Deep brain stimulation for chronic pain investigated with magnetoencephalography

Deep brain stimulation has shown remarkable potential in alleviating otherwise treatment-resistant chronic pain, but little is currently known about the underlying neural mechanisms. Here for the first time, we used noninvasive neuroimaging by magnetoencephalography to map changes in neural activity induced by deep brain stimulation in a patient with severe phantom limb pain. When the stimulator was turned off, the patient reported significant increases in subjective pain. Corresponding significant changes in neural activity were found in a network including the mid-anterior orbitofrontal and subgenual cingulate cortices; these areas are known to be involved in pain relief. Hence, they could potentially serve as future surgical targets to relieve chronic pain. © 2007 Lippincott Williams & Wilkins, Inc.

Pain management programmes for non-English-speaking black and minority ethnic groups with long-term or chronic pain

Increasing ethnic diversity in the UK means that there is a growing need for National Health Service care to be delivered to non-English-speaking patients. The aims of the present systematic review were to: (1) better understand the outcomes of chronic pain management programmes (PMPs) for ethnic minority and non-English-speaking patients and (2) explore the perspectives on and experiences of chronic pain for these groups. A systematic review identified 26 papers meeting the inclusion criteria; no papers reported on the outcomes of PMPs delivered in the UK. Of the papers obtained, four reported on PMPs conducted outside the UK; eight reported on ethnic differences in patients seeking support from pain management services in America; and the remaining papers included literature reviews, an experimental pain study, a collaborative enquiry, and a survey of patient and clinician ratings of pain. The findings indicate a lack of research into UK-based pain management for ethnic minorities and non-English-speaking patients. The literature suggests that effective PMPs must be tailored to meet cultural experiences of pain and beliefs about pain management. There is a need for further research to explore these cultural beliefs in non-English-speaking groups in the UK. Culturally sensitive evaluations of interpreted PMPs with long-term follow-up are needed to assess the effectiveness of current provision. Copyright © 2015 John Wiley & Sons, Ltd.

Psychological risk factors for chronic post-surgical pain after inguinal hernia repair surgery:a prospective cohort study.

A significant proportion of patients experience chronic post-surgical pain (CPSP) following inguinal hernia surgery. Psychological models are useful in predicting acute pain after surgery, and in predicting the transition from acute to chronic pain in non-surgical contexts. This is a prospective cohort study to investigate psychological (cognitive and emotional) risk factors for CPSP after inguinal hernia surgery. Participants were asked to complete questionnaires before surgery and 1 week and 4 months after surgery. Data collected before surgery and 1 week after surgery were used to predict pain at 4 months. Psychological risk factors assessed included anxiety, depression, fear-avoidance, activity avoidance, catastrophizing, worry about the operation, activity expectations, perceived pain control and optimism. The study included 135 participants; follow-up questionnaires were returned by 119 (88.1%) and 115 (85.2%) participants at 1 week and 4 months after surgery respectively. The incidence of CPSP (pain at 4 months) was 39.5%. After controlling for age, body mass index and surgical variables (e.g. anaesthetic, type of surgery and mesh type used), lower pre-operative optimism was an independent risk factor for CPSP at 4 months; lower pre-operative optimism and lower perceived control over pain at 1 week after surgery predicted higher pain intensity at 4 months. No emotional variables were independently predictive of CPSP. Further research should target these cognitive variables in pre-operative psychological preparation for surgery. © 2011 European Federation of International Association for the Study of Pain Chapters.

