Test Order of Quantitative Sensory Testing Facilitates Mechanical Hyperalgesia in Healthy Volunteers

Non-obese lipedema patients show a distinctly altered quantitative sensory testing profile with high diagnostic potential

Introduction and Objectives

Lipedema is a widespread severe chronic disease affecting mostly women. Characterized by painful bilateral fat accumulation in extremities sparing hands and feet, objective measurement-based diagnosis is currently missing. We tested for characteristic psychometric and/or sensory alterations including pain and for their potential for medical routine diagnosis.

Methods

Pain psychometry was assessed using the German Pain Questionnaire. Sensory sensitivity toward painful and nonpainful stimuli was characterized in non-obese lipedema patients and matched controls using the validated quantitative sensory testing (QST) protocol of the German Research Network on Neuropathic Pain.

Results

Lipedema patients showed no overt psychometric abnormalities. Pain was reported as somatic rather than psychosomatic aversive. All QST measurements were normal, but the z-score of pressure pain thresholds (PPT) was twofold reduced and the z-score of vibration detection thresholds (VDT) was two and a half times increased. Both thresholds were selectively altered at the affected thigh but not the unaffected hand. Receiver operating characteristic analysis of the combination of PPT and VDT of thigh vs hand into a PVTH score (PPT, VDT, thigh, hand-score) shows high sensitivity and specificity, categorizing correctly 95.8% of the participants as lipedema patients or healthy controls. Bayesian inference analysis corroborated the diagnostic potential of such a combined PVTH score.

Conclusion

We propose to assess PPT and VDT at the painful thigh and the pain-free hand. Combination in a PVTH score may allow a convenient lipedema diagnosis early during disease development.

Pain perception during baroreceptor unloading by lower body negative pressure

BACKGROUND

People with high blood pressure have reduced sensitivity to pain, known as blood pressure hypoalgesia. One proposed mechanism for this is altered baroreceptor sensitivity. In healthy volunteers, stimulating the carotid baroreceptors causes reduced sensitivity to acute pain; however, this effect may be confounded by a rise in blood pressure due to baroreflex stimulation. The present study tests whether baroreceptor unloading contributes to the physiological mechanism of blood pressure-related hypoalgesia.

METHODS

In the present study, pain perception to thermal stimulation of the forearm was studied in 20 healthy volunteers during baroreceptor unloading by lower body negative pressure (LBNP) at -5 and -20 mmHg. Blood pressure and heart rate were measured continuously throughout. To address issues relating to stimulation order, the sequence of LBNP stimulation was counterbalanced across participants.

RESULTS

Increased heart rate was observed at a LBNP of -20 mmHg, but not -5 mmHg, but neither stimulus had an effect on blood pressure. There was no change in warm or cold sensory detection thresholds, heat or cold pain thresholds nor perceived pain from a 30s long thermal heat stimulus during LBNP.

CONCLUSION

Therefore, baroreceptor unloading with maintained systemic blood pressure did not alter pain perception. The current study does not support the hypothesis that an altered baroreflex may underlie the physiological mechanism of blood pressure-related hypoalgesia.

SIGNIFICANCE

This work provides evidence that, when measured in normotensive healthy young adults, the baroreflex response to simulated hypovolaemia did not lead to reduced pain sensitivity (known as blood pressure hypoalgesia).

Secondary analysis: heat and self-report pain sensitivity associate with biological sex and racialized sociocultural group but may not be mediated by anxiety or pain catastrophizing

Introduction

Previous studies have demonstrated associations between sex and racialized group on pain sensitivity and tolerance. We analyzed the association of sex and racialized group on heat pain sensitivity, sensibility to painful suprathreshold mechanical pain (STMP), and pain sensitivity questionnaire (PSQ). We hypothesized that anxiety and pain catastrophizing reported by racialized minority groups and women would mediate enhanced pain sensitivity. Our secondary aim was to evaluate validity of the PSQ in a diverse population.

Methods

Using quantitative sensory testing for painful heat, STMP (forces: 64, 128, 256, and 512 mN), and PSQ, we evaluated pain sensitivity in 134 healthy participants [34 (18 women) Asian, 25 (13 women) Black, and 75 (41 women) White]. We used general linear and linear mixed models to analyze outcomes. We assessed mediation of state and trait anxiety and pain catastrophizing on pain sensitivity.

Results

Racialized minority status was associated with greater heat pain sensitivity (F = 7.63; P = 0.00074) and PSQ scores (F = 15.45; P = 9.84 × 10-7) but not associated with STMP (F = 1.50; P = 0.23). Female sex was associated with greater heat pain sensitivity (F = 4.9; P = 0.029) and lower PSQ (F = 9.50; P = 0.0025) but not associated with STMP (F = 0.0018; P = 0.97). Neither anxiety nor pain catastrophizing mediated associations between sex or racialized group with heat pain threshold or PSQ. Differential experience of individual items (F = 19.87; P = 3.28 × 10-8) limited PSQ face validity in racialized minorities.

Conclusion

Consistent with previous research, sensitivity to painful heat was associated with racialized minority status and female sex. By contrast, there was no significant effect of racialized minority status or female sex on STMP. Some PSQ items are inapplicable to participants from racialized minority groups.

The perception of pain, discriminative touch and affective touch in patients suffering from Borderline Personality Disorder

Borderline Personality Disorder (BPD) is often characterized by self-injurious behaviors, with one-half to two-third of these patients reporting hypalgesic or analgesic phenomena during self-harming. Research on pain perception in BPD suggested abnormal processing of nociception either within the sensory-discriminative and/or motivational-affective systems of pain. Nevertheless, it is still unclear whether pain insensitivity could be generalized to other somatosensory submodalities. To investigate this question, 30 BPD patients and 30 matched healthy controls were enrolled in the current study and underwent a somatosensory battery composed of well-established psychophysical test assessing all the principal submodalities of somatosensation, namely pain perception (i.e., warm, cold and mechanical), discriminative touch (i.e., tactile acuity and tactile sensitivity) as well as affective touch. Results showed abnormal warm detection threshold, warm pain threshold, mechanical pain perception, and tactile sensitivity in BPD patients, but no differences emerged neither for tactile acuity nor for cold pain thresholds, cold tolerance, or for affective touch perception. Findings point to a deficit in nociception, as well as in tactile sensitivity in BPD individuals, and were discussed in relation to BPD clinical features including self-injurious behaviors.

