Subgroups based on thermal and pressure pain thresholds in women with chronic whiplash display differences in clinical presentation - an explorative study

Triad Multisystem Phenotype with High-risk for Developing Temporomandibular Disorders- Characteristics and Potential Pathophysiology Results from the OPPERA Dataset

ABSTRACT

A multisystem phenotype with the Triad of bodily pain, psychological distress, and sleep disturbance was found to have high risk for developing initial onset of painful temporomandibular disorders (TMDs) in the multicenter Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) dataset. In this study, we systemically examined phenotypic characteristics and explored potential pathophysiology in quantitative sensory testing (QST) and autonomic nervous system (ANS) domains in this multisystem Triad phenotype. Secondary analysis was performed on 1199 non-Triad and 154 Triad TMD-free OPPERA enrollees at baseline. Results indicate that prior to developing TMDs, the Triad phenotype demonstrated both orofacial and systemic signs and symptoms that can only be captured through multisystem assessment. In addition, we found significantly lower resting heart rate variability and higher resting heart rate in the Triad phenotype as compared to the non-Triad group. However, pain sensitivity measured by QST was not different between groups. These findings highlight the importance of whole-person multisystem assessment at the stage prior to developing complex pain conditions such as TMDs, and suggest that, in addition to a "tissue damage monitor", pain should be considered in a broader context, such as a component within a "distress monitoring system" at the whole-person level when multisystem issues co-present. Therefore, the presence or absence of multisystem issues may carry critical information when searching for disease mechanisms and developing mechanism-based intervention and prevention strategies for TMDs and related pain conditions. Cardiovascular autonomic function should be further researched when multisystem issues co-present prior to developing TMDs.

Changes in Pain Sensitivity and Conditioned Pain Modulation During Recovery From Whiplash-associated Disorders

OBJECTIVE

The objective of this study was to investigate the pain-sensory profile of patients with whiplash-associated disorders (WADs) prior and post 2 weeks of standardized rehabilitation and after a 6-month follow-up.

MATERIALS AND METHODS

Twenty-two WAD participants (grade II; 14 women) and 22 sex-matched and age-matched healthy pain-free controls were enrolled. Pressure pain thresholds (PPTs) were assessed at local and distal muscles. Conditioned pain modulation (CPM) of PPTs was assessed using cuff pressure around the upper arm. Referred area of pain following supra-threshold pressure stimulation of the infraspinatus muscle was recorded on a body chart. Psychometric variables (pain intensity, area of perceived pain, pain catastrophizing, kinesiophobia, sleep problems, and depression level) were assessed. WAD group additionally completed the Neck Disability Index.

RESULTS

The WAD group demonstrated lower local PPTs compared with controls at all time points (P<0.05) and lower distal PPTs at baseline and at 2 weeks when compared with 6 months (within-group) (P<0.05). The WAD group had a reduced CPM response and larger induced referred pain areas compared with controls (P<0.05), while no within-group changes were observed at any time point. The WAD group reported higher pain intensity and perceived area of pain compared with controls at all time points (P<0.05) and a mean Neck Disability Index score of 41% at baseline, 16% at 2 weeks, and 4% at 6 months. Furthermore, the WAD group reported improvements in all other psychometric variables (P<0.05), although only pain catastrophizing levels were comparable to controls at 2 weeks.

DISCUSSION

PPTs but not CPM improved in the WAD group and were comparable to controls following 2 weeks following standardized rehabilitation, indicating that normalization of CPM may not be required to recover from WAD.

