the esophagus was electrically stimulated at the pain threshold using a nasal endoscope. The electroencephalogram (EEG) was recorded from 64 surface electrodes and “topographic matching pursuit” was used to extract the EEG information in the early brain activation after stimulation.

RESULTS: A major difference between controls and patients were seen in delta and theta bands, whereas there were only minor differences in other frequency bands. In the theta band, the patients showed higher activity than controls persisting throughout the 450 ms of analysis with synchronous brain activation between the channels. The main theta components oscillated with 4.4 Hz in the patients and 5.5 Hz in the controls. The energy in the delta (0.5-3.5 Hz) band was higher in the controls, whereas the patients only showed scattered activity in this band.

CONCLUSION: The differences in the theta band indicate that neuropathic pain mechanisms are involved in chronic pancreatitis. This has important implications for the understanding and treatment of pain in these patients, which should be directed against drugs with effects on neuropathic pain disorders.

Assessment of experimental pain from skin, muscle, and esophagus in patients with chronic pancreatitis

OBJECTIVES

Comprehensive experimental methods are of major relevance assessing pain mechanisms in patients with chronic pain. Chronic pancreatitis is thought to involve the sensory response in other visceral organs and somatic tissue. We, therefore, aimed at exploring the pain mechanisms in chronic pancreatitis (CP) using a multimodal and multitissue stimulation approach.

METHODS

Ten patients (mean age, 50 years) with CP and 13 healthy controls (mean age, 35 years) participated. None of the patients took analgesics regularly. All were exposed to multimodal (mechanical, thermal, and electrical) experimental pain in the skin, muscles, and esophagus.

RESULTS

The patients were hyposensitive to mechanical stimulations of the skin (P = 0.001), but there were no differences in the pain to thermal and electrical stimulations. In the muscle and esophagus, no differences in pain thresholds were found. The difference between single and repeated stimulations reflecting the degree of central sensitization was 17% in controls and 36% in patients (P = 0.001). The referred pain area to electrical stimulation was 30.1 cm2 in the patients and 7.7 cm2 for the controls (P = 0.02).

CONCLUSIONS

The findings suggest that the balance among central hyperexcitability, neuroplastic changes, and descending pain-modulating pathways may explain the pain response to experimental multimodal stimulations in CP. This will likely also reflect the clinical pain mechanisms and may have important impact in selection of treatment, where drugs with potential effects on these mechanisms should be used.

Pain in chronic pancreatitis: the role of reorganization in the central nervous system

BACKGROUND & AIMS

In various chronic pain conditions cortical reorganization seems to play a role in the manifestations. The aim of this study was to investigate cortical reorganization in patients with pain caused by chronic pancreatitis.

METHODS

Twelve healthy subjects and 10 patients with chronic pancreatitis were included. The esophagus, stomach, and duodenum were stimulated electrically at the pain threshold using a nasal endoscope. The electroencephalogram was recorded from 64 surface electrodes and event-related brain potentials (EPs) were obtained.

RESULTS

As compared with healthy subjects, the patient group showed decreased latencies of the early EP components (N1, P < .001; P1, P = .02), which is thought to reflect the exogenous brain pain processing specifically. Source analysis showed that the dipolar activities corresponding to the early EPs were located consistently in the bilateral insula, in the anterior cingulate gyrus, and in the bilateral secondary somatosensory area. The bilateral insular dipoles were localized more medial in the patient group than in the healthy subjects after stimulation of all 3 gut segments (P < .01). There also were changes in the cingulate cortex where the neuronal source was more posterior in patients than in controls to stimulation of the esophagus (P < .05).

CONCLUSIONS

The findings indicate that pain in chronic pancreatitis leads to changes in cortical projections of the nociceptive system. Such findings also have been described in somatic pain disorders, among them neuropathic pain. Taken together with the clinical data this suggests a neuropathic component in pancreatic pain, which may influence the approach to treatment.