MRI Study of Cerebral Cortical Thickness in Patients with Herpes Zoster and Postherpetic Neuralgia

The basolateral amygdala-anterior cingulate cortex circuit contributes to postherpetic neuralgia-anxiety comorbidity

Background: Postherpetic neuralgia (PHN) causes chronic pain and emotional dysfunction, but its underlying mechanisms are unknown. Methods: We first compared the structural and functional magnetic resonance imaging (MRI) of PHN-anxiety patients with healthy controls (HCs). Then, we created a PHN comorbid anxiety-like model by injecting resiniferatoxin (RTX) intraperitoneally and used Fos-CreER::Ai9 mice to validate brain regions with volume differences in MRI. Furthermore, we combined behavioral experiments with electrophysiology, viral tracing, in vivo fiber-photometry, optogenetics, and chemogenetics, to analyze the role of the basolateral amygdala (BLA)-anterior cingulate cortex (ACC) circuit in PHN comorbid anxiety-like mice multi-dimensionally. Results: According to neuroimages, patients with PHN-anxiety comorbidity have decreased amygdala volume and decreased functional connection (FC) of the BLA and ACC. Furthermore, we created a PHN comorbid anxiety-like model by injection of RTX intraperitoneally, and these mice showed dysesthesia and anxiety-like behaviors 3 weeks after RTX injection. Then, we discovered that BLA and ACC were related to PHN comorbid anxiety-like behaviors using Fos-CreER::Ai9 mice. Immunohistochemistry and electrophysiology revealed enhanced activation of BLA glutamatergic (BLAGlu) neurons in PHN comorbid anxiety-like mice. Opto/chemogenetic activating BLAGlu neurons aggravated pain threshold in PHN comorbid anxiety-like mice. Inhibiting BLAGlu alleviates mechanical nociception, thermal hyperalgesia, and anxiety-like behavior. Moreover, the elevated excitability of BLAGlu neurons resulted in increased excitatory inputs to the ACC. Selective activation or inhibition of the BLAGlu-ACC pathway exacerbated or alleviated the pain and anxiety behavior, respectively. Conclusion: Findings in this study will provide new insight for understanding the central pathomechanism underlying PHN-anxiety comorbidity, as well as serve as solid theoretical underpinnings for the management of PHN.

Local Structural Indices Changes During Different Periods of Postherpetic Neuralgia: A Graphical Study in Structural Covariance Networks

Purpose

In this study, we aim to explore the changes in network graph theory indices of structural covariance networks (SCNs) in PHN patients with different disease durations.

Patients and Methods

High-resolution T1 magnetic resonance images were collected from 109 subjects. We constructed SCNs based on cortical thickness data and analyzed the changes in global and regional network measures of PHN patients and herpes zoster (HZ) patients, and get hubs of each group.

Results

(1) PHN patients with a disease duration >6 months had reduced global efficiency (P=0.035) and increased characteristic shortest path length (P=0.028). (2) Nodal efficiency of the right pars opercularis was greater in both HZ and PHN patients with a disease duration of 1 to 3 months (P<0.001); in PHN patients with a disease duration > 6 months, the nodal degree of the left pars triangularis and nodal efficiency of the right middle temporal gyrus were greater (P<0.001). (3) The right supramarginal gyrus was the common hub of healthy controls (HCs) and HZ patients, the right pars opercularis was the common hub of HZ patients and PHN patients with a disease duration of 1 to 3 months, and the bilateral superior frontal gyrus was the common hub of HZ patients and PHN patients with a disease duration >6 months.

Conclusion

There have changes in SCN indices in PHN patients with different disease durations. PHN patients with a disease duration >6 months had increased SCN integration and diminished information transfer capability between nodes, which complemented the topological properties of previous PHN networks. Eglobal and Lp can be considered as potential imaging markers for future clinical restaging of PHN.

