Experimental and Clinical Applications of Quantitative Sensory Testing Applied to Skin, Muscles and Viscera

Relationships Between Psychological, Social, Physical Activity, and Sleep Measures and Somatosensory Function in Individuals With Spinal Pain: A Systematic Review and Meta-analysis

OBJECTIVE

Somatosensory abnormalities are linked to clinical pain outcomes in individuals with spinal pain. However, a range of factors might confound the relationship between altered somatosensory function and clinical pain outcomes. This systematic review aimed to evaluate the literature to assess the level of evidence of associations between psychological, social, physical activity, and sleep measures and somatosensory function (assessed via sensory psychophysical testing) among individuals with spinal pain.

METHODS

A comprehensive literature search was performed in 6 electronic databases from their inception to June 2018. Two reviewers independently assessed the methodological quality using a modified Quality in Prognostic Studies (QUIPS) tool and supplemented with recommendations from the Critical Appraisal and Data Extraction for the Systematic Review of Prediction Modelling Studies (CHARMS) checklist and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. The level of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system. Data were pooled to evaluate the strength of the relationships of interest.

RESULTS

Among the 17 factors identified in the included studies, pain catastrophizing, depression, and pain-related fear have significant negative (small to fair) associations with pain thresholds. A "very low" to "moderate" quality of evidence was found for all the investigated factors. Subgroup analysis showed a smaller effect size for pain catastrophizing/fear of movement and pain thresholds in individuals with low back pain.

CONCLUSIONS

Psychological factors are associated negatively with pain thresholds and they need to be adjusted when establishing predictive relationships between somatosensory function and pain outcomes in individuals with spinal pain.

Effects of transcutaneous electrical nervous stimulation (TENS) associated with vocal therapy on musculoskeletal pain of women with behavioral dysphonia: A randomized, placebo-controlled double-blind clinical trial

Recently, electrical stimulation in vocal rehabilitation has been the subject of studies. This treatment has shown promising results regarding the decrease of vocal/laryngeal symptoms, pain and the improvement of vocal tension. In addition to decreasing pain symptoms, TENS treatments may lead to muscle relaxation. There is no data on the effects of this resource as a vocal therapy in women with behavioral dysphonia. Research in this area may provide evidence to assist the clinical decision related to the treatment of women with complaints of behavioral dysphonia and musculoskeletal pain.

OBJECTIVE

To verify the effects of low-frequency TENS in association with vocal therapy on musculoskeletal pain in women with behavioral dysphonia.

METHODS

Participants included 27 women with vocal nodules randomized into two groups. The experimental group (EG) - 13 women received 12 sessions of TENS (pulse of 200 μs, frequency at 10 Hz, in motor threshold) with electrodes placed bilaterally on the trapezius muscle and submandibular area for 20 min followed by 30 min of vocal therapy, and the control group (CG) - 14 women received 12 sessions of 20 min of a placebo TENS followed by 30 min of vocal therapy. We investigated the frequency and intensity of the musculoskeletal pain in several body regions, as well as the intensity of pain at rest and in the application of pressure with an algometer applied to the descending fibers of the trapezius muscle. The pressure-pain threshold (PPT) was also investigated. All evaluations occurred before, immediately after, and at one and three months after treatment in both groups.

RESULTS

We observed a reduction in the frequency of pain in the larynx after treatment of both groups, but only the EG showed a decrease in pain intensity in this region. It was verified with an algometer to the trapezius muscle that the electrical stimulation associated with the vocal therapy decreased the intensity of pain during the application of pressure and increased the PPT. There were no significant differences with regard to variables investigated in the comparison between the interventions. On the other hand, there was decreased pain in the trapezius muscle for the EG in comparison to the pre- and post-intervention.

CONCLUSION

The vocal therapyprogram reduced the frequency and intensity of the musculoskeletal pain in the regions proximal to the larynx of women with behavioral dysphonia. In addition, TENS followed by vocal therapy increased the threshold of sensitivity to muscular pain in the trapezius, demonstrating that it is a good resource to use in conjunction with traditional vocal therapy in cases of behavioral dysphonia associated with pain and muscle tension.

Quantitative sensory testing and predicting outcomes for musculoskeletal pain, disability, and negative affect: a systematic review and meta-analysis

Hypersensitivity due to central pain mechanisms can influence recovery and lead to worse clinical outcomes, but the ability of quantitative sensory testing (QST), an index of sensitisation, to predict outcomes in chronic musculoskeletal disorders remains unclear. We systematically reviewed the evidence for ability of QST to predict pain, disability, and negative affect using searches of CENTRAL, MEDLINE, EMBASE, AMED, CINAHL, and PubMed databases up to April 2018. Title screening, data extraction, and methodological quality assessments were performed independently by 2 reviewers. Associations were reported between baseline QST and outcomes using adjusted (β) and unadjusted (r) correlations. Of the 37 eligible studies (n = 3860 participants), 32 were prospective cohort studies and 5 randomised controlled trials. Pain was an outcome in 30 studies, disability in 11, and negative affect in 3. Meta-analysis revealed that baseline QST predicted musculoskeletal pain (mean r = 0.31, 95% confidence interval [CI]: 0.23-0.38, n = 1057 participants) and disability (mean r = 0.30, 95% CI: 0.19-0.40, n = 290 participants). Baseline modalities quantifying central mechanisms such as temporal summation and conditioned pain modulation were associated with follow-up pain (temporal summation: mean r = 0.37, 95% CI: 0.17-0.54; conditioned pain modulation: mean r = 0.36, 95% CI: 0.20-0.50), whereas baseline mechanical threshold modalities were predictive of follow-up disability (mean r = 0.25, 95% CI: 0.03-0.45). Quantitative sensory testing indices of pain hypersensitivity might help develop targeted interventions aiming to improve outcomes across a range of musculoskeletal conditions.

Sensory Modulation Disorder (SMD) and Pain: A New Perspective

Sensory modulation disorder (SMD) affects sensory processing across single or multiple sensory systems. The sensory over-responsivity (SOR) subtype of SMD is manifested clinically as a condition in which non-painful stimuli are perceived as abnormally irritating, unpleasant, or even painful. Moreover, SOR interferes with participation in daily routines and activities (Dunn, 2007; Bar-Shalita et al., 2008; Chien et al., 2016), co-occurs with daily pain hyper-sensitivity, and reduces quality of life due to bodily pain. Laboratory behavioral studies have confirmed abnormal pain perception, as demonstrated by hyperalgesia and an enhanced lingering painful sensation, in children and adults with SMD. Advanced quantitative sensory testing (QST) has revealed the mechanisms of altered pain processing in SOR whereby despite the existence of normal peripheral sensory processing, there is enhanced facilitation of pain-transmitting pathways along with preserved but delayed inhibitory pain modulation. These findings point to central nervous system (CNS) involvement as the underlying mechanism of pain hypersensitivity in SOR. Based on the mutual central processing of both non-painful and painful sensory stimuli, we suggest shared mechanisms such as cortical hyper-excitation, an excitatory-inhibitory neuronal imbalance, and sensory modulation alterations. This is supported by novel findings indicating that SOR is a risk factor and comorbidity of chronic non-neuropathic pain disorders. This is the first review to summarize current empirical knowledge investigating SMD and pain, a sensory modality not yet part of the official SMD realm. We propose a neurophysiological mechanism-based model for the interrelation between pain and SMD. Embracing the pain domain could significantly contribute to the understanding of this condition’s pathogenesis and how it manifests in daily life, as well as suggesting the basis for future potential mechanism-based therapies.

