Associations of limbic-affective brain activity and severity of ongoing chronic arthritis pain are explained by trait anxiety

Brain functional imaging contributions in osteoarthritis-related pain: A viewpoint

Objective

Neuroimaging investigations are critical to provide a more direct assessment of brain disturbances associated with osteoarthritis (OA)-related pain, and to better understand its pathophysiology to develop new treatment strategies. This viewpoint aims to summarize the importance of the brain in OA pain.

Method

A European working group on pain in osteoarthritis GO-PAIN (Going Inside Osteoarthritis-related Pain Phenotyping) has been created to work on a global assessment of the OA-related pain. Relevant scientific literature was evaluated, summarized and discussed to expose advances in functional brain alterations related-to OA pain.

Results

Findings of neuroimaging studies are highly heterogenous and based on small sample size, but some key brain alterations associated with OA pain can be identified across experiments. A systematic literature review conducted by Hall and colleagues (2023) found lower activity, connectivity, and grey matter volume in the right anterior insula in patients with OA than in healthy controls. Other works also pointed out that activity of specific brain regions could serve as a potential surrogate biomarker, but several limitations and confounding factors needs to be addressed.

Conclusions

Brain functional imaging provides opportunities to accurately address an OA-related pain endophenotype. To encompass limitations and fill the gaps from the previous studies, we propose a blueprint for the next 5 years and stimulate ideas for others working in the field.

High-definition tDCS over primary motor cortex modulates brain signal variability and functional connectivity in episodic migraine

OBJECTIVE

This study investigated how high-definition transcranial direct current stimulation (HD-tDCS) over the primary motor cortex (M1) affects brain signal variability and functional connectivity in the trigeminal pain pathway, and their association with changes in migraine attacks.

METHODS

Twenty-five episodic migraine patients were randomized for ten daily sessions of active or sham M1 HD-tDCS. Resting-state blood-oxygenation-level-dependent (BOLD) signal variability and seed-based functional connectivity were assessed pre- and post-treatment. A mediation analysis was performed to test whether BOLD signal variability mediates the relationship between treatment group and moderate-to-severe headache days.

RESULTS

The active M1 HD-tDCS group showed reduced BOLD variability in the spinal trigeminal nucleus (SpV) and thalamus, but increased variability in the rostral anterior cingulate cortex (rACC) compared to the sham group. Connectivity decreased between medial pulvinar-temporal pole, medial dorsal-precuneus, and the ventral posterior medial nucleus-SpV, but increased between the rACC-amygdala, and the periaqueductal gray-parahippocampal gyrus. Changes in medial pulvinar variability mediated the reduction in moderate-to-severe headache days at one-month post-treatment.

CONCLUSIONS

M1 HD-tDCS alters BOLD signal variability and connectivity in the trigeminal somatosensory and modulatory pain system, potentially alleviating migraine headache attacks.

SIGNIFICANCE

M1 HD-tDCS realigns brain signal variability and connectivity in migraineurs closer to healthy control levels.

7 T characterization of excitatory and inhibitory systems of acute pain in healthy female participants

Current understanding of the physiological underpinnings of normative pain processing is incomplete. Enhanced knowledge of these systems is necessary to advance our understanding of pain processes as well as to develop effective therapeutic interventions. Previous neuroimaging research suggests a network of interrelated brain regions that seem to be implicated in the processing and experience of pain. Among these, the dorsal anterior cingulate cortex (dACC) plays an important role in the affective aspects of pain signals. The current study leveraged functional MRS to investigate the underlying dynamic shifts in the neurometabolic signature of the human dACC at rest and during acute pain. Results provide support for increased glutamate levels following acute pain administration. Specifically, a 4.6% increase in glutamate was observed during moderate pressure pain compared with baseline. Exploratory analysis also revealed meaningful changes in dACC gamma aminobutyric acid in response to pain stimulation. These data contribute toward the characterization of neurometabolic shifts, which lend insight into the role of the dACC in the pain network. Further research in this area with larger sample sizes could contribute to the development of novel therapeutics or other advances in pain-related outcomes.

Bidirectional causal relationship between psychiatric disorders and osteoarthritis: A univariate and multivariate Mendelian randomization study

BACKGROUND

Observational studies have shown associations between psychiatric disorders and osteoarthritis (OA). However, the causal impact of different psychiatric disorder types on specific sites of osteoarthritis remains unclear. This study aimed to comprehensively understand the potential causal associations between psychiatric disorders and osteoarthritis using Mendelian randomization (MR) analysis.

METHODS

We collected data from genome-wide association studies of knee osteoarthritis (KOA) (n = 403,124), hip osteoarthritis (HOA) (n = 393,873), osteoarthritis of the knee or hip (KHOA) (n = 417,596), as well as three psychiatric disorders: bipolar disorder (n = 41,917), major depressive disorder (n = 170,756), and schizophrenia (n = 76,755) among European populations. We applied bidirectional univariate and multivariate MR analyses, including inverse variance weighted, Mendelian randomization-Egger, weighted median, simple mode, and weighted mode. We considered p < .05 as a criterion for identifying potential evidence of association. Bonferroni correction was used for multiple tests.

RESULTS

Our univariate MR analysis results demonstrated that bipolar disorder is a protective factor for KOA (OR = 0.90, 95% CI = 0.83 to 0.97, p = 0.0048) and may also be protective for KHOA (p = 0.02). Conversely, major depression has a positive causal effect on both KOA (OR = 1.27; 95% CI = 1.08 to 1.49; p = 0.0036) and KHOA (OR = 1.24; 95% CI = 1.12 to 1.37; p = 3.62×10-05 ). Furthermore, our analysis suggested that KHOA may be a risk factor for major depression (OR = 1.06; 95% CI = 1.00 to 1.12; p = 0.0469) in reverse MR. After adjusting smoking (OR = 1.46; 95% CI = 1.19 to 1.65; p = 0.0032) and body mass index (OR = 1.44; 95% CI = 1.09 to 1.81; p = 8.56×10-04 ), the casual association between major depression and KHOA remained.

CONCLUSION

Our study indicates that major depression is a great risk factor for KHOA, increasing the likelihood of their occurrence. However, further in-depth studies will be required to validate these results and elucidate the underlying molecular mechanisms.

