A phenomenological approach to understanding the psychological response to chronic low back pain

Chronic low back pain (CLBP) is a complex health problem of psychological manifestations not fully understood. Using interpretive phenomenological analysis, 11 semi-structured interviews were conducted to help understand the meaning of the lived experience of CLBP; focusing on the psychological response to pain and the role of depression, catastrophizing, fear-avoidance behavior, anxiety and somatization. Participants characterized CLBP as persistent tolerable low back pain (TLBP) interrupted by periods of intolerable low back pain (ILBP). ILBP contributed to recurring bouts of helplessness, depression, frustration with the medical system and increased fear based on the perceived consequences of anticipated recurrences, all of which were mediated by the uncertainty of such pain. During times of TLBP all participants pursued a permanent pain consciousness as they felt susceptible to experience a recurrence. As CLBP progressed, participants felt they were living with a weakness, became isolated from those without CLBP and integrated pain into their self-concept.

Test-retest reliability of the nociceptive withdrawal reflex and electrical pain thresholds after single and repeated stimulation in patients with chronic low back pain

Recent studies have shown that the nociceptive withdrawal reflex threshold (NWR-T) and the electrical pain threshold (EP-T) are reliable measures in pain-free populations. However, it is necessary to investigate the reliability of these measures in patients with chronic pain in order to translate these techniques from laboratory to clinic. The aims of this study were to determine the test-retest reliability of the NWR-T and EP-T after single and repeated (temporal summation) electrical stimulation in a group of patients with chronic low back pain, and to investigate the association between the NWR-T and the EP-T. To this end, 25 patients with chronic pain participated in three identical sessions, separated by 1 week in average, in which the NWR-T and the EP-T to single and repeated stimulation were measured. Test-retest reliability was assessed using intra-class correlation coefficient (ICC), coefficient of variation (CV), and Bland-Altman analysis. The association between the thresholds was assessed using the coefficient of determination (r (2)). The results showed good-to-excellent reliability for both NWR-T and EP-T in all cases, with average ICC values ranging 0.76-0.90 and average CV values ranging 12.0-17.7%. The association between thresholds was better after repeated stimulation than after single stimulation, with average r (2) values of 0.83 and 0.56, respectively. In conclusion, the NWR-T and the EP-T are reliable assessment tools for assessing the sensitivity of spinal nociceptive pathways in patients with chronic pain.

[Drug therapy of acute and chronic abdominal pain]

For drug therapy a differentiation of acute and chronic pain is essential. In emergency situations of acute abdominal pain a fast diagnosis is mandatory. Analgesia should be provided as soon as possible. The different groups of analgesics should be used according to their known effects, side effects and contraindications. Postoperative pain after abdominal surgery has to be considered as a special condition of acute abdominal pain. Main treatment options are non opioid analgesics and opioids. Opioids can be administered intravenously via patient controlled analgesia (PCA) devices. In major abdominal surgery neuroaxial analgesia, preferentially administered via an epidural catheter provides excellent pain relief with positive impact on gastrointestinal motility and patients' recovery. Because of difficulties to allocate chronic abdominal pain to a specific organ, causal treatment often turns out to be difficult. Peripheral and central sensitization, as well as an alteration of the endogenous pain modulation comes to the fore in these chronic pain conditions. Co-analgesics like anticonvulsants and antidepressants are utilized to reduce sensitization and improve the endogenous pain modulating system. Non drug approaches and alternative treatment options might be useful. In contrast, orally or transcutaneously administered opioids are the principal corner stone for the treatment of cancer pain.

Chronic Pelvic Pain Syndrome in Men is Associated with Reduction of Relative Gray Matter Volume in the Anterior Cingulate Cortex Compared to Healthy Controls

Although chronic pelvic pain syndrome impairs the life of millions of people worldwide, the exact pathomechanisms involved remain to be elucidated. As with other chronic pain syndromes, the central nervous system may have an important role in chronic pelvic pain syndrome. Thus, we assessed brain alterations associated with abnormal pain processing in patients with chronic pelvic pain syndrome.

Do Central Hypersensitivity and Altered Pain Modulation Predict the Course of Chronic Low Back and Neck Pain?