Slowly Repeated Evoked Pain as a Marker of Central Sensitization in Fibromyalgia: Diagnostic Accuracy and Reliability in Comparison With Temporal Summation of Pain

OBJECTIVE

This study examined the diagnostic accuracy and test-retest reliability of a novel dynamic evoked pain protocol (slowly repeated evoked pain [SREP]) compared with temporal summation of pain (TSP), a standard index of central sensitization.

METHODS

Thirty-five fibromyalgia (FM) patients and 30 rheumatoid arthritis (RA) patients completed, in pseudorandomized order, a standard mechanical TSP protocol (10 stimuli of 1-second duration at the thenar eminence using a 300-g monofilament with 1 second interstimulus interval) and the SREP protocol (9 suprathreshold pressure stimuli of 5-second duration applied to the fingernail with a 30-second interstimulus interval). To evaluate reliability for both protocols, they were repeated in a second session 4-7 days later.

RESULTS

Evidence for significant pain sensitization over trials (increasing pain intensity ratings) was observed for SREP in FM (p < .001) but not in RA (p = .35), whereas significant sensitization was observed in both diagnostic groups for the TSP protocol (p < .008). Compared with TSP, SREP demonstrated higher overall diagnostic accuracy (87.7% versus 64.6%), greater sensitivity (0.89 versus 0.57), and greater specificity (0.87 versus 0.73) in discriminating between FM and RA patients. Test-retest reliability of SREP sensitization was good in FM (intraclass correlations = 0.80), and moderate in RA (intraclass correlations = 0.68).

CONCLUSIONS

SREP seems to be a dynamic evoked pain index tapping into pain sensitization that allows for greater diagnostic accuracy in identifying FM patients compared with a standard TSP protocol. Further research is needed to study mechanisms underlying SREP and the potential utility of adding SREP to standard pain evaluation protocols.

Increased pain sensitivity but normal pain modulation in adolescents with migraine

Inhibitory pain modulation has been reported to be deficient in adults across different types of chronic pain, including migraine. To determine whether a similar phenomenon occurs in youth, we performed a quantitative sensory testing investigation in adolescents with migraine (N = 19). These patients were compared to healthy adolescents with (Fam-His; N = 20) or without (Healthy; N = 29) a family history of migraine (eg, first-degree relative with migraine). Subjects were first familiarized with the stimuli and visual analogue rating scales using graded noxious stimuli (0°C, 43-49°C range). These data were used to explore potential pain sensitivity differences between the groups. Pain inhibition was assessed by conditioned pain modulation (CPM), which used both suprathreshold heat pain (heat CPM) and pressure pain thresholds (pressure CPM) as the test stimuli before and during cold-water immersion (8°C). In response to the graded heat stimuli, Fam-His participants reported higher pain intensity ratings compared with patients with migraine, who in turn reported higher pain intensity ratings than the healthy controls (F = 3.6, [df = 2, 459], P = 0.027). For heat and pressure CPM, there was no significant group difference in the magnitude of CPM responses. Thus, adolescents with migraine and healthy adolescents have similar inhibitory pain modulation capability, despite having marked differences in pain sensitivity. Although Fam-His participants are asymptomatic, they demonstrate alterations in pain processing, which may serve as markers for prediction of migraine development.

Menthol cigarette use and pain reporting among African American adults seeking treatment for smoking cessation

Nicotine has acute pain-relieving properties, and tobacco smokers often report using cigarettes to cope with pain. The proportion of smokers using menthol cigarettes has increased in recent years, and there is reason to suspect that menthol may enhance the analgesic effects of nicotine. Up to 90% of African American smokers report using menthol cigarettes, and African Americans tend to report more severe pain and greater difficulty quitting. Yet no known research has examined the relationship between menthol cigarette use and pain reporting. Thus, the goal of the current study was to test associations between menthol (vs. nonmenthol) cigarette use and pain among a sample of African American smokers. Current daily cigarette smokers (N = 115; 70% male; Mage = 47.05; MCPD = 15.2) were recruited to participate in a smoking cessation study. These data were collected at the baseline session. Daily menthol (vs. nonmenthol) cigarette use was associated with lower current pain intensity, lower average and worst pain over the past 3 months, and less pain-related physical impairment over the past 3 months. This study demonstrates that menthol (vs. nonmenthol) cigarette use is associated with less pain and pain-related functional interference among African American smokers seeking tobacco cessation treatment. Future research is needed to examine the potential acute analgesic effects of menthol versus nonmenthol cigarette use, examine temporal covariation between menthol cigarette use and pain reporting, and test whether pain-relevant processes contribute to the maintenance of menthol cigarette smoking among those with and without chronic pain. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Short- and long-term impact of remifentanil on thermal detection and pain thresholds after cardiac surgery: A randomised controlled trial

BACKGROUND

The clinical relevance of the suggested hyperalgesic effects of remifentanil is still unclear, especially in the long term.

OBJECTIVE

The current study evaluated the impact of remifentanil on thermal thresholds 3 days and 12 months after surgery, measured with Quantitative Sensory Testing.

DESIGN

A single-blind, randomised controlled trial.

SETTING

A tertiary care teaching hospital in The Netherlands, from 2014 to 2016.

PATIENTS

A total of 126 patients aged between 18 and 85 years, undergoing cardiothoracic surgery via sternotomy (coronary artery bypass grafts and/or valve replacement) were included. Exclusion criteria were BMI above 35 kg m, history of cardiac surgery, chronic pain conditions, neurological conditions, allergy to opioids or paracetamol, language barrier and pregnancy.

INTERVENTIONS

Patients were allocated randomly to receive intra-operatively either a continuous remifentanil infusion or intermittent intra-operative fentanyl as needed in addition to standardised anaesthesia with propofol and intermittent intravenous fentanyl at predetermined time points.

MAIN OUTCOME MEASURES

Warm and cold detection and pain thresholds 3 days and 12 months after surgery. In addition the use of remifentanil, presence of postoperative chronic pain, age, opioid consumption and pre-operative quality of life were tested as a predictor for altered pain sensitivity 12 months after surgery.

RESULTS

Both warm and cold detection, and pain thresholds, were not significantly different between the remifentanil and fentanyl groups 3 days and 12 months after surgery (P > 0.05). No significant predictors for altered pain sensitivity were identified.

CONCLUSION

Earlier reports of increased pain sensitivity 1 year after the use of remifentanil could not be confirmed in this randomised study using Quantitative Sensory Testing. This indicates that remifentanil plays a minor role in the development of chronic thoracic pain. Still, the relatively high incidence of chronic thoracic pain and its accompanying impact on quality of life remain challenging problems.

