The experiences and needs of people seeking primary care for low-back pain in Australia Introduction: There is a knowledge gap about the current experiences and needs of people with low back pain (LBP) seeking primary care in Australia. Objectives: The aim of this study was to understand the experiences and needs of Australians who have received treatment for LBP in primary care. Methods: This was a prospective, cross-sectional internet survey conducted between July 2017 and September 2017. Participants were adults who had experienced an episode of LBP in the past year, had sought primary care in Australia, and were proficient in English. Outcomes were patient-reported experiences about primary care treatment, including reasons for seeking care, health care practitioners consulted, components of care received, and patients' evaluations of the importance and helpfulness of treatment. Results: A total of 426 Australians completed the survey. The response rate of survey completion was 50%. Participants reported seeking primary care for LBP not only for pain relief, but for difficulties with activities and participation with usual social roles as well as quality of life and mood. Participants consulted multiple health care practitioners and used numerous treatment modalities. Only half reported they received education and a very low proportion were aware of receiving guideline-based advice. The level of satisfaction with care was below moderate for 42% of respondents. Participants reported that they want LBP care to be more person-centred and better tailored to their needs; they also reported wanting more education, particularly about prevention of future episodes and self-management. Conclusions: The needs of people currently seeking primary care for LBP in Australia do not seem to be adequately met. Improving patients' experiences and outcomes may require better integration of health care across providers and delivery of more person-centred care.

Truncal blocks and teenager postoperative pain perception after laparoscopic surgical procedures Introduction: The prevalence of moderate to severe pain is high in hospitalized teenage patients admitted to surgical services. Objectives: The aims of this study were to determine (1) the preoperative and postoperative factors influencing teenager postoperative pain perception; and (2) suffering, defined as the patient's anxiety, pain catastrophizing thoughts, and mood. Methods: Data were collected from medical records and from 2 medical interviews at the time of enrollment and postoperative day 1. Stepwise linear regression was conducted to assess variables that predicted teenagers' pain scores and suffering. Results: Two hundred two patients (mean age = 13.8 years, SD = 1.9), 56.4% females, scheduled for laparoscopic surgical procedures completed the study. The variables found to be significant predictors of pain response in teenagers were pain on the day of surgery (6.81, 95% confidence interval [CI] = 0.08–13.55, P = 0.05) and use of regional anesthesia (single-injection rectus sheath, transversus abdominis plane, and paravertebral nerve blocks) (−6.58, 95% CI = −12.87 to −0.30, P = 0.04). The use of regional anesthesia was found to predict mood responses (all patients: 2.60, 95% CI = 0.68–4.52, P = 0.01; girls: 3.45, 95% CI = 0.96–5.93, P = 0.01; 14–17-year-old teens: 2.77, 95% CI = 0.44–5.10, P = 0.02) and to negatively predict catastrophic thoughts among all patients as a group (−4.35, 95% CI = −7.51 to −1.19, P = 0.01) and among 14- to 17-year-old teens (−5.17, 95% CI = −9.44 to −0.90, P = 0.02). Conclusion: A comprehensive pain approach that includes truncal blocks may improve teenagers' postoperative pain control after laparoscopic surgeries.

The relationship between guarding, pain, and emotion Introduction: Pain-related behavior in people with chronic pain is often overlooked in a focus on increasing the amount of activity, yet it may limit activity and maintain pain and disability. Targeting it in treatment requires better understanding of the role of beliefs, emotion, and pain in pain behavior. Objectives: This study aimed to clarify the interrelationships between guarding, pain, anxiety, and confidence in movement in people with chronic pain in everyday movements. Methods: Physiotherapists rated extent of guarding on videos of people with chronic pain and healthy controls making specific movements. Bayesian modelling was used to determine how guarding was related to self-reported pain intensity, anxiety, and emotional distress, and observer-rated confidence in movement. Results: The absence of guarding was associated with low levels of pain, anxiety, distress, and higher movement self-efficacy, but guarding behavior occurred at high and low levels of each of those variables. Guarding was not directly dependent on pain but on anxiety; the relationship between pain and guarding was mediated by anxiety, with a high probability. Nor was guarding directly related to the broader distress score, but to self-efficacy for movement, again with a high probability. Conclusion: Pain-related guarding is more likely to be effectively addressed by intervention to reduce anxiety rather than pain (such as analgesia); more attention to how people move with chronic pain, rather than only how much they move, is likely to help to extend activity.

