Evidence for central sensitization in chronic whiplash: A systematic literature review

The Association between Sleep and Chronic Spinal Pain: A Systematic Review from the Last Decade

Chronic spinal pain, including both neck and low back pain, is a common disabling disorder in which sleep problems are frequently reported as a comorbidity. The complex processes of both sleep and chronic pain seem to have overlapping mechanisms, which may explain their often established bidirectional relationship. This systematic review aims to investigate the assumed association between sleep and chronic spinal pain by providing an overview of the literature from the last decade. Eligible studies were obtained by searching four databases (PubMed, Embase, Web of Science, and PsycARTICLES). Articles were found relevant if they included a human adult population and investigated the possible association between sleep parameters and chronic spinal pain. Only studies published after January 2009 were included, as this review aimed to provide an update of a previous literature overview on this topic. The quality of the studies was assessed by risk of bias and level of evidence. A total of twenty-seven studies (6 cohort, 5 case-control, and 16 cross-sectional studies) were included in this systematic review. The methodological quality of these studies was low to moderate. The majority of studies reported weak to moderate evidence for an association between sleep parameters and chronic spinal pain, with more severe pain accompanied by more disturbed sleep. Addressing frequently reported sleep problems in chronic spinal pain patients therefore appears to be a necessary complement to pain management to achieve optimal treatment outcomes.

Conditioned pain modulation and pain sensitivity in functional somatic disorders: The DanFunD study

Background

Disrupted pain regulation has been proposed as a component in functional somatic disorders (FSD). The objective of this study was to examine a general population sample, encompassing three delimitations of FSD while assessing pain sensitivity and conditioning pain modulation (CPM).

Methods

Pressure pain thresholds (PPTs) at the tibialis and trapezius muscles were recorded at baseline. During cold pressor stimulation of the hand, the tibialis PPTs were re‐assessed and the difference from baseline measures defined the CPM effect. Participants (n = 2,198, 53% females) were randomly selected from the adult Danish population. FSD was established by self‐reported symptom questionnaires.

Results

With a few exceptions, only weak associations were seen between PPTs and CPM in cases with FSD (p > .1). A high PPT was associated with lower odds of having multi‐organ bodily distress syndrome (OR^{PPT trapezius}: 0.66, 95% CI: 0.49–0.88, p = .005), with the symptom profile characterized by all symptoms (OR^{PPT trapezius}: 0.72, 95% CI: 0.58–0.90, p = .003 and OR^{PPT tibialis}: 0.75, 95% CI: 0.62–0.91, p = .004), and with multiple chemical sensitivity (OR^{PPT trapezius}: 0.81, 95% CI: 0.67–0.97, p = .022). High CPM was associated with high odds of having irritable bowel (OR^{CPM relative}: 1.22, 95% CI: 1.04–1.43, p = .013 and OR^{CPM absolute} = 2.66, 95% CI: 1.07–6.45, p = .033).

Conclusion

However, only PPT measured over the trapezius muscle were still significant after correction for multiple testing for the symptom profile characterized by all symptoms. Findings from this study do not support altered pain regulation in questionnaire‐based FSD which is in contrast with the existing presumption. Further epidemiological studies in this field are needed.

Significance

Disrupted pain regulation as measured by abnormal pain thresholds has been hypothesized as a central mechanism in Functional Somatic Disorders (FSD). The hypothesis has been raised in clinical setting where patients presented subjective and objective features of hypersensitivity. The present population‐based study does not support this notion. This points to the importance of further studies into the underlying pathophysiology mechanisms of FSD.

Nociplastic Pain Criteria or Recognition of Central Sensitization? Pain Phenotyping in the Past, Present and Future

Recently, the International Association for the Study of Pain (IASP) released clinical criteria and a grading system for nociplastic pain affecting the musculoskeletal system. These criteria replaced the 2014 clinical criteria for predominant central sensitization (CS) pain and accounted for clinicians' need to identify (early) and correctly classify patients having chronic pain according to the pain phenotype. Still, clinicians and researchers can become confused by the multitude of terms and the variety of clinical criteria available. Therefore, this paper aims at (1) providing an overview of what preceded the IASP criteria for nociplastic pain ('the past'); (2) explaining the new IASP criteria for nociplastic pain in comparison with the 2014 clinical criteria for predominant CS pain ('the present'); and (3) highlighting key areas for future implementation and research work in this area ('the future'). It is explained that the 2021 IASP clinical criteria for nociplastic pain are in line with the 2014 clinical criteria for predominant CS pain but are more robust, comprehensive, better developed and hold more potential. Therefore, the 2021 IASP clinical criteria for nociplastic pain are important steps towards precision pain medicine, yet studies examining the clinimetric and psychometric properties of the criteria are urgently needed.

Combining Stress Management With Pain Neuroscience Education and Exercise Therapy in People With Whiplash-Associated Disorders: A Clinical Perspective

Individuals classified as having whiplash-associated disorder (WAD) grade II, which reflects approximately 93% of people with WAD who are commonly managed by health care professionals, exhibit both physical (eg, pain and disability) and psychological (eg, fear of movement, anxiety, posttraumatic stress) problems that, in approximately 50% of cases, persist beyond 3 months. There is still much ongoing debate regarding factors predictive of poor recovery. The strongest associations have been found for high initial pain and disability following whiplash injury. In addition, a growing body of evidence supports the clinical importance of characteristic features, such as disturbed nociceptive processing (eg, local or general hyperalgesia to cold and mechanical stimuli), inefficient cognitions and beliefs about pain/movement/recovery, and posttraumatic stress symptoms, in the development and maintenance of physical and psychological manifestations in individuals with WAD. For this reason, the field shifted away from single interventions that mainly follow a biomedical approach, such as exercise therapy and activity programs, to gold standard multimodal care (at least 2 distinct therapeutic modalities given by 1 or more health care professionals) that acknowledges the biopsychological nature of WAD. To date, there exist several multimodal care approaches to managing WAD; however, for most, the efficacy has been found to be rather limited. One may argue that the limited success of some approaches can be attributed to the fact that they focused mainly on rehabilitating the physical symptoms (eg, pain, disability) rather than also the associated cognitive (eg, catastrophizing) and psychological (eg, posttraumatic stress symptoms) symptoms of the condition, leaving much room for improvement. In this article, current and previous evidence is used to explain why and how a comprehensive and multimodal treatment for people with WAD-consisting of a combination of pain neuroscience education, cognition-targeted exercise therapy, and stress management-can be applied in clinical practice.

The feasibility of gym-based exercise therapy for patients with persistent neck pain

Background and aims Persistent neck pain is common and can be detrimental to the health of those who are affected. This is particularly common after neck trauma, where it poses a challenge to health care providers. In this paper, we present the design and results of a study aimed primarily at assessing the feasibility of a supervised exercise intervention for patients with persistent neck pain after trauma. As a secondary aim, we analyzed the results of the intervention. Methods We designed and conducted a feasibility study using a mixed methods design. Ten patients with persistent neck pain (nine with a history of neck trauma and one with sudden onset of neck pain) were recruited from a specialized pain rehabilitation center and underwent a gym-based individual exercise therapy intervention, supervised by a physical therapist. We assessed the feasibility of the exercise therapy intervention based on the experiences of the patients and physical therapists. We analyzed both quantitative and qualitative results using descriptive statistics, content analysis, and questionnaires. Results The study found the exercise therapy to be a feasible alternative for patients with persistent neck pain. Most of the practical aspects of the intervention and study were executed as planned, and the study was well received by the patients, who found it a valuable part of their rehabilitation. In the quantitative analysis, improvements were observed on the Neck Disability Index, numerical rating scale for pain, EuroQol 5D, and physical activity, with scores on the Neck Disability Index showing a statistically significant improvement. Scores on the Disability Rating Index showed a non-significant deterioration. The qualitative analysis uncovered one overarching theme and four themes for the patients and three themes for the physical therapist. Conclusions The exercise therapy intervention seems to be feasible with favorable outcomes for the patients. The quantitative and qualitative analyses demonstrated exercise therapy to be beneficial from several different perspectives. However, although structured, the training needs customization and individual adaption from a clinical reasoning perspective in order to meet each patient's individual needs. Implications This study shows that supervised gym-based exercise therapy is feasible for patients with severe, persistent neck pain. It facilitates and motivates the execution of a larger, controlled trial, which might then lead to a new and potentially effective addition to the toolbox of all health care providers treating patients with persistent neck pain.

