Pretreatment Brain White Matter Integrity Associated With Neuropathic Pain Relief and Changes in Temporal Summation of Pain Following Ketamine.

Neuropathic pain (NP) is a prevalent condition often associated with heightened pain responsiveness suggestive of central sensitization. Neuroimaging biomarkers of treatment outcomes may help develop personalized treatment strategies, but white matter (WM) properties have been underexplored for this purpose. Here we assessed whether WM pathways of the default mode network (DMN: medial prefrontal cortex [mPFC], posterior cingulate cortex, and precuneus) and descending pain modulation system (periaqueductal gray [PAG]) are associated with ketamine analgesia and attenuated temporal summation of pain (TSP, reflecting central sensitization) in NP. We used a fixel-based analysis of diffusion-weighted imaging data to evaluate WM microstructure (fiber density [FD]) and macrostructure (fiber bundle cross-section) within the DMN and mPFC-PAG pathways in 70 individuals who underwent magnetic resonance imaging and TSP testing; 35 with NP who underwent ketamine treatment and 35 age- and sex-matched pain-free individuals. Individuals with NP were assessed before and 1 month after treatment; those with ≥30% pain relief were considered responders (n = 18), or otherwise as nonresponders (n = 17). We found that WM structure within the DMN and mPFC-PAG pathways did not differentiate responders from nonresponders. However, pretreatment FD in the anterior limb of the internal capsule correlated with pain relief (r=.48). Moreover, pretreatment FD in the DMN (left mPFC-precuneus/posterior cingulate cortex; r=.52) and mPFC-PAG (r=.42) negatively correlated with changes in TSP. This suggests that WM microstructure in the DMN and mPFC-PAG pathway is associated with the degree to which ketamine reduces central sensitization. Thus, fixel metrics of WM structure may hold promise to predict ketamine NP treatment outcomes. PERSPECTIVE: We used advanced fixel-based analyses of MRI diffusion-weighted imaging data to identify pretreatment WM microstructure associated with ketamine outcomes, including analgesia and markers of attenuated central sensitization. Exploring associations between brain structure and treatment outcomes could contribute to a personalized approach to treatment for individuals with NP.

Improving access to chronic pain care with central referral and triage: The 6-year findings from a single-entry model.

Background: Despite the established efficacy of multidisciplinary chronic pain care, barriers such as inflated referral wait times and uncoordinated care further hinder patient health care access. Aims: Here we describe the evolution of a single-entry model (SEM) for coordinating access to chronic pain care across seven hospitals in Toronto and explore the impact on patient care 6 years after implementation. Methods: In 2017, an innovative SEM was implemented for chronic pain referrals in Toronto and surrounding areas. Referrals are received centrally, triaged by a clinical team, and assigned an appointment according to the level of urgency and the most appropriate care setting/provider. To evaluate the impact of the SEM, a retrospective analysis was undertaken to determine referral patterns, patient characteristics, and referral wait times over the past 6 years. Results: Implementation of an SEM streamlined the number of steps in the referral process and led to a standardized referral form with common inclusion and exclusion criteria across sites. Over the 6-year period, referrals increased by 93% and the number of unique providers increased by 91%. Chronic pain service wait times were reduced from 299 (±158) days to 176 (±103) days. However, certain pain diagnoses such as chronic pelvic pain and fibromyalgia far exceed the average. Conclusions: The results indicate that the SEM helped reduce wait times for pain conditions and standardized the referral pathway. Continued data capture efforts can help identify gaps in care to enable further health care refinement and improvement.

