The Journal of Headache and Pain

BackgroundThe Delta-opioid receptor (DOR) has gained attention as a promising target for the treatment of migraine and headache disorders. This is largely attributed to its unique pharmacological profile, which suggests that DOR-targeting treatment offers effective therapeutic benefit with a lower risk of medication overuse headache (MOH), reduced abuse liability, and minimal potential for physical dependence. These advantages have driven the development of a novel DOR agonist PN6047 (3-[[4-(dimethylcarbamoyl) phenyl]-[1-(thiazol-5-ylmethyl)-4-piperidylidene] methyl]benzamide), which has completed Phase I clinical trial and showed a favorable safety and tolerability profile. Although PN6047 has shown promising effects in neuropathic pain models, its efficacy in preclinical models of headache-associated pain remains to be evaluated. Here, we investigated the effects of PN6047 in models of migraine-associated pain and aura as well as post-traumatic headache (PTH) and MOH. MethodsC57BL6/J mice were used to examine the effects of PN6047 in the following migraine models: chronic intermittent nitroglycerin (NTG)-induced migraine-associated pain, PTH, KCl-induced cortical spreading depression (CSD), and optogenetic evoked CSD in a freely behaving transgenic mice expressing ChR2-eYFP. In addition, we tested whether chronic PN6047 induced MOH and whether it could prevent the development of MOH induced by sumatriptan. ResultsA single injection of PN6047 blocked chronic cephalic allodynia established by chronic intermittent NTG and PTH. Moreover, chronic PN6047 treatment prevented the development of MOH induced by sumatriptan, without causing MOH itself. In addition, PN6047 significantly reduced the number of CSD events in the KCl-induced CSD model, and delayed CSD onset triggered in freely behaving mice along with subsequent CSD-evoked allodynia. ConclusionPN6047, a novel DOR agonist, strikingly blocks headache-associated mechanism and symptoms in preclinical models of chronic migraine, migraine aura, PTH, and MOH. Importantly, prolonged PN6047 treatment did not induce MOH or analgesic tolerance. Together, these data demonstrate that despite the distinct mechanisms underlying migraine and headache disorder, PN6047 exhibits robust efficacy without inducing MOH, and displays a favorable safety and tolerability profile.

Objective: To describe the self-reported effects of incobotulinumtoxinA treatments on migraine-like headache in participants who experienced traumatic brain injury versus Anomalous Health Incidents. Background: Persistent headache attributed to traumatic injury to the head has been widely recognized as among the most common sequelae of concussion/mild traumatic brain injury. Such persistent headaches often have migraine-like characteristics and are typically treated similarly to idiopathic migraine. Patients who have experienced Anomalous Health Incidents have also commonly reported migraine-like headaches, but to our knowledge, no reports describing treatment for persistent headaches attributed to Anomalous Health Incidents have been published. Methods: We describe the self-reported effects of incobotulinumtoxinA treatments on headache with migraine-like characteristics in 19 participants with traumatic brain injury and 11 who had experienced Anomalous Health Incidents from a single center. Results: Self-reported benefits from incobotulinumtoxinA treatments were generally similar and statistically indistinguishable between groups. The Headache Impact Test-6 score decreased by a mean of 12 points in the traumatic brain injury group and 9.5 points in the Anomalous Health Incidents group from baseline to peak efficacy (p = 0.43), with concomitant reductions in work/school hours lost (62% vs. 50%) and family/leisure hours lost (75% vs. 33%). Furthermore, reductions in headache frequency (67% for the traumatic brain injury group vs. 57% for the Anomalous Health Incidents group), headache severity (36% vs. 23%), headache duration (37% vs. 50%), nausea/vomiting (50% vs. 25%), photophobia (34% vs. 29%), phonophobia (30% vs. 37%), visual aura (50% vs. 29%), vestibular aura (50% vs. 33%), and other aura (21% vs. 25%) from baseline to peak efficacy were similar in both groups. Likewise, time from treatment to response (6.5 vs. 7 days), duration of response (10.2 vs. 9.1 weeks), adverse effects (3/19 for the traumatic brain injury group, 3/11 for the Anomalous Health Incidents group), and improved efficacy of concomitant abortive treatments (30% vs. 50% for pain, 50% vs. 55% for aura) did not differ between groups. Osmophobia and cogniphobia, when present, did not improve on average in either group. Notably, the mean duration of response was less than 12 weeks in both groups, with only 3 participants with traumatic brain injury and 1 participant who had experienced Anomalous Health Incidents reporting benefit beyond the typical 12-week incobotulinumtoxinA treatment interval. Conclusion: Overall, these findings provisionally indicate that at least some patients who have experienced Anomalous Health Incidents may subjectively benefit from incobotulinumtoxinA treatment for persistent migraine-like headaches similarly to patients with traumatic brain injury. Limitations include the open-label, single-center, primarily retrospective design; small sample size; and limited representativeness. Further prospective controlled studies are needed to determine whether these groups truly respond similarly to incobotulinumtoxinA and other standard treatments.