Central Sensitization in Chronic Musculoskeletal Pain Disorders in Different Populations: A Cross-Sectional Study

OBJECTIVE

Chronic musculoskeletal pain disorders (CMPDs) are among the leading causes of disabilities across populations, resulting in high social and financial burden. This persistent pain condition may include the central sensitization (CS) phenomenon, which implies a wide range of symptoms and that may be taken into account in CMPD treatment. CS symptoms can be measured by the Central Sensitization Inventory (CSI). The aims of the study were to describe CS symptoms in patients suffering from several CMPDs and to analyze differences due to gender, age, and body mass index (BMI).

DESIGN

This cross-sectional study recruited a total of 395 Spanish participants suffering from several CMPDs.

SETTING

CS symptoms were measured with the Spanish Version of the CSI. The total score (0-100) and a cutoff score of 40 were recorded.

SUBJECTS

A total of 395 participants were included.

RESULTS

The mean CSI total score for the whole sample was 24.6 ± 12.0 points. CSI total score had subclinical values in the whole sample, whereas participants with scores >40 were found across different CMPDs, such as low back pain (37.8%) and neck pain (32.4%); 14.6% of females and 1.7% of males presented CSI scores >40. Patients showed significant differences in CSI cutoff point by gender (P = 0.010) and CSI total score by age (P = 0.014).

CONCLUSIONS

Given the high prevalence of clinically relevant CSI scores (>40) in people with a CMPD, especially low back pain and neck pain, we recommend that clinicians supplement their assessment with the CSI for improved decision-making during treatment.

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

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

A contemporary neuroscience approach compared to biomedically focused education combined with symptom-contingent exercise therapy in people with chronic whiplash associated disorders: a randomized controlled trial protocol

BACKGROUND

To address the need for a better treatment of chronic whiplash associated disorders (WAD), a contemporary neuroscience approach can be proposed.

OBJECTIVE

To examine the effectiveness of a contemporary neuroscience approach, comprising pain neuroscience education, stress management, and cognition-targeted exercise therapy versus conventional physical therapy for reducing disability (primary outcome measure) and improving quality of life and reducing pain, central sensitization, and psychological problems (secondary outcome measures) in people with chronic WAD.

METHODS

The study is a multi-center, two-arm randomized, controlled trial with 1-year follow-up and will be performed in two university-based and one regional hospital. People with chronic WAD (n=120) will be recruited. The experimental group will receive pain neuroscience education followed by cognition-targeted exercise therapy, and stress management. The control group will receive biomedically focused education followed by graded and active exercise therapy focusing on muscle endurance, strength, and flexibility, and ergonomic principles. The treatment will have a duration of 16 weeks. Functional status (Neck Disability Index) is the primary outcome measure. Secondary outcome measures include quality of life, pain, central sensitization, and psychological and socio-economic factors. In addition, electroencephalography will measure brain activity at rest and during a conditioned pain modulation paradigm. Assessments will take place at baseline, immediately post-treatment and at 6 and 12 months follow-up.

CONCLUSIONS

This study will examine whether a contemporary neuroscience approach is superior over conventional physical therapy for improving functioning, quality of life, and reducing pain, central sensitization, and psychological problems in people with chronic WAD.

Combination of Pain Location and Pain Duration is Associated with Central Sensitization-Related Symptoms in Patients with Musculoskeletal Disorders: A Cross-Sectional Study

OBJECTIVES

Increased evidence indicates that pain location affects central sensitization (CS)-related symptoms. In addition, pain location and pain duration may be intricately related to CS-related symptoms. However, these factors have been investigated separately. This study aimed to investigate the association between CS-related symptoms and pain location and/or pain duration in patients with musculoskeletal disorders.

METHODS

Six hundred thirty-five participants with musculoskeletal disorders were included in this cross-sectional study. All participants were assessed for pain location, pain duration, central sensitization inventory (CSI), EuroQol-5 dimension, and brief pain inventory. The participants were categorized into 3 groups based on pain location (spinal, limb, and both spinal and limb pain) and into 2 groups based on pain duration (acute and chronic pain).

RESULTS

The interaction between pain location and pain duration were not significant on CSI score (P > 0.05). The odds ratio for higher CSI score (≥ 40) in patients with both spinal and limb pain vs. those with spinal or limb pain was 2.64 (P < 0.01) and that in patients with chronic pain vs. those with acute pain was 1.31 (P = 0.52). In addition, the prevalence of higher CSI scores in the combination of chronic and "both spinal and limb" pain was high (23.1%, adjusted residual = 4.48).

CONCLUSIONS

Pain location independently influenced CSI scores, and the combination of both spinal and limb pain and chronic pain indicated high CSI scores. The combination of pain location and pain duration is an important clue that points to CS-related symptoms.

Enhanced amygdala-frontal operculum functional connectivity during rest in women with chronic neck pain: Associations with impaired conditioned pain modulation

BACKGROUND

Chronic neck pain is a leading cause of disability worldwide, affecting the lives of millions of people. Research investigating functional brain alterations in relation to somatosensory function is necessary to better understand mechanisms underlying pain development and maintenance in individuals with chronic neck pain, yet remains scarce. This case-control study aimed to examine resting-state functional connectivity alterations and associations with pain outcomes, self-reported central sensitization-related symptoms and quantitative sensory testing (QST) measures in patients with chronic non-traumatic (idiopathic/CINP) neck pain and chronic traumatic (whiplash associated/CWAD) neck pain compared to pain-free controls.

METHODS

Resting-state functional magnetic resonance images were acquired in 107 female participants (38 CINP, 37 CWAD, 32 healthy controls). After data pre-processing, seed-to-seed analyses were conducted focusing on resting-state functional connectivity involving pre-defined regions of interest that have previously been observed to be structurally or functionally altered and/or associated with pain-related measures in this patient population.

RESULTS

Findings demonstrate enhanced left amygdala functional coupling during rest with the left frontal operculum in women with CINP and CWAD compared to controls. This increased resting-state functional connectivity was associated with more self-reported symptoms related to central sensitization and decreased efficacy of conditioned pain modulation. Furthermore, enhanced connectivity between the left amygdala and left frontal orbital cortex, and between the left pallidum and the left frontal operculum was observed only in patients with CWAD compared to healthy controls. In patients, additional associations between local hyperalgesia and enhanced connectivity between the left superior parietal cortex and the left and right precentral gyrus were found.

CONCLUSIONS

In line with our hypotheses, patients with CWAD showed the most pronounced alterations in resting-state functional connectivity, encompassing subcortical limbic (amygdala) and basal ganglia (pallidum), and ventral frontal regions (frontal operculum, orbitofrontal cortex) when compared to CINP and controls. Findings are generally in line with the idea of a continuum, in absence of significant group differences across CINP and CWAD. Enhanced amygdala-frontal operculum functional connectivity was the most robust and only connectivity pair in the cluster that was associated with QST (i.e., dynamic QST; endogenous pain inhibition), and that was observed in both patient groups. In addition, independent of group differences, enhanced resting-state functional connectivity between superior parietal cortex (involved in attention) and primary motor cortex was associated with static QST (i.e., greater local hyperalgesia). Taken together, our findings show a key role for enhanced amygdala-ventral frontal circuitry in chronic neck pain, and its association with diminished endogenous pain inhibition further emphasizes the link between cognitive-affective and sensory modulations of pain in women with chronic non-traumatic and traumatic neck pain.

Central Sensitization in Neurological, Psychiatric, and Pain Disorders: A Multicenter Case-Controlled Study

Background

The role of central sensitization in refractory pain-related diseases has not yet been clarified.