Reversible tactile hypoesthesia associated with myofascial trigger points: a pilot study on prevalence and clinical implications Introduction: Tactile hypoesthesia observed in patients with myofascial pain syndrome (MPS) is sometimes reversible when pain is relieved by trigger point injections (TPIs). We aimed to investigate the prevalence of such reversible hypoesthesia during TPI therapy and topographical relations between areas of tactile hypoesthesia and myofascial trigger points (MTrP) in patients with MPS. Methods: Forty-six consecutive patients with MTrP were enrolled in this study. We closely observed changes in areas of tactile hypoesthesia in patients who had tactile hypoesthesia at the first visit, and throughout TPI therapy. Tactile stimulation was given using cotton swabs, and the areas of tactile hypoesthesia were delineated with an aqueous marker and recorded in photographs. Results: A reduction in the size of hypoesthetic area with TPI was observed in 27 (58.7%) patients. All the 27 patients experienced a reduction in pain intensity by more than 50% in a numerical rating scale score through TPI therapy. In 9 patients, the reduction in the sizes of hypoesthetic areas occurred 10 minutes after TPI. Complete disappearance of tactile hypoesthesia after TPI therapy was observed in 6 of the 27 patients. Myofascial trigger points were located in the muscles in the vicinity of ipsilateral cutaneous dermatomes to which the hypoesthetic areas belonged. Conclusion: Our results indicate a relatively high prevalence of reversible tactile hypoesthesia in patients with MPS. Mapping of tactile hypoesthetic areas seems clinically useful for detecting MTrP. In addition, treating MTrP with TPI may be important for distinguishing tactile hypoesthesia associated with MPS from that with neuropathic pain.

Peripheral nerve pathology in sickle cell disease mice Introduction: Many patients with sickle cell disease (SCD) suffer from chronic pain, which is often described as neuropathic in nature. Although vascular and inflammatory pathology undoubtedly contribute to the SCD pain experience, the nociceptive signals that ultimately drive symptoms are detected and transmitted by peripheral sensory neurons. To date, no systematic histological examination of peripheral nerves has been completed in patients or mouse models of SCD to diagnose disease-related neuropathy. Objectives: In this brief report, we compared peripheral nerve morphology in tissues obtained from Berkeley transgenic SCD mice and control animals. Methods: Sciatic nerves were visualized using light and transmission electron microscopy. Myelin basic protein expression was assessed through Western blot. Blood–nerve barrier permeability was measured using Evan's blue plasma extravasation. Results: Peripheral fibers from SCD mice have thinner myelin sheaths than control mice and widespread myelin instability as evidenced by myelin sheath infolding and unwrapping. Deficits are also observed in nonmyelinating Schwann cell structures; Remak bundles from SCD nerves contain fewer C fibers, some of which are not fully ensheathed by the corresponding Schwann cell. Increased blood–nerve barrier permeability and expression of myelin basic protein are noted in SCD tissue. Conclusions: These data are the first to characterize Berkeley SCD mice as a naturally occurring model of peripheral neuropathy. Widespread myelin instability is observed in nerves from SCD mice. This pathology may be explained by increased permeability of the blood–nerve barrier and, thus, increased access to circulating demyelinating agents at the level of primary sensory afferents.

A protocol for the systematic review and meta-analysis of studies in which cannabinoids were tested for antinociceptive effects in animal models of pathological or injury-related persistent pain Introduction: The International Association for the Study of Pain has established a global task force to comprehensively investigate the use of cannabinoids and cannabis-based medicines for pain management. This systematic review, the first in this field, will assess the preclinical literature that investigates the antinociceptive effects of cannabinoids, cannabis-based medicines, and endocannabinoid system modulators in animal models of tissue damage, inflammation, or neuropathy. Methods: A systematic electronic search of 3 online databases will identify relevant studies in which cannabinoids, cannabis-based medicines, and endocannabinoid system modulators have been tested in animal models of injury-related or pathological persistent pain. Data will be extracted for pain-associated behavioural outcomes, study design, and the reporting of measures to avoid bias. Standardised mean difference meta-analysis will be used to provide summary estimates of efficacy, with the effects of study quality and study design explored using stratified meta-analysis. Perspective: The evaluation of the preclinical evidence will quantify the antinociceptive effects of cannabinoids on pain behaviour in animal models of pathological pain in an effort to quantify the presence and prevalence of analgesic efficacy. It will also provide an understanding of the strengths and weaknesses of the preclinical field and inform an agenda for future research.

