The cerebellum and pain: passive integrator or active participator?

Coordinate-based (ALE) meta-analysis of acupuncture for musculoskeletal pain

Background

Neuroimaging studies have been widely used to investigate brain regions' alterations in musculoskeletal pain patients. However, inconsistent results have hindered our understanding of the central modulatory effects of acupuncture for musculoskeletal pain. The main objective of our investigation has been to obtain comprehensive evidence of acupuncture for musculoskeletal pain diseases.

Methods

The PubMed, Web of Science, Google Scholar, Embase, China National Knowledge Infrastructure (CNKI), VIP Database, China Biology Medicine disc Database, Clinical Trial Registration Platform, and Wanfang Database were searched for neuroimaging studies on musculoskeletal pain diseases published from inception up to November 2021. Then, the relevant literature was screened to extract the coordinates that meet the criteria. Finally, the coordinate-based meta-analysis was performed using the activation likelihood estimation algorithm.

Results

A total of 15 neuroimaging studies with 183 foci of activation were included in this study. The ALE meta-analysis revealed activated clusters in multiple cortical and sub-cortical brain structures in response to acupuncture across studies, including the thalamus, insula, caudate, claustrum, and lentiform nucleus.

Conclusions

The studies showed that acupuncture could modulate different brain regions, including the thalamus, insula, caudate, claustrum, and lentiform nucleus. The findings offer several insights into the potential mechanisms of acupuncture for musculoskeletal pain and provide a possible explanation for the observed clinical benefit of this therapy.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=227850, identifier: CRD42021227850.

Cerebro-Cerebellar Networks in Migraine Symptoms and Headache

The cerebellum is associated with the biology of migraine in a variety of ways. Clinically, symptoms such as fatigue, motor weakness, vertigo, dizziness, difficulty concentrating and finding words, nausea, and visual disturbances are common in different types of migraine. The neural basis of these symptoms is complex, not completely known, and likely involve activation of both specific and shared circuits throughout the brain. Posterior circulation stroke, or neurosurgical removal of posterior fossa tumors, as well as anatomical tract tracing in animals, provided the first insights to theorize about cerebellar functions. Nowadays, with the addition of functional imaging, much progress has been done on cerebellar structure and function in health and disease, and, as a consequence, the theories refined. Accordingly, the cerebellum may be useful but not necessary for the execution of motor, sensory or cognitive tasks, but, rather, would participate as an efficiency facilitator of neurologic functions by improving speed and skill in performance of tasks produced by the cerebral area to which it is reciprocally connected. At the subcortical level, critical regions in these processes are the basal ganglia and thalamic nuclei. Altogether, a modulatory role of the cerebellum over multiple brain regions appears compelling, mainly by considering the complexity of its reciprocal connections to common neural networks involved in motor, vestibular, cognitive, affective, sensory, and autonomic processing—all functions affected at different phases and degrees across the migraine spectrum. Despite the many associations between cerebellum and migraine, it is not known whether this structure contributes to migraine initiation, symptoms generation or headache. Specific cerebellar dysfunction via genetically driven excitatory/inhibitory imbalances, oligemia and/or increased risk to white matter lesions has been proposed as a critical contributor to migraine pathogenesis. Therefore, given that neural projections and functions of many brainstem, midbrain and forebrain areas are shared between the cerebellum and migraine trigeminovascular pathways, this review will provide a synopsis on cerebellar structure and function, its role in trigeminal pain, and an updated overview of relevant clinical and preclinical literature on the potential role of cerebellar networks in migraine pathophysiology.

Abnormal Dynamics of Functional Connectivity Density Associated With Chronic Neck Pain

Background: Chronic neck pain (CNP) is highly prevalent and complicated, associated with limited movement, and accompanied by shoulder pain and other clinical manifestations such as dizziness, anxiety, and insomnia. Brain structural and functional abnormalities often occur in patients with CNP. However, knowledge of the brain’s functional organization and temporal dynamics in CNP patients is limited. Dynamic functional connectivity density (dFCD) can reflect the ability of brain areas or voxels to integrate information, and could become neuroimaging markers for objectively reflecting pain to a certain extent. Therefore, this study compared the dFCD between CNP patients and healthy controls (HCs) and investigated potential associations of the abnormal density variability in dynamic functional connectivity with pain characteristics in CNP patients.

Methods: Resting functional magnetic resonance imaging was performed for 89 CNP patients and 57 HCs. After preprocessing resting-state fMRI images by the Data Processing and Analysis of Brain Imaging toolbox, the sliding window method was applied to investigate dFCD changes in CNP patients and HCs using the DynamicBC toolbox. Then we quantified dFCD variability using their standard deviation. Based on the pain-associated factors collected from the case report form of CNP patients, the mean dFCD variability values of each dFCD from region of interest were extracted to calculate Pearson’s correlation coefficient to study the potential correlation between dFCD abnormal variability and pain.

Results: Compared with HCs, the dFCD values of the anterior cingulate cortex, occipital lobe, temporal lobe, and cerebellum were statistically different in patients with CNP. Subsequent correlation analysis showed that the variable dFCD in the related brain region was correlative with the course of the disease and clinical symptoms, such as pain and depression, in patients with CNP.

Conclusion: Dynamic functional alterations were observed in the brain regions of CNP patients, and the dFCD of these brain regions could become neuroimaging markers for objectively reflecting pain to a certain extent. This suggests that chronic pain may cause changes in pain processing and emotional feedback and highlights the link between dynamic neural communication in brain regions and disease conditions, deepening our understanding of chronic pain diseases, and guiding clinical practice.

Changes in the Brain Metabolism Associated with Central Post-Stroke Pain in Hemorrhagic Pontine Stroke: An 18F-FDG-PET Study of the Brain

Central post-stroke pain (CPSP) is an intractable neuropathic pain that can occur following central nervous system injuries. Spino-thalamo-cortical pathway damage contributes to CPSP development. However, brain regions involved in CPSP are unknown and previous studies were limited to supratentorial strokes with cortical lesion involvement. We analyzed the brain metabolism changes associated with CPSP following pontine hemorrhage. Thirty-two patients with isolated pontine hemorrhage were examined; 14 had CPSP, while 18 did not. Brain glucose metabolism was evaluated using 18F-fluorodeoxyglucose-positron emission tomography images. Additionally, regions revealing metabolic correlation with CPSP severity were analyzed. Patients with CPSP showed changes in the brain metabolism in the cerebral cortices and cerebellum. Compared with the control group, the CPSP group showed significant hypometabolism in the contralesional rostral anterior cingulum and ipsilesional primary motor cortex (Puncorrected < 0.001). However, increased brain metabolism was observed in the ipsilesional cerebellum (VI) and contralesional cerebellum (lobule VIIB) (Puncorrected < 0.001). Moreover, increased pain intensity correlated with decreased metabolism in the ipsilesional supplementary motor area and contralesional angular gyrus. This study emphasizes the role of the many different areas of the cortex that are involved in affective and cognitive processing in the development of CPSP.

Aberrant Modulations of Neurocognitive Network Dynamics in Migraine Comorbid With Tinnitus

Purpose

The possible relationship between migraine and tinnitus still remains elusive although migraine is often accompanied by chronic tinnitus. Several neuroimaging studies have reinforced the cognitive network abnormality in migraine and probably as well as tinnitus. The present work aims to investigate the dynamic neurocognitive network alterations of migraine comorbid with tinnitus.

Materials and Methods

Participants included migraine patients (n = 32), tinnitus patients (n = 20), migraine with tinnitus (n = 27), and healthy controls (n = 47), matched for age and gender. Resting-state functional magnetic resonance imaging (rs-fMRI) with independent component analysis (ICA), sliding window cross-correlation, and clustering state analysis was used to detect the dynamic functional network connectivity (dFNC) of each group. Correlation analyses illustrated the association between clinical symptoms and abnormal dFNC in migraine as well as tinnitus.

