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

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.

Understanding the Psychological, Physiological, and Genetic Factors Affecting Precision Pain Medicine: A Narrative Review

PURPOSE

Precision pain medicine focuses on employing methods to assess each patient individually, identify their risk profile for disproportionate pain and/or the development of chronic pain, and optimize therapeutic strategies to target specific pathological processes underlying chronic pain. This review aims to provide a concise summary of the current body of knowledge regarding psychological, physiological, and genetic determinants of chronic pain related to precision pain medicine.

METHODS

Following the Scale for the Assessment of Narrative Review Articles (SANRA) criteria, we employed PubMed/Medline to identify relevant articles using primary database search terms to query articles such as: precision medicine, non-modifiable factors, pain, anesthesiology, quantitative sensory testing, genetics, pain medicine, and psychological.

RESULTS

Precision pain medicine provides an opportunity to identify populations at risk, develop personalized treatment strategies, and reduce side effects and cost through elimination of ineffective treatment strategies. As in other complex chronic health conditions, there are two broad categories that contribute to chronic pain risk: modifiable and non-modifiable patient factors. This review focuses on three primary determinants of health, representing both modifiable and non-modifiable factors, that may contribute to a patient's profile for risk of developing pain and most effective management strategies: psychological, physiological, and genetic factors.

CONCLUSION

Consideration of these three domains is already being integrated into patient care in other specialties, but by understanding the role they play in development and maintenance of chronic pain, we can begin to implement both precision and personalized treatment regimens.

Development of a novel brief quantitative sensory testing protocol that integrates static and dynamic pain assessments: Test-retest performance in healthy adults

OBJECTIVE

Quantitative sensory testing is an expanding pain research domain with numerous clinical and research applications. There is a recognized need for brief reliable quantitative sensory testing protocols that enhance assessment feasibility. This study aimed to integrate static (pain threshold, tolerance, suprathreshold) and dynamic (conditioned pain modulation, offset analgesia, temporal summation) pain reactivity measures into a brief 20-minute protocol that uses a single portable device. The test-retest performance of this optimized protocol was evaluated.

DESIGN

Using a test-retest design, the brief quantitative sensory testing assessment was administered to participants on two occasions separated by exactly 7 days.

SETTING

A clinical psychology research laboratory at Syracuse University.

SUBJECTS

Participants were 33 healthy adults recruited from Syracuse University's online research participation pool.

METHODS

A portable computerized quantitative sensory testing device delivered contact-heat pain to assess static and dynamic pain measures in participants. Dynamic responses were continuously recorded using a computerized visual analog scale.

RESULTS

Pain threshold, tolerance, and suprathreshold exhibited excellent reliability (intraclass correlations ranged from 0.80 to 0.83). Conditioned pain modulation, offset analgesia, temporal summation yielded reliability in the good to excellent range (intraclass correlations ranged from 0.66 to 0.71).

CONCLUSIONS

Findings suggested that this brief integrated QST protocol may reliably monitor human pain reactivity over brief periods. This protocol may enhance quantitative sensory testing feasibility in clinical and research settings.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Predicting pain after Cesarean delivery: pressure algometry, temporal summation, three-item questionnaire

PURPOSE

Approximately one in five women will experience severe postoperative pain after Cesarean delivery (CD). Previously, a bedside three-item questionnaire (3-IQ) has shown to predict women experiencing higher evoked pain intensity after CD, with an area under the receiver operator characteristics (ROC) curve of 0.72. We hypothesized that the addition of psychophysical pain tests to the existing 3-IQ would improve the ability to predict severe pain in women undergoing elective CD under spinal anesthesia METHODS: This was a prospective cohort study on women undergoing elective CD under spinal anesthesia. Women were assessed preoperatively using the 3-IQ, pressure algometry (PA) and mechanical temporal summation (TS) response. All women received standard perioperative care, including a multimodal analgesia regimen that included intrathecal fentanyl and morphine. A 0-100 mm visual analogue scale (VAS) was used to assess the severity of pain at rest (VASr) and on movement (VASm) at 24 and 48 hr after surgery. Patient satisfaction and opioid consumption were also recorded. We performed ROC curve analyses to assess whether we could improve the ability to predict our primary outcome of severe pain on movement at 24 hr (VASm24 ≥ 70).

RESULTS

We studied 195 women. Median [interquartile range] VASm24 was 53 [32-72] and 28% of patients experienced a VASm24 ≥ 70. The ability to predict a VASm24 ≥ 70 assessed by the area under the ROC curve was 0.64 using the 3-IQ and 0.67 using the 3-IQ combined with TS and PA.

CONCLUSION

The addition of PA and TS to the 3-IQ model resulted in a predictive model that performed similarly to the 3-IQ model alone. Further research is warranted in this area to better predict women at risk of severe pain post CD.

Has the Phase of the Menstrual Cycle Been Considered in Studies Investigating Pressure Pain Sensitivity in Migraine and Tension-Type Headache: A Scoping Review

OBJECTIVE

The aim of this scoping review was to identify if the phase of the menstrual cycle was considered in observational studies comparing pressure pain sensitivity between women with migraine or tension-type headache (TTH) and headache-free women.

METHODS

A systematic electronic literature search in PubMed, Medline, Web of Science, Scopus, and CINAHL databases was conducted. Observational studies including one or more groups with TTH and/or migraine comparing pressure pain thresholds (PPTs) were included. The methodological quality (risk of bias) was assessed with the Newcastle-Ottawa Scale. Authors, objectives, inclusion/exclusion criteria, size sample, female sample, tool to assess PPTs, mean age, and the use of any medication were extracted and analyzed independently by two authors.

RESULTS

From a total of 1404 and 1832 identified articles for TTH and migraine, 30 and 18 studies satisfied the criteria and were included. Nineteen (63.4%) studies assessing TTH patients and eleven (61.1%) assessing migraine patients showed a high risk of bias. The most common flaws were attributed to improper selection of control and control over other additional factors. Based on the systematic review, just one study including TTH and one including migraine patients considered the menstrual cycle.

CONCLUSION

The results of this scoping review identified that the phase of the menstrual cycle has been rarely considered in studies investigating sensitivity to pressure pain in primary headaches, such as TTH or migraine, although there is evidence showing the relevance of the phase of the menstrual cycle in pain perception.

A cross-sectional analysis of persistent low back pain, using correlations between lumbar stiffness, pressure pain threshold, and heat pain threshold

Introduction

Little is known about the underlying biomechanical cause of low back pain (LBP). Recently, technological advances have made it possible to quantify biomechanical and neurophysiological measurements, potentially relevant factors in understanding LBP etiology. However, few studies have explored the relation between these factors. This study aims to quantify the correlation between biomechanical and neurophysiological outcomes in non-specific LBP and examine whether these correlations differ when considered regionally vs. segmentally.

Methods

This is a secondary cross-sectional analysis of 132 participants with persistent non-specific LBP. Biomechanical data included spinal stiffness (global stiffness) measured by a rolling indenter. Neurophysiological data included pain sensitivity (pressure pain threshold and heat pain threshold) measured by a pressure algometer and a thermode. Correlations were tested using Pearson’s product-moment correlation or Spearman’s rank correlation as appropriate. The association between these outcomes and the segmental level was tested using ANOVA with post-hoc Tukey corrected comparisons.

Results

A moderate positive correlation was found between spinal stiffness and pressure pain threshold, i.e., high degrees of stiffness were associated with high pressure pain thresholds. The correlation between spinal stiffness and heat pain threshold was poor and not statistically significant. Aside from a statistically significant minor association between the lower and the upper lumbar segments and stiffness, no other segmental relation was shown.

Conclusions

The moderate correlation between spinal stiffness and mechanical pain sensitivity was the opposite of expected, meaning higher degrees of stiffness was associated with higher pressure pain thresholds. No clinically relevant segmental association existed.

A Phase 1, Randomized, Double-Blind, Placebo-Controlled, Crossover Study to Evaluate the Pharmacodynamic Effects of VX-150, a Highly Selective NaV1.8 Inhibitor, in Healthy Male Adults

OBJECTIVE

To evaluate the analgesic potential, safety, tolerability, and pharmacokinetics of VX-150, a pro-drug of a highly selective NaV1.8 inhibitor, in healthy subjects.

DESIGN

This was a randomized, double-blind, placebo-controlled, crossover study in healthy subjects.

