Reference values of mechanical and thermal pain tests in a pain-free population

Pain From a Distance: Can Third-Person Self-Talk Mitigate Pain Sensitivity and Pain Related Distress During Experimentally Induced Pain?

Pain is self-immersive, leading to a narrow, egocentric focus on the self in the here and now. Preliminary evidence suggests that distancing oneself from the pain can reduce experimentally induced pain. The primary aim of this experimental study was to examine whether a hitherto unexplored, simple self-distancing strategy - "third-person self-talk" - has an analgesic effect on physiological and psychological pain variables. Participants (N = 292) were randomly assigned to one of four conditions (third-person self-talk, first-person self-talk, and two control conditions). Pain was induced with a cold pressor apparatus and pain tolerance, pain intensity, negative affect and blood pressure were measured for each group. While in pain, participants engaged in strategic self-talk aided by cue-cards. Data were analyzed with univariate planned comparisons. Few significant differences emerged for the third-person self-talk versus the other conditions. It is concluded that third-person self-talk does not seem to have a meaningful effect on physiological and psychological pain variables, although a small effect size could not be ruled out. Practical implications are discussed.The study was registered at ClinicalTrials.gov with the ClinicalTrials.gov ID NCT05511857.

Adverse childhood experiences, brain efficiency, and the development of pain symptoms in youth

BACKGROUND

Adverse childhood experiences (ACEs) are often reported by youths with chronic pain, and both ACEs and chronic pain disrupt how information is processed. However, it is unknown whether changes to shared neural networks underlie the relationship between ACEs and the development of pain symptoms. This study explored the relationships between ACEs, brain efficiency, and pain symptomology in youth.

METHODS

A community sample of youths aged 14-18 years underwent MRIs, answered trauma and pain questionnaires, and underwent pain sensory testing, twice, 3 months apart (Nbaseline = 44; Nfollow-up = 42). Sensory testing determined thresholds for mechanical and thermal stimuli. Global and local network efficiencies were evaluated using graph theory. Generalized estimating equations were applied to examine whether brain efficiency moderated the relationships between ACEs, pain intensity, and pain sensitivity (i.e., mechanical detection, heat pain, and temperature change thresholds).

RESULTS

There was a significant interaction between ACEs and global brain efficiency in association with pain intensity (β = -0.31, p = 0.02) and heat pain (β = -0.29, p = 0.004). Lower global brain efficiency exacerbated the relationship between ACEs and pain intensity (θX → Y|W = -1.16 = 0.37, p = 0.05), and heat pain sensitivity (θX → Y|W = -1.30 = 0.44, p = 0.05). Higher global brain efficiency ameliorated the relationship between ACEs and pain intensity (θX → Y|W = 1.75 = -0.53, p = 0.05).

CONCLUSIONS

The relationship between ACEs and pain symptomology was comparable to chronic pain phenotypes (i.e., higher pain intensity and pain thresholds) and may vary as a function of brain efficiency in youth. This stresses the importance of assessing for pain symptoms in trauma-exposed youth, as earlier identification and intervention are critical in preventing the chronification of pain.

SIGNIFICANCE

This article explores the relationship between ACEs, pain symptomology, and brain efficiency in youth. ACEs may affect how the brain processes information, including pain. Youths with lower brain efficiencies that were exposed to more ACEs have pain symptomology comparable to youths with chronic pain. Understanding this relationship is important for the earlier identification of pain symptoms, particularly in vulnerable populations such as youths exposed to trauma, and is critical for preventing the chronification of pain.

Pressure Pain Sensitivity and Chronotype: A Population-based Study of Middle-aged Finns

Evening chronotype individuals experience pain more often than morning chronotypes, but relationships with pain sensitivity have rarely been studied. We examined whether chronotype is associated with pressure pain sensitivity, with special reference to mental health disorders, insomnia, and chronic musculoskeletal (MSK) pain as potential moderating factors. The study sample consisted of members of the Northern Finland Birth Cohort 1966 aged 46. Pressure pain threshold and tolerance were measured via the standardized protocol, categorized as lowest quartile versus others. Chronotype (morning [M; the reference], intermediate [I], and evening [E]) was defined using the Short Morningness-Eveningness questionnaire. Sex-stratified binary logistic regression models were separately adjusted for education, body mass index, long-term diseases (fully adjusted model), and for mental health disorders, insomnia, and chronic MSK pain (a residual confounding analysis). Interaction terms (Chronotype × Mental health/insomnia/chronic MSK pain) were tested. The study had 2,132 males and 2,830 females. The E-type males had 1.5-fold odds of having a low pain threshold (fully adjusted odds ratio [OR] 1.45, 95% confidence interval 1.05-2.00) and pressure pain tolerance (fully adjusted OR 1.47, 1.07-2.02), in comparison to M-types. Having a mental health disorder intensified the association with low pain threshold fourfold (4.06, 1.56-10.6). Being an E-type female was also associated with a low pain threshold, but the association was statistically nonsignificant (fully adjusted OR 1.18, .90-1.53). No statistically significant interactions were found among females. These results emphasize the role of chronotype in pain sensitivity and add an understanding of pain experience in light of innate circadian types. PERSPECTIVE: Male evening chronotypes are more sensitive to pain than morning chronotypes. Diagnosed mental health disorders in particular indicate a low pain threshold for evening chronotype males.

Sexual differences in locus coeruleus neurons and related behavior in C57BL/6J mice

BACKGROUND

In addition to social and cultural factors, sex differences in the central nervous system have a critical influence on behavior, although the neurobiology underlying these differences remains unclear. Interestingly, the Locus Coeruleus (LC), a noradrenergic nucleus that exhibits sexual dimorphism, integrates signals that are related to diverse activities, including emotions, cognition and pain. Therefore, we set-out to evaluate sex differences in behaviors related to LC nucleus, and subsequently, to assess the sex differences in LC morphology and function.

METHODS

Female and male C57BL/6J mice were studied to explore the role of the LC in anxiety, depressive-like behavior, well-being, pain, and learning and memory. We also explored the number of noradrenergic LC cells, their somatodendritic volume, as well as the electrophysiological properties of LC neurons in each sex.

RESULTS

While both male and female mice displayed similar depressive-like behavior, female mice exhibited more anxiety-related behaviors. Interestingly, females outperformed males in memory tasks that involved distinguishing objects with small differences and they also showed greater thermal pain sensitivity. Immunohistological analysis revealed that females had fewer noradrenergic cells yet they showed a larger dendritic volume than males. Patch clamp electrophysiology studies demonstrated that LC neurons in female mice had a lower capacitance and that they were more excitable than male LC neurons, albeit with similar action potential properties.

CONCLUSIONS

Overall, this study provides new insights into the sex differences related to LC nucleus and associated behaviors, which may explain the heightened emotional arousal response observed in females.

Development of a model to investigate the effects of prolonged ischaemia on the muscles of mastication of male Sprague Dawley rats

OBJECTIVE

The aims of this study were to develop a novel rodent model of masticatory muscle ischaemia via unilateral ligation of the external carotid artery (ECA), and to undertake a preliminary investigation to characterize its downstream effects on mechanosensitivity and cellular features of the masseter and temporalis muscles.

DESIGN

The right ECA of 18 male Sprague-Dawley rats was ligated under general anaesthesia. Mechanical detection thresholds (MDTs) at the masseter and temporalis bilaterally were measured immediately before ECA ligation and after euthanasia at 10-, 20-, and 35-days (n = 6 rats/timepoint). Tissue samples from both muscles and sides were harvested for histological analyses and for assessing changes in the expression of markers of hypoxia and muscle degeneration (Hif-1α, VegfA, and Fbxo32) via real time PCR. Data were analyzed using mixed effect models and non-parametric tests. Statistical significance was set at p < 0.05.

RESULTS

MDTs were higher in the right than left hemiface (p = 0.009) after 20 days. Histological changes indicative of muscle degeneration and fibrosis were observed in the right muscles. Hif-1α, VegfA, and Fbxo32 were more highly expressed in the masseter than temporalis muscles (all p < 0.05). Hif-1α and, VegfA did not change significantly with time in all muscles (all p > 0.05). Fbxo32 expression gradually increased in the right masseter (p = 0.024) and left temporalis (p = 0.05).

CONCLUSIONS

ECA ligation in rats induced hyposensitivity in the homolateral hemiface after 20 days accompanied by tissue degenerative changes. Our findings support the use of this model to study pathophysiologic mechanisms of masticatory muscle ischaemia in larger investigations.