Contexte: Malgré l'efficacité établie des soins multidisciplinaires dans le traitement de la douleur chronique, des obstacles tels que des délais d'attente prolongés et l'absence de coordination des soins entravent davantage l'accès des patients aux services de santé.Objectifs: Nous décrivons ici l'évolution d'un modèle à entrée unique visant à coordonner l'accès aux soins pour la douleur chronique dans sept hôpitaux de Toronto. Nous examinons également l'effet de ce modèle sur les soins aux patients six ans après sa mise en œuvre.Méthodes: En 2017, un modèle à entrée unique novateur a été mis en place pour orienter les patients souffrant de douleur chronique à Toronto et dans les régions avoisinantes. Les patients sont reçus de manière centralisée, triés par une équipe clinique et un rendez-vous leur est attribué en fonction du degré d'urgence et de l'établissement de soins ou du prestataire le plus approprié.Pour évaluer l'impact du modèle à entrée unique, une analyse rétrospective a été entreprise afin de déterminer les schémas de consultation, les caractéristiques des patients et les temps d'attente pour les demandes de consultation au cours des six dernières années.Résultats: La mise en œuvre d'un modèle à entrée unique a permis de rationaliser le nombre d'étapes du processus de demande de consultation et a conduit à l'élaboration d'un formulaire de demande de consultation normalisé comprenant des critères d'inclusion et d'exclusion communs à tous les sites. Au cours de la période de six ans, le nombre de demandes de consultation a augmenté et le nombre de prestataires uniques a augmenté de 91 %.Les temps d'attente pour les services de traitement de la douleur chronique ont diminué de 299 (±158) jours à 176 (±103) jours. Cependant, certains diagnostics de douleur, comme la douleur pelvienne chronique et la fibromyalgie, dépassent de loin la moyenne.Conclusions: Les résultats indiquent que le modèle à entrée unique a contribué à réduire les temps d'attente pour les affections douloureuses et à normaliser le parcours de consultation. La poursuite des efforts de collecte des données peut aider à recenser les lacunes dans les soins, permettant ainsi une amélioration continue des soins de santé.

Empowered management for pelvic pain: The experiences of women with persistent pelvic pain participating in an online self-directed self-management program while they wait for interprofessional care.

BACKGROUND: Persistent pelvic pain is pain sensed in or around the pelvis and is often associated with negative cognitive, behavioral, sexual, and emotional consequences. The lack of interprofessional persistent pelvic pain management programs that address the complex interplay of biopsychosocial factors result in lengthy wait times and negative health outcomes. Limited access to evidence informed self-management educational resources contributes to poor coping strategies. Evidence shows that self-management education and strategies support patients while they wait for care. However, very few studies explore the patient's lived experience of participating in an online educational program designed for persistent pelvic pain. OBJECTIVES: This study aims to understand the experience of women with persistent pelvic pain participating in an online, self-management education program ("Pelvic Pain Empowered Management" program) while awaiting care at an interprofessional pelvic pain clinic. DESIGN: A descriptive qualitative approach was used to explore the experiences of women participating in an online educational program designed for cis women with persistent pelvic pain. METHODS: We conducted semi-structured interviews with 11 women, transcribed the data verbatim using NVivo software (NVivo 12, QSR International Pty Ltd.), and analyzed inductively using previously established methods. RESULTS: We identified four main themes relevant to women's experiences of the program: (1) the program shaped expectations around upcoming pelvic pain appointments, (2) the program content is relevant and resonates with people with lived experience of persistent pelvic pain, (3) the program enhanced understanding of persistent pelvic pain, and (4) the program empowered people with skills and strategies to better manage their persistent pelvic pain. CONCLUSION: Our findings highlight how self-directed online patient education can be leveraged while persistent pelvic pain patients wait for care to support them in setting expectations around care and in engaging in pain self-management.

Resilience is associated with cortical gray matter of the antinociceptive pathway in people with chronic pain.

Resilience is an important personal characteristic that influences health and recovery. Previous studies of chronic pain suggest that highly resilient people may be more effective at modulating their pain. Since brain gray matter in the antinociceptive pathway has also been shown to be abnormal in people with chronic pain, we examined whether resilience is related to gray matter in regions of interest (ROIs) of the antinociceptive pathway (rostral and subgenual anterior cingulate cortex (rACC, sgACC), anterior insula (aINS), dorsolateral prefrontal cortex (dlPFC)) normally and in people who are experiencing chronic pain. We extracted gray matter volume (GMV) and cortical thickness (CT) from 3T MRIs of 88 people with chronic pain (half males/females) and 86 healthy controls (HCs), who completed The Resilience Scale and Brief Pain Inventory. We found that resilience scores were significantly lower in people with chronic pain compared to HCs, whereas ROI GMV and CT were not different between groups. Resilience negatively correlated with average pain scores and positively correlated with GMV in the bilateral rACC, sgACC, and left dlPFC of people with chronic pain. Mediation analyses revealed that GMV in the right rACC and left sgACC partially co-mediated the relationship between resilience and average pain in people with chronic pain. The resilience-pain and some resilience-GMV relationships were sex-dependent. These findings suggest that the antinociceptive pathway may play a role in the impact of resilience on one's ability to modulate chronic pain. A better understanding of the brain-resilience relationship may help advance evidence-based approaches to pain management.