OBJECTIVES:: Widespread central hypersensitivity and altered conditioned pain modulation (CPM) have been documented in chronic pain conditions. Information on their prognostic values is limited. This study tested the hypothesis that widespread central hypersensitivity (WCH) and altered CPM, assessed during the chronic phase of low back and neck pain, predict poor outcome. METHODS:: A total of 169 consecutive patients with chronic low back or neck pain, referred to the pain clinic during 1 year, were analyzed. Pressure pain tolerance threshold at the second toe and tolerance time during cold pressor test at the hand assessed WCH. CPM was measured by the change in pressure pain tolerance threshold (test stimulus) after cold pressor test (conditioning stimulus). A structured telephone interview was performed 12 to 15 months after testing to record outcome parameters. Linear regression models were used, with average and maximum pain intensity of the last 24 hours at follow-up as endpoints. Multivariable analyses included sex, age, catastrophizing scale, Beck Depression Inventory, pain duration, intake of opioids, and type of pain syndrome. RESULTS:: Statistically significant reductions from baseline to follow-up were observed in pain intensity (P<0.001). No evidence for an association between the measures of WCH or CPM and intensity of chronic pain at follow-up was found. DISCUSSION:: A major predictive value of the measures that we used is unlikely. Future studies adopting other assessment modalities and possibly standardized treatments are needed to further elucidate the prognostic value of WCH and altered CPM in chronic pain.

Ranking of parameters of pain hypersensitivity according to their discriminative ability in chronic low back pain

Low back pain is associated with plasticity changes and central hypersensitivity in a subset of patients. We performed a case-control study to explore the discriminative ability of different quantitative sensory tests in distinguishing between 40 cases with chronic low back pain and 300 pain-free controls, and to rank these tests according to the extent of their association with chronic pain. Gender, age, height, weight, body mass index, and psychological measures were recorded as potential confounders. We used 26 quantitative sensory tests, including different modalities of pressure, heat, cold, and electrical stimulation. As measures of discrimination, we estimated receiver operating characteristics (ROC) and likelihood ratios. Six tests seemed useful (in order of their discriminative ability): (1) pressure pain detection threshold at the site of most severe pain (fitted area under the ROC, 0.87), (2) single electrical stimulation pain detection threshold (0.87), (3) single electrical stimulation reflex threshold (0.83), (4) pressure pain tolerance threshold at the site of most severe pain (0.81), (5) pressure pain detection threshold at suprascapular region (0.80), and (6) temporal summation pain threshold (0.80). Pressure and electrical pain modalities seemed most promising and may be used for diagnosis of pain hypersensitivity and potentially for identifying individuals at risk of developing chronic low back pain over time.

Coping resources in a sample of chronic low back pain patients: Evaluation of the questionnaire for back pain

BACKGROUND The coping resources questionnaire for back pain (FBR) uses 12 items to measure the perceived helpfulness of different coping resources (CRs, social emotional support, practical help, knowledge, movement and relaxation, leisure and pleasure, spirituality and cognitive strategies). The aim of the study was to evaluate the instrument in a clinical patient sample assessed in a primary care setting. SAMPLE AND METHODS The study was a secondary evaluation of empirical data from a large cohort study in general practices. The 58 participating primary care practices recruited patients who reported chronic back pain in the consultation. Besides the FBR and a pain sketch, the patients completed scales measuring depression, anxiety, resilience, sociodemographic factors and pain characteristics. To allow computing of retested parameters the FBR was sent to some of the original participants again after 6 months (90% response rate). We calculated consistency and retest reliability coefficients as well as correlations between the FBR subscales and depression, anxiety and resilience scores to account for validity. By means of a cluster analysis groups with different resource profiles were formed. Results. RESULTS For the study 609 complete FBR baseline data sets could be used for statistical analysis. The internal consistency scores ranged fromα=0.58 to α=0.78 and retest reliability scores were between rTT=0.41 and rTT=0.63. Correlation with depression, fear and resilience ranged from r=-0.38 to r=0.42. The cluster analysis resulted in four groups with relatively homogenous intragroup profiles (high CRs, low spirituality, medium CRs, low CRs). The four groups differed significantly in fear and depression (the more inefficient the resources the higher the difference) as well as in resilience (the more inefficient the lower the difference). The group with low CRs also reported permanent pain with no relief. The groups did not otherwise differ. CONCLUSIONS The FBR is an economic instrument that is suitable for practical use e.g. in primary care practices to identify strengths and deficits in the CRs of chronic pain patients that can then be specified in face to face consultation. However, due to the rather low reliability, the use of subscales for profile differentiation and follow-up measurement in individual diagnoses is limited.