Results

Compared with healthy controls, migraine patients exhibited decreased cerebellar network and visual network (CN-VN) connectivity in State 2; migraine with tinnitus patients showed not only decreased CN-VN connectivity in State 2 but also decreased cerebellar network and executive control network (CN-ECN) connectivity in State 2 and increased cerebellar network and somatomotor network (SMN-VN) connectivity in State 1. The abnormal cerebellum dFNC with the executive control network (CN-ECN) was negatively correlated with headache frequency of migraine (rho = −0.776, p = 0.005).

Conclusion

Brain network characteristics of migraine with tinnitus patients may indicate different mechanisms for migraine and tinnitus. Our results demonstrated a transient pathologic state with atypical cerebellar-cortical connectivity in migraine with tinnitus patients, which might be used to identify the neuro-pathophysiological mechanisms in migraine accompanied by tinnitus.

Aberrant Spontaneous Brain Activity in Coronary Heart Disease Using Fractional Amplitude of Low-Frequency Fluctuations: A Preliminary Resting-State Functional MRI Study

Objective

This study is aimed at exploring the spontaneous brain activity changes by measuring the fractional amplitude of low-frequency fluctuations (fALFF) and their relationship with clinical characteristics in patients with coronary heart disease (CHD).

Methods

Coronary heart disease patients (n = 25) and age, gender, and education level-matched control subjects (controls, n = 35) were included. The grey matter volume (GMV) and fALFF values were calculated to assess the difference in brain structure and function between the two groups, respectively. Correlation analyses between the fALFF values and clinical characteristics were further assessed in CHD patients. In addition, receiver operating characteristic (ROC) curves were conducted to access the diagnostic ability of the fALFF method.

Results

There was no significant difference in GMV between the CHD and control groups. Compared with the control group, patients with CHD showed significantly decreased fALFF in the left precentral/postcentral gyrus and increased fALFF in the right inferior cerebellum. Patients with a history of myocardial infarction (MI) showed significantly decreased fALFF values of the right inferior cerebellum than patients without MI. There was no significant correlation between the fALFF values in specific brain regions and disease duration. Furthermore, the ROC curves of abnormal brain regions showed the perfect accuracy of the fALFF value in distinguishing between CHD patients and controls.

Conclusion

CHD demonstrated aberrant neural activity in specific brain regions mainly related to sensorimotor networks and pain processing, which may contribute to understanding the underlying neurological mechanism of CHD.

Novel Cerebello-Amygdala Connections Provide Missing Link Between Cerebellum and Limbic System

The cerebellum is emerging as a powerful regulator of cognitive and affective processing and memory in both humans and animals and has been implicated in affective disorders. How the cerebellum supports affective function remains poorly understood. The short-latency (just a few milliseconds) functional connections that were identified between the cerebellum and amygdala—a structure crucial for the processing of emotion and valence—more than four decades ago raise the exciting, yet untested, possibility that a cerebellum-amygdala pathway communicates information important for emotion. The major hurdle in rigorously testing this possibility is the lack of knowledge about the anatomy and functional connectivity of this pathway. Our initial anatomical tracing studies in mice excluded the existence of a direct monosynaptic connection between the cerebellum and amygdala. Using transneuronal tracing techniques, we have identified a novel disynaptic circuit between the cerebellar output nuclei and the basolateral amygdala. This circuit recruits the understudied intralaminar thalamus as a node. Using ex vivo optophysiology and super-resolution microscopy, we provide the first evidence for the functionality of the pathway, thus offering a missing mechanistic link between the cerebellum and amygdala. This discovery provides a connectivity blueprint between the cerebellum and a key structure of the limbic system. As such, it is the requisite first step toward obtaining new knowledge about cerebellar function in emotion, thus fundamentally advancing understanding of the neurobiology of emotion, which is perturbed in mental and autism spectrum disorders.

CGRP Administration Into the Cerebellum Evokes Light Aversion, Tactile Hypersensitivity, and Nociceptive Squint in Mice

The neuropeptide calcitonin gene-related peptide (CGRP) is a major player in migraine pathophysiology. Previous preclinical studies demonstrated that intracerebroventricular administration of CGRP caused migraine-like behaviors in mice, but the sites of action in the brain remain unidentified. The cerebellum has the most CGRP binding sites in the central nervous system and is increasingly recognized as both a sensory and motor integration center. The objective of this study was to test whether the cerebellum, particularly the medial cerebellar nuclei (MN), might be a site of CGRP action. In this study, CGRP was directly injected into the right MN of C57BL/6J mice via a cannula. A battery of tests was done to assess preclinical behaviors that are surrogates of migraine-like symptoms. CGRP caused light aversion measured as decreased time in the light zone even with dim light. The mice also spent more time resting in the dark zone, but not the light, along with decreased rearing and transitions between zones. These behaviors were similar for both sexes. Moreover, significant responses to CGRP were seen in the open field assay, von Frey test, and automated squint assay, indicating anxiety, tactile hypersensitivity, and spontaneous pain, respectively. Interestingly, CGRP injection caused significant anxiety and spontaneous pain responses only in female mice, and a more robust tactile hypersensitivity in female mice. No detectable effect of CGRP on gait was observed in either sex. These results suggest that CGRP injection in the MN causes light aversion accompanied by increased anxiety, tactile hypersensitivity, and spontaneous pain. A caveat is that we cannot exclude contributions from other cerebellar regions in addition to the MN due to diffusion of the injected peptide. These results reveal the cerebellum as a new site of CGRP actions that may contribute to migraine-like hypersensitivity.

Combining Regional and Connectivity Metrics of Functional Magnetic Resonance Imaging and Diffusion Tensor Imaging for Individualized Prediction of Pain Sensitivity

Characterization and prediction of individual difference of pain sensitivity are of great importance in clinical practice. MRI techniques, such as functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI), have been popularly used to predict an individual's pain sensitivity, but existing studies are limited by using one single imaging modality (fMRI or DTI) and/or using one type of metrics (regional or connectivity features). As a result, pain-relevant information in MRI has not been fully revealed and the associations among different imaging modalities and different features have not been fully explored for elucidating pain sensitivity. In this study, we investigated the predictive capability of multi-features (regional and connectivity metrics) of multimodal MRI (fMRI and DTI) in the prediction of pain sensitivity using data from 210 healthy subjects. We found that fusing fMRI-DTI and regional-connectivity features are capable of more accurately predicting an individual's pain sensitivity than only using one type of feature or using one imaging modality. These results revealed rich information regarding individual pain sensitivity from the brain's both structural and functional perspectives as well as from both regional and connectivity metrics. Hence, this study provided a more comprehensive characterization of the neural correlates of individual pain sensitivity, which holds a great potential for clinical pain management.

New Insights on Metabolic and Genetic Basis of Migraine: Novel Impact on Management and Therapeutical Approach

Migraine is a hereditary disease, usually one-sided, sometimes bilateral. It is characterized by moderate to severe pain, which worsens with physical activity and may be associated with nausea and vomiting, may be accompanied by photophobia and phonophobia. The disorder can occur at any time of the day and can last from 4 to 72 h, with and without aura. The pathogenic mechanism is unclear, but extensive preclinical and clinical studies are ongoing. According to electrophysiology and imaging studies, many brain areas are involved, such as cerebral cortex, thalamus, hypothalamus, and brainstem. The activation of the trigeminovascular system has a key role in the headache phase. There also appears to be a genetic basis behind the development of migraine. Numerous alterations have been identified, and in addition to the genetic cause, there is also a close association with the surrounding environment, as if on the one hand, the genetic alterations may be responsible for the onset of migraine, on the other, the environmental factors seem to be more strongly associated with exacerbations. This review is an analysis of neurophysiological mechanisms, neuropeptide activity, and genetic alterations that play a fundamental role in choosing the best therapeutic strategy. To date, the goal is to create a therapy that is as personalized as possible, and for this reason, steps forward have been made in the pharmacological field in order to identify new therapeutic strategies for both acute treatment and prophylaxis.

