Abnormal Local Brain Activity Beyond the Pain Matrix in Postherpetic Neuralgia Patients: A Resting-State Functional MRI Study

Abstract

Background: Postherpetic neuralgia (PHN) patients suffer debilitating chronic pain, hyperalgesia, and allodynia, as well as emotional disorders such as insomnia, anxiety, and depression. The brain structure and functional basis of PHN are still not fully understood. Objectives: To identify the changes of regional brain activity in resting-state PHN patients using regional homogeneity (ReHo) and fractional aptitude of low-frequency fluctuation (fALFF) methods. Correlations between spontaneous pain intensity and ReHo or fALFF were analyzed. Study Design: Observational study. Setting: University hospital. Methods: ReHo, fALFF change was analyzed in 19 PHN patients and 19 healthy controls to detect the functional abnormality in the brains of PHN patients. Correlations between ReHo, fALFF, and PHN pain intensity were assessed in the PHN group. Results: PHN patients exhibited significantly abnormal ReHo and fALFF intensity in several brain regions, including the brainstem, thalamus, limbic system, temporal lobe, prefrontal lobe, and cerebellum compared with healthy controls. Correlation analysis showed that most of the ReHo values of the aforementioned brain regions positively correlated with visual analog scale (VAS) values. But much less correlation was found between fALFF and VAS. Limitations: (a) No specific emotional assessment was given for PHN patients before fMRI scans, therefore we cannot exclude whether the emotional disorders exist in these patients. (b) Relatively short pain duration (mean 5.4 months) and small sample size (n = 19) for the PHN group. Conclusions: For PHN patients, the local brain activity abnormality was not restricted to the pain matrix. Besides regions related to pain perception, areas in charge of affective processes, emotional activity, and pain modulation also showed abnormal local brain activity in a resting state, which may suggest complicated supraspinal function and plasticity change in PHN patients. ReHo was more closely correlated with pain intensity of PHN patients than fALFF. This work indicates that besides physical and emotional pain perception, mood disorder and pain modulation could be characteristics of PHN patients. This also supports the potential use of therapeutic interventions not only restricted to pain alleviation, but also those that attempt to ameliorate the cognitive and emotional comorbidities. Key words: Postherpetic neuralgia, resting-state fMRI (rs-fMRI), mood disorder, limbic sy

Abnormal Intrinsic Brain Activity and Neuroimaging-Based fMRI Classification in Patients With Herpes Zoster and Postherpetic Neuralgia

“…In addition to the precuneus/PCC, decreased ALFF values were also detected in the right MTG of both patient groups. This finding was consistent with previous studies which reported functional impairment of the right MTG in patients with PHN and HZ (11,12,17). However, there was no significant difference in ALFF between HZ and PHN.…”

“…In this study, a significant decrease of ALFF in the right MFG was found in patients with PHN, but not in patients with HZ. This result is consistent with previous studies that decreased ALFF value and cerebral blood flow in the MFG were detected in the patients with PHN (5,12). The patients with PHN also showed notably abnormal tissue microstructure in the MFG (9).…”

“…All these regions are pain-related areas. Previous neuroimaging studies have found that the brain activity and the gray matter volume in the right MTG have a significant correlation with pain duration and intensity of patients with PHN (12,17). The functional connectivity density of bilateral precuneus in PHN patients also showed a significant correlation with VAS scores (16).…”

“…PHN's effects on brain activity have been studied by resting-state functional magnetic resonance imaging (MRI) and task-functional MRI. Abnormal functional activation and intrinsic activity were detected in regions including the thalamus, insula, somatosensory, putamen, amygdala, brainstem, prefrontal lobe, and cerebellum (10)(11)(12). Quantitative cerebral blood flow (CBF) mapping in PHN patients showed significantly increased CBF values in the striatum, thalamus, insula, amygdala, and primary somatosensory cortex and decreased CBF values in the frontal cortex (5).…”

Characterizing the Structural Pattern Predicting Medication Response in Herpes Zoster Patients Using Multivoxel Pattern Analysis

“…Over the last decade, functional MRI (fMRI) has been increasingly applied in studying abnormal brain activity of HZ and PHN patients (Geha et al, 2007, 2008; Liu et al, 2013; Zhang et al, 2014; Jiang et al, 2016; Cao et al, 2017a, 2018; Yu and Yu, 2017; Hong et al, 2018). By contrast, few structural changes of these patients, which potentially underlie the functional abnormalities, have been explored.…”