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

Quantitative sensory testing of temperature, pain, and touch in adults with Down syndrome

The spinothalamic pathway mediates sensations of temperature, pain, and touch. These functions seem impaired in children with Down syndrome (DS), but have not been extensively examined in adults. The objective of the present study was to compare the spinothalamic-mediated sensory functions between adults with DS and adults from the general population and to examine in the DS group the relationship between the sensory functions and level of intellectual functioning. Quantitative sensory testing (QST) was performed in 188 adults with DS (mean age 37.5 years) and 142 age-matched control participants (median age 40.5 years). Temperature, pain, and touch were evaluated with tests for cold-warm discrimination, sharp-dull discrimination (pinprick), and tactile threshold, respectively. Level of intellectual functioning was estimated with the Social Functioning Scale for Intellectual Disability (intellectual disability level) and the Wechsler Preschool and Primary Scale of Intelligence--Revised (intelligence level). Overall, the difference in spinothalamic-mediated sensory functions between the DS and control groups was not statistically significant. However, DS participants with a lower intelligence level had a statistically significant lower performance on the sharp-dull discrimination test than DS participants with higher intelligence level (adjusted p=.006) and control participants (adjusted p=.017). It was concluded that intellectual functioning level is an important factor to take into account for the assessment of spinothalamic-mediated sensory functioning in adults with DS: a lower level could coincide with impaired sensory functioning, but could also hamper QST assessment.

Quantitative sensory testing of dentinal sensitivity in healthy humans

OBJECTIVE

The study was to provide information on quantitative sensory testing (QST) of normal teeth to establish a sensory profile and investigate the possible gender and regional differences.

MATERIALS AND METHODS

A modified QST protocol was applied on both left and right upper-jaw incisors and pre-molar sof 14 healthy men and 14 age-matched healthy women (18-25 years). Mechanical stimulus sensitivity (MSS), cold detection threshold (CDT), cold pain threshold (CPT), warm detection threshold (WDT), heat pain threshold (HPT), electrical detection threshold (EDT) and electrical pain threshold (EPT) were determined from the four teeth (labial side of incisor and buccal side of the first premolar). The QST parameters were analysed by ANOVA.

RESULTS

The applied mechanical or thermal stimuli did not evoke any pain sensation. A normal tooth did not seem to be able to distinguish between the warm or cold stimuli applied. No significant differences were found between genders (p > 0.099) or teeth (p > 0.053) regarding mechanical and thermal stimuli. The EDT and EPT were significantly higher in the pre-molar compared with incisor (p < 0.002) without gender differences (p > 0.573).

CONCLUSION

The established methods and results provided important information on diagnosis and treatment evaluation of dentinal hypersensitivity.

Structural Brain Alterations in Community Dwelling Individuals with Chronic Joint Pain

BACKGROUND AND PURPOSE

Central sensitization in chronic pain involves structural brain changes that influence vulnerability to pain. Identifying brain regions involved in pain processing and sensitization can provide more insight into chronic pain. This study examines structural brain changes in chronic pain and experimental pain in a large population-based study.

MATERIALS AND METHODS

For 3892 participants in the Rotterdam study, global and regional MR imaging brain volumes were automatically segmented and quantified. Chronic joint pain was defined as pain for more than half of all days during the past 6 weeks. Heat pain thresholds were measured in a subset of 1538 individuals. The association between the presence of chronic joint pain and global and lobar brain volumes was studied. Subsequently, literature was reviewed and the association of chronic pain and heat pain thresholds with 11 brain regions associated with musculoskeletal pain in previous publications was studied.

RESULTS

Total gray matter volume was smaller in women with chronic pain (β = -0.066, P = .016). This effect was primarily driven by lower gray matter volume in the temporal lobe (β = 0.086, P = .005), the frontal lobe (β = -0.060, P = .039), and the hippocampus (β = -0.099, P = .002). In addition, we observed that a lower heat pain threshold was associated with smaller volumes of the hippocampus (β = 0.017, P = .048), the thalamus (β = 0.018, P = .009), and the anterior cingulate cortex (β = -0.016, P = .037). In men, no significant associations were observed.

CONCLUSIONS

The primary identified brain areas, the temporal and frontal lobes and the hippocampus, indicated involvement of emotional processing. The volumetric differences found indicated a sex-specific neuroplasticity in chronic pain. These results emphasized sex-specific and multidisciplinary pain treatment.

Pain sensitivity of children with Down syndrome and their siblings: quantitative sensory testing versus parental reports

AIM

The aim of this study was to compare thermal detection and pain thresholds in children with Down syndrome with those of their siblings.

METHOD

Sensory detection and pain thresholds were assessed in children with Down syndrome and their siblings using quantitative testing methods. Parental questionnaires addressing developmental age, pain coping, pain behaviour, and chronic pain were also utilized.

RESULTS

Forty-two children with Down syndrome (mean age 12y 10mo) and 24 siblings (mean age 15y) participated in this observational study. The different sensory tests proved feasible in 13 to 29 (33-88%) of the children with Down syndrome. These children were less sensitive to cold and warmth than their siblings, but only when measured with a reaction time-dependent method, and not with a reaction time-independent method. Children with Down syndrome were more sensitive to heat pain, and only 6 (14%) of them were able to adequately self-report pain, compared with 22 (92%) of siblings (p<0.001).

INTERPRETATION

Children with Down syndrome will remain dependent on pain assessment by proxy, since self-reporting is not adequate. Parents believe that their children with Down syndrome are less sensitive to pain than their siblings, but this was not confirmed by quantitative sensory testing.

Effect of temporal stimulus properties on the nociceptive detection probability using intra-epidermal electrical stimulation

Chronic pain disorders can be initiated and maintained by malfunctioning of one or several mechanisms underlying the nociceptive function. Although several quantitative sensory testing methods exist to characterize the nociceptive function, it remains difficult to distinguish the contributions of individual mechanisms. Intra-epidermal electrical stimulation of nociceptive fibers allows defining stimuli with temporal properties within the timescale of these mechanisms. Here, we studied the effect of stimulus properties on the psychophysical detection probability. A psychophysical detection experiment was conducted including 30 healthy human participants. Participants were presented with electrical stimuli having various temporal properties. The pulse-width was varied for single pulse stimuli (either 420 or 840 μs), and the inter-pulse interval for double pulse stimuli (10, 50, or 100 ms). Generalized linear mixed models were used to obtain estimates of thresholds and slopes of the psychophysical function. The 840-μs single pulse resulted in a lower threshold and steeper slope of the psychophysical function than the 420-μs single pulse. Moreover, a double-pulse stimulus resulted in a lower threshold and steeper slope than single pulse stimuli. The slopes were similar between the double pulse stimuli, but thresholds slightly increased with increasing inter-pulse intervals. In the present study, it was demonstrated that varying the temporal properties of intra-epidermal electrical stimuli results in variations in nociceptive processing. The estimated thresholds and slopes corresponding to the selection of temporal properties suggest that contributions of peripheral and central nociceptive mechanisms can be reflected in psychophysical functions.

