Role of endogenous pain modulation in chronic pain mechanisms and treatment

Psychological mechanisms of offset analgesia: The effect of expectancy manipulation

A frequently used paradigm to quantify endogenous pain modulation is offset analgesia, which is defined as a disproportionate large reduction in pain following a small decrease in a heat stimulus. The aim of this study was to determine whether suggestion influences the magnitude of offset analgesia in healthy participants. A total of 97 participants were randomized into three groups (hypoalgesic group, hyperalgesic group, control group). All participants received four heat stimuli (two constant trials and two offset trials) to the ventral, non-dominant forearm while they were asked to rate their perceived pain using a computerized visual analogue scale. In addition, electrodermal activity was measured during each heat stimulus. Participants in both intervention groups were given a visual and verbal suggestion about the expected pain response in an hypoalgesic and hyperalgesic manner. The control group received no suggestion. In all groups, significant offset analgesia was provoked, indicated by reduced pain ratings (p < 0.001) and enhanced electrodermal activity level (p < 0.01). A significant group difference in the magnitude of offset analgesia was found between the three groups (F[2,94] = 4.81, p < 0.05). Participants in the hyperalgesic group perceived significantly more pain than the hypoalgesic group (p = 0.031) and the control group (p < 0.05). However, the electrodermal activity data did not replicate this trend (p > 0.05). The results of this study indicate that suggestion can be effective to reduce but not increase endogenous pain modulation quantified by offset analgesia in healthy participants.

Central Sensitization and Psychological State Distinguishing Complex Regional Pain Syndrome from Other Chronic Limb Pain Conditions: A Cluster Analysis Model

Complex regional pain syndrome (CRPS) taxonomy has been updated with reported subtypes and is defined as primary pain alongside other chronic limb pain (CLP) conditions. We aimed at identifying CRPS clinical phenotypes that distinguish CRPS from other CLP conditions. Cluster analysis was carried out to classify 61 chronic CRPS and 31 CLP patients based on evoked pain (intensity of hyperalgesia and dynamic allodynia, allodynia area, and after-sensation) and psychological (depression, kinesiophobia, mental distress, and depersonalization) measures. Pro-inflammatory cytokine IL-6 and TNF-α serum levels were measured. Three cluster groups were created: ‘CRPS’ (78.7% CRPS; 6.5% CLP); ‘CLP’ (64.5% CLP; 4.9% CRPS), and ‘Mixed’ (16.4% CRPS; 29% CLP). The groups differed in all measures, predominantly in allodynia and hyperalgesia (p < 0.001, η² > 0.58). ‘CRPS’ demonstrated higher psychological and evoked pain measures vs. ‘CLP’. ‘Mixed’ exhibited similarities to ‘CRPS’ in psychological profile and to ‘CLP’ in evoked pain measures. The serum level of TNF-αwas higher in the ‘CRPS’ vs. ‘CLP’ (p < 0.001) groups. In conclusion, pain hypersensitivity reflecting nociplastic pain mechanisms and psychological state measures created different clinical phenotypes of CRPS and possible CRPS subtypes, which distinguishes them from other CLP conditions, with the pro-inflammatory TNF-α cytokine as an additional potential biomarker.

Inter-subject variability of pleasant pain relief using a data-driven approach in healthy volunteers

Background

The offset of a painful and unpleasant sensation can elicit pleasure. This phenomenon, namely pleasant pain relief (PPR), is attracting growing interest in research. While the cold pressor test (CPT) has been frequently used to study the inhibition of pain by the administration of another painful stimulation (inhibitory conditioned pain modulation; ICPM), a preliminary study from our research team has shown that CPT can also elicit a robust and long-lasting PPR. However, its effects on pain relief and inhibition vary greatly between subjects. Although substantial research has been carried out on inter-individual variability in the case of ICPM, the same cannot be said of PPR. Therefore, the current study sought to identify clusters of healthy volunteers with similar dynamic pain responses during the CPT, using a data-driven approach, and to investigate the inter-subject variability for PPR and ICPM.

Methods

One hundred and twenty-two healthy volunteers were recruited. A sequential ICPM paradigm was carried out with CPT (water at 10°C) and a Peltier Thermode to evaluate pain intensity and unpleasantness. Moreover, PPR was measured for four minutes at CPT offset. Statistical analyses were performed using group-based trajectory modelling.

Results

Four trajectories (groups) were identified for CPT pain intensity and unpleasantness ratings with varying levels of tonic pain and pain sensitization (e.g., temporal summation). PPR scores were correlated with both pain ratings trajectories (p &lt; 0.001). On the other hand, no differences were found between groups regarding ICPM efficacy (percentage pain inhibition).

Discussion

This study has provided a first step into the investigation of PPR and ICPM interindividual variability. Using a data-driven approach, it was shown that PPR at CPT offset differs between clusters of participants identified based on dynamic pain intensity and unpleasantness responses from CPT. Thus, it was brought to light that both the levels of tonic pain and pain sensitization underlie individual differences in PPR. The lack of correlation between CPT pain trajectories and ICPM efficacy may be explained by the hypotheses that eliciting ICPM requires only a certain threshold of stimulation which doesn’t need to be noxious. In the future, studies on the inter-subject variability of PPR in large samples of chronic pain patients are warranted.

Clusters of facilitatory and inhibitory conditioned pain modulation responses in a large sample of children, adolescents, and young adults with chronic pain

Supplemental Digital Content is Available in the Text.

Findings from the current study add to the literature by describing different clinical phenotypes of central pain mechanisms of youth with chronic pain.

Introduction:

When investigating the role of facilitatory and inhibitory pain mechanisms such as conditioned pain modulation (CPM) and temporal summation of pain (TSP), it is important to take both into consideration in a single experimental model to provide the most information on subgroups of patients. Therefore, the objective of this study was to identify subgroups in a large population of pediatric patients with chronic pain based on their facilitatory and inhibitory pain mechanisms and compare them with control subjects.

Methods:

Five hundred twenty-one female subjects and 147 male subjects between 8 and 21 years old underwent a CPM assessment using a 2-minute tonic noxious heat stimulation as the test stimulus and a 2-minute cold-pressor task (CPT) (12°C) as the conditioning stimulus.

Results:

The best partition of clusters of patients was 3 clusters accounting for 27.15% of the total variation in the data. Cluster 1 (n = 271) was best characterized by high pain intensity during the CPT, lack of TSP during the test stimuli, and efficient inhibitory CPM. Cluster 2 (n = 186) was best characterized by low pain intensity during the CPT, lack of TSP during the test stimuli, and efficient inhibitory CPM. Cluster 3 (n = 151) was best characterized by high pain intensity during the CPT, presence of TSP during the test stimuli, and inefficient inhibitory CPM.

Discussion:

A single thermal CPM experimental design can identify combinations of facilitatory and inhibitory pain modulation responses. Findings from the current study add to the literature by describing different clinical phenotypes of central pain mechanisms of youth with chronic pain.

Mechanism-Based Pharmacological Treatment for Chronic Non-cancer Pain in Adolescents: Current Approaches and Future Directions

Chronic non-cancer pain in pediatrics is a widespread phenomenon that affects about 20% of adolescents (10-19 years old). Although interdisciplinary pain treatment programs, which often include pharmacological treatment, have emerged as the standard of care in management of this patient population, evidence regarding an optimal treatment is lacking. The efficacy and safety profiles of pharmacological treatments used to help adolescents suffering from chronic non-cancer pain remain understudied. This lack of evidence may increase polypharmacy and the risk of drug interactions and adverse events. This review examines evidence for the use of pharmacological treatments prescribed to treat chronic pain in adolescents (10-19 years old), with a focus on mechanism-based pharmacology. The objectives of this review are to: (a) review the evidence for mechanism-based pharmacological treatments for chronic non-cancer pain in adolescents and (b) describe the pharmacological agents that are commonly prescribed to manage chronic pain in adolescents, including dosage information, mechanism, and potential adverse effects. Pharmacological treatments should be used carefully with adolescents, ideally within an interdisciplinary treatment program that will incorporate physical rehabilitation, integrative medicine/active mind-body techniques, psychology, and global efforts to normalize daily activities.

Anti- and Pro-Nociceptive mechanisms in neuropathic pain after human spinal cord injury

BACKGROUND

Deficient endogenous pain modulation and increased nociceptive excitability are key features of central sensitization and can be assessed in humans by conditioned pain modulation (CPM, anti-nociceptive) and temporal summation of pain (TSP, pro-nociceptive), respectively. This study aimed to investigate these measures as proxies for central sensitization in subjects with chronic neuropathic pain (NP) after spinal cord injury (SCI).

METHODS

In paraplegic subjects with NP (SCI-NP; n = 17) and healthy controls (HC; n = 17), parallel and sequential sham-controlled CPM paradigms were performed using pressure pain threshold at the hand, that is, above lesion level, as test stimulus. The conditioning stimulus was a noxious cold (verum) or lukewarm water bath (sham) applied contralaterally. Regarding pro-nociceptive mechanisms, a TSP protocol with individually-adjusted pressure pain stimuli at the thenar eminence was used. CPM and TSP magnitudes were related to intensity and spatial extent of spontaneous NP.

RESULTS

Neither the parallel nor sequential sham-controlled CPM paradigm showed any significant inhibition of above-level pressure pain thresholds for SCI-NP or HC. Accordingly, no group difference in CPM capacity was found, however, subjects with more intense spontaneous NP showed lower inhibitory CPM capacity. TSP was observed for both groups but was not enhanced in SCI-NP.

