Band 18, Heft 3

Background and aims Carpal tunnel syndrome (CTS) is a common debilitating condition. As the reliability of CTS-specific physical tests and its clinical grading remain a matter of debate, we determined the correlations between these assessments with nerve conduction study (NCS). Methods In this cross-sectional study, patients with uni or bilateral CTS, which was confirmed in electrodiagnosis, were enrolled. Clinical grading was based on the modified criteria of the Italian CTS Study Group. Numeric Pain Rating Scale (NPRS) and Boston Questionnaire (BQ) were used. Physical tests [Phalen’s, reverse Phalen’s, Tinel’s and manual carpal compression test (mCCT)] were performed by a single blinded neurologist. A p -value<0.05 was considered statistically significant. Results A total of 100 patients (age=47.48±11.44 years; 85% female) with 181 involved hands were studied. The majority of hands (59.7%) were classified as grade 2 of clinical grading. On NCS, hands with mild (64%), moderate (27%) and severe (9%) CTS were identified. Sensory (velocity, latency and amplitude) and motor parameters (latency and amplitude) were significantly correlated with clinical grades ( p -value<0.001). The correlation of NPRS ( p -value=0.009) and BQ ( p -value<0.001) scores with NCS was significant. None of the physical tests were significantly correlated with NCS in terms of result or duration ( p -value>0.05). Conclusions We found that physical tests are not a reliable screening method for evaluation of CTS severity. However, the BQ and clinical grading can be more valuable due to their significant correlation with NCS. Implications Physicians might benefit from employing clinical grading and BQ in practice for better assessment of CTS severity.

Background and aims Chronic pain including temporomandibular disorder (TMD) pain involves a complex interplay between peripheral and central sensitization, endogenous modulatory pathways, cortical processing and integration and numerous psychological, behavioral and social factors. The aim of this study was to compare spectroscopic patterns of N-Acetyl-aspartate (NAA), total creatine (tCr), choline (Cho), myo-inositol (MI), glutamate (Glu), and the combination of Glu and glutamine in the posterior insula in patients with chronic generalized or regional chronic TMD pain (gTMD and rTMD, respectively) compared to healthy individuals (HI) in relation to clinical findings of TMD pain. Methods Thirty-six female patients with chronic rTMD or gTMD with at least 3 months duration were included in the study. Ten healthy women were included as controls. All participants completed a questionnaire that comprised assessment of degrees of depression, anxiety, stress, catastrophizing, pain intensity, disability and locations. A clinical Diagnostic Criteria for Temporomandibular Disorders examination that comprised assessment of pain locations, headache, mouth opening capacity, pain on mandibular movement, pain on palpation and temporomandibular joint noises was performed. Pressure-pain threshold (PPT) over the masseter muscle and temporal summation to pressure stimuli were assessed with an algometer. Within a week all participants underwent non-contrast enhanced MRI on a 3T MR scanner assessing T1-w and T2-w fluid attenuation inversion recovery. A single-voxel 1 H-MRS examination using point-resolved spectroscopy was performed. The metabolite concentrations of NAA, tCr, Cho, MI, Glu and Glx were analyzed with the LC model. Metabolite levels were calculated as absolute concentrations, normalized to the water signal. Metabolite concentrations were used for statistical analysis from the LC model if the Cramér–Rao bounds were less than 20%. In addition, the ratios NAA/tCr, Cho/tCr, Glu/tCr and MI/tCr were calculated. Results The results showed significantly higher tCr levels within the posterior insula in patients with rTMD or gTMD pain than in HI ( p =0.029). Cho was negatively correlated to maximum mouth opening capacity with or without pain (r s =−0.42, n =28, p= 0.031 and r s =−0.48, n =28, p =0.034, respectively) as well as pressure-pain threshold on the hand (r s =−0.41, n =28, p =0.031). Glu was positively correlated to temporal summation to painful mechanical stimuli (r s =0.42, n =26, p =0.034). Conclusions The present study found that increased concentrations of Cho and Glu in the posterior insular cortex is related to clinical characteristics of chronic TMD pain, including generalized pain. These findings provide new evidence about the critical involvement of the posterior insular cortex and the neurobiology underlying TMD pain in both regional and generalized manifestations. Implications The findings in this study have indirect implications for the diagnosis and management of TMD patients. That said, the findings provide new evidence about the critical involvement of the posterior insular cortex and the neurobiology underlying TMD pain in both regional and generalized manifestations. It is also a further step towards understanding and accepting chronic pain as a disorder in itself.

