Individual differences in pain sensitivity: measurement, causation, and consequences.
Nielsen CS, Staud R, Price DD
J Pain. 2009 Mar;10(3):231-7.
Not only are some clinical conditions experienced as more painful than others, but the variability in pain ratings of patients with the same disease or trauma is enormous. Available evidence indicates that to a large extent these differences reflect individual differences in pain sensitivity. Pain sensitivity can be estimated only through the use of well-controlled experimental pain stimuli. Such estimates show substantial heritability but equally important environmental effects. The genetic and environmental factors that influence pain sensitivity differ across pain modalities. For example, genetic factors that influence cold pressor pain have little impact on phasic heat pain and visa versa. Individual differences in pain sensitivity can complicate diagnosis, among other reasons because low sensitivity to pain may delay self-referral. Inclusion of patients with reduced pain sensitivity can attenuate treatment effects in clinical trials, unless controlled for. Measures of pain sensitivity are predictive of acute postoperative pain, and there is preliminary evidence that heightened pain sensitivity increases risk for future chronic pain conditions. At this time, however, it is unclear which experimental pain modalities should be used as predictors for future pain conditions. Careful assessment of each individual's pain sensitivity may become invaluable for the prevention, evaluation, and treatment of pain. PERSPECTIVE: Large individual differences in pain sensitivity can complicate diagnosis and pain treatment and can confound clinical trials. Pain sensitivity may also be of great importance for the development of clinical pain. Thus, assessment of pain sensitivity may be relevant for the prevention, evaluation, and treatment of acute and chronic pain.
Sex, Gender, and Pain: A Review of Recent Clinical and Experimental Findings
Fillingim RB, King CD, Ribeiro-Dasilva MC, et al.
J Pain. 2009 May; 10(5): 447–485.
Sex-related influences on pain and analgesia have become a topic of tremendous scientific and clinical interest, especially in the last 10 to 15 years. Members of our research group published reviews of this literature more than a decade ago, and the intervening time period has witnessed robust growth in research regarding sex, gender, and pain. Therefore, it seems timely to revisit this literature. Abundant evidence from recent epidemiologic studies clearly demonstrates that women are at substantially greater risk for many clinical pain conditions, and there is some suggestion that postoperative and procedural pain may be more severe among women than men. Consistent with our previous reviews, current human findings regarding sex differences in experimental pain indicate greater pain sensitivity among females compared with males for most pain modalities, including more recently implemented clinically relevant pain models such as temporal summation of pain and intramuscular injection of algesic substances. The evidence regarding sex differences in laboratory measures of endogenous pain modulation is mixed, as are findings from studies using functional brain imaging to ascertain sex differences in pain-related cerebral activation. Also inconsistent are findings regarding sex differences in responses to pharmacologic and non-pharmacologic pain treatments. The article concludes with a discussion of potential biopsychosocial mechanisms that may underlie sex differences in pain, and considerations for future research are discussed.
Assessment of Celiac Plexus Block and Neurolysis Outcomes and Technique in the Management of Refractory Visceral Cancer Pain.
Erdek MA, Halpert DE, Fernández MG, Cohen SP.
Pain Med. [Epub ahead of print]
Objective. To assess demographic and clinical factors associated with celiac plexus neurolysis outcomes. Design. Retrospective clinical data analysis. Setting. A tertiary care, academic medical center. Patients. Forty-four patients with terminal visceral (mostly pancreatic) cancer who failed conservative measures. Interventions. Fifty celiac plexus alcohol neurolytic procedures done for pain control after a positive diagnostic block. Outcome Measures. A successful treatment was predefined as >50% pain relief sustained for >/=1 month. The following variables were analyzed for their association with treatment outcome: age, gender, duration of pain, origin of tumor, opioid dose, type of radiological guidance used, single- vs double-needle approach, type of block (e.g., antero- vs retrocrural), immediate vs delayed neurolysis, volume of local anesthetic employed for both diagnostic and neurolytic blocks, and use of sedation. Results. Those variables correlated with a positive outcome included lower opioid dose and the absence of sedation. Strong trends for a positive association with outcome were found for the use of computed tomography (vs fluoroscopy), and using <20 mL of local anesthetic for the diagnostic block. Conclusions. Celiac plexus neurolysis may provide intermediate pain relief to a significant percentage of cancer sufferers. Both careful selection of candidates based on clinical variables, and technical factors aimed at enhancing the specificity of blocks may lead to improved outcomes.
