Brain imaging of pain sensitization in patients with knee osteoarthritis

Characterization of clinical data for patient stratification in moderate osteoarthritis with support vector machines, regulatory network models, and verification against osteoarthritis Initiative data

Knee osteoarthritis (OA) diagnosis is based on symptoms, assessed through questionnaires such as the WOMAC. However, the inconsistency of pain recording and the discrepancy between joint phenotype and symptoms highlight the need for objective biomarkers in knee OA diagnosis. To this end, we study relationships among clinical and molecular data in a cohort of women (n = 51) with Kellgren-Lawrence grade 2-3 knee OA through a Support Vector Machine (SVM) and a regulation network model. Clinical descriptors (i.e., pain catastrophism, depression, functionality, joint pain, rigidity, sensitization and synovitis) are used to classify patients. A Youden's test is performed for each classifier to determine optimal binarization thresholds for the descriptors. Thresholds are tested against patient stratification according to baseline WOMAC data from the Osteoarthritis Initiative, and the mean accuracy is 0.97. For our cohort, the data used as SVM inputs are knee OA descriptors, synovial fluid proteomic measurements (n = 25), and transcription factor activation obtained from regulatory network model stimulated with the synovial fluid measurements. The relative weights after classification reflect input importance. The performance of each classifier is evaluated through ROC-AUC analysis. The best classifier with clinical data is pain catastrophism (AUC = 0.9), highly influenced by funcionality and pain sensetization, suggesting that kinesophobia is involved in pain perception. With synovial fluid proteins used as input, leptin strongly influences every classifier, suggesting the importance of low-grade inflammation. When transcription factors are used, the mean AUC is limited to 0.608, which can be related to the pleomorphic behaviour of osteoarthritic chondrocytes. Nevertheless, funcionality has an AUC of 0.7 with a decisive importance of FOXO downregulation. Though larger and longitudinal cohorts are needed, this unique combination of SVM and regulatory network model shall help to stratify knee OA patients more objectively.

Deficient gait function despite effect index of the Western Ontario and McMaster university osteoarthritis index score considered cured one year after bilateral total knee arthroplasty

BACKGROUND

To clarify the value of gait analysis and its consistency with traditional scoring scales for the evaluation of knee joint function after total knee arthroplasty (TKA).

METHODS

This study included 25 patients with knee osteoarthritis (KOA) who underwent bilateral TKA, and 25 conditionally matched healthy individuals, categorised into the experimental and control groups, respectively. Patients in the experimental group underwent gait analysis and Western Ontario and McMaster University Osteoarthritis Index (WOMAC) evaluation before and 1 year after TKA. Weight-bearing balance and walking stability were assessed using discrete trends of relevant gait indicators. Pearson's correlation analysis was performed on the gait and WOMAC score data of the experimental group before and after TKA.

RESULTS

One year after TKA, patients' gait indices (except gait cycle) were significantly better than before surgery, but significantly worse than that of the control group (P < 0.01). The shape of patients' plantar pressure curves did not return to normal. Additionally, the discrete trend of related gait indicators reflecting weight-bearing balance and walking stability were smaller than before TKA, but still greater than that of the control group. The WOMAC scores of patients 1 year after TKA were significantly lower than those before TKA (P < 0.001), and the efficacy index was > 80%. The WOMAC scores and gait analysis results were significantly correlated before TKA (P < 0.05).

CONCLUSIONS

Gait analysis should be used in conjunction with scoring scales to assess joint functions.

Assessment of Pain in Osteoarthritis of the Knee

Knee osteoarthritis (KOA) pain is a subjective and personal experience, making it challenging to characterise patients' experiences and assess their pain. In addition, there is no global standard for the assessment of pain in KOA. Therefore, this article examines the possible methods of assessing and characterising pain in patients with KOA using clinical symptoms, pain assessment tools, and imaging. We examine the current methods of assessment of pain in KOA and their application in clinical practice and clinical trials. Furthermore, we explore the possibility of creating individualised pain management plans to focus on different pain characteristics. With better evaluation and standardisation of pain assessment in these patients, it is hoped that patients would benefit from improved quality of life. At the same time, improvement in pain assessment would enable better data collection regarding symptom response in clinical trials for the treatment of osteoarthritis.

Myofascial Pain as an Unseen Comorbidity in Osteoarthritis: A Scoping Review

OBJECTIVE

This review aimed to identify, summarize, and appraise the evidence supporting the coexistence of myofascial pain (MPS) and trigger points (MTrP) in osteoarthritis (OA), and the effectiveness of MTrPs treatments in OA-related pain and physical function outcomes.

METHODS

Three databases were searched from inception to June 2022. We included observational and experimental studies to fulfill our 2 study aims. Two independent reviewers conducted 2-phase screening procedures and risk of bias using checklist tools for cross-sectional, quasi-experimental, and randomized control trials. Patient characteristics, findings of active and latent MTrPs in relevant muscles, treatments, and pain and physical function outcomes were extracted from low-risk bias studies.

RESULTS

The literature search yielded 2898 articles, of which 6 observational and 7 experimental studies had a low bias risk and the data extracted. Active MTrPs in knee OA patients was more evident in the quadriceps and hamstring muscles than in healthy individuals. Dry needling on active MTrPs improved pain and physical function in the short term compared with sham treatment in hip OA patients. In knee OA, dry needling on latent or active MTrPs improved pain and functional outcomes compared with sham needling but did not result in better pain and physical outcomes when combined with a physical exercise program.

DISCUSSION

The presence of active versus latent MTrPs seems to be a more sensitive discriminating feature of OA given that latent is often present in OA and healthy individuals. Dry needling on active MTrPs improved pain and physical function in the short term compared with sham treatment in hip OA patients. However, the small sample size and the few number of studies limit any firm recommendation on the treatment.

REGISTRY

The study protocol was prospectively registered in Open Science Framework (https://doi.org/10.17605/OSF.IO/8DVU3).

Modulation effects of different treatments on periaqueductal gray resting state functional connectivity in knee osteoarthritis knee pain patients

BACKGROUND

The analgesic effect of acupuncture is widely recognized, but the mechanical characteristics of acupuncture for pain relief, compared to non-steroidal anti-inflammatory (NSAIDs) and placebo medication, remain unknown.

AIMS

To compare the modulation effects of acupuncture treatment with NSAIDs and placebo medication on descending pain modulation system (DPMS) in knee osteoarthritis (KOA) patients.