Botulinum Toxin Type a as a Therapeutic Agent against Headache and Related Disorders

Botulinum neurotoxin A (BoNT/A) is a toxin produced by the naturally-occurring Clostridium botulinum that causes botulism. The potential of BoNT/A as a useful medical intervention was discovered by scientists developing a vaccine to protect against botulism. They found that, when injected into a muscle, BoNT/A causes a flaccid paralysis. Following this discovery, BoNT/A has been used for many years in the treatment of conditions of pathological muscle hyperactivity, like dystonias and spasticities. In parallel, the toxin has become a “glamour” drug due to its power to ward off facial wrinkles, particularly frontal, due to the activity of the mimic muscles. After the discovery that the drug also appeared to have a preventive effect on headache, scientists spent many efforts to study the potentially-therapeutic action of BoNT/A against pain. BoNT/A is effective at reducing pain in a number of disease states, including cervical dystonia, neuropathic pain, lower back pain, spasticity, myofascial pain and bladder pain. In 2010, regulatory approval for the treatment of chronic migraine with BoNT/A was given, notwithstanding the fact that the mechanism of action is still not completely elucidated. In the present review, we summarize experimental evidence that may help to clarify the mechanisms of action of BoNT/A in relation to the alleviation of headache pain, with particular emphasis on preclinical studies, both in animals and humans. Moreover, we summarize the latest clinical trials that show evidence on headache conditions that may obtain benefits from therapy with BoNT/A.

Linking altered central pain processing and genetic polymorphism to drug efficacy in chronic low back pain

Background

Inability to predict the therapeutic effect of a drug in individual pain patients prolongs the process of drug and dose finding until satisfactory pharmacotherapy can be achieved. Many chronic pain conditions are associated with hypersensitivity of the nervous system or impaired endogenous pain modulation. Pharmacotherapy often aims at influencing these disturbed nociceptive processes. Its effect might therefore depend on the extent to which they are altered. Quantitative sensory testing (QST) can evaluate various aspects of pain processing and might therefore be able to predict the analgesic efficacy of a given drug. In the present study three drugs commonly used in the pharmacological management of chronic low back pain are investigated. The primary objective is to examine the ability of QST to predict pain reduction. As a secondary objective, the analgesic effects of these drugs and their effect on QST are evaluated.

Methods/Design

In this randomized, double blinded, placebo controlled cross-over study, patients with chronic low back pain are randomly assigned to imipramine, oxycodone or clobazam versus active placebo. QST is assessed at baseline, 1 and 2 h after drug administration. Pain intensity, side effects and patients’ global impression of change are assessed in intervals of 30 min up to two hours after drug intake. Baseline QST is used as explanatory variable to predict drug effect. The change in QST over time is analyzed to describe the pharmacodynamic effects of each drug on experimental pain modalities. Genetic polymorphisms are analyzed as co-variables.

Discussion

Pharmacotherapy is a mainstay in chronic pain treatment. Antidepressants, anticonvulsants and opioids are frequently prescribed in a “trial and error” fashion, without knowledge however, which drug suits best which patient. The present study addresses the important need to translate recent advances in pain research to clinical practice. Assessing the predictive value of central hypersensitivity and endogenous pain modulation could allow for the implementation of a mechanism-based treatment strategy in individual patients.

Trial registration

Clinicaltrials.gov, NCT01179828

The role of sensitization in musculoskeletal shoulder pain

INTRODUCTION

Peripheral and central sensitization are neurophysiological processes that can prolong painful conditions. Painful shoulder conditions are often persistent, perhaps due to the presence of sensitization.

METHOD

This manuscript summarizes six studies that have evaluated those with musculoskeletal shoulder pain for the presence of sensitization.

RESULTS

All six manuscripts report evidence of peripheral sensitization, while central sensitization was described in five of the studies. The chronicity of symptoms in subjects who were included in the studies is probably influencing this finding. The primary somatosensory test used to assess sensitization in these studies was Pressure Pain Threshold, a test for lowered nociceptive thresholds.

DISCUSSION

It appears that peripheral sensitization manifests consistently in those with musculoskeletal shoulder pathology, probably due to the inflammatory processes related to tissue injury. Central sensitization, while not universally present, was reported in a majority of the manuscripts. Because central sensitization is thought to be a key step on the pathway to chronic pain, evidence for its presence in those with shoulder pain is significant. Clinicians should expect the presence of sensitization with shoulder pathology and make appropriate choices about interventions so as not to exacerbate pain.

Altered Central Sensitization and Pain Modulation in the CNS in Chronic Joint Pain

Musculoskeletal pain disorders are the second largest contributor to global disability underlining the significance of effective treatments. However, treating chronic musculoskeletal pain, and chronic joint pain (osteoarthritis (OA)) in particular, is challenging as the underlying peripheral and central pain mechanisms are not fully understood, and safe and efficient analgesic drugs are not available. The pain associated with joint pain is highly individual, and features from radiological imaging have not demonstrated robust associations with the pain manifestations. In recent years, a variety of human quantitative pain assessment tools (quantitative sensory testing (QST)) have been developed providing new opportunities for profiling patients and reaching a greater understanding of the mechanisms involved in chronic joint pain. As joint pain is a complex interaction between many different pain mechanisms, available tools are important for patent profiling and providing the basic knowledge for development of new drugs and for developing pain management regimes.

Measuring mechanical pain: the refinement and standardization of pressure pain threshold measurements

Pain thresholds are widely used in behavioral research, but unlike other pain modalities, a standardized assessment of pressure pain remains a challenge. In this research, we describe the application of an automatic pressure algometer with a linear increase in force. Ergonomically designed fixation devices were developed to increase the accuracy and to shorten the time of each measurement. Ten healthy volunteers were included in a pilot study to test the algometry method. Pressure pain thresholds (PPTs) were investigated over 2 experimental days in three nonconsecutive runs at 29 measurement sites. During the experiment, subjects reported their subjective sleepiness, level of state-anxiety, psychological status and the perceived pain intensity of each measurement. Pain intensity ratings indicate that instructions were followed. State-anxiety and subjective sleepiness levels were low throughout the experiment. The method has proven to be suitable for standardized PPT measurements across the body in an ergonomic, safe, and user-friendly fashion.

Individually based measurement of temporal summation evoked by a noxious tonic heat paradigm

BACKGROUND

A model for measuring temporal summation (TS) by tonic noxious stimulation was recently proposed. However, methodological variations between studies make it difficult to reach a consensus regarding the way TS should be applied and calculated. The present study aimed to present a calculation method of TS magnitude produced by a tonic heat model in a large cohort of healthy subjects.

METHODS

Noxious heat stimulation (46.5°C/2 minutes) was applied to the forearm of 154 subjects who continuously rated pain intensity using a computerized visual analog scale. TS was calculated by "mean group" and "individual" approaches.

RESULTS

A "typical" pattern of pain response, characterized by a peak pain followed by a decrease in intensity to a nadir and subsequently a progressive increase in pain scores, was exhibited by 86.4% of the subjects. Using the "mean group" and "individual" calculation approaches, the mean ± standard deviation magnitudes of TS were 31.4±27.5 and 41.0±26.0, respectively (P<0.001). Additionally, using the individualized approach, we identified a different ("atypical") response pattern among the rest of the subjects (13.6%).

CONCLUSION

The results support the tonic heat model of TS for future utilization. The individualized TS calculation method seems advantageous since it better reflects individual magnitudes of TS.

Pain Sensitivity and Pain Catastrophizing Are Associated With Persistent Pain and Disability After Lumbar Spine Surgery

OBJECTIVE

To examine whether pain sensitivity and pain catastrophizing are associated with persistent pain and disability after lumbar spine surgery.

DESIGN

Prospective observational cohort study.

