Neuro-immune signatures in chronic low back pain subtypes

Systemic low-grade C-reactive protein is associated with proximal symptom spread in carpal tunnel syndrome

Introduction

Neuropathic pain is a highly prevalent condition associated with persistent disability. Some patients with neuropathic pain experience symptom spread outside neuroanatomical boundaries; these patients report more severe sensory symptoms and greater disability. However, the mechanisms behind such symptom spread are not fully understood.

Objective

We used pre-surgical carpal tunnel syndrome (CTS) as a human model system of neuropathic pain to identify differences in the concentration of serologic inflammatory mediators between patients with CTS with territorial symptoms and those with proximal symptom spread to either the elbow or shoulder/neck.

Methods

We performed a post-hoc analysis, comparing levels of serologic inflammatory mediators in a discovery cohort among 3 symptoms spread profiles (n = 55; n = 25 no spread, n = 21 spread to elbow, n = 9 spread to shoulder/neck). We then de-novo analysed the significantly dysregulated mediators in an independent validation cohort (n = 72; n = 34 no spread, n = 16 spread to elbow, n = 22 spread to shoulder/neck).

Results

The discovery cohort revealed higher serum concentrations of C-reactive protein (CRP) and interleukin-6 in patients with any symptom spread proximal to the wrist; interferon-γ was higher in patients with symptom spread to the elbow compared with those without proximal spread. The validation study replicated the association of higher CRP concentrations in patients with proximal spread to the elbow (no spread: median [interquartile range] 2.5 [5.4]; spread to elbow 6.2 [4.6]; spread to shoulder/neck 2.6 [3.7], P = 0.006). No other markers replicated in the validation cohort.

Conclusions

Our findings suggest that proximal symptom spread in the context of neuropathic symptoms is associated with low-grade inflammation.

Recent developments and challenges in positron emission tomography imaging of gliosis in chronic neuropathic pain

ABSTRACT

Understanding the mechanisms that underpin the transition from acute to chronic pain is critical for the development of more effective and targeted treatments. There is growing interest in the contribution of glial cells to this process, with cross-sectional preclinical studies demonstrating specific changes in these cell types capturing targeted timepoints from the acute phase and the chronic phase. In vivo longitudinal assessment of the development and evolution of these changes in experimental animals and humans has presented a significant challenge. Recent technological advances in preclinical and clinical positron emission tomography, including the development of specific radiotracers for gliosis, offer great promise for the field. These advances now permit tracking of glial changes over time and provide the ability to relate these changes to pain-relevant symptomology, comorbid psychiatric conditions, and treatment outcomes at both a group and an individual level. In this article, we summarize evidence for gliosis in the transition from acute to chronic pain and provide an overview of the specific radiotracers available to measure this process, highlighting their potential, particularly when combined with ex vivo/in vitro techniques, to understand the pathophysiology of chronic neuropathic pain. These complementary investigations can be used to bridge the existing gap in the field concerning the contribution of gliosis to neuropathic pain and identify potential targets for interventions.

[ 11 C]-PBR28 positron emission tomography signal as an imaging marker of joint inflammation in knee osteoarthritis

ABSTRACT

Although inflammation is known to play a role in knee osteoarthritis (KOA), inflammation-specific imaging is not routinely performed. In this article, we evaluate the role of joint inflammation, measured using [ 11 C]-PBR28, a radioligand for the inflammatory marker 18-kDa translocator protein (TSPO), in KOA. Twenty-one KOA patients and 11 healthy controls (HC) underwent positron emission tomography/magnetic resonance imaging (PET/MRI) knee imaging with the TSPO ligand [ 11 C]-PBR28. Standardized uptake values were extracted from regions-of-interest (ROIs) semiautomatically segmented from MRI data, and compared across groups (HC, KOA) and subgroups (unilateral/bilateral KOA symptoms), across knees (most vs least painful), and against clinical variables (eg, pain and Kellgren-Lawrence [KL] grades). Overall, KOA patients demonstrated elevated [ 11 C]-PBR28 binding across all knee ROIs, compared with HC (all P 's < 0.005). Specifically, PET signal was significantly elevated in both knees in patients with bilateral KOA symptoms (both P 's < 0.01), and in the symptomatic knee ( P < 0.05), but not the asymptomatic knee ( P = 0.95) of patients with unilateral KOA symptoms. Positron emission tomography signal was higher in the most vs least painful knee ( P < 0.001), and the difference in pain ratings across knees was proportional to the difference in PET signal ( r = 0.74, P < 0.001). Kellgren-Lawrence grades neither correlated with PET signal (left knee r = 0.32, P = 0.19; right knee r = 0.18, P = 0.45) nor pain ( r = 0.39, P = 0.07). The current results support further exploration of [ 11 C]-PBR28 PET signal as an imaging marker candidate for KOA and a link between joint inflammation and osteoarthritis-related pain severity.