Post-amputation pain: Comparing pain presentations between adults with and without increased amputated-region sensitivity

OBJECTIVE

Among adults with persistent post-amputation pain, increased amputated-region pain sensitivity may reflect peripheral sensitization or indicate underlying central sensitization. To determine whether underlying central sensitization may contribute to increased pain sensitivity in this population, this study compared clinical signs and symptoms associated with central sensitization between adults with post-amputation pain who demonstrate or lack increased amputated-region sensitivity (as compared to reference data).

DESIGN

Cross-sectional.

SUBJECTS

Ninety-nine adults (60 with a unilateral, transtibial amputation and post-amputation pain, 39 pain-free controls with intact limbs).

METHODS

Participants underwent pain-pressure threshold testing of amputated-region and secondary (non-amputated region) sites and completed outcome measures assessing central sensitization symptoms (Patient-Reported Outcomes Measurement Information System® pain intensity and interference domains, Central Sensitization Inventory). Among the full sample, the presence and frequency of specific central sensitization symptoms were evaluated. Participants with post-amputation pain were then grouped based on whether normalized, amputated-region pain-pressure thresholds fell below (i.e., sensitive) or above (i.e., non-sensitive) the 25th percentile of sex-specific reference data. Between-group differences in normalized secondary-site sensitivity were evaluated using a multivariate analysis of variance; central sensitization symptom scores were compared using a Kruskal-Wallis test.

RESULTS

Noteworthy symptoms associated with central sensitization (e.g., fatigue, sleep disturbance, cognitive difficulty) were reported by 33%-62% of participants. Secondary-site pain sensitivity was greater among individuals with increased amputated-region sensitivity (n = 24) compared to peers without increased amputated-region sensitivity ([n = 36], mean difference > 1.33 standard deviation [SD], p < 0.001). Central sensitization symptom scores, however, were similar between groups (p > 0.187).

CONCLUSIONS

Participants with increased amputated-region sensitivity demonstrate generalized, secondary-site pain hypersensitivity, potentially indicating underlying central sensitization. Central sensitization symptom scores, however, were similar between groups, suggesting differences in physiological pain sensitivity may not manifest in subjective post-amputation pain descriptions.

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.

Somatosensory Outcomes Following Re-Surgery in Persistent Severe Pain After Groin Hernia Repair: A Prospective Observational Study

Purpose

After groin hernia repair (globally more than 20 million/year) 2-4% will develop persistent severe pain (PSPG). Pain management is challenging and may require multimodal interventions, including re-surgery. Quantitative somatosensory testing (QST) is an investigational psychophysiological tool with the potential to uncover the pathophysiological mechanisms behind the pain, ie, revealing neuropathic or inflammatory components. The primary objective was to examine and describe the underlying pathophysiological changes in the groin areas by QST before and after re-surgery with mesh removal and selective neurectomy.

Patients and Methods

Sixty patients with PSPG scheduled for re-surgery and with an inflammatory "component" indicated by blunt pressure algometry were examined in median (95% CI) 7.9 (5.8-11.5) months before and 4.0 (3.5-4.6) months after re-surgery. The QST-analyses included standardized assessments of cutaneous mechanical/thermal detection and pain thresholds. Suprathreshold heat stimuli were applied. Deep tissue sensitivity was tested by pressure algometry. Testing sites were the groin areas and the lower arm. Before/after QST data were z-transformed.

Results

Re-surgery resulted in median changes in rest, average, and maximal pain intensity scores of -2.0, -2.5, and -2.0 NRS (0/10) units, respectively (P = 0.0001), and proportional increases in various standardized functional scores (P = 0.0001). Compared with the control sites, the cutaneous somatosensory detection thresholds of the painful groin were increased before re-surgery and increased further after re-surgery (median difference: 1.28 z-values; P = 0.001), indicating a successive post-surgical loss of nerve fiber function ("deafferentation"). Pressure algometry thresholds increased after re-surgery (median difference: 0.30 z-values; P = 0.001).

Conclusion

In this subset of patients with PSPG who underwent re-surgery, the procedure was associated with improved pain and functional outcomes. While the increase in somatosensory detection thresholds mirrors the surgery-induced cutaneous deafferentation, the increase in pressure algometry thresholds mirrors the removal of the deep "pain generator". The QST-analyses are useful adjuncts in mechanism-based somatosensory research.

Pressure Pain Threshold of the Upper Trapezius Trigger Point: A Systematic Review with Meta-Analysis of Baseline Values and Their Modification after Physical Therapy

BACKGROUND

Myofascial trigger points (TrP) are diagnosed upon the presence of clinical signs among which hypersensitivity is considered one of the most important. The detection of the pressure pain threshold (PPT) is used to quantify the degree of hypersensitivity. However, there is a lack of normative data about how hypersensitive a TrP is. Therefore, the objective was to quantify the PPT for myofascial TrP in the upper trapezius muscle and its modification after manual or instrumental physical therapy interventions.

METHODS

A systematic review and meta-analysis were conducted among three databases (MEDLINE, Cochrane Library, and PEDro). Two independent reviewers conducted the electronic search and assessed the methodological quality of the included studies.

RESULTS

Eleven studies with a high-risk bias indicated that the PPT at TrP sites was 105.11 kPa lower (95% CI: -148.93; -61.28) at active TrP sites (Chi-squared = 1.07, df = 1 (p = 0.30), I² = 7%) compared to the PPT of the upper trapezius muscles of healthy subjects. In addition, the PPT of TrP was also lower than the reference values coming from the pain-free population. Moreover, the PPT increased after both manual and instrumental treatment by 28.36 kPa (95% CI: 10.75; 45.96) and 75.49 kPa (95% CI: 18.02; 132.95), respectively.

CONCLUSIONS

The results of the present study show that TrP has a decreased PPT when compared to healthy muscles and that physical therapy may increase the PPT. However, the clinical relevance of this decreased PPT needs to be further elucidated. Further, the high risk of bias in all the retrieved studies undermines the validity of the results.

Effect of single end-range and not end-range Maitland mobilization on pressure pain threshold and functional measures in knee osteoarthritis: randomised, controlled clinical trial

BACKGROUND

Hyperalgesia is attributed to peripheral and central sensitization in knee osteoarthritis (OA). Pressure pain threshold (PPT) is a relevant method for evaluating pain sensitivity in knee OA. The effect of end-range and not end-range Maitland mobilization for certain time-period on pain sensitivity has not been investigated in knee OA.

AIM

The aim of this study was to investigate the effect of end-range and not end-range Maitland mobilization compared to sham manual therapy technique on PPT and functional measures.

DESIGN

Randomised, controlled clinical trial.

SETTING

Outpatient setting.

POPULATION

Sixty-six patients with mild-to-severe knee OA.

METHODS

Twenty-one patients (N.=21) received end-range Maitland mobilization (EMGr), twenty patients (N.=20) received not end-range Maitland mobilization (nEMGr) and twenty-two patients (N.=22) received sham manual therapy technique (CG). All interventions were performed once. Evaluation was conducted pre-, postintervention and on the following consecutive second days within a 6-day period. Outcomes were local and distant PPT, Timed Up and Go Test (TUG) and strength of passive resistance of knee at onset of pain.

RESULTS

Local and distant PPT increased, TUG time and strength of passive resistance decreased immediately, local and distant PPT remained decreased in 6-day and 4-day period, TUG time remained decreased in 6-day period in EMGr (all changes P≤0.017). Local PPT increased immediately compared to baseline in nEMGr. In between group comparison, increase of local, distant PPT and strength of passive resistance endures on 2^nd day, 4^th day and postintervention, respectively, in EMGr compared to CG. EMGr compared to nEMGr presented significant difference on 6^th day and 4^th day in local and distant PPT, respectively (all changes P≤0.021). NEMGr presented no significant difference compared to CG on either follow-up.

CONCLUSIONS

Single end-range Maitland mobilization is effective immediately and in 4-day period on pain sensitization and immediately on physical function compared to not end-range Maitland mobilization and sham manual therapy technique in knee OA.

CLINICAL REHABILITATION IMPACT

Based on the present results, applying end-range Maitland mobilization is suggested on every second day to maintain alleviation of pain sensitization and increasing passive knee joint mobility effectively in knee OA.

