Pain-related reorganization in the primary somatosensory cortex of patients with postherpetic neuralgia

Uncovering brain functional connectivity disruption patterns of lung cancer-related pain

Pain is a pervasive symptom in lung cancer patients during the onset of the disease. This study aims to investigate the connectivity disruption patterns of the whole-brain functional network in lung cancer patients with cancer pain (CP+). We constructed individual whole-brain, region of interest (ROI)-level functional connectivity (FC) networks for 50 CP+ patients, 34 lung cancer patients without pain-related complaints (CP-), and 31 matched healthy controls (HC). Then, a ROI-based FC analysis was used to determine the disruptions of FC among the three groups. The relationships between aberrant FCs and clinical parameters were also characterized. The ROI-based FC analysis demonstrated that hypo-connectivity was present both in CP+ and CP- patients compared to HC, which were particularly clustered in the somatomotor and ventral attention, frontoparietal control, and default mode modules. Notably, compared to CP- patients, CP+ patients had hyper-connectivity in several brain regions mainly distributed in the somatomotor and visual modules, suggesting these abnormal FC patterns may be significant for cancer pain. Moreover, CP+ patients also showed increased intramodular and intermodular connectivity strength of the functional network, which could be replicated in cancer stage IV and lung adenocarcinoma. Finally, abnormal FCs within the prefrontal cortex and somatomotor cortex were positively correlated with pain intensity and pain duration, respectively. These findings suggested that lung cancer patients with cancer pain had disrupted connectivity in the intrinsic brain functional network, which may be the underlying neuroimaging mechanisms.

Aging-associated decrease of PGC-1α promotes pain chronification

Aging is generally associated with declining somatosensory function, which seems at odds with the high prevalence of chronic pain in older people. This discrepancy is partly related to the high prevalence of degenerative diseases such as osteoarthritis in older people. However, whether aging alters pain processing in the primary somatosensory cortex (S1), and if so, whether it promotes pain chronification is largely unknown. Herein, we report that older mice displayed prolonged nociceptive behavior following nerve injury when compared with mature adult mice. The expression of peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) in S1 was decreased in older mice, whereas PGC-1α haploinsufficiency promoted prolonged nociceptive behavior after nerve injury. Both aging and PGC-1α haploinsufficiency led to abnormal S1 neural dynamics, revealed by intravital two-photon calcium imaging. Manipulating S1 neural dynamics affected nociceptive behavior after nerve injury: chemogenetic inhibition of S1 interneurons aggravated nociceptive behavior in naive mice; chemogenetic activation of S1 interneurons alleviated nociceptive behavior in older mice. More interestingly, adeno-associated virus-mediated expression of PGC-1α in S1 interneurons ameliorated aging-associated chronification of nociceptive behavior as well as aging-related S1 neural dynamic changes. Taken together, our results showed that aging-associated decrease of PGC-1α promotes pain chronification, which might be harnessed to alleviate the burden of chronic pain in older individuals.

Humoral Cytokine Levels in Patients with Herpes Zoster: A Meta-Analysis

Background

The neurocutaneous disease caused by the reactivation of varicella-zoster virus (VZV) is called herpes zoster (HZ). The virus remains in the spinal cord back root after the chickenpox disappears. Diminished immune function can reactivate VZV, causing severe neuropathic pain that can last for months or even years, leading to postherpetic neuralgia (PHN), which severely affects the patient's quality of life. Much literature compares various cytokine levels in the body fluids HZ and PHN patients; however, no studies comprehensively evaluate them.

Methods

The Cochrane Library, PubMed, Web of Science, and Medline were screened for studies on cytokine levels in body fluids of HZ and PHN patients in the English language. Healthy individuals were selected as the control group, and the standardized mean difference (SMD) between the case and control groups was imputed using a fixed-effects or random-effects model and expressed as a 95% confidence interval (CI). The Newcastle-Ottawa Scale (NOS) was used to assess article quality.

Results

This meta-analysis included 13 articles with 1373 participants. Compared with the control group, the HZ group had significantly higher levels of interleukin (IL)-4, IL-6, IL-10, Hcy, and C-reactive protein (CRP), whereas the levels of CD3+ T and CD4+ T lymphocytes were reduced. Additionally, PHN patients had significantly higher levels of IL-6 and IL-1β compared with the control group.

Conclusion

This meta-analysis provides compelling evidence that CRP, Hcy, IL-1β, IL-4, IL-6, IL-8, and IL-10 are associated with the genesis and development of HZ and PHN. These markers can be used to improve the diagnosis and treatment of these diseases.Furthermore, for making the results more convincing, it is necessary to harmonize sample acquisition techniques and analytical methods and also require larger, more rigorously designed studies with broader subgroups and sex/age-matched controls.