Self-regulation training for people with knee osteoarthritis: a protocol for a feasibility randomised control trial (MiNT trial)

Introduction

Knee osteoarthritis (OA) is a chronic secondary musculoskeletal pain condition resulting in disability, reduced quality of life, and high societal costs. Pain associated with knee OA is linked to increased sensitivity in sensory, cognitive, and emotional areas of the brain. Self-regulation training targeting brain functioning related to pain experience could reduce pain and its associated disability. Self-regulatory treatments such as mindfulness meditation (MM) and electroencephalography neurofeedback (EEG-NF) training improve clinical outcomes in people with knee OA. A feasibility clinical trial can address factors that could inform the design of the full trial investigating the effectiveness of self-regulation training programmes in people with knee OA. This clinical trial will evaluate the feasibility, safety, acceptability, experience and perceptions of the self-regulatory training programmes.

Methods

The proposed feasibility trial is based on a double-blind (outcome assessor and investigators), three-arm (MM usual care, EEG-NF + usual care and usual care control group) randomised controlled parallel clinical trial. Participants with knee OA will be recruited from the community and healthcare practices. A research assistant (RA) will administer both interventions (20-min sessions, four sessions each week, and 12 sessions over three successive weeks). Feasibility measures (participant recruitment rate, adherence to interventions, retention rate), safety, and acceptability of interventions will be recorded. An RA blinded to the group allocation will record secondary outcomes at baseline, immediately post-intervention (4th week), and 3 months post-intervention. The quantitative outcome measures will be descriptively summarised. The qualitative interviews will evaluate the participants' experiences and perceptions regarding various aspects of the trial, which includes identifying the barriers and facilitators in participating in the trial, evaluating their opinions on the research procedures, such as their preferences for the study site, and determining the level of acceptability of the interventions as potential clinical treatments for managing knee OA. Māori participant perceptions of how assessment and training practices could be acceptable to a Māori worldview will be explored. The interviews will be audio-recorded and analysed thematically.

Discussion

This trial will provide evidence on the feasibility, safety, and acceptability of the MM and EEG-NF training in people with knee OA, thus informing the design of a full randomised clinical control trial.

Structural and functional brain changes in people with knee osteoarthritis: a scoping review

Background

Knee osteoarthritis is a highly prevalent disease worldwide that leads to functional disability and chronic pain. It has been shown that not only changes are generated at the joint level in these individuals, but also neuroplastic changes are produced in different brain areas, especially in those areas related to pain perception, therefore, the objective of this research was to identify and compare the structural and functional brain changes in knee OA versus healthy subjects.

Methodology

Searches in MEDLINE (PubMed), EMBASE, WOS, CINAHL, SCOPUS, Health Source, and Epistemonikos databases were conducted to explore the available evidence on the structural and functional brain changes occurring in people with knee OA. Data were recorded on study characteristics, participant characteristics, and brain assessment techniques. The methodological quality of the studies was analysed with Newcastle Ottawa Scale.

Results

Sixteen studies met the inclusion criteria. A decrease volume of the gray matter in the insular region, parietal lobe, cingulate cortex, hippocampus, visual cortex, temporal lobe, prefrontal cortex, and basal ganglia was found in people with knee OA. However, the opposite occurred in the frontal lobe, nucleus accumbens, amygdala region and somatosensory cortex, where an increase in the gray matter volume was evidenced. Moreover, a decreased connectivity to the frontal lobe from the insula, cingulate cortex, parietal, and temporal areas, and an increase in connectivity from the insula to the prefrontal cortex, subcallosal area, and temporal lobe was shown.

Conclusion

All these findings are suggestive of neuroplastic changes affecting the pain matrix in people with knee OA.

Neurobiology of osteoarthritis: a systematic review and activation likelihood estimation meta-analysis

Osteoarthritis (OA) affects 240 million people worldwide. Neuroimaging has been increasingly used to investigate brain changes in OA, however, there is considerable heterogeneity in reported results. The goal of this systematic review and meta-analysis was to synthesise existing literature and identify consistent brain alterations in OA. Six databases were searched from inception up to June, 2022. Full-texts of original human studies were included if they had: (i) neuroimaging data by site of OA (e.g. hand, knee, hip); (ii) data in healthy controls (HC); (iii) > 10 participants. Activation likelihood estimation (ALE) was conducted using GingerALE software on studies that reported peak activation coordinates and sample size. Our search strategy identified 6250 articles. Twenty-eight studies fulfilled the eligibility criteria, of which 18 were included in the meta-analysis. There were no significant differences in brain structure or function between OA and healthy control contrasts. In exploratory analysis, the right insula was associated with OA vs healthy controls, with less activity, connectivity and brain volume in OA. This region was implicated in both knee and hip OA, with an additional cluster in the medial prefrontal cortex observed only in the contrast between healthy controls and the hip OA subgroup, suggesting a possible distinction between the neural correlates of OA subtypes. Despite the limitations associated with heterogeneity and poor study quality, this synthesis identified neurobiological outcomes associated with OA, providing insight for future research. PROSPERO registration number: CRD42021238735.

The development of functional connectivity within the dorsal striatum from early childhood to adulthood

Dorsal striatum, principally comprising of caudate and putamen, is well-known to support motor function but also various higher-order cognitive functions. This is enabled by developing short- and long-range connections to distributed cortical regions throughout the life span, but few studies have examined developmental changes from young children to adults in the same cohort. Here we investigated the development of dorsal-striatal network in a large (n = 476), single-site sample of healthy subjects 3-42 years of age in three groups (children, adolescence, adults). The results showed that the connectivity within the striatum and to sensorimotor regions was established at an early stage of life and remained strong in adolescence, supporting that sensory-seeking behaviours and habit formation are important learning mechanisms during the developmental periods. This connectivity diminished with age, as many behaviours become more efficient and automated. Adolescence demonstrated a remarkable transition phase where the connectivity to dorsolateral prefrontal cortex emerged but connectivity to the dorsomedial prefrontal and posterior brain, which belong to the ventral attentional and default mode networks, was only seen in adults. This prolonged maturation in between-network integration may explain the behavioural characteristics of adolescents in that they exhibit elaborated cognitive performance but also demonstrate high risk-taking behaviours.

