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

An update on improving long-term outcomes for patients with chronic pancreatitis post-surgery

INTRODUCTION

Chronic pancreatitis is a common inflammatory disease that severely impairs patients' quality of life, mainly due to abdominal pain which is the most frequent symptom. Current guidelines suggest medical therapy as the first line intervention based on a stepwise use of analgesics (i.e. NSAIDs followed by weak opioids and later by strong oppioids), which is rarely effective in improving pain and often leads to opioid addiction. Interventional procedures are therefore frequently needed. Endoscopic therapy is suggested as the second line of intervention, aiming at decompressing the main pancreatic duct via structure dilatation and ductal stone removal. Endoscopic therapy is usually effective in reducing pain in the short term, but its effects frequently decrease with time and multiple procedures are often required. Surgery is usually reserved as a last resource when medical and endoscopic therapy have failed. Pancreatic surgery is burdened with non negligible morbidity and mortality but is effective in reducing pain and improving quality of life in chronic pancratitis with long lasting effects.

AREAS COVERED

Surgical treatment of chronic pancreatitis is based on resection of inflammatory head mass or decompression of the ductal system, alone or in combination, which can be performed using different techniques. In this paper we reviewed the current evidence on the long-term outcomes of this type of surgery in terms of pain relief, quality of life, exocrine end endocrine function, and long-term mortality.

EXPERT OPINION

Quality of current evidence on this field is on average poor; a consensus to define clinically significant outcomes is needed in order to correctly design prospective studies that will enable gastroenterologists to understand which patients, and when, will benefit most from surgery and should therefore be referred to surgeons.

Brain Wave Patterns in Patients With Chronic Low Back Pain: A Case-control Study

Introduction

Research evidence indicates that maladaptive reorganization of the brain plays a critical role in amplifying pain experiences and pain chronification; however, no clear evidence of change exists in brain wave activity among patients with chronic low back pain (CLBP). The objective of this study was to assess brain wave activity in patients with CLBP, compared to healthy controls.

Methods

Twenty-five patients with CLBP and twenty-four healthy controls participated in the study. A quantitative electroencephalography device was used to assess brain wave activity in eyes-open and eyes-closed (EO and EC) conditions. The regional absolute and relative power of brain waves were compared between the groups.

Results

Our results showed a significant increase in the absolute power of theta (F=5.905, P=0.019), alpha (F=5.404, P=0.024) waves in patients with CLBP compared to healthy subjects in both EC and EO conditions. Patients with CLBP showed a reduced delta absolute power in the frontal region (F=5.852, P=0.019) and augmented delta absolute power in the central region (F=5.597, P=0.022) in the EO condition. An increased delta absolute power was observed in the frontal (F=7.563 P=0.008), central (F=10.430, P=0.002), and parietal (F=4.596, P=0.037) regions in patients with CLBP compared to the healthy subjects in the EC condition. In the EC condition, significant increases in theta relative power (F=4.680, P=0.036) in the parietal region were also found in patients with CLBP.

Conclusion

The increased absolute power of brain waves in people with CLBP may indicate cortical overactivity and changes in the pain processing mechanisms in these patients.

Highlights

Chronic low back pain (CLBP) increases the alpha, theta, and delta power in the brain.CLBP is associated with increased brain wave activity in the frontal, central, and parietal regions.Our findings suggest altered central pain processing in CLBP.

Plain Language Summary

Traditional diagnosis and treatment of CLBP are mainly focused on peripheral pathology. But, the modern neuroscience approach to pain highlights the role of cortical plasticity in chronic musculoskeletal pain. In this regard, several studies found structural and functional changes in the brain in patients with chronic pain. Detailed knowledge about cortical changes in CLBP can improve our understanding of mechanisms involved in CLBP, opening a new window to better treatment of LBP (Low back pain). This study investigated brain wave activity in patients with CLBP compared to healthy individuals. Our findings suggest increased brain activity in various parts of the brain in patients with chronic LBP. This finding indicates that CLBP treatment should focus on both peripheral and cortical factors rather than local tissue damage.

Synchronized activity of sensory neurons initiates cortical synchrony in a model of neuropathic pain

Increased low frequency cortical oscillations are observed in people with neuropathic pain, but the cause of such elevated cortical oscillations and their impact on pain development remain unclear. By imaging neuronal activity in a spared nerve injury (SNI) mouse model of neuropathic pain, we show that neurons in dorsal root ganglia (DRG) and somatosensory cortex (S1) exhibit synchronized activity after peripheral nerve injury. Notably, synchronized activity of DRG neurons occurs within hours after injury and 1-2 days before increased cortical oscillations. This DRG synchrony is initiated by axotomized neurons and mediated by local purinergic signaling at the site of nerve injury. We further show that synchronized DRG activity after SNI is responsible for increasing low frequency cortical oscillations and synaptic remodeling in S1, as well as for inducing animals' pain-like behaviors. In naive mice, enhancing the synchrony, not the level, of DRG neuronal activity causes synaptic changes in S1 and pain-like behaviors similar to SNI mice. Taken together, these results reveal the critical role of synchronized DRG neuronal activity in increasing cortical plasticity and oscillations in a neuropathic pain model. These findings also suggest the potential importance of detection and suppression of elevated cortical oscillations in neuropathic pain states.

Anterior Cingulate Cortex Mediates Hyperalgesia and Anxiety Induced by Chronic Pancreatitis in Rats

Central sensitization is essential in maintaining chronic pain induced by chronic pancreatitis (CP), but cortical modulation of painful CP remains elusive. Here, we examined the role of the anterior cingulate cortex (ACC) in the pathogenesis of abdominal hyperalgesia in a rat model of CP induced by intraductal administration of trinitrobenzene sulfonic acid (TNBS). TNBS treatment resulted in long-term abdominal hyperalgesia and anxiety in rats. Morphological data indicated that painful CP induced a significant increase in FOS-expressing neurons in the nucleus tractus solitarii (NTS) and ACC, and some FOS-expressing neurons in the NTS projected to the ACC. In addition, a larger portion of ascending fibers from the NTS innervated pyramidal neurons, the neural subpopulation primarily expressing FOS under the condition of painful CP, rather than GABAergic neurons within the ACC. CP rats showed increased expression of vesicular glutamate transporter 1, and increased membrane trafficking and phosphorylation of the N-methyl-D-aspartate receptor (NMDAR) subunit NR2B and the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) subunit GluR1 within the ACC. Microinjection of NMDAR and AMPAR antagonists into the ACC to block excitatory synaptic transmission significantly attenuated abdominal hyperalgesia in CP rats, which was similar to the analgesic effect of endomorphins injected into the ACC. Specifically inhibiting the excitability of ACC pyramidal cells via chemogenetics reduced both hyperalgesia and comorbid anxiety, whereas activating these neurons via optogenetics failed to aggravate hyperalgesia and anxiety in CP rats. Taken together, these findings provide neurocircuit, biochemical, and behavioral evidence for involvement of the ACC in hyperalgesia and anxiety in CP rats, as well as novel insights into the cortical modulation of painful CP, and highlights the ACC as a potential target for neuromodulatory interventions in the treatment of painful CP.