Current Concept of Quantitative Sensory Testing and Pressure Pain Threshold in Neck/Shoulder and Low Back Pain

In recent years, several published articles have shown that quantitative sensory testing (QST) and pressure pain threshold (PPT) are useful in the analysis of neck/shoulder and low back pain. A valid reference for normal PPT values might be helpful for the clinical diagnosis of abnormal tenderness or muscle pain. However, there have been no reliable references for PPT values of neck/shoulder and back pain because the data vary depending on the devices used, the measurement units, and the area examined. In this article, we review previously published PPT articles on neck/shoulder and low back pain, discuss the measurement properties of PPT, and summarize the current data on PPT values in patients with chronic pain and healthy volunteers. We also reveal previous issues related to PPT evaluation and discuss the future of PPT assessment for widespread use in general clinics. We outline QST and PPT measurements and what kinds of perceptions can be quantified with the PPT. Ninety-seven articles were selected in the present review, in which we focused on the normative values and abnormal values in volunteers/patients with neck/shoulder and low back pain. We conducted our search of articles using PubMed and Medline, a medical database. We used a combination of “Pressure pain threshold” and “Neck shoulder pain” or “Back pain” as search terms and searched articles from 1 January 2000 to 1 June 2022. From the data extracted, we revealed the PPT values in healthy control subjects and patients with neck/shoulder and low back pain. This database could serve as a benchmark for future research with pressure algometers for the wide use of PPT assessment in clinics.

Sex differences in choice-based thermal nociceptive tests in adult rats

Interest in the role of sex as a biological variable has increased, including a mandate for the study of both sexes in NIH-funded research. As sex differences exist in both human chronic pain conditions and rodent models of nociception, it is critical to understand the impact of sex in nociceptive assays. Choice-based thermal nociceptive tests permit the study of avoidance responses to thermal stimuli compared to traditional nociceptive assays, which measure nocifensive reactions. However, to date no comparison of male and female responses to choice-based tests has been published. Herein, we examined the effect of sex on two choice-based thermal nociceptive tests, the thermal gradient test and the temperature place preference test, in adult rats. The activation of a 10 °C-to-47 °C thermal gradient results in an increase in time spent in the 10 °C zone in females, compared to a reduction in males. Additionally, in a temperature place preference test pairing a surface temperature of 22 °C with either 5 °C, 10 °C, 47 °C, or 50 °C, females appeared to have overall greater tolerance for non-ambient temperatures. Males spent less than 50% of their time in every non-22 °C zone, whereas in females this was only observed when testing 5 °C and 50 °C. Together, these results suggest that male rats show more avoidance behavior than females to both hot and cold non-ambient temperatures when given free access to multiple zones, including at milder temperatures than those typically used to evoke a nociceptive response in traditional hot and cold plate tests.

Cervical musculoskeletal impairments in the 4 phases of the migraine cycle in episodic migraine patients

OBJECTIVE

To assess cervical musculoskeletal impairments during the 4 phases of a migraine cycle in episodic migraine patients, controlling for the presence of concomitant neck pain.

METHODS

Differences in cervical musculoskeletal impairments were assessed during the 4 migraine phases in episodic migraine patients and compared with healthy controls controlling for concomitant neck pain. Cervical musculoskeletal impairments were assessed as follow: cervical active range of motion; flexion rotation test; craniocervical flexion test and calculation of activation pressure score; the total number of myofascial trigger points in head/neck muscles; the number of positivevertebral segments (headache's reproduction) during passive accessory intervertebral movement; pressure pain thresholds over C1, C2, C4, C6 vertebral segments bilaterally, trigeminal area, hand, and leg. Signs of pain sensitization were assessed by evaluating mechanical pain threshold over trigeminal area and hand, pressure pain thresholds, and the wind-up ratio. The Bonferroni-corrected p-value (05/4 = 0.013) was adopted to assess the difference between groups, while a p-value of 0.05 was considered significant for the correlation analysis.

RESULTS

A total of 159 patients and 52 controls were included. Flexion rotation test and craniocervical flexion test were reduced in all 4 phases of the migraine cycle versus healthy controls (p < 0.001). The number of myofascial trigger points and positive vertebral segments was increased in all 4 phases of the migraine cycle versus healthy controls (p < 0.001). Flexion, extension, and total cervical active range of motion and cervical pressure pain thresholds were reduced in episodic migraine in the ictal phase versus controls (p < 0.007) with no other significant differences. Outside the ictal phase, the total cervical active range of motion was positively correlated with trigeminal and leg pressure pain threshold (p < 0.026), the number of active myofascial trigger points and positive positive vertebral segments were positively correlated with higher headache frequency (p=0.045), longer headache duration (p < 0.008), and with headache-related disability (p = 0.031). Cervical pressure pain thresholds were positively correlated with trigeminal, hand, and leg pressure pain threshold (p < 0.001), and trigeminal and leg mechanical pain thresholds (p < 0.005), and negatively correlated with the wind-up ratio (p < 0.004).

CONCLUSION

In all phases of the migraine cycle, independent of the presence of concomitant neck pain, episodic migraine patients showed reduced flexion rotation test and craniocervical flexion test and an increased number of myofascial trigger points and passive accessory vertebral segments. These impairments are correlated with enhanced headache duration, headache-related disability, and signs of widespread pain sensitization. Reduction in active cervical movement and increased mechanical hyperalgesia of the cervical was consistent in ictal episodic migraine patients and the subgroups of episodic migraine patients with more pronounced widespread sensitization.

Associated Risk Factors with Low Back Pain in White-Collar Workers-A Cross-Sectional Study

Objective: The purpose of the study was to compare the pressure pain threshold (PPT) of soft tissue and the curvatures of the spine in a sitting position and to estimate associated physical risk factors with low back pain (LBP) in young adults. Subjects: White-collar workers (n= 139), both women (n = 51) and men (n = 88) were separated into a control group (n = 82) and a low-intensity LBP (NRS < 3) (n = 57). Methods: The PPTs were tested utilizing the Wagner algometer. The curvatures of the spine were measured employing the photogrammetric method. In the logistic regression model, the odds ratio (OR) was estimated with ±95% confidence interval (CI) indicating the probability of the reported LBP. Results: The PPTs of soft tissue (OR = 1.1; CI = 1.02−1.19; p < 0.05) and the angle of the thoracolumbar spine in the everyday, habitual sitting position (OR = 1.19; CI = 1.05−1.34; p < 0.05) were associated with low-intensity LBP in female subjects. Additionally, the low intensity LBP were associated with the angles of the torso (OR = 1.14; CI = 1.01−1.29; p < 0.05) and the lumbosacral spine in the corrected sitting position (OR = 1.06; CI = 0.98−1.15; p > 0.05) and BMI (OR = 1.56; CI = 0.84−2.90; p > 0.05) in male subjects. Conclusion: Individual risk factors were associated with the low-intensity LBP only in females utilizing the PPT and the thoracolumbar angle in the habitual sitting position study factors. Men from the LBP group did not effectively correct the lumbosacral angle. Therefore, re-educated, self-corrected posture with specific postural training would be expected to improve proprioception in postural control capacity and result in decreasing pain.

Modified Sensory Testing in Non-verbal Patients Receiving Novel Intrathecal Therapies for Neurological Disorders

Several neurological disorders may be amenable to treatment with gene-targeting therapies such as antisense oligonucleotides (ASOs) or viral vector-based gene therapy. The US FDA has approved several of these treatments; many others are in clinical trials. Preclinical toxicity studies of ASO candidates have identified dose-dependent neurotoxicity patterns. These include degeneration of dorsal root ganglia, the cell bodies of peripheral sensory neurons. Quantitative sensory testing (QST) refers to a series of standardized mechanical and/or thermal measures that complement clinical neurologic examination in detecting sensory dysfunction. QST primarily relies on patient self-report or task performance (i.e., button-pushing). This brief report illustrates individualized pragmatic approaches to QST in non-verbal subjects receiving early phase investigational intrathecal drug therapies as a component of clinical trial safety protocols. Three children with neurodevelopmental disorders that include Neuronal Ceroid Lipofuscinosis Type 7, Ataxia-Telangiectasia, and Epilepsy of Infancy with Migrating Focal Seizures are presented. These case studies discuss individualized testing protocols, accounting for disease presentation, cognitive and motor function. We outline specific considerations for developing assessments for detecting changes in sensory processing in diverse patient groups and safety monitoring trials of early phase investigational intrathecal drug therapies. QST may complement information obtained from the standard neurologic examination, electrophysiologic studies, skin biopsies, and imaging. QST has limitations and challenges, especially in non-verbal subjects, as shown in the three cases discussed in this report. Future directions call for collaborative efforts to generate sensory datasets and share data registries in the pediatric neurology field.