Unveiling the link between chronic pain and misuse of opioids and cannabis

Over 50 million Americans endure chronic pain where many do not receive adequate treatment and self-medicate to manage their pain by taking substances like opioids and cannabis. Research has shown high comorbidity between chronic pain and substance use disorders (SUD) and these disorders share many common neurobiological underpinnings, including hypodopaminergic transmission. Drugs commonly used for self-medication such as opioids and cannabis relieve emotional, bothersome components of pain as well as negative emotional affect that perpetuates misuse and increases the risk of progressing towards drug abuse. However, the causal effect between chronic pain and the development of SUDs has not been clearly established. In this review, we discuss evidence that affirms the proposition that chronic pain is a risk factor for the development of opioid and cannabis use disorders by outlining the clinical evidence and detailing neurobiological mechanisms that link pain and drug misuse. Central to the link between chronic pain and opioid and cannabis misuse is hypodopaminergic transmission and the modulation of dopamine signaling in the mesolimbic pathway by opioids and cannabis. Moreover, we discuss the role of kappa opioid receptor activation and neuroinflammation in the context of dopamine transmission, their contribution to opioid and cannabis withdrawal, along with potential new treatments.

Gray Matter Abnormalities in Patients with Chronic Low Back Pain: A Systematic Review and Meta-Analysis of Voxel-Based Morphometry Studies

BACKGROUND

Numerous studies utilizing voxel-based morphometry (VBM) have documented gray matter (GM) alterations in patients with chronic low back pain (CLBP) compared to healthy controls. However, the inconsistency in GM abnormalities observed across different studies has hindered their potential application as objective neuroimaging biomarkers or therapeutic targets. To address this issue, we conducted a comprehensive meta-analysis of VBM studies to identify robust GM differences between CLBP patients and healthy controls.

METHODS

The databases including PubMed, Embase, and Web of Science were systematically searched from January 2000 to September 2022 to identify eligible neuroimaging studies. In this coordinate-based meta-analysis of VBM studies, the Seed-based d Mapping with Permutation of Subject Images method was used to quantitatively assess regional differences in GM between CLBP patients and healthy controls.

RESULTS

Thirteen VBM studies, involving a total of 574 CLBP patients and 1239 healthy controls, were included in the meta-analysis. The findings revealed that CLBP patients exhibited increased GM in the left striatum and left postcentral gyrus and decreased GM in the left superior frontal gyrus, left cerebellum, right striatum, left insula, and right middle occipital gyrus compared to healthy controls. The jackknife sensitivity analysis confirmed the robustness of these neuroimaging findings.

CONCLUSIONS

This study provides new insights into potential treatment strategies for CLBP and identifies neuroimaging biomarkers for pain chronification. These findings highlight the importance of considering regional GM abnormalities in the development of clinical interventions for CLBP.

The Emotion Regulation of Acupuncture in Chronic Low Back Pain: A Clinical Neuroimaging Protocol

Introduction

Acupuncture is effective for patients with chronic low back pain (CLBP), which can relieve pain intensity and regulate negative emotional states such as pain-related anxiety and depression. Previous studies mainly discuss the analgesic mechanism of acupuncture treatment of CLBP, but there are multiple dimensions to pain, including sensation, emotion and cognition. Therefore, this study aims to investigate the central mechanism of acupuncture for CLBP from the perspective of emotional regulation by functional magnetic resonance imaging (fMRI).