Psychophysiological responses to pain identify reproducible human clusters

Pain is a ubiquitous yet highly variable experience. The psychophysiological and genetic factors responsible for this variability remain unresolved. We hypothesised the existence of distinct human pain clusters (PCs) composed of distinct psychophysiological and genetic profiles coupled with differences in the perception and the brain processing of pain. We studied 120 healthy subjects in whom the baseline personality and anxiety traits and the serotonin transporter-linked polymorphic region (5-HTTLPR) genotype were measured. Real-time autonomic nervous system parameters and serum cortisol were measured at baseline and after standardised visceral and somatic pain stimuli. Brain processing reactions to visceral pain were studied in 29 subjects using functional magnetic resonance imaging (fMRI). The reproducibility of the psychophysiological responses to pain was assessed at 1 year. In group analysis, visceral and somatic pain caused an expected increase in sympathetic and cortisol responses and activated the pain matrix according to fMRI studies. However, using cluster analysis, we found 2 reproducible PCs: at baseline, PC1 had higher neuroticism/anxiety scores (P ≤ 0.01); greater sympathetic tone (P < 0.05); and higher cortisol levels (P ≤ 0.001). During pain, less stimulus was tolerated (P ≤ 0.01), and there was an increase in parasympathetic tone (P ≤ 0.05). The 5-HTTLPR short allele was over-represented (P ≤ 0.005). PC2 had the converse profile at baseline and during pain. Brain activity differed (P ≤ 0.001); greater activity occurred in the left frontal cortex in PC1, whereas PC2 showed greater activity in the right medial/frontal cortex and right anterior insula. In health, 2 distinct reproducible PCs exist in humans. In the future, PC characterization may help to identify subjects at risk for developing chronic pain and may reduce variability in brain imaging studies. © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Psychophysiological responses to visceral and somatic pain in functional chest pain identify clinically relevant pain clusters

Background: Despite chronic pain being a feature of functional chest pain (FCP) its experience is variable. The factors responsible for this variability remain unresolved. We aimed to address these knowledge gaps, hypothesizing that the psychophysiological profiles of FCP patients will be distinct from healthy subjects. Methods: 20 Rome III defined FCP patients (nine males, mean age 38.7 years, range 28-59 years) and 20 healthy age-, sex-, and ethnicity-matched controls (nine males, mean 38.2 years, range 24-49) had anxiety, depression, and personality traits measured. Subjects had sympathetic and parasympathetic nervous system parameters measured at baseline and continuously thereafter. Subjects received standardized somatic (nail bed pressure) and visceral (esophageal balloon distension) stimuli to pain tolerance. Venous blood was sampled for cortisol at baseline, post somatic pain and post visceral pain. Key Results: Patients had higher neuroticism, state and trait anxiety, and depression scores but lower extroversion scores vs controls (all p < 0.005). Patients tolerated less somatic (p < 0.0001) and visceral stimulus (p = 0.009) and had a higher cortisol at baseline, and following pain (all p < 0.001). At baseline, patients had a higher sympathetic tone (p = 0.04), whereas in response to pain they increased their parasympathetic tone (p ≤ 0.008). The amalgamating the data, we identified two psychophysiologically distinct 'pain clusters'. Patients were overrepresented in the cluster characterized by high neuroticism, trait anxiety, baseline cortisol, pain hypersensitivity, and parasympathetic response to pain (all p < 0.03). Conclusions & Inferences: In future, such delineations in FCP populations may facilitate individualization of treatment based on psychophysiological profiling. © 2013 John Wiley & Sons Ltd.

Psychological therapies for chronic pelvic pain:systematic review of randomized controlled trials

Chronic pelvic pain (CPP), a common cause of disability in women, is a condition best viewed in the biopsychosocial framework. Psychological interventions are frequently considered alongside medical and surgical treatments. Our objective was to evaluate the effectiveness of psychological therapies for the treatment of CPP. Electronic literature searches were conducted in Medline, Embase, PsycInfo and DARE databases from database inception to April 2010. Reference lists of selected articles were searched for further articles. The studies selected were randomized controlled trials of psychological therapies in patients with CPP compared with no treatment, standard gynecological treatment or another form of psychological therapy. Two reviewers independently selected articles without language restrictions and extracted data covering study characteristics, study quality and results. Reduction in pain, measured using visual analog scales or other measurements, was the main outcome measure. Of the 107 citations identified, four studies satisfied the inclusion criteria. Compared with no psychological intervention, therapy produced a standardized mean pain score of -3.27 [95% confidence interval (CI) -4.52 to -2.02] and 1.11 (95% CI -0.05 to 2.27) at 3 months and -3.95 (95% CI -5.35 to -2.55) and 0.54 (95% CI -0.78 to 1.86) at 6 months and greater, based on a visual analog scale score of 0-10. The current evidence does not allow us to conclude whether psychological interventions have an effect on self-reported pain scores in women with CPP.

