Temporal summation of pain evoked by mechanical stimulation in deep and superficial tissue

Pain sensitization and pain-related psychological factors in patients with temporomandibular disorders: an observational cross-sectional study

BACKGROUND

There is conflicting evidence on how central processing impairments affect patients with temporomandibular disorders (TMD). Moreover, there is sparse research on the assessment of endogenous pain modulation in this population through conditioned pain modulation (CPM) testing.

OBJECTIVE(S)

The main objective of this observational study was to evaluate the possible differences between myofascial TDM patients and healthy pain-free controls on psychophysical variables suggestive of central processing impairments (including temporal summation (TSP), pressure pain threshold (PPT) and conditioned pain modulation (CPM)).

METHODS

This is a cross-sectional observational study including a sample of patients with TMD and pain-free controls recruited from private and university clinics in Spain. Outcome measures included local and distal PPTs, temporal summation, conditioned pain modulation and psychological factors of depression, anxiety, kinesiophobia, fear avoidance beliefs and pain catastrophizing.

RESULTS

Fifty-nine patients with TMD of myofascial origin (32 years [IR: 25-43]) and 30 healthy, pain-free controls (29.5 years [IR: 25-41]) participated in the study and completed the evaluations. Patients with TMD showed significantly reduced CPM (p = 0.001; t = 3.31) and both local and distal PPTs (p < 0.05) when compared with controls, after adjusting for the influence of age and sex. TSP did not show any difference between the groups (p = 0.839; Z = 0.20). All psychological factors were higher in patients with TMD (p < 0.005), except for anxiety (p = 0.134).

CONCLUSION

Patients with myofascial TMD included in this study exhibited signs of altered central processing, linked to impaired descending pain modulation, distal hyperalgesia and psychological factors like depression, kinesiophobia, fear avoidance beliefs and pain catastrophizing but not anxiety.

A myriad of methods to determine temporal summation of pain in people with musculoskeletal pain and healthy participants: a scoping review

Temporal summation of pain (TSP) is a human proxy for wind-up of dorsal horn neurons as assessed in animals. The common paradigm for eliciting TSP is evoked by repetitive nociceptive stimuli of equal intensity. Various stimulation and assessment protocols have been used. This scoping review aims to provide insight into key elements of TSP stimulation and assessment: modality, instruments, test location, familiarization, train characteristics, and calculations. PubMed, Embase, and Ebsco/CINAHL were searched for studies that measured TSP in adults with musculoskeletal conditions and healthy people. Four hundred six studies were included. Mechanical stimuli were the most commonly used modality (250 studies), followed by thermal stimuli (125 studies). Forty-six different instruments were used. Disregarding studies on widespread musculoskeletal pain and healthy participants, 40 studies evaluated TSP at painful sites, 77 in remote areas, and 66 in both locations. Of the 13 tested locations in patients, the hand (74 studies), lower leg (64 studies), and forearm (59 studies) were most commonly tested. A single practice round was the most common familiarization method (46 studies). Repeated stimuli were applied using 31 different frequencies (0.03-200 Hz) and sustained stimulations ranging from 5 to 1080 seconds were used. Twenty-two different train lengths, 63 different calculations (37 absolute, 19 relative, and 7 alternatives using data directly), and 14 different outcome measures (eg, self-reported pain rating scales and reflex thresholds) were used. Temporal summation of pain protocols vary excessively, hindering the comparison and pooling of results. None of the studies provided substantiation for their protocol choice.

Widespread Pressure Pain Hyperalgesia Is Not Associated With Morphological Changes of the Wrist Extensor Tendon in Unilateral Lateral Epicondylalgia: A Case-Control Study

OBJECTIVE

The aims of the current study were to investigate the presence of widespread pressure hyperalgesia, the presence of structural changes in the wrist extensor tendon and muscle, and their association in people with lateral epicondylalgia (LE).

METHODS

Thirty-seven patients with LE (43% women; mean age = 45.5 [SD = 9.5] years) and 37 controls matched for age and sex and free of pain participated in this study. Pressure pain thresholds (PPTs) were assessed bilaterally over the symptomatic area (elbow), 2 segment-related areas (C5-C6 joint, second intermetacarpal space), and 1 remote area (tibialis anterior) in a blinded design. Ultrasound measurements (eg, cross-sectional area, thickness, and width) of the common wrist extensor tendon and extensor carpi radialis brevis muscle as well as the thickness of the supinator muscle were assessed.

RESULTS

Patients with LE exhibited lower PPTs bilaterally at all points and lower PPTs at the lateral epicondyle and second intermetacarpal space on the symptomatic side as compared to the nonsymptomatic side (η2 from 0.123-0.369; large effects). Patients exhibited higher cross-sectional area and width of the common wrist extensor tendon (η2 from 0.268-0.311; large effects) than controls bilaterally, whereas tendon thickness was also higher (η2 = 0.039; small effects) on the painful side than on the nonpainful side.

CONCLUSIONS

This study reported bilateral widespread pressure pain hyperalgesia and morphological changes in the tendon, but not the muscle, in LE. Pressure pain sensitivity and morphological changes were not associated in individuals with LE.

IMPACT

Management of LE should consider altered nociceptive pain processing and structural tendon changes as 2 different phenomena in patients with LE.

Laryngeal and Global Somatosensation in Primary Muscle Tension Dysphonia

INTRODUCTION

Primary muscle tension dysphonia (pMTD) is a functional voice disorder that reduces communicative abilities and adversely impacts occupational productivity and quality of life. Patients with pMTD report increased vocal effort, fatigue, discomfort, and odynophonia. Although laryngeal and paralaryngeal muscle tension and hyperfunction are the most commonly proposed mechanisms underlying these symptoms, recent studies suggest pMTD may have more to do with the somatosensory system. However, relationships between voice symptoms and somatosensory mechanisms are poorly understood, creating challenges for mechanistic-based pMTD management. The first objective was to compare laryngeal, paralaryngeal, and global somatosensation between subjects with and without pMTD. The second was to determine relationships between pMTD symptoms and somatosensation.

METHODS

Fifty-two (20 pMTD and 32 control) subjects underwent laryngeal sensory testing with aesthesiometers, as well as peripheral mechanosensory and dynamic temporal summation testing to paralaryngeal and limb regions. Voice symptom severities (vocal effort, fatigue, discomfort, and odynophonia) were collected on 100-mm visual analog scales before and after laryngeal sensory testing. Participants also completed the Central Sensitization Inventory.

RESULTS

Patients with pMTD reported significantly higher laryngeal sensations (P = 0.0072) and voice symptom severities (P < 0.001) compared with the control group, and had significantly more vocal tract discomfort postlaryngeal sensory testing compared with the prelaryngeal sensory testing timepoint (P = 0.0023). However, there were no significant group differences in laryngeal airway protection responses suggestive of peripheral laryngeal hypersensitivities (P = 0.444). There were also no significant group differences on paralaryngeal or global sensitivities (P > 0.05), and no correlations between severity of voice symptoms and perceptual laryngeal sensations or hypersensitivities (P > 0.05).

CONCLUSION

Patients with pMTD perceive more sensitivities in the larynx and feel more sensations related to the voice (vocal effort, fatigue, discomfort, and pain). However, in general, patients with pMTD do not have abnormal peripheral laryngeal hypersensitivities, increased global somatosensation, or heightened central sensitivity. The lack of significant correlations between peripheral laryngeal hypersensitivities and voice symptom severity ratings suggests these outcome variables target distinct mechanistic constructs.

Spatiotemporal characterization of an experimental model of muscle pain in humans based on short-wave diathermy

BACKGROUND

Commonly used models for eliciting muscle pain involve the injection of algesic substances or the induction of delayed onset muscle soreness. The former require invasive procedures, and the time frame for pain induction and subsidence in the latter can be inconvenient. This study presents a detailed spatiotemporal characterization of a new experimental model of muscle pain based on short-wave diathermy (SWD), developed to overcome the limitations of existing models.

METHODS

The shoulder was selected as target site and the effects of the model were tested in two sessions to assess its reliability. Pain intensity profiles were recorded during the application of SWD, and changes in pressure pain threshold (PPT) in the infraspinatus muscle, together with pain intensity, duration, and quality were assessed 30 min after induction.

RESULTS

SWD-induced pain intensity scores averaged 4 points on a visual analogue scale, whereas PPT showed a consistent decrease of about 25% relative to baseline values. Pain was localized in the shoulder area, and was described as continuous, dull, well-delimited, heavy, and bearable. Pain lasted for an average of 145 min without requiring reinduction and was reliably elicited in both experimental sessions.

CONCLUSION

SWD can be used to elicit experimental muscle pain in a non-invasive, long-lasting, and reliable way and allows for repeated within- and between-session testing in the shoulder.