A Quantitative Measure of Pain with Current Perception Threshold, Pain Equivalent Current, and Quantified Pain Degree: A Retrospective Study

Background: As a subjective sensation, pain is difficult to evaluate objectively. The assessment of pain degree is largely dependent on subjective methods such as the numeric rating scale (NRS). The PainVisionTM system has recently been introduced as an objective pain degree measurement tool. The purpose of this study was to analyze correlations between the NRS and the current perception threshold (CPT), pain equivalent current (PEC), and quantified pain degree (QPD). Methods: Medical records of 398 subjects who visited the pain clinic in a university hospital from March 2017 to February 2019 were retrospectively reviewed. To evaluate the pain degree, NRS, CPT, PEC, and QPD were measured. Subjects were categorized into two groups: the Pain group (n = 355) and the No-pain group (n = 43). Results: The NRS showed a negative correlation with CPT (R = -0.10, p = 0.054) and a positive correlation with QPD (R = 0.13, p = 0.008). Among various diseases, only spinal disease patients showed a negative correlation between CPT and NRS (R = -0.22, p = 0.003). Additionally, there were significant differences in CPT and QPD between the Pain and No-pain groups (p = 0.005 and p = 0.002, respectively). Conclusions: CPT and QPD measured using the PainVisionTM system could be used to estimate pain intensity and the presence of pain. These parameters would be considered useful for predicting pain itself and its intensity.

We need to talk: The urgent conversation on chronic pain, mental health, prescribing patterns and the opioid crisis

The opioid crisis’ pathways from first exposure onwards to eventual illnesses and fatalities are multiple, intertwined and difficult to dissect. Here, we offer a multidisciplinary appraisal of the relationships among mental health, chronic pain, prescribing patterns worldwide and the opioid crisis. Because the opioid crisis’ toll is especially harsh on young people, emphasis is given on data regarding the younger strata of the population. Because analgesic opioid prescription constitute a recognised entry point towards misuse, opioid use disorder, and ultimately overdose, prescribing patterns across different countries are examined as a modifiable hazard factor along these pathways of risk. Psychiatrists are called to play a more compelling role in this urgent conversation, as they are uniquely placed to provide synthesis and lead action among the different fields of knowledge and care that lie at the crossroads of the opioid crisis. Psychiatrists are also ideally positioned to gauge and disseminate the foundations for diagnosis and clinical management of mental conditions associated with chronic pain, including the identification of hazardous and protective factors. It is our hope to spark more interdisciplinary exchanges and encourage psychiatrists worldwide to become leaders in an urgent conversation with interlocutors from the clinical and basic sciences, policy makers and stakeholders including clients and their families.

Sensitivity to movement-evoked pain, central sensitivity symptoms, and pro-nociceptive profiles in people with chronic shoulder pain: A parallel-group cross-sectional investigation

OBJECTIVE

To investigate whether sensitivity to movement-evoked pain (SMEP), central sensitivity symptom burden, and quantitative sensory testing (QST) outcomes differ between healthy controls and people with chronic shoulder pain.

METHODS

People with chronic shoulder pain (n = 39) and healthy controls (n = 26) completed validated questionnaires measuring demographic, pain characteristics, psychological factors, social support, sleep quality, central sensitivity inventory (CSI), and physical activity levels. A blinded assessor administered QST measuring pressure pain threshold, temporal summation, conditioned pain modulation, and cold hyperalgesia. All participants performed repeated lifting of weighted canisters and reported severity of pain over successive lifts of the weighted canisters. Between-group differences in the QST, SMEP and CSI scores were investigated. Demographic and psychosocial variables were adjusted in the analyses.

RESULTS

Dynamic mechanical allodynia, mechanical temporal summation, movement-evoked pain scores, SMEP index, and CSI scores were significantly (p ≤ 0.05) higher in the chronic shoulder pain group than in healthy controls. A significant proportion of people with chronic shoulder pain presented with pro-nociceptive profiles and experienced higher pain severity, interference, and disability.

CONCLUSIONS

People with chronic shoulder pain displayed symptoms and signs of central sensitization. Future research should investigate the predictive role of central sensitization on clinical outcomes in shoulder pain.

Clinical Assessment of Chronic Musculoskeletal Pain-A Framework Proposal Based on a Narrative Review of the Literature

The assessment of chronic musculoskeletal pain (CMP) is a challenge shared by several health professionals. Fragmented or incomplete assessment can cause deleterious consequences for the patient's function. The objective of this paper was to propose a framework for clinical assessment of CMP based on the current literature and following the conceptual model of the International Classification of Functioning and Health (ICF). We propose that the ICF rationale may help to guide the processes, acting as a moderator of the clinical assessment, since it changes the perspective used to obtain and interpret findings during anamnesis and physical examination. Additionally, updated specific knowledge about pain, including that of pain domains and mechanisms, along with effective patient-clinician communication may act as a mediator of CMP assessment. We conduct the readers through the steps of the clinical assessment of CMP using both the proposed moderator and mediators and present a clinical example of application. We suggest that the proposed framework may help clinicians to implement a CMP assessment based on the biopsychosocial model using a critical and updated rationale, potentially improving assessment outcomes, i.e., clinical diagnosis.

Investigating the effects of mobilization with movement and exercise on pain modulation processes in shoulder pain - a single cohort pilot study with short-term follow up

OBJECTIVE

To explore the association between manual therapy and exercise and pain modulation and clinical characteristics in people with musculoskeletal shoulder pain.

METHODS

This is a prospective, longitudinal, single cohort pilot study. People with shoulder pain for longer than 6 weeks underwent 4 weeks of glenohumeral mobilization with movement and shoulder exercises. Measures of pain modulation, shoulder pain, disability, range of motion and psychosocial factors were assessed at baseline and immediately after the 4-week period of treatment. Treatment effectiveness was assessed through parametric, non-parametric and multilevel modeling statistics.

RESULTS

Twenty-three individuals participatedwith no loss to follow-up. Significant and meaningful improvements in shoulder pain (NRS mean change 1.6/10, 95% CI 0.4 to 2.7), disability (SPADI mean change 20.5/100, 95% CI 13.1 to 27.9) and range of motion (mean change 33°, 95% CI 23 to 43°) were observed following treatment. Statistical but non-clinically meaningful changes were observed in temporal summation of pain (mean change 0.3/10, 95% CI 0.1 to 0.4) and anxiety (mean change 0.86/21, 95% CI 0.18 to 1.55). Significant reductions were observed in temporal summation of pain (mean change 0.3/10, 95% CI 0.1 to 0.4) and anxiety (mean change 0.86/21, 95% CI 0.18 to 1.55), however these were not considered clinically important. No association was found between clinical characteristics and sensory measures. No association was found between clinical characteristics and sensory measures.

CONCLUSION

Glenohumeral mobilization with movement and exercise did not improve pain modulation, despite improvements in pain, function and range of motion, in people with shoulder pain.

Interoception as independent cardiac, thermosensory, nociceptive, and affective touch perceptual submodalities

Interoception includes signals from inner organs and thin afferents in the skin, providing information about the body's physiological state. However, the functional relationships between interoceptive submodalities are unclear, and thermosensation as skin-based interoception has rarely been considered. We used five tasks to examine the relationships among cardiac awareness, thermosensation, affective touch, and nociception. Thermosensation was probed with a classic temperature detection task and the new dynamic thermal matching task, where participants matched perceived moving thermal stimuli in a range of colder/warmer stimuli around thermoneutrality. We also examined differences between hairy and non-hairy skin and found superior perception of dynamic temperature and static cooling on hairy skin. Notably, no significant correlations were observed across interoceptive submodality accuracies (except for cold and pain perception in the palm), which indicates that interoception at perceptual levels should be conceptualised as a set of relatively independent processes and abilities rather than a single construct. DATA AVAILABILITY STATEMENT: Data of this study are available as a supplementary file.