SUBJECTS

Twenty healthy male subjects with an age of 18-55 years, inclusive, were enrolled. Eligibility was based on general fitness, absence of current or previous medical conditions that could compromise subject safety, and a training assessment of pain tolerance across pain tests to exclude highly tolerant individuals whose tolerance could compromise the ability to detect analgesic responses. All dosed subjects completed the study.

METHODS

Subjects were randomized 1:1 to one of two sequences receiving a single VX-150 dose and subsequently placebo, or vice versa, with at least 7 days between dosing. A battery of pain tests (pressure, electrical stair, [capsaicin-induced] heat, and cold pressor) was administered before dosing and repetitively up to 10 h after dosing, with blood sampling up to 24 h after dosing. Safety was monitored throughout the study. Data were analyzed with a repeated-measures mixed-effects model.

RESULTS

VX-150 induced analgesia in a variety of evoked pain tests, without affecting subject safety. Significant effects were reported for the cold pressor and heat pain thresholds. Maximum median concentration for the active moiety was 4.30 µg/mL at 4 h after dosing.

CONCLUSION

Results of this proof-of-mechanism study are supportive of the potential of VX-150, a highly selective NaV1.8 channel inhibitor, to treat various pain indications.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Disability, burden, and symptoms related to sensitization in migraine patients associate with headache frequency

OBJECTIVES

This observational study aimed to assess the difference in disability, burden, and sensitization between migraine patients with low-frequency headache attack (1-8 headache days/month), high-frequency headache attack (9-14 headache days/months), and patients with chronic migraine (>14 headache days/months).

METHODS

Migraine patients with or without aura were divided into three groups according to headache frequency (low-frequency episodic migraine; high-frequency episodic migraine; chronic migraine). Questionnaires were used to assess the burden of headache, quality of life, phycological burden, and symptoms related to sensitization (estimated by the Central Sensitization Inventory). Differences among migraine groups were assessed using Chi-Quadro test, ANOVA, or Kruskal-Wallis as appropriate.

RESULTS

136 patients were included (68 low-frequency episodic migraine, 45 high-frequency episodic migraine, 23 chronic migraine). Patients with high frequency episodic migraine and chronic migraine differed from patients with low frequency episodic migraine showing a worse burden of headache (p=0.002; p=0.002), worse level of physical (p=0.001; p<0.001) and mental (p=0.002; p=0.001) quality of life, worse level of depression (p=0.008; p=0.003), and increase presence of symptoms related to sensitization (p<0.001; p=0.003). No differences were found in any variables between patients with high-frequency episodic migraine and patients with chronic migraine (p>0.05).

CONCLUSIONS

Patients with high-frequency episodic migraine and chronic migraine could be considered in the same segment of the migraine population, with similar degrees of disability and sensitization related symptoms.

Predictive value of quantitative sensory testing for acute and chronic postsurgical pain after total joint arthroplasty: a systematic review

ABSTRACT

Quantitative sensory testing (QST) can be useful to identify high-risk patients for the development of chronic postsurgical pain. This systematic review aims to assess if presurgical sensory sensitivity measured using QST is associated with acute and chronic postsurgical pain after total joint arthroplasty. A systematic search was performed in September 2020 in PubMed, EMBASE, Web of Science, and Scopus, using terms related to total joint arthroplasty and QST. Prospective studies were included if they reported an association between presurgical QST and postsurgical pain in adults with osteoarthritis undergoing primary unilateral total joint arthroplasty. From 2994 identified studies, 18 met the inclusion criteria (1869 patients). Total knee arthroplasty was the most common surgery (16 studies), and pressure pain threshold was the most common test (11 studies), followed by dynamic measures (9 studies). Postsurgical pain was assessed at acute (5 studies), subacute (2 studies), and chronic (13 studies) time points. Risk of bias was assessed using the Quality in Prognosis Studies tool and evaluated as low to moderate in most domains. Fourteen studies reported at least one statistically significant association between QST and pain (acute: 4 studies, subacute: 1 study, and chronic: 9 studies). Pressure pain threshold was associated with postsurgical pain in 6 studies (of 11, 55%), heat pain threshold in 2 studies (of 6, 33%), conditioned pain modulation in 1 study (of 6, 17%), and temporal summation of pain in 5 studies (of 8, 63%). The predictive role of presurgical QST for postarthroplasty pain remains unclear, mainly because of heterogeneous methodologies and inconsistent results.

Patients with symptomatic permanent atrial fibrillation show quantitative signs of pain sensitisation

Objective

Most patients with atrial fibrillation (AF) report symptoms, while one-third are asymptomatic. We hypothesised that sensory processing, in particular pain, differs in patients with symptomatic and asymptomatic AF.

Methods

Thirty individuals with permanent AF (15 symptomatic and 15 asymptomatic) completed the Atrial Fibrillation 6 (AF6) and short form 36 Health Survey questionnaires and underwent quantitative pain sensitisation testing using pressure algometry at the sternum (referred pain area) and the tibialis anterior muscle (generalised pain area). The primary objective was to assess differences in pressure pain thresholds (PPT), temporal summation of pain (TSP) and conditioned pain modulation (CPM) in the two groups. The secondary objective was to determine association of demographic and clinical parameters to measures of pain sensitisation.

Results

The symptomatic group had lower PPTs at both tibialis (p=0.004) and sternum (p=0.01), and impaired CPM (p=0.025) and facilitated TSP (p=0.008) at the tibialis but not sternum, compared with the asymptomatic group. The AF6 sum score was negatively correlated to PPT on both tibialis (r=−0.50, p=0.005) and sternum (r=−0.42, p=0.02) and positively correlated to TSP on both tibialis (r=0.57, p=0.001) and sternum (r=0.45, p=0.01), but not to CPM. The physical component summary score was positively correlated to the PPT on both tibialis (r=0.52, p=0.003) and sternum (r=0.40, p=0.03) and negatively to TSP on the tibialis (r=−0.53, p=0.003) but not sternum.

Conclusions

Patients with symptomatic AF exhibit lower pain tolerance than patients with asymptomatic AF, as well as impaired pain inhibitory control and facilitated summation of pain, indicating that pain sensitisation may be of importance in symptomatic AF.

Trial registration number

NCT04649437.

Exposure to an Immersive Virtual Reality Environment can Modulate Perceptual Correlates of Endogenous Analgesia and Central Sensitization in Healthy Volunteers

Virtual reality (VR) has been shown to produce analgesic effects during different experimental and clinical pain states. Despite this, the top-down mechanisms are still poorly understood. In this study, we examined the influence of both a real and sham (ie, the same images in 2D) immersive arctic VR environment on conditioned pain modulation (CPM) and in a human surrogate model of central sensitization in 38 healthy volunteers. CPM and acute heat pain thresholds were assessed before and during VR/sham exposure in the absence of any sensitization. In a follow-on study, we used the cutaneous high frequency stimulation model of central sensitization and measured changes in mechanical pain sensitivity in an area of heterotopic sensitization before and during VR/sham exposure. There was an increase in CPM efficiency during the VR condition compared to baseline (P < .01). In the sham condition, there was a decrease in CPM efficiency compared to baseline (P < .01) and the real VR condition (P < .001). Neither real nor sham VR had any effect on pain ratings reported during the conditioning period or on heat pain threshold. There was also an attenuation of mechanical pain sensitivity during the VR condition indicating a lower sensitivity compared to sham (P < .05). We conclude that exposure to an immersive VR environment has no effect over acute pain thresholds but can modulate dynamic CPM responses and mechanical hypersensitivity in healthy volunteers. PERSPECTIVE: This study has demonstrated that exposure to an immersive virtual reality environment can modulate perceptual correlates of endogenous pain modulation and secondary hyperalgesia in a human surrogate pain model. These results suggest that virtual reality could provide a novel mechanism-driven analgesic strategy in patients with altered central pain processing.

Pain in Parkinson's disease and the role of the subthalamic nucleus

Pain is a frequent and poorly treated symptom of Parkinson's disease, mainly due to scarce knowledge of its basic mechanisms. In Parkinson's disease, deep brain stimulation of the subthalamic nucleus is a successful treatment of motor symptoms, but also might be effective in treating pain. However, it has been unclear which type of pain may benefit and how neurostimulation of the subthalamic nucleus might interfere with pain processing in Parkinson's disease. We hypothesized that the subthalamic nucleus may be an effective access point for modulation of neural systems subserving pain perception and processing in Parkinson's disease. To explore this, we discuss data from human neurophysiological and psychophysical investigations. We review studies demonstrating the clinical efficacy of deep brain stimulation of the subthalamic nucleus for pain relief in Parkinson's disease. Finally, we present some of the key insights from investigations in animal models, healthy humans and Parkinson's disease patients into the aberrant neurobiology of pain processing and consider their implications for the pain-relieving effects of subthalamic nucleus neuromodulation. The evidence from clinical and experimental studies supports the hypothesis that altered central processing is critical for pain generation in Parkinson's disease and that the subthalamic nucleus is a key structure in pain perception and modulation. Future preclinical and clinical research should consider the subthalamic nucleus as an entry point to modulate different types of pain, not only in Parkinson's disease but also in other neurological conditions associated with abnormal pain processing.