SIGNIFICANCE STATEMENT

SWD produces deep heating in muscles by converting electromagnetic energy to thermal energy. It was previously shown that it can be used to elicit experimental pain in the forearm muscles, and the present study demonstrates that this can be reliably generalized to other body sites, such as the shoulder. Furthermore, SWD application is non-invasive and presents a convenient time frame for pain induction and subsidence, thus overcoming limitations associated with traditional muscle pain models.

TDCS for parkinson's disease disease-related pain: A randomized trial

OBJECTIVE

To evaluate the effects of transcranial direct current stimulation (tDCS) on Parkinson's disease (PD)-related pain.

METHODS

This triple-blind randomized controlled trial included twenty-two patients (age range 38-85, 10 male) with PD-related pain. Eleven subjects received ten sessions of 20 minutes tDCS over the primary motor cortex contralateral to pain at 2 mA intensity. Eleven subjects received sham stimulation. Outcome measures included changes in the Kinǵs Parkinsońs Pain Scale (KPPS), Brief Pain Inventory (BPI), widespread mechanical hyperalgesia (WMH), temporal summation of pain (TS), and conditioned pain modulation (CPM).

RESULTS

Significant differences were found in KPPS between groups favoring the active-tDCS group compared to the sham-tDCS group at 15-days follow-up (p = 0.014) but not at 2 days post-intervention (p = 0.059). The active-group showed significant improvements over the sham-group after 15 days (p = 0.017). Significant changes were found in CPM between groups in favor of active-tDCS group at 2 days post-intervention (p = 0.002) and at 15 days (p = 0.017). No meaningful differences were observed in BPI or TS.

CONCLUSIONS

tDCS of the primary motor cortex alleviates perceived PD-related pain, reduces pain sensitization, and enhances descending pain inhibition.

SIGNIFICANCE

This is the first study to test and demonstrate the use of tDCS for improving PD-related pain.

Sensitization-Associated Symptoms and Neuropathic-like Features in Patients with Cervical Dystonia and Pain

Background: This exploratory study evaluated the presence of sensitization-associated and neuropathic-like symptoms and identified their association with pressure sensitivity, pain, and disability in patients with cervical dystonia (CD). Methods: Thirty-one patients with CD (74.2% women, age: 61.2 years, SD 10.1) participated. Data collected included clinical variables, the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS), the Central Sensitization Inventory (CSI), the Self-administered Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS), the Hospital Anxiety and Depression Scale (HADS) and the Pittsburgh Sleep Quality Index (PSQI), as well as widespread pressure pain thresholds (PPTs). Results: Patients with CD with pain (n = 20, 64.5%) showed higher scores on the TWSTRS disability subscale and the CSI (p < 0.001), and lower PPTs (p < 0.05). Fifteen patients (15/31, 48%) showed sensitization-associated symptoms (CSI ≥ 40), whereas five of the patients with pain (5/20, 25%) exhibited neuropathic-like symptoms (S-LANSS ≥ 12). The CSI and S-LANSS were positively associated with the TWSTRS, HADS-A and HADS-D, and negatively associated with PPTs. HADS-D and S-LANSS explained 72.5% of the variance of the CSI (r2: 0.725), whereas CSI explained 42.3% of the variance of the S-LANSS (r2: 0.423). Conclusions: Pain is an important source of disability in CD, and may be a consequence of different mechanisms, including sensitization.

Validation of a spring loaded probe for single and repeat pressure pain testing, including public domain specifications for design and manufacture

Temporal summation of pressure pain is technically more challenging than simple pressure pain thresholds. The current study describes the design, manufacture and validation of a simple mechanical test apparatus to assess the temporal summation of deep pressure pain. We release design details into the public domain with the intention of providing free access for researchers especially in low income countries. Utility and validity of the probes were assessed by pressure application in three different experimental setups: A. Identifying potential issues which needed to be addressed to ensure a reliable test procedure (189 tests with 24 testers using four different probes). B. Selecting the most reliable target force curve (one tester conducted 20 tests). C. Estimating classic inter and intra-examiner reliability and comparing probe measures to other QST measures (repeated measures study with counterbalancing). We make recommendations on best use of the probes. Pressure pain thresholds assessed using probes were affected by anatomical test site and testing tool, but not by tester, day or session. Temporal summation of pressure pain was significantly greater than that of a single pressure application. We found no correlation between temporal summation using the probes on the Infra-Spinatus muscle and temporal summation using a pneumatic cuff on the lower leg. The probe was a useful tool for assessing pain intensity and temporal summation of pressure pain intensity, but not for pain thresholds. A number of caveats need to be considered when using the probe, including but not limited to audio cues and target ideal wave function.

Painful Cutaneous Laser Stimulation for Temporal Summation of Pain Assessment

Variability in pain sensitivity arises not only from the differences in peripheral sensory receptors but also from the differences in central nervous system (CNS) pain inhibition and facilitation mechanisms. Temporal summation of pain (TSP) is an experimental protocol commonly used in human studies of pain facilitation but is susceptible to confounding when elicited with the skin-contact thermode, which adds the responses of touch-related Aβ low-threshold mechanoreceptors to nociceptive receptors. In the present study, we evaluate an alternative method involving the use of a contactless cutaneous laser for TSP assessment. We show that repetitive laser stimulations with a one second inter-stimulus interval evoked reliable TSP responses in a significant proportion of healthy subjects (N = 36). Female subjects (N = 18) reported greater TSP responses than male subjects confirming earlier studies of sex differences in central nociceptive excitability. Furthermore, repetitive laser stimulations during TSP induction elicited increased time-frequency electroencephalography (EEG) responses. The present study demonstrates that repetitive laser stimulation may be an alternative to skin-contact methods for TSP assessment in patients and healthy controls. PERSPECTIVE: Temporal summation of pain (TSP) is an experimental protocol commonly used in human studies of pain facilitation. We show that contactless cutaneous laser stimulation is a reliable alternative to the skin contact approaches during TSP assessment.

Effectiveness of different percutaneous electrolysis protocols in the endogenous modulation of pain: A Double-Blinded Randomized Clinical Trial

OBJECTIVE

This randomized clinical trial investigated if the application of percutaneous electrolysis (PE) enhances endogenous pain mechanisms (EPM) when compared with a simple needle application (acting as sham).

METHODS

Forty-six asymptomatic subjects, aged 18-40 years, were randomized into three groups receiving a single ultrasound-guided PE intervention consisting of a needle insertion on the lateral epicondyle: sham (without electrical current), low-intensity (0.3 mA, 90s), or high-intensity (three pulses of 3 mA, 3s) PE. Widespread pressure pain thresholds (PPT), conditioned pain modulation (CPM), and temporal summation (TS) were bilaterally assessed in the lateral epicondyle, bicipital groove, transverse process of C5 and tibialis anterior muscle. Outcomes were obtained by an assessor blinded to the treatment allocation of the subjects.

RESULTS

No significant changes in CPM were observed in either group (omnibus ANOVA all, P > .05). A significant bilateral increase in PPT in the lateral epicondyle in the high intensity group as compared with the sham group was observed (P < .01). A significant decrease of TS in both low (P = .002) and high (P = .049) intensity groups on the right, but not on the left, tibialis anterior was also observed when compared with the sham group.

CONCLUSIONS

One session of PE is able to slightly stimulate modulatory pathways related to nociceptive gain, particularly pressure pain sensitivity and temporal summation but not conditioning pain modulation, when compared with a sham needle intervention, with changes even contralaterally. No significant differences were found between low- and high-intensity doses of percutaneous electrolysis.

Motor Imagery and Pain Processing in Patients With Entrapment Neuropathies: A Cross-sectional Study

OBJECTIVES

(1) To assess the ability to generate both kinesthetic and visual motor imagery in participants with carpal tunnel syndrome (CTS), compared with asymptomatic participants. (2) To assess the influence of psychophysiological and functional variables in the motor imagery process.

METHODS

Twenty patients with unilateral CTS and 18 pain-free individuals were recruited. An observational case-control study with a nonprobability sample was conducted to assess visual and kinesthetic movement imagery ability and psychophysiological variables in patients with CTS compared with asymptomatic participants in a control group. The trial was conducted in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology statement.

RESULTS

CTS patients have more difficulties in generating visual motor images compared with asymptomatic individuals ( t =-2.099; P <0.05; d=0.70). They need more time to complete the mental tasks (visual t =-2.424; P <0.05 and kinesthetic t =-2.200; P <0.05). A negative correlation was found between the ability to imagine and functional deficits ( r =-0.569; P =0.021) for the kinesthetic subscale and temporal summation ( r =-0.515; P <0.5). A positive correlation was found between pain pressure threshold homolateral (homolateral) and time to generate the visual mental images ( r =0.537; P <0.05).

DISCUSSION

CTS patients have greater difficulty generating motor images than asymptomatic individuals. Patients also spend more time during mental tasks. CTS patients present a relationship between temporal summation and the capacity to generate kinesthetic images. In addition, the CST patients presented a correlation between chronometry mental tasking and mechanical hyperalgesia.