Background and aims Evaluating the degree to which pain has become chronic beyond mere duration poses several problems. The IASP Pain Taxonomy Axis IV employs intensity and duration combined to nine ordered categories. The Chronic Pain Grade links intensity and disability, but only the latter contributes to higher grades. The Mainz Pain Staging System includes temporal and spatial aspects, medication and health care utilization. Their interrelations, scale properties and construct validity are not always known or debatable. The study challenges the generality and homogeneity of the chronicity construct of musculoskeletal pain aiming at necessary and sufficient sub-constructs identified by separable marker clusters. We show chronicity to vary in content and structure with severity and duration and between different populations. This raises the question of validity conditions of general chronicity indices and requires further work on adequate chronicity measures. Methods Diagnostic entrance data of 185 patients with chronic regional vs. widespread musculoskeletal pain (unspecific back pain, fibromyalgia) from regional pain clinics and 170 active employees in a nationwide prevention program were included in a retrospective cross-sectional analysis of the combined marker sets of the three chronicity indices above. The samples of patients and employees provided intensity, duration and disability degrees over the whole range of the assumed chronicity. Intensity-duration relations were quantified by correlations and frequency distributions of successive duration classes. The dimensional structure of pain and chronicity variables was assessed by factor and cluster analyses. Results Pain intensity distributions showed inhomogeneous courses from short to long durations – lowest intensities predominating at longer durations in patients and at shorter in employees. Moreover, pain intensity and duration related nonlinearly to Chronic Pain Grade and Mainz Pain Stage and differently in patients compared to employees, and these indices correlated only moderately to each other. Factor and cluster analyses revealed different dimensions and clusters of chronicity markers for patients and employees. In the former, three dimensions with four clusters were identified with clinical characteristics (intensity, temporal and spatial aspects) separated from direct consequences (disability/interference with activities, medication usage) and chronic development (duration, healthcare utilization). In employees, only two dimensions with three clusters were obtained and clinical pain characteristics clustered with direct consequences both separated from chronic development. Similar differences were shown between unspecific back pain and fibromyalgia but were less well defined. Conclusions There appears to be no coherent “chronicity” entity over the entire range of severity and duration for all pain populations with different clinical pictures and social contexts. Statements about chronicity must be differentiated with respect to those aspects relative to patient career. Implications General indices do not capture the complex and changing composition of chronicity. There is evidence for at least three weakly coupled core domains of chronicity, i.e. the primary clinical characteristics, the direct consequences of current interference with activities, and aspects of the patient history. Hence, multivariate assessment is recommended. The particular syndrome, the diagnostic context and the population under investigation should likewise be considered.

Background and aims Persistent pain is a pervasive condition that is often associated with a distorted body image. Most research into pain and body image investigated neural or physiological correlates (e.g. phantom limb pain), and much less is known about the psychological experience of body image changes in response to pain such as appearance concerns. The aim was to examine body image concerns in people with persistent pain, in particular appearance concerns and related coping behaviours and appearance-related emotions such as anger and shame. Methods Design was cross-sectional and data was collected through in-depth semi-structured interviews with people suffering from persistent musculoskeletal pain ( n =7; six females; age=19–56), and analysed with inductive thematic analysis (TA). Results Two main themes were identified: “Relationship to the painful body” and “Dissatisfaction with the body”, each containing three subthemes, along with the side-theme “Appearance concerns affected by pain and mood”. All participants reported appearance concerns, predominantly about their weight and related coping behaviours such as avoidance of mirrors, exercising or dieting and pain-induced mood changes that were associated with a negative body image. Conclusions People with persistent pain report appearance concerns, often related to pain-induced negative mood changes, and reduced functioning. It remains unclear to what extent attitudes towards the body change over time in accordance with pain. A wider concept of body image is required, including the perception of reduced functioning, related appraisals (e.g. “I look weak and old”) and appearance investment.

Background and aims Chronic and recurrent pain is prevalent in adolescents and generally girls report more pain symptoms than boys. Also, pain symptoms and sleep problems often co-occur. Pain symptoms have negative effects on school achievement, emotional well-being, sleep, and overall health and well-being. For effective intervention and prevention there is a need for defining factors associated with pain symptoms and daytime sleepiness. The aim of this longitudinal study was to investigate the prevalence and association between neck-shoulder pain, back pain, psychological symptoms and daytime sleepiness in 10-, 12- and 15-year-old children. This study is the first that followed up the same cohort of children from the age of 10 to 15. Methods A cohort study design with three measurement points was used. Participants ( n =568) were recruited from an elementary school cohort in a city of 1,75,000 inhabitants in South-Western Finland. Symptoms and daytime sleepiness were measured with self-administered questionnaires. Regression models were used to analyze the associations. Results Frequent neck-shoulder pain and back pain, and psychological symptoms, as well as daytime sleepiness, are already common at the age of 10 and increase strongly between the ages 12 and 15. Overall a greater proportion of girls suffered from pain symptoms and daytime sleepiness compared to boys. Daytime sleepiness in all ages associated positively with the frequency of neck-shoulder pain and back pain. The more that daytime sleepiness existed, the more neck-shoulder pain and back pain occurred. Daytime sleepiness at the age of 10 predicted neck-shoulder pain at the age of 15, and back pain at the age of 10 indicated that there would also be back pain at the age of 15. In addition, positive associations between psychological symptoms and neck-shoulder pain, as well as back pain, were observed. Subjects with psychological problems suffered neck-shoulder pain and back pain more frequently. Conclusions This study is the first study that has followed up the same cohort of children from the age of 10 to 15. The studied symptoms were all already frequent at the age of 10. An increase mostly happened between the ages of 12 and 15. Moreover, the self-reported daytime sleepiness at the age of 10 predicted neck-shoulder pain at the age of 15. More attention should be paid to the daytime sleepiness of children at an early stage as it has a predictive value for other symptoms later in life. Implications School nurses, teachers and parents are in a key position to prevent adolescents’ sleep habits and healthy living habits. Furthermore, the finding that daytime sleepiness predicts neck-shoulder pain later in adolescence suggests that persistent sleep problems in childhood need early identification and treatment. Health care professionals also need take account of other risk factors, such as psychological symptoms and pain symptoms. The early identification and treatment of sleep problems in children might prevent the symptoms’ development later in life. There is a need for an individuals’ interventions to treat adolescents’ sleep problems.