Randomized cross-over evaluation of investigator gender on pain thresholds in healthy volunteers

Background and aims: This randomized cross-over study in healthy volunteers was designed primarily to evaluate the potential impact of investigator gender on electrical pain threshold (EPT) and corresponding pain intensity levels, and secondly to evaluate potential differences in those interventions between female and male study participants. Methods: Forty adult volunteers (22 females) were included. An electrical stimulation device was used to determine EPT levels (in pain magnitude scores) in series of three in each study participant - once by a female, and once by a male investigator - according to a predefined cross-over design schedule. Corresponding levels of pain intensity were scored on a visual analog scale (VAS) slide ruler. Results: Study data was obtained and analysed in all participants. Significantly higher EPT levels were determined by the female investigator compared with the male investigator (median 22 (IQR 12-31) vs. 8 (6-10) pain magnitude scores; p<0.0001), despite similar levels of reported pain intensity (1.9 (1.2-3.0) vs. 2.0 (1.1-3.4) VAS units; p>0.300). There were no differences in EPT levels between female and male subjects evaluated by female (p>0.300) and male (p=0.125) investigators, or between the first and second series of stimulation (p>0.300). Conclusions: Our finding of significantly higher EPT levels when study participants of both genders - despite no difference in reported pain intensity - were evaluated by a female than by a male investigator, indicates a potential impact of investigator gender on the individual perception of pain. Implications: By contributing to a better understanding of how individual pain threshold levels are potentially influenced by investigator gender, this study might facilitate future evaluation of pain conditions in both preclinical and clinical settings.

Tests for central sensitization in general practice: a Delphi study

INTRODUCTION

Central sensitization (CS) may explain the persistence of symptoms in patients with chronic pain and persistent physical symptoms (PPS). There is a need for assessing CS in the consultation room. In a recently published systematic review, we made an inventory of tests for CS. In this study we aimed to assess which tests might have added value, might be feasible and thus be suitable for use in general practice.

METHODS

We conducted a Delphi study consisting of two e-mail rounds to reach consensus among experts in chronic pain and PPS. We invited 40 national and international experts on chronic pain and PPS, 27 agreed to participate. We selected 12 tests from our systematic review and additional searches; panellists added three more tests in the first round. We asked the panellists, both clinicians and researchers, to rate these 15 tests on technical feasibility for use in general practice, added value and to provide an overall judgement for suitability in general practice.

RESULTS

In two rounds the panellists reached consensus on 14 of the 15 tests: three were included, eleven excluded. Included were the Central Sensitization Inventory (CSI), pressure pain thresholds (PPTs) and monofilaments. No consensus was reached on the Sensory Hypersensitivity Scale.

CONCLUSION

In a Delphi study among an international panel of experts, three tests for measuring CS were considered to be suitable for use in general practice: the Central Sensitization Inventory (CSI), pressure pain thresholds (PPTs) and monofilaments.

Bedside clinical tests to assess sensitization in office workers with chronic neck pain

OBJECTIVE

This study aimed to assess pain sensitization in individual office workers with chronic neck pain through simple bedside quantitative sensory tests (QST) and to associate the findings with pain intensity and pain catastrophizing.

METHODS

One hundred-and-four office workers with chronic neck pain were assessed using pressure pain threshold (PPT) considering pain sensitive if PPTs were lower than 155 kPa in the upper trapezius and 245 kPa in the tibialis anterior. Pain sensitive to temporal summation of pain (TSP) was considered if there was a difference of two points in the visual analogue scale (VAS) comparing the first and last stimulus. Pain sensitive was considered to conditioned pain modulation (CPM) if the CPM-effect was less than -7.5%. Pain intensity and catastrophizing were measured using VAS and with the Pain Catastrophizing Scale.

RESULTS

There was at least one pain sensitive QST finding in 66 office workers (63.5%). TSP findings were the most common (48.1%), followed by PPT's (31.7%) and CPM (20.2%). Based on the QST findings, office workers were divided based on the number of individual QST findings, and higher pain intensity and pain catastrophizing scores were found in office workers with one (N = 38, P < 0.05) or two (N = 28, P < 0.05) compared with office workers with no QST findings (N = 38).

CONCLUSION

This study demonstrated that most office workers with chronic neck pain exhibit either widespread pressure hyperalgesia, facilitated TSP or impaired CPM, indicating pain sensitization within the central nervous system. This was associated with increased clinical pain and pain catastrophizing rumination scores.

Mechanical Pain Sensitivity in Postamputation Pain

OBJECTIVES

Postamputation, clinical markers of pain-related peripheral and central nervous system hypersensitivity remain understudied. This study aimed to identify whether adults with postamputation pain demonstrate greater pain sensitivity in primary (ie, amputated region) and secondary (ie, nonamputated region) sites, as compared with pain-free peers and controls with intact limbs.

METHODS

Ninety-four participants postunilateral, transtibial amputation (59 with pain, 35 pain-free) and 39 controls underwent pain-pressure threshold (PPT) testing at 10 sites. Pain-pressure thresholds were normalized to sex-specific control data using Z score conversions. Normalized primary-site and secondary-site PPTs were compared between groups using multivariate analysis of variance (P<0.050).

RESULTS

Compared with pain-free peers, adults with postamputation pain demonstrated reduced normalized PPTs across primary and secondary sites (mean difference=0.61-0.74, P=0.001 to 0.007). Compared with controls, adults with postamputation pain demonstrated reduced normalized PPTs (mean difference=0.52, P=0.026) only at primary sites.

DISCUSSION

Adults with postamputation pain demonstrate greater amputated region pain sensitivity as compared with pain-free peers or controls with intact limbs, indicating peripheral sensitization persists even after limb healing. Secondary-site pain sensitivity was similar between controls and adults with postamputation pain, suggesting central nervous system hypersensitivity may not be ubiquitous with postamputation pain. Studies are needed to investigate mechanisms underlying pain sensitivity differences between adults with and without postamputation pain.

Pain sensitivity does not differ between obese and healthy weight individuals

Introduction

There is emerging evidence suggesting a relationship between obesity and chronic pain.

Objectives

The aim of this study was to determine whether pain-free obese individuals display altered pain responses to acute noxious stimuli, thus raising the possibility of greater pain sensitivity and potential susceptibility for chronic pain development.

Methods

Psychophysical and anthropometric data were collected from 38 individuals with an obese body mass index (BMI) classification (BMI ≥ 30) and 41 age/sex-matched individuals of a healthy BMI (BMI < 24.9). Because BMI may be an inaccurate index of obesity, additional anthropometric parameters of central adiposity and percent body fat were examined. Pain responses to suprathreshold noxious heat and cold stimuli were examined. Subjects provided pain intensity and unpleasantness ratings to noxious heat (49°C) applied at varying durations and locations (ventral forearm/lower leg). Cold pain ratings, thresholds, and tolerances were obtained after immersion of the hand in a cold-water bath (0-2°C). Between-group differences in pain responses, as well as relationships between pain responses and obesity parameters, were examined. Importantly, confounds that may influence pain such as anxiety, depression, impulsivity, sleepiness, and quality of life were assessed.

Results

No between-group differences in pain sensitivity to noxious heat and cold stimuli were found. No relationships were found between central adiposity or body fat (percentage or distribution) and pain responses to noxious heat or cold stimuli.

Conclusions

Obesity has minimal influence on pain sensitivity. Accordingly, it is unlikely that obesity alone increases susceptibility for chronic pain development through amplification of nociceptive processes.

The Effects of Gender, Functional Condition, and ADL on Pressure Pain Threshold in Stroke Patients

Background

Somatosensory impairments and pain are common symptoms following stroke. However, the condition of perception and pain threshold for pressure stimuli and the factors that can influence this in individuals with stroke are still unclear. This study aimed to investigate the gender differences in pressure pain threshold (PPT) and positive somatosensory signs for pressure stimuli, and explore the effects of joint pain, motor function, and activities of daily living (ADL) on pain threshold in post-stroke patients.

Design

A cross-sectional study.

Methods

A total of 60 participants with stroke were recruited, and their pain condition, motor functions, and ADL were evaluated by the Fugl-Meyer assessment of joint pain scale, motor function scale, and Barthel index, respectively. PPTs in eight tested points at the affected and unaffected sides were assessed.

Results

Significant differences in PPTs were found between male and female patients in all measured muscles (p < 0.05). Positive somatosensory signs for pressure stimuli, including hypoalgesia and hyperalgesia, were frequently found at the affected side, particularly in the extremity muscles, but such signs were not significantly influenced by gender (p > 0.05). More equal PPTs between both sides and relatively lower PPTs at the affected side in the trunk and medial gastrocnemius muscles (p < 0.05) were observed in patients with less pain, better motor functions, and ADL.