Can we characterize A-P/IAP behavioural phenotypes in people with chronic pain?

Two behavioural phenotypes in healthy people have been delineated based on their intrinsic attention to pain (IAP) and whether their reaction times (RT) during a cognitively-demanding task are slower (P-type) or faster (A-type) during experimental pain. These behavioural phenotypes were not previously studied in chronic pain populations to avoid using experimental pain in a chronic pain context. Since pain rumination (PR) may serve as a supplement to IAP without needing noxious stimuli, we attempted to delineate A-P/IAP behavioural phenotypes in people with chronic pain and determined if PR can supplement IAP. Behavioural data acquired in 43 healthy controls (HCs) and 43 age-/sex-matched people with chronic pain associated with ankylosing spondylitis (AS) was retrospectively analyzed. A-P behavioural phenotypes were based on RT differences between pain and no-pain trials of a numeric interference task. IAP was quantified based on scores representing reported attention towards or mind-wandering away from experimental pain. PR was quantified using the pain catastrophizing scale, rumination subscale. The variability in RT was higher during no-pain trials in the AS group than HCs but was not significantly different in pain trials. There were no group differences in task RTs in no-pain and pain trials, IAP or PR scores. IAP and PR scores were marginally significantly positively correlated in the AS group. RT differences and variability were not significantly correlated with IAP or PR scores. Thus, we propose that experimental pain in the A-P/IAP protocols can confound testing in chronic pain populations, but that PR could be a supplement to IAP to quantify attention to pain.

Experience-based design: Empowering individuals while they wait for interprofessional chronic pain care.

OBJECTIVES: Chronic pain is highly prevalent and a leading cause of disability. Long wait times for interprofessional care provide an opportunity to introduce web-based interventions that improve psychosocial function and patients' readiness and ability to manage their condition. Here we describe the process of partnering with people with lived experience (PWLE) to develop an online self-management program enhanced by motivational interviewing. We also report the multiphase usability testing of the program. METHODS: PWLE were included in all aspects of this project from program inception to content creation, module development, usability testing, and knowledge dissemination. Phase 1 included the development of the interactive, web-based modules. This process involved weekly meetings and asynchronous content creation with a core team of interprofessional pain experts, researchers, and PWLE. Phase 2 included usability testing by our PWLE and clinical expert advisory. Phase 3 included survey-based usability testing with a sample of 10 PWLE. RESULTS: We created a chronic pain & motivational empowerment program includes a series of eight interactive educational web-based modules. Topics included: setting expectations, chronic pain explained, biopsychosocial factors, empowered management, self-awareness & compassion & acceptance, values, goal setting, and communication. The program is accompanied by a reflection journal and can be enhanced by one-on-one coaching sessions using a motivational interviewing approach. Phase two usability testing resulted in numerous content changes and the addition of accessibility features. Phase 3 usability testing with PWLE found the program highly accessible and easy to use. CONCLUSIONS: The engagement of our PWLE team member and advisors made the online program more relevant, sensitive and helpful to the needs of people with pain. PRACTICAL VALUE: This PWLE-centric project sets the foundation for future work to examine the feasibility and effectiveness of the program for supporting individuals with chronic pain self-manage.

Virtual care exercise interventions in multidisciplinary chronic pain clinics: a qualitative study of perspectives of adults living with chronic pain.