SETTING

Academic medical center.

PARTICIPANTS

Patients (N=68; mean age, 57.9±13.1y; 40 women [58.8%]) undergoing spine surgery for a degenerative condition from March 1, 2012 to April 30, 2013 were assessed 6 weeks, 3 months, and 6 months after surgery.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The main outcome measures were persistent back pain intensity, pain interference, and disability. Patients with persistent back pain intensity, pain interference, or disability were identified as those patients reporting Brief Pain Inventory scores ≥4 and Oswestry Disability Index scores ≥21 at all postoperative time points.

RESULTS

From 6 weeks to 6 months after surgery, approximately 12.9%, 24.2%, and 46.8% of patients reported persistent back pain intensity, pain interference, or disability, respectively. Increased pain sensitivity at 6 weeks was associated with having persistent back pain intensity (odds ratio [OR], 2.0; 95% confidence interval [CI], 1.0-4.1) after surgery. Increased pain catastrophizing at 6 weeks was associated with having persistent back pain intensity (OR, 1.1; 95% CI, 1.0-1.2), pain interference (OR, 1.1; 95% CI, 1.0-1.2), and disability (OR, 1.3; 95% CI, 1.1-1.4). An interaction effect was not found between pain sensitivity and pain catastrophizing on persistent outcomes (P>.05).

CONCLUSIONS

The findings suggest the importance of early postoperative screening for pain sensitivity and pain catastrophizing to identify patients at risk for poor postoperative pain intensity, pain interference, and/or disability outcomes. Future research should consider the benefit of targeted therapeutic strategies for patients with these postoperative prognostic factors.

Race effects on temporal summation to heat pain in youth

Racial differences in pain responsiveness have been demonstrated in adults. However, it is unclear whether racial differences are also present in youth and whether they extend to experimental pain indices assessing temporal summation of second pain (TSSP). Temporal summation of second pain provides an index of pain sensitivity and may be especially relevant in determining risk for chronic pain. This study assessed pain tolerance and TSSP to evoked thermal pain in 78 healthy youth (age range, 10-17), 51% of whom were African American and 49% were non-Hispanic white. Multilevel models revealed within-individual increases in pain ratings during the temporal summation task in non-Hispanic white youth that were consistent with TSSP. Pain ratings did not change significantly during the temporal summation task in African-American youth. Baseline evoked pain ratings were significantly higher in African-American compared with non-Hispanic white youth. These findings suggest that enhanced responsiveness to evoked thermal pain in African Americans is present in adolescence but is unlikely to be related to elevated TSSP. These results may have implications for understanding racial differences in chronic pain experience in adulthood.

Association between pressure pain sensitivity and autonomic function as assessed by a tilt table test

BACKGROUND

We tested the hypothesis that pressure sensitivity of the sternum (PPS) is associated with autonomic nervous system (ANS) function as assessed by tilt table test (TTT). in patients with stable ischemic heart disease.

OBJECTIVES

(1) To evaluate an association between PPS and systolic blood pressure (SBP) and heart rate (HR) responses to TTT; and (2) to test the hypothesis that a reduction of resting PPS raises the PPS, SBP and HR responses to TTT response and lowers risk factors for ANS dysfunction (ANSD).

METHODS

Cross-sectional study: In 361 patients with stable ischemic heart disease we measured PPS, SBP, and HR during TTT. Intervention study: We reassessed subjects with persistent stress who concluded a stress intervention trial by a second TTT.

RESULTS

Cross-sectional study: Resting PPS and the PPS response to TTT were correlated (r = - 0.37). The PPS response to TTT was correlated with that of SBP (r = 0.44) and HR (r = 0.49), and with the number of risk factors for ANSD (r = - 0.21) (all p < 0.0001). Intervention study: A reduction in resting PPS was associated with an increment in PPS response to TTT (r = - 0.52, p < 0.0001). The greater this increment, the greater was the reduction in ANSD risk factors (r = - 0.23; p = 0.003).

CONCLUSION

The results are consistent with the hypothesis that PPS at rest and in response to TTT reflects ANS function.

The comparative effects of spinal and peripheral thrust manipulation and exercise on pain sensitivity and the relation to clinical outcome: a mechanistic trial using a shoulder pain model

STUDY DESIGN

Single-blind randomized trial.

OBJECTIVES

To compare the effects of cervical and shoulder thrust manipulation (TM) and exercise on pain sensitivity, and to explore associations with clinical outcomes in patients with shoulder pain.

BACKGROUND

Experimental studies indicate that spinal TM has an influence on central pain processes, supporting its application for treatment of extremity conditions. Direct comparison of spinal and peripheral TM on pain sensitivity has not been widely examined.

METHODS

Seventy-eight participants with shoulder pain (36 female; mean ± SD age, 39.0 ± 14.5 years) were randomized to receive 3 treatments of cervical TM (n = 26), shoulder TM (n = 27), or shoulder exercise (n = 25) over 2 weeks. Twenty-five healthy participants (13 female; mean ± SD age, 35.2 ± 11.1 years) were assessed to compare pain sensitivity with that in clinical participants at baseline. Primary outcomes were changes in local (eg, shoulder) and remote (eg, tibialis anterior) pressure pain threshold and heat pain threshold occurring over 2 weeks. Secondary outcomes were shoulder pain intensity and patient-rated function at 4, 8, and 12 weeks. Analysis-of-variance models and partial-correlation analyses were conducted to examine comparative effects and the relationship between measures.

RESULTS

At baseline, clinical participants demonstrated lower local (mean difference, - 1.63 kg; 95% confidence interval [CI]: -2.40, -0.86) and remote pressure pain threshold (mean difference, -1.96 kg; 95% CI: -3.09, -0.82) and heat pain threshold (mean difference, -1.15°C; 95% CI: -2.06, -0.24) compared to controls, suggesting enhanced pain sensitivity. Following intervention, there were no between-group differences in pain sensitivity or clinical outcome (P>.05). However, improvements were noted, regardless of intervention, for pressure pain threshold (range of mean differences, 0.22-0.32 kg; 95% CI: 0.03, 0.43), heat pain threshold (range of mean differences, 0.30-0.58; 95% CI: 0.06, 0.96), pain intensity (range of mean differences, -1.79 to -1.45; 95% CI: -2.34, -0.94), and function (range of mean differences, 3.15-3.82; 95% CI: 0.69, 6.20) at all time points. We did not find an association between pain sensitivity changes and clinical outcome (P>.05). Conclusion Clinical participants showed enhanced pain sensitivity, but did not respond differently to cervical or peripheral TM. In fact, in this sample, cervical TM, shoulder TM, and shoulder exercise had similar pain sensitivity and clinical effects. The lack of association between pain sensitivity and clinical pain and function outcomes suggests different (eg, nonspecific) pain pathways for clinical benefit following TM or exercise.

LEVEL OF EVIDENCE

Therapy, level 1b.

Dynamic Pain Phenotypes are Associated with Spinal Cord Stimulation-Induced Reduction in Pain: A Repeated Measures Observational Pilot Study

OBJECTIVE

Spinal cord stimulation (SCS) has become a widely used treatment option for a variety of pain conditions. Substantial variability exists in the degree of benefit obtained from SCS and patient selection is a topic of expanding interest and importance. However, few studies have examined the potential benefits of dynamic quantitative sensory testing (QST) to develop objective measures of SCS outcomes or as a predictive tool to help patient selection. Psychological characteristics have been shown to play an important role in shaping individual differences in the pain experience and may aid in predicting responses to SCS. Static laboratory pain-induction measures have also been examined in their capacity for predicting SCS outcomes.