Conclusion

Gender differences widely exist in post-stroke survivors either at the affected or unaffected side, which are multifactorial. Sensory loss and central and/or peripheral sensitization, such as hypoalgesia and hyperalgesia for pressure stimuli, caused by a brain lesion are common signs in male and female stroke patients. Moreover, patients who are in a better condition show a more symmetrical pain sensitivity between both sides in the trunk and in female lower extremities, indicating the bidirectional improvement of somatosensory abnormalities caused by a possible neural plasticity.

Pain and social cognition: does pain lead to more stereotyped judgments based on ethnicity and age?

Background and aims Previous research on pain and cognition has largely focused on non-social cognitive outcomes (e.g. attention, problem solving). This study examines the relationship between pain and stereotyping, which constitutes a fundamental dimension of social cognition. Drawing on dual process theories of cognition, it was hypothesized that higher levels of pain would increase stereotyped judgments based on ethnicity and age. The hypothesis was tested in conjunction with experimentally induced pain (Study 1) and clinical pain (Study 2). Methods In Study 1, experimental pain was induced with the cold pressor method on a between-subjects basis. Participants (n = 151) completed a judgment task that assessed to what extent they relied on stereotypes (ethnic and age) when estimating other people's cognitive performance. In Study 2, 109 participants with clinical, musculoskeletal pain completed the same stereotype judgment task. Correlations between stereotyped judgments and various pain qualities (intensity, interference with daily activities, duration, and persistence) were performed. Results In Study 1, pain induced participants did not form significantly more stereotyped judgments compared to pain-free participants. However, higher reported pain intensity was associated with more ethnically stereotyped judgments. In Study 2, there were no significant correlations between different aspects of clinical pain and stereotyped judgments. Conclusions The results provide weak support for the hypothesis that pain increases stereotyped judgments. This was the case for both experimentally induced pain and clinical pain. The present study is the first to investigate the link between pain and stereotyping, suggesting that stereotypical judgments may be a social cognitive outcome that is relatively unaffected by pain. Implications The results have practical implications for the clinic, for example, where chronic pain patients may not have greater difficulties interacting with health care professionals that are members of a stereotyped social group (e.g. ethnic).

Sources of Individual Differences in Pain

Pain is an immense clinical and societal challenge, and the key to understanding and treating it is variability. Robust interindividual differences are consistently observed in pain sensitivity, susceptibility to developing painful disorders, and response to analgesic manipulations. This review examines the causes of this variability, including both organismic and environmental sources. Chronic pain development is a textbook example of a gene-environment interaction, requiring both chance initiating events (e.g., trauma, infection) and more immutable risk factors. The focus is on genetic factors, since twin studies have determined that a plurality of the variance likely derives from inherited genetic variants, but sex, age, ethnicity, personality variables, and environmental factors are also considered.

Determination of Pain Phenotypes in Knee Osteoarthritis Using Latent Profile Analysis

OBJECTIVE

To identify clinical phenotypes of knee osteoarthritis (OA) using measures from the following domains: 1) multimorbidity; 2) psychological distress; 3) pain sensitivity; and 4) knee impairment or pathology.

DESIGN

Data were collected from 152 people with knee OA and from 31 pain-free individuals. In participants with knee OA, latent profile analysis (LPA) was applied to the following measures: normalized knee extensor strength, Functional Comorbidity Index (FCI), Pain Catastrophizing Scale (PCS), and local (knee) pressure pain threshold. Comparisons were performed between empirically derived phenotypes from the LPA and healthy older adults on these measures. Comparisons were also made between pheonotypes on pain intensity, functional measures, use of health care, and history of knee injury.

RESULTS

LPA resulted in a four-group solution. Compared with all other groups, group 1 (9% of the study population) had higher FCI scores. Group 2 (63%) had elevated pain sensitivity and quadriceps weakness relative to group 4 and healthy older adults. Group 3 (11%) had higher PCS scores than all other groups. Group 4 (17%) had greater leg strength, except relative to healthy older adults, and reduced pain sensitivity relative to all groups. Groups 1 and 3 demonstrated higher pain and worse function than other groups, and group 4 had higher rates of knee injury.

CONCLUSION

Four phenotypes of knee OA were identified using psychological factors, comorbidity status, pain sensitivity, and leg strength. Follow-up analyses supported the replicability of this phenotype structure, but future research is needed to determine its usefulness in knee OA care.

Pressure pain thresholds in office workers with chronic neck pain: A systematic review and meta-analysis

OBJECTIVES

The purpose of this study was to (a) compare pressure pain threshold (PPT) values between office workers with chronic neck pain and asymptomatic controls; (b) establish reference PPT values in chronic neck pain; and (c) evaluate associations between PPTs and pain intensity, and disability.

METHODS

Seven English/Portuguese databases were searched for relevant literature. Studies investigating adult office workers (age >18 years) with chronic neck pain were included if PPTs were an outcome. The risk of bias was assessed using the Downs and Black checklist. Meta-analysis was conducted if a cluster contained at least two studies reporting the same PPTs.

RESULTS

Ten high quality, two low quality, and one poor quality studies were included. The meta-analysis revealed decreased PPT values in the upper trapezius, extensor carpi ulnaris, and tibialis anterior in office workers with chronic neck pain when compared with healthy workers, without a statistical difference (p > 0.05). The PPT reference value in the upper trapezius was 263 kPa (95% confidence interval [CI] = 236.35 to 289.70), and 365 kPa (95% CI = 316.66 to 415.12) for the tibialis anterior in office workers with chronic neck pain. No correlations were found between the upper trapezius PPT and pain intensity and disability.

CONCLUSION

This meta-analysis found that all the PPT measurements were not significantly reduced in office workers with chronic neck pain compared with healthy workers. These assumptions were based on a small sample of existing studies, and therefore further studies are necessary to quantify the differences in PPTs. Hypersensitivity PPT reference values are proposed for localized and extrasegmental sites in office workers with chronic neck pain.

Central sensitisation in chronic pain conditions: latest discoveries and their potential for precision medicine

Chronic pain is a leading cause of disability globally and associated with enormous health-care costs. The discrepancy between the extent of tissue damage and the magnitude of pain, disability, and associated symptoms represents a diagnostic challenge for rheumatology specialists. Central sensitisation, defined as an amplification of neural signalling within the CNS that elicits pain hypersensitivity, has been investigated as a reason for this discrepancy. Features of central sensitisation have been documented in various pain conditions common in rheumatology practice, including fibromyalgia, osteoarthritis, rheumatoid arthritis, Ehlers-Danlos syndrome, upper extremity tendinopathies, headache, and spinal pain. Within individual pain conditions, there is substantial variation among patients in terms of presence and magnitude of central sensitisation, stressing the importance of individual assessment. Central sensitisation predicts poor treatment outcomes in multiple patient populations. The available evidence supports various pharmacological and non-pharmacological strategies to reduce central sensitisation and to improve patient outcomes in several conditions commonly seen in rheumatology practice. These data open up new treatment perspectives, with the possibility for precision pain medicine treatment according to pain phenotyping as a logical next step. With this view, studies suggest the possibility of matching non-pharmacological approaches, or medications, or both to the central sensitisation pain phenotypes.

An Experimental Analogue Study on the "Dose-Response Relationship" of Different Therapeutic Instructions for Pain Exposures: The More, The Better?

Objective

Novel suggestions derived from the inhibitory learning model on how to optimize exposure therapy have been debated with enthusiasm in the last few years, particularly with respect to the focus on expectancy violations. However, little is known about how this new approach directly compares to the traditional habituation rationale of exposure therapy. In the present study, we examined these two competing therapeutic instructions among healthy female participants in an experimental heat pain paradigm.

Design and Methods

Participants (N= 116) received a therapeutic instruction derived from either a habituation-based approach or the inhibitory learning model (expectation violation). Participants were repeatedly exposed to painful thermal stimulations until a predefined exposure goal was reached.

Results

The expectation violation instruction led to faster goal attainment and higher response rates than the habituation instruction. Both instructions led to increased pain tolerance in the short and long term (one-week follow-up).

Conclusion

Our results suggest that exposure treatments using an expectation violation instruction are especially time-effective. Although the findings from this analogue design cannot be directly generalized to populations with clinically relevant levels of chronic pain, they do point to some important theoretical and clinical implications for the treatment of pain.