Sensitization-associated and neuropathic-associated symptoms in patients with unilateral lateral elbow tendinopathy: an exploratory study

OBJECTIVES

We evaluate the presence of sensitization-associated symptoms and neuropathic pain features and identify if there is an association between these symptoms and pressure pain sensitivity, pain, and related-disability in lateral elbow tendinopathy.

METHODS

Thirty-seven (43% women, age: 45.5 ± 9.5 years) patients with lateral elbow tendinopathy completed: demographic (i.e. age, height, and weight); clinical (i.e. pain history, pain intensity, and Disabilities of the Arm, Shoulder and Hand); and psychophysical (i.e. pressure pain thresholds at the elbow, cervical spine, hand, and leg) outcomes, and the Central Sensitization Inventory and Self-administered Leeds Assessment of Neuropathic Symptoms and Signs questionnaires. Step-wise multiple linear regression models were performed to identify predictors of sensitization- or neuropathic-associated symptoms.

RESULTS

Six (16%) patients exhibited sensitization-associated symptoms (mean: 46.5, SD: 6.1), whereas 13 (35%) patients showed neuropathic-associated symptoms (mean: 13.5; SD: 1.4). Sensitization-associated symptoms were positively associated with neuropathic-associated symptoms (r = 0.538, P = .001) and negatively associated with pressure pain thresholds at the leg (r = -0.378, P = .021). Neuropathic-associated symptoms were positively associated with related-disability (r = 0.479, P = .003) and negatively associated with pressure pain threshold at the elbow (r = -0.394, P = .017). Stepwise regression analyses revealed that neuropathic-like symptoms explained 26.8% of the variance of sensitization symptoms (r2: 0.268), whereas pressure pain threshold at the elbow explained an additional 6.6% to neuropathic-like symptoms (r2: 0.334).

CONCLUSION

This explorative study identified sensitization- and neuropathic-associated symptoms in 16% and 35% of the people with lateral elbow tendinopathy. Sensitization- and neuropathic-associated symptoms were associated. Pressure pain sensitivity at the elbow (peripheral sensitization) was associated with neuropathic -associated symptoms.

Intra- and inter-session reliability of electrical detection and pain thresholds of cutaneous and muscle primary afferents in the lower back of healthy individuals

To advance evidence-based practice and targeted treatments of low back pain (LBP), a better pathophysiological understanding and reliable outcome measures are required. The processing of nociceptive information from deeper somatic structures (e.g., muscle, fascia) might play an essential role in the pathophysiology of LBP. In this study, we measured the intra- and inter-session reliability of electrical detection and pain thresholds of cutaneous and muscle primary afferents of the lower back. Twenty healthy participants attended two study visits separated by 27.7 ± 1.7 days. To determine the location-specific electrical detection threshold (EDT) and pain threshold (EPT), needle electrodes were inserted in the epidermal layer over, and in the lumbar erector spinae muscle. Additionally, established quantitative sensory testing (QST) parameters were assessed. Reliability was determined by differences between measurements, intraclass correlation coefficients (ICC2,1), Bland-Altman plots, and standard error of measurement (SEM). Correspondence between QST parameters and electrical thresholds was assessed using Pearson's correlation. Except for cutaneous EPT, no significant (p ≤ 0.05) intra- and inter-session differences were observed. Excellent intra-session reliability was shown for cutaneous and intramuscular electrical stimulations and all QST parameters (ICC: 0.76-0.93). Inter-session reliabilities were good (ICC: 0.74-0.75) except for electrical stimulations (ICC: 0.08-0.36). Limits of agreement and SEM were higher for inter-session than intra-session. A medium to strong relationship was found between electrical and mechanical/pressure pain thresholds. In conclusion, cutaneous and intramuscular electrical stimulation will potentially close an important diagnostic gap regarding the selective examination of deep tissue afferents and provide location-specific information for the excitability of non-nociceptive and nociceptive afferents.

Does feeling pain help prepare future clinicians to treat pain? A qualitative exploration of a novel experiential approach to teaching health professional students about pain

BACKGROUND AND INTRODUCTION

Pain is a subjective phenomenon, that is often misunderstood and invalidated. Despite recent advances in health professional training, it remains unclear how students should be taught about the subjectivity of pain. This study explored how a novel teaching activity that integrated physiotherapy students' first-hand experiences with laboratory-induced pain could address this gap.

OBJECTIVE

The study aimed to explore the experiences and perceptions of physiotherapy students in relation to a workshop where physiotherapy students experienced laboratory induced pain.

METHODS

We used a descriptive qualitative research design. Eighteen students participated in interviews. Transcripts were analyzed using an inductive conventional content analysis.

RESULTS

We identified four overarching themes: 1) First-hand pain experiences facilitated engagement in learning; 2) Reflecting on these personal and peer pain experiences helped students make sense of pain; 3) The learning activity helped students understand the inherent subjectivity and complexity of pain; and 4) Students saw benefits for clinical practice.

CONCLUSION

Integrating first-hand pain experiences within entry-level physiotherapy training appears to have novel value in helping students understand pain subjectivity. Future research should use robust and controlled designs to explore how this novel approach can be used to facilitate further understanding and empathy within clinical interactions with people living with pain.

Pressure Pain Hypersensitivity and Ultrasound Changes in the Radial Nerve in Patients with Unilateral Lateral Epicondylalgia: A Case-Control Study

Some authors have proposed the potential role of the radial nerve in lateral epicondylalgia. The aims of this study were to investigate the presence of pressure pain hyperalgesia and nerve swelling (increased cross-sectional area) assessed with ultrasound imaging on the radial nerve in people with lateral epicondylalgia, and to investigate if an association exists between pressure pain sensitivity and cross-sectional area. A total of 37 patients with lateral epicondylalgia (43% women, age: 45.5 ± 9.5 years) and 37 age- and sex-matched pain-free controls were recruited for participation. Pressure pain thresholds (PPTs) were assessed bilaterally on the radial nerve at the spiral groove, the arcade of Frohse, and the anatomic snuffbox in a blinded design. Further, the cross-sectional area of the radial nerve at the spiral groove and antecubital fossa was also assessed. The results demonstrated lower PPTs on the radial nerve of the affected side in individuals with lateral epicondylalgia as compared with the unaffected side (p < 0.01) and with both sides in healthy controls (p < 0.001). Additionally, the cross-sectional area of the radial nerve on the affected side in patients was higher compared with the unaffected side (p < 0.01) and both sides in healthy controls (p < 0.001). The cross-sectional area of the radial nerve at the spiral groove was negatively associated with PPTs over the radial nerve at the spiral groove (r = -0.496, p = 0.002) and positively associated with function (r = 0.325, p = 0.045). Our findings revealed generalized pressure pain hyperalgesia and also nerve swelling of the radial nerve in people with lateral epicondylalgia, suggesting the presence of a widespread sensitization of nerve tissues in this population. The radial nerve could represent a potential peripheral drive to initial and maintain altered pain processing in lateral epicondylalgia.

Manual Therapy Effects on Nonspecific Neck Pain Are Not Mediated by Mechanisms Related to Conditioned Pain Modulation: A Randomized Clinical Trial

BACKGROUND

Manual therapy (MT) is a treatment recommended by clinical practice guidelines in the management of patients with neck pain. However, the mechanisms through which MT works remain unknown. The aim of the present study is to investigate if MT is mediated by mechanisms related to conditioned pain modulation (CPM), comparing the effects of painful with a pain-free MT treatment.

METHODS

A two-arm, parallel, randomized controlled clinical trial with concealed allocation and blinding of the outcome assessor was conducted in university students with chronic or recurrent nonspecific neck pain (NSNP). Participants received either a painful or pain-free MT session. Psychophysical variables including pressure pain thresholds, CPM, temporal summation of pain and cold pain intensity were assessed before and immediately after treatment. In addition, changes in neck pain intensity over the following 7 days and self-perceived improvement immediately and 7 days after treatment were assessed.

RESULTS

No significant differences were found between groups in any of the psychophysical variables or in patients' self-perceived improvement. Only a significantly greater decrease in neck pain intensity immediately after treatment was found in the pain-free MT group compared to the painful MT group.

CONCLUSION

The results suggest that the immediate and short-term effects of MT on NSNP are not mediated by CPM-related mechanisms.