Background and aims Pain management for hospital inpatients remains suboptimal. Previously identified barriers to optimal pain management include staff communication difficulties, confusion around pain management roles and a lack of suitable resources for clinical staff. The emotional, relational and contextual complexities of gastrointestinal (GI) pain create particular challenges for frontline clinical staff attempting to implement a biopsychosocial approach to its management. The current study took place over 2 years, comprised an ethnographic and a feedback phase, and aimed to examine pain management processes with clinical staff in order to generate hypotheses and initiatives for improvement. This paper focuses on two overarching themes identified in the ethnographic phase of the study, centred on the neglected role of both staff and patient distress in GI pain management. Methods Grounded theory and thematic analysis methods were used as part of action research, which involves collaborative working with clinical staff. The study took place on a 60 bed GI ward in a university hospital in London. Participants were clinical staff who were either ward-based or involved in the care of particular patients. This latter group included doctors, nurses, psychologists and physiotherapists from the Acute and Complex Pain Teams. Qualitative data on pain management processes was gathered from staff interviews, consultation groups, and observations of patient-staff interactions. Recruitment was purposive and collaborative in that early participants suggested targets and staff groups for subsequent enquiry. Following the identification of initial ethnographic themes, further analysis and the use of existing literature led to the identification of two overarching pain management processes. As such the results are divided into three sections: (i) illustration of initial ethnographic themes, (ii) summary of relevant theory used, (iii) exploration of hypothesised overarching processes. Results Initially, two consultation groups, five nursing staff and five junior doctors, provided key issues that were included in subsequent interviews ( n =18) and observations ( n =5). Initial ethnographic themes were divided into challenges and resources, reflecting the emergent structure of interviews and observations. Drawing on attachment, psychodynamic and evolutionary theories, themes were then regrouped around two overarching processes, centred on the neglected role of distress in pain management. The first process elucidates the lack of recognition during pain assessment of the emotional impact of patient distress on staff decision-making and pain management practice. The second process demonstrates that, as a consequence of resultant staff distress, communication between staff groups was fraught and resources, such as expert team referral and pharmacotherapy, appeared to function, at times, to protect staff rather than to help patients. Interpersonal skills used by staff to relieve patient distress were largely outside systems for pain care. Conclusions Findings suggest that identified “barriers” to optimal pain management likely serve an important defensive function for staff and organisations. Implications Unless the impact of patient distress on staff is recognised and addressed within the system, these barriers will persist.

Background and aims Research investigating differences in pain location and distribution across conditions is lacking. Mapping a patient’s pain may be a useful way of understanding differences in presentations, however the use of pain mapping during a pain provocation task has not been investigated. The aim of this study was to assess the reliability of patient and clinician rated pain maps during a pain provocation task for the anterior knee. Methods Participants were recruited from a larger study of professional Australian rules football players ( n =17). Players were invited to participate if they reported a current or past history of patellar tendon pain. No clinical diagnosis was performed for this reliability study. Participants were asked to point on their own knee where they usually experienced pain, which was recorded by a clinician on a piloted photograph of the knee using an iPad. Participants then completed a single leg decline squat (SLDS), after which participants indicated where they experienced pain during the task with their finger, which was recorded by a clinician. Participants then recorded their own self-rated pain map. This process was repeated 10 min later. Pain maps were subjectively classified into categories of pain location and spread by two raters. Pain area was quantified by the number of pixels shaded. Intra- and inter-rater reliability (between participants and clinicians) were analysed for pain area, similarity of location as well as subjective classification. Results Test-retest reliability was good for participants (intraclass correlation coefficients [ICC]=0.81) but only fair for clinicians (ICC=0.47) for pain area. There was poor agreement between participants and clinicians for pain area (ICC=0.16) and similarity of location (Jaccard index=0.19). Clinicians had good inter- and intra-rater reliability of classification of pain spread (k=0.75 and 0.67). Conclusions Participant completed pain maps were more reliable than clinician pain maps. Clinicians were reliable at classifying pain based on location and type of spread. Implications Clinicians should ask patients to complete their own pain maps following a pain provocation test, to elicit the most reliable and consistent understanding of their pain perception.

Background and aims Health-related quality of life (Hr-QoL) reflects the burden of a condition on an overarching level. Pain intensity, disability and other factors influence how patients with chronic pain perceive their condition, e.g. Hr-QoL. However, the relative importance of these factors is unclear and there is an ongoing debate as to what importance pain measures have in this group. We investigated the importance of current pain level and mood on aspects of Hr-QoL in patients with chronic pain and investigated whether such relationships are influenced by demographics. Methods Data was obtained from the Swedish Quality Registry for Pain Rehabilitation (SQRP), between 2008 and 2016 on patients ≥18 years old who suffered from chronic pain and were referred to participating specialist clinics. Dependent variables were general Hr-QoL [using two scales from European Quality of Life instrument: EQ5D Index and the European Quality of Life instrument health scale (EQ thermometer)] and specific Hr-QoL [from the Short Form Health Survey (SF36) the physical component summary (SF36-PCS) and the mental (psychological) component summary (SF36-MCS)]. Independent variables were sociodemographic variables, pain variables, psychological distress and pain attitudes. Principal component analysis (PCA) was used for multivariate correlation analyses of all investigated variables and Orthogonal Partial Least Square Regression (OPLS) for multivariate regressions on health aspects. Results There was 40,518 patients (72% women). Pain intensity and interference showed the strongest multivariate correlations with EQ5D Index, EQ thermometer and SF36-PCS. Psychological distress variables displayed the strongest multivariate correlations with SF36-MCS. Demographic properties did not significantly influence variations in the investigated Hr-QoL variables. Conclusions Pain, mood and pain attitudes were significantly correlated with Hr-QoL variables, but these variables cannot explain most of variations in Hr-QoL variables. The results pinpoint that broad assessments (including pain intensity aspects) are needed to capture the clinical presentation of patients with complex chronic pain conditions.