PURPOSE: Chronic pain affects 1 in 4 Canadians and is a leading contributor of disability. Although virtual care has become more prevalent, it is unclear how adults living with chronic pain perceive virtual delivery of exercise interventions within multidisciplinary chronic pain clinics (MCPC). This study explores the perspectives of adults living with chronic pain regarding their perceived barriers and facilitators and recommendations when implementing virtual care exercise interventions within MCPCs. METHODS: We conducted an interpretive description qualitative study based on semi-structured interviews with adults (age ≥18 years) living with chronic pain from a MCPC in Toronto, Canada, between March 1 and April 30, 2021. RESULTS: We completed fifteen (N = 15) interviews of adults living with chronic pain. We identified eight themes that addressed the study objectives: 1) virtual care supplements in-person care, 2) virtual care improves accessibility, 3) impact of technology on participation, 4) navigating the home environment, 5) impact of pain on participation, 6) impact of supervision and feedback, 7) the need for tailored care, and 8) the need for preparation and additional support. CONCLUSION: Our results reveal that adults living with chronic pain view virtual care exercise interventions positively however, the implementation of these interventions must be carefully considered within MCPCs. Specifically, virtual care was considered an excellent adjunct to in-person care but should not replace it completely.Implications for RehabilitationChronic pain is a leading contributor of disability.Exercise interventions are recommended component of comprehensive pain management.Virtual delivery of exercise interventions are becoming more prevalent.Adults living with chronic pain view virtual care exercise interventions positively as they can supplement in-person care and improve access to this type of care.

Carpal tunnel surgery dampens thalamocortical and normalizes corticocortical functional connectivity.

Carpal tunnel syndrome is the most common entrapment neuropathy and is associated with altered brain function and structure. However, little is understood of the central mechanisms associated with its pain, symptom presentation, and treatment-related resolution. This longitudinal study evaluated carpal tunnel syndrome-related alterations in brain network communication and relationships to behavioural signs of central sensitization before and after carpal tunnel release surgery. We tested the hypothesis that carpal tunnel syndrome is associated with condition- and treatment-related plasticity in brain regions involved in somatosensation. We used quantitative sensory testing and clinical and pain questionnaires to assess sensory and pain function in 25 patients with carpal tunnel syndrome before (18 women, 7 men) and after (n = 16) surgery, and 25 sex- and age-matched healthy controls. We also acquired resting-state functional MRI to determine functional connectivity of two key nodes in the somatosensory system, the thalamus and primary somatosensory cortex. Seed-to-whole brain resting-state static functional connectivity analyses revealed abnormally low functional connectivity for the hand area of the primary somatosensory cortex with the contralateral somatosensory association cortex (supramarginal gyrus) before surgery (P < 0.01). After clinically effective surgery: (i) Primary somatosensory functional connectivity was normalized with the contralateral somatosensory association cortex and reduced with the dorsolateral prefrontal cortex (a region associated with cognitive and emotional modulation of pain) and primary visual areas (P < 0.001) from pre-op levels; and (ii) Functional connectivity of the thalamus with the primary somatosensory and motor cortices was attenuated from pre-op levels (P < 0.001) but did not correlate with temporal summation of pain (a behavioural measure of central sensitization) or clinical measures. This study is the first to reveal treatment-related neuroplasticity in resting-state functional connectivity of the somatosensory system in carpal tunnel syndrome. The findings of dysfunctional resting-state functional connectivity point to aberrant neural synchrony between the brain's representation of the hand with regions involved in processing and integrating tactile and nociceptive stimuli and proprioception in carpal tunnel syndrome. Aberrant neural communication between the primary somatosensory hand area and the dorsolateral prefrontal cortex could reflect increased attention to pain, paraesthesia, and altered sensation in the hand. Finally, reduced thalamocortical functional connectivity after surgery may reflect central plasticity in response to the resolution of abnormal sensory signals from the periphery. Our findings support the concept of underlying brain contributions to this peripheral neuropathy, specifically aberrant thalamocortical and corticocortical communication, and point to potential central therapeutic targets to complement peripheral treatments.

A Hidden Markov Model reveals magnetoencephalography spectral frequency-specific abnormalities of brain state power and phase-coupling in neuropathic pain.

Neuronal populations in the brain are engaged in a temporally coordinated manner at rest. Here we show that spontaneous transitions between large-scale resting-state networks are altered in chronic neuropathic pain. We applied an approach based on the Hidden Markov Model to magnetoencephalography data to describe how the brain moves from one activity state to another. This identified 12 fast transient (~80 ms) brain states including the sensorimotor, ascending nociceptive pathway, salience, visual, and default mode networks. Compared to healthy controls, we found that people with neuropathic pain exhibited abnormal alpha power in the right ascending nociceptive pathway state, but higher power and coherence in the sensorimotor network state in the beta band, and shorter time intervals between visits of the sensorimotor network, indicating more active time in this state. Conversely, the neuropathic pain group showed lower coherence and spent less time in the frontal attentional state. Therefore, this study reveals a temporal imbalance and dysregulation of spectral frequency-specific brain microstates in patients with neuropathic pain. These findings can potentially impact the development of a mechanism-based therapeutic approach by identifying brain targets to stimulate using neuromodulation to modify abnormal activity and to restore effective neuronal synchrony between brain states.