Methods

We performed a multicenter case-controlled study including 551 patients with various neurological, psychological, and pain disorders and 5,188 healthy controls to investigate the impact of central sensitization in these patients. Symptoms related to central sensitization syndrome (CSS) were assessed by the Central Sensitization Inventory (CSI) parts A and B. Patients were categorized into 5 groups based on CSI-A scores from subclinical to extreme. The Brief Pain Inventory (BPI), addressing pain severity and pain interference with daily activities, and the Patient Health Questionnaire (PHQ)-9, assessing depressive symptoms, were also administered.

Results

CSI-A scores and CSI-B disease numbers were significantly greater in patients than in controls (p < 0.001). Medium effect sizes (r = 0.37) for CSI-A scores and large effect sizes (r = 0.64) for CSI-B disease numbers were found between patients and control groups. Compared with the CSI-A subclinical group, the CSI-A mild, moderate, severe, and extreme groups had significantly higher BPI pain interference and severity scores, PHQ-9 scores, and CSS-related disease numbers based on ANCOVA. Greater CSI-B numbers resulted in higher CSI-A scores (p < 0.001) and a higher odds ratio (p for trend <0.001). CSS-related symptoms were associated with pain severity, pain interference with daily activities, and depressive symptoms in various pain-related diseases.

Conclusions

Our findings suggest that CSS may participate in these conditions as common pathophysiology.

Measures of central sensitization and their measurement properties in musculoskeletal trauma: A systematic review

BACKGROUND AND OBJECTIVE

Chronic pain following musculoskeletal trauma is common, which may partially be attributed to the early presence of central sensitization (CS). Multiple measures are suggested to assess clinical features of CS, yet no systematic review has evaluated the measurement properties of these measures in a musculoskeletal trauma population.

DATABASES AND DATA TREATMENT

This systematic review, which followed a published and PROSPERO registered protocol (CRD42018091531), aimed to establish the scope of CS measures used within a musculoskeletal trauma population and evaluate their measurement properties. Searches were conducted in two stages by two independent reviewers. The Consensus-based Standards for the selection of Health Measurement Instruments (COSMIN) checklist was used to evaluate risk of bias and overall quality was assessed using the modified Grading of Recommendations Assessment, Development and Evaluation.

RESULTS

From 86 studies, 30 different CS outcome measures were identified. Nine studies evaluated measurement properties of nine outcome measures; eight evaluated reliability and one evaluated construct validity. Measures included seven quantitative sensory testing methods (pressure, cold and electrical pain thresholds; warm, cold and vibration detection thresholds; vibration perception thresholds), pain drawings and a pinwheel. Risk of bias was assessed as doubtful/inadequate for all but one study, overall quality of evidence was low/very low for all measures. Reliability of measures ranged from poor to excellent.

CONCLUSIONS

Many measures are used to evaluate CS but with limited established measurement properties in musculoskeletal trauma. High quality research to establish measurement properties of CS outcome measures is required.

Prescription of exercises for the treatment of chronic pain along the continuum of nociplastic pain: A systematic review with meta-analysis

BACKGROUND AND OBJECTIVE

To compare different exercise prescriptions for patients with chronic pain along the continuum of nociplastic pain: fibromyalgia, chronic whiplash-associated disorders (CWAD), and chronic idiopathic neck pain (CINP).

DATABASES AND DATA TREATMENT

Randomized controlled trials comparing different exercise parameters were included. The search was performed in the databases Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL and PEDro. Data on the parameters for the physical exercise programs for pain management were extracted for analysis.

RESULTS

Fifty studies with 3,562 participants were included. For fibromyalgia, both aerobic strengthening exercises were similar and better than stretching exercises alone. Exercises could be performed in 50- to 60-min supervised sessions, 2 to 3 times a week, for 13 weeks or more. For CWAD, body awareness exercises were similar to combined exercises, and there was no difference in adding sling exercises to a strengthening exercise program. The exercises could be performed in 90-min supervised sessions, twice a week, for 10 to 16 weeks. For CINP, motor control exercises and nonspecific muscle strengthening had a similar effect. Exercises could be performed in 30- to 60-min supervised sessions, 2 to 3 times a week, for 7 to 12 weeks.

CONCLUSIONS

The choice of parameters regarding exercises should emphasize global exercises in nociplastic pain conditions (such as fibromyalgia and CWAD) and specific exercises in non-nociplastic pain conditions (such as CINP) and be based on patient's preference and therapist's skills.

PROSPERO REGISTRATION NUMBER

CRD42019123271.

SIGNIFICANCE

The pain mechanism must be considered to optimize exercise prescription in patients with different chronic pain profiles. The main message of this article is that low to moderate intensity global exercises performed for a long period of treatment should be performed in patients with nociplastic pain predominance. Additionally, focused and intense exercises for a short period of treatment can be prescribed for patients with nociceptive pain predominance.

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.

Detection of illness worry in the general population: A specific item on illness rumination improves the Whiteley Index

OBJECTIVE

The Whiteley Index (WI) is the most widely used screening tool for health anxiety/illness worry. Diverse versions (different number of items and factors) have been used. We aimed to examine psychometric properties of 7 items of the WI besides adding a new item on obsessive illness rumination for better future detection of health anxiety.

METHODS

Data from a large population-based study in Denmark (N = 9656). Construct validity was examined by exploratory (EFA) and confirmatory factor analysis (CFA) plus hypothesis testing. Criterion validity was evaluated via Receiver Operating Characteristic curves and area under the curve (AUC) using a diagnostic criterion as gold standard.

RESULTS

Factor loadings of EFA revealed viable one-factor models (6, 7, or 8 items) and two-factor models (7 or 8 items). Factor one indicated a dimension of illness worry. Factor two indicated a somatic symptoms dimension. The new item on obsessive illness rumination merged well with the existing items. EFA of two-factor models and one-factor 6-item model showed good fit. CFA resembles these findings. A one-factor 6-item model (including the item on obsessive illness rumination and excluding two items concerning somatic symptoms) was chosen as the optimal model and presented good criterion validity: AUC 0.88 (95%CI(0.84;0.92)). Main hypotheses concerning associations with somatic symptoms, anxiety, and depression were met.

CONCLUSIONS

We found good psychometric properties for a new one-factor 6-item version of the WI. Through elimination of items concerning somatic symptoms and inclusion of obsessive illness rumination, we propose a clear, unidimensional and improved measure of illness worry: Whiteley-6-R.

Evaluation of the Central Sensitization Inventory Score in elderly adults with musculoskeletal examination

OBJECTIVES

The present study aimed to conduct an epidemiological survey of Central Sensitization Inventory (CSI) scores in an older adult population and to investigate the association between the CSI scores, age, sex, pain intensity, site of pain, and health-related quality of life (QOL).

METHODS

Participants were 373 Japanese adults aged ≥ 50 years who underwent a health checkup in 2018. We collected demographic data and clinical characteristics along with the CSI scores, QOL questionnaire, site of pain (neck, lower back, upper limb, and lower limb) and pain severity. We performed an epidemiological survey of the CSI scores and investigated the gender difference in CSI scores and the relationship between the CSI scores, site of pain, and QOL.

RESULTS

The prevalence of low back pain was the highest (67.6%). The average CSI score was 14.2 points; 8% of volunteers had a high (> 30) CSI score. The CSI scores among women were significantly higher than those among men (p = .016). The CSI scores had a significantly moderate correlation with the numerical rating scale and QOL scores (all p < .001). Volunteers with neck pain showed the highest CSI scores (average 22.4 points).

CONCLUSIONS

The CSI total score showed sex differences and had a significant correlation with pain severity and QOL.

STUDY DESIGN

Cross-sectional study.