Controlled manual loading of body tissues: towards the next generation of pressure algometer

Assessing the responses of body tissue subjected to mechanical load is a fundamental component of the clinical examination, psychophysical assessments and bioengineering research. The forces applied during such assessments are usually generated manually, via the hands of the tester, and aimed at discreet tissue sites. It is therefore desirable to objectively quantify and optimise the control of manually applied force. However, current laboratory-grade manual devices and commercial software packages, in particular pressure algometer systems, are generally inflexible and expensive. This paper introduces and discusses several principles that should be implemented as design goals within a flexible, generic software application, given currently available force measurement hardware. We also discuss pitfalls that clinicians and researchers might face when using current pressure algometer systems and provide examples of these. Finally, we present our implementation of a pressure algometer system that achieves these goals in an efficient and affordable way for researchers and clinicians. As part of this effort, we will be sharing our configurable software application via a software repository.

Common Biological Modulators of Acute Pain: An Overview Within the AAAPT Project (ACTTION-APS-AAPM Acute Pain Taxonomy)

OBJECTIVE

The ACTTION-APS-AAPM Acute Pain Taxonomy (AAAPT) project relies on the identification of modulators to improve characterization and classification of acute pain conditions. In the frame of the AAAPT effort, this paper presents an overview of common biological modulators of acute pain.

METHODS

Nonsystematic overview.

RESULTS

Females may experience more acute pain than males, but the clinical significance may be modest. Increasing age is associated with decreasing analgesic requirement and decreasing pain intensity after surgery and with higher risk of acute low back pain. Racial and ethnic minorities have worse pain, function, and perceived well-being. Patients with preexisting chronic pain and opioid use are at higher risk of severe acute pain and high opioid consumption. The OPRM1 gene A118G polymorphism is associated with pain severity and opioid consumption, with modest quantitative impact. Most studies have found positive associations between pain sensitivity and intensity of acute clinical pain. However, the strength of the association is unclear. Surgical techniques, approaches, and complications influence postoperative pain.

CONCLUSIONS

Sex, age, race, ethnicity, preexisting chronic pain and opioid use, surgical approaches, genetic factors, and pain sensitivity are biological modulators of acute pain. Large studies with multisite replication will quantify accurately the association between modulators and acute pain and establish the value of modulators for characterization and classification of acute pain conditions, as well as their ability to identify patients at risk of uncontrolled pain. The development and validation of quick, bed-side pain sensitivity tests would allow their implementation as clinical screening tools. Acute nonsurgical pain requires more investigation.

Age and Gender as Factors of Pressure Sensitivity of Pain-Free Persons: Are They Meaningful?

Purpose

Prior findings suggest that women and elderly persons are more sensitive to pressure than men and younger persons; however, the magnitudes of these differences are substantially inconsistent. We answered the question whether the higher sensitivity of women and elderly persons is quantitatively meaningful. Specifically, we investigated if it is large enough to hamper the diagnosis, classification and follow-up of pain conditions by clinicians.

Materials and Methods

From each age stratum (18–20, 21–30, 31–40, 41–50, 51–60, 61–70, 71–80, and >80 years), 40 pain-free women and 40 pain-free men were recruited. They rated the intensity of pressure of ten Newtons over ten seconds on an analogue zero to ten rating scale. The pressure was applied on their middle fingers and ear lobes with a threshold algometer. Centile curves visualized the sex- and age-dependent fluctuation of pressure sensitivity.

Results

Over the entire age range from 20 to 80 years, the median curves fluctuated within the interval of less than two points. The distance between the median curves of men and women was also less than two points. On the average, the median difference was half a point on the finger (p = 0.249) and the ear lobe (p = 0.083).

Conclusion

Less than two points is below the minimal clinically important difference for a zero to ten analogue pain rating scale; differences smaller than one point are even below the resolution of the scale. Sex differences and age fluctuations of pressure sensitivity are negligible.

Pressure pain sensitivity in patients with traumatic first-time and recurrent anterior shoulder dislocation: a cross-sectional analysis

Background and aims Traumatic anterior shoulder dislocation (ASD) is frequent in active populations and associated with a 39% higher risk of recurrent dislocation, which may cause persistent shoulder problems, pain, and impaired shoulder-related quality of life. While local and distant pressure pain sensitivity has been demonstrated in other shoulder conditions, little is known about the link between pressure pain sensitivity and ASD. The interesting aspect is whether recurrent dislocation - resulting in symptoms of longer duration - is associated with more pronounced pressure pain sensitivity, or if presence of pressure pain sensitivity may be part of the reasons why patients develop recurrent dislocation. Therefore, this study aimed at evaluating whether patients with recurrent ASD display greater pressure pain sensitivity and more painful body sites than patients with first-time ASD. Methods This was a cross-sectional analysis of baseline data from a randomized controlled trial including 34 patients with first-time ASD [82% male, mean (SD) age 26 (7) years] and 22 patients with recurrent ASD [96% male, mean (SD) age 25 (5) years]. Patients were assessed as follows: (1) assessment of local and distant pressure pain sensitivity evaluated by pressure pain thresholds (PPTs) using a handheld algometer on mm. trapezius superior, levator scapula, pectorales major, deltoideus, and tibialis anterior, (2) pain intensity at rest during the previous 24 h, (3) number of ASD, and (4) number of painful body sites on a region-divided body chart. Results The PPTs were not significantly different between first-time and recurrent ASD [mean (SD) kPa for m. trapezius superior 264 (110) vs. 261 (88), m. levator scapula 301 (157) vs. 325 (163), m. pectorales major 234 (163) vs. 269 (130), m. deltoideus 290 (166) vs. 352 (173), m. tibialis anterior 420 (202) vs. 449 (184)], two-way ANCOVA, adjusted for sex and age, F (4,263) = 0.29, p = 0.88. For both groups, the PPTs were lower at the shoulder sites than at m. tibialis anterior (difference 117-184 kPa, 95% CI range 33-267). Females had lower PPTs than males (difference 124 kPa, 95% CI 64-183). The number (SD) of painful body sites were 2.2 (1.9) for first-time ASD and 2.6 (5.4) for recurrent ASD, with no between-group differences, one-way ANCOVA, adjusted for sex and age, F (1, 52) = 0.24, p = 0.63. There was a strong correlation between PPTs at the shoulder and lower leg, r = 0.84, p < 0.01. Conclusions This study demonstrated no differences in local and distant pressure pain sensitivity or number of painful body sites between patients with first-time and recurrent ASD. Females had lower PPTs than males, and a strong correlation was found between PPTs at the shoulder and lower leg. Implications Patients with first-time and recurrent ASD seem to have similar pressure pain sensitivity, but lower PPTs compared to existing normative data, suggesting that it is relevant to evaluate the status of the pain system in these patients to prevent triggering or worsening of their symptoms. However, it remains unanswered how these changes affect the patients' ability to undergo rehabilitation, symptom response and long-term shoulder function.

Pain Neuroscience Education and Physical Therapeutic Exercise for Patients with Chronic Spinal Pain in Spanish Physiotherapy Primary Care: A Pragmatic Randomized Controlled Trial

Chronic musculoskeletal pain affects more than 20% of the population, leading to high health care overload and huge spending. The prevalence is increasing and negatively affects both physical and mental health, being one of the leading causes of disability. The most common location is the spine. Most treatments used in the Public Health Services are passive (pharmacological and invasive) and do not comply with current clinical guidelines, which recommend treating pain in primary care (PC) with education and exercise as the first-line treatments. A randomized multicentre clinical trial has been carried out in 12 PC centres. The experimental group (EG) conducted a program of pain neuroscience education (6 sessions, 10 h) and group physical exercise with playful, dual-tasking, and socialization-promoting components (18 sessions in 6 weeks, 18 h), and the control group performed the usual physiotherapy care performed in PC. The experimental treatment improved quality of life (d = 1.8 in physical component summary), catastrophism (d = 1.7), kinesiophobia (d = 1.8), central sensitization (d = 1.4), disability (d = 1.4), pain intensity (d = 3.3), and pressure pain thresholds (d = 2). Differences between the groups (p < 0.001) were clinically relevant in favour of the EG. Improvements post-intervention (week 11) were maintained at six months. The experimental treatment generates high levels of satisfaction.

Risk of Injury in Physically Active Students: Associated Factors and Quality of Life Aspects

Background: The aim of this study was to assess the potential factors of hypermobility and pain threshold on the risk of injury in physically active students and to verify which domains of quality of life are rated lower by young people with a history of injuries. Methods: The study included 278 students (138 women and 140 men) who regularly undertake physical activity. Anthropometric measurements, body composition, pain threshold, incidence of hypermobility syndrome, information on the history of injuries to the locomotor system, and the quality of life of the study participants were collected. Results: In the group studied, hypermobility and pain threshold had a statistically significant related on the risk of injury. Participants with a history of injuries had lower scores for an individual’s overall perception of their own health and the physical domain. There were also significant differences in the psychological domain of the quality of life between males and females with a history of injuries. Conclusion: In the studied group, the risk of injuries was related to diagnosed hypermobility and pain threshold measured on the lower limbs. The study also showed that people with a history of injuries had statistically significantly lower scores in the individual general perception of their own health and in the physical domain. Gender had a significant impact on the quality of life of people with injuries.