TRIAL REGISTRATION

The study was registered at EudraCT (ref: 2013-000201-23) and ClinicalTrials.gov (https://clinicaltrials.gov/ct2/show/NCT02031016).

Effects of Combining a Brief Cognitive Intervention with Transcranial Direct Current Stimulation on Pain Tolerance: A Randomized Controlled Pilot Study

Objective

Cognitive behavioral therapy has been shown to be effective for treating chronic pain, and a growing literature shows the potential analgesic effects of minimally invasive brain stimulation. However, few studies have systematically investigated the potential benefits associated with combining approaches. The goal of this pilot laboratory study was to investigate the combination of a brief cognitive restructuring intervention and transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex in affecting pain tolerance.

Design

Randomized, double-blind, placebo-controlled laboratory pilot.

Setting

Medical University of South Carolina.

Subjects

A total of 79 healthy adult volunteers.

Methods

Subjects were randomized into one of six groups: 1) anodal tDCS plus a brief cognitive intervention (BCI); 2) anodal tDCS plus pain education; 3) cathodal tDCS plus BCI; 4) cathodal tDCS plus pain education; 5) sham tDCS plus BCI; and 6) sham tDCS plus pain education. Participants underwent thermal pain tolerance testing pre- and postintervention using the Method of Limits.

Results

A significant main effect for time (pre-post intervention) was found, as well as for baseline thermal pain tolerance (covariate) in the model. A significant time × group interaction effect was found on thermal pain tolerance. Each of the five groups that received at least one active intervention outperformed the group receiving sham tDCS and pain education only (i.e., control group), with the exception of the anodal tDCS + education-only group. Cathodal tDCS combined with the BCI produced the largest analgesic effect.

Conclusions

Combining cathodal tDCS with BCI yielded the largest analgesic effect of all the conditions tested. Future research might find stronger interactive effects of combined tDCS and a cognitive intervention with larger doses of each intervention. Because this controlled laboratory pilot employed an acute pain analogue and the cognitive intervention did not authentically represent cognitive behavioral therapy per se, the implications of the findings on chronic pain management remain unclear.

Quantitative sensory testing in children with sickle cell disease: additional insights and future possibilities

Quantitative sensory testing (QST) is used in a variety of pain disorders to characterize pain and predict prognosis and response to specific therapies. In this study, we aimed to confirm results in the literature documenting altered QST thresholds in sickle cell disease (SCD) and assess the test-retest reliability of results over time. Fifty-seven SCD and 60 control subjects aged 8-20 years underwent heat and cold detection and pain threshold testing using a Medoc TSAII. Participants were tested at baseline and 3 months; SCD subjects were additionally tested at 6 months. An important facet of our study was the development and use of a novel QST modelling approach, allowing us to model all data together across modalities. We have not demonstrated significant differences in thermal thresholds between subjects with SCD and controls. Thermal thresholds were consistent over a 3- to 6-month period. Subjects on whom hydroxycarbamide (HC) was initiated shortly before or after baseline testing (new HC users) exhibited progressive decreases in thermal sensitivity from baseline to 6 months, suggesting that thermal testing may be sensitive to effective therapy to prevent vasoocclusive pain. These findings inform the use of QST as an endpoint in the evaluation of preventative pain therapies.

Preliminary evidence that hydroxyurea is associated with attenuated peripheral sensitization in adults with sickle cell disease

Introduction:

Hydroxyurea (HU) is a drug that targets the underlying pathophysiology of sickle cell disease (SCD); however, it continues to be an underutilized treatment for adults. Previous research suggests that HU treatment can result in fewer hospital contacts for acute vaso-occlusive pain crises (VOC). Hydroxyurea's impact on non-VOC pain, however, is not well established.

Objectives:

This study examined whether HU moderated patterns of static and dynamic pain processing and clinical pain in SCD individuals.

Methods:

Fifty-eight patients with SCD (N taking HU = 17) underwent quantitative sensory testing (QST) and completed twice daily symptom diaries for 12 weeks. Quantitative sensory testing established thermal threshold and tolerance, mechanical thresholds, and thermal and mechanical temporal summation of pain.

Results:

Groups did not differ in age, sex, or opioid use. After controlling for morphine use, QST results showed that participants taking HU had higher heat and mechanical pain thresholds (static QST measures) but not thermal and mechanical temporal summation (dynamic QST measures). Participants taking HU also reported lower VOC pain compared with SCD participants not taking HU; however, HU did not moderate non-VOC clinical pain ratings.

Conclusion:

Findings cautiously suggest that HU acts on pain hypersensitivity and VOC pain, rather than inhibiting pain facilitation and non-VOC pain. These differences may reflect HU's influence on peripheral rather than central sensitization. Future research is warranted to replicate these findings in a larger sample and determine whether early HU administration can prevent peripheral sensitization in SCD individuals.

Motor corticospinal excitability: a novel facet of pain modulation?

Introduction

Increase in excitability of the primary motor cortex (M1) is associated with pain inhibition by analgesics, which is, in turn, associated with the psychophysical antinociceptive pain modulation profile. However, the relationship between neurophysiological M1 excitability and psychophysical pain modulation has not yet been explored.

Objectives

We aim to study these relationships in healthy subjects.

Methods

Forty-one young healthy subjects (22 women) underwent a wide battery of psychophysical testing that included conditioned pain modulation (CPM) and pain temporal summation, and a transcranial magnetic stimulation neurophysiological assessment of the motor corticospinal excitability, including resting motor threshold, motor-evoked potentials (MEPs), and cortical silent period.

Results

Increased motor corticospinal excitability in 2 parameters was associated with more efficient CPM: (1) higher MEP amplitude (r = -0.574; P _{_Bonferroni} = 0.02) and (2) longer MEP duration (r = -0.543; P _{_Bonferroni} = 0.02). The latter also correlated with the lower temporal summation magnitude (r = -0.421; P = 0.007); however, on multiplicity adjustment, significance was lost.

Conclusions

Increased corticospinal excitability of the primary motor cortex is associated with more efficient inhibitory pain modulation as assessed by CPM, in healthy subjects. Motor-evoked potential amplitude and duration may be considered as an additional, objective and easy to measure parameter to allow for better individual assessment of pain modulation profile.

Evaluating the novel added value of neurophysiological pain sensitivity within the fear-avoidance model of pain

BACKGROUND

The fear-avoidance model (FAM) is a leading theoretical paradigm for explaining persistent pain following musculoskeletal injury. The model suggests that as injuries heal, pain-related outcomes are increasingly determined by psychological, rather than physiological factors. Increasing literature, however, suggests that neurophysiological processes related to pain sensitivity also play an important role in chronicity. To date, there has been limited research that has specifically explored the role of pain sensitivity within the FAM. This study addresses this gap by evaluating whether clinical measures of pain sensitivity help explain FAM-related outcomes, beyond model-relevant psychological predictors.