Migraine is a disabling neurological disorder that frequently co-occurs with depression and anxiety. While prior research suggests a genetic association between these conditions, little is known about the genetic relationships underlying specific migraine subtypes. Bivariate genetic correlations between migraine with depression and anxiety were estimated using Linkage-Disequilibrium Score Regression (LDSC), drawing on publicly available large-scale Genome-Wide Association Study data for these traits. In addition, PGS were constructed using the same data and applied to two target cohorts for out-of-sample prediction of migraine and its subtypes. These were a depression-enriched cohort (Australian Genetics of Depression Study; N=12,601), and an unselected population cohort (QSkin Study of Sun and Health; N=16,532). Migraine subtypes were defined according to standard criteria and comprised a broad migraine without aura phenotype and three nested subtypes: migraine with aura, and chronic migraine with and without aura. We found significant genetic correlations between migraine and depression (rg=0.29), as well as between migraine and anxiety (rg=0.32). Across both cohorts, Migraine (OR{approx}1.35) and Depression PGS (OR{approx}1.12) were significantly associated with all measures of migraine and its subtypes. Depression PGS remained significantly associated with all non-chronic migraine subtypes after controlling for migraine and anxiety PGS, suggesting an independent contribution of depression genetic risk on migraine. Anxiety PGS were significantly associated with all non-chronic migraine subtypes (OR{approx}1.09). However, these associations did not persist after adjustment for migraine and/or depression PGS. These results provide insight into the genetic relationships between migraine and its subtypes with depression and anxiety.

Background: Growing evidence implicates the hypothalamus as a key structure in migraine pathophysiology; however, our understanding of its precise role and of the specific nuclei involved remains limited. We combined MRI data from our laboratory with publicly available MRI datasets from OpenNeuro to examine hypothalamic subunit volumes in episodic migraine and assess the specificity of these alterations relative to chronic pain conditions. Methods: Structural MRI combined with an automated atlas-based segmentation algorithm and a discovery-replication design was employed to investigate cross-sectional volumetric differences across 5 bilateral hypothalamic subunits in two independent migraine cohorts: DS1-MIG (DS1-MIG-base, n = 111 patients, n = 35 controls) and DS2-MIG (n = 27 patients, n = 31 controls). The adjusted volumes were compared between groups using MANOVA as an omnibus test, followed by Welch t-tests to test univariate follow-up. Longitudinal volumetric changes were additionally assessed in DS1-MIG participants with available follow-up scans using linear mixed models. To assess the specificity of findings to migraine, the same pipeline was applied to two chronic pain datasets, one including patients with fibromyalgia (DS-FM, n = 33 patients, n = 33 controls) and the other including patients with trigeminal neuralgia (n = 119 patients, n = 55 controls). Results: MANOVA revealed significant multivariate group differences in the discovery and replication migraine cohorts (DS1-MIG-base: = .006; DS2-MIG: = .008). Follow-up univariate analyses identified a consistent enlargement of the left anterior-superior subunit across both cohorts (FDR = .023 in DS1-MIG-base and FDR = .046 in DS2-MIG), representing the only cross-cohort replication finding. Beyond this shared signature, DS2-MIG exhibited additional significant enlargements of the right anterior-inferior and right tubular-inferior subunits. Longitudinal analyses in DS1-MIG showed that hypothalamic subunit volumes remained broadly stable over time within both migraine patients and control participants. No significant volumetric alterations were detected in the fibromyalgia or trigeminal neuralgia cohorts, either in multivariate or univariate analyses, underscoring migraine-specific findings. Conclusions: These findings provide evidence for subunit-specific hypothalamic structural alterations in migraine localized in the left anterior hypothalamic subunit. The stability of these differences over time and their absence in other chronic pain conditions suggest a migraine-specific structural organisation of hypothalamic circuitry.