Effect of Acupuncture on the Cognitive Control Network of Patients with Knee Osteoarthritis: Study Protocol for a Randomized Controlled Trial

Purpose

Materials and Methods

Discussion

Study Registration

Disrupted Dynamic Functional Connectivity of the Visual Network in Episodic Patients with Migraine without Aura

Background

Visual symptoms are common in patients with migraine, even in interictal periods. The purpose was to assess the association between dynamic functional connectivity (dFC) of the visual cortex and clinical characteristics in migraine without aura (MwoA) patients.

Methods

We enrolled fifty-five MwoA patients as well as fifty gender- and age-matched healthy controls. Regional visual cortex alterations were investigated using regional homogeneity (ReHo) and amplitude of low-frequency fluctuation (ALFF). Then, significant regions were selected as seeds for conducting dFC between the visual cortex and the whole brain.

Results

Relative to healthy controls, MwoA patients exhibited decreased ReHo and ALFF values in the right lingual gyrus (LG) and increased ALFF values in the prefrontal cortex. The right LG showed abnormal dFC within the visual cortex and with other core brain networks. Additionally, ReHo values for the right LG were correlated with duration of disease and ALFF values of the right inferior frontal gyrus and middle frontal gyrus were correlated with headache frequency and anxiety scores, respectively. Moreover, the abnormal dFC of the right LG with bilateral cuneus was positively correlated with anxiety scores.

Conclusions

The dFC abnormalities of the visual cortex may be involved in pain integration with multinetworks and associated with anxiety disorder in episodic MwoA patients.

Structural and Functional Abnormalities in Knee Osteoarthritis Pain Revealed With Multimodal Magnetic Resonance Imaging

The knee osteoarthritis (KOA) pain is the most common form of arthritis pain affecting millions of people worldwide. Long-term KOA pain causes motor impairment and affects affective and cognitive functions. However, little is known about the structural and functional abnormalities induced by long-term KOA pain. In this work, high-resolution structural magnetic resonance imaging (sMRI) and resting-state functional MRI (rs-fMRI) data were acquired in patients with KOA and age-, sex-matched healthy controls (HC). Gray matter volume (GMV) and fractional amplitude of low-frequency fluctuation (fALFF) were used to study the structural and functional abnormalities in patients with KOA. Compared with HC, patients with KOA showed reduced GMV in bilateral insula and bilateral hippocampus, and reduced fALFF in left cerebellum, precentral gyrus, and the right superior occipital gyrus. Patients with KOA also showed increased fALFF in left insula and bilateral hippocampus. In addition, the abnormal GMV in left insula and fALFF in left fusiform were closely correlated with the pain severity or disease duration. These results indicated that long KOA pain leads to brain structural and functional impairments in motor, visual, cognitive, and affective functions that related to brain areas. Our findings may facilitate to understand the neural basis of KOA pain and the future therapy to relieve disease symptoms.

Cross-Disorder Genomics Data Analysis Elucidates a Shared Genetic Basis Between Major Depression and Osteoarthritis Pain

Osteoarthritis (OA) and major depression (MD) are two debilitating disorders that frequently co-occur and affect millions of the elderly each year. Despite the greater symptom severity, poorer clinical outcomes, and increased mortality of the comorbid conditions, we have a limited understanding of their etiologic relationships. In this study, we conducted the first cross-disorder investigations of OA and MD, using genome-wide association data representing over 247K cases and 475K controls. Along with significant positive genome-wide genetic correlations (r g = 0.299 ± 0.026, p = 9.10 × 10-31), Mendelian randomization (MR) analysis identified a bidirectional causal effect between OA and MD (βOA → MD = 0.09, SE = 0.02, z-score p-value < 1.02 × 10-5; βMD → OA = 0.19, SE = 0.026, p < 2.67 × 10-13), indicating genetic variants affecting OA risk are, in part, shared with those influencing MD risk. Cross-disorder meta-analysis of OA and MD identified 56 genomic risk loci (P meta ≤ 5 × 10-8), which show heightened expression of the associated genes in the brain and pituitary. Gene-set enrichment analysis highlighted "mechanosensory behavior" genes (GO:0007638; P gene_set = 2.45 × 10-8) as potential biological mechanisms that simultaneously increase susceptibility to these mental and physical health conditions. Taken together, these findings show that OA and MD share common genetic risk mechanisms, one of which centers on the neural response to the sensation of mechanical stimulus. Further investigation is warranted to elaborate the etiologic mechanisms of the pleiotropic risk genes, as well as to develop early intervention and integrative clinical care of these serious conditions that disproportionally affect the aging population.

Alterations in brain structure and function in patients with osteonecrosis of the femoral head: a multimodal MRI study

Background

Pain, a major symptom of osteonecrosis of the femoral head (ONFH), is a complex sensory and emotional experience that presents therapeutic challenges. Pain can cause neuroplastic changes at the cortical level, leading to central sensitization and difficulties with curative treatments; however, whether changes in structural and functional plasticity occur in patients with ONFH remains unclear.

Methods

A total of 23 ONFH inpatients who did not undergo surgery (14 males, nine females; aged 55.61 ± 13.79 years) and 20 controls (12 males, eight females; aged 47.25 ± 19.35 years) were enrolled. Functional indices of the amplitude of low-frequency fluctuation (ALFF), regional homogeneity (ReHo), and a structural index of tract-based spatial statistics (TBSS) were calculated for each participant. The probability distribution of fiber direction was determined according to the ALFF results.

Results

ONFH patients demonstrated increased ALFF in the bilateral dorsolateral superior frontal gyrus, right medial superior frontal gyrus, right middle frontal gyrus, and right supplementary motor area. In contrast, ONFH patients showed decreased ReHo in the left superior parietal gyrus and right inferior temporal gyrus. There were no significant differences in TBSS or probabilistic tractography.

Conclusion

These results indicate cerebral pain processing in ONFH patients. It is advantageous to use functional magnetic resonance imaging to better understand pain pathogenesis and identify new therapeutic targets in ONFH patients.

