Functional and Structural Changes in Postherpetic Neuralgia Brain Before and Six Months After Pain Relieving

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.

Alteration of static and dynamic intrinsic brain activity induced by short-term spinal cord stimulation in postherpetic neuralgia patients

Introduction

Short-term spinal cord stimulation (stSCS) is an effective treatment for postherpetic neuralgia (PHN). However, how exactly stSCS affects time-dynamic intrinsic brain activity in PHN patients is not clear. The purpose of this study was to examine the static and dynamic variability of neural activity in PHN patients after stSCS.

Methods

In this study, 10 patients with PHN underwent resting-state functional magnetic resonance imaging (rs-fMRI) at baseline and after SCS. The amplitude of low-frequency fluctuations (ALFF) and dynamic ALFF (dALFF) were used to investigate the static and dynamic variability of neural activity in PHN patients after stSCS. We additionally examined the associations between clinical parameters and functional changes in the brain.

Results

There was a significant increase in dALFF in the left precuneus and right superior parietal gyrus, and a decrease in dALFF in the left inferior temporal gyrus, right gyrus rectus, left superior temporal gyrus, right orbitofrontal cortex, and left orbitofrontal cortex. There was significantly increased ALFF in the right inferior temporal gyrus, and decreased ALFF in the right lingual gyrus, left superior parietal gyrus, right superior parietal gyrus, and left precuneus. Furthermore, Pittsburgh sleep quality index scores were positively associated with dALFF changes in the left superior temporal gyrus and left orbitofrontal cortex. Hospital anxiety and depression scale scores and continuous pain scores exhibited significant negative correlation with dALFF changes in the right superior parietal gyrus.

Conclusion

This study indicated that stSCS is able to cause dALFF changes in PHN patients, thus stSCS might alter brain functions to relieve pain, sleep, and mood symptoms. The findings provide new insights into the mechanisms of stSCS efficacy in the treatment of patients with PHN.

Abnormal activation of brain regions in idiopathic trigeminal neuralgia patients by fMRI: An activation likelihood estimation meta-analysis

BACKGROUND

Idiopathic trigeminal neuralgia (ITN) is one of the most common types of neuropathic pain, severely affecting the physiological and psychological wellbeing of patients. Recently, fMRI has been used to examine abnormal activation of brain regions in patients with ITN. However, sample sizes have been small in these few studies, and the abnormally activated brain regions remain unclear. Therefore, in the present study, we retrieved and analyzed literature on the brain areas with abnormal or reduced activation in ITN patients, with the aim of providing insight into the neuropathological basis of the disease and to provide new targets for treatment.

METHODS

We retrieved resting state fMRI studies on trigeminal neuralgia patients from PubMed, the Web of Science and Scopus databases until November 2022, and we extracted the coordinates of the sites with increased or decreased activation. We used activation likelihood estimation (ALE) meta-analysis to identify regions of abnormal activation in ITN patients.

RESULTS

ALE meta-analysis revealed that the left caudate nucleus and right anterior ventral nucleus of the thalamus are abnormally hyperactivated in ITN patients. Moreover, ITN patients showed reduced activation in the left precuneus, middle temporal gyrus, lingual gyrus, and medial frontal gyrus.

CONCLUSION

ALE meta-analysis identified several brain regions with abnormally high or decreased activation in ITN patients. Sites with altered activation may be potential targets for non-invasive brain stimulation as adjunct therapy for ITN.

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.

Amplitude of low-frequency fluctuation after a single-trigger pain in patients with classical trigeminal neuralgia

Objective

This study aimed to explore the central mechanism of classical trigeminal neuralgia (CTN) by analyzing the static amplitude of low-frequency fluctuation (sALFF) and dynamic amplitude of low-frequency fluctuation (dALFF) in patients with CTN before and after a single-trigger pain.

Methods

This study included 48 patients (37 women and 11 men, age 55.65 ± 11.41 years) with CTN. All participants underwent 3D-T1WI and three times resting-state functional magnetic resonance imaging. The images were taken before stimulating the trigger zone (baseline), within 5 s after stimulating the trigger zone (triggering-5 s), and in the 30th minute after stimulating the trigger zone (triggering-30 min). The differences between the three measurements were analyzed using a repeated-measures analysis of variance.

Results

The sALFF values of the bilateral middle occipital gyrus and right cuneus gradually increased, and the values of the left posterior cingulum gyrus and bilateral superior frontal gyrus gradually decreased in triggering-5 s and triggering-30 min. The values of the right middle temporal gyrus and right thalamus decreased in triggering-5 s and subsequently increased in triggering-30 min. The sALFF values of the left superior temporal gyrus increased in triggering-5 s and then decreased in triggering-30 min. The dALFF values of the right fusiform gyrus, bilateral lingual gyrus, left middle temporal gyrus, and right cuneus gyrus gradually increased in both triggering-5 s and triggering-30 min.