Significant Structural Alterations and Functional Connectivity Alterations of Cerebellar Gray Matter in Patients With Somatic Symptom Disorder

Objective

Recent studies have revealed a strong association between the cerebellum and psychiatric disorders. However, the structural changes in the cerebellar regions and functional connectivity (FC) patterns in patients with somatic symptom disorder (SSD) have not been elucidated.

Methods

Thirty-seven patients with SSD (29 drug-naive and 8 medicated patients) and 37 sex- and age-matched healthy controls (HCs) were recruited and underwent resting-state functional magnetic resonance imaging scans. The spatially unbiased infratentorial (SUIT) cerebellar atlas-based voxel-based morphometry was used to investigate the changes in cerebellar regional gray matter (GM). Seed-based FC was further computed to explore the pattern of abnormal FC across the whole brain. Correlations were calculated to investigate the relationship between cerebellar structural (and FC) changes and clinical characteristics.

Results

After controlling for age, sex, total intracranial volume, medication, and mean FD covariates, all patients with SSD had increased mean GM volume (GMV) in the posterior lobules of the cerebellum bilaterally when compared with HCs, specifically, in the bilateral cerebellar crura I and II. Patients with SSD showed significantly stronger FC between the right crura I and II and bilateral precuneus inferior parietal region, and postcentral gyrus, extending to the superior parietal lobe, cingulate gyrus, and the white matter subgyral. In addition to the two clusters, right lingual gyrus was also a surviving cluster with significantly higher FC. Partial correlation analysis revealed that the degree of regional GMV increases in the two significant clusters and the Hamilton Depression Scale (HAMD) score was negatively correlated. Moreover, the FC of right crura I and II with the left parietal lobe and right lingual gyrus were also negatively associated with the HAMD score.

Conclusions

SSD exhibited significant microstructural changes and changes in FC pattern in the posterior cerebellar lobe. These results shed new light on the psychological and neural substrates of SSD and may serve as a potential treatment target for SSD based on the cerebellar area.

Supraspinal Mechanisms Underlying Ocular Pain

Supraspinal mechanisms of pain are increasingly understood to underlie neuropathic ocular conditions previously thought to be exclusively peripheral in nature. Isolating individual causes of centralized chronic conditions and differentiating them is critical to understanding the mechanisms underlying neuropathic eye pain and ultimately its treatment. Though few functional imaging studies have focused on the eye as an end-organ for the transduction of noxious stimuli, the brain networks related to pain processing have been extensively studied with functional neuroimaging over the past 20 years. This article will review the supraspinal mechanisms that underlie pain as they relate to the eye.

A Longitudinal Study on Attenuated Structural Covariance in Patients With Somatic Symptom Disorder

OBJECTIVE

This study was performed to investigate altered regional gray matter volume (rGMV) and structural covariance related to somatic symptom disorder (SSD) and longitudinal changes after treatment. Additionally, this study examined the relationships of structural alteration with its phenotypic subtypes.

METHODS

Forty-three unmedicated patients with SSD and thirty normal controls completed psychological questionnaires and neurocognitive tests, as well as brain magnetic resonance imaging. Voxel-based morphometry and structural covariances were compared between groups and between subgroups within the SSD group. After 6 months of treatment, SSD patients were followed up for assessments.

RESULTS

Patients with SSD exhibited attenuated structural covariances in the pallidal-cerebellar circuit (FDR < 0.05-0.1), as well as regions in the default mode and sensorimotor network (FDR < 0.2), compared to normal controls. The cerebellar rGMVs were negatively correlated with the severity of somatic symptoms. In subgroup analyses, patients with somatic pain showed denser structural covariances between the bilateral superior temporal pole and left angular gyrus, the left middle temporal pole and left angular gyrus, and the left amygdala and right inferior orbitofrontal gyrus, while patients with headache and dizziness had greater structural covariance between the right inferior temporal gyrus and right cerebellum (FDR < 0.1-0.2). After 6 months of treatment, patients showed improved symptoms, however there was no significant structural alteration.

CONCLUSION

The findings suggest that attenuated structural covariance may link to dysfunctional brain network and vulnerability to SSD; they also suggested that specific brain regions and networks may contribute to different subtypes of SSD.

Cerebral processing of sharp mechanical pain measured with arterial spin labeling

INTRODUCTION

Arterial spin labeling (ASL) is a functional neuroimaging technique that has been frequently used to investigate acute pain states. A major advantage of ASL as opposed to blood-oxygen-level-dependent functional neuroimaging is its applicability for low-frequency designs. As such, ASL represents an interesting option for studies in which repeating an experimental event would reduce its ecological validity. Whereas most ASL pain studies so far have used thermal stimuli, to our knowledge, no ASL study so far has investigated pain responses to sharp mechanical pain.

METHODS

As a proof of concept, we investigated whether ASL has the sensitivity to detect brain activation within core areas of the nociceptive network in healthy controls following a single stimulation block based on 96 s of mechanical painful stimulation using a blunt blade.

RESULTS

We found significant increases in perfusion across many regions of the nociceptive network such as primary and secondary somatosensory cortices, premotor cortex, posterior insula, inferior parietal cortex, parietal operculum, temporal gyrus, temporo-occipital lobe, putamen, and the cerebellum. Contrary to our hypothesis, we did not find any significant increase within ACC, thalamus, or PFC. Moreover, we were able to detect a significant positive correlation between pain intensity ratings and pain-induced perfusion increase in the posterior insula.

CONCLUSION

We demonstrate that ASL is suited to investigate acute pain in a single event paradigm, although to detect activation within some regions of the nociceptive network, the sensitivity of our paradigm seemed to be limited. Regarding the posterior insula, our paradigm was sensitive enough to detect a correlation between pain intensity ratings and pain-induced perfusion increase. Previous experimental pain studies have proposed that intensity coding in this region may be restricted to thermal stimulation. Our result demonstrates that the posterior insula encodes intensity information for mechanical stimuli as well.

Gray matter volume reduction with different disease duration in trigeminal neuralgia

PURPOSE

Structural magnetic resonance imaging is widely used to explore brain gray and white matter structure in trigeminal neuralgia (TN) but has yielded conflicting findings. This study investigated the relationship between disease duration as a clinical feature of TN and changes in brain structure.

METHODS

We divided 49 TN patients into three groups (TN1-TN3) based on disease duration (TN1 = 1.1 ± 0.7 (0-2) years, TN2 = 4.8 ± 1.5 (3-7) years, TN3 = 15.1 ± 5.5 (10-30) years). We used voxel-based morphometry (VBM) to compare the gray matter volume (GMV) across groups and between TN patients and 18 matched healthy control subjects.

RESULTS

The TN1 group showed reduced GMV of pain-related regions in the cerebellum; the TN2 group showed reduced GMV in the thalamus and the motor/sensory cortex; and the TN3 group showed reduced GMV in the emotional and reward circuits compared with healthy controls. Similar brain regions, including bilateral hippocampi, caudate, left insular cortex, and medial superior frontal cortex, were affected in TN2 and TN3 compared with TN1.

CONCLUSION

Disease duration can explain differences in structural alterations-especially in pain-related brain regions-in TN. These results highlight the advanced structural neuroimaging method that are valuable tools to assess the trigeminal system in TN and may further our current understanding of TN pathology.