METHODS

The current study evaluated clinical, psychological and laboratory pain measures at baseline, during trial SCS lead placement, as well as 1 month and 3 months following permanent SCS implantation in chronic pain patients who received SCS treatment. Several QST measures were conducted, with specific focus on examination of dynamic models (central sensitization and conditioned pain modulation [CPM]) and their association with pain outcomes 3 months post SCS implantation.

RESULTS

Results suggest few changes in QST over time. However, central sensitization and CPM at baseline were significantly associated with clinical pain at 3 months following SCS implantation, controlling for psycho/behavioral factors and pain at baseline. Specifically, enhanced central sensitization and reduced CPM were associated with less self-reported pain 3 months following SCS implantation.

CONCLUSIONS

These findings suggest a potentially important role for dynamic pain assessment in individuals undergoing SCS, and hint at potential mechanisms through which SCS may impart its benefit.

The common link between functional somatic syndromes may be central sensitisation

OBJECTIVES

Functional somatic syndromes are common and disabling conditions that all include chronic pain, and which may be related to central nervous system sensitisation. Here, we address the concept of central sensitisation as a physiological basis for the functional somatic syndromes.

METHODS

A narrative review of the current literature on central sensitisation and physiological studies in the functional somatic syndromes.

RESULTS

Central sensitisation may be a common neurophysiological process that is able to explain non-painful as well as painful symptoms in these disorders. Furthermore, central sensitisation may represent an endophenotypic vulnerability to the development of these syndromes that potentially explains why they cluster together.

CONCLUSIONS

Further research is needed to verify these findings, including prospective studies and the standardisation of combined methods of investigation in the study of central sensitisation in functional somatic syndromes. In turn, this may lead to new explanatory mechanisms and treatments being evaluated. Our conclusions add to the debate over the nomenclature of these syndromes but importantly also provide an explanation for our patients.

Effects of testosterone replacement in men with opioid-induced androgen deficiency: a randomized controlled trial

Symptomatic androgen deficiency is common in patients taking opioid analgesics, as these drugs potently suppress the hypothalamic-pituitary-gonadal axis. However, the efficacy of testosterone replacement in this setting remains unclear. The objective of this trial was to evaluate the efficacy of testosterone replacement on pain perception and other androgen-dependent outcomes in men with opioid-induced androgen deficiency. We conducted a randomized, double-blind, parallel placebo-controlled trial at an outpatient academic research center. Participants were men aged 18 to 64 years on opioid analgesics for chronic noncancer pain, and total testosterone levels were <350 ng/dL. Participants were randomly assigned to 14 weeks of daily transdermal gel that contained 5 g of testosterone or placebo. Primary outcomes were changes in self-reported clinical pain and objectively assessed pain sensitivity. Sexual function, quality of life, and body composition were also assessed. The mean age was 49 years. The median total and free testosterone levels at baseline were 243 ng/dL and 47 pg/mL and 251 ng/dL and 43 pg/mL in the testosterone and placebo arm, respectively. Of the 84 randomized participants, 65 had follow-up data on efficacy outcomes. Compared with men assigned to the placebo arm, those assigned to testosterone replacement experienced greater improvements in pressure and mechanical hyperalgesia, sexual desire, and role limitation due to emotional problems. Testosterone administration was also associated with an improvement in body composition. There were no between-group differences in changes in self-reported pain. In conclusion, in men with opioid-induced androgen deficiency, testosterone administration improved pain sensitivity, sexual desire, body composition, and aspects of quality of life.

The Association between Serum Cytokines and Damage to Large and Small Nerve Fibers in Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) is a frequent complication of type 2 diabetes mellitus (DM) and may involve small and large peripheral nerve fibers. Recent evidence suggests a role of cytokines in DPN. The paper is aimed at exploring whether the serum concentration of cytokines is associated with small and large nerve fiber function and with neuropathic pain (NP). We recruited a group of 32 type 2 DM patients who underwent serum cytokines (TNF-α, IL-2, IL-4, IL-6, and IL-10) dosage as well as electrodiagnostic and quantitative sensory testing (QST) assessment to explore damage to large and small nerve fibers. Raised serum levels of IL-6 and IL-10 correlated with markers of large nerve fiber sensory and motor axonal damage. Raised IL-10 serum level was associated with signs of motor nerve demyelination. No differences were found in pain characteristics and electrodiagnostic and QST markers of small nerve fiber function in relation to cytokines serum levels. IL-6 and IL-10 serum levels were associated with large nerve fiber damage but not to small fibers function or NP. IL-6 and IL-10 cytokines might play a role in the pathogenesis of nerve fiber damage or represent a compensatory or neuroprotective mechanism.

Central sensitization in humans: assessment and pharmacology

It is evident that chronic pain can modify the excitability of central nervous system which imposes a specific challenge for the management and for the development of new analgesics. The central manifestations can be difficult to quantify using standard clinical examination procedures, but quantitative sensory testing (QST) may help to quantify the degree and extend of the central reorganization and effect of pharmacological interventions. Furthermore, QST may help in optimizing the development programs for new drugs.Specific translational mechanistic QST tools have been developed to quantify different aspects of central sensitization in pain patients such as threshold ratios, provoked hyperalgesia/allodynia, temporal summation (wind-up like pain), after sensation, spatial summation, reflex receptive fields, descending pain modulation, offset analgesia, and referred pain areas. As most of the drug development programs in the area of pain management have not been very successful, the pharmaceutical industry has started to utilize the complementary knowledge obtained from QST profiling. Linking patients QST profile with drug efficacy profile may provide the fundamentals for developing individualized, targeted pain management programs in the future. Linking QST-assessed pain mechanisms with treatment outcome provides new valuable information in drug development and for optimizing the management regimes for chronic pain.

Investigating dynamic pain sensitivity in the context of the fear-avoidance model

BACKGROUND

Although nearly everyone at some point in their lives experiences back pain; the amount of interference with routine activity varies significantly. The fear-avoidance (FA) model of chronic pain explains how psychological variables, such as fear, act as mediating factors influencing the relationship between clinical pain intensity and the amount of interference with daily activities. What remains less clear is how other mediating factors fit within this model. The primary objective of this report was to examine the extent to which a dynamic measure of pain sensitivity provides additional information within the context of the FA model.

METHOD

To address our primary objective, classic mediation and moderated mediation analyses were conducted on baseline clinical, psychological and quantitative sensory measures obtained on 67 subjects with back pain (mean age, 31.4 ± 12.1 years; 70% female).

RESULTS

There was a moderately strong relationship (r = 0.52; p < 0.01) between clinical pain intensity and interference, explaining about 27% of the variance in the outcome. Mediation analyses confirmed fear partially mediated the total effect of clinical pain intensity on interference (Δβ = 0.27; p < 0.01), and accounted for an additional 16% of the variance. In our FA model, pain sensitivity did not demonstrate additional indirect effects; however, it did moderate the strength of indirect effects of fear.

CONCLUSION

This preliminary modelling suggests complex interactions exist between pain-related fear and pain sensitivity measures that further explain individual differences in behaviour.