The Effects of Recovery Sleep on Experimental Pain

Recent research suggests that recovery sleep (RS) has the potential to restore pain sensitivity and modulation after hyperalgesia due to preceding sleep deprivation. However, it has not yet been systematically examined whether the restoration of these pain parameters is driven by sleep characteristics of RS. Thus, the present study assessed changes in experimental pain during RS after total sleep deprivation (TSD) to test whether RS parameters predicted the restoration of the pain system. Thirty healthy participants completed one night of habitual sleep, one night of TSD and a subsequent recovery night. At-home sleep during baseline and recovery was assessed using portable polysomnography and a questionnaire. Before and after each night pressure pain thresholds (PPTs), temporal pain summation (TSP) and conditioned pain modulation (CPM) were assessed. PPTs decreased after TSD and increased following RS, indicating a restoration of pain sensitivity after hyperalgesia. RS characteristics did not predict this restoration, suggesting other mechanisms (eg, changes in serotonergic activity) underlying the observed pain changes. TSP indicated a lack of effect of experimental sleep manipulations on excitatory processes whereas CPM lacked sufficient reliability to investigate inhibitory processes. Thus, results indicate moderate effects of sleep manipulations on pain sensitivity, but not on pain modulation. PERSPECTIVE: This article highlights the potential of recovery sleep to let pain thresholds return to normal following their decrease after a night of total sleep deprivation. In contrast, endogenous pain modulation (temporal pain summation, conditioned pain modulation) was not affected by sleep deprivation and recovery sleep.

Pressure pain threshold map of thoracolumbar paraspinal muscles after lengthening contractions in young male asymptomatic volunteers

This study aimed to characterise topographic distribution of pressure pain thresholds (PPTs) of thoracolumbar paraspinal muscles and its change after lengthening contractions (LCs) of the back muscles. Using young male asymptomatic participants in Experiment 1, we systematically examined the distribution of PPTs bilaterally in the range of Th1–L5 at measurement points 2 and 4 cm from the midline. PPTs were found to be higher in the lumbar segments of the paraspinal muscles than in the thoracic segments, and in muscles closer to the vertebrae (2 vs. 4 cm from the midline). The PPTs did not differ between the left and right sides in each segment. In Experiment 2, LC was applied by asking a part of participants recruited in Experiment 1 to fall their trunk from a starting position (parallel to the floor) to 40° flexed position, and then made it back as quickly as possible to the starting position. This cycle was repeated until participants could not keep contractions (30 times/set, 25.4 ± 10.6 sets). PPTs of the LC group decreased prominently in the lower thoracic and lumbar segments, and the decrease was more evident 24 h after LC compared to that 48 h after. In contrast, PPTs in the control group without LC remained unchanged. These results provided broad topographic images of PPTs in the thoracolumbar paraspinal muscles of young male participants with and without LC, and the obtained PPT maps could be a useful guide for better treatment of exercise-induced myofascial pain in the lower back.

Analyzing the Interaction between Clinical, Neurophysiological and Psychological Outcomes Underlying Chronic Plantar Heel Pain: A Network Analysis Study

Plantar heel pain (PHP) is one of the most common foot pain conditions in adults. Several biological and psychological factors could be involved in chronic PHP in a complex matrix. However, reciprocal interactions between these factors are unknown. The aim of the present study was to use network analysis to quantify potential multivariate relationships between pain-related, function, clinical, mechanosensitivity, psychological, and health-related variables in individuals with PHP. Demographic (age, gender), pain-related (pain intensity), function, clinical (myofascial trigger points [TrPs]), mechanosensitivity (pressure pain thresholds), psychological (Beck Depression Inventory), and health-related variables (EQ-5D-5L) were collected in 81 PHP patients. Network connectivity analysis was conducted to quantify the adjusted correlations between the modeled variables and to assess their centrality indices. The connectivity network showed local associations between pain-related variables, foot function, and mechanosensitivity. Additionally, associations between quality of life, depression, and pain-related variables were found, while TrPs was associated with quality of life and mechanosensitivity. The node with the highest strength centrality was the worst pain intensity, while mechanosensitivity and worst pain intensity showed the highest closeness and betweenness centrality. This is the first study to apply network modeling to understand the connections between pain-related, function, clinical, mechanosensitivity, psychological, and health-related variables in PHP. The role of pain severity and mechanosensitivity is highlighted and supported by the network. Thus, this study reveals potential factors that could be the target in the management of PHP, promoting a comprehensive and effective therapeutic approach.

Convergent Validity of the Central Sensitization Inventory in Women with Fibromyalgia: Association with Clinical, Psychological and Psychophysical Outcomes

BACKGROUND

To assess the relationship between demographic, clinical, psychological, and pressure pain sensitivity outcomes with the central sensitization inventory (CSI) in female with fibromyalgia (FMS).

METHODS

One hundred twenty-six (n=126) females with FMS completed demographic (age, body mass index, height, weight), clinical (pain history, pain intensity at rest and during daily living activities), psychological (depression/anxiety levels) outcomes and widespread pressure pain sensitivity as well as the central sensitization inventory (CSI). After conducting a multivariable correlation analysis to identify the association between variables, a multiple linear regression model was performed to identify CSI predictors.

RESULTS

The CSI was negatively associated with age (r=-0.262) and PPTs (r ranged from -0.221 to -0.372) and positively associated with anxiety (r=0.541), depression (r=0.415), mean intensity (r=0.305), worst pain (r=0.249), and pain during daily living activities (r= 0.398). The stepwise regression analysis revealed that 47.4% of CSI variance in this sample was explained by anxiety levels (27.8%), PPT at greater trochanter (10.5%), age (1.4%), years with pain (4.8%) and pain during daily living activities (2.9%).

CONCLUSION

The current study found that age, pain intensity at rest and pain during daily living activities, anxiety levels, and pressure pain sensitivity are associated with the CSI (associated sensitization symptoms) in women with FMS.

Endogenous Pain Modulation in Response to a Single Session of Percutaneous Electrolysis in Healthy Population: A Double-Blinded Randomized Clinical Trial

The purpose of this double-blinded randomized controlled trial was to investigate whether percutaneous electrolysis (PE) is able to activate endogenous pain modulation and whether its effects are dependent on the dosage of the galvanic current. A total of 54 asymptomatic subjects aged 18–40 years were randomized into three groups, receiving a single ultrasound-guided PE intervention that consisted of a needle insertion on the lateral epicondyle tendon: sham (without electrical current), low-intensity (0.3 mA, 90 s), and high-intensity (three pulses of 3 mA, 3 s). Widespread pressure pain thresholds (PPT), conditioned pain modulation (CPM), and temporal summation (TS) were assessed in the elbow, shoulder, and leg before and immediately after the intervention. Both high and low intensity PE protocols produced an increase in PPT in the shoulder compared to sham (p = 0.031 and p = 0.027). The sham group presented a significant decrease in the CPM (p = 0.006), and this finding was prevented in PE groups (p = 0.043 and p = 0.025). In addition, high-intensity PE decreased TS respect to sham in the elbow (p = 0.047) and both PE groups reduced TS in the leg (p = 0.036 and p = 0.020) without significant differences compared to sham (p = 0.512). Consequently, a single PE intervention modulated pain processing in local and widespread areas, implying an endogenous pain modulation. The pain processing effect was independent of the dosage administrated.

Detection of altered pain facilitatory and inhibitory mechanisms in patients with knee osteoarthritis by using a simple bedside tool kit (QuantiPain)

Supplemental Digital Content is Available in the Text.

A simple bedside quantitative sensory testing tool kit demonstrated acceptable reliability and assessment validity for detecting altered pain facilitatory and inhibitory mechanisms in patients with painful osteoarthritis.

Purpose:

Altered pain facilitatory and inhibitory mechanisms have been recognized as an important manifestation in patients with chronic pain, and quantitative sensory testing (QST) can act as a proxy for this process. We have recently developed a simple bedside QST tool kit (QuantiPain) for more clinical use. The purpose of this study was to investigate its test–retest reliability and to evaluate its validity compared with the laboratory-based QST protocols in patients with knee osteoarthritis (OA).

Methods:

QuantiPain consists of 3 items: “pressure algometer” (for pressure pain thresholds [PPTs]), “pinprick” (for temporal summation of pain [TSP]), and “conditioning clamp” (for conditioned pain modulation [CPM]). In experiment-A, intrarater and interrater test–retest reliabilities were investigated in 21 young healthy subjects by using interclass correlation coefficient (ICC). In experiment-B, 40 unilateral painful patients with OA and 40 age-matched, healthy control subjects were included to compare the bedside tool kit against the computerized pressure algometry.

Results:

In experiment-A, excellent to moderate intrarater and interrater reliabilities were achieved in PPT and TSP (ICC: 0.60–0.92) while the agreements of CPM were good to poor (ICC: 0.37–0.80). In experiment-B, localized and widespread decrease of PPT, facilitated TSP, and impaired CPM was found by using the bedside tool kit in patients with OA compared with controls (P < 0.05). The data were significantly correlated with the established laboratory-based tools (R = 0.281–0.848, P < 0.05).

Conclusion:

QuantiPain demonstrated acceptable test–retest reliability and assessment validity with the sensitivity to separate patients with painful OA from controls, which has a potential to create more practical approach for quantifying altered pain mechanisms in clinical settings.

Effects of previous experience with dry needling therapy on blinding effectiveness and pain outcomes in people with neck pain: A preliminary sham-controlled study

BACKGROUND

Participants' previous experience with an intervention may be an important variable when conducting sham-controlled trials.