Randomized controlled trial of an Internet-delivered family CBT intervention for children and adolescents with chronic pain
Palermo TM, Wilson AC, Peters M, et al.
Pain. 2009;146(1-2):205-13.
Cognitive-behavioral therapy (CBT) interventions show promise for decreasing chronic pain in youth. However, the availability of CBT is limited by many factors including distance to major treatment centers and expense. This study evaluates a more accessible treatment approach for chronic pediatric pain using an Internet-delivered family CBT intervention. Participants included 48 children, aged 11-17years, with chronic headache, abdominal, or musculoskeletal pain and associated functional disability, and their parents. Children were randomly assigned to a wait-list control group or an Internet treatment group. Primary treatment outcomes were pain intensity ratings (0-10 NRS) and activity limitations on the Child Activity Limitations Interview, both completed via an online daily diary. In addition to their medical care, the Internet treatment group completed 8weeks of online modules including relaxation training, cognitive strategies, parent operant techniques, communication strategies, and sleep and activity interventions. Youth randomized to the wait-list control group continued with the current medical care only. Findings demonstrated significantly greater reduction in activity limitations and pain intensity at post-treatment for the Internet treatment group and these effects were maintained at the three-month follow-up. Rate of clinically significant improvement in pain was also greater for the Internet treatment group than for the wait-list control group. There were no significant group differences in parental protectiveness or child depressive symptoms post-treatment. Internet treatment was rated as acceptable by all children and parents. Findings support the efficacy and acceptability of Internet delivery of family CBT for reducing pain and improving function among children and adolescents with chronic pain.
A Pilot Study Investigating the Effects of Fast Left Prefrontal rTMS on Chronic Neuropathic Pain
Borckardt JJ, Smith AR, Reeves ST, et al.
Pain Med. 2009;10(5):840-9.
ABSTRACT Objective. Stimulating the human cortex using transcranial magnetic stimulation (TMS) temporarily reduces clinical and experimental pain; however, it is unclear which cortical targets are the most effective. The motor cortex has been a popular target for managing neuropathic pain, while the prefrontal cortex has been investigated for an array of nociceptive pain conditions. It is unclear whether the motor cortex is the only effective cortical target for managing neuropathic pain, and no published studies to date have investigated the effects of prefrontal stimulation on neuropathic pain. Design. This preliminary pilot trial employed a sham-controlled, within-subject, crossover design to evaluate clinical pain as well as laboratory pain thresholds among four patients with chronic neuropathic pain. Each participant underwent three real and three sham 20-minute sessions of 10 Hz left prefrontal repetitive TMS. Daily pain diaries were collected for 3 weeks before and after each treatment phase along with a battery of self-report pain and mood questionnaires. Results. Time-series analysis at the individual patient level indicated that real TMS was associated with significant improvements in average daily pain in 3 of the 4 participants. These effects were independent of changes in mood in two of the participants. At the group level, a decrease of 19% in daily pain on average, pain at its worst, and pain at its least was observed while controlling for changes in mood, activity level and sleep. The effects of real TMS were significantly greater than sham. Real TMS was associated with increases in thermal and mechanical pain thresholds, whereas sham was not. No statistically significant effects were observed across the questionnaire data. Conclusions. The prefrontal cortex may be an important TMS cortical target for managing certain types of pain, including certain neuropathic pain syndromes.