Background: Chronic pain is associated with impaired muscle health, but whether these changes reflect site-specific factors, broader systemic factors, or both remains unclear. The purpose of this study is to determine whether normative markers of muscle health derived from MRI show site-specific patterns in chronic pain. Methods: UK Biobank participants who underwent whole-body MRI from 2006 to 2010 were included in this retrospective cross-sectional study. The MuscleMap Toolbox quantified volume and intramuscular fat (IMF) in 42 muscles of the abdomen, pelvis, and thigh. Normative models trained on a no pain group generated muscle-specific deviations from normal (i.e., Z-scores) for single- and multi-site chronic and acute pain. Results: Of 17,843 participants, the primary site-specific analysis included 9,704 no pain, 885 single-site chronic back pain (CBP), 438 single-site chronic hip pain (CHP), and 1,315 single-site chronic knee pain (CKP) participants (n=12,342; mean age 63.7{+/-}7.5 years; 52.7% female). Additional analyses included single-site chronic neck/shoulder pain, acute pain, and multi-site chronic pain groups. In CBP, deviations were localized to abdominal muscles, with decreased volume in 6/8 and increased IMF in 6/8. In CHP, deviations were broad, with decreased volume in 3/8 of the abdominal and 14/26 of the thigh muscles, and increased IMF in 6/8 of the abdominal, 5/8 of the pelvic, and 4/26 of the thigh muscles. In CKP, deviations were localized to thigh muscles, with decreased volume in 8/26 and increased IMF in 6/26. Acute pain groups showed no significant differences except for decreased volume in one thigh muscle in acute knee pain. With each additional chronic pain site, volume decreased ({beta}=-.078;IQR:-0.100-0.051), and IMF increased ({beta}=.085;IQR:0.066-0.101). Combined Z-scores classified chronic pain groups better than chance (accuracy: 48.6%;p<.001), but not acute pain groups (accuracy: 39.0%;p=.20). Conclusions: Whole-body MRI combined with AI-driven muscle segmentation and normative modeling revealed site-specific patterns of muscle health in single-site chronic pain.

Myofascial pain syndrome (MPS) is a major cause of chronic neck pain, with tissue ischemia implicated as a contributing factor. This prospective, single-arm interventional study evaluated the analgesic effect of ultrasound-guided fascia hydrorelease (US-FHR) performed around arteries supplying the neck in patients with chronic neck MPS. Thirteen adults (median age 53.0 years; 38.5% female) underwent US-FHR targeting the perivascular fascia of either the transverse cervical or dorsal scapular artery using 2 mL of normal saline. Pain intensity was assessed by visual analog scale (VAS) at rest and during movement; disability by the 5-item Pain Disability Index, Japanese version (PDI-5-J); and arterial blood flow volume before and after the procedure. The primary outcome, pain VAS during movement, decreased from 49.0 mm (interquartile range [IQR], 44.5-64.0) at baseline to 22.0 mm (IQR, 14.5-31.5) at 15 min and 22.0 mm (IQR, 14.0-34.0) at 1 week (Hodges&-Lehmann median difference, 30.5 mm [95% CI, 24.5 to 36.5] and 28.5 mm [95% CI, 18.5 to 37.0]; both P < 0.001). Pain VAS at rest improved from 21.0 mm (IQR, 13.0-43.5) to 8.0 mm at 15 min and 1 week (median difference, 14.5 mm [95% CI, 9.0 to 24.0; P = 0.001] and 13.5 mm [95% CI, 6.0 to 21.0; P = 0.007]). PDI-5-J decreased from 17.0 (IQR, 10.5-23.0) to 13.0 (IQR, 4.0-17.5) at 1 week (median difference, 5 [95% CI, 2 to 8; P = 0.004]). Blood flow volume increased from 11.2 mL/min (IQR, 4.5-14.4) to 17.2 mL/min (IQR, 6.1-23.7) immediately after US-FHR (median difference, +4.1 mL/min [95% CI, +2.5 to +8.9; P = 0.001]), although transient. One patient experienced transient bleeding that was promptly controlled. In this single-arm feasibility study, US-FHR around the target artery was simple and safe to perform and was associated with reduced neck pain. Because the study lacked a control group, these preliminary findings should be regarded as hypothesis-generating and require confirmation in controlled trials; they may also inform the future evaluation of MPS in other anatomical regions. Trial registration: UMIN Clinical Trials Registry, UMIN000053612.