OBJECTIVE

This study explored if previous experience with dry needling (DN) influenced blinding effectiveness and pain outcomes, after the application of DN in patients with neck pain.

DESIGN

A preliminary randomized, sham-controlled study.

METHODS

Participants were randomized to receive a single session of real or sham DN. Previous experience with DN (yes/no) was recorded. Blinding effectiveness was assessed by asking participants to guess their group allocation (real/sham/not sure) 5 min post-intervention. Outcomes including pain intensity, pressure pain thresholds, and self-perceived improvement, were assessed by a blinded assessor at baseline, one- and seven-days post-intervention.

RESULTS

Of 50 patients recruited, 30 had previous experience and 20 did not. Fifty-seven percent (n = 17/30) with previous experience and 35% (n = 7/20) without experience correctly identified their group allocation, but this difference was not significant (χ² = 2.333; P = 0.127). No interaction between previous experience and clinical outcomes were found, except that participants with previous experience receiving real DN showed greater improvements in pain during cervical rotation than those without previous experience at one (Δ -11.5 mm 95%CI -22.0 to -1.0 mm) and seven days (Δ -8.5 mm, -16.00 to -1.0 mm) post-intervention.

CONCLUSIONS

Participants with previous experience were 22% more accurate at identifying their group allocation than those without experience, but the difference was not significant. Previous experience did not influence most clinical outcomes, except for pain intensity after real DN. Future studies evaluating effects of previous experience of DN should include more detailed information of previous experience.

Pain extent is associated with Central Sensitization Inventory but not widespread pressure pain sensitivity or psychological variables in women with fibromyalgia

OBJECTIVE

To investigate the relationship between pain extent, as a clinical sign of central sensitization, and clinical, psychological, and pressure sensitivity in women with fibromyalgia syndrome (FMS).

METHOD

In this study, 126 females with FMS completed demographic (age, gender, body mass index, height, weight), clinical (pain history, and pain intensity at rest and during daily living activities), psychological (depression and anxiety levels), and neurophysiological [pressure pain threshold (PPT)] assessments. The Central Sensitization Inventory (CSI) was also used to collect self-reported symptoms of sensitization. Pain extent and frequency maps were obtained from pain drawings using customized software. After conducting a multivariable correlation analysis to determine the relationships between variables, a stepwise linear regression model analysis was performed to identify variables associated with pain extent.

RESULTS

Pain extent was positively associated with age (r = 0.17), years with pain (r = 0.27), pain during daily life activities (r = 0.27), and CSI (r = 0.42) (all p < 0.05). The stepwise regression analysis revealed that 27.8% of the pain extent was explained by CSI, age, and years with pain.

CONCLUSIONS

This study found that larger pain extent was associated with self-reported outcomes, i.e. CSI, but not neurophysiological outcomes, i.e. PPTs, of sensitization in women with FMS. Older age and a longer history with pain symptoms were also associated with larger pain extent.

Association of Neuropathic Pain Symptoms with Sensitization Related Symptomatology in Women with Fibromyalgia

We aimed to analyze potential correlations between S-LANSS and PainDETECT with proxies for pain sensitization, e.g., the Central Sensitization Inventory (CSI) and pressure pain hyperalgesia (construct validity), pain-related or psychological variables (concurrent validity) in women with fibromyalgia (FMS). One-hundred-and-twenty-six females with FMS completed demographic, pain-related variables, psychological, and sensitization outcomes as well as the S-LANSS and the PainDETECT questionnaires. S-LANSS was positively associated with BMI (r = 0.206), pain intensity (r = 0.206 to 0.298) and CSI score (r = 0.336) and negatively associated with all PPTs (r = -0.180 to -0.336). PainDETECT was negatively associated with age (r = -0.272) and all PPTs (r = -0.226 to -0.378) and positively correlated with pain intensity (r = 0.258 to 0.439), CSI (r = 0.538), anxiety (r = 0.246) and depression (r = 0.258). 51.4% of the S-LANSS was explained by PainDETECT (45.3%), posterior iliac PPT (0.2%) and mastoid PPT (5.9%), whereas the 56.4% of PainDETECT was explained by S-LANSS (43.4%), CSI (10.4%), and pain intensity (2.6%). This study found good convergent association between S-LANSS and PainDETECT in women with FMS. Additionally, S-LANSS was associated with PPTs whereas PainDETECT was associated with pain intensity and CSI, suggesting that both questionnaires assess different spectrums of the neuropathic and pain sensitization components of a condition and hence provide synergistic information.

Signs Indicative of Central Sensitization Are Present but Not Associated with the Central Sensitization Inventory in Patients with Focal Nerve Injury

Objective: Carpal tunnel syndrome (CTS) is the most common focal nerve injury. People with CTS may show alterations in central processing of nociceptive information. It remains unclear whether the central sensitization inventory (CSI) is capable of detecting such altered central pain processing. Methods: Thirty healthy volunteers were matched with 30 people with unilateral CTS from the orthopaedic waitlist. Changes to central pain processing were established through psychophysical sensory testing (bilateral pressure pain thresholds (PPT), conditioned pain modulation, temporal summation) and pain distribution on body charts. Patients also completed pain severity and function questionnaires, psychological questionnaires and the CSI. Results: Compared to healthy volunteers, patients with CTS have lower PPTs over the carpal tunnel bilaterally (t = −4.06, p < 0.0001 ipsilateral and t = −4.58, p < 0.0001 contralateral) and reduced conditioned pain modulation efficacy (t = −7.31, p <0.0001) but no differences in temporal summation (t = 0.52, p = 0.60). The CSI was not associated with psychophysical measures or pain distributions indicative of altered central pain processing. However, there was a correlation of the CSI with the Beck Depression Inventory (r = 0.426; p = 0.019). Conclusion: Patients with CTS show signs of altered central pain mechanisms. The CSI seems unsuitable to detect changes in central pain processing but is rather associated with psychological factors in people with focal nerve injuries.

Both Gender and Agonistic Experience Affect Perceived Pain during the Cold Pressor Test

Background. Differences in pain perception in athletes have recently been highlighted in the literature. Objectives. To compare gender ratings of perceived pain in athletes with low and high agonistic experiences (N = 200) using the Cold Pressor Test (CPT). Methods. A three-way repeated measures ANOVA to assess both the effects of the athletes’ gender and lower vs. higher agonistic experiences in the intensity of perceived pain at the beginning of the cold box hand immersion (L₀) and after a 90 s interval (L₁). Results. There was a statistically significant interaction effect between the level of the agonistic experience and gender in the two moments: p < 0.001; η_p² = 0.266; F(1,49) = 9.771. Simple main effects analysis showed a significative difference for females at L₀: F(1,99) = 93.567, p < 0.025, partial η² = 0.302) and for males at L₁: F(1,99) = 173.420, p < 0.025, partial η² = 0.666. At the initial moment of CPT, the female athletes showed significantly higher perceived intensity than males, regardless of their experience level. After a 90 s interval, a significantly lower pain perception effect associated with the increased competitive experience of male athletes was observed. Female athletes did not appear to benefit from the experience effect on their pain tolerance. Conclusions. The study confirmed a significant difference in pain perception associated with the athletes’ gender and agonistic experience. Separate explanations related to the pattern of pain inhibition and the acquired reduction in pain sensitivity are reported.

Challenges and solutions for application and wider adoption of wearable robots

The science and technology of wearable robots are steadily advancing, and the use of such robots in our everyday life appears to be within reach. Nevertheless, widespread adoption of wearable robots should not be taken for granted, especially since many recent attempts to bring them to real-life applications resulted in mixed outcomes. The aim of this article is to address the current challenges that are limiting the application and wider adoption of wearable robots that are typically worn over the human body. We categorized the challenges into mechanical layout, actuation, sensing, body interface, control, human-robot interfacing and coadaptation, and benchmarking. For each category, we discuss specific challenges and the rationale for why solving them is important, followed by an overview of relevant recent works. We conclude with an opinion that summarizes possible solutions that could contribute to the wider adoption of wearable robots.

Effects of Percutaneous Electrolysis on Endogenous Pain Modulation: A Randomized Controlled Trial Study Protocol

Percutaneous electrolysis consists of the application of a galvanic electrical current throughout an acupuncture needle. It has been previously hypothesized that needling procedures' neurophysiological effects may be related to endogenous pain modulation (EPM). This protocol study describes the design of a double-blind (participant, assessor) randomized controlled trial with the aim to investigate whether percutaneous electrolysis is able to enhance EPM and whether the effect is different between two applications depending on the dosage of the galvanic electrical current. Seventy-two asymptomatic subjects not reporting the presence of pain symptoms the previous 6 months before the study, aged 18-40 years, are randomized into one of four groups: a control group who does not receive any intervention, a needling group who receives a needling intervention without electrical current, a low-intensity percutaneous electrolysis group (0.3 mA × 90 s), and a high-intensity percutaneous electrolysis group (three bouts of 3 mA × 3 s). Needling intervention consists of ultrasound-guided insertion of the needle on the common extensor tendon of the lateral epicondyle. The primary outcome is conditioned pain modulation (CPM), and secondary outcomes include widespread pressure pain sensitivity (pressure pain thresholds (PPT) over the lateral epicondyle, the cervical spine, and the tibialis anterior muscle) and temporal summation (TS). We expected that percutaneous electrolysis would have a greater influence on CPM than an isolated needling procedure and no intervention. In addition, we also postulated that there might be differences in outcome measures depending on the intensity of the electrical current during the percutaneous electrolysis application. This study makes a new contribution to the field of neurophysiological effects of percutaneous electrolysis and needling interventions.