Dyspnea

The clinical term dyspnea (a.k.a. breathlessness or shortness of breath) encompasses at least three qualitatively distinct sensations that warn of threats to breathing: air hunger, effort to breathe, and chest tightness. Air hunger is a primal homeostatic warning signal of insufficient alveolar ventilation that can produce fear and anxiety and severely impacts the lives of patients with cardiopulmonary, neuromuscular, psychological, and end-stage disease. The sense of effort to breathe informs of increased respiratory muscle activity and warns of potential impediments to breathing. Most frequently associated with bronchoconstriction, chest tightness may warn of airway inflammation and constriction through activation of airway sensory nerves. This chapter reviews human and functional brain imaging studies with comparison to pertinent neurorespiratory studies in animals to propose the interoceptive networks underlying each sensation. The neural origins of their distinct sensory and affective dimensions are discussed, and areas for future research are proposed. Despite dyspnea's clinical prevalence and impact, management of dyspnea languishes decades behind the treatment of pain. The neurophysiological bases of current therapeutic approaches are reviewed; however, a better understanding of the neural mechanisms of dyspnea may lead to development of novel therapies and improved patient care.

Cortical mechanisms in migraine

Migraine is the second most prevalent disorder in the world; yet, its underlying mechanisms are still poorly understood. Cumulative studies have revealed pivotal roles of cerebral cortex in the initiation, propagation, and termination of migraine attacks as well as the interictal phase. Investigation of basic mechanisms of the cortex in migraine not only brings insight into the underlying pathophysiology but also provides the basis for designing novel treatments. We aim to summarize the current research literatures and give a brief overview of the cortex and its role in migraine, including the basic structure and function; structural, functional, and biochemical neuroimaging; migraine-related genes; and theories related to cortex in migraine pathophysiology. We propose that long-term plasticity of synaptic transmission in the cortex encodes migraine.

Brain circuits for pain and its treatment

[Figure: see text].

Alterations in Effective Connectivity of the Hippocampus in Migraine without Aura

Purpose

Neuroimaging studies on migraine have revealed structural and functional alterations in the hippocampus, a region involved in pain processing and stress response. This study was designed to investigate whether effective connectivity of this region is disrupted in migraine and relates to chronicity of this disease.

Patients and Methods

In 39 episodic migraine (EM) patients, 17 chronic migraine (CM) patients, and 35 healthy controls, we investigated differences in the directional influences between the hippocampus and the rest of the brain by combining resting-state functional magnetic resonance imaging and Granger causality analysis (GCA), with bilateral hippocampus as seed regions. The associations between directional influences and the clinical variables were also examined.

Results

Comparing each patient group to the control group, we found increased and decreased negative influence on the hippocampus exerted by the bilateral visual areas and right dorsolateral prefrontal cortex (dlPFC), respectively. The hippocampus showed increased positive influence on the right posterior insula and medial prefrontal cortex (mPFC), as well as increased negative influence on the left cerebellum in CM patients relative to EM patients and healthy controls. Furthermore, across all patients, the migraine frequency exhibited a positive and negative association with causal influence from the hippocampus to mPFC and left cerebellum, respectively.

Conclusion

Migraine patients have abnormal effective connectivity between the hippocampus and multiple brain regions involved in the sensory and cognitive processing of pain. Disrupted directional influences to the hippocampus exerted by dlPFC and bilateral visual areas were common features of EM and CM patients. Directional influences from the hippocampus to mPFC and left cerebellum may be useful imaging biomarkers for assessing migraine frequency.

Addiction and the cerebellum with a focus on actions of opioid receptors

Increasing evidence suggests that the cerebellum could play a role in the higher cognitive processes involved in addiction as the cerebellum contains anatomical and functional pathways to circuitry controlling motivation and saliency. In addition, the cerebellum exhibits a widespread presence of receptors, including opioid receptors which are known to play a prominent role in synaptic and circuit mechanisms of plasticity associated with drug use and development of addiction to opioids and other drugs of abuse. Further, the presence of perineural nets (PNNs) in the cerebellum which contain proteins known to alter synaptic plasticity could contribute to addiction. The role the cerebellum plays in processes of addiction is likely complex, and could depend on the particular drug of abuse, the pattern of use, and the stage of the user within the addiction cycle. In this review, we discuss functional and structural modifications shown to be produced in the cerebellum by opioids that exhibit dependency-inducing properties which provide support for the conclusion that the cerebellum plays a role in addiction.

Hypothalamic structural integrity and temporal complexity of cortical information processing at rest in migraine without aura patients between attacks

The hypothalamus has been attributed an important role during the premonitory phase of a migraine attack. Less is known about the role played by the hypothalamus in the interictal period and its relationship with the putative neurocognitive networks previously identified in the pathophysiology of migraine. Our aim was to test whether the hypothalamic microstructure would be altered during the interictal period and whether this co-existed with aberrant connectivity at cortical level. We collected multimodal MRI data from 20 untreated patients with migraine without aura between attacks (MO) and 20 healthy controls (HC) and studied fractional anisotropy, mean (MD), radial (RD), and axial diffusivity of the hypothalamus ROI as a whole from diffusion tensor imaging (DTI). Moreover, we performed an exploratory analysis of the same DTI metrics separately for the anterior and posterior hypothalamic ROIs bilaterally. From resting-state functional MRI, we estimated the Higuchi's fractal dimension (FD), an index of temporal complexity sensible to describe non-periodic patterns characterizing BOLD signature. Finally, we correlated neuroimaging findings with migraine clinical features. In comparison to HC, MO had significantly higher MD, AD, and RD values within the hypothalamus. These findings were confirmed also in the exploratory analysis on the sub-regions of the hypothalamus bilaterally, with the addition of lower FA values on the posterior ROIs. Patients showed higher FD values within the salience network (SN) and the cerebellum, and lower FD values within the primary visual (PV) network compared to HC. We found a positive correlation between cerebellar and SN FD values and severity of migraine. Our findings of hypothalamic abnormalities between migraine attacks may form part of the neuroanatomical substrate that predisposes the onset of the prodromal phase and, therefore, the initiation of an attack. The peculiar fractal dimensionality we found in PV, SN, and cerebellum may be interpreted as an expression of abnormal efficiency demand of brain networks devoted to the integration of sensory, emotional, and cognitive information related to the severity of migraine.

A volumetric magnetic resonance imaging study in migraine

Background

Although migraine phenotype has been widely described, the explanation of migraine pathophysiology still has a gap that might be partly bridged by neuroimaging investigations. The aim of the study is to assess volumetric brain changes in migraineurs compared with controls, and in episodic migraine in comparison to chronic type. Structural brain changes in migraineurs (with and without aura) were assessed by an automated segmentation method (Free Surfer). T1-weighted MRIs of 25 migraineurs (14 diagnosed as episodic type and 11 diagnosed as chronic migraine) and 25 headache-free controls were evaluated and processed.

Results

Migraine patients had significant reduction of the volume of total brain, grey matter, brain stem, cerebellum, basal ganglia, thalamus, hippocampus and amygdala in comparison to control subjects. Patients with chronic migraine had significant reduction in volume of total brain, grey matter, cerebellum and frontal lobe thickness in comparison to those with episodic migraine.

Conclusion

Migraineurs showed volumetric brain changes mainly in areas related to central processing of pain and in areas specific for migraine (such as brain stem) when compared to healthy controls. Chronic migraineurs showed significant reduction in grey matter, in areas involved in processing of pain, cognition and multisensory integration versus patients with episodic migraine, which adds insight into the pathophysiology of migraine as a progressive disorder that may have long-term impacts on the brain as regards structure and function.