Cortical reorganization in neuropathic pain due to peripheral nerve degeneration: altered cortical surface morphometry and hierarchical topography

ABSTRACT

Degeneration of peripheral nerves causes neuropathic pain. Previous studies have documented structural and functional brain alterations in peripheral neuropathy, which may be attributed to maladaptive plasticity following chronic neuropathic pain. Nevertheless, the effects of peripheral neuropathic pain on the macroscale organization of the cerebral cortex have not been explored. This study investigated altered surface morphology and topographic hierarchy of the cerebral cortex in patients with neuropathic pain due to peripheral neuropathy. T1-weighted magnetic resonance imaging data were acquired from 52 patients with peripheral neuropathic pain and 50 age- and sex-matched healthy controls. Cortical morphometric features including thickness and gyrification index were obtained using surface-based morphometry. A topographic gradient encoding interregional similarity in cortical thickness was extracted using a machine-learning technique named diffusion map embedding. Compared with controls, patients with neuropathic pain exhibited cortical thinning in the frontal and sensorimotor cortices, with the severity increasing with greater neuropathic pain. The patients also showed decreased gyrification in the insula, with a greater reduction in gyrification linked to more severe skin nerve degeneration. Moreover, the patients exhibited altered topographic organization of the cerebral cortex, where the direction of the topographic gradient deviated from the occipital-to-frontal axis observed in the controls in this study and reported in the literature. Our findings provided a novel perspective for macroscale cortical structural reorganization after neuropathic pain, showing thinning and gyral flattening in pain-related areas and deviation from the normal topographic axis of the cerebral cortex.

Altered white matter microstructural integrity in patients with postherpetic neuralgia: a combined DTI and DTI-NODDI study

Background

Postherpetic neuralgia (PHN) is a debilitating condition resulting from herpes zoster infection, characterized by persistent pain that significantly impacts quality of life. This study aimed to investigate the white matter microstructural alterations associated with PHN and to assess the relationship between diffusion metrics and clinical symptoms.

Methods

A total of 29 patients with PHN, 28 patients recovering from herpes zoster (RHZ), and 27 healthy controls (HC) were recruited, and clinical assessments were obtained to evaluate pain intensity and psychological distress. Diffusion tensor imaging (DTI) data was collected, followed by analysis of diffusion and neurite orientation dispersion and density imaging (NODDI) metrics. Statistical analyses included ANOVA to compare groups and Pearson correlation coefficients to assess relationships between imaging metrics and clinical outcomes.

Results

PHN patients exhibited significantly altered white matter integrity, specifically in neurite density index (NDI) and orientation dispersion index, compared to both RHZ patients and HC. Significant correlations were also found between altered imaging metrics and clinical assessments of pain and emotional distress, with lower fractional anisotropy (FA) and NDI associated with higher pain scores and psychological symptoms.

Conclusion

Our study highlights significant microstructural changes in white matter tracts in patients with PHN, indicating compromised neural integrity that correlates with increased pain perception and emotional distress. NODDI demonstrated superior sensitivity in detecting these alterations compared to traditional DTI metrics, underscoring its potential for enhancing diagnostic and therapeutic approaches in managing chronic pain conditions like PHN.

Thread fragrant moxibustion for a young women with atypical hand herpes zoster: A case report

RATIONALE

Hand herpes zoster (HHZ) is a very rare skin disease in clinical practice. Due to the lack of specificity in its early clinical manifestations, HHZ is easily misdiagnosed as hand eczema or other lesions. Herein, we present a case with atypical HHZ.

PATIENT CONCERNS

A 25-year-old woman experienced left palm pain accompanied by upper limb stabbing pain, general weakness, and low-grade fever after staying up late. At first, she was diagnosed with peripheral nerve compression and hand eczema, and received relevant symptomatic treatment, but her condition did not improve. Diagnosed with herpes zoster on the hand after skin biopsy, treated with thread fragrant moxibustion (TFM).

DIAGNOSES

The HHZ diagnosis was established based on clinical appearance and dermatological findings eventually.

INTERVENTIONS

The intervention project was TFM treatment once a day in the acupuncture and moxibustion department, and the whole treatment period lasted for 10 days.

OUTCOMES

After 3 more TFM treatments were given, the burning sensation and itching in her palms as well as the pulsatility of the finger blood vessels had significantly reduction, the visual analog scale scores significantly decreased. After 10 treatments, the patient's herpes gradually falls off, revealing pink new skin without any discomfort.