Functional and histological improvements of small nerve neuropathy after high-concentration capsaicin patch application: A case study Introduction: Small fiber neuropathy has been found to occur in a large variety of pathological onditions, and the gold standard for diagnosis of small fiber neuropathy is skin biopsy. Sudorimetry is now considered an accurate technique to evaluate small fiber function with a good sensitivity and specificity for the diagnosis of small fiber neuropathy. Capsaicin high-concentration patch is approved for the treatment of peripheral neuropathic pain in adults either alone or in combination with other medicinal products for pain. Methods: We describe the case of a 50-year-old woman diagnosed with small fiber neuropathy. After 2 previous treatment failures, she was proposed a treatment with high-dose capsaicin patches on the sole of her foot. The patient experienced an important diminution of her neuropathic pain. There was a 50% decrease in the pain numeric scale. Electrochemical skin conductance and skin biopsy were repeated 3 months after patch application. Results: At 3 months, the patient then experienced an important diminution of her neuropathic pain, electrochemical skin conductance had normalized both in the hands and feet and intraepidermal nerve fiber density at distal leg increased almost reaching normal range. Conclusion: This case report shows the correlation between clinical improvement, electrochemical skin conductance normalization, and intraepidermal nerve fiber density improvement after a high-dose capsaicin patch in a patient with small fiber neuropathy.

Introduction to a Special Issue on Innovations and Controversies in Brain Imaging of Pain: Methods and Interpretations This special issue comprised 14 articles from leaders in the field, that provide opinions and reviews of concepts that are central to the next generation of pain imaging studies. Topics include cutting-edge technologies and approaches that are at the forefront of such studies, as well as developments toward biomarkers of pain and clinical applications that bring us closer to harnessing understanding of pains and its modulation to offer better options to those suffering from pain.

Neuroimaging of pain in animal models: a review of recent literature Neuroimaging of pain in animals allows us to better understand mechanisms of pain processing and modulation. In this review, we discuss recently published brain imaging studies in rats, mice, and monkeys, including functional magnetic resonance imaging (MRI), manganese-enhanced MRI, positron emission tomography, and electroencephalography. We provide an overview of innovations and limitations in neuroimaging techniques, as well as results of functional brain imaging studies of pain from January 1, 2016, to October 10, 2018. We then discuss how future investigations can address some bias and gaps in the field. Despite the limitations of neuroimaging techniques, the 28 studies reinforced that transition from acute to chronic pain entails considerable changes in brain function. Brain activations in acute pain were in areas more related to the sensory aspect of noxious stimulation, including primary somatosensory cortex, insula, cingulate cortex, thalamus, retrosplenial cortex, and periaqueductal gray. Pharmacological and nonpharmacological treatments modulated these brain regions in several pain models. On the other hand, in chronic pain models, brain activity was observed in regions commonly associated with emotion and motivation, including prefrontal cortex, anterior cingulate cortex, hippocampus, amygdala, basal ganglia, and nucleus accumbens. Neuroimaging of pain in animals holds great promise for advancing our knowledge of brain function and allowing us to expand human subject research. Additional research is needed to address effects of anesthesia, analysis approaches, sex bias and omission, and potential effects of development and aging.

Differentiating trait pain from state pain: a window into brain mechanisms underlying how we experience and cope with pain Across various biological and psychological attributes, individuals have a set point around which they can fluctuate transiently into various states. However, if one remains in a different state other than their set point for a considerable period (eg, induced by a disease), this different state can be considered to be a new set point that also has associated surrounding states. This concept is instructive for understanding chronic pain, where an individual's set point may maladaptively shift such that they become stuck at a new set point of pain (trait pain), from which pain can fluctuate on different timescales (ie, pain states). Here, we discuss the importance of considering trait and state pains in neuroimaging studies of brain structure and function to gain an understanding of not only an individual's current pain state but also more broadly to their trait pain, which may be more reflective of their general condition.