Methods and Analysis

A total of 72 patients with CLBP will be recruited in the study and randomly assigned to the verum acupuncture group or the sham acupuncture group. The trail will last for 18 weeks including a 2-week baseline, a 4-week treatment and a 12-week for follow-up period. The primary outcomes are the visual analog scale (VAS) and the Japanese Orthopaedic Association Scores (JOA) score. The secondary outcomes are the 12-item short form health survey (SF-12), the state trait anxiety inventory (STAI), the self-rating anxiety scale (SAS) and self-rating depression scale (SDS). The VAS, JOA, STAI SAS and SDS will be collected at baseline, week 2, week 4, and after follow-up. The SF-12 will be evaluated at baseline, week 2 and week 4. Functional magnetic resonance imaging (MRI) data will be collected at baseline and the end of treatment. Emotion-related brain regions will be chosen as regions of interest (ROIs). The gray matter volume (GMV), amplitude of low-frequency fluctuation (ALFF), regional homogeneity (ReHo), functional connectivity (FC), and large-scale functional brain network based on these ROIs will be analyzed within and between the two groups.

Discussion

This study will verify the emotional regulation of acupuncture and explore the mechanism of acupuncture for emotion regulation in patients with CLBP.

Trial Registration Number

https://www.chictr.org.cn/showproj.html?proj=195486, identifier: ChiCTR2300070557.

Is low back pain a risk/prognostic factor for the development and/or progression of temporomandibular disorders? A systematic review with meta-analysis

OBJECTIVES

To evaluate the association between low back pain (LBP) and painful temporomandibular disorders (TMDs).

METHODS

Systematic review of observational studies. Searches were conducted using OVID MEDLINE, CINHAL, Web of Science and PUBMED databases up to 21 October 2022. Qualitative and quantitative analyses were performed. Risk of bias (RoB) was assessed using the Quality in Prognosis Studies tool (QUIPS).

RESULTS

Eight studies were included in the present review with meta-analysis. The first onset of TMDs was more likely in patients with previous chronic LBP (hazard ratio (HR) 1.53 [95% confidence interval (CI): 1.28; 1.83, p < .00001]). In addition, patients with chronic LBP had 3.25 times the odds (OR) [95% CI: 1.94; 5.43, p < .00001] of having chronic TMDs than those who did not have chronic LBP. In addition, the higher the exposure to chronic LBP, the higher the risk of developing a first onset of TMDs.

CONCLUSIONS

Chronic LBP can be considered a risk/contributing factor for painful TMDs. Although there is a high certainty in the evidence linking chronic LBP with the risk of a first onset of TMDs, there are insufficient studies to draw definitive conclusions. Furthermore, while an association between chronic LBP and chronic TMDs and a dose-effect was observed between these two conditions, a limited number of studies and evidence exist to support these findings. Future studies are needed to increase the body of evidence.

Investigating the brain functional abnormalities underlying pain hypervigilance in chronic neck and shoulder pain: a resting-state fMRI study

PURPOSE

To investigate pain hypervigilance in individuals suffering from chronic neck and shoulder pain (CNSP) and its underlying brain mechanism.

METHODS

The evaluation of pain vigilance was conducted through the utilization of pain vigilance and awareness questionnaires. Voxel-wise regional homogeneity (ReHo) from 60 CNSP patients and 60 healthy controls (HCs) using resting-state fMRI data. Voxel-wise two-sample T-test was conducted to reveal the ReHo variations between CNSP and HC. Correlation analyses were utilized to reveal the connection between brain abnormalities and medical measurements. Furthermore, a mediation analysis was conducted to elucidate the pathway-linking changes in brain function with medical measurements.

RESULTS

Our present study revealed three main findings. Firstly, patients with CSNP demonstrated a heightened vigilance of pain in comparison to healthy adults, a common occurrence among individuals with chronic pain conditions. Secondly, we observed brain abnormalities in various brain regions in CSNP patients, and these alterations were associated with the extent of pain vigilance. Lastly, the pain hypervigilance impact on the severity of pain was found to be controlled by regional neural activity in the anterior cingulate cortex (ACC) in subjects with CSNP.

CONCLUSION

Our findings suggested that long-term repetitive nociceptive input caused by chronic pain further aggravates the pain intensity by impairing the vigilance-related pain processing within the anterior cingulate cortex in CNSP patients.