LESSONS

Herpes zoster can appear in any part of the human body with different clinical manifestations. Herpes zoster in the hands is very rare in clinical practice, and it is often misdiagnosed as hand eczema or other lesions in the early stages of the disease. The case is not only highlights the challenging diagnosis in the absence of a characteristic rash at the initial stage but also confirmed the definite therapeutic effect of TFM on herpes zoster.

Signatures of chronic pain in multiple sclerosis: a machine learning approach to investigate trigeminal neuralgia

ABSTRACT

Chronic pain is a pervasive, disabling, and understudied feature of multiple sclerosis (MS), a progressive demyelinating and neurodegenerative disease. Current focus on motor components of MS disability combined with difficulties assessing pain symptoms present a challenge for the evaluation and management of pain in MS, highlighting the need for novel methods of assessment of neural signatures of chronic pain in MS. We investigate chronic pain in MS using MS-related trigeminal neuralgia (MS-TN) as a model condition focusing on gray matter structures as predictors of chronic pain. T1 imaging data from people with MS (n = 75) and MS-TN (n = 77) using machine learning (ML) was analyzed to derive imaging predictors at the level of cortex and subcortical gray matter. The ML classifier compared imaging metrics of patients with MS and MS-TN and distinguished between these conditions with 93.4% individual average testing accuracy. Structures within default-mode, somatomotor, salience, and visual networks (including hippocampus, primary somatosensory cortex, occipital cortex, and thalamic subnuclei) were identified as significant imaging predictors of trigeminal neuralgia pain. Our results emphasize the multifaceted nature of chronic pain and demonstrate the utility of imaging and ML in assessing and understanding MS-TN with greater objectivity.

Identifying and Evaluating Biological Markers of Postherpetic Neuralgia: A Comprehensive Review

Postherpetic neuralgia (PHN) manifests as persistent chronic pain that emerges after a herpes zoster outbreak and greatly diminishes quality of life. Unfortunately, its treatment efficacy has remained elusive, with many therapeutic efforts yielding less than satisfactory results. The research to discern risk factors predicting the onset, trajectory, and prognosis of PHN has been extensive. However, these risk factors often present as nonspecific and diverse, indicating the need for more reliable, measurable, and objective detection methods. The exploration of potential biological markers, including hematological indices, pathological insights, and supportive tests, is increasing. This review highlights potential biomarkers that are instrumental for the diagnosis, management, and prognosis of PHN while also delving deeper into its genesis. Drawing from prior research, aspects such as immune responsiveness, neuronal injury, genetic makeup, cellular metabolism, and pain signal modulation have emerged as prospective biomarkers. The immune spectrum spans various cell subtypes, with an emphasis on T cells, interferons, interleukins, and other related cytokines. Studies on nerve injury are directed toward pain-related proteins and the density and health of epidermal nerve fibers. On the genetic and metabolic fronts, the focus lies in the detection of predisposition genes, atypical protein manifestations, and energy-processing dynamics, with a keen interest in vitamin metabolism. Tools such as functional magnetic resonance imaging, electromyography, and infrared imaging have come to the forefront in the pain signaling domain. This review compiles the evidence, potential clinical implications, and challenges associated with these promising biomarkers, paving the way for innovative strategies for predicting, diagnosing, and addressing PHN.

Trigeminal Postherpetic Neuralgia: From Pathophysiology to Treatment

PURPOSE OF REVIEW

Trigeminal postherpetic neuralgia (TG-PHN) is a neuropathic pain condition complicating herpes zoster (HZ) attributed to the trigeminal nerve. It poses significant challenges due to its persistent and debilitating nature. This review explores the clinical characteristics of TG-PHN, analyzes its pathophysiological underpinnings, and addresses existent and potential therapies.

RECENT FINDINGS

TG-PHN is one of the most common and complex PHN locations. It has distinguishing clinical and pathophysiological characteristics, starting with viral triggered injuries to the trigeminal ganglion (TG) and peripheral tissue and involving the ascending and descending brain modulation pathways. Current therapies include vaccines, oral and topical medications, and interventional approaches, like nerve blocks and neurostimulation. This review covers TG-PHN's clinical and physiological components, treatment options, and potential future targets for improved management. By exploring the complexities of this condition, we aim to contribute to developing more effective and targeted therapies for patients suffering from trigeminal PHN.