Structural and functional biomarkers of efficacy of navigated repetitive transcranial magnetic stimulation in therapy for trigeminal neuralgia

Repetitive transcranial magnetic stimulation (rTMS) is an alternative treatment option for patients with drug-resistant trigeminal neuralgia (TN). However, the effect of rTMS is variable. The aim of this study was to find neuroimaging biomarkers of clinical efficacy of navigated rTMS. Seventeen patients with TN (14 women and 3 men, median age 56 years) received 10 sessions of high-frequency rTMS of the motor cortex contralateral to pain side. The data were analyzed for correlations between functional connectivity (FC), the grey matter (GM) volume and the reduction in pain intensity. Positive correlations were established between the reduction in average pain intensity and GM volume in caudate nuclei in both hemispheres (p(unc) = 0.03), both cerebellar hemispheres (p(unc) = 0.002) and the postcentral gyrus contralateral to pain side (p(unc) = 0.005); between the reduction in peak pain intensity and GM volume in the caudate nucleus contralateral to pain side (p(unc) = 0.04) and the cerebellar hemisphere ipsilateral to pain (p(unc) = 0.03). Significant positive correlations were discovered between the reduction in average pain intensity and FC between the thalamus contralateral to pain side, the postcentral gyrus and the insular operculum (both ipsilateral to pain side; (p(FWE) = 0.018), as well as between the cingulate cortex and the anterior cingulate cortex ipsilateral to pain (p(FWE) = 0.017), between the contralateral subcallosal gyrus and the cerebellar hemisphere ipsilateral to pain (p(FWE) = 0.018). A negative correlation was established for FC between the contralateral putamen and the occipital lobes in both hemispheres (p(FWE) = 0.001). Our findings may spur the development of individual predictors of rTMS efficacy in patients with chronic pain.

Associations of Regional and Network Functional Connectivity With Exercise-Induced Low Back Pain

Musculoskeletal pain is an aversive experience that exists within a variety of conditions and can result in significant impairment for individuals. Gaining greater understanding of the factors related to pain vulnerability and resilience to musculoskeletal pain may help target at-risk individuals for early intervention. This analysis builds on our previous work identifying regions where greater gray matter density was associated with lower pain following standardized, exercise induced musculoskeletal injury. Here we sought to examine the relationship between baseline resting state functional connectivity in a priori regions and networks, and delayed onset muscle soreness (DOMS) pain intensity following a single session of eccentric exercise in healthy adults. Participants completed a baseline functional MRI scan and a high intensity trunk exercise protocol in the erector spinae. Pain intensity ratings were collected 48-hours later. Resting state functional connectivity from four seed regions and 3 networks were separately regressed on pain intensity scores. Results revealed that connectivity between left middle frontal gyrus, the left occipital gyrus and cerebellar network seeds and clusters associated with discriminative, emotional, and cognitive aspects of pain were associated with lower post-DOMS pain. Results suggest resilience to clinically relevant pain is associated with aspects of regional and network neural coherence. Investigations of pain modulatory capacity that integrate multimodal neuroimaging metrics are called for. Perspective: Our results provide key support for the role of structural and functional coherence in regional and network connectivity in adaptive pain response and represent an important step in clarifying neural mechanisms of resilience to clinically relevant pain.

Differential Modulating Effect of Acupuncture in Patients With Migraine Without Aura: A Resting Functional Magnetic Resonance Study

Introduction: Migraine is a recurrent neurological disorder, the symptoms of which can be significantly relieved by acupuncture. However, the central mechanism via which acupuncture exerts its therapeutic effect in migraine is unclear. The aim of this study was to compare the differences in regional homogeneity (ReHo) between patients with migraine without aura (MwoA) and healthy controls (HCs) and to explore the immediate and cumulative therapeutic effect of acupuncture in patients with MwoA using resting-state functional magnetic resonance imaging (fMRI).

Methods: The study subjects were 40 patients with MwoA and 16 matched HCs. The patients with MwoA received acupuncture on 2 days per week for 6 weeks for a total of 12 sessions followed by 24 weeks of follow-up. The primary clinical efficacy outcomes were the number of days with migraine and the average severity of headache. Secondary outcomes were the Migraine-Specific Quality of Life Questionnaire, Self-Rating Anxiety Scale, and Self-Rating Depression Scale scores. In the migraine group, resting-state blood-oxygen-level-dependent fMRI scans were obtained at baseline and after the first and 12th acupuncture sessions to measure the ReHo value. In the HCs, only a baseline resting-state blood-oxygen-level-dependent fMRI scan was obtained.

Results: Compared with the control group, the migraine group had a significantly lower ReHo value in the cerebellum, which increased after the first acupuncture session. Long-term acupuncture significantly improved migraine symptoms and mood with a therapeutic effect that lasted for at least 6 months. After 12 acupuncture sessions, there were significant increase of cerebellum and angular gyrus in the migraine group.

Conclusion: These findings suggest that migraine is related to cerebellar dysfunction. Acupuncture can relieve the symptoms of migraine, improve dysfunction of cerebellum, and activate brain regions involved in modulation of pain and emotion The cumulative therapeutic effect of acupuncture is more extensive and significant than its immediate effect.

Brain networks and endogenous pain inhibition are modulated by age and sex in healthy rats

Endogenous pain inhibition is less efficient in chronic pain patients. Diffuse noxious inhibitory control (DNIC), a form of endogenous pain inhibition, is compromised in women and older people, making them more vulnerable to chronic pain. However, the underlying mechanisms remain unclear. Here, we used a capsaicin-induced DNIC test and resting-state functional MRI to investigate the impact of aging and sex on endogenous pain inhibition and associated brain circuitries in healthy rats. We found that DNIC was less efficient in young females compared with young males. Diffuse noxious inhibitory control response was lost in old rats of both sexes, but the brain networks engaged during DNIC differed in a sex-dependent manner. Young males had the most efficient analgesia with the strongest connectivity between anterior cingulate cortex (ACC) and periaqueductal gray (PAG). The reduced efficiency of DNIC in young females seemed to be driven by widespread brain connectivity. Old males showed increased connectivity between PAG, raphe nuclei, pontine reticular nucleus, and hippocampus, which may not be dependent on connections to ACC, whereas old females showed increased connectivity between ACC, PAG, and more limbic regions. These findings suggest that distinct brain circuitries including the limbic system may contribute to higher susceptibility to pain modulatory deficits in the elderly population, and sex may be a risk factor for developing age-related chronic pain.

Chronic Migraine Preventive Treatment by Prefrontal-Occipital Transcranial Direct Current Stimulation (tDCS): A Proof-of-Concept Study on the Effect of Psychiatric Comorbidities

Chronic migraine (CM) is often complicated by medication overuse headache (MOH) and psychiatric comorbidities that may influence the clinical outcome. This study aimed to investigate the relationship between psychiatric comorbidities and the effect of transcranial direct current stimulation (tDCS) in patients with CM with or without MOH. We recruited 16 consecutive CM patients who had an unsatisfactory response to at least three pharmacological preventive therapies. They were treated with anodal right-prefrontal and cathodal occipital tDCS (intensity: 2 mA, time: 20 min) three times per week for 4 weeks. All patients underwent a psychopathological assessment before and after treatment, and five of them were diagnosed with bipolar disorder (BD). After treatment, all the patients showed a significant decrease of severe and overall headache days per month. Despite having a higher migraine burden at baseline, patients with CM and BD showed a significantly greater reduction of severe headaches and psychiatric symptoms. Overall, tDCS seems to be effective in the treatment of CM patients with a poor response to different classes of pharmacological therapies, whereas BD status positively influences the response of migraineurs to tDCS.

TRPV1 Responses in the Cerebellum Lobules VI, VII, VIII Using Electroacupuncture Treatment for Chronic Pain and Depression Comorbidity in a Murine Model

Depression is a prominent complex psychiatric disorder, usually complicated through expression of comorbid conditions, with chronic pain being among the most prevalent. This comorbidity is consistently associated with a poor prognosis and has been shown to negatively impact patient outcomes. With a global rise in this condition presenting itself, the importance of discovering long-term, effective, and affordable treatments is crucial. Electroacupuncture has demonstrated renowned success in its use for the treatment of pain and is a widely recognized therapy in clinical practice for the treatment of various psychosomatic disorders, most notably depression. Our study aimed to investigate the effects and mechanisms of Acid-Saline (AS) inducing states of chronic pain and depression comorbidity in the cerebellum, using the ST36 acupoint as the therapeutic intervention. Furthermore, the role of TRPV1 was relatedly explored through the use of TRPV1^−/− mice (KO). The results indicated significant differences in the four behavioral tests used to characterize pain and depression states in mice. The AS and AS + SHAM group showed significant differences when compared to the Control and AS + EA groups in the von Frey and Hargreaves’s tests, as well as the Open-Field and Forced Swimming tests. This evidence was further substantiated in the protein levels observed in immunoblotting, with significant differences between the AS and AS + SHAM groups when compared to the AS + EA and AS + KO groups being identified. In addition, immunofluorescence visibly served to corroborate the quantitative outcomes. Conclusively these findings suggest that AS-induced chronic pain and depression comorbidity elicits changes in the cerebellum lobules VI, VII, VIII, which are ameliorated through the use of EA at ST36 via its action on TRPV1 and related molecular pathways. The action of TRPV1 is not singular in CPDC, which would suggest other potential targets such as acid-sensing ion channel subtype 3 (ASIC3) or voltage-gated sodium channels (Navs) that could be explored in future studies.