METHODS

The study sample consisted of 80 adults with chronic and widespread musculoskeletal pain. Participants completed a single testing session that included measures of all of the major constructs of the FAM, including pain catastrophizing, pain-related fear, activity avoidance (self-report and functional measures), pain-related disability, depression and pain severity, as well as a battery of quantitative sensory testing that included measures of pressure pain threshold and temporal summation of mechanical pain across eight body sites.

RESULTS

A series of hierarchical regression analyses revealed that after controlling for the psychological predictors of the FAM, indices of pain sensitivity significantly predicted 4 of the 5 FAM-related outcomes (p < 0.05). Depression was the only outcome not significantly predicted by pain sensitivity. Interestingly, measures of pain sensitivity, but not FAM psychological factors, predicted the functional measure of activity avoidance.

CONCLUSIONS

These findings provide further evidence for the importance of neurophysiological factors within the FAM and have important clinical and theoretical implications.

SIGNIFICANCE

This study provides evidence for the unique and added value of neurophysiological factors within the Fear Avoidance Model of pain and for the importance of integrating both sensory and psychological factors within both theoretical paradigms and clinical management strategies.

Pain characterization and response to palliative care in dogs with naturally-occurring appendicular osteosarcoma: An open label clinical trial

This study aimed to characterize bone cancer pain (quantitative sensory testing (QST), stance asymmetry index, actimetry, scores of pain and quality of life (QoL)) in dogs with appendicular osteosarcoma (OSA), and to evaluate a stepwise palliative analgesic treatment.

The pain profile of thirteen client-owned dogs with OSA was compared with seven healthy dogs. Dogs with OSA were then enrolled in a prospective, open-label, clinical trial. Outcome measures included: primary and secondary mechanical thresholds (MT), conditioned pain modulation (CPM), stance asymmetry index, actimetry (most and least active periods), visual analog scales and QoL. After baseline assessments, stepwise treatment comprised orally administered cimicoxib (2 mg/kg q 24h), amitriptyline (1–1.5 mg/kg q 24h) and gabapentin (10 mg/kg q 8h); re-evaluations were performed after 14 (D14), 21 (D21) and 28 (D28) days, respectively. Statistics used mixed linear models (α = 5%; one-sided). Centralized nociceptive sensitivity (primary and secondary MT, and dynamic allodynia) was recorded in OSA dogs. Healthy dogs had responsive CPM, but CPM was deficient in OSA dogs. Construct validity was observed for the QST protocol. Asymmetry index was significantly present in OSA dogs. The CPM improved significantly at D14. When compared with baseline (log mean ± SD: 4.1 ± 0.04), most active actimetry significantly improved at D14 (4.3 ± 0.04), D21 and D28 (4.2 ± 0.04 for both). When compared with baseline, least active actimetry significantly decreased after treatment at all time-points indicating improvement in night-time restlessness. No other significant treatment effect was observed. Except for tactile threshold and actimetry, all outcomes worsened when gabapentin was added to cimicoxib-amitriptyline. Dogs with bone cancer are affected by widespread somatosensory sensitivity characterized by peripheral and central sensitization and have a deficient inhibitory system. This severe pain is mostly refractory to palliative analgesic treatment, and the latter was only detected by specific and sensitive outcomes.

Can disbudding of calves (one versus four weeks of age) induce chronic pain?

BACKGROUND

Calf disbudding is a welfare-relevant invasive husbandry procedure. While it is widely recognized that disbudding elicits acute pain, its chronic consequences are currently unknown.

OBJECTIVES

Primary aim of this study was to investigate whether disbudding leads to chronic pain in calves; secondary aim was to evaluate the influence of age at disbudding (1 week versus 4 weeks).

METHODS

Thirty-four Holstein bull calves, enrolled in a prospective, controlled, randomized trial, underwent either early disbudding (ED) or late disbudding (LD) or sham treatment (control) at 1 and 4 weeks of age. Pain scoring and quantitative sensory tests (von Frey filaments and algometry) were performed at regular intervals up to 105 days of life; neurophysiological determination of nociceptive reflex thresholds and conditioned pain modulation (CPM) up to 90 days. Data was analyzed with the Brunner and Langer model followed by post-hoc test, with level of significance set at 0.05.

RESULTS

Thirty-one calves completed the data collection. Signs of chronic sensitization were observed in 38% of disbudded calves (4 in ED and 4 in LD). Pain scores (until 105 days) and allodynia scores (until 60 days) were significantly higher while pressure thresholds (until 105 days) were significantly lower in both groups ED and LD compared to control. Late disbudded calves showed impairment of trigeminal CPM. Lower laser-evoked trigeminal reflex thresholds were found in clinically painful calves compared to control.

CONCLUSIONS

The sequelae of disbudding can extend beyond the acute post-procedural phase. Chronic trigeminal sensitization, independently from the age at disbudding can affect individual calves.

The LURN Research Network Neuroimaging and Sensory Testing (NIST) Study: Design, protocols, and operations

The Neuroimaging and Sensory Testing (NIST) Study of the Symptoms of Lower Urinary Tract Dysfunction Research Network (LURN) is a cross-sectional, case-control study designed to investigate whether disrupted brain connectivity and sensory processing are associated with abnormal lower urinary tract symptoms (LUTS) in patients with overactive bladder syndrome (OAB). The NIST Study tests the hypotheses that patients with urinary urgency will demonstrate: (1) abnormal functional and structural connectivity of brain regions involved in urinary sensation on magnetic resonance imaging (MRI), and (2) hypersensitivity to painful (pressure) and non-painful (auditory) sensory stimuli on quantitative sensory testing (QST), compared to controls. Male and female adults (18 years or older) who present at one of the six participating LURN clinical centers for clinical care of their LUTS, with symptoms of urinary urgency with or without urgency urinary incontinence, are eligible to participate. The NIST Study is the largest MRI and QST study of its kind, yielding a neuroimaging and sensory testing dataset unprecedented in OAB research. Advanced multi-modal techniques are used to understand brain functional and structural connectivity, including gray matter volume, and sensory function. Unlike previous MRI studies which involved invasive catheterization and repeated cycles of non-physiologic bladder filling and emptying via a catheter, we use a water ingestion protocol to mimic more physiological bladder filling through natural diuresis. Furthermore, these data will be used in concert with other phenotyping data to improve our understanding of clinically meaningful subtypes of patients with LUTS in order to improve patient care and management outcomes.

Association of Cannabinoid Administration With Experimental Pain in Healthy Adults: A Systematic Review and Meta-analysis

Importance

Cannabinoid drugs are widely used as analgesics, but experimental pain studies have produced mixed findings. The analgesic properties of cannabinoids remain unclear.

Objective

To conduct a systematic review and meta-analysis of the association between cannabinoid drug administration and experimental pain outcomes in studies of healthy adults.

Design, Setting, and Participants

A systematic search of PubMed, EMBASE, MEDLINE, PsycINFO, and CINAHL was conducted from the inception of each database to September 30, 2017. Studies were eligible for inclusion if they met criteria, including healthy participants and an experimentally controlled administration of any cannabinoid preparation in a quantified dose. Studies that used participants with chronic pain were excluded. Data extracted included study characteristics, cannabinoid types and doses, sex composition, and outcomes. Study quality was assessed using a validity measure previously established in published reviews. Random-effects meta-analyses were used to pool data and generate summary estimates.

