Robby De Pauw

Relations Between Brain Alterations and Clinical Pain Measures in Chronic Musculoskeletal Pain: A Systematic Review

UNLABELLED Compelling evidence has shown chronic widespread and exaggerated pain experience in chronic musculoskeletal pain (MSKP) conditions. In addition, neuroimaging research has revealed morphological and functional brain alterations in these patients. It is hypothesized that brain alterations play a role in the persistent pain complaints of patients with chronic MSKP. Nevertheless, lack of overview exists regarding the relations between brain alterations and clinical measures of pain. The present systematic review was performed according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines, to investigate the relations between structural or functional brain alterations, using magnetic resonance imaging scans, and clinical pain measures in patients with chronic MSKP. PubMed, Web of Science, Cinahl, and Cochrane databases were searched. First, the obtained articles were screened according to title and abstract. Second, the screening was on the basis of full-text. Risk of bias in included studies was investigated according to the modified Newcastle-Ottawa Scale. Twenty studies met the inclusion criteria. Moderate evidence shows that higher pain intensity and pressure pain sensitivity are related to decreased regional gray matter (GM) volume in brain regions encompassing the cingulate cortex, the insula, and the superior frontal and temporal gyrus. Further, some evidence exists that longer disease duration in fibromyalgia is correlated with decreased total GM volume. Yet, inconclusive evidence exists regarding the association of longer disease duration with decreased or increased regional GM volume in other chronic MSKP conditions. Inconclusive evidence was found regarding the direction of the relation of pain intensity and pressure pain sensitivity with microstructural white matter and functional connectivity alterations. In conclusion, preliminary to moderate evidence demonstrates relations between clinical pain measures, and structural and functional connectivity alterations within brain regions involved in somatosensory, affective, and cognitive processing of pain in chronic MSKP. Nevertheless, inconclusive results exist regarding the direction of these relations. Further research is warranted to unravel whether these brain alterations are positively or negatively correlated to clinical pain measures. PERSPECTIVE Structural and functional brain alterations within regions involved in somatosensory, affective, and cognitive pain processing play a crucial role in the persistent pain of chronic MSKP patients. Accordingly, these brain alterations have to be taken into account when assessing and treating patients with chronic MSKP.

Lumbar muscle structure and function in chronic versus recurrent low back pain: a cross-sectional study

BACKGROUND CONTEXT Heterogeneity exists within the low back pain (LBP) population. Some patients recover after every pain episode, whereas others suffer daily from LBP complaints. Until now, studies rarely make a distinction between recurrent low back pain (RLBP) and chronic low back pain (CLBP), although both are characterized by a different clinical picture. Clinical experiences also indicate that heterogeneity exists within the CLBP population. Muscle degeneration, like atrophy, fat infiltration, alterations in muscle fiber type, and altered muscle activity, compromises proper biomechanics and motion of the spinal units in LBP patients. The amount of alterations in muscle structure and muscle function of the paraspinal muscles might be related to the recurrence or chronicity of LBP. PURPOSE The aim of this experimental study is to evaluate differences in muscle structure (cross-sectional area and lean muscle fat index) and muscle activity of the multifidus (MF) and erector spinae (ES) during trunk extension, in patients with RLBP, non-continuous CLBP, and continuous CLBP. STUDY DESIGN AND SETTING This cross-sectional study took place in the university hospital of Ghent, Belgium. Muscle structure characteristics and muscle activity were assessed by magnetic resonance imaging (MRI). PATIENT SAMPLE Fifty-five adults with non-specific LBP (24 RLBP in remission, 15 non-continuous CLBP, 16 continuous CLBP) participated in this study. OUTCOME MEASURES Total cross-sectional area, muscle cross-sectional area, fat cross-sectional area, lean muscle fat index, T2-rest and T2-shift were assessed. METHODS A T1-weighted Dixon MRI scan was used to evaluate spinal muscle cross-sectional area and fat infiltration in the lumbar MF and ES. Muscle functional MRI was used to evaluate the muscle activity of the lumbar MF and ES during a lumbar extension exercise. Before and after the exercise, a pain assessment was performed. This study was supported by grants from the Special Research Fund of Ghent University (DEF12/AOP/022) without potential conflict of interest-associated biases in the text of the paper. RESULTS Fat cross-sectional area and lean muscle fat index were significantly higher in MF and ES in continuous CLBP compared with non-continuous CLBP and RLBP (p<.05). No differencesbetween groups were found for total cross-sectional area and muscle cross-sectional area in MF or ES (p>.05). Also, no significant differences between groups for T2-rest were established. T2-shift, however, was significantly lower in MF and ES in RLBP compared with, respectively, non-continuous CLBP and continuous CLBP (p<.05). CONCLUSIONS These results indicate a higher amount of fat infiltration in the lumbar muscles, in the absence of clear atrophy, in continuous CLBP compared with RLBP. A lower metabolic activity of the lumbar muscles was seen in RLBP replicating a relative lower intensity in contractions performed by the lumbar muscles in RLBP compared with non-continuous and continuous CLBP. In conclusion, RLBP differs from continuous CLBP for both muscle structure and muscle function, whereas non-continuous CLBP seems comparable with RLBP for lumbar muscle structure and with continuous CLBP for lumbar muscle function. These results underline the differences in muscle structure and muscle function between different LBP populations.