METHODS

This study recruited 180 KOA patients with knee pain and 41 healthy controls (HCs). Individuals with KOA knee pain were divided randomly into groups of verum acupuncture (VA), sham acupuncture (SA), celecoxib (SC), placebo (PB), and waiting list (WT), with 36 patients in each group. VA and SA groups included ten sessions of puncturing acupoints or puncturing non-acupoints acupuncture treatment for two successive weeks. Celecoxib capsules were continuously given orally to patients in the SC group at a dosage of 200 mg daily for 2 weeks. In the PB group, patients received a placebo capsule once a day for 2 weeks at the same dosage as celecoxib capsules. In the WL group, patients did not receive any treatment. Patients underwent a resting-state BOLD-fMRI scan pre- and post-receiving the therapy, whereas HCs only underwent a baseline scan. Seed (ventrolateral periaqueductal gray, vlPAG, a key node in DPMS) based resting-state functional connectivity (rs-FC) was applied in the data analysis.

RESULTS

All groups demonstrated improved knee pain scores relative to the initial state. There was no statistical difference between the VA and SA groups in all clinical outcomes, and vlPAG rs-FC alterations. KOA knee pain individuals reported higher vlPAG rs-FC in the bilateral thalamus than HCs. KOA knee pain patients in the acupuncture group (verum + sham, AG) exhibited increased vlPAG rs-FC with the right dorsolateral prefrontal cortex (DLPFC) and the right angular, which is associated with knee pain improvement. In contrast with the SC and PB group, the AG exhibited significantly increased vlPAG rs-FC with the right DLPFC and angular. Contrary to the WT group, the AG showed greater vlPAG rs-FC with the right DLPFC and precuneus.

CONCLUSIONS

Acupuncture treatment, celecoxib, and placebo medication have different modulation effects on vlPAG DPMS in KOA knee pain patients. Acupuncture could modulate vlPAG rs-FC with brain regions associated with cognitive control, attention, and reappraisal for knee pain relief in KOA patients, compared with celecoxib and placebo medication.

Effects of remifentanil on brain responses to noxious stimuli during deep propofol sedation

BACKGROUND

The safety of anaesthesia has improved as a result of better control of anaesthetic depth. However, conventional monitoring does not inform on the nature of nociceptive processes during unconsciousness. A means of inferring the quality of potentially painful experiences could derive from analysis of brain activity using neuroimaging. We have evaluated the dose effects of remifentanil on brain response to noxious stimuli during deep sedation and spontaneous breathing.

METHODS

Optimal data were obtained in 26 healthy subjects. Pressure stimulation that proved to be moderately painful before the experiment was applied to the thumbnail. Functional MRI was acquired in 4-min periods at low (0.5 ng ml^-1), medium (1 ng ml^-1), and high (1.5 ng ml^-1) target plasma concentrations of remifentanil at a stable background infusion of propofol adjusted to induce a state of light unconsciousness.

RESULTS

At low remifentanil doses, we observed partial activation in brain areas processing sensory-discriminative and emotional-affective aspects of pain. At medium doses, relevant changes were identified in structures highly sensitive to general brain arousal, including the brainstem, cerebellum, thalamus, auditory and visual cortices, and the frontal lobe. At high doses, no significant activation was observed.

CONCLUSIONS

The response to moderately intense focal pressure in pain-related brain networks is effectively eliminated with safe remifentanil doses. However, the safety margin in deep sedation-analgesia would be narrowed in minimising not only nociceptive responses, but also arousal-related biological stress.

Pain Empathy and Its Association with the Clinical Pain in Knee Osteoarthritis Patients

Objective

Knee osteoarthritis (KOA) is a painful chronic disorder. Evidence has shown that a history of chronic pain plays an important role in shaping empathy. Empathy, a valuable indicator of social functioning that refers to an individual's ability to share the experiences of others, however, has been overlooked in KOA patients. This study aimed to investigate empathy and its association with clinical pain in KOA patients.

Methods

KOA patients (n=47) and healthy controls (HCs, n=44) completed two empathy-for-pain tasks: a pain judgment task in which participants judged whether a person in an image felt pain or not, and a pain rating task in which they estimated pain intensity for themselves and others. The Interpersonal Reactivity Index was used to measure participants' trait empathy, and clinical severity and psychological factors were assessed using relevant instruments.

Results

Compared to HCs, KOA patients showed higher accuracy when judging pain and non-pain images and reported overall higher pain intensity when rating for themselves and others. KOA patients also showed greater personal distress than HCs in terms of their self-reported empathy. Moreover, pain catastrophizing particularly mediated the relationship between pain severity and pain ratings for others, and depression, anxiety, and pain catastrophizing all mediated the association between pain severity and empathy-induced personal distress.

Conclusion

These findings suggest that patients with KOA have increased empathy, demonstrated by elevated sensitivity to pain-related scenes and intense emotional responses.

Distinctive alterations in the functional anatomy of the cerebral cortex in pain-sensitized osteoarthritis and fibromyalgia patients

Background

Pain-sensitized osteoarthritis and fibromyalgia patients characteristically show nociceptive system augmented responsiveness as a common feature. However, sensitization can be originally related to the peripheral injury in osteoarthritis patients, whereas pain and bodily discomfort spontaneously occur in fibromyalgia with no apparent origin. We investigated the distinct functional repercussion of pain sensitization in the cerebral cortex in both conditions.

Methods

Thirty-one pain-sensitized knee osteoarthritis patients and 38 fibromyalgia patients were compared with matched control groups. And new samples of 34 sensitized knee osteoarthritis and 63 fibromyalgia patients were used to directly compare each condition. A combined measure of local functional connectivity was estimated to map functional alterations in the cerebral cortex at rest.

Results

In osteoarthritis, weaker local connectivity was identified in the insula, which is a cortical area processing important aspects of the brain response to painful stimulation. In contrast, fibromyalgia patients showed weaker connectivity in the sensorimotor cortex extensively affecting the cortical representation of the body.

Conclusions

In osteoarthritis, weaker insular cortex connectivity is compatible with reduced neural activity during metabolic recovery after repeated activation. In the fibromyalgia neurophysiological context, weaker connectivity may better express both reduced neural activity and increased excitability, particularly affecting the sensorimotor cortex in patients with spontaneous body pain. Such a combination is compatible with a central gain enhancement mechanism, where low sensory tolerance results from the over-amplification of central sensory reception to compensate a presumably weak sensory input. We propose that deficient proprioception could be a factor contributing to weak sensory input.