CONCLUSIONS

Our results do not support altered above-level anti- or pro-nociceptive mechanisms in SCI-NP compared with HC; however, they also highlight the relevance of spontaneous NP intensity with regards to the capacity of endogenous pain modulation in SCI subjects.

SIGNIFICANCE

Central sensitization encompasses deficient endogenous pain modulation and increased nociceptive excitability. These two mechanisms can be assessed in humans by conditioned pain modulation and temporal summation of pain, respectively. Our data demonstrates a lack of descending pain inhibition only in subjects with severe neuropathic pain which may hint towards central sensitization at spinal and/or supra-spinal levels. Disentangling the mechanisms of endogenous pain modulation and neuronal hyperexcitability might improve mechanism-based treatment of neuropathic pain in subjects with spinal cord injury.

Monoamine control of descending pain modulation after mild traumatic brain injury

Traumatic brain injury (TBI) is a significant public health concern, with the majority of injuries being mild. Many TBI victims experience chronic pain. Unfortunately, the mechanisms underlying pain after TBI are poorly understood. Here we examined the contribution of spinal monoamine signaling to dysfunctional descending pain modulation after TBI. For these studies we used a well-characterized concussive model of mild TBI. Measurements included mechanical allodynia, the efficacy of diffuse noxious inhibitory control (DNIC) endogenous pain control pathways and lumber norepinephrine and serotonin levels. We observed that DNIC is strongly reduced in both male and female mice after mild TBI for at least 12 weeks. In naïve mice, DNIC was mediated through α2 adrenoceptors, but sensitivity to α2 adrenoceptor agonists was reduced after TBI, and reboxetine failed to restore DNIC in these mice. The intrathecal injection of ondansetron showed that loss of DNIC was not due to excess serotonergic signaling through 5-HT₃ receptors. On the other hand, the serotonin-norepinephrine reuptake inhibitor, duloxetine and the serotonin selective reuptake inhibitor escitalopram both effectively restored DNIC after TBI in both male and female mice. Therefore, enhancing serotonergic signaling as opposed to noradrenergic signaling alone may be an effective pain treatment strategy after TBI.

The analgesic power of pleasant touch in individuals with chronic pain: Recent findings and new insights

This mini-review covers recent works on the study of pleasant touch in patients with chronic pain (CP) and its potential use as a treatment. While experiments have demonstrated that pleasant touch, through the activation of CT-afferents and the brain regions involved in its affective value, might reduce the unpleasantness and intensity of induced pain, the interaction between pleasant touch and CP remains under-examined. Some experiments show that CP might disrupt the positive aspects of receiving pleasant touch, while in other studies the perception of pleasantness is preserved. Moreover, only a few attempts have been made to test whether touch can have a modulatory effect on CP, but these results also remain inconclusive. Indeed, while one recent study demonstrated that CT-touch can diminish CP after a short stimulation, another study suggested that pleasant touch might not be sufficient. Future studies should further investigate the psychological and neural interplay between pleasant touch and CP. In the conclusion of this mini-review, we propose a new tool we have recently developed using immersive virtual reality (IVR).

Frozen shoulder

Frozen shoulder is a common debilitating disorder characterized by shoulder pain and progressive loss of shoulder movement. Frozen shoulder is frequently associated with other systemic conditions or occurs following periods of immobilization, and has a protracted clinical course, which can be frustrating for patients as well as health-care professionals. Frozen shoulder is characterized by fibroproliferative tissue fibrosis, whereby fibroblasts, producing predominantly type I and type III collagen, transform into myofibroblasts (a smooth muscle phenotype), which is accompanied by inflammation, neoangiogenesis and neoinnervation, resulting in shoulder capsular fibrotic contractures and the associated clinical stiffness. Diagnosis is heavily based on physical examination and can be difficult depending on the stage of disease or if concomitant shoulder pathology is present. Management consists of physiotherapy, therapeutic modalities such as steroid injections, anti-inflammatory medications, hydrodilation and surgical interventions; however, their effectiveness remains unclear. Facilitating translational science should aid in development of novel therapies to improve outcomes among individuals with this debilitating condition.

Effects of psychosocial stress and performance feedback on pain processing and its correlation with subjective and neuroendocrine parameters

OBJECTIVES

Previous research on stress-induced pain modulation suggests that moderate psychological stress usually leads to hyperalgesia while more severe threat results in hypoalgesia. However, existing studies often lack suitable control conditions imperative to identify mere stress effects. Similarly, research mainly focused on pure anticipation of a social threat, not taking into consideration actual experiences of social evaluation. Therefore, we set out to investigate actual social up- and downgrading combined with a standardized stress paradigm to evaluate short-term and prolonged changes in pain perception and their potential association with neuroendocrine and subjective stress parameters.

METHODS

We allocated 177 healthy women to four experimental conditions, either the standard version of the Trier Social Stress Test (TSST) followed by positive, negative or no performance feedback, or a well-matched but less demanding placebo version of the TSST. Stress responses were assessed with ratings, salivary alpha-amylase, and salivary cortisol. To capture putative effects of stress on pain, heat pain threshold, ratings of phasic heat pain stimuli, and conditioned pain modulation were measured.

RESULTS

Despite a largely successful stress induction, results do not support a reliable influence of experimentally induced social stress-with or without subsequent performance feedback-on pain in women. Further, we found no clear association of pain modulation and changes in neuroendocrine or subjective stress responses.

CONCLUSIONS

Our results contrast previous studies, which repeatedly demonstrated stress-induced hypo- or hyperalgesia. This might be due to methodological reasons as former research was often characterized by high heterogeneity regarding the applied stressors, low sample sizes, and lacking or inconclusive control conditions. Thus, our results raise the question whether pain modulation in women by experimental psychosocial stress might have been overestimated in the past. Future research is necessary, which should employ parametric stress induction methods including well-matched control tasks, taking into consideration the participants' gender/sex and the time course of the stress response relative to pain assessment. The study is registered as DRKS00026946 at 'Deutsches Register Klinischer Studien' (DRKS) and can be also found at the World Health Organization's search portal.

Association between the Use of Quantitative Sensory Testing and Conditioned Pain Modulation and the Prescription of Medication and Interventional Procedures in Children with Chronic Pain Conditions

The evidence supporting the use of pharmacological treatments in pediatric chronic pain is limited. Quantitative sensory testing (QST) and conditioned pain modulation evaluation (CPM) provide information on pain phenotype, which may help clinicians to tailor the treatment. This retrospective study aimed to evaluate the association between the use of QST/CPM phenotyping on the selection of the treatment for children with chronic pain conditions. We retrospectively analyzed the medical records of 208 female patients (mean age 15 ± 2 years) enrolled in an outpatient interdisciplinary pediatric complex pain center. Pain phenotype information (QST/CPM) of 106 patients was available to the prescribing physician. The records of 102 age- and sex-matched patients without QST/CPM were used as controls. The primary endpoint was the proportion of medications and interventions prescribed. The secondary endpoint was the duration of treatment. The QST/CPM group received less opioids (7% vs. 28%, respectively, p < 0.001), less anticonvulsants (6% vs. 25%, p < 0.001), and less interventional treatments (29% vs. 44%, p = 0.03) than controls. Patients with an optimal CPM result tended to be prescribed fewer antidepressants (2% vs. 18%, p = 0.01), and patients with signs of allodynia and/or temporal summation tended to be prescribed fewer NSAIDs (57% vs. 78%, p = 0.04). There was no difference in the duration of the treatments between the groups. QST/CPM testing appears to provide more targeted therapeutic options resulting in the overall drop in polypharmacy and reduced use of interventional treatments while remaining at least as effective as the standard of care.

Switch of serotonergic descending inhibition into facilitation by a spinal chloride imbalance in neuropathic pain

Descending control from the brain to the spinal cord shapes our pain experience, ranging from powerful analgesia to extreme sensitivity. Increasing evidence from both preclinical and clinical studies points to an imbalance toward descending facilitation as a substrate of pathological pain, but the underlying mechanisms remain unknown. We used an optogenetic approach to manipulate serotonin (5-HT) neurons of the nucleus raphe magnus that project to the dorsal horn of the spinal cord. We found that 5-HT neurons exert an analgesic action in naïve mice that becomes proalgesic in an experimental model of neuropathic pain. We show that spinal KCC2 hypofunction turns this descending inhibitory control into paradoxical facilitation; KCC2 enhancers restored 5-HT-mediated descending inhibition and analgesia. Last, combining selective serotonin reuptake inhibitors (SSRIs) with a KCC2 enhancer yields effective analgesia against nerve injury-induced pain hypersensitivity. This uncovers a previously unidentified therapeutic path for SSRIs against neuropathic pain.

AMAZONE: prevention of persistent pain after breast cancer treatment by online cognitive behavioral therapy-study protocol of a randomized controlled multicenter trial

Background

Surviving breast cancer does not necessarily mean complete recovery to a premorbid state of health. Among the multiple psychological and somatic symptoms that reduce the quality of life of breast cancer survivors, persistent pain after breast cancer treatment (PPBCT) with a prevalence of 15–65% is probably the most invalidating. Once chronic, PPBCT is difficult to treat and requires an individualized multidisciplinary approach. In the past decades, several somatic and psychological risk factors for PPBCT have been identified. Studies aiming to prevent PPBCT by reducing perioperative pain intensity have not yet shown a significant reduction of PPBCT prevalence. Only few studies have been performed to modify psychological distress around breast cancer surgery. The AMAZONE study aims to investigate the effect of online cognitive behavioral therapy (e-CBT) on the prevalence of PPBCT.