Tonic thermonociceptive stimulation selectively modulates ongoing neural oscillations in the human posterior insula: Evidence from intracerebral EEG

The human insula is an important target for spinothalamic input, but there is still no consensus on its role in pain perception and nociception. In this study, we show that the human insula exhibits activity preferential for sustained thermonociception. Using intracerebral EEG recorded from the insula of 8 patients (2 females) undergoing a presurgical evaluation of focal epilepsy (53 contacts: 27 anterior, 26 posterior), we "frequency-tagged" the insular activity elicited by sustained thermonociceptive and vibrotactile stimuli, by periodically modulating stimulation intensity at a fixed frequency of 0.2 Hz during 75 s. Both types of stimuli elicited an insular response at the frequency of stimulation (0.2 Hz) and its harmonics, whose magnitude was significantly greater in the posterior insula compared to the anterior insula. Compared to vibrotactile stimulation, thermonociceptive stimulation exerted a markedly greater 0.2 Hz modulation of ongoing theta-band (4-8 Hz) and alpha-band (8-12 Hz) oscillations. These modulations were also more prominent in the posterior insula compared to the anterior insula. The identification of oscillatory activities preferential for thermonociception could lead to new insights into the physiological mechanisms of nociception and pain perception in humans.

Membrane potential synchrony of neurons in anterior cingulate cortex plays a pivotal role in generation of neuropathic pain

The pathophysiology of neuropathic pain generation has not been fully investigated. Previous studies have primarily focused on changes in the properties of single neurons in the brain after nerve injury; however, little is known concerning the role of neuron-to-neuron connections in neuropathic pain pathogenesis. Synaptic transmission potentiation in anterior cingulate cortex (ACC) has been confirmed to be responsible for the formation of neuropathic pain. Thus, analysis of interneuronal connections in the ACC is an important approach for understanding the mechanism of neuropathic pain since it provides information on the potency of synaptic transmission. Here, we recorded membrane potentials from pairs of ACC neurons in anaesthetised rats and found that cross-correlations between pairs of ACC neurons significantly increased after surgery for chronic constriction injury (CCI). Moreover, CCI surgery could also enhance the power spectrum density of lower and higher-frequency membrane oscillations while having no effect on middle-frequency oscillations. The activation of membrane potential synchrony and power spectrum was reversed by the electrical synapse blocker mefloquine and pain behaviour was simultaneously alleviated. Our results may indicate that activation of membrane potential synchrony contributes to generation of neuropathic pain.

Towards a neurobiological understanding of pain in chronic pancreatitis: mechanisms and implications for treatment

We summarize the evidence for a neurobiological understanding of pain in patients with chronic pancreatitis and discuss its potential impact on prevention and treatment.

Introduction:

Chronic pancreatitis (CP) is a disease characterized by inflammation of the pancreas resulting in replacement of the normal functioning parenchyma by fibrotic connective tissue. This process leads to progressively impairment of exocrine and endocrine function and many patients develop a chronic pain syndrome.

Objectives:

We aimed to characterize the neurobiological signature of pain associated with CP and to discuss its implications for treatment strategies.

Methods:

Relevant basic and clinical articles were selected for review following an extensive search of the literature.

Results:

Pathophysiological changes in the peripheral (pancreatic gland) and central nervous system characterize the pain syndrome associated with CP; involved mechanisms can be broken down to 3 main branches: (1) peripheral sensitization, (2) pancreatic neuropathy, and (3) neuroplastic changes in the central pain pathways. Disease flares (recurrent pancreatitis) may accelerate the pathophysiological process and further sensitize the pain system, which ultimately results in an autonomous and self-perpetuating pain state that may become independent of the peripheral nociceptive drive. These findings share many similarities with those observed in neuropathic pain disorders and have important implications for treatment; adjuvant analgesics are effective in a subset of patients, and neuromodulation and neuropsychological interventions may prove useful in the future.

Conclusion:

Chronic pancreatitis is associated with abnormal processing of pain at the peripheral and central level of the pain system. This neurobiological understanding of pain has important clinical implications for treatment and prevention of pain chronification.

Laparoscopic Total Pancreatectomy With Islet Autotransplantation and Intraoperative Islet Separation as a Treatment for Patients With Chronic Pancreatitis

Importance

Pain management of patients with chronic pancreatitis (CP) can be challenging. Laparoscopy has been associated with markedly reduced postoperative pain but has not been widely applied to total pancreatectomy with islet autotransplantation (TPIAT).

Objective

To examine the feasibility of using laparoscopic TPIAT (L-TPIAT) in the treatment of CP.

Design, Setting, and Participants

Thirty-two patients with CP presented for TPIAT at a tertiary hospital from January 1, 2013, through December 31, 2015. Of the 22 patients who underwent L-TPIAT, 2 patients converted to an open procedure because of difficult anatomy and prior surgery. Pain and glycemic outcomes were recorded at follow-up visits every 3 to 6 months postoperatively.

Main Outcomes and Measures

Operative outcomes included operative time, islet isolation time, warm ischemia time, islet equivalent (IE) counts, estimated blood loss, fluid resuscitation, and blood transfusions. Postoperative outcomes included length of stay, all-cause 30-day readmission rate, postoperative complications, mortality rate, subjective pain measurements, opioid use, random C-peptide levels, insulin requirements, and glycated hemoglobin level.

Results

Of the 32 patients who presented for TPIAT, 20 underwent L-TPIAT (8 men and 12 women; mean [SD] age, 39 [13] years; age range, 21-58 years). Indication for surgery was CP attributable to genetic mutation (n = 9), idiopathic pancreatitis (n = 6), idiopathic pancreatitis with pancreas divisum (n = 3), and alcohol abuse (n = 2). Mean (SD) operative time was 493 (78) minutes, islet isolation time was 185 (37) minutes, and warm ischemia time was 51 (62) minutes. The mean (SD) IE count was 1325 (1093) IE/kg. The mean (SD) length of stay was 11 (5) days, and the all-cause 30-day readmission rate was 35% (7 of 20 patients). None of the patients experienced postoperative surgical site infection, hernia, or small-bowel obstruction, and none died. Eighteen patients (90%) had a decrease or complete resolution of pain, and 12 patients (60%) no longer required opioid therapy at a median follow-up period of 6 months. Postoperative random insulin C-peptide levels were detectable in 19 patients (95%) at a median follow-up of 10.4 months. At a median follow-up of 12.5 months, 5 patients (25%) were insulin independent, whereas 9 patients (45%) required 1 to 10 U/d, 5 patients (25%) required 11 to 20 U/d, and 1 patient (5%) required greater than 20 U/d of basal insulin. The mean (SD) glycated hemoglobin level was 7.4% (0.5%).