Potential Alterations of Functional Connectivity Analysis in the Patients with Chronic Prostatitis/Chronic Pelvic Pain Syndrome

Background

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is one of the most common diseases in urology, but its pathogenesis remains unclear. As a kind of chronic pain which the patients suffered for more than 3 months, we investigated the influence on patients' brain functional connectivity in resting state.

Methods

We recruited a cohort of 18 right-handed male patients with CP/CPPS and 21 healthy male right-handed age-matched controls. Their resting-state fMRI data and structural MRI data were preprocessed and processed by RESTPlus V1.22. To assess the integrity of the default mode network (DMN), we utilized the voxel-wised analysis that we set medial prefrontal cortex (mPFC) and posterior cingulate gyrus (PCC) as seed points to compare the global functional connectivity (FC) strength.

Results

Compared with healthy control, the FC strength between left mPFC and posterior DMN decreased in the group of CP/CPPS (P < 0.05, GFR correction, voxel P < 0.01, cluster P < 0.05), and the FC strength between the left anterior cerebellar lobe and posterior DMN increased (P < 0.05, GFR correction, voxel P < 0.01, cluster P < 0.05). In the patient group, there was a positive correlation between the increased FC strength and the score of the Hospital Anxiety and Depression Scale (HADS) anxiety subscale (r = 0.5509, P = 0.0178) in the left anterior cerebellar lobe, a negative correlation between the decreased FC strength and the score of the National Institutes of Health Chronic Prostatitis Symptom Index (r = -0.6281, P = 0.0053) in the area of left mPFC, and a negative correlation between the decreased FC strength and the score of HADS anxiety subscale (r = -0.5252, P = 0.0252).

Conclusion

Patients with CP/CPPS had alterations in brain function, which consisted of the default mode network's compromised integrity. These alterations might play a crucial role in the pathogenesis and development of CP/CPPS.

Neuropathic corneal pain and dry eye: a continuum of nociception

Throughout the body, damage to peripheral nerves normally involved in nociception may produce a constellation of symptoms-including irritation, itchiness and pain. The neurobiological processes involved in corneal symptoms of dry eye (DE) and neuropathic corneal pain (NCP) have not been clearly considered in terms of nociceptive processing. The conventional underlying presumption is that a labelled line principle is responsible; that these distinct perceptions are hard coded by primary afferent inputs to the central nervous system. This presumption oversimplifies the neurobiological mechanisms underlying somatosensory perception. The labelled line perspective that DE represents a chronic pain condition does not make intuitive sense: how can an eye condition that is not painful in most cases be considered a pain condition? Does not chronic pain by definition require pain to be present? On the other hand, NCP, a term that clearly denotes a painful condition, has historically seemed to resonate with clinical significance. Both DE and NCP can share similar features, yet their differentiation is not always clear. As is often the case, clinical terms arise from different disciplines, with DE evolving from ophthalmological findings and NCP inspired by pain neurophysiology. This review evaluates the current definition of these terms, the rationale for their overlap and how the neurophysiology of itch impacts our understanding of these conditions as a continuum of the same disease. Despite the complexity of nociceptive physiology, an understanding of these mechanisms will allow us a more precise therapeutic approach.

Detangling red hair from pain: phenotype-specific contributions from different genetic variants in melanocortin-1 receptor

Genetic variation in melanocortin-1 receptor (MC1R) has a known role in red hair. Studies on responses to noxious stimuli in red-haired individuals have also been conducted, with mixed findings. To investigate a possible divergence between variants responsible for red hair and pain sensitivity, we performed a genewide association analysis in the Orofacial Pain: Prospective Evaluation and Risk Assessment cohort. All genotyped (17) MC1R variants were tested for association with heat pain temporal summation and sensitivity. Our analyses showed an association for pain sensitivity with the 5'-UTR, tagged by rs3212361, and 1 missense variant, rs885479 (R163Q), previously shown to be weakly associated with red hair. For both variants, the minor allele was protective. These results were validated in the 500,000-person UK Biobank cohort, where the minor alleles of rs3212361 and rs885479 were associated with a reduced count of persistent pain conditions as well as individual pain conditions. Haplotype association analysis revealed a possible joint effect from the 2 individual variants. The 5'-UTR variant rs3212361 was further identified as an expression quantitative trait locus, associated with reduced transcript levels of MC1R in the brain and in the peripheral tibial nerve. Hair colour association analysis of the loss-of-function 5'-UTR rs3212361 allele identified association with red hair, and red hair colour itself was associated with a reduced count of persistent pain conditions. Together, our results suggest that primarily different mechanisms-affecting expression levels vs protein activity-mediated by different genetic variants in the MC1R locus contribute to red hair and pain.

Feasibility of Auricular Field Stimulation in Fibromyalgia: Evaluation by Functional Magnetic Resonance Imaging, Randomized Trial

OBJECTIVE

To evaluate the feasibility of recruitment, preliminary efficacy, and acceptability of auricular percutaneous electrical nerve field stimulation (PENFS) for the treatment of fibromyalgia in veterans, using neuroimaging as an outcome measure and a biomarker of treatment response.

DESIGN

Randomized, controlled, single-blind.

SETTING

Government hospital.

SUBJECTS

Twenty-one veterans with fibromyalgia were randomized to standard therapy (ST) control or ST with auricular PENFS treatment.

METHODS

Participants received weekly visits with a pain practitioner over 4 weeks. The PENFS group received reapplication of PENFS at each weekly visit. Resting-state functional connectivity magnetic resonance imaging (rs-fcMRI) data were collected within 2 weeks prior to initiating treatment and 2 weeks following the final treatment. Analysis of rs-fcMRI used a right posterior insula seed. Pain and function were assessed at baseline and at 2, 6, and 12 weeks post-treatment.

RESULTS

At 12 weeks post-treatment, there was a nonsignificant trend toward improved pain scores and significant improvements in pain interference with sleep among the PENFS treatment group as compared with the ST controls. Neuroimaging data displayed increased connectivity to areas of the cerebellum and executive control networks in the PENFS group as compared with the ST control group following treatment.

CONCLUSIONS

There was a trend toward improved pain and function among veterans with fibromyalgia in the ST + PENFS group as compared with the ST control group. Pain and functional outcomes correlated with altered rs-fcMRI network connectivity. Neuroimaging results differed between groups, suggesting an alternative underlying mechanism for PENFS analgesia.