Ranking of tests for pain hypersensitivity according to their discriminative ability in chronic neck pain

BACKGROUND AND OBJECTIVES Quantitative sensory testing (QST) is widely used to investigate peripheral and central sensitization. However, the comparative performance of different QST for diagnostic or prognostic purposes is unclear. We explored the discriminative ability of different quantitative sensory tests in distinguishing between patients with chronic neck pain and pain-free control subjects and ranked these tests according to the extent of their association with pain hypersensitivity. METHODS We performed a case-control study in 40 patients and 300 control subjects. Twenty-six tests, including different modalities of pressure, heat, cold, and electrical stimulation, were used. As measures of discrimination, we estimated receiver operating characteristic curves and likelihood ratios. RESULTS The following quantitative sensory tests displayed the best discriminative value: (1) pressure pain threshold at the site of the most severe neck pain (fitted area under the receiver operating characteristic curve, 0.92), (2) reflex threshold to single electrical stimulation (0.90), (3) pain threshold to single electrical stimulation (0.89), (4) pain threshold to repeated electrical stimulation (0.87), and (5) pressure pain tolerance threshold at the site of the most severe neck pain (0.86). Only the first 3 could be used for both ruling in and out pain hypersensitivity. CONCLUSIONS Pressure stimulation at the site of the most severe pain and parameters of electrical stimulation were the most appropriate QST to distinguish between patients with chronic neck pain and asymptomatic control subjects. These findings may be used to select the tests in future diagnostic and longitudinal prognostic studies on patients with neck pain and to optimize the assessment of localized and spreading sensitization in chronic pain patients.

Chronic spontaneous activity generated in the somata of primary nociceptors is associated with pain-related behavior after spinal cord injury.

Mechanisms underlying chronic pain that develops after spinal cord injury (SCI) are incompletely understood. Most research on SCI pain mechanisms has focused on neuronal alterations within pain pathways at spinal and supraspinal levels associated with inflammation and glial activation. These events might also impact central processes of primary sensory neurons, triggering in nociceptors a hyperexcitable state and spontaneous activity (SA) that drive behavioral hypersensitivity and pain. SCI can sensitize peripheral fibers of nociceptors and promote peripheral SA, but whether these effects are driven by extrinsic alterations in surrounding tissue or are intrinsic to the nociceptor, and whether similar SA occurs in nociceptors in vivo are unknown. We show that small DRG neurons from rats (Rattus norvegicus) receiving thoracic spinal injury 3 d to 8 months earlier and recorded 1 d after dissociation exhibit an elevated incidence of SA coupled with soma hyperexcitability compared with untreated and sham-treated groups. SA incidence was greatest in lumbar DRG neurons (57%) and least in cervical neurons (28%), and failed to decline over 8 months. Many sampled SA neurons were capsaicin sensitive and/or bound the nociceptive marker, isolectin B4. This intrinsic SA state was correlated with increased behavioral responsiveness to mechanical and thermal stimulation of sites below and above the injury level. Recordings from C- and Aδ-fibers revealed SCI-induced SA generated in or near the somata of the neurons in vivo. SCI promotes the entry of primary nociceptors into a chronic hyperexcitable-SA state that may provide a useful therapeutic target in some forms of persistent pain.

Correlation between altered central pain processing and concentration of peritoneal fluid inflammatory cytokines in endometriosis patients with chronic pelvic pain

Translational research has not yet elucidated whether alterations in central pain processes are related to peripheral inflammatory processes in chronic pain patients. We tested the hypothesis that the concentration of cytokines in the peritoneal fluid of endometriosis patients with chronic pain correlate with parameters of hyperexcitability of the nociceptive system. The concentrations of 15 peritoneal fluid cytokines were measured in 11 patients with chronic pelvic pain and a diagnosis of endometriosis. Six parameters assessing central pain processes were recorded. Positive correlations between concentration of some cytokines in the peritoneal fluid and amplification of central pain processing were found. The results suggest that inflammatory mechanisms may be important in the pathophysiology of altered central pain processes and that cytokines produced in the environment of endometriosis could act as mediators between the peripheral lesion and changes in central nociceptive processes.

Chronic postsurgical pain in Europe: An observational study.