The anatomy of pain and suffering in the brain and its clinical implications

Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage. Chronic pain, with a prevalence of 20-30 % is the major cause of human suffering worldwide, because effective, specific and safe therapies have yet to be developed. It is unevenly distributed among sexes, with women experiencing more pain and suffering. Chronic pain can be anatomically and phenomenologically dissected into three separable but interacting pathways, a lateral 'painfulness' pathway, a medial 'suffering' pathway and a descending pain inhibitory pathway. One may have pain(fullness) without suffering and suffering without pain(fullness). Pain sensation leads to suffering via a cognitive, emotional and autonomic processing, and is expressed as anger, fear, frustration, anxiety and depression. The medial pathway overlaps with the salience and stress networks, explaining that behavioural relevance or meaning determines the suffering associated with painfulness. Genetic and epigenetic influences trigger chronic neuroinflammatory changes which are involved in transitioning from acute to chronic pain. Based on the concept of the Bayesian brain, pain (and suffering) can be regarded as the consequence of an imbalance between the two ascending and the descending pain inhibitory pathways under control of the reward system. The therapeutic clinical implications of this simple pain model are obvious. After categorizing the working mechanisms of each of the available treatments (pain killers, psychopharmacology, psychotherapy, neuromodulation, psychosurgery, spinal cord stimulation) to 1 or more of the 3 pathways, a rational combination can be proposed of activating the descending pain inhibitory pathway in combination with inhibition of the medial and lateral pathway, so as to rebalance the pain (and suffering) pathways.

Correlation between pain severity and levels of anxiety and depression in osteoarthritis patients: a systematic review and meta-analysis

OBJECTIVES

Osteoarthritis (OA) is a chronic degenerative musculoskeletal disease that causes articular damage and chronic pain, with a prevalence of up to 50% in individuals >60 years of age. Patients suffering from chronic painful conditions, including OA, also frequently report anxiety or depression. A systematic review and meta-analysis were performed to assess the correlation between pain severity and depressive and anxious symptomatology in OA patients.

METHODS

A systematic search was conducted using four databases (PubMed, Medline, Scopus, and Web of Science) from inception up to 14th January of 2020. We included original articles evaluating pain severity and anxiety and/or depression severity in OA-diagnosed patients. Detailed data were extracted from each study, including patients' characteristics and pain, anxiety, and depression severity. When available, the Pearson correlation coefficient between pain and depression severity and pain and anxiety severity was collected and a meta-analysis of random effects was applied.

RESULTS

This systematic review included 121 studies, with a total of 38085 participants. The mean age was 64.3 years old and subjects were predominantly female (63%). The most used scale to evaluate pain severity was the Western Ontario and the McMaster Universities Osteoarthritis Index, while for anxiety and depression, the Hospital Anxiety and Depression Scale was the most used. The meta-analysis showed a moderate positive correlation between pain severity and both anxious (r = 0.31, p < 0.001) and depressive symptomatology (r = 0.36, p < 0.001).

CONCLUSIONS

Our results demonstrate a significant correlation between pain and depression/anxiety severity in OA patients, highlighting the need for its routine evaluation by clinicians.

Pain and Trauma: The Role of Criterion A Trauma and Stressful Life Events in the Pain and PTSD Relationship

Chronic pain and post-traumatic stress disorder (PTSD) frequently co-occur, and research suggests that these 2 conditions exacerbate one another producing greater impact on normal functioning in combination than separately. The influence of traumatic experiences on both pain and PTSD has been shown, but the nature of this interplay remains unclear. Although Criterion A trauma is required for the diagnosis of PTSD, whether the association between PTSD and chronic pain is dependent on Criterion A is underexplored. In this observational cohort study, we examined the association between pain and PTSD-like symptoms in the context of Criterion A trauma in 5,791 men from the Vietnam Era Twin Registry. Correlations and mixed-effects regression models were used to evaluate the relationship between PTSD Checklist-Civilian Version symptoms and multiple indicators of pain from the Short Form McGill Pain Questionnaire across trauma history and chronic pain conditions. 53.21% of the participants experienced trauma consistent with DSM-IV Criterion A for PTSD. The associations between pain indicators and PTSD-like symptoms was stronger for individuals with a history of trauma but remained robust for individuals without trauma history. Small but significant interactions between past trauma and pain indicators and PTSD-like symptoms were observed. Findings were similar in a subsample of participants with history of chronic pain conditions. The relationship between PTSD-like symptoms and indicators of pain were largely independent of trauma consistent with Criterion A, highlighting the need to better understand and address stressful life events in chronic pain patients and pain concerns in individuals reporting trauma. PERSPECTIVE: This article demonstrates that the relationship between PTSD-like symptoms and indicators of pain is largely independent of trauma consistent with Criterion A. This finding highlights the need to better understand and address stressful life events in chronic pain patients and pain concerns in individuals reporting trauma.

Pain modulatory network is influenced by sex and age in a healthy state and during osteoarthritis progression in rats

Old age and female sex are risk factors for the development of osteoarthritis (OA) and chronic pain. We investigated the effects of sex and age on pain modulatory networks in a healthy state and during OA progression. We used functional MRI to determine the effects of sex and age on periaqueductal gray functional connectivity (PAG FC) in a healthy state (pre‐OA) and during the early and late phases of monosodium iodoacetate‐induced OA in rats. We then examined how sex and age affect longitudinal changes in PAG FC in OA. In a healthy state, females exhibited more widespread PAG FC than males, and this effect was exaggerated with aging. Young males had moderate PAG FC changes during the early phase but recruited additional brain regions, including the rostral anterior cingulate cortex (ACC), during the late phase. Young females exhibited widespread PAG FC in the early phase, which includes connections to insula, caudal ACC, and nucleus accumbens (NAc). Older groups had strong PAG FC with fewer regions in the early phase, but they recruited additional brain regions, including NAc, in the late phase. Overall, our findings show that PAG FC is modulated by sex and age in a healthy state. A widespread PAG network in the early phase of OA pain may contribute to the transition from acute to chronic OA pain and the increased risk of developing chronic pain for females. Enhanced PAG FC with the reward system may represent a potential mechanism underlying chronic OA pain in elderly patients.

Posttraumatic Stress Disorder and Chronic Pain Conditions in Men: A Twin Study

OBJECTIVE

Posttraumatic stress disorder (PTSD) is highly comorbid with chronic pain conditions that often co-occur such as migraine headaches, temporomandibular disorder, irritable bowel syndrome, fibromyalgia, chronic fatigue syndrome, chronic prostatitis/chronic pelvic pain syndrome, and tension headaches. Using a genetically informative sample, the current study evaluated the genetic and environmental factors contributing to the co-occurrence of PTSD and chronic pain conditions.