Development of a bedside pain assessment kit for the classification of patients with osteoarthritis

There are no standardized bedside assessments for subtyping patients with osteoarthritis (OA) based on pain mechanisms. Thus, we developed a bedside sensory testing kit (BSTK) to classify OA patients based on sensory profiles potentially indicative of pain mechanism. After usability and informal reliability testing (n = 22), the kit was tested in a formal reliability study (n = 20). Patients completed questionnaires and sensory testing: pressure algometry to detect hyperalgesia; repeat algometry after heterotopic noxious conditioning stimulation to measure diffuse noxious inhibitory control (DNIC); light touch using Von Frey filaments; and cold allodynia using a brass rod. The procedure was brief and well tolerated. Algometry and filament testing were highly reliable [intra-class correlation coefficients (ICCs) 0.71-0.91]; DNIC was acceptably reliable (ICCs 0.53-0.91); brass rod reliability was inconclusive. Patients were classified empirically into four groups: "All abnormal findings" (primary and secondary hyperalgesia and dysfunctional DNIC); "all normal findings"; and two intermediate groups. The "all abnormal findings" group had more neuropathic pain symptoms, and lower WOMAC total, stiffness, and activity scores than the "all normal findings" group. Simple BSTK procedures, consolidated in a kit, reliably classified OA patients into subgroups based on sensory profile, suggesting that OA patients differ in underlying pain mechanisms. Further research is needed to confirm these subgroups and determine their validity in predicting response to treatment.

Hypnotic relaxation results in elevated thresholds of sensory detection but not of pain detection

Background

Many studies show an effectiveness of hypnotic analgesia. It has been discussed whether the analgesic effect is mainly caused by the relaxation that is concomitant to hypnosis. This study was designed to evaluate the effects of hypnotic relaxation suggestion on different somatosensory detection and pain thresholds.

Methods

Quantitative sensory testing (QST) measurements were performed before and during hypnosis in twenty-three healthy subjects on the dorsum of the right hand. Paired t-test was used to compare threshold changes. The influence of hypnotic susceptibility was evaluated by calculating correlation coefficients for threshold changes and hypnotic susceptibility (Harvard group scale).

Results

During hypnosis significantly changed somatosensory thresholds (reduced function) were observed for the following sensory detection thresholds: Cold Detection Threshold (CDT), Warm Detection Threshold (WDT), Thermal Sensory Limen (TSL) and Mechanical Detection Threshold (MDT). The only unchanged sensory detection threshold was Vibration Detection Threshold (VDT). No significant changes were observed for the determined pain detection thresholds (Cold Pain Thresholds, Heat Pain Thresholds, Mechanical Pain Sensitivity, Dynamic Mechanical Allodynia, Wind-up Ratio and Pressure Pain Threshold). No correlation of hypnotic susceptibility and threshold changes were detected.

Conclusion

Hypnotic relaxation without a specific analgesic suggestion results in thermal and mechanical detection, but not pain threshold changes. We thus conclude that a relaxation suggestion has no genuine effect on sensory pain thresholds.

Trial Registration

ClinicalTrials.gov, Identifier: NCT02261155 (9^th October 2014).

Effects of acupuncture on sensory perception: a systematic review and meta-analysis

BACKGROUND

The effect of acupuncture on sensory perception has never been systematically reviewed; although, studies on acupuncture mechanisms are frequently based on the idea that changes in sensory thresholds reflect its effect on the nervous system.

METHODS

Pubmed, EMBASE and Scopus were screened for studies investigating the effect of acupuncture on thermal or mechanical detection or pain thresholds in humans published in English or German. A meta-analysis of high quality studies was performed.

RESULTS

Out of 3007 identified articles 85 were included. Sixty five studies showed that acupuncture affects at least one sensory threshold. Most studies assessed the pressure pain threshold of which 80% reported an increase after acupuncture. Significant short- and long-term effects on the pressure pain threshold in pain patients were revealed by two meta-analyses including four and two high quality studies, respectively. In over 60% of studies, acupuncture reduced sensitivity to noxious thermal stimuli, but measuring methods might influence results. Few but consistent data indicate that acupuncture reduces pin-prick like pain but not mechanical detection. Results on thermal detection are heterogeneous. Sensory threshold changes were equally frequent reported after manual acupuncture as after electroacupuncture. Among 48 sham-controlled studies, 25 showed stronger effects on sensory thresholds through verum than through sham acupuncture, but in 9 studies significant threshold changes were also observed after sham acupuncture. Overall, there is a lack of high quality acupuncture studies applying comprehensive assessments of sensory perception.

CONCLUSIONS

Our findings indicate that acupuncture affects sensory perception. Results are most compelling for the pressure pain threshold, especially in pain conditions associated with tenderness. Sham acupuncture can also cause such effects. Future studies should incorporate comprehensive, standardized assessments of sensory profiles in order to fully characterize its effect on sensory perception and to explore the predictive value of sensory profiles for the effectiveness of acupuncture.

Diabetes and ischemic heart disease: double jeopardy with regard to depressive mood and reduced quality of life

The aim of this study was to test i) whether patients having diabetes and ischemic heart disease (IHD), i.e., patients suffering from two chronic diseases, demonstrate a higher degree of chronic stress when compared with patients suffering from IHD alone, and ii) whether suffering from the two chronic diseases results in an elevation in specific elements of the chronic stress concept. A total of 361 participants with IHD were included, of whom 47 suffered from concomitant diabetes. Stress was measured by pressure pain sensitivity (PPS) and by the following questionnaires: the Major Depression Inventory (MDI), the SF-36 Quality of Life questionnaire (SF-36 QOL), the WHO-5 Well-being Index, and the clinical stress signs (CSSs) scale. Participants with diabetes and IHD had a higher MDI score, a lower SF-36 physical component summary score, and a lower score of several sub-measurements of the SF-36 mental component score when compared with patients with IHD without diabetes. No significant differences were observed regarding stress measured by the PPS measure, the WHO-5 Well-being Index, or the number of CSSs. In conclusion, the combination of diabetes and IHD seems to be associated with increased depressive symptoms, lower overall physical QOL, and reduced mental QOL on several sub-elements of the questionnaire. This should be recognized in the management of patients with double diagnoses.

The effect of pressure pain sensitivity and patient factors on self-reported pain-disability in patients with chronic neck pain

The study was conducted to estimate the extent to which pressure pain sensitivity (PPS) and patient factors predict pain-related disability in patients with neck pain (NP), and to determine if PPS differs by gender. Forty-four participants with a moderate level of chronic NP were recruited for this cross sectional study. All participants were asked to complete self-reported assessments of pain, disability and comorbidity and then underwent PPS testing at 4-selected body locations. Pearson`s r w was computed to explore relationships between the PPS measures and the self-reported assessments. Regression models were built to identify predictors of pain and disability. An independent sample t-test was done to identify gender-related differences in PPS, pain-disability and comorbidity. In this study, greater PPS (threshold and tolerance) was significantly correlated to lower pain-disability (r = -.30 to -.53, p≤0.05). Age was not correlated with pain or disability but comorbidity was (r= 0.42-.43, p≤0.01). PPS at the 4-selected body locations was able to explain neck disability (R²=25-28%). Comorbidity was the strongest predictor of neck disability (R² =30%) and pain (R²=25%). Significant mean differences for gender were found in PPS, disability and comorbidity, but not in pain intensity or rating. This study suggests that PPS may play a role in outcome measures of pain and disability but between-subject comparisons should consider gender and comorbidity issues.