Predictive Value of Pain Sensitization Associated with Response to Exercise Therapy in Patients with Knee Osteoarthritis: A Prospective Cohort Study

PURPOSE

Knee osteoarthritis (KOA) is a degenerative disease with inflammation, becoming persistent as it progresses, resulting in reduced quality of life. Exercise is the recommended treatment for KOA; however, the extent of pain reduction with exercise is heterogeneous and the prognostic implications of baseline factors in patients undergoing exercise are still unknown. This study examined the association between the response to exercise therapy and clinical outcomes, radiologic severity, and pain sensitization, and investigated the optimal predictive value for the effectiveness of exercise.

PATIENTS AND METHODS

Demographics, radiologic severity, pressure pain threshold (PPT), and temporal summation of pain (TSP) at the knee, tibia, and forearm were assessed at baseline. The pain numeric rating scale (NRS) was assessed before and after 12 weeks of exercise. Patients were divided into responder/non-responder groups according to recommended criteria: responder, ≥30% reduction in pain; non-responder, <30% reduction in pain, and each variable was compared between the groups. The area under the curve (AUC) and cutoff points were determined by receiver operating characteristic curve analysis.

RESULTS

Sixty-five patients were categorized as responders and 26 as non-responders. In the non-responder group, baseline NRS (P<0.01), pain duration (P<0.01), and TSP at the knee (P<0.001) and tibia (P<0.05) were significantly higher, and PPT at the knee (P<0.001), tibia (P<0.001), and forearm (P<0.001) were significantly lower, than those in the responder group; however, no significant differences between groups were found in other demographics and radiologic severity. The variables that showed moderate or better predictive ability (AUC≥0.7) were PPT at the knee (cutoff points: 241.5 kPa), tibia (307.5 kPa), forearm (318.5 kPa), and TSP at the knee (15.5 mm).

CONCLUSION

Our findings suggest that pain sensitization is associated with the response to exercise therapy. Furthermore, we provide clinically predictive values for PPT and TSP in predicting the outcome to exercise in KOA.

Cerebral mechanism of Tuina analgesia in management of knee osteoarthritis using multimodal MRI: study protocol for a randomised controlled trial

Background

The chronic pain of patients with knee osteoarthritis (KOA) seriously affects their quality of life and leads to heavy social and economic burden. As a nondrug therapy in Traditional Chinese Medicine (TCM), Tuina is generally recognised as safe and effective for reducing the chronic pain of KOA. However, the underlying central mechanisms of Tuina for improving the pain of KOA are not fully understood.

Methods/design

This study will be a randomised controlled trial with a parallel-group design. A total of 60 eligible participants will be assigned to the Tuina group or healthcare education group (Education group) at 1:1 ratio using stratified randomisation with gender and age as factors. The interventions of both groups will last for 30 min per session and be conducted twice each week for 12 weeks. This study will primarily focus on pain evaluation assessed by detecting the changes in brain grey matter (GM) structure, white matter (WM) structure, and the cerebral functional connectivity (FC) elicited by Tuina treatment, e.g., thalamus, hippocampus, anterior cingulate gyrus, S1, insula, and periaqueductal grey subregions (PAG). The two groups of patients will be evaluated by clinical assessments and multimodal magnetic resonance imaging (MRI) to observe the alterations in the GM, WM, and FC of participants at the baseline and the end of 6 and 12 weeks’ treatment and still be evaluated by clinical assessments but not MRI for 48 weeks of follow-up. The visual analogue scale of current pain is the primary outcome. The Short-Form McGill Pain Questionnaire, Western Ontario and McMaster Universities Osteoarthritis Index, 36-Item Short Form Health Survey, Hamilton Depression Scale, and Hamilton Anxiety Scale will be used to evaluate the pain intensity, pain feeling, pain emotion, clinical symptoms, and quality of life, respectively. MRI assessments, clinical data evaluators, data managers, and statisticians will be blinded to the group allocation in the outcome evaluation procedure and data analysis to reduce the risk of bias. The repeated measures analysis of variance (2 groups × 6 time points ANOVA) will be used to analyse numerical variables of the clinical and neuroimaging data obtained in the study. P<0.05 will be the statistical significance level.

Discussion

The results of this randomised controlled trial with clinical assessments and multimodal MRI will help reveal the influence of Tuina treatment on the potential morphological changes in cortical and subcortical brain structures, the white matter integrity, and the functional activities and connectivity of brain regions of patients with KOA, which may provide scientific evidence for the clinical application of Tuina in the management of KOA.

Trial registration

Chinese Clinical Trial Registry ChiCTR2000037966. Registered on Sep. 8, 2020.

Dissemination

The results will be published in peer-reviewed journals and disseminated through the study’s website, and conferences.

Altered cerebral blood flow patterns in ankylosing spondylitis: A three-dimensional pseudo-continuous arterial spin labeling study

Objective

This study aimed to detect the cerebral blood flow (CBF) values changes in patients with ankylosing spondylitis (AS) and to evaluate the correlation between the CBF values and the specific clinical characteristics.

Materials and methods

Forty-eight patients with AS (43 male and 5 female) and 42 healthy controls (HCs) (38 male and 4 female) were recruited. Three-dimensional pseudo-continuous arterial spin labeling (3D-pCASL) was performed on a 3.0T magnetic resonance imaging (MRI). CBF values were obtained on the Philips post-processing workstation based on arterial spin labeling (ASL) data. The two-sample t-test was used to compare CBF differences. The correlation between CBF values and specific clinical characteristics of AS was evaluated.

Results

The AS group showed increased CBF values in the right precentral gyrus, the left inferior frontal gyrus, and the left temporal pole compared with HCs the AS group also showed decreased CBF values in the left precuneus and the left superior occipital gyrus compared with HCs. There were no significant correlations between the CBF values and the clinical characteristics including total back pain (TBP), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).

Conclusion

Patients with AS displayed CBF changes compared with HCs using 3D-PCASL. These results may enhance our understanding of the neural substrates of AS and provide evidence of AS-related neurological impairment.

Aberrant functional connectivity between anterior cingulate cortex and left insula in association with therapeutic response to biologics in inflammatory arthritis

BACKGROUND

Brain activity is reported to be associated with individual pain susceptibility and inflammatory status, possibly contributing to disease activity assessment in inflammatory arthritis (IA) including rheumatoid arthritis (RA) and spondyloarthritis (SpA). However, what alteration of brain function associated with disease activity and therapeutic effectiveness in IA remains unclear. We aimed to identify the alterations of brain functional connectivity (FC) shared in both RA and SpA, and evaluate its relationship to anti-rheumatic treatment response using functional magnetic resonance imaging (MRI).