Conclusions and Relevance

This study represents the first series of L-TPIAT, demonstrating its safety and feasibility. Our approach enables patients to experience shorter operative times and the benefits of laparoscopy, including reduced length of stay and quicker opioid independence.

Narcotic Independence After Pancreatic Duct Stenting Predicts Narcotic Independence After Lateral Pancreaticojejunostomy for Chronic Pancreatitis

OBJECTIVE

This study aimed to determine if the improved pain response to endoscopic retrograde cholangiopancreatogrphy (ERCP) and pancreatic stent placement (EPS) predicts pain response in patients with chronic pancreatitis after modified lateral pancreaticojejunostomy (LPJ).

METHODS

A multi-institutional, retrospective review of patients who underwent successful EPS before LPJ between 2001 and 2010 was performed. The primary outcome was narcotic independence (NI) within 2 months after ERCP or LPJ.

RESULTS

A total of 31 narcotic-dependent patients with chronic pancreatitis underwent successful EPS before LPJ. Ten (32%) achieved post-LPJ NI (median follow-up, 8.5 months; interquartile range [IQR], 2-38 months). Eight (80%) of 10 patients with NI post-ERCP achieved NI post-LPJ. Two (10%) without NI post-ERCP achieved NI post-LPJ. Narcotic independence post-EPS was associated strongly with NI post-LPJ with an odds ratio of 38 (P = 0.0025) and predicted post-LPJ NI with a sensitivity, specificity, positive predictive value, and negative predictive value of 80%, 90.5%, 80%, and 90.5%, respectively.

CONCLUSIONS

Narcotic independence after EPS is associated with NI after LPJ. Failure to achieve NI post-ERCP predicts failure to achieve NI post-LPJ. These results support the need for larger studies to confirm the predictive value of pancreatic duct stenting for better selection of chronic pancreatitis patients who will benefit from LPJ.

Patients with Rheumatoid Arthritis and Chronic Pain Display Enhanced Alpha Power Density at Rest

Patients with chronic pain due to neuropathy or musculoskeletal injury frequently exhibit reduced alpha and increased theta power densities. However, little is known about electrical brain activity and chronic pain in patients with rheumatoid arthritis (RA). For this purpose, we evaluated power densities of spontaneous electroencephalogram (EEG) band frequencies (delta, theta, alpha, and beta) in females with persistent pain due to RA. This was a cross-sectional study of 21 participants with RA and 21 healthy controls (mean age = 47.20; SD = 10.40). EEG was recorded at rest over 5 min with participant's eyes closed. Twenty electrodes were placed over five brain regions (frontal, central, parietal, temporal, and occipital). Significant differences were observed in depression and anxiety with higher scores in RA participants than healthy controls (p = 0.002). Participants with RA exhibited increased average absolute alpha power density in all brain regions when compared to controls [F_(1.39) = 6.39, p = 0.016], as well as increased average relative alpha power density [F_(1.39) = 5.82, p = 0.021] in all regions, except the frontal region, controlling for depression/anxiety. Absolute theta power density also increased in the frontal, central, and parietal regions for participants with RA when compared to controls [F_{(1, 39)} = 4.51, p = 0.040], controlling for depression/anxiety. Differences were not exhibited on beta and delta absolute and relative power densities. The diffuse increased alpha may suggest a possible neurogenic mechanism for chronic pain in individuals with RA.

Multivariate analysis of single-sweep evoked brain potentials for pharmaco-electroencephalography

BACKGROUND AND AIMS

Current findings on altered evoked potentials (EPs) caused by morphine are based on common alterations for a group of subjects after drug administration. However, this ignores the analysis of individual responses, which may explain the clinical differences in efficacy. Therefore, we explored the individual responses to morphine in terms of the altered single-sweep characteristics in a placebo-controlled crossover study. To account for multifactorial mechanisms, several characteristics were assessed simultaneously by multivariate pattern analysis (MVPA).

METHODS

EPs were recorded from 62 channels and obtained before and after morphine and placebo administration during repeated electrical stimulations of the oesophagus in 12 healthy males. Additionally, the pain detection threshold was recorded to reflect the subjective analgesic effect in each subject. The characteristics of the sweeps were extracted by a multivariate matching pursuit algorithm with Gabor atoms implemented with a variable amplitude and constant phase across the sweeps. The single-sweep amplitudes were used as input to an MVPA algorithm to discriminate individual responses. The accuracy of the MVPA for each individual subject was used for correlation analysis of the analgesic effect.

RESULTS

The mean classification accuracy when discriminating pre- and posttreatment morphine responses was 72% (p = 0.01). The individual classification accuracy was positively correlated to the analgesic effect of morphine (p = 0.03). Furthermore, the 2 posttreatment responses were classified and validated by the classification of the 2 pretreatment responses (p = 0.001).

CONCLUSIONS

The alterations in the single-sweep EPs after morphine reflect the analgesic effect. The MVPA approach is a novel methodology for monitoring the individual efficacy of analgesics.

Electroencephalographic Patterns in Chronic Pain: A Systematic Review of the Literature

The main objective of this study is to review and summarize recent findings on electroencephalographic patterns in individuals with chronic pain. We also discuss recent advances in the use of quantitative Electroencephalography (qEEG) for the assessment of pathophysiology and biopsychosocial factors involved in its maintenance over time. Data collection took place from February 2014 to July 2015 in PubMed, SciELO and PEDro databases. Data from cross-sectional studies and longitudinal studies, as well as clinical trials involving chronic pain participants were incorporated into the final analysis. Our primary findings related to chronic pain were an increase of theta and alpha EEG power at rest, and a decrease in the amplitude of evoked potentials after sensory stimulation and cognitive tasks. This review suggests that qEEG could be considered as a simple and objective tool for the study of brain mechanisms involved in chronic pain, as well as for identifying the specific characteristics of chronic pain condition. In addition, results show that qEEG probably is a relevant outcome measure for assessing changes in therapeutic studies.