Exploration of Functional Connectivity Changes Previously Reported in Fibromyalgia and Their Relation to Psychological Distress and Pain Measures

Neural functional connectivity changes in the default mode network (DMN), Central executive network (CEN), and insula have been implicated in fibromyalgia (FM) but stem from a sparse set of small-scale studies with limited power for the investigation of confounding effects. We investigated whether anxiety, depression, pain sensitivity, and pain intensity modulated functional connectivity related to DMN nodes, CEN nodes, and insula. Resting-state functional magnetic resonance imaging data were collected from 31 females with FM and 28 age-matched healthy controls. Connectivity was analysed with a region-based connectivity analysis between DMN nodes in ventromedial prefrontal cortex (vmPFC) and posterior cingulate cortex, CEN nodes in the intraparietal sulcus (IPS), and bilateral insula. FM patients displayed significantly higher levels of anxiety and depressive symptoms than controls. The right IPS node of the CEN showed a higher level of connectivity strength with right insula in FM with higher pain intensity compared to controls. More anxiety symptoms in FM correlated with higher levels of connectivity strength between the vmPFC DMN node and right sensorimotor cortex. These findings support the theory of altered insular connectivity in FM and also suggest altered IPS connectivity in FM. Interestingly, no change in insular connectivity with DMN was observed.

Pain intensity and pressure pain thresholds after a light dynamic physical load in patients with chronic neck-shoulder pain

Background

To investigate the development of pain intensity and pressure pain thresholds during and 24 h after a light dynamic physical load among patients with chronic neck-shoulder pain.

Methods

Twenty-six patients with chronic neck-shoulder pain and 12 healthy controls were included. The participants arm-cycled on an ergometer. Effort was rated with the Borg Rating of Perceived Exertion scale (RPE), and pain intensity with an numeric rating scale (NRS). Pressure pain thresholds were measured by an algometer. Participants started a pain diary 1 week before the physical exercise and continued until 1 week after. Pain intensity was assessed before, during and the following two evenings after arm-cycling. Pressure pain thresholds were assessed before, 15 min after, 105 min after and 24 h after.

Results

The chronic pain group showed increased pain intensity during, and the following two evenings after the arm cycling, and decreased pain thresholds immediately after the arm cycling involving painful regions. In the patient group there were no impact on pain thresholds in the neck the following day.

Conclusions

Patients with chronic neck-shoulder pain reported increased pain intensity during and in the evenings after a light dynamic load involving painful regions. In addition, they showed decreased pain thresholds close to the exercise, indicating mechanical hyperalgesia.

Selective cold pain inhibition by targeted block of TRPM8-expressing neurons with quaternary lidocaine derivative QX-314

Treatment of pain with local anesthetics leads to an unfavorable decrease in general sensory acuity due to their indiscriminate block of both pain sensing (nociceptors) and non-pain sensing nerves. However, the cell impermeant lidocaine derivative QX-314 can be selectively targeted to only nociceptors by permeation through ligand-gated cation channels. Here we show that localized injection of QX-314 with agonists for the menthol receptor TRPM8 specifically blocks cold-evoked behaviors in mice, including cold allodynia and hyperalgesia. Remarkably, cooling stimuli also promotes QX-314-mediated inhibition of cold behaviors, and can be used to block cold allodynia, while retaining relatively normal cold sensation. The effects of both agonist and thermally evoked uptake of QX-314 are TRPM8-dependent, results demonstrating an effective approach to treat localized cold pain without altering general somatosensation.

Serra Ongun, Angela Sarkisian and David McKemy show that localized co-injection of lidocaine derivative QX-314 and receptor agonists is able to block cold sensitivity in mice in a targeted way, with implications for treating cold pain associated with injury and disease.

Cluster subgroups based on overall pressure pain sensitivity and psychosocial factors in chronic musculoskeletal pain: Differences in clinical outcomes