Empathy, defending, and functional connectivity while witnessing social exclusion.

Peers are present for most bullying episodes. Peers who witness bullying can play an important role in either stopping or perpetuating the behavior. Defending can greatly benefit victimized peers. Empathy is strongly associated with defending. Yet, less is known about defenders' neural response to witnessing social distress, and how this response may relate to the link between empathy and defending. Forty-six first-year undergraduate students (Mage = 17.7; 37 women), with varied history of peer defending, underwent fMRI scanning while witnessing a depiction of social exclusion. Functional connectivity analysis was performed across brain regions that are involved in cognitive empathy, empathetic distress, and compassion. History of defending was positively associated with functional connectivity (Exclusion > Inclusion) between the left orbitofrontal cortex (OFC) - medial prefrontal cortex (MPFC), and right OFC - left and right amygdalae. Defending was negatively associated with functional connectivity between the left OFC - anterior cingulate cortex. The relationship between history of defending and empathy (specifically, empathetic perspective taking) was moderated by functional connectivity of the right OFC - left amygdala. These findings suggest that coactivation of brain regions involved in compassionate emotion regulation and empathetic distress play a role in the relationship between empathy and peer defending.

Defining Success in Transitions from Pediatric to Adult Chronic Pain Care: A Descriptive Qualitative Study of Perspectives of Young Adults Living with Chronic Pain.

OBJECTIVE: To explore how young adults with chronic pain define a successful transition from pediatric to adult chronic pain care and how they would like to be empowered to achieve a successful transition. DESIGN: A descriptive qualitative design. SETTING: Participants were recruited from a hospital-based chronic pain clinic in Toronto, Canada, and through social media. SUBJECTS: Young adults (18-25 years of age, inclusive) who received chronic pain care in a pediatric setting and continued to self-identify as having a need for chronic pain care in an adult chronic pain care setting. METHODS: Semistructured interviews were used to understand the perspectives of young adults with chronic pain. Interviews were audio-recorded, transcribed verbatim, and checked for accuracy. Qualitative inductive content analysis was used to analyze the interview data. RESULTS: Eight young adults with chronic pain were interviewed (all women; median age=19 years). Five themes that addressed the study objectives are described: 1) Young adults value skill-building and knowledge about the transition, 2) establishment of a strong therapeutic alliance with health care providers, 3) coordinated and planned transition, 4) social and environmental support, and 5) respect for young adults' independence and autonomy. CONCLUSION: Findings suggest the need for a collaborative and individualized approach to the successful transition of young adults across the continuum of chronic pain care that addresses their unique needs. To promote successful transition, clinicians should build relationships with young adults that facilitate choice and autonomy while enhancing skill-building and education on available resources.

Exploring sex differences in alpha brain activity as a potential neuromarker associated with neuropathic pain.

ABSTRACT: Alpha oscillatory activity (8-13 Hz) is the dominant rhythm in the awake brain and is known to play an important role in pain states. Previous studies have identified alpha band slowing and increased power in the dynamic pain connectome (DPC) of people with chronic neuropathic pain. However, a link between alpha-band abnormalities and sex differences in brain organization in healthy individuals and those with chronic pain is not known. Here, we used resting-state magnetoencephalography to test the hypothesis that peak alpha frequency (PAF) abnormalities are general features across chronic central and peripheral conditions causing neuropathic pain but exhibit sex-specific differences in networks of the DPC (ascending nociceptive pathway [ANP], default mode network, salience network [SN], and subgenual anterior cingulate cortex). We found that neuropathic pain (N = 25 men and 25 women) was associated with increased PAF power in the DPC compared with 50 age- and sex-matched healthy controls, whereas slower PAF in nodes of the SN (temporoparietal junction) and the ANP (posterior insula) was associated with higher trait pain intensity. In the neuropathic pain group, women exhibited lower PAF power in the subgenual anterior cingulate cortex and faster PAF in the ANP and SN than men. The within-sex analyses indicated that women had neuropathic pain-related increased PAF power in the ANP, SN, and default mode network, whereas men with neuropathic pain had increased PAF power restricted to the ANP. These findings highlight neuropathic pain-related and sex-specific abnormalities in alpha oscillations across the DPC that could underlie aberrant neuronal communication in nociceptive processing and modulation.