Pain Related Cortical Oscillations: Methodological Advances and Potential Applications

Alongside the time-locked event-related potentials (ERPs), nociceptive somatosensory inputs can induce modulations of ongoing oscillations, appeared as event-related synchronization or desynchronization (ERS/ERD) in different frequency bands. These ERD/ERS activities are suggested to reflect various aspects of pain perception, including the representation, encoding, assessment, and integration of the nociceptive sensory inputs, as well as behavioral responses to pain, even the precise details of their roles remain unclear. Previous studies investigating the functional relevance of ERD/ERS activities in pain perception were normally done by assessing their latencies, frequencies, magnitudes, and scalp distributions, which would be then correlated with subjective pain perception or stimulus intensity. Nevertheless, these temporal, spectral, and spatial profiles of stimulus induced ERD/ERS could only partly reveal the dynamics of brain oscillatory activities. Indeed, additional parameters, including but not limited to, phase, neural generator, and cross frequency couplings, should be paid attention to comprehensively and systemically evaluate the dynamics of oscillatory activities associated with pain perception and behavior. This would be crucial in exploring the psychophysiological mechanisms of neural oscillation, and in understanding the neural functions of cortical oscillations involved in pain perception and behavior. Notably, some chronic pain (e.g., neurogenic pain and complex regional pain syndrome) patients are often associated with the occurrence of abnormal synchronized oscillatory brain activities, and selectively modulating cortical oscillatory activities has been showed to be a potential therapy strategy to relieve pain with the application of neurostimulation techniques, e.g., repeated transcranial magnetic stimulation (rTMS) and transcranial alternating current stimulation (tACS). Thus, the investigation of the oscillatory activities proceeding from phenomenology to function, opens new perspectives to address questions in human pain psychophysiology and pathophysiology, thereby promoting the establishment of rational therapeutic strategy.

Single dose delta-9-tetrahydrocannabinol in chronic pancreatitis patients: analgesic efficacy, pharmacokinetics and tolerability

AIM

We aimed to assess the analgesic efficacy, pharmacokinetics, tolerability and safety of a single dose of Δ9-THC in patients with chronic abdominal pain resulting from chronic pancreatitis (CP).

METHODS

This was a randomized, single dose, double-blinded, placebo-controlled, two way crossover study in patients suffering from abdominal pain as result of CP (n = 24), post hoc subdivided into opioid and non-opioid users. Δ9-THC (8 mg) or active placebo (5 mg/10 mg diazepam) was administered orally in a double dummy design.

RESULTS

No treatment effect was shown for delta VAS pain scores after Δ9-THC compared with diazepam. Δ9-THC was well absorbed with a mean tmax of 123 min. No significant differences were found between Δ9-THC vs. diazepam for alertness, mood, calmness or balance. Feeling anxious and heart rate were significantly increased after Δ9-THC compared with diazepam. The most frequently reported adverse events (AEs) after Δ9-THC administration were somnolence, dry mouth, dizziness and euphoric mood.

CONCLUSIONS

A single dose of Δ9-THC was not efficacious in reducing chronic pain resulting from CP, but was well tolerated with only mild or moderate AEs. The PK results in CP patients showed delayed absorption and an increased variability compared with healthy volunteers.

Adrenergic signaling mediates mechanical hyperalgesia through activation of P2X3 receptors in primary sensory neurons of rats with chronic pancreatitis

The mechanism of pain in chronic pancreatitis (CP) is poorly understood. The aim of this study was designed to investigate roles of norepinephrine (NE) and P2X receptor (P2XR) signaling pathway in the pathogenesis of hyperalgesia in a rat model of CP. CP was induced in male adult rats by intraductal injection of trinitrobenzene sulfonic acid (TNBS). Mechanical hyperalgesia was assessed by referred somatic behaviors to mechanical stimulation of rat abdomen. P2XR-mediated responses of pancreatic dorsal root ganglion (DRG) neurons were measured utilizing calcium imaging and whole cell patch-clamp-recording techniques. Western blot analysis and immunofluorescence were performed to examine protein expression. TNBS injection produced a significant upregulation of P2X3R expression and an increase in ATP-evoked responses of pancreatic DRG neurons. The sensitization of P2X3Rs was reversed by administration of β-adrenergic receptor antagonist propranolol. Incubation of DRG neurons with NE significantly enhanced ATP-induced intracellular calcium signals, which were abolished by propranolol, and partially blocked by protein kinase A inhibitor H-89. Interestingly, TNBS injection led to a significant elevation of NE concentration in DRGs and the pancreas, an upregulation of β2-adrenergic receptor expression in DRGs, and amplification of the NE-induced potentiation of ATP responses. Importantly, pancreatic hyperalgesia was markedly attenuated by administration of purinergic receptor antagonist suramin or A317491 or β2-adrenergic receptor antagonist butoxamine. Sensitization of P2X3Rs, which was likely mediated by adrenergic signaling in primary sensory neurons, contributes to pancreatic pain, thus identifying a potential target for treating pancreatic pain caused by inflammation.

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.

Dynamic spectral indices of the electroencephalogram provide new insights into tonic pain

OBJECTIVE

This study aimed to investigate reliability of electroencephalography (EEG) during rest and tonic pain. Furthermore, changes in EEG between the two states as well as dynamics and relation to pain ratings were investigated.

METHODS

On two separate days EEG was recorded in 39 subjects during rest and tonic pain (cold pressor test: left hand held in 2°C water for 2 min.) while pain intensity was rated continuously. Dynamic spectral analysis was performed on the EEG. Between-day reliability of spectral indices was assessed and correlations to pain ratings were investigated.

RESULTS

EEG reliability was high during both states. The relative spectral indices increased in delta (1-4 Hz; P=0.0002), beta3 (18-32 Hz; P<0.0001) and gamma (32-70 Hz; P<0.0001) bands during tonic pain, and decreased in theta (4-8 Hz; P<0.0001), alpha1 (8-10 Hz; P<0.0001), alpha2 (10-12 Hz; P<0.0001) bands. Theta, beta3 and gamma bands correlated significantly to the area-under-curve of pain ratings, but only theta was dynamic and correlated to the pain ratings (R=0.88, P<0.0001).

CONCLUSIONS

EEG assessed during tonic pain is a valid experimental pain model both in terms of reliability between days and in connection between cortical activity and pain perception.

SIGNIFICANCE

EEG during tonic pain is more pain-specific and should be used in future basic and pharmacological studies.

Pain sensation in pancreatic diseases is not uniform: The different facets of pancreatic pain

AIM: To systematically characterize specific pain patterns in the most frequent pancreatic diseases.