Background The DoloTest is a newer health-related quality of life (HRQoL) monitoring instrument for pain, not yet validated for headache. Aims To examine the usefulness of the DoloTest in a specialized headache center. Methods The sample consisted of patients referred to psychologists from the Danish Headache Center (DHC) for whom the test was carried out at start of, end of, and 6 months after treatment. Points on eight scales of the test were measured (values ranged from 0 to 100), then totaled (0 to 800). Scores were analyzed using Wilcoxon Signed Ranks test. The correlation between headache days and DoloTest scores were computed using linear regression adjusted for age. Qualitative feedback on usefulness of the test were gathered from psychologists. Results Of 135 patients included, 105 completed treatment. On average, headache days decreased from 22 days per month at start of treatment (SD 9.0, median 29) to 18 days at end of treatment (SD 10.8, median 19) ( p <0.001). At end of treatment, DoloTest scores improved for pain ( p =0.015) and reduced energy and strength ( p =0.034). At 6 months’ follow-up, total scores improved ( p =0.034), as well as component scores for pain ( p =0.010), problems with strenuous activity ( p =0.045) and reduced energy and strength ( p =0.012). Correlation between reduced headache days and improved DoloTest scores was 0.303 ( p =0.028). Psychologists found the test useful in monitoring and evaluating patients. Conclusions The DoloTest was useful for psychoeducation and for monitoring the effect of headache treatment. Implications The DoloTest is a potential HRQoL monitoring instrument for headache patients. We recommend further validation studies.

Background and aims Chronic pelvic pain (CPP) impacts significantly on the lives of women. Negative coping responses such as pain catastrophizing are thought to be significant in predicting both pain severity and outcome. The combined effect of the individual’s response to pain and its severity on their quality of life (QoL) has not been well studied in women with CPP. Aims were to determine the prevalence of pain catastrophizing in women with CPP and to examine the associations between pain catastrophizing and levels of dysmenorrhea, non-cyclical pelvic pain, dyspareunia, dysuria, dyschezia and QoL. Methods A cross-sectional study including women aged 18–50 years, referred to a tertiary gynecology outpatients department at an Australian women’s hospital in 2015. Participants completed questionnaires including: pain catastrophizing scale (PCS); pelvic pain levels in the prior 3 months; and the World Health Organisation Quality of life – Bref Questionnaire (WHOQoL-Bref). Statistical analysis was performed using STATA (StataCorp, USA Version13). Results Participants ( n = 115) had a median age of 29.0 [interquartile range (IQR): 23.0–38.0] years. The Pain catastrophizing score revealed that 60/113 [95% confidence interval (CI): 48.6, 71.2] of participants had a clinically relevant total score ≥30. There were statistically significant positive correlations between pain catastrophizing scores and pelvic pain levels in all five pain categories studied, dysmenorrhea (ρ = 0.37, p = 0.0001), non-cyclical pelvic pain (ρ = 0.46, p <0.0001), dyspareunia (ρ = 0.32, p = 0.0008), dysuria (ρ = 0.32, p = 0.0005) and dyschezia (ρ = 0.38, p = 0.0012). Participants who reported maximal pain levels (5/5) had significantly higher median pain catastrophizing scores when compared to those who reported no pain (0/5) in all categories. Overall QoL was considered as “good” in 71/113 (95% CI: 60.1, 81.0) participants and “poor” in 42/113 (95% CI: 32.0, 53.0) participants. Comparison to Australian female norms revealed significantly lower QoL scores in the physical domain, across all ages, and in psychological domain for those aged <30 and 30–40 years. There was a significant association between increased catastrophizing scores and reduced odds of good QoL. An increase in PCS by one point is associated with a 6.3% decrease in the odds of good QoL [odds ratio (OR) per one-point increase: 0.94 (95% CI: 0.89, 0.98), p = 0.008]. Conclusions Pain catastrophizing is prevalent at clinically relevant levels in women with CPP across all domains. It is associated with higher pain levels and decreased QoL. Implications There is potential for further studies to investigate the predictive nature of pain catastrophizing and management targeting catastrophizing to improve outcomes in women with CPP.

Background and aims The prevalence of chronic non-cancer pain has not been specifically reported in Chile. Methods In order to assess its prevalence and impact, we designed a tool based on previously published survey studies. We analyzed a sample of 784 subjects to determine the prevalence of chronic non-cancer pain, with a maximum variability of 50%, a confidence interval (CI) of 95%, and an estimation error of 3.5%. Finally, a cross-sectional cell phone survey was conducted on a nationally representative probability sample of 865 subjects of over 18 years, in November 2013. The prevalence of chronic non-cancer pain was estimated by using expansion factors according to national projections by age group and gender, from the Chilean National Institute of Statistics for the year 2010. Results The estimated prevalence of chronic non-cancer pain was 32.1% (95% CI: 26.5–36.0). The respondents with chronic non-cancer pain presented the following results: 65.7% had moderate pain, and 20.8%, severe pain; 65.6% had somatic pain, 31.7% neuropathic pain, and 2.7% visceral pain. Approximately 70% reported they were receiving some kind of pharmacological treatment with certain frequency. In 64.9%, medication was prescribed by a physician. The prevalence of sick leave in workers was 30.22%, with a median duration of 14 days (interquartile range: 14; range: 1–60). Conclusions Chronic non-oncological pain occurs in 32% of Chilean adults. These figures provide the first measurement of chronic non-cancer pain in the Chilean population. Implications Chronic non-oncological pain impact as a public health problem is revealed, given the high prevalence found, and the elevated private and social costs involved.