Neuroimmune activation and increased brain aging in chronic pain patients after the COVID-19 pandemic onset

The COVID-19 pandemic has exerted a global impact on both physical and mental health, and clinical populations have been disproportionally affected. To date, however, the mechanisms underlying the deleterious effects of the pandemic on pre-existing clinical conditions remain unclear. Here we investigated whether the onset of the pandemic was associated with an increase in brain/blood levels of inflammatory markers and MRI-estimated brain age in patients with chronic low back pain (cLBP), irrespective of their infection history. A retrospective cohort study was conducted on 56 adult participants with cLBP (28 'Pre-Pandemic', 28 'Pandemic') using integrated Positron Emission Tomography/ Magnetic Resonance Imaging (PET/MRI) and the radioligand [11C]PBR28, which binds to the neuroinflammatory marker 18 kDa Translocator Protein (TSPO). Image data were collected between November 2017 and January 2020 ('Pre-Pandemic' cLBP) or between August 2020 and May 2022 ('Pandemic' cLBP). Compared to the Pre-Pandemic group, the Pandemic patients demonstrated widespread and statistically significant elevations in brain TSPO levels (P =.05, cluster corrected). PET signal elevations in the Pandemic group were also observed when 1) excluding 3 Pandemic subjects with a known history of COVID infection, or 2) using secondary outcome measures (volume of distribution -VT- and VT ratio - DVR) in a smaller subset of participants. Pandemic subjects also exhibited elevated serum levels of inflammatory markers (IL-16; P <.05) and estimated BA (P <.0001), which were positively correlated with [11C]PBR28 SUVR (r's ≥ 0.35; P's < 0.05). The pain interference scores, which were elevated in the Pandemic group (P <.05), were negatively correlated with [11C]PBR28 SUVR in the amygdala (r = -0.46; P<.05). This work suggests that the pandemic outbreak may have been accompanied by neuroinflammation and increased brain age in cLBP patients, as measured by multimodal imaging and serum testing. This study underscores the broad impact of the pandemic on human health, which extends beyond the morbidity solely mediated by the virus itself.

Thalamic neurometabolite alterations in chronic low back pain: a common phenomenon across musculoskeletal pain conditions?

ABSTRACT

Recently, we showed that patients with knee osteoarthritis (KOA) demonstrate alterations in the thalamic concentrations of several metabolites compared with healthy controls: higher myo-inositol (mIns), lower N-acetylaspartate (NAA), and lower choline (Cho). Here, we evaluated whether these metabolite alterations are specific to KOA or could also be observed in patients with a different musculoskeletal condition, such as chronic low back pain (cLBP). Thirty-six patients with cLBP and 20 healthy controls were scanned using 1 H-magnetic resonance spectroscopy (MRS) and a PRESS (Point RESolved Spectroscopy) sequence with voxel placement in the left thalamus. Compared with healthy controls, patients with cLBP demonstrated lower absolute concentrations of NAA ( P = 0.0005) and Cho ( P < 0.05) and higher absolute concentrations of mIns ( P = 0.01) when controlling for age, as predicted by our previous work in KOA. In contrast to our KOA study, mIns levels in this population did not significantly correlate with pain measures (eg, pain severity or duration). However, exploratory analyses revealed that NAA levels in patients were negatively correlated with the severity of sleep disturbance ( P < 0.01), which was higher in patients compared with healthy controls ( P < 0.001). Additionally, also in patients, both Cho and mIns levels were positively correlated with age ( P < 0.01 and P < 0.05, respectively). Altogether, these results suggest that thalamic metabolite changes may be common across etiologically different musculoskeletal chronic pain conditions, including cLBP and KOA, and may relate to symptoms often comorbid with chronic pain, such as sleep disturbance. The functional and clinical significance of these brain changes remains to be fully understood.