METHODS: Pain in patients with chronic pancreatitis (n = 314), pancreatic cancer (n = 469), and other pancreatic tumors (n = 249) including mucinous (n = 20) and serous cystadenoma (n = 31), invasive (n = 37) and non-invasive intraductal papillary mucinous neoplasia (IPMN; n = 48), low stage (n = 18) and high stage neuroendocrine neoplasia (n = 44), and ampullary cancer (n = 51) was registered and correlated with clinicopathological data. Survival times were estimated by the Kaplan-Meier method. Patients alive at the follow-up time were censored. Survival curves were compared statistically using the log-rank test.

RESULTS: Forty-nine point one percent of pancreatic cancer patients revealed no pain, whereas in chronic pancreatitis only 18.3% were pain free. In contrary, moderate/severe pain was registered in 15.1% in pancreatic cancer patients that was increased in chronic pancreatitis with up to 34.2%. Serous cystadenoma was asymptomatic in most cases (58.1%), whereas 78.9% of all mucinous cystadenoma patients suffered pain. In neuroendocrine neoplasia pain was not a key clinical symptom since 64% of low stage neuroendocrine neoplasia and 59% of high stage neuroendocrine neoplasia patients were pain free. Cancer localization in the pancreatic body and patients with malignant pancreatic neoplasms were associated with more severe pain. Tumor grading and stage did not show any impact on pain. Only in pancreatic cancer, pain was directly associated with impaired survival.

CONCLUSION: Pancreatic pain depicts different patterns of abdominal pain sensation according to the respective pancreatic disorder and does not allow a unification of the term pancreatic pain.

Altered central pain processing after pancreatic surgery for chronic pancreatitis

BACKGROUND

Chronic abdominal pain is common in chronic pancreatitis (CP) and may involve altered central pain processing. This study evaluated the relationship between pain processing and pain outcome after pancreatic duct decompression and/or pancreatic resection in patients with CP.

METHODS

Patients with CP underwent quantitative sensory testing. Pain processing was measured via electrical pain detection (ePDT) and electrical pain tolerance (ePTT) thresholds in dermatomes C5 and L4. Inhibitory descending pain control mechanisms were assessed using the conditioned pain modulation (CPM) paradigm. Healthy controls and patients with CP were compared, and patients with CP and a poor pain outcome (visual analogue scale (VAS) score greater than 30) were compared with those with a good pain outcome (VAS score 30 or less).

RESULTS

Forty-eight patients with CP had lower ePDT, ePTT and CPM responses compared with values in 15 healthy controls (P < 0·030). The sum of ePDT values was lower in patients with a poor pain outcome than in those with a good outcome (median 7·1 versus 11·2 mA; P = 0·008). There was a correlation with the VAS score and the sum of ePDT values (rs  = -0·45, P = 0·016) and ePTT values (rs  = -0·46, P = 0·011), and CPM response (rs  = -0·43, P = 0·006) in patients with CP.

CONCLUSION

After pain-relieving pancreatic surgery, patients with CP exhibit altered central pain processing compared with that in healthy controls. Poor pain outcomes are associated with more central sensitization and more pronociceptive descending pain modulation, and this should be considered when managing persistent pain after pain-relieving surgery for CP.

Altered resting state EEG in chronic pancreatitis patients: toward a marker for chronic pain

OBJECTIVES

Electroencephalography (EEG) may be a promising source of physiological biomarkers accompanying chronic pain. Several studies in patients with chronic neuropathic pain have reported alterations in central pain processing, manifested as slowed EEG rhythmicity and increased EEG power in the brain's resting state. We aimed to investigate novel potential markers of chronic pain in the resting state EEG of patients with chronic pancreatitis.

PARTICIPANTS

Resting state EEG data from 16 patients with persistent abdominal pain due to chronic pancreatitis (CP) were compared to data from healthy controls matched for age, sex and education.

METHODS

The peak alpha frequency (PAF) and power amplitude in the alpha band (7.5-13 Hz) were compared between groups in four regions of interest (frontal, central, parietal, and occipital) and were correlated with pain duration.

RESULTS

The average PAF was lowered in CP patients compared with that in healthy controls, observed as a statistically significant between-group effect (mean 9.9 versus 9.5 Hz; P=0.049). Exploratory post hoc analysis of average PAF per region of interest revealed a significant difference, particularly in the parietal and occipital regions. In addition, we observed a significant correlation between pain duration and PAF and showed increased shifts in PAF with longer pain durations. No significant group differences were found in peak power amplitudes.

CONCLUSION

CP pain is associated with alterations in spontaneous brain activity, observed as a shift toward lower PAF. This shift correlates with the duration of pain, which demonstrates that PAF has the potential to be a clinically feasible biomarker for chronic pain. These findings could be helpful for assisting diagnosis, establishing optimal treatment, and studying efficacy of new therapeutic agents in chronic pain patients.

Central response to painful electrical esophageal stimulation in well-defined patients suffering from functional chest pain

BACKGROUND

Functional chest pain (FCP) of presumed esophageal origin is considered a common cause for chest pain in which central nervous system hyperexcitability is thought to play an important role. We aimed to compare cerebral responses with painful esophageal stimuli between FCP patients and healthy subjects (HS).

METHODS

Thirteen patients with FCP (seven females, mean age 50.4 ± 7.5 years) and 15 HS (eight females, mean age 49.1 ± 12.9 years) were enrolled. Inclusion criteria consisted of typical chest pain, normal coronary angiogram, and normal upper gastrointestinal evaluation. Electrical stimulations evoking the pain threshold were applied in the distal esophagus, while cortical evoked potentials were recorded from the scalp. Pain scores, resting electroencephalogram (EEG), evoked potential characteristics and brain electrical sources to pain stimulation were compared between groups.

KEY RESULTS

No differences were seen between patients and HS regarding (i) pain thresholds (patients: 20.1 ± 7.4 mA vs HS: 22.4 ± 8.3 mA, all P > 0.05), (ii) resting-EEG (P > 0.05), (iii) evoked brain potential latencies (N2: patients 181.7 ± 25.7 mS vs HS 182.2 ± 25.8 mS, all P > 0.05) and amplitudes (N2P2: patients 8.2 ± 7.2 μV vs HS: 10.1 ± 3.4 μV, all P > 0.05), (iv) topography (P > 0.05), and (v) brain source location (P > 0.05).

CONCLUSIONS & INFERENCES

No differences in activation of brain areas to painful esophageal stimulation were seen in this group of well characterized patients with FCP compared with sex- and age-matched HS. The mechanism of pain in FCP and whether it originates in the esophagus remains unsolved.

Multivariate matching pursuit in optimal Gabor dictionaries: theory and software with interface for EEG/MEG via Svarog

BACKGROUND

Matching pursuit algorithm (MP), especially with recent multivariate extensions, offers unique advantages in analysis of EEG and MEG.