Main Outcomes and Measures

Experimental pain threshold, pain tolerance, pain intensity, pain unpleasantness, and mechanical hyperalgesia.

Results

Eighteen placebo-controlled studies (with 442 participants) were identified. Of the 442 participants, 233 (52.7%) were male and 209 (47.3%) were female. For sample ages, 13 (72%) of the 18 studies reported a mean sample age (26.65 years), 4 (22%) reported a range, and 1 (6%) reported a median value. The search yielded sufficient data to analyze 18 pain threshold comparisons, 22 pain intensity comparisons, 9 pain unpleasantness comparisons, 13 pain tolerance comparisons, and 9 mechanical hyperalgesia comparisons. Cannabinoid administration was associated with small increases in pain threshold (Hedges g = 0.186; 95% CI, 0.054-0.318; P = .006), small to medium increases in pain tolerance (Hedges g = 0.225; 95% CI, 0.015-0.436; P = .04), and a small to medium reduction in the unpleasantness of ongoing experimental pain (Hedges g = 0.288; 95% CI, 0.104-0.472; P = .002). Cannabinoid administration was not reliably associated with a decrease in experimental pain intensity (Hedges g = 0.017; 95% CI, -0.120 to 0.154; P = .81) or mechanical hyperalgesia (Hedges g = 0.093; 95% CI, -0.059 to 0.244; P = .23). The mean quality rating across studies was good.

Conclusions and Relevance

Cannabinoid drugs may prevent the onset of pain by producing small increases in pain thresholds but may not reduce the intensity of experimental pain already being experienced; instead, cannabinoids may make experimental pain feel less unpleasant and more tolerable, suggesting an influence on affective processes. Cannabis-induced improvements in pain-related negative affect may underlie the widely held belief that cannabis relieves pain.

The Central Sensitization Inventory and Pain Sensitivity Questionnaire: An exploration of construct validity and associations with widespread pain sensitivity among individuals with shoulder pain

BACKGROUND

The Central Sensitization Inventory (CSI) and Pain Sensitivity Questionnaire (PSQ) are alternatives to quantitative sensory testing (QST) for inferring central sensitization.

OBJECTIVE

Explore 1) comparative validity of the CSI and PSQ with QST (construct validity) and pain-related psychological questionnaires (concurrent validity), and 2) associations with widespread pain sensitivity.

METHODS

Seventy-eight participants with unilateral shoulder pain less than 6 months (mean ± SD age = 39.0 ± 14.5 years, N (%) females = 36 (46.2%)) completed the CSI, PSQ, psychological questionnaires, and underwent QST for local and remote pressure pain thresholds (PPT), heat pain threshold, and suprathreshold heat pain ratings. Data from 25 age and sex-matched healthy participants (mean ± SD age = 35.2 ± 11.1 year, N (%) females = 13 (52.0%)) were used to determine a composite index for widespread pressure pain sensitivity in the shoulder pain group. Analyses included correlations between measures and between-group comparisons.

RESULTS

Only the PSQ was associated with remote PPT (rho range = -0.25 to -0.27). Both the CSI and PSQ were associated with resilience (rho range = -0.29 to -0.39), anxiety (rho range = 0.25 to 0.66), and negative affect (rho range = 0.27 to 0.67). Neither the CSI nor PSQ were associated with widespread pain sensitivity (p > 0.05). Resilience (adjusted OR = 0.41, 95% CI = 0.18; 0.94) was a distinctive feature for widespread pain sensitivity.

CONCLUSIONS

These preliminary findings challenge the exclusive use of the CSI or PSQ for inferring central sensitization among individuals with shoulder pain.

A new clinical model for facilitating the development of pattern recognition skills in clinical pain assessment

Common, enigmatic musculoskeletal conditions such as whiplash-associated disorder, myofascial pain syndrome, low back pain, headache, fibromyalgia, osteoarthritis, and rotator cuff pathology, account for significant social, economic, and personal burdens on a global scale. Despite their primacy (and shared sequelae) there remains a paucity of available and effective management options for patients with both acute and chronic conditions. Establishing an accurate prognostic or diagnostic profile on a patient-by-patient basis can challenge the insight of both novice and expert clinicians. Questions remain on how and when to choose the right tool(s), at the right time(s), for the right patient(s), for the right problem(s). The aim of this paper is to introduce a new clinical reasoning framework that is simple in presentation but allows interpretation of complex clinical patterns, and is adaptable across patient populations with acute or chronic, traumatic or non-traumatic pain. The concepts of clinical phenotyping (e.g. identifying observable characteristics of an individual resulting from the interaction of his/her genotype and their environment) and triangulation serve as the foundation for this framework. Based on our own clinical and research programs, we present these concepts using two patient cases; a) whiplash-associated disorder (WAD) following a motor vehicle collision and b) mechanical low back pain.

Serotonin-gated inward currents are three times more frequent in rat hairy skin sensory afferents than in those innervating the skeletal muscle

Tight whole-cell patch clamp was performed in 191 DiI (1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate) retrogradely labeled rat sensory afferents from skin shoulders ( n = 93) and biceps femoris muscles ( n = 98). 5-HT-gated inward currents were evoked with 50-µM serotonin (5-HT; 5-hydroxytryptamine), and their frequency and current densities were compared between skin and skeletal muscle sensory afferents. To evaluate if 5-HT-gated inward currents coexist with other ligand-gated currents, the skin and skeletal muscle sensory afferents were also sequentially exposed to external solution at pH 6.8, ATP (50 µM), and capsaicin (1 µM). 5-HT evoked inward currents in 72% (67 of 93) of hairy skin sensory afferents and in only 24% (24 of 98) of skeletal muscle sensory afferents, and this difference was statistically significant ( p < 0.0000, chi-square test). The current densities obtained in hairy skin and skeletal muscle sensory afferents were not significantly different. They were -45.8 ± 7.7 and -32.4 ± 10.5 pA/pF, respectively (mean ± SEM, p < 0.30734). These results indicate that 5-HT-gated inward currents are three times more frequently evoked in small- to medium-sized sensory afferents (25-40 µm) innervating the hairy skin than on those innervating the skeletal muscle. When cells were gathered in two clusters, the difference was four times larger in the small-sized cluster (25-32 µm) and two times larger in the medium-sized cluster (33-40 µm). The results can be explained if the superficial somatic (cutaneous) nociceptive system is more exposed than the deep somatic nociceptive system (musculoskeletal) to physical and chemical stimuli inducing 5-HT-mediated inflammatory pain.

An investigation of contextual factors in the application of multisensory illusions for analgesia in hand osteoarthritis

Objective

Emerging evidence suggests that multisensory illusions can modulate pain and can lead to changes in body perception. The aim of this study was to investigate whether contextual factors could explain the analgesic effects of multisensory body illusions on pain and body perception in people with hand OA (HOA).

Methods

In a crossover study, 28 individuals with painful HOA viewed their most affected hand in and outside of a real-time mediated reality system, with illusory stretching of the hand and changes in sensory input. The outcome measures were pain ratings, pressure pain thresholds, hand function and the subjective experience of the illusion.