A non-surgical approach to the management of lumbar spinal stenosis: Prospective observational cohort study with follow-up.
Murphy DR, Hurwitz EL, McGovern EE.
J Manipulative Physiol Ther. 2009;32(9):723-733.
OBJECTIVE: This study presents the outcomes of patients with lumbar radiculopathy secondary to disk herniation treated after a diagnosis-based clinical decision rule. METHODS: A prospective observational cohort study was conducted at a multidisciplinary, integrated clinic that includes chiropractic and physical therapy health care services. Data on 49 consecutive patients were collected at baseline, at the end of conservative, nonsurgical treatment and a mean of 14.5 months after cessation of treatment. Disability was measured using the Bournemouth Disability Questionnaire (BDQ) and pain using the Numerical Rating Scale for pain. Fear beliefs were measured with the Fear-Avoidance Beliefs Questionnaire (FABQ). Patients also self-rated improvement. RESULTS: Mean duration of complaint was 60.5 weeks. Mean self-rated improvement at the end of treatment was 77.5%. Improvement was described as "good" or "excellent" in nearly 90% of patients. Mean percentage improvement on the BDQ was 60.4%. Numerical Rating Scale improved 4.1 points and FABQ improved 4.8 points. Clinically meaningful improvements in pain and disability were seen in 79% and 70% of patients, respectively. Mean number of visits was 13.2. After an average long-term follow-up of 14.5 months, mean self-rated improvement was 81.1%. "Good" or "excellent" improvement was reported by 80% of patients. Mean percentage improvement in BDQ was 67.4%. Numerical Rating Scale improved 4.2 points and FABQ 4.5 points. Clinically meaningful improvements in pain and disability were seen in 79% and 73% of patients, respectively. CONCLUSIONS: Management based on the decision rule yielded favorable outcomes in this cohort study. Improvement appeared to be maintained over the long term.
Evaluation of the Effectiveness and Efficacy of Iyengar Yoga Therapy on Chronic Low Back Pain.
Williams K, Abildso C, Steinberg L, et al.
Spine (Phila Pa 1976). 2009 Aug 21.
STUDY DESIGN.: The effectiveness and efficacy of Iyengar yoga for chronic low back pain (CLBP) were assessed with intention-to-treat and per-protocol analysis. Ninety subjects were randomized to a yoga (n = 43) or control group (n = 47) receiving standard medical care. Participants were followed 6 months after completion of the intervention.
OBJECTIVE.: This study aimed to evaluate Iyengar yoga therapy on chronic low back pain. Yoga subjects were hypothesized to report greater reductions in functional disability, pain intensity, depression, and pain medication usage than controls.
SUMMARY OF BACKGROUND DATA.: CLBP is a musculoskeletal disorder with public health and economic impact. Pilot studies of yoga and back pain have reported significant changes in clinically important outcomes. METHODS.: Subjects were recruited through self-referral and health professional referrals according to explicit inclusion/exclusion criteria. Yoga subjects participated in 24 weeks of biweekly yoga classes designed for CLBP. Outcomes were assessed at 12 (midway), 24 (immediately after), and 48 weeks (6-month follow-up) after the start of the intervention using the Oswestry Disability Questionnaire, a Visual Analog Scale, the Beck Depression Inventory, and a pain medication-usage questionnaire.
RESULTS.: Using intention-to-treat analysis with repeated measures ANOVA (group x time), significantly greater reductions in functional disability and pain intensity were observed in the yoga group when compared to the control group at 24 weeks. A significantly greater proportion of yoga subjects also reported clinical improvements at both 12 and 24 weeks. In addition, depression was significantly lower in yoga subjects. Furthermore, while a reduction in pain medication occurred, this was comparable in both groups. When results were analyzed using per-protocol analysis, improvements were observed for all outcomes in the yoga group, including a greater trend for reduced pain medication usage. Although slightly less than at 24 weeks, the yoga group had statistically significant reductions in functional disability, pain intensity, and depression compared to standard medical care 6-months postintervention.