Conclusions

The sALFF and dALFF values changed differently in multiple brain regions in triggering-5 s and triggering-30 min of CTN patients after a single trigger of pain, and dALFF is complementary to sALFF. The results might help explore the therapeutic targets for relieving pain and improving the quality of life of patients with CTN.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-022-01488-8.

Structural and Functional Abnormalities in Knee Osteoarthritis Pain Revealed With Multimodal Magnetic Resonance Imaging

The knee osteoarthritis (KOA) pain is the most common form of arthritis pain affecting millions of people worldwide. Long-term KOA pain causes motor impairment and affects affective and cognitive functions. However, little is known about the structural and functional abnormalities induced by long-term KOA pain. In this work, high-resolution structural magnetic resonance imaging (sMRI) and resting-state functional MRI (rs-fMRI) data were acquired in patients with KOA and age-, sex-matched healthy controls (HC). Gray matter volume (GMV) and fractional amplitude of low-frequency fluctuation (fALFF) were used to study the structural and functional abnormalities in patients with KOA. Compared with HC, patients with KOA showed reduced GMV in bilateral insula and bilateral hippocampus, and reduced fALFF in left cerebellum, precentral gyrus, and the right superior occipital gyrus. Patients with KOA also showed increased fALFF in left insula and bilateral hippocampus. In addition, the abnormal GMV in left insula and fALFF in left fusiform were closely correlated with the pain severity or disease duration. These results indicated that long KOA pain leads to brain structural and functional impairments in motor, visual, cognitive, and affective functions that related to brain areas. Our findings may facilitate to understand the neural basis of KOA pain and the future therapy to relieve disease symptoms.

Cerebral current-source distribution associated with pain improvement by non-invasive painless signaling therapy in patients with failed back surgery syndrome

Background

Non-invasive painless signaling therapy (NPST) is an electro-cutaneous treatment that converts endogenous pain information into synthetic non-pain information. This study explored whether pain improvement by NPST in failed back surgery syndrome (FBSS) patients is related to cerebral modulation.

Methods

Electroencephalography (EEG) analysis was performed in 11 patients with FBSS. Subjects received daily NPST for 5 days. Before the first treatment, patients completed the Brief Pain Inventory (BPI) and Beck Depression Inventory and underwent baseline EEG. After the final treatment, they responded again to the BPI, reported the percent pain improvement (PPI), and then underwent post-treatment EEG. If the PPI grade was zero, they were assigned to the ineffective group, while all others were assigned to the effective group. We used standardized low-resolution brain electromagnetic tomography (sLORETA) to explore the EEG current-source distribution (CSD) associated with pain improvement by NPST.

Results

The 11 participants had a median age of 67.0 years, and 63.6% were female. The sLORETA images revealed a beta-2 CSD increment in 12 voxels of the right anterior cingulate gyrus (ACG) and the right medial frontal area. The point of maximal CSD changes was in the right ACG. The alpha band CSD increased in 2 voxels of the left transverse gyrus.

Conclusions

Pain improvement by NPST in FBSS patients was associated with increased cerebral activity, mainly in the right ACG. The change in afferent information induced by NPST seems to be associated with cerebral pain perception.

Altered gray matter volume and functional connectivity in patients with herpes zoster and postherpetic neuralgia

Numerous neuroimaging studies on postherpetic neuralgia (PHN) and herpes zoster (HZ) have revealed abnormalities in brain structure/microstructure and function. However, few studies have focused on changes in gray matter (GM) volume and intrinsic functional connectivity (FC) in the transition from HZ to PHN. This study combined voxel-based morphometry and FC analysis methods to investigate GM volume and FC differences in 28 PHN patients, 25 HZ patients, and 21 well-matched healthy controls (HCs). Compared to HCs, PHN patients exhibited a reduction in GM volume in the bilateral putamen. Compared with HZ patients, PHN patients showed decreased GM volume in the left parahippocampal gyrus, putamen, anterior cingulate cortex, and right caudate and increased GM volume in the right thalamus. However, no regions with significant GM volume changes were found between the HZ and HC groups. Correlation analysis revealed that GM volume in the right putamen was positively associated with illness duration in PHN patients. Furthermore, lower FCs between the right putamen and right middle frontal gyrus/brainstem were observed in PHN patients than in HCs. These results indicate that aberrant GM volumes and FC in several brain regions, especially in the right putamen, are closely associated with chronification from HZ to PHN; moreover, these changes profoundly affect multiple dimensions of pain processing. These findings may provide new insights into the pathophysiological mechanisms of PHN.