Up-and-coming Radiotracers for Imaging Pain Generators

Chronic musculoskeletal pain is among the most highly prevalent diseases worldwide. Managing patients with chronic pain remains very challenging because current imaging techniques focus on morphological causes of pain that can be inaccurate and misleading. Moving away from anatomical constructs of disease, molecular imaging has emerged as a method to identify diseases according to their molecular, physiologic, or cellular signatures that can be applied to the variety of biomolecular changes that occur in nociception and pain processing and therefore have tremendous potential for precisely pinpointing the source of a patient's pain. Several molecular imaging approaches to image the painful process are now available, including imaging of voltage-gated sodium channels, calcium channels, hypermetabolic processes, the substance P receptor, the sigma-1 receptor, and imaging of macrophage trafficking. This article provides an overview of promising molecular imaging approaches for the imaging of musculoskeletal pain with a focus on preclinical methods.

Neuroinflammation in post-acute sequelae of COVID-19 (PASC) as assessed by [11C]PBR28 PET correlates with vascular disease measures

The COVID-19 pandemic caused by SARS-CoV-2 has triggered a consequential public health crisis of post-acute sequelae of COVID-19 (PASC), sometimes referred to as long COVID. The mechanisms of the heterogeneous persistent symptoms and signs that comprise PASC are under investigation, and several studies have pointed to the central nervous and vascular systems as being potential sites of dysfunction. In the current study, we recruited individuals with PASC with diverse symptoms, and examined the relationship between neuroinflammation and circulating markers of vascular dysfunction. We used [11C]PBR28 PET neuroimaging, a marker of neuroinflammation, to compare 12 PASC individuals versus 43 normative healthy controls. We found significantly increased neuroinflammation in PASC versus controls across a wide swath of brain regions including midcingulate and anterior cingulate cortex, corpus callosum, thalamus, basal ganglia, and at the boundaries of ventricles. We also collected and analyzed peripheral blood plasma from the PASC individuals and found significant positive correlations between neuroinflammation and several circulating analytes related to vascular dysfunction. These results suggest that an interaction between neuroinflammation and vascular health may contribute to common symptoms of PASC.

What Do We Know about Nociplastic Pain?

Nociplastic pain is a recently distinguished type of pain, distinct from neuropathic and nociceptive pain, and is well described in the literature. It is often mistaken for central sensitization. Pathophysiology has not been clearly established with regard to alteration of the concentration of spinal fluid elements, the structure of the white and gray matter of the brain, and psychological aspects. Many different diagnostic tools, i.e., the painDETECT and Douleur Neuropathique 4 questionnaires, have been developed to diagnose neuropathic pain, but they can also be applied for nociplastic pain; however, more standardized instruments are still needed in order to assess its occurrence and clinical presentation. Numerous studies have shown that nociplastic pain is present in many different diseases such as fibromyalgia, complex regional pain syndrome type 1, and irritable bowel syndrome. Current pharmacological and nonpharmacological treatments for nociceptive and neuropathic pain are not entirely suitable for treating nociplastic pain. There is an ongoing effort to establish the most efficient way to manage it. The significance of this field has led to several clinical trials being carried out in a short time. The aim of this narrative review was to discuss the currently available evidence on pathophysiology, associated diseases, treatment possibilities, and clinical trials. It is important that physicians widely discuss and acknowledge this relatively new concept in order to provide optimized pain control for patients.

Do Chronic Low Back Pain and Chronic Widespread Pain differ in their association with Depression Symptoms in the 1958 British Cohort?

OBJECTIVE

Depression frequently coexists with chronic pain. Contemporary models suggest that these conditions share pathobiological mechanisms, prompting a need to investigate their temporal association. This investigation aimed to explore two distinctly different chronic pain conditions, and their cross-sectional and prospective associations with depression.

METHODS

Self-reported information was available on chronic widespread pain (CWP), chronic low back pain (CLBP) (45 years), and depression symptoms (45 and 50 years) from up to 9,377 participants in the 1958 British cohort. Depression symptom outcomes were derived by "Clinical Interview Schedule-Revised" (45 years) and "Short Form-36" (50 years). Relationships between both chronic pain conditions and depression symptoms were investigated by fitting four separate logistic regression models, each with varying levels of covariate adjustment, including depression at baseline.