The predictive value of quantitative sensory testing: a systematic review on chronic postoperative pain and the analgesic effect of pharmacological therapies in patients with chronic pain

Studies have suggested that quantitative sensory testing (QST) might hold a predictive value for the development of chronic postoperative pain and the response to pharmacological interventions. This review systematically summarizes the current evidence on the predictive value of QST for chronic postoperative pain and the effect of pharmacological interventions. The main outcome measures were posttreatment pain intensity, pain relief, presence of moderate-to-severe postoperative pain, responders of 30% and 50% pain relief, or validated questionnaires on pain and disability. A systematic search of MEDLINE and EMBASE yielded 25 studies on surgical interventions and 11 on pharmacological interventions. Seventeen surgical and 11 pharmacological studies reported an association between preoperative or pretreatment QST and chronic postoperative pain or analgesic effect. The most commonly assessed QST modalities were pressure stimuli (17 studies), temporal summation of pain (TSP, 14 studies), and conditioned pain modulation (CPM, 16 studies). Of those, the dynamic QST parameters TSP (50%) and CPM (44%) were most frequently associated with chronic postoperative pain and analgesic effects. A large heterogeneity in methods for assessing TSP (n = 4) and CPM (n = 7) was found. Overall, most studies demonstrated low-to-moderate levels of risk of bias in study design, attrition, prognostic factors, outcome, and statistical analyses. This systematic review demonstrates that TSP and CPM show the most consistent predictive values for chronic postoperative pain and analgesic effect, but the heterogeneous methodologies reduce the generalizability and hence call for methodological guidelines.

Noninvasive motor cortex stimulation effects on quantitative sensory testing in healthy and chronic pain subjects: a systematic review and meta-analysis

ABSTRACT

One of the potential mechanisms of motor cortex stimulation by noninvasive brain stimulation (NIBS) effects on pain is through the restoration of the defective endogenous inhibitory pain pathways. However, there are still limited data on quantitative sensory testing (QST), including conditioned pain modulation (CPM), supporting this mechanism. This systematic review and meta-analysis aimed to evaluate the effects of noninvasive motor cortex stimulation on pain perception as indexed by changes in QST outcomes. Database searches were conducted until July 2019 to include randomized controlled trials that performed sham-controlled NIBS on the motor cortex in either the healthy and/or pain population and assessed the QST and CPM. Quality of studies was assessed through the Cochrane tool. We calculated the Hedge's effect sizes of QST and CPM outcomes and their 95% confidence intervals (95% CIs) and performed random-effects meta-analyses. Thirty-eight studies were included (1178 participants). We found significant increases of pain threshold in healthy subjects (ES = 0.16, 95% CI = 0.02-0.31, I2 = 22.2%) and pain populations (ES = 0.48, 95% CI = 0.15-0.80, I2 = 68.8%), and homogeneous higher CPM effect (pain ratings reduction) in healthy subjects (ES = -0.39, 95% CI = -0.64 to -0.14, I2 = 17%) and pain populations (ES = -0.35, 95% CI = -0.60 to -0.11, I2 = 0%) in the active NIBS group compared with sham. These results support the idea of top-down modulation of endogenous pain pathways by motor cortex stimulation as one of the main mechanisms of pain reduction assessed by QST, which could be a useful predictive and prognostic biomarker for chronic pain personalized treatment with NIBS.

The Modulatory Effect of QST in Shoulder Pain: A Systematic Review and Meta-Analysis

BACKGROUND

The underlying mechanisms for shoulder pain (SP) are still widely unknown. Previous reviews report signs of altered pain processing in SP measured using quantitative sensory testing (QST). Evidence suggests that QST might hold predictive value for SP after intervention, yet it is not known whether QST profiles can be modulated in response to different treatments. Therefore, this systematic review and meta-analysis aimed to assess if QST-parameters can be modified by interventions for patients with SP.

METHODS

Three databases were searched to identify eligible studies. Eligible studies had a prospective design, with at least one QST variable as an outcome in conjunction with an intervention measured before and after intervention. Studies that involved SP caused by spinal or brain injury and studies looking at combined chronic neck/shoulder pain were excluded.

RESULTS

19 studies investigating SP were eligible for inclusion for this review. Pressure pain threshold (PPT) was the most frequently used QST-parameter investigating local and widespread hyperalgesia. A meta-analysis was performed with data from 10 studies with a total of 16 interventions. Results demonstrated an overall acute effect (<24 hours after intervention) of interventions in favour of local decreased pain sensitivity and of remote decreased pain sensitivity comparing PPTs before and after interventions.

CONCLUSIONS

This study demonstrates that interventions such as exercise and manual therapy can modulate PPTs acutely both locally and remotely in patients with shoulder pain. Further research investigating the acute and long-term modulatory ability of these interventions on other QST-parameters is needed in patients with shoulder pain.

Serum artemin is not correlated with sensitivity within dogs with naturally occurring osteoarthritis pain

Osteoarthritis (OA) pain is associated with peripheral and central sensitization in humans and results in widespread increased sensitivity across the body. Sensitization contributes to the OA-associated pain (OAP) state. We recently identified increased levels of an endogenous neurotrophic factor, artemin (ARTN), in dogs with OAP compared to healthy pain-free controls. Circulating ARTN released from damaged tissues in OA, may play a central role in widespread sensitivity and pain. However, the relationship between ARTN and somatosensory sensitivity remains unknown. The study aimed to assess the relationship between serum ARTN concentrations and measures of sensitivity in dogs with OAP using quantitative sensory testing. We hypothesized that there would be a positive association between circulating ARTN and increased sensitivity to mechanical and thermal stimuli in dogs with OAP. We used linear and logistic regression models to assess the relationship between ARTN, sensitization, and pain within a cohort of 43 dogs with spontaneous OAP. Serum ARTN was not associated with the degree of sensitization within dogs with OAP. Further, across dogs with varying OAP severity, we did not find any association between ARTN, and clinical measures of joint pain and disability. Although a relationship between ARTN and joint pain was not ruled out.

Slowly repeated evoked pain (SREP) as a central sensitization marker in episodic migraine patients

Migraine headache is a pain condition characterized by severe and recurrent unilateral head pain. Among other mechanisms, central pain sensitization processes seem to be involved in the disorder. An experimental protocol based on slowly repeated evoked pain (SREP) has been shown to indicate pain sensitization in fibromyalgia patients and differentiate these patients from healthy individuals and rheumatoid arthritis patients. This study examined SREP sensitization in migraine patients and explored its potential usefulness as a central sensitization marker. The SREP protocol was administered to 40 episodic migraine (EM) patients not currently experiencing a headache and 40 healthy controls. SREP consisted of a series of 9 suprathreshold painful pressure stimuli of 5 s duration and a 30 s interstimulus interval. SREP sensitization was indexed by the increase in pain ratings across the stimuli. Pain threshold, pain tolerance and temporal summation of pain were also assessed. SREP sensitization was observed in EM, but not in healthy individuals (p < .001). SREP differentiated between EM and healthy individuals with up to 75% diagnostic accuracy. Pain threshold, pain tolerance and temporal summation of pain did not show significant discriminative ability. An SREP index value of 0.5 was the most sensitive cut-off for detecting central pain sensitization when prioritizing diagnostic sensitivity (0.88). Results provide evidence for SREP as a possible central sensitization marker with potential clinical utility in migraine patients. Inclusion of SREP in Quantitative Sensory Testing protocols may enhance the assessment of altered pain modulation in different pain conditions.

Spinal manipulation and modulation of pain sensitivity in persistent low back pain: a secondary cluster analysis of a randomized trial

BACKGROUND

Pain hypersensitivity can be assessed using Quantitative Sensory Testing (QST) and is associated with persistent low back pain. Spinal manipulation appears to modify pain hypersensitivity, and this could function as one mechanism leading to clinical improvements. In the current study, we applied a comprehensive QST battery to assess pain sensitivity in a cohort of low back pain patients before and after spinal manipulation to improve our understanding of the association between QST and clinical improvements. This study addresses two questions: Are clinical improvements following spinal manipulation in low back pain patients contingent on pain hypersensitivity, and does pain sensitivity change following spinal manipulation?