Processing of Laser-Evoked Potentials in Patients with Chronic Whiplash-Associated Disorders, Chronic Fatigue Syndrome, and Healthy Controls: A Case-Control Study

OBJECTIVE

Laser-evoked potentials (LEPs) are among the reliable neurophysiological tools to investigate patients with neuropathic pain, as they can provide an objective account of the functional status of thermo-nociceptive pathways. The goal of this study was to explore the functioning of the nociceptive afferent pathways by examining LEPs in patients with chronic whiplash-associated disorders (cWAD), patients with chronic fatigue syndrome (CFS), and healthy controls (HCs).

DESIGN

Case-control study.

SETTING

A single medical center in Belgium.

SUBJECTS

The LEPs of 21 patients with cWAD, 19 patients with CFS, and 18 HCs were analyzed in this study.

METHODS

All participants received brief nociceptive CO2 laser stimuli applied to the dorsum of the left hand and left foot while brain activity was recorded with a 32-channel electroencephalogram (EEG). LEP signals and transient power modulations were compared between patient groups and HCs.

RESULTS

No between-group differences were found for stimulus intensity, which was supraliminal for Aδ fibers. The amplitudes and latencies of LEP wave components N1, N2, and P2 in patients with cWAD and CFS were statistically similar to those of HCs. There were no significant differences between the time-frequency maps of EEG oscillation amplitude between HCs and both patient populations.

CONCLUSIONS

EEG responses of heat-sensitive Aδ fibers in patients with cWAD and CFS revealed no significant differences from the responses of HCs. These findings thus do not support a state of generalized central nervous system hyperexcitability in those patients.

Systemic inflammatory markers in neck pain: A systematic review with meta-analysis

BACKGROUND AND OBJECTIVE

Mechanisms underpinning symptoms in non-traumatic neck pain (NTNP) and whiplash-associated disorder (WAD) are not comprehensively understood. There is emerging evidence of systemic inflammation in musculoskeletal pain conditions, including neck and back pain. The aim of this systematic review was to determine if raised blood inflammatory markers are associated with neck pain.

DATABASES AND DATA TREATMENT

MEDLINE, EMBASE, Cochrane Library, CINAHL and Web of Science databases were searched. Two independent reviewers identified studies for inclusion and extracted data. Meta-analysis was performed by random effects model to calculate standard mean differences (SMDs). Risk of bias of individual studies was assessed using the Newcastle-Ottawa Scale. Overall quality of evidence from meta-analysis was assessed by Grades of Recommendation, Assessment, Development and Evaluation approach.

RESULTS

In total, 10 studies were included comprising 706 participants. Three studies provided data for acute WAD, two for chronic WAD, four for chronic NTNP and one for chronic mixed WAD and NTNP. Meta-analysis indicated increased interleukin 1β (SMD: 0.84 [95% CI 0.24, 1.44], p = .01, I2  = 59%) and tumour necrosis factor α (SMD: 0.59 [0.09, 1.09], p = .02, I2  = 45%) in chronic neck pain compared to controls, but no increase in monocyte chemoattractant protein-1. Some inflammatory markers were associated with clinical variables (including pain intensity and disability). Quality of evidence was mostly low due to small samples and high heterogeneity.

CONCLUSIONS

Findings imply that raised blood inflammatory markers are present in chronic neck pain, which may represent an ongoing inflammatory process in this population.

SIGNIFICANCE

This systematic review advances our understanding of neck pain pathophysiology by demonstrating the presence of systemic inflammation in chronic neck pain, in the form of raised IL-1β and TNFα. Further, numerous inflammatory markers were associated with clinical variables, including pain intensity, disability and hyperalgesia. These findings imply that systemic inflammation may contribute to mechanisms underlying neck pain.

Nutritional intervention in chronic pain: an innovative way of targeting central nervous system sensitization?

INTRODUCTION

Few treatment programs for chronic pain nowadays take a dietary pattern or adipose status into account.

AREAS COVERED

An important role of neuroinflammation in chronic pain is now well established, at least in part due to increased central nervous system glial activation. Based on preclinical studies, it is postulated that the interaction between nutrition and central sensitization is mediated via bidirectional gut-brain interactions. This model of diet-induced neuroinflammation and consequent central sensitization generates a rationale for developing innovative treatments for patients with chronic pain. Methods: An umbrella approach to cover the authors' expert opinion within an evidence-based viewpoint.

EXPERT OPINION

A low-saturated fat and low-added sugar dietary pattern potentially decreases oxidative stress, preventing Toll-like receptor activation and subsequent glial activation. A low-saturated fat and low-added sugar diet might also prevent afferent vagal nerve fibers sensing the pro-inflammatory mediators that come along with a high-(saturated) fat or energy-dense dietary pattern, thereby preventing them to signal peripheral inflammatory status to the brain. In addition, the gut microbiota produces polyamines, which hold the capacity to excite N-methyl-D-aspartate receptors, an essential component of the central nervous system sensitization. Hence, a diet reducing polyamine production by the gut microbiota requires exploration as a therapeutic target for cancer-related and non-cancer chronic pain.

Hub disruption in patients with chronic neck pain: a graph analytical approach

Chronic pain is known to alter the brain's network dynamics. These dynamics are often demonstrated by identifying alterations in the brain network topology. A common approach used for this purpose is graph theory. To date, little is known on how these potentially altered networks in chronic pain relate to the symptoms reported by these patients. Here, we applied a graph theoretical approach to identify network changes in patients suffering from chronic neck pain, a group that is often neglected in chronic pain research. Participants with chronic traumatic and nontraumatic neck pain were compared to healthy pain-free controls. They showed higher levels of self-reported symptoms of sensitization, higher levels of disability, and impaired sensorimotor control. Furthermore, the brain suffering from chronic neck pain showed altered network properties in the posterior cingulate cortex, amygdala, and pallidum compared with the healthy pain-free brain. These regions have been identified as brain hubs (ie, regions that are responsible for orchestrating communication between other brain regions) and are therefore known to be more vulnerable in brain disorders including chronic pain. We were furthermore able to uncover associations between these altered brain network properties and the symptoms reported by patients. Our findings indicate that chronic neck pain patients reflect brain network alterations and that targeting the brain in patients might be of utmost importance.

Small fibre pathology in chronic whiplash-associated disorder: A cross-sectional study

BACKGROUND

Mechanisms underpinning ongoing symptoms in chronic whiplash associated-disorder (WAD) are not well understood. People with chronic WAD can exhibit sensory dysfunction consistent with small nerve fibre pathology, including thermal hypoaesthesia and hyperalgesia. This study investigated small fibre structure and function in chronic WAD.

METHODS

Twenty-four people with chronic WAD (median [IQR] age 49 [15] years, 16 females) and 24 pain-free controls (50 [17] years, 16 females) were recruited. Intraepidermal nerve fibre density (IENFD) and dermal innervation were assessed by skin biopsy. This was performed at (a) the lateral index finger on the primary side of pain and (b) superior to the lateral malleolus on the contralateral side. Quantitative sensory testing was performed over the hand.

RESULTS

The WAD group exhibited lower IENFD at the finger (WAD: median [IQR] 4.5 [4.9] fibres/mm; control 7.3 [3.9]; p = .010), but not the ankle (WAD: mean [SD] 7.3 [3.7] fibres/mm; control 9.3 [3.8]; p = .09). Dermal innervation was lower in the WAD group at the finger (WAD: median [IQR] 3.7 [2.8] nerve bundles/mm² ; controls: 4.9 [2.1]; p = .017) but not the ankle (WAD: median [IQR] 2.1 [1.9] nerve bundles/mm² ; controls: 1.8 [1.8]; p = .70). In the WAD group, hand thermal and light touch detection were impaired, and heat pain thresholds were lowered (p ≤ .037).

CONCLUSIONS

Findings suggest small fibre structural and functional deficits in chronic WAD, implicating potential involvement of small fibre pathology.

SIGNIFICANCE

Our study found decreased intraepidermal nerve fibre density, reduced dermal innervation, thermal hypoaesthesia and hypersensitivity in people with chronic WAD, suggestive of small fibre pathology. This observation of peripheral nervous system pathology in chronic whiplash provides novel insights on mechanisms underpinning symptoms and challenges commonly held beliefs regarding this condition.