Human pressure tolerance and effects of different padding materials with implications for development of exoskeletons and similar devices

In this study, we assessed pressure tolerance in 16 healthy participants at the thigh, chest, and pelvic area, using different surfaces (1 cm², 20 cm² and different components, used in exoskeleton design), and the effects of different padding materials. Our results showed substantial variability in pressure tolerance among the participants, as well as lower pressure tolerance in females. Regarding the force applied with the exoskeleton components, male participants had higher discomfort threshold (230.3 ± 44.9 N compared to females (116.1 ± 24.6 N) in the chest area. For the applications with 20 cm² surface, the males also showed higher pain threshold at the thigh (89.3 ± 41.8 N vs. 34.6 ± 27.2 N) and the pelvis (97.6 ± 37.0 N vs. 56.1 ± 29.5 N). All padding materials increased pressure tolerance for 10-38% (p < 0.001), but little differences between materials were observed.

Can Patient Expectations Modulate the Short-Term Effects of Dry Needling on Sensitivity Outcomes in Patients with Mechanical Neck Pain? A Randomised Clinical Trial

OBJECTIVE

Dry needling is commonly used for the management of musculoskeletal pain patients. However, the effects of patient expectations are uncertain. Our aim was to determine the effect of patient expectations on short-term clinical outcomes after the application of a single session of dry needling in individuals with neck pain.

METHODS

We conducted a randomized, placebo controlled, clinical trial including fifty patients with mechanical neck pain. Participants received a single session of dry needling or sham needling in a blinded design. Predicted patient expectation was categorized as positive, neutral, or negative. Outcomes including neck pain intensity (visual analogue scale, 0-100), pressure pain thresholds (PPTs) and self-perceived improvement (Global Rating of Change [GROC], -7 to + 7) were assessed at baseline, one day (immediately post), and 7 days (one week) after the intervention by a blinded assessor. Repeated measures ANCOVAs were conducted to assess the effects of real/sham needling adjusted by patient expectations.

RESULTS

Individuals receiving dry needling exhibited better outcomes than those receiving sham needling immediately and one-week after (all, P < 0.01). No general effects of patient expectations, either related to pain recovery or function improvement, were observed on the clinical outcomes, except for a small association of questionable clinical relevance between positive expectations and localized PPTs in the dry needling group.

CONCLUSION

This study did not find a significant effect of predicted patient expectations on the short-term effects of dry needling on pain intensity and PPTs in people with mechanical neck pain.

Effectiveness of Unihemispheric Concurrent Dual-Site Stimulation over M1 and Dorsolateral Prefrontal Cortex Stimulation on Pain Processing: A Triple Blind Cross-Over Control Trial

BACKGROUND

Transcranial direct current stimulation (tDCS) of the motor cortex (M1) produces short-term inhibition of pain. Unihemispheric concurrent dual-site tDCS (UHCDS-tDCS) over the M1 and dorsolateral prefrontal cortex (DLPFC) has greater effects on cortical excitability than when applied alone, although its effect on pain is unknown. The aim of this study was to test if anodal UHCDS-tDCS over the M1 and DLPFC in healthy participants could potentiate conditioned pain modulation (CPM) and diminish pain temporal summation (TS).

METHODS

Thirty participants were randomized to receive a sequence of UHCDS-tDCS, M1-tDCS and sham-tDCS. A 20 min 0.1 mA/cm2 anodal or sham-tDCS intervention was applied to each participant during three test sessions, according to a triple-blind cross-over trial design. For the assessment of pain processing before and after tDCS intervention, the following tests were performed: tourniquet conditioned pain modulation (CPM), pressure pain temporal summation (TS), pressure pain thresholds (PPTs), pressure pain tolerance, mechanosensitivity and cold hyperalgesia. Motor function before and after tDCS intervention was assessed with a dynamometer to measure maximal isometric grip strength.

RESULTS

No statistically significant differences were found between groups for CPM, pressure pain TS, PPT, pressure pain tolerance, neural mechanosensitivity, cold hyperalgesia or grip strength (p > 0.05).

CONCLUSIONS

Neither UHCDS-tDCS nor M1-tDCS facilitated CPM or inhibited TS in healthy subjects following one intervention session.

New Approaches Based on Non-Invasive Brain Stimulation and Mental Representation Techniques Targeting Pain in Parkinson's Disease Patients: Two Study Protocols for Two Randomized Controlled Trials

Pain is an under-reported but prevalent symptom in Parkinson’s Disease (PD), impacting patients’ quality of life. Both pain and PD conditions cause cortical excitability reduction and non-invasive brain stimulation. Mental representation techniques are thought to be able to counteract it, also resulting effectively in chronic pain conditions. We aim to conduct two independent studies in order to evaluate the efficacy of transcranial direct current stimulation (tDCS) and mental representation protocol in the management of pain in PD patients during the ON state: (1) tDCS over the Primary Motor Cortex (M1); and (2) Action Observation (AO) and Motor Imagery (MI) training through a Brain-Computer Interface (BCI) using Virtual Reality (AO + MI-BCI). Both studies will include 32 subjects in a longitudinal prospective parallel randomized controlled trial design under different blinding conditions. The main outcomes will be score changes in King’s Parkinson’s Disease Pain Scale, Brief Pain Inventory, Temporal Summation, Conditioned Pain Modulation, and Pain Pressure Threshold. Assessment will be performed pre-intervention, post-intervention, and 15 days post-intervention, in both ON and OFF states.

Convergent Validity of the Central Sensitization Inventory in Chronic Whiplash-Associated Disorders; Associations with Quantitative Sensory Testing, Pain Intensity, Fatigue, and Psychosocial Factors

OBJECTIVE

Central sensitization is present in different pain conditions, including chronic whiplash-associated disorders. In the absence of a gold standard method of assessment to determine the presence of central sensitization, quantitative sensory testing is currently understood as an optimal proxy. Laboratory sensory testing is, however, not feasible in clinical practice, and the Central Sensitization Inventory was developed as an alternative. The aim of the current study was to evaluate the convergent validity of the Central Sensitization Inventory in chronic whiplash-associated patients by determining the association between the Central Sensitization Inventory and quantitative sensory testing, pain intensity, fatigue, and psychosocial factors.

METHODS

A total of 125 chronic whiplash-associated patients completed multiple questionnaires and were subjected to pressure pain thresholds and temporal summation.

RESULTS

. The Central Sensitization Inventory showed a strong association with constructs of general psychopathology, anxiety, distress, depression, and somatization in chronic whiplash-associated disorders. Moderate correlations were found with fatigue and intrusive and avoidant phenomena after a variety of traumatic events. No significant association was found between the Central Sensitization Inventory and pressure pain thresholds and temporal summation, nor between the Central Sensitization Inventory and other pain measurements.

CONCLUSIONS

Overall, we found that the Central Sensitization Inventory is better in identifying the psychosocial factors related to central sensitization in chronic whiplash-associated disorders than the central nervous system adaptations. Thus, the convergent validity of the Central Sensitization Inventory appears to be only partially present in chronic whiplash-associated disorders.

Patient Profiling Based on Spectral Clustering for an Enhanced Classification of Patients with Tension-Type Headache

Profiling groups of patients in clusters can provide meaningful insights into the features of the population, thus helping to identify people at risk of chronification and the development of specific therapeutic strategies. Our aim was to determine if spectral clustering is able to distinguish subgroups (clusters) of tension-type headache (TTH) patients, identify the profile of each group, and argue about potential different therapeutic interventions. A total of 208 patients (n = 208) with TTH participated. Headache intensity, frequency, and duration were collected with a 4-week diary. Anxiety and depressive levels, headache-related burden, sleep quality, health-related quality of life, pressure pain thresholds (PPTs), dynamic pressure thresholds (DPT) and evoked-pain, and the number of trigger points (TrPs) were evaluated. Spectral clustering was used to identify clusters of patients without any previous assumption. A total of three clusters of patients based on a main difference on headache frequency were identified: one cluster including patients with chronic TTH (cluster 2) and two clusters including patients with episodic TTH (clusters 0–1). Patients in cluster 2 showed worse scores in all outcomes than those in clusters 0–1. A subgroup of patients with episodic TTH exhibited pressure pain hypersensitivity (cluster 0) similarly to those with chronic TTH (cluster 2). Spectral clustering was able to confirm subgrouping of patients with TTH by headache frequency and to identify a group of patients with episodic TTH with higher sensitization, which may need particular attention and specific therapeutic programs for avoiding potential chronification.