Heritability of musculoskeletal pain and pain sensitivity phenotypes: two generations of the Raine Study

ABSTRACT

There is a need to better understand biological factors that increase the risk of persistent musculoskeletal pain and heightened pain sensitivity. Knowing the heritability (how genes account for differences in people's traits) can enhance the understanding of genetic versus environmental influences of pain and pain sensitivity. However, there are gaps in current knowledge, including the need for intergenerational studies to broaden our understanding of the genetic basis of pain. Data from Gen1 and Gen2 of the Raine Study were used to investigate the heritability of musculoskeletal pain, and pressure and cold pain sensitivity. Participants included parents (Gen 1, n=1092) and their offspring (Gen 2, n=688) who underwent a battery of testing and questionnaires including pressure and cold pain threshold testing and assessments of physical activity, sleep, musculoskeletal pain, mental health and adiposity. Heritability estimates were derived using the Sequential Oliogenic Linkage Analysis Routines (SOLAR) software. Heritability estimates for musculoskeletal pain and pressure pain sensitivity were significant, accounting for between 0.190 and 0.289 of the variation in the phenotype. In contrast, heritability of cold pain sensitivity was not significant. This is the largest intergenerational study to date to comprehensively investigate the heritability of both musculoskeletal pain and pain sensitivity, using robust statistical analysis. This study provides support for the heritability of musculoskeletal pain and pain sensitivity to pressure, suggesting the need for further convergence of genetic and environmental factors in models for the development and/or maintenance of these pain disorders.

Increased Experimental Pain Sensitivity in Chronic Pain Patients Who Developed Opioid Use Disorder

OBJECTIVE

Although the great majority of individuals who take opioids for chronic pain use them appropriately and to good effect, a certain minority will develop the problematic outcome of opioid use disorder (OUD). Characteristics associated with the development of OUD in individuals with chronic pain have been described; however, relatively unexplored is how sensitivity to pain is associated with OUD outcomes.

MATERIALS AND METHODS

We examined for differences in response to static and dynamic experimental pain stimuli between individuals with chronic nonmalignant pain who developed OUD after starting opioid therapy (n=20) and those on opioid therapy who did not (n=20). During a single experimental session, participants underwent cold pressor and quantitative sensory testing pain assays, and objective and subjective responses were compared between groups; the role of pain catastrophizing in mediating pain responses was examined.

RESULTS

Results suggested that both groups of opioid-dependent patients were similarly hyperalgesic to the cold pressor pain stimulus, with nonparametric testing revealing worsened central pain sensitization (temporal summation) in those who developed OUD. Significant group differences were evident on subjective ratings of experimental pain, such that those who developed OUD rated the pain as more severe than those who did not. Pain catastrophizing was unrelated to pain responses.

DISCUSSION

Despite the small sample size and cross-sectional design, these findings suggest that experimental pain testing may be a novel technique in identifying patients with chronic pain likely to develop OUD, in that they are likely to evidence exacerbated temporal summation and to rate the associated pain as more severe.

Modality-specific facilitation of noninjurious sharp mechanical pain by topical capsaicin

We had previously shown that a "blunt blade" stimulator can mimic the noninjurious strain phase of incisional pain, but not its sustained duration. Here, we tested whether acute sensitization of the skin with topical capsaicin can add the sustained phase to this noninvasive surrogate model of intraoperative pain. Altogether, 110 healthy volunteers (55 male and 55 female; 26 ± 5 years) participated in several experiments using the "blunt blade" (0.25 × 4 mm) on normal skin (n = 36) and on skin pretreated by a high-concentration capsaicin patch (8%, Qutenza; n = 36). These data were compared with an experimental incision (n = 40) using quantitative and qualitative pain ratings by numerical rating scale and SES Pain Perception Scale descriptors. Capsaicin sensitization increased blade-induced pain magnitude and duration significantly (both P < 0.05), but it failed to fully match the sustained duration of incisional pain. In normal skin, the SES pattern of pain qualities elicited by the blade matched incision in pain magnitude and pattern of pain descriptors. In capsaicin-treated skin, the blade acquired a significant facilitation only of the perceived heat pain component (P < 0.001), but not of mechanical pain components. Thus, capsaicin morphed the descriptor pattern of the blade to become more capsaicin-like, which is probably explained best by peripheral sensitization of the TRPV1 receptor. Quantitative sensory testing in capsaicin-sensitized skin revealed hyperalgesia to heat and pressure stimuli, and loss of cold and cold pain sensitivity. These findings support our hypothesis that the blade models the early tissue-strain-related mechanical pain phase of surgical incisions.

Cold pain hypersensitivity predicts trajectories of pain and disability after low back surgery: a prospective cohort study

Improving the ability to predict persistent pain after spine surgery would allow identification of patients at risk and guide treatment decisions. Quantitative sensory tests (QST) are measures of altered pain processes, but in our previous study, preoperative QST did not predict pain and disability at single time-points. Trajectory analysis accounts for time-dependent patterns. We hypothesized that QST predict trajectories of pain and disability during 1 year after low back surgery. We performed a trajectory analysis on the cohort of our previous study (n = 141). Baseline QST included electrical, pressure, heat, and cold stimulation of the low back and lower extremity, temporal summation, and conditioned pain modulation. Pain intensity and Oswestry Disability Index were measured before, and 2, 6, and 12 months after surgery. Bivariate trajectories for pain and disability were computed using group-based trajectory models. Multivariable regressions were used to identify QST as predictors of trajectory groups, with sociodemographic, psychological, and clinical characteristics as covariates. Cold pain hypersensitivity at the leg, not being married, and long pain duration independently predicted worse recovery (complete-to-incomplete, incomplete-to-no recovery). Cold pain hypersensitivity increased the odds for worse recovery by 3.8 (95% confidence intervals 1.8-8.0, P < 0.001) and 3.0 (1.3-7.0, P = 0.012) in the univariable and multivariable analyses, respectively. Trajectory analysis, but not analysis at single time-points, identified cold pain hypersensitivity as strong predictor of worse recovery, supporting altered pain processes as predisposing factor for persisting pain and disability, and a broader use of trajectory analysis. Assessment of cold pain sensitivity may be a clinically applicable, prognostic test.

Mechanical detection and pain thresholds: comparability of devices using stepped and ramped stimuli

Nylon monofilaments may substitute for German Research Network on Neuropathic Pain standards in tactile but not pinprick testing. Ramped stimuli are faster but underestimate thresholds due to reaction time artefacts.

Quantitative sensory testing is used to assess somatosensory function in humans. The protocol of the German Research Network on Neuropathic Pain (DFNS) provides comprehensive normative values using defined tools; however, some of these may not be feasible in low-resource settings.