Differences Between Women With Traumatic and Idiopathic Chronic Neck Pain and Women Without Neck Pain: Interrelationships Among Disability, Cognitive Deficits, and Central Sensitization

Background To date, a clear differentiation of disability, cognitive deficits, and central sensitization between chronic neck pain of a traumatic nature and that of a nontraumatic nature is lacking. Objective This study aimed to examine differences in disability, cognitive deficits, and central sensitization between women with traumatic and idiopathic (nontraumatic) chronic neck pain and women who were healthy. In addition, interrelationships among these variables were investigated. Design This was a case-control study. Methods Ninety-five women (28 women who were healthy [controls], 35 women with chronic idiopathic neck pain [CINP], and 32 women with chronic whiplash-associated disorders [CWAD] [traumatic]) were enrolled in the study. First, all participants completed standardized questionnaires to investigate pain-related disability and health-related quality of life. Next, cognitive performance was assessed. Finally, pressure pain thresholds and conditioned pain modulation were examined to investigate central sensitization. Results Pain-related disability, reduced health-related quality of life, and cognitive deficits were present in participants with CWAD and, to a significantly lesser extent, in participants with CINP. Local hyperalgesia was demonstrated in participants with CWAD and CINP but not in women who were healthy. However, distant hyperalgesia and decreased conditioned pain modulation efficacy were shown only in participants with CWAD; this result is indicative of the presence of central sensitization. Moderate to strong Spearman correlations (ρ=.456-.701) among disability, cognitive deficits, and hyperalgesia (local and distant) were observed in participants with CWAD. In participants with CINP, only local hyperalgesia and subjective cognitive deficits were moderately (ρ=.463) correlated. Limitations No conclusions about the causality of the observed correlations can be drawn. Conclusions This innovative research revealed important differences between women with CWAD and women with CINP and thus provided evidence of the clinical importance of distinguishing the assessment and rehabilitation approaches for both pain conditions.

Morphological and physiological differences in the upper trapezius muscle in patients with work-related trapezius myalgia compared to healthy controls: A systematic review

BACKGROUND Trapezius myalgia is a common musculoskeletal complaint, characterized by pain, stiffness and tightness of the upper trapezius muscle. It is often work-related and caused by prolonged static and repetitive work tasks. It is hypothesized that this leads to various morphological and physiological alterations in muscle tissue but the pathophysiology is poorly understood. These alterations can be investigated by analysing muscle biopsies in order to reveal the underlying cellular mechanisms. OBJECTIVES This systematic review aimed at providing a summary of the existing literature regarding morphological and physiological differences between people with work-related trapezius myalgia and healthy controls, obtained by analysing muscle biopsies. DESIGN Systematic review. METHODS A systematic literature search was performed in following databases: Pubmed, Web of Science and Embase by using different keyword combinations. This systematic review is reported following the PRISMA guidelines. RESULTS Generally, low to moderate evidence was found for the absence of differences in muscle morphology in people with trapezius myalgia, compared to healthy controls. However, significant differences were mainly found in comparison with the control group with another occupation than the myalgic group. It can thus be hypothesized that morphological alterations in muscle tissue are related to work load and not to pain. Low to moderate evidence was also found for the absence of differences at the physiological level. CONCLUSIONS Based on this systematic review, there are no clear differences in muscle morphology and physiology between subjects with trapezius myalgia and healthy controls.

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.

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

Abstract 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.

Effect of Pain Neuroscience Education Combined With Cognition-Targeted Motor Control Training on Chronic Spinal Pain: A Randomized Clinical Trial

Importance Effective treatments for chronic spinal pain are essential to reduce the related high personal and socioeconomic costs. Objective To compare pain neuroscience education combined with cognition-targeted motor control training with current best-evidence physiotherapy for reducing pain and improving functionality, gray matter morphologic features, and pain cognitions in individuals with chronic spinal pain. Design, Setting, and Participants Multicenter randomized clinical trial conducted from January 1, 2014, to January 30, 2017, among 120 patients with chronic nonspecific spinal pain in 2 outpatient hospitals with follow-up at 3, 6, and 12 months. Interventions Participants were randomized into an experimental group (combined pain neuroscience education and cognition-targeted motor control training) and a control group (combining education on back and neck pain and general exercise therapy). Main Outcomes and Measures Primary outcomes were pain (pressure pain thresholds, numeric rating scale, and central sensitization inventory) and function (pain disability index and mental health and physical health). Results There were 22 men and 38 women in the experimental group (mean [SD] age, 39.9 [12.0] years) and 25 men and 35 women in the control group (mean [SD] age, 40.5 [12.9] years). Participants in the experimental group experienced reduced pain (small to medium effect sizes): higher pressure pain thresholds at primary test site at 3 months (estimated marginal [EM] mean, 0.971; 95% CI, –0.028 to 1.970) and reduced central sensitization inventory scores at 6 months (EM mean, –5.684; 95% CI, –10.589 to –0.780) and 12 months (EM mean, –6.053; 95% CI, –10.781 to –1.324). They also experienced improved function (small to medium effect sizes): significant and clinically relevant reduction of disability at 3 months (EM mean, –5.113; 95% CI, –9.994 to –0.232), 6 months (EM mean, –6.351; 95% CI, –11.153 to –1.550), and 12 months (EM mean, –5.779; 95% CI, –10.340 to –1.217); better mental health at 6 months (EM mean, 36.496; 95% CI, 7.998-64.995); and better physical health at 3 months (EM mean, 39.263; 95% CI, 9.644-66.882), 6 months (EM mean, 53.007; 95% CI, 23.805-82.209), and 12 months (EM mean, 32.208; 95% CI, 2.402-62.014). Conclusions and Relevance Pain neuroscience education combined with cognition-targeted motor control training appears to be more effective than current best-evidence physiotherapy for improving pain, symptoms of central sensitization, disability, mental and physical functioning, and pain cognitions in individuals with chronic spinal pain. Significant clinical improvements without detectable changes in brain gray matter morphologic features calls into question the relevance of brain gray matter alterations in this population. Trial Registration clinicaltrials.gov Identifier: NCT02098005