Association of dynamic and widespread mechanical sensitivity in cluster headache

We investigated if dynamic pressure pain sensitivity in the symptomatic area is associated with pressure sensitivity in local and distant pain-free areas in cluster headache (CH). A pressure algometry set consisting of 8 rollers with fixed pressure levels ranging from 500 to 5300 g was used to assess dynamic pressure pain sensitivity in men with episodic CH. Each roller was moved from an anterior-to-posterior direction over the temporalis muscle. The load level of the first painful roller was considered the dynamic pain threshold (DPT). Further, pain elicited during DPT (roller evoked pain) was also assessed. We used a pressure algometer to determine pressure pain thresholds (PPTs) over the temporalis muscle, C5/C6 joint, second metacarpal, and tibialis anterior. Patients were assessed in an asymptomatic (remission) phase, at least 6 months after their last cluster period and without taking pharmacological treatment. Forty men with episodic CH (mean age 42 years) were included. Both outcomes, DPTs (r = 0.781, P < 0.001) and roller-evoked pain (r = 0.586; P < 0.001) were bilaterally correlated. Further, DPT, but not roller-evoked pain, was moderately associated with PPTs measured at the symptomatic (temporalis: r = 0.665, P < 0.001) and distant pain-free (C5-C6 joint: r = 0.389, P = 0.013; second metacarpal: r = 0.551, P < 0.001; and, tibialis anterior: r = 0.308, P = 0.035) points. Dynamic pressure sensitivity in the trigeminal area was correlated to pressure pain sensitivity at both symptomatic and distant pain-free areas in men with CH supporting the use of roller pressure algometry. Dynamic pressure algometry may be a new tool for assessing the status of sensitization in primary headaches.

Reliability of temporal summation, thermal and pressure pain thresholds in a healthy cohort and musculoskeletal trauma population

Traumatic injuries affect approximately 978 million people worldwide with 56.2 million requiring inpatient care. Quantitative sensory testing (QST) can be useful in predicting outcome following trauma, however the reliability of multiple QST including temporal summation (TS), heat and cold pain thresholds (HPT, CPT) and pressure pain thresholds (PPT) is unknown. We assessed intra (between day) and inter-rater (within day) reliability of QST in asymptomatic participants (n = 21), and inter-rater (within day) reliability in participants presenting with acute musculoskeletal trauma (n = 25). Intra-class correlations with 95% confidence intervals (ICC 3,2), standard error of measurement (SEM) and Bland Altman Plots for limits of agreement were calculated. For asymptomatic participants, reliability was good to excellent for HPT (ICC range 0.76–0.95), moderate to good for PPT (ICC range 0.52–0.93), with one site rated poor (ICC 0.41), and poor to excellent for TS scores (ICC range 0.20–0.91). For musculoskeletal trauma participants reliability was good to excellent for HPT and PPT (ICC range 0.76–0.86), and moderate to good reliability for TS (ICC range 0.69–0.91). SEM for HPT for both sets of participants was ~1°C and an average of 7N for asymptomatic participants and less than 8N for acute musculoskeletal trauma participants for PPT. This study demonstrates moderate to excellent intra and inter-rater reliability for HPT and PPT in asymptomatic participants and good to excellent inter-rater reliability for acute musculoskeletal trauma participants, with TS showing more variability for both sets of participants. This study provides foundations for future work evaluating the sensory function over time following acute musculoskeletal trauma.

Effect of transcutaneous electrical nerve stimulation on jaw movement-evoked pain in patients with TMJ disc displacement without reduction and healthy controls

Objective: Transcutaneous electrical nerve stimulation (TENS) may serve as non-invasive intervention for painful temporomandibular disorders (TMD) to improve jaw motor function, but its efficacy is still debated. This parallel study evaluated the effect of TENS on pain and movement patterns after repeated jaw movements in patients with painful temporomandibular joints (TMJ) and disc displacement without reduction (DDwoR), and compared with healthy controls.Material and Methods: 20 patients with TMJ pain and DDwoR and 20 age- and gender-matched healthy volunteers were randomly assigned to TENS/sham TENS (sTENS) intervention groups in a block design (10 in each group). Participants performed 20 repeated jaw movements (4 x 5 sessions), and reported pain intensity on a 0-10 Numerical Rating Scale (NRS) subsequently both before and after the intervention. Data were tested by repeated measures analysis of variance (ANOVA).Results: Significant increase of pain intensity and reduction of opening range were shown within repeated jaw movements in TMJ pain patients in contrast to healthy participants (p ≤ .001). Pain was significantly reduced during repeated open-close (p = .007), fast open-close (p = .016) and horizontal movements (p = .023), accompanied with increased opening range (p = .033) and open-close velocity (p = .019) with TENS intervention when compared with sTENS group (p > .05) in TMJ pain patients.Conclusions: This study indicated that movement-evoked pain was reduced either spontaneously or by sTENS in TMJ pain patients with DDwoR, and interestingly, that TENS could attenuate movement-evoked pain and improve jaw motor function during repeated jaw movements. The findings may have implications for TENS treatment in TMJ pain patients with DDwoR.

Inter- and intra-observer reliability of quantitative sensory testing performed with the SMall animal ALGOmeter (SMALGO) to evaluate pain associated with feline gingivostomatitis

OBJECTIVES

The aim of this study was to evaluate the inter- and intra-observer reliability of quantitative sensory testing performed with the SMall animal ALGOmeter (SMALGO) in healthy cats and in cats with chronic gingivostomatitis (CGS), and to evaluate the SMALGO as a tool to detect and quantify pain in cats with CGS.

METHODS

Thirty cats from a private shelter were included and assigned to one of two groups: group C (healthy cats; n = 15) or group CGS (cats with CGS; n = 15). In all cats the mechanical thresholds were measured with the SMALGO, with the sensor tip applied to the superior lip above the canine root, by two independent investigators (A, experienced; B, unexperienced), on two different occasions (day 1 and day 2) with a 24 h interval. A CGS scale was used in the diseased cats to assess the severity of the condition. For the reliability analysis, intra-class correlation coefficients (ICCs) were calculated. Other statistical tests used were Pearson correlation coefficient and a paired t-test.

RESULTS

The inter- and intra-observer levels of agreement were fair (ICC = 0.50) and good, respectively (ICC = 0.73 for investigator A; ICC = 0.60 for investigator B). However, the thresholds measured in healthy cats (169 ± 59 g) did not differ from those obtained from diseased cats (156 ± 82 g; P = 0.35). There was no correlation between the scores of the CGS scale and the thresholds measured in diseased cats (Pearson correlation coefficient = 0.047; P = 0.87).

CONCLUSIONS AND RELEVANCE

Quantitative sensory testing performed with the SMALGO in cats is repeatable and reliable, regardless of the expertise of the investigator. However, the findings of this study suggest that the mechanical thresholds measured with the SMALGO may not be a valuable indicator of pain in cats with CGS.

Pain Expansion and Severity Reflect Central Sensitization in Primary Care Patients with Greater Trochanteric Pain Syndrome

OBJECTIVES

The aims of this study were twofold: 1) to evaluate the differences in pain sensitivity of patients with greater trochanteric pain syndrome (GTPS) and 2) to examine the association between pain expansion, pain severity, and pain-related central sensitization somatosensory variables in patients with GTPS.

STUDY DESIGN

A cross-sectional study.

SETTING

Primary health care centers.

SUBJECTS

The sample consisted of 49 participants with a mean age of 48.28 ± 8.13 years and included eight males (16.3%) and 41 females (83.7%).

METHODS

Conditioned pain modulation (CPM), pain location, temporal summation, pressure pain detection threshold (PPDT), and pain intensity were recorded. Pain severity was determined with the Graded Chronic Pain Scale (GCPS).

RESULTS

Several participants (34.7%) showed a negative conditioned pain modulation and a statistically significant negative moderate correlation (P < 0.05; r = -0.316) between conditioned pain modulation and right view percentage of pain location. Temporal summation at the major trochanter showed a statistically significant low negative correlation (P < 0.05; r = -0.298). The GCPS exhibited a statistically significant moderately positive correlation (P < 0.01; r = 0.467) with the PPDT at the trochanter and a significant correlation with the postero-superior iliac spine (P < 0.01; r = 0.515) and epicondyle (P < 0.01; r = 0.566).

CONCLUSIONS

Patients with GTPS presented altered CPM, a relationship with more pain areas associated with negative CPM, and a positive association between pain severity and mechanical hyperalgesia at remote sites. Thus, physicians could apply these outcome measurements to assess primary care patients with GTPS and determine the central sensitization presence to prescribe adequate multimodal treatment approaches.