Air Hunger: A Primal Sensation and a Primary Element of Dyspnea

The sensation that develops as a long breath hold continues is what this article is about. We term this sensation of an urge to breathe "air hunger." Air hunger, a primal sensation, alerts us to a failure to meet an urgent homeostatic need maintaining gas exchange. Anxiety, frustration, and fear evoked by air hunger motivate behavioral actions to address the failure. The unpleasantness and emotional consequences of air hunger make it the most debilitating component of clinical dyspnea, a symptom associated with respiratory, cardiovascular, and metabolic diseases. In most clinical populations studied, air hunger is the predominant form of dyspnea (colloquially, shortness of breath). Most experimental subjects can reliably quantify air hunger using rating scales, that is, there is a consistent relationship between stimulus and rating. Stimuli that increase air hunger include hypercapnia, hypoxia, exercise, and acidosis; tidal expansion of the lungs reduces air hunger. Thus, the defining experimental paradigm to evoke air hunger is to elevate the drive to breathe while mechanically restricting ventilation. Functional brain imaging studies have shown that air hunger activates the insular cortex (an integration center for perceptions related to homeostasis, including pain, food hunger, and thirst), as well as limbic structures involved with anxiety and fear. Although much has been learned about air hunger in the past few decades, much remains to be discovered, such as an accepted method to quantify air hunger in nonhuman animals, fundamental questions about neural mechanisms, and adequate and safe methods to mitigate air hunger in clinical situations. © 2021 American Physiological Society. Compr Physiol 11:1449-1483, 2021.

Predicting Individual Pain Thresholds From Morphological Connectivity Using Structural MRI: A Multivariate Analysis Study

Pain sensitivity is highly variable among individuals, and it is clinically important to predict an individual’s pain sensitivity for individualized diagnosis and management of pain. Literature has shown that pain sensitivity is associated with regional structural features of the brain, but it remains unclear whether pain sensitivity is also related to structural brain connectivity. In the present study, we investigated the relationship between pain thresholds and morphological connectivity (MC) inferred from structural MRI based on data of 221 healthy participants. We found that MC was highly predictive of an individual’s pain thresholds and, importantly, it had a better prediction performance than regional structural features. We also identified a number of most predictive MC features and confirmed the crucial role of the prefrontal cortex in the determination of pain sensitivity. These results suggest the potential of using structural MRI-based MC to predict an individual’s pain sensitivity in clinical settings, and hence this study has important implications for diagnosis and treatment of pain.

Implications of the putamen in pain and motor deficits in complex regional pain syndrome

Complex regional pain syndrome (CRPS) develops after-limb injury, with persistent pain and deficits in movement frequently co-occurring. The striatum is critical for mediating multiple mechanisms that are often aberrant in CRPS, which includes sensory and pain processing, motor function, and goal-directed behaviors associated with movement. Yet, much remains unknown with regards to the morphological and functional properties of the striatum and its subregions in this disease. Thus, we investigated 20 patients (15 female, age 58 ± 9 years, right-handed) diagnosed with chronic (6+ months of pain duration) CRPS in the right hand and 20 matched, healthy controls with anatomical and resting-state, functional magnetic resonance imaging. In addition, a comprehensive clinical and behavioral evaluation was performed, where each participant's pain, motor function, and medical history were assessed. Complex regional pain syndrome patients harbored significant abnormalities in hand coordination, dexterity, and strength. These clinical pain- and movement-related findings in CRPS patients were concomitant with bilateral decreases in gray matter density in the putamen as well as functional connectivity increases and decreases among the putamen and pre-/postcentral gyri and cerebellum, respectively. Importantly, higher levels of clinical pain and motor impairment were associated with increased putamen-pre-/postcentral gyri functional connectivity strengths. Collectively, these findings suggest that putaminal alterations, specifically the functional interactions with sensorimotor structures, may underpin clinical pain and motor impairment in chronic CRPS patients.

Thalamocortical Connectivity in Experimentally-Induced Migraine Attacks: A Pilot Study

In this study we used nitroglycerin (NTG)-induced migraine attacks as a translational human disease model. Static and dynamic functional connectivity (FC) analyses were applied to study the associated functional brain changes. A spontaneous migraine-like attack was induced in five episodic migraine (EM) patients using a NTG challenge. Four task-free functional magnetic resonance imaging (fMRI) scans were acquired over the study: baseline, prodromal, full-blown, and recovery. Seed-based correlation analysis (SCA) was applied to fMRI data to assess static FC changes between the thalamus and the rest of the brain. Wavelet coherence analysis (WCA) was applied to test time-varying phase-coherence changes between the thalamus and salience networks (SNs). SCA results showed significantly FC changes between the right thalamus and areas involved in the pain circuits (insula, pons, cerebellum) during the prodromal phase, reaching its maximal alteration during the full-blown phase. WCA showed instead a loss of synchronisation between thalami and SN, mainly occurring during the prodrome and full-blown phases. These findings further support the idea that a temporal change in thalamic function occurs over the experimentally induced phases of NTG-induced headache in migraine patients. Correlation of FC changes with true clinical phases in spontaneous migraine would validate the utility of this model.

Altered Brain Network Connectivity Underlies Persistent Post-Traumatic Headache following Mild Traumatic Brain Injury in Youth

Post-traumatic headaches (PTHs) are associated with mild traumatic brain injuries (mTBI) and may predict the persistence of concussion symptoms. Altered brain networks implicated in brain injury and the affective components of headache-related pain may underlie the resolution of PTH. This is a hypothesis-generating investigation to evaluate the extent to which pain symptom reporting and functional brain changes are different in a cohort of young mTBI patients with resolved (PTH-R) and persistent (PTH-P) post-traumatic headache symptoms relative to healthy controls. This was a cross-sectional investigation involving 59 participants between the ages of 12-24 (PTH-P, n = 21; PTH-R, n = 18; healthy control, n = 20). Participants had no significant history of pre-existing headaches, chronic pain, or psychiatric neurological conditions. The primary outcome was resting-state functional connectivity (RS-Fc) alterations between cohorts. Secondary outcomes were self-reported pain-related symptoms. Elevated scores were reported for fear of pain in both PTH cohorts. Using a false discovery rate of p = 0.05, the PTH-P cohort showed altered connectivity relative to healthy controls in brain regions such as the frontal, temporal, and cerebellar regions, as well as sub-cortical regions including the amygdala and accumbens. The PTH-R cohort showed altered RS-Fc between cerebellar and temporal lobe sub-regions. Our results indicate that a core network of brain regions implicated in the affective pain response are functionally altered in PTH cohorts. Results should be interpreted given limitations on sample size and multiple comparisons. Despite the resolution of symptoms, persons who experience PTH may experience ongoing functional brain abnormalities, which may underlie symptom chronification.

Analysis of brain functional response to cutaneous prickling stimulation by single fiber

BACKGROUND

It is now well understood that, as an uncomfortable sensation evoked by special fabric, prickle derives from the mechanical stimulation of protruding hairiness from fabric surface against the human skin, in which some nociceptors are easy to be triggered by stiff fiber ends. However, up to now, the neural mechanism of the brain for perceiving fabric-evoked prickle is still unclear.

MATERIALS AND METHODS

In this work, A type of single-fiber stimulus made from nylon filament was used to repetitively prick the skin of volar forearm at a specific frequency, and the technology of functional magnetic resonance imaging (fMRI) was adopted to detect the brain response synchronously.

RESULTS

The results show that repetitive prickling stimulation from the single fiber applied to the volar forearm aroused distributed activation in several brain regions, such as primary somatosensory cortex, secondary somatosensory cortex, motor cortex, bilateral occipital lobe, insular cortex, and ipsilateral limbic lobe. Although the brain activation distribution is similar to pain, the single fiber-evoked prickle sensation possesses unique activation characteristics in several brain regions.

CONCLUSION

It is suggested that the sensation evoked by cutaneous prickling stimulation from single fiber belongs to a kind of multidimensional experience involving somatosensory, motor, emotional, cognitive, etc Our study constitutes an important step toward identifying the brain mechanism of fabric-evoked prickle.

Management of Procedural Pain in Children

In recent years, there has been increased interest in the study of pain in children and its treatment. It is known that when facing diagnostic and therapeutic procedures similar to those performed on adults, children either do not receive specific pain treatment or receive it on a significantly lower scale. However, recent research suggests a change in attitude and an improvement in the current treatment of children's pain. Although current knowledge demonstrates the falsity of many preconceived ideas about pain and its management, our results suggest that attitudinal change towards childhood pain remains slow and that real improvement in the training and practical application of the pediatrician who has to treat childhood pain is urgently needed. In this context, this manuscript has prepared standards and guidelines to improve pain management practices in a large number of national and international professional settings.