Methods

The AMAZONE study is a multicenter randomized controlled trial, with an additional control arm. Patients (n=138) scheduled for unilateral breast cancer surgery scoring high for surgical or cancer-related fears, general anxiety or pain catastrophizing are randomized to receive either five sessions of e-CBT or online education consisting of information about surgery and a healthy lifestyle (EDU). The first session is scheduled before surgery. In addition to the online sessions, patients have three online appointments with a psychotherapist. Patients with low anxiety or catastrophizing scores (n=322) receive treatment as usual (TAU, additional control arm).

Primary endpoint is PPBCT prevalence 6 months after surgery.

Secondary endpoints are PPBCT intensity, the intensity of acute postoperative pain during the first week after surgery, cessation of postoperative opioid use, PPBCT prevalence at 12 months, pain interference, the sensitivity of the nociceptive and non-nociceptive somatosensory system as measured by quantitative sensory testing (QST), the efficiency of endogenous pain modulation assessed by conditioned pain modulation (CPM) and quality of life, anxiety, depression, catastrophizing, and fear of recurrence until 12 months post-surgery.

Discussion

With perioperative e-CBT targeting preoperative anxiety and pain catastrophizing, we expect to reduce the prevalence and intensity of PPBCT. By means of QST and CPM, we aim to unravel underlying pathophysiological mechanisms. The online application facilitates accessibility and feasibility in a for breast cancer patients emotionally and physically burdened time period.

Trial registration

NTR NL9132, registered December 16 2020.

Virtual Reality and the Mediation of Acute and Chronic Pain in Adult and Pediatric Populations: Research Developments

The use of virtual reality (VR) in the mediation of acute pain in adults has shown real benefit to patients for the past 20 years. This review of the literature provides a descriptive synthesis of the types of VR technology, the mechanisms by which VR mediates pain, and a history of early research in the area. A review of the use of VR to mediate chronic pain in adults, and both acute and chronic pain in pediatric populations follows. The studies reviewed provide mixed results and it is noted that many studies have small sample sizes, are case studies, and do not control for extraneous variables such as the dosage and type of VR technology used. Although VR is an exciting area of inquiry that promises to yield multiple applications, there is a necessity to conduct larger random controlled trials to better understand the use cases for which VR is most effective.

Conditioned pain modulation is more efficient in patients with painful diabetic polyneuropathy than those with nonpainful diabetic polyneuropathy

ABSTRACT

Endogenous pain modulation, as tested by the conditioned pain modulation (CPM) protocol, is typically less efficient in patients with chronic pain compared with healthy controls. We aimed to assess whether CPM is less efficient in patients with painful diabetic polyneuropathy (DPN) compared with those with nonpainful DPN. Characterization of the differences in central pain processing between these 2 groups might provide a central nervous system explanation to the presence or absence of pain in diabetic neuropathy in addition to the peripheral one. Two hundred seventy-one patients with DPN underwent CPM testing and clinical assessment, including quantitative sensory testing. Two modalities of the test stimuli (heat and pressure) conditioned to cold noxious water were assessed and compared between patients with painful and nonpainful DPN. No significant difference was found between the groups for pressure pain CPM; however, patients with painful DPN demonstrated unexpectedly more efficient CPMHEAT (-7.4 ± 1.0 vs -2.3 ± 1.6; P = 0.008). Efficient CPMHEAT was associated with higher clinical pain experienced in the 24 hours before testing (r = -0.15; P = 0.029) and greater loss of mechanical sensation (r = -0.135; P = 0.042). Moreover, patients who had mechanical hypoesthesia demonstrated more efficient CPMHEAT (P = 0.005). More efficient CPM among patients with painful DPN might result from not only central changes in pain modulation but also from altered sensory messages coming from tested affected body sites. This calls for the use of intact sites for proper assessment of pain modulation in patients with neuropathy.

Family History of Alcohol Use Disorder as a Predictor of Endogenous Pain Modulation Among Moderate to Heavy Drinkers

Family history of alcohol use disorder (AUD) is frequently endorsed by persons with chronic pain. Although individuals with a family history of AUD have demonstrated enhanced sensitivity to painful stimulation, previous research has not examined endogenous pain modulation in this population. The goal of this study was to test family history of AUD as a predictor of conditioned pain modulation, offset analgesia, and temporal summation among a sample of moderate and heavy drinkers. Adults with no current pain (N = 235; 58.3% male; M_age = 34.3; 91.9% non-Hispanic; 60% white) were evaluated for family history of AUD at baseline and pain modulatory outcomes were assessed via quantitative sensory testing. Participants with a family history of AUD (relative to those without) evinced a pro-nociceptive pain modulation profile in response to experimental pain. Specifically, family history of AUD was associated with deficits in pain-inhibitory processes. Approximately 4% of the variance in endogenous pain modulation was accounted for by family history, and exploratory analyses suggested these effects may be driven by paternal AUD. PERSPECTIVE: The current findings suggest individuals with a family history of AUD demonstrate pain modulatory function that may predispose them to the development of chronic pain. Clinically, these data may inform pain management approaches for individuals with a family history of AUD.

Outcomes of a controlled trial with visiting therapy dog teams on pain in adults in an emergency department

CONTEXT

Pain is a primary reason individuals attend an Emergency Department (ED), and its management is a concern.

OBJECTIVES

Change in symptoms and physiologic variables at 3 time points pre-post a ten-minute St. John Ambulance therapy dog team visit compared to no visit in ED patients who experienced pain.

DESIGN, SETTING AND PARTICIPANTS

Using a controlled clinical trial design, pain, anxiety, depression and well-being were measured with the Edmonton Symptom Assessment System (revised version) (ESAS-r) 11-point rating scales before, immediately after, and 20 minutes post- therapy dog team visit with Royal University Hospital ED patients participating in the study (n = 97). Blood pressure and heart rate were recorded at the time points. Control data was gathered twice (30 minutes apart) for comparison (n = 101). There were no group differences in age, gender or ethnicity among the control and intervention groups (respectively mean age 59.5/57.2, ethnicity 77.2% Caucasian/87.6%, female 43.6% /39.2%, male 56.4%/60.8%,).

INTERVENTION

10 minute therapy dog team visit in addition to usual care.

MAIN OUTCOME MEASURES

Change in reported pain from pre and post therapy dog team visit and comparison with a control group.

RESULTS

A two-way ANOVA was conducted to compare group effects. Significant pre- post-intervention differences were noted in pain for the intervention (mean changeint. = -0.9, SD = 2.05, p = .004, 95% confidence interval [CI] = [0.42, 1.32], ηp2 = 04) but not the control group. Anxiety (mean changeint. = -1.13, SD = 2.80, p = .005, 95% CI = [0.56, 1.64], ηp2 = .04), depression (mean changeint. = -0.72, SD = 1.71, p = .002, 95% CI = [0.39, 1.11], ηp2 = .047), and well-being ratings (mean changeint. = -0.87, SD = 1.84, p < .001, 95% CI = [0.49, 1.25], ηp2 = .07) similarly improved for the intervention group only. There were no pre-post intervention differences in blood pressure or heart rate for either group. Strong responders to the intervention (i.e. >50% reduction) were observed for pain (43%), anxiety (48%), depression (46%), and well-being (41%).

CONCLUSIONS

Clinically significant changes in pain as well as significant changes in anxiety, depression and well-being were observed in the therapy dog intervention compared to control. The findings of this novel study contribute important knowledge towards the potential value of ED therapy dogs to affect patients' experience of pain, and related measures of anxiety, depression and well-being.

TRIAL REGISTRATION

This controlled clinical trial is registered with ClinicalTrials.gov, registration number NCT04727749.

Epigenome-wide DNA methylation profiling of conditioned pain modulation in individuals with non-specific chronic low back pain

BACKGROUND

The pathoanatomic cause of chronic low back pain (cLBP) cannot be identified for up to 90% of individuals. However, dysfunctional processing of endogenous nociceptive input, measured as conditioned pain modulation (CPM), has been associated with cLBP and may involve changes in neuronal gene expression. Epigenetic-induced changes such as DNA methylation (DNAm) have been associated with cLBP.

METHODS

In the present study, the relationship between CPM and DNAm changes in a sample of community-dwelling adults with nonspecific cLBP (n = 48) and pain-free controls (PFC; n = 50) was examined using reduced representation bisulfite sequencing. Gene ontology (GO) term enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were applied to identify key pathways involved in efficient versus deficient CPM.

RESULTS

Based on CPM efficiency, we identified 6006 and 18,305 differentially methylated CpG sites (DMCs) with q values < 0.01 among individuals with cLBP and PFCs, respectively. Most of the DMCs were hypomethylated and annotated to genes of relevance to pain, including OPRM1, ADRB2, CACNA2D3, GNA12, LPL, NAXD, and ASPHD1. In both cLBP and PFC groups, the DMCs annotated genes enriched many GO terms relevant to pain processing, including transcription regulation by RNA polymerase II, nervous system development, generation of neurons, neuron differentiation, and neurogenesis. Both groups also enriched the pathways involved in Rap1-signaling, cancer, and dopaminergic neurogenesis. However, MAPK-Ras signaling pathways were enriched in the cLBP, not the PFC group.

CONCLUSIONS

This is the first study to investigate the genome-scale DNA methylation profiles of CPM phenotype in adults with cLBP and PFCs. Based on CPM efficiency, fewer DMC enrichment pathways were unique to the cLBP than the PFCs group. Our results suggest that epigenetically induced modification of neuronal development/differentiation pathways may affect CPM efficiency, suggesting novel potential therapeutic targets for central sensitization. However, CPM efficiency and the experience of nonspecific cLBP may be independent. Further mechanistic studies are required to confirm the relationship between CPM, central sensitization, and nonspecific cLBP.