Background and aims Previous studies have suggested there is an association between preoperative expectations about the outcome and outcomes of total knee and total hip arthroplasty (TKA/THA). However, expectations have been rarely examined on their clinical relevance relative to other well-known predictive factors. Furthermore expectations can be measured on a more generic level (e.g. does one expect their symptoms to improve after surgery) or on a more specific level (e.g. does one expect to be able to squat again after surgery). Aim of this study was to examine whether patients’ general and specific preoperative outcome expectations predict function and pain 12-months after TKA/THA, when assessed as one of the candidate predictive variables alongside other relevant clinical and sociodemographic variables. Moreover, we explored whether a more generic or a more specific assessment of expectations would better predict outcome. Methods A prospective cohort study on consecutive TKA/THA patients, with assessments done preoperatively and 12-months postoperative. Primary outcomes were the knee injury and osteoarthritis outcome score (KOOS) and hip injury and osteoarthritis outcome score (HOOS) activities of daily living (ADL) and pain subscale scores at 12-months. The pain subscales consist of nine-(KOOS) and 10-(HOOS) items and the ADL of 17 items. Patients’ preoperative outcome expectations were measured with the credibility expectancy questionnaire (CEQ), which contains three items scored on a 0–9 scale and sum score 0–27 and the Hospital for Special Surgery expectations surveys (HSS expectation surveys) for 17(TKA) or 18(THA) outcomes on 0–4 scale. Other candidate predictors: preoperative pain and function as measured with HOOS/KOOS, sex, age, education level, body mass index, Kellgren/Lawrence score, preoperative mental health and treatment credibility as measured with CEQ. Eight prediction models were constructed using multivariate linear regression analysis with a backward selection procedure. Results The 146 TKA patients included in this study had a mean age of 66.9 years (SD 9.2) and 69% was female. The 148 THA patients had a mean age 67.2 (SD 9.5) and 57% was female. Mean outcomes: postoperative HOOS-ADL 84.3 (SD 16.6), pain 88.2 (SD 15.4), KOOS-ADL 83.9 (SD 15.8) and pain 83.6 (SD 17.1). CEQ-expectancy median was in THA 23 (IQR 21;24) and TKA 23 (IQR 20;24). HSS-expectation surveys function was for THA 21.0 (18.0;24.0) and 19.0 (14.0;22.0) in TKA. Patients’ outcome expectations were consistently part of the combination of variables that best predicted outcomes for both TKA/THA 1-year post-operatively. Expectations alone explained between 17.0 and 30.3% of the variance in outcomes. The CEQ expectancy subscale explained more variance of postoperative function in TKA and of function and pain in THA as compared to the HSS expectation surveys. Conclusions In planning of surgical treatment, orthopedic surgeons should take a range of variables into account of which the patient’s expectations about outcome of surgery is one. The CEQ expectancy subscale predicted outcomes slightly better as the HSS expectation surveys, but differences in predictive value of the two measurements were too small to prefer between the two. Future studies are advised to replicate these findings and externally validate the models presented.

Background and aims Twin studies have found that approximately half of the variance in pain tolerance can be explained by genetic factors, while shared family environment has a negligible effect. Hence, a large proportion of the variance in pain tolerance is explained by the (non-shared) unique environment. The social environment beyond the family is a potential candidate for explaining some of the variance in pain tolerance. Numerous individual traits have previously shown to be associated with friendship ties. In this study, we investigate whether pain tolerance is associated with friendship ties. Methods We study the friendship effect on pain tolerance by considering data from the Tromsø Study: Fit Futures I, which contains pain tolerance measurements and social network information for adolescents attending first year of upper secondary school in the Tromsø area in Northern Norway. Pain tolerance was measured with the cold-pressor test (primary outcome), contact heat and pressure algometry. We analyse the data by using statistical methods from social network analysis. Specifically, we compute pairwise correlations in pain tolerance among friends. We also fit network autocorrelation models to the data, where the pain tolerance of an individual is explained by (among other factors) the average pain tolerance of the individual’s friends. Results We find a significant and positive relationship between the pain tolerance of an individual and the pain tolerance of their friends. The estimated effect is that for every 1 s increase in friends’ average cold-pressor tolerance time, the expected cold-pressor pain tolerance of the individual increases by 0.21 s ( p -value: 0.0049, sample size n =997). This estimated effect is controlled for sex. The friendship effect remains significant when controlling for potential confounders such as lifestyle factors and test sequence among the students. Further investigating the role of sex on this friendship effect, we only find a significant peer effect of male friends on males, while there is no significant effect of friends’ average pain tolerance on females in stratified analyses. Similar, but somewhat lower estimates were obtained for the other pain modalities. Conclusions We find a positive and significant peer effect in pain tolerance. Hence, there is a significant tendency for students to be friends with others with similar pain tolerance. Sex-stratified analyses show that the only significant effect is the effect of male friends on males. Implications Two different processes can explain the friendship effect in pain tolerance, selection and social transmission. Individuals might select friends directly due to similarity in pain tolerance, or indirectly through similarity in other confounding variables that affect pain tolerance. Alternatively, there is an influence effect among friends either directly in pain tolerance, or indirectly through other variables that affect pain tolerance. If there is indeed a social influence effect in pain tolerance, then the social environment can account for some of the unique environmental variance in pain tolerance. If so, it is possible to therapeutically affect pain tolerance through alteration of the social environment.