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

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

Structural and functional brain abnormalities in postherpetic neuralgia: A systematic review of neuroimaging studies

In recent decades, an increasing number of neuroimaging studies utilizing magnetic resonance imaging (MRI) have explored the differential effects of postherpetic neuralgia (PHN) on brain structure and function. We systematically reviewed and integrated the findings from relevant neuroimaging studies in PHN patients. A total of 15 studies with 16 datasets were ultimately included in the present study, which were categorized by the different neuroimaging modalities. The results revealed that PHN was closely associated with structural/microstructural and functional abnormalities of the brain mainly located in the 'pain matrix', including the thalamus, insula, parahippocampus, amygdala, dorsolateral prefrontal cortex, precentral gyrus and inferior parietal lobe, as well as other regions, such as the precuneus, lentiform nucleus and brainstem. Furthermore, a disruption of multiple networks, including the default-mode network, salience network and limbic system, may contribute to the neurophysiological mechanisms underlying PHN. The findings indicate that the cerebral abnormalities of PHN were not restricted to the pain matrix but extended to other regions, profoundly affecting the regulation and moderation of pain processing in PHN. Future prospective and longitudinal neuroimaging studies with larger samples will elucidate the progressive trajectory of neural changes in the pathophysiological process of PHN.

The Association Between Pain and Fall Among Middle-Aged and Older Chinese

BACKGROUND

Falls and fall-induced injuries in elderly people are common worldwide. However, few reports have examined the association between body pain and fall in middle-aged and older Chinese adults. The objective of this study is to access the association between pain and fall among middle-aged and older Chinese.

METHODS

Data were drawn from the 2011 China Health and Retirement Longitudinal Study (CHARLS) from respondents who were middle-aged and older (over 45 years old). A logistic regression model was used to estimate the odds ratios (AOR) and 95% confidence interval (95% CI) of the association between body pain and fall, after controlling for confounders.

RESULTS

After adjusting for demographic characteristics, socioeconomic status, lifestyle, health status and comorbidity, those participants who had pain were 73% more likely to report falls than those who did not have pain (AOR = 1.73, 95% CI 1.56-1.92). Elder age was associated with a higher risk of fall (AOR = 1.77, 95% CI 1.47-2.13). Comparing to female, male was associated with a lower risk of fall (AOR = 0.64, 95% CI 0.56-0.74). Lifestyle such as drinking status, self-reported health status, chronic diseases, vision impairment and disability were significantly associated with fall.

CONCLUSION

Body pain is significantly associated with fall among middle-aged and older Chinese adults. Appropriate pain management programs and policies are needed in fall prevention.

Dimensions of pain catastrophising and specific structural and functional alterations in patients with chronic pain: Evidence in medication-overuse headache

OBJECTIVES

We examined the neuroanatomical substrate of different pain catastrophising (PC) dimensions (i.e. rumination; magnification; helplessness) in patients with medication-overuse headache (MOH).

METHODS

We included 18 MOH patients who were administered the Pain Catastrophizing Scale (PCS) and scanned in a 3T-MRI. We conducted whole-brain volumetric and resting-state functional connectivity (FC) analysis to examine the association between grey matter (GM) density and FC strength and PCS dimensions controlling for depression and anxiety.

RESULTS

Higher total PCS score was associated with decreased GM density in precentral and inferior temporal gyrus, increased FC between middle temporal gyrus and cerebellum and reduced FC between precuneus and inferior temporal gyrus, as well as between frontal pole and temporal fusiform cortex. Regarding PCS dimensions, we mainly observed the involvement of (1) somatosensory cortex, supramarginal gyrus, basal ganglia, core default-mode network (DMN) in rumination; (2) somatosensory cortex, core DMN, dorsal medial prefrontal cortex (DMPFC)-DMN subsystem and cerebellum in magnification; and (3) temporal regions, DMN and basal ganglia in helplessness.

CONCLUSIONS

PC dimensions are associated with a specific structural and functional neuroanatomical pattern, which is different from the pattern observed when PC is considered as a single score. The involvement of basal ganglia and cerebellum needs further investigation.

Hierarchical models of pain: Inference, information-seeking, and adaptive control

Computational models of pain consider how the brain processes nociceptive information and allow mapping neural circuits and networks to cognition and behaviour. To date, they have generally have assumed two largely independent processes: perceptual inference, typically modelled as an approximate Bayesian process, and action control, typically modelled as a reinforcement learning process. However, inference and control are intertwined in complex ways, challenging the clarity of this distinction. Here, we consider how they may comprise a parallel hierarchical architecture that combines inference, information-seeking, and adaptive value-based control. This sheds light on the complex neural architecture of the pain system, and takes us closer to understanding from where pain 'arises' in the brain.

Functional Alterations in the Posterior Insula and Cerebellum in Migraine Without Aura: A Resting-State MRI Study

Background: Hypothesis-driven functional connectivity (FC) analyses have revealed abnormal functional interaction of regions or networks involved in pain processing in episodic migraine patients. We aimed to investigate the resting-state FC patterns in episodic migraine by combining data-driven voxel-wise degree centrality (DC) calculation and seed-based FC analysis.

Methods: Thirty-nine patients suffering from episodic migraine without aura and 35 healthy controls underwent clinical assessment and functional MRI. DC was analyzed voxel-wise and compared between groups, and FC of regions with DC differences were further examined using a seed-based approach.

Results: Compared with the control group, the migraine group showed increased and decreased DC in the right posterior insula and left crus I, respectively. Seed-based FC analyses revealed that migraine patients demonstrated increased right posterior insula connections with the postcentral gyrus, supplementary motor area/paracentral lobule, fusiform gyrus and temporal pole. The left crus I showed decreased FC with regions of the default mode network (DMN), including the medial prefrontal cortex (mPFC), angular gyrus, medial and lateral temporal cortex in patients with migraine. Furthermore, pain intensity positively correlated with DC in the right amygdala/parahippocampal gyrus, and migraine frequency negatively correlated with FC between the left crus I and mPFC.

Conclusion: Patients with episodic migraine without aura have increased FC with the right posterior insula and decreased FC within the DMN, which may underlie disturbed sensory integration and cognitive processing of pain. The left crus I-mPFC connectivity may be a useful biomarker for assessing migraine frequency.

Compensatory brainstem functional and structural connectivity in patients with degenerative cervical myelopathy by probabilistic tractography and functional MRI

Degenerative cervical myelopathy (DCM) is the most common cause of spinal cord impairment in adults. Previous supraspinal investigations have primarily focused on cortical changes in this patient population. As the nexus between the brain and the spinal cord, the brainstem has been understudied in patients with DCM. The current study examined the structural and functional connectivity between the brainstem and cortex in DCM patients using probabilistic tractography and resting-state functional MRI. A total of 26 study patients and 32 neurologically intact, healthy volunteers (HCs) participated in this prospective analysis. The study cohort included DCM patients (n = 18), as well as neurologically asymptomatic patients with evidence of cervical spine degenerative changes and spinal cord compression (n = 8). Results of the study demonstrated significant differences in fiber density (FD), fiber cross-section (FDC), and the functional connectivity (FC) between the study cohort and HCs. Through seeding the brainstem, the study cohort showed reductions in FD and FDC along the corticospinal tract, including regions extending through the corona radiata and internal capsule. By correlating FD and FDC with the Neck Disability Index (NDI), and the modified Japanese Orthopaedic Association (mJOA), we identified increasing total volume of projections to the thalamus, basal ganglia, and internal capsule, and increased functional connectivity to visual network and the posterior parietal cortices. These results support our hypothesis that DCM patients tend to have long-term FC reorganization not only localized to sensorimotor regions, but also to regulatory and visual processing regions, designed to ultimately preserve neurological function.