The Potential Clinical Utility of Pressure-Based vs. Heat-Based Paradigms to Measure Conditioned Pain Modulation in Healthy Individuals and Those With Chronic Pain

Conditioned pain modulation (CPM) is a physiological measure thought to reflect an individual's endogenous pain modulation system. CPM varies across individuals and provides insight into chronic pain pathophysiology. There is growing evidence that CPM may help predict individual pain treatment outcome. However, paradigm variabilities and practical issues have impeded widespread clinical adoption of CPM assessment. This study aimed to compare two CPM paradigms in people with chronic pain and healthy individuals. A total of 30 individuals (12 chronic pain, 18 healthy) underwent two CPM paradigms. The heat CPM paradigm acquired pain intensity ratings evoked by a test stimulus (TS) applied before and during the conditioning stimulus (CS). The pressure CPM paradigm acquired continuous pain intensity ratings of a gradually increasing TS, before and during CS. Pain intensity was rated from 0 (no pain) to 100 (worst pain imaginable); Pain50 is the stimulus level for a response rated 50. Heat and pressure CPM were calculated as a change in TS pain intensity ratings at Pain50, where negative CPM scores indicate pain inhibition. We also determined CPM in the pressure paradigm as change in pressure pain detection threshold (PDT). We found that in healthy individuals the CPM effect was significantly more inhibitory using the pressure paradigm than the heat paradigm. The pressure CPM effect was also significantly more inhibitory when based on changes at Pain50 than at PDT. However, in individuals with chronic pain there was no significant difference in pressure CPM compared to heat or PDT CPM. There was no significant correlation between clinical pain measures (painDETECT and Brief Pain Inventory) and paradigm type (heat vs. pressure), although heat-based CPM and painDETECT scores showed a trend. Importantly, the pressure paradigm could be administered in less time than the heat paradigm. Thus, our study indicates that in healthy individuals, interpretation of CPM findings should consider potential modality-dependent effects. However, in individuals with chronic pain, either heat or pressure paradigms can similarly be used to assess CPM. Given the practical advantages of the pressure paradigm (e.g., short test time, ease of use), we propose this approach to be well-suited for clinical adoption.

Analgesia and pain: Dual effect of dopamine on the peripheral nociceptive system is dependent on D2-or D1-like receptor activation

In this study, a pharmacological approach, together with the paw pressure test, was used to investigate the role of dopamine and its receptors in the peripheral processing of the nociceptive response in mice. Initially, the administration of dopamine (5, 20, and 80 ng/paw) in the hind paw of male Swiss mice (30-40 g) promoted antinociceptive effects in a dose-dependent manner. This was considered a peripheral effect, as it did not produce changes in the nociceptive threshold of the contralateral paw. The D₂, D₃, and D₄ dopamine receptor antagonists remoxipride (4 μg/paw), U99194 (16 μg/paw), and L-745,870 (16 μg/paw), respectively, reversed the dopamine-mediated antinociception in mice with PGE₂-induced hyperalgesia. The D₁ and D₅ dopamine receptor antagonists SKF 83566 (2 μg/paw) and SCH 23390 (1.6 μg/paw), respectively, did not alter dopamine antinociception. In contrast, dopamine at higher doses (0.1, 1, and 10 μg/paw) caused hyperalgesia in the animals, and the D₁ and D₅ receptor antagonists reversed this pronociceptive effect (10 μg/paw), whereas the D₂ receptor antagonist remoxipride did not. Our data suggest that dopamine has a dual effect that depends on the dose, as it causes peripheral antinociceptive effects at small doses via the activation of D₂-like receptors and nociceptive effects at higher doses via the activation of D₁-like receptors.

Reflections of the sensory findings in the central nervous system in patients with neuropathic pain

This study aimed to evaluate whether there was a difference in functional magnetic resonance imaging (fMRI) findings in patients who were found having hyperalgesia or hypoesthesia according to Quantitative Sensory Tests (QST). Forty participants were included in the study: 20 with neuropathic pain (NP) due to cervical disc pathology (NP group) and 20 healthy volunteers. After obtaining the socio-demographic and clinical data of the participants, the painDETECT questionnaire was administered, followed by QST analysis to show the presence of hypoesthesia and/or hyperalgesia, and fMRI examinations, which included sensory stimulation of both extremities. Sensory threshold tests were found to be higher in the NP group compared with the healthy volunteers, and the heat pain threshold was found to be lower in the tests showing pain thresholds in the intergroup analyses (p < 0.05). The changes described were found in both painful and non-painful limbs. In the hypoesthetic NP group, a lower somatosensory cortex activity was found in non-painful limbs compared with the healthy volunteers (p < 0.05). In the unilateral hyperalgesic NP group, a lower somatosensory cortex activity was found on the painful side, and if the hyperalgesia was widespread, lower blood oxygen-level-dependent activity was also found in the operculum and insular cortex (p < 0.05). The patients with different phenotypes of NP had different activities in the areas related to the processing of pain, and were more prominent in patients with widespread hyperalgesia. Studies with larger numbers of patients are required for a definite statement.

Phenotyping Chronic Musculoskeletal Pain in Male and Female Adolescents: Psychosocial Profiles, Somatosensory Profiles and Pain Modulatory Profiles

Purpose

A major limitation in treatment outcomes for chronic pain is the heterogeneity of the population. Therefore, a personalized approach to the assessment and treatment of children and adolescents with chronic pain conditions is needed. The objective of the study was to subgroup pediatric patients with chronic MSK pain that will be phenotypically different from each other based on their psychosocial profile, somatosensory function, and pain modulation.

Patients and Methods

This observational cohort study recruited 302 adolescents (10–18 years) with chronic musculoskeletal pain and 80 age-matched controls. After validated self-report questionnaires on psychosocial factors were completed, quantitative sensory tests (QST) and conditioned pain modulation (CPM) were performed.

Results

Three psychosocial subgroups were identified: adaptive pain (n=125), high pain dysfunctional (n=115), high somatic symptoms (n=62). Based on QST, four somatosensory profiles were observed: normal QST (n=155), thermal hyperalgesia (n=98), mechanical hyperalgesia (n=34) and sensory loss (n=15). Based on CPM and temporal summation of pain (TSP), four distinct groups were formed, dysfunctional central processing group (n=27) had suboptimal CPM and present TSP, dysfunctional inhibition group (n=136) had suboptimal CPM and absent TSP, facilitation group (n=18) had optimal CPM and present TSP, and functional central processing (n=112) had optimal CPM and absent TSP. A significant association between the psychosocial and somatosensory profiles. However, no association was observed between the psychosocial or somatosensory profiles and pain modulatory profiles.

Conclusion

Our results provide evidence that adolescents with chronic musculoskeletal pain are a heterogenous population comprising subgroups that may reflect distinct mechanisms and may benefit from different treatment approaches. The combination of screening self-reported questionnaires, QST, and CPM facilitate subgrouping of adolescents with chronic MSK pain in the clinical context and may ultimately contribute to personalized therapy.

Modulation of offset analgesia in patients with chronic pain and healthy subjects - a systematic review and meta-analysis

OBJECTIVES

Offset analgesia (OA) induces a brief pain inhibition and studies suggest OA impairment in patients with chronic pain when compared to healthy subjects. Conditioned pain modulation remains the most studied descending pain inhibitory control mechanism and is modulated by centrally-acting analgesics. Since OA may be mediated by similar neural substrates as conditioned pain modulation, understanding if OA is a peripheral or central proxy of pain modulation is important. The modulatory effect of centrally-acting drugs on OA in healthy and chronic pain populations has not yet been systematically reviewed and meta-analyzed, and this systematic review and meta-analysis aimed to identify studies employing interventions for modulating OA magnitude.

METHODS

A systematic search of PubMed, Embase, Web of Science, and the Cochrane Library yielded 146 records of which 11 (172 healthy pain-free subjects, 106 chronic pain patients) were eligible for qualitative synthesis, and 10 for meta-analysis on overall modulatory effect of interventions on OA, and subgroup analysis of patients and healthy pain-free subjects.

RESULTS

Risk of bias was evident for study participation and study confounding in the included studies. Several different methods for assessing and calculating OA magnitude were identified, which may affect interpretability of findings and warrants standardization. The meta-analysis showed no modulatory effects on OA overall (standardized mean difference (SMD) [95%CI]: 0.04 [-0.22, 0.30], Z=0.29, p=0.77), or in the subgroup analysis for patients (SMD [95%CI]: -0.04 [-0.63, 0.71], Z=0.13, p=0.90) or healthy pain-free subjects (SMD [95%CI]: 0.01 [-0.21, 0.24], Z=0.11, p=0.91). Moderate to substantial heterogeneity was found for the overall analysis (I2=47%, p=0.03) and patient subgroup analysis (I2=75%, p=0.003).

CONCLUSIONS

The current systematic review and meta-analysis conclude that centrally-acting drugs and exercise do not influence OA. Evidence on the peripheral contribution to OA response requires further investigations. Preclinical models of OA should be established to identify the neurophysiology and -biology behind OA.