Sex-Specific Abnormalities and Treatment-Related Plasticity of Subgenual Anterior Cingulate Cortex Functional Connectivity in Chronic Pain.

The subgenual anterior cingulate cortex (sgACC) is a key node of the descending antinociceptive system with sex differences in its functional connectivity (FC). We previously reported that, in a male-prevalent chronic pain condition, sgACC FC is abnormal in women but not in men. This raises the possibility that, within a sex, sgACC FC may be either protective or represent a vulnerability to develop a sex-dominant chronic pain condition. The aim of this study was to characterize sgACC FC in a female-dominant chronic pain condition, carpal tunnel syndrome (CTS), to investigate whether sgACC abnormalities are a common feature in women with chronic pain or unique to individuals with pain conditions that are more prevalent in the opposite sex. We used fMRI to determine the resting state FC of the sgACC in healthy controls (HCs, n = 25, 18 women; 7 men) and people with CTS before (n = 25, 18 women; 7 men) and after (n = 17, 13 women; 4 men) successful surgical treatment. We found reduced sgACC FC with the medial pre-frontal cortex (mPFC) and temporal lobe in CTS compared with HCs. The group-level sgACC-mPFC FC abnormality was driven by men with CTS, while women with CTS did not have sgACC FC abnormalities compared with healthy women. We also found that age and sex influenced sgACC FC in both CTS and HCs, with women showing greater FC with bilateral frontal poles and men showing greater FC with the parietal operculum. After surgery, there was reduced sgACC FC with the orbitofrontal cortex, striatum, and premotor areas and increased FC with the posterior insula and precuneus compared with pre-op scans. Abnormally reduced sgACC-mPFC FC in men but not women with a female-prevalent chronic pain condition suggests pain-related sgACC abnormalities may not be specific to women but rather to individuals who develop chronic pain conditions that are more dominant in the opposite sex. Our data suggest the sgACC plays a role in chronic pain in a sex-specific manner, and its communication with other regions of the dynamic pain connectome undergoes plasticity following pain-relieving treatment, supporting it as a potential therapeutic target for neuromodulation in chronic pain.

Abnormal subgenual anterior cingulate circuitry is unique to women but not men with chronic pain.

The subgenual anterior cingulate cortex (sgACC) plays an important role in pain modulation. We previously demonstrated sex differences in sgACC functional connectivity (FC) in healthy individuals. Given that many chronic pain conditions show sex differences in prevalence, here we tested the hypothesis that people with chronic pain exhibit a sex-specific pattern of abnormal sgACC FC. We acquired resting-state functional magnetic resonance imaging data from 156 (82 W: 74 M) healthy participants and 38 (19 W: 19 M) people with chronic low back pain resulting from ankylosing spondylitis, a condition that predominantly affects men. We confirmed that there are sex differences in sgACC FC in our large cohort of healthy adults; women had greater sgACC FC with the precuneus, a key node of the default mode network, and men had greater sgACC FC with the posterior insula and the operculum. Next, we identified an interaction effect between sex and pain status (healthy/chronic pain) for sgACC FC. Within the chronic pain group, women had greater sgACC FC than men to the default mode and sensorimotor networks. Compared to healthy women, women with chronic pain also had greater sgACC FC to the precuneus and lower FC to the hippocampus and frontal regions. No differences in sgACC FC were seen in men with vs without chronic pain. Our findings indicate that abnormal sgACC circuitry is unique to women but not men with ankylosing spondylitis-related chronic pain. These sex differences may impact the benefit of therapeutics that target the sgACC for chronic pain.

Sex differences in brain modular organization in chronic pain.