METHODS

We performed a secondary analysis of data from a randomized clinical trial. One hundred and thirty-two participants with persistent LBP were treated with spinal manipulation four times over two weeks. Patient-reported outcomes and QST were assessed at baseline, after the fourth spinal manipulation session, and 14-days later. The clinical outcomes were changes in low back pain intensity and disability. Using latent profile analysis, we categorized the participants into clusters depending on their baseline QST scores. We used linear mixed models to examine the association between clusters and changes in patient-reported outcomes and QST.

RESULTS

Two clusters emerged: a Sensitized and a Not sensitized. The former had significantly lower regional pressure and thermal pain thresholds, remote pressure pain tolerance, and lower inhibitory conditioned pain modulation than the Not sensitized group. However, we only found between-cluster differences for regional pressure pain threshold following spinal manipulation. Thus, the clusters were not associated with patient-reported pain and disability changes or the remaining QST outcomes.

CONCLUSIONS

We report that the baseline QST profile was not associated with clinical improvements following spinal manipulation. We did observe a substantial change for regional pressure pain threshold, which suggests that any effect of spinal manipulation on pain sensitivity is most likely to be observed as changes in regional, mechanical pain threshold. However, the mechanism that invokes clinical improvement and pain sensitivity changes appear distinct. Due to methodological caveats, we advise caution when interpreting the results.

TRIAL REGISTRATION

Clinical.Trial.gov identifier: NCT04086667 , registered 11 September 2019 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04086667.

Identification of neural and psychophysical predictors of headache reduction after cognitive behavioral therapy in adolescents with migraine

ABSTRACT

Cognitive behavioral therapy (CBT) is a psychological intervention that involves development of coping strategies to reduce the experience of pain. Although CBT is a promising intervention to reduce headache days in patients with migraine, it may not be effective for all patients. Thus, there is a need to identify markers that could predict which patients will respond to CBT. We aimed to determine whether baseline brain function and amygdalar connectivity, assessed by functional magnetic resonance imaging, or pain modulation capacities, assessed by the conditioned pain modulation (CPM) response, can predict a reduction in headache days after CBT in adolescents with migraine. Patients with migraine (n = 20; age range 10-17 years) completed 8 weekly CBT sessions. The CPM response was examined in the trapezius and the leg. Headache days significantly decreased after CBT (P < 0.001). Greater functional connectivity before CBT between the right amygdala and frontal gyrus, anterior cingulate cortex, and precentral gyrus was related to greater headache reduction after CBT. Greater reduction in headache days after CBT was related with less efficient CPM response before CBT at the trapezius (r = -0.492, P = 0.028) but not at the leg. This study found that headache reduction after CBT was related to right amygdala connectivity with frontal and sensorimotor regions at baseline as well as baseline pain modulation capacities. These findings suggest that individual differences in brain function and pain modulation can be associated with clinical improvements and help with determination of CBT responsiveness.

A Cumulative Impact of Psychological and Sensitization Risk Factors on Pain-Related Outcomes

OBJECTIVE

Risk constructs based on psychological risk factors (eg, pain catastrophizing, PC) and sensitization risk factors (eg, pressure pain threshold, PPT) are important in research and clinical practice. Most research looks at individual constructs but does not consider how different constructs might interact within the same individual. An evaluation of the cumulative impact of psychological and sensitization risk factors on pain-related outcomes may help guide us in the risk assessment of patients with pain conditions. The aim of this study is to evaluate the cumulative impact of these psychological (PC) and sensitization (PPT) risk factors on pain-related outcomes (activity avoidance, pain severity, and disability) considering covariates.

METHODS

We included 109 participants (70.60% women; mean ± SD age 53.6 ± 12.3 years) with chronic musculoskeletal pain for data analysis, who completed all measures of this study. Participants completed a single testing session that included measures of risk factors (PC and PPT) and pain-related outcomes (self-reported avoidance, functional avoidance, disability, and pain severity). Subgroups were constructed by dichotomizing of PC and PPT scores, resulting in four groups: (1) low catastrophizing and low sensitivity (N = 26), (2) high catastrophizing and low sensitivity (N = 27), (3) low catastrophizing and high sensitivity (N = 25), and (4) high catastrophizing and high sensitivity (N = 31).

RESULTS

One-way analysis of variance (ANOVA) revealed significant group differences (P < 0.05, η²  = 0.08 to 0.14) in all outcomes of this study (except functional avoidance), and post hoc analysis indicated the significant differences are between group 1 and 4. A cumulative impact is reflected by large effect sizes between group 1 and 4 (d = 0.8 to 1). The group 2 and 3 (one risk dimension groups: either high-PC or high-PPT) represent 47% of the total participants.

CONCLUSIONS

The study suggests both higher level of PC and pressure sensitivity have a cumulative impact on risk screening for pain-related outcomes, considering gender in functional avoidance (task-related outcome). A clinical presentation with high-PC (one dimension of risk) is not associated with high-PPT (another dimension of risk). This finding has important clinical and theoretical implications.

Quantitative Sensory Testing of Spinal Cord and Dorsal Root Ganglion Stimulation in Chronic Pain Patients

BACKGROUND/OBJECTIVES

The physiological mechanisms underlying the pain-modulatory effects of clinical neurostimulation therapies, such as spinal cord stimulation (SCS) and dorsal root ganglion stimulation (DRGS), are only partially understood. In this pilot prospective study, we used patient-reported outcomes (PROs) and quantitative sensory testing (QST) to investigate the physiological effects and possible mechanisms of action of SCS and DRGS therapies.

MATERIALS AND METHODS

We tested 16 chronic pain patients selected for SCS and DRGS therapy, before and after treatment. PROs included pain intensity, pain-related symptoms (e.g., pain interference, pain coping, sleep interference) and disability, and general health status. QST included assessments of vibration detection theshold (VDT), pressure pain threshold (PPT) and tolerance (PPToL), temporal summation (TS), and conditioned pain modulation (CPM), at the most painful site.

RESULTS

Following treatment, all participants reported significant improvements in PROs (e.g., reduced pain intensity [p < 0.001], pain-related functional impairment [or pain interference] and disability [p = 0.001 for both]; better pain coping [p = 0.03], sleep [p = 0.002]), and overall health [p = 0.005]). QST showed a significant treatment-induced increase in PPT (p = 0.002) and PPToL (p = 0.011), and a significant reduction in TS (p = 0.033) at the most painful site, but showed no effects on VDT and CPM. We detected possible associations between a few QST measures and a few PROs. Notably, higher TS was associated with increased pain interference scores at pre-treatment (r = 0.772, p = 0.009), and a reduction in TS was associated with the reduction in pain interference (r = 0.669, p = 0.034) and pain disability (r = 0.690, p = 0.027) scores with treatment.

CONCLUSIONS

Our preliminary findings suggest significant clinical and therapeutic benefits associated with SCS and DRGS therapies, and the possible ability of these therapies to modulate pain processing within the central nervous system. Replication of our pilot findings in future, larger studies is necessary to characterize the physiological mechanisms of SCS and DRGS therapies.

Within-session test-retest reliability of pressure pain threshold and mechanical temporal summation in healthy subjects

Objective

To determine the absolute and relative intra-rater within-session test-retest reliability of pressure pain threshold (PPT) and mechanical temporal summation of pain (TSP) at the low back and the forearm in healthy participants and to test the influence of the number and sequence of measurements on reliability metrics.

Methods

In 24 participants, three PPT and TSP measures were assessed at four sites (2 at the low back, 2 at the forearm) in two blocks of measurements separated by 20 minutes. The standard error of measurement, the minimal detectable change (MDC) and the intraclass correlation coefficient (ICC) were investigated for five different sequences of measurements (e.g. measurement 1, 1–2, 1-2-3).

Results

The MDC for the group (MDC_gr) for PPT ranged from 28.71 to 50.56 kPa across the sites tested, whereas MDC_gr for TSP varied from 0.33 to 0.57 out of 10 (numeric scale). Almost all ICC showed an excellent relative reliability (between 0.80 and 0.97), except when only the first measurement was considered (moderate). Although minimal differences in absolute PPT reliability were present between the different sequences, in general, using only the first measurement increase measurement error. Three TSP measures reduced the measurement error.