Time-Dependent Changes in Protein Composition of Medial Prefrontal Cortex in Rats with Neuropathic Pain

Chronic pain is associated with time-dependent structural and functional reorganization of the prefrontal cortex that may reflect adaptive pain compensatory and/or maladaptive pain-promoting mechanisms. However, the molecular underpinnings of these changes and whether there are time-dependent relationships to pain progression are not well characterized. In this study, we analyzed protein composition in the medial prefrontal cortex (mPFC) of rats at two timepoints after spinal nerve ligation (SNL) using two-dimensional gel electrophoresis (2D-ELFO) and liquid chromatography with tandem mass spectrometry (LC–MS/MS). SNL, but not sham-operated, rats developed persistent tactile allodynia and thermal hyperalgesia, confirming the presence of experimental neuropathic pain. Two weeks after SNL (early timepoint), we identified 11 proteins involved in signal transduction, protein transport, cell homeostasis, metabolism, and apoptosis, as well as heat-shock proteins and chaperones that were upregulated by more than 1.5-fold compared to the sham-operated rats. Interestingly, there were only four significantly altered proteins identified at 8 weeks after SNL (late timepoint). These findings demonstrate extensive time-dependent modifications of protein expression in the rat mPFC under a chronic neuropathic pain state that might underlie the evolution of chronic pain characterized by early pain-compensatory and later aberrant mechanisms.

Are Reports of Pain, Disability, Quality of Life, Psychological Factors, and Central Sensitization Related to Outcomes of Quantitative Sensory Testing in Patients Suffering From Chronic Whiplash Associated Disorders?

BACKGROUND

Chronic whiplash associated disorders (CWAD) are characterized by long-lasting symptoms of neck pain occurring after an acceleration-deceleration injury. Central sensitization (CS) has been suggested as the possible underlying mechanism for these symptoms, and is characterized by changes in the central nervous system. Besides CS, psychological factors are believed to play an important role in the experience of (chronic) pain.

OBJECTIVE

Investigating the relationships between self-reported pain, disability, quality of life, psychological factors, and symptoms of CS; and electrical-based quantitative sensory testing (QST) outcomes in CWAD patients. Secondly, to investigate the differences in QST between CWAD patients and pain-free controls.

METHODS

Seventy-two individuals with CWAD and 55 pain-free controls underwent electrical stimuli-based QST. Detection and pain thresholds (EPT), temporal summation (TS), and conditioned pain modulation were examined. Spearman correlation and linear mixed models analyses were performed to assess, respectively, the hypothesized associations and group differences in QST.

RESULTS

The Pain Catastrophizing magnification subscale correlated with the left wrist EPT (r=-0.332; P=0.004), and the Pain Anxiety Symptom Scale-20 with the left wrist (r=-0.325; P=0.005) and ankle (r=-0.330; P=0.005) EPT. TS at the ankle correlated with the CS inventory (r=0.303; P=0.010), Short Form 36 pain subscale (r=-0.325; P=0.005), and Illness Perception Questionnaire revised consequences subscale (r=0.325; P=0.005). EPTs left (P=0.011) and right wrist (P=0.023) were lower in the CWAD group, but conditioned pain modulation and TS did not differ between groups.

CONCLUSION

QST outcomes relate to psychological constructs, rather than to self-reported pain intensity and distribution. Local hyperalgesia was found in individuals with CWAD, but no differences in endogenous pain facilitation nor inhibition.

Association between temporal summation and conditioned pain modulation in chronic low back pain: baseline results from 2 clinical trials

Introduction

Temporal summation (TS) and conditioned pain modulation (CPM) represent different aspects of central pain processing. Their relationship and differential performance within distinct body locations are not well understood.

Objectives

To examine the association between TS and CPM in chronic low back pain and the influence of testing location on this relationship.

Methods

We analyzed baseline data from 2 clinical trials on participants with chronic low back pain (n = 264; 47.3% female; mean age = 41 years, SD = 12; mean pain = 5.3/10, SD = 1.4). Measures used included questionnaires assessing pain and negative affect, phasic thermal TS at the hand (thenar) and the lower back (lumbar), followed by CPM that included a thermal testing stimulus (Heat-6, the temperature where pain rating is 6/10) and a cold-pressor conditioning stimulus. Nonparametric, proportional odds logistic regression was used to model thenar, and separately, lumbar TS, using CPM, Heat-6, negative affect, and demographics.

Results

Our models revealed a small association (βs = 0.17, P = 0.01) between reduced CPM and heightened TS at both testing sites, regardless of demographics or negative affect.

Conclusion

Results suggest a modest association between TS and CPM, irrespective of anatomical testing location, demographics, and negative affect. These findings will help improve the methodology and interpretation of TS and CPM measurement in clinical pain populations.

Descending pain modulatory efficiency in healthy subjects is related to structure and resting connectivity of brain regions

The descending pain modulatory system in humans is commonly investigated using conditioned pain modulation (CPM). Whilst variability in CPM efficiency, i.e., inhibition and facilitation, is normal in healthy subjects, exploring the inter-relationship between brain structure, resting-state functional connectivity (rsFC) and CPM readouts will provide greater insight into the underlying CPM efficiency seen in healthy individuals. Thus, this study combined CPM testing, voxel-based morphometry (VBM) and rsFC to identify the neural correlates of CPM in a cohort of healthy subjects (n =40), displaying pain inhibition (n = 29), facilitation (n = 10) and no CPM effect (n = 1). Clusters identified in the VBM analysis were implemented in the rsFC analysis alongside key constituents of the endogenous pain modulatory system. Greater pain inhibition was related to higher volume of left frontal cortices and stronger rsFC between the motor cortex and periaqueductal grey. Conversely, weaker pain inhibition was related to higher volume of the right frontal cortex - coupled with stronger rsFC to the primary somatosensory cortex, and rsFC between the amygdala and posterior insula. Overall, healthy subjects showed higher volume and stronger rsFC of brain regions involved with descending modulation, while the lateral and medial pain systems were related to greater pain inhibition and facilitation during CPM, respectively. These findings reveal structural alignments and functional interactions between supraspinal areas involved in CPM efficiency. Ultimately understanding these underlying variations and how they may become affected in chronic pain conditions, will advance a more targeted subgrouping in pain patients for future cross-sectional studies investigating endogenous pain modulation.

Conditioned Pain Modulation Is Not Impaired in Individuals with Frozen Shoulder: A Case-Control Study

Frozen shoulder (FS) is a poorly understood condition resulting in substantial shoulder pain and mobility deficits. The mechanisms behind FS are not yet fully understood, but, similar to other persistent pain states, central pain mechanisms may contribute to ongoing symptoms in this population. The objective of this research was to investigate conditioned pain modulation (CPM) in people with FS compared with pain-free individuals. A total of 64 individuals with FS and 64 healthy volunteers participated in this cross-sectional study. CPM was assessed by using the pressure pain threshold (PPT) and an occlusion cuff (tourniquet test) as the test and conditioning stimulus, respectively. The absolute and percentage of change in PPT (CPM effect) as well as pain profiles (pro-nociceptive vs. anti-nociceptive) of individuals with FS and healthy controls were calculated. No significant differences in the absolute change in the PPT or CPM effect were found in people with FS compared to pain-free controls. Moreover, no between-group differences in the percentage of subjects with pro-nociceptive and anti-nociceptive pain profiles were observed. These results suggest that endogenous pain inhibition is normally functioning in people with FS. Altered central pain-processing mechanisms may thus not be a characteristic of this population.

Effect of High-definition Transcranial Direct Current Stimulation on Conditioned Pain Modulation in Healthy Adults: A Crossover Randomized Controlled Trial

The disorder of the conditioned pain modulation (CPM) system is one of the main causes of pain perception in individuals. High-definition transcranial direct current stimulation (HD-tDCS) targeting specific brain areas was indicated to have an analgesic effect possibly by activating the endogenous pain inhibition pathway evident in CPM. However, discrepancies were found in previous limited studies of varied homogeneity and quality. Therefore, the present study applied 2 mA HD-tDCS (20 min) in the left primary motor cortex (M1) among 35 healthy adults with a blinded crossover study design, to investigate its effectiveness on optimizing the analgesic effect in healthy individuals through assessing changes of the CPM. The univariate and multivariate general linear models were used to evaluate the intervention effect between-group on the Δ-value (after-intervention minus before-intervention) during CPM (primary outcome), pressure pain threshold (PPT), and cold pressure threshold (CPT) (secondary outcome), respectively. A significant between-group difference in Δ-CPM was found for active stimulation. HD-tDCS significantly improved the analgesic efficiency of Δ-CPM, compared with the sham control, after adjusting the confounding factors including age, gender, psychological status, as well as the sequence effect. The changes of CPM were positively correlated with the total physical activity volume. In conclusion, our findings provide evidence support to the effectiveness of HD-tDCS on endogenous pain modulation among healthy adults. Further studies are required to explore the analgesic effect of tDCS among patients with chronic pain, thereby facilitating optimal chronic pain management.

Electroencephalography Signatures for Conditioned Pain Modulation and Pain Perception in Non-Specific Chronic Low Back Pain-an Exploratory Study

 

Conditioned pain modulation (CPM) can discriminate between healthy and chronic pain patients. However, its relationship with neurophysiological pain mechanisms is poorly understood. Brain oscillations measured by electroencephalography (EEG) might help gain insight into this complex relationship.

OBJECTIVE

To investigate the relationship between CPM response and self-reported pain intensity in non-specific chronic low back pain (NSCLBP) and explore respective EEG signatures associated to these mechanisms.

DESIGN

Cross-sectional analysis. Participants: Thirty NSCLBP patients participated.

METHODS

Self-reported low back pain, questionnaires, mood scales, CPM (static and dynamic quantitative sensory tests), and resting surface EEG data were collected and analyzed. Linear regression models were used for statistical analysis.