Chronic preoperative pain and psychological robustness predict acute postoperative pain outcomes after surgery for breast cancer

Background - Few epidemiological studies have prospectively investigated preoperative and surgical risk factors for acute postoperative pain after surgery for breast cancer. We investigated demographic, psychological, pain-related and surgical risk factors in women undergoing resectional surgery for breast cancer. Methods - Primary outcomes were pain severity, at rest (PAR) and movement-evoked pain (MEP), in the first postoperative week. Results - In 338 women undergoing surgery, those with chronic preoperative pain were three times more likely to report moderate to severe MEP after breast cancer surgery (OR 3.18, 95% CI 1.45–6.99). Increased psychological ‘robustness’, a composite variable representing positive affect and dispositional optimism, was associated with lower intensity acute postoperative PAR (OR 0.63, 95% CI 0.48–0.82) and MEP (OR 0.71, 95% CI 0.54–0.93). Sentinel lymph node biopsy (SLNB) and intraoperative nerve division were associated with reduced postoperative pain. No relationship was found between preoperative neuropathic pain and acute pain outcomes; altered sensations and numbness postoperatively were more common after axillary sample or clearance compared with SLNB. Conclusion - Chronic preoperative pain, axillary surgery and psychological robustness significantly predicted acute pain outcomes after surgery for breast cancer. Preoperative identification and targeted intervention of subgroups at risk could enhance the recovery trajectory in cancer survivors.

Brain activity modifications following spinal cord stimulation for chronic neuropathic pain:a systematic review

Background and objective: Spinal cord stimulation (SCS) is believed to exert supraspinal effects; however, these mechanisms are still far from fully elucidated. This systematic review aims to assess existing neurophysiological and functional neuroimaging literature to reveal current knowledge regarding the effects of SCS for chronic neuropathic pain on brain activity, to identify gaps in knowledge, and to suggest directions for future research. Databases and data treatment: Electronic databases and hand-search of reference lists were employed to identify publications investigating brain activity associated with SCS in patients with chronic neuropathic pain, using neurophysiological and functional neuroimaging techniques (fMRI, PET, MEG, EEG). Studies investigating patients with SCS for chronic neuropathic pain and studying brain activity related to SCS were included. Demographic data (age, gender), study factors (imaging modality, patient diagnoses, pain area, duration of SCS at recording, stimulus used) and brain areas activated were extracted from the included studies. Results: Twenty-four studies were included. Thirteen studies used neuroelectrical imaging techniques, eight studies used haemodynamic imaging techniques, two studies employed both neuroelectrical and haemodynamic techniques separately, and one study investigated cerebral neurobiology. Conclusions: The limited available evidence regarding supraspinal mechanisms of SCS does not allow us to develop any conclusive theories. However, the studies included appear to show an inhibitory effect of SCS on somatosensory evoked potentials, as well as identifying the thalamus and anterior cingulate cortex as potential mediators of the pain experience. The lack of substantial evidence in this area highlights the need for large-scale controlled studies of this kind.

Should topical opioid analgesics be regarded as effective and safe when applied to chronic cutaneous lesions?

Objectives: The induction of analgesia for many chronic cutaneous lesions requires treatment with an opioid analgesic. In many patients suffering with these wounds such drugs are either contraindicated or shunned because of their association with death. There are now case reports involving over 100 patients with many different types of chronic superficial wounds, which suggest that the topical application of an opioid in a suitable gel leads to a significant reduction in the level of perceived pain. Key findings: Some work has been undertaken to elucidate the mechanisms by which such a reduction is achieved. To date there have been no proven deleterious effects of such an analgesic system upon wound healing. Although morphine is not absorbed through the intact epidermis, an open wound provides no such barrier and for large wounds drug absorption can be problematic. However, for most chronic cutaneous lesions, where data has been gathered, the blood levels of the drug applied ranges from undetectable to below that required for a systemic effect. Summary If proven, the use of opioids in this way would provide adequate analgesia for a collection of wounds, which are difficult to treat in patients who are often vulnerable. Proof of this concept is now urgently required. © 2011 Royal Pharmaceutical Society.