Characteristics and economic burden of hospitalized patients with herpes zoster in China, before vaccination

Herpes zoster (HZ) brings a significant economic burden. The HZ vaccine was introduced in China for the first time in 2020, and there is a lack of up-to-date information on the hospitalization costs and characteristics prior to vaccination. This study aimed to describe the characteristics and economic burden of HZ inpatients in Hunan Province, China, and analyze the factors influencing the length of stay (LOS) and costs. This was a retrospective study and we extracted information from the Chinese National Health Statistics Network Reporting System on HZ inpatients in Hunan Province, China from 2017 to 2019. Spatial join tools and Global or Local Moran's Index were used for the geographic analysis of hospitalized HZ incidence. Multivariate linear regression models were used to analyze the factors influencing LOS and costs. There were 44,311 HZ inpatients included in this study, incurring a total of $31,857,734 medical costs. These patients had a median LOS of 8 days and a median expenditure of $573.47. Older age, more comorbidities, and the presence of complications with nervous system involved were all significantly associated with longer LOS and higher costs. HZ infection resulted in a large direct medical cost and heavy disease burden, especially in patients with advanced age or underlying medical conditions. The HZ vaccine has the potential to effectively reduce the disease burden and should be widely popularized especially among high-risk groups.

The influence of aggressive exercise on responses to self-perceived and others' pain

Previous studies have reported relationships between exercise and pain. However, little is known about how aggressive exercise modulates individuals' responses to their own and others' pain. This present study addresses this question by conducting 2 studies employing event-related potential (ERP). Study 1 included 38 participants whose self-perceived pain was assessed after intervention with aggressive or nonaggressive exercises. Study 2 recruited 36 participants whose responses to others' pain were assessed after intervention with aggressive or nonaggressive exercise. Study 1's results showed that P2 amplitudes were smaller, reaction times were longer, and participants' judgments were less accurate in response to self-perceived pain stimuli, especially to high-pain stimuli, after intervention with aggressive exercise compared to nonaggressive exercise. Results of study 2 showed that both P3 and LPP amplitudes to others' pain were larger after intervention with aggressive exercise than with nonaggressive exercise. These results suggest that aggressive exercise decreases individuals' self-perceived pain and increases their empathic responses to others' pain.

Decreased Functional Connectivity of the Core Pain Matrix in Herpes Zoster and Postherpetic Neuralgia Patients

The purpose of this study was to explore the resting-state functional connectivity (FC) changes among the pain matrix and other brain regions in herpes zoster (HZ) and postherpetic neuralgia (PHN) patients. Fifty-four PHN patients, 52 HZ patients, and 54 healthy controls (HCs) underwent resting-state functional magnetic resonance imaging (rs-fMRI) scans. We used a seed-based FC approach to investigate whether HZ and PHN patients exhibited abnormal FC between the pain matrix and other brain regions compared to HCs. A random forest (RF) model was constructed to explore the feasibility of potential neuroimaging indicators to distinguish the two groups of patients. We found that PHN patients exhibited decreased FCs between the pain matrix and the putamen, superior temporal gyrus, middle frontal gyrus, middle cingulate gyrus, amygdala, precuneus, and supplementary motor area compared with HCs. Similar results were observed in HZ patients. The disease durations of PHN patients were negatively correlated with those aforementioned impaired FCs. The results of machine learning experiments showed that the RF model combined with FC features achieved a classification accuracy of 75%. Disrupted FC among the pain matrix and other regions in HZ and PHN patients may affect multiple dimensions of pain processing.

Tuina therapy promotes behavioral improvement and brain plasticity in rats with peripheral nerve injury and repair

INTRODUCTION

Tuina is currently one of the popular complementary and alternative methods of rehabilitation therapy. Tuina can improve patients' pain and mobility function. However, the underlying physiological mechanism remains largely unknown, which might limit its further popularization in clinical practice. The aim of this study is to explore the short-term and long-term changes in brain functional activity following Tuina intervention for peripheral nerve injury repair.

METHODS

A total of 16 rats were equally divided into the intervention group and the control group. Rats in the intervention group received Tuina therapy applying on the gastrocnemius muscle of the right side for 4 months following sciatic nerve transection and immediate repair, while the control group received nerve transection and repair only. The block-design functional magnetic resonance imaging scan was applied in both groups at 1 and 4 months after the surgery. During the scan, both the injured and intact hindpaw was electrically stimulated according to a "boxcar" paradigm.

RESULTS

When stimulating the intact hindpaw, the intervention group exhibited significantly lower activation in the somatosensory area, limbic/paralimbic areas, pain-regulation areas, and basal ganglia compared to the control group, with only the prefrontal area showing higher activation. After 4 months of sciatic nerve injury, the control group exhibited decreased motor cortex activity compared to the activity observed at 1 month, and the intervention group demonstrated stronger bilateral motor cortex activity compared to the control group.

CONCLUSION

Tuina therapy on the gastrocnemius muscle of rats with sciatic nerve injury can effectively alleviate pain and maintain the motor function of the affected limb. In addition, Tuina therapy reduced the activation level of pain-related brain regions and inhibited the decreased activity of the motor cortex caused by nerve injury, reflecting the impact of peripheral stimulation on brain plasticity.