PATIENTS AND METHODS

Structural and resting-state functional MRI data were acquired from patients with IA, patients with osteoarthritis (OA) and heathy controls (HCs). Two datasets were adopted to derive (51 IA, 56 OA, and 17 HCs) and validate (31 IA) the observations. 33 IA patients in the derivation dataset and all the patients in validation dataset required biological treatment and were clinically evaluated before and after therapy. Via whole-brain pair-wise FC analyses, we analyzed IA-specific FC measures relevant to therapeutic response to biologics.

RESULTS

The value of FC between left insular cortex (IC) and anterior cingulate cortex (ACC) was significantly low in IA patients compared with OA patients and HCs. We demonstrated that the FC between left anterior long insular gyrus as a subdivision of IC and ACC was significantly associated with therapeutic response to biologics regarding the improvement of patients' global assessment (PGA) in both derivation and validation datasets.

CONCLUSION

Disease-specific resting-state FC provides a means to assess the therapeutic improvement of PGA and would be a clinical decision-making tool with predictability for treatment response in both RA and SpA.

Evaluation of mindfulness based stress reduction in symptomatic knee or hip osteoarthritis patients: a pilot randomized controlled trial

Background

To evaluate the efficacy for symptomatic knee and hip osteoarthritis (OA) patients of a mindfulness-based stress reduction (MBSR) program versus usual care.

Methods

Randomized, physician-blind, clinical trial in a monocentric prospective pilot study. Adult participants with symptomatic knee or hip OA were randomized into either intervention or control groups. The intervention group completed the MBSR program for a two-and-a-half-hour weekly session for 8 weeks. Usual care management was similar in both groups. All patients were evaluated at baseline, 3 months and 6 months. The primary objective was to evaluate the change in WOMAC pain score between baseline and 3 months in the MBSR group compared to usual care group. Secondary objectives were to evaluate changes in pain VAS, WOMAC scores, quality of life (SF-36), HAD scores between baseline and 3/6 months.

Results

Forty patients were enrolled in the study. No differences in the WOMAC pain score between the two groups were observed in the different time points. A similar pattern was found for the other assessment outcomes. However, a significant pain VAS reduction in favor of the MBSR group between baseline and 6 months (− 29.6 ± 26.6 vs − 9.3 ± 27.3; p = 0.03) has been reached.

Conclusions

Our pilot RCT found contrasting results with no benefit on WOMAC pain and function and a delayed but long-term efficacy in pain VAS following a MBSR program in symptomatic knee or hip OA patients. Future studies with larger sample size are mandatory to confirm these preliminary results.

Trial registration The study was registered in ClinicalTrials.gov (NCT03644615, 23/08/2018).

Supplementary Information

The online version contains supplementary material available at 10.1186/s41927-022-00277-9.

High Prevalence of Pain Sensitization in Knee Osteoarthritis: A Meta-Analysis with Meta-Regression

OBJECTIVE

The aim of this meta-analysis was to study the evidence on pain sensitization in knee osteoarthritis (OA), providing a quantitative synthesis of its prevalence and impact. Factors associated with pain sensitization were also investigated.

METHODS

Meta-analysis; PubMed (MEDLINE), Cochrane Central Register (CENTRAL), and Web of Science were searched on February 2021. Level I to level IV studies evaluating the presence of pain sensitization in patients with symptomatic knee OA, documented through a validated method (questionnaires or quantitative sensory testing), were included. The primary outcome was the prevalence of pain sensitization. Factors influencing the prevalence were also evaluated, as well as differences in terms of pain thresholds between knee OA patients and healthy controls.

RESULTS

Fifty-three articles including 7,117 patients were included. The meta-analysis of proportion documented a prevalence of pain sensitization of 20% (95% confidence interval [CI] = 16%-26%) with a significant heterogeneity of results (I² = 89%, P < 0.001). The diagnostic tool used was the main factor influencing the documented prevalence of pain sensitization (P = 0.01). Knee OA patients presented higher pain sensitivity compared with healthy controls, both in terms of local pressure pain threshold (standardized mean difference [SMD] = -1.00, 95% CI = -1.67 to -0.32, P = 0.007) and distant pressure pain threshold (SMD = -0.54, 95% CI = -0.76 to -0.31, P < 0.001).

CONCLUSIONS

Knee OA pain presents features that are consistent with a significant degree of pain sensitization. There is a high heterogeneity in the reported results, mainly based on the diagnostic tool used. The identification of the best methods to detect pain sensitization is warranted to correctly evaluate and manage symptoms of patients affected by knee OA.

REGISTRATION

PROSPERO CRD42019123347.

Altered Intra- and Inter-Network Functional Connectivity in Patients With Crohn’s Disease: An Independent Component Analysis-Based Resting-State Functional Magnetic Resonance Imaging Study

Background

Many studies have reported changes in the structure and function of several brain areas in patients with Crohn’s disease (CD). However, little is known about whether the possible functional connectivity of resting-state networks (RSNs) is altered in CD patients.

Purpose

Aim to investigate the intra- and inter-network alterations between related RSNs in patients with CD and the potential relationships between altered neuroimaging and CD clinical indices.

Materials and Methods

In this study, 20 CD patients and 22 age- and sex-matched healthy controls were included. All participants underwent functional magnetic resonance imaging examination. We used independent component analysis (ICA) to explore the changes in RSNs and evaluated functional connectivity between different RSNs using functional network connectivity (FNC) analysis, and Pearson correlation analysis was performed between altered intra- and inter-network functional connectivity and CD clinical index.

Results

Six CD-related RSNs were identified via ICA, namely the high visual, prime visual, language, dorsal default mode, posterior insula, and precuneus networks. Compared to healthy controls, patients with CD showed significant changes in prime visual and language networks. Additionally, the functional connectivity (FC) values of the left calcarine within the prime visual network were negatively correlated with CD duration. The inter-alterations showed that a significantly increased FNC existed between the language and dorsal default mode networks.

Conclusion

The results showed CD-related changes in brain functional networks. This evidence provides more insights into the pathophysiological mechanisms of brain plasticity in CD.