Reference values of conditioned pain modulation

Background and aims Endogenous pain modulation can be studied in humans by conditioned pain modulation (CPM): pain induced by a test stimulus is attenuated by a distantly applied noxious conditioning stimulus. The detection of impaired CPM in individual patients is of potential importance to understand the pathophysiology and predict outcomes. However, it requires the availability of reference values. Methods We determined reference values of CPM in 146 pain-free subjects. Pressure and electrical stimulation were the test stimuli. For electrical stimuli, we recorded both pain threshold and threshold for the nociceptive withdrawal reflex. Cold pressor test was the conditioning stimulus. The 5th, 10th and 25th percentiles for the three tests were computed by quantile regression analyses. Results The average thresholds increased after the conditioning stimulus for all three tests. However, a subset of subjects displayed a decrease in thresholds during the conditioning stimulus. This produced negative values for most of the computed percentiles. Conclusions This study determined percentile reference values of CPM that can be used to better phenotype patients for clinical and research purposes. The negative value of percentiles suggests that a slightly negative CPM effect can be observed in pain-free volunteers. Implications Pain facilitation rather than inhibition during the conditioning stimulus occurs in some pain-free volunteers and may not necessarily represent an abnormal finding.

A clinically feasible method for the assessment and characterization of pain in patients with chronic pancreatitis

BACKGROUND AND AIMS

Pain is the primary symptom of chronic pancreatitis (CP), but methods for sensory testing and pain characterization have not previously been validated for clinical use. We present a clinically feasible method for the assessment and characterization of pain mechanisms in patients with CP based on quantitative sensory testing (QST).

METHODS

This was a cross-sectional, multicenter study of 122 control subjects without pancreatic disease and another 60 patients with painful CP. All subjects underwent standardized QST assessments including a cold pressor test, a conditioned pain modulation paradigm, repetitive pin-prick stimuli (temporal summation) and pressure stimulation of the upper abdominal (pancreatic) and control dermatomes. The effects of age and gender on QST assessment parameters were investigated and normative reference values based on quartile regression were derived and implemented in algorithms to categorize patients according to their patterns of central pain processing (normal vs. segmental sensitization vs. widespread sensitization).

RESULTS

Absolute pressure thresholds were subject to clinically relevant gender effects (all p < 0.001), while the remainder of QST parameters were unaffected by age and gender. The algorithm with the best discriminatory capacity showed good separation between patients and controls (p < 0.001); 50% of patients had normal central pain processing, 23% had evidence of segmental sensitization and 27% had evidence of widespread sensitization.

CONCLUSION

We show normative reference values for a clinically feasible method for assessment and characterization of pain mechanisms in patients with CP. Application of this method streamlines the evaluation of pancreatic pain and may be used to inform treatment. CLINICALTRIALS.

GOV ID

NCT03434392.

Gender Differences in Pre- and Postoperative Health-Related Quality of Life Measures in Patients Who Have Had Decompression Surgery for Lumbar Spinal Stenosis

Study Design

Retrospective chart audit.

Purpose

This study aimed to investigate the gender difference in pre- and postoperative health-related quality of life (HRQOL) in patients who have had decompression surgery for lumbar spinal stenosis (LSS).

Overview of Literature

Gender differences may contribute to variations in disease presentations and health outcomes. The influence of gender on pre- and postoperative HRQOL in spinal disorders remains unclear.

Methods

We reviewed 125 patients (79 men and 46 women) who had lumbar spinous process splitting laminectomy (LSPSL) for LSS. We assessed the following clinical information: Japanese Orthopedic Association (JOA) score; numerical rating scale (NRS) for low back pain (LBP), leg pain, and leg numbness; Zurich Claudication Questionnaire; JOA Back Pain Evaluation Questionnaire; Roland- Morris Disability Questionnaire (RMDQ); and Short Form 8 (SF-8) as HRQOL. We compared the HRQOLs of men and women pre- and postoperatively.

Results

Although the preoperative NRS results for LBP were significantly higher in women (p <0.05), there were no significant differences in clinical outcomes between men and women postoperatively. For HRQOL, the RMDQ scores were significantly worse in women preoperatively (p <0.05), but no significant differences were found postoperatively between men and women. Similarly, the SF-8 mental health score was also significantly lower in women preoperatively (p <0.05), but no significant differences were noted between the two groups postoperatively.

Conclusions

LSPSL greatly reduced LBP, leg pain, and leg numbness in both genders. There were limited differences in pain and several HRQOL questionnaire responses between men and women after surgery. We found that women had greater sensitivity to and/or lower tolerance for pain than men, which led to lower HRQOL mental health scores preoperatively.

Pain neuroscience education and physical exercise for patients with chronic spinal pain in primary healthcare: a randomised trial protocol

BACKGROUND

Chronic musculoskeletal pain affects more than 20% of the population, and the prevalence is increasing, causing suffering, loss of quality of life, disability, and an enormous expenditure on healthcare resources. The most common location for chronic pain is the spine. Many of the treatments used are mainly passive (pharmacological and invasive) and poor outcomes. The treatments currently applied in the public health system do not comply with the recommendations of the main clinical practice guidelines, which suggest the use of educational measures and physical exercise as the first-line treatment. A protocol based on active coping strategies is described, which will be evaluated through a clinical trial and which could facilitate the transfer of the recommendations of the clinical practice guidelines to a primary care setting.

METHODS

Randomised and multicentre clinical trials, which will be carried out in 10 Primary Care centres. The trial will compare the effect of a Pain Neuroscience Education program (six sessions, 10 h) and group physical exercise (18 sessions program carried out in six weeks, 18 h), with usual care physiotherapy treatment. Group physical exercise incorporates dual tasks, gaming, and reinforcement of contents of the educational program. The aim is to assess the effect of the intervention on quality of life, as well as on pain, disability, catastrophism, kinesiophobia, central sensitisation, and drug use. The outcome variables will be measured at the beginning of the intervention, after the intervention (week 11), at six months, and a year.

DISCUSSION

Therapeutic interventions based on active coping strategies are essential for the treatment of chronic pain and the sustainability of the Public Health System. Demonstrating whether group interventions have an effect size is essential for optimising resources in such a prevalent problem.

TRIAL REGISTRATION

NCT03654235 "Retrospectively registered" 31 August 2018.

Thermal and mechanical quantitative sensory testing values among healthy African American adults

PURPOSE

Only a few studies have reported quantitative sensory testing (QST) reference values for healthy African Americans, and those studies are limited in sample size and age of participants. The study purpose was to characterize QST values in healthy, pain-free African American adults and older adults whose prior pain experiences and psychological status were also measured. We examined the QST values for differences by sex, age, and body test site.

PATIENTS AND METHODS

A cross-sectional sample of 124 pain-free African American adults (age 18-69 years, 49% female) completed demographic and self-reported pain, fatigue and psychosocial measures. QST was performed to obtain thermal and mechanical responses and associated pain intensity levels.

RESULTS

We found thermal detection values at the anterior forearm were (29.2 °C±1.6) for cool detection (CD) and (34.5 °C±1.2) for warm detection (WD). At that site the sample had cold pain threshold (CPTh) (26.3 °C±5.0), heat pain threshold (HPTh) (37.8 °C±3.6), and mechanical pain thresholds (MPTH) (16.7±22.2 grams of force, gF). There was a significant between sex difference for WD, with women being more sensitive (q=0.027). Lower body sites were less sensitive than upper body sites across all thermal modalities (q<0.003), but not for the mechanical modality.

CONCLUSION

The QST values from this protocol at the anterior forearm indicate that the healthy African American adults had average thermal pain thresholds close to the temperature of adaptation and average MPTh under 20 gF. Differences in responses to thermal and mechanical stimuli for upper verses lower body were consistent with prior research.

Sex Differences in Opioid Use in Patients With Symptomatic Lumbar Stenosis or Spondylolisthesis Undergoing Lumbar Decompression and Fusion

STUDY DESIGN

Retrospective analysis.

OBJECTIVE

To investigate sex differences in opioid use after lumbar decompression and fusion surgery for patients with symptomatic lumbar stenosis or spondylolisthesis.