Neural indices of multimodal sensory and autonomic hyperexcitability in fibromyalgia

Fibromyalgia (FM) is characterized by chronic widespread musculoskeletal pain and psychological distress. Research suggests people with FM experience increased somatosensory sensitization which generalizes to other sensory modalities and may indicate neural hyperexcitability. However, the available evidence is limited, and studies including measures of neural responsivity across sensory domains and both central and peripheral aspects of the neuraxis are lacking. Thirty-nine participants (51.5 ± 13.6 years of age) with no history of neurological disorders, psychosis, visual, auditory, or learning deficits, were recruited for this study. People with FM (N = 19) and control participants (CNT, N = 20) did not differ on demographic variables and cognitive capacity. Participants completed a task that combined innocuous auditory stimuli with electrocutaneous stimulation (ECS), delivered at individually-selected levels that were uncomfortable but not painful. Event-related potentials (ERPs) and electrodermal activity were analyzed to examine the central and sympathetic indices of neural responsivity. FM participants reported greater sensitivity to ECS and auditory stimulation, as well as higher levels of depression, anxiety, ADHD, and an array of pain-related experiences than CNT. In response to ECS, the P50 deflection was greater in FM than CNT participants, reflecting early somatosensory hyperexcitability. The P50 amplitude was positively correlated with the FM profile factor obtained with a principal component analysis. The N100 to innocuous tones and sympathetic reactivity to ECS were greater in FM participants, except in the subgroup treated with gabapentinoids, which aligns with previous evidence of symptomatic improvement with GABA-mimetic medications. These results support the principal tenet of generalized neural hyperexcitability in FM and provide preliminary mechanistic insight into the impact of GABA-mimetic pharmacological therapy on ameliorating the neural excitation dominance.

Bidirectional two-sample Mendelian randomization analysis reveals a causal effect of interleukin-18 levels on postherpetic neuralgia risk

Background

Postherpetic neuralgia (PHN) is a debilitating complication of herpes zoster, characterized by persistent neuropathic pain that significantly impairs patients' quality of life. Identifying factors that determine PHN susceptibility is crucial for its management. Interleukin-18 (IL-18), a pro-inflammatory cytokine implicated in chronic pain, may play a critical role in PHN development.

Methods

In this study, we conducted bidirectional two-sample Mendelian randomization (MR) analyses to assess genetic relationships and potential causal associations between IL-18 protein levels increasing and PHN risk, utilizing genome-wide association study (GWAS) datasets on these traits. Two IL-18 datasets obtained from the EMBL's European Bioinformatics Institute database which contained 21,758 individuals with 13,102,515 SNPs and Complete GWAS summary data on IL-18 protein levels which contained 3,394 individuals with 5,270,646 SNPs. The PHN dataset obtained from FinnGen biobank had 195,191 individuals with 16,380,406 SNPs.

Results

Our findings from two different datasets of IL-18 protein levels suggest a correlation between genetically predicted elevations in IL-18 protein levels and an increased susceptibility to PHN.(IVW, OR and 95% CI: 2.26, 1.07 to 4.78; p = 0.03 and 2.15, 1.10 to 4.19; p =0.03, respectively), potentially indicating a causal effect of IL-18 protein levels increasing on PHN risk. However, we did not detect any causal effect of genetic liability to PHN risk on IL-18 protein levels.

Conclusion

These findings suggest new insights into identifying IL-18 protein levels increasing at risk of developing PHN and may aid in the development of novel prevention and treatment approaches for PHN.

The role of ascending arousal network in patients with chronic insomnia disorder

The ascending arousal system plays a crucial role in individuals' consciousness. Recently, advanced functional magnetic resonance imaging (fMRI) has made it possible to investigate the ascending arousal network (AAN) in vivo. However, the role of AAN in the neuropathology of human insomnia remains unclear. Our study aimed to explore alterations in AAN and its connections with cortical networks in chronic insomnia disorder (CID). Resting-state fMRI data were acquired from 60 patients with CID and 60 good sleeper controls (GSCs). Changes in the brain's functional connectivity (FC) between the AAN and eight cortical networks were detected in patients with CID and GSCs. Multivariate pattern analysis (MVPA) was employed to differentiate CID patients from GSCs and predict clinical symptoms in patients with CID. Finally, these MVPA findings were further verified using an external data set (32 patients with CID and 33 GSCs). Compared to GSCs, patients with CID exhibited increased FC within the AAN, as well as increased FC between the AAN and default mode, cerebellar, sensorimotor, and dorsal attention networks. These AAN-related FC patterns and the MVPA classification model could be used to differentiate CID patients from GSCs with 88% accuracy in the first cohort and 77% accuracy in the validation cohort. Moreover, the MVPA prediction models could separately predict insomnia (data set 1, R²  = .34; data set 2, R²  = .15) and anxiety symptoms (data set 1, R²  = .35; data set 2, R²  = .34) in the two independent cohorts of patients. Our findings indicated that AAN contributed to the neurobiological mechanism of insomnia and highlighted that fMRI-based markers and machine learning techniques might facilitate the evaluation of insomnia and its comorbid mental symptoms.