Cross-Cultural Adaptation and Psychometric Properties of the European Portuguese Version of the Central Sensitization Inventory in Adolescents With Musculoskeletal Chronic Pain

BACKGROUND

Central sensitization (CS) is an important feature in musculoskeletal chronic pain, and associated symptoms can be assessed using the Central Sensitization Inventory (CSI).

OBJECTIVES

This study aimed to translate and cross-culturally adapt the CSI to the European Portuguese language and to assess its validity and reliability in adolescents with musculoskeletal chronic pain.

METHODS

The European Portuguese version of the CSI was established following the translation and testing processes recommended by international guidelines. Then, this version of the CSI was completed by 1,730 adolescents, who also completed the Nordic Musculoskeletal Questionnaire; the Pain Catastrophizing Scale; the Depression, Anxiety and Stress Scale; the Tampa Scale of Kinesiophobia; and the Basic Scale on Insomnia Complaints and Quality of Sleep. Test-retest reliability and measurement error, internal consistency, hypothesis testing, and factor analysis were assessed for the translated version of the CSI.

RESULTS

Cronbach's alpha was 0.91, the intraclass correlation coefficient was 0.94 (95% confidence interval: 0.90, 0.96), and the standard error of measurement and smallest detectable change were 4.15 and 11.50, respectively. Fair correlations were found between CSI and fear of movement (Spearman's correlation [r_s ] = 0.46), sleep (r_s  = 0.46), and catastrophizing (r_s  = 0.49). Moderate to good correlations were found between CSI and depression (r_s  = 0.60), anxiety (r_s  = 0.59), and stress (r_s  = 0.65).

CONCLUSION

The European Portuguese version of the CSI was considered easy to understand and showed very good internal consistency, excellent test-retest reliability, and excellent construct validity in a community sample of adolescents with musculoskeletal chronic pain.

Cross-cultural adaptation and validity of the Spanish fear-avoidance components scale and clinical implications in primary care

BACKGROUND

Pain-related fear-avoidance (FA) is a common problem affecting many patients with painful medical conditions. As there is great interest in the clinical importance of the relationship between FA and disability, several questionnaires have been developed to measure FA. The Fear-Avoidance Components Scale (FACS) is a recently developed patient-reported instrument that addresses critical issues not previously considered in previous FA-related questionnaires. The original English version of the FACS demonstrated good reliability, internal consistency, and construct, criterion, and predictive validity. Two factors were determined: General Fear Avoidance and Types of Activities That are Avoided. The aim of this study was to to translate the FACS into European-style Spanish (FACS-Sp), and validate its psychometric properties.

METHODS

This two-stage psychometric study included 330 subjects with various chronic musculoskeletal pain disorders. An initial translation and cross-cultural adaptation of the FACS, from English to Spanish, was performed. Then, critical psychometric properties were analysed, including internal consistency by Cronbach's α coefficients, structural validity from the Maximum Likelihood Extraction (MLE), and convergent validity by Pearson correlation with the Central Sensitization Inventory (CSI).

RESULTS

This study reports for the first time the psychometric properties of the Spanish version of the FACS. Total scores ranged from 0 to 88 points, with a mean of 30.49 (±17.18). The FACS-Sp showed a high internal consistency for factor 1 (α = 0.902) and factor 2 (α = 0.88). Factor structure was two-dimensional and supported structural validity, accounting for 48.75% of the total variance. Convergent validity analysis found a significant Pearson correlation r = 0.414.

CONCLUSION

This study reports for the first time the psychometric properties of the Spanish version of the FACS-Sp. Psychometric properties supported the validation of FACS-Sp and ensured the conceptual equivalence with the original English version. In primary care and chronic pain rehabilitation, FA assessment is crucial for clinical decision-making and treatment guidance. The FACS-Sp offers a new measure of FA in Spanish speaking populations. Future research on the FACS-Sp should evaluate test-retest reliability, treatment responsiveness and psychometric comparisons with other translated versions.

Cross-cultural adaptation and validity of the Spanish fear-avoidance components scale and clinical implications in primary care

BACKGROUND

Pain-related fear-avoidance (FA) is a common problem affecting many patients with painful medical conditions. As there is great interest in the clinical importance of the relationship between FA and disability, several questionnaires have been developed to measure FA. The Fear-Avoidance Components Scale (FACS) is a recently developed patient-reported instrument that addresses critical issues not previously considered in previous FA-related questionnaires. The original English version of the FACS demonstrated good reliability, internal consistency, and construct, criterion, and predictive validity. Two factors were determined: General Fear Avoidance and Types of Activities That are Avoided. The aim of this study was to to translate the FACS into European-style Spanish (FACS-Sp), and validate its psychometric properties.

METHODS

This two-stage psychometric study included 330 subjects with various chronic musculoskeletal pain disorders. An initial translation and cross-cultural adaptation of the FACS, from English to Spanish, was performed. Then, critical psychometric properties were analysed, including internal consistency by Cronbach's α coefficients, structural validity from the Maximum Likelihood Extraction (MLE), and convergent validity by Pearson correlation with the Central Sensitization Inventory (CSI).

RESULTS

This study reports for the first time the psychometric properties of the Spanish version of the FACS. Total scores ranged from 0 to 88 points, with a mean of 30.49 (±17.18). The FACS-Sp showed a high internal consistency for factor 1 (α = 0.902) and factor 2 (α = 0.88). Factor structure was two-dimensional and supported structural validity, accounting for 48.75% of the total variance. Convergent validity analysis found a significant Pearson correlation r = 0.414.

CONCLUSION

This study reports for the first time the psychometric properties of the Spanish version of the FACS-Sp. Psychometric properties supported the validation of FACS-Sp and ensured the conceptual equivalence with the original English version. In primary care and chronic pain rehabilitation, FA assessment is crucial for clinical decision-making and treatment guidance. The FACS-Sp offers a new measure of FA in Spanish speaking populations. Future research on the FACS-Sp should evaluate test-retest reliability, treatment responsiveness and psychometric comparisons with other translated versions.

Relationships Between Psychological, Social, Physical Activity, and Sleep Measures and Somatosensory Function in Individuals With Spinal Pain: A Systematic Review and Meta-analysis

OBJECTIVE

Somatosensory abnormalities are linked to clinical pain outcomes in individuals with spinal pain. However, a range of factors might confound the relationship between altered somatosensory function and clinical pain outcomes. This systematic review aimed to evaluate the literature to assess the level of evidence of associations between psychological, social, physical activity, and sleep measures and somatosensory function (assessed via sensory psychophysical testing) among individuals with spinal pain.

METHODS

A comprehensive literature search was performed in 6 electronic databases from their inception to June 2018. Two reviewers independently assessed the methodological quality using a modified Quality in Prognostic Studies (QUIPS) tool and supplemented with recommendations from the Critical Appraisal and Data Extraction for the Systematic Review of Prediction Modelling Studies (CHARMS) checklist and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. The level of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system. Data were pooled to evaluate the strength of the relationships of interest.

RESULTS

Among the 17 factors identified in the included studies, pain catastrophizing, depression, and pain-related fear have significant negative (small to fair) associations with pain thresholds. A "very low" to "moderate" quality of evidence was found for all the investigated factors. Subgroup analysis showed a smaller effect size for pain catastrophizing/fear of movement and pain thresholds in individuals with low back pain.

CONCLUSIONS

Psychological factors are associated negatively with pain thresholds and they need to be adjusted when establishing predictive relationships between somatosensory function and pain outcomes in individuals with spinal pain.

Do features of central sensitisation exist in Greater Trochanteric Pain Syndrome (GTPS)? A case control study

BACKGROUND

Greater Trochanteric Pain Syndrome (GTPS), which is commonly due to Gluteal Tendinopathy, refers to pain over the lateral hip that can become persistent and disabling. Central nervous sensitisation has been implicated in upper limb tendinopathy, but no studies have investigated if it plays a role in GTPS.