Suprathreshold heat pain response predicts activity-related pain, but not rest-related pain, in an exercise-induced injury model

Exercise-induced injury models are advantageous for studying pain since the onset of pain is controlled and both pre-injury and post-injury factors can be utilized as explanatory variables or predictors. In these studies, rest-related pain is often considered the primary dependent variable or outcome, as opposed to a measure of activity-related pain. Additionally, few studies include pain sensitivity measures as predictors. In this study, we examined the influence of pre-injury and post-injury factors, including pain sensitivity, for induced rest and activity-related pain following exercise induced muscle injury. The overall goal of this investigation was to determine if there were convergent or divergent predictors of rest and activity-related pain. One hundred forty-three participants provided demographic, psychological, and pain sensitivity information and underwent a standard fatigue trial of resistance exercise to induce injury of the dominant shoulder. Pain at rest and during active and resisted shoulder motion were measured at 48- and 96-hours post-injury. Separate hierarchical models were generated for assessing the influence of pre-injury and post-injury factors on 48- and 96-hour rest-related and activity-related pain. Overall, we did not find a universal predictor of pain across all models. However, pre-injury and post-injury suprathreshold heat pain response (SHPR), a pain sensitivity measure, was a consistent predictor of activity-related pain, even after controlling for known psychological factors. These results suggest there is differential prediction of pain. A measure of pain sensitivity such as SHPR appears more influential for activity-related pain, but not rest-related pain, and may reflect different underlying processes involved during pain appraisal.

Acute psychosocial stress reduces pain modulation capabilities in healthy men

Anecdotes on the ability of individuals to continue to function under stressful conditions despite injuries causing excruciating pain suggest that acute stress may induce analgesia. However, studies exploring the effect of acute experimental stress on pain perception show inconsistent results, possibly due to methodological differences. Our aim was to systematically study the effect of acute stress on pain perception using static and dynamic, state-of-the-art pain measurements. Participants were 29 healthy men who underwent the measurement of heat-pain threshold, heat-pain intolerance, temporal summation of pain, and conditioned pain modulation (CPM). Testing was conducted before and during exposure to the Montreal Imaging Stress Task (MIST), inducing acute psychosocial stress. Stress levels were evaluated using perceived ratings of stress and anxiety, autonomic variables, and salivary cortisol. The MIST induced a significant stress reaction. Although pain threshold and pain intolerance were unaffected by stress, an increase in temporal summation of pain and a decrease in CPM were observed. These changes were significantly more robust among individuals with stronger reaction to stress ("high responders"), with a significant correlation between the perception of stress and the performance in the pain measurements. We conclude that acute psychosocial stress seems not to affect the sensitivity to pain, however, it significantly reduces the ability to modulate pain in a dose-response manner. Considering the diverse effects of stress in this and other studies, it appears that the type of stress and the magnitude of its appraisal determine its interactions with the pain system.

Repetitive transcranial magnetic stimulation over primary motor vs non-motor cortical targets; effects on experimental hyperalgesia in healthy subjects

Background

High frequency repetitive transcranial magnetic stimulation (rTMS) targetted to different cortical regions (primary motor/sensory, prefrontal) are known to alter somatosensory responses. The mechanism(s) for these effects are unclear. We compared the analgesic effects of rTMS at different cortical sites on hyperalgesia induced using topical capsaicin cream.

Methods

Fourteen healthy subjects had capsaicin cream applied to a 16 cm² area of the medial aspect of the right wrist (60 min) on 4 separate occasions over 6 weeks. rTMS (10Hz for 10s/min = 2000 stimuli @ 90% resting motor threshold of first dorsal interosseus muscle) was applied to the optimum site for right hand (M1), left dorsolateral prefrontal (DLFPC) and occipital midline (OCC) in a pseudo-randomised order. Thermal and mechanical perception and pain thresholds were determined using standardised quantitative sensory testing (QST) methods at the capsaicin site. Subjective responses to thermal stimuli (pain score on a numerical rating scale) from −2.5°C to +2.5°C of the individualised heat pain threshold (HPT) resulted in a hyperalgesia curve. Sensory testing took place prior to capsaicin application (PRE-CAP), after 30 min of capsaicin (POST-CAP) and following rTMS (30 min = POST-TMS).

Results

Capsaicin application resulted in substantial changes in thermal (but not mechanical) sensitivity to both heat and cold (eg. HPT PRE-CAP = 43.6°C to POST-CAP = 36.7°C (p < 0.001)) with no differences between groups pre-rTMS. POST-TMS HPT showed no changes for any of the treatment groups, however the pain scores for the hyperalgesia curve were significantly lower for M1 vs OCC (−24.7%, p < 0.001) and for M1 vs DLFPC (−18.3%, p < 0.02).

Conclusion

rTMS over the primary motor cortex results in a significant analgesic effect compared to other cortical areas.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-014-0166-3) contains supplementary material, which is available to authorized users.

Experimental pain responses support peripheral and central sensitization in patients with unilateral shoulder pain

OBJECTIVE

The aims of this study were to (1) examine the pattern of experimental pain responses in the affected and nonaffected extremities in patients with shoulder pain and (2) explore the intraindividual association between sensitization states derived from experimental pain testing.

METHODS

Experimental pain responses from 58 patients with shoulder pain (17 women, aged 18 to 52 y) were compared with those from 56 age-matched and sex-matched pain-free volunteers (16 women, aged 21 to 58 y). Experimental pain responses included pressure pain threshold (PPT), thermal pain threshold and tolerance, and suprathreshold heat pain response. Comparisons were made between the affected and nonaffected extremities of clinical participants and the average response of extremities in control participants. Peripheral and central sensitization indexes were computed for clinical participants using standardized scores and percentile cutoffs on the basis of the data from the control sample. Experimental pain responses in clinical participants observed beyond the 25th and 75th percentile of control sample responses were used for investigation of intraindividual association of sensitization states.

RESULTS

PPT at the acromion and masseter on the affected side of clinical participants were diminished compared with that on their nonaffected side (P<0.015). Bilateral sensitivity in clinical participants was noted for PPT at the acromion and suprathreshold heat pain response (P<0.015). Peripheral and central sensitization indexes demonstrated that individuals with shoulder pain present with variable patterns of peripheral and central sensitization.

CONCLUSIONS

Collectively, experimental pain responses supported peripheral and central sensitization in response to pressure and thermal stimuli. No clear association was made between individuals exhibiting peripheral or central sensitization, thus suggesting heterogeneity in pain processing in this clinical population.

MicroRNAs as modulators and biomarkers of inflammatory and neuropathic pain conditions

The post-transcriptional regulator molecules, microRNAs, have emerged as important biomarkers and modulators of numerous pathophysiological processes including oncogenesis and cardiovascular diseases. Recently, a significant number of dysregulations in microRNAs have been reported in patients suffering from painful disorders such as complex regional pain syndrome, cystitis-induced chronic pain and irritable bowel disorder, in both affected tissues and the circulation. Moreover, microRNAs are known to be involved in pain processing based on several recent findings in animal models of inflammatory and neuropathic pain. The basis of this review was to cover and summarize available articles in English encompassing "microRNA and pain". In animal pain models widespread microRNA modulation is present and manifests on multiple levels i.e.: the dorsal root ganglia, the spinal dorsal horn and the brain. Numerous functional in vivo studies have found that dysregulated microRNAs are involved in the post-transcriptional modulation of genes implicated in pain generation and maintenance. Lastly, a few animal studies have delivered promising results as to the possibility of applying microRNAs as therapeutics to alleviate established pain and several clinical studies have highlighted the potential in applying microRNAs as biomarkers in painful conditions such as complex regional pain syndrome and fibromyalgia. This review briefly introduces the basics of microRNAs, their biogenesis and function, and mainly focuses on the recent advances made in understanding the role of microRNAs in relation to pain processing and painful conditions. It also provides an overview of widely diverse methodological approaches and results with a potential for future implications of microRNAs in the diagnosis and treatment of pain.