Background and aims The autonomic nervous system (ANS) is capable of modulating pain. Aberrations in heart rate variability (HRV), reflective of ANS activity, are associated with experimental pain sensitivity, chronic pain, and more recently, pain modulatory mechanisms but the underlying mechanisms are still unclear. HRV is lowered during experimental pain as well as in chronic pain conditions and HRV can be increased by propranolol, which is a non-selective β-blocker. Sensitization of central pain pathways have been observed in several chronic pain conditions and human mechanistic pain biomarkers for these central pain pathways include temporal summation of pain (TSP) and conditioned pain modulation (CPM). The current study aimed to investigate the effect of the β-blocker propranolol, and subsequently assessing the response to standardized, quantitative, mechanistic pain biomarkers. Methods In this placebo-controlled, double-blinded, randomized crossover study, 25 healthy male volunteers (mean age 25.6 years) were randomized to receive 40 mg propranolol and 40 mg placebo. Heart rate, blood pressure, and HRV were assessed before and during experimental pain tests. Cuff pressure pain stimulation was used for assessment of pain detection (cPDTs) and pain tolerance (cPTTs) thresholds, TSP, and CPM. Offset analgesia (OA) was assessed using heat stimulation. Results Propranolol significantly reduced heart rate ( p <0.001), blood pressure ( p <0.02) and increased HRV ( p <0.01) compared with placebo. No significant differences were found comparing cPDT ( p >0.70), cPTT ( p >0.93), TSP ( p >0.70), OA-effect ( p >0.87) or CPM ( p >0.65) between propranolol and placebo. Conclusions The current study demonstrated that propranolol increased HRV, but did not affect pressure pain sensitivity or any pain facilitatory or modulatory outcomes. Implications Analgesic effects of propranolol have been reported in clinical pain populations and the results from the current study could indicate that increased HRV from propranolol is not associated with peripheral and central pain pathways in healthy male subjects.

Background and aims Depression is a common feature of chronic pain, but there is only limited research into the content and frequency of depressed cognitions in pain patients. This study describes the development of the Sentence Completion Test for Chronic Pain (SCP), an idiographic measure for assessing depressive thinking in chronic pain patients. The sentence completion task requires participants to finish incomplete sentences using their own words to a set of predefined stems that include negative, positive and neutral valenced self-referenced words. In addition, the stems include past, future and world stems, which reflect the theoretical negative triad typical to depression. Complete responses are coded by valence (negative, positive and neutral), pain and health-related content. Methods A total of 89 participants were included in this study. Forty seven adult out-patients formed the depressed pain group and were compared to a non-clinical control sample of 42 healthy control participants. This study comprised several phases: (1) theory-driven generation of coding rules; (2) the development of a coding manual by a panel of experts (3) comparing reliability of coding by expert raters without the use of the coding manual and with the use of the coding manual; (4) preliminary analyses of the construct validity of the SCP. The internal consistency of the SCP was tested using the Kuder-Richardson coefficient (KR-20). Inter-rater agreement was assessed by intra-class correlations (ICC). The content and construct validity of the SCP was investigated by correlation coefficients between SCP negative completions, the Hospital Anxiety and Depression Scale (HADS) depression scores and the number of symptoms on the Structured Clinical Interview for DSM-IV-TR (SCID). Results As predicted for content validity, the number of SCP negative statements was significantly greater in the depressed pain group and this group also produced significantly fewer positive statements, compared to the healthy control group. The number of negative pain completions and negative health completions was significantly greater in the depressed pain group. As expected, in the depressed pain group, the correlation between SCP negatives and the HADS Depression score was r =0.60 and the correlation between SCP negatives and the number of symptoms on the SCID was r =0.56. Conclusions The SCP demonstrated good content validity, internal consistency and inter-rater reliability. Implications Uses for this measure, such as complementing questionnaire measures by an idiographic assessment of depressive thinking and generating hypotheses about key problems within a cognitive-behavioural case-formulation, are suggested.

Background and aims Anterior cutaneous nerve entrapment syndrome (ACNES) may result in chronic abdominal pain. Therapeutic options include local injection therapy. Data on the efficacy of adding corticosteroids to these injections is lacking. Methods Patients ≥18 years with ACNES were randomized to receive an injection of lidocaine with (LC-group) or without (LA-group) the addition of methylprednisolone into the point of maximal abdominal wall pain. Pain was recorded using a numeric rating scale (NRS: 0–10) and a verbal rating scale (VRS: 0=no pain, 5=unbearable pain) at baseline and 6 weeks after the start of a bi-weekly injection regimen consisting of a total of three injections. A minimal 50% reduction on NRS and/or two points on VRS were considered successful responses. Results Between February 2014 and August 2016, 136 patients (median age 46 year, range 18–79, 75% females) were randomized (68 vs. 68). The proportion of patients demonstrating a successful response after 6 weeks did not significantly differ between groups (LA 38%, LC 31%, p =0.61). At 12 weeks, the number of patients still experiencing a minimal 50% pain relief had decreased but no group difference was observed (LA 20%, LC 18%, p =0.80). Minor side effects included temporary increase of pain, tenderness at injection sites or transient malaise (LA23/68, LC 29/68, p =0.46). Conclusions Adding corticosteroids to a lidocaine does not increase the proportion of ACNES patients with a successful response to injection therapy. Lidocaine alone can provide long term pain relief after one or multiple injections, in approximately 1 of 5 patients.