Aberrant functional and causal connectivity of the amygdala in herpes zoster and post-herpetic neuralgia patients

OBJECTIVE

Resting-state functional magnetic resonance imaging (rs-fMRI) and Granger causality analysis (GCA) were used to observe the characteristics of amygdala and whole-brain effect connections in patients with herpes zoster (HZ) and post-herpetic neuralgia (PHN) and to determine their relationship with clinical features.

METHODS

Rs-fMRI scans were performed on 50 HZ; 50 PHN; and 50 age-, sex- and education-year-matched healthy controls (HCs). Bilateral amygdala subregions were used as seeds for functional connectivity (FC). GCA was used to analyze the effective connection of brain regions that were significantly different among groups. Then, the correlation between FC, and GCA values and clinical indices was investigated.

RESULTS

PHN had impaired FC between the amygdala subregion with the putamen, cortex, anterior cingulate cortex (ACC) to HCs and reduced FC of medial amygdala (MeA) with the parieto-occipital lobe and motor cortex to HZ; HZ had reduced FC of the lateral amygdala (LA) with the insula to HCs. GCA values from the bilateral LA to the bilateral ACC, left MeA to the bilateral ACC and left putamen, and right ACC to the bilateral MeA were reduced in PHN patients compared to HCs. Compared with HCs, the GCA values from the left MeA to the left ACC and right putamen were reduced in HZ. The GCA values from the amygdala subregion to the ACC were positively correlated with HAMA or HAMD scores in PHN.

CONCLUSION

PHN showed reduced FC between the amygdala subregions and cortico-putamen and decreased effective connectivity from the amygdala subregion to the ACC and putamen.

ADVANCES IN KNOWLEDGE

HZ and PHN patients had significant changes in effective connectivity in brain regions, including diverse functional areas emanating from and projecting to the amygdala. The current findings will provide a new perspective for understanding the neuropathophysiological mechanism HZ and PHN.

Altered White Matter Microstructure in Herpes Zoster and Postherpetic Neuralgia Determined by Automated Fiber Quantification

This study aimed to explore changes in the white matter microstructure in herpes zoster (HZ) and postherpetic neuralgia (PHN) patients and to estimate the correlation of these changes with clinical data. Diffusion tensor imaging (DTI) data were collected from 33 HZ patients, 32 PHN patients, and 35 well-matched healthy controls (HCs). Subsequently, these data were analyzed by automated fiber quantification (AFQ) to accurately locate alterations in the white matter microstructure. Compared with HCs, HZ and PHN patients both showed a wide range of changes in the diffusion properties of fiber tracts. HZ patients exhibited changes primarily in the left superior longitudinal fasciculus (SLF), whereas PHN patients predominantly exhibited changes in the left inferior fronto-occipital fasciculus. The bilateral SLF and the left corticospinal tract were altered in the PHN patients compared with HZ patients. In addition, PHN patients showed a trend toward more expansive white matter alterations compared with those observed in HZ patients; additionally, in PHN patients, changes in the left cingulum cingulate were significantly correlated with changes in emotion and the duration of disease. These findings may help to elucidate the transformation from HZ to PHN and provide new ideas regarding the reasons for intractable neuropathic pain in PHN.

Diffusion tensor imaging study of the microstructural changes in the white matter of patients with herpes zoster and postherpetic neuralgia

OBJECTIVE

To determine the association between white matter structural changes and PHN by analyzing the diffusion tensor imaging data of patients with herpes zoster (HZ) or postherpetic neuralgia (PHN), and the volunteered healthy controls (HC).

METHODS

A total of 48 participants with HZ, 40 participants with PHN, and 28 age and sex matched HC were enrolled in this study. The diffusion tensor imaging data were collected by a Siemens 3.0T magnetic resonance scanner, and FSL (FMRIB's software) was used to analyze the differences in diffusion indexes among the HZ, PHN and HC groups. In addition, the correlation between the image and the clinical parameters was analyzed.

RESULTS

The results indicated that the microstructural integrity of the white matter, which affects the information exchange and integration between pain and non-pain related brain regions, showed difference in patients with HZ and PHN.

CONCLUSION

The study may provide an experimental basis for more thorough longitudinal research in the future to explore the changes of brain structure in patients with PHN from HZ and develop adequate treatment strategy.