RESULTS

CWP was associated with depression symptoms cross-sectionally (odds ratio [OR] = 2.04, 95% confidence interval [CI] 1.65, 2.52; P < 0.001, n = 7,629), and prospectively when fully adjusted for baseline, sociodemographic, lifestyle, and health covariates (OR = 1.45, 95% CI 1.17, 1.80; P = < 0.001, n = 6,275). CLBP was associated with depression symptoms prospectively (full model: OR = 1.28, 95% CI 1.01, 1.61; P = 0.04, n = 6,288). In fully adjusted models the prospective association of CWP with depression symptoms was more heavily influenced by our covariates than CLBP with depression symptoms.

CONCLUSION

Pain may be a stressor from which depression can arise. Development of depression may be differentially dependant upon the type of pain experienced. Screening for depression symptoms among individuals with both chronic pain conditions is indicated and should be repeated over time.

Microbiological and Physiological Effects of Pain

Pain is an important innate defense mechanism that can dramatically alter a person's quality of life. Understanding the microbiological and physiological effects of pain may be important in the pursuit of novel pain interventions. The three descriptors of pain recognized by the International Association for the Study of Pain are nociceptive, neuropathic, and nociplastic pain. Our review examined the current understanding of all three pain types, focusing on the key molecules involved in the manifestation of each type as well as physiological effects. Additionally, we compared the differences in painful and painless neuropathies and discussed the neuroimmune interaction involved in the manifestation of pain.

Assessing the potential anti-neuroinflammatory effect of minocycline in chronic low back pain: Protocol for a randomized, double-blind, placebo-controlled trial

INTRODUCTION

Both preclinical studies, and more recent clinical imaging studies, suggest that glia-mediated neuroinflammation may be implicated in chronic pain, and therefore might be a potential treatment target. However, it is currently unknown whether modulating neuroinflammation effectively alleviates pain in humans. This trial tests the hypothesis that minocycline, an FDA-approved tetracycline antibiotic and effective glial cell inhibitor in animals, reduces neuroinflammation and may reduce pain symptoms in humans with chronic low back pain.

METHODS AND ANALYSIS

This study is a randomized, double-blind, placebo-controlled clinical trial. Subjects, aged 18-75, with a confirmed diagnosis of chronic (≥ six months) low back pain (cLBP) and a self-reported pain rating of at least four out of ten (for at least half of the days during an average week) are enrolled via written, informed consent. Eligible subjects are randomized to receive a 14-day course of either active drug (minocycline) or placebo. Before and after treatment, subjects are scanned with integrated Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) using [¹¹C]PBR28, a second-generation radiotracer for the 18 kDa translocator protein (TSPO), which is highly expressed in glial cells and thus a putative marker of neuroinflammation. Pain levels are evaluated via daily surveys, collected seven days prior to the start of medication, and throughout the 14 days of treatment. General linear models will be used to assess pain levels and determine the treatment effect on brain (and spinal cord) TSPO signal.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov (NCT03106740).

Association between nociplastic pain and premature endocrine therapy discontinuation in breast cancer patients

PURPOSE

At least 5 years of adjuvant endocrine therapy (ET) is recommended for patients with hormone receptor-positive invasive breast cancer to reduce cancer recurrence risk. Up to half of patients prematurely discontinue ET, often due to musculoskeletal pain. Nociplastic pain is abnormal central nervous system pain processing without evidence of tissue or neuronal damage. This study aimed to evaluate the relationship between baseline nociplastic pain and ET discontinuation.

METHODS

This was a retrospective, single center, cohort study. Included patients were female, had stage 0-III invasive breast cancer, did not receive neoadjuvant therapy, and completed quality of life questionnaires prior to breast surgery, including Fibromyalgia Survey for nociplastic pain. Clinical data including duration of ET were abstracted from the medical record. Patient characteristics were analyzed with t-tests and Chi-squared tests, as appropriate. Univariate and multivariable regressions were performed with Cox proportional hazard models.

RESULTS

Six hundred eighty-one patients diagnosed between 2012 and 2019 met inclusion criteria; 480 initiated ET and were included in the analysis. Of these 480 patients, 203 (42.3%) prematurely discontinued initial ET therapy. On univariate analysis, tamoxifen use (hazard ratio [HR] 0.70, p = 0.021) and premenopausal status (HR 0.73, p = 0.04) were inversely associated with ET discontinuation, while Fibromyalgia Score was positively associated (HR 1.04, p = 0.043). On multivariable analysis, baseline Fibromyalgia Score remained associated with ET discontinuation.