Background and aims Impairment of endogenous analgesia has been associated with the development, maintenance and persistence of pain. Endogenous analgesia can be evaluated using exercise-induced hypoalgesia (EIH) and offset analgesia (OffA) paradigms, which measure temporal filtering of sensory information. It is not clear if these paradigms are underpinned by common mechanisms, as EIH and OffA have not previously been directly compared. A further understanding of the processes responsible for these clinically relevant phenomena may have future diagnostic and therapeutic utility in management of individuals with persistent pain conditions. The primary aim of this study was to investigate if there is a correlation between the magnitudes of EIH and OffA. The secondary aim of the study was to examine whether exercise influences OffA. Methods Thirty-six healthy, pain-free participants were recruited. EIH was evaluated using pressure pain thresholds (PPT) and pain ratings to suprathreshold pressure stimuli over tibialis anterior and the cervical spine. OffA evaluation utilised a three-step protocol, whereby individualised heat pain thermal stimuli [Numerical Rating Scale (NRS)=50/100] were applied (T1), before increasing 1 °C (T2), followed by 1 °C reduction (T3). The magnitude of OffA was calculated as the percentage reduction in the NRS from T2 to T3. PPT/suprathreshold pain ratings and OffA measures were recorded, before and after 5 min of isometric quadriceps exercise performed at 20–25% maximum voluntary contraction (MVC); and following a 15 min rest period. Data were analysed using repeated measures (RM) ANCOVA and correlational analyses. Results There was no correlation between EIH measures (PPTs or pain ratings to suprathreshold pressure stimuli over tibialis anterior or the cervical spine) and OffA ( p >0.11 for all). OffA was induced and not modulated by exercise ( p =0.28). Conclusions Five minutes of 20–25% MVC lower limb isometric exercise provided non-pharmacological pain modulation in young, active adults. Magnitude of EIH was not correlated with that of OffA, and exercise did not influence magnitude of OffA. Implications These results suggest that in young, pain-free individuals, separate testing of these two paradigms is required to comprehensively evaluate efficacy of endogenous analgesia. If these results are replicated in patient populations, alternative or complementary methods to exercise interventions may be required to modulate impaired OffA.

Background and aims Pain is not a linear result of nociception, but is dependent on multisensory inputs, psychological factors, and prior experience. Since nociceptive models appear insufficient to explain chronic pain, understanding non-nociceptive contributors is imperative. Several recent models propose that cues associatively linked to painful events might acquire the capacity to augment, or even cause, pain. This experiment aimed to determine whether contexts associated with pain, could modulate mechanical pain thresholds and pain intensity. Methods Forty-eight healthy participants underwent a contextual conditioning procedure, where three neutral virtual reality contexts were paired with either unpredictable noxious stimulation, unpredictable vibrotactile stimulation, or no stimulation. Following the conditioning procedure, mechanical pain thresholds and pain evoked by a test stimulus were examined in each context. In the test phase, the effect of expectancy was equalised across conditions by informing participants when thresholds and painful stimuli would be presented. Results Contrary to our hypothesis, scenes that were associated with noxious stimulation did not increase mechanical sensitivity ( p =0.08), or increase pain intensity ( p =0.46). However, an interaction with sex highlighted the possibility that pain-associated contexts may alter pain sensitivity in females but not males ( p =0.03). Conclusions Overall, our data does not support the idea that pain-associated contexts can alter pain sensitivity in healthy asymptomatic individuals. That an effect was shown in females highlights the possibility that some subgroups may be susceptible to such an effect, although the magnitude of the effect may lack real-world significance. If pain-associated cues prove to have a relevant pain augmenting effect, in some subgroups, procedures aimed at extinguishing pain-related associations may have therapeutic potential.

Background and aims Medical students receive training in the management of chronic pain, but the training is often suboptimal. Considering that the basis for physician’s knowledge is their medical education, it is important to explore the attitudes and beliefs of medical students with respect both to chronic pain management and to their views on current pain education. Therefore, the aim of this study was to compare Swedish and Australian medical student’s attitudes and beliefs about patients with chronic pain, and their perceptions regarding their chronic pain management education. Methods An online survey was conducted with final year Australian and Swedish medical students from two different universities between December 2016 and February 2017. Attitudes and beliefs towards chronic pain patients were measured using the Health Care Providers’ Pain and Impairment Scale (HC-PAIRS). A thematic analysis was conducted on open end questions regarding their views on their education and important skills for chronic pain management. Results A total of 57 Swedish and 26 Australian medical students completed the HC-PAIRS scale. The Swedish medical students showed statistically significantly lower total mean HC-PAIRS scores compared to Australian medical students (46 and 51, respectively). Australian students had statistically significantly higher scores than the Swedish students for two of four factors: functional expectations and need for cure, whereas no significant differences were seen for the factors social expectations or for projected cognition. From the open end questions it was evident that final year medical students are knowledgeable about key chronic pain items described in clinical guidelines. However, both cohorts described their chronic pain training as poor and in need of improvement in several areas such as more focus on the biopsychosocial model, working in multidisciplinary teams, seeing chronic pain patients and pharmacological training. Conclusions Attitudes and beliefs are formed during medical education, and our study exploring attitudes of medical students towards chronic pain and how it is taught have provided valuable information. Our survey provided detailed and cohesive suggestions for education improvement that also are in line with current clinical guidelines. This study indicates that the Swedish final year students have a more positive attitude towards chronic pain patients compared to their Australian counterparts. The majority of students in both cohorts perceived chronic pain management education in need of improvement. Implications This study highlights several areas of interest that warrant further investigation, for example, the impact of a changed medical curriculum in alignment with these clinical guidelines requested by students in this survey, and correspondingly if their attitudes towards chronic pain patients can be improved through education. Further, we conclude that it would be valuable to align the implementation of the HC-PAIRS instrument in order to achieve comparable results between future studies.