RESULTS

CPM was not significantly correlated with self-reported pain intensity scores. Relative power of EEG in the beta and high beta bands as recorded from the frontal, central, and parietal cortical areas were significantly associated with CPM. EEG relative power at delta and theta bands as recorded from the central area were significantly correlated with self-reported pain intensity scores while controlling for self-reported depression.

CONCLUSIONS

Faster EEG frequencies recorded from pain perception areas may provide a signature of a potential cortical compensation caused by chronic pain states. Slower EEG frequencies may have a critical role in abnormal pain processing.

Central sensitization, illness perception and obesity should be considered when interpreting disease activity in axial spondyloarthritis

OBJECTIVES

Many patients with axial spondyloarthritis (axSpA) report persistent pain even when treated with anti-inflammatory agents. Our aim was to explore the presence of central sensitization (CS) and different types of illness perceptions in patients with axSpA, and to assess their associations with disease activity assessments.

METHODS

Consecutive outpatients from the Groningen Leeuwarden Axial Spondyloarthritis (GLAS) cohort were included. Besides standardized assessments, patients filled out the Central Sensitization Inventory (CSI), Illness Perception Questionnaire (IPQ-R) and Pain Catastrophizing Scale (PCS). Univariable and multivariable linear regression analyses were used to investigate the association between questionnaire scores, patient characteristics and disease activity assessments ASDASCRP, BASDAI and CRP.

RESULTS

We included 182 patients with a mean symptom duration of 21.6 years. Mean ASDASCRP was 2.1, mean BASDAI 3.9, and median CRP 2.9. Mean CSI score was 37.8 (scale 0-100) and 45% of patients scored ≥40, indicating a high probability of CS. CSI score, IPQ-R domain identity (number of symptoms the patient attributes to their illness), and IPQ-R domain treatment control (perceived treatment efficacy), and obesity were significantly and independently associated with both ASDASCRP and BASDAI, explaining a substantial proportion of variation in these disease activity scores (R2=0.35 and R2=0.47, respectively). Only obesity was also independently associated with CRP.

CONCLUSION

CS may be common in patients with long-term axSpA. CS, as well as specific illness perceptions and obesity were all independently associated with the widely used (partially) patient-reported disease activity assessments ASDASCRP and BASDAI. Treating physicians should take this into account in the follow-up and treatment of their patients.

Exploring multidimensional characteristics in cervicogenic headache: Relations between pain processing, lifestyle, and psychosocial factors

OBJECTIVE

Although multidimensional interventions including physiotherapy, psychology, and education are generally recommended in managing headache, and to prevent chronification, such approach is lacking in cervicogenic headache (CeH). Therefore, exploring CeH within a biopsychosocial framework is deemed an essential first step.

METHODS

Non-randomized cross-sectional design to compare pain processing, lifestyle, and psychosocial characteristics between 18 participants with CeH (CeH group) (40.2 ± 10.9 years) and 18 matched controls (control group) (39.2 ± 13.1 years). Pain processing characteristics included degree of central sensitization (Central Sensitization Inventory), and (extra)-cephalic pressure pain thresholds (kPa/cm²/s). Lifestyle characteristics included sleep quality (Pittsburgh Sleep Quality Index), physical activity, screen time, and sedentary time (hours a week). Psychosocial characteristics included degree of depression, anxiety and stress (Depression Anxiety Stress Scale-21), and quality of life (Headache Impact Test-6).

RESULTS

Pain processing characteristics: More (p = .04) participants in the CeH group showed higher degrees of central sensitization compared to the control group. Lower (p < .05) (extra)-cephalic pressure pain thresholds were revealed in the CeH group compared to the control group for each muscle. Lifestyle and psychosocial characteristics: Compared to the control group, sleep quality and headache-related quality of life were worse (p < .0001) in the CeH group. Severe to extreme stress was experienced by more participants in the CeH group (p = .02). Further, significant relations between pain processing and (1) lifestyle characteristics and (2) psychosocial characteristics were seen in the CeH group.

CONCLUSION

Exploring multidimensional characteristics in CeH exposed relations between pain processing, lifestyle, and psychosocial characteristics. These novel findings fill a gap in the current scientific literature, and highlight the need for outcome research targeting lifestyle and psychosocial factors.

Comparison of Thermal and Electrical Modalities in the Assessment of Temporal Summation of Pain and Conditioned Pain Modulation

Temporal summation of pain (TSP) and conditioned pain modulation (CPM) can be measured using a thermode and a cold pressor test (CPT). Unfortunately, these tools are complex, expensive, and are ill-suited for routine clinical assessments. Building on the results from an exploratory study that attempted to use transcutaneous electrical nerve stimulation (TENS) to measure CPM and TSP, the present study assesses whether a “new” TENS protocol can be used instead of the thermode and CPT to measure CPM and TSP. The objective of this study was to compare the thermode/CPT protocol with the new TENS protocol, by (1) measuring the association between the TSP evoked by the two protocols; (2) measuring the association between the CPM evoked by the two protocols; and by (3) assessing whether the two protocols successfully trigger TSP and CPM in a similar number of participants. We assessed TSP and CPM in 50 healthy participants, using our new TENS protocol and a thermode/CPT protocol (repeated measures and randomized order). In the TENS protocol, both the test stimulus (TS) and the conditioning stimulus (CS) were delivered using TENS; in the thermode/CPT protocol, the TS was delivered using a thermode and the CS consisted of a CPT. There was no association between the response evoked by the two protocols, neither for TSP nor for CPM. The number of participants showing TSP [49 with TENS and 29 with thermode (p < 0.001)] and CPM [16 with TENS and 30 with thermode (p = 0.01)] was different in both protocols. Our results suggest that response to one modality does not predict response to the other; as such, TENS cannot be used instead of a thermode/CPT protocol to assess TSP and CPM without significantly affecting the results. Moreover, while at first glance it appears that TENS is more effective than the thermode/CPT protocol to induce TSP, but less so to induce CPM, these results should be interpreted carefully. Indeed, TSP and CPM response appear to be modality-dependent as opposed to an absolute phenomenon, and the two protocols may tap into entirely different mechanisms, especially in the case of TSP.

Effects of Transcutaneous Spinal Direct Current Stimulation (tsDCS) in Patients With Chronic Pain: A Clinical and Neurophysiological Study

Background and Aims: Chronic pain is a complex clinical condition, often devastating for patients and unmanageable with pharmacological treatments. Converging evidence suggests that transcutaneous spinal Direct Current Stimulation (tsDCS) might represent a complementary therapy in managing chronic pain. In this randomized, double-blind and sham-controlled crossover study, we assessed tsDCS effects in chronic pain patients.

Methods: Sixteen patients (aged 65.06 ± 16.16 years, eight women) with chronic pain of different etiology underwent sham and anodal tsDCS (anode over the tenth thoracic vertebra, cathode over the somatosensory cortical area: 2.5 mA, 20 min, 5 days for 1 week). As outcomes, we considered the Visual Analog Scale (VAS), the Neuropathic Pain Symptom Inventory (NPSI), and the components of the lower limb flexion reflex (LLFR), i.e., RIII threshold, RII latency and area, RIII latency and area, and flexion reflex (FR) total area. Assessments were conducted before (T0), immediately at the end of the treatment (T1), after 1 week (T2) and 1 month (T3).

Results: Compared to sham, anodal tsDCS reduced RIII area at T2 (p = 0.0043) and T3 (p = 0.0012); similarly, FR total area was reduced at T3 (p = 0.03). Clinically, anodal tsDCS dampened VAS at T3 (p = 0.015), and NPSI scores at T1 (p = 0.0012), and T3 (p = 0.0015), whereas sham condition left them unchanged. Changes in VAS and NPSI scores linearly correlated with the reduction in LLFR areas (p = 0.0004).

Conclusions: Our findings suggest that tsDCS could modulate nociceptive processing and pain perception in chronic pain syndromes.

Somatosensory dysfunction in patients with posttraumatic headache: A systematic review

OBJECTIVES

Aim of the review is to summarize the knowledge about the sensory function and pain modulatory systems in posttraumatic headache and discuss its possible role in patients with posttraumatic headache.

BACKGROUND

Posttraumatic headache is the most common complication after traumatic brain injury, and significantly impacts patients' quality of life. Even though it has a high prevalence, its origin and pathophysiology are poorly understood. Thereby, the existing treatment options are insufficient. Identifying its mechanisms can be an important step forward to develop target-based personalized treatment.

METHODS

We searched the PubMed database for studies examining pain modulation and/or quantitative sensory testing in individuals with headache after brain injury.

RESULTS

The studies showed heterogenous alterations in sensory profiles (especially in heat and pressure pain perception) compared to healthy controls and headache-free traumatic brain injury-patients. Furthermore, pain inhibition capacity was found to be diminished in subjects with posttraumatic headache.

CONCLUSIONS

Due to the small number of heterogenous studies a distinct sensory pattern for patients with posttraumatic headache could not be identified. Further research is needed to clarify the underlying mechanisms and biomarkers for prediction of development and persistence of posttraumatic headache.

Pain Catastrophizing, Self-reported Disability, and Temporal Summation of Pain Predict Self-reported Pain in Low Back Pain Patients 12 Weeks After General Practitioner Consultation: A Prospective Cohort Study

OBJECTIVES

Patients with low back pain (LBP) often demonstrate pain sensitization, high degree of pain catastrophizing, and psychological distress. This study investigated whether pain sensitization mechanisms, the Pain Catastrophizing Scale (PCS), and Start Back Screening Tool were associated with pain in recurrent LBP patients 12 weeks after consulting their general practitioner (GP).