Variables associated with use of symptomatic medication during a headache attack in individuals with tension-type headache: a European study

Background

Pharmacological treatment of patients with tension-type headache (TTH) includes symptomatic (acute) and prophylactic (preventive) medication. No previous study has investigated variables associated to symptomatic medication intake in TTH. Our aim was to assess the association of clinical, psychological and neurophysiological outcomes with the use and timing of the use of symptomatic medication in TTH.

Methods

A longitudinal observational study was conducted. One hundred and sixty-eight (n = 168) patients with TTH participated. Pain features of the headache (intensity, frequency, duration), burden of headache (Headache Disability Inventory), sleep quality (Pittsburgh Sleep Quality Index), anxiety/depression (Hospital Anxiety and Depression Scale), trait/state anxiety levels (State-Trait Anxiety Inventory), and bilateral pressure pain thresholds on the temporalis, C5-C6 joint, second metacarpal and tibialis anterior were assessed. Symptomatic medication intake was also collected for a 6-months follow-up period. Differences between patients using or not using symptomatic medication, depending on self-perceived effectiveness, and time (early during an attack, i.e., the first 5 min, or when headache attack is intense) when the symptomatic medication was taken were calculated.

Results

One hundred and thirty-six (n = 136, 80%) reported symptomatic medication intake for headache (73% NSAIDs). Sixteen (12%) reported no pain relief, 81 (59%) experienced moderate relief and 39 (29%) total pain relief. Fifty-eight (43%) took ‘early medication’ whereas 78 (57%) took ‘late medication’. Patients taking symptomatic medication in general showed lower headache frequency and lower depressive levels than those patients not taking medication. Symptomatic medication was more effective in patients with lower headache history, frequency, and duration, and lower emotional burden. No differences in pressure pain sensitivity were found depending on the self-perceived effectiveness of medication. Patients taking ‘late symptomatic’ medication exhibited more widespread pressure pain sensitivity than those taking ‘early medication’.

Conclusions

This study found that the effectiveness of symptomatic medication was associated with better headache parameters (history, frequency, or duration) and lower emotional burden. Further, consuming early symptomatic medication at the beginning of a headache attack (the first 5 min) could limit widespread pressure pain sensitivity.

Sleep, Experimental Pain and Clinical Pain in Patients with Chronic Musculoskeletal Pain and Healthy Controls

Purpose

Everyday variations in night sleep in healthy pain-free subjects are at most weakly associated with pain, whereas strong alterations (eg, sleep deprivation, insomnia) lead to hyperalgesic pain changes. Since it remains unclear how substantial sleep alterations need to be in order to affect the pain system and lead to a coupling of both functions, the present study aimed at providing sufficient variance for co-variance analyses by examining a sample consisting of both healthy subjects and chronic pain patients.

Methods

A sample of 20 chronic musculoskeletal pain patients and 20 healthy controls was examined. This sample was assumed to show high inter-individual variability in sleep and pain, as pain patients frequently report sleep disturbances, whereas healthy subjects were required to be pain-free and normal sleepers. Sleep of two non-consecutive nights was measured using portable polysomnography and questionnaires. Experimental pain parameters (pressure pain thresholds (PPT), temporal summation of pain (TSP), conditioned pain modulation (CPM)) and situational pain catastrophizing (SCQ) were assessed in laboratory sessions before and after sleep. Pain patients’ clinical pain was assessed via questionnaire.

Results

As expected, both groups differed in several sleep parameters (reduced total sleep time and sleep efficiency, more time awake after sleep onset, lower subjective sleep quality in the patients) and in a few pain parameters (lower PPTs in the patients). In contrast, no differences were found in TSP, CPM, and SCQ. Contrary to our expectations, regression analyses indicated no prediction of overnight pain changes by sleep parameters.

Conclusion

Since sleep parameters were hardly apt to predict overnight pain changes, this leaves the association of both systems mainly unproven when using between-subject variance for verification.

Spatial Distribution of Temporalis Pressure Pain Sensitivity in Men with Episodic Cluster Headache

(1) Background: Spatial changes in pressure sensitivity have been described in migraine and tension-type headaches. Our aim was to determine differences in the spatial distribution of pressure pain sensitivity of the temporalis muscle between cluster headache (CH) patients and headache-free controls; (2) Methods: Pressure pain thresholds (PPTs) were determined over nine points covering the temporalis muscle in 40 men with episodic CH and 40 matched headache-free controls in a blinded fashion. Topographical pressure pain sensitivity maps were constructed based on interpolation of the PPTs. Patients were evaluated in a pain-free period (remission phase), at least 3 months from the last attack and without medication; (3) Results: The analysis of covariance (ANCOVA) found significant difference between points (F = 21.887; P < 0.001) and groups (F = 24.416; P = 0.602), but not between sides (F = 0.440; P = 0.508). No effect of depression (F = 0.014; P = 0.907) or anxiety (F = 0.696; F = 0.407) was observed. A post-hoc analysis revealed: 1) lower PPTs at all points in patients than in controls, 2) an anterior-to-posterior gradient in patients but not in controls, with lower PPTs located in the anterior column. Large between-groups effects were shown in all points (standardized mean difference, SMD > 0.8); (4) Conclusions: Bilateral pressure pain hypersensitivity to pressure pain in the temporalis muscle and an anterior-to-posterior gradient to pressure pain was observed in men with episodic CH.

Inter-rater and inter-device reliability of mechanical thresholds measurement with the Electronic von Frey Anaesthesiometer and the SMALGO in healthy cats

OBJECTIVES

The aim of this study was to compare the Electronic von Frey Anaesthesiometer (EVF) and the Small Animal ALGOmeter (SMALGO), used to measure sensory thresholds in 13 healthy cats at both the stifle and the lumbosacral joint, in terms of inter-rater and inter-device reliability.

METHODS

Two independent observers carried out the sets of measurements in a randomised order, with a 45 min interval between them, in each cat. The inter-rater and inter-device reliability were evaluated by calculating the inter-rater correlation coefficient (ICC) for each pair of measurements. The Bland-Altman method was used as an additional tool to assess the level of agreement between the two algometers.

RESULTS

The mean ± SD sensory thresholds measured with the EVF were 311 ± 116 g and 378 ± 178 g for the stifle and for the lumbosacral junction, respectively, whereas those measured with the SMALGO were 391 ±172 g and 476 ± 172 g. The inter-rater reliability was fair (ICC >0.4) for each pair of measurements except those taken at the level of the stifle with the SMALGO, for which the level of agreement between observers A and B was poor (ICC = 0.01). The inter-device reliability was good (ICC = 0.73; P = 0.001). The repetition of the measurements affected reliability, as the thresholds obtained after the 45 min break were consistently lower than those measured during the first part of the trial (P = 0.02).

CONCLUSIONS AND RELEVANCE

The EVF and the SMALGO may be used interchangeably in cats, especially when the area to be tested is the lumbosacral joint. However, when the thresholds are measured at the stifle, the inter-observer reliability is better with the EVF than with the SMALGO. The reliability decreases when the measurements are repeated within a short time interval, suggesting a limited clinical applicability of quantitative sensory testing with both algometers in cats.

Topographical Pressure Pain Sensitivity Maps of the Feet Reveal Bilateral Pain Sensitivity in Patients With Unilateral Plantar Heel Pain

BACKGROUND

Plantar heel pain is one of the most common foot pain conditions treated by health care providers.

OBJECTIVES

To investigate differences in topographical pressure pain sensitivity maps of the feet between patients with unilateral plantar heel pain and healthy individuals, and to determine the relationship between topographical pressure maps, pain intensity, disability, and fascia thickness.

METHODS

Thirty-five patients with unilateral plantar heel pain and 35 matched healthy controls participated in this cross-sectional, case-control study. Pressure pain thresholds (PPTs) were assessed over 7 plantar locations on each foot. Topographical pressure pain sensitivity maps of the plantar region were generated using the averaged PPT of each assessed point. Pain and related disability were assessed with a numeric pain-rating scale (0-10) and the Foot and Ankle Ability Measure, respectively. Plantar fascia thickness was measured via ultrasound. All outcomes were obtained by an assessor blinded to the participants' condition.

RESULTS

Topographical pressure sensitivity maps revealed lower bilateral PPTs in patients with plantar heel pain compared to healthy controls, and a higher PPT on the calcaneus bone (P<.01). Women had lower PPTs than men in all areas (P<.001). Individuals with plantar heel pain also had thicker fascia, but only on the affected side, compared to healthy controls. Higher pressure pain sensitivity in the foot was associated with higher pain intensity at first step in the morning and thicker fascia at the calcaneus bone.

CONCLUSION

People with unilateral plantar heel pain had generalized bilateral pressure pain sensitivity in the plantar region of the foot. Greater pain intensity and fascia thickness were associated with higher pressure pain sensitivity in people with plantar heel pain.

LEVEL OF EVIDENCE

Case-control study, level 4. J Orthop Sports Phys Ther 2019;49(9):640-646. Epub 26 Mar 2019. doi:10.2519/jospt.2019.8813.