The neurologic pain signature responds to nonsteroidal anti-inflammatory treatment vs placebo in knee osteoarthritis

Supplemental Digital Content is Available in the Text.

fMRI-based measures, validated for nociceptive pain, respond to acute osteoarthritis pain, are not sensitive to placebo, and are mild-to-moderately sensitive to naproxen.

Introduction:

Many drug trials for chronic pain fail because of high placebo response rates in primary endpoints. Neurophysiological measures can help identify pain-linked pathophysiology and treatment mechanisms. They can also help guide early stop/go decisions, particularly if they respond to verum treatment but not placebo. The neurologic pain signature (NPS), an fMRI-based measure that tracks evoked pain in 40 published samples and is insensitive to placebo in healthy adults, provides a potentially useful neurophysiological measure linked to nociceptive pain.

Objectives:

This study aims to validate the NPS in knee osteoarthritis (OA) patients and test the effects of naproxen on this signature.

Methods:

In 2 studies (50 patients, 64.6 years, 75% females), we (1) test the NPS and other control signatures related to negative emotion in knee OA pain patients; (2) test the effect of placebo treatments; and (3) test the effect of naproxen, a routinely prescribed nonsteroidal anti-inflammatory drug in OA.

Results:

The NPS was activated during knee pain in OA (d = 1.51, P < 0.001) and did not respond to placebo (d = 0.12, P = 0.23). A single dose of naproxen reduced NPS responses (vs placebo, NPS d = 0.34, P = 0.03 and pronociceptive NPS component d = 0.38, P = 0.02). Naproxen effects were specific for the NPS and did not appear in other control signatures.

Conclusion:

This study provides preliminary evidence that fMRI-based measures, validated for nociceptive pain, respond to acute OA pain, do not appear sensitive to placebo, and are mild-to-moderately sensitive to naproxen.

Altered activity of pain processing brain regions in association with hip osteoarthritis

Hip osteoarthritis (OA) is characterized by chronic pain, but there remains a mismatch between symptoms and radiological findings. Recently, brain connectivity has been implicated in the modulation of chronic peripheral pain, however its association with perceived pain in hip OA is not understood. We used resting-state functional magnetic resonance imaging (fMRI) to examine functional connectivity associated with pain in hip OA patients. Thirty participants with hip OA and 10 non-OA controls were recruited. Using the visual analogue scale (VAS), pain scores were obtained before and after performing a painful hip activity. All participants underwent 3.0 T resting-state fMRI, and functional connectivity of brain regions associated with pain was determined and compared between participants, and before and after hip activity. Relative to controls, functional connectivity between the secondary somatosensory cortex and left posterior insula was increased, and functional connectivity between the bilateral posterior insula and motor cortices was significantly decreased in hip OA participants. In response to painful hip activity, functional connectivity increased between the thalamus, periaqueductal grey matter and brainstem. Functional connections between brain regions associated with pain are altered in hip OA patients, and several connections are modulated by performing painful activity. Unique lateralization of left posterior insula and linked brain functional connectivity patterns allows assessment of pain perception in hip OA providing an unbiased method to evaluate pain perception and pain modulation strategies.

Acupuncture (superficial dry-needling) as a treatment for chronic postherpetic neuralgia - a randomized clinical trial

BACKGROUND

Postherpetic neuralgia is a painful condition where finding sufficient treatment poses a great challenge. Acupuncture is often used as an alternative treatment for these pains, yet no randomized trials, using a sham-placebo have been performed to confirm its effect. Our objective was to investigate the efficacy of acupuncture compared to sham-acupuncture when treating chronic postherpetic dermal pain.

METHODS

We performed a sham-controlled double-blinded randomized clinical trial (RCT) with two arms. The intervention group received superficial dry-needling, and the control group received sham acupuncture using blunted needles. Twenty-six patients received two treatments. They filled out questionnaires at baseline and 1 month after treatment: (1) average and maximum pain (Numeric Rating Scale), (2) neuropathic pain (Neuropathic Pain Scale Inventory) and (3) Quality of Life (QoL) (Short-form 36).

RESULTS

Thirteen patients were allocated to the intervention group and 15 to the control group. We did not detect any significant changes in levels of pain and neuropathic pain. One QoL parameter, regarding emotional problems, reached a level of statistical significance. The sham-blinding was successful. This is the first RCT on the effect of acupuncture (superficial dry-needling) on postherpetic neuralgia (PHN), using a sham procedure as control. We observed no significant changes or tendencies in the measured levels of pain. One QoL parameter had significant improvement in the intervention group compared to the control group.

CONCLUSION

In conclusion, acupuncture was not superior to treatment with sham acupuncture. Though individual patients may experience some pain relief from acupuncture, our results do not support the routine use of this type of acupuncture to treat PHN.

Tai Chi Improves Brain Functional Connectivity and Plasma Lysophosphatidylcholines in Postmenopausal Women With Knee Osteoarthritis: An Exploratory Pilot Study

Objective: A pre/post pilot study was designed to investigate neurobiological mechanisms and plasma metabolites in an 8-week Tai-Chi (TC) group intervention in subjects with knee osteoarthritis.

Methods: Twelve postmenopausal women underwent Tai-Chi group exercise for 8 weeks (60 min/session, three times/week). Outcomes were measured before and after Tai Chi intervention including pain intensity (VAS), Brief Pain Inventory (BPI), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), plasma metabolites (amino acids and lipids), as well as resting-state functional magnetic resonance imaging (rs-fMRI, 10 min, eyes open), diffusion tensor imaging (DTI, 12 min), and structural MRI (4.5 min) in a subgroup. Clinical data was analyzed using paired t-tests; plasma metabolites were analyzed using Wilcoxon signed-rank tests; and rs-fMRI data were analyzed using seed-based correlations of the left and right amygdala in a two-level mixed-effects model (FSL software). Correlations between amygdala-medial prefrontal cortex (mPFC) connectivity and corresponding changes in clinical outcomes were examined. DTI connectivity of each amygdala was modeled using a Bayesian approach and probabilistic tractography. The associations between neurobiological effects and pain/physical function were examined.