OBJECTIVES

To investigate if features of central sensitisation were present in people with GTPS.

METHODS

Eighteen people with GTPS were matched with 18 healthy controls in this cross-sectional study. The VISA-G and Central Sensitisation Inventory (CSI) self-report questionnaires were completed and pressure pain detection thresholds (PPDTs) at local and remote sites were measured in all participants. Data were analysed for between-group differences using Mann-Whitney U tests. Correlation between CSI and PPDTs were assessed using Pearson correlation co-efficients.

RESULTS

PPDT values were lower at local (symptomatic greater trochanter) and remote sites in the GTPS group, indicative of central sensitisation, resulting in statistically significant between-group differences. 44.4% of the GTPS group were classified as having symptoms of central sensitisation, based on the CSI.

CONCLUSION

There is preliminary evidence of central sensitisation in people with GTPS. Results need to be validated using other objective quantitative sensory testing measures in larger samples.

Translation and cross-cultural adaptation of the Polish Central Sensitization Inventory

Objectives

The Central Sensitization Inventory (CSI) is a new, simple clinimetric instrument intended to help doctors who deal with pain of unclear origin. It may be particularly useful when there is a large component of neuropathic pain and to assess non-specific symptoms associated with the phenomenon of central sensitization known under the common name of the central sensitization syndrome. The aim of this study is to perform translation of the CSI into Polish, its cultural adaptation and its preparation for further validation. The proposed adaptation of the scale may be applied both at the clinical level and at the level of primary care.

Material and methods

The CSI translation process took place in several stages. Firstly, the text of the questionnaire was translated from English to Polish by five independent translators. Secondly, the optimal version of the text was determined and, at the third stage, it was submitted to a linguist in order to assess it in the context of the idiomatic and semantic clarity. Thirdly, the translation was passed on to a native speaker who verified the congruence of the Polish translation with its original version. At a later stage, the effect of translating the scale and its usefulness were discussed by a group of experts in order to adapt a cultural tool. The final step was to provide it to be completed and evaluated by twenty anonymous patients with the aim of pre-assessing the level of its understanding.

Results

The final result of the undertaken activities is the Polish version of the CSI ready for validation.

Conclusions

After the multistage preparation and thorough verification of the Polish questionnaire at conceptual, empirical, semantic and idiomatic levels, necessary due to numerous cultural and linguistic differences, the Polish translation of the CSI seems to be a product ready for further validation and introduction to clinical practice.

Hyperexcitability of the Central Nervous System in Children with Chronic Pain: A Systematic Review

Objective

Hyperexcitability of the central nervous system plays an important role in the development and maintenance of chronic pain in adults. This knowledge has led to improved treatment strategies within this population. In children, however, research on the presence of central hyperexcitability is scarce. To further investigate this topic in children with chronic pain, there is a need for a clear literature overview.

Design

Systematic review.

Methods

The literature search was performed using the electronic databases PubMed and Web of Science. An article was considered eligible if it included children (age two to 12 years) diagnosed with chronic pain. Articles had to report original research outcomes related to central hyperexcitability, and a comparison with a healthy control group was necessary. Characteristics of the study sample, the assessment, and conclusions regarding central hyperexcitability were extracted from each included article.

Results

Twelve case-control studies were included with moderate to good methodological quality (510 children with chronic pain and 670 healthy controls). After summarizing the articles' results on indices of central hyperexcitability, we concluded that secondary hyperalgesia might be present in children with recurrent abdominal pain, juvenile fibromyalgia, and juvenile idiopathic arthritis. Preliminary evidence exists for altered cortical nociceptive processing in children with migraine and recurrent abdominal pain.

Conclusion

Based on the results of this review, central hyperexcitability might be present in in several pediatric chronic pain conditions. Further research on other manifestations of central hyperexcitability (e.g., bottom-up and top-down mechanisms and nociceptive brain changes) is necessary to provide firm evidence about its presence in children with chronic pain.

Brainstem neuroimaging of nociception and pain circuitries

The brainstem is known to be an important brain area for nociception and pain processing, and both relaying and coordinating signaling between the cerebrum, cerebellum, and spinal cord. Although preclinical models of pain have characterized the many roles that brainstem nuclei play in nociceptive processing, the degree to which these circuitries extend to humans is not as well known. Unfortunately, the brainstem is also a very challenging region to evaluate in humans with neuroimaging. The challenges for human brainstem imaging arise from the location of this elongated brain structure, proximity to cardiorespiratory noise sources, and the size of its constituent nuclei. These challenges can require dedicated approaches to brainstem imaging, which should be adopted when study hypotheses are focused on brainstem processing of nociception or modulation of pain perception. In fact, our review will highlight many pain neuroimaging studies that have reported some brainstem involvement in nociceptive processing and chronic pain pathology. However, we note that with recent advances in neuroimaging leading to improved spatial and temporal resolution, more studies are needed that take advantage of data collection and analysis methods focused on the challenges of brainstem neuroimaging.

Difference in the impact of central sensitization on pain-related symptoms between patients with chronic low back pain and knee osteoarthritis

Purpose: The aims of the present study were to investigate whether the association between the Central Sensitization Inventory (CSI) score, pain-related symptoms, pain-related disability, and health-related quality of life differed by disease (chronic low back pain [CLBP] vs knee osteoarthritis [KOA]), and to determine optimal cutoff scores for the CSI reflecting disease-specific characteristics.

Patients and methods: A total of 104 patients with CLBP and 50 patients with KOA were recruited. Central sensitization-related symptoms (CSI), EuroQol 5-dimension (EQ-5D), Brief Pain Inventory, widespread pain (Widespread Pain Index [WPI]), pressure pain threshold (PPT), and temporal summation (TS) were assessed and compared between the CLBP and KOA groups. Univariate correlation analysis was performed in each group. The receiver operating characteristic (ROC) curve analysis was performed to identify 1) presence/absence of central sensitization (CS), 2) presence/absence of central sensitivity syndromes (CSSs), and 3) pain intensity and pain interference in each group.

Results: The CSI and WPI scores were significantly higher in the CLBP group than in the KOA group. EQ-5D and pain interference scores significantly correlated with the CSI score in both the CLBP and KOA groups. The WPI score, PPT, and TS did not correlate with the CSI score in either the CLBP or KOA group. The suggested cutoff scores were 28 in the CLBP group and 17 in the KOA group to identify presence or absence of CSSs, and 34 in the CLBP group and 18–19 in the KOA group to identify pain severity.

Conclusion: The impact of CS on pain could differ between CLBP and KOA and that cutoff scores differ by each parameter we attempted to identify. Therefore, we should use the appropriate cutoff scores for the purposes and consider the difference in the impact of CS on pain by the patient group.

The association between back muscle characteristics and pressure pain sensitivity in low back pain patients

BACKGROUND AND AIMS

Some low back pain (LBP) patients recover after every pain episode whereas others develop chronicity. Research indicates that the amount of atrophy and fat infiltration differs between patients with LBP. Also enhanced pain sensitivity is present only in a subgroup of LBP patients. The relationship between pain sensitivity and muscular deformations in LBP, is however unexplored. This study examined the association between pressure pain sensitivity and the structural characteristics of the lumbar muscles in three different groups of non-specific LBP patients.

METHODS

This cross-sectional study examined the total cross-sectional area (CSA), fat CSA, muscle CSA and muscle fat index (MFI) of the lumbar multifidus (MF) and erector spinae (ES) at level L4 by magnetic resonance imaging in 54 patients with non-specific LBP (23 recurrent LBP, 15 non-continuous chronic LBP and 16 continuous chronic LBP). Pressure pain thresholds were measured at four locations (lower back, neck, hand and leg) by a manual pressure algometer and combined into one "pain sensitivity" variable. As a primary outcome measure, the association between pain sensitivity and muscle structure characteristics was investigated by multiple independent general linear regression models. Secondly, the influence of body mass index (BMI) and age on muscle characteristics was examined.