CONCLUSION.: Yoga improves functional disability, pain intensity, and depression in adults with CLBP. There was also a clinically important trend for the yoga group to reduce their pain medication usage compared to the control group.
Racial and ethnic disparities in pain: causes and consequences of unequal care.
Anderson KO, Green CR, Payne R.
J Pain. 2009;10(12):1187-204.
The purpose of our review is to evaluate critically the recent literature on racial and ethnic disparities in pain and to determine how far we have come toward reducing and eliminating disparities in pain. We examined peer-reviewed research articles published between 1990 and early 2009 that focused on racial and ethnic disparities in pain in the United States. The databases used were PubMed, Medline, Scopus, CINAHL, and PsycInfo. The probable causes of minority group disparities in pain are discussed, along with suggested strategies for eliminating pain-related disparities. This review reveals the persistence of racial and ethnic disparities in acute, chronic, cancer, and palliative pain care across the lifespan and treatment settings, with minorities receiving lesser quality pain care than non-Hispanic whites. Although health and health care disparities attract local, state, and federal attention, disparities in pain care continue to be missing from publicized public health agendas and health care reform plans. Ensuring optimal pain care for all is critically important from a public health and policy perspective. A robust research program on disparities in pain is needed, and the results must be successfully translated into practices and policies specifically designed to reduce and eliminate disparities in care. PERSPECTIVE: This review evaluates the recent literature on racial and ethnic disparities in pain and pain treatment. Racial and ethnic disparities in acute pain, chronic cancer pain, and palliative pain care continue to persist. Rigorous research is needed to develop interventions, practices, and policies for eliminating disparities in pain.
A clinical trial of gene therapy for chronic pain.
Wolfe D, Wechuck J, Krisky D, Mata M, Fink DJ.
Pain Med. 2009 Oct;10(7):1325-30.
The first human trial of gene therapy for chronic pain, a phase 1 study of a nonreplicating herpes simplex virus (HSV)-based vector engineered to express preproenkephalin in patients with intractable pain from cancer, began enrolling subjects in December 2008. In this article, we describe the rationale underlying this potential approach to treatment of pain, the preclinical animal data in support of this approach, the design of the study, and studies with additional HSV-based vectors that may be used to develop treatment for other types of pain.
Do Pain Patients at High Risk for Substance Misuse Experience More Pain?: A Longitudinal Outcomes Study.
Jamison RN, Link CL, Marceau LD.
Pain Med. 2009;10(6):1084-94.
ABSTRACT Objectives. The Screener and Opioid Assessment of Pain Patients (SOAPP v.1) has been shown to be a reliable measure of risk potential for substance misuse and to correlate with a history of substance abuse, legal problems, craving, smoking, and mood disorders among chronic pain patients. The aim of this study was to examine differences over time on a number of measures among chronic pain patients who were classified as high or low risk for opioid misuse based on scores on the SOAPP.
Methods. From an initial sample of one hundred thirty-four participants (N = 134), one hundred and ten (N = 110) completed the SOAPP and were grouped as high or low risk for misuse of medication based on SOAPP scores of >/=7. All subjects were asked to complete baseline measures and in-clinic monthly diaries of their pain, mood, activity interference, medication, and side effects over a 10-month study period.
Results. The results showed that although those who were classified as high-risk for opioid misuse reported significantly higher levels of pain intensity, activity interference, pain catastrophizing, disability, and depressed mood at baseline (P < 0.05), only pain intensity ratings were found to differentiate groups over time (P < 0.01). These results were unrelated to perceived helpfulness of pain treatment.
Conclusions. Differences in subjective pain intensity were found between those who are high risk for opioid misuse compared with those at low risk for medication misuse, implying that higher-risk patients may experience more subjective pain. Consequently, these patients may be more challenging to treat.
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