Objective: We aimed to empirically derive psychosocial and pain sensitivity subgroups using cluster analysis within a sample of individuals with chronic musculoskeletal pain (CMP) and to investigate derived subgroups for differences in pain and disability outcomes. Methods: Eighty female participants with CMP answered psychosocial and disability scales and were assessed for pressure pain sensitivity. A cluster analysis was used to derive subgroups, and analysis of variance (ANOVA) was used to investigate differences between subgroups. Results: Psychosocial factors (kinesiophobia, pain catastrophizing, anxiety, and depression) and overall pressure pain threshold (PPT) were entered into the cluster analysis. Three subgroups were empirically derived: cluster 1 (high pain sensitivity and high psychosocial distress; n = 12) characterized by low overall PPT and high psychosocial scores; cluster 2 (high pain sensitivity and intermediate psychosocial distress; n = 39) characterized by low overall PPT and intermediate psychosocial scores; and cluster 3 (low pain sensitivity and low psychosocial distress; n = 29) characterized by high overall PPT and low psychosocial scores compared to the other subgroups. Cluster 1 showed higher values for mean pain intensity (F_(2,77) = 10.58, p < 0.001) compared with cluster 3, and cluster 1 showed higher values for disability (F_(2,77) = 3.81, p = 0.03) compared with both clusters 2 and 3. Conclusions: Only cluster 1 was distinct from cluster 3 according to both pain and disability outcomes. Pain catastrophizing, depression, and anxiety were the psychosocial variables that best differentiated the subgroups. Overall, these results call attention to the importance of considering pain sensitivity and psychosocial variables to obtain a more comprehensive characterization of CMP patients' subtypes.

Altered somatosensory profile according to quantitative sensory testing in patients with degenerative lumbar spine disorders scheduled for surgery

Background

Somatosensory profiling in affected and non-affected body regions can strengthen our insight regarding the underlying pain mechanisms, which can be valuable in treatment decision making and to improve outcomes, in patients with degenerative lumbar spine disorders pre-surgery. The aim was to describe somatosensory profiles in patients with degenerative lumbar spine disorders, to identify the proportion with altered somatosensory profile, and to analyze demographic characteristics, self-reported function, pain, and health pre- and 3 months post-surgery.

Methods

In this prospective cohort study in a Spine Clinic, 105 patients scheduled for surgery for spinal stenosis, disc herniation, degenerative disc disease, or spondylolisthesis were consecutively recruited. Exclusion criteria were; indication for acute surgery or previous surgery at the same spinal level or severe grade of pathology. Quantitative sensory testing (QST) and self-reported function, pain, and health was measured pre- and 3 months post-surgery. The somatosensory profile included cold detection threshold, warmth detection threshold, cold pain threshold, heat pain threshold and pressure pain threshold in affected and non-affected body regions.

Results

On a group level, the patients’ somatosensory profiles were within the 95% confidence interval (CI) from normative reference data means. On an individual level, an altered somatosensory profile was defined as having two or more body regions (including a non-affected region) with QST values outside of normal ranges for reference data. The 23 patients (22%) with altered somatosensory profiles, with mostly loss of function, were older (P = 0.031), more often female (P = 0.005), had higher back and leg pain (P = 0.016, 0.020), lower mental health component summary score (SF-36 MCS) (P = 0.004) and larger pain distribution (P = 0.047), compared to others in the cohort. Post-surgery there was a tendency to worse pain, function and health in the group with altered somatosensory profile pre-surgery.

Conclusions

On a group level, patients with degenerative lumbar spine disorders scheduled for surgery were within normal range for the QST measurements compared to reference values. On an individual level, an altered somatosensory profile outside of normal range in both affected and non-affected body regions occurred in 22% of patients, which may indicate disturbed somatosensory function. Those patients had mostly loss of sensory function and had worse self-reported outcome pre-surgery, compared to the rest of the cohort. Future prospective studies are needed to further examine whether these dimensions can be useful in predicting post-surgery outcome and guide need of additional treatments.