Biopsychosocial Aspects in Individuals with Acute and Chronic Rotator Cuff Related Shoulder Pain: Classification Based on a Decision Tree Analysis

Biopsychosocial aspects seem to influence the clinical condition of rotator cuff related shoulder pain (RCRSP). However, traditional bivariate and linear analyses may not be sufficiently robust to capture the complex relationships among these aspects. This study determined which biopsychosocial aspects would better classify individuals with acute and chronic RCRSP and described how these aspects interact to create biopsychosocial phenotypes in individuals with acute and chronic RCRSP. Individuals with acute (<six months of pain, n = 15) and chronic (≥six months of pain, n = 38) RCRSP were included. Sociodemographic data, biological data related to general clinical health status, to shoulder clinical condition and to sensory function, and psychosocial data were collected. Outcomes were compared between groups and a decision tree was used to classify the individuals with acute and chronic RCRSP into different phenotypes hierarchically organized in nodes. Only conditioned pain modulation was different between the groups. However, the tree combined six biopsychosocial aspects to identify seven distinct phenotypes in individuals with RCRSP: three phenotypes of individuals with acute, and four with chronic RCRSP. While the majority of the individuals with chronic RCRSP have no other previous painful complaint besides the shoulder pain and low efficiency of endogenous pain modulation with no signs of biomechanical related pain, individuals with acute RCRSP are more likely to have preserved endogenous pain modulation and unilateral pain with signs of kinesiophobia.

A Quantitative Sensory Testing Approach to Pain in Autism Spectrum Disorders

Sensory abnormalities in autism has been noted clinically, with pain insensitivity as a specified diagnostic criterion. However, there is limited research using psychophysically robust techniques. Thirteen adults with ASD and 13 matched controls completed an established quantitative sensory testing (QST) battery, supplemented with measures of pain tolerance and central modulation. The ASD group showed higher thresholds for light touch detection and mechanical pain. Notably, the ASD group had a greater range of extreme scores (the number of z-scores outside of the 95% CI > 2), dynamic mechanical allodynia and paradoxical heat sensation; phenomena not typically seen in neurotypical individuals. These data support the need for research examining central mechanisms for pain in ASD and greater consideration of individual difference.

Clinical and Psychosocial Factors Over Time Following an Acute Low Back Pain Episode

BACKGROUND

Low back pain (LBP) is a prevalent condition with overwhelming healthcare costs and high disability rates. Characterization of clinical and psychosocial variables over time in patients experiencing an episode of acute LBP and the identification of factors that differ between those who develop chronic LBP and those who do not could aid in the development of improved targeted treatment.

PURPOSE

The purpose of this study was to evaluate the trajectory of depression, pain catastrophizing, life purpose, pain sensitivity, and disability in persons presenting with an acute/subacute episode of LBP, evaluating whether there are changes over time and differences in these variables between those who developed chronic LBP and those who did not.

METHODS

Prospective analysis (baseline, 2.5 months, 6 months, and weekly diaries) of 42 patients experiencing an acute LBP episode was performed. Descriptive statistics, repeated-measures mixed modeling, and Fisher's least significant differences method were used during data analysis.

RESULTS

Depressive symptoms vary over time. There was no difference over time in pain catastrophizing, life purpose, pain sensitivity, or disability. Those who met the criteria for chronic LBP at 6 months had increased pain catastrophizing scores and higher disability scores compared with those who do not meet the criteria for chronic LBP. Depressive symptoms, life purpose, and pain sensitivity were not different between those who met the criteria for chronic LBP and those who did not.

CONCLUSION

Findings from this study characterize factors potentially contributory to the development of chronic LBP over time. Those participants who developed chronic LBP had higher pain catastrophizing scores averaged across all time points in this study, suggesting it could be an interesting factor to target to improve LBP chronicity.

Sub-maximal endurance exercise does not mediate alterations of somatosensory thresholds

Physical exercise has been shown to alter sensory functions, such as sensory detection or perceived pain. However, most contributing studies rely on the assessment of single thresholds, and a systematic testing of the sensory system is missing. This randomised, controlled cross-over study aims to determine the sensory phenotype of healthy young participants and to assess if sub-maximal endurance exercise can impact it. We investigated the effects of a single bout of sub-maximal running exercise (30 min at 80% heart rate reserve) compared to a resting control in 20 healthy participants. The sensory profile was assessed applying quantitative sensory testing (QST) according to the protocol of the German Research Network on Neuropathic Pain. QST comprises a broad spectrum of thermal and mechanical detection and pain thresholds. It was applied to the forehead of study participants prior and immediately after the intervention. Time between cross-over sessions was one week. Sub-maximal endurance exercise did not significantly alter thermal or mechanical sensory function (time × group analysis) in terms of detection and pain thresholds. The sensory phenotypes did not indicate any clinically meaningful deviation of sensory function. The alteration of sensory thresholds needs to be carefully interpreted, and only systematic testing allows an improved understanding of mechanism. In this context, sub-maximal endurance exercise is not followed by a change of thermal and mechanical sensory function at the forehead in healthy volunteers.

Can quantitative sensory tests predict failed back surgery?: A prospective cohort study

BACKGROUND

Failed back surgery syndrome (FBSS) is a pain condition refractory to therapy, and is characterised by persistent low back pain after spinal surgery. FBSS is associated with severe disability, low quality of life and high unemployment. We are currently unable to identify patients who are at risk of developing FBSS. Patients with chronic low back pain may display signs of central hypersensitivity as assessed by quantitative sensory tests (QST). This can contribute to the risk of developing persistent pain after surgery.

OBJECTIVE

We tested the hypothesis that central hypersensitivity as assessed by QST predicts FBSS.

DESIGN

Prospective cohort study.

SETTING

Three tertiary care centres.

PATIENTS

141 patients scheduled for up to three segment spinal surgery for chronic low back pain (defined as at least 3 on a numerical rating scale on most days during the week and with a minimum duration of 3 months) due to degenerative changes.

OUTCOMES

We defined FBSS as persistent pain, persistent disability or a composite outcome defined as either persistent pain or disability. The primary outcome was persistent pain 12 months after surgery. We applied 14 QST using electrical, pressure and temperature stimulation to predict FBSS and assessed the association of QST with FBSS in multivariable analyses adjusted for sociodemographic, psychological and clinical and surgery-related characteristics.

RESULTS

None of the investigated 14 QST predicted FBSS, with 95% confidence intervals of crude and adjusted associations of all QST including one as a measure of no association. Results remained robust in all sensitivity and secondary analyses.

CONCLUSION

The study indicates that assessment of altered central pain processing using current QST is unlikely to identify patients at risk of FBSS and is therefore unlikely to inform clinical decisions.

Sedentary behaviour facilitates conditioned pain modulation in middle-aged and older adults with persistent musculoskeletal pain: a cross-sectional investigation

INTRODUCTION

Higher physical activity (PA) and lower sedentary behaviour (SB) levels have demonstrated beneficial effects on temporal summation (TS) and conditioned pain modulation (CPM) in healthy adults. This cross-sectional study investigated the relationships between PA and SB and TS/CPM responses in individuals with chronic musculoskeletal pain.