BACKGROUND Chronic postsurgical pain (CPSP) is an important clinical problem. Prospective studies of the incidence, characteristics and risk factors of CPSP are needed. OBJECTIVES The objective of this study is to evaluate the incidence and risk factors of CPSP. DESIGN A multicentre, prospective, observational trial. SETTING Twenty-one hospitals in 11 European countries. PATIENTS Three thousand one hundred and twenty patients undergoing surgery and enrolled in the European registry PAIN OUT. MAIN OUTCOME MEASURES Pain-related outcome was evaluated on the first postoperative day (D1) using a standardised pain outcome questionnaire. Review at 6 and 12 months via e-mail or telephonic interview used the Brief Pain Inventory (BPI) and the DN4 (Douleur Neuropathique four questions). Primary endpoint was the incidence of moderate to severe CPSP (numeric rating scale, NRS ≥3/10) at 12 months. RESULTS For 1044 and 889 patients, complete data were available at 6 and 12 months. At 12 months, the incidence of moderate to severe CPSP was 11.8% (95% CI 9.7 to 13.9) and of severe pain (NRS ≥6) 2.2% (95% CI 1.2 to 3.3). Signs of neuropathic pain were recorded in 35.4% (95% CI 23.9 to 48.3) and 57.1% (95% CI 30.7 to 83.4) of patients with moderate and severe CPSP, respectively. Functional impairment (BPI) at 6 and 12 months increased with the severity of CPSP (P < 0.01) and presence of neuropathic characteristics (P < 0.001). Multivariate analysis identified orthopaedic surgery, preoperative chronic pain and percentage of time in severe pain on D1 as risk factors. A 10% increase in percentage of time in severe pain was associated with a 30% increase of CPSP incidence at 12 months. CONCLUSION The collection of data on CPSP was feasible within the European registry PAIN OUT. The incidence of moderate to severe CPSP at 12 months was 11.8%. Functional impairment was associated with CPSP severity and neuropathic characteristics. Risk factors for CPSP in the present study were chronic preoperative pain, orthopaedic surgery and percentage of time in severe pain on D1. TRIAL REGISTRATION Clinicaltrials.gov identifier: NCT01467102.

Linking altered central pain processing and genetic polymorphism to drug efficacy in chronic low back pain.

BACKGROUND Inability to predict the therapeutic effect of a drug in individual pain patients prolongs the process of drug and dose finding until satisfactory pharmacotherapy can be achieved. Many chronic pain conditions are associated with hypersensitivity of the nervous system or impaired endogenous pain modulation. Pharmacotherapy often aims at influencing these disturbed nociceptive processes. Its effect might therefore depend on the extent to which they are altered. Quantitative sensory testing (QST) can evaluate various aspects of pain processing and might therefore be able to predict the analgesic efficacy of a given drug. In the present study three drugs commonly used in the pharmacological management of chronic low back pain are investigated. The primary objective is to examine the ability of QST to predict pain reduction. As a secondary objective, the analgesic effects of these drugs and their effect on QST are evaluated. METHODS/DESIGN In this randomized, double blinded, placebo controlled cross-over study, patients with chronic low back pain are randomly assigned to imipramine, oxycodone or clobazam versus active placebo. QST is assessed at baseline, 1 and 2 h after drug administration. Pain intensity, side effects and patients' global impression of change are assessed in intervals of 30 min up to two hours after drug intake. Baseline QST is used as explanatory variable to predict drug effect. The change in QST over time is analyzed to describe the pharmacodynamic effects of each drug on experimental pain modalities. Genetic polymorphisms are analyzed as co-variables. DISCUSSION Pharmacotherapy is a mainstay in chronic pain treatment. Antidepressants, anticonvulsants and opioids are frequently prescribed in a "trial and error" fashion, without knowledge however, which drug suits best which patient. The present study addresses the important need to translate recent advances in pain research to clinical practice. Assessing the predictive value of central hypersensitivity and endogenous pain modulation could allow for the implementation of a mechanism-based treatment strategy in individual patients. TRIAL REGISTRATION Clinicaltrials.gov, NCT01179828.

Core stability exercise in chronic low back pain

Exercise is commonly used in the management of chronic musculoskeletal conditions, including chronic low back pain (CLBP). The focus of exercise is varied and may include parameters ranging from strength and endurance training, to specific training of muscle coordination and control. The assumption underpinning these approaches is that improved neuromuscular function will restore or augment the control and support of the spine and pelvis. In a biomechanical model of CLBP, which assumes that pain recurrence is caused by repeated mechanical irritation of pain sensitive structures [1], it is proposed that this improved control and stability would reduce mechanical irritation and lead to pain relief [1]. Although this model provides explanation for the chronicity of LBP, perpetuation of pain is more complex, and contemporary neuroscience holds the view that chronic pain is mediated by a range of changes including both peripheral (eg, peripheral sensitization) and central neuroplastic changes [2]. Although this does not exclude the role of improved control of the lumbar spine and pelvis in management of CLBP, particularly when there is peripheral sensitization, it highlights the need to look beyond outdated simplistic models. One factor that this information highlights is that the refinement of control and coordination may be more important than simple strength and endurance training for the trunk muscles. The objective of this article is to discuss the rationale for core stability exercise in the management of CLBP, to consider critical factors for its implementation, and to review evidence for efficacy of the approach.