MATERIALS AND METHODS

In 45 LBP patients, pressure pain thresholds, temporal summation of pain (TSP), conditioned pain modulation (CPM), the Roland Morris Disability Questionnaire (RMDQ), and the PCS were assessed before consultation. Patients were classified into low to medium or high risk of poor prognosis on the basis of the Start Back Screening Tool. Worst pain within the last 24 hours was assessed on a visual analogue scale (VAS) at inclusion and 12 weeks after GP consultation.

RESULTS

VAS scores were reduced after 12 weeks in the low-to-medium (N=30, P<0.05), but not the high-risk group (N=15, P=0.40). RMDQ was reduced after 12 weeks (P<0.001), but with no difference between the groups. PCS was reduced in the low-to-medium and the high-risk group (P<0.05). TSP was significantly higher at follow-up in the high-risk group compared with the low-to-medium-risk group (P<0.05). A linear regression model explained 54.9% of the variance in VAS scores at follow-up utilizing baseline assessments of TSP, RMDQ, and PCS.

DISCUSSION

This study indicate that patients with LBP and high self-reported disability, high pain catastrophizing, and facilitated TSP assessed when consulting the GP might predictive poor pain progression 12 weeks after the consultation.

Health-related quality of life deviations from population norms in patients with lumbar radiculopathy: associations with pain, pain cognitions, and endogenous nociceptive modulation

PURPOSE

The primary goal of this study was to compare the health-related quality of life (HRQoL) of people with lumbar radiculopathy to age- and sex-adjusted population norms. Additionally, it aimed to explore the associations between the HRQoL difference scores and measures related to pain cognitions, pain intensity, and endogenous nociceptive modulation.

METHODS

Using answers from the Short Form 36-item Health Survey and UK population norms, SF-6D difference scores were calculated. A one-sample t test was used to assess the SF-6D difference scores. Univariate and multivariate regression analyses were used to assess the associations between SF-6D difference scores and pain intensity [Visual Analogue Scale (VAS) for back and leg pain], pain cognitions [Pain Catastrophizing Scale (PCS), Tampa Scale for Kinesiophobia (TSK), Pain Vigilance and Awareness Questionnaire (PVAQ)], and correlates for endogenous nociceptive modulation using quantitative sensory testing.

RESULTS

One hundred and twenty people with lumbar radiculopathy scheduled for surgery were included in this study. The mean SF-6D difference score of - 0.26 [SD = 0.09] was found to be significantly less than 0 [95%CI: - 0.27 to - 0.24]. Univariate analyses showed a significant influence from PCS, TSK, and PVAQ on the SF-6D difference scores. The final multivariate regression model included PCS and PVAQ, with only PCS maintaining a statistically significant regression coefficient [b = - 0.002; 95% CI: - 0.004 to - 0.001].

CONCLUSION

People diagnosed with lumbar radiculopathy report significantly lower HRQoL scores when compared with age- and sex-adjusted UK norm values. Even though all examined pain cognitions were found to have a significant association, pain catastrophizing showed the most significant relation to the SF-6D difference scores.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier No. NCT02630732. Date of registration: November 25, 2015.

Do chronic low back pain subgroups derived from dynamic quantitative sensory testing exhibit differing multidimensional profiles?

OBJECTIVES

The relationship of pain sensitivity with pain and disability in low back pain (LBP) is complicated. It has been suggested increased understanding of dynamic quantitative sensory testing (QST) might be useful in increasing understanding of these relationships. This study aimed to create subgroups based on participant responses to dynamic QST, profile these subgroups based on multidimensional variables (including clinical measures of pain and disability, psychological and lifestyle variables and static QST), and investigate the association of subgroup membership with levels of pain intensity, LBP-related disability and disability risk at 12-month follow up.

METHODS

Participants (n=273) with dominant axial chronic non-specific LBP with duration of pain >3 months were included in this study. At baseline, eligible participants completed a self-report questionnaire to collect demographic, clinical, psychological and lifestyle data prior to dynamic and static QST. Dynamic QST measures were conditioned pain modulation (CPM) and temporal summation (TS). At 12-months follow up, clinical data were collected, including pain intensity and LBP-related disability. Sub-groups were formed by cross-tabulation. Analysis was undertaken to profile dynamic QST subgroup on demographic, clinical, psychological, lifestyle and static QST measures. Associations between dynamic QST subgroups and follow-up clinical variables were examined.

RESULTS

Based on dynamic QST, participants were allocated into four subgroups; normal CPM and normal TS (n=34, 12.5%); normal CPM and facilitated TS (n=6, 2.2%); impaired CPM and normal TS (n=186, 68.1%); impaired CPM and facilitated TS (n=47, 17.2%). At baseline no differences were demonstrated between subgroups across most clinical variables, or any psychological or lifestyle measures. The two subgroups with impaired CPM were more likely to have a higher number of painful body areas. Cold pain sensitivity was heightened in both the subgroups with facilitated TS. Subgroups did not differ across pain intensity, LBP-related disability and disability risk stratification at follow-up.

CONCLUSIONS

The profiles of people with axial LBP did not vary significantly across dynamic QST subgroups, save for those in groups with impaired CPM being more likely to have more widespread symptoms and those with facilitated TS having heightened cold pain sensitivity. Further, subgroup membership was not related to future pain and disability. The role of dynamic QST profiles in LBP remains unclear. Further work is required to understand the role of pain sensitivity in LBP. The utility of dynamic QST subgrouping might not be in determining of future disability. Future research might focus on treatment modifying effects of dynamic QST subgroups.

Psychophysical evaluation of somatosensory function in oro-facial pain: achievements and challenges

AIM

This critical review describes key methodological aspects for a successful oro-facial psychophysical evaluation of the somatosensory system and highlights the diagnostic value of somatosensory assessment and management perspectives based on somatosensory profiling.

METHODS

This topical review was based on a non-systematic search for studies about somatosensory evaluation in oro-facial pain in PubMed and Embase.

RESULTS

The recent progress regarding the psychophysical evaluation of somatosensory function was largely possible due to the development and application of valid, reliable and standardised psychophysical methods. Qualitative sensory testing may be useful as a screening tool to rule out relevant somatosensory abnormalities. Nevertheless, the patient should preferably be referred to a more comprehensive assessment with the quantitative sensory testing battery if confirmation of somatosensory abnormalities is necessary. Moreover, the identification of relevant somatosensory alterations in chronic pain disorders that do not fulfil the current criteria to be regarded as neuropathic has also increased the usefulness of somatosensory evaluation as a feasible method to better characterise the patients and perhaps elucidate some underpinnings of the so-called 'nociplastic' pain disorders. Finally, an additional benefit of oro-facial pain treatment based on somatosensory profiling still needs to be demonstrated and convincing evidence of somatosensory findings as predictors of treatment efficacy in chronic oro-facial pain awaits further studies.

CONCLUSION

Psychophysical evaluation of somatosensory function in oro-facial pain is still in its infancy but with a clear potential to continue to improve the assessment, diagnosis and management of oro-facial pain patients.

Sex-Specific Abnormalities and Treatment-Related Plasticity of Subgenual Anterior Cingulate Cortex Functional Connectivity in Chronic Pain

The subgenual anterior cingulate cortex (sgACC) is a key node of the descending antinociceptive system with sex differences in its functional connectivity (FC). We previously reported that, in a male-prevalent chronic pain condition, sgACC FC is abnormal in women but not in men. This raises the possibility that, within a sex, sgACC FC may be either protective or represent a vulnerability to develop a sex-dominant chronic pain condition. The aim of this study was to characterize sgACC FC in a female-dominant chronic pain condition, carpal tunnel syndrome (CTS), to investigate whether sgACC abnormalities are a common feature in women with chronic pain or unique to individuals with pain conditions that are more prevalent in the opposite sex. We used fMRI to determine the resting state FC of the sgACC in healthy controls (HCs, n = 25, 18 women; 7 men) and people with CTS before (n = 25, 18 women; 7 men) and after (n = 17, 13 women; 4 men) successful surgical treatment. We found reduced sgACC FC with the medial pre-frontal cortex (mPFC) and temporal lobe in CTS compared with HCs. The group-level sgACC-mPFC FC abnormality was driven by men with CTS, while women with CTS did not have sgACC FC abnormalities compared with healthy women. We also found that age and sex influenced sgACC FC in both CTS and HCs, with women showing greater FC with bilateral frontal poles and men showing greater FC with the parietal operculum. After surgery, there was reduced sgACC FC with the orbitofrontal cortex, striatum, and premotor areas and increased FC with the posterior insula and precuneus compared with pre-op scans. Abnormally reduced sgACC-mPFC FC in men but not women with a female-prevalent chronic pain condition suggests pain-related sgACC abnormalities may not be specific to women but rather to individuals who develop chronic pain conditions that are more dominant in the opposite sex. Our data suggest the sgACC plays a role in chronic pain in a sex-specific manner, and its communication with other regions of the dynamic pain connectome undergoes plasticity following pain-relieving treatment, supporting it as a potential therapeutic target for neuromodulation in chronic pain.