METHODS

Sixty-seven middle-aged and older adults with chronic musculoskeletal pain were recruited from the community. Questionnaires measuring demographics, pain, and psychological measures were completed. Physical activity/SB levels were measured using the International Physical Activity Questionnaire-short form and Sedentary Behaviour Questionnaire, respectively. Semmes monofilament was used to assess mechanical TS (MTS) at the most symptomatic (MTS-S) and a reference region (MTS-R); change in the pain scores (baseline-10th application) was used for analysis. Conditioned pain modulation procedure involved suprathreshold pressure pain threshold (PPT-pain4) administered before and after (CPM30sec, CPM60sec, and CPM90sec) conditioning stimulus (2 minutes; ∼12°C cold bath immersion). For analysis, PPT-pain4 (%) change scores were used.

RESULTS

PPT-pain4 (%) change scores at CPM30sec and CPM60sec demonstrated significant weak positive correlations with SB levels and weak negative correlations with PA measures. After adjusting for confounding variables, a significant positive association was found between SB (h/d) and PPT-pain4 (%) change scores at CPM30sec and CPM60sec. No significant associations between MTS and PA/SB measures.

CONCLUSION

Sedentariness is associated with higher pain inhibitory capacity in people with chronic musculoskeletal pain. The observed relationship may be characteristic of a protective (sedentary) behaviour to enhance pain modulatory mechanism. Prospective longitudinal studies using objective PA/SB measures are required to validate the observed relationship in a larger sample size.

Somatosensory profiles in acute herpes zoster and predictors of postherpetic neuralgia

This prospective cohort study aimed to characterize the sensory profile during acute herpes zoster (AHZ) and to explore sensory signs as well as physical and psychosocial health as predictors for postherpetic neuralgia (PHN). Results of quantitative sensory testing of 74 patients with AHZ at the affected site and at the distant contralateral control site were compared to a healthy control group. Pain characteristics (Neuropathic Pain and Symptom Inventory and SES), physical functioning, and psychosocial health aspects (Pain Disability Index, SF-36, and STAI) were assessed by questionnaires. Patients with PHN (n = 13) at 6-month follow-up were compared to those without PHN (n = 45). Sensory signs at the affected site were thermal and vibratory hypesthesia, dynamic mechanical allodynia (DMA), pressure hyperalgesia, and high wind-up (18%-29%), as well as paradoxical heat sensations and pinprick hypalgesia (13.5%). The unaffected control site exhibited thermal and vibratory hypesthesia, DMA, and pressure hyperalgesia. Dynamic mechanical allodynia and pinprick hypalgesia were mutually exclusive. Postherpetic neuralgia was associated with DMA (38.5% vs 6.7%; P = 0.010) and vibratory hypesthesia (38.5% vs 11.1%; P = 0.036) at the control site, with mechanical gain and/or loss combined with normal thermal detection (affected site: 69.2% vs 31.1%; P = 0.023; control site: 53.8% vs 15.5%; P = 0.009). Pain Disability Index (P = 0.036) and SES affective pain perception scores (P = 0.031) were over 50% higher, and 6 of 8 SF-36 subscores were over 50% lower (P < 0.045) in PHN. Sensory profiles in AHZ indicate deafferentation and central but not peripheral sensitization. Sensory signs at distant body sites, strong affective pain perception, as well as reduced quality of life and physical functioning in the acute phase may reflect risk factors for the transition to PHN.

Associations of physical activity or sedentary behaviour with pain sensitivity in young adults of the Raine Study

Background and aims

There is high level evidence for physical activity (PA) improving outcomes in persistent pain disorders and one of the mechanisms proposed is the effect of exercise on central nociceptive modulation. Although laboratory studies and small field intervention studies suggest associations between physical activity and pain sensitivity, the association of objectively measured, habitual PA and sedentary behaviour (SB) with pain sensitivity requires further investigation. Current evidence suggests PA typically lowers pain sensitivity in people without pain or with single-site pain, whereas PA is frequently associated with an increase in pain sensitivity for those with multisite pain. The aim of this study was to explore the relationships of PA and SB with pain sensitivity measured by pressure pain thresholds and cold pain thresholds, considering the presence of single-site and multisite pain and controlling for potential confounders.

Methods

Participants from the Western Australian Pregnancy Cohort (Raine) Study (n = 714) provided data at age 22-years. PA and SB were measured via accelerometry over a 7-day period. Pain sensitivity was measured using pressure pain threshold (4 sites) and cold pain threshold (wrist). Participants were grouped by number of pain areas into “No pain areas” (n = 438), “Single-site pain” (n = 113) and “Multisite pain” (n = 163) groups. The association of PA and SB variables with pain sensitivity was tested separately within each pain group by multivariable regression, adjusting for potential confounders.

Results

For those with “Single-site pain”, higher levels (>13 min/day) of moderate-vigorous PA in ≥10 min bouts was associated with more pressure pain sensitivity (p = 0.035). Those with “Multisite pain” displayed increased cold pain sensitivity with greater amounts of vigorous PA (p = 0.011). Those with “No pain areas” displayed increased cold pain sensitivity with decreasing breaks from sedentary time (p = 0.046).

Conclusions

This study was a comprehensive investigation of a community-based sample of young adults with “No pain areas”, “Single-site pain” and “Multisite pain” and suggests some associations of measures of PA and SB with pain sensitivity.

Implications

The findings suggest that the pattern of accumulation of PA and SB may be important to inform improved clinical management of musculoskeletal pain disorders. This study provides a baseline for follow-up studies using the Raine Study cohort. Future research should consider temporal influences of PA and SB on pain sensitivity, pain experience and consider using a broader range of pain sensitivity measures.

People with musculoskeletal shoulder pain demonstrate no signs of altered pain processing

BACKGROUND

Central sensitisation may contribute to persistent musculoskeletal shoulder pain. Few studies have provided a comprehensive sensory and psychosocial evaluation of this population.

OBJECTIVE

To comprehensively assess whether sensory function and psychosocial aspects are impaired in people with shoulder pain and whether age, gender and clinical outcomes are related to impaired sensory function.

STUDY DESIGN

Observational case-control study.

METHODS

Twenty-three participants with musculoskeletal shoulder pain and 23 age- and gender-matched healthy participants were included. Static (pressure and thermal pain thresholds) and dynamic (temporal summation) quantitative sensory testing was performed bilaterally at the shoulder and remote tibialis anterior muscle. Conditioned pain modulation was measured at the affected/matched shoulder. Shoulder function (SPADI), depression, anxiety and stress (DASS-21) and health-related quality of life (EQ-5D-5L) were also measured. Comparisons were performed between body regions and groups. Age and gender were included as factors in analyses. Clinical outcomes were tested for correlation with sensory measures.