Background: Chronic pain affects approximately 20% of children and youth worldwide and is associated with mental and physical health impacts. Canada-specific data on the prevalence of chronic pain in children and youth are limited, highlighting the need for current high-quality population-based estimates Aims: The aim of this study is to provide national estimates of self-reported chronic pain among Canadian children and youth by pain type (headache stomach ache, backache), sex (female, male), age group (5-11, 12-17 years) and province or territory. Methods: Publicly available data were used from the 2019 Canadian Health Survey on Children and Youth (CHSCY), a population-based survey conducted by Statistics Canada using a nationally representative sample of Canadian children and youth Results: Overall, headaches were the most commonly reported pain type (15.4%), followed by stomach aches (12.5%), and backaches (11.1%). Prevalence was consistently higher among females than males and among youth than children, with youth girls reporting the highest prevalence across all pain types. Prevalence also varied geographically, with some of the highest estimates observed in the Atlantic Provinces. Conclusions: Chronic pain affects substantial proportions of Canadian children and youth with disparities observed by pain type, sex, age, and geography. These findings under score pediatric chronic pain as an important public health issue and highlight the need for equity-oriented approaches that address the needs of populations experiencing the greatest burden.

Background: Fluctuations in pain intensity are intrinsic to non-specific chronic low back pain (nsCLBP). Nevertheless, pain fluctuations have rarely been considered when investigating pathophysiological mechanisms. Therefore, a novel study protocol was developed and implemented to systematically assess the impact of fluctuating pain states on pain-related measures. Methods: The final study cohort consisted of 45 nsCLBP patients and 47 age- and sex-matched healthy controls (HCs). Patients participated in three visits, conducted during different pain states (i.e. clinically relevant pain, low-intensity clinical pain / pain-free, clinically irrelevant pain induced using a Qutenza 8% capsaicin patch). Pain fluctuations were monitored through online assessments every four days and guided the pseudorandomized visit scheduling. HCs participated in a single visit. Each study visit comprised a multimodal battery of pain-related measures. Results: 93.33% of patients completed all three visit types in a pseudorandomized order (chi-squared=1.50, p=0.826). Visit scheduling was possible due to the high self-report adherence (median=93.48%), unrelated to self-report burden (rho=-0.097, p=0.53). Study visits were conducted during different pain states, as indicated by: i) the significantly higher low back pain intensity in the clinically relevant pain visit (mean[SD]: 3.98[0.90]), compared to the low-intensity clinical pain (1.03[0.86]) and clinically irrelevant pain (1.13[0.82]) visits (p-values<0.001), as well as by ii) the successful induction of a moderate-to-high clinically irrelevant pain across assessments. Conclusion: Despite scheduling complexity and pain state transition uncertainty, a pain state-dependent pseudorandomized study design is feasible and could improve the understanding of nsCLBP mechanisms.

The excitability of afferents involved in nociceptive signaling reflects the interaction of several co-expressed membrane receptors. Current studies have shown that Toll-like receptor-4 (TLR-4) signaling can exacerbate excitation evoked by transient receptor potential vanilloid type 1 (TRPV1) activity, and this interaction plays a key role in driving and sustaining facilitated pain states. The mechanism by which this potentiated TRPV1 activity secondary to TLR-4 agonism occurs in sensory neurons remains unknown, although intracellular kinase activity is a strong candidate. To address this hypothesized linkage, neuronal cell cultures prepared from dorsal root ganglia (DRG) of male wildtype (WT) and Tlr4-/- mice were used to evaluate calcium transients of neurons after capsaicin administration in culture, pre-treated for 30 minutes with the TLR-4 agonist, lipopolysaccharide (LPS). TRPV1 protein expression at the neuron surface in cultured DRG cells with or without LPS treatment was quantified by flow cytometry assay. The roles of protein kinase A (PKA) and C were assessed using selective inhibitors (KT5720 for PKA and Chelerythrine chloride for PKC) applied to WT-DRG neurons or administered in vivo by intraplantar or intrathecal injection, prior to LPS and capsaicin administration. Behavioral effects of in vivo TRPV1 activation were assessed through paw flinch responses evoked by intraplantar capsaicin injection and by hind paw tactile thresholds measured by von Frey filaments. LPS incubation in cultured DRG neurons enhances the intensity of calcium influx following TRPV1 activation in WT but not Tlr4-/ cells. The augmented calcium influx evoked by capsaicin was prevented by the inhibition of PKA but not PKC. Similarly, mice treated with LPS in the hind paw displayed greater nociceptive responding after capsaicin and increased tactile allodynia. The facilitated component was prevented by the local pre-treatment with the PKA inhibitor. Correspondingly, lumbar spinal blockade of PKA resulted in temporary reversal of hyperalgesia induced by intrathecal LPS injection in mice. Together, these results demonstrate the relevance of TLR-4 in modulating the excitability of nociceptor signaling by regulating TRPV1, thereby influencing pain transmission through PKA signaling.