ABSTRACT: Men and women can exhibit different pain sensitivities, and many chronic pain conditions are more prevalent in one sex. Although there is evidence of sex differences in the brain, it is not known whether there are sex differences in the organization of large-scale functional brain networks in chronic pain. Here, we used graph theory with modular analysis and machine-learning of resting-state-functional magnetic resonance imaging data from 220 participants: 155 healthy controls and 65 individuals with chronic low back pain due to ankylosing spondylitis, a form of arthritis. We found an extensive overlap in the graph partitions with the major brain intrinsic systems (ie, default mode, central, visual, and sensorimotor modules), but also sex-specific network topological characteristics in healthy people and those with chronic pain. People with chronic pain exhibited higher cross-network connectivity, and sex-specific nodal graph properties changes (ie, hub disruption), some of which were associated with the severity of the chronic pain condition. Females exhibited atypically higher functional segregation in the mid cingulate cortex and subgenual anterior cingulate cortex and lower connectivity in the network with the default mode and frontoparietal modules, whereas males exhibited stronger connectivity with the sensorimotor module. Classification models on nodal graph metrics could classify an individual's sex and whether they have chronic pain with high accuracies (77%-92%). These findings highlight the organizational abnormalities of resting-state-brain networks in people with chronic pain and provide a framework to consider sex-specific pain therapeutics.

Sex-differences in network level brain dynamics associated with pain sensitivity and pain interference.

Neural dynamics can shape human experience, including pain. Pain has been linked to dynamic functional connectivity within and across brain regions of the dynamic pain connectome (consisting of the ascending nociceptive pathway (Asc), descending antinociceptive pathway (Desc), salience network (SN), and the default mode network (DMN)), and also shows sex differences. These linkages are based on fMRI-derived slow hemodynamics. Here, we utilized the fine temporal resolution of magnetoencephalography (MEG) to measure resting state functional coupling (FCp) related to individual pain perception and pain interference in 50 healthy individuals (26 women, 24 men). We found that pain sensitivity and pain interference were linked to within- and cross-network broadband FCp across the Asc and SN. We also identified sex differences in these relationships: (a) women exhibited greater within-network static FCp, whereas men had greater dynamic FCp within the dynamic pain connectome; (b) relationship between pain sensitivity and pain interference with FCp in women was commonly found in theta, whereas in men, these relationships were predominantly in the beta and low gamma bands. These findings indicate that dynamic interactions of brain networks underlying pain involve fast brain communication in men but slower communication in women.

Individual variability and sex differences in conditioned pain modulation and the impact of resilience, and conditioning stimulus pain unpleasantness and salience.

Distinct pain experiences are shaped both by personal attributes and characteristics of noxious stimuli. An Individual's capacity for endogenous pain inhibition (reflected by conditioned pain modulation [CPM]), their resilience, and the pain unpleasantness and salience of painful stimuli can impact their pain perception. Here, we aimed to determine how individual variability in CPM relates to sex and resilience as personal attributes, and pain unpleasantness and salience of the CPM conditioning stimulus (CS). We evaluated CPM in 106 healthy participants (51 female and 55 male) based on the change in test stimulus pain applied concurrently with a painful CS, both delivered by painful heat. The CS reduced test stimulus pain in only half of the participants (CPM subgroup), but did not do so for the other half (no-CPM subgroup), many who exhibited pain facilitation. A regression model explained CPM effects after accounting for sex, resilience, CS pain unpleasantness and salience. In the CPM subgroup regression model, the CPM effect was positively related to CS pain unpleasantness, while the CPM effect was not related to any variable in the no-CPM subgroup model. Correlation analyses revealed that the CPM effect was anticorrelated with resilience in males with no-CPM. The CPM effect was correlated with CS pain unpleasantness in males with CPM and in females with no-CPM. The CPM effect and CS salience were correlated in the whole group more strongly than in the subgroups. These data reveal that the complexity of contributors to CPM variability include both personal attributes and attributes of the CS.

Abnormal alpha band power in the dynamic pain connectome is a marker of chronic pain with a neuropathic component.