RESULTS

Shoulder pain group had higher local pressure pain threshold (i.e., hypoalgesia; p = 0.03; Z = 0-5.04), higher SPADI score (p < 0.01; Z = -5.76) and higher EQ-5D-5L (p < 0.01; Z = 5.23) compared to the control group. There was no difference between groups for thermal pain sensitivity, dynamic sensory testing or psychological measures.

CONCLUSION

People with shoulder pain demonstrated mechanical hypoalgesia, increased upper limb disability and poorer quality of life compared with healthy controls. Central sensitisation seems not be a characteristic of musculoskeletal shoulder pain although it could be present in a subgroup of patients.

Spinal cord stimulation modulates descending pain inhibition and temporal summation of pricking pain in patients with neuropathic pain

BACKGROUND

Spinal cord stimulation (SCS) is an established treatment option for patients with refractory chronic pain conditions. While effects of SCS on dorsal horn neuronal circuitries are intensively studied, current knowledge on the impact of SCS on descending pain pathways is scarce and relies on preclinical data. We aimed to address this topic and hypothesized a significant effect of SCS on descending pain modulation. In light of current efforts to determine the sensitivity of "static" versus "dynamic" somatosensory parameters to characterize pathophysiological pain conditions, all SCS patients were carefully investigated using both classes of somatosensory outcome parameters.

METHODS

Descending pain pathways were investigated by using a "Cold Pressor Test." This test enables to evaluate the efficacy of conditioned pain modulation (CPM) at the individual level. CPM efficacy was assessed in eight neuropathic pain patients (age 55.5 ± 10.6) during the two conditions stimulator "ON" and "OFF." The impact of SCS on "static" and "dynamic" somatosensory parameters was explored by using a quantitative sensory testing (QST) battery.

RESULTS

CPM efficacy on pressure pain sensitivity was nearly absent during "OFF" (- 1.2 ± 5.6% facilitation), but increased significantly to 16.3 ± 3.4% inhibition during "ON" (p = 0.03). While most "static" nociceptive QST parameters, represented by mechanical/thermal pain thresholds, exhibited only small effects of SCS (p > 0.05), the wind-up ratio was strongly reduced to within the normal range during "ON" (p = 0.04; Cohen's d = 1.0). Dynamic mechanical allodynia was abolished in six of seven patients.

CONCLUSIONS

Our study provides first human evidence for an impact of SCS on descending pain pathways in the dorsolateral funiculus and emphasizes the significance of "dynamic" pain measures like "CPM"-efficacy and "temporal summation" to evaluate SCS treatment effects. Future prospective studies may use these measures of nociceptive processing to predict SCS therapy response.

Multicenter assessment of quantitative sensory testing (QST) for the detection of neuropathic-like pain responses using the topical capsaicin model

Background

The use of quantitative sensory testing (QST) in multicenter studies has been quite limited, due in part to lack of standardized procedures among centers.

Aim

The aim of this study was to assess the application of the capsaicin pain model as a surrogate experimental human model of neuropathic pain in different centers and verify the variation in reports of QST measures across centers.

Methods

A multicenter study conducted by the Quebec Pain Research Network in six laboratories allowed the evaluation of nine QST parameters in 60 healthy subjects treated with topical capsaicin to model unilateral pain and allodynia. The same measurements (without capsaicin) were taken in 20 patients with chronic neuropathic pain recruited from an independent pain clinic.

Results

Results revealed that six parameters detected a significant difference between the capsaicin-treated and the control skin areas: (1) cold detection threshold (CDT) and (2) cold pain threshold (CPT) are lower on the capsaicin-treated side, indicating a decreased in cold sensitivity; (3) heat pain threshold (HPT) was lower on the capsaicin-treated side in healthy subjects, suggesting an increased heat pain sensitivity; (4) dynamic mechanical allodynia (DMA); (5) mechanical pain after two stimulations (MPS2); and (6) mechanical pain summation after ten stimulations (MPS10), are increased on the capsaicin-treated side, suggesting an increased in mechanical pain (P < 0.002). CDT, CPT and HPT showed comparable effects across all six centers, with CPT and HPT demonstrating the best sensitivity. Data from the patients showed significant difference between affected and unaffected body side but only with CDT.

Conclusion

These results provide further support for the application of QST in multicenter studies examining normal and pathological pain responses.

Quantitative sensory testing after macroreplantation: evidence for a specific somatosensory profile

A comprehensive functional recovery is one of the criteria for successful replantation of an amputated limb. Functionality of a replanted limb is strongly dependent on its regained sensibility. In previous studies concerning the sensibility of replanted limbs, only a few somatosensory submodalities were examined in small samples. The purpose of this study is to provide a full pattern of somatosensory symptoms after replantation. Quantitative sensory testing was performed according to a standardized protocol in a sample of 15 patients who underwent replantation of their upper limb proximal to the radiocarpal joint (macroreplantation). Results indicate that most of these patients showed a specific somatosensory profile characterized by thermal and mechanical hypoesthesia and hyperalgesia in response to pressure pain, whereas no single case of hyperalgesia to heat pain occurred. This distinct profile of impaired somatosensation shares some features of the somatosensory profile of neuropathic pain syndromes. Patients' limbs that were replanted many years before the present quantitative sensory testing showed more sensory deficits than patients with more recent replantations. This knowledge might be helpful in the development of more specific and more successful rehabilitation programs with replanted patients and improves the behavioral function of the replanted limb.

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.

"Lacking warmth": Alexithymia trait is related to warm-specific thermal somatosensory processing

Alexithymia is a personality trait involving deficits in emotional processing. The personality construct has been extensively validated, but the underlying neural and physiological systems remain controversial. One theory suggests that low-level somatosensory mechanisms act as somatic markers of emotion, underpinning cognitive and affective impairments in alexithymia. In two separate samples (total N=100), we used an established Quantitative Sensory Testing (QST) battery to probe multiple neurophysiological submodalities of somatosensation, and investigated their associations with the widely-used Toronto Alexithymia Scale (TAS-20). Experiment one found reduced sensitivity to warmth in people with higher alexithymia scores, compared to individuals with lower scores, without deficits in other somatosensory submodalities. Experiment two replicated this result in a new group of participants using a full-sample correlation between threshold for warm detection and TAS-20 scores. We discuss the relations between low-level thermoceptive function and cognitive processing of emotion.

Somatosensory function in patients with secondary adrenal insufficiency treated with two different doses of hydrocortisone-Results from a randomized controlled trial

Background

Low cortisol levels are associated with several functional pain syndromes. In patients with secondary adrenal insufficiency (SAI), the lack in endogenous cortisol production is substituted by the administration of oral hydrocortisone (HC). Our previous study showed that a lower dose of HC led to an increase in reported subjective pain symptoms. Whether different doses of HC substitution alter somatosensory functioning in SAI patients has not been established yet.