Nociceptive pain is the most common pain condition, and moderate-to-severe nociceptive pain substantially impacts daily functioning, constituting a significant public health burden. Despite this, most studies investigating the neural mechanisms underlying somatosensory processing and inhibition have focused on other pain conditions (e.g., neuropathic, nociplastic, or mixed pain). Thus, the extent to which neural aberrancies detected in these other populations extend to or differentiate from nociceptive pain conditions remains largely unknown. In this study, 29 individuals with moderate-to-severe nociceptive pain (MSNP) and 47 pain-free (PF) controls underwent magnetoencephalography (MEG) alongside a paired-pulse somatosensory stimulation paradigm to examine somatosensory cortical processing and functional inhibition. Pain status and intensity were determined using validated pain questionnaires, painDETECT and PROMIS-29, respectively. MEG oscillatory responses were source localized via a beamformer to the primary somatosensory cortex (S1) and time series data were extracted from the peak voxel to quantify the dynamics of somatosensory gating (SG; index of cortical inhibitory processing), oscillatory response power, and spontaneous power. We found that adults with MSNP exhibit aberrant theta SG in contralateral S1 compared to PF controls, reflecting reduced functional inhibition of innocuous stimulus processing in this region. Additionally, individuals with MSNP demonstrated exaggerated gamma responses but blunted alpha responses in contralateral S1 to innocuous stimulation. Finally, individuals with MSNP were characterized by weaker spontaneous alpha in contralateral S1 that scaled with self-reported pain intensity. Together, these findings suggest that experiencing MSNP is associated with disrupted somatosensory and cortical inhibitory processing.

Background: Neuropathic pain (NP) remains a therapeutic challenge, with conventional repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex (M1) yielding a response rate of approximately 40%. Personalised targeting based on dysfunctional neurocircuitry offers a promising strategy to enhance efficacy, yet its application in NP is unexplored. This open-label trial investigated a novel targeting approach guided by the recently described cingulo-opercular and somato-cognitive action (CON-SCAN) network, a circuit integrating cognitive and affective dimensions of pain. Methods: Twenty patients with NP received 10 sessions of M1-rTMS over two weeks, with the stimulation site individually localised based on maximal functional connectivity to a CON template. Results: Increased CON-SCAN connectivity from baseline to post-treatment was associated with reduction in pain interference, anxiety and depression scores. The response rate was 50% post-treatment, which was maintained at the 1-month follow-up. Improvements were also observed in neuropathic pain symptoms, negative affect, and overall health. Conclusions: As the first connectivity-guided rTMS trial for NP, this study provides preliminary evidence that personalised targeting of the CON-SCAN network is feasible and associated with the analgesic effects of M1-rTMS, supporting further investigation in randomised controlled trials. Trial registration: Chinese Clinical Trial Registry, ChiCTR2500104679. Registered 20 June 2025, http://www.chictr.org.cn. Chinese Clinical Trial Registry, ChiCTR2400094568. Registered 24 December 2024, http://www.chictr.org.cn. Keywords: Personalised TMS; Pain; M1; CON; SCAN

Cerebral Palsy (CP) is the most common motor disability in childhood, and the most frequent comorbidity is pain. Rabbit kits subjected to prenatal hypoxia-ischemia (HI) exhibit allodynia and an expansion of nociceptive afferents in the lumbar spinal cord at postnatal day (P5). In this study, we examined how HI alters the development of multiple sensory modalities and its effect on psychosocial measures and C-fiber distribution in the spinal cord. To do this, we performed an HI surgery to occlude blood flow to fetal New Zealand White rabbits for 40 minutes, or a sham surgery. We performed von Frey, Hargreaves, and a cold allodynia test at P1, P5, P11, and P18. Additionally, we performed open field, a two-texture preference test, and immunofluorescence assays at P18. HI kits exhibit altered development and allodynia in von Frey and Hargreaves and minor decreased sensitivity in cold allodynia. HI kits spend less time on the aversive side of the two-texture preference apparatus and more time in the center of an open field but a higher ratio of that time immobile. This is accompanied by changes in the distribution of C-fibers in the dorsal horn of the cervical and lumbar spinal cord. A principal components analysis revealed altered nociception and psychosocial changes are important for differentiating between control and HI kits but not distribution of C-fibers. Overall, HI rabbits kits exhibit altered sensory development, allodynia, anxiety-like behavior, and changes to the distribution of nociceptive afferents in the dorsal horn of the spinal cord.