CONCLUSION

Nociplastic pain present prior to surgery was associated with premature ET discontinuation. Fibromyalgia Score screening may be useful for evaluating ET discontinuation risk. Treatments targeting nociplastic pain may be more effective for treating ET-emergent pain.

Energy metabolism disturbance in migraine: From a mitochondrial point of view

Migraine is a serious central nervous system disease with a high incidence rate. Its pathogenesis is very complex, which brings great difficulties for clinical treatment. Recently, many studies have revealed that mitochondrial dysfunction may play a key role in migraine, which affects the hyperosmotic of Ca²⁺, the excessive production of free radicals, the decrease of mitochondrial membrane potential, the imbalance of mPTP opening and closing, and the decrease of oxidative phosphorylation level, which leads to neuronal energy exhaustion and apoptosis, and finally lessens the pain threshold and migraine attack. This article mainly introduces cortical spreading depression, a pathogenesis of migraine, and then damages the related function of mitochondria, which leads to migraine. Oxidative phosphorylation and the tricarboxylic acid cycle are the main ways to provide energy for the body. 95 percent of the energy needed for cell survival is provided by the mitochondrial respiratory chain. At the same time, hypoxia can lead to cell death and migraine. The pathological opening of the mitochondrial permeability transition pore can promote the interaction between pro-apoptotic protein and mitochondrial, destroy the structure of mPTP, and further lead to cell death. The increase of mPTP permeability can promote the accumulation of reactive oxygen species, which leads to a series of changes in the expression of proteins related to energy metabolism. Both Nitric oxide and Calcitonin gene-related peptide are closely related to the attack of migraine. Recent studies have shown that changes in their contents can also affect the energy metabolism of the body, so this paper reviews the above mechanisms and discusses the mechanism of brain energy metabolism of migraine, to provide new strategies for the prevention and treatment of migraine and promote the development of individualized and accurate treatment of migraine.

Hybrid PET/MRI in Infection and Inflammation: An Update About the Latest Available Literature Evidence

PET/MRI has been reported to be promising in the diagnosis and evaluation of infection and inflammation including brain disorders, bone and soft tissue infections and inflammations, cardiovascular, abdominal, and systemic diseases. However, evidence came out manly from anecdotal cases or small cohorts. The present review aimed to update the latest available evidence about the role of PET/MRI in infection and inflammation. The search (January, 1 2018-July, 8 2022) on PubMed produced 504 results. Sixty-five articles were selected and included in the qualitative synthesis. The number of publications on PET/MRI in the 3 years 2018-2020 was comparable, while it increased in 2021 and 2022 (from 11 to 17 and 15, respectively). [¹⁸F]FDG and ⁶⁸Ga-DOTA-FAPI-04 were the most frequently used (42/65) and innovative radiopharmaceuticals, respectively. [¹⁸F]fluoride (9/65), translocator protein (TSPO)-targeted PET agents (6/65), CXCR4 receptor targeting tracer and β-amyloid plaques binding radiopharmaceuticals (2/65 and 2/65, respectively) were also used. Most PET/MRI studies in the period 2018-2022 focused on inflammation (55/65), and cardiovascular diseases represented the most frequent field of interest (30/65), also when considering each year singularly. An increasing trend in bone and joint publications was observed in the considered period (12/65). Other topics included neurology (11/65), inflammatory bowel disease (8/65), and other (4/65). PET/MRI technology demonstrated to be useful in infection and inflammation, being superior to each single modality and/or facilitating diagnosis in a number of conditions (eg, cardiac sarcoidosis, myocarditis, endocarditis), and/or allowing to provide insightful information about disease biology and apply innovative radiopharmaceuticals (eg, neurology, atherosclerosis). Publications focused on PET/MRI in large vessel vasculitis and aortic diseases include both diagnostic and discovery objectives. The current review corroborates the potential of PET/MRI - combining in a single examination the high soft tissue contrast, high resolution, and functional information of MRI, with molecular data provided by PET technology - to positively impact on the management of infectious diseases and inflammatory conditions.