METHODS

We propose a novel construction of an optimal Gabor dictionary, based upon the metrics introduced in this paper. We implement this construction in a freely available software for MP decomposition of multivariate time series, with a user friendly interface via the Svarog package (Signal Viewer, Analyzer and Recorder On GPL, http://braintech.pl/svarog), and provide a hands-on introduction to its application to EEG. Finally, we describe numerical and mathematical optimizations used in this implementation.

RESULTS

Optimal Gabor dictionaries, based on the metric introduced in this paper, for the first time allowed for a priori assessment of maximum one-step error of the MP algorithm. Variants of multivariate MP, implemented in the accompanying software, are organized according to the mathematical properties of the algorithms, relevant in the light of EEG/MEG analysis. Some of these variants have been successfully applied to both multichannel and multitrial EEG and MEG in previous studies, improving preprocessing for EEG/MEG inverse solutions and parameterization of evoked potentials in single trials; we mention also ongoing work and possible novel applications.

CONCLUSIONS

Mathematical results presented in this paper improve our understanding of the basics of the MP algorithm. Simple introduction of its properties and advantages, together with the accompanying stable and user-friendly Open Source software package, pave the way for a widespread and reproducible analysis of multivariate EEG and MEG time series and novel applications, while retaining a high degree of compatibility with the traditional, visual analysis of EEG.

Patients with persistent pain after breast cancer treatment show enhanced alpha activity in spontaneous EEG

OBJECTIVE

The aim of the present study was to investigate whether patients with persistent pain after breast cancer treatment show an enhanced and slowed dominant alpha activity in their electroencephalogram (EEG) recorded during rest in comparison with patients that also had undergone breast cancer treatment but do not have pain.

METHODS

The spontaneous EEG was recorded during rest and before painful stimulation of the calf and analyzed with spectral analysis (Fast Fourier Transformation). Outcome measures, i.e., alpha indices (center of gravity and overall amplitude), were statistically tested between patients with and without persistent pain.

RESULTS

In comparison with patients without pain, patients with persistent pain after breast cancer treatment show more alpha activity in their spontaneous EEG observed from parietal-occipital brain regions.

CONCLUSION

Persistent pain after breast cancer treatment affects spontaneous brain activity, which might influence cognitive functioning.

Transient receptor potential ankyrin 1 mediates chronic pancreatitis pain in mice

Chronic pancreatitis (CP) is a devastating disease characterized by persistent and uncontrolled abdominal pain. Our lack of understanding is partially due to the lack of experimental models that mimic the human disease and also to the lack of validated behavioral measures of visceral pain. The ligand-gated cation channel transient receptor potential ankyrin 1 (TRPA1) mediates inflammation and pain in early experimental pancreatitis. It is unknown if TRPA1 causes fibrosis and sustained pancreatic pain. We induced CP by injecting the chemical agent trinitrobenzene sulfonic acid (TNBS), which causes severe acute pancreatitis, into the pancreatic duct of C57BL/6 trpa1(+/+) and trpa1(-/-) mice. Chronic inflammatory changes and pain behaviors were assessed after 2-3 wk. TNBS injection caused marked pancreatic fibrosis with increased collagen-staining intensity, atrophy, fatty replacement, monocyte infiltration, and pancreatic stellate cell activation, and these changes were reflected by increased histological damage scores. TNBS-injected animals showed mechanical hypersensitivity during von Frey filament probing of the abdomen, decreased daily voluntary wheel-running activity, and increased immobility scores during open-field testing. Pancreatic TNBS also reduced the threshold to hindpaw withdrawal to von Frey filament probing, suggesting central sensitization. Inflammatory changes and pain indexes were significantly reduced in trpa1(-/-) mice. In conclusion, we have characterized in mice a model of CP that resembles the human condition, with marked histological changes and behavioral measures of pain. We have demonstrated, using novel and objective pain measurements, that TRPA1 mediates inflammation and visceral hypersensitivity in CP and could be a therapeutic target for the treatment of sustained inflammatory abdominal pain.

Is altered central pain processing related to disease stage in chronic pancreatitis patients with pain? An exploratory study

Background

The most dominant feature in chronic pancreatitis is intense abdominal pain. Changes in spinal and/or supraspinal central nervous system pain processing due to visceral nociceptive input play an important role in this pain. How altered pain processing is related to disease stage still needs study.

Methodology/Principal Findings

Sixty chronic pancreatitis patients were compared to 15 healthy controls. Two subgroups of pancreatitis patients were defined based on the M-ANNHEIM severity index of chronic pancreatitis; i.e. moderate and severe. Pain detection and tolerance thresholds for pressure and electric stimuli were measured in six selected dermatomes (C5, T4, T10, L1, L4 and T10BACK). In addition, the conditioned pain modulation response to cold pressor task was determined. These measures were compared between the healthy controls and chronic pancreatitis patients. Severe pancreatitis patients showed lower pain thresholds than moderate pancreatitis patients or healthy volunteers. Healthy controls showed a significantly larger conditioned pain modulation response compared to all chronic pancreatitis patients taken together.

Conclusions/Significance

The present study confirms that chronic pancreatitis patients show signs of altered central processing of nociception compared to healthy controls. The study further suggests that these changes, i.e. central sensitization, may be influenced by disease stage. These findings underline the need to take altered central pain processing into account when managing the pain of 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.

S-ketamine modulates hyperalgesia in patients with chronic pancreatitis pain

BACKGROUND AND OBJECTIVES

Upper abdominal pain is a dominant feature of chronic pancreatitis. A key phenomenon in this context is hyperalgesia, typically associated with N-methyl-d-aspartate receptor activation. This exploratory study evaluates acute effects of S-ketamine, a noncompetitive N-methyl-d-aspartate antagonist, in modulating generalized hyperalgesia in chronic pancreatitis pain.

METHODS

In a blinded crossover trial, 10 chronic pancreatitis pain patients received S-ketamine for 3 hrs at 2 μg · kg · min or placebo infusion at an equivalent rate in randomized order. Clinical pain was assessed via visual analog scale (VAS) and short Dutch Language Version McGill Pain Questionnaire (sf-MPQ-DLV). Pressure pain thresholds (PPTs) were measured in dermatome C5, T4, dorsal T10, L1, and L4, and the sum of PPTs (SOPPT) calculated before, at end of, and after infusion.

RESULTS

Nine patients completed the study. Median pain VAS before infusion was 29 mm at rest, 32 mm during activity; sf-MPQ-DLV score was 4. For the S-ketamine session median SOPPT change at infusion end was significantly higher than in the placebo session (218; interquartile range [IQR], 116-527, versus -123 [IQR, -330 to 24]; P = 0.005) and significant versus preinfusion values (2109 [IQR, 964-3035] vs 1914 [IQR, 842-2884]; P = 0.03). The SOPPT was unchanged versus preinfusion values and similar between groups at 1 hr after infusion end. No significant changes in VAS and sf-MPQ-DLV occurred.