Results

Stretching the hand both inside and outside the virtual environment led to a reduction in subjective pain ratings (all P < 0.05). Virtual stretching led to changes in body perception (P < 0.05) with no changes in pressure pain threshold (all P > 0.05). Higher pain at baseline predicted susceptibility to the stretch illusion and mean susceptibility ratings were greatest after the stretch illusion.

Conclusion

The current study highlights the importance of the context in which pain occurs and in which potential treatments may be applied. In this case, virtual and physical stretching modulated pain, but not viewing the hand alone. The research opens important implications for future research, including the use of contextual control conditions and the development of visual feedback interventions for a range of similarly visible chronic conditions for which pain, body image disturbances and body dissatisfaction may be apparent.

The added value of bedside examination and screening QST to improve neuropathic pain identification in patients with chronic pain

Background

The assessment of a neuropathic pain component (NePC) to establish the neurological criteria required to comply with the clinical description is based on history taking, clinical examination, and quantitative sensory testing (QST) and includes bedside examination (BSE). The objective of this study was to assess the potential association between the clinically diagnosed presence or absence of an NePC, BSE, and the Nijmegen–Aalborg screening QST (NASQ) paradigm in patients with chronic (≥3 months) low back and leg pain or with neck shoulder arm pain or in patients with chronic pain due to suspected peripheral nerve damage.

Methods

A total of 291 patients participated in the study. Pain (absence or presence of neuro-pathic pain) was assessed independently by two physicians and compared with BSE (measurements of touch [finger, brush], heat, cold, pricking [safety pin, von Frey hair], and vibration). The NASQ paradigm (pressure algometry, electrical pain thresholds, and conditioned pain modulation) was assessed in 58 patients to generate new insights.

Results

BSE revealed a low association of differences between patients with either absent or present NePC: heat, cold, and pricking sensations with a von Frey hair were statistically significantly less common in patients with present NePC. NASQ did not reveal any differences between patients with and without an NePC.

Conclusion

Currently, a standardized BSE appears to be more useful than the NASQ paradigm when distinguishing between patients with and without an NePC.

TRPV1-Like Immunoreactivity in the Human Locus K, a Distinct Subregion of the Cuneate Nucleus

The presence of transient receptor potential vanilloid type-1 receptor (TRPV1)-like immunoreactivity (LI), in the form of nerve fibres and terminals, is shown in a set of discrete gray matter subregions placed in the territory of the human cuneate nucleus. We showed previously that those subregions share neurochemical and structural features with the protopathic nuclei and, after the ancient name of our town, collectively call them Locus Karalis, and briefly Locus K. TRPV1-LI in the Locus K is codistributed, though not perfectly overlapped, with that of the neuropeptides calcitonin gene-related peptide and substance P, the topography of the elements immunoreactive to the three markers, in relation to each other, reflecting that previously described in the caudal spinal trigeminal nucleus. Myelin stainings show that myelinated fibres, abundant in the cuneate, gracile and trigeminal magnocellular nuclei, are scarce in the Locus K as in the trigeminal substantia gelatinosa. Morphometric analysis shows that cell size and density of Locus K neurons are consistent with those of the trigeminal substantia gelatinosa and significantly different from those of the magnocellular trigeminal, solitary and dorsal column nuclei. We propose that Locus K is a special component of the human dorsal column nuclei. Its functional role remains to be determined, but TRPV1 appears to play a part in it.

Effect of low-level laser therapy on tooth-related pain and somatosensory function evoked by orthodontic treatment

Low-level laser therapy (LLLT) may have an effect on the pain associated with orthodontic treatment. The aim of this study was to evaluate the effect of LLLT on pain and somatosensory sensitization induced by orthodontic treatment. Forty individuals (12–33 years old; mean ± standard deviations: 20.8 ± 5.9 years) scheduled to receive orthodontic treatment were randomly divided into a laser group (LG) or a placebo group (PG) (1:1). The LG received LLLT (810-nm gallium-aluminium-arsenic diode laser in continuous mode with the power set at 400 mW, 2 J·cm^–2) at 0 h, 2 h, 24 h, 4 d, and 7 d after treatment, and the PG received inactive treatment at the same time points. In both groups, the non-treated side served as a control. A numerical rating scale (NRS) of pain, pressure pain thresholds (PPTs), cold detection thresholds (CDTs), warmth detection thresholds (WDTs), cold pain thresholds (CPTs), and heat pain thresholds (HPTs) were tested on both sides at the gingiva and canine tooth and on the hand. The data were analysed by a repeated measures analysis of variance (ANOVA). The NRS pain scores were significantly lower in the LG group (P = 0.01). The CDTs, CPTs, WDTs, HPTs, and PPTs at the gingiva and the PPTs at the canine tooth were significantly less sensitive on the treatment side of the LG compared with that of the PG (P < 0.033). The parameters tested also showed significantly less sensitivity on the non-treatment side of the LG compared to that of the PG (P < 0.043). There were no differences between the groups for any quantitative sensory testing (QST) measures of the hand. The application of LLLT appears to reduce the pain and sensitivity of the tooth and gingiva associated with orthodontic treatment and may have contralateral effects within the trigeminal system but no generalized QST effects. Thus, the present study indicated a significant analgesia effect of LLLT application during orthodontic treatment. Further clinical applications are suggested.

Repeated applications of low-level laser therapy during and after orthodontic procedures could help reduce pain and discomfort. Many orthodontic patients experience pain in the hours and days following treatment, which impacts on treatment participation. Wenjing Chen at Nanjing Medical University and co-workers assessed whether low-level laser therapy (LLLT) can reduce pain and sensitivity in teeth and surrounding tissues. They divided 40 patients into two groups; one was given repeated LLLT in the hours and days following procedures, while the other group received a placebo course. They tested both groups for sensitivity to stimuli including heat and pressure, in the mouth and on the hands. LLLT significantly reduced pain in the mouth relative to the placebo group. No differences were found in tests on the hands, suggesting LLLT works as a targeted analgesia.