RESULTS

A positive association was found between pain sensitivity and the total CSA of the MF (p=0.006) and ES (p=0.001), and the muscle CSA of the MF (p=0.003) and ES (p=0.001), irrespective of the LBP group. No association was found between pain sensitivity and fat CSA or MFI (p>0.01). Furthermore, a positive association was found between BMI and the fat CSA of the MF (p=0.004) and ES (p=0.006), and the MFI of the MF (p<0.01) and ES (p=0.003). Finally, a positive association was found between age with the fat CSA of the MF (p=0.008) but not with the fat CSA of the ES (p>0.01), nor the MFI of the MF (p>0.01) and ES (p>0.01).

CONCLUSIONS

A higher pain sensitivity is associated with a smaller total and muscle CSA in the lumbar MF and ES, and vice versa, but results are independent from the LBP subgroup. On the other hand, the amount of fat infiltration in the lumbar muscles is not associated with pain sensitivity. Instead, a higher BMI is associated with more lumbar fat infiltration. Finally, older patients with LBP are associated with higher fat infiltration in the MF but not in the ES muscle.

IMPLICATIONS

These results imply that reconditioning muscular tissues might possibly decrease the pain sensitivity of LBP patients. Vice versa, therapy focusing on enhancement of pain sensitivity might also positively influence the CSA and that way contribute to the recovery of LBP. Furthermore, the amount of lumbar muscle fat seems not susceptible to pain sensitivity or vice versa, but instead a decrease in BMI might decrease the fat infiltration in the lumbar muscles and therefore improve the muscle structure quality in LBP. These hypothesis apply for all non-specific LBP patients, despite the type of LBP.

Measures of central sensitisation and their measurement properties in the adult musculoskeletal trauma population: a protocol for a systematic review and data synthesis

INTRODUCTION

Pain following musculoskeletal trauma is common with poor outcomes and disability well documented. Pain is complex in nature and can include the four primary mechanisms of pain: nociceptive, neuropathic, inflammatory and central sensitisation (CS). CS can be measured in multiple ways; however, no systematic review has evaluated the measurement properties of such measures in the musculoskeletal trauma population. This systematic review aims to evaluate the measurement properties of current measures of CS in this population.

METHODS/ANALYSIS

This protocol is informed and reported in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis-P. MEDLINE, EMBASE, CINAHL, ZETOC, Web of Science, PubMed and Google Scholar as well as key journals and grey literature will be searched in two stages to (1) identify what measures are being used to assess CS in this population and (2) evaluate the measurement properties of the identified measures. Two independent reviewers will conduct the search, extract the data, assess risk of bias for included studies and assess overall quality. The Consensus-based Standards for the selection of Health Measurement Instruments Risk of Bias Checklist and a modified Grading of Recommendations, Assessment, Development and Evaluation guidelines will be used. Meta-analysis will be conducted if deemed appropriate. Alternatively, a narrative synthesis will be conducted and summarised per measurement property per outcome measure.

ETHICS AND DISSEMINATION

This review will aid clinicians in using the most appropriate tool for assessing central sensitisation in this population and is the first step towards a more standardised approach in pain assessment. The results of this study will be submitted to a peer reviewed journal and presented at conferences.

PROSPERO REGISTRATIONNUMBER

CRD42018091531.

Motor corticospinal excitability: a novel facet of pain modulation?

Introduction

Increase in excitability of the primary motor cortex (M1) is associated with pain inhibition by analgesics, which is, in turn, associated with the psychophysical antinociceptive pain modulation profile. However, the relationship between neurophysiological M1 excitability and psychophysical pain modulation has not yet been explored.

Objectives

We aim to study these relationships in healthy subjects.

Methods

Forty-one young healthy subjects (22 women) underwent a wide battery of psychophysical testing that included conditioned pain modulation (CPM) and pain temporal summation, and a transcranial magnetic stimulation neurophysiological assessment of the motor corticospinal excitability, including resting motor threshold, motor-evoked potentials (MEPs), and cortical silent period.

Results

Increased motor corticospinal excitability in 2 parameters was associated with more efficient CPM: (1) higher MEP amplitude (r = -0.574; P _{_Bonferroni} = 0.02) and (2) longer MEP duration (r = -0.543; P _{_Bonferroni} = 0.02). The latter also correlated with the lower temporal summation magnitude (r = -0.421; P = 0.007); however, on multiplicity adjustment, significance was lost.

Conclusions

Increased corticospinal excitability of the primary motor cortex is associated with more efficient inhibitory pain modulation as assessed by CPM, in healthy subjects. Motor-evoked potential amplitude and duration may be considered as an additional, objective and easy to measure parameter to allow for better individual assessment of pain modulation profile.

Central sensitization in chronic pain and medically unexplained symptom research: A systematic review of definitions, operationalizations and measurement instruments

OBJECTIVE

Central sensitization (CS), a mechanism explaining the persistence of symptoms, has been the focus of many research projects. Explanations given to patients with chronic pain are often based on this mechanism. It is hypothesized that CS also plays an important role in the persistence of medically unexplained symptoms (MUS). However, definitions and operationalizations of CS vary. We conducted a systematic review of definitions, operationalizations and measurement instruments of CS.

METHODS

We searched in PubMed, EMBASE, PsycINFO, Cinahl and The Cochrane Library till September 2017 and included papers that addressed CS in relation to chronic pain and/or MUS. Two reviewers independently selected, analysed and classified information from the selected publications. We performed a thematic analysis of definitions and operationalizations. We listed the measurement instruments.

RESULTS

We included 126 publications, 79 publications concerned chronic pain, 47 publications concerned MUS. Definitions of CS consistently encompass the theme hyperexcitability of the central nervous system (CNS). Additional themes are variably present: CNS locations, nature of sensory input, reduced inhibition and activation and modulation of the NDMA receptor. Hyperalgesia and allodynia are widely mentioned as operationalizations of CS. Quantitative sensory testing (QST) and (f)MRI are the most reported measurement instruments.

CONCLUSIONS

There is consensus that hyperexcitability is the central mechanism of CS. Operationalizations are based on this mechanism and additional components. There are many measurement instruments available, whose clinical value has still to be determined. There were no systematic differences in definitions and operationalizations between the publications addressing MUS and those addressing chronic pain.

Central Sensitization Is Modulated Following Trigger Point Anesthetization in Patients with Chronic Pain from Whiplash Trauma. A Double-Blind, Placebo-Controlled, Crossover Study

Objective

Central sensitization (CS) with low peripheral pain thresholds (PPTs) is a common finding among patients with chronic pain after whiplash (CPWI). While it has been proposed that myofascial myofascial trigger points (MTrPs) may act as modulators of central sensitization, previously reported findings are conflicting and inconclusive. The present study was designed to investigate immediate responsiveness of CS to alterations in nociceptive input.

Design

Controlled, double-blind, cross-over.

Subjects

Thirty-one patients with chronic pain (trapezius myalgia) and CS after whiplash.

Methods

Participants were referred by randomization to group A for injection of a single peripheral pain generator (MTrP or other discrete tender point) with local anesthetic or to group B for sham injection and cross-over. Documentation of PPT (Algometer), maximum jaw opening (caliper), and grip strength (Vigorimeter), as well as subjective overall pain (visual analog scale [VAS]), was made before and after each intervention.

Results

Statistical analysis of data (Student's t test, analysis of variance) confirmed that peripheral pain thresholds were significantly higher and maximum jaw opening significantly greater after anesthetizing a focal pain generator in the trapezius, but not after a sham injection. In contrast with the objective variables, subjective generalized pain improved (VAS) after not only an injection of local anesthetic, but also, and to a similar extent, after a sham injection.

Conclusions

CS, as expressed by lowered PPT, is a rapidly adjusting physiological response to nociceptive stimuli in some patients with chronic pain after whiplash. PPT are likely modulated by myofascial tender points in selected patients with CS. With reference to the present findings, surgical ablation of MTrPs is discussed as a potential treatment modality for CS.