CONCLUSIONS

S-ketamine infusion is more effective than placebo in increasing PPTs in chronic pancreatitis pain patients immediately after infusion. This effect did not outlast the infusion. Further research is warranted into S-ketamine use for reducing generalized hyperalgesia and chronic pancreatitis pain.

Dynamics of Circadian Thalamocortical Flow of Information during a Peripheral Neuropathic Pain Condition

It is known that the thalamocortical loop plays a crucial role in the encoding of sensory–discriminative features of painful stimuli. However, only a few studies have addressed the changes in thalamocortical dynamics that may occur after the onset of chronic pain. Our goal was to evaluate how the induction of chronic neuropathic pain affected the flow of information within the thalamocortical loop throughout the brain states of the sleep–wake cycle. To address this issue we recorded local field potentials (LFPs) – both before and after the establishment of neuropathic pain in awake freely moving adult rats chronically implanted with arrays of multielectrodes in the lateral thalamus and primary somatosensory cortex. Our results show that the neuropathic injury induced changes in the number of wake and slow-wave-sleep (SWS) state episodes, and especially in the total number of transitions between brain states. Moreover, partial directed coherence – analysis revealed that the amount of information flow between cortex and thalamus in neuropathic animals decreased significantly, indicating that the overall thalamic activity had less weight over the cortical activity. However, thalamocortical LFPs displayed higher phase-locking during awake and SWS episodes after the nerve lesion, suggesting faster transmission of relevant information along the thalamocortical loop. The observed changes are in agreement with the hypothesis of thalamic dysfunction after the onset of chronic pain, and may result from diminished inhibitory effect of the primary somatosensory cortex over the lateral thalamus.

Neurodegenerative properties of chronic pain: cognitive decline in patients with chronic pancreatitis

Chronic pain has been associated with impaired cognitive function. We examined cognitive performance in patients with severe chronic pancreatitis pain. We explored the following factors for their contribution to observed cognitive deficits: pain duration, comorbidity (depression, sleep disturbance), use of opioids, and premorbid alcohol abuse. The cognitive profiles of 16 patients with severe pain due to chronic pancreatitis were determined using an extensive neuropsychological test battery. Data from three cognitive domains (psychomotor performance, memory, executive functions) were compared to data from healthy controls matched for age, gender and education. Multivariate multilevel analysis of the data showed decreased test scores in patients with chronic pancreatitis pain in different cognitive domains. Psychomotor performance and executive functions showed the most prominent decline. Interestingly, pain duration appeared to be the strongest predictor for observed cognitive decline. Depressive symptoms, sleep disturbance, opioid use and history of alcohol abuse provided additional explanations for the observed cognitive decline in some of the tests, but to a lesser extent than pain duration. The negative effect of pain duration on cognitive performance is compatible with the theory of neurodegenerative properties of chronic pain. Therefore, early and effective therapeutic interventions might reduce or prevent decline in cognitive performance, thereby improving outcomes and quality of life in these patients.

Neuroimaging of the human visceral pain system–A methodological review

During the last decades there has been a tremendous development of non-invasive methods for assessment of brain activity following visceral pain. Improved methods for neurophysiological and brain imaging techniques have vastly increased our understanding of the central processing of gastrointestinal sensation and pain in both healthy volunteers as well as in patients suffering from gastrointestinal disorders. The techniques used are functional magnetic resonance imaging (fMRI), positron emission tomography (PET), electroencephalography (EEG)/evoked brain potentials (EPs), magnetoencephalography (MEG), single photon emission computed tomography (SPECT), and the multimodal combinations of these techniques. The use of these techniques has brought new insight into the complex brain processes underlying pain perception, including a number of subcortical and cortical regions, and paved new ways in our understanding of acute and chronic pain. The pathways are dynamic with a delicate balance between facilitatory and inhibitory pain mechanisms, and with modulation of the response to internal or external stressors with a high degree of plasticity. Hence, the ultimate goal in imaging of pain is to follow the stimulus response throughout the neuraxis.

Brain activity measured by fMRI is based on subtracting regional changes in blood oxygenation during a resting condition from the signal during a stimulus condition, and has high spatial resolution but low temporal resolution. SPECT and PET are nuclear imaging techniques where radiolabeled molecules are injected with visualization of the distribution, density and activity of receptors in the brain allowing not only assessment of brain activity but also study of receptor sites. EEG is based on assessment of electrical activity in the brain, and recordings of the resting EEG and evoked potentials following an external stimulus are used to study normal visceral pain processing, alterations of pain processing in different patient groups and the effect of pharmacological intervention. EEG has high temporal resolution, but relative poor spatial resolution, which however to some extent can be overcome by applying inverse modelling algorithms and signal decomposition procedures. MEG is based on recording the magnetic fields produced by electrical currents in the brain, has high spatial resolution and is especially suitable for the study cortical activation.

The treatment of chronic abdominal pain is often ineffective and dissapointing, which leads to search for optimized treatment achieved on the basis of a better understanding of underlying pain mechanisms. Application of the recent improvements in neuroimaging on the visceral pain system may likely in near future contribute substantially to our understanding of the functional and structural pathophysiology underlying chronic visceral pain disorders, and pave the road for optimized individual and mechanism based treatments.

The purpose of this review is to give a state-of-the-art overview of these methods, with focus on EEG, and especially the advantages and limitations of the single methods in clinical gastrointestinal pain esearch including examples from relevant studies.

Increased sympathetic activity in chronic pancreatitis patients is associated with hyperalgesia

Pain treatment in chronic pancreatitis patients is difficult, with pain frequently relapsing or persisting. Recent studies suggest that altered central nervous system pain processing underlies the chronic pain state in these patients. There is evidence that increased sympathetic activity may also play a role in some chronic pain syndromes. This study assessed sympathetic nervous system activity and its relation to pain processing in patients with severe painful chronic pancreatitis. The authors postulated that chronic pancreatitis patients with more sympathetic activity exhibit more generalized hyperalgesia. In 16 chronic pancreatitis patients, sympathetic activity was measured via venous plasma norepinephrine (NE) levels (supine, standing). Pain processing was quantified via pressure pain tolerance thresholds (PPTs) in dermatomes T10 (pancreatic area), C5, T4, L1. Five patients showed increased supine plasma NE levels (NE ≥ 3.0 nmol/L). PPTs were lower in patients with increased NE levels (INE) compared with patients with normal NE (NNE) (means [95% confidence interval]: INE 402 kPa [286-517] versus NNE 522 kPa [444-600]; P = .042). In severe chronic pancreatitis patients, increased sympathetic activity and hyperalgesia appear associated, suggesting that sympathetic activity may also play a role in these patients' pain.

