The journal of pain : official journal of the American Pain Society
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Editorial
New proposals for the International Classification of Diseases-11 revision of pain diagnoses.
The representation of pain diagnoses in current classification systems like International Classification of Diseases (ICD)-10 and Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV does not adequately reflect the state of the art of pain research, and does not sufficiently support the clinical management and research programs for pain conditions. Moreover, there is an urgent need to harmonize classification of pain syndromes of special expert groups (eg, International Classification of Headache Disorders) and general classification systems (eg, ICD-11, DSM-V). Therefore, this paper summarizes new developments, and proposals for pain diagnoses in revised classification systems. A qualitative review of the literature concerning new proposals for classification of pain syndromes that are based on consensus groups was conducted. Selected proposals of national and international pain societies that are based on consensual processes are presented. These proposals can be condensed to be used in ICD-11 classification. The benefits of considering multidimensional and transdiagnostic processes for the classification process are also outlined. The manuscript provides options how to transform current pain-specific classification proposals to the revision of ICD-11. ⋯ Pain research and expertise must be more visible in the ICD-11 revision process. A general category for pain diagnoses as well as specific pain diagnoses under existing categories of organ-specific sections are needed.
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Timing of assessment of psychological construct is controversial and results differ based on the model of pain induction. Previous studies have not used an exercise-induced injury model to investigate timing of psychological assessment. Exercise-induced injury models may be appropriate for these investigations because they approximate clinical pain conditions better than other experimental stimuli. In this study we examined the changes of psychological constructs over time and determined whether timing of assessment affected the construct's association with reports of pain intensity and disability. One-hundred twenty-six healthy volunteers completed the Fear of Pain Questionnaire (FPQ-III), Pain Catastrophizing Scale (PCS), and Tampa Scale of Kinesiophobia (TSK) prior to inducing muscle injury to the shoulder. The PCS and TSK were measured again 48 and 96 hours postinjury induction. Pain intensity and disability were collected at 48 and 96 hours and served as dependent variables in separate regression models. Results indicated that the FPQ-III had the strongest prediction of pain intensity from baseline to 96 hours. After baseline the PCS and TSK were stronger predictors of pain intensity and disability, respectively. These data provide support for the use of psychological constructs in predicting outcomes from shoulder pain. However, they deviate from the current theoretical model indicating that fear of pain is a consequence of injury and instead suggests that fear of pain before injury may influence reports of pain intensity. ⋯ The current study provides evidence that fear of pain can be assessed prior to injury. Furthermore, it supports that after injury pain catastrophizing and kinesiophobia are independently associated with pain and disability. Overall these data suggest that timing of psychological assessment may be an important consideration in clinical environments.
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Comparative Study
Effective connectivity among brain regions associated with slow temporal summation of C-fiber-evoked pain in fibromyalgia patients and healthy controls.
Temporal summation of "second pain" (TSSP) or "windup" results from the summation of C-fiber-evoked responses of dorsal-horn neurons. This phenomenon is dependent on stimulus frequency (≥.33 Hz) and relevant to central sensitization and chronic pain. Our previous neuroimaging studies characterized brain regions associated with TSSP in normal control (NC) and fibromyalgia (FM) groups. During an fMRI scan, subjects received sensitivity-adjusted repetitive heat pulses at .33 on the right foot. FM subjects required significantly lower stimulus intensities than NC to achieve similar TSSP and no significant group differences in the pain-related brain activity were detected. In our current study, we asked whether the effective connectivity among a set of TSSP-related brain regions identified in our previous work differs amongst FM and NC groups. Structural equation modeling was used to characterize the effective connectivity amongst a priori selected brain areas, including the thalamus, S1, S2, posterior insula, and the anterior midcingulate cortex (aMCC) within the left and right hemispheres. This analysis confirmed our a priori models of effective connectivity among these regions mainly confirmed those hypothesized, yet some unpredicted connections were additionally identified (thalamus to aMCC and aMCC to S1). While the models of effective connectivity were not identical in the FM and NC groups, they were very similar. Additionally, the TSSP related effective connectivity of right and left hemisphere regions was very similar. These results provide evidence for significant overlap of the fundamental brain mechanisms that process sensory and affective information related to TSSP in NC and FM groups. ⋯ Models of effective connectivity involving pain-related processes were estimated with fMRI data from chronic pain and healthy populations. Models were estimated in both hemispheres, and although similar, fibromyalgia was associated with unique models of pain-related processes. Group differences involved the left hemisphere and S1, S2, and posterior insula.