Discussion

We established that two measurements of PPT and three of TSP reduced the measurement error and demonstrated an excellent relative reliability. Our results could be used in future pain research to confirm the presence of true hypo/hyperalgesia for paradigms such as conditioned pain modulation or exercise-induced hypoalgesia, indicated by a change exceeding the measurement variability.

Widespread myofascial dysfunction and sensitisation in women with endometriosis-associated chronic pelvic pain: A cross-sectional study

BACKGROUND

Chronic pelvic pain persists in some women with endometriosis even after lesion removal and optimized hormonal treatment.

OBJECTIVE

Characterize the presence and distribution of pain, myofascial dysfunction and sensitisation beyond the pelvis in women with endometriosis-associated chronic pelvic pain.

METHODS

Cross-sectional study of 30 women prior to participation in a clinical trial. Evaluation included pain-focused abdominopelvic gynaecologic examination with the identification of pelvic floor muscle spasm. Neuro-musculoskeletal examination assessed paraspinal allodynia and hyperalgesia bilaterally and myofascial trigger points in 13 paired muscles. Pressure-pain thresholds were measured over interspinous ligaments and trigger points. Women completed the body territories element of the Body Pain Index.

RESULTS

All women had a pelvic floor muscle spasm that they self-identified as a major focus of pain. Twenty of 30 women described their pelvic pain as focal. However, all demonstrated widespread myofascial dysfunction with low pressure-pain thresholds and trigger points in over two-thirds of 26 assessed regions. Widespread spinal segmental sensitisation was present in 17/30, thoracic in 21/30 and lumbosacral/pelvic in 18/30. Cervical sensitisation manifested as low pressure-pain thresholds with 23/30 also reporting recurrent, severe headaches and 21/30 experiencing orofacial pain. Those reporting diffuse pelvic pain were more likely to have widespread (p = .024) and lumbosacral/pelvic (p = .036) sensitisation and report over 10 painful body areas (p = .009).

CONCLUSIONS

Women with endometriosis-associated chronic pelvic pain often have myofascial dysfunction and sensitisation beyond the pelvic region that may be initiated or maintained by on-going pelvic floor spasm. These myofascial and nervous system manifestations warrant consideration when managing pain in this population. Clinicaltrials.gov identifier: NCT01553201.

SIGNIFICANCE

Women with endometriosis often have pelvic pain persisting after surgery despite hormonal therapies and these women have regional pelvic sensitisation and myofascial dysfunction. Pelvic floor muscle spasm is a major pain focus in this population. Sensitisation and myofascial dysfunction are widespread, beyond the pelvic region. On-going pelvic floor spasm may initiate or maintain sensitisation. Myofascial/sensitisation manifestations warrant consideration when managing pain in this population.

A Systematic Review Into the Influence of Temperature on Fibromyalgia Pain: Meteorological Studies and Quantitative Sensory Testing

Fibromyalgia syndrome (FMS) is a chronic widespread pain condition of unknown aetiology. The role of temperature in FMS pain has not been reviewed systematically. The goal of this study was to review the influences of temperature on pain in FMS, from meteorological and quantitative sensory testing (QST) studies. The review was registered with Prospero: ID-CRD42020167687, and followed PRISMA guidance. Databases interrogated were: MEDLINE (via OVID), EMBASE, PubMed, Web of Science, ScienceDirect, CINAHL, and ProQuest (Feb'20). Exclusion criteria were: age <18, animal studies, non-English, and noncontrolled articles. Thirteen studies pertaining to ambient temperature and FMS pain were identified; 9 of these found no uniform relationship. Thirty-five QST studies were identified, 17 of which assessed cold pain thresholds (CPTs). All studies showed numerically reduced CPTs in patients, ranging from 10.9°C to 26.3°C versus 5.9°C to 13.5°C in controls; this was statistically significant in 14/17. Other thermal thresholds were often abnormal. We conclude that the literature provides consistent evidence for an abnormal sensitization of FMS patients' temperature-sensation systems. Additional work is required to elucidate the factors that determine why a subgroup of patients perceive low ambient temperatures as painful, and to characterize that group. PERSPECTIVE: Patients often report increased pain with changes in ambient temperature; even disabling, extreme temperature sensitivity in winter. Understanding this phenomenon may help clinicians provide reassurance and advice to patients and may guide research into the everyday impact of such hypersensitivity, whilst directing future work into the pathophysiology of FMS.

Quantitative Sensory Testing Protocols to Evaluate Central and Peripheral Sensitization in Knee OA: A Protocol for a Scoping Review

BACKGROUND

Quantitative sensory testing (QST) methods have become widely used for the assessment of nervous system sensitization to nociceptive signalling in studies of people with knee osteoarthritis (OA). However, few standardised QST protocols have been developed. Variability in their execution may lead to differences in their interpretation.

OBJECTIVE

The proposed scoping review will seek to identify various QST methodologies being used in the assessment of sensitization and how sensitization is being defined in people with knee OA. Methods and Analysis: This scoping review will be guided by existing scoping review methodologies. Relevant studies will be extracted from the following electronic databases: Medical Literature Analysis and Retrieval System Online, ExcerptaMedica Database, Allied and Complementary Medicine Database and the Cumulative Index to Nursing Allied Health Literature. Independent screening of the abstracts and full articles and data extraction will be performed in pairs. Information extracted will focus on qualitative and quantitative data relevant to the content of the protocols from included studies. Data will be summarised in order to draw conclusions on the common elements used in QST protocols and definitions of sensitization for knee OA.

CONCLUSION

This scoping review will provide insight into the most common methods of QST used in the assessment of nociceptive signaling in people with knee OA. This will potentially identify areas where a systematic review or other primary research may be required in order to develop fixed evidence-based protocols for QST in patients with knee OA.

Patient phenotyping in clinical trials of chronic pain treatments: IMMPACT recommendations

There is tremendous interpatient variability in the response to analgesic therapy (even for efficacious treatments), which can be the source of great frustration in clinical practice. This has led to calls for “precision medicine” or personalized pain therapeutics (ie, empirically based algorithms that determine the optimal treatments, or treatment combinations, for individual patients) that would presumably improve both the clinical care of patients with pain and the success rates for putative analgesic drugs in phase 2 and 3 clinical trials. However, before implementing this approach, the characteristics of individual patients or subgroups of patients that increase or decrease the response to a specific treatment need to be identified. The challenge is to identify the measurable phenotypic characteristics of patients that are most predictive of individual variation in analgesic treatment outcomes, and the measurement tools that are best suited to evaluate these characteristics. In this article, we present evidence on the most promising of these phenotypic characteristics for use in future research, including psychosocial factors, symptom characteristics, sleep patterns, responses to noxious stimulation, endogenous pain-modulatory processes, and response to pharmacologic challenge. We provide evidence-based recommendations for core phenotyping domains and recommend measures of each domain.

Addition of Slowly Repeated Evoked Pain Responses to Clinical Symptoms Enhances Fibromyalgia Diagnostic Accuracy

OBJECTIVE

Fibromyalgia is a chronic pain syndrome characterized by central sensitization. A novel protocol based on slowly repeated evoked pain (SREP) appears to be a useful marker of pain sensitization in fibromyalgia patients. Whether SREP enhances diagnostic accuracy beyond key clinical symptoms that characterize fibromyalgia has not been examined.

METHODS

Fifty fibromyalgia patients, 30 rheumatoid arthritis patients, and 50 healthy individuals were evaluated to assess clinical pain, as well as fatigue, insomnia, pain catastrophizing, and negative mood. The SREP protocol consisted of a series of nine low-intensity painful pressure stimuli of five seconds' duration with 30-second interstimulus intervals. SREP sensitization was indexed by increases in pain intensity ratings across stimuli.

RESULTS

SREP sensitization was observed in fibromyalgia but not in rheumatoid arthritis or healthy individuals. As expected, fibromyalgia patients exhibited a more negative psychosocial profile than did rheumatoid arthritis patients and healthy individuals. SREP was positively associated with clinical pain, fatigue, insomnia, and catastrophizing, but not with negative mood. SREP discriminated fibromyalgia cases from rheumatoid arthritis and healthy individuals even when current clinical pain was included in the analysis. Combining fatigue, insomnia, and SREP led to near perfect diagnostic accuracy (99%) in differentiating fibromyalgia from healthy individuals and 86.3% accuracy in discriminating fibromyalgia from rheumatoid arthritis.