Chiari I malformation (CM-I) is conventionally defined by cerebellar tonsil position, yet tonsil position is an indirect surrogate for the anatomic obstruction that impairs cerebrospinal fluid (CSF) flow across the craniocervical junction (CCJ). We hypothesized that CCJ crowding, quantified as subarachnoid space narrowing at the foramen magnum and C1, would explain CSF flow impairment more directly than tonsil position. Using non-invasive low b-value diffusion-weighted MRI (low-b dMRI), we quantified effective CSF motility, indexed by mean pseudo diffusivity (M{psi}), across the upper cervical spine, CCJ, and posterior fossa. Voxel-wise CCJ CSF pseudo-diffusion spatial statistics were integrated with CSF Waterways atlas-based regional analyses. We applied this approach in 81 pediatric and adult participants with CM I to determine how CCJ structural features shape regional CSF dynamics and clinical outcomes. Voxel wise analyses revealed that crowding at the foramen magnum was the dominant structural determinant of reduced intracranial CSF effective motility across the CCJ, basilar cisterns, and fourth ventricular outflow pathways (family-wise error corrected p < 0.05). While lower tonsil position and C1 level crowding were also associated with reduced CSF effective motility across the CCJ and fourth ventricular outflow pathways, but their associations within the basilar cisterns were spatially restricted to regions adjacent to the Liliequist membrane. Atlas-based region-of-interest analyses confirmed that greater foramen magnum crowding was associated with lower M{psi} across multiple basilar cisterns, but with higher M{psi} in the ventral spinal CSF compartment. Mediation analyses indicated that CCJ crowding at the foramen magnum and C1 accounted for the majority of the relationship between tonsil position and reduced CSF motility in the basilar cisterns. Multivariate M{psi} profiles across the CSF regions identified data-driven foramen magnum crowding thresholds of 69.5% and 77.5%, stratifying patients into mild, moderate, and severe physiological crowding groups. Exploratory analyses linked lower pre-operative CSF M{psi} to greater pain-related functional impairment, reduced cognitive function, and a higher likelihood of subsequent decompression surgery. Together, these findings demonstrate that CCJ crowding, particularly at the foramen magnum, exerts a quantifiable, region specific impact on CSF effective motility in CM I, and that low b dMRI provides a sensitive, complementary marker of CSF flow impairment. This integrative CCJ structural and CSF flow imaging framework establishes a mechanistic link between CCJ anatomy, CSF dynamics, and symptom burden, offering a scalable tool for phenotyping CM I and informing clinical decision making.

Chronic pain is highly heterogeneous, with individuals varying substantially in symptoms. pain severity, disability, affective distress, cognitive functioning, and trauma-related symptoms. This study examined whether working memory, post-traumatic stress symptoms (PTSS), trauma exposure, and pain modulation explain distinct or shared dimensions of chronic pain variability. Individuals with chronic pain completed clinical, cognitive, trauma-related, and behavioural pain modulation measures, as well as resting-state functional magnetic resonance imaging. Multivariate regressions were used to determine whether working memory, PTSS, trauma exposure, and pain modulation independently predicted chronic pain outcomes. Principal component analysis was used to identify latent dimensions of chronic pain, and mediation analyses tested whether behavioural pain modulation explained relationships between dlPFC to vlPAG resting-state functional connectivity and clinical pain outcomes. PTSS independently predicted affective outcomes, including depression, state anxiety, and trait anxiety, whereas working memory independently predicted pain severity and pain interference. Trauma exposure was associated with greater PTSS and poorer working memory, but did not independently predict core pain outcomes after accounting for these more proximal factors. Principal component analysis identified partially distinct affective and sensory-disability dimensions, while trauma exposure loaded primarily on a separate component characterized by greater PTSS and poorer working memory. Behavioural pain modulation showed broader relationships across symptom dimensions and was associated with dlPFC to vlPAG connectivity. Exploratory mediation analyses demonstrated that pain modulation mediated relationships between dlPFC to vlPAG connectivity and both pain severity and affective distress. These findings support an integrated model where PTSS and working memory are more proximal predictors of affect and severity respectively, and trauma exposure represents a more distal vulnerability factor that predicts both. Thus, pain modulation represents a shared mechanism linking cortico-brainstem connectivity to chronic pain intensity and affect. These variables need further testing for phenotyping people with chronic pain based on their specific clinical needs.