METHODS

Data from 4680 male twins in the Vietnam Era Twin Registry were examined. Biometric modeling was used to estimate genetic and environmental variance components and genetic and environmental correlations between PTSD and multiple chronic pain conditions.

RESULTS

Heritabilities were estimated at 43% (95% confidence interval [CI] = 15%-63%) for PTSD and 34% (95% CI = 27%-41%) for the combined history of any one or more pain condition. Specific pain condition heritabilities ranged from 15% (95% CI = 0%-48%) for tension headaches to 41% (95% CI = 27%-54%) for migraine headaches. Environmental influences accounted for the remaining variance in pain conditions. The genetic correlation between PTSD and combined history of any one or more pain condition was rg= 0.61 (95% CI = 0.46-0.89) and ranged for individual pain conditions from rg= 0.44 (95% CI = 0.24-0.77) for migraine headache to rg= 0.75 (95% CI = 0.52-1.00) for tension headaches.

CONCLUSIONS

PTSD and chronic pain conditions are highly comorbid, and this relationship can be explained by both genetic and environmental overlap. The precise mechanisms underlying these relationships are likely diverse and multifactorial.

Neural plasticity secondary to carpal tunnel syndrome: a pseudo-continuous arterial spin labeling study

Conventional neuroimaging techniques cannot truly reflect the change of regional cerebral blood flow in patients with carpal tunnel syndrome. Pseudo-continuous arterial spinning labeling (pCASL) as an efficient non-invasive neuroimaging technique can be applied to directly quantify the neuronal activities of individual brain regions that show the persistent symptoms owing to its better spatial resolution and increased signal-to-noise ratio. Therefore, this prospective observational study was conducted in 27 eligible female carpal tunnel syndrome, aged 57.7 ± 6.51 years. Psychometric tests, nerve conduction studies and pCASL neuroimaging assessment were performed. The results showed that the relevant activated brain regions in the cortical, subcrotical, and cerebral regions were correlated with numbness, pain, functionality, median nerve status and motor amplitude of median nerve (K = 21-2849, r = -0.77-0.76, P < 0.05). There was a tendency of pain processing which shifted from the nociceptive circuitry to the emotional and cognitive one during the process of chronic pain caused by carpal tunnel syndrome. It suggests the necessity of addressing the ignored cognitive or emotional state when managing patients with carpal tunnel syndrome. Approval for this study was obtained from the Institutional Review Board of The University of Hong Kong/Hospital Authority Hong Kong West, China (HKU/HA HKW IRB, approval No. UW17-129) on April 11, 2017. This study was registered in Clinical Trial Registry of The University of Hong Kong, China (registration number: HKUCTR-2220) on April 24, 2017.

Adverse effects of COVID-19-related lockdown on pain, physical activity and psychological well-being in people with chronic pain

Countries across the world imposed lockdown restrictions during the COVID-19 pandemic. It has been proposed that lockdown conditions, including social and physical distancing measures, may disproportionately impact those living with chronic pain and require rapid adaptation to treatment and care strategies. Using an online methodology, we investigated how lockdown restrictions in the United Kingdom impacted individuals with chronic pain (N = 431) relative to a healthy control group (N = 88). Data were collected during the most stringent period of lockdown in the United Kingdom (mid-April to early-May 2020). In accordance with the fear-avoidance model, we hypothesised lockdown-related increases in pain and psychological distress, which would be mediated by levels of pain catastrophising. Responses indicated that people with chronic pain perceived increased pain severity, compared to their estimation of typical pain levels prior to lockdown (p < .001). They were also more adversely affected by lockdown conditions compared to pain-free individuals, demonstrating greater self-perceived increases in anxiety and depressed mood, increased loneliness and reduced levels of physical exercise (p ⩽ .001). Hierarchical regression analysis revealed that pain catastrophising was an important factor relating to the extent of self-perceived increases in pain severity during lockdown (β = .27, p < .001) and also mediated the relationship between decreased mood and pain. Perceived decreases in levels of physical exercise also related to perceptions of increased pain (β = .15, p < .001). Interestingly, levels of pain intensity (measured at two time points at pre and during lockdown) in a subgroup (N = 85) did not demonstrate a significant change. However, individuals in this subgroup still reported self-perceived pain increases during lockdown, which were also predicted by baseline levels of pain catastrophising. Overall, the findings indicate that people with chronic pain suffer adverse effects of lockdown including self-perceived increases in their pain. Remote pain management provision to target reduction of pain catastrophising and increase health behaviours including physical activity could be beneficial for this vulnerable population.

Regional cerebral perfusion correlates with anxiety in neuropsychiatric SLE: evidence for a mechanism distinct from depression

The study examined the hypothesis that hypoperfusion in brain areas known to be involved in emotional disturbances in primary psychiatric disorders is also linked to emotional difficulties in systemic lupus erythematosus (SLE) and that these are not secondary to the physical and social burden incurred by the disease. Nineteen SLE patients without overt neuropsychiatric manifestations (non-NPSLE), 31 NPSLE patients, and 23 healthy controls were examined. Dynamic susceptibility contrast MRI was used and cerebral blood flow and cerebral blood volume values were estimated in six manually selected regions of interest of brain regions suspected to play a role in anxiety and depression (dorsolateral prefrontal cortex, ventromedial prefrontal cortex, anterior cingulate cortex, hippocampi, caudate nuclei and putamen). NPSLE patients reported high rates of anxiety and depression symptomatology. Significantly reduced cerebral blood flow and cerebral blood volume values were detected in the NPSLE group compared to healthy controls in the dorsolateral prefrontal cortex and ventromedial prefrontal cortex, bilaterally. Within the NPSLE group, anxiety symptomatology was significantly associated with lower perfusion in frontostriatal regions and in the right anterior cingulate gyrus. Importantly, the latter associations appeared to be specific to anxiety symptoms, as they persisted after controlling for depression symptomatology and independent of the presence of visible lesions on conventional MRI. In conclusion, hypoperfusion in specific limbic and frontostriatal regions is associated with more severe anxiety symptoms in the context of widespread haemodynamic disturbances in NPSLE.