SUMMARY OF BACKGROUND DATA

Recent studies have demonstrated higher prevalence of chronic pain states and greater pain sensitivity among women compared with men. Furthermore, differences in responsivity to pharmacological and non-pharmacological treatments have been observed. Whether sex differences in perioperative opioid use exists in patients undergoing lumbar fusion for symptomatic stenosis or spondylolisthesis remains unknown.

METHODS

An insurance database, including private/commercially insured and Medicare Advantage beneficiaries, was queried for patients with symptomatic lumbar stenosis or spondylolisthesis undergoing index 1,2, or 3-level index lumbar decompression and fusion procedures between 2007 and 2016. Records were searchable by International Classification of diseases diagnosis and procedure codes, and generic drug codes specific to Humana. Opioid use 6-months prior to through 2-years after index surgery was assessed. The primary outcome was sex differences in opioid use after index lumbar surgery. The secondary outcome was independent predictors of prolonged opioid use after lumbar fusion.

RESULTS

Of the 13,257 participants (females: 7871, 59.8%), 58.4% of women used opioids compared with 56.9% of men prior to index surgery. At 1-year after surgery, continuous opioid use was observed in 67.1% of women compared with 64.2% of men (P < 0.001). Within 2-years postoperatively, opioid use was observed in 83.1% of women versus 82.5% men. In a multivariate logistic regression analysis, female sex (odds ration [OR] 1.14, 95% confidence interval [CI]: 1.058-1.237), obesity (OR 1.10, 95% CI: 1.004-1.212), and preoperative narcotic use (OR 3.43, 95% CI: 3.179-3.708) was independently associated with prolonged (>1 yr) opioid use after index surgery.

CONCLUSION

We observed a higher prevalence of chronic opioid use among women following lumbar fusion surgery. Female sex was independently associated with prolonged opioid use after index surgery.

LEVEL OF EVIDENCE

3.

Postoperative treatment after partial nail ablation of ingrown toenails - does it matter what we recommend? A blinded randomised study

Trial design: In this blinded randomized study we analyzed patient reported outcome of three different treatments after nail surgery. We compared daily footbath with either alkaline or acidic soap or just a simple bandage of gauze dressing. Method: After partial nail ablation surgery, patients were randomized into three postoperative treatment modalities. Outcome in terms of reduction in pain, improvement of function, reduction of signs of infection and postoperative soothing effect were reported after one and two weeks. A generalized linear mixed model was used to analyze possible statistical differences between the groups. Results: 97 patients, 57% women, mean age 31 years, were included. Men reported significantly less pain and better function than women. Despite a registered lower growth of invasive pathogenic microbes following the use of acidic soaps, this did not lead to less infections than in the groups using either alkaline soap baths or bandaging. On the contrary, patients keeping the bandage on had significantly lower signs of infection after one week. Two patients using soap baths had growth of MRSA. Two weeks postoperatively, all three treatment alternatives had similar patient reported outcome in all parameters, and nobody needed antibiotics. Conclusions: This prospective randomized study was unable to prove that footbath with either acidic or alkaline soap should be preferred to just leave the postoperative bandage on for a week after partial nail ablation. We recommend that postoperative advice should be given on an individual basis, especially since our study did not involve patients with high risk of infections.

Manual therapy for chronic migraine: a pragmatic randomised controlled trial study protocol

Introduction

Chronic migraine is a largely refractory condition affecting between 1 and 2.2% of the overall population worldwide, with females more affected than males. There are also high health and socioeconomic costs associated both for the individual and society. The mainstay of chronic migraine management is pharmacological, but the options available have limited efficacy and there are often unwanted side effects. There is some evidence for manual therapy as a treatment option for migraine, but its effectiveness for chronic migraine is unknown. Therefore, we have designed a pragmatic randomised control trial to investigate whether adding manual therapy to the tertiary specialist treatment of chronic migraine improves patient-reported outcomes.

Methods

A pragmatic, randomised controlled trial in a hospital tertiary headache clinic. Participants will be randomised into one of two groups: treatment as usual or treatment as usual plus manual therapy. The primary outcome measure will be a change in the Headache Impact Test score. Secondary outcomes will also be measured over the 12-week study period including changes in headache frequency, migraine specific quality of life and reductions in relevant medicine consumption. The manual therapy group will have five treatment sessions each lasting 30 min. The recruitment target of 64 participants will allow power at 80% with p = 0.05 using minimal clinical difference for Headache Impact Test of 3.7 and includes provision for a 10% dropout rate. Recruitment will take place between August 2018 and February 2019. The results will form part of a doctoral study and be published in peer-reviewed journals and presented at national/international conferences.

Discussion

Current pharmacological approaches have limited effects in the management of chronic migraine and there is a requirement to improve treatment options and reduce the health and economic burden of the condition. Manual therapy has been shown to be effective in other chronic pain conditions as well as other primary headaches. This study will explore the effectiveness of manual therapy as an adjunctive approach to the management of chronic migraine.

Trial registration

The trial has received a favourable opinion from the UK Health Research Authority (IRAS 228901) and is registered at ClinicalTrials.gov.number NCT03395457. Registered 1st March 2018.

Mutations affecting glycinergic neurotransmission in hyperekplexia increase pain sensitivity

See Dickenson (doi:10.1093/brain/awx334) for a scientific commentary on this article.Inhibitory interneurons in the spinal cord use glycine and GABA for fast inhibitory neurotransmission. While there is abundant research on these inhibitory pain pathways in animal models, their relevance in humans remains unclear, largely due to the limited possibility to manipulate selectively these pathways in humans. Hyperekplexia is a rare human disease that is caused by loss-of-function mutations in genes encoding for glycine receptors and glycine transporters. In the present study, we tested whether hyperekplexia patients display altered pain perception or central pain modulation compared with healthy subjects. Seven patients with genetically and clinically confirmed hyperekplexia were compared to 14 healthy age- and sex-matched controls. The following quantitative sensory tests were performed: pressure pain detection threshold (primary outcome), ice water tolerance, single and repeated electrical pain detection thresholds, nociceptive withdrawal reflex threshold, and conditioned pain modulation. Statistical analysis was performed using linear mixed models. Hyperekplexia patients displayed lower pain thresholds than healthy controls for all of the quantitative sensory tests [mean (standard deviation)]: pressure pain detection threshold [273 (170) versus 475 (115) kPa, P = 0.003], ice water tolerance [49.2 (36.5) versus 85.7 (35.0) s, P = 0.015], electrical single pain detection threshold [5.42 (2.64) versus 7.47 (2.62) mA, P = 0.012], electrical repeated pain detection threshold [3.76 (1.41) versus 5.8 (1.73) mA, P = 0.003], and nociceptive withdrawal reflex [7.42 (3.63) versus 14.1 (6.9) mA, P = 0.015]. Conditioned pain modulation was significantly reduced in hyperekplexia [increase to baseline: 53.2 (63.7) versus 105 (57) kPa, P = 0.030]. Our data demonstrate increased pain sensitivity and impaired central pain modulation in hyperekplexia patients, supporting the importance of glycinergic neurotransmission for central pain modulation in humans.

Quantitative sensory testing response patterns to capsaicin- and ultraviolet-B-induced local skin hypersensitization in healthy subjects: a machine-learned analysis

The comprehensive assessment of pain-related human phenotypes requires combinations of nociceptive measures that produce complex high-dimensional data, posing challenges to bioinformatic analysis. In this study, we assessed established experimental models of heat hyperalgesia of the skin, consisting of local ultraviolet-B (UV-B) irradiation or capsaicin application, in 82 healthy subjects using a variety of noxious stimuli. We extended the original heat stimulation by applying cold and mechanical stimuli and assessing the hypersensitization effects with a clinically established quantitative sensory testing (QST) battery (German Research Network on Neuropathic Pain). This study provided a 246 × 10-sized data matrix (82 subjects assessed at baseline, following UV-B application, and following capsaicin application) with respect to 10 QST parameters, which we analyzed using machine-learning techniques. We observed statistically significant effects of the hypersensitization treatments in 9 different QST parameters. Supervised machine-learned analysis implemented as random forests followed by ABC analysis pointed to heat pain thresholds as the most relevantly affected QST parameter. However, decision tree analysis indicated that UV-B additionally modulated sensitivity to cold. Unsupervised machine-learning techniques, implemented as emergent self-organizing maps, hinted at subgroups responding to topical application of capsaicin. The distinction among subgroups was based on sensitivity to pressure pain, which could be attributed to sex differences, with women being more sensitive than men. Thus, while UV-B and capsaicin share a major component of heat pain sensitization, they differ in their effects on QST parameter patterns in healthy subjects, suggesting a lack of redundancy between these models.