Background: Stroke remains a leading cause of death and disability worldwide. Matrix metalloproteinases (MMPs), particularly MMP-9 and MMP-12, contribute to early blood-brain barrier (BBB) disruption, neuroinflammation, haemorrhagic transformation, and intracerebral haemorrhage (ICH). Intravenous thrombolysis is the only widely used pharmacological therapy for acute ischaemic stroke, but its utility is limited by narrow eligibility criteria and haemorrhagic risk. Inhibition of MMPs in the acute phase may offer a complementary neurovascular protective strategy. Methods: AZD1236, a selective dual MMP-9/-12 inhibitor, was evaluated in transient and permanent middle cerebral artery occlusion models and in a collagenase-induced ICH model in young, aged, obese, and female mice. Drug or vehicle was administered 2-6 hours after stroke onset. Outcomes included infarct or haematoma volume, BBB integrity, neurological function, and pain-related behaviours. Results: AZD1236 given within 2-4 hours after ischaemic or haemorrhagic insult significantly reduced infarct and haematoma volumes, improved short- and long-term neurological scores, and preserved BBB integrity, whereas treatment at 6 hours was largely ineffective. AZD1236 also attenuated the development of post-stroke mechanical allodynia and thermal hyperalgesia. Mechanistically, treatment reduced MMP-9 and MMP-12 activity, increased tight junction protein expression, and dampened inflammatory responses. Conclusions: Dual inhibition of MMP-9/-12 with AZD1236 confers robust neurovascular protection and mitigates post-stroke pain across clinically relevant models of ischaemic and haemorrhagic stroke. These findings provide a strong preclinical rationale for clinical evaluation of dual MMP-9/12 inhibition as an adjunctive neuroprotective strategy for acute stroke.

Chemotherapy-induced peripheral neuropathy (CIPN) is a common and painful side effect of paclitaxel (PTX) treatment. The most common measures of painful neuropathy focus on evoked mechanical hypersensitivity, but clinically relevant ongoing pain remains understudied in preclinical models. Automated machine learning methods for pose estimation and behavioral classification have been proposed to capture non-evoked pain-like behaviors, though these approaches have primarily been applied to unilateral injury models such as spared nerve injury or unilateral inflammatory compound injection. Here, we evaluated the extent to which paclitaxel-induced CIPN affects the posture and spontaneous behavior of freely moving mice using a commercially available automated recording system (BlackBox). We found that paclitaxel-treated mice develop a broad and reproducible behavioral and postural phenotype relative to vehicle-treated controls, characterized by reduced front paw luminance and print size, increased front paw lifting, and altered body measurements consistent with a guarded posture. This phenotype was replicated across two independent cohorts and was detectable at both day 2 and day 6 following the final paclitaxel injection. To identify behavioral features specific to CIPN, we administered gabapentin, an analgesic often used to treat neuropathic pain in patients, to determine whether paclitaxel-induced behavioral changes could be attenuated. Gabapentin reduced several behavioral features in both paclitaxel-treated and vehicle-treated animals, suggesting that its effects on posture and gait are not specific pain in CIPN. These findings demonstrate that automated behavioral recording captures a robust paclitaxel-induced postural phenotype but question whether captured behaviors are indicative of ongoing pain as alleviated by gabapentin.

Cervical spondylotic myelopathy (CSM) is the most common cause of nontraumatic spinal cord dysfunction in adults and is an increasingly important source of disability as populations age. Gabapentin is widely prescribed for neuropathic pain and may therefore be used for symptoms related to known or undiagnosed CSM. However, there is sparse evidence related specifically to gabapentin's use for CSM-related pain. We investigate gabapentin use and trends over time in patients with CSM compared to matched controls. We observed that gabapentin prescriptions were higher in CSM patients compared to controls across two multi-hospital datasets. These results highlight the need for further research into pharmacologic treatment for chronic pain in CSM.