We previously identified alpha frequency slowing and beta attenuation in the dynamic pain connectome related to pain severity and interference in patients with multiple sclerosis-related neuropathic pain (NP). Here, we determined whether these abnormalities, are markers of aberrant temporal dynamics in non-neuropathic inflammatory pain (non-NP) or when NP is also suspected. We measured resting-state magnetoencephalography (MEG) spectral density in 45 people (17 females, 28 males) with chronic back pain due to ankylosing spondylitis (AS) and 38 age/sex matched healthy controls. We used painDETECT scores to divide the chronic pain group into those with only non-NP (NNP) and those who likely also had a component of NP in addition to their inflammatory pain. We also assessed pain severity, pain interference, and disease activity with the Brief Pain Inventory and Bath AS Disease Activity Index (BASDAI). We examined spectral power in the dynamic pain connectome, including nodes of the ascending nociceptive pathway (ANP), default mode (DMN), and salience networks (SN). Compared to the healthy controls, the AS patients exhibited increased theta power in the DMN and decreased low-gamma power in the DMN and ANP, but did not exhibit beta-band attenuation or peak-alpha slowing. The NNP patients were not different from HCs. Compared to both healthy controls and NNP, NP patients had increased alpha power in the ANP. Increased alpha power within the ANP was associated with reduced BASDAI in the NNP group, and increased pain in the mixed-NP group within the DMN, SN, and ANP. Thus, high theta and low gamma activity may be markers of chronic pain but high alpha-band activity may relate to particular features of neuropathic chronic pain.

Cross-network coupling of neural oscillations in the dynamic pain connectome reflects chronic neuropathic pain in multiple sclerosis.

Sensory perceptions are coded by complex neural dynamics of regional communication in the brain. Thus, sensory abnormalities such as chronic pain may occur when neural dynamics go awry. Previous studies of cross-network dynamic functional connectivity in chronic pain identified abnormalities but were based on functional MRI which only captures slow temporal features. Here we conducted a magnetoencephalography (MEG) study to investigate fine temporal dynamics of aberrant cross-regional and cross-network communication of the dynamic pain connectome in patients with chronic pain. We also introduced a novel measure, dynamic functional coupling, to quantify the variability of brain communication. The study was performed in 33 people who had chronic pain associated with multiple sclerosis and 30 healthy controls. We found that patients with chronic pain exhibited abnormalities in cross-network functional coupling across multiple frequency bands (theta, alpha, beta, gamma), between the salience network and 3 other networks: the ascending nociceptive pathway, descending anti-nociceptive pathway, and the default mode network. However, these cross-network abnormalities involved different frequency bands in patients with neuropathic versus non-neuropathic chronic pain. Furthermore, cross-network abnormalities were linked to pain severity and pain interference. Our findings implicate broadband cross-network abnormalities as hallmark features of chronic pain in multiple sclerosis.

Functional connectivity across social inclusion and exclusion is related to peer victimization and depressive symptoms in young adults.

BACKGROUND: Peer victimization is associated with increased risk for depression, as well as increased neural response to social exclusion in the anterior cingulate cortex (ACC) and the amygdala. Altered functional connectivity (FxC) of fronto-limbic circuitry is associated with risk for various affective disorders. The present study examined the relationship between fronto-limbic FxC during social exclusion, prior peer victimization experience and depressive symptoms. METHODS: Three mutually exclusive groups were formed: peer victimized (with a history of peer victimization), defenders (history of defending peers), and controls (no prior peer victimization experience) (n = 15/group; Mage = 17.7 years). Functional Magnetic Resonance Imaging data were collected while participants completed the Cyberball paradigm (simulating the experience of social exclusion). FxC between the Medial Prefrontal Cortex (MPFC), ACC, right insula and left amygdala, was compared between groups and examined in relation to depressive symptoms. RESULTS: Prior peer victimization experience was associated with differences in fronto-limbic FxC across social inclusion and exclusion. Defenders displayed distinct shifts in FxC across the transition from being included to excluded. Peer victimized individuals exhibited a unique pattern of amygdala-specific FxC during inclusive interaction with peers, and in the continuous FxC across inclusion and exclusion. FxC of the MPFC-amygdala across inclusion and exclusion moderated the relationship between peer victimization and depressive symptoms. LIMITATIONS: Small sample size and cross-sectional design limit interpretation of the findings. CONCLUSIONS: Peer victimized individuals who exhibit continuous positive FxC of the MPFC-left amygdala across inclusion and exclusion may be at greater risk for depressive symptoms.