Association of decrease in insula fMRI activation with changes in trait anxiety in patients with craniomandibular disorder (CMD)

Patients with chronic pain and especially with craniomandibular disorder (CMD) show specific psychopathology in trait anxiety. In a previous longitudinal functional imaging study on CMD we found that the anterior insula was modulated by successful therapy intervention and pain relief. We here intended to investigate possible associations between anterior insula fMRI-activation during occlusal movements and trait anxiety over a splint therapy approach in patients with CMD. Three fMRI-investigations of a craniomandibular occlusion task were performed together with pain score evaluations and scoring of trait anxiety (State -Trait Anxiety Inventory; STAI) before, after two weeks and after three months of a DIR-mandibular splint therapy in a small group (n = 9) of CMD patients. Patients showed increased anxiety levels before therapy assessed with the STAI and the depression and anxiety scale (DASS). Besides of relevant reduction in pain the STAI decreased over time. Reduction in STAI was associated with anterior insular fMRI-activation reduction on both hemispheres. We conclude that the anxiety driven anticipation of pain related to occlusal trigger is processed in the anterior insula and might therefore be a main driver of therapeutic intervention by the splint therapy in CMD.

Determining Brain Mechanisms that Underpin Analgesia Induced by the Use of Pain Coping Skills

Objective

Cognitive behavioral therapies decrease pain and improve mood and function in people with osteoarthritis. This study assessed the effects of coping strategies on the central processing of knee pain in people with osteoarthritis of the knees.

Methods

Mechanical pressure was applied to exacerbate knee pain in 28 people with osteoarthritis of the knee. Reports of pain intensity and functional magnetic resonance imaging measures of pain-related brain activity were recorded with and without the concurrent use of pain coping skills.

Results

Coping skills led to a significant reduction in pain report (Coping = 2.64 ± 0.17, Not Coping = 3.28 ± 0.15, P < 0.001). These strategies were associated with increased activation in pain modulatory regions of the brain (medial prefrontal and rostral anterior cingulate cortices, Pcorrected < 0.05) and decreased pain-related activation in regions that process noxious input (midcingulate cortex, supplementary motor area, secondary somatosensory cortex, and anterior parietal lobule, Pcorrected < 0.05). The magnitude of the decrease in pain report during the use of pain coping strategies was found to be proportional to the decrease in pain-related activation in brain regions that code the aversive/emotional dimension of pain (anterior insula, inferior frontal gyrus, orbitofrontal cortex, Pcorrected < 0.05) but did not differ between groups with and without training in coping skills. However, training in coping skills reduced the extent to which brain responses to noxious input were influenced by anxiety.

Conclusions

The results of this study support previous reports of pain modulation by cognitive pain coping strategies and contribute to the current understanding of how analgesia associated with the use of pain coping strategies is represented in the brain.

Structural Brain Alterations Before and After Total Knee Arthroplasty: A Longitudinal Assessment

Objective

Many studies have provided evidence of altered brain structure in chronic pain conditions, as well as further adaptations following treatment that are coincident with changes in pain. Less is known regarding how these structural brain adaptations relate to assessments of nociceptive processing. The current study aimed to investigate brain structure in people with knee osteoarthritis (OA) before and after total knee arthroplasty (TKA) and to investigate the relationships between these findings and quantitative sensory testing (QST) of the nociceptive system.

Methods

Twenty-nine people with knee OA underwent magnetic resonance imaging (MRI) scans and QST before and six months after TKA and were compared with a pain-free control group (N = 18). MRI analyses involved voxel-based morphometry and fractional anisotropy.

Results

Before TKA, there was reduced gray matter volume and impaired fractional anisotropy in areas associated with nociceptive processing, with further gray matter adaptations and improvements in fractional anisotropy evident after TKA. QST revealed increased nociceptive facilitation and impaired inhibition in knee OA that was reversed after TKA. There were minimal relationships found between MRI data and QST assessments or pain report.

Conclusions

In people with end-stage knee OA, region-specific gray matter atrophy was detected, with further changes in gray matter volume and improvements in white matter integrity observed after joint replacement. Despite coincident alterations in nociceptive inhibition and facilitation processes, there did not appear to be any association between these functional assessments of the nociceptive system and changes in brain structure.

Imaging Clinically Relevant Pain States Using Arterial Spin Labeling

Arterial Spin Labeling (ASL) is a perfusion-based functional magnetic resonance imaging technique that uses water in arterial blood as a freely diffusible tracer to measure regional cerebral blood flow (rCBF) noninvasively. To date its application to the study of pain has been relatively limited. Yet, ASL possesses key features that make it uniquely positioned to study pain in certain paradigms. For instance, ASL is sensitive to very slowly fluctuating brain signals (in the order of minutes or longer). This characteristic makes ASL particularly suitable to the evaluation of brain mechanisms of tonic experimental, post-surgical and ongoing/or continuously varying pain in chronic or acute pain conditions (whereas BOLD fMRI is better suited to detect brain responses to short-lasting or phasic/evoked pain). Unlike positron emission tomography or other perfusion techniques, ASL allows the estimation of rCBF without requiring the administration of radioligands or contrast agents. Thus, ASL is well suited for within-subject longitudinal designs (e.g., to study evolution of pain states over time, or of treatment effects in clinical trials). ASL is also highly versatile, allowing for novel paradigms exploring a flexible array of pain states, plus it can be used to simultaneously estimate not only pain-related alterations in perfusion but also functional connectivity. In conclusion, ASL can be successfully applied in pain paradigms that would be either challenging or impossible to implement using other techniques. Particularly when used in concert with other neuroimaging techniques, ASL can be a powerful tool in the pain imager's toolbox.

The impact of anxiety on chronic musculoskeletal pain and the role of astrocyte activation

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Anxiety predicts onset of knee pain and drives greater osteoarthritis pain in humans. Our validated preclinical model identifies supraspinal astrocytosis as a potential mechanism.