Background and aims Compared to White individuals, Black individuals demonstrate a lower pain tolerance. Research suggests that differences in pain coping strategies, such as prayer, may mediate this race difference. However, previous research has been cross-sectional and has not determined whether prayer in and of itself or rather the passive nature of prayer is driving the effects on pain tolerance. The aim of this study was to clarify the relationships among race, prayer (both active and passive), and pain tolerance. Methods We randomly assigned 208 pain-free participants (47% Black, 53% White) to one of three groups: active prayer (“God, help me endure the pain”), passive prayer (“God, take the pain away”), or no prayer (“The sky is blue”). Participants first completed a series of questionnaires including the Duke University Religion Index, the Coping Strategies Questionnaire-Revised (CSQ-R), and the Pain Catastrophizing Scale. Participants were then instructed to repeat a specified prayer or distractor coping statement while undergoing a cold pressor task. Cold pain tolerance was measured by the number of seconds that had elapsed while the participant’s hand remained in the cold water bath (maximum 180 s). Results Results of independent samples t-tests indicated that Black participants scored higher on the CSQ-R prayer/hoping subscale. However, there were no race differences among other coping strategies, religiosity, or catastrophizing. Results of a 2 (Race: White vs. Black)×3 (Prayer: active vs. passive vs. no prayer) ANCOVA controlling for a general tendency to pray and catastrophizing in response to prayer indicated a main effect of prayer that approached significance ( p =0.06). Pairwise comparisons indicated that those in the active prayer condition demonstrated greater pain tolerance than those in the passive ( p =0.06) and no prayer ( p =0.03) conditions. Those in the passive and no prayer distractor conditions did not significantly differ ( p =0.70). There was also a trending main effect of race [ p =0.08], with White participants demonstrating greater pain tolerance than Black participants. Conclusions Taken together, these results indicate that Black participants demonstrated a lower pain tolerance than White participants, and those in the active prayer condition demonstrated greater tolerance than those in the passive and no prayer conditions. Furthermore, Black participants in the passive prayer group demonstrated the lowest pain tolerance, while White participants in the active prayer group exhibited the greatest tolerance. Results of this study suggest that passive prayer, like other passive coping strategies, may be related to lower pain tolerance and thus poorer pain outcomes, perhaps especially for Black individuals. On the other hand, results suggest active prayer is associated with greater pain tolerance, especially for White individuals. Implications These results suggest that understanding the influence of prayer on pain may require differentiation between active versus passive prayer strategies. Like other active coping strategies for pain, active prayer may facilitate self-management of pain and thus enhance pain outcomes independent of race. Psychosocial interventions may help religiously-oriented individuals, regardless of race, cultivate a more active style of prayer to improve their quality of life.

Background Complex regional pain syndrome (CRPS) is a debilitating painful disorder, cryptic in its pathophysiology and refractory condition with limited therapeutic options. Type I CRPS with its variable relationship to trauma has often no discernible fractures or nerve injuries and remains enigmatic in its response to conservative treatment as well as the other limited interventional therapies. Neuromodulation in the form of spinal cord and dorsal root ganglion stimulation (SCS, DRGS) has shown encouraging results, especially of causalgia or CRPS I of lower extremities. Upper extremity CRPS I is far more difficult. Objective To report a case of upper extremity CRPS I treated by wireless peripheral nerve stimulation (WPNS) for its unique features and minimally invasive technique. The system does not involve implantation of battery or its connections. Case report A 47 year old female patient presented with refractory CRPS I following a blunt trauma to her right forearm. As interventional treatment in the form of local anesthetics (Anesthesia of peripheral branches of radial nerve) and combined infusions of ketamine/lidocaine failed to provide any significant relief she opted for WPNS treatment. Based on the topographic distribution, two electrodes (Stimwave Leads: FR4A-RCV-A0 with tines, Generation 1 and FR4A-RCV-B0 with tines, Generation 1), were placed along the course of radial and median nerves under ultrasonography monitoring and guided by intraoperative stimulation. This procedure did not involve implantation of extension cables or the power source. At a frequency of 60 Hz and 300 μs the stimulation induced paresthesia along the distribution of the nerves. Therapeutic relief was observed with high frequency (HF) stimulation (HF 10 kHz/32 μs, 2.0 mA) reducing her pain from a visual analogue scale (VAS) score of 7–4 postoperatively. Three HF stimulations programs were provided at the time of discharge, as she improved in her sensory impairment to touch, pressure and temperature at her first follow up visit. At 5-months she was able to drive, did not require opioids and allodynia disappeared. Conclusions In a case with difficult CRPS I involving upper extremity, a minimally invasive WPNS of radial and median nerves provided good symptomatic relief. The procedure was tolerated well and both electrodes remained in place without any adverse events. Implications In view of the very limited options currently available to manage CRPS, WPNS can be a promising therapeutic modality.