Patients with bowel disease can develop referred somatic pain at a later time with unknown molecular mechanisms. Using experimental mice with colitis induced by intracolonic installation of 2,4,6-Trinitrobenzenesulfonic acid (TNBS), we find an increase in the percentage of hind paw primary afferent neurons expressing Piezo2 or calcitonin gene-related peptide (CGRP), which are attenuated by TrkB.T1 knockout (KO). Concomitantly, TrkB.T1 KO also attenuates colitis-induced hind paw mechanical hypersensitivity and pain. Next, we find that TrkB.T1 is expressed in spinal cord astrocytes and its expression level is increased by colitis. TrkB.T1 KO reduces colitis-induced upregulation of Tumor necrosis factor-alpha (TNF-) mRNA but not upregulation of interleukin (IL)-6 mRNA in the spinal cord. Using calcium (Ca2+) imaging and ex vivo approaches, we find that TNF- elicits Ca2+ transients in capsaicin-sensitive as well as capsaicin-insensitive DRG neurons, and increases Piezo2 and CGRP expression in DRG neurons via distinct signaling pathways. Notably, TNF-or colitis-induced Piezo2 upregulation in L4 DRG neurons is mediated by or associated with the PI3K/Akt pathway that does not participate in CGRP upregulation. In contrast, CGRP upregulation in hind paw primary afferent neurons is associated with an upregulation of phosphorylated cAMP response element binding protein (p-CREB). Finally, we find that TrkB.T1 KO does not change the expression level of transient receptor potential cation channel subfamily V member 1 (TrpV1) in L4 DRG in colitis, explaining the ineffectiveness of TrkB.T1 KO on colitis-induced hind paw thermal hyperalgesia. These results suggest complex and distinct molecular pathways in colitis-induced somatic pain modalities and provide information for specific pain modality management.

In human dorsal root ganglia (DRG), and trigeminal (TG) neurons, the various voltage-gated sodium channel (Nav) isoforms play critical roles in the firing of action potentials, which drive electrical impulses that encode somatosensations including, itch, and pain. The SCN11A gene encodes the tetrodotoxin (TTX)-resistant voltage-gated sodium channel Nav1.9, characterized by unique gating properties. Unlike other isoforms, the Nav1.9 channel activates and inactivates slowly and has a hyperpolarized voltage-dependence of activation and depolarized voltage-dependence of inactivation. This leads to a large window current that has been suggested to function as a regulator of the resting membrane potential of neurons. Mutations in Nav1.9 channels lead to congenital insensitivity to pain (gain-of-function) or familial episodic pain syndrome (loss-of-function) suggesting the channel is a critical mediator of pain. Despite its relevance in pain pathophysiology, most existing data relies on rodent models or heterologous expression systems, leaving the specific pharmacology and biophysical behavior of these channels in human primary neurons largely unknown. In this study, we pharmacologically isolated and characterized native Nav1.9 channel currents in human DRG and TG neurons to compare their biophysical profiles. Our findings reveal significant kinetic and voltage-dependent differences between the two populations. Specifically, Nav1.9 channels in TG neurons exhibit a right-shifted steady-state inactivation curve, a larger window current, and faster activation kinetics compared to those in DRG neurons. In addition, conditions that simulate inflammatory states in-vivo greatly potentiates the Nav1.9 currents consistent with similar observations in rodent models. By detailing these distinct biophysical properties, this research offers crucial insights into Nav1.9 channel function relevant for drug discovery efforts aimed at developing analgesics for both acute and chronic pain.

Background Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a poorly understood, debilitating multisystem condition. Converging evidence implicates impaired cellular bioenergetics, neuroinflammation and defective neurovascular coupling that may manifest as "virtual hypoxia" only under physiological stress. Methods We performed a single-session multimodal 3T MRI study combining brain volumetry, arterial spin labelling (ASL) and multivoxel proton magnetic resonance spectroscopy under normoxia and two controlled hypoxic challenges (oxygen saturation 87 {+/-} 3%) in 26 ME/CFS patients and 27 age- and sex-matched healthy controls. Results After intracranial-volume normalization, patients showed a reduced brainstem volume (1.46 0.14 vs. 1.55 {+/-} 0.18 % of eTIV; p = 0.013, FDR-p = 0.039), whereas deep grey matter and whole-brain parenchymal fraction did not differ between groups. Whole-brain cerebral blood flow (CBF) rose under hypoxia in both groups (controls +4.8 {+/-} 13.0%, patients +3.7 {+/-} 11.7%), with greater initial inter-individual variability in patients (patient-to-control variance ratio up to 6.94; FDR-p = 0.001). Thalamic lactate-to-creatine (Lac/tCr) ratios increased with hypoxia in controls (FDR-p = 0.028) but were already elevated at normoxia in patients (0.171 vs. 0.135; FDR-p = 0.021) and did not rise further (FDR-p = 0.38). In exploratory analyses, patients showed exaggerated inverse coupling between thalamic total N-acetylaspartate (tNAA/tCr) and white-matter CBF. Conclusions These findings provide in vivo evidence of impaired neuro-metabolic and vascular adaptive capacity in ME/CFS, supporting the virtual hypoxia hypothesis and highlighting candidate imaging markers for stratification that warrant validation.