Results: Significant pre/post changes were observed with reduced knee pain (VAS with most pain: p = 0.018; WOMAC-pain: p = 0.021; BPI with worst level: p = 0.018) and stiffness (WOMAC-stiffness, p = 0.020), that likely contributed to improved physical function (WOMAC-physical function: p = 0.018) with TC. Moderate to large effect sizes pre/post increase in rs-fMRI connectivity were observed between bilateral mPFC and the amygdala seed regions (i.e., left: d = 0.988, p = 0.355; right: d = 0.600, p = 0.282). Increased DTI connectivity was observed between bilateral mPFC and left amygdala (d = 0.720, p = 0.156). There were moderate-high correlations (r = 0.28–0.60) between TC-associated pre-post changes in amygdala-mPFC functional connectivity and pain/physical function improvement. Significantly higher levels of lysophosphatidylcholines were observed after TC but lower levels of some essential amino acids. Amino acid levels (alanine, lysine, and methionine) were lower after 8 weeks of TC and many of the lipid metabolites were higher after TC. Further, plasma non-HDL cholesterol levels were lower after TC.

Conclusion: This pilot study showed moderate to large effect sizes, suggesting an important role that cortico-amygdala interactions related to TC have on pain and physical function in subjects with knee osteoarthritis pain. Metabolite analyses revealed a metabolic shift of higher lyso-lipids and lower amino acids that might suggest greater fatty acid catabolism, protein turnover and changes in lipid redistribution in response to TC exercise. The results also support therapeutic strategies aimed at strengthening functional and structural connectivity between the mPFC and the amygdala. Controlled clinical trials are warranted to confirm these observed preliminary effects.

Brain Imaging Biomarkers for Chronic Pain

The prevalence of chronic pain has reached epidemic levels. In addition to personal suffering chronic pain is associated with psychiatric and medical co-morbidities, notably substance misuse, and a huge a societal cost amounting to hundreds of billions of dollars annually in medical cost, lost wages, and productivity. Chronic pain does not have a cure or quantitative diagnostic or prognostic tools. In this manuscript we provide evidence that this situation is about to change. We first start by summarizing our current understanding of the role of the brain in the pathogenesis of chronic pain. We particularly focus on the concept of learning in the emergence of chronic pain, and the implication of the limbic brain circuitry and dopaminergic signaling, which underly emotional learning and decision making, in this process. Next, we summarize data from our labs and from other groups on the latest brain imaging findings in different chronic pain conditions focusing on results with significant potential for translation into clinical applications. The gaps in the study of chronic pain and brain imaging are highlighted in throughout the overview. Finally, we conclude by discussing the costs and benefits of using brain biomarkers of chronic pain and compare to other potential markers.

Tapentadol effects on brain response to pain in sensitized patients with knee osteoarthritis

OBJECTIVE

Pain sensitization, in the form of knee tenderness and anatomically spread hyperalgesia, is notably common in patients with knee osteoarthritis and is often refractory to conventional interventions. Tapentadol, as an opioid receptor agonist and noradrenaline reuptake inhibitor, has been proposed as a potentially effective symptomatic treatment for pain-sensitized osteoarthritis patients. We empirically tested whether tapentadol could attenuate brain response to painful stimulation on the tender knee using functional MRI.

METHODS

Pressure painful stimulation was applied to the articular interline and the tibial surface, a commonly sensitized site surrounding the joint. Thirty patients completed the crossover trial designed to compare prolonged release tapentadol and placebo effects administered over 14 days.

RESULTS

We found no effects in the direction of the prediction. Instead, patients administered with tapentadol showed stronger activation in response to pressure on the tender site in the right prefrontal cortex and somatosensory cortices. The somatosensory effect was compatible with the spread of neural activation around the knee cortical representation. Consistent with the functional MRI findings, the patients showed higher clinical ratings of pain sensitization under tapentadol and a significant positive association was identified between the number of tapentadol tablets and the evoked subjective pain.

CONCLUSION

The tapentadol effect paradoxically involved both the spread of the somatosensory cortex response and a stronger activation in prefrontal areas with a recognized role in the appraisal of pain sensations. Further studies are warranted to explore how osteoarthritis patients may benefit from powerful analgesic drugs without the associated risks of prolonged use. EudraCT-[2016-005082-31].

Functional and structural neuroplastic changes related to sensitization proxies in patients with Osteoarthritis: a systematic review

OBJECTIVE

Several reports in literature have identified sensitization as a possible basis for the enhanced pain reactions associated with Osteoarthritis (OA). The aim of this current systematic review is to summarize functional and structural brain changes associated with surrogate sensitization parameters assessed in patients with OA-related pain.

DESIGN

Systematic review.

SUBJECTS

Patients with OA related pain.

METHODS

A literature search was conducted systematically in MEDLINE, CINAHL, EMBASE databases for human studies up to December 2019. Articles were included if they assessed brain imaging and senzitisation parameters (quantitative sensory testing and questionnaires) in adults with OA related pain. Methodological quality was assessed using the Methodological Index for Non-Randomized Studies (MINORS) score.

RESULTS

Five studies reporting on 138 patients were included in this review. The MINORS scale yielded mean scores of 8.5/16 and 12.3/24, for the cohort and case-control studies respectively. Four low-quality studies suggest a greater pain matrix activation associated with clinical measures of sensitization in patients with OA, while another study underlined the presence of structural changes (reduced gray matter volume) in the cortical areas involved in the nociceptive processing possible also related to sensitization.

CONCLUSION

This review shows conflicting evidence for structural and functional neuroplastic brain changes related to sensitization proxies in patients with OA.

Quantitative Sensory Testing Protocols to Evaluate Central and Peripheral Sensitization in Knee OA: A Scoping Review

OBJECTIVE

This scoping review analyzed various quantitative sensory testing methodologies used in the assessment of sensitization and how sensitization is defined in people with knee osteoarthritis.

DESIGN

A scoping review.

SETTING

All clinical and research settings.

SUBJECTS

Non-surgical adults with knee osteoarthritis.

METHODS

This scoping review was guided by existing scoping review methodologies. Relevant studies were extracted from the following electronic databases: Medical Literature Analysis and Retrieval System Online, Excerpta Medica Database, Allied and Complementary Medicine Database and the Cumulative Index to Nursing Allied Health Literature. Abstract and full article screening and data extraction were performed in pairs. Information on quantitative sensory testing techniques and parameters was extracted and summarized in tables. General and technique specific definitions of sensitization were extracted from included texts.

RESULTS

Our search yielded 4199 articles, of which 50 were included in our review. The most common quantitative sensory test was pressure pain threshold. In total 28 unique testing sites were found speaking to the high degree of variability between studies. Sensitization was poorly defined with only 8 studies fully operationalizing it, 22 partially, and the remainder did not provide sufficient information to meet our criteria.