Anxiety and depression are associated with increased pain responses in chronic pain states. The extent to which anxiety drives chronic pain, or vice versa, remains an important question that has implications for analgesic treatment strategies. Here, the effect of existing anxiety on future osteoarthritis (OA) pain was investigated, and potential mechanisms were studied in an animal model. Pressure pain detection thresholds, anxiety, and depression were assessed in people with (n = 130) or without (n = 100) painful knee OA. Separately, knee pain and anxiety scores were also measured twice over 12 months in 4730 individuals recruited from the general population. A preclinical investigation of a model of OA pain in normo-anxiety Sprague-Dawley (SD) and high-anxiety Wistar Kyoto (WKY) rats assessed underlying neurobiological mechanisms. Higher anxiety, independently from depression, was associated with significantly lower pressure pain detection thresholds at sites local to (P < 0.01) and distant from (P < 0.05) the painful knee in patients with OA. Separately, high anxiety scores predicted increased risk of knee pain onset in 3274 originally pain-free people over the 1-year period (odds ratio = 1.71; 95% confidence interval = 1.25-2.34, P < 0.00083). Similarly, WKY rats developed significantly lower ipsilateral and contralateral hind paw withdrawal thresholds in the monosodium iodoacetate model of OA pain, compared with SD rats (P = 0.0005). Linear regressions revealed that baseline anxiety-like behaviour was predictive of lowered paw withdrawal thresholds in WKY rats, mirroring the human data. This augmented pain phenotype was significantly associated with increased glial fibrillary acidic protein immunofluorescence in pain-associated brain regions, identifying supraspinal astrocyte activation as a significant mechanism underlying anxiety-augmented pain behaviour.

Regional Differences Within the Anterior Cingulate Cortex in the Generation Versus Suppression of Pain Affect in Rats

The anterior cingulate cortex (ACC) modulates emotional responses to pain. Whereas, the caudal ACC (cACC) promotes expression of pain affect, the rostral ACC (rACC) contributes to its suppression. Both subdivisions receive glutamatergic innervation, and the present study evaluated the contribution of N-methyl-d-aspartic acid (NMDA) receptors within these subdivisions to rats' expression of pain affect. Vocalizations that follow a brief noxious tail shock (vocalization afterdischarges, VAD) are a validated rodent model of pain affect. The threshold current for eliciting VAD was increased in a dose-dependent manner by injecting NMDA into the rACC, but performance (latency, amplitude, and duration) at threshold was not altered. Alternately, the threshold current for eliciting VAD was not altered following injection of NMDA into the cACC, but its amplitude and duration at threshold were increased in a dose-dependent manner. These effects were limited to Cg1 of the rACC and cACC, and blocked by pretreatment of the ACC with the NMDA receptor antagonist d-2-amino-5-phosphonovalerate. These findings demonstrate that NMDA receptor agonism within the cACC and rACC either increases or decreases emotional responses to noxious stimulation, respectively. PERSPECTIVE: NMDA receptor activation of the rostral and caudal ACC respectively inhibited or enhanced rats' emotional response to pain. These findings mirror those obtained from human neuroimaging studies; thereby, supporting the use of this model system in evaluating the contribution of ACC to pain affect.

A systematic review of structural and functional MRI studies on pain catastrophizing

Objectives: Pain catastrophizing is reliably associated with pain reports during experimental pain in healthy, pain-free subjects and in people with chronic pain. It also correlates with self-reports of clinical pain intensity/severity in a variety of disorders characterized by chronic pain in adults, adolescents and children. However, processes, through which it exerts its effects are yet unclear. In this paper, our primary aim was to synthesize neuroimaging research to open a window to possible mechanisms underlying pain catastrophizing in both chronic pain patients and healthy controls. We also aimed to compare whether the neural correlates of pain catastrophizing are similar in these two groups.

Methods: PubMed and the Web of Science were searched for magnetic resonance imaging (MRI) studies that explored neural correlates of pain catastrophizing.

Results: Twenty articles met the inclusion criteria. The results of our review show a connection between pain catastrophizing and brain areas tightly connected to pain perception (including the somatosensory cortices, anterior insula, anterior cingulate cortex and thalamus) and/or modulation (eg, the dorsolateral prefrontal cortex). Our results also highlight that these processes - in relation to pain catastrophizing - are more pronounced in chronic pain patients, suggesting that structural and functional brain alterations (and perhaps mechanisms) related to pain catastrophizing may depend on prior and/or relatively stable/constant pain experience. However, we also found methodological issues and differences that could lead to divergent results.

Discussion: Based on our results, pain catastrophizing might be related to salience detection, pain processing, and top-down attentional processes. More research is recommended to explore neural changes to specific types of catastrophizing thoughts (eg, experimentally induced and/or state). Furthermore, we provide ideas regarding pain catastrophizing studies in the future for a more standardized approach.

Altered connectivity of the right anterior insula drives the pain connectome changes in chronic knee osteoarthritis

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A resting-state functional magnetic resonance imaging study of chronic knee osteoarthritis pain using a range of functional connectivity analyses to better understand brain network changes.

Resting-state functional connectivity (FC) has proven a powerful approach to understand the neural underpinnings of chronic pain, reporting altered connectivity in 3 main networks: the default mode network (DMN), central executive network, and the salience network (SN). The interrelation and possible mechanisms of these changes are less well understood in chronic pain. Based on emerging evidence of its role to drive switches between network states, the right anterior insula (rAI, an SN hub) may play a dominant role in network connectivity changes underpinning chronic pain. To test this hypothesis, we used seed-based resting-state FC analysis including dynamic and effective connectivity metrics in 25 people with chronic osteoarthritis (OA) pain and 19 matched healthy volunteers. Compared with controls, participants with painful knee OA presented with increased anticorrelation between the rAI (SN) and DMN regions. Also, the left dorsal prefrontal cortex (central executive network hub) showed more negative FC with the right temporal gyrus. Granger causality analysis revealed increased negative influence of the rAI on the posterior cingulate (DMN) in patients with OA in line with the observed enhanced anticorrelation. Moreover, dynamic FC was lower in the DMN of patients and thus more similar to temporal dynamics of the SN. Together, these findings evidence a widespread network disruption in patients with persistent OA pain and point toward a driving role of the rAI.

Delineation between different components of chronic pain using dimension reduction - an ASL fMRI study in hand osteoarthritis

Background

Traditional psychometric measures aimed at characterizing the pain experience often show considerable overlap, due to interlinked affective and modulatory processes under central nervous system control. Neuroimaging studies have been employed to investigate this complexity of pain processing, in an attempt to provide a quantifiable, adjunctive description of pain perception. In this exploratory study, we examine psychometric and neuroimaging data from 38 patients with painful osteoarthritis of the carpometacarpal joint. We had two aims: first, to utilize principal component analysis (PCA) as a dimension reduction strategy across multiple self‐reported endpoints of pain, cognitive and affective functioning; second, to investigate the relationship between identified dimensions and regional cerebral blood flow (rCBF) as an indirect measure of brain activity underpinning their ongoing pain experiences.