Methods

In this randomized double blind cross-over trial, forty-six patients with SAI participated. Patients randomly received either first a lower dose (0.2–0.3 mg HC/kg body weight/day) for 10 weeks followed by a higher dose (0.4–0.6 mg HC/kg body weight/day) for another 10 weeks, or vice versa. After each treatment period, blood samples were drawn and somatosensory functioning was assessed by determining the mechanical detection threshold (MDT), mechanical pain threshold (MPT), mechanical pain sensitivity (MPS) and the pain pressure threshold (PPT), according to the Quantitative Sensory Testing (QST) battery by the German Network on Neuropathic Pain.

Results

The administration of the higher dose of HC resulted in significantly higher levels of cortisol (mean [SD] 748 [245] nmol/L) than the lower dose (537 [250] nmol/L, P<0.001). No differences were found in MDT, MPT, MPS and PPT z-scores between the two doses of HC. Furthermore, the number of patients showing sensory abnormalities did not differ between the two different doses.

Conclusions

The results suggest that the dose of HC has no impact on somatosensory functioning in response to mechanical stimuli in patients with SAI, despite previously found altered subjective pain reports.

Changes in Cytokines, Sensory Tests, and Self-reported Pain Levels After Manual Treatment of Low Back Pain

STUDY DESIGN

Unbalanced 3-factor design with repeated measures on 1 factor.

OBJECTIVE

To determine the effect of manual treatment (MT) on cytokine and pain sensations in those with and without low back pain (LBP).

SUMMARY OF BACKGROUND DATA

Evidence suggests that MT reduces LBP but by unknown mechanisms. Certain cytokines have been elevated in patients with LBP and may be affected by MT.

METHODS

Participants aged 20-60 years with chronic LBP or without LBP were recruited and randomly assigned to MT, sham ultrasound treatment, or no treatment groups. Venous blood samples were collected and pain levels assessed at baseline, 1 hour later, and 24 hours later. Blood was analyzed for interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and C-reactive protein. Pain levels were measured by pressure pain threshold (PPT), mechanical detection threshold (MDT), dynamic mechanical allodynia, and self-report.

RESULTS

Forty (30 women, age 36±11 y) participants completed the study, 33 with LBP (13 MT, 13 sham ultrasound treatment, and 7 no treatment) and 7 without LBP. Participants with or without LBP could not be differentiated on the basis of serum cytokine levels, PPT, or MDT (P≥0.08). There were no significant differences between the groups at 1 hour or 24 hours on serum cytokines, PPT, or MDT (P≥0.07). There was a significant decrease from baseline in IL-6 for the no treatment (LBP) group (P=0.04), in C-reactive protein for the sham ultrasound treatment group (P=0.03), in MDT for all 3 LBP groups (P≤0.02), and in self-reported pain for the MT and sham ultrasound treatment groups (P=0.03 and 0.01).

CONCLUSIONS

Self-reported pain was reduced with MT and sham ultrasound treatment 24 hours after treatment, but inflammatory markers within venous circulation and quantitative sensory tests were unable to differentiate between study groups. Therefore, we were unable to characterize mechanisms underlying chronic LBP.

Quantitative sensory testing measures individual pain responses in emergency department patients

Background

Refining and individualizing treatment of acute pain in the emergency department (ED) is a high priority, given that painful complaints are the most common reasons for ED visits. Few tools exist to objectively measure pain perception in the ED setting. We speculated that variation in perception of fixed painful stimuli would explain individual variation in reported pain and response to treatment among ED patients.

Materials and methods

In three studies, we 1) describe performance characteristics of brief quantitative sensory testing (QST) in 50 healthy volunteers, 2) test effects of 10 mg oxycodone versus placebo on QST measures in 18 healthy volunteers, and 3) measure interindividual differences in nociception and treatment responses in 198 ED patients with a painful complaint during ED treatment. QST measures adapted for use in the ED included pressure sensation threshold, pressure pain threshold (PPT), pressure pain response (PPR), and cold pain tolerance (CPT) tests.

Results

First, all QST measures had high inter-rater reliability and test–retest reproducibility. Second, 10 mg oxycodone reduced PPR, increased PPT, and prolonged CPT. Third, baseline PPT and PPR revealed hyperalgesia in 31 (16%) ED subjects relative to healthy volunteers. In 173 (88%) ED subjects who completed repeat testing 30 minutes after pain treatment, PPT increased and PPR decreased (Cohen’s d_z 0.10–0.19). Verbal pain scores (0–10) for the ED complaint decreased by 2.2 (95% confidence intervals [CI]: 1.9, 2.6) (Cohen’s d_z 0.97) but did not covary with the changes in PPT and PPR (r=0.05–0.13). Treatment effects were greatest in ED subjects with a history of treatment for anxiety or depression (Cohen’s d_z 0.26–0.43) or with baseline hyperalgesia (Cohen’s d_z 0.40–0.88).

Conclusion

QST reveals individual differences in perception of fixed painful stimuli in ED patients, including hyperalgesia. Subgroups of ED patients with hyperalgesia and psychiatric history report larger treatment effects on ED pain and QST measures.

Pressure and cold pain threshold reference values in a large, young adult, pain-free population

Background and aims

Currently there is a lack of large population studies that have investigated pain sensitivity distributions in healthy pain free people. The aims of this study were: (1) to provide sex-specific reference values of pressure and cold pain thresholds in young pain-free adults; (2) to examine the association of potential correlates of pain sensitivity with pain threshold values.

Methods

This study investigated sex specific pressure and cold pain threshold estimates for young pain free adults aged 21–24 years. A cross-sectional design was utilised using participants (n =617) from the Western Australian Pregnancy Cohort (Raine) Study at the 22-year follow-up. The association of site, sex, height, weight, smoking, health related quality oflife, psychological measures and activity with pain threshold values was examined. Pressure pain threshold (lumbar spine, tibialis anterior, neck and dorsal wrist) and cold pain threshold (dorsal wrist) were assessed using standardised quantitative sensory testing protocols.

Results

Reference values for pressure pain threshold (four body sites) stratified by sex and site, and cold pain threshold (dorsal wrist) stratified by sex are provided. Statistically significant, independent correlates of increased pressure pain sensitivity measures were site (neck, dorsal wrist), sex (female), higher waist-hip ratio and poorer mental health. Statistically significant, independent correlates of increased cold pain sensitivity measures were, sex (female), poorer mental health and smoking.

Conclusions

These data provide the most comprehensive and robust sex specific reference values for pressure pain threshold specific to four body sites and cold pain threshold at the dorsal wrist for young adults aged 21–24 years. Establishing normative values in this young age group is important given that the transition from adolescence to adulthood is a critical temporal period during which trajectories for persistent pain can be established.

Implications

These data will provide an important research resource to enable more accurate profiling and interpretation of pain sensitivity in clinical pain disorders in young adults. The robust and comprehensive data can assist interpretation of future clinical pain studies and provide further insight into the complex associations of pain sensitivity that can be used in future research.