Non-invasive brain neuromodulation techniques for chronic low back pain

Structural and functional changes of the brain occur in many chronic pain conditions, including chronic low back pain (CLBP), and these brain abnormalities can be reversed by effective treatment. Research on the clinical applications of non-invasive brain neuromodulation (NIBS) techniques for chronic pain is increasing. Unfortunately, little is known about the effectiveness of NIBS on CLBP, which limits its application in clinical pain management. Therefore, we summarized the effectiveness and limitations of NIBS techniques on CLBP management and described the effects and mechanisms of NIBS approaches on CLBP in this review. Overall, NIBS may be effective for the treatment of CLBP. And the analgesic mechanisms of NIBS for CLBP may involve the regulation of pain signal pathway, synaptic plasticity, neuroprotective effect, neuroinflammation modulation, and variations in cerebral blood flow and metabolism. Current NIBS studies for CLBP have limitations, such as small sample size, relative low quality of evidence, and lack of mechanistic studies. Further studies on the effect of NIBS are needed, especially randomized controlled trials with high quality and large sample size.

Microstructural Evidence of Neuroinflammation for Psychological Symptoms and Pain in Patients with Fibromyalgia

Objective

In patients with fibromyalgia (FM), the brain shows altered structure and functional connectivity, but the mechanisms underlying these changes remain unclear. This study investigated the associated changes in brain microstructures and neuroinflammation of patients with FM.

Methods

We recruited 14 patients with FM and 14 healthy controls. Visual analog scale (VAS), Beck's Anxiety Inventory (BAI), and Beck's Depression Inventory-II (BDI-II) were used for assessing their pain, anxiety, and depression levels, respectively. Diffusion kurtosis imaging (DKI) was used to visualize microstructural alterations associated with neuroinflammation in specific brain regions. The biomarkers for the neuron damage, including serum tau and amyloid β protein fragment 1-42 (Aβ1-42) levels, were assessed. Spearman correlation of DKI parameters with VAS, BAI, and BDI-II scores and tau and Aβ1-42 levels were assessed.

Results

The patients with FM had significantly higher levels of Aβ1-42 levels compared with the controls. Compared with the controls, the patients showed significantly lower DKI parameters in the bilateral dorsal–lateral prefrontal cortex and orbital–frontal cortex. The patients showed a significant correlation between the axial kurtosis values of the amygdala and VAS scores (left: rho = -0.603, p = 0.022; right: rho = -7.04, p = 0.005).

Conclusion

To the best of our knowledge, this is the first study to use DKI to examine the brain of FM patients. We noted significant DKI changes at specific areas associated with neuroinflammation in patients with FM. Our results provide valuable information on brain neuroinflammation and pathophysiological changes in patients with FM.

Characterisation of motor cortex organisation in patients with different presentations of persistent low back pain

Persistence of low back pain is thought to be associated with different underlying pain mechanisms, including ongoing nociceptive input and central sensitisation. We hypothesised that primary motor cortex (M1) representations of back muscles (a measure of motor system adaptation) would differ between pain mechanisms, with more consistent observations in individuals presumed to have an ongoing contribution of nociceptive input consistently related to movement/posture. We tested 28 participants with low back pain sub-grouped by the presumed underlying pain mechanisms: nociceptive pain, nociplastic pain and a mixed group with features consistent with both. Transcranial magnetic stimulation was used to study M1 organisation of back muscles. M1 maps of multifidus (deep and superficial) and longissimus erector spinae were recorded with fine-wire electromyography and thoracic erector spinae with surface electromyography. The nociplastic pain group had greater variability in M1 map location (centre of gravity) than other groups (p < .01), which may suggest less consistency, and perhaps relevance, of motor cortex adaptation for that group. The mixed group had greater overlap of M1 representations between deep/superficial muscles than nociceptive pain (deep multifidus/longissimus: p = .001, deep multifidus/thoracic erector spinae: p = .008) and nociplastic pain (deep multifidus/longissimus: p = .02, deep multifidus/thoracic erector spinae: p = .02) groups. This study provides preliminary evidence of differences in M1 organisation in subgroups of low back pain classified by likely underlying pain mechanisms. Despite the sample size, differences in cortical re-organisation between subgroups were detected. Differences in M1 organisation in subgroups of low back pain supports tailoring of treatment based on pain mechanism and motor adaptation.