Methods

Psychometric data were collected using validated questionnaires. Quantitative estimates of rCBF were acquired using pseudo‐continuous arterial spin‐labelled functional magnetic resonance imaging.

Results

Two principal components were identified that accounted for 73% of data variance; one related to pain scores and a second to psychological traits. Voxel‐wise multiple regression analysis revealed a significant negative association between the ‘pain score’ component and rCBF to a right temporal lobe cluster, including the amygdala and the parahippocampal cortex.

Conclusion

We suggest this association may represent a coping mechanism that aims to reduce fear‐related pain‐anxiety. Further investigation of central brain processing mechanisms in osteoarthritis‐related pain may offer insights into more effective therapeutic strategies.

Significance

This study demonstrates that dimension reduction using PCA allows insight into pain perception and its affective components in relation to brain activation patterns in patients with painful hand osteoarthritis.

A critical evaluation of validity and utility of translational imaging in pain and analgesia: Utilizing functional imaging to enhance the process

Assessing clinical pain and metrics related to function or quality of life predominantly relies on patient reported subjective measures. These outcome measures are generally not applicable to the preclinical setting where early signs pointing to analgesic value of a therapy are sought, thus introducing difficulties in animal to human translation in pain research. Evaluating brain function in patients and respective animal model(s) has the potential to characterize mechanisms associated with pain or pain-related phenotypes and thereby provide a means of laboratory to clinic translation. This review summarizes the progress made towards understanding of brain function in clinical and preclinical pain states elucidated using an imaging approach as well as the current level of validity of translational pain imaging. We hypothesize that neuroimaging can describe the central representation of pain or pain phenotypes and yields a basis for the development and selection of clinically relevant animal assays. This approach may increase the probability of finding meaningful new analgesics that can help satisfy the significant unmet medical needs of patients.

Gamma-Hydroxybutyrate Increases Resting-State Limbic Perfusion and Body and Emotion Awareness in Humans

Gamma-hydroxybutyrate (GHB) is a GHB-/GABA-B receptor agonist inducing a broad spectrum of subjective effects including euphoria, disinhibition, and enhanced vitality. It is used as treatment for neuropsychiatric disorders including narcolepsy and alcohol withdrawal, but is also a drug of abuse. Non-medical users report enhancement of body and emotion awareness during intoxication. However, the neuronal underpinnings of such awareness alterations under GHB are unknown so far. The assessment of regional cerebral blood flow (rCBF) by pharmacological magnetic resonance imaging (phMRI) enables the elucidation of drug-induced functional brain alterations. Thus, we assessed the effects of GHB (35 mg/kg p.o.) in 17 healthy males on rCBF and subjective drug effects, using a placebo-controlled, double-blind, randomized, cross-over design employing arterial spin labeling phMRI. Compared to placebo, GHB increased subjective ratings for body and emotion awareness, and for dizziness (p<0.01-0.001, Bonferroni-corrected). A whole-brain analysis showed increased rCBF in the bilateral anterior cingulate cortex (ACC) and the right anterior insula under GHB (p<0.05, cluster-corrected). ACC and insula rCBF are correlated with relaxation, and body and emotion awareness (p<0.05-0.001, uncorrected). Interaction analyses revealed that GHB-induced increase of body awareness was accompanied by increased rCBF in ACC, whereas relaxation under GHB was accompanied by elevated rCBF in right anterior insula (p<0.05, uncorrected). In conclusion, enhancement of emotion and body awareness, and increased perfusion of insula and ACC bears implications both for the properties of GHB as a drug of abuse as well as for its putative personalized potential for specific therapeutic indications in affective disorders.

Manganese-enhanced magnetic resonance imaging depicts brain activity in models of acute and chronic pain: A new window to study experimental spontaneous pain?

Application of functional imaging techniques to animal models is vital to understand pain mechanisms, but is often confounded by the need to limit movement artefacts with anaesthesia, and a focus on evoked responses rather than clinically relevant spontaneous pain and related hyperalgesia. The aim of the present study was to investigate the potential of manganese-enhanced magnetic resonance imaging (MEMRI) to measure neural responses during on-going pain that underpins hyperalgesia in pre-clinical models of nociception. As a proof of concept that MEMRI is sensitive to the neural activity of spontaneous, intermittent behaviour, we studied a separate positive control group undergoing a voluntary running wheel experiment. In the pain models, pain behaviour (weight bearing asymmetry and hindpaw withdrawal thresholds (PWTs)) was measured at baseline and following either intra-articular injection of nerve growth factor (NGF, 10µg/50µl; acute pain model, n=4 rats per group), or the chondrocyte toxin monosodium iodoacetate (MIA, 1mg/50µl; chronic model, n=8 rats per group), or control injection. Separate groups of rats underwent a voluntary wheel running protocol (n=8 rats per group). Rats were administered with paramagnetic ion Mn²⁺ as soluble MnCl₂ over seven days (subcutaneous osmotic pump) to allow cumulative activity-dependent neural accumulation in the models of pain, or over a period of running. T1-weighted MR imaging at 7T was performed under isoflurane anaesthesia using a receive-only rat head coil in combination with a 72mm volume coil for excitation. The pain models resulted in weight bearing asymmetry (NGF: 20.0 ± 5.2%, MIA: 15 ± 3%), and a reduction in PWT in the MIA model (8.3 ± 1.5g) on the final day of assessment before undergoing MR imaging. Voxel-wise and region-based analysis of MEMRI data did not identify group differences in T1 signal. However, MnCl₂ accumulation in the VTA, right Ce amygdala, and left cingulate was negatively correlated with pain responses (greater differences in weight bearing), similarly MnCl₂ accumulation was reduced in the VTA in line with hyperalgesia (lower PWTs), which suggests reduced regional activation as a result of the intensity and duration of pain experienced during the 7 days of MnCl₂ exposure. Motor cortex T1-weighted signal increase was associated with the distance ran in the wheel running study, while no between group difference was seen. Our data suggest that on-going pain related signal changes identified using MEMRI offers a new window to study the neural underpinnings of spontaneous pain in rats.