Cross-cultural adaptation and validity of the Italian version of the Central Sensitization Inventory

BACKGROUND

Central sensitization (CS) is an important feature in patients with chronic pain. The Central Sensitization Inventory (CSI) was developed with the goal of detecting the patients' symptoms related to CS.

OBJECTIVES

This study aimed at cross-culturally adapting the CSI into Italian, and at assessing its structural and construct validity in patients with different chronic pain disorders.

DESIGN

Clinimetric study.

METHODS

The Italian version of the CSI (CSI-I) was generated following forward and backward translations, expert committee review, and pilot-testing. Patients with pain for ≥3 months were eligible if diagnosed with: low back pain (LBP), temporomandibular disorder (TMD), hand osteoarthritis (HOA), fibromyalgia (FM), or rheumatoid arthritis (RA). Structural validity was assessed with exploratory factor analysis and parallel analysis based on minimum rank factor analysis; construct validity was evaluated by testing ten hypotheses on: 1) expected differences between relevant subgroups, 2) expected correlations with other instruments measuring pain intensity, physical functioning, psychological functioning, headache symptoms, and pain self-efficacy.

RESULTS

220 patients were included: 35% with LBP, 17% with TMD, 19% with HOA, 9% with FM, and 20% with RA. Factor analyses revealed that the CSI-I is a unidimensional instrument. Construct validity was satisfactory since 80% of the hypotheses were met.

CONCLUSIONS

The CSI-I was successfully developed and exhibited satisfactory validity in patients with chronic pain. Its reliability, responsiveness and content validity should be investigated in future studies. Until robust evidence indicates a strong relationship between CS and the CSI-I, caution should be adopted in claiming that the CSI-I measures CS.

Psychophysic-psychological dichotomy in very early acute mTBI pain: A prospective study

OBJECTIVE

To characterize the pain-related somatosensory and psychological presentation of very early acute patients with a mild traumatic brain injury (mTBI).

METHODS

Patients with an mTBI participated in a prospective observational study undergoing clinical, psychophysic, and psychological assessment within 72 hours after the accident. Healthy controls underwent similar protocol.

RESULTS

One hundred acute patients with an mTBI (age 36 ± 12.5 [SD] years, range 19-67 years, 42 women) and 80 healthy controls (age 43 ± 14.3 years, range 24-74 years, 40 women) participated. Patients with an mTBI demonstrated a pronociceptive psychophysic response in most tests such as less efficient pressure-pain threshold-conditioned pain modulation (0.19 ±0.19±.09 vs. 0.91±.10 kg, p < 0.001) and lower temperature needed to elicit a Pain50 response (44.72 ± 0.26°C vs 46.41 ± 0.30°C, p < 0.001). Their psychophysic findings correlated with clinical pain measures, e.g., Pain50 temperature and mean head (r = -0.21, p = 0.045) and neck (r = -0.26, p = 0.011) pain. The pain-catastrophizing magnification subscale was the only psychological variable to show a difference from the controls, while no significant correlations were found between any psychological measures and the clinical or psychophysic pain measures.

CONCLUSIONS

There appears to be a dichotomy between somatosensory and psychological findings in the very early acute post-mTBI stage; while the first is altered and is associated with the clinical picture, the second is unchanged. In the context of the ongoing debate on the pathophysiologic nature of the post-mTBI syndrome, our findings support its "physical" basis, free of mental influence, at least in the short time window after the injury.

Motor impairment in patients with chronic neck pain: does the traumatic event play a significant role? A case-control study

BACKGROUND CONTEXT

Motor impairment is a key sign in patients with traumatic (whiplash-associated disorder [WAD]) and non-traumatic (idiopathic neck pain [INP]) neck pain.

PURPOSE

This study aimed to analyze differences in motor impairment between two patient groups and to assess the association between motor performance and self-reported symptoms.

STUDY DESIGN

This is a case-control study.

PATIENT SAMPLE

A total of 38 patients with chronic INP, 35 patients with chronic WAD, and 30 healthy pain-free controls were included in the study.

OUTCOME MEASURES

Outcome measures used in this study were mobility (°), strength (N), repositioning accuracy (°), endurance (seconds), sway velocity (cm/s), sway area (cm²), and neuromuscular control.

METHODS

Group differences of motor impairment, together with questionnaires to evaluate pain intensity, fear avoidance, pain catastrophizing, symptoms of central sensitization, and disability, were analyzed with analysis of covariance, including age as a covariate.

RESULTS

Motor impairment was observed in both patient groups with a higher degree in patients with chronic WAD. These impairments were moderately linked to self-reported disability and were in most cases associated with pain, fear avoidance, and symptoms of central sensitization (|ρ| ranging from 0.28 to 0.59).

CONCLUSIONS

Motor impairment should be addressed when treating both groups of patients, keeping in mind the association with self-reported pain and disability, fear-avoidance, and central sensitization.

Development and psychometric properties of short form of central sensitization inventory in participants with musculoskeletal pain: A cross-sectional study

Background

The central sensitization inventory (CSI) comprises 25 items and is commonly used to measure somatic and emotional symptoms related to central sensitization symptoms. CSI was developed as an easy-to-administer screening instrument for patients at high risk of developing central sensitization in whom it was essential to quickly evaluate the condition. The purpose of the present study was to develop a short form of CSI and evaluate its psychometric properties using a contemporary approach called Rasch analysis.

Methods

A total of 505 patients with musculoskeletal disorders were recruited in this study. The CSI, pain intensity, pain interference, and the health-related quality of life (QOL) were evaluated for each participant. The original CSI items were consecutively analyzed using the Rasch model. Successive Rasch analyses were performed until a final set of items satisfied the model fit requirements. We also analyzed the psychometric properties of the original and short forms of CSI.

Results

Four consecutive Rasch analyses identified the removable items. Finally, the shortest questionnaire obtained that maintained the correct psychometric properties based on the Rasch model contained only 9 items (CSI-9). Rasch analysis showed that the CSI-9 had acceptable internal consistency, exhibited unidimensionality, had no notable differential item functioning, and was functional on the category rating scale.

Conclusions

The nine-item short form of CSI has acceptable psychometric properties and is suitable for use for patients with musculoskeletal pain. Thus, the CSI-9 can be used as a brief instrument to evaluate central sensitization.

McKenzie mechanical syndromes coincide with biopsychosocial influences, including central sensitization: a descriptive study of individuals with chronic neck pain

BACKGROUND

Mechanical diagnosis and therapy (MDT) aims to assess and classify patients into theoretically mutually exclusive subgroups, in order to direct treatment. However, the latest evidence for biopsychosocial influence-central sensitization (CS) and psychological distress-have not been assessed in conjunction with MDT.

OBJECTIVES

(1) Determine the percentage of patients categorized into the MDT subgroups; (2) characterize the biopsychosocial clinical profile (presence of CS and psychological distress); and (3) identify associations between pain, disability, and biopsychosocial influences among this cohort.

METHODS

Eighty four patients with chronic neck pain were recruited by 10 certified MDT therapists using a convenience (consecutive) sampling method. Patients were evaluated using MDT principles and also completed an online survey to measure CS (using the Central Sensitization Inventory [CSI]), pain catastrophizing and kinesiophobia.

RESULTS

The proportions of the subgroups derangement (DER), dysfunction, postural and 'other' were 74.4, 2.4, 1.2, 20.7%, respectively. CS was observed in 62% of our sample (CSI score ≥ 40). CS was also observed in 64.7% of patients of the DER subgroup. Almost half of our sample (47.8%) demonstrated the co-occurrence of CS and DER, while 38% presented with DER syndrome, CS, and kinesiophobia.

CONCLUSION

The majority of our patients were classified as DER; they also presented with high levels of CS and/or psychological distress. This suggests that MDT mechanical subgroups, particularly DER, can present with co-occurring biopsychosocial influences. Without assessing CS and psychological distress, MDT therapists may miss crucial information. Further research is required to determine the optimal management of patients presenting with mechanical and non-mechanical drivers of pain.