Hyperexcitability of Cortical Oscillations in Patients with Somatoform Pain Disorder: A Resting-State EEG Study

Qian Ye,Dong Yan,Weiwei Peng,Manlin Yao,Wutao Lou

doi:10.1155/2019/2687150

Abstract

Patients with somatoform pain disorder (SPD) suffer from somatic pain that cannot be fully explained by specific somatic pathology. While the pain experience requires the integration of sensory and contextual processes, the cortical oscillations have been suggested to play a crucial role in pain processing and integration. The present study is aimed at identifying the abnormalities of spontaneous cortical oscillations among patients with SPD, thus for a better understanding of the ongoing brain states in these patients. Spontaneous electroencephalography data during a resting state with eyes open were recorded from SPD patients and healthy controls, and their cortical oscillations as well as functional connectivity were compared using both electrode-level and source-level analysis. Compared with healthy controls, SPD patients exhibited greater resting-state alpha oscillations (8.5-12.5 Hz) at the parietal region, as reflected by both electrode-level spectral power density and exact low-resolution brain electromagnetic tomography (eLORETA) cortical current density. A significant correlation between parietal alpha oscillation and somatization severity was observed in SPD patients, after accounting for the influence of anxiety and depression. Functional connectivity analysis further revealed a greater frontoparietal connectivity of the resting-state alpha oscillations in SPD patients, which was indexed by the coherence between pairs of electrodes and the linear connectivity between pairs of eLORETA cortical sources. The enhanced resting-state alpha oscillation in SPD patients could be relevant with attenuated sensory information gating and excessive integration of pain-related information, while the enhanced frontoparietal connectivity could be reflecting their sustained attention to bodily sensations and hypervigilance to somatic sensations.

Highlights

Patients with somatoform pain disorder (SPD) suffer from somatic pain that cannot be fully explained by a specific somatic pathology [1]
Functional neuroimaging studies revealed that patients with somatoform pain had enhanced cerebral processing of experimental nociceptive stimuli than healthy controls [6], including greater cortical activations of brain regions of pain neuromatrix
Correlation analysis across all SPD patients revealed that the pain severity was significantly and positively correlated with somatization (r = 0 66, p = 0 004) and depression (r = 0 64, p = 0 006)

Summary

Introduction

Patients with somatoform pain disorder (SPD) suffer from somatic pain (widespread pain or localized head, back, and abdominal pain) that cannot be fully explained by a specific somatic pathology [1]. Somatosensory amplification is considered to play a crucial role in somatization [3], manifested as exaggerated and sustained attention to bodily sensations or symptoms,as well as hypervigilance to somatic sensations with excessive affect and cognitions, which intensifies these patients more distressing and alarming. Somatoform patients with greater somatization severity tend to have less behavioral activities (e.g., shopping, watching TV) requiring attention distracted from pain bodily symptoms [4, 5]. Functional neuroimaging studies revealed that patients with somatoform pain had enhanced cerebral processing of experimental nociceptive stimuli than healthy controls [6], including greater cortical activations of brain regions of pain neuromatrix (e.g., primary and secondary somatosensory cortex, amygdala, anterior insula, and inferior parietal cortex).

Methods

Results

Conclusion