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Objectives: Pain catastrophizing has been associated with higher pain intensity, increased risk of developing chronic pain and poorer outcomes after treatment. Despite this, the mechanisms by which pain catastrophizing influences pain remain poorly understood. It has been hypothesized that pain catastrophizing may impair descending inhibition of spinal level nociception. The aims of this study were to compare spinal nociceptive processing in people with chronic widespread pain and pain-free controls and examine potential relationships between measures of pain catastrophizing and spinal nociception., Materials and Methods: Twenty-six patients with chronic widespread pain and 22 pain-free individuals participated in this study. Spinal nociception was measured using the nociceptive flexion reflex (NFR) threshold and NFR inhibition, measured as the change in NFR area during exposure to a second, painful conditioning stimulus (cold water immersion). Pain catastrophizing was assessed using the Pain Catastrophizing Scale and a situational pain catastrophizing scale., Results: Compared with pain-free controls, patients with chronic widespread pain had higher pain catastrophizing scores and lower NFR thresholds. Although NFR area was reduced by a painful conditioning stimulus in controls, this was not apparent in individuals with chronic widespread pain. No significant correlations were observed between measures of pain catastrophizing and spinal nociception., Discussion: Despite increased excitability and decreased inhibition of spinal nociception in patients with chronic widespread pain, we could find no evidence of a significant relationship between pain catastrophizing and measures of spinal nociceptive processing.

Objectives: Previous studies have shown a tendency for reduced motor cortex inhibition in chronic pain populations. People with chronic pain also routinely demonstrate motor deficiencies, including skill learning. The goals of the current study were to (1) provide a thorough analysis of corticomotor and intracortical excitability in people with chronic arthritic hand pain, and (2) examine the relationship between these measures and performance on a motor skill learning task., Methods: Twenty-three people with arthritic hand pain and 20 pain-free controls participated in a cross-sectional study. Transcranial magnetic stimulation was used to assess corticomotor and intracortical excitability of the first dorsal interosseus muscle. Participants then completed a 30-minute motor skill training task involving the index finger of the same hand., Results: Hand arthritis participants showed evidence of reduced intracortical inhibition and enhanced facilitation, which correlated with duration of hand pain. Arthritis participants were initially poorer at the motor skill task but over the total training time performance was equivalent between groups. There were no associations found between measures of intracortical excitability and motor skill learning., Discussion: Our findings are the first to provide evidence of cortical disinhibition in people with painful arthritis, as previously demonstrated in other chronic pain populations. Cortical excitability changes may progress the longer pain persists, with increased pain duration being associated with greater cortical disinhibition. There was no evidence that these changes in cortical excitability are related to impaired motor function or skill learning.

Background: Chronic pain is characterised by maladaptive neuroplasticity in many systems, including the motor system. There is evidence that patients with chronic pain demonstrate altered corticospinal and intracortical excitability; however, findings are inconsistent and existing literature in this area has not been systematically reviewed., Objective: To systematically review studies examining corticospinal and intracortical excitability using transcranial magnetic stimulation in people with chronic pain compared to healthy controls and to provide a meta-analysis of study outcomes., Methods: Databases were searched for controlled studies evaluating corticospinal and intracortical excitability in chronic pain conditions. Outcome measure data were entered into separate meta-analyses and effect sizes calculated. A subgroup analysis based on the type of chronic pain population was also performed., Results: Forty-three studies were included, encompassing a pooled total of 1009 people with chronic pain and 658 control participants. Significant effect sizes (P < 0.05) indicated that in chronic pain populations the duration of the silent period and the extent of short-interval intracortical inhibition were both reduced and short-interval intracortical facilitation was enhanced. The subgroup analysis revealed that only the neuropathic pain group exhibited significant effect sizes for these outcome measures. Effect sizes for the remaining outcome measures were not significant, Conclusions: There is evidence of motor cortex disinhibition in chronic pain populations, suggestive of a disruption in GABA-mediated intracortical inhibition. Disinhibition was more pronounced in populations with neuropathic pain. These findings provide new insights into the relationship between chronic pain and motor cortex excitability, which may have meaningful implications for the future treatment of chronic pain conditions., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Unlabelled: A systematic literature review and meta-analysis were undertaken to determine if conditioned pain modulation is dysfunctional in populations with chronic pain. Studies that used a standardized protocol to evaluate conditioned pain modulation in a chronic pain population and in a healthy control population were selected and reviewed. Thirty studies were included in the final review, encompassing data from 778 patients and 664 control participants. Across all studies there was a large effect size of .78, reflecting reduced conditioned pain modulation in the patient group. Analysis of moderator variables indicated a significant influence of participant gender and age on the effect size. Methodological moderator variables of type of outcome measure, type of test stimulus, type of conditioning stimulus, and the level of conditioning stimulus pain were not significant. A risk of bias assessment indicated that poor blinding of assessors and a lack of control of confounding variables were common. It is concluded that conditioned pain modulation is impaired in populations with chronic pain. Future studies should ensure adequate matching of participant age and gender between patient and control groups, blinding of the assessors obtaining the outcome measures, and more rigorous control for variables known to influence the level of modulation., Perspective: This review compared the efficacy of conditioned pain modulation between chronic pain and healthy populations. The finding of impaired modulation in the chronic pain groups highlights the dysfunction of endogenous pain modulatory mechanisms in this population., (Copyright © 2012 American Pain Society. Published by Elsevier Inc. All rights reserved.)

Objective The development of persistent pain following total knee arthroplasty (TKA) is common, but its underlying mechanisms are unknown. The goal of the study was to assess brain grey matter structure and its correlation with function of the nociceptive system in people with good and poor outcomes following TKA. Subjects Thirty-one people with LOW_PAIN (<3/10 on the numerical ratings scale [NRS]) at six months following TKA and 15 people with HIGH_PAIN (≥3/10 on the NRS) were recruited into the study. Methods Grey matter in key brain areas related to nociception was analyzed using voxel-based morphometry (VBM). Nociceptive facilitatory and inhibitory processes were evaluated using quantitative sensory testing (QST). QST scores and grey matter density in prespecified brain regions were compared between the LOW_PAIN and HIGH_PAIN groups. Regression analyses were used to analyze the associations between the grey matter and QST scores. Results There were no between-group differences in QST measures. In the VBM analysis, the HIGH_PAIN group had a higher grey matter density in the right amygdala, right nucleus accumbens, and in the periaqueductal grey (PAG), but lower grey matter density in the dorsal part of the left caudate nucleus. Grey matter density in the right amygdala and PAG correlated positively with temporal summation of pain. Conclusions Persistent pain at six months after TKA is associated with a higher grey matter density in the regions involved in central sensitization and pain-related fear, which may contribute to the development of persistent pain after surgery. [ABSTRACT FROM AUTHOR]