CONCLUSION

This scoping review has provided an overview of the most common methods of quantitative sensory testing being implemented in the assessment of nervous system sensitization to nociceptive signaling in people with knee osteoarthritis. This study provides a foundation for future development of quantitative sensory testing methodology for research and clinical practice in the osteoarthritis population.

A Randomized Controlled Trial to Compare Analgesia and Functional Improvement After Continuous Neuroablative and Pulsed Neuromodulative Radiofrequency Treatment of the Genicular Nerves in Patients with Knee Osteoarthritis up to One Year After the Intervention

OBJECTIVES

To compare the analgesic and functional outcomes of continuous neuroablative radiofrequency (CNARF) and pulsed neuromodulative radiofrequency (PNMRF) treatment of genicular nerves up to 1 year after the intervention and to identify predictors associated with a successful outcome (defined as an at least 50% reduction in the pre-interventional visual analog scale [VAS] rating) after genicular radiofrequency treatment.

DESIGN

A prospective randomized controlled trial.

SETTING

The Pain Department of the Jerez de la Frontera University Hospital, Cadíz, Spain, from January 2018 until May 2019.

SUBJECTS

Patients with grade 3-4 gonarthritis suffering from knee pain, with a VAS score ≥5 for >6 months.

METHODS

Eligible participants were randomly assigned to receive either CNARF or PNMRF of the superior medial, superior lateral, and inferior medial genicular nerves. The VAS and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) scores were assessed before and at 1, 6, and 12 months after treatment. Medication use was quantified before and at 6 months after the intervention. Potential characteristics associated with the efficacy of radiofrequency intervention were explored by using multivariable statistical models.

RESULTS

A total of 188 participants were included. The magnitude and duration of beneficial effect and reduction in analgesic use were significantly greater in the CNARF group. Success at 6 months after radiofrequency treatment decreased with grade 4 gonarthritis; higher pre-interventional VAS score; and concomitant depression, anxiety disorder, and diabetes mellitus.

CONCLUSIONS

Therapeutic efficacy and reduction in analgesic consumption were superior after CNARF. Treatment success at 6 months after radiofrequency intervention decreased with more severe gonarthritis; higher pre-interventional pain intensity; and concomitant depression, anxiety disorder, and diabetes mellitus.

Pain- and Fatigue-Related Functional and Structural Changes in Ankylosing Spondylitis: An fRMI Study

Background: Chronic pain and fatigue are two cardinal features of ankylosing spondylitis (AS) and how to effectively treat these conditions continues to be a challenge. The underlying mechanisms and the relationship between AS-related pain and fatigue remain poorly understood. The present study was conducted, therefore, to explore the brain functional and structural changes associated with pain and fatigue in AS.

Methods: A total of 65 AS patients (48 men and 17 women; 32.33 ± 8.6 years) and 53 age- and sex-matched controls were enrolled in the study. The patients underwent clinical assessment based on Total Back Pain scores, Fatigue Severity Scale, Bath Ankylosing Spondylitis Disease Activity Index, (BASDAI), high-sensitivity C-reactive Protein (hsCRP), erythrocyte sedimentation rate (ESR), and Beck Depression Inventory (BDI). Using 3T magnetic resonance imaging (3T-MRI), we analyzed the brain functional (connectivity and nodal properties) and structural (covariance and gray matter volumes) differences between AS patients and controls. Furthermore, we extracted the values of the significantly changed regions in the AS cohort and explored their association with pain and fatigue.

Results: In AS patients, there were functional and structural abnormalities distributed in the default mode network (DMN), salience network (SN), sensory/somatomotor network (SMN), dorsal attention network (DAN), task control network (TCN), and visual network, and some regions showed both types of changes. Among these, the functional connectivity (FC) between the left insula and medial prefrontal cortex, the betweenness centrality of the left medial prefrontal cortex and the gray matter volume of the right putamen tracked both pain and fatigue. In addition, pain was related to within-DMN FC disruption and nodal function / gray matter volumes changes in DMN, SN, and the visual network, while fatigue mainly involved the SMN, DAN, and TCN. Moreover, certain changes were also related to BASDAI and inflammation level.

Conclusion: This study offers new insights into understanding the neural mechanism of AS-related pain and fatigue, and could help to stratify patients based on the correlation features and ultimately move towards a personalized therapy.

Brain Functional Alternations of the Pain-related Emotional and Cognitive Regions in Patients with Chronic Shoulder Pain

Objective

Chronic shoulder pain (CSP) is a common health problem associated with shoulder dysfunction and persistent pain for many different reasons. However, the studies of pain-related functional brain regions in CSP have been poorly investigated. The main purpose of our study was to observe whether there are abnormal functional changes in brain regions in patients with CSP by using functional magnetic resonance imaging (fMRI).

Patients and Methods

We compared the differences of brain regions between 37 patients with CSP and 24 healthy controls (HC) using regional homogeneity (ReHo) method. The patients with chronic shoulder pain and healthy controls were matched for age and gender. Brain regions which had abnormal ReHo values were defined as seed region of interests. The approach of seed-based functional connectivity (FC) was further performed to analyze the connectivity between the seeds and whole brain regions. The relationship between abnormal regions and current clinical pain was also evaluated.

Results

Compared to healthy controls, the patients with CSP showed increased ReHo values in the left middle temporal gyrus and decreased ReHo values in right orbitofrontal cortex (OFC). The seed-based analyses demonstrated decreased connectivity between the right OFC and right rectus, superior frontal gyrus in patients with chronic shoulder pain. However, a correlation between ReHo values and clinical characteristics in CSP patients was not found.

Conclusion

The observed results indicate that there are abnormal ReHo values in brain regions of patients with CSP, especially in the OFC and middle temporal gyrus. Our findings demonstrate that the experience of CSP patients may be mainly associated with cognitive-affective pain processing, rather than nociception.

Brain Resting-State Network Alterations Associated With Crohn's Disease

Inflammatory bowel disease (IBD) is a chronic disease that is associated with aspects of brain anatomy and activity. In this preliminary MRI study, we investigated differences in brain structure and in functional connectivity (FC) of brain regions in 35 participants with Crohn's disease (CD) and 21 healthy controls (HC). Voxel-based morphometry (VBM) analysis was performed to contrast CD and HC structural images. Region of interest (ROI) analyses were run to assess FC for resting-state network nodes. Independent component analysis (ICA) identified whole brain differences in FC associated with resting-state networks. Though no structural differences were found, ROI analyses showed increased FC between the frontoparietal (FP) network and salience network (SN), and decreased FC between nodes of the default mode network (DMN). ICA results revealed changes involving cerebellar (CER), visual (VIS), and SN components. Differences in FC associated with sex were observed for both ROI analysis and ICA. Taken together, these changes are consistent with an influence of CD on the brain and serve to direct future research hypotheses.