CONCLUSIONS

These results provide further evidence of SREP as a marker of pain sensitization in fibromyalgia and suggest that it captures aspects of fibromyalgia not fully captured by clinical features. Combining SREP with assessment of clinical features could potentially improve fibromyalgia diagnosis.

Spatial aspects of pain modulation are not disrupted in adolescents with migraine

OBJECTIVE

To compare spatial pain modulation capabilities between adolescents with and without migraine.

BACKGROUND

Conditioned pain modulation (CPM) responses at the leg are similar in adolescents with versus without migraine. However, the anatomical region of testing may affect spatial pain modulation capabilities as differences in nociceptive processing between patients with migraine and healthy controls are found in local areas that are near the site of clinical pain but not in nonlocal areas. This study aimed to examine spatial pain modulation capabilities tested by the CPM paradigm using test stimulus applied to a local body area.

METHODS

Nineteen adolescents with migraine (age 14.9 ± 2.3, mean ± SD; 16 female) and 20 healthy adolescents (age 13.8 ± 2.5, mean ± SD; 16 female) completed this case-control study at Cincinnati Children's Hospital Medical Center. Pressure pain thresholds (PPT) were assessed at the trapezius before and during immersion of the foot in a cold water bath (8°C).

RESULTS

In the migraine group (146.0 ± 79.1, mean ± SD), compared to healthy controls (248.0 ± 145.5, mean ± SD), significantly lower PPT (kilopascal) values were found (estimate = 124.28, 95% CI: 58.98, 189.59, p < 0.001; effect size: d = 1.40). No differences between the groups were found for pain intensity and unpleasantness ratings of cold-water immersion nor the CPM response.

CONCLUSIONS

This study found altered ascending nociceptive processing of mechanical stimuli at the neck in adolescents with migraine. However, endogenous pain modulatory mechanisms were functional and not altered. In light of other studies, impairments in inhibitory control may not be involved in migraine pathophysiology in pediatric patients regardless of stimulus location.

Healthy Pain-Free Individuals with a History of Distal Radius Fracture Demonstrate an Expanded Distribution of Experimental Referred Pain Toward the Wrist

OBJECTIVE

Nociception caused by injuries may sensitize central mechanisms causing expanded pain areas. After recovery, the status of such pain distribution and sensitivity mechanisms is unknown. The present study investigated whether individuals who have fully recovered from a distal radius fracture demonstrate increased pain sensitivity and expanded distribution of pressure-induced pain.

DESIGN

Cross-sectional single-blinded study.

SETTING

Clinical setting.

SUBJECTS

Twenty-three pain-free individuals with a history of painful distal radius fracture and 22 nonfractured, age/gender-matched controls participated in two experimental sessions (day 0, day 1) 24 hours apart.

METHODS

Pressure pain thresholds (PPTs) were recorded bilaterally at the extensor carpi radialis longus (ECRL), infraspinatus, and gastrocnemius muscles. Spatial distribution of pain was assessed following 60-second painful pressure stimulation at the ECRL (bilateral) and the infraspinatus muscles on the fractured or dominant side. Participants drew pain areas on a body map. After day 0 assessments, prolonged pain was induced by eccentric exercise of wrist extensors on the fractured/dominant side.

RESULTS

Compared with controls, pressure-induced ECRL pain in the fracture group referred more frequently toward the distal forearm (P < 0.005) on day 0. Both groups showed larger pain areas on day 1 compared with day 0 (P < 0.005), although the fracture group showed a larger relative change between days (P < 0.005). The fracture group showed larger pain areas on the fracture side compared with the contralateral side on both days (P < 0.005).

CONCLUSIONS

Prolonged pain and recovered prior painful injuries like fractures may sensitize pain mechanisms manifested as expanded pain distribution. Pressure-induced referred pain can be a simple pain biomarker for clinical use.

Symptoms of central sensitization in patients with inflammatory bowel diseases: a case-control study examining the role of musculoskeletal pain and psychological factors

OBJECTIVES

Musculoskeletal (MSK) pain is a common complaint in patients with inflammatory bowel diseases (IBD). MSK pain in IBD has previously demonstrated association with symptoms of central sensitization; however it is uncertain whether these symptoms are influenced simply by the presence of MSK pain and/or IBD. Primary aim of this study was to investigate whether symptoms of central sensitization differed across three groups: IBD patients with and without MSK pain and healthy controls. Secondary aim was to investigate between-group differences for measures of somatosensory functioning.

METHODS

Cross-sectional study was performed on adults with IBD. Assessments included: central sensitization inventory (CSI), pressure pain threshold, temporal summation, conditioned pain modulation, perceived stress, affect style, anxiety, depression, and pain catastrophizing. One-way analyses of variance and covariance were used to investigate between-group differences for measures of central sensitization and potential confounding by psychological factors.

RESULTS

Study participants (n=66) were age/gender matched across three study groups. Between-group differences were solely demonstrated for CSI scores [F(2,63)=19.835, p<0.001, r=0.62], with IBD patients with MSK pain demonstrating the highest CSI scores and healthy controls the lowest. After controlling for individual psychological features, post hoc comparisons indicated that CSI scores were significantly different between-groups (p≤0.025) after controlling for most psychological variables, with the exception of perceived stress (p=0.063) and pain catastrophizing (p=0.593).

CONCLUSIONS

IBD patients as a whole demonstrated significantly greater symptoms of central sensitization compared to healthy controls. However, IBD patients with persistent MSK pain demonstrated the greatest symptoms of central sensitization compared to patients without MSK pain and healthy controls. Between-group differences for CSI in IBD patients with MSK were not confounded by psychological features.

IMPLICATIONS

Study results indicate that persistent MSK pain in IBD represents patients with greater central sensitization symptomology. This increased symptomology is suggestive of underlying mechanisms related to central sensitization, highlighting patient potentially at risk for worse pain experiences.

Pain complications of oral implants: Is that an issue?

The use of oral implants as a form of replacing missing teeth in partial or total edentulous patients is considered the gold standard in oral rehabilitation. Although considered a history of success in contemporary dentistry, surgical complications may occur, as excessive bleeding, damage to the adjacent teeth and mandibular fractures. Persistent pain and abnormal somatosensory responses after the surgery ordinary healing time are also potential problems and may lead to the development of a condition named posttraumatic trigeminal neuropathic pain (PTNP). Though relatively rare, PTNP has a profound impact on patient's quality of life. Appropriated previous image techniques, effective anaesthetic procedures and caution during the surgical procedure and implant installation are recommended for the prevention of this condition. In case of the PTNP, different management modalities, including antidepressant and membrane stabilizer medications, as well as peripheral strategies, as the use of topical medication and the botulin toxin are presented and discussed.

Preoperative quantitative sensory testing and robot-assisted laparoscopic hysterectomy for endometrial cancer: can chronic postoperative pain be predicted?

Objectives Chronic postoperative pain is prevalent after robot-assisted laparoscopic hysterectomy for endometrial cancer. Preoperative Quantitative Sensory Testing (QST) has been utilized to identify patients at risk of developing chronic postoperative pain after a range of surgical procedures. The aim of this prospective, observational study was to (1) determine the prevalence of chronic postoperative pain, (2) assess selected preoperative risk factors for chronic postoperative pain, and (3) evaluate if preoperative QST profiling could predict the development of chronic postoperative pain following robot-assisted laparoscopic hysterectomy for endometrial cancer. Methods One-hundred and sixty consecutive patients were included and handheld pressure algometry, cuff pressure algometry, temporal summation of pain, conditioned pain modulation, and heat pain thresholds were assessed prior to surgery. Patients were asked to fill out a questionnaire concerning pain in the pre- and post-operative time period six months after surgery. Chronic postoperative pain was defined as persistent, moderate to severe pain (mean visual analogue scale (VAS)≥3) on a daily basis six months after surgery. Results The prevalence of chronic postoperative pain after robot-assisted laparoscopic hysterectomy for endometrial cancer was of 13.6% (95% CI 8.4-20.4%). Patients that would develop chronic postoperative pain had a lower BMI (p=0.032), a higher prevalence of preoperative pelvic pain (p<0.001), preoperative heat pain hyperalgesia (p=0.043) and a higher level of acute postoperative pain (p<0.001) when compared to patients that would not develop chronic postoperative pain. A logistic regression model demonstrated that the presence of preoperative pelvic pain was a significant, independent predictive risk factor for development of chronic postoperative pain (OR=6.62, 95% CI 2.26-19.44), whereas none of the QST parameters could predict postoperative pain. Conclusions Preoperative QST assessment could not predict the development of chronic postoperative pain despite preoperative heat pain hyperalgesia in patients that would develop chronic postoperative pain.