Pain sensitivity subgroups in individuals with spine pain: potential relevance to short-term clinical outcome

BACKGROUND

Cluster analysis can be used to identify individuals similar in profile based on response to multiple pain sensitivity measures. There are limited investigations into how empirically derived pain sensitivity subgroups influence clinical outcomes for individuals with spine pain.

OBJECTIVE

The purposes of this study were: (1) to investigate empirically derived subgroups based on pressure and thermal pain sensitivity in individuals with spine pain and (2) to examine subgroup influence on 2-week clinical pain intensity and disability outcomes.

DESIGN

A secondary analysis of data from 2 randomized trials was conducted.

METHODS

Baseline and 2-week outcome data from 157 participants with low back pain (n=110) and neck pain (n=47) were examined. Participants completed demographic, psychological, and clinical information and were assessed using pain sensitivity protocols, including pressure (suprathreshold pressure pain) and thermal pain sensitivity (thermal heat threshold and tolerance, suprathreshold heat pain, temporal summation). A hierarchical agglomerative cluster analysis was used to create subgroups based on pain sensitivity responses. Differences in data for baseline variables, clinical pain intensity, and disability were examined.

RESULTS

Three pain sensitivity cluster groups were derived: low pain sensitivity, high thermal static sensitivity, and high pressure and thermal dynamic sensitivity. There were differences in the proportion of individuals meeting a 30% change in pain intensity, where fewer individuals within the high pressure and thermal dynamic sensitivity group (adjusted odds ratio=0.3; 95% confidence interval=0.1, 0.8) achieved successful outcomes.

LIMITATIONS

Only 2-week outcomes are reported.

CONCLUSIONS

Distinct pain sensitivity cluster groups for individuals with spine pain were identified, with the high pressure and thermal dynamic sensitivity group showing worse clinical outcome for pain intensity. Future studies should aim to confirm these findings.

The current perception threshold test differentiates categories of mechanical neck disorder

STUDY DESIGN

Cross-sectional discriminative analysis.

OBJECTIVE

To determine whether current perception threshold (CPT) can differentiate between categories of patients with mechanical neck disorders (MNDs).

BACKGROUND

Neck pain is the third most common musculoskeletal disorder and affects a third of all adults each year. It can present as neck pain without musculoskeletal signs, neck pain with musculoskeletal signs but no neurological signs, or neck pain with neurological signs. CPT testing can assess altered sensory perception that may reflect neurological changes.

METHODS

Patients with MNDs (n = 106) were classified into 3 groups, based on a standardized musculoskeletal examination process performed by an experienced physiotherapist who was blinded to CPT scores. The 3 groups were defined as neck pain without musculoskeletal signs (MND I) (n = 60), neck pain with musculoskeletal signs (MND II) (n = 29), and neck pain with neurological signs (MND III) (n = 17). A rapid protocol of CPT testing was performed at 3 frequencies (5, 250, and 2000 Hz), using 3 dermatomal locations on the hand. A 1-way analysis of variance with post hoc comparison and effect sizes was calculated to compare the mean CPT scores between the groups. A binary logistic-regression model was used to predict probability of higher CPT in MND III and to create a receiver-operating-characteristic curve.

RESULTS

Mean CPT differed significantly across the 3 MND groups (MND I, 9.7; MND II, 10.6; and MND III, 11.8; P<.001; η(2) = 0.6). Post hoc comparisons indicated differences between MND I and MND II (P = .05) and between MND II and MND III (P = .01) that had large effect sizes (MND I versus II, d = 1 and MND II versus III, d = 2.2). CPT testing was able to distinguish between MND II and III when a threshold value of greater than 11 was used to indicate MND III. The predicted probability of abnormal CPT in MND III had an estimated 73% sensitivity and 81% specificity; the odds ratio was 11.5 (P = .001) for the differentiation capacity of CPT between MND II and III, with a cutoff of 11. The area under the receiver-operating-characteristic curve was 0.84 (95% confidence interval: 0.72, 0.96; P<.001).

CONCLUSION

CPT testing has moderate discriminatory accuracy, specificity, and sensitivity for classification of MND categories into neck pain with or without neurological signs. J Orthop Sports Phys Ther 2014;44(7):532-540. Epub 10 May 2014. doi:10.2519/jospt.2014.4691.

Effect of written emotional disclosure on secondary hyperalgesia in women with trauma history

OBJECTIVE

This study investigated the effects of written emotional disclosure on a model of chronic pain in healthy women with and without trauma history.

METHOD

Participants were prescreened for their trauma history (N = 78) and randomized to a disclosure or a control writing condition. Pain testing occurred either 1 day or 1 month after disclosure. Capsaicin was applied to the forearm to evoke spontaneous burning pain at the application site and mechanical secondary hyperalgesia in the surrounding untreated skin.

RESULTS

As hypothesized, the effect of disclosure on the area and intensity of secondary hyperalgesia depended on trauma history and time of testing (F(1,69) ≥ 7.37, p = .008). Disclosure increased secondary hyperalgesia in participants with trauma history compared with those without trauma when testing occurred 1 day after writing (F(1,69) ≥ 5.27, p ≤ .025), whereas the opposite pattern was observed 1 month later (F(1,69) ≥ 4.88, p ≤ .031). Of the participants with trauma history in the disclosure condition, secondary hyperalgesia was reduced at 1 month compared with 1 day after writing (p = .001). Moreover, greater use of positive emotional words predicted reduced secondary hyperalgesia at 1 month (β = -0.71, p = .022). In contrast, disclosure had no effect on spontaneous pain.

CONCLUSIONS

Disclosure modulates secondary hyperalgesia observed in women with trauma history, producing a short-term enhancement and a long-term reduction. This suggests that disclosure has a long-term protective effect that reduces sensitization of pain, which may explain the therapeutic effects of disclosure in patients with chronic pain.

Management of a patient with chronic low back pain and multiple health conditions using a pain mechanisms-based classification approach

STUDY DESIGN

Case report.

BACKGROUND

Pain can lead to a significant reduction in quality of life. A pain mechanisms-based classification scheme has been outlined to improve management of patients with pain, but studies describing its use are limited. Evidence for physical therapy interventions in those with chronic pain and multiple health conditions is also lacking. This case report describes management of a patient with chronic pain and multiple health conditions.

CASE DESCRIPTION

A 29-year-old man presented with a 3-year history of low back pain and 11-month history of lower extremity paresthesia. Current health conditions included left-sided hemiparesis secondary to a stroke, pancreatic kidney transplant, left-sided blindness, and osteoporosis secondary to hyperparathyroidism. Inability to walk to school and sit through class, and pain-related sleep disruption were the primary activity and participation restrictions. Outcome measures included the numeric pain rating scale, global rating of change, Oswestry Disability Index, and pain medication usage. A score of 12 on the Leeds assessment of neuropathic symptoms and signs (LANSS) pain scale indicated the presence of neuropathic pain, but other pain mechanisms were also hypothesized to be present. Treatment was designed to improve patient goals considering these pain mechanisms.