NerveCheck: An inexpensive quantitative sensory testing device for patients with diabetic neuropathy

AIMS

Sensory neuropathy is central to the development of painful neuropathy, and foot ulceration in patients with diabetes. Currently, available QST devices take considerable time to perform and are expensive. NerveCheck is the first inexpensive ($500), portable QST device to perform both vibration and thermal testing and hence evaluate diabetic peripheral neuropathy (DPN). This study was undertaken to establish the reproducibility and diagnostic validity of NerveCheck for detecting neuropathy.

METHODS

130 subjects (28 with DPN, 46 without DPN and 56 control subjects) underwent QST assessment with NerveCheck; vibration perception and thermal testing. DPN was defined according to the Toronto criteria.

RESULTS

NerveCheck's intra correlation coefficient for vibration, cold and warm sensation testing was 0.79 (95% LOA: -4.20 to 6.60), 0.86 (95% LOA: -1.38 to 2.72) and 0.71 (95% LOA: -2.36 to 3.83), respectively. The diagnostic accuracy (AUC) for vibration, cold and warm sensation testing was 86% (SE: 0.038, 95% CI 0.79-0.94), 79% (SE: 0.058, 95% CI 0.68-0.91) and 72% (SE: 0.058, 95% CI 0.60-0.83), respectively.

CONCLUSIONS

This study shows that NerveCheck has good reproducibility and comparable diagnostic accuracy to established QST equipment for the diagnosis of DPN.

A Phase 1, Dose-escalation, Double-blind, Block-randomized, Controlled Trial of Safety and Efficacy of Neosaxitoxin Alone and in Combination with 0.2% Bupivacaine, with and without Epinephrine, for Cutaneous Anesthesia

Background:

Neosaxitoxin (NeoSTX) is a site-1 sodium channel blocker that produces prolonged local anesthesia in animals and humans. Under a Food and Drug Administration–approved phase 1 Investigational New Drug trial, the authors evaluated safety and efficacy of NeoSTX alone and combined with 0.2% bupivacaine (Bup) with and without epinephrine.

Methods:

The authors conducted a double-blind, randomized, controlled trial involving healthy male volunteers aged 18 to 35 yr receiving two 10-ml subcutaneous injections. Control sites received Bup. In part 1, active sites received (1) 5 to 40 μg NeoSTX+Saline (NeoSTX-Saline), (2) 5 to 40 μg NeoSTX+Bup (NeoSTX-Bup), or (3) placebo (Saline). In part 2, active sites received 10 or 30 μg NeoSTX+Bup+Epinephrine (NeoSTX-Bup-Epi) or placebo. Primary outcome measures were safety and adverse events associated with NeoSTX. Secondary outcomes included clinical biochemistry, NeoSTX pharmacokinetics, and cutaneous hypoesthesia.

Results:

A total of 84 subjects were randomized and completed the two-part trial with no serious adverse events or clinically significant physiologic impairments. Perioral numbness and tingling increased with NeoSTX dose for NeoSTX-Saline and NeoSTX-Bup. All symptoms resolved without intervention. NeoSTX-Bup-Epi dramatically reduced symptoms compared with other NeoSTX combinations (tingling: 0 vs. 70%, P = 0.004; numbness: 0 vs. 60%, P = 0.013) at the same dose. Mean peak plasma NeoSTX concentration for NeoSTX-Bup-Epi was reduced at least two-fold compared with NeoSTX-Saline and NeoSTX-Bup (67 ± 14, 134 ± 63, and 164 ± 81 pg/ml, respectively; P = 0.016). NeoSTX-Bup showed prolonged cutaneous block duration compared with Bup, NeoSTX-Saline, or placebo, at all doses. Median time to near-complete recovery for 10 μg NeoSTX-Bup-Epi was almost five-fold longer compared with Bup (50 vs. 10 h, P = 0.007).

Conclusion:

NeoSTX combinations have a tolerable side effect profile and appear promising for prolonged local anesthesia.

Pain sensitisation and the risk of poor outcome following physiotherapy for patients with moderate to severe knee osteoarthritis: protocol for a prospective cohort study

INTRODUCTION

Pain is the dominant symptom of knee osteoarthritis (OA), and recent evidence suggests factors outside of local joint pathology, such as pain sensitisation, can contribute significantly to the pain experience. It is unknown how pain sensitisation influences outcomes from commonly employed interventions such as physiotherapy. The aims of this study are, first, to provide a comprehensive description of the somatosensory characteristics of people with pain associated with knee OA. Second, we will investigate if indicators of pain sensitisation in patients with knee osteoarthritis are predictive of non-response to physiotherapy.

METHODS AND ANALYSIS

This is a multicentre prospective cohort study with 140 participants. Eligible patients with moderate to severe symptomatic knee osteoarthritis will be identified at outpatient orthopaedic and rheumatology clinics. A baseline assessment will provide a comprehensive description of the somatosensory characteristics of each participant by means of clinical examination, quantitative sensory testing, and validated questionnaires measuring pain and functional capacity. Participants will then undergo physiotherapy treatment. The primary outcome will be non-response to physiotherapy on completion of the physiotherapy treatment programme as defined by the Osteoarthritis Research Society International treatment responder criteria. A principal component analysis will identify measures related to pain sensitisation to include in the predictive model. Regression analyses will explore the relationship between responder status and pain sensitisation while accounting for confounders.

ETHICS AND DISSEMINATION

This study has been approved by St James' Hospital/AMNCH Research Ethics Committee and by the St Vincent's Healthcare Group Ethics and Medical Research Committee. The results will be presented at international conferences and published in a peer review journal.

TRIAL REGISTRATION NUMBER

NCT02310945.

Expectations and positive emotional feelings accompany reductions in ongoing and evoked neuropathic pain following placebo interventions

Research on placebo analgesia and nocebo hyperalgesia has primarily included healthy subjects or acute pain patients, and it is unknown whether these effects can be obtained in ongoing pain in patients with chronic pain caused by an identifiable nerve injury. Eighteen patients with postthoracotomy neuropathic pain were exposed to placebo and nocebo manipulations, in which they received open and hidden administrations of pain-relieving (lidocaine) or pain-inducing (capsaicin) treatment controlled for the natural history of pain. Immediately after the open administration, patients rated their expected pain levels on a mechanical visual analogue scale (M-VAS). They also reported their emotional feelings via a quantitative/qualitative experiential method. Subsequently, patients rated their ongoing pain levels on the M-VAS and underwent quantitative sensory testing of evoked pain (brush, pinprick, area of hyperalgesia, wind-up-like pain). There was a significant placebo effect on both ongoing (P=.009 to .019) and evoked neuropathic pain (P=.0005 to .053). Expected pain levels accounted for significant amounts of the variance in ongoing (53.4%) and evoked pain (up to 34.5%) after the open lidocaine administration. Furthermore, patients reported high levels of positive and low levels of negative emotional feelings in the placebo condition compared with the nocebo condition (P⩽.001). Pain increases during nocebo were nonsignificant (P=.394 to 1.000). To our knowledge, this is the first study to demonstrate placebo effects in ongoing neuropathic pain. It provides further evidence for placebo-induced reduction in hyperalgesia and suggests that patients' expectations coexist with emotional feelings about treatments.