Stretch-induced hypoalgesia: a pilot study

Objectives Stretching is an intervention often used in various kinds of rehabilitation protocols and the effects on pain sensitivity has sparsely been investigated, especially when addressing potential effects on pain. The objective is to investigate the immediate effects of an axial and peripheral prolonged stretch on pressure pain sensitivity (PPT) and temporal summation (TS) on local and distal sites in healthy subjects. Methods Twenty-two healthy volunteers were recruited to participate in this pilot study. Two prolonged stretching protocols were performed: low back and wrist extensors stretches. PPT and pinprick TS were measured pre- and post-intervention at local and remote sites. Repeated measures analysis of variance (ANOVA) was used to examine the effects and significance of the interventions. Results The low back stretch induced an increase in PPT for both local and remote sites, and the wrist stretch produced a PPT increase only at the local site. TS did not change. Conclusions Low back stretching induced an increase in PPT at both local and remote sites whereas the wrist stretch only increased PPT locally, suggesting hypoalgesia at these sites. Further studies are needed to confirm the effect and mechanisms using randomised, controlled and parallel study design. Considering that pain sensitivity is different than clinical pain, results are difficult to extrapolate to clinical practice. Future studies testing clinical pain are needed to better understand the clinical implication of these results.

Test–Retest Instability of Temporal Summation and Conditioned Pain Modulation Measures in Older Adults

Objective

The temporal stability (test–retest reliability) of temporal summation of pain (TS) and conditioned pain modulation (CPM) has yet to be established in healthy older adults. The purpose of this study was to compare the temporal stability of TS and CPM in healthy older and younger adults and to investigate factors that might influence TS and CPM stability.

Methods

In a test–retest study, 40 healthy older adults and 30 healthy younger adults completed two sessions of quantitative sensory testing within a two-week period that included TS of heat pain, TS of mechanical pain, and CPM with pressure pain thresholds and suprathreshold heat pain as test stimuli and a cold water immersion as a conditioning stimulus. Participants also completed self-report measures of situational catastrophizing, anxiety, clinical pain, and physical activity. Absolute and relative stability were examined for each variable. Bivariate correlations examined the associations of age, clinical, behavioral, and psychological variables with the intra-individual stability of TS and CPM.

Results

The results revealed moderate to excellent stability for the TS measures and poor to moderate stability for CPM. The results also revealed significant age differences for two of the TS measures and CPM, with younger adults having greater stability compared with older adults. Additionally, the magnitude and stability of psychological factors were correlated with stability of TS.

Conclusions

These findings suggest that TS and CPM may be more reliable in younger compared with older adults. Furthermore, psychological states may be an important factor influencing the stability of TS in healthy adults.

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.

The effect of mindful attention training for pain modulation capacity: Exploring the mindfulness-pain link

OBJECTIVE

Mindfulness has been shown to be beneficial for chronic pain. The underlying mechanisms of the mindfulness-pain link, however, are yet to be established. Particularly, the effects of mindfulness on pain modulation, which is shown to be dysfunctional among chronic pain patients, barely has been tested. This study investigated whether a short mindful attention training based on Langerian mindfulness mitigates reductions in pain modulation.

METHOD

Systemic quantitative-somatosensory testing of conditioned pain modulation (CPM) was conducted in 60 undergraduates, who were randomly assigned to one of three groups: (1) Pain-specific mindful attention training; (2) nonspecific mindful attention training; and (3) no mindful attention training. CPM was tested before and after the intervention.

RESULTS

As hypothesized, a reduction in CPM magnitude was observed only in the control group, whereas this reduction was abolished in the two mindfulness groups.

CONCLUSIONS

Langerian mindfulness may mitigate pain modulation reduction as observed in chronic pain, thus shedding light on its potential advantages.

Dysfunctional pain perception and modulation among torture survivors: The role of pain personification

OBJECTIVE

Individuals exposed to trauma, especially those who develop posttraumatic stress disorder (PTSD), are at a higher risk of suffering from chronic pain as well as altered pain perception and modulation. However, the underlying mechanisms of these processes are yet to be established. Recent findings have indicated that trauma survivors tend to personify chronic pain that is developed after the exposure, in a way that resonates with the traumatic experience. The aim of this study was to test whether pain personification plays a significant role in explaining the long-term links between trauma, PTSD and pain.

METHODS

This study is part of a large-scale longitudinal study on ex-prisoners of war (ex-POWs) from the 1973 Yom-Kippur war, who were followed over 35 years after the war. Fifty-nine ex-POWs who were exposed to torture and 44 matched combatants were assessed for PTSD at 18, 30, and 35 post-war. Quantitative somatosensory testing of heat-pain threshold, pain tolerance, conditioned pain modulation (CPM), and temporal summation of pain (TSP), as well as torturing personification, were assessed at 35 years after the war.

RESULTS

Sequential mediation analyses revealed that the associations between torture and heat pain threshold, as well as pain tolerance were mediated by PTSD at several time-points (-1.43<indirect effect < 1.47). Torturing personification significantly mediated the associations between torture, PTSD, CPM and TSP (-0.16 < indirect effect).

CONCLUSIONS

These findings point to the effect of trauma on the subjective orientation towards bodily signals as a key factor in dysfunctional pain modulation.

Central Sensitisation and functioning in patients with chronic low back pain: protocol for a cross-sectional and cohort study

INTRODUCTION

A relevant subsample of patients with chronic low back pain (CLBP) have manifested augmented central pain processing, central sensitisation (CS). Patients with CLBP have limited functioning and participation. Theoretically, physical functioning in patients with CLBP can plausibly be linked to CS; however, evidence to explain such association is scarce. Moreover, there is no gold standard for CS diagnosis. The objectives of the study are: (1) to analyse the association between instruments assessing reference symptoms and signs attributed to CS; (2) to analyse whether reference symptoms and signs attributed to CS are associated with functioning measurement outcomes; and (3) to analyse whether changes (between baseline and discharge) in reference symptoms and signs attributed to CS are related to changes in each of the functioning measurement outcomes.

METHODS AND ANALYSIS

A cross-sectional and longitudinal observational study is performed with measurements taken at baseline and discharge of an interdisciplinary rehabilitation programme. A sample size of 110 adult patients with CLBP has been calculated for the study. CS measurements are: Central Sensitisation Inventory, quantitative sensory testing and heart rate variability. Functioning measurements are: lifting capacity, maximal aerobic capacity, accelerometry and reported functioning. Statistical analyses to be performed are: (1) correlation between CS measurements, (2) multiple regression between functioning (dependent variable) and CS measurements (independent variable), and (3) multiple regression between changes in scores of functioning (dependent variable) and CS measurements (independent variable), and corrected for sex and age.

ETHICS AND DISSEMINATION

The study obtained the clearance to its implementation from the Medical Research Ethics Committee of the University Medical Center Groningen in July 2017. The results will be disseminated through scientific publications in peer-reviewed journals, presentations at relevant conferences, and reports to stakeholders.

TRIAL REGISTRATION NUMBER

NTR7167/NL6980.

An Exploratory Randomized Trial of Physical Therapy for the Treatment of Chemotherapy-Induced Peripheral Neuropathy

Background. Chemotherapy-induced peripheral neuropathy (CIPN) is a common side effect of taxane treatment and cannot currently be prevented or adequately treated. Physical therapy is often used for neural rehabilitation following injury but has not been evaluated in this patient population. Methods. Single-blind, randomized controlled exploratory study compared standard care to a physical therapy home program (4 visits) throughout adjuvant taxane chemotherapy for stage I-III patients with breast cancer (n = 48). Patient questionnaires and quantitative sensory testing evaluated the treatment effect throughout chemotherapy to 6 months post treatment. Nonrandomized subgroup analysis observed effect of general exercise on sensory preservation comparing those reporting moderate exercise throughout chemotherapy to those that did not exercise regularly. Clinical Trial Registration. clinicaltrials.gov (NCT02239601). Results. The treatment group showed strong trends toward less pain (odds ratio [OR] 0.41, 95% confidence interval [CI] 0.17-1.01; P = .053) and pain decreased over time (OR 0.85, 95% CI 0.76-0.94; P = .002). Pain pressure thresholds (P = .034) and grip dynamometry (P < .001) were improved in the treatment group. For the nonrandomized subgroup analysis, participants reporting general exercise had preservation of vibration (Left P = .001, Right P = .001) and normal heat pain thresholds (Left P = .021, Right P = .039) compared with more sedentary participants. Conclusion. Physical therapy home program may improve CIPN pain in the upper extremity for patients with breast cancer, and general exercise throughout chemotherapy treatment was observed to have correlated to preservation of sensory function. Further research is required to confirm the impact of a physical therapy home program on CIPN symptoms.