Nicotine deprivation increases pain intensity, neurogenic inflammation, and mechanical hyperalgesia among daily tobacco smokers

An evolving reciprocal model posits that pain and tobacco smoking behavior interact in the manner of a positive feedback loop, resulting in greater pain and the maintenance of nicotine dependence. There is also reason to believe that abstaining from smoking may increase pain during the early stages of smoking cessation. The goal of this study was to test the effects of nicotine deprivation on experimental pain reactivity. Daily tobacco cigarette smokers (N = 165; 43% female) were randomized to either extended nicotine deprivation (12-24 hr smoking abstinence), minimal deprivation (2 hr smoking abstinence), or continued smoking conditions, prior to undergoing pain induction via topical capsaicin. As hypothesized, results indicated that extended deprivation (relative to continued smoking) increased capsaicin-induced pain intensity ratings, neurogenic inflammation, and mechanical hyperalgesia, thus implicating both central and peripheral mechanisms of action in the effects of smoking abstinence on pain reactivity. Pain intensity ratings were also positively correlated with nicotine withdrawal symptoms, and exploratory analyses suggest that pain sensitivity may increase with duration of smoking abstinence. Collectively, these findings indicate that smokers may experience a variety of negative pain-related sequelae during the early stages of a quit attempt. Future research should examine pain as a consequence or correlate of the nicotine withdrawal syndrome, and determine whether smokers may benefit from tailored cessation interventions that account for nicotine deprivation-induced amplification of pain. (PsycINFO Database Record

Assessment and manifestation of central sensitisation across different chronic pain conditions

Different neuroplastic processes can occur along the nociceptive pathways and may be important in the transition from acute to chronic pain and for diagnosis and development of optimal management strategies. The neuroplastic processes may result in gain (sensitisation) or loss (desensitisation) of function in relation to the incoming nociceptive signals. Such processes play important roles in chronic pain, and although the clinical manifestations differ across condition processes, they share some common mechanistic features. The fundamental understanding and quantitative assessment of particularly some of the central sensitisation mechanisms can be translated from preclinical studies into the clinic. The clinical perspectives are implementation of such novel information into diagnostics, mechanistic phenotyping, prevention, personalised treatment, and drug development. The aims of this paper are to introduce and discuss (1) some common fundamental central pain mechanisms, (2) how they may translate into the clinical signs and symptoms across different chronic pain conditions, (3) how to evaluate gain and loss of function using quantitative pain assessment tools, and (4) the implications for optimising prevention and management of pain. The chronic pain conditions selected for the paper are neuropathic pain in general, musculoskeletal pain (chronic low back pain and osteoarthritic pain in particular), and visceral pain (irritable bowel syndrome in particular). The translational mechanisms addressed are local and widespread sensitisation, central summation, and descending pain modulation.

Significance

Central sensitisation is an important manifestation involved in many different chronic pain conditions. Central sensitisation can be different to assess and evaluate as the manifestations vary from pain condition to pain condition. Understanding central sensitisation may promote better profiling and diagnosis of pain patients and development of new regimes for mechanism based therapy. Some of the mechanisms underlying central sensitisation can be translated from animals to humans providing new options in development of therapies and profiling drugs under development.

Effects of Androgen Deprivation Therapy on Pain Perception, Quality of Life, and Depression in Men With Prostate Cancer

CONTEXT

Previous animal and human research suggests that testosterone has antinociceptive properties. Castration in male rodents increases pain perception which is reversed by testosterone replacement. Pain perception also improves in hypogonadal men with testosterone therapy. However, it remains unclear whether androgen deprivation therapy (ADT) in men with prostate cancer (PCa) is associated with an increase in pain perception.

OBJECTIVES

To evaluate the effects of ADT on pain perception, depression and quality of life (QOL) in men with PCa.

METHODS

Thirty-seven men with PCa about to undergo ADT with leuprolide acetate (ADT group) were followed prospectively for six months to evaluate changes in clinical and experimental pain. Forty men who had previously undergone prostatectomy for localized PCa and were in remission served as controls (non-ADT group). All participants were eugonadal at study entry. Primary outcomes were changes in clinical pain (assessed with Brief Pain Inventory questionnaire) and experimental pain (assessed with quantitative sensory testing). Secondary outcomes included evaluation of depression, anxiety levels, and quality of life.

RESULTS

Serum testosterone levels significantly decreased in the ADT group but remained unchanged in the non-ADT group. There were no significant changes in pain thresholds, ratings, or other responses to quantitative sensory tests over the 6-month course of the study. Clinical pain did not differ between the two groups, and no changes from baseline were observed in either group. Men undergoing ADT did experience worsening of depression (0.93; 95% CI = 0.04-1.82; P = 0.042) and QOL related to physical role limitation (-18.28; 95% CI = -30.18 to -6.37; P = 0.003).

CONCLUSION

ADT in men with PCa is associated with worsening of depression scores and QOL but is not associated with changes in clinical pain or pain sensitivity.

Test Procedures to Assess Somatosensory Abnormalities in Individuals with Peripheral Joint Pain: A Systematic Review of Psychometric Properties

BACKGROUND

Test procedures that were developed to assess somatosensory abnormalities should possess optimal psychometric properties (PMPs) to be used in clinical practice. The aim of this systematic review was to evaluate the literature to assess the level of evidence for PMPs of test procedures investigated in individuals with peripheral joint pain (PJP).

METHODS

A comprehensive electronic literature search was conducted in 7 databases from inception to March 2016. The Quality Appraisal for Reliability Studies (QAREL) checklist and the Consensus-based Standards for the Selection of Health Status Measurement Instruments (COSMIN) tool were used to assess risk for bias of the included studies. Level of evidence was evaluated based on the methodological quality and the quality of the measurement properties.

RESULTS

Forty-one studies related to PJP were included. The majority of included studies were considered to be of insufficient methodological quality, and the level of evidence for PMPs varied across different test procedures. The level of evidence for PMPs varied across different test procedures in different types of PJP. Hand-held pressure algometry is the only test procedure that showed moderate positive evidence of intrarater reliability, agreement, and responsiveness, simultaneously, when it was investigated in patients with chronic knee osteoarthritis.

CONCLUSIONS

This systematic review identified that the level of evidence for PMPs varied across different testing procedures to assess somatosensory abnormalities for different PJP populations. Further research with standardized protocols is recommended to further investigate the predictive ability and responsiveness of reported test procedures in order to warrant their extended utility in clinical practice.

Differences in pain intensity in anti- and pro-nociceptive pain profile subgroups in patients with knee osteoarthritis

Aim: Facilitated temporal summation is one component of central sensitization. The aim of this exploratory study was to classify pro-, eu- and antinociceptive subgroups based on wind-up ratio cut-off scores in patients with knee osteoarthritis (OA). Patients & methods: A total of 56 patients with knee OA met the inclusion criteria. Temporal summation was measured and wind-up ratio was calculated. Reference values of 180 healthy subjects were used to define wind-up ratio cut-off scores. Results: Twenty-seven percent of patients showed a pro-nociceptive pain profile. Sixteen percent of patients showed an anti-nociceptive pain profile. A eu-nociceptive pain profile was present in 57% of patients. Conclusion: Central pain sensitization was present in approximately a third of knee OA patients. The results should be confirmed in larger studies.

Association between physical activity and pain processing in adults with chronic low back pain compared to pain-free controls

BACKGROUND

Pain sensitivity has been negatively associated with physical activity levels. Few studies have examined associations between experimentally induced pain sensitivity and physical activity in adults with chronic low back pain and pain-free controls.

OBJECTIVE

The objective of this study was to examine associations between physical activity levels and how an individual processes pain using experimentally induced pain stimuli.

METHODS

Seventy subjects (CLBP = 49; mean age = 46.8 ± 14.9; Pain-free = 21; mean age = 45.3 ± 18.2, n of females = 46) participated. A self-report questionnaire derived from the International Physical Activity Questionnaire (IPAQ) was used to calculate an activity level index. Pain sensitivity was assessed via quantitative sensory testing (QST) at the right lower extremity.