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The amygdala contributes to generation of affective behaviors to threats. The prototypical threat to an individual is exposure to a noxious stimulus and the amygdaloid central nucleus (CeA) receives nociceptive input that is mediated by glutamatergic neurotransmission. The present study evaluated the contribution of glutamate receptors in CeA to generation of the affective response to acute pain in rats. Vocalizations that occur following a brief noxious tail shock (vocalization afterdischarges) are a validated rodent model of pain affect, and were preferentially suppressed by bilateral injection into CeA of the NMDA receptor antagonist D-2-amino-5-phosphonovalerate (AP5, 1 μg, 2 μg, or 4 μg) or the non-NMDA receptor antagonist 6-Cyano-7-nitroquinoxaline-2,3-dione disodium (CNQX, .25 μg, .5 μg, 1 μg, or 2 μg). Vocalizations that occur during tail shock were suppressed to a lesser degree, whereas spinal motor reflexes (tail flick and hind limb movements) were unaffected by injection of AP5 or CNQX into CeA. Unilateral administration of AP5 or CNQX into CeA of either hemisphere also selectively elevated vocalization thresholds. Bilateral administration of AP5 or CNQX produced greater increases in vocalization thresholds than the same doses of antagonists administered unilaterality into either hemisphere indicating synergistic hemispheric interactions. ⋯ The amygdala contributes to production of emotional responses to environmental threats. Blocking glutamate neurotransmission within the central nucleus of the amygdala suppressed rats' emotional response to acute painful stimulation. Understanding the neurobiology underlying emotional responses to pain will provide insights into new treatments for pain and its associated affective disorders.
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Randomized Controlled Trial Multicenter Study Comparative Study
Dose equivalence of immediate-release hydromorphone and once-daily osmotic-controlled extended-release hydromorphone: a randomized, double-blind trial incorporating a measure of assay sensitivity.
Dose selection of a once-daily, osmotic-controlled extended-release (ER) hydromorphone assumes that this drug and immediate-release (IR) hydromorphone are dose equivalent. This trial evaluated dose equivalence using a measure of assay sensitivity. Patients were converted to open-label IR hydromorphone, underwent dose titration, and those on a satisfactory dose entered a randomized, double-blind phase receiving 7 days of: 1) hydromorphone IR 5 times/day at approximately this dose; 2) once-daily hydromorphone ER at this dose; or 3) once-daily hydromorphone ER at one-half this dose. Efficacy was measured using breakthrough medication use, pain, sleep, and global assessments. Of 148 patients, 113 (76%) were randomized. IR and full-dose ER groups produced comparable effects on all measures. Although the prespecified primary analysis of the difference in total daily dose of breakthrough medication between the full-dose ER and half-dose ER groups was not significant, more patients in the half-dose ER group required an increase in breakthrough medication (P = .026) and the half-dose ER group both increased the number of breakthrough doses (P = .026) and had greater percent change in the total daily dose of breakthrough medication (P = .037) than the full-dose group, suggesting that switching from IR to ER hydromorphone at the same daily dose provides equivalent analgesia. ⋯ In a randomized, double-blind trial, the same total daily dose of immediate-release hydromorphone and once-daily osmotic-controlled extended-release hydromorphone had comparable effects. Detection of different effects between blinded dose levels was used as a measure of assay sensitivity. The measure of assay sensitivity can enhance the interpretation of dose equivalence or noninferiority trials.