Central Sensitization in Knee Osteoarthritis: Relating Presurgical Brainstem Neuroimaging and PainDETECT-Based Patient Stratification to Arthroplasty Outcome

OBJECTIVE

The neural mechanisms of pain in knee osteoarthritis (OA) are not fully understood, and some patients have neuropathic-like pain associated with central sensitization. To address this, we undertook the present study in order to identify central sensitization using neuroimaging and PainDETECT and to relate it to postarthroplasty outcome.

METHODS

Patients awaiting arthroplasty underwent quantitative sensory testing, psychological assessment, and functional magnetic resonance imaging (fMRI). Neuroimaging (fMRI) was conducted during punctate stimulation (n = 24) and cold stimulation (n = 20) to the affected knee. The postoperative outcome was measured using the Oxford Knee Score, patient-reported moderate-to-severe long-term pain postarthroplasty, and a range of pain-related questionnaires.

RESULTS

Patients with neuropathic-like pain presurgery (identified using PainDETECT; n = 14) reported significantly higher pain in response to punctate stimuli and cold stimuli near the affected joint (P < 0.05). Neural activity in these patients, compared to those without neuropathic-like pain, was significantly lower in the rostral anterior cingulate cortex (P < 0.05) and higher in the rostral ventromedial medulla (RVM) during punctate stimulation (P < 0.05), with significant functional connectivity between these two areas (r = 0.49, P = 0.018). Preoperative neuropathic-like pain and higher neural activity in the RVM were associated with moderate-to-severe long-term pain after arthroplasty (P = 0.0356).

CONCLUSION

The psychophysical and neuroimaging data suggest that a subset of OA patients have centrally mediated pain sensitization. This was likely due to supraspinally mediated reductions in inhibition and increases in facilitation of nociceptive signaling, and was associated with a worse outcome following arthroplasty. The neurobiologic confirmation of central sensitization in patients with features of neuropathic pain, identified using PainDETECT, provides further support for the investigation of such bedside measures for patient stratification, to better predict postsurgical outcomes.

Visual network alterations in brain functional connectivity in chronic low back pain: A resting state functional connectivity and machine learning study

Chronic low back pain (cLBP) is associated with widespread functional and structural changes in the brain. This study aims to investigate the resting state functional connectivity (rsFC) changes of visual networks in cLBP patients and the feasibility of distinguishing cLBP patients from healthy controls using machine learning methods. cLBP (n = 90) and control individuals (n = 74) were enrolled and underwent resting-state BOLD fMRI scans. Primary, dorsal, and ventral visual networks derived from independent component analysis were used as regions of interest to compare resting state functional connectivity changes between the cLBP patients and healthy controls. We then applied a support vector machine classifier to distinguish the cLBP patients and control individuals. These results were further verified in a new cohort of subjects. We found that the functional connectivity between the primary visual network and the somatosensory/motor areas were significantly enhanced in cLBP patients. The rsFC between the primary visual network and S1 was negatively associated with duration of cLBP. In addition, we found that the rsFC of the visual network could achieve a classification accuracy of 79.3% in distinguishing cLBP patients from HCs, and these results were further validated in an independent cohort of subjects (accuracy = 66.7%). Our results demonstrate significant changes in the rsFC of the visual networks in cLBP patients. We speculate these alterations may represent an adaptation/self-adjustment mechanism and cross-model interaction between the visual, somatosensory, motor, attention, and salient networks in response to cLBP. Elucidating the role of the visual networks in cLBP may shed light on the pathophysiology and development of the disorder.

•

We investigated rsFC changes of visual networks in cLBP patients.

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rsFC of the primary visual network with S1 and M1 increased in cLBP patients.

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rsFC of the visual networks can differentiate cLBP patients from controls (with 79.3% accuracy).

•

Classification results can be validated in an independent cohort (with 66.7% accuracy).

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.

Mechanisms Underlying Bone and Joint Pain

PURPOSE OF REVIEW

The goal of this review is to provide a broad overview of the current understanding of mechanisms underlying bone and joint pain.

RECENT FINDINGS

Bone or joint pathology is generally accompanied by local release of pro-inflammatory cytokines, growth factors, and neurotransmitters that activate and sensitize sensory nerves resulting in an amplified pain signal. Modulation of the pain signal within the spinal cord and brain that result in net increased facilitation is proposed to contribute to the development of chronic pain. Great strides have been made in our understanding of mechanisms underlying bone and joint pain that will guide development of improved therapeutic options for these patients. Continued research is required for improved understanding of mechanistic differences driving different components of bone and/or joint pain such as movement related pain compared to persistent background pain. Advances will guide development of more individualized and comprehensive therapeutic options.

Influence of centrally mediated symptoms on functional outcomes after carpal tunnel release

Patients with carpal tunnel syndrome (CTS) often show bilaterally increased pain sensitivity and widespread symptoms. We evaluated the influence of centrally mediated symptoms on functional outcomes of carpal tunnel release (CTR). A total of 120 patients with surgically treated CTS were enrolled. Centrally mediated symptoms were preoperatively measured by administering a self-reported central sensitization inventory (CSI) questionnaire and peripheral sensitization was measured by assessing patient's pressure pain thresholds (PPT) in the forearm. Boston Carpal Tunnel Questionnaires (BCTQ) were assessed preoperatively and postoperatively at 3 and 12 months. CSI scores slightly correlated with symptom duration and moderately correlated with preoperative BCTQ scores, while PPT slightly correlated with the BCTQ scores. At 3 months, BCTQ symptom and function scores moderately correlated with lower PPTs and higher CSI scores. At 12 months, only severe electrophysiological grade was associated with BCTQ function scores. Multivariable analysis revealed that preoperative PPT, CSI, and female gender were associated with BCTQ scores at 3 months; these factors failed to be associated for 12-month outcomes. Centrally mediated symptoms measured by CSI and peripheral sensitization measured by PPTs correlated with symptom severity and duration. They were associated with poorer functional outcomes after CTR up to 3 months. However, they did not show persistent effects in the long term.