Urologic chronic pelvic pain syndrome: insights from the MAPP Research Network

Urologic chronic pelvic pain syndrome (UCPPS), which encompasses interstitial cystitis/bladder pain syndrome and chronic prostatitis/chronic pelvic pain syndrome, is characterized by chronic pain in the pelvic region or genitalia that is often accompanied by urinary frequency and urgency. Despite considerable research, no definite aetiological risk factors or effective treatments have been identified. The Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network uses a novel integrated strategy to characterize UCPPS as a systemic disorder that potentially involves multiple aetiologies. The first phase, MAPP I, included >1,000 participants who completed an intensive baseline assessment followed by a 12-month observational follow-up period. MAPP I studies showed that UCPPS pain and urinary symptoms co-vary, with only moderate correlation, and should be evaluated separately and that symptom flares are common and can differ considerably in intensity, duration and influence on quality of life. Longitudinal clinical changes in UCPPS correlated with structural and functional brain changes, and many patients experienced global multisensory hypersensitivity. Additionally, UCPPS symptom profiles were distinguishable by biological correlates, such as immune factors. These findings indicate that patients with UCPPS have objective phenotypic abnormalities and distinct biological characteristics, providing a new foundation for the study and clinical management of UCPPS.

How Does Myofascial Physical Therapy Attenuate Pain in Chronic Pelvic Pain Syndrome?

Background

Chronic pelvic pain syndrome (CPPS) is a multifactorial disorder comprising structural and functional muscular abnormalities, a dysfunctional pain system, and psychological distress. Myofascial physical Therapy (MPT) that is targeted at improving pelvic muscle functioning is considered a first line nonpharmacological treatment for CPPS, although the precise mechanisms that lead to symptoms alleviation have not yet been elucidated.

Purpose

This longitudinal study aimed to examine the local and systemic effects of MPT intervention, including biopsychophysiological processes, among CPPS patients.

Methods

The study included 50 CPPS women. Morphologic assessment of the levator ani and quantitative sensory testing of the pain system were applied alongside with evaluation of pain-related psychological factors using designated questionnaires. All measures were evaluated both before and after MPT in 39 patients. The long-term effects of MPT were evaluated by clinical pain reports obtained at 3 and 9 months following MPT that were compared with a nontreated group of 11 untreated CPPS women.

Results

Along with an improvement in the clinical pain intensity (p = 0.001) and sensitivity to experimental pain tests (p = 0.001) following MPT, the results also indicate that MPT has anatomical, psychological, and social therapeutic effects (p = 0.04; p = 0.001; p = 0.01, respectively). Furthermore, clinical pain evaluation at 3 and 9 months after MPT revealed a significant improvement in women who received treatment (p = 0.001).

Conclusions

The findings of this pilot study suggest multisystemic (direct and indirect anatomical, neurophysiological, and psychological) effects of MPT on the multifactorial pain disorder of CPPS and therefore place MPT as a mechanism-based intervention.

The effects of kinesiology taping on experimentally-induced thermal and mechanical pain in otherwise pain-free healthy humans: A randomised controlled repeated-measures laboratory study

Background

Kinesiology taping (KT) is used to manage musculoskeletal-related pain. There is a paucity of physiological studies evaluating the effect of KT on stimulus-evoked experimental pain.

Objective

To investigate the effect of KT (applied to lumbar region) on cutaneous somatosensation to noxious and innocuous stimuli in humans with a non-sensitised normally functioning nociceptive system using quantitative sensory testing (QST).

Methods

Fifty-four participants were randomised to one of three interventions: (i) KT (ii) standard ‘rigid’ taping (ST) (iii) sham taping (ShT). QST measurements were taken at lumbar sites pre-intervention (T1), during-intervention (T2) and during-intervention (T3) in the following sequence: warm-detection-threshold (WDT), heat-pain-threshold (HTPh), heat-pain-tolerance (HPTo), mechanical-detection-threshold (MDT), mechanical-pain-threshold (MPT) and pressure-pain-threshold (PPT).

Results

Mixed ANOVA revealed statistically significant interaction between Intervention and Time on MDT (p < .0005) and MPT (p < .0005) but not on WDT (p = .09), HPTh (p = .09), HPTo (p = .51) and PPT (p = .52) datasets. There was no significant simple main effect of Intervention on MDT at T2 (p = .68) and T3 (p = .24), and MPT at T2 (p = .79) and T3 (p = .54); post-hoc tests found KT and ST groups had higher (but non-significant) MDT and MPT than the ShT group. There was a significant simple main effect of Time on MDT and MPT for KT (p < .0005) and ST (p < .0005) groups; post-hoc tests found significant increases in MDT and MPT at T3 and T2 compared with T1 in both KT and ST groups. There was no significant simple main effect of Time on MDT (p = .13) nor MPT (p = .08) for the ShT group.

Conclusion

Taping, irrespective of the elasticity, may modulate cutaneous mechanosensation. KT, ST and ShT seemed to have similar influence on cutaneous thermal and deep pressure nociception.

Novel Characterization Of Thermal Temporal Summation Response By Analysis Of Continuous Pain Vs Time Curves And Exploratory Modeling

Background

Temporal summation (TS) refers to the increased perception of pain with repetitive noxious stimuli. While thermal TS is generally considered a behavioral correlate of spinal windup, noxious heat pulses also trigger additional sensory processes which were modeled in this study.

Methods

Nineteen healthy volunteers (9 females, mean age 29.2, SD 10.5) underwent two identical TS experiments, spaced a week apart. The TS paradigm consisted of 10 identical heat pulses with individualized temperatures at the thenar eminence (0.5Hz). We extracted 3 features from continuous TS response curves: Lag, time to first feel pain; Slope, the rate of pain increase between the first and most painful heat pulse; and Delta, the maximum drop in pain after peak pain is reached. We then examined the within-individual stability of these features, followed by the Pearson’s correlations among these features and between the features and negative affect.

Results

All 3 features were stable over 1 week. Lag and Delta were negatively correlated (r = −0.5, p = 0.042). Slope did not correlate with Lag or Delta, but strongly correlated with a traditional TS measure, first pulse pain and peak pain difference (r = 0.91, p < 0.0001). Negative affects such as trait and state anxiety were negatively correlated with baseline (r = −0.49, p = 0.031) and peak stimulating temperature (r = −0.48, p = 0.039), respectively, suggesting an association between anxiety and greater pain sensitivity.

Conclusion

We were able to decouple spinal windup from other perceptual processes generated by phasic thermal TS paradigms and demonstrate temporal stability of these curve features. These curve features may help better characterize the complex sensory response to noxious heat pulses and serve as biomarkers to profile patients with chronic pain.

Pack-years of tobacco cigarette smoking as a predictor of spontaneous pain reporting and experimental pain reactivity

The pack-years formula is a widely used estimate of lifetime tobacco smoking exposure, and greater pack-years have been associated with greater risk of chronic pain development and poorer pain-related outcomes among smokers with chronic pain. The pathophysiology underlying these associations is poorly understood. Regular tobacco smoking exposure may dysregulate homeostatic pain processes, producing an allostatic state of pain facilitation. Maladaptive pain mechanisms, such as central and peripheral sensitization, are chronic pain risk factors. Yet no published research has examined the relation between lifetime-smoking exposure and dysregulated pain processing. The current study used hierarchical linear regression analyses to test pack-years of tobacco smoking as a predictor of (a) pain reporting (current pain severity, pain frequency in the last 180 days) among a sample of 228 daily smokers without chronic pain, and (b) experimental capsaicin-induced pain reactivity (pain intensity, area of flare, mechanical pain sensitivity, and area of mechanical hyperalgesia) among 101 daily smokers without chronic pain. As hypothesized, results indicated that pack-years smoking was positively and significantly associated with current pain severity, past 180-day pain frequency, experimental pain intensity, mechanical pain sensitivity ratings, and area of mechanical hyperalgesia. Pack-years smoking was not significantly associated with neurogenic flare. These findings implicate central sensitization as a factor that may underlie the association between chronic tobacco smoking and increased risk for persistent pain. (PsycINFO Database Record (c) 2019 APA, all rights reserved).