OUTCOMES

The patient was seen for 20 visits over 6 months. Ten months after the initial evaluation, the patient's Oswestry Disability Index scores improved by more than 50% and the patient achieved all initially stated goals without pain medication.

DISCUSSION

A pain mechanisms-based approach assisted in the management of a patient with chronic pain and multiple health conditions. Using this approach may enhance clinical decision making when managing individuals with chronic pain.

LEVEL OF EVIDENCE

Therapy, level 4.

The effect of daily self-measurement of pressure pain sensitivity followed by acupressure on depression and quality of life versus treatment as usual in ischemic heart disease: a randomized clinical trial

BACKGROUND

Depressive symptoms and reduced quality of life (QOL) are parts of the chronic stress syndrome and predictive of adverse outcome in patients with ischemic heart disease (IHD). Chronic stress is associated with increased sensitivity for pain, which can be measured by algometry as Pressure Pain Sensitivity (PPS) on the sternum.

AIM

To evaluate if stress focus by self-measurement of PPS, followed by stress reducing actions including acupressure, can decrease depressive symptoms and increase psychological well-being in people with stable IHD.

DESIGN

Observer blinded randomized clinical trial over 3 months of either intervention or treatment as usual (TAU).

STATISTICAL ANALYSIS

Intention to treat.

METHODS

Two hundred and thirteen participants with IHD were included: 106 to active treatment and 107 to TAU. Drop-out: 20 and 12, respectively. The active intervention included self-measurement of PPS twice daily followed by acupressure as mandatory action, aiming at a reduction in PPS. Primary endpoint: change in depressive symptoms as measured by Major depression inventory (MDI). Other endpoints: changes in PPS, Well-being (WHO-5) and mental and physical QOL (SF-36).

RESULTS

At 3 months PPS decreased 28%, to 58, in active and 11%, to 72, in TAU, p<0.001. MDI decreased 22%, to 6.5, in active group vs. 12%, to 8.3 in TAU, p = 0.040. WHO-5 increased to 71.0 and 64.8, active group and TAU, p = 0.015. SF-36 mental score sum increased to 55.3 and 53.3, active and TAU, p = 0.08.

CONCLUSIONS

PPS measurements followed by acupressure reduce PPS, depressive symptoms and increase QOL in patients with stable IHD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01513824.

Conditioned pain modulation: a predictor for development and treatment of neuropathic pain

Psychophysical evaluation of endogenous pain inhibition via conditioned pain modulation (CPM) represents a new generation of laboratory tests for pain assessment. In this review we discuss recent findings on CPM in neuropathic pain and refer to psychophysical, neurophysiological, and methodological aspects of its clinical implications. Typically, chronic neuropathic pain patients express less efficient CPM, to the extent that incidence of acquiring neuropathic pain (e.g. post-surgery) and its intensity can be predicted by a pre-surgery CPM assessment. Moreover, pre-treatment CPM evaluation may assist in the correct choice of serotonin-noradrenalin reuptake inhibitor analgesic agents for individual patients. Evaluation of pain modulation capabilities can serve as a step forward in individualizing pain medicine.

A brief cognitive-behavioural intervention for pain reduces secondary hyperalgesia

Repeated exposure to pain can result in sensitization of the central nervous system, enhancing subsequent pain and potentially leading to chronicity. The ability to reverse this sensitization in a top-down manner would be of tremendous clinical benefit, but the degree that this can be accomplished volitionally remains unknown. Here we investigated whether a brief (~5 min) cognitive-behavioural intervention could modify pain perception and reduce central sensitization (as reflected by secondary hyperalgesia). In each of 8 sessions, 2 groups of healthy human subjects received a series of painful thermal stimuli that resulted in secondary hyperalgesia. One group (regulate) was given brief pain-focused cognitive training at each session, while the other group (control) received a non-pain-focused intervention. The intervention selectively reduced pain unpleasantness but not pain intensity in the regulate group. Furthermore, secondary hyperalgesia was significantly reduced in the regulate group compared with the control group. Reduction in secondary hyperalgesia was associated with reduced pain catastrophizing, suggesting that changes in central sensitization are related to changes in pain-related cognitions. Thus, we demonstrate that central sensitization can be modified volitionally by altering pain-related thoughts.

Exercise-induced hypoalgesia - interval versus continuous mode

Aerobic exercise at approximately 70% of maximal aerobic capacity moderately reduces pain sensitivity and attenuates pain, even after a single session. If the analgesic effects depend on exercise intensity, then high-intensity interval exercise at 85% of maximal aerobic capacity should further reduce pain. The aim of this study was to explore the exercise-induced analgesic effects of high-intensity interval aerobic exercise and to compare them with the analgesic effects of moderate continuous aerobic exercise. Twenty-nine young untrained healthy males were randomly assigned to aerobic-continuous (70% heart rate reserve (HRR)) and interval (4 × 4 min at 85% HRR and 2 min at 60% HRR between cycles) exercise modes, each lasting 30 min. Psychophysical pain tests, pressure and heat pain thresholds (HPT), and tonic heat pain (THP) were conducted before and after exercise sessions. Repeated measures ANOVA was used for data analysis. HPT increased (p = 0.056) and THP decreased (p = 0.013) following exercise unrelated to exercise type. However, the main time effect (pre-/postexercise) was a trend of increased HPT (45.6 ± 1.9 °C to 46.2 ± 1.8 °C; p = 0.082) and a significant reduction in THP (from 50.7 ± 25 to 45.9 ± 25.4 numeric pain scale; p = 0.043) following interval exercise. No significant change was found for the pressure pain threshold following either exercise type. In conclusion, interval exercise (85% HRR) has analgesic effects on experimental pain perception. This, in addition to its cardiovascular, muscular, and metabolic advantages may promote its inclusion in pain management programs.

Translational pain biomarkers in the early development of new neurotherapeutics for pain management

Translation of the analgesic efficacy of investigational neurotherapeutics from pre-clinical pain models into clinical trial phases is associated with a high risk of failure. Application of human pain biomarkers in early stages of clinical trials can potentially enhance the rate of successful translation, which would eventually reduce both length and costs of drug development after the pre-clinical stage. Human pain biomarkers are based on the standardized activation of pain pathways followed by the assessment of ongoing and paroxysmal pain, plus evoked responses which can be applied to healthy individuals and patients prior to and after pharmacological interventions. This review discusses the rationality and feasibility of advanced human pain biomarkers in early phases of drug development for pain management which is still an unmet medical need.

Central pain processing in osteoarthritis: implications for treatment

SUMMARY Osteoarthritis (OA) is a major cause of pain and is characterized by loss of articular cartilage integrity, synovitis and remodeling of subchondral bone. However, OA pain mechanisms remain incompletely understood. Pain severity does not always correlate with the extent of joint damage. Furthermore, many people with OA continue to experience pain despite optimal use of standard therapies that target the joints, including joint-replacement surgery. There is compelling evidence that altered central pain processing plays an important role in maintaining pain and increasing pain severity in some people with OA. A key challenge is to identify this subgroup of patients with abnormal central pain processing in order to improve their clinical outcomes by developing and targeting specific analgesic treatments.