Pathophysiology of neuropathic pain

Background: Neuropathic pain is notoriously difficult to manage properly, not only because of its varied nature and the absence of objective diagnostic tools but also because of extensive reciprocal neuronal interactive pathogenic mechanism from the molecular level to patient’s own psychophysical characteristics. This paper briefly reviews the pathophysiology of neuropathic pain to the level of clinicians’ interest and its potential in clinical practiceCurrent Concepts: Recent research progress now allows us to obtain a bird view of neuropathic pain pathophysiology: peripheral and central sensitization. For peripheral sensitization, a local inflammatory milieu of the injured nerve primarily drives sequential phenotypic changes, which are critical and shared by both neuropathic and inflammatory pain. Central sensitization is led either by the hyperexcitability of the second-order afferent neuron itself or loss of physiological inhibitory control of the transmission of pain signal to the higher nervous system. Peripheral and central sensitization work synergistically but can also introduce neuropathic pain alone.Discussion and Conclusion: The cause of neuropathic pain is diverse, and understanding of its pathophysiology is still insufficient to realize a mechanism-based approach to clinical phenotypes or therapeutic applications. In dealing with chronic neuropathic pain, it is highly desirable to assess key aspects of a patient’s pain based on a plausible mechanism and select the best management method accordingly.

Re-Examining Myofascial Pain Syndrome: Toward Biomarker Development and Mechanism-Based Diagnostic Criteria

PURPOSE OF REVIEW

We discuss the need for a mechanism-based diagnostic framework with a focus on the development of objective measures (e.g., biomarkers) that can potentially be added to the diagnostic criteria of the syndrome. Potential biomarkers are discussed in relation to current knowledge on the pathophysiology of myofascial pain syndrome (MPS), including alterations in redox status, inflammation, and the myofascial trigger point (MTrP) biochemical milieu, as well as imaging and neurophysiological outcomes. Finally, we discuss the long-term goal of conducting a Delphi survey, to assess the influence of putative MPS biomarkers on clinician opinion, in order to ultimately develop new criteria for the diagnosis of MPS.

RECENT FINDINGS

Myofascial pain syndrome (MPS) is a prevalent healthcare condition associated with muscle weakness, impaired mood, and reduced quality of life. MPS is characterized by the presence of myofascial trigger points (MTrPs): stiff and discrete nodules located within taut bands of skeletal muscle that are painful upon palpation. However, physical examination of MTrPs often yields inconsistent results, and there is no gold standard by which to diagnose MPS. The current MPS diagnostic paradigm has an inherent subjectivity and the absence of correlation with the underlying pathophysiology. Recent advancements in ultrasound imaging, systemic biomarkers, MTrP-specific biomarkers, and the assessment of dysfunction in the somatosensorial system may all contribute to improved diagnostic effectiveness of MPS.

Exercise induced hypoalgesia profile in rats is associated with IL-10 and IL-1 β levels and pain severity following nerve injury

BACKGROUND

Pain may undergo modulation in the central nervous system prior to reaching the primary somatosensory cortex and being perceived as pain. Faulty pain modulation mechanisms have been linked to various chronic pain conditions. Cytokines such as IL-10 and IL-1beta, are known to be involved in initiation and maintenance of neuropathic pain. In this study, we investigated the association between pain modulation profile, pain intensity and cytokines (IL-10 and IL-1beta) levels in a rat model of neuropathic pain.

METHODS

Exercise-Induced Hypoalgesia (EIH) was assessed by evaluating the percentage of responses to a train of 60g mechanical stimuli before and after 180 seconds of exercise on a rotating rod. The differences in the response rates before and after the exercise were used to divide the rats into low and high EIH responders. Rats from low and high EIH groups underwent constriction injury of the left sciatic nerve. Pain behavior (allodynia and hyperalgesia) were assessed by measuring responses to mechanical and thermal stimuli applied to the plantar surface of the foot. Serum, sciatic nerve and the related Dorsal Root Ganglia (DRG) levels of IL-10 and IL-1beta were determined by ELISA. The DRG mRNA levels of IL-10 and IL-1beta measured with PCR. A comparison between the low and high EIH rats of all measured parameters was made.

RESULTS

The low EIH rats developed significantly more severe allodynia and hyperalgesia in the affected paw and allodynia in the contralateral paw compared to the high EIH rats, 7 days following the injury. The low EIH rats had higher IL-1beta protein levels in serum prior to and following injury, higher affected and contralateral sciatic nerve IL-1beta levels following injury and higher IL-1beta levels in the contralateral DRG (protein and mRNA) following injury when compared to high EIH rats. The high EIH rats had higher affected sciatic nerve IL-10 levels following nerve injury and higher IL-10 levels of both protein and mRNA in the affected and contralateral DRG at baseline and following injury.

CONCLUSION

EIH profile was found to be predictive of pain behavior following nerve injury, low EIH rats developed more severe allodynia and hyperalgesia. IL-1beta may be associated with painful neuropathy developed in rats with low EIH while the anti-inflammatory cytokine IL-10 may have a protective role, inhibiting the development of painful.

Effects of acute mental stress on conditioned pain modulation in temporomandibular disorders patients and healthy individuals

Stress is a contributing factor to painful temporomandibular disorders (TMD). Nevertheless, the underpinnings of this relationship are not fully understood.

Neuropathic pain modeling: Focus on synaptic and ion channel mechanisms

Animal models of pain consist of modeling a pain-like state and measuring the consequent behavior. The first animal models of neuropathic pain (NP) were developed in rodents with a total lesion of the sciatic nerve. Later, other models targeting central or peripheral branches of nerves were developed to identify novel mechanisms that contribute to persistent pain conditions in NP. Objective assessment of pain in these different animal models represents a significant challenge for pre-clinical research. Multiple behavioral approaches are used to investigate and to validate pain phenotypes including withdrawal reflex to evoked stimuli, vocalizations, spontaneous pain, but also emotional and affective behaviors. Furthermore, animal models were very useful in investigating the mechanisms of NP. This review will focus on a detailed description of rodent models of NP and provide an overview of the assessment of the sensory and emotional components of pain. A detailed inventory will be made to examine spinal mechanisms involved in NP-induced hyperexcitability and underlying the current pharmacological approaches used in clinics with the possibility to present new avenues for future treatment. The success of pre-clinical studies in this area of research depends on the choice of the relevant model and the appropriate test based on the objectives of the study.

Peripheral and Central Pathological Mechanisms of Chronic Low Back Pain: A Narrative Review

Chronic low back pain (CLBP), lasting >3 months, is the end result of multiple pathogenic factors. Unfortunately, little is known about CLBP pathogenesis, which limits its advancements in clinical therapy and disease management. This paper summarizes the known pathological axes of CLBP, involving both peripheral and central systems. In particular, this paper details injurious nerve stimulation, inflammation-induced peripheral pathway, and central sensitization. Lumbar components, such as intervertebral disc (IVD), facet joints, muscles, fascia, ligaments, and joint capsules, contain pain receptors called nociceptors. Degeneration of the aforementioned lumbar components activates inflammatory pathways, which can directly damage nerves, lower nociceptor threshold to fire action potentials (AP), and cause pain. Additionally, damaged lumbar IVDs and endplates can also lead to the pathologic invasion of nerve growth and innervation, followed by the compression of herniated IVDs on nerve roots, thereby causing traumatic neuropathic pain. The central mechanism of CLBP involves alteration of the sensory processing of the brain and malfunction of the descending pain modulatory system, which facilitates pain amplification in the center nervous system (CNS). Lastly, abnormalities in the brain biochemical metabolism, activation of glial cells, and subsequent inflammation also play important roles in CLBP development. Taken together, inflammation plays an important role in both peripheral and central sensitization of CLBP. Due to the heterogeneity of CLBP, its pathological mechanism remains complex and difficult to understand. Therefore, it is a worthy field for future research into the subcomponents of CLBP pathogenesis, in order to distinguish the specific form of the disease, identify its origins, and develop corresponding highly effective comprehensive therapy against CLBP.

Phenotyping peripheral neuropathic pain in male and female adolescents: pain descriptors, somatosensory profiles, conditioned pain modulation, and child-parent reported disability

ABSTRACT

Neuropathic pain (NeuP) can be difficult to diagnose and manage in children. Data regarding prevalence and sex-dependent differences are limited, and more detailed phenotyping is needed. This observational cohort study recruited adolescents (10-17 years) with NeuP or complex regional pain syndrome (CRPS). After pain history and NeuP questionnaires, quantitative sensory testing was performed. Individual z-score plots were calculated with body-region control measures and matched to mechanism-related sensory profiles (sensory loss, thermal hyperalgesia, and mechanical hyperalgesia). Conditioned pain modulation was assessed with pressure pain threshold and a contralateral cold conditioning stimulus, and meaningful conditioned pain modulation defined as twice the standard error of measurement. Patients and parents completed validated questionnaires for child quality of life (QoL), pain catastrophizing, and self-reported anxiety/depression. Males (n = 23) and females (n = 43) with NeuP (n = 52) or CRPS (n = 14) reported moderate-severe pain with neuropathic sensory descriptors. Mixed patterns of sensory gain/loss at pain sites were not sex-dependent. Thermal hyperalgesia was common in both NeuP and CRPS, whereas sensory loss occurred only with NeuP and in a smaller proportion than adult cohorts. Conditioned pain modulation was inhibitory in 54%, facilitatory in 14%, and nonresponders had variable cold conditioning sensitivity. Males and females reported marked impairment of QoL, increased emotional distress, and pain catastrophising. Child-parent QoL scores correlated, but catastrophizing scores were discordant when parents or adolescents reported higher anxiety/depression. NeuP in adolescents is associated with significant pain, physical impairment, and psychosocial impairment. Quantifying alterations in somatosensory profiles, descending modulation, child and parent psychological function will inform individualized therapy and stratification for future clinical trials.