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.

Use and perceived effectiveness of non-analgesic medical therapies for chronic pancreatitis in the United States

BACKGROUND

Effectiveness of medical therapies in chronic pancreatitis has been described in small studies of selected patients.

AIM

To describe frequency and perceived effectiveness of non-analgesic medical therapies in chronic pancreatitis patients evaluated at US referral centres.

METHODS

Using data on 516 chronic pancreatitis patients enrolled prospectively in the NAPS2 Study, we evaluated how often medical therapies [pancreatic enzyme replacement therapy (PERT), vitamins/antioxidants (AO), octreotide, coeliac plexus block (CPB)] were utilized and considered useful by physicians.

RESULTS

Oral PERT was commonly used (70%), more frequently in the presence of exocrine insufficiency (EI) (88% vs. 61%, P < 0.001) and pain (74% vs. 59%, P < 0.002). On multivariable analyses, predictors of PERT usage were EI (OR 5.14, 95% CI 2.87-9.18), constant (OR 3.42, 95% CI 1.93-6.04) or intermittent pain (OR 1.98, 95% CI 1.14-3.45). Efficacy of PERT was predicted only by EI (OR 2.16, 95% CI 1.36-3.42). AO were tried less often (14%) and were more effective in idiopathic and obstructive vs. alcoholic chronic pancreatitis (25% vs. 4%, P = 0.03). Other therapies were infrequently used (CPB - 5%, octreotide - 7%) with efficacy generally <50%.

CONCLUSIONS

Pancreatic enzyme replacement therapy is commonly utilized, but is considered useful in only subsets of chronic pancreatitis patients. Other medical therapies are used infrequently and have limited efficacy.

Fate of nerves in chronic pancreatitis: Neural remodeling and pancreatic neuropathy

There is probably no other gastrointestinal disorder which is as much characterized by concomitant local, intra-organ and central neuropathic and neuroplastic alterations as chronic pancreatitis (CP). While some key features of this neuropathy have recently been elucidated, there is still no satisfying pathophysiological explanation for the generation of neuropathic pain in CP. It is becoming increasingly clear that an effective pain treatment in CP can probably not be achieved without consideration of the exact fate of intrapancreatic nerves and central neuroplastic alterations. This review is intended to illustrate the temporal and spatial alterations of intrapancreatic nerves in the course of CP. At the same time, it depicts the reciprocal relationship between these plastic changes and thus underlines the notion of a 'common fate' for all these alterations. Moreover, it points out numerous aspects of this fate that are yet to be unveiled and should therefore be subject to future investigation.

Alcoholic pancreatitis: pathogenesis, incidence and treatment with special reference to the associated pain

Alcoholic pancreatitis continues to stir up controversy. One of the most debated points is whether from onset it is a chronic disease or whether it progresses to a chronic form after repeated episodes of acute pancreatitis. Histological studies on patients with alcoholic pancreatitis have shown that the disease is chronic from onset and that alcoholic acute pancreatitis occurs in a pancreas already damaged by chronic lesions. Genetic factors may also play a role in the pathogenesis of alcoholic disease. The incidence of chronic alcoholic pancreatitis seems to have decreased in the last twenty years. Finally, recent therapeutic studies which have shown medical or surgical approaches capable of reducing the pain episodes in chronic pancreatitis patients will be described.

New technologies to investigate the brain-gut axis

Functional gastrointestinal disorders are commonly encountered in clinical practice, and pain is their commonest presenting symptom. In addition, patients with these disorders often demonstrate a heightened sensitivity to experimental visceral stimulation, termed visceral pain hypersensitivity that is likely to be important in their pathophysiology. Knowledge of how the brain processes sensory information from visceral structures is still in its infancy. However, our understanding has been propelled by technological imaging advances such as functional Magnetic Resonance Imaging, Positron Emission Tomography, Magnetoencephalography, and Electroencephalography (EEG). Numerous human studies have non-invasively demonstrated the complexity involved in functional pain processing, and highlighted a number of subcortical and cortical regions involved. This review will focus on the neurophysiological pathways (primary afferents, spinal and supraspinal transmission), brain-imaging techniques and the influence of endogenous and psychological processes in healthy controls and patients suffering from functional gastrointestinal disorders. Special attention will be paid to the newer EEG source analysis techniques. Understanding the phenotypic differences that determine an individual’s response to injurious stimuli could be the key to understanding why some patients develop pain and hyperalgesia in response to inflammation/injury while others do not. For future studies, an integrated approach is required incorporating an individual’s psychological, autonomic, neuroendocrine, neurophysiological, and genetic profile to define phenotypic traits that may be at greater risk of developing sensitised states in response to gut inflammation or injury.

Pancreatic neuropathy and neuropathic pain--a comprehensive pathomorphological study of 546 cases

BACKGROUND & AIMS

Chronic pancreatitis (CP) and pancreatic adenocarcinoma (PCa) are characterized by intrapancreatic neural alterations and pain. Our aims were to: (a) Investigate whether neuropathic changes like pancreatic neuritis, increased neural density, and hypertrophy are phenomena only in CP or whether they are also evident in other pancreatic disorders as well, (b) study possible variations in neural cancer cell invasion among malignant pancreatic tumors, and (c) explore whether these neuropathic changes contribute to pain sensation.

METHODS

Neuropathic changes were studied in PCa (n=149), in CP (n=141), in pancreatic tumors (PTm) including serous/mucinous cystadenomas, invasive/noninvasive intraductal papillary mucinous neoplasias, benign/malignant neuroendocrine tumors, ampullary cancers (n=196), and in normal pancreas (n=60). The results were correlated with GAP-43 expression, tissue inflammation, pancreatic neuritis, neural invasion, fibrosis, desmoplasia, pain, and patient survival.

RESULTS

Increased neural density and hypertrophy were only detected in PCa and CP and were strongly associated with GAP-43 over expression and abdominal pain. The severity of pancreatic neuritis was strongest in PCa and was closely linked to changes in neural density and hypertrophy. The aggressiveness of neural cancer cell invasion was most prominent in PCa and was related to neuropathic changes, desmoplasia, and pain. Severe and enduring pain were strongly associated with poor prognosis in PCa patients.

CONCLUSIONS

Enhanced neural density and hypertrophy are only typical features of CP and PCa among all investigated pancreatic disorders. Such neuropathic changes, including damage to nerves by inflammatory and/or cancer cells, seem to enhance and generate pancreatic neuropathic pain.