Cellular permeation of large molecules mediated by TRPM8 channels

While most membrane channels are only capable of passing small ions, certain non-selective cation channels have been recently shown to have the capacity to permeate large cations. The mechanisms underlying large molecule permeation are unclear, but this property has been exploited pharmacologically to target molecules, such as nerve conduction blockers, to specific subsets of pain-sensing neurons (nociceptors) expressing the heat-gated transient receptor potential (TRP) channel TRPV1. However, it is not clear if the principal mediator of cold stimuli TRPM8 is capable of mediating the permeation large molecules across cell membranes, suggesting that TRPM8-positive nerves cannot be similarly targeted. Here we show that both heterologous cells and native sensory neurons expressing TRPM8 channels allow the permeation of the large fluorescent cation Po-Pro3. Po-Pro3 influx is blocked by TRPM8-specific antagonism and when channel activity is desensitized. The effects of the potent agonist WS-12 are TRPM8-specific and dye uptake mediated by TRPM8 channels is similar to that observed with TRPV1. Lastly, we find that as with TRPV1, activation of TRPM8 channels can be used as a means to target intracellular uptake of cell-impermeable sodium channel blockers. In a neuronal cell line expressing TRPM8 channels, voltage-gated sodium currents are blocked in the presence of the cell-impermeable, charged lidocaine derivative QX-314 and WS-12. These results show that the ability of somatosensory TRP channels to promote the permeation of large cations also includes TRPM8, thereby suggesting that novel approaches to alter cold pain can also be employed via conduction block in TRPM8-positive sensory neurons.

The Role of the Trigemino Cervical Complex in Chronic Whiplash Associated Headache: A Cross Sectional Study

OBJECTIVE

To investigate signs of central sensitization in a cohort of patients with chronic whiplash associated headache (CWAH).

BACKGROUND

Central sensitization is one of the mechanisms leading to chronicity of primary headache, and thus might contribute to CWAH. However, the pathophysiological mechanism of CWAH is poorly understood and whether it is simply an expression of the primary headache or has a distinct pathogenesis remains unclear. Thus, the factors involved in the genesis of CWAH require further investigation.

METHODS

Twenty-two patients with CWAH (20 females, 2 males; age 25-50 years, mean age 36.3 years) and 25 asymptomatic participants (13 females, 12 males; age 18-50 years, mean age 35.6 years) rated glare and light-induced discomfort in response to light from an ophthalmoscope. Hyperalgesia evoked by a pressure algometer was assessed bilaterally on the forehead, temples, occipital base, and the middle phalanx of the third finger. The number, latency, area under the curve, and recovery cycle of nociceptive blink reflexes elicited by a supraorbital electrical stimulus were also recorded.

RESULTS

Eight and 6 CWAH patients had migrainous and tension-type headache (TTH) profiles, respectively; the remainder had features attributable to both migraine and TTH. Patients in the whiplash group reported significantly greater light-induced pain than controls (8.48 ± .35 vs 6.66 ± .43 on a 0-10 scale; P = .001). The CWAH patients reported significantly lower pressure pain thresholds at all sites. For stimuli delivered at 20 second intervals, whiplash patients were more responsive than controls (4.8 ± .6 blinks vs 3.0 ± .6 blinks in a block of 10 stimuli; P = .036). While R2 latencies and the area under the curve for the 20 second interval trials were comparable in both groups, there was a significant reduction of the area under the curve from the first to the second of the 2-second interval trials only in controls (99 ± 8% of baseline in whiplash patients vs 68 ± 7% in controls; P = .009). The recovery cycle was comparable for both groups.

CONCLUSIONS

Our results corroborate previous findings of mechanical hypersensitivity and photophobia in CWAH patients. The neurophysiological data provide further evidence for hyperexcitability in central nociceptive pathways, and endorse the hypothesis that CWAH may be driven by central sensitization.

Clinical Ratings of Pain Sensitivity Correlate With Quantitative Measures in People With Chronic Neck Pain and Healthy Controls: Cross-Sectional Study

BACKGROUND

Correlations between clinical and quantitative measures of pain sensitivity are poor, making it difficult for clinicians to detect people with pain sensitivity. Clinical detection of pain sensitivity is important because these people have a different prognosis and may require different treatment.

OBJECTIVE

The purpose of this study was to investigate the relationship between clinical and quantitative measures of pain sensitivity across individuals with and without neck pain.

METHODS

This cross-sectional study included 40 participants with chronic neck pain and 40 age- and sex-matched controls. Participants underwent quantitative sensory testing of cold pain thresholds (CPTs) and pressure pain thresholds (PPTs). Clinical tests for pain sensitivity were the ice pain test and the pressure pain test. All tests were undertaken at standardized local (neck and upper trapezius muscles) and remote (wrist and tibialis anterior muscles) sites. Median and interquartile range (IQR) were calculated for neck pain and control groups, and parametric and nonparametric tests were used to compare groups. Correlation coefficients were calculated between quantitative and clinical measures.