RESULTS

Moderate (U = 688, p< 0.05) and vigorous (U = 649, p< 0.05) physical activity levels were higher in pain-free vs. individuals with CLBP. Activity level was not associated with pain sensitivity (Pain-free: R2 = 0.02, p> 0.05; CLBP: R2 = 0.01, p> 0.05). Both moderate (R2 = 0.49, p< 0.05) and vigorous (R2 = 0.68, p< 0.01) physical activity were associated with pain modulation amongst pain-free individuals.

CONCLUSIONS

Findings suggest that physical activity influences pain modulation amongst pain-free individuals, however no relationship exists once CLBP is present. However, future investigation will elucidate the extent to which physical activity level either prevents CLBP or is effective in alleviating CLBP.

Somatosensory Test Responses and Physical and Psychological Functioning of Children and Adolescents with Chronic Non-neuropathic Pain: An Exploratory Study

OBJECTIVES

This study was designed to establish preliminary feasibility testing of a set of inherently benign somatosensory stimulus-response tests (to cutaneous and deep stimuli) for bedside or office evaluation of pain disorders in children and adolescents. Associations between, and the relative influence of, cutaneous somatosensory testing (SST) responses, deep SST responses, and psychological factors (depression, pain-related catastrophizing) on pain outcomes (worst pain intensity, pain-related disability) were considered.

METHODS

Sixty participants (6 to 18 y) were recruited from the pediatric chronic pain clinic. SST responses were assessed at the pain site (PS) and control sites to diverse stimuli (static/dynamic touch, punctate pressure, vibration, cool, deep pressure) using Colored Analogue Scales (CAS) with modified anchors. Validated measures of depression, pain-related catastrophizing, and pain-related functional interference were administered.

RESULTS

Responses at the PS were more frequently hypersensitive than hyposensitive for all SST measures except vibration. Deep pressure responses were the only statistically significant predictor of worst pain intensity. Depression and pain-related catastrophizing accounted for a statistically significant amount of variance of pain-related disability, over and above that which was accounted for by SST responses.

DISCUSSION

Preliminary feasibility of a set of somatosensory stimulus-response tests for bedside or office evaluation of pain disorders in children and adolescents was established. Deep pressure responses contributed unique information in predicting worst pain intensity but not functional interference. Although cutaneous SST responses at the PSs were frequently abnormal, cutaneous SST responses were not confirmed in this study to have clinical utility, but rather might be centrally mediated epiphenomena.

Effects of a Worksite Supervised Adapted Physical Activity Program on Trunk Muscle Endurance, Flexibility, and Pain Sensitivity Among Vineyard Workers

OBJECTIVES

In viticulture, the prevalence of low back pain is particularly high among vineyard workers exposed to sustained and awkward postures. One promising setting for low back pain prevention resides in the implementation of workplace physical activity.

METHODS

This nonrandomized pilot study aims at evaluating the effects of a worksite supervised adapted physical activity program among 17 vineyard workers volunteered to enter either an intervention group (n = 10) or a control group (n = 7).The intervention group followed a physical activity program for 8 weeks involving (1) 15 minutes of warm-up every working day and (2) two weekly 1-hour adapted physical activity sessions targeting trunk muscle endurance and flexibility. The control group was advised to continue normal physical activity. Evaluations were carried out at weeks 0, 4, 8, and 12. Physical capacity was assessed using flexibility tests for the trunk, along with trunk muscle flexor and extensor endurance tests. Finally, pain sensitivity was evaluated by assessing pressure pain thresholds over 14 anatomical locations in the low back region.

RESULTS

For the intervention group, the endurance of the trunk extensor and flexor significantly increased from baseline to week 8 as well as the pressure pain thresholds. No change was observed for the control group over the same period.

CONCLUSIONS

These encouraging results in combination with the high adherence rate set interesting foundations for the promotion of worksite supervised adapted physical activity and, most likely, offer a new promising approach to prevent low back pain among vineyard workers.

Facilitatory and inhibitory pain mechanisms are altered in patients with carpal tunnel syndrome

Preliminary evidence from studies using quantitative sensory testing suggests the presence of central mechanisms in patients with carpal tunnel syndrome (CTS) as apparent by widespread hyperalgesia. Hallmarks of central mechanisms after nerve injuries include nociceptive facilitation and reduced endogenous pain inhibition. Methods to study nociceptive facilitation in CTS so far have been limited to quantitative sensory testing and the integrity of endogenous inhibition remains unexamined. The aim of this study was therefore to investigate changes in facilitatory and inhibitory processing in patients with CTS by studying hypersensitivity following experimentally induced pain (facilitatory mechanisms) and the efficacy of conditioned pain modulation (CPM, inhibitory mechanisms). Twenty-five patients with mild to moderate CTS and 25 age and sex matched control participants without CTS were recruited. Increased pain facilitation was evaluated via injection of hypertonic saline into the upper trapezius. Altered pain inhibition through CPM was investigated through cold water immersion of the foot as the conditioning stimulus and pressure pain threshold over the thenar and hypothenar eminence bilaterally as the test stimulus. The results demonstrated that patients with CTS showed a greater duration (p = 0.047), intensity (p = 0.044) and area (p = 0.012) of pain in response to experimentally induced pain in the upper trapezius and impaired CPM compared to the control participants (p = 0.006). Although typically considered to be driven by peripheral mechanisms, these findings indicate that CTS demonstrates characteristics of altered central processing with increased pain facilitation and reduced endogenous pain inhibition.

Childhood Adversity and Pain Sensitization

OBJECTIVE

Childhood adversity is a vulnerability factor for chronic pain. However, the underlying pain mechanisms influenced by childhood adversity remain unknown. The aim of the current study was to evaluate the impact of childhood adversity on dynamic pain sensitivity in young adults.

METHODS

After screening for childhood adverse events and health status, healthy individuals reporting low (below median; n = 75) or high levels of adversity (the top 5%; n = 51) were invited for pain testing. Both groups underwent heat pain threshold and temporal summation of second pain (TSSP) testing after reporting depressive symptoms. TSSP refers to a progressive increase in pain intensity with repetition of identical noxious stimuli and is attributed to central sensitization. Changes in pain ratings over time (slope) were computed for TSSP sensitization and decay of subsequent aftersensations.

RESULTS

The high-adversity group showed greater TSSP sensitization (meanslope, 0.75; SDpositive slope, 1.78), and a trend toward a slower decay (meanslope, -11.9; SD, 3.4), whereas the low-adversity group showed minimal sensitization (meanslope, 0.07; SDnear-zero slope, 1.77), F(1,123) = 5.84, p = .017 and faster decay (meanslope, -13.1; SD, 3.4), F(1,123) = 3.79, p = .054. This group difference remained significant even after adjusting for adult depressive symptoms (p = .033). No group difference was found in heat pain threshold (p = .85). Lastly, the high-adversity group showed blunted cardiac and skin conductance responses.

CONCLUSIONS

These findings suggest that enhancement of central sensitization may provide a mechanism underlying the pain hypersensitivity and chronicity linked to childhood adversity.