RESULTS

There were significant differences for clinical and quantitative measures of cold and pressure sensitivity between the neck pain and control groups (eg, CPT neck pain group: median=22.31°C, IQR=18.58°C; control group: median=5.0°C, IQR=0.74°C). Moderate-to-good correlations were found between the clinical ice pain test and CPT at all sites (.46 to .68) except at the wrist (.29 to .40). Fair correlations were found for the clinical pressure pain test and PPT (-.26 to -.45). Psychological variables contributing to quantitative measures of pain sensitivity included catastrophization, sleep quality, and female sex.

LIMITATIONS

Clinical pressure pain tests were not quantitatively standardized in this study.

CONCLUSIONS

The ice pain test may be useful as a clinical correlate of CPT at all sites except the wrist, whereas the pressure pain test is less convincing as a clinical correlate of PPT.

Effects of two different intensities of transcutaneous electrical nerve stimulation on pain thresholds of contralateral muscles in healthy subjects

[Purpose] This study aimed to investigate the differential effects of high-intensity and low-intensity transcutaneous electrical nerve stimulation on the contralateral side on the pain threshold in healthy subjects. [Subjects and Methods] Twenty-five healthy adults, volunteers received two intensity levels (motor-level, 1.5 times the muscle motor threshold; sensory-level, sensory threshold of the common peroneal nerve), for 30 s on separate days. Pressure pain threshold was recorded on the contralateral tibialis anterior and deltoid muscle before, during, and after stimulation. [Results] Motor-level stimulation significantly increased the pressure pain threshold at both muscle sites, while effects of sensory-level stimulation on pressure pain thresholds were significant only at the deltoid site. The percent change in pressure pain thresholds at both sites was significantly higher during motor-level stimulation. [Conclusion] Motor-level stimulation, applied unilaterally to one leg, produced immediate contralateral diffuse and segmental analgesic effects. This may be of therapeutic benefit in patients for whom transcutaneous electrical nerve stimulation cannot be directly used at the painful site.

[Expert evidence in whiplash injury: interdisciplinary orthopaedic and biomechanical approach]

Considering the controversially discussed issue of whiplash injury a pragmatic approach based on our own experience in the area of forensic expert opinion is presented. Findings of accident analysis and biomechanics are correlated with the individual situation after the accident (initial clinical appearance), the course of the ailment and the indispensable physical examination. The latter leads to determination of the individual vulnerability (not increased/increased) which is important for the evaluation of the physical condition and estimation of the physical stress limit. These limits vary widely between individuals and must be considered carefully when relating dose and effect of accident severity to a possible physical injury. Determination of the accident severity is especially important when there are no objective signs of injury and the existence of a minor whiplash injury (Quebec Task Force degree 1 or 2) is in question.

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.

Effects of Temperature on Chronic Trapezius Myofascial Pain Syndrome during Dry Needling Therapy

The purpose of this study was to investigate the effects of temperature on chronic trapezius myofascial pain syndrome during dry needling therapy. Sixty patients were randomized into two groups of dry needling (DN) alone (group A) and DN combined with heat therapy group (group B). Each patient was treated once and the therapeutic effect was assessed by the visual analogue scale (VAS), pressure pain threshold (PPT), and the 36-item short form health survey (SF-36) at seven days, one month, and three months after treatment. Evaluation based on VAS and PPT showed that the pain of patients in groups A and B was significantly (P < 0.05) relieved at seven days, one month, and three months after treatment Compared to before treatment. There was significantly (P < 0.05) less pain in group B than group A at one and three months after treatment. The SF-36 evaluation demonstrated that the physical condition of patients in both groups showed significant (P < 0.05) improvement at one month and three months after treatment than before treatment. Our study suggests that both DN and DN heating therapy were effective in the treatment of trapezius MPS, and